The Emacs Editor

Emacs is the advanced, extensible, customizable, self-documenting editor. This manual describes how to edit with Emacs and some of the ways to customize it; it corresponds to GNU Emacs version 29.2.

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For information on extending Emacs, see Emacs Lisp in The Emacs Lisp Reference Manual.

This is the GNU Emacs Manual, updated for Emacs version 29.2.

Copyright © 1985–2024 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with the Invariant Sections being “The GNU Manifesto,” “Distribution” and “GNU GENERAL PUBLIC LICENSE,” with the Front-Cover Texts being “A GNU Manual,” and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled “GNU Free Documentation License.”

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Table of Contents

Short Table of Contents


Distribution

GNU Emacs is free software; this means that everyone is free to use it and free to redistribute it under certain conditions. GNU Emacs is not in the public domain; it is copyrighted and there are restrictions on its distribution, but these restrictions are designed to permit everything that a good cooperating citizen would want to do. What is not allowed is to try to prevent others from further sharing any version of GNU Emacs that they might get from you. The precise conditions are found in the GNU General Public License that comes with Emacs and also appears in this manual1. See GNU GENERAL PUBLIC LICENSE.

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Introduction

You are reading about GNU Emacs, the GNU incarnation of the advanced, self-documenting, customizable, extensible editor Emacs. (The ‘G’ in GNU (GNU’s Not Unix) is not silent.)

We call Emacs advanced because it can do much more than simple insertion and deletion of text. It can control subprocesses, indent programs automatically, show multiple files at once, edit remote files like they were local files, and more. Emacs editing commands operate in terms of characters, words, lines, sentences, paragraphs, and pages, as well as expressions and comments in various programming languages.

Self-documenting means that at any time you can use special commands, known as help commands, to find out what your options are, or to find out what any command does, or to find all the commands that pertain to a given topic. See Help.

Customizable means that you can easily alter the behavior of Emacs commands in simple ways. For instance, if you use a programming language in which comments start with ‘<**’ and end with ‘**>’, you can tell the Emacs comment manipulation commands to use those strings (see Manipulating Comments). To take another example, you can rebind the basic cursor motion commands (up, down, left and right) to any keys on the keyboard that you find comfortable. See Customization.

Extensible means that you can go beyond simple customization and create entirely new commands. New commands are simply programs written in the Lisp language, which are run by Emacs’s own Lisp interpreter. Existing commands can even be redefined in the middle of an editing session, without having to restart Emacs. Most of the editing commands in Emacs are written in Lisp; the few exceptions could have been written in Lisp but use C instead for efficiency. Writing an extension is programming, but non-programmers can use it afterwards. See Preface in An Introduction to Programming in Emacs Lisp, if you want to learn Emacs Lisp programming.


1 The Organization of the Screen

On a graphical display, such as on GNU/Linux using the X Window System, Emacs occupies a graphical window. On a text terminal, Emacs occupies the entire terminal screen. We will use the term frame to mean a graphical window or terminal screen occupied by Emacs. Emacs behaves very similarly on both kinds of frames. It normally starts out with just one frame, but you can create additional frames if you wish (see Frames and Graphical Displays).

Each frame consists of several distinct regions. At the top of the frame is a menu bar, which allows you to access commands via a series of menus. On a graphical display, directly below the menu bar is a tool bar, a row of icons that perform editing commands when you click on them. At the very bottom of the frame is an echo area, where informative messages are displayed and where you enter information when Emacs asks for it.

The main area of the frame, below the tool bar (if one exists) and above the echo area, is called the window. Henceforth in this manual, we will use the word “window” in this sense. Graphical display systems commonly use the word “window” with a different meaning; but, as stated above, we refer to those graphical windows as “frames”.

An Emacs window is where the buffer—the text or other graphics you are editing or viewing—is displayed. On a graphical display, the window possesses a scroll bar on one side, which can be used to scroll through the buffer. The last line of the window is a mode line. This displays various information about what is going on in the buffer, such as whether there are unsaved changes, the editing modes that are in use, the current line number, and so forth.

When you start Emacs, there is normally only one window in the frame. However, you can subdivide this window horizontally or vertically to create multiple windows, each of which can independently display a buffer (see Multiple Windows).

At any time, one window is the selected window. On a graphical display, the selected window shows a more prominent cursor (usually solid and blinking); other windows show a less prominent cursor (usually a hollow box). On a text terminal, there is only one cursor, which is shown in the selected window. The buffer displayed in the selected window is called the current buffer, and it is where editing happens. Most Emacs commands implicitly apply to the current buffer; the text displayed in unselected windows is mostly visible for reference. If you use multiple frames on a graphical display, selecting a particular frame selects a window in that frame.


1.1 Point

The cursor in the selected window shows the location where most editing commands take effect, which is called point2. Many Emacs commands move point to different places in the buffer; for example, you can place point by clicking mouse button 1 (normally the left button) at the desired location.

By default, the cursor in the selected window is drawn as a solid block and appears to be on a character, but you should think of point as between two characters; it is situated before the character under the cursor. For example, if your text looks like ‘frob’ with the cursor over the ‘b’, then point is between the ‘o’ and the ‘b’. If you insert the character ‘!’ at that position, the result is ‘fro!b’, with point between the ‘!’ and the ‘b’. Thus, the cursor remains over the ‘b’, as before.

If you are editing several files in Emacs, each in its own buffer, each buffer has its own value of point. A buffer that is not currently displayed remembers its value of point if you later display it again. Furthermore, if a buffer is displayed in multiple windows, each of those windows has its own value of point.

See Displaying the Cursor, for options that control how Emacs displays the cursor.


1.2 The Echo Area

The line at the very bottom of the frame is the echo area. It is used to display small amounts of text for various purposes.

The echo area is so-named because one of the things it is used for is echoing, which means displaying the characters of a multi-character command as you type. Single-character commands are not echoed. Multi-character commands (see Keys) are echoed if you pause for more than a second in the middle of a command. Emacs then echoes all the characters of the command so far, to prompt you for the rest. Once echoing has started, the rest of the command echoes immediately as you type it. This behavior is designed to give confident users fast response, while giving hesitant users maximum feedback.

The echo area is also used to display an error message when a command cannot do its job. Error messages may be accompanied by beeping or by flashing the screen.

Some commands display informative messages in the echo area to tell you what the command has done, or to provide you with some specific information. These informative messages, unlike error messages, are not accompanied with a beep or flash. For example, C-x = (hold down Ctrl and type x, then let go of Ctrl and type =) displays a message describing the character at point, its position in the buffer, and its current column in the window. Commands that take a long time often display messages ending in ‘...’ while they are working (sometimes also indicating how much progress has been made, as a percentage), and add ‘done’ when they are finished.

Informative echo area messages are saved in a special buffer named *Messages*. (We have not explained buffers yet; see Using Multiple Buffers, for more information about them.) If you miss a message that appeared briefly on the screen, you can switch to the *Messages* buffer to see it again. The *Messages* buffer is limited to a certain number of lines, specified by the variable message-log-max. (We have not explained variables either; see Variables, for more information about them.) Beyond this limit, one line is deleted from the beginning whenever a new message line is added at the end.

See Customization of Display, for options that control how Emacs uses the echo area.

The echo area is also used to display the minibuffer, a special window where you can input arguments to commands, such as the name of a file to be edited. When the minibuffer is in use, the text displayed in the echo area begins with a prompt string, and the active cursor appears within the minibuffer, which is temporarily considered the selected window. You can always get out of the minibuffer by typing C-g. See The Minibuffer.


1.3 The Mode Line

At the bottom of each window is a mode line, which describes what is going on in the current buffer. When there is only one window, the mode line appears right above the echo area; it is the next-to-last line in the frame. On a graphical display, the mode line is drawn with a 3D box appearance. Emacs also usually draws the mode line of the selected window with a different color from that of unselected windows, in order to make it stand out.

The text displayed in the mode line has the following format:

 cs:ch-fr  buf      pos line   (major minor)

On a text terminal, this text is followed by a series of dashes extending to the right edge of the window. These dashes are omitted on a graphical display.

The cs string and the colon character after it describe the character set and newline convention used for the current buffer. Normally, Emacs automatically handles these settings for you, but it is sometimes useful to have this information.

cs describes the character set of the text in the buffer (see Coding Systems). If it is a dash (‘-’), that indicates no special character set handling (with the possible exception of end-of-line conventions, described in the next paragraph). ‘=’ means no conversion whatsoever, and is usually used for files containing non-textual data. Other characters represent various coding systems—for example, ‘1’ represents ISO Latin-1.

On a text terminal, cs is preceded by two additional characters that describe the coding systems for keyboard input and terminal output. Furthermore, if you are using an input method, cs is preceded by a string that identifies the input method (see Input Methods).

The character after cs is usually a colon. If a different string is displayed, that indicates a nontrivial end-of-line convention for encoding a file. Usually, lines of text are separated by newline characters in a file, but two other conventions are sometimes used. The MS-DOS convention uses a carriage return character followed by a linefeed character; when editing such files, the colon changes to either a backslash (‘\’) or ‘(DOS)’, depending on the operating system. Another convention, employed by older Macintosh systems, uses a carriage return character instead of a newline; when editing such files, the colon changes to either a forward slash (‘/’) or ‘(Mac)’. On some systems, Emacs displays ‘(Unix)’ instead of the colon for files that use newline as the line separator.

On frames created for emacsclient (see Invoking emacsclient), the next character is ‘@’. This indication is typical for frames of an Emacs process running as a daemon (see Using Emacs as a Server).

The next element on the mode line is the string indicated by ch. This shows two dashes (‘--’) if the buffer displayed in the window has the same contents as the corresponding file on the disk; i.e., if the buffer is unmodified. If the buffer is modified, it shows two stars (‘**’). For a read-only buffer, it shows ‘%*’ if the buffer is modified, and ‘%%’ otherwise.

The character after ch is normally a dash (‘-’). However, if default-directory (see File Names) for the current buffer is on a remote machine, ‘@’ is displayed instead.

fr gives the selected frame name (see Frames and Graphical Displays). It appears only on text terminals. The initial frame’s name is ‘F1’.

buf is the name of the buffer displayed in the window. Usually, this is the same as the name of a file you are editing. See Using Multiple Buffers.

pos tells you whether there is additional text above the top of the window, or below the bottom. If your buffer is small and all of it is visible in the window, pos is ‘All’. Otherwise, it is ‘Top’ if you are looking at the beginning of the buffer, ‘Bot’ if you are looking at the end of the buffer, or ‘nn%’, where nn is the percentage of the buffer above the top of the window. With Size Indication mode, you can display the size of the buffer as well. See Optional Mode Line Features.

line is the character ‘L’ followed by the line number at point. (You can display the current column number too, by turning on Column Number mode. See Optional Mode Line Features.)

major is the name of the major mode used in the buffer. A major mode is a principal editing mode for the buffer, such as Text mode, Lisp mode, C mode, and so forth. See Major Modes. Some major modes display additional information after the major mode name. For example, Compilation buffers and Shell buffers display the status of the subprocess.

minor is a list of some of the enabled minor modes, which are optional editing modes that provide additional features on top of the major mode. See Minor Modes.

Some features are listed together with the minor modes whenever they are turned on, even though they are not really minor modes. ‘Narrow’ means that the buffer being displayed has editing restricted to only a portion of its text (see Narrowing). ‘Def’ means that a keyboard macro is currently being defined (see Keyboard Macros).

In addition, if Emacs is inside a recursive editing level, square brackets (‘[…]’) appear around the parentheses that surround the modes. If Emacs is in one recursive editing level within another, double square brackets appear, and so on. Since recursive editing levels affect Emacs globally, such square brackets appear in the mode line of every window. See Recursive Editing Levels.

You can change the appearance of the mode line as well as the format of its contents. See Optional Mode Line Features. In addition, the mode line is mouse-sensitive; clicking on different parts of the mode line performs various commands. See Mode Line Mouse Commands. Also, hovering the mouse pointer above mouse-sensitive portions of the mode line shows tooltips (see Tooltips) with information about commands you can invoke by clicking on the mode line.


2 Kinds of User Input

GNU Emacs is primarily designed for use with the keyboard. While it is possible to use the mouse to issue editing commands through the menu bar and tool bar, that is usually not as efficient as using the keyboard.

Keyboard input into Emacs is based on a heavily-extended version of ASCII. Simple characters, like ‘a’, ‘B’, ‘3’, ‘=’, and the space character (denoted as SPC), are entered by typing the corresponding key. Control characters, such as RET, TAB, DEL, ESC, F1, Home, and LEFT, are also entered this way, as are certain characters found on non-English keyboards (see International Character Set Support).

Emacs also recognizes control characters that are entered using modifier keys. Two commonly-used modifier keys are Control (usually labeled Ctrl), and Meta (usually labeled Alt)3. For example, Control-a is entered by holding down the Ctrl key while pressing a; we will refer to this as C-a for short. Similarly, Meta-a, or M-a for short, is entered by holding down the Alt key and pressing a. Modifier keys can also be applied to non-alphanumerical characters, e.g., C-F1 or M-LEFT.

You can also type Meta characters using two-character sequences starting with ESC. Thus, you can enter M-a by typing ESC a. You can enter C-M-a (holding down both Ctrl and Alt, then pressing a) by typing ESC C-a. Unlike Meta, ESC is entered as a separate character. You don’t hold down ESC while typing the next character; instead, press ESC and release it, then enter the next character. This feature is useful on certain text terminals where the Meta key does not function reliably.

Emacs supports 3 additional modifier keys, see Modifier Keys.

Emacs has extensive support for using mouse buttons, mouse wheels and other pointing devices like touchpads and touch screens. See Mouse Input, for details.

On graphical displays, the window manager might block some keyboard inputs, including M-TAB, M-SPC, C-M-d and C-M-l. If you have this problem, you can either customize your window manager to not block those keys, or rebind the affected Emacs commands (see Customization).

Simple characters and control characters, as well as certain non-keyboard inputs such as mouse clicks, are collectively referred to as input events. For details about how Emacs internally handles input events, see Input Events in The Emacs Lisp Reference Manual.


3 Keys

Some Emacs commands are invoked by just one input event; for example, C-f moves forward one character in the buffer. Other commands take two or more input events to invoke, such as C-x C-f and C-x 4 C-f.

A key sequence, or key for short, is a sequence of one or more input events that is meaningful as a unit. If a key sequence invokes a command, we call it a complete key; for example, C-f, C-x C-f and C-x 4 C-f are all complete keys. If a key sequence isn’t long enough to invoke a command, we call it a prefix key; from the preceding example, we see that C-x and C-x 4 are prefix keys. Every key sequence is either a complete key or a prefix key.

A prefix key combines with the following input event to make a longer key sequence. For example, C-x is a prefix key, so typing C-x alone does not invoke a command; instead, Emacs waits for further input (if you pause for longer than a second, it echoes the C-x key to prompt for that input; see The Echo Area). C-x combines with the next input event to make a two-event key sequence, which could itself be a prefix key (such as C-x 4), or a complete key (such as C-x C-f). There is no limit to the length of key sequences, but in practice they are seldom longer than three or four input events.

You can’t add input events onto a complete key. For example, because C-f is a complete key, the two-event sequence C-f C-k is two key sequences, not one.

By default, the prefix keys in Emacs are C-c, C-h, C-x, C-x RET, C-x @, C-x a, C-x n, C-x r, C-x t, C-x v, C-x 4, C-x 5, C-x 6, ESC, and M-g. (F1 and F2 are aliases for C-h and C-x 6.) This list is not cast in stone; if you customize Emacs, you can make new prefix keys. You could even eliminate some of the standard ones, though this is not recommended for most users; for example, if you remove the prefix definition of C-x 4, then C-x 4 C-f becomes an invalid key sequence. See Customizing Key Bindings.

Typing the help character (C-h or F1) after a prefix key displays a list of the commands starting with that prefix. The sole exception to this rule is ESC: ESC C-h is equivalent to C-M-h, which does something else entirely. You can, however, use F1 to display a list of commands starting with ESC.


4 Mouse Input

By default, Emacs supports all the normal mouse actions like setting the cursor by clicking on the left mouse button, and selecting an area by dragging the mouse pointer. All mouse actions can be used to bind commands in the same way you bind them to keyboard events (see Keys). This section provides a general overview of using the mouse in Emacs; see Mouse Commands for Editing, and the sections that follow it, for more details about mouse commands in Emacs.

When you click the left mouse button, Emacs receives a mouse-1 event. To see what command is bound to that event, you can type C-h c and then press the left mouse button. Similarly, the middle mouse button is mouse-2 and the right mouse button is mouse-3. If you have a mouse with a wheel, the wheel events are commonly bound to either wheel-down or wheel-up, or mouse-4 and mouse-5, but that depends on the operating system configuration.

In general, legacy X systems and terminals (see Using a Mouse in Text Terminals) will report mouse-4 and mouse-5, while all other systems will report wheel-down and wheel-up.

Some mice also have a horizontal scroll wheel, and touchpads usually support scrolling horizontally as well. These events are reported as wheel-left and wheel-right on all systems other than terminals and legacy X systems, where they are mouse-6 and mouse-7.

You can also combine keyboard modifiers with mouse events, so you can bind a special command that triggers when you, for instance, holds down the Meta key and then uses the middle mouse button. In that case, the event name will be M-mouse-2.

On some systems, you can also bind commands for handling touch screen events. In that case, the events are called touchscreen-update and touchscreen-end.


5 Keys and Commands

This manual is full of passages that tell you what particular keys do. But Emacs does not assign meanings to keys directly. Instead, Emacs assigns meanings to named commands, and then gives keys their meanings by binding them to commands.

Every command has a name chosen by a programmer. The name is usually made of a few English words separated by dashes; for example, next-line or forward-word. Internally, each command is a special type of Lisp function, and the actions associated with the command are performed by running the function. See What Is a Function in The Emacs Lisp Reference Manual.

The bindings between keys and commands are recorded in tables called keymaps. See Keymaps.

When we say that “C-n moves down vertically one line” we are glossing over a subtle distinction that is irrelevant in ordinary use, but vital for Emacs customization. The command next-line does a vertical move downward. C-n has this effect because it is bound to next-line. If you rebind C-n to the command forward-word, C-n will move forward one word instead.

In this manual, we will often speak of keys like C-n as commands, even though strictly speaking the key is bound to a command. Usually, we state the name of the command which really does the work in parentheses after mentioning the key that runs it. For example, we will say that “The command C-n (next-line) moves point vertically down”, meaning that the command next-line moves vertically down, and the key C-n is normally bound to it.

Since we are discussing customization, we should tell you about variables. Often the description of a command will say, “To change this, set the variable mumble-foo.” A variable is a name used to store a value. Most of the variables documented in this manual are meant for customization: some command or other part of Emacs examines the variable and behaves differently according to the value that you set. You can ignore the information about variables until you are interested in customizing them. Then read the basic information on variables (see Variables) and the information about specific variables will make sense.


6 Entering Emacs

The usual way to invoke Emacs is with the shell command emacs. From a terminal window running a Unix shell on a GUI terminal, you can run Emacs in the background with emacs &; this way, Emacs won’t tie up the terminal window, so you can use it to run other shell commands. (For comparable methods of starting Emacs on MS-Windows, see How to Start Emacs on MS-Windows.)

When Emacs starts up, the initial frame displays a special buffer named ‘*GNU Emacs*’. This startup screen contains information about Emacs and links to common tasks that are useful for beginning users. For instance, activating the ‘Emacs Tutorial’ link opens the Emacs tutorial; this does the same thing as the command C-h t (help-with-tutorial). To activate a link, either move point onto it and type RET, or click on it with mouse-1 (the left mouse button).

Using a command line argument, you can tell Emacs to visit one or more files as soon as it starts up. For example, emacs foo.txt starts Emacs with a buffer displaying the contents of the file ‘foo.txt’. This feature exists mainly for compatibility with other editors, which are designed to be launched from the shell for short editing sessions. If you call Emacs this way, the initial frame is split into two windows—one showing the specified file, and the other showing the startup screen. See Multiple Windows.

Generally, it is unnecessary and wasteful to start Emacs afresh each time you want to edit a file. The recommended way to use Emacs is to start it just once, just after you log in, and do all your editing in the same Emacs session. See File Handling, for information on visiting more than one file. If you use Emacs this way, the Emacs session accumulates valuable context, such as the kill ring, registers, undo history, and mark ring data, which together make editing more convenient. These features are described later in the manual.

To edit a file from another program while Emacs is running, you can use the emacsclient helper program to open a file in the existing Emacs session. See Using Emacs as a Server.

Emacs accepts other command line arguments that tell it to load certain Lisp files, where to put the initial frame, and so forth. See Command Line Arguments for Emacs Invocation.

If the variable inhibit-startup-screen is non-nil, Emacs does not display the startup screen. In that case, if one or more files were specified on the command line, Emacs simply displays those files; otherwise, it displays a buffer named *scratch*, which can be used to evaluate Emacs Lisp expressions interactively. See Lisp Interaction Buffers. You can set the variable inhibit-startup-screen using the Customize facility (see Easy Customization Interface), or by editing your initialization file (see The Emacs Initialization File).4

You can also force Emacs to display a file or directory at startup by setting the variable initial-buffer-choice to a string naming that file or directory. The value of initial-buffer-choice may also be a function (of no arguments) that should return a buffer which is then displayed. If initial-buffer-choice is non-nil, then if you specify any files on the command line, Emacs still visits them, but does not display them initially.


7 Exiting Emacs

C-x C-c

Kill Emacs (save-buffers-kill-terminal).

C-z

On a text terminal, suspend Emacs; on a graphical display, iconify (or “minimize”) the selected frame (suspend-frame).

Killing Emacs means terminating the Emacs program. To do this, type C-x C-c (save-buffers-kill-terminal). A two-character key sequence is used to make it harder to type by accident. If there are any modified file-visiting buffers when you type C-x C-c, Emacs first offers to save these buffers. If you do not save them all, it asks for confirmation again, since the unsaved changes will be lost. Emacs also asks for confirmation if any subprocesses are still running, since killing Emacs will also kill the subprocesses (see Running Shell Commands from Emacs).

C-x C-c behaves specially if you are using Emacs as a server. If you type it from a client frame, it closes the client connection. See Using Emacs as a Server.

Emacs can, optionally, record certain session information when you kill it, such as the files you were visiting at the time. This information is then available the next time you start Emacs. See Saving Emacs Sessions.

If the value of the variable confirm-kill-emacs is non-nil, C-x C-c assumes that its value is a predicate function, and calls that function. If the result of the function call is non-nil, the session is killed, otherwise Emacs continues to run. One convenient function to use as the value of confirm-kill-emacs is the function yes-or-no-p. The default value of confirm-kill-emacs is nil.

If the value of the variable confirm-kill-processes is nil, C-x C-c does not ask for confirmation before killing subprocesses started by Emacs. The value is t by default.

To further customize what happens when Emacs is exiting, see Killing Emacs in The GNU Emacs Lisp Reference Manual.

To kill Emacs without being prompted about saving, type M-x kill-emacs.

C-z runs the command suspend-frame. On a graphical display, this command minimizes (or iconifies) the selected Emacs frame, hiding it in a way that lets you bring it back later (exactly how this hiding occurs depends on the window system). On a text terminal, the C-z command suspends Emacs, stopping the program temporarily and returning control to the parent process (usually a shell); in most shells, you can resume Emacs after suspending it with the shell command %emacs.

Text terminals usually listen for certain special characters whose meaning is to kill or suspend the program you are running. This terminal feature is turned off while you are in Emacs. The meanings of C-z and C-x C-c as keys in Emacs were inspired by the use of C-z and C-c on several operating systems as the characters for stopping or killing a program, but that is their only relationship with the operating system. You can customize these keys to run any commands of your choice (see Keymaps).


8 Basic Editing Commands

Here we explain the basics of how to enter text, make corrections, and save the text in a file. If this material is new to you, we suggest you first run the Emacs learn-by-doing tutorial, by typing C-h t (help-with-tutorial).


8.1 Inserting Text

You can insert an ordinary graphic character (e.g., ‘a’, ‘B’, ‘3’, and ‘=’) by typing the associated key. This adds the character to the buffer at point. Insertion moves point forward, so that point remains just after the inserted text. See Point.

To end a line and start a new one, type RET (newline). (The RET key may be labeled Return, or Enter, or with a funny-looking left-pointing arrow on your keyboard, but we refer to it as RET in this manual.) This command inserts a newline character into the buffer, then indents (see Indentation) according to the major mode. If point is at the end of the line, the effect is to create a new blank line after it and indent the new line; if point is in the middle of a line, the line is split at that position. To turn off the auto-indentation, you can either disable Electric Indent mode (see Convenience Features for Indentation) or type C-j, which inserts just a newline, without any auto-indentation.

As we explain later in this manual, you can change the way Emacs handles text insertion by turning on minor modes. For instance, the minor mode called Auto Fill mode splits lines automatically when they get too long (see Filling Text). The minor mode called Overwrite mode causes inserted characters to replace (overwrite) existing text, instead of shoving it to the right. See Minor Modes.

Only graphic characters can be inserted by typing the associated key; other keys act as editing commands and do not insert themselves. For instance, DEL runs the command delete-backward-char by default (some modes bind it to a different command); it does not insert a literal ‘DEL’ character (ASCII character code 127).

To insert a non-graphic character, or a character that your keyboard does not support, first quote it by typing C-q (quoted-insert). There are two ways to use C-q:

  • C-q followed by any non-graphic character (even C-g) inserts that character. For instance, C-q DEL inserts a literal ‘DEL’ character.
  • C-q followed by a sequence of octal digits inserts the character with the specified octal character code. You can use any number of octal digits; any non-digit terminates the sequence. If the terminating character is RET, that RET serves only to terminate the sequence. Any other non-digit terminates the sequence and then acts as normal input—thus, C-q 1 0 1 B inserts ‘AB’.

    The use of octal sequences is disabled in ordinary non-binary Overwrite mode, to give you a convenient way to insert a digit instead of overwriting with it.

To use decimal or hexadecimal instead of octal, set the variable read-quoted-char-radix to 10 or 16. If the radix is 16, the letters a to f serve as part of a character code, just like digits. Case is ignored.

A few common Unicode characters can be inserted via a command starting with C-x 8. For example, C-x 8 [ inserts which is Unicode code-point U+2018 LEFT SINGLE QUOTATION MARK, sometimes called a left single “curved quote” or “curly quote”. Similarly, C-x 8 ], C-x 8 { and C-x 8 } insert the curved quotes , and , respectively. Also, a working Alt key acts like C-x 8 (unless followed by RET); e.g., A-[ acts like C-x 8 [ and inserts . To see which characters have C-x 8 shorthands, type C-x 8 C-h.

Alternatively, you can use the command C-x 8 RET (insert-char). This prompts for the Unicode name or code-point of a character, using the minibuffer. If you enter a name, the command provides completion (see Completion). If you enter a code-point, it should be as a hexadecimal number (the convention for Unicode), or a number with a specified radix, e.g., #o23072 (octal); See Integer Basics in The Emacs Lisp Reference Manual. The command then inserts the corresponding character into the buffer.

For example, the following all insert the same character:

C-x 8 RET left single quotation mark RET
C-x 8 RET left sin TAB RET
C-x 8 RET 2018 RET
C-x 8 [
A-[  (if the Alt key works)
`    (in Electric Quote mode)

A numeric argument to C-q or C-x 8 ... specifies how many copies of the character to insert (see Numeric Arguments).

As an alternative to C-x 8, you can select the corresponding transient input method by typing C-u C-x \ iso-transl RET, then temporarily activating this transient input method by typing C-x \ [ will insert the same character (see transient input method).

In addition, in some contexts, if you type a quotation using grave accent and apostrophe `like this', it is converted to a form ‘like this’ using single quotation marks, even without C-x 8 commands. Similarly, typing a quotation ``like this'' using double grave accent and apostrophe converts it to a form “like this” using double quotation marks. See Quotation Marks.


8.2 Changing the Location of Point

To do more than insert characters, you have to know how to move point (see Point). The keyboard commands C-f, C-b, C-n, and C-p move point to the right, left, down, and up, respectively. You can also move point using the arrow keys present on most keyboards: RIGHT, LEFT, DOWN, and UP; however, many Emacs users find that it is slower to use the arrow keys than the control keys, because you need to move your hand to the area of the keyboard where those keys are located.

You can also click the left mouse button to move point to the position clicked. Emacs also provides a variety of additional keyboard commands that move point in more sophisticated ways.

C-f

Move forward one character (forward-char).

RIGHT

This command (right-char) behaves like C-f, except when point is in a right-to-left paragraph (see Bidirectional Editing).

C-b

Move backward one character (backward-char).

LEFT

This command (left-char) behaves like C-b, except if the current paragraph is right-to-left (see Bidirectional Editing).

C-n
DOWN

Move down one screen line (next-line). This command attempts to keep the horizontal position unchanged, so if you start in the middle of one line, you move to the middle of the next.

C-p
UP

Move up one screen line (previous-line). This command preserves position within the line, like C-n.

C-a
Home

Move to the beginning of the line (move-beginning-of-line).

C-e
End

Move to the end of the line (move-end-of-line).

M-f

Move forward one word (forward-word). See Words.

C-RIGHT
M-RIGHT

This command (right-word) behaves like M-f, except it moves backward by one word if the current paragraph is right-to-left. See Bidirectional Editing.

M-b

Move backward one word (backward-word). See Words.

C-LEFT
M-LEFT

This command (left-word) behaves like M-b, except it moves forward by one word if the current paragraph is right-to-left. See Bidirectional Editing.

M-r

Without moving the text on the screen, reposition point on the left margin of the center-most text line of the window; on subsequent consecutive invocations, move point to the left margin of the top-most line, the bottom-most line, and so forth, in cyclic order (move-to-window-line-top-bottom).

A numeric argument says which screen line to place point on, counting downward from the top of the window (zero means the top line). A negative argument counts lines up from the bottom (−1 means the bottom line). See Numeric Arguments, for more information on numeric arguments.

M-<

Move to the top of the buffer (beginning-of-buffer). With numeric argument n, move to n/10 of the way from the top. On graphical displays, C-HOME does the same.

M->

Move to the end of the buffer (end-of-buffer). On graphical displays, C-END does the same.

C-v
PageDown
next

Scroll the display one screen forward, and move point onscreen if necessary (scroll-up-command). See Scrolling.

M-v
PageUp
prior

Scroll one screen backward, and move point onscreen if necessary (scroll-down-command). See Scrolling.

M-g c

Read a number n and move point to buffer position n. Position 1 is the beginning of the buffer. If point is on or just after a number in the buffer, that is the default for n. Just type RET in the minibuffer to use it. You can also specify n by giving M-g c a numeric prefix argument.

M-g M-g
M-g g

Read a number n and move point to the beginning of line number n (goto-line). Line 1 is the beginning of the buffer. If point is on or just after a number in the buffer, that is the default for n. Just type RET in the minibuffer to use it. You can also specify n by giving M-g M-g a numeric prefix argument. See Creating and Selecting Buffers, for the behavior of M-g M-g when you give it a plain prefix argument. Alternatively, you can use the command goto-line-relative to move point to the line relative to the accessible portion of the narrowed buffer.

goto-line has its own history list (see Minibuffer History). You can have either a single list shared between all buffers (the default) or a separate list for each buffer, by customizing the user option goto-line-history-local.

M-g TAB

Read a number n and move to column n in the current line. Column 0 is the leftmost column. If called with a prefix argument, move to the column number specified by the argument’s numeric value.

C-x C-n

Use the current column of point as the semipermanent goal column (set-goal-column) in the current buffer. When a semipermanent goal column is in effect, C-n, C-p, <prior> and <next> always try to move to this column, or as close as possible to it, after moving vertically. The goal column remains in effect until canceled.

C-u C-x C-n

Cancel the goal column. Henceforth, C-n and C-p try to preserve the horizontal position, as usual.

When a line of text in the buffer is longer than the width of the window, Emacs usually displays it on two or more screen lines, a.k.a. visual lines. For convenience, C-n and C-p move point by screen lines, as do the equivalent keys down and up. You can force these commands to move according to logical lines (i.e., according to the text lines in the buffer) by setting the variable line-move-visual to nil; if a logical line occupies multiple screen lines, the cursor then skips over the additional screen lines. For details, see Continuation Lines. See Variables, for how to set variables such as line-move-visual.

Unlike C-n and C-p, most of the Emacs commands that work on lines work on logical lines. For instance, C-a (move-beginning-of-line) and C-e (move-end-of-line) respectively move to the beginning and end of the logical line. Whenever we encounter commands that work on screen lines, such as C-n and C-p, we will point these out.

When line-move-visual is nil, you can also set the variable track-eol to a non-nil value. Then C-n and C-p, when starting at the end of the logical line, move to the end of the next logical line. Normally, track-eol is nil.

C-n normally stops at the end of the buffer when you use it on the last line in the buffer. However, if you set the variable next-line-add-newlines to a non-nil value, C-n on the last line of a buffer creates an additional line at the end and moves down into it.


8.3 Erasing Text

DEL
BACKSPACE

Delete the character before point, or the region if it is active (delete-backward-char).

Delete

Delete the character after point, or the region if it is active (delete-forward-char).

C-d

Delete the character after point (delete-char).

C-k

Kill to the end of the line (kill-line).

M-d

Kill forward to the end of the next word (kill-word).

M-DEL
M-BACKSPACE

Kill back to the beginning of the previous word (backward-kill-word).

The DEL (delete-backward-char) command removes the character before point, moving the cursor and the characters after it backwards. If point was at the beginning of a line, this deletes the preceding newline, joining this line to the previous one.

If, however, the region is active, DEL instead deletes the text in the region. See The Mark and the Region, for a description of the region.

On most keyboards, DEL is labeled BACKSPACE, but we refer to it as DEL in this manual. (Do not confuse DEL with the Delete key; we will discuss Delete momentarily.) On some text terminals, Emacs may not recognize the DEL key properly. See If DEL Fails to Delete, if you encounter this problem.

The Delete (delete-forward-char) command deletes in the opposite direction: it deletes the character after point, i.e., the character under the cursor. If point was at the end of a line, this joins the following line onto this one. Like DEL, it deletes the text in the region if the region is active (see The Mark and the Region).

C-d (delete-char) deletes the character after point, similar to Delete, but regardless of whether the region is active.

See Deletion, for more detailed information about the above deletion commands.

C-k (kill-line) erases (kills) a line at a time. If you type C-k at the beginning or middle of a line, it kills all the text up to the end of the line. If you type C-k at the end of a line, it joins that line with the following line.

See Killing and Moving Text, for more information about C-k and related commands.


8.4 Undoing Changes

C-/
C-x u
C-_

Undo one entry of the undo records—usually, one command worth (undo). (The first key might be unavailable on text-mode displays.)

Emacs records a list of changes made in the buffer text, so you can undo recent changes. This is done using the undo command, which is bound to C-/ (as well as C-x u and C-_). Normally, this command undoes the last change, moving point back to where it was before the change. The undo command applies only to changes in the buffer; you can’t use it to undo cursor motion.

On a terminal that supports the Control modifier on all other keys, the easiest way to invoke undo is with C-/, since that doesn’t need the Shift modifier. On terminals which allow only the ASCII control characters, C-/ does not exist, but for many of them C-/ still works because it actually sends C-_ to Emacs, while many others allow you to omit the Shift modifier when you type C-_ (in effect pressing C--), making that the most convenient way to invoke undo.

Although each editing command usually makes a separate entry in the undo records, very simple commands may be grouped together. Sometimes, an entry may cover just part of a complex command.

If you repeat C-/ (or its aliases), each repetition undoes another, earlier change, back to the limit of the undo information available. If all recorded changes have already been undone, the undo command displays an error message and does nothing.

To learn more about the undo command, see Undo.


8.5 Files

Text that you insert in an Emacs buffer lasts only as long as the Emacs session. To keep any text permanently, you must put it in a file.

Suppose there is a file named test.emacs in your home directory. To begin editing this file in Emacs, type

C-x C-f test.emacs RET

Here the file name is given as an argument to the command C-x C-f (find-file). That command uses the minibuffer to read the argument, and you type RET to terminate the argument (see The Minibuffer).

Emacs obeys this command by visiting the file: it creates a buffer, copies the contents of the file into the buffer, and then displays the buffer for editing. If you alter the text, you can save the new text in the file by typing C-x C-s (save-buffer). This copies the altered buffer contents back into the file test.emacs, making them permanent. Until you save, the changed text exists only inside Emacs, and the file test.emacs is unaltered.

To create a file, just visit it with C-x C-f as if it already existed. This creates an empty buffer, in which you can insert the text you want to put in the file. Emacs actually creates the file the first time you save this buffer with C-x C-s.

To learn more about using files in Emacs, see File Handling.


8.6 Help

If you forget what a key does, you can find out by typing C-h k (describe-key), followed by the key of interest; for example, C-h k C-n tells you what C-n does.

The prefix key C-h stands for “help”. The key F1 serves as an alias for C-h. Apart from C-h k, there are many other help commands providing different kinds of help.

See Help, for details.


8.7 Blank Lines

Here are special commands and techniques for inserting and deleting blank lines.

C-o

Insert a blank line after the cursor (open-line).

C-x C-o

Delete all but one of many consecutive blank lines (delete-blank-lines).

We have seen how RET (newline) starts a new line of text. However, it may be easier to see what you are doing if you first make a blank line and then insert the desired text into it. This is easy to do using the key C-o (open-line), which inserts a newline after point but leaves point in front of the newline. After C-o, type the text for the new line.

You can make several blank lines by typing C-o several times, or by giving it a numeric argument specifying how many blank lines to make. See Numeric Arguments, for how. If you have a fill prefix, the C-o command inserts the fill prefix on the new line, if typed at the beginning of a line. See The Fill Prefix.

The easy way to get rid of extra blank lines is with the command C-x C-o (delete-blank-lines). If point lies within a run of several blank lines, C-x C-o deletes all but one of them. If point is on a single blank line, C-x C-o deletes it. If point is on a nonblank line, C-x C-o deletes all following blank lines, if any exists.


8.8 Continuation Lines

Sometimes, a line of text in the buffer—a logical line—is too long to fit in the window, and Emacs displays it as two or more screen lines, or visual lines. This is called line wrapping or continuation, and the long logical line is called a continued line. On a graphical display, Emacs indicates line wrapping with small bent arrows in the left and right window fringes. On a text terminal, Emacs indicates line wrapping by displaying a ‘\’ character at the right margin.

Most commands that act on lines act on logical lines, not screen lines. For instance, C-k kills a logical line. As described earlier, C-n (next-line) and C-p (previous-line) are special exceptions: they move point down and up, respectively, by one screen line (see Changing the Location of Point).

Emacs can optionally truncate long logical lines instead of continuing them. This means that every logical line occupies a single screen line; if it is longer than the width of the window, the rest of the line is not displayed. On a graphical display, a truncated line is indicated by a small straight arrow in the right fringe; on a text terminal, it is indicated by a ‘$’ character in the right margin. See Line Truncation.

By default, continued lines are wrapped at the right window edge. Since the wrapping may occur in the middle of a word, continued lines can be difficult to read. The usual solution is to break your lines before they get too long, by inserting newlines. If you prefer, you can make Emacs insert a newline automatically when a line gets too long, by using Auto Fill mode. See Filling Text.

Sometimes, you may need to edit files containing many long logical lines, and it may not be practical to break them all up by adding newlines. In that case, you can use Visual Line mode, which enables word wrapping: instead of wrapping long lines exactly at the right window edge, Emacs wraps them at the word boundaries (i.e., space or tab characters) nearest to the right window edge. Visual Line mode also redefines editing commands such as C-a, C-n, and C-k to operate on screen lines rather than logical lines. See Visual Line Mode.


8.9 Cursor Position Information

Here are commands to get information about the size and position of parts of the buffer, and to count words and lines.

M-x what-line

Display the line number of point.

M-x line-number-mode
M-x column-number-mode

Toggle automatic display of the current line number or column number. See Optional Mode Line Features. If you want to have a line number displayed before each line, see Customization of Display.

M-=

Display the number of lines, sentences, words, and characters that are present in the region (count-words-region). See The Mark and the Region, for information about the region.

M-x count-words

Display the number of lines, sentences, words, and characters that are present in the buffer. If the region is active (see The Mark and the Region), display the numbers for the region instead.

C-x =

Display the character code of character after point, character position of point, and column of point (what-cursor-position).

M-x hl-line-mode

Enable or disable highlighting of the current line. See Displaying the Cursor.

M-x size-indication-mode

Toggle automatic display of the size of the buffer. See Optional Mode Line Features.

M-x what-line displays the current line number in the echo area. This command is usually redundant because the current line number is shown in the mode line (see The Mode Line). However, if you narrow the buffer, the mode line shows the line number relative to the accessible portion (see Narrowing). By contrast, what-line displays both the line number relative to the narrowed region and the line number relative to the whole buffer.

M-= (count-words-region) displays a message reporting the number of lines, sentences, words, and characters in the region (see The Mark and the Region, for an explanation of the region). With a prefix argument, C-u M-=, the command displays a count for the entire buffer.

The command M-x count-words does the same job, but with a different calling convention. It displays a count for the region if the region is active, and for the buffer otherwise.

The command C-x = (what-cursor-position) shows information about the current cursor position and the buffer contents at that position. It displays a line in the echo area that looks like this:

Char: c (99, #o143, #x63) point=28062 of 36168 (78%) column=53

After ‘Char:’, this shows the character in the buffer at point. The text inside the parenthesis shows the corresponding decimal, octal and hex character codes; for more information about how C-x = displays character information, see Introduction to International Character Sets. After ‘point=’ is the position of point as a character count (the first character in the buffer is position 1, the second character is position 2, and so on). The number after that is the total number of characters in the buffer, and the number in parenthesis expresses the position as a percentage of the total. After ‘column=’ is the horizontal position of point, in columns counting from the left edge of the window.

If the user option what-cursor-show-names is non-nil, the name of the character, as defined by the Unicode Character Database, is shown as well. The part in parentheses would then become:

(99, #o143, #x63, LATIN SMALL LETTER C)

If the buffer has been narrowed, making some of the text at the beginning and the end temporarily inaccessible, C-x = displays additional text describing the currently accessible range. For example, it might display this:

Char: C (67, #o103, #x43) point=252 of 889 (28%) <231-599> column=0

where the two extra numbers give the smallest and largest character position that point is allowed to assume. The characters between those two positions are the accessible ones. See Narrowing.

Related, but different feature is display-line-numbers-mode (see Customization of Display).


8.10 Numeric Arguments

In the terminology of mathematics and computing, argument means “data provided to a function or operation”. You can give any Emacs command a numeric argument (also called a prefix argument). Some commands interpret the argument as a repetition count. For example, giving C-f an argument of ten causes it to move point forward by ten characters instead of one. With these commands, no argument is equivalent to an argument of one, and negative arguments cause them to move or act in the opposite direction.

The easiest way to specify a numeric argument is to type a digit and/or a minus sign while holding down the Meta key. For example,

M-5 C-n

moves down five lines. The keys M-1, M-2, and so on, as well as M--, are bound to commands (digit-argument and negative-argument) that set up an argument for the next command. M-- without digits normally means −1.

If you enter more than one digit, you need not hold down the Meta key for the second and subsequent digits. Thus, to move down fifty lines, type

M-5 0 C-n

Note that this does not insert five copies of ‘0’ and move down one line, as you might expect—the ‘0’ is treated as part of the prefix argument.

(What if you do want to insert five copies of ‘0’? Type M-5 C-u 0. Here, C-u terminates the prefix argument, so that the next keystroke begins the command that you want to execute. Note that this meaning of C-u applies only to this case. For the usual role of C-u, see below.)

Instead of typing M-1, M-2, and so on, another way to specify a numeric argument is to type C-u (universal-argument) followed by some digits, or (for a negative argument) a minus sign followed by digits. A minus sign without digits normally means −1.

C-u alone has the special meaning of “four times”: it multiplies the argument for the next command by four. C-u C-u multiplies it by sixteen. Thus, C-u C-u C-f moves forward sixteen characters. Other useful combinations are C-u C-n, C-u C-u C-n (move down a good fraction of a screen), C-u C-u C-o (make sixteen blank lines), and C-u C-k (kill four lines).

You can use a numeric argument before a self-inserting character to insert multiple copies of it. This is straightforward when the character is not a digit; for example, C-u 6 4 a inserts 64 copies of the character ‘a’. But this does not work for inserting digits; C-u 6 4 1 specifies an argument of 641. You can separate the argument from the digit to insert with another C-u; for example, C-u 6 4 C-u 1 does insert 64 copies of the character ‘1’.

Some commands care whether there is an argument, but ignore its value. For example, the command M-q (fill-paragraph) fills text; with an argument, it justifies the text as well. (See Filling Text, for more information on M-q.) For these commands, it is enough to specify the argument with a single C-u.

Some commands use the value of the argument as a repeat count but do something special when there is no argument. For example, the command C-k (kill-line) with argument n kills n lines, including their terminating newlines. But C-k with no argument is special: it kills the text up to the next newline, or, if point is right at the end of the line, it kills the newline itself. Thus, two C-k commands with no arguments can kill a nonblank line, just like C-k with an argument of one. (See Killing and Moving Text, for more information on C-k.)

A few commands treat a plain C-u differently from an ordinary argument. A few others may treat an argument of just a minus sign differently from an argument of −1. These unusual cases are described when they come up; they exist to make an individual command more convenient, and they are documented in that command’s documentation string.

We use the term prefix argument to emphasize that you type such arguments before the command, and to distinguish them from minibuffer arguments (see The Minibuffer), which are entered after invoking the command.

On graphical displays, C-0, C-1, etc. act the same as M-0, M-1, etc.


8.11 Repeating a Command

Many simple commands, such as those invoked with a single key or with M-x command-name RET, can be repeated by invoking them with a numeric argument that serves as a repeat count (see Numeric Arguments). However, if the command you want to repeat prompts for input, or uses a numeric argument in another way, that method won’t work.

The command C-x z (repeat) provides another way to repeat an Emacs command many times. This command repeats the previous Emacs command, whatever that was. Repeating a command uses the same arguments that were used before; it does not read new arguments each time.

To repeat the command more than once, type additional z’s: each z repeats the command one more time. Repetition ends when you type a character other than z or press a mouse button.

For example, suppose you type C-u 2 0 C-d to delete 20 characters. You can repeat that command (including its argument) three additional times, to delete a total of 80 characters, by typing C-x z z z. The first C-x z repeats the command once, and each subsequent z repeats it once again.

You can also activate repeat-mode which allows repeating commands bound to sequences of two or more keys by typing a single character. For example, after typing C-x u (undo, see Undo) to undo the most recent edits, you can undo many more edits by typing u u u…. Similarly, type C-x o o o… instead of C-x o C-x o C-x o… to switch to the window several windows away. This works by entering a transient repeating mode after you type the full key sequence that invokes the command; the single-key shortcuts are shown in the echo area.

Only some commands support repetition in repeat-mode; type M-x describe-repeat-maps RET to see which ones.

The single-character shortcuts enabled by the transient repeating mode do not need to be identical: for example, after typing C-x {, either { or } or ^ or v, or any series that mixes these characters in any order, will resize the selected window in respective ways. Similarly, after M-g n or M-g p, typing any sequence of n and/or p in any mix will repeat next-error and previous-error to navigate in a *compilation* or *grep* buffer (see Compilation Mode).

Typing any key other than those defined to repeat the previous command exits the transient repeating mode, and then the key you typed is executed normally. You can also define a key which will exit the transient repeating mode without executing the key which caused the exit. To this end, customize the user option repeat-exit-key to name a key; one natural value is RET. Finally, it’s possible to break the repetition chain automatically after some amount of idle time: customize the user option repeat-exit-timeout to specify the idle time in seconds after which this transient repetition mode will be turned off automatically.


9 The Minibuffer

The minibuffer is where Emacs commands read complicated arguments, such as file names, buffer names, Emacs command names, or Lisp expressions. We call it the “minibuffer” because it’s a special-purpose buffer with a small amount of screen space. You can use the usual Emacs editing commands in the minibuffer to edit the argument text.


9.1 Using the Minibuffer

When the minibuffer is in use, it appears in the echo area, with a cursor. The minibuffer starts with a prompt, usually ending with a colon. The prompt states what kind of input is expected, and how it will be used. The prompt is highlighted using the minibuffer-prompt face (see Text Faces).

The simplest way to enter a minibuffer argument is to type the text, then RET to submit the argument and exit the minibuffer. Alternatively, you can type C-g to exit the minibuffer by canceling the command asking for the argument (see Quitting and Aborting).

Sometimes, the prompt shows a default argument, inside parentheses before the colon. This default will be used as the argument if you just type RET. For example, commands that read buffer names usually show a buffer name as the default; you can type RET to operate on that default buffer. You can customize how the default argument is shown with the user option minibuffer-default-prompt-format.

If you enable Minibuffer Electric Default mode, a global minor mode, Emacs hides the default argument as soon as you modify the contents of the minibuffer (since typing RET would no longer submit that default). If you ever bring back the original minibuffer text, the prompt again shows the default. To enable this minor mode, type M-x minibuffer-electric-default-mode.

Since the minibuffer appears in the echo area, it can conflict with other uses of the echo area. If an error message or an informative message is emitted while the minibuffer is active, the message is displayed in brackets after the minibuffer text for a few seconds, or until you type something; then the message disappears. While the minibuffer is in use, Emacs does not echo keystrokes.

While using the minibuffer, you can switch to a different frame, perhaps to note text you need to enter (see Frame Commands). By default, the active minibuffer moves to this new frame. If you set the user option minibuffer-follows-selected-frame to nil, then the minibuffer stays in the frame where you opened it, and you must switch back to that frame in order to complete (or abort) the current command. If you set that option to a value which is neither nil nor t, the minibuffer moves frame only after a recursive minibuffer has been opened in the current command (see (elisp)Recursive Mini). This option is mainly to retain (approximately) the behavior prior to Emacs 28.1. Note that the effect of the command, when you finally finish using the minibuffer, always takes place in the frame where you first opened it. The sole exception is that when that frame no longer exists, the action takes place in the currently selected frame.


9.2 Minibuffers for File Names

Commands such as C-x C-f (find-file) use the minibuffer to read a file name argument (see Files). When the minibuffer is used to read a file name, it typically starts out with some initial text ending in a slash. This is the default directory. For example, it may start out like this:

Find file: /u2/emacs/src/

Here, ‘Find file: ’ is the prompt and ‘/u2/emacs/src/’ is the default directory. If you now type buffer.c as input, that specifies the file /u2/emacs/src/buffer.c. See File Names, for information about the default directory.

Alternative defaults for the file name you may want are available by typing M-n, see Minibuffer History.

You can specify a file in the parent directory with ..: /a/b/../foo.el is equivalent to /a/foo.el. Alternatively, you can use M-DEL to kill directory names backwards (see Words).

To specify a file in a completely different directory, you can kill the entire default with C-a C-k (see Editing in the Minibuffer). Alternatively, you can ignore the default, and enter an absolute file name starting with a slash or a tilde after the default directory. For example, you can specify /etc/termcap as follows:

Find file: /u2/emacs/src//etc/termcap

A double slash causes Emacs to ignore everything before the second slash in the pair. In the example above, /u2/emacs/src/ is ignored, so the argument you supplied is /etc/termcap. The ignored part of the file name is dimmed if the terminal allows it. (To disable this dimming, turn off File Name Shadow mode with the command M-x file-name-shadow-mode.)

When completing remote file names (see Remote Files), a double slash behaves slightly differently: it causes Emacs to ignore only the file-name part, leaving the rest (method, host and username, etc.) intact. Typing three slashes in a row ignores everything in remote file names. See File name completion in The Tramp Manual.

Emacs interprets ~/ as your home directory. Thus, ~/foo/bar.txt specifies a file named bar.txt, inside a directory named foo, which is in turn located in your home directory. In addition, ~user-id/ means the home directory of a user whose login name is user-id. Any leading directory name in front of the ~ is ignored: thus, /u2/emacs/~/foo/bar.txt is equivalent to ~/foo/bar.txt.

On MS-Windows and MS-DOS systems, where a user doesn’t always have a home directory, Emacs uses several alternatives. For MS-Windows, see HOME and Startup Directories on MS-Windows; for MS-DOS, see File Names on MS-DOS. On these systems, the ~user-id/ construct is supported only for the current user, i.e., only if user-id is the current user’s login name.

To prevent Emacs from inserting the default directory when reading file names, change the variable insert-default-directory to nil. In that case, the minibuffer starts out empty. Nonetheless, relative file name arguments are still interpreted based on the same default directory.

You can also enter remote file names in the minibuffer. See Remote Files.


9.3 Editing in the Minibuffer

The minibuffer is an Emacs buffer, albeit a peculiar one, and the usual Emacs commands are available for editing the argument text. (The prompt, however, is read-only, and cannot be changed.)

Since RET in the minibuffer submits the argument, you can’t use it to insert a newline. You can do that with C-q C-j, which inserts a C-j control character, which is formally equivalent to a newline character (see Inserting Text). Alternatively, you can use the C-o (open-line) command (see Blank Lines).

Inside a minibuffer, the keys TAB, SPC, and ? are often bound to completion commands, which allow you to easily fill in the desired text without typing all of it. See Completion. As with RET, you can use C-q to insert a TAB, SPC, or ‘?’ character. If you want to make SPC and ? insert normally instead of starting completion, you can put the following in your init file:

(keymap-unset minibuffer-local-completion-map "SPC")
(keymap-unset minibuffer-local-completion-map "?")

For convenience, C-a (move-beginning-of-line) in a minibuffer moves point to the beginning of the argument text, not the beginning of the prompt. For example, this allows you to erase the entire argument with C-a C-k.

When the minibuffer is active, the echo area is treated much like an ordinary Emacs window. For instance, you can switch to another window (with C-x o), edit text there, then return to the minibuffer window to finish the argument. You can even kill text in another window, return to the minibuffer window, and yank the text into the argument. There are some restrictions on the minibuffer window, however: for instance, you cannot split it. See Multiple Windows.

Normally, the minibuffer window occupies a single screen line. However, if you add two or more lines’ worth of text into the minibuffer, it expands automatically to accommodate the text. The variable resize-mini-windows controls the resizing of the minibuffer. The default value is grow-only, which means the behavior we have just described. If the value is t, the minibuffer window will also shrink automatically if you remove some lines of text from the minibuffer, down to a minimum of one screen line. If the value is nil, the minibuffer window never changes size automatically, but you can use the usual window-resizing commands on it (see Multiple Windows).

The variable max-mini-window-height controls the maximum height for resizing the minibuffer window. A floating-point number specifies a fraction of the frame’s height; an integer specifies the maximum number of lines; nil means do not resize the minibuffer window automatically. The default value is 0.25.

The C-M-v command in the minibuffer scrolls the help text from commands that display help text of any sort in another window. You can also scroll the help text with M-PageUp and M-PageDown (or, equivalently, M-prior and M-next). This is especially useful with long lists of possible completions. See Using Other Windows.

Emacs normally disallows most commands that use the minibuffer while the minibuffer is active. To allow such commands in the minibuffer, set the variable enable-recursive-minibuffers to t. You might need also to enable minibuffer-depth-indicate-mode to show the current recursion depth in the minibuffer prompt on recursive use of the minibuffer.

When active, the minibuffer is usually in minibuffer-mode. This is an internal Emacs mode without any special features.

When not active, the minibuffer is in minibuffer-inactive-mode, and clicking mouse-1 there shows the *Messages* buffer. If you use a dedicated frame for minibuffers, Emacs also recognizes certain keys there, for example, n to make a new frame.


9.4 Completion

You can often use a feature called completion to help enter arguments. This means that after you type part of the argument, Emacs can fill in the rest, or some of it, based on what was typed so far.

When completion is available, certain keys (usually TAB, RET, and SPC) are rebound in the minibuffer to special completion commands (see Completion Commands). These commands attempt to complete the text in the minibuffer, based on a set of completion alternatives provided by the command that requested the argument. You can usually type ? to see a list of completion alternatives.

Although completion is usually done in the minibuffer, the feature is sometimes available in ordinary buffers too. See Completion for Symbol Names.


9.4.1 Completion Example

A simple example may help here. M-x uses the minibuffer to read the name of a command, so completion works by matching the minibuffer text against the names of existing Emacs commands. Suppose you wish to run the command auto-fill-mode. You can do that by typing M-x auto-fill-mode RET, but it is easier to use completion.

If you type M-x a u TAB, the TAB looks for completion alternatives (in this case, command names) that start with ‘au’. There are several, including auto-fill-mode and autoconf-mode, but they all begin with auto, so the ‘au’ in the minibuffer completes to ‘auto’. (More commands may be defined in your Emacs session. For example, if a command called authorize-me was defined, Emacs could only complete as far as ‘aut’.)

If you type TAB again immediately, it cannot determine the next character; it could be ‘-’, ‘a’, or ‘c’. So it does not add any characters; instead, TAB displays a list of all possible completions in another window.

Next, type -f. The minibuffer now contains ‘auto-f’, and the only command name that starts with this is auto-fill-mode. If you now type TAB, completion fills in the rest of the argument ‘auto-fill-mode’ into the minibuffer.

Hence, typing just a u TAB - f TAB allows you to enter ‘auto-fill-mode’.

TAB also works while point is not at the end of the minibuffer. In that case, it will fill in text both at point and at the end of the minibuffer. If you type M-x autocm, then press C-b to move point before the ‘m’, you can type TAB to insert the text ‘onf-’ at point and ‘ode’ at the end of the minibuffer, so that the minibuffer contains ‘autoconf-mode’.


9.4.2 Completion Commands

Here is a list of the completion commands defined in the minibuffer when completion is allowed.

TAB

Complete the text in the minibuffer as much as possible; if unable to complete, display a list of possible completions (minibuffer-complete).

SPC

Complete up to one word from the minibuffer text before point (minibuffer-complete-word). This command is not available for arguments that often include spaces, such as file names.

RET

Submit the text in the minibuffer as the argument, possibly completing first (minibuffer-complete-and-exit). See Completion Exit.

?

Display a list of completions (minibuffer-completion-help).

TAB (minibuffer-complete) is the most fundamental completion command. It searches for all possible completions that match the existing minibuffer text, and attempts to complete as much as it can. See How Completion Alternatives Are Chosen, for how completion alternatives are chosen.

SPC (minibuffer-complete-word) completes like TAB, but only up to the next hyphen or space. If you have ‘auto-f’ in the minibuffer and type SPC, it finds that the completion is ‘auto-fill-mode’, but it only inserts ‘ill-’, giving ‘auto-fill-’. Another SPC at this point completes all the way to ‘auto-fill-mode’.

If TAB or SPC is unable to complete, it displays a list of matching completion alternatives (if there are any) in another window. You can display the same list with ? (minibuffer-completion-help). The following commands can be used with the completion list:

M-DOWN
M-UP

While in the minibuffer, M-DOWN (minibuffer-next-completion and M-UP (minibuffer-previous-completion) navigate through the completions and displayed in the completions buffer. When minibuffer-completion-auto-choose is non-nil (which is the default), using these commands also inserts the current completion candidate into the minibuffer. If minibuffer-completion-auto-choose is nil, you can use the M-RET command (minibuffer-choose-completion) to insert the completion candidates into the minibuffer. By default, that exits the minibuffer, but with a prefix argument, C-u M-RET inserts the currently active candidate without exiting the minibuffer.

M-v
PageUp
prior

Typing M-v, while in the minibuffer, selects the window showing the completion list (switch-to-completions). This paves the way for using the commands below. PageUp, prior and M-g M-c do the same. You can also select the window in other ways (see Multiple Windows).

RET
mouse-1
mouse-2

While in the completion list buffer, this chooses the completion at point (choose-completion). With a prefix argument, C-u RET inserts the completion at point into the minibuffer, but doesn’t exit the minibuffer—thus, you can change your mind and choose another candidate.

TAB
RIGHT
n

While in the completion list buffer, these keys move point to the following completion alternative (next-completion).

S-TAB
LEFT
p

While in the completion list buffer, these keys move point to the previous completion alternative (previous-completion).

q

While in the completion list buffer, this quits the window showing it and selects the window showing the minibuffer (quit-window).

z

While in the completion list buffer, kill it and delete the window showing it (kill-current-buffer).


9.4.3 Completion Exit

When a command reads an argument using the minibuffer with completion, it also controls what happens when you type RET (minibuffer-complete-and-exit) to submit the argument. There are four types of behavior:

  • Strict completion accepts only exact completion matches. Typing RET exits the minibuffer only if the minibuffer text is an exact match, or completes to one. Otherwise, Emacs refuses to exit the minibuffer; instead it tries to complete, and if no completion can be done it momentarily displays ‘[No match]’ after the minibuffer text. (You can still leave the minibuffer by typing C-g to cancel the command.)

    An example of a command that uses this behavior is M-x, since it is meaningless for it to accept a non-existent command name.

  • Cautious completion is like strict completion, except RET exits only if the text is already an exact match. If the text completes to an exact match, RET performs that completion but does not exit yet; you must type a second RET to exit.

    Cautious completion is used for reading file names for files that must already exist, for example.

  • Permissive completion allows any input; the completion candidates are just suggestions. Typing RET does not complete, it just submits the argument as you have entered it.
  • Permissive completion with confirmation is like permissive completion, with an exception: if you typed TAB and this completed the text up to some intermediate state (i.e., one that is not yet an exact completion match), typing RET right afterward does not submit the argument. Instead, Emacs asks for confirmation by momentarily displaying ‘[Confirm]’ after the text; type RET again to confirm and submit the text. This catches a common mistake, in which one types RET before realizing that TAB did not complete as far as desired.

    You can tweak the confirmation behavior by customizing the variable confirm-nonexistent-file-or-buffer. The default value, after-completion, gives the behavior we have just described. If you change it to nil, Emacs does not ask for confirmation, falling back on permissive completion. If you change it to any other non-nil value, Emacs asks for confirmation whether or not the preceding command was TAB.

    This behavior is used by most commands that read file names, like C-x C-f, and commands that read buffer names, like C-x b.


9.4.4 How Completion Alternatives Are Chosen

Completion commands work by narrowing a large list of possible completion alternatives to a smaller subset that matches what you have typed in the minibuffer. In Completion Example, we gave a simple example of such matching. The procedure of determining what constitutes a match is quite intricate. Emacs attempts to offer plausible completions under most circumstances.

Emacs performs completion using one or more completion styles—sets of criteria for matching minibuffer text to completion alternatives. During completion, Emacs tries each completion style in turn. If a style yields one or more matches, that is used as the list of completion alternatives. If a style produces no matches, Emacs falls back on the next style.

The list variable completion-styles specifies the completion styles to use. Each list element is the name of a completion style (a Lisp symbol). The available style symbols are stored in the variable completion-styles-alist (see Completion Variables in The Emacs Lisp Reference Manual). The default completion styles are (in order):

basic

A matching completion alternative must have the same beginning as the text in the minibuffer before point. Furthermore, if there is any text in the minibuffer after point, the rest of the completion alternative must contain that text as a substring.

partial-completion

This aggressive completion style divides the minibuffer text into words separated by hyphens or spaces, and completes each word separately. (For example, when completing command names, ‘em-l-m’ completes to ‘emacs-lisp-mode’.)

Furthermore, a ‘*’ in the minibuffer text is treated as a wildcard—it matches any string of characters at the corresponding position in the completion alternative.

emacs22

This completion style is similar to basic, except that it ignores the text in the minibuffer after point. It is so-named because it corresponds to the completion behavior in Emacs 22.

The following additional completion styles are also defined, and you can add them to completion-styles if you wish (see Customization):

substring

A matching completion alternative must contain the text in the minibuffer before point, and the text in the minibuffer after point, as substrings (in that same order).

Thus, if the text in the minibuffer is ‘foobar’, with point between ‘foo’ and ‘bar’, that matches ‘afoobbarc’, where a, b, and c can be any string including the empty string.

flex

This aggressive completion style, also known as flx or fuzzy or scatter completion, attempts to complete using in-order substrings. For example, it can consider ‘foo’ to match ‘frodo’ or ‘fbarbazoo’.

initials

This very aggressive completion style attempts to complete acronyms and initialisms. For example, when completing command names, it matches ‘lch’ to ‘list-command-history’.

There is also a very simple completion style called emacs21. In this style, if the text in the minibuffer is ‘foobar’, only matches starting with ‘foobar’ are considered.

You can use different completion styles in different situations, by setting the variable completion-category-overrides. For example, the default setting says to use only basic and substring completion for buffer names.


9.4.5 Completion Options

Case is significant when completing case-sensitive arguments, such as command names. For example, when completing command names, ‘AU’ does not complete to ‘auto-fill-mode’. Case differences are ignored when completing arguments in which case does not matter.

When completing file names, case differences are ignored if the variable read-file-name-completion-ignore-case is non-nil. The default value is nil on systems that have case-sensitive file-names, such as GNU/Linux; it is non-nil on systems that have case-insensitive file-names, such as Microsoft Windows. When completing buffer names, case differences are ignored if the variable read-buffer-completion-ignore-case is non-nil; the default is nil.

When completing file names, Emacs usually omits certain alternatives that are considered unlikely to be chosen, as determined by the list variable completion-ignored-extensions. Each element in the list should be a string; any file name ending in such a string is ignored as a completion alternative. Any element ending in a slash (/) represents a subdirectory name. The standard value of completion-ignored-extensions has several elements including ".o", ".elc", and "~". For example, if a directory contains ‘foo.c’ and ‘foo.elc’, ‘foo’ completes to ‘foo.c’. However, if all possible completions end in otherwise-ignored strings, they are not ignored: in the previous example, ‘foo.e’ completes to ‘foo.elc’. Emacs disregards completion-ignored-extensions when showing completion alternatives in the completion list.

Shell completion is an extended version of filename completion, see Shell Mode Options.

If completion-auto-help is set to nil, the completion commands never display the completion list buffer; you must type ? to display the list. If the value is lazy, Emacs only shows the completion list buffer on the second attempt to complete. In other words, if there is nothing to complete, the first TAB echoes ‘Next char not unique’; the second TAB shows the completion list buffer. If the value is always, the completion list buffer is always shown when completion is attempted.

The display of the completion list buffer after it is shown for the first time is also controlled by completion-auto-help. If the value is t or lazy, the window showing the completions pops down when Emacs is able to complete (and may pop up again if Emacs is again unable to complete after you type some more text); if the value is always, the window pops down only when you exit the completion. The value visible is a hybrid: it behaves like t when it decides whether to pop up the window showing the completion list buffer, and like always when it decides whether to pop it down.

Emacs can optionally select the window showing the completions when it shows that window. To enable this behavior, customize the user option completion-auto-select to t, which changes the behavior of TAB when Emacs pops up the completions: pressing TAB will switch to the completion list buffer, and you can then move to a candidate by cursor motion commands and select it with RET. If the value of completion-auto-select is second-tab, then the first TAB will pop up the completions list buffer, and the second one will switch to it.

If completion-cycle-threshold is non-nil, completion commands can cycle through completion alternatives. Normally, if there is more than one completion alternative for the text in the minibuffer, a completion command completes up to the longest common substring. If you change completion-cycle-threshold to t, the completion command instead completes to the first of those completion alternatives; each subsequent invocation of the completion command replaces that with the next completion alternative, in a cyclic manner. If you give completion-cycle-threshold a numeric value n, completion commands switch to this cycling behavior only when there are n or fewer alternatives.

When displaying completions, Emacs will normally pop up a new buffer to display the completions. The completions will by default be sorted horizontally, using as many columns as will fit in the window-width, but this can be changed by customizing the completions-format user option. If its value is vertical, Emacs will sort the completions vertically instead, and if it’s one-column, Emacs will use just one column.

The completions-sort user option controls the order in which the completions are sorted in the ‘*Completions*’ buffer. The default is alphabetical, which sorts in alphabetical order. The value nil disables sorting. The value can also be a function, which will be called with the list of completions, and should return the list in the desired order.

When completions-max-height is non-nil, it limits the size of the completions window. It is specified in lines and include mode, header line and a bottom divider, if any. For a more complex control of the Completion window display properties, you can use display-buffer-alist (see Action Alists for Buffer Display in The Emacs Lisp Reference Manual).

The variable completions-header-format is a format spec string to control the informative line shown before the completions list of candidates. If it contains a ‘%s’ construct, that get replaced by the number of completions shown in the completion list buffer. To suppress the display of the heading line, customize this variable to nil. The string that is the value of this variable can have text properties to change the visual appearance of the heading line; some useful properties face or cursor-intangible (see Properties with Special Meanings in The Emacs Lisp Reference Manual).

When completions-highlight-face names a face, the current completion candidate, the one that will be selected by typing RET or clicking the mouse, will be highlighted using that face. The default value of this variable is completions-highlight; the value is nil disables this highlighting. This feature uses the special text property cursor-face.


9.5 Minibuffer History

Everything you type in the minibuffer is saved in a minibuffer history list so you can easily use it again later. This includes completion candidates (such as file names, buffer names, command names, etc.) and any other kind of minibuffer input. You can use the following commands to quickly fetch an earlier or alternative response into the minibuffer:

M-p

Move to the previous item in the minibuffer history, an earlier argument (previous-history-element).

M-n

Move to the next item in the minibuffer history (next-history-element).

UP
DOWN

Like M-p and M-n, but move to the previous or next line of a multi-line item before going to the previous history item (previous-line-or-history-element and next-line-or-history-element) .

M-r regexp RET

Move to an earlier item in the minibuffer history that matches regexp (previous-matching-history-element).

M-s regexp RET

Move to a later item in the minibuffer history that matches regexp (next-matching-history-element).

While in the minibuffer, M-p (previous-history-element) moves through the minibuffer history list, one item at a time. Each M-p fetches an earlier item from the history list into the minibuffer, replacing its existing contents. Typing M-n (next-history-element) moves through the minibuffer history list in the opposite direction, fetching later entries into the minibuffer.

If you type M-n in the minibuffer when there are no later entries in the minibuffer history (e.g., if you haven’t previously typed M-p), Emacs tries fetching from a list of default arguments: values that you are likely to enter. You can think of this as moving through the “future history”.

The “future history” for file names includes several possible alternatives you may find useful, such as the file name or the URL at point in the current buffer. The defaults put into the “future history” in this case are controlled by the functions mentioned in the value of the option file-name-at-point-functions. By default, its value invokes the ffap package (see Finding Files and URLs at Point), which tries to guess the default file or URL from the text around point. To disable this guessing, customize the option to a nil value, then the “future history” of file names will include only the file, if any, visited by the current buffer, and the default directory.

The arrow keys UP and DOWN work like M-p and M-n, but if the current history item is longer than a single line, they allow you to move to the previous or next line of the current history item before going to the previous or next history item.

If you edit the text inserted by the M-p or M-n minibuffer history commands, this does not change its entry in the history list. However, the edited argument does go at the end of the history list when you submit it.

You can use M-r (previous-matching-history-element) to search through older elements in the history list, and M-s (next-matching-history-element) to search through newer entries. Each of these commands asks for a regular expression as an argument, and fetches the first matching entry into the minibuffer. See Syntax of Regular Expressions, for an explanation of regular expressions. A numeric prefix argument n means to fetch the nth matching entry. These commands are unusual, in that they use the minibuffer to read the regular expression argument, even though they are invoked from the minibuffer. An upper-case letter in the regular expression makes the search case-sensitive (see Lax Matching During Searching).

You can also search through the history using an incremental search. See Searching the Minibuffer.

Emacs keeps separate history lists for several different kinds of arguments. For example, there is a list for file names, used by all the commands that read file names. Other history lists include buffer names, command names (used by M-x), and command arguments (used by commands like query-replace).

The variable history-length specifies the maximum length of a minibuffer history list; adding a new element deletes the oldest element if the list gets too long. If the value is t, there is no maximum length.

The variable history-delete-duplicates specifies whether to delete duplicates in history. If it is non-nil, adding a new element deletes from the list all other elements that are equal to it. The default is nil.


9.6 Repeating Minibuffer Commands

Every command that uses the minibuffer once is recorded on a special history list, the command history, together with the values of its arguments, so that you can repeat the entire command. In particular, every use of M-x is recorded there, since M-x uses the minibuffer to read the command name.

C-x ESC ESC

Re-execute a recent minibuffer command from the command history (repeat-complex-command).

M-x list-command-history

Display the entire command history, showing all the commands C-x ESC ESC can repeat, most recent first.

C-x ESC ESC re-executes a recent command that used the minibuffer. With no argument, it repeats the last such command. A numeric argument specifies which command to repeat; 1 means the last one, 2 the previous, and so on.

C-x ESC ESC works by turning the previous command into a Lisp expression and then entering a minibuffer initialized with the text for that expression. Even if you don’t know Lisp, it will probably be obvious which command is displayed for repetition. If you type just RET, that repeats the command unchanged. You can also change the command by editing the Lisp expression before you execute it. The executed command is added to the front of the command history unless it is identical to the most recent item.

Once inside the minibuffer for C-x ESC ESC, you can use the usual minibuffer history commands (see Minibuffer History) to move through the history list. After finding the desired previous command, you can edit its expression as usual and then execute it by typing RET.

Incremental search does not, strictly speaking, use the minibuffer. Therefore, although it behaves like a complex command, it normally does not appear in the history list for C-x ESC ESC. You can make incremental search commands appear in the history by setting isearch-resume-in-command-history to a non-nil value. See Incremental Search.

The list of previous minibuffer-using commands is stored as a Lisp list in the variable command-history. Each element is a Lisp expression that describes one command and its arguments. Lisp programs can re-execute a command by calling eval with the command-history element.


9.7 Entering passwords

Sometimes, you may need to enter a password into Emacs. For instance, when you tell Emacs to visit a file on another machine via a network protocol such as FTP, you often need to supply a password to gain access to the machine (see Remote Files).

Entering a password is similar to using a minibuffer. Emacs displays a prompt in the echo area (such as ‘Password: ’); after you type the required password, press RET to submit it. To prevent others from seeing your password, every character you type is displayed as an asterisk (‘*’) instead of its usual form.

Most of the features and commands associated with the minibuffer cannot be used when entering a password. There is no history or completion, and you cannot change windows or perform any other action with Emacs until you have submitted the password.

While you are typing the password, you may press DEL to delete backwards, removing the last character entered. C-u deletes everything you have typed so far. C-g quits the password prompt (see Quitting and Aborting). C-y inserts the current kill into the password (see Killing and Moving Text). You may type either RET or ESC to submit the password. Any other self-inserting character key inserts the associated character into the password, and all other input is ignored.


9.8 Yes or No Prompts

An Emacs command may require you to answer a yes-or-no question during the course of its execution. Such queries come in two main varieties.

For the first type of yes-or-no query, the prompt ends with ‘(y or n). You answer the query by typing a single key, either ‘y’ or ‘n’, which immediately exits the minibuffer and delivers the response. For example, if you type C-x C-w (write-file) to save a buffer, and enter the name of an existing file, Emacs issues a prompt like this:

File ‘foo.el’ exists; overwrite? (y or n)

The second type of yes-or-no query is typically employed if giving the wrong answer would have serious consequences; it thus features a longer prompt ending with ‘(yes or no)’. For example, if you invoke C-x k (kill-buffer) on a file-visiting buffer with unsaved changes, Emacs activates the minibuffer with a prompt like this:

Buffer foo.el modified; kill anyway? (yes or no)

To answer, you must type ‘yes’ or ‘no’ into the minibuffer, followed by RET.

With both types of yes-or-no query the minibuffer behaves as described in the previous sections; you can recenter the selected window with C-l, scroll that window (C-v or PageDown scrolls forward, M-v or PageUp scrolls backward), switch to another window with C-x o, use the history commands M-p and M-n, etc. Type C-g to dismiss the query, and quit the minibuffer and the querying command (see Quitting and Aborting).


10 Running Commands by Name

Every Emacs command has a name that you can use to run it. For convenience, many commands also have key bindings. You can run those commands by typing the keys, or run them by name. Most Emacs commands have no key bindings, so the only way to run them is by name. (See Customizing Key Bindings, for how to set up key bindings.)

By convention, a command name consists of one or more words, separated by hyphens; for example, auto-fill-mode or manual-entry. Command names mostly use complete English words to make them easier to remember.

To run a command by name, start with M-x, type the command name, then terminate it with RET. M-x uses the minibuffer to read the command name. The string ‘M-x’ appears at the beginning of the minibuffer as a prompt to remind you to enter a command name to be run. RET exits the minibuffer and runs the command. See The Minibuffer, for more information on the minibuffer.

You can use completion to enter the command name. For example, to invoke the command forward-char, you can type

M-x forward-char RET

or

M-x forw TAB c RET

Note that forward-char is the same command that you invoke with the key C-f. The existence of a key binding does not stop you from running the command by name.

When M-x completes on commands, it ignores the commands that were declared obsolete in any previous major version of Emacs; for these, you will have to type their full name. Commands that were marked obsolete in the current version of Emacs are listed. (Obsolete commands are those for which newer, better alternatives exist, and which are slated for removal in some future Emacs release.)

In addition, M-x completion can exclude commands that are not relevant to, and generally cannot work with, the current buffer’s major mode (see Major Modes) and minor modes (see Minor Modes). By default, no commands are excluded, but you can customize the option read-extended-command-predicate to exclude those irrelevant commands from completion results.

Conversely, Emacs can exclude all commands except those that are particularly relevant to the current buffer. The M-S-x (that’s “meta shift x”) command works just like M-x, but instead of listing all (or most) of the commands Emacs knows about, it will only list the commands that have been marked as “belonging” to the current major mode, or any enabled minor modes.

To cancel the M-x and not run a command, type C-g instead of entering the command name. This takes you back to command level.

To pass a numeric argument to the command you are invoking with M-x, specify the numeric argument before M-x. The argument value appears in the prompt while the command name is being read, and finally M-x passes the argument to that command. For example, to pass the numeric argument of 42 to the command forward-char you can type C-u 42 M-x forward-char RET.

When the command you run with M-x has a key binding, Emacs mentions this in the echo area after running the command. For example, if you type M-x forward-word, the message says that you can run the same command by typing M-f. You can turn off these messages by setting the variable suggest-key-bindings to nil. The value of suggest-key-bindings can also be a number, in which case Emacs will show the binding for that many seconds before removing it from display. The default behavior is to display the binding for 2 seconds.

Additionally, when suggest-key-bindings is non-nil, the completion list of M-x shows equivalent key bindings for all commands that have them.

Commands that don’t have key bindings, can still be invoked after typing less than their full name at the ‘M-x’ prompt. Emacs mentions such shorthands in the echo area if they are significantly shorter than the full command name, and extended-command-suggest-shorter is non-nil. The setting of suggest-key-bindings affects these hints as well.

In this manual, when we speak of running a command by name, we often omit the RET that terminates the name. Thus we might say M-x auto-fill-mode rather than M-x auto-fill-mode RET. We mention the RET only for emphasis, such as when the command is followed by arguments.

M-x works by running the command execute-extended-command, which is responsible for reading the name of another command and invoking it.


11 Help

Emacs provides a wide variety of help commands, all accessible through the prefix key C-h (or, equivalently, the function key F1). These help commands are described in the following sections. You can also type C-h C-h to view a list of help commands (help-for-help). You can scroll the list with SPC and DEL, then type the help command you want. To cancel, type C-g.

Many help commands display their information in a special help buffer. In this buffer, you can type SPC and DEL to scroll and type RET to follow hyperlinks. See Help Mode Commands.

By default, help commands display the help buffer in a separate window without selecting that window. The variable help-window-select controls this: its default value is nil; if it’s customized to the value t, the help window is unconditionally selected by help commands, and if its value is other, the help window is selected only if there are more than two windows on the selected frame.

Conversely, many commands in the ‘*Help*’ buffer will pop up a new window to display the results. For instance, clicking on the link to show the source code, or using the i command to display the manual entry, will (by default) pop up a new window. If help-window-keep-selected is changed to non-nil, the window displaying the ‘*Help*’ buffer will be reused instead.

If you are looking for a certain feature, but don’t know what it is called or where to look, we recommend three methods. First, try an apropos command, then try searching the manual index, then look in the FAQ and the package keywords, and finally try listing external packages.

C-h a topics RET

This searches for commands whose names match the argument topics. The argument can be a keyword, a list of keywords, or a regular expression (see Syntax of Regular Expressions). See Apropos.

C-h i d m emacs RET i topic RET

This searches for topic in the indices of the Emacs Info manual, displaying the first match found. Press , to see subsequent matches. You can use a regular expression as topic.

C-h i d m emacs RET s topic RET

Similar, but searches the text of the manual rather than the indices.

C-h C-f

This displays the Emacs FAQ, using Info.

C-h p

This displays the available Emacs packages based on keywords. See Keyword Search for Packages.

M-x list-packages

This displays a list of external packages. See Emacs Lisp Packages.

C-h or F1 mean “help” in various other contexts as well. For instance, you can type them after a prefix key to view a list of the keys that can follow the prefix key. (You can also use ? in this context. A few prefix keys don’t support C-h or ? in this way, because they define other meanings for those inputs, but they all support F1.)


11.1 Help Summary

Here is a summary of help commands for accessing the built-in documentation. Most of these are described in more detail in the following sections.

C-h a topics RET

Display a list of commands whose names match topics (apropos-command). See Apropos.

C-h b

Display all active key bindings; minor mode bindings first, then those of the major mode, then global bindings (describe-bindings). See Other Help Commands.

C-h C-q

Toggle display of a window showing popular commands and their key bindings. See Other Help Commands.

C-h c key

Show the name of the command that the key sequence key is bound to (describe-key-briefly). Here c stands for “character”. For more extensive information on key, use C-h k. See Documentation for a Key.

C-h d topics RET

Display the commands and variables whose documentation matches topics (apropos-documentation). See Apropos.

C-h e

Display the *Messages* buffer (view-echo-area-messages). See Other Help Commands.

C-h f function RET

Display documentation on the Lisp function named function (describe-function). Since commands are Lisp functions, this works for commands too, but you can also use C-h x. See Help by Command or Variable Name.

C-h h

Display the HELLO file, which shows examples of various character sets.

C-h i

Run Info, the GNU documentation browser (info). The Emacs manual is available in Info. See Other Help Commands.

C-h k key

Display the name and documentation of the command that key runs (describe-key). See Documentation for a Key.

C-h l

Display a description of your last 300 keystrokes (view-lossage). See Other Help Commands.

C-h m

Display documentation of the current major mode and minor modes (describe-mode). See Other Help Commands.

C-h n

Display news of recent Emacs changes (view-emacs-news). See Help Files.

C-h o symbol

Display documentation of the Lisp symbol named symbol (describe-symbol). This will show the documentation of all kinds of symbols: functions, variables, and faces. See Help by Command or Variable Name.

C-h p

Find packages by topic keyword (finder-by-keyword). See Keyword Search for Packages. This lists packages using a package menu buffer. See Emacs Lisp Packages.

C-h P package RET

Display documentation about the specified package (describe-package). See Keyword Search for Packages.

C-h r

Display the Emacs manual in Info (info-emacs-manual).

C-h s

Display the contents of the current syntax table (describe-syntax). See Other Help Commands. The syntax table says which characters are opening delimiters, which are parts of words, and so on. See Syntax Tables in The Emacs Lisp Reference Manual, for details.

C-h t

Enter the Emacs interactive tutorial (help-with-tutorial).

C-h v var RET

Display the documentation of the Lisp variable var (describe-variable). See Help by Command or Variable Name.

C-h w command RET

Show which keys run the command named command (where-is). See Documentation for a Key.

C-h x command RET

Display documentation on the named command (describe-command). See Help by Command or Variable Name.

C-h C coding RET

Describe the coding system coding (describe-coding-system). See Coding Systems.

C-h C RET

Describe the coding systems currently in use.

C-h F command RET

Enter Info and go to the node that documents the Emacs command command (Info-goto-emacs-command-node). See Help by Command or Variable Name.

C-h I method RET

Describe the input method method (describe-input-method). See Selecting an Input Method.

C-h K key

Enter Info and go to the node that documents the key sequence key (Info-goto-emacs-key-command-node). See Documentation for a Key.

C-h L language-env RET

Display information on the character sets, coding systems, and input methods used in language environment language-env (describe-language-environment). See Language Environments.

C-h S symbol RET

Display the Info documentation on symbol symbol according to the programming language you are editing (info-lookup-symbol). See Other Help Commands.

C-h .

Display the help message for a special text area, if point is in one (display-local-help). (These include, for example, links in *Help* buffers.) See Help on Active Text and Tooltips. If you invoke this command with a prefix argument, C-u C-h ., and point is on a button or a widget, this command will pop a new buffer that describes that button/widget.


11.2 Documentation for a Key

The help commands to get information about a key sequence are C-h c (describe-key-briefly) and C-h k (describe-key).

C-h c key displays in the echo area the name of the command that key is bound to. For example, C-h c C-f displays ‘forward-char’.

C-h k key is similar but gives more information: it displays a help buffer containing the command’s documentation string, which describes exactly what the command does.

C-h K key displays the section of the Emacs manual that describes the command corresponding to key.

C-h c, C-h k and C-h K work for any sort of key sequences, including function keys, menus, and mouse events (except that C-h c ignores mouse movement events). For instance, after C-h k you can select a menu item from the menu bar, to view the documentation string of the command it runs.

C-h w command RET lists the keys that are bound to command. It displays the list in the echo area. If it says the command is not on any key, that means you must use M-x to run it. C-h w runs the command where-is.

Some modes in Emacs use various buttons (see Buttons in The Emacs Lisp Reference Manual) and widgets (see Introduction in Emacs Widgets) that can be clicked to perform some action. To find out what function is ultimately invoked by these buttons, Emacs provides the button-describe and widget-describe commands, that should be run with point over the button.


11.3 Help by Command or Variable Name

C-h x command RET (describe-command) displays the documentation of the named command, in a window. For example,

C-h x auto-fill-mode RET

displays the documentation of auto-fill-mode. This is how you would get the documentation of a command that is not bound to any key (one which you would normally run using M-x).

C-h f function RET (describe-function) displays the documentation of Lisp function. This command is intended for Lisp functions that you use in a Lisp program. For example, if you have just written the expression (make-vector len) and want to check that you are using make-vector properly, type C-h f make-vector RET. Additionally, since all commands are Lisp functions, you can also use this command to view the documentation of any command.

If you type C-h f RET, it describes the function called by the innermost Lisp expression in the buffer around point, provided that function name is a valid, defined Lisp function. (That name appears as the default while you enter the argument.) For example, if point is located following the text ‘(make-vector (car x)’, the innermost list containing point is the one that starts with ‘(make-vector’, so C-h f RET describes the function make-vector.

C-h f is also useful just to verify that you spelled a function name correctly. If the minibuffer prompt for C-h f shows the function name from the buffer as the default, it means that name is defined as a Lisp function. Type C-g to cancel the C-h f command if you don’t really want to view the documentation.

If you request help for an autoloaded function whose autoload form (see Autoload in The Emacs Lisp Reference Manual) doesn’t provide a doc string, the *Help* buffer won’t have any doc string to display. In that case, if help-enable-symbol-autoload is non-nil, Emacs will try to load the file in which the function is defined to see whether there’s a doc string there.

You can get an overview of functions relevant for a particular topic by using the M-x shortdoc command. This will prompt you for an area of interest, e.g., string, and pop you to a buffer where many of the functions relevant for handling strings are listed.

C-h v (describe-variable) is like C-h f but describes Lisp variables instead of Lisp functions. Its default is the Lisp symbol around or before point, if that is the name of a defined Lisp variable. See Variables.

Help buffers that describe Emacs variables and functions normally have hyperlinks to the corresponding source code, if you have the source files installed (see Hyperlinking and Web Navigation Features).

To find a command’s documentation in a manual, use C-h F (Info-goto-emacs-command-node). This knows about various manuals, not just the Emacs manual, and finds the right one.

C-h o (describe-symbol) is like C-h f and C-h v, but it describes any symbol, be it a function, a variable, or a face. If the symbol has more than one definition, like it has both definition as a function and as a variable, this command will show the documentation of all of them, one after the other.

If the completions-detailed user option is non-nil, some commands provide details about the possible values when displaying completions. For instance, C-h o TAB will then include the first line of the doc string, and will also say whether each symbol is a function or a variable (and so on). Which details are included varies depending on the command used.


11.4 Apropos

The apropos commands answer questions like, “What are the commands for working with files?” More precisely, you specify your query as an apropos pattern, which is either a word, a list of words, or a regular expression.

Each of the following apropos commands reads an apropos pattern in the minibuffer, searches for items that match the pattern, and displays the results in a different window.

C-h a

Search for commands (apropos-command). With a prefix argument, search for noninteractive functions too.

M-x apropos

Search for functions and variables. Both interactive functions (commands) and noninteractive functions can be found by this.

M-x apropos-user-option

Search for user-customizable variables. With a prefix argument, search for non-customizable variables too.

M-x apropos-variable

Search for variables. With a prefix argument, search for customizable variables only.

M-x apropos-local-variable

Search for buffer-local variables.

M-x apropos-value

Search for variables whose values match the specified pattern. With a prefix argument, search also for functions with definitions matching the pattern, and Lisp symbols with properties matching the pattern.

M-x apropos-local-value

Search for buffer-local variables whose values match the specified pattern.

C-h d

Search for functions and variables whose documentation strings match the specified pattern (apropos-documentation).

The simplest kind of apropos pattern is one word. Anything containing that word matches the pattern. Thus, to find commands that work on files, type C-h a file RET. This displays a list of all command names that contain ‘file’, including copy-file, find-file, and so on. Each command name comes with a brief description and a list of keys you can currently invoke it with. In our example, it would say that you can invoke find-file by typing C-x C-f.

By default, the window showing the apropos buffer with the results of the query is not selected, but you can cause it to be selected by customizing the variable help-window-select to any non-nil value.

For more information about a function definition, variable or symbol property listed in an apropos buffer, you can click on it with mouse-1 or mouse-2, or move there and type RET.

When you specify more than one word in the apropos pattern, a name must contain at least two of the words in order to match. Thus, if you are looking for commands to kill a chunk of text before point, you could try C-h a kill back backward behind before RET. The real command name kill-backward will match that; if there were a command kill-text-before, it would also match, since it contains two of the specified words.

For even greater flexibility, you can specify a regular expression (see Syntax of Regular Expressions). An apropos pattern is interpreted as a regular expression if it contains any of the regular expression special characters, ‘^$*+?.\[’.

Following the conventions for naming Emacs commands, here are some words that you’ll find useful in apropos patterns. By using them in C-h a, you will also get a feel for the naming conventions.

char, line, word, sentence, paragraph, region, page, sexp, list, defun, rect, buffer, frame, window, face, file, dir, register, mode, beginning, end, forward, backward, next, previous, up, down, search, goto, kill, delete, mark, insert, yank, fill, indent, case, change, set, what, list, find, view, describe, default.

If the variable apropos-do-all is non-nil, most apropos commands behave as if they had been given a prefix argument. There is one exception: apropos-variable without a prefix argument will always search for all variables, no matter what the value of apropos-do-all is.

By default, all apropos commands except apropos-documentation list their results in alphabetical order. If the variable apropos-sort-by-scores is non-nil, these commands instead try to guess the relevance of each result, and display the most relevant ones first. The apropos-documentation command lists its results in order of relevance by default; to list them in alphabetical order, change the variable apropos-documentation-sort-by-scores to nil.


11.5 Help Mode Commands

Help buffers have Help mode as their major mode. Help mode provides the same commands as View mode (see View Mode); for instance, SPC scrolls forward, and DEL or S-SPC scrolls backward. It also provides a few special commands:

RET

Follow a cross reference at point (help-follow).

TAB

Move point forward to the next hyperlink (forward-button).

S-TAB

Move point back to the previous hyperlink (backward-button).

mouse-1
mouse-2

Follow a hyperlink that you click on.

n
p

Move forward and back between pages in the Help buffer.

C-c C-c

Show all documentation about the symbol at point (help-follow-symbol).

C-c C-f
r

Go forward in history of help commands (help-go-forward).

C-c C-b
l

Go back in history of help commands (help-go-back).

s

View the source of the current help topic (if any) (help-view-source).

i

Look up the current topic in the manual(s) (help-goto-info).

I

Look up the current topic in the Emacs Lisp manual (help-goto-lispref-info).

c

Customize the variable or the face (help-customize).

When a function name, variable name, or face name (see Text Faces) appears in the documentation in the help buffer, it is normally an underlined hyperlink. To view the associated documentation, move point there and type RET (help-follow), or click on the hyperlink with mouse-1 or mouse-2. Doing so replaces the contents of the help buffer; to retrace your steps, type C-c C-b or l (help-go-back). While retracing your steps, you can go forward by using C-c C-f or r (help-go-forward).

To move between hyperlinks in a help buffer, use TAB (forward-button) to move forward to the next hyperlink and S-TAB (backward-button) to move back to the previous hyperlink. These commands act cyclically; for instance, typing TAB at the last hyperlink moves back to the first hyperlink.

By default, many links in the help buffer are displayed surrounded by quote characters. If the help-clean-buttons user option is non-nil, these quote characters are removed from the buffer.

Help buffers produced by some Help commands (like C-h b, which shows a long list of key bindings) are divided into pages by the ‘^L’ character. In such buffers, the n (help-goto-next-page) command will take you to the next start of page, and the p (help-goto-previous-page) command will take you to the previous start of page. This way you can quickly navigate between the different kinds of documentation in a help buffer.

A help buffer can also contain hyperlinks to Info manuals, source code definitions, and URLs (web pages). The first two are opened in Emacs, and the third using a web browser via the browse-url command (see Following URLs).

To view all documentation about any symbol in the text, move point to the symbol and type C-c C-c (help-follow-symbol). This shows the documentation for all the meanings of the symbol—as a variable, as a function, and/or as a face.


11.6 Keyword Search for Packages

Most optional features in Emacs are grouped into packages. Emacs contains several hundred built-in packages, and more can be installed over the network (see Emacs Lisp Packages).

To make it easier to find packages related to a topic, most packages are associated with one or more keywords based on what they do. Type C-h p (finder-by-keyword) to bring up a list of package keywords, together with a description of what the keywords mean. To view a list of packages for a given keyword, type RET on that line; this displays the list of packages in a Package Menu buffer (see The Package Menu Buffer).

C-h P (describe-package) prompts for the name of a package (see Emacs Lisp Packages), and displays a help buffer describing the attributes of the package and the features that it implements. The buffer lists the keywords that relate to the package in the form of buttons. Click on a button with mouse-1 or mouse-2 to see the list of other packages related to that keyword.


11.7 Help for International Language Support

For information on a specific language environment (see Language Environments), type C-h L (describe-language-environment). This displays a help buffer describing the languages supported by the language environment, and listing the associated character sets, coding systems, and input methods, as well as some sample text for that language environment.

The command C-h h (view-hello-file) displays the file etc/HELLO, which demonstrates various character sets by showing how to say “hello” in many languages.

The command C-h I (describe-input-method) describes an input method—either a specified input method, or by default the input method currently in use. See Input Methods.

The command C-h C (describe-coding-system) describes coding systems—either a specified coding system, or the ones currently in use. See Coding Systems.


11.8 Other Help Commands

C-h i (info) runs the Info program, which browses structured documentation files. C-h 4 i (info-other-window) does the same, but shows the Info buffer in another window. The entire Emacs manual is available within Info, along with many other manuals for the GNU system. Type h after entering Info to run a tutorial on using Info.

With a numeric argument n, C-h i selects the Info buffer ‘*info*<n>’. This is useful if you want to browse multiple Info manuals simultaneously. If you specify just C-u as the prefix argument, C-h i prompts for the name of a documentation file, so you can browse a file which doesn’t have an entry in the top-level Info menu.

The help commands C-h F function RET and C-h K key, described above, enter Info and go straight to the documentation of function or key.

When editing a program, if you have an Info version of the manual for the programming language, you can use C-h S (info-lookup-symbol) to find an entry for a symbol (keyword, function or variable) in the proper manual. The details of how this command works depend on the major mode.

If something surprising happens, and you are not sure what you typed, use C-h l (view-lossage). C-h l displays your last input keystrokes and the commands they invoked. By default, Emacs stores the last 300 keystrokes; if you wish, you can change this number with the command lossage-size. If you see commands that you are not familiar with, you can use C-h k or C-h f to find out what they do.

To review recent echo area messages, use C-h e (view-echo-area-messages). This displays the buffer *Messages*, where those messages are kept.

Each Emacs major mode typically redefines a few keys and makes other changes in how editing works. C-h m (describe-mode) displays documentation on the current major mode, which normally describes the commands and features that are changed in this mode, and also its key bindings.

C-h b (describe-bindings) and C-h s (describe-syntax) show other information about the current environment within Emacs. C-h b displays a list of all the key bindings now in effect: first the local bindings of the current minor modes, then the local bindings defined by the current major mode, and finally the global bindings (see Customizing Key Bindings). C-h s displays the contents of the syntax table, with explanations of each character’s syntax (see Syntax Tables in The Emacs Lisp Reference Manual).

C-h C-q (help-quick-toggle) toggles on and off the display of a buffer showing the most popular Emacs commands and their respective key bindings (a.k.a. “cheat sheet”). The contents of that buffer are created by the command help-quick. Each key binding shown in this buffer is a button: click on it with mouse-1 or mouse-2 to show the documentation of the command bound to that key sequence.

You can get a list of subcommands for a particular prefix key by typing C-h, ?, or F1 (describe-prefix-bindings) after the prefix key. (There are a few prefix keys for which not all of these keys work—those that provide their own bindings for that key. One of these prefix keys is ESC, because ESC C-h and ESC ? are actually C-M-h (mark-defun) and M-? (xref-find-references), respectively. However, ESC F1 works fine.)

Finally, M-x describe-keymap prompts for the name of a keymap, with completion, and displays a listing of all key bindings in that keymap.


11.9 Help Files

Apart from the built-in documentation and manuals, Emacs contains several other files describing topics like copying conditions, release notes, instructions for debugging and reporting bugs, and so forth. You can use the following commands to view these files. Apart from C-h g, they all have the form C-h C-char.

C-h C-c

Display the rules under which you can copy and redistribute Emacs (describe-copying).

C-h C-d

Display help for debugging Emacs (view-emacs-debugging).

C-h C-e

Display information about where to get external packages (view-external-packages).

C-h C-f

Display the Emacs frequently-answered-questions list (view-emacs-FAQ).

C-h g

Visit the page with information about the GNU Project (describe-gnu-project).

C-h C-m

Display information about ordering printed copies of Emacs manuals (view-order-manuals).

C-h C-n

Display the news, which lists the new features in this version of Emacs (view-emacs-news).

C-h C-o

Display how to order or download the latest version of Emacs and other GNU software (describe-distribution).

C-h C-p

Display the list of known Emacs problems, sometimes with suggested workarounds (view-emacs-problems).

C-h C-t

Display the Emacs to-do list (view-emacs-todo).

C-h C-w

Display the full details on the complete absence of warranty for GNU Emacs (describe-no-warranty).


11.10 Help on Active Text and Tooltips

In Emacs, stretches of active text (text that does something special in response to mouse clicks or RET) often have associated help text. This includes hyperlinks in Emacs buffers, as well as parts of the mode line. On graphical displays, as well as some text terminals which support mouse tracking, moving the mouse over the active text displays the help text as a tooltip. See Tooltips.

On terminals that don’t support mouse-tracking, you can display the help text for active buffer text at point by typing C-h . (display-local-help). This shows the help text in the echo area. To display help text automatically whenever it is available at point, set the variable help-at-pt-display-when-idle to t.


12 The Mark and the Region

Emacs, like many other applications, lets you select some arbitrary part of the buffer text and invoke commands that operate on such selected text. In Emacs, we call the selected text the region; its handling is very similar to that of selected text in other programs, but there are also important differences.

The region is the portion of the buffer between the mark and the current point. You define a region by setting the mark somewhere (with, for instance, the C-SPC command), and then moving point to where you want the region to end. (Or you can use the mouse to define a region.)

The region always extends between point and the mark, no matter which of them comes earlier in the text; each time you move point, the region changes.

Setting the mark at a position in the text activates it. When the mark is active, we say also that the region is active; Emacs indicates its extent by highlighting the text within it, using the region face (see Customizing Faces).

After certain non-motion commands, including any command that changes the text in the buffer, Emacs automatically deactivates the mark; this turns off the highlighting. You can also explicitly deactivate the mark at any time, by typing C-g (see Quitting and Aborting).

Many commands limit the text on which they operate to the active region. For instance, the M-% command (which replaces matching text) normally works on the entire accessible portion of the buffer, but if you have an active region, it’ll work only on that region instead.

The mark is useful even if it is not active. For example, you can move to previous mark locations using the mark ring. See The Mark Ring. Additionally, some commands will have an effect even on an inactive region (for example upcase-region). You can also reactivate the region with commands like C-x C-x.

The above behavior, which is the default in interactive sessions, is known as Transient Mark mode. Disabling Transient Mark mode switches Emacs to an alternative behavior, in which the region is usually not highlighted. See Disabling Transient Mark Mode.

Setting the mark in one buffer has no effect on the marks in other buffers. When you return to a buffer with an active mark, the mark is at the same place as before. When multiple windows show the same buffer, they can have different values of point, and thus different regions, but they all share one common mark position. See Multiple Windows. Ordinarily, only the selected window highlights its region; however, if the variable highlight-nonselected-windows is non-nil, each window highlights its own region.

There is another kind of region: the rectangular region. See Rectangles.


12.1 Setting the Mark

Here are some commands for setting the mark:

C-SPC

Set the mark at point, and activate it (set-mark-command).

C-@

The same.

C-x C-x

Set the mark at point, and activate it; then move point where the mark used to be (exchange-point-and-mark).

Drag-mouse-1

Set point and the mark around the text you drag across.

mouse-3

Set the mark at point, then move point to where you click (mouse-save-then-kill).

Shifted cursor motion keys

Set the mark at point if the mark is inactive, then move point. See Shift Selection.

The most common way to set the mark is with C-SPC (set-mark-command)5. This sets the mark where point is, and activates it. You can then move point away, leaving the mark behind.

For example, suppose you wish to convert part of the buffer to upper case. To accomplish this, go to one end of the desired text, type C-SPC, and move point until the desired portion of text is highlighted. Now type C-x C-u (upcase-region). This converts the text in the region to upper case, and then deactivates the mark.

Whenever the mark is active, you can deactivate it by typing C-g (see Quitting and Aborting). Most commands that operate on the region also automatically deactivate the mark, like C-x C-u in the above example.

Instead of setting the mark in order to operate on a region, you can also use it to remember a position in the buffer (by typing C-SPC C-SPC), and later jump back there (by typing C-u C-SPC). See The Mark Ring, for details.

The command C-x C-x (exchange-point-and-mark) exchanges the positions of point and the mark. C-x C-x is useful when you are satisfied with the position of point but want to move the other end of the region (where the mark is). Using C-x C-x a second time, if necessary, puts the mark at the new position with point back at its original position. Normally, if the mark is inactive, this command first reactivates the mark wherever it was last set, to ensure that the region is left highlighted. However, if you call it with a prefix argument, it leaves the mark inactive and the region unhighlighted; you can use this to jump to the mark in a manner similar to C-u C-SPC.

You can also set the mark with the mouse. If you press the left mouse button (down-mouse-1) and drag the mouse across a range of text, this sets the mark where you first pressed the mouse button and puts point where you release it. Alternatively, clicking the right mouse button (mouse-3) sets the mark at point and then moves point to where you clicked. See Mouse Commands for Editing, for a more detailed description of these mouse commands.

Finally, you can set the mark by holding down the shift key while typing certain cursor motion commands (such as S-RIGHT, S-C-f, S-C-n, etc.). This is called shift-selection. It sets the mark at point before moving point, but only if there is no active mark set via a previous shift-selection or mouse commands. The mark set by mouse commands and by shift-selection behaves slightly differently from the usual mark: any subsequent unshifted cursor motion command deactivates it automatically. For details, see Shift Selection.

Many commands that insert text, such as C-y (yank), set the mark at the other end of the inserted text, without activating it. This lets you easily return to that position (see The Mark Ring). You can tell that a command does this when it shows ‘Mark set’ in the echo area.

Under X, every time the active region changes, Emacs saves the text in the region to the primary selection. This lets you insert that text into other X applications with mouse-2 clicks. See Cut and Paste with Other Window Applications.


12.2 Commands to Mark Textual Objects

Here are commands for placing point and the mark around a textual object such as a word, list, paragraph or page:

M-@

Set mark at the end of the next word (mark-word). This does not move point.

C-M-@

Set mark after end of following balanced expression (mark-sexp). This does not move point.

M-h

Move point to the beginning of the current paragraph, and set mark at the end (mark-paragraph).

C-M-h

Move point to the beginning of the current defun, and set mark at the end (mark-defun).

C-x C-p

Move point to the beginning of the current page, and set mark at the end (mark-page).

C-x h

Move point to the beginning of the buffer, and set mark at the end (mark-whole-buffer).

M-@ (mark-word) sets the mark at the end of the next word (see Words, for information about words). Repeated invocations of this command extend the region by advancing the mark one word at a time. As an exception, if the mark is active and located before point, M-@ moves the mark backwards from its current position one word at a time.

This command also accepts a numeric argument n, which tells it to advance the mark by n words. A negative argument −n moves the mark back by n words.

Similarly, C-M-@ (mark-sexp) puts the mark at the end of the next balanced expression (see Expressions with Balanced Parentheses). Repeated invocations extend the region to subsequent expressions, while positive or negative numeric arguments move the mark forward or backward by the specified number of expressions.

The other commands in the above list set both point and mark, so as to delimit an object in the buffer. M-h (mark-paragraph) marks paragraphs (see Paragraphs), C-M-h (mark-defun) marks top-level definitions (see Moving by Defuns), and C-x C-p (mark-page) marks pages (see Pages). Repeated invocations again play the same role, extending the region to consecutive objects; similarly, numeric arguments specify how many objects to move the mark by.

C-x h (mark-whole-buffer) sets up the entire buffer as the region, by putting point at the beginning and the mark at the end.


12.3 Operating on the Region

Once you have a region, here are some of the ways you can operate on it:

Some commands have a default behavior when the mark is inactive, but operate on the region if the mark is active. For example, M-$ (ispell-word) normally checks the spelling of the word at point, but it checks the text in the region if the mark is active (see Checking and Correcting Spelling). Normally, such commands use their default behavior if the region is empty (i.e., if mark and point are at the same position). If you want them to operate on the empty region, change the variable use-empty-active-region to t.

As described in Erasing Text, the DEL (backward-delete-char) and Delete (delete-forward-char) commands also act this way. If the mark is active, they delete the text in the region. (As an exception, if you supply a numeric argument n, where n is not one, these commands delete n characters regardless of whether the mark is active). If you change the variable delete-active-region to nil, then these commands don’t act differently when the mark is active. If you change the value to kill, these commands kill the region instead of deleting it (see Killing and Moving Text).

Other commands always operate on the region, and have no default behavior. Such commands usually have the word region in their names, like C-w (kill-region) and C-x C-u (upcase-region). If the mark is inactive, they operate on the inactive region—that is, on the text between point and the position at which the mark was last set (see The Mark Ring). To disable this behavior, change the variable mark-even-if-inactive to nil. Then these commands will instead signal an error if the mark is inactive.

By default, text insertion occurs normally even if the mark is active—for example, typing a inserts the character ‘a’, then deactivates the mark. Delete Selection mode, a minor mode, modifies this behavior: if you enable that mode, then inserting text while the mark is active causes the text in the region to be deleted first. However, you can tune this behavior by customizing the delete-selection-temporary-region option. Its default value is nil, but you can set it to t, in which case only temporarily-active regions will be replaced: those which are set by dragging the mouse (see Setting the Mark) or by shift-selection (see Shift Selection), as well as by C-u C-x C-x when Transient Mark Mode is disabled. You can further tune the behavior by setting delete-selection-temporary-region to selection: then temporary regions by C-u C-x C-x won’t be replaced, only the ones activated by dragging the mouse or shift-selection. To toggle Delete Selection mode on or off, type M-x delete-selection-mode.


12.4 The Mark Ring

Each buffer remembers previous locations of the mark, in the mark ring. Commands that set the mark also push the old mark onto this ring. One of the uses of the mark ring is to remember spots that you may want to go back to.

C-SPC C-SPC

Set the mark, pushing it onto the mark ring, without activating it.

C-u C-SPC

Move point to where the mark was, and restore the mark from the ring of former marks.

The command C-SPC C-SPC is handy when you want to use the mark to remember a position to which you may wish to return. It pushes the current point onto the mark ring, without activating the mark (which would cause Emacs to highlight the region). This is actually two consecutive invocations of C-SPC (set-mark-command); the first C-SPC sets the mark, and the second C-SPC deactivates it. (When Transient Mark mode is off, C-SPC C-SPC instead activates Transient Mark mode temporarily; see Disabling Transient Mark Mode.)

To return to a marked position, use set-mark-command with a prefix argument: C-u C-SPC. This moves point to where the mark was, and deactivates the mark if it was active. Each subsequent C-u C-SPC jumps to a prior position stored in the mark ring. The positions you move through in this way are not lost; they go to the end of the ring.

If you set set-mark-command-repeat-pop to non-nil, then immediately after you type C-u C-SPC, you can type C-SPC instead of C-u C-SPC to cycle through the mark ring. By default, set-mark-command-repeat-pop is nil.

Each buffer has its own mark ring. All editing commands use the current buffer’s mark ring. In particular, C-u C-SPC always stays in the same buffer.

The variable mark-ring-max specifies the maximum number of entries to keep in the mark ring. This defaults to 16 entries. If that many entries exist and another one is pushed, the earliest one in the list is discarded. Repeating C-u C-SPC cycles through the positions currently in the ring.

If you want to move back to the same place over and over, the mark ring may not be convenient enough. If so, you can record the position in a register for later retrieval (see Saving Positions in Registers).


12.5 The Global Mark Ring

In addition to the ordinary mark ring that belongs to each buffer, Emacs has a single global mark ring. Each time you set a mark, this is recorded in the global mark ring in addition to the current buffer’s own mark ring, if you have switched buffers since the previous mark setting. Hence, the global mark ring records a sequence of buffers that you have been in, and, for each buffer, a place where you set the mark. The length of the global mark ring is controlled by global-mark-ring-max, and is 16 by default.

The command C-x C-SPC (pop-global-mark) jumps to the buffer and position of the latest entry in the global ring. It also rotates the ring, so that successive uses of C-x C-SPC take you to earlier buffers and mark positions.


12.6 Shift Selection

If you hold down the shift key while typing a cursor motion command, this sets the mark before moving point, so that the region extends from the original position of point to its new position. This feature is referred to as shift-selection. It is similar to the way text is selected in other editors.

The mark set via shift-selection behaves a little differently from what we have described above. Firstly, in addition to the usual ways of deactivating the mark (such as changing the buffer text or typing C-g), the mark is deactivated by any unshifted cursor motion command. Secondly, any subsequent shifted cursor motion command avoids setting the mark anew. Therefore, a series of shifted cursor motion commands will continuously adjust the region.

Shift-selection only works if the shifted cursor motion key is not already bound to a separate command (see Customization). For example, if you bind S-C-f to another command, typing S-C-f runs that command instead of performing a shift-selected version of C-f (forward-char).

A mark set via mouse commands behaves the same as a mark set via shift-selection (see Setting the Mark). For example, if you specify a region by dragging the mouse, you can continue to extend the region using shifted cursor motion commands. In either case, any unshifted cursor motion command deactivates the mark.

To turn off shift-selection, set shift-select-mode to nil. Doing so does not disable setting the mark via mouse commands. If you set shift-select-mode to the value permanent, cursor motion keys that were not shift-translated will not deactivate the mark, so, for example, the region set by prior commands can be extended by shift-selection, and unshifted cursor motion keys will extend the region set by shift-selection.


12.7 Disabling Transient Mark Mode

The default behavior of the mark and region, in which setting the mark activates it and highlights the region, is called Transient Mark mode. This is a minor mode that is enabled by default in interactive sessions. It can be toggled with M-x transient-mark-mode, or with the ‘Highlight Active Region’ menu item in the ‘Options’ menu. Turning it off switches Emacs to an alternative mode of operation:

  • Setting the mark, with commands like C-SPC or C-x C-x, does not highlight the region. Therefore, you can’t tell by looking where the mark is located; you have to remember.

    The usual solution to this problem is to set the mark and then use it soon, before you forget where it is. You can also check where the mark is by using C-x C-x, which exchanges the positions of the point and the mark (see Setting the Mark).

  • Some commands, which ordinarily act on the region when the mark is active, no longer do so. For example, normally M-% (query-replace) performs replacements within the region, if the mark is active. When Transient Mark mode is off, it always operates from point to the end of the buffer. Commands that act this way are identified in their own documentation.

While Transient Mark mode is off, you can activate it temporarily using C-SPC C-SPC or C-u C-x C-x.

C-SPC C-SPC

Set the mark at point (like plain C-SPC) and enable Transient Mark mode just once, until the mark is deactivated. (This is not really a separate command; you are using the C-SPC command twice.)

C-u C-x C-x

Exchange point and mark, activate the mark and enable Transient Mark mode temporarily, until the mark is next deactivated. (This is the C-x C-x command, exchange-point-and-mark, with a prefix argument.)

These commands set or activate the mark, and enable Transient Mark mode only until the mark is deactivated. One reason you may want to use them is that some commands operate on the entire buffer instead of the region when Transient Mark mode is off. Enabling Transient Mark mode momentarily gives you a way to use these commands on the region.

When you specify a region with the mouse (see Setting the Mark), or with shift-selection (see Shift Selection), this likewise activates Transient Mark mode temporarily and highlights the region.


13 Killing and Moving Text

In Emacs, killing means erasing text and copying it into the kill ring. Yanking means bringing text from the kill ring back into the buffer. (Some applications use the terms “cutting” and “pasting” for similar operations.) The kill ring is so-named because it can be visualized as a set of blocks of text arranged in a ring, which you can access in cyclic order. See The Kill Ring.

Killing and yanking are the most common way to move or copy text within Emacs. It is very versatile, because there are commands for killing many different types of syntactic units.


13.1 Deletion and Killing

Most commands which erase text from the buffer save it in the kill ring (see The Kill Ring). These are known as kill commands, and their names normally contain the word ‘kill’ (e.g., kill-line). The kill ring stores several recent kills, not just the last one, so killing is a very safe operation: you don’t have to worry much about losing text that you previously killed. The kill ring is shared by all buffers, so text that is killed in one buffer can be yanked into another buffer.

When you use C-/ (undo) to undo a kill command (see Undo), that brings the killed text back into the buffer, but does not remove it from the kill ring.

On graphical displays, killing text also copies it to the system clipboard. See “Cut and Paste” Operations on Graphical Displays.

Commands that erase text but do not save it in the kill ring are known as delete commands; their names usually contain the word ‘delete’. These include C-d (delete-char) and DEL (delete-backward-char), which delete only one character at a time, and those commands that delete only spaces or newlines. Commands that can erase significant amounts of nontrivial data generally do a kill operation instead.

You can also use the mouse to kill and yank. See “Cut and Paste” Operations on Graphical Displays.


13.1.1 Deletion

Deletion means erasing text and not saving it in the kill ring. For the most part, the Emacs commands that delete text are those that erase just one character or only whitespace.

DEL
BACKSPACE

Delete the previous character, or the text in the region if it is active (delete-backward-char).

Delete

Delete the next character, or the text in the region if it is active (delete-forward-char).

C-d

Delete the next character (delete-char).

M-\

Delete spaces and tabs around point (delete-horizontal-space).

M-SPC

Delete spaces and tabs around point, leaving one space (just-one-space).

C-x C-o

Delete blank lines around the current line (delete-blank-lines).

M-^

Join two lines by deleting the intervening newline, along with any indentation following it (delete-indentation).

We have already described the basic deletion commands DEL (delete-backward-char), delete (delete-forward-char), and C-d (delete-char). See Erasing Text. With a numeric argument, they delete the specified number of characters. If the numeric argument is omitted or one, DEL and delete delete all the text in the region if it is active (see Operating on the Region).

The other delete commands are those that delete only whitespace characters: spaces, tabs and newlines. M-\ (delete-horizontal-space) deletes all the spaces and tab characters before and after point. With a prefix argument, this only deletes spaces and tab characters before point.

just-one-space does likewise but leaves a single space before point, regardless of the number of spaces that existed previously (even if there were none before). With a numeric argument n, it leaves n spaces before point if n is positive; if n is negative, it deletes newlines in addition to spaces and tabs, leaving −n spaces before point.

The command cycle-spacing (M-SPC) acts like a more flexible version of just-one-space. It performs different space cleanup actions defined by cycle-spacing-actions, in a cyclic manner, if you call it repeatedly in succession.

C-x C-o (delete-blank-lines) deletes all blank lines after the current line. If the current line is blank, it deletes all blank lines preceding the current line as well (leaving one blank line, the current line). On a solitary blank line, it deletes that line.

M-^ (delete-indentation) joins the current line and the previous line, by deleting a newline and all surrounding spaces, usually leaving a single space. See M-^.

The command delete-duplicate-lines searches the region for identical lines, and removes all but one copy of each. Normally it keeps the first instance of each repeated line, but with a C-u prefix argument it keeps the last. With a C-u C-u prefix argument, it only searches for adjacent identical lines. This is a more efficient mode of operation, useful when the lines have already been sorted. With a C-u C-u C-u prefix argument, it retains repeated blank lines.


13.1.2 Killing by Lines

C-k

Kill rest of line or one or more lines (kill-line).

C-S-backspace

Kill an entire line at once (kill-whole-line)

The simplest kill command is C-k (kill-line). If used at the end of a line, it kills the line-ending newline character, merging the next line into the current one (thus, a blank line is entirely removed). Otherwise, C-k kills all the text from point up to the end of the line; if point was originally at the beginning of the line, this leaves the line blank.

Spaces and tabs at the end of the line are ignored when deciding which case applies. As long as point is after the last non-whitespace character in the line, you can be sure that C-k will kill the newline. To kill an entire non-blank line, go to the beginning and type C-k twice.

In this context, “line” means a logical text line, not a screen line (see Continuation Lines).

When C-k is given a positive argument n, it kills n lines and the newlines that follow them (text on the current line before point is not killed). With a negative argument −n, it kills n lines preceding the current line, together with the text on the current line before point. C-k with an argument of zero kills the text before point on the current line.

If the variable kill-whole-line is non-nil, C-k at the very beginning of a line kills the entire line including the following newline. This variable is normally nil.

C-S-backspace (kill-whole-line) kills a whole line including its newline, regardless of the position of point within the line. Note that many text terminals will prevent you from typing the key sequence C-S-backspace.


13.1.3 Other Kill Commands

C-w

Kill the region (kill-region).

M-w

Copy the region into the kill ring (kill-ring-save).

M-d

Kill the next word (kill-word). See Words.

M-DEL

Kill one word backwards (backward-kill-word).

C-x DEL

Kill back to beginning of sentence (backward-kill-sentence). See Sentences.

M-k

Kill to the end of the sentence (kill-sentence).

C-M-k

Kill the following balanced expression (kill-sexp). See Expressions with Balanced Parentheses.

M-z char

Kill through the next occurrence of char (zap-to-char).

M-x zap-up-to-char char

Kill up to, but not including, the next occurrence of char.

One of the commonly-used kill commands is C-w (kill-region), which kills the text in the region (see The Mark and the Region). Similarly, M-w (kill-ring-save) copies the text in the region into the kill ring without removing it from the buffer. If the mark is inactive when you type C-w or M-w, the command acts on the text between point and where you last set the mark (see Operating on the Region).

Emacs also provides commands to kill specific syntactic units: words, with M-DEL and M-d (see Words); balanced expressions, with C-M-k (see Expressions with Balanced Parentheses); and sentences, with C-x DEL and M-k (see Sentences).

The command M-z (zap-to-char) combines killing with searching: it reads a character and kills from point up to (and including) the next occurrence of that character in the buffer. A numeric argument acts as a repeat count; a negative argument means to search backward and kill text before point. A history of previously used characters is maintained and can be accessed via the M-p/M-n keystrokes. This is mainly useful if the character to be used has to be entered via a complicated input method. A similar command zap-up-to-char kills from point up to, but not including the next occurrence of a character, with numeric argument acting as a repeat count.


13.1.4 Options for Killing

Some specialized buffers contain read-only text, which cannot be modified and therefore cannot be killed. The kill commands work specially in a read-only buffer: they move over text and copy it to the kill ring, without actually deleting it from the buffer. Normally, they also beep and display an error message when this happens. But if you set the variable kill-read-only-ok to a non-nil value, they just print a message in the echo area to explain why the text has not been erased.

Before saving the kill to the kill ring, you can transform the string using kill-transform-function. It’s called with the string to be killed, and it should return the string you want to be saved. It can also return nil, in which case the string won’t be saved to the kill ring. For instance, if you never want to save a pure white space string to the kill ring, you can say:

(setq kill-transform-function
      (lambda (string)
        (and (not (string-blank-p string))
             string)))

If you change the variable kill-do-not-save-duplicates to a non-nil value, identical subsequent kills yield a single kill-ring entry, without duplication.


13.2 Yanking

Yanking means reinserting text previously killed. The usual way to move or copy text is to kill it and then yank it elsewhere.

C-y

Yank the last kill into the buffer, at point (yank).

M-y

Either replace the text just yanked with an earlier batch of killed text (yank-pop), or allow to select from the list of previously-killed batches of text. See Yanking Earlier Kills.

C-M-w

Cause the following command, if it is a kill command, to append to the previous kill (append-next-kill). See Appending Kills.

The basic yanking command is C-y (yank). It inserts the most recent kill, leaving the cursor at the end of the inserted text. It also sets the mark at the beginning of the inserted text, without activating the mark; this lets you jump easily to that position, if you wish, with C-u C-SPC (see The Mark Ring).

With a plain prefix argument (C-u C-y), the command instead leaves the cursor in front of the inserted text, and sets the mark at the end. Using any other prefix argument specifies an earlier kill; e.g., C-u 4 C-y reinserts the fourth most recent kill. See Yanking Earlier Kills.

On graphical displays and on capable text-mode displays, C-y first checks if another application has placed any text in the system clipboard more recently than the last Emacs kill. If so, it inserts the clipboard’s text instead. Thus, Emacs effectively treats “cut” or “copy” clipboard operations performed in other applications like Emacs kills, except that they are not recorded in the kill ring. See “Cut and Paste” Operations on Graphical Displays, for details.


13.2.1 The Kill Ring

The kill ring is a list of blocks of text that were previously killed. There is only one kill ring, shared by all buffers, so you can kill text in one buffer and yank it in another buffer. This is the usual way to move text from one buffer to another. (There are several other methods: for instance, you could store the text in a register; see Registers. See Accumulating Text, for some other ways to move text around.)

The maximum number of entries in the kill ring is controlled by the variable kill-ring-max. The default is 120. If you make a new kill when this limit has been reached, Emacs makes room by deleting the oldest entry in the kill ring.

The actual contents of the kill ring are stored in a variable named kill-ring; you can view the entire contents of the kill ring with C-h v kill-ring.


13.2.2 Yanking Earlier Kills

As explained in Yanking, you can use a numeric argument to C-y to yank text that is no longer the most recent kill. This is useful if you remember which kill ring entry you want. If you don’t, you can use the M-y (yank-pop) command to cycle through the possibilities or to select one of the earlier kills.

If the previous command was a yank command, M-y takes the text that was yanked and replaces it with the text from an earlier kill. So, to recover the text of the next-to-the-last kill, first use C-y to yank the last kill, and then use M-y to replace it with the previous kill. This works only after a C-y or another M-y. (If M-y is invoked after some other command, it works differently, see below.)

You can understand this operation mode of M-y in terms of a last-yank pointer which points at an entry in the kill ring. Each time you kill, the last-yank pointer moves to the newly made entry at the front of the ring. C-y yanks the entry which the last-yank pointer points to. M-y after a C-y or another M-y moves the last-yank pointer to the previous entry, and the text in the buffer changes to match. Enough M-y commands one after another can move the pointer to any entry in the ring, so you can get any entry into the buffer. Eventually the pointer reaches the end of the ring; the next M-y loops back around to the first entry again.

M-y moves the last-yank pointer around the ring, but it does not change the order of the entries in the ring, which always runs from the most recent kill at the front to the oldest one still remembered.

When used after C-y or M-y, M-y can take a numeric argument, which tells it how many entries to advance the last-yank pointer by. A negative argument moves the pointer toward the front of the ring; from the front of the ring, it moves around to the last entry and continues forward from there.

Once the text you are looking for is brought into the buffer, you can stop doing M-y commands and the last yanked text will stay there. It’s just a copy of the kill ring entry, so editing it in the buffer does not change what’s in the ring. As long as no new killing is done, the last-yank pointer remains at the same place in the kill ring, so repeating C-y will yank another copy of the same previous kill.

When you call C-y with a numeric argument, that also sets the last-yank pointer to the entry that it yanks.

You can also invoke M-y after a command that is not a yank command. In that case, M-y prompts you in the minibuffer for one of the previous kills. You can use the minibuffer history commands (see Minibuffer History) to navigate or search through the entries in the kill ring until you find the one you want to reinsert. Or you can use completion commands (see Completion Commands) to complete on an entry from the list of entries in the kill ring or pop up the *Completions* buffer with the candidate entries from which you can choose. After selecting the kill-ring entry, you can optionally edit it in the minibuffer. Finally, type RET to exit the minibuffer and insert the text of the selected kill-ring entry. Like in case of M-y after another yank command, the last-yank pointer is left pointing at the text you just yanked, whether it is one of the previous kills or an entry from the kill-ring that you edited before inserting it. (In the latter case, the edited entry is added to the front of the kill-ring.) So here, too, typing C-y will yank another copy of the text just inserted.

When invoked with a plain prefix argument (C-u M-y) after a command that is not a yank command, M-y leaves the cursor in front of the inserted text, and sets the mark at the end, like C-y does.


13.2.3 Appending Kills

Normally, each kill command pushes a new entry onto the kill ring. However, two or more kill commands in a row combine their text into a single entry, so that a single C-y yanks all the text as a unit, just as it was before it was killed.

Thus, if you want to yank text as a unit, you need not kill all of it with one command; you can keep killing line after line, or word after word, until you have killed it all, and you can still get it all back at once.

Commands that kill forward from point add onto the end of the previous killed text. Commands that kill backward from point add text onto the beginning. This way, any sequence of mixed forward and backward kill commands puts all the killed text into one entry without rearrangement. Numeric arguments do not break the sequence of appending kills. For example, suppose the buffer contains this text:

This is a line ∗of sample text.

with point shown by ∗. If you type M-d M-DEL M-d M-DEL, killing alternately forward and backward, you end up with ‘a line of sample’ as one entry in the kill ring, and ‘This is  text. in the buffer. (Note the double space between ‘is’ and ‘text’, which you can clean up with M-SPC or M-q.)

Another way to kill the same text is to move back two words with M-b M-b, then kill all four words forward with C-u M-d. This produces exactly the same results in the buffer and in the kill ring. M-f M-f C-u M-DEL kills the same text, all going backward; once again, the result is the same. The text in the kill ring entry always has the same order that it had in the buffer before you killed it.

If a kill command is separated from the last kill command by other commands (not just numeric arguments), it starts a new entry on the kill ring. But you can force it to combine with the last killed text, by typing C-M-w (append-next-kill) right beforehand. The C-M-w tells its following command, if it is a kill command, to treat the kill as part of the sequence of previous kills. As usual, the kill is appended to the previous killed text if the command kills forward, and prepended if the command kills backward. In this way, you can kill several separated pieces of text and accumulate them to be yanked back in one place.

A kill command following M-w (kill-ring-save) does not append to the text that M-w copied into the kill ring.


13.3 “Cut and Paste” Operations on Graphical Displays

In most graphical desktop environments, you can transfer data (usually text) between different applications using a system facility called the clipboard. On X, two other similar facilities are available: the primary selection and the secondary selection. When Emacs is run on a graphical display, its kill and yank commands integrate with these facilities, so that you can easily transfer text between Emacs and other graphical applications.

By default, Emacs uses UTF-8 as the coding system for inter-program text transfers. If you find that the pasted text is not what you expected, you can specify another coding system by typing C-x RET x or C-x RET X. You can also request a different data type by customizing x-select-request-type. See Coding Systems for Interprocess Communication.


13.3.1 Using the Clipboard

The clipboard is the facility that most graphical applications use for “cutting and pasting”. When the clipboard exists, the kill and yank commands in Emacs make use of it.

When you kill some text with a command such as C-w (kill-region), or copy it to the kill ring with a command such as M-w (kill-ring-save), that text is also put in the clipboard.

When an Emacs kill command puts text in the clipboard, the existing clipboard contents are normally lost. Optionally, Emacs can save the existing clipboard contents to the kill ring, preventing you from losing the old clipboard data. If save-interprogram-paste-before-kill has been set to a number, then the data is copied over if it’s smaller (in characters) than this number. If this variable is any other non-nil value, the data is always copied over—at the risk of high memory consumption if that data turns out to be large.

Yank commands, such as C-y (yank), also use the clipboard. If another application “owns” the clipboard—i.e., if you cut or copied text there more recently than your last kill command in Emacs—then Emacs yanks from the clipboard instead of the kill ring.

Normally, rotating the kill ring with M-y (yank-pop) does not alter the clipboard. However, if you change yank-pop-change-selection to t, then M-y saves the new yank to the clipboard.

To prevent kill and yank commands from accessing the clipboard, change the variable select-enable-clipboard to nil.

Programs can put other things than plain text on the clipboard. For instance, a web browser will usually let you choose “Copy Image” on images, and this image will be put on the clipboard. On capable platforms, Emacs can yank these objects with the yank-media command—but only in modes that have support for it (see Yanking Media in The Emacs Lisp Reference Manual).

Many X desktop environments support a feature called the clipboard manager. If you exit Emacs while it is the current “owner” of the clipboard data, and there is a clipboard manager running, Emacs transfers the clipboard data to the clipboard manager so that it is not lost. In some circumstances, this may cause a delay when exiting Emacs; if you wish to prevent Emacs from transferring data to the clipboard manager, change the variable x-select-enable-clipboard-manager to nil.

Since strings containing NUL bytes are usually truncated when passed through the clipboard, Emacs replaces such characters with “\0” before transferring them to the system’s clipboard.

Prior to Emacs 24, the kill and yank commands used the primary selection (see Cut and Paste with Other Window Applications), not the clipboard. If you prefer this behavior, change select-enable-clipboard to nil, select-enable-primary to t, and mouse-drag-copy-region to t. In this case, you can use the following commands to act explicitly on the clipboard: clipboard-kill-region kills the region and saves it to the clipboard; clipboard-kill-ring-save copies the region to the kill ring and saves it to the clipboard; and clipboard-yank yanks the contents of the clipboard at point.


13.3.2 Cut and Paste with Other Window Applications

Under the X Window System, PGTK and Haiku, there exists a primary selection containing the last stretch of text selected in an X application (usually by dragging the mouse). Typically, this text can be inserted into other X applications by mouse-2 clicks. The primary selection is separate from the clipboard. Its contents are more fragile; they are overwritten each time you select text with the mouse, whereas the clipboard is only overwritten by explicit cut or copy commands.

Under X, whenever the region is active (see The Mark and the Region), the text in the region is saved in the primary selection. This applies regardless of whether the region was made by dragging or clicking the mouse (see Mouse Commands for Editing), or by keyboard commands (e.g., by typing C-SPC and moving point; see Setting the Mark).

If you change the variable select-active-regions to only, Emacs saves only temporarily active regions to the primary selection, i.e., those made with the mouse or with shift selection (see Shift Selection). If you change select-active-regions to nil, Emacs avoids saving active regions to the primary selection entirely.

To insert the primary selection into an Emacs buffer, click mouse-2 (mouse-yank-primary) where you want to insert it. See Mouse Commands for Editing. You can also use the normal Emacs yank command (C-y) to insert this text if select-enable-primary is set (see Using the Clipboard).

By default, Emacs keeps the region active even after text is selected in another program; this is contrary to typical X behavior. To make Emacs deactivate the region after another program places data in the primary selection, enable the global minor mode lost-selection-mode.

MS-Windows provides no primary selection, but Emacs emulates it within a single Emacs session by storing the selected text internally. Therefore, all the features and commands related to the primary selection work on Windows as they do on X, for cutting and pasting within the same session, but not across Emacs sessions or with other applications.


13.3.3 Secondary Selection

In addition to the primary selection, the X Window System provides a second similar facility known as the secondary selection. Nowadays, few X applications make use of the secondary selection, but you can access it using the following Emacs commands:

M-Drag-mouse-1

Set the secondary selection, with one end at the place where you press down the button, and the other end at the place where you release it (mouse-set-secondary). The selected text is highlighted, using the secondary-selection face, as you drag. The window scrolls automatically if you drag the mouse off the top or bottom of the window, just like mouse-set-region (see Mouse Commands for Editing).

This command does not alter the kill ring.

M-mouse-1

Set one endpoint for the secondary selection (mouse-start-secondary); use M-mouse-3 to set the other end and complete the selection. This command cancels any existing secondary selection, when it starts a new one.

M-mouse-3

Set the secondary selection (mouse-secondary-save-then-kill), with one end at the position you click M-mouse-3, and the other at the position specified previously with M-mouse-1. This also puts the selected text in the kill ring. A second M-mouse-3 at the same place kills the text selected by the secondary selection just made.

M-mouse-2

Insert the secondary selection where you click, placing point at the end of the yanked text (mouse-yank-secondary).

Double or triple clicking of M-mouse-1 operates on words and lines, much like mouse-1.

If mouse-yank-at-point is non-nil, M-mouse-2 yanks at point. Then it does not matter precisely where you click, or even which of the frame’s windows you click on. See Mouse Commands for Editing. This user option also effects interactive search: if it is non-nil, yanking with the mouse anywhere in the frame will add the text to the search string.


13.4 Accumulating Text

Usually we copy or move text by killing it and yanking it, but there are other convenient methods for copying one block of text in many places, or for copying many scattered blocks of text into one place. Here we describe the commands to accumulate scattered pieces of text into a buffer or into a file.

M-x append-to-buffer

Append region to the contents of a specified buffer.

M-x prepend-to-buffer

Prepend region to the contents of a specified buffer.

M-x copy-to-buffer

Copy region into a specified buffer, deleting that buffer’s old contents.

M-x insert-buffer

Insert the contents of a specified buffer into current buffer at point.

M-x append-to-file

Append region to the contents of a specified file, at the end.

To accumulate text into a buffer, use M-x append-to-buffer. This reads a buffer name, then inserts a copy of the region into the buffer specified. If you specify a nonexistent buffer, append-to-buffer creates the buffer. The text is inserted wherever point is in that buffer. If you have been using the buffer for editing, the copied text goes into the middle of the text of the buffer, starting from wherever point happens to be at that moment.

Point in that buffer is left at the end of the copied text, so successive uses of append-to-buffer accumulate the text in the specified buffer in the same order as they were copied. Strictly speaking, append-to-buffer does not always append to the text already in the buffer—it appends only if point in that buffer is at the end. However, if append-to-buffer is the only command you use to alter a buffer, then point is always at the end.

M-x prepend-to-buffer is just like append-to-buffer except that point in the other buffer is left before the copied text, so successive uses of this command add text in reverse order. M-x copy-to-buffer is similar, except that any existing text in the other buffer is deleted, so the buffer is left containing just the text newly copied into it.

The command C-x x i (insert-buffer) can be used to retrieve the accumulated text from another buffer. This prompts for the name of a buffer, and inserts a copy of all the text in that buffer into the current buffer at point, leaving point at the beginning of the inserted text. It also adds the position of the end of the inserted text to the mark ring, without activating the mark. See Using Multiple Buffers, for background information on buffers.

Instead of accumulating text in a buffer, you can append text directly into a file with M-x append-to-file. This prompts for a filename, and adds the text of the region to the end of the specified file. The file is changed immediately on disk.

You should use append-to-file only with files that are not being visited in Emacs. Using it on a file that you are editing in Emacs would change the file behind Emacs’s back, which can lead to losing some of your editing.

Another way to move text around is to store it in a register. See Registers.


13.5 Rectangles

Rectangle commands operate on rectangular areas of the text: all the characters between a certain pair of columns, in a certain range of lines. Emacs has commands to kill rectangles, yank killed rectangles, clear them out, fill them with blanks or text, or delete them. Rectangle commands are useful with text in multicolumn formats, and for changing text into or out of such formats.

To specify a rectangle for a command to work on, set the mark at one corner and point at the opposite corner. The rectangle thus specified is called the region-rectangle. If point and the mark are in the same column, the region-rectangle is empty. If they are in the same line, the region-rectangle is one line high.

The region-rectangle is controlled in much the same way as the region is controlled. But remember that a given combination of point and mark values can be interpreted either as a region or as a rectangle, depending on the command that uses them.

A rectangular region can also be marked using the mouse: click and drag C-M-mouse-1 from one corner of the rectangle to the opposite.

C-x r k

Kill the text of the region-rectangle, saving its contents as the last killed rectangle (kill-rectangle).

C-x r M-w

Save the text of the region-rectangle as the last killed rectangle (copy-rectangle-as-kill).

C-x r d

Delete the text of the region-rectangle (delete-rectangle).

C-x r y

Yank the last killed rectangle with its upper left corner at point (yank-rectangle).

C-x r o

Insert blank space to fill the space of the region-rectangle (open-rectangle). This pushes the previous contents of the region-rectangle to the right.

C-x r N

Insert line numbers along the left edge of the region-rectangle (rectangle-number-lines). This pushes the previous contents of the region-rectangle to the right.

C-x r c

Clear the region-rectangle by replacing all of its contents with spaces (clear-rectangle).

M-x delete-whitespace-rectangle

Delete whitespace in each of the lines on the specified rectangle, starting from the left edge column of the rectangle.

C-x r t string RET

Replace rectangle contents with string on each line (string-rectangle).

M-x string-insert-rectangle RET string RET

Insert string on each line of the rectangle.

C-x SPC

Toggle Rectangle Mark mode (rectangle-mark-mode). When this mode is active, the region-rectangle is highlighted and can be shrunk/grown, and the standard kill and yank commands operate on it.

The rectangle operations fall into two classes: commands to erase or insert rectangles, and commands to make blank rectangles.

There are two ways to erase the text in a rectangle: C-x r d (delete-rectangle) to delete the text outright, or C-x r k (kill-rectangle) to remove the text and save it as the last killed rectangle. In both cases, erasing the region-rectangle is like erasing the specified text on each line of the rectangle; if there is any following text on the line, it moves backwards to fill the gap.

Killing a rectangle is not killing in the usual sense; the rectangle is not stored in the kill ring, but in a special place that only records the most recent rectangle killed. This is because yanking a rectangle is so different from yanking linear text that different yank commands have to be used. Yank-popping is not defined for rectangles.

C-x r M-w (copy-rectangle-as-kill) is the equivalent of M-w for rectangles: it records the rectangle as the last killed rectangle, without deleting the text from the buffer.

To yank the last killed rectangle, type C-x r y (yank-rectangle). The rectangle’s first line is inserted at point, the rectangle’s second line is inserted at the same horizontal position one line vertically below, and so on. The number of lines affected is determined by the height of the saved rectangle.

For example, you can convert two single-column lists into a double-column list by killing one of the single-column lists as a rectangle, and then yanking it beside the other list.

You can also copy rectangles into and out of registers with C-x r r r and C-x r i r. See Saving Rectangles in Registers.

There are two commands you can use for making blank rectangles: C-x r c (clear-rectangle) blanks out existing text in the region-rectangle, and C-x r o (open-rectangle) inserts a blank rectangle.

M-x delete-whitespace-rectangle deletes horizontal whitespace starting from a particular column. This applies to each of the lines in the rectangle, and the column is specified by the left edge of the rectangle. The right edge of the rectangle does not make any difference to this command.

The command C-x r N (rectangle-number-lines) inserts line numbers along the left edge of the region-rectangle. Normally, the numbering begins from 1 (for the first line of the rectangle). With a prefix argument, the command prompts for a number to begin from, and for a format string with which to print the numbers (see Formatting Strings in The Emacs Lisp Reference Manual).

The command C-x r t (string-rectangle) replaces the contents of a region-rectangle with a string on each line. The string’s width need not be the same as the width of the rectangle. If the string’s width is less, the text after the rectangle shifts left; if the string is wider than the rectangle, the text after the rectangle shifts right.

The command M-x string-insert-rectangle is similar to string-rectangle, but inserts the string on each line, shifting the original text to the right.

The command C-x SPC (rectangle-mark-mode) toggles whether the region-rectangle or the standard region is highlighted (first activating the region if necessary). When this mode is enabled, commands that resize the region (C-f, C-n etc.) do so in a rectangular fashion, and killing and yanking operate on the rectangle. See Killing and Moving Text. The mode persists only as long as the region is active.

The region-rectangle works only when the mark is active. In particular, when Transient Mark mode is off (see Disabling Transient Mark Mode), in addition to typing C-x SPC you will need to activate the mark.

Unlike the standard region, the region-rectangle can have its corners extended past the end of buffer, or inside stretches of white space that point normally cannot enter, like in the middle of a TAB character.

When the region is active (see The Mark and the Region) and in rectangle-mark-mode, C-x C-x runs the command rectangle-exchange-point-and-mark, which cycles between the four corners of the region-rectangle. This comes in handy if you want to modify the dimensions of the region-rectangle before invoking an operation on the marked text.


13.6 CUA Bindings

The command M-x cua-mode sets up key bindings that are compatible with the Common User Access (CUA) system used in many other applications.

When CUA mode is enabled, the keys C-x, C-c, C-v, and C-z invoke commands that cut (kill), copy, paste (yank), and undo respectively. The C-x and C-c keys perform cut and copy only if the region is active. Otherwise, they still act as prefix keys, so that standard Emacs commands like C-x C-c still work. Note that this means the variable mark-even-if-inactive has no effect for C-x and C-c (see Operating on the Region).

To enter an Emacs command like C-x C-f while the mark is active, use one of the following methods: either hold Shift together with the prefix key, e.g., S-C-x C-f, or quickly type the prefix key twice, e.g., C-x C-x C-f.

To disable the overriding of standard Emacs binding by CUA mode, while retaining the other features of CUA mode described below, set the variable cua-enable-cua-keys to nil.

CUA mode by default activates Delete-Selection mode (see Mouse Commands for Editing) so that typed text replaces the active region. To use CUA without this behavior, set the variable cua-delete-selection to nil.

CUA mode provides enhanced rectangle support with visible rectangle highlighting. Use C-RET to start a rectangle, extend it using the movement commands, and cut or copy it using C-x or C-c. RET moves the cursor to the next (clockwise) corner of the rectangle, so you can easily expand it in any direction. Normal text you type is inserted to the left or right of each line in the rectangle (on the same side as the cursor).

You can use this rectangle support without activating CUA by calling the cua-rectangle-mark-mode command. There’s also the standard command rectangle-mark-mode, see Rectangles.

With CUA you can easily copy text and rectangles into and out of registers by providing a one-digit numeric prefix to the kill, copy, and yank commands, e.g., C-1 C-c copies the region into register 1, and C-2 C-v yanks the contents of register 2.

CUA mode also has a global mark feature which allows easy moving and copying of text between buffers. Use C-S-SPC to toggle the global mark on and off. When the global mark is on, all text that you kill or copy is automatically inserted at the global mark, and text you type is inserted at the global mark rather than at the current position.

For example, to copy words from various buffers into a word list in a given buffer, set the global mark in the target buffer, then navigate to each of the words you want in the list, mark it (e.g., with S-M-f), copy it to the list with C-c or M-w, and insert a newline after the word in the target list by pressing RET.


14 Registers

Emacs registers are compartments where you can save text, rectangles, positions, and other things for later use. Once you save text or a rectangle in a register, you can copy it into the buffer once or many times; once you save a position in a register, you can jump back to that position once or many times.

Each register has a name that consists of a single character, which we will denote by r; r can be a letter (such as ‘a’) or a number (such as ‘1’); case matters, so register ‘a’ is not the same as register ‘A’. You can also set a register in non-alphanumeric characters, for instance ‘*’ or ‘C-d’. Note, it’s not possible to set a register in ‘C-g’ or ‘ESC’, because these keys are reserved for quitting (see Quitting and Aborting).

A register can store a position, a piece of text, a rectangle, a number, a window or frame configuration, a buffer name, or a file name, but only one thing at any given time. Whatever you store in a register remains there until you store something else in that register. To see what register r contains, use M-x view-register:

M-x view-register RET r

Display a description of what register r contains.

All of the commands that prompt for a register will display a preview window that lists the existing registers (if there are any) after a short delay. To change the length of the delay, customize register-preview-delay. To prevent this display, set that option to nil. You can explicitly request a preview window by pressing C-h or F1.

Bookmarks record files and positions in them, so you can return to those positions when you look at the file again. Bookmarks are similar in spirit to registers, so they are also documented in this chapter.


14.1 Saving Positions in Registers

C-x r SPC r

Record the position of point and the current buffer in register r (point-to-register).

C-x r j r

Jump to the position and buffer saved in register r (jump-to-register).

Typing C-x r SPC (point-to-register), followed by a character r, saves both the position of point and the current buffer in register r. The register retains this information until you store something else in it.

The command C-x r j r switches to the buffer recorded in register r, pushes a mark, and moves point to the recorded position. (The mark is not pushed if point was already at the recorded position, or in successive calls to the command.) The contents of the register are not changed, so you can jump to the saved position any number of times.

If you use C-x r j to go to a saved position, but the buffer it was saved from has been killed, C-x r j tries to create the buffer again by visiting the same file. Of course, this works only for buffers that were visiting files.


14.2 Saving Text in Registers

When you want to insert a copy of the same piece of text several times, it may be inconvenient to yank it from the kill ring, since each subsequent kill moves that entry further down the ring. An alternative is to store the text in a register and later retrieve it.

C-x r s r

Copy region into register r (copy-to-register).

C-x r i r

Insert text from register r (insert-register).

M-x append-to-register RET r

Append region to text in register r.

When register r contains text, you can use C-x r + (increment-register) to append to that register. Note that command C-x r + behaves differently if r contains a number. See Keeping Numbers in Registers.

M-x prepend-to-register RET r

Prepend region to text in register r.

C-x r s r stores a copy of the text of the region into the register named r. If the mark is inactive, Emacs first reactivates the mark where it was last set. The mark is deactivated at the end of this command. See The Mark and the Region. C-u C-x r s r, the same command with a prefix argument, copies the text into register r and deletes the text from the buffer as well; you can think of this as moving the region text into the register.

M-x append-to-register RET r appends the copy of the text in the region to the text already stored in the register named r. If invoked with a prefix argument, it deletes the region after appending it to the register. The command prepend-to-register is similar, except that it prepends the region text to the text in the register instead of appending it.

When you are collecting text using append-to-register and prepend-to-register, you may want to separate individual collected pieces using a separator. In that case, configure a register-separator and store the separator text in to that register. For example, to get double newlines as text separator during the collection process, you can use the following setting.

(setq register-separator ?+)
(set-register register-separator "\n\n")

C-x r i r inserts in the buffer the text from register r. Normally it leaves point after the text and sets the mark before, without activating it. With a prefix argument, it instead puts point before the text and the mark after.


14.3 Saving Rectangles in Registers

A register can contain a rectangle instead of linear text. See Rectangles, for basic information on how to specify a rectangle in the buffer.

C-x r r r

Copy the region-rectangle into register r (copy-rectangle-to-register). With prefix argument, delete it as well.

C-x r i r

Insert the rectangle stored in register r (if it contains a rectangle) (insert-register).

The C-x r i r (insert-register) command, previously documented in Saving Text in Registers, inserts a rectangle rather than a text string, if the register contains a rectangle.


14.4 Saving Window and Frame Configurations in Registers

You can save the window configuration of the selected frame in a register, or even the configuration of all windows in all frames, and restore the configuration later. See Convenience Features for Window Handling, for information about window configurations.

C-x r w r

Save the state of the selected frame’s windows in register r (window-configuration-to-register).

C-x r f r

Save the state of all frames, including all their windows (a.k.a. frameset), in register r (frameset-to-register).

Use C-x r j r to restore a window or frame configuration. This is the same command used to restore a cursor position. When you restore a frame configuration, any existing frames not included in the configuration become invisible. If you wish to delete these frames instead, use C-u C-x r j r.


14.5 Keeping Numbers in Registers

There are commands to store a number in a register, to insert the number in the buffer in decimal, and to increment it. These commands can be useful in keyboard macros (see Keyboard Macros).

C-u number C-x r n r

Store number into register r (number-to-register).

C-u number C-x r + r

If r contains a number, increment the number in that register by number. Note that command C-x r + (increment-register) behaves differently if r contains text. See Saving Text in Registers.

C-x r i r

Insert the number from register r into the buffer.

C-x r i is the same command used to insert any other sort of register contents into the buffer. C-x r + with no numeric argument increments the register value by 1; C-x r n with no numeric argument stores zero in the register.


14.6 Keeping File and Buffer Names in Registers

If you visit certain file names frequently, you can visit them more conveniently if you put their names in registers. Here’s the Lisp code used to put a file name into register r:

(set-register r '(file . name))

For example,

(set-register ?z '(file . "/gd/gnu/emacs/19.0/src/ChangeLog"))

puts the file name shown in register ‘z’.

To visit the file whose name is in register r, type C-x r j r. (This is the same command used to jump to a position or restore a frame configuration.)

Similarly, if there are certain buffers you visit frequently, you can put their names in registers. For instance, if you visit the ‘*Messages*’ buffer often, you can use the following snippet to put that buffer into the ‘m’ register:

(set-register ?m '(buffer . "*Messages*"))

To switch to the buffer whose name is in register r, type C-x r j r.


14.7 Keyboard Macro Registers

If you need to execute a keyboard macro (see Keyboard Macros) frequently, it is more convenient to put it in a register or save it (see Naming and Saving Keyboard Macros). C-x C-k x r (kmacro-to-register) stores the last keyboard macro in register r.

To execute the keyboard macro in register r, type C-x r j r. (This is the same command used to jump to a position or restore a frameset.)


14.8 Bookmarks

Bookmarks are somewhat like registers in that they record positions you can jump to. Unlike registers, they have long names, and they persist automatically from one Emacs session to the next. The prototypical use of bookmarks is to record where you were reading in various files.

C-x r m RET

Set the bookmark for the visited file, at point.

C-x r m bookmark RET

Set the bookmark named bookmark at point (bookmark-set).

C-x r M bookmark RET

Like C-x r m, but don’t overwrite an existing bookmark.

C-x r b bookmark RET

Jump to the bookmark named bookmark (bookmark-jump).

C-x r l

List all bookmarks (list-bookmarks).

M-x bookmark-save

Save all the current bookmark values in the default bookmark file.

To record the current position in the visited file, use the command C-x r m, which sets a bookmark using the visited file name as the default for the bookmark name. If you name each bookmark after the file it points to, then you can conveniently revisit any of those files with C-x r b, and move to the position of the bookmark at the same time.

The command C-x r M (bookmark-set-no-overwrite) works like C-x r m, but it signals an error if the specified bookmark already exists, instead of overwriting it.

To display a list of all your bookmarks in a separate buffer, type C-x r l (list-bookmarks). If you switch to that buffer, you can use it to edit your bookmark definitions or annotate the bookmarks. Type C-h m in the bookmark buffer for more information about its special editing commands.

When you kill Emacs, Emacs saves your bookmarks, if you have changed any bookmark values. You can also save the bookmarks at any time with the M-x bookmark-save command. Bookmarks are saved to the file ~/.emacs.d/bookmarks (for compatibility with older versions of Emacs, if you have a file named ~/.emacs.bmk, that is used instead). The bookmark commands load your default bookmark file automatically. This saving and loading is how bookmarks persist from one Emacs session to the next.

If you set the variable bookmark-save-flag to 1, each command that sets a bookmark will also save your bookmarks; this way, you don’t lose any bookmark values even if Emacs crashes. The value, if a number, says how many bookmark modifications should go by between saving. If you set this variable to nil, Emacs only saves bookmarks if you explicitly use M-x bookmark-save.

The variable bookmark-default-file specifies the file in which to save bookmarks by default.

If you set the variable bookmark-use-annotations to t, setting a bookmark will query for an annotation. If a bookmark has an annotation, it is automatically shown in a separate window when you jump to the bookmark.

Bookmark position values are saved with surrounding context, so that bookmark-jump can find the proper position even if the file is modified slightly. The variable bookmark-search-size says how many characters of context to record on each side of the bookmark’s position. (In buffers that are visiting encrypted files, no context is saved in the bookmarks file no matter the value of this variable.)

Here are some additional commands for working with bookmarks:

M-x bookmark-load RET filename RET

Load a file named filename that contains a list of bookmark values. You can use this command, as well as bookmark-write, to work with other files of bookmark values in addition to your default bookmark file.

M-x bookmark-write RET filename RET

Save all the current bookmark values in the file filename.

M-x bookmark-delete RET bookmark RET

Delete the bookmark named bookmark.

M-x bookmark-insert-location RET bookmark RET

Insert in the buffer the name of the file that bookmark bookmark points to.

M-x bookmark-insert RET bookmark RET

Insert in the buffer the contents of the file that bookmark bookmark points to.


15 Controlling the Display

Since only part of a large buffer fits in the window, Emacs has to show only a part of it. This chapter describes commands and variables that let you specify which part of the text you want to see, and how the text is displayed.


15.1 Scrolling

If a window is too small to display all the text in its buffer, it displays only a portion of it. Scrolling commands change which portion of the buffer is displayed.

Scrolling forward or up advances the portion of the buffer displayed in the window; equivalently, it moves the buffer text upwards relative to the window. Scrolling backward or down displays an earlier portion of the buffer, and moves the text downwards relative to the window.

In Emacs, scrolling up or down refers to the direction that the text moves in the window, not the direction that the window moves relative to the text. This terminology was adopted by Emacs before the modern meaning of “scrolling up” and “scrolling down” became widespread. Hence, the strange result that PageDown scrolls up in the Emacs sense.

The portion of a buffer displayed in a window always contains point. If you move point past the bottom or top of the window, scrolling occurs automatically to bring it back onscreen (see Automatic Scrolling). You can also scroll explicitly with these commands:

C-v
PageDown
next

Scroll forward by nearly a full window (scroll-up-command).

M-v
PageUp
prior

Scroll backward (scroll-down-command).

C-v (scroll-up-command) scrolls forward by nearly the whole window height. The effect is to take the two lines at the bottom of the window and put them at the top, followed by lines that were not previously visible. If point was in the text that scrolled off the top, it ends up on the window’s new topmost line. The PageDown (or next) key is equivalent to C-v.

M-v (scroll-down-command) scrolls backward in a similar way. The PageUp (or prior) key is equivalent to M-v.

The number of lines of overlap left by these scroll commands is controlled by the variable next-screen-context-lines, whose default value is 2. You can supply the commands with a numeric prefix argument, n, to scroll by n lines; Emacs attempts to leave point unchanged, so that the text and point move up or down together. C-v with a negative argument is like M-v and vice versa.

By default, these commands signal an error (by beeping or flashing the screen) if no more scrolling is possible, because the window has reached the beginning or end of the buffer. If you change the variable scroll-error-top-bottom to t, these commands move point to the farthest possible position. If point is already there, the commands signal an error.

Some users like scroll commands to keep point at the same screen position, so that scrolling back to the same screen conveniently returns point to its original position. You can enable this behavior via the variable scroll-preserve-screen-position. If the value is t, Emacs adjusts point to keep the cursor at the same screen position whenever a scroll command moves it off-window, rather than moving it to the topmost or bottommost line. With any other non-nil value, Emacs adjusts point this way even if the scroll command leaves point in the window. This variable affects all the scroll commands documented in this section, as well as scrolling with the mouse wheel (see Mouse Commands for Editing); in general, it affects any command that has a non-nil scroll-command property. See Property Lists in The Emacs Lisp Reference Manual. The same property also causes Emacs not to exit incremental search when one of these commands is invoked and isearch-allow-scroll is non-nil (see Not Exiting Incremental Search).

Sometimes, particularly when you hold down keys such as C-v and M-v, activating keyboard auto-repeat, Emacs fails to keep up with the rapid rate of scrolling requested; the display doesn’t update and Emacs can become unresponsive to input for quite a long time. You can counter this sluggishness by setting the variable fast-but-imprecise-scrolling to a non-nil value. This instructs the scrolling commands not to fontify (see Font Lock mode) any unfontified text they scroll over, instead to assume it has the default face. This can cause Emacs to scroll to somewhat wrong buffer positions when the faces in use are not all the same size, even with single (i.e., without auto-repeat) scrolling operations.

As an alternative to setting fast-but-imprecise-scrolling you might prefer to enable jit-lock deferred fontification (see Font Lock mode). To do this, customize jit-lock-defer-time to a small positive number such as 0.25, or even 0.1 if you type quickly. This gives you less jerky scrolling when you hold down C-v, but the window contents after any action which scrolls into a fresh portion of the buffer will be momentarily unfontified.

Finally, a third alternative to these variables is redisplay-skip-fontification-on-input. If this variable is non-nil, skip some fontifications if there’s input pending. This usually does not affect the display because redisplay is completely skipped anyway if input was pending, but it can make scrolling smoother by avoiding unnecessary fontification.

The commands M-x scroll-up and M-x scroll-down behave similarly to scroll-up-command and scroll-down-command, except they do not obey scroll-error-top-bottom. Prior to Emacs 24, these were the default commands for scrolling up and down. The commands M-x scroll-up-line and M-x scroll-down-line scroll the current window by one line at a time. If you intend to use any of these commands, you might want to give them key bindings (see Rebinding Keys in Your Init File).


15.2 Recentering

C-l

Scroll the selected window so the current line is the center-most text line; on subsequent consecutive invocations, make the current line the top line, the bottom line, and so on in cyclic order. Possibly redisplay the screen too (recenter-top-bottom).

C-M-S-l

Scroll the other window; this is equivalent to C-l acting on the other window.

M-x recenter

Scroll the selected window so the current line is the center-most text line. Possibly redisplay the screen too.

C-M-l

Scroll heuristically to bring useful information onto the screen (reposition-window).

The C-l (recenter-top-bottom) command recenters the selected window, scrolling it so that the current screen line is exactly in the center of the window, or as close to the center as possible.

Typing C-l twice in a row (C-l C-l) scrolls the window so that point is on the topmost screen line. Typing a third C-l scrolls the window so that point is on the bottom-most screen line. Each successive C-l cycles through these three positions.

You can change the cycling order by customizing the list variable recenter-positions. Each list element should be the symbol top, middle, or bottom, or a number; an integer means to move the line to the specified screen line, while a floating-point number between 0.0 and 1.0 specifies a percentage of the screen space from the top of the window. The default, (middle top bottom), is the cycling order described above. Furthermore, if you change the variable scroll-margin to a non-zero value n, C-l always leaves at least n screen lines between point and the top or bottom of the window (see Automatic Scrolling).

You can also give C-l a prefix argument. A plain prefix argument, C-u C-l, simply recenters the line showing point. A positive argument n moves line showing point n lines down from the top of the window. An argument of zero moves point’s line to the top of the window. A negative argument −n moves point’s line n lines from the bottom of the window. When given an argument, C-l does not clear the screen or cycle through different screen positions.

If the variable recenter-redisplay has a non-nil value, each invocation of C-l also clears and redisplays the screen; the special value tty (the default) says to do this on text-terminal frames only. Redisplaying is useful in case the screen becomes garbled for any reason (see Garbage on the Screen).

The more primitive command M-x recenter behaves like recenter-top-bottom, but does not cycle among screen positions.

C-M-l (reposition-window) scrolls the current window heuristically in a way designed to get useful information onto the screen. For example, in a Lisp file, this command tries to get the entire current defun onto the screen if possible.


15.3 Automatic Scrolling

Emacs performs automatic scrolling when point moves out of the visible portion of the text. Normally, automatic scrolling centers point vertically in the window, but there are several ways to alter this behavior.

If you set scroll-conservatively to a small number n, then moving point just a little off the screen (no more than n lines) causes Emacs to scroll just enough to bring point back on screen; if doing so fails to make point visible, Emacs scrolls just far enough to center point in the window. If you set scroll-conservatively to a large number (larger than 100), automatic scrolling never centers point, no matter how far point moves; Emacs always scrolls text just enough to bring point into view, either at the top or bottom of the window depending on the scroll direction. By default, scroll-conservatively is 0, which means to always center point in the window. This said, in minibuffer windows, scrolling is always conservative by default because scroll-minibuffer-conservatively is non-nil, which takes precedence over scroll-conservatively.

Another way to control automatic scrolling is to customize the variable scroll-step. Its value determines the number of lines by which to automatically scroll, when point moves off the screen. If scrolling by that number of lines fails to bring point back into view, point is centered instead. The default value is zero, which (by default) causes point to always be centered after scrolling.

A third way to control automatic scrolling is to customize the variables scroll-up-aggressively and scroll-down-aggressively, which directly specify the vertical position of point after scrolling. The value of scroll-up-aggressively should be either nil (the default), or a floating point number f between 0 and 1. The latter means that when point goes below the bottom window edge (i.e., scrolling forward), Emacs scrolls the window so that point is f parts of the window height from the bottom window edge. Thus, larger f means more aggressive scrolling: more new text is brought into view. The default value, nil, is equivalent to 0.5.

Likewise, scroll-down-aggressively is used when point goes above the top window edge (i.e., scrolling backward). The value specifies how far point should be from the top margin of the window after scrolling. Thus, as with scroll-up-aggressively, a larger value is more aggressive.

Note that the variables scroll-conservatively, scroll-step, and scroll-up-aggressively / scroll-down-aggressively control automatic scrolling in contradictory ways. Therefore, you should pick no more than one of these methods to customize automatic scrolling. In case you customize multiple variables, the order of priority is: scroll-conservatively, then scroll-step, and finally scroll-up-aggressively / scroll-down-aggressively.

The variable scroll-margin restricts how close point can come to the top or bottom of a window (even if aggressive scrolling specifies a fraction f that is larger than the window portion between the top and the bottom margins). Its value is a number of screen lines; if point comes within that many lines of the top or bottom of the window, Emacs performs automatic scrolling. By default, scroll-margin is 0. The effective margin size is limited to a quarter of the window height by default, but this limit can be increased up to half (or decreased down to zero) by customizing maximum-scroll-margin.


15.4 Horizontal Scrolling

Horizontal scrolling means shifting all the lines sideways within a window, so that some of the text near the left margin is not displayed. When the text in a window is scrolled horizontally, text lines are truncated rather than continued (see Line Truncation). If a window shows truncated lines, Emacs performs automatic horizontal scrolling whenever point moves off the left or right edge of the screen. By default, all the lines in the window are scrolled horizontally together, but if you set the variable auto-hscroll-mode to the special value of current-line, only the line showing the cursor will be scrolled. To disable automatic horizontal scrolling entirely, set the variable auto-hscroll-mode to nil. Note that when the automatic horizontal scrolling is turned off, if point moves off the edge of the screen, the cursor disappears to indicate that. (On text terminals, the cursor is left at the edge instead.)

The variable hscroll-margin controls how close point can get to the window’s left and right edges before automatic scrolling occurs. It is measured in columns. For example, if the value is 5, then moving point within 5 columns of an edge causes horizontal scrolling away from that edge.

The variable hscroll-step determines how many columns to scroll the window when point gets too close to the edge. Zero, the default value, means to center point horizontally within the window. A positive integer value specifies the number of columns to scroll by. A floating-point number (whose value should be between 0 and 1) specifies the fraction of the window’s width to scroll by.

You can also perform explicit horizontal scrolling with the following commands:

C-x <

Scroll text in current window to the left (scroll-left).

C-x >

Scroll to the right (scroll-right).

C-x < (scroll-left) scrolls text in the selected window to the left by the full width of the window, less two columns. (In other words, the text in the window moves left relative to the window.) With a numeric argument n, it scrolls by n columns.

If the text is scrolled to the left, and point moves off the left edge of the window, the cursor will freeze at the left edge of the window, until point moves back to the displayed portion of the text. This is independent of the current setting of auto-hscroll-mode, which, for text scrolled to the left, only affects the behavior at the right edge of the window.

C-x > (scroll-right) scrolls similarly to the right. The window cannot be scrolled any farther to the right once it is displayed normally, with each line starting at the window’s left margin; attempting to do so has no effect. This means that you don’t have to calculate the argument precisely for C-x >; any sufficiently large argument will restore the normal display.

If you use those commands to scroll a window horizontally, that sets a lower bound for automatic horizontal scrolling. Automatic scrolling will continue to scroll the window, but never farther to the right than the amount you previously set by scroll-left. When auto-hscroll-mode is set to current-line, all the lines other than the one showing the cursor will be scrolled by that minimal amount.


15.5 Narrowing

Narrowing means focusing in on some portion of the buffer, making the rest temporarily inaccessible. The portion which you can still get to is called the accessible portion. Canceling the narrowing, which makes the entire buffer once again accessible, is called widening. The bounds of narrowing in effect in a buffer are called the buffer’s restriction.

Narrowing can make it easier to concentrate on a single subroutine or paragraph by eliminating clutter. It can also be used to limit the range of operation of a replace command or repeating keyboard macro.

C-x n n

Narrow down to between point and mark (narrow-to-region).

C-x n w

Widen to make the entire buffer accessible again (widen).

C-x n p

Narrow down to the current page (narrow-to-page).

C-x n d

Narrow down to the current defun (narrow-to-defun).

When you have narrowed down to a part of the buffer, that part appears to be all there is. You can’t see the rest, you can’t move into it (motion commands won’t go outside the accessible part), you can’t change it in any way. However, it is not gone, and if you save the file all the inaccessible text will be saved. The word ‘Narrow’ appears in the mode line whenever narrowing is in effect.

The primary narrowing command is C-x n n (narrow-to-region). It sets the current buffer’s restrictions so that the text in the current region remains accessible, but all text before the region or after the region is inaccessible. Point and mark do not change.

Alternatively, use C-x n p (narrow-to-page) to narrow down to the current page. See Pages, for the definition of a page. C-x n d (narrow-to-defun) narrows down to the defun containing point (see Top-Level Definitions, or Defuns).

The way to cancel narrowing is to widen with C-x n w (widen). This makes all text in the buffer accessible again.

You can get information on what part of the buffer you are narrowed down to using the C-x = command. See Cursor Position Information.

Because narrowing can easily confuse users who do not understand it, narrow-to-region is normally a disabled command. Attempting to use this command asks for confirmation and gives you the option of enabling it; if you enable the command, confirmation will no longer be required for it. See Disabling Commands.


15.6 View Mode

View mode is a minor mode that lets you scan a buffer by sequential screenfuls. It provides commands for scrolling through the buffer conveniently but not for changing it. Apart from the usual Emacs cursor motion commands, you can type SPC to scroll forward one windowful, S-SPC or DEL to scroll backward, and s to start an incremental search.

Typing q (View-quit) disables View mode, and switches back to the buffer and position before View mode was enabled. Typing e (View-exit) disables View mode, keeping the current buffer and position.

M-x view-buffer prompts for an existing Emacs buffer, switches to it, and enables View mode. M-x view-file prompts for a file and visits it with View mode enabled.


15.7 Follow Mode

Follow mode is a minor mode that makes two windows, both showing the same buffer, scroll as a single tall virtual window. To use Follow mode, go to a frame with just one window, split it into two side-by-side windows using C-x 3, and then type M-x follow-mode. From then on, you can edit the buffer in either of the two windows, or scroll either one; the other window follows it.

In Follow mode, if you move point outside the portion visible in one window and into the portion visible in the other window, that selects the other window—again, treating the two as if they were parts of one large window.

To turn off Follow mode, type M-x follow-mode a second time.


15.8 Text Faces

Emacs can display text in several different styles, called faces. Each face can specify various face attributes, such as the font, height, weight, slant, foreground and background color, and underlining or overlining. Most major modes assign faces to the text automatically, via Font Lock mode. See Font Lock mode, for more information about how these faces are assigned.

To see what faces are currently defined, and what they look like, type M-x list-faces-display. With a prefix argument, this prompts for a regular expression, and displays only faces with names matching that regular expression (see Syntax of Regular Expressions).

It’s possible for a given face to look different in different frames. For instance, some text terminals do not support all face attributes, particularly font, height, and width, and some support a limited range of colors. In addition, most Emacs faces are defined so that their attributes are different on light and dark frame backgrounds, for reasons of legibility. By default, Emacs automatically chooses which set of face attributes to display on each frame, based on the frame’s current background color. However, you can override this by giving the variable frame-background-mode a non-nil value. A value of dark makes Emacs treat all frames as if they have a dark background, whereas a value of light makes it treat all frames as if they have a light background.

You can customize a face to alter its attributes, and save those customizations for future Emacs sessions. See Customizing Faces, for details.

The default face is the default for displaying text, and all of its attributes are specified. Its background color is also used as the frame’s background color. See Colors for Faces.

Another special face is the cursor face. On graphical displays, the background color of this face is used to draw the text cursor. None of the other attributes of this face have any effect; the foreground color for text under the cursor is taken from the background color of the underlying text. On text terminals, the appearance of the text cursor is determined by the terminal, not by the cursor face.

You can also use X resources to specify attributes of any particular face. See X Resources.

Emacs can display variable-width fonts, but some Emacs commands, particularly indentation commands, do not account for variable character display widths. Therefore, we recommend not using variable-width fonts for most faces, particularly those assigned by Font Lock mode.


15.9 Colors for Faces

Faces can have various foreground and background colors. When you specify a color for a face—for instance, when customizing the face (see Customizing Faces)—you can use either a color name or an RGB triplet.

15.9.1 Color Names

A color name is a pre-defined name, such as ‘dark orange’ or ‘medium sea green’. To view a list of color names, type M-x list-colors-display. To control the order in which colors are shown, customize list-colors-sort. If you run this command on a graphical display, it shows the full range of color names known to Emacs (these are the standard X11 color names, defined in X’s rgb.txt file). If you run the command on a text terminal, it shows only a small subset of colors that can be safely displayed on such terminals. However, Emacs understands X11 color names even on text terminals; if a face is given a color specified by an X11 color name, it is displayed using the closest-matching terminal color.

15.9.2 RGB Triplets

An RGB triplet is a string of the form ‘#RRGGBB’. Each of the primary color components is represented by a hexadecimal number between ‘00’ (intensity 0) and ‘FF’ (the maximum intensity). It is also possible to use one, three, or four hex digits for each component, so ‘red’ can be represented as ‘#F00’, ‘#fff000000’, or ‘#ffff00000000’. The components must have the same number of digits. For hexadecimal values A to F, either upper or lower case are acceptable.

The M-x list-colors-display command also shows the equivalent RGB triplet for each named color. For instance, ‘medium sea green’ is equivalent to ‘#3CB371’.

You can change the foreground and background colors of a face with M-x set-face-foreground and M-x set-face-background. These commands prompt in the minibuffer for a face name and a color, with completion, and then set that face to use the specified color. They affect the face colors on all frames, but their effects do not persist for future Emacs sessions, unlike using the customization buffer or X resources. You can also use frame parameters to set foreground and background colors for a specific frame; See Frame Parameters.


15.10 Standard Faces

Here are the standard faces for specifying text appearance. You can apply them to specific text when you want the effects they produce.

default

This face is used for ordinary text that doesn’t specify any face. Its background color is used as the frame’s background color.

bold

This face uses a bold variant of the default font.

italic

This face uses an italic variant of the default font.

bold-italic

This face uses a bold italic variant of the default font.

underline

This face underlines text.

fixed-pitch

This face forces use of a fixed-width font. It’s reasonable to customize this face to use a different fixed-width font, if you like, but you should not make it a variable-width font.

fixed-pitch-serif

This face is like fixed-pitch, except the font has serifs and looks more like traditional typewriting.

variable-pitch

This face forces use of a variable-width (i.e., proportional) font. The font size picked for this face matches the font picked for the default (usually fixed-width) font.

variable-pitch-text

This is like the variable-pitch face (from which it inherits), but is slightly larger. A proportional font of the same height as a monospace font usually appears visually smaller, and can therefore be harder to read. When displaying longer texts, this face can be a good choice over the (slightly smaller) variable-pitch face.

shadow

This face is used for making the text less noticeable than the surrounding ordinary text. Usually this can be achieved by using shades of gray in contrast with either black or white default foreground color.

Here’s an incomplete list of faces used to highlight parts of the text temporarily for specific purposes. (Many other modes define their own faces for this purpose.)

highlight

This face is used for text highlighting in various contexts, such as when the mouse cursor is moved over a hyperlink.

isearch

This face is used to highlight the current Isearch match (see Incremental Search).

query-replace

This face is used to highlight the current Query Replace match (see Replacement Commands).

lazy-highlight

This face is used to highlight lazy matches for Isearch and Query Replace (matches other than the current one).

region

This face is used for displaying an active region (see The Mark and the Region). When Emacs is built with GTK+ support, its colors are taken from the current GTK+ theme.

secondary-selection

This face is used for displaying a secondary X selection (see Secondary Selection).

trailing-whitespace

The face for highlighting excess spaces and tabs at the end of a line when show-trailing-whitespace is non-nil (see Useless Whitespace).

escape-glyph

The face for displaying control characters and escape sequences (see How Text Is Displayed).

homoglyph

The face for displaying lookalike characters, i.e., characters that look like but are not the characters being represented (see How Text Is Displayed).

nobreak-space

The face for displaying no-break space characters (see How Text Is Displayed).

nobreak-hyphen

The face for displaying no-break hyphen characters (see How Text Is Displayed).

The following faces control the appearance of parts of the Emacs frame:

mode-line

This is the base face used for the mode lines, as well as header lines and for menu bars when toolkit menus are not used. By default, it’s drawn with shadows for a raised effect on graphical displays, and drawn as the inverse of the default face on text terminals.

The mode-line-active and mode-line-inactive faces (which are the ones used on the mode lines) inherit from this face.

mode-line-active

Like mode-line, but used for the mode line of the currently selected window. This face inherits from mode-line, so changes in that face affect mode lines in all windows.

mode-line-inactive

Like mode-line, but used for mode lines of the windows other than the selected one (if mode-line-in-non-selected-windows is non-nil). This face inherits from mode-line, so changes in that face affect mode lines in all windows.

mode-line-highlight

Like highlight, but used for mouse-sensitive portions of text on mode lines. Such portions of text typically pop up tooltips (see Tooltips) when the mouse pointer hovers above them.

mode-line-buffer-id

This face is used for buffer identification parts in the mode line.

header-line

Similar to mode-line for a window’s header line, which appears at the top of a window just as the mode line appears at the bottom. Most windows do not have a header line—only some special modes, such Info mode, create one.

header-line-highlight

Similar to highlight and mode-line-highlight, but used for mouse-sensitive portions of text on header lines. This is a separate face because the header-line face might be customized in a way that does not interact well with highlight.

tab-line

Similar to mode-line for a window’s tab line, which appears at the top of a window with tabs representing window buffers. See Window Tab Line.

vertical-border

This face is used for the vertical divider between windows on text terminals.

minibuffer-prompt

This face is used for the prompt strings displayed in the minibuffer. By default, Emacs automatically adds this face to the value of minibuffer-prompt-properties, which is a list of text properties (see Text Properties in the Emacs Lisp Reference Manual) used to display the prompt text. (This variable takes effect when you enter the minibuffer.)

fringe

The face for the fringes to the left and right of windows on graphic displays. (The fringes are the narrow portions of the Emacs frame between the text area and the window’s right and left borders.) See Window Fringes.

cursor

The :background attribute of this face specifies the color of the text cursor. See Displaying the Cursor.

tooltip

This face is used for tooltip text. By default, if Emacs is built with GTK+ support, tooltips are drawn via GTK+ and this face has no effect. See Tooltips.

mouse

This face determines the color of the mouse pointer.

The following faces likewise control the appearance of parts of the Emacs frame, but only on text terminals, or when Emacs is built on X with no toolkit support. (For all other cases, the appearance of the respective frame elements is determined by system-wide settings.)

scroll-bar

This face determines the visual appearance of the scroll bar. See Scroll Bars.

tool-bar

This face determines the color of tool bar icons. See Tool Bars.

tab-bar

This face determines the color of tab bar icons. See Tab Bars.

menu

This face determines the colors and font of Emacs’s menus. See Menu Bars.

tty-menu-enabled-face

This face is used to display enabled menu items on text-mode terminals.

tty-menu-disabled-face

This face is used to display disabled menu items on text-mode terminals.

tty-menu-selected-face

This face is used to display on text-mode terminals the menu item that would be selected if you click a mouse or press RET.


15.11 Icons

Emacs sometimes displays clickable buttons (or other informative icons), and you can customize how these look on display.

The main customization point here is the icon-preference user option. By using this, you can tell Emacs your overall preferences for icons. This is a list of icon types, and the first icon type that’s supported will be used. The supported types are:

image

Use an image for the icon.

emoji

Use a colorful emoji for the icon.

symbol

Use a monochrome symbol for the icon.

text

Use a simple text for the icon.

In addition, each individual icon can be customized with M-x customize-icon, and themes can further alter the looks of the icons.

To get a quick description of an icon, use the M-x describe-icon command.


15.12 Text Scale

To increase the font size of the default face in the current buffer, type C-x C-+ or C-x C-=. To decrease it, type C-x C--. To restore the default (global) font size, type C-x C-0. These keys are all bound to the same command, text-scale-adjust, which looks at the last key typed to determine which action to take and adjusts the font size accordingly by changing the height of the default face.

Most faces don’t have an explicit setting of the :height attribute, and thus inherit the height from the default face. Those faces are also scaled by the above commands.

Faces other than default that have an explicit setting of the :height attribute are not affected by these font size changes. The header-line face is an exception: it will be scaled even if it has an explicit setting of the :height attribute.

Similarly, scrolling the mouse wheel with the Ctrl modifier pressed, when the mouse pointer is above buffer text, will increase or decrease the font size of the affected faces, depending on the direction of the scrolling.

The final key of these commands may be repeated without the leading C-x and without the modifiers. For instance, C-x C-= C-= C-= and C-x C-= = = increase the face height by three steps. Each step scales the text height by a factor of 1.2; to change this factor, customize the variable text-scale-mode-step. A numeric argument of 0 to the text-scale-adjust command restores the default height, the same as typing C-x C-0.

Similarly, to change the sizes of the fonts globally, type C-x C-M-+, C-x C-M-=, C-x C-M-- or C-x C-M-0, or scroll the mouse wheel with both the Ctrl and Meta modifiers pressed. To enable frame resizing when the font size is changed globally, customize the variable global-text-scale-adjust-resizes-frames (see Easy Customization Interface).

The commands text-scale-increase and text-scale-decrease increase or decrease the size of the font in the current buffer, just like C-x C-+ and C-x C-- respectively. You may find it convenient to bind to these commands, rather than text-scale-adjust.

The command text-scale-set scales the size of the font in the current buffer to an absolute level specified by its prefix argument.

The above commands automatically enable the minor mode text-scale-mode if the current font scaling is other than 1, and disable it otherwise.

The command text-scale-pinch increases or decreases the text scale based on the distance between fingers on a touchpad when a pinch gesture is performed by placing two fingers on a touchpad and moving them towards or apart from each other. This is only available on some systems with supported hardware.

The command mouse-wheel-text-scale also changes the text scale. Normally, it is run when you press Ctrl while moving the mouse wheel. The text scale is increased when the wheel is moved downwards, and it is decreased when the wheel is moved upwards.


15.13 Font Lock mode

Font Lock mode is a minor mode, always local to a particular buffer, which assigns faces to (or fontifies) the text in the buffer. Each buffer’s major mode tells Font Lock mode which text to fontify; for instance, programming language modes fontify syntactically relevant constructs like comments, strings, and function names.

Font Lock mode is enabled by default in major modes that support it. To toggle it in the current buffer, type M-x font-lock-mode. A positive numeric argument unconditionally enables Font Lock mode, and a negative or zero argument disables it.

Type M-x global-font-lock-mode to toggle Font Lock mode in all buffers. To impose this setting for future Emacs sessions, customize the variable global-font-lock-mode (see Easy Customization Interface), or add the following line to your init file:

(global-font-lock-mode 0)

If you have disabled Global Font Lock mode, you can still enable Font Lock for specific major modes by adding the function font-lock-mode to the mode hooks (see Hooks). For example, to enable Font Lock mode for editing C files, you can do this:

(add-hook 'c-mode-hook 'font-lock-mode)

Font Lock mode uses several specifically named faces to do its job, including font-lock-string-face, font-lock-comment-face, and others. The easiest way to find them all is to use M-x customize-group RET font-lock-faces RET. You can then use that customization buffer to customize the appearance of these faces. See Customizing Faces.

Fontifying very large buffers can take a long time. To avoid large delays when a file is visited, Emacs initially fontifies only the visible portion of a buffer. As you scroll through the buffer, each portion that becomes visible is fontified as soon as it is displayed; this type of Font Lock is called Just-In-Time (or JIT) Lock. You can control how JIT Lock behaves, including telling it to perform fontification while idle, by customizing variables in the customization group ‘jit-lock’. See Customizing Specific Items.

The information that major modes use for determining which parts of buffer text to fontify and what faces to use can be based on several different ways of analyzing the text:

  • Search for keywords and other textual patterns based on regular expressions (see Regular Expression Search).
  • Find syntactically distinct parts of text based on built-in syntax tables (see Syntax Tables in The Emacs Lisp Reference Manual).
  • Use syntax tree produced by a full-blown parser, via a special-purpose library, such as the tree-sitter library (see Parsing Program Source in The Emacs Lisp Reference Manual), or an external program.

15.13.1 Traditional Font Lock

“Traditional” methods of providing font-lock information are based on regular-expression search and on syntactic analysis using syntax tables built into Emacs. This subsection describes the use and customization of font-lock for major modes which use these traditional methods.

You can control the amount of fontification applied by Font Lock mode by customizing the variable font-lock-maximum-decoration, for major modes that support this feature. The value of this variable should be a number (with 1 representing a minimal amount of fontification; some modes support levels as high as 3); or t, meaning “as high as possible” (the default). To be effective for a given file buffer, the customization of font-lock-maximum-decoration should be done before the file is visited; if you already have the file visited in a buffer when you customize this variable, kill the buffer and visit the file again after the customization.

You can also specify different numbers for particular major modes; for example, to use level 1 for C/C++ modes, and the default level otherwise, use the value

'((c-mode . 1) (c++-mode . 1)))

Comment and string fontification (or “syntactic” fontification) relies on analysis of the syntactic structure of the buffer text. For the sake of speed, some modes, including Lisp mode, rely on a special convention: an open-parenthesis or open-brace in the leftmost column always defines the beginning of a defun, and is thus always outside any string or comment. Therefore, you should avoid placing an open-parenthesis or open-brace in the leftmost column, if it is inside a string or comment. See Left Margin Convention, for details.

Font Lock highlighting patterns already exist for most modes, but you may want to fontify additional patterns. You can use the function font-lock-add-keywords, to add your own highlighting patterns for a particular mode. For example, to highlight ‘FIXME:’ words in C comments, use this:

(add-hook 'c-mode-hook
          (lambda ()
           (font-lock-add-keywords nil
            '(("\\<\\(FIXME\\):" 1
               font-lock-warning-face t)))))

To remove keywords from the font-lock highlighting patterns, use the function font-lock-remove-keywords. See Search-based Fontification in The Emacs Lisp Reference Manual. Alternatively, you can selectively disable highlighting due to some keywords by customizing the font-lock-ignore option, see Customizing Keywords in The Emacs Lisp Reference Manual.


15.13.2 Parser-based Font Lock

If your Emacs was built with the tree-sitter library, it can use the results of parsing the buffer text by that library for the purposes of fontification. This is usually faster and more accurate than the “traditional” methods described in the previous subsection, since the tree-sitter library provides full-blown parsers for programming languages and other kinds of formatted text which it supports. Major modes which utilize the tree-sitter library are named foo-ts-mode, with the ‘-ts-’ part indicating the use of the library. This subsection documents the Font Lock support based on the tree-sitter library.

You can control the amount of fontification applied by Font Lock mode of major modes based on tree-sitter by customizing the variable treesit-font-lock-level. Its value is a number between 1 and 4:

Level 1

This level usually fontifies only comments and function names in function definitions.

Level 2

This level adds fontification of keywords, strings, and data types.

Level 3

This is the default level; it adds fontification of assignments, numbers, etc.

Level 4

This level adds everything else that can be fontified: operators, delimiters, brackets, other punctuation, function names in function calls, property look ups, variables, etc.

What exactly constitutes each of the syntactical categories mentioned above depends on the major mode and the parser grammar used by tree-sitter for the major-mode’s language. However, in general the categories follow the conventions of the programming language or the file format supported by the major mode. The buffer-local value of the variable treesit-font-lock-feature-list holds the fontification features supported by a tree-sitter based major mode, where each sub-list shows the features provided by the corresponding fontification level.

Once you change the value of treesit-font-lock-level via M-x customize-variable (see Customizing Specific Items), it takes effect immediately in all the existing buffers and for files you visit in the future in the same session.


15.14 Interactive Highlighting

Highlight Changes mode is a minor mode that highlights the parts of the buffer that were changed most recently, by giving that text a different face. To enable or disable Highlight Changes mode, use M-x highlight-changes-mode.

Hi Lock mode is a minor mode that highlights text that matches regular expressions you specify. For example, you can use it to highlight all the references to a certain variable in a program source file, highlight certain parts in a voluminous output of some program, or highlight certain names in an article. To enable or disable Hi Lock mode, use the command M-x hi-lock-mode. To enable Hi Lock mode for all buffers, use M-x global-hi-lock-mode or place (global-hi-lock-mode 1) in your .emacs file.

Hi Lock mode works like Font Lock mode (see Font Lock mode), except that you specify explicitly the regular expressions to highlight. You can control them with the following commands. (The key bindings below that begin with C-x w are deprecated in favor of the global M-s h bindings, and will be removed in some future Emacs version.)

M-s h r regexp RET face RET
C-x w h regexp RET face RET

Highlight text that matches regexp using face face (highlight-regexp). The highlighting will remain as long as the buffer is loaded. For example, to highlight all occurrences of the word “whim” using the default face (a yellow background), type M-s h r whim RET RET. Any face can be used for highlighting, Hi Lock provides several of its own and these are pre-loaded into a list of default values. While being prompted for a face use M-n and M-p to cycle through them. A prefix numeric argument limits the highlighting to the corresponding subexpression.

Setting the option hi-lock-auto-select-face to a non-nil value causes this command (and other Hi Lock commands that read faces) to automatically choose the next face from the default list without prompting.

You can use this command multiple times, specifying various regular expressions to highlight in different ways.

M-s h u regexp RET
C-x w r regexp RET

Unhighlight regexp (unhighlight-regexp). If you invoke this from the menu, you select the expression to unhighlight from a list. If you invoke this from the keyboard, you use the minibuffer. It will show the most recently added regular expression; use M-n to show the next older expression and M-p to select the next newer expression. (You can also type the expression by hand, with completion.) When the expression you want to unhighlight appears in the minibuffer, press RET to exit the minibuffer and unhighlight it.

M-s h l regexp RET face RET
C-x w l regexp RET face RET

Highlight entire lines containing a match for regexp, using face face (highlight-lines-matching-regexp).

M-s h p phrase RET face RET
C-x w p phrase RET face RET

Highlight matches of phrase, using face face (highlight-phrase). phrase can be any regexp, but spaces will be replaced by matches to whitespace and initial lower-case letters will become case insensitive.

M-s h .
C-x w .

Highlight the symbol found near point, using the next available face (highlight-symbol-at-point).

M-s h w
C-x w b

Insert all the current highlighting regexp/face pairs into the buffer at point, with comment delimiters to prevent them from changing your program. (This key binding runs the hi-lock-write-interactive-patterns command.)

These patterns are extracted from the comments, if appropriate, if you invoke M-x hi-lock-find-patterns, or if you visit the file while Hi Lock mode is enabled (since that runs hi-lock-find-patterns).

M-s h f
C-x w i

Extract regexp/face pairs from comments in the current buffer (hi-lock-find-patterns). Thus, you can enter patterns interactively with highlight-regexp, store them into the file with hi-lock-write-interactive-patterns, edit them (perhaps including different faces for different parenthesized parts of the match), and finally use this command (hi-lock-find-patterns) to have Hi Lock highlight the edited patterns.

The variable hi-lock-file-patterns-policy controls whether Hi Lock mode should automatically extract and highlight patterns found in a file when it is visited. Its value can be nil (never highlight), ask (query the user), or a function. If it is a function, hi-lock-find-patterns calls it with the patterns as argument; if the function returns non-nil, the patterns are used. The default is ask. Note that patterns are always highlighted if you call hi-lock-find-patterns directly, regardless of the value of this variable.

Also, hi-lock-find-patterns does nothing if the current major mode’s symbol is a member of the list hi-lock-exclude-modes.


15.15 Window Fringes

On graphical displays, each Emacs window normally has narrow fringes on the left and right edges. The fringes are used to display symbols that provide information about the text in the window. You can type M-x fringe-mode to toggle display of the fringes or to modify their width. This command affects fringes in all frames; to modify fringes on the selected frame only, use M-x set-fringe-style. You can make your changes to the fringes permanent by customizing the variable fringe-mode.

The most common use of the fringes is to indicate a continuation line (see Continuation Lines). When one line of text is split into multiple screen lines, the left fringe shows a curving arrow for each screen line except the first, indicating that this is not the real beginning. The right fringe shows a curving arrow for each screen line except the last, indicating that this is not the real end. If the line’s direction is right-to-left (see Bidirectional Editing), the meanings of the curving arrows in the fringes are swapped.

The fringes indicate line truncation (see Line Truncation) with short horizontal arrows meaning there’s more text on this line which is scrolled horizontally out of view. Clicking the mouse on one of the arrows scrolls the display horizontally in the direction of the arrow.

The fringes can also indicate other things, such as buffer boundaries (see Displaying Boundaries), unused lines near the end of the window (see indicate-empty-lines), and where a program you are debugging is executing (see Running Debuggers Under Emacs).

The fringe is also used for drawing the cursor, if the current line is exactly as wide as the window and point is at the end of the line. To disable this, change the variable overflow-newline-into-fringe to nil; this causes Emacs to continue or truncate lines that are exactly as wide as the window.

If you customize fringe-mode to remove the fringes on one or both sides of the window display, the features that display on the fringe are not available. Indicators of line continuation and truncation are an exception: when fringes are not available, Emacs uses the leftmost and rightmost character cells to indicate continuation and truncation with special ASCII characters, see Continuation Lines, and Line Truncation. This reduces the width available for displaying text on each line, because the character cells used for truncation and continuation indicators are reserved for that purpose. Since buffer text can include bidirectional text, and thus both left-to-right and right-to-left paragraphs (see Bidirectional Editing), removing only one of the fringes still reserves two character cells, one on each side of the window, for truncation and continuation indicators, because these indicators are displayed on opposite sides of the window in right-to-left paragraphs.


15.16 Displaying Boundaries

Emacs can display an indication of the fill-column position (see Explicit Fill Commands). The fill-column indicator is a useful functionality especially in prog-mode and its descendants (see Major Modes) to indicate the position of a specific column that has some special meaning for formatting the source code of a program. This assumes the buffer uses a fixed-pitch font, where all the characters (with the possible exception of double-width characters) have the same width on display. If the buffer uses variable-pitch fonts, the fill-column indicators on different lines might appear unaligned.

To activate the fill-column indication display, use the minor modes display-fill-column-indicator-mode and global-display-fill-column-indicator-mode, which enable the indicator locally or globally, respectively.

Alternatively, you can set the two buffer-local variables display-fill-column-indicator and display-fill-column-indicator-character to activate the indicator and control the character used for the indication. Note that both variables must be non-nil for the indication to be displayed. (Turning on the minor mode sets both these variables.)

There are 2 buffer local variables and a face to customize this mode:

display-fill-column-indicator-column

Specifies the column number where the indicator should be set. It can take positive numerical values for the column, or the special value t, which means that the value of the variable fill-column will be used.

Any other value disables the indicator. The default value is t.

display-fill-column-indicator-character

Specifies the character used for the indicator. This character can be any valid character including Unicode ones if the font supports them. The value nil disables the indicator. When the mode is enabled through the functions display-fill-column-indicator-mode or global-display-fill-column-indicator-mode, they will use the character specified by this variable, if it is non-nil; otherwise Emacs will use the character U+2502 BOX DRAWINGS LIGHT VERTICAL, falling back to ‘|’ if U+2502 cannot be displayed.

fill-column-indicator

Specifies the face used to display the indicator. It inherits its default values from the face shadow, but without background color. To change the indicator color, you need only set the foreground color of this face.

On graphical displays, Emacs can indicate the buffer boundaries in the fringes. If you enable this feature, the first line and the last line are marked with angle images in the fringes. This can be combined with up and down arrow images which say whether it is possible to scroll the window.

The buffer-local variable indicate-buffer-boundaries controls how the buffer boundaries and window scrolling is indicated in the fringes. If the value is left or right, both angle and arrow bitmaps are displayed in the left or right fringe, respectively.

If value is an alist (see Association Lists in the Emacs Lisp Reference Manual), each element (indicator . position) specifies the position of one of the indicators. The indicator must be one of top, bottom, up, down, or t which specifies the default position for the indicators not present in the alist. The position is one of left, right, or nil which specifies not to show this indicator.

For example, ((top . left) (t . right)) places the top angle bitmap in left fringe, the bottom angle bitmap in right fringe, and both arrow bitmaps in right fringe. To show just the angle bitmaps in the left fringe, but no arrow bitmaps, use ((top . left) (bottom . left)).


15.17 Useless Whitespace

It is easy to leave unnecessary spaces at the end of a line, or empty lines at the end of a buffer, without realizing it. In most cases, this trailing whitespace has no effect, but sometimes it can be a nuisance.

You can make trailing whitespace at the end of a line visible by setting the buffer-local variable show-trailing-whitespace to t. Then Emacs displays trailing whitespace, using the face trailing-whitespace.

This feature does not apply when point is at the end of the line containing the whitespace. Strictly speaking, that is trailing whitespace nonetheless, but displaying it specially in that case looks ugly while you are typing in new text. In this special case, the location of point is enough to show you that the spaces are present.

Type M-x delete-trailing-whitespace to delete all trailing whitespace. This command deletes all extra spaces at the end of each line in the buffer, and all empty lines at the end of the buffer; to ignore the latter, change the variable delete-trailing-lines to nil. If the region is active, the command instead deletes extra spaces at the end of each line in the region.

On graphical displays, Emacs can indicate unused lines at the end of the window with a small image in the left fringe (see Window Fringes). The image appears for screen lines that do not correspond to any buffer text, so blank lines at the end of the buffer stand out because they lack this image. To enable this feature, set the buffer-local variable indicate-empty-lines to a non-nil value. You can enable or disable this feature for all new buffers by setting the default value of this variable, e.g., (setq-default indicate-empty-lines t).

Whitespace mode is a buffer-local minor mode that lets you visualize many kinds of whitespace in the buffer, by either drawing the whitespace characters with a special face or displaying them as special glyphs. To toggle this mode, type M-x whitespace-mode. The kinds of whitespace visualized are determined by the list variable whitespace-style. Individual elements in that list can be toggled on or off in the current buffer by typing M-x whitespace-toggle-options. Here is a partial list of possible elements (see the variable’s documentation for the full list):

face

Enable all visualizations which use special faces. This element has a special meaning: if it is absent from the list, none of the other visualizations take effect except space-mark, tab-mark, and newline-mark.

trailing

Highlight trailing whitespace.

tabs

Highlight tab characters.

spaces

Highlight space and non-breaking space characters.

lines

Highlight lines longer than 80 columns. To change the column limit, customize the variable whitespace-line-column.

newline

Highlight newlines.

missing-newline-at-eof

Highlight the final character if the buffer doesn’t end with a newline character.

empty

Highlight empty lines at the beginning and/or end of the buffer.

big-indent

Highlight too-deep indentation. By default any sequence of at least 4 consecutive tab characters or 32 consecutive space characters is highlighted. To change that, customize the regular expression whitespace-big-indent-regexp.

space-mark

Draw space and non-breaking characters with a special glyph.

tab-mark

Draw tab characters with a special glyph.

newline-mark

Draw newline characters with a special glyph.

Global Whitespace mode is a global minor mode that lets you visualize whitespace in all buffers. To toggle individual features, use M-x global-whitespace-toggle-options.


15.18 Selective Display

Emacs has the ability to hide lines indented more than a given number of columns. You can use this to get an overview of a part of a program.

To hide lines in the current buffer, type C-x $ (set-selective-display) with a numeric argument n. Then lines with at least n columns of indentation disappear from the screen. The only indication of their presence is that three dots (‘’) appear at the end of each visible line that is followed by one or more hidden ones.

The commands C-n and C-p move across the hidden lines as if they were not there.

The hidden lines are still present in the buffer, and most editing commands see them as usual, so you may find point in the middle of the hidden text. When this happens, the cursor appears at the end of the previous line, after the three dots. If point is at the end of the visible line, before the newline that ends it, the cursor appears before the three dots.

To make all lines visible again, type C-x $ with no argument.

If you set the variable selective-display-ellipses to nil, the three dots do not appear at the end of a line that precedes hidden lines. Then there is no visible indication of the hidden lines. This variable becomes local automatically when set.

See also Outline Mode for another way to hide part of the text in a buffer.


15.19 Optional Mode Line Features

The buffer percentage pos indicates the percentage of the buffer above the top of the window. You can additionally display the size of the buffer by typing M-x size-indication-mode to turn on Size Indication mode. The size will be displayed immediately following the buffer percentage like this:

pos of size

Here size is the human readable representation of the number of characters in the buffer, which means that ‘k’ for 10^3, ‘M’ for 10^6, ‘G’ for 10^9, etc., are used to abbreviate.

The current line number of point appears in the mode line when Line Number mode is enabled. Use the command M-x line-number-mode to turn this mode on and off; normally it is on. The line number appears after the buffer percentage pos, with the letter ‘L’ to indicate what it is.

Similarly, you can display the current column number by turning on Column Number mode with M-x column-number-mode. The column number is indicated by the letter ‘C’. However, when both of these modes are enabled, the line and column numbers are displayed in parentheses, the line number first, rather than with ‘L’ and ‘C’. For example: ‘(561,2)’. See Minor Modes, for more information about minor modes and about how to use these commands.

In Column Number mode, the displayed column number counts from zero starting at the left margin of the window. If you would prefer for the displayed column number to count from one, you may set column-number-indicator-zero-based to nil.

If you have narrowed the buffer (see Narrowing), the displayed line number is relative to the accessible portion of the buffer. Thus, it isn’t suitable as an argument to goto-line. (The command what-line shows the line number relative to the whole file.) You can use goto-line-relative command to move point to the line relative to the accessible portion of the narrowed buffer.

If the buffer is very large (larger than the value of line-number-display-limit), Emacs won’t compute the line number, because that would be too slow; therefore, the line number won’t appear on the mode-line. To remove this limit, set line-number-display-limit to nil.

Line-number computation can also be slow if the lines in the buffer are too long. For this reason, Emacs doesn’t display line numbers if the average width, in characters, of lines near point is larger than the value of line-number-display-limit-width. The default value is 200 characters.

Emacs can optionally display the time and system load in all mode lines. To enable this feature, type M-x display-time or customize the option display-time-mode. The information added to the mode line looks like this:

hh:mmPM l.ll

Here hh and mm are the hour and minute, followed always by ‘AM’ or ‘PM’. l.ll is the average number, collected for the last few minutes, of processes in the whole system that were either running or ready to run (i.e., were waiting for an available processor). (Some fields may be missing if your operating system cannot support them.) If you prefer time display in 24-hour format, set the variable display-time-24hr-format to t.

The word ‘Mail’ appears after the load level if there is mail for you that you have not read yet. On graphical displays, you can use an icon instead of ‘Mail’ by customizing display-time-use-mail-icon; this may save some space on the mode line. You can customize display-time-mail-face to make the mail indicator prominent. Use display-time-mail-file to specify the mail file to check, or set display-time-mail-directory to specify the directory to check for incoming mail (any nonempty regular file in the directory is considered to be newly arrived mail).

When running Emacs on a laptop computer, you can display the battery charge on the mode-line, by using the command display-battery-mode or customizing the variable display-battery-mode. The variable battery-mode-line-format determines the way the battery charge is displayed; the exact mode-line message depends on the operating system, and it usually shows the current battery charge as a percentage of the total charge. The functions in battery-update-functions are run after updating the mode line, and can be used to trigger actions based on the battery status.

On graphical displays, the mode line is drawn as a 3D box. If you don’t like this effect, you can disable it by customizing the mode-line face and setting its box attribute to nil. See Customizing Faces.

By default, the mode line of nonselected windows is displayed in a different face, called mode-line-inactive. Only the selected window is displayed in the mode-line face. This helps show which window is selected. When the minibuffer is selected, since it has no mode line, the window from which you activated the minibuffer has its mode line displayed using mode-line; as a result, ordinary entry to the minibuffer does not change any mode lines.

You can disable use of mode-line-inactive by setting variable mode-line-in-non-selected-windows to nil; then all mode lines are displayed in the mode-line face.

You can customize the mode line display for each of the end-of-line formats by setting each of the variables eol-mnemonic-unix, eol-mnemonic-dos, eol-mnemonic-mac, and eol-mnemonic-undecided to the strings you prefer.


15.20 How Text Is Displayed

Most characters are printing characters: when they appear in a buffer, they are displayed literally on the screen. Printing characters include ASCII numbers, letters, and punctuation characters, as well as many non-ASCII characters.

The ASCII character set contains non-printing control characters. Two of these are displayed specially: the newline character (Unicode code point U+000A) is displayed by starting a new line, while the tab character (U+0009) is displayed as a space that extends to the next tab stop column (normally every 8 columns). The number of spaces per tab is controlled by the buffer-local variable tab-width, which must have an integer value between 1 and 1000, inclusive. Note that the way the tab character in the buffer is displayed has nothing to do with the definition of TAB as a command.

Other ASCII control characters, whose codes are below U+0020 (octal 40, decimal 32), are displayed as a caret (‘^’) followed by the non-control version of the character, with the escape-glyph face. For instance, the ‘control-A’ character, U+0001, is displayed as ‘^A’.

The raw bytes with codes U+0080 (octal 200) through U+009F (octal 237) are displayed as octal escape sequences, with the escape-glyph face. For instance, character code U+0098 (octal 230) is displayed as ‘\230’. If you change the buffer-local variable ctl-arrow to nil, the ASCII control characters are also displayed as octal escape sequences instead of caret escape sequences. (You can also request that raw bytes be shown in hex, see display-raw-bytes-as-hex.)

Some non-ASCII characters have the same appearance as an ASCII space or hyphen (minus) character. Such characters can cause problems if they are entered into a buffer without your realization, e.g., by yanking; for instance, source code compilers typically do not treat non-ASCII spaces as whitespace characters. To deal with this problem, Emacs displays such characters specially: it displays U+00A0 NO-BREAK SPACE and other characters from the Unicode horizontal space class with the nobreak-space face, and it displays U+00AD SOFT HYPHEN, U+2010 HYPHEN, and U+2011 NON-BREAKING HYPHEN with the nobreak-hyphen face. To disable this, change the variable nobreak-char-display to nil. If you give this variable a non-nil and non-t value, Emacs instead displays such characters as a highlighted backslash followed by a space or hyphen.

You can customize the way any particular character code is displayed by means of a display table. See Display Tables in The Emacs Lisp Reference Manual.

On graphical displays, some characters may have no glyphs in any of the fonts available to Emacs. These glyphless characters are normally displayed as boxes containing the hexadecimal character code. Similarly, on text terminals, characters that cannot be displayed using the terminal encoding (see Coding Systems for Terminal I/O) are normally displayed as question signs. You can control the display method by customizing the variable glyphless-char-display-control. You can also customize the glyphless-char face to make these characters more prominent on display. See Glyphless Character Display in The Emacs Lisp Reference Manual, for details.

The glyphless-display-mode minor mode can be used to toggle the display of glyphless characters in the current buffer. The glyphless characters will be displayed as boxes with acronyms of their names inside.

Emacs tries to determine if the curved quotes and can be displayed on the current display. By default, if this seems to be so, then Emacs will translate the ASCII quotes (‘`’ and ‘'’), when they appear in messages and help texts, to these curved quotes. You can influence or inhibit this translation by customizing the user option text-quoting-style (see Keys in Documentation in The Emacs Lisp Reference Manual).

If the curved quotes , , , and are known to look just like ASCII characters, they are shown with the homoglyph face. Curved quotes that are known not to be displayable are shown as their ASCII approximations ‘`’, ‘'’, and ‘"’ with the homoglyph face.


15.21 Displaying the Cursor

On a text terminal, the cursor’s appearance is controlled by the terminal, largely out of the control of Emacs. Some terminals offer two different cursors: a visible static cursor, and a very visible blinking cursor. By default, Emacs uses the very visible cursor, and switches to it when you start or resume Emacs. If the variable visible-cursor is nil when Emacs starts or resumes, it uses the normal cursor.

On a graphical display, many more properties of the text cursor can be altered. To customize its color, change the :background attribute of the face named cursor (see Customizing Faces). (The other attributes of this face have no effect; the text shown under the cursor is drawn using the frame’s background color.) To change its shape, customize the buffer-local variable cursor-type; possible values are box (the default), (box . size) (box cursor becoming a hollow box under masked images larger than size pixels in either dimension), hollow (a hollow box), bar (a vertical bar), (bar . n) (a vertical bar n pixels wide), hbar (a horizontal bar), (hbar . n) (a horizontal bar n pixels tall), or nil (no cursor at all).

By default, the cursor stops blinking after 10 blinks, if Emacs does not get any input during that time; any input event restarts the count. You can customize the variable blink-cursor-blinks to control that: its value says how many times to blink without input before stopping. Setting that variable to a zero or negative value will make the cursor blink forever. To disable cursor blinking altogether, change the variable blink-cursor-mode to nil (see Easy Customization Interface), or add the line

  (blink-cursor-mode 0)

to your init file. Alternatively, you can change how the cursor looks when it blinks off by customizing the list variable blink-cursor-alist. Each element in the list should have the form (on-type . off-type); this means that if the cursor is displayed as on-type when it blinks on (where on-type is one of the cursor types described above), then it is displayed as off-type when it blinks off.

Some characters, such as tab characters, are extra wide. When the cursor is positioned over such a character, it is normally drawn with the default character width. You can make the cursor stretch to cover wide characters, by changing the variable x-stretch-cursor to a non-nil value.

The cursor normally appears in non-selected windows as a non-blinking hollow box. (For a bar cursor, it instead appears as a thinner bar.) To turn off cursors in non-selected windows, change the variable cursor-in-non-selected-windows to nil.

To make the cursor even more visible, you can use HL Line mode, a minor mode that highlights the line containing point. Use M-x hl-line-mode to enable or disable it in the current buffer. M-x global-hl-line-mode enables or disables the same mode globally.


15.22 Line Truncation

As an alternative to continuation (see Continuation Lines), Emacs can display long lines by truncation. This means that all the characters that do not fit in the width of the screen or window do not appear at all. On graphical displays, a small straight arrow in the fringe indicates truncation at either end of the line. On text terminals, this is indicated with ‘$’ signs in the rightmost and/or leftmost columns.

Horizontal scrolling automatically causes line truncation (see Horizontal Scrolling). You can explicitly enable line truncation for a particular buffer with the command C-x x t (toggle-truncate-lines). This works by locally changing the variable truncate-lines. If that variable is non-nil, long lines are truncated; if it is nil, they are continued onto multiple screen lines. Setting the variable truncate-lines in any way makes it local to the current buffer; until that time, the default value, which is normally nil, is in effect.

Since line truncation and word wrap (described in the next section) are contradictory, toggle-truncate-lines disables word wrap when it turns on line truncation.

If a split window becomes too narrow, Emacs may automatically enable line truncation. See Splitting Windows, for the variable truncate-partial-width-windows which controls this.


15.23 Visual Line Mode

Another alternative to ordinary line continuation (see Continuation Lines) is to use word wrap. Here, each long logical line is divided into two or more screen lines, or “visual lines”, like in ordinary line continuation. However, Emacs attempts to wrap the line at word boundaries near the right window edge. (If the line’s direction is right-to-left, it is wrapped at the left window edge instead.) This makes the text easier to read, as wrapping does not occur in the middle of words.

Word wrap is enabled by Visual Line mode, an optional minor mode. To turn on Visual Line mode in the current buffer, type M-x visual-line-mode; repeating this command turns it off. You can also turn on Visual Line mode using the menu bar: in the Options menu, select the ‘Line Wrapping in this Buffer’ submenu, followed by the ‘Word Wrap (Visual Line mode)’ menu item. While Visual Line mode is enabled, the mode line shows the string ‘wrap’ in the mode display. The command M-x global-visual-line-mode toggles Visual Line mode in all buffers.

Since word wrap and line truncation (described in the previous section) are contradictory, turning on visual-line-mode disables line truncation.

In Visual Line mode, some editing commands work on screen lines instead of logical lines: C-a (beginning-of-visual-line) moves to the beginning of the screen line, C-e (end-of-visual-line) moves to the end of the screen line, and C-k (kill-visual-line) kills text to the end of the screen line.

To move by logical lines, use the commands M-x next-logical-line and M-x previous-logical-line. These move point to the next logical line and the previous logical line respectively, regardless of whether Visual Line mode is enabled. If you use these commands frequently, it may be convenient to assign key bindings to them. See Rebinding Keys in Your Init File.

By default, word-wrapped lines do not display fringe indicators. Visual Line mode is often used to edit files that contain many long logical lines, so having a fringe indicator for each wrapped line would be visually distracting. You can change this by customizing the variable visual-line-fringe-indicators.

By default, Emacs only breaks lines after whitespace characters like SPC and TAB, but does not break after whitespace characters like EN QUAD. Emacs provides a minor mode called word-wrap-whitespace-mode that switches on word wrapping in the current mode, and sets up which characters to wrap lines on based on the word-wrap-whitespace-characters user option. There’s also a globalized version of that mode called global-word-wrap-whitespace-mode.

Only breaking after whitespace character produces incorrect results when CJK and Latin text are mixed together (because CJK characters don’t use whitespace to separate words). You can customize the option word-wrap-by-category to allow Emacs to break lines after any character with ‘|’ category (see Categories in the Emacs Lisp Reference Manual), which provides better support for CJK characters. Also, if this variable is set using Customize, Emacs automatically loads kinsoku.el. When kinsoku.el is loaded, Emacs respects kinsoku rules when breaking lines. That means characters with the ‘>’ category don’t appear at the beginning of a line (e.g., U+FF0C FULLWIDTH COMMA), and characters with the ‘<’ category don’t appear at the end of a line (e.g., U+300A LEFT DOUBLE ANGLE BRACKET). You can view the category set of a character using the commands char-category-set and category-set-mnemonics, or by typing C-u C-x = with point on the character and looking at the “category” section in the report. You can add categories to a character using the command modify-category-entry.


15.24 Customization of Display

This section describes variables that control miscellaneous aspects of the appearance of the Emacs screen. Beginning users can skip it.

If you want to have Emacs display line numbers for every line in the buffer, customize the buffer-local variable display-line-numbers; it is nil by default. This variable can have several different values to support various modes of line-number display:

t

Display (an absolute) line number before each non-continuation screen line that displays buffer text. If the line is a continuation line, or if the entire screen line displays a display or an overlay string, that line will not be numbered.

relative

Display relative line numbers before non-continuation lines which show buffer text. The line numbers are relative to the line showing point, so the numbers grow both up and down as lines become farther from the current line.

visual

This value causes Emacs to count lines visually: only lines actually shown on the display will be counted (disregarding any lines in invisible parts of text), and lines which wrap to consume more than one screen line will be numbered that many times. The displayed numbers are relative, as with relative value above. This is handy in modes that fold text, such as Outline mode (see Outline Mode), and when you need to move by exact number of screen lines.

anything else

Any other non-nil value is treated as t.

The command M-x display-line-numbers-mode provides a convenient way to turn on display of line numbers. This mode has a globalized variant, global-display-line-numbers-mode. The user option display-line-numbers-type controls which sub-mode of line-number display, described above, these modes will activate.

Note that line numbers are not displayed in the minibuffer and in the tooltips, even if you turn on display-line-numbers-mode globally.

When Emacs displays relative line numbers, you can control the number displayed before the current line, the line showing point. By default, Emacs displays the absolute number of the current line there, even though all the other line numbers are relative. If you customize the variable display-line-numbers-current-absolute to a nil value, the number displayed for the current line will be zero. This is handy if you don’t care about the number of the current line, and want to leave more horizontal space for text in large buffers.

In a narrowed buffer (see Narrowing) lines are normally numbered starting at the beginning of the narrowing. However, if you customize the variable display-line-numbers-widen to a non-nil value, line numbers will disregard any narrowing and will start at the first character of the buffer.

If the value of display-line-numbers-offset is non-zero, it is added to each absolute line number, and lines are counted from the beginning of the buffer, as if display-line-numbers-widen were non-nil. It has no effect when set to zero, or when line numbers are not absolute.

In selective display mode (see Selective Display), and other modes that hide many lines from display (such as Outline and Org modes), you may wish to customize the variables display-line-numbers-width-start and display-line-numbers-grow-only, or set display-line-numbers-width to a large enough value, to avoid occasional miscalculations of space reserved for the line numbers.

The line numbers are displayed in a special face line-number. The current line number is displayed in a different face, line-number-current-line, so you can make the current line’s number have a distinct appearance, which will help locating the line showing point. Additional faces line-number-major-tick and line-number-minor-tick can be used to highlight the line numbers of lines which are a multiple of certain numbers. Customize display-line-numbers-major-tick and display-line-numbers-minor-tick respectively to set those numbers.

If the variable visible-bell is non-nil, Emacs attempts to make the whole screen blink when it would normally make an audible bell sound. This variable has no effect if your terminal does not have a way to make the screen blink.

The variable echo-keystrokes controls the echoing of multi-character keys; its value is the number of seconds of pause required to cause echoing to start, or zero, meaning don’t echo at all. The value takes effect when there is something to echo. See The Echo Area.

On graphical displays, Emacs displays the mouse pointer as an hourglass if Emacs is busy. To disable this feature, set the variable display-hourglass to nil. The variable hourglass-delay determines the number of seconds of busy time before the hourglass is shown; the default is 1.

If the mouse pointer lies inside an Emacs frame, Emacs makes it invisible each time you type a character to insert text, to prevent it from obscuring the text. (To be precise, the hiding occurs when you type a self-inserting character. See Inserting Text.) Moving the mouse pointer makes it visible again. To disable this feature, set the variable make-pointer-invisible to nil.

On graphical displays, the variable underline-minimum-offset determines the minimum distance between the baseline and underline, in pixels, for underlined text. By default, the value is 1; increasing it may improve the legibility of underlined text for certain fonts. (However, Emacs will never draw the underline below the current line area.) The variable x-underline-at-descent-line determines how to draw underlined text. The default is nil, which means to draw it at the baseline level of the font; if you change it to t, Emacs draws the underline at the same height as the font’s descent line. (If non-default line spacing was specified for the underlined text, see Line Height in The Emacs Lisp Reference Manual, Emacs draws the underline below the additional spacing.)

The variable overline-margin specifies the vertical position of an overline above the text, including the height of the overline itself, in pixels; the default is 2.

On some text terminals, bold face and inverse video together result in text that is hard to read. Call the function tty-suppress-bold-inverse-default-colors with a non-nil argument to suppress the effect of bold-face in this case.

Raw bytes are displayed in octal format by default, for example a byte with a decimal value of 128 is displayed as \200. To change display to the hexadecimal format of \x80, set the variable display-raw-bytes-as-hex to t. Care may be needed when interpreting a raw byte when copying text from a terminal containing an Emacs session, or when a terminal’s escape-glyph face looks like the default face. For example, by default Emacs displays the four characters ‘\’, ‘2’, ‘0’, ‘0’ with the same characters it displays a byte with decimal value 128. The problem can be worse with hex displays, where the raw byte 128 followed by the character ‘7’ is displayed as \x807, which Emacs Lisp reads as the single character U+0807 SAMARITAN LETTER IT; this confusion does not occur with the corresponding octal display \2007 because octal escapes contain at most three digits.


17 Commands for Fixing Typos

In this chapter we describe commands that are useful when you catch a mistake while editing. The most fundamental of these commands is the undo command C-/ (also bound to C-x u and C-_). This undoes a single command, or a part of a command (as in the case of query-replace), or several consecutive character insertions. Consecutive repetitions of C-/ undo earlier and earlier changes, back to the limit of the undo information available.

Aside from the commands described here, you can erase text using deletion commands such as DEL (delete-backward-char). These were described earlier in this manual. See Erasing Text.


17.1 Undo

The undo command reverses recent changes in the buffer’s text. Each buffer records changes individually, and the undo command always applies to the current buffer. You can undo all the changes in a buffer for as far back as the buffer’s records go. Usually, each editing command makes a separate entry in the undo records, but some commands such as query-replace divide their changes into multiple entries for flexibility in undoing. Consecutive character insertion commands are usually grouped together into a single undo record, to make undoing less tedious.

C-/
C-x u
C-_

Undo one entry in the current buffer’s undo records (undo).

To begin to undo, type C-/ (or its aliases, C-_ or C-x u)6. This undoes the most recent change in the buffer, and moves point back to where it was before that change. Consecutive repetitions of C-/ (or its aliases) undo earlier and earlier changes in the current buffer. If all the recorded changes have already been undone, the undo command signals an error.

Any command other than an undo command breaks the sequence of undo commands. Starting from that moment, the entire sequence of undo commands that you have just performed are themselves placed into the undo record. Therefore, to re-apply changes you have undone, type C-f or any other command that harmlessly breaks the sequence of undoing; then type C-/ one or more times to undo some of the undo commands.

Alternatively, if you want to resume undoing, without redoing previous undo commands, use M-x undo-only. This is like undo, but will not redo changes you have just undone. To complement it, M-x undo-redo will undo previous undo commands (and will not record itself as an undoable command).

If you notice that a buffer has been modified accidentally, the easiest way to recover is to type C-/ repeatedly until the stars disappear from the front of the mode line (see The Mode Line). Whenever an undo command makes the stars disappear from the mode line, it means that the buffer contents are the same as they were when the file was last read in or saved. If you do not remember whether you changed the buffer deliberately, type C-/ once. When you see the last change you made undone, you will see whether it was an intentional change. If it was an accident, leave it undone. If it was deliberate, redo the change as described above.

Alternatively, you can discard all the changes since the buffer was last visited or saved with M-x revert-buffer (see Reverting a Buffer).

When there is an active region, any use of undo performs selective undo: it undoes the most recent change within the region, instead of the entire buffer. However, when Transient Mark mode is off (see Disabling Transient Mark Mode), C-/ always operates on the entire buffer, ignoring the region. In this case, you can perform selective undo by supplying a prefix argument to the undo command: C-u C-/. To undo further changes in the same region, repeat the undo command (no prefix argument is needed).

Some specialized buffers do not make undo records. Buffers whose names start with spaces never do; these buffers are used internally by Emacs to hold text that users don’t normally look at or edit.

When the undo information for a buffer becomes too large, Emacs discards the oldest records from time to time (during garbage collection). You can specify how much undo information to keep by setting the variables undo-limit, undo-strong-limit, and undo-outer-limit. Their values are expressed in bytes.

The variable undo-limit sets a soft limit: Emacs keeps undo data for enough commands to reach this size, and perhaps exceed it, but does not keep data for any earlier commands beyond that. Its default value is 160000. The variable undo-strong-limit sets a stricter limit: any previous command (though not the most recent one) that pushes the size past this amount is forgotten. The default value of undo-strong-limit is 240000.

Regardless of the values of those variables, the most recent change is never discarded unless it gets bigger than undo-outer-limit (normally 24,000,000). At that point, Emacs discards the undo data and warns you about it. This is the only situation in which you cannot undo the last command. If this happens, you can increase the value of undo-outer-limit to make it even less likely to happen in the future. But if you didn’t expect the command to create such large undo data, then it is probably a bug and you should report it. See Reporting Bugs.


17.2 Transposing Text

C-t

Transpose two characters (transpose-chars).

M-t

Transpose two words (transpose-words).

C-M-t

Transpose two balanced expressions (transpose-sexps).

C-x C-t

Transpose two lines (transpose-lines).

M-x transpose-sentences

Transpose two sentences (transpose-sentences).

M-x transpose-paragraphs

Transpose two paragraphs (transpose-paragraphs).

M-x transpose-regions

Transpose two regions.

The common error of transposing two characters can be fixed, when they are adjacent, with the C-t command (transpose-chars). Normally, C-t transposes the two characters on either side of point. When given at the end of a line, rather than transposing the last character of the line with the newline, which would be useless, C-t transposes the last two characters on the line. So, if you catch your transposition error right away, you can fix it with just a C-t. If you don’t catch it so fast, you must move the cursor back between the two transposed characters before you type C-t. If you transposed a space with the last character of the word before it, the word motion commands (M-f, M-b, etc.) are a good way of getting there. Otherwise, a reverse search (C-r) is often the best way. See Searching and Replacement.

M-t transposes the word before point with the word after point (transpose-words). It moves point forward over a word, dragging the word preceding or containing point forward as well. The punctuation characters between the words do not move. For example, ‘FOO, BAR transposes into ‘BAR, FOO rather than ‘BAR FOO,. When point is at the end of the line, it will transpose the word before point with the first word on the next line.

C-M-t (transpose-sexps) is a similar command for transposing two expressions (see Expressions with Balanced Parentheses), and C-x C-t (transpose-lines) exchanges lines. M-x transpose-sentences and M-x transpose-paragraphs transpose sentences and paragraphs, respectively. These commands work like M-t except as regards the units of text they transpose.

A numeric argument to a transpose command serves as a repeat count: it tells the transpose command to move the character (or word or expression or line) before or containing point across several other characters (or words or expressions or lines). For example, C-u 3 C-t moves the character before point forward across three other characters. It would change ‘f∗oobar’ into ‘oobf∗ar’. This is equivalent to repeating C-t three times. C-u - 4 M-t moves the word before point backward across four words. C-u - C-M-t would cancel the effect of plain C-M-t.

A numeric argument of zero is assigned a special meaning (because otherwise a command with a repeat count of zero would do nothing): to transpose the character (or word or expression or line) ending after point with the one ending after the mark.

M-x transpose-regions transposes the text between point and mark with the text between the last two marks pushed to the mark ring (see Setting the Mark). With a numeric prefix argument, it transposes the text between point and mark with the text between two successive marks that many entries back in the mark ring. This command is best used for transposing multiple characters (or words or sentences or paragraphs) in one go.


17.3 Case Conversion

M-- M-l

Convert last word to lower case. Note Meta-- is Meta-minus.

M-- M-u

Convert last word to all upper case.

M-- M-c

Convert last word to lower case with capital initial.

A very common error is to type words in the wrong case. Because of this, the word case-conversion commands M-l, M-u, and M-c have a special feature when used with a negative argument: they do not move the cursor. As soon as you see you have mistyped the last word, you can simply case-convert it and go on typing. See Case Conversion Commands.


17.4 Checking and Correcting Spelling

This section describes the commands to check the spelling of a single word or of a portion of a buffer. These commands only work if a spelling checker program, one of Hunspell, Aspell, Ispell or Enchant, is installed. These programs are not part of Emacs, but one of them is usually installed on GNU/Linux and other free operating systems. See Aspell in The Aspell Manual.

If you have only one of the spelling checker programs installed, Emacs will find it when you invoke for the first time one of the commands described here. If you have more than one of them installed, you can control which one is used by customizing the variable ispell-program-name.

M-$

Check and correct spelling of the word at point (ispell-word). If the region is active, do it for all words in the region instead.

C-u M-$

If a previous spelling operation was interrupted, continue that operation (ispell-continue).

M-x ispell

Check and correct spelling of all words in the buffer. If the region is active, do it for all words in the region instead.

M-x ispell-buffer

Check and correct spelling in the buffer.

M-x ispell-region

Check and correct spelling in the region.

M-x ispell-message

Check and correct spelling in a draft mail message, excluding cited material.

M-x ispell-comments-and-strings

Check and correct spelling of comments and strings in the buffer or region.

M-x ispell-comment-or-string-at-point

Check the comment or string at point.

M-x ispell-change-dictionary RET dict RET

Restart the spell-checker process, using dict as the dictionary.

M-x ispell-kill-ispell

Kill the spell-checker subprocess.

M-TAB
ESC TAB
C-M-i

Complete the word before point based on the spelling dictionary (ispell-complete-word).

M-x flyspell-mode

Enable Flyspell mode, which highlights all misspelled words.

M-x flyspell-prog-mode

Enable Flyspell mode for comments and strings only.

To check the spelling of the word around or before point, and optionally correct it as well, type M-$ (ispell-word). If a region is active, M-$ checks the spelling of all words within the region. See The Mark and the Region. (When Transient Mark mode is off, M-$ always acts on the word around or before point, ignoring the region; see Disabling Transient Mark Mode.) When invoked with a prefix argument, C-u M-$, this calls ispell-continue, which continues the spelling operation, if any, which was interrupted with X or C-g.

Similarly, the command M-x ispell performs spell-checking in the region if one is active, or in the entire buffer otherwise. The commands M-x ispell-buffer and M-x ispell-region explicitly perform spell-checking on the entire buffer or the region respectively. To check spelling in an email message you are writing, use M-x ispell-message; that command checks the whole buffer, except for material that is indented or appears to be cited from other messages. See Sending Mail. When dealing with source code, you can use M-x ispell-comments-and-strings or M-x ispell-comment-or-string-at-point to check only comments or string literals.

When one of these commands encounters what appears to be an incorrect word, it asks you what to do. It usually displays a list of numbered near-misses—words that are close to the incorrect word. Then you must type a single-character response. Here are the valid responses:

digit

Replace the word, just this time, with one of the displayed near-misses. Each near-miss is listed with a digit; type that digit to select it.

SPC

Skip this word—continue to consider it incorrect, but don’t change it here.

r new RET

Replace the word, just this time, with new. (The replacement string will be rescanned for more spelling errors.)

R new RET

Replace the word with new, and do a query-replace so you can replace it elsewhere in the buffer if you wish. (The replacements will be rescanned for more spelling errors.)

a

Accept the incorrect word—treat it as correct, but only in this editing session.

A

Accept the incorrect word—treat it as correct, but only in this editing session and for this buffer.

i

Insert this word in your private dictionary file so that it will be considered correct from now on, even in future sessions.

m

Like i, but you can also specify dictionary completion information.

u

Insert the lower-case version of this word in your private dictionary file.

l word RET

Look in the dictionary for words that match word. These words become the new list of near-misses; you can select one of them as the replacement by typing a digit. You can use ‘*’ in word as a wildcard.

C-g
X

Interrupt the interactive spell-checking, leaving point at the word that was being checked. You can restart checking again afterward with C-u M-$.

x

Quit interactive spell-checking and move point back to where it was when you started spell-checking.

q

Quit interactive spell-checking and kill the spell-checker subprocess.

C-r

Enter recursive-edit (see Recursive Editing Levels). When you exit recursive-edit with C-M-c, the interactive spell-checking will resume. This allows you to consult the buffer text without interrupting the spell-checking. Do not modify the buffer in the recursive editing, and especially don’t modify the misspelled word, as the edits will be undone when you exit recursive-edit. If you need to edit the misspelled word, use r or R instead, or use X, edit the buffer, then resume with C-u M-$.

C-z

Suspend Emacs or iconify the selected frame.

?

Show the list of options.

In Text mode and related modes, M-TAB (ispell-complete-word) performs in-buffer completion based on spelling correction. Insert the beginning of a word, and then type M-TAB; this shows a list of completions. (If your window manager intercepts M-TAB, type ESC TAB or C-M-i.) Each completion is listed with a digit or character; type that digit or character to choose it.

Once started, the spell-checker subprocess continues to run, waiting for something to do, so that subsequent spell-checking commands complete more quickly. If you want to get rid of the process, use M-x ispell-kill-ispell. This is not usually necessary, since the process uses no processor time except when you do spelling correction.

Spell-checkers look up spelling in two dictionaries: the standard dictionary and your personal dictionary. The standard dictionary is specified by the variable ispell-local-dictionary or, if that is nil, by the variable ispell-dictionary. If both are nil, the spelling program’s default dictionary is used. The command M-x ispell-change-dictionary sets the standard dictionary for the buffer and then restarts the subprocess, so that it will use a different standard dictionary. Your personal dictionary is specified by the variable ispell-personal-dictionary. If that is nil, the spelling program looks for a personal dictionary in a default location, which is specific to each spell-checker.

A separate dictionary is used for word completion. The variable ispell-complete-word-dict specifies the file name of this dictionary. The completion dictionary must be different because it cannot use the information about roots and affixes of the words, which spell-checking uses to detect variations of words. For some languages, there is a spell-checking dictionary but no word completion dictionary.

Flyspell mode is a minor mode that performs automatic spell-checking of the text you type as you type it. When it finds a word that it does not recognize, it highlights that word. Type M-x flyspell-mode to toggle Flyspell mode in the current buffer. To enable Flyspell mode in all text mode buffers, add flyspell-mode to text-mode-hook. See Hooks. Note that, as Flyspell mode needs to check each word across which you move, it will slow down cursor motion and scrolling commands. It also doesn’t automatically check the text you didn’t type or move across; use flyspell-region or flyspell-buffer for that.

When Flyspell mode highlights a word as misspelled, you can click on it with mouse-2 (flyspell-correct-word) to display a menu of possible corrections and actions. If you want this menu on mouse-3 instead, enable context-menu-mode. In addition, C-. or ESC TAB (flyspell-auto-correct-word) will propose various successive corrections for the word at point, and C-c $ (flyspell-correct-word-before-point) will pop up a menu of possible corrections. Of course, you can always correct the misspelled word by editing it manually in any way you like.

Flyspell Prog mode works just like ordinary Flyspell mode, except that it only checks words in comments and string constants. This feature is useful for editing programs. Type M-x flyspell-prog-mode to enable or disable this mode in the current buffer. To enable this mode in all programming mode buffers, add flyspell-prog-mode to prog-mode-hook (see Hooks).


18 Keyboard Macros

In this chapter we describe how to record a sequence of editing commands so you can repeat it conveniently later.

A keyboard macro is a command defined by an Emacs user to stand for another sequence of keys. For example, if you discover that you are about to type C-n M-d C-d forty times, you can speed your work by defining a keyboard macro to do C-n M-d C-d, and then executing it 39 more times.

You define a keyboard macro by executing and recording the commands which are its definition. Put differently, as you define a keyboard macro, the definition is being executed for the first time. This way, you can see the effects of your commands, so that you don’t have to figure them out in your head. When you close the definition, the keyboard macro is defined and also has been, in effect, executed once. You can then do the whole thing over again by invoking the macro.

Keyboard macros differ from ordinary Emacs commands in that they are written in the Emacs command language rather than in Lisp. This makes it easier for the novice to write them, and makes them more convenient as temporary hacks. However, the Emacs command language is not powerful enough as a programming language to be useful for writing anything intelligent or general. For such things, Lisp must be used.


18.1 Basic Use

F3

Start defining a keyboard macro (kmacro-start-macro-or-insert-counter).

F4

If a keyboard macro is being defined, end the definition; otherwise, execute the most recent keyboard macro (kmacro-end-or-call-macro).

C-u F3

Re-execute last keyboard macro, then append keys to its definition.

C-u C-u F3

Append keys to the last keyboard macro without re-executing it.

C-x C-k r

Run the last keyboard macro on each line that begins in the region (apply-macro-to-region-lines).

C-x (

Start defining a keyboard macro (old style) (kmacro-start-macro); with a prefix argument, append keys to the last macro.

C-x )

End a macro definition (old style) (kmacro-end-macro); prefix argument serves as the repeat count for executing the macro.

C-x e

Execute the most recently defined keyboard macro (kmacro-end-and-call-macro); prefix argument serves as repeat count.

To start defining a keyboard macro, type F3. From then on, your keys continue to be executed, but also become part of the definition of the macro. ‘Def’ appears in the mode line to remind you of what is going on. When you are finished, type F4 (kmacro-end-or-call-macro) to terminate the definition. For example,

F3 M-f foo F4

defines a macro to move forward a word and then insert ‘foo’. Note that F3 and F4 do not become part of the macro.

After defining the macro, you can call it with F4. For the above example, this has the same effect as typing M-f foo again. (Note the two roles of the F4 command: it ends the macro if you are in the process of defining one, or calls the last macro otherwise.) You can also supply F4 with a numeric prefix argument ‘n’, which means to invoke the macro ‘n’ times. An argument of zero repeats the macro indefinitely, until it gets an error or you type C-g (or, on MS-DOS, C-Break).

The above example demonstrates a handy trick that you can employ with keyboard macros: if you wish to repeat an operation at regularly spaced places in the text, include a motion command as part of the macro. In this case, repeating the macro inserts the string ‘foo’ after each successive word.

After terminating the definition of a keyboard macro, you can append more keystrokes to its definition by typing C-u F3. This is equivalent to plain F3 followed by retyping the whole definition so far. As a consequence, it re-executes the macro as previously defined. If you change the variable kmacro-execute-before-append to nil, the existing macro will not be re-executed before appending to it (the default is t). You can also add to the end of the definition of the last keyboard macro without re-executing it by typing C-u C-u F3.

When a command reads an argument with the minibuffer, your minibuffer input becomes part of the macro along with the command. So when you replay the macro, the command gets the same argument as when you entered the macro. For example,

F3 C-a C-k C-x b foo RET C-y C-x b RET F4

defines a macro that kills the current line, yanks it into the buffer ‘foo’, then returns to the original buffer.

Most keyboard commands work as usual in a keyboard macro definition, with some exceptions. Typing C-g (keyboard-quit) quits the keyboard macro definition. Typing C-M-c (exit-recursive-edit) can be unreliable: it works as you’d expect if exiting a recursive edit that started within the macro, but if it exits a recursive edit that started before you invoked the keyboard macro, it also necessarily exits the keyboard macro too. Mouse events are also unreliable, even though you can use them in a keyboard macro: when the macro replays the mouse event, it uses the original mouse position of that event, the position that the mouse had while you were defining the macro. The effect of this may be hard to predict.

The command C-x C-k r (apply-macro-to-region-lines) repeats the last defined keyboard macro on each line that begins in the region. It does this line by line, by moving point to the beginning of the line and then executing the macro.

In addition to the F3 and F4 commands described above, Emacs also supports an older set of key bindings for defining and executing keyboard macros. To begin a macro definition, type C-x ( (kmacro-start-macro); as with F3, a prefix argument appends this definition to the last keyboard macro. To end a macro definition, type C-x ) (kmacro-end-macro). To execute the most recent macro, type C-x e (kmacro-end-and-call-macro). If you enter C-x e while defining a macro, the macro is terminated and executed immediately. Immediately after typing C-x e, you can type e repeatedly to immediately repeat the macro one or more times. You can also give C-x e a repeat argument, just like F4 (when it is used to execute a macro).

C-x ) can be given a repeat count as an argument. This means to repeat the macro right after defining it. The macro definition itself counts as the first repetition, since it is executed as you define it, so C-u 4 C-x ) executes the macro immediately 3 additional times.

While executing a long-running keyboard macro, it can sometimes be useful to trigger a redisplay (to show how far we’ve gotten). The C-x C-k d command can be used for this. As a not very useful example, C-x ( M-f C-x C-k d C-x ) will create a macro that will redisplay once per iteration when saying C-u 42 C-x e.


18.2 The Keyboard Macro Ring

All defined keyboard macros are recorded in the keyboard macro ring. There is only one keyboard macro ring, shared by all buffers.

C-x C-k C-k

Execute the keyboard macro at the head of the ring (kmacro-end-or-call-macro-repeat).

C-x C-k C-n

Rotate the keyboard macro ring to the next macro (defined earlier) (kmacro-cycle-ring-next).

C-x C-k C-p

Rotate the keyboard macro ring to the previous macro (defined later) (kmacro-cycle-ring-previous).

All commands which operate on the keyboard macro ring use the same C-x C-k prefix. Most of these commands can be executed and repeated immediately after each other without repeating the C-x C-k prefix. For example,

C-x C-k C-p C-p C-k C-k C-k C-n C-n C-k C-p C-k C-d

will rotate the keyboard macro ring to the second-previous macro, execute the resulting head macro three times, rotate back to the original head macro, execute that once, rotate to the previous macro, execute that, and finally delete it from the macro ring.

The command C-x C-k C-k (kmacro-end-or-call-macro-repeat) executes the keyboard macro at the head of the macro ring. You can repeat the macro immediately by typing another C-k, or you can rotate the macro ring immediately by typing C-n or C-p.

When a keyboard macro is being defined, C-x C-k C-k behaves like F4 except that, immediately afterward, you can use most key bindings of this section without the C-x C-k prefix. For instance, another C-k will re-execute the macro.

The commands C-x C-k C-n (kmacro-cycle-ring-next) and C-x C-k C-p (kmacro-cycle-ring-previous) rotate the macro ring, bringing the next or previous keyboard macro to the head of the macro ring. The definition of the new head macro is displayed in the echo area. You can continue to rotate the macro ring immediately by repeating just C-n and C-p until the desired macro is at the head of the ring. To execute the new macro ring head immediately, just type C-k.

Note that Emacs treats the head of the macro ring as the last defined keyboard macro. For instance, F4 will execute that macro, and C-x C-k n will give it a name.

The maximum number of macros stored in the keyboard macro ring is determined by the customizable variable kmacro-ring-max.


18.3 The Keyboard Macro Counter

Each keyboard macro has an associated counter, which is initialized to 0 when you start defining the macro. This current counter allows you to insert a number into the buffer that depends on the number of times the macro has been called. The counter is normally incremented each time its value is inserted into the buffer.

In addition to the current counter, keyboard macros also maintain the previous counter, which records the value the current counter had last time it was incremented or set. Note that incrementing the current counter by zero, e.g., with C-u 0 C-x C-k C-i, also records the value of the current counter as the previous counter value.

F3

In a keyboard macro definition, insert the keyboard macro counter value in the buffer (kmacro-start-macro-or-insert-counter).

C-x C-k C-i

Insert the keyboard macro counter value in the buffer (kmacro-insert-counter).

C-x C-k C-c

Set the keyboard macro counter (kmacro-set-counter).

C-x C-k C-a

Add the prefix arg to the keyboard macro counter (kmacro-add-counter).

C-x C-k C-f

Specify the format for inserting the keyboard macro counter (kmacro-set-format).

When you are defining a keyboard macro, the command F3 (kmacro-start-macro-or-insert-counter) inserts the current value of the keyboard macro’s counter into the buffer, and increments the counter by 1. (If you are not defining a macro, F3 begins a macro definition instead. See Basic Use.) You can use a numeric prefix argument to specify a different increment. If you just specify a C-u prefix, that inserts the previous counter value, and doesn’t change the current value.

As an example, let us show how the keyboard macro counter can be used to build a numbered list. Consider the following key sequence:

F3 C-a F3 . SPC F4

As part of this keyboard macro definition, the string ‘0. ’ was inserted into the beginning of the current line. If you now move somewhere else in the buffer and type F4 to invoke the macro, the string ‘1. ’ is inserted at the beginning of that line. Subsequent invocations insert ‘2. ’, ‘3. ’, and so forth.

The command C-x C-k C-i (kmacro-insert-counter) does the same thing as F3, but it can be used outside a keyboard macro definition. When no keyboard macro is being defined or executed, it inserts and increments the counter of the macro at the head of the keyboard macro ring.

The command C-x C-k C-c (kmacro-set-counter) sets the current macro counter to the value of the numeric argument. If you use it inside the macro, it operates on each repetition of the macro. If you specify just C-u as the prefix, while executing the macro, that resets the counter to the value it had at the beginning of the current repetition of the macro (undoing any increments so far in this repetition).

The command C-x C-k C-a (kmacro-add-counter) adds the prefix argument to the current macro counter. With just C-u as argument, it resets the counter to the last value inserted by any keyboard macro. (Normally, when you use this, the last insertion will be in the same macro and it will be the same counter.)

The command C-x C-k C-f (kmacro-set-format) prompts for the format to use when inserting the macro counter. The default format is ‘%d’, which means to insert the number in decimal without any padding. You can exit with empty minibuffer to reset the format to this default. You can specify any format string that the format function accepts and that makes sense with a single integer extra argument (see Formatting Strings in The Emacs Lisp Reference Manual). Do not put the format string inside double quotes when you insert it in the minibuffer.

If you use this command while no keyboard macro is being defined or executed, the new format affects all subsequent macro definitions. Existing macros continue to use the format in effect when they were defined. If you set the format while defining a keyboard macro, this affects the macro being defined from that point on, but it does not affect subsequent macros. Execution of the macro will, at each step, use the format in effect at that step during its definition. Changes to the macro format during execution of a macro, like the corresponding changes during its definition, have no effect on subsequent macros.

The format set by C-x C-k C-f does not affect insertion of numbers stored in registers.

If you use a register as a counter, incrementing it on each repetition of the macro, that accomplishes the same thing as a keyboard macro counter. See Keeping Numbers in Registers. For most purposes, it is simpler to use a keyboard macro counter.


18.4 Executing Macros with Variations

In a keyboard macro, you can create an effect similar to that of query-replace, in that the macro asks you each time around whether to make a change.

C-x q

When this point is reached during macro execution, ask for confirmation (kbd-macro-query).

While defining the macro, type C-x q at the point where you want the query to occur. During macro definition, the C-x q does nothing, but when you run the macro later, C-x q asks you interactively whether to continue.

The valid responses when C-x q asks are:

SPC (or y)

Continue executing the keyboard macro.

DEL (or n)

Skip the remainder of this repetition of the macro, and start right away with the next repetition.

RET (or q)

Skip the remainder of this repetition and cancel further repetitions.

C-r

Enter a recursive editing level, in which you can perform editing which is not part of the macro. When you exit the recursive edit using C-M-c, you are asked again how to continue with the keyboard macro. If you type a SPC at this time, the rest of the macro definition is executed. It is up to you to leave point and the text in a state such that the rest of the macro will do what you want.

C-u C-x q, which is C-x q with a prefix argument, performs a completely different function. It enters a recursive edit reading input from the keyboard, both when you type it during the definition of the macro, and when it is executed from the macro. During definition, the editing you do inside the recursive edit does not become part of the macro. During macro execution, the recursive edit gives you a chance to do some particularized editing on each repetition. See Recursive Editing Levels.


18.5 Naming and Saving Keyboard Macros

C-x C-k n

Give a command name (for the duration of the Emacs session) to the most recently defined keyboard macro (kmacro-name-last-macro).

C-x C-k b

Bind the most recently defined keyboard macro to a key sequence (for the duration of the session) (kmacro-bind-to-key).

M-x insert-kbd-macro

Insert in the buffer a keyboard macro’s definition, as Lisp code.

If you wish to save a keyboard macro for later use, you can give it a name using C-x C-k n (kmacro-name-last-macro). This reads a name as an argument using the minibuffer and defines that name to execute the last keyboard macro, in its current form. (If you later add to the definition of this macro, that does not alter the name’s definition as a macro.) The macro name is a Lisp symbol, and defining it in this way makes it a valid command name for calling with M-x or for binding a key to with keymap-global-set (see Keymaps). If you specify a name that has a prior definition other than a keyboard macro, an error message is shown and nothing is changed.

You can also bind the last keyboard macro (in its current form) to a key, using C-x C-k b (kmacro-bind-to-key) followed by the key sequence you want to bind. You can bind to any key sequence in the global keymap, but since most key sequences already have other bindings, you should select the key sequence carefully. If you try to bind to a key sequence with an existing binding (in any keymap), this command asks you for confirmation before replacing the existing binding.

To avoid problems caused by overriding existing bindings, the key sequences C-x C-k 0 through C-x C-k 9 and C-x C-k A through C-x C-k Z are reserved for your own keyboard macro bindings. In fact, to bind to one of these key sequences, you only need to type the digit or letter rather than the whole key sequences. For example,

C-x C-k b 4

will bind the last keyboard macro to the key sequence C-x C-k 4.

Once a macro has a command name, you can save its definition in a file. Then it can be used in another editing session. First, visit the file you want to save the definition in. Then use this command:

M-x insert-kbd-macro RET macroname RET

This inserts some Lisp code that, when executed later, will define the same macro with the same definition it has now. (You don’t need to understand Lisp code to do this, because insert-kbd-macro writes the Lisp code for you.) Then save the file. You can load the file later with load-file (see Libraries of Lisp Code for Emacs). If the file you save in is your init file ~/.emacs (see The Emacs Initialization File) then the macro will be defined each time you run Emacs.

If you give insert-kbd-macro a prefix argument, it makes additional Lisp code to record the keys (if any) that you have bound to macroname, so that the macro will be reassigned the same keys when you load the file.


18.6 Editing a Keyboard Macro

C-x C-k C-e

Edit the last defined keyboard macro (kmacro-edit-macro).

C-x C-k e name RET

Edit a previously defined keyboard macro name (edit-kbd-macro).

C-x C-k l

Edit the last 300 keystrokes as a keyboard macro (kmacro-edit-lossage).

You can edit the last keyboard macro by typing C-x C-k C-e or C-x C-k RET (kmacro-edit-macro). This formats the macro definition in a buffer and enters a specialized major mode for editing it. Type C-h m once in that buffer to display details of how to edit the macro. When you are finished editing, type C-c C-c.

You can edit a named keyboard macro or a macro bound to a key by typing C-x C-k e (edit-kbd-macro). Follow that with the keyboard input that you would use to invoke the macro—C-x e or M-x name or some other key sequence.

You can edit the last 300 keystrokes as a macro by typing C-x C-k l (kmacro-edit-lossage).


18.7 Stepwise Editing a Keyboard Macro

You can interactively replay and edit the last keyboard macro, one command at a time, by typing C-x C-k SPC (kmacro-step-edit-macro). Unless you quit the macro using q or C-g, the edited macro replaces the last macro on the macro ring.

This macro editing feature shows the last macro in the minibuffer together with the first (or next) command to be executed, and prompts you for an action. You can enter ? to get a summary of your options. These actions are available:

  • SPC and y execute the current command, and advance to the next command in the keyboard macro.
  • n, d, and DEL skip and delete the current command.
  • f skips the current command in this execution of the keyboard macro, but doesn’t delete it from the macro.
  • TAB executes the current command, as well as all similar commands immediately following the current command; for example, TAB may be used to insert a sequence of characters (corresponding to a sequence of self-insert-command commands).
  • c continues execution (without further editing) until the end of the keyboard macro. If execution terminates normally, the edited macro replaces the original keyboard macro.
  • C-k skips and deletes the rest of the keyboard macro, terminates step-editing, and replaces the original keyboard macro with the edited macro.
  • q and C-g cancels the step-editing of the keyboard macro; discarding any changes made to the keyboard macro.
  • i key… C-j reads and executes a series of key sequences (not including the final C-j), and inserts them before the current command in the keyboard macro, without advancing over the current command.
  • I key reads one key sequence, executes it, and inserts it before the current command in the keyboard macro, without advancing over the current command.
  • r key… C-j reads and executes a series of key sequences (not including the final C-j), and replaces the current command in the keyboard macro with them, advancing over the inserted key sequences.
  • R key reads one key sequence, executes it, and replaces the current command in the keyboard macro with that key sequence, advancing over the inserted key sequence.
  • a key… C-j executes the current command, then reads and executes a series of key sequences (not including the final C-j), and inserts them after the current command in the keyboard macro; it then advances over the current command and the inserted key sequences.
  • A key… C-j executes the rest of the commands in the keyboard macro, then reads and executes a series of key sequences (not including the final C-j), and appends them at the end of the keyboard macro; it then terminates the step-editing and replaces the original keyboard macro with the edited macro.

19 File Handling

The operating system stores data permanently in named files, so most of the text you edit with Emacs comes from a file and is ultimately stored in a file.

To edit a file, you must tell Emacs to read the file and prepare a buffer containing a copy of the file’s text. This is called visiting the file. Editing commands apply directly to text in the buffer; that is, to the copy inside Emacs. Your changes appear in the file itself only when you save the buffer back into the file.

In addition to visiting and saving files, Emacs can delete, copy, rename, and append to files, keep multiple versions of them, and operate on file directories.


19.1 File Names

Many Emacs commands that operate on a file require you to specify the file name, using the minibuffer (see Minibuffers for File Names).

While in the minibuffer, you can use the usual completion and history commands (see The Minibuffer). Note that file name completion ignores file names whose extensions appear in the variable completion-ignored-extensions (see Completion Options). Note also that most commands use permissive completion with confirmation for reading file names: you are allowed to submit a nonexistent file name, but if you type RET immediately after completing up to a nonexistent file name, Emacs prints ‘[Confirm]’ and you must type a second RET to confirm. See Completion Exit, for details.

Minibuffer history commands offer some special features for reading file names, see Minibuffer History.

Each buffer has a default directory, stored in the buffer-local variable default-directory. Whenever Emacs reads a file name using the minibuffer, it usually inserts the default directory into the minibuffer as the initial contents. You can inhibit this insertion by changing the variable insert-default-directory to nil (see Minibuffers for File Names). Regardless, Emacs always assumes that any relative file name is relative to the default directory, e.g., entering a file name without a directory specifies a file in the default directory.

When you visit a file, Emacs sets default-directory in the visiting buffer to the directory of its file. When you create a new buffer that is not visiting a file, via a command like C-x b, its default directory is usually copied from the buffer that was current at the time (see Creating and Selecting Buffers). You can use the command M-x pwd to see the value of default-directory in the current buffer. The command M-x cd prompts for a directory’s name, and sets the buffer’s default-directory to that directory (doing this does not change the buffer’s file name, if any).

As an example, when you visit the file /u/rms/gnu/gnu.tasks, the default directory is set to /u/rms/gnu/. If you invoke a command that reads a file name, entering just ‘foo’ in the minibuffer, with a directory omitted, specifies the file /u/rms/gnu/foo; entering ‘../.login’ specifies /u/rms/.login; and entering ‘new/foo’ specifies /u/rms/gnu/new/foo.

When typing a file name into the minibuffer, you can make use of a couple of shortcuts: a double slash ignores everything before the second slash in the pair, and ‘~/’ is your home directory. See Minibuffers for File Names.

The character ‘$’ is used to substitute an environment variable into a file name. The name of the environment variable consists of all the alphanumeric characters after the ‘$’; alternatively, it can be enclosed in braces after the ‘$’. For example, if you have used the shell command export FOO=rms/hacks to set up an environment variable named FOO, then both /u/$FOO/test.c and /u/${FOO}/test.c are abbreviations for /u/rms/hacks/test.c. If the environment variable is not defined, no substitution occurs, so that the character ‘$’ stands for itself. Note that environment variables set outside Emacs affect Emacs only if they are applied before Emacs is started.

To access a file with ‘$’ in its name, if the ‘$’ causes expansion, type ‘$$’. This pair is converted to a single ‘$’ at the same time that variable substitution is performed for a single ‘$’. Alternatively, quote the whole file name with ‘/:’ (see Quoted File Names). File names which begin with a literal ‘~’ should also be quoted with ‘/:’.

You can include non-ASCII characters in file names. See Coding Systems for File Names.


19.2 Visiting Files

C-x C-f

Visit a file (find-file).

C-x C-r

Visit a file for viewing, without allowing changes to it (find-file-read-only).

C-x C-v

Visit a different file instead of the one visited last (find-alternate-file).

C-x 4 f

Visit a file, in another window (find-file-other-window). Don’t alter what is displayed in the selected window.

C-x 5 f

Visit a file, in a new frame (find-file-other-frame). Don’t alter what is displayed in the selected frame.

M-x find-file-literally

Visit a file with no conversion of the contents.

Visiting a file means reading its contents into an Emacs buffer so you can edit them. Emacs makes a new buffer for each file that you visit.

To visit a file, type C-x C-f (find-file) and use the minibuffer to enter the name of the desired file. While in the minibuffer, you can abort the command by typing C-g. See File Names, for details about entering file names into minibuffers.

If the specified file exists but the system does not allow you to read it, an error message is displayed in the echo area (on GNU and Unix systems you might be able to visit such a file using the ‘su’ or ‘sudo’ methods; see Remote Files). Otherwise, you can tell that C-x C-f has completed successfully by the appearance of new text on the screen, and by the buffer name shown in the mode line (see The Mode Line). Emacs normally constructs the buffer name from the file name, omitting the directory name. For example, a file named /usr/rms/emacs.tex is visited in a buffer named ‘emacs.tex’. If there is already a buffer with that name, Emacs constructs a unique name; the normal method is to add a suffix based on the directory name (e.g., ‘<rms>’, ‘<tmp>’, and so on), but you can select other methods. See Making Buffer Names Unique.

To create a new file, just visit it using the same command, C-x C-f. Emacs displays ‘(New file)’ in the echo area, but in other respects behaves as if you had visited an existing empty file.

After visiting a file, the changes you make with editing commands are made in the Emacs buffer. They do not take effect in the visited file, until you save the buffer (see Saving Files). If a buffer contains changes that have not been saved, we say the buffer is modified. This implies that some changes will be lost if the buffer is not saved. The mode line displays two stars near the left margin to indicate that the buffer is modified.

If you visit a file that is already in Emacs, C-x C-f switches to the existing buffer instead of making another copy. Before doing so, it checks whether the file has changed since you last visited or saved it. If the file has changed, Emacs offers to reread it.

If you try to visit a file larger than large-file-warning-threshold (the default is 10000000, which is about 10 megabytes), Emacs asks you for confirmation first. You can answer y to proceed with visiting the file or l to visit the file literally (see below). Visiting large files literally speeds up navigation and editing of such files, because various potentially-expensive features are turned off. Note, however, that Emacs cannot visit files that are larger than the maximum Emacs buffer size, which is limited by the amount of memory Emacs can allocate and by the integers that Emacs can represent (see Using Multiple Buffers). If you try, Emacs displays an error message saying that the maximum buffer size has been exceeded.

If you try to visit a file whose major mode (see Major Modes) uses the tree-sitter parsing library, Emacs will display a warning if the file’s size in bytes is larger than the value of the variable treesit-max-buffer-size. The default value is 40 megabytes for 64-bit Emacs and 15 megabytes for 32-bit Emacs. This avoids the danger of having Emacs run out of memory by preventing the activation of major modes based on tree-sitter in such large buffers, because a typical tree-sitter parser needs about 10 times as much memory as the text it parses.

If the file name you specify contains shell-style wildcard characters, Emacs visits all the files that match it. (On case-insensitive filesystems, Emacs matches the wildcards disregarding the letter case.) Wildcards include ‘?’, ‘*’, and ‘[…]’ sequences. To enter the wild card ‘?’ in a file name in the minibuffer, you need to type C-q ?. See Quoted File Names, for information on how to visit a file whose name actually contains wildcard characters. You can disable the wildcard feature by customizing find-file-wildcards.

If you’re asking to visit a file that’s already visited in a buffer, but the file has changed externally, Emacs normally asks you whether you want to re-read the file from disk. But if you set query-about-changed-file to nil, Emacs won’t query you, but will instead just display the buffer’s contents before the changes, and show an echo-area message telling you how to revert the buffer from the file.

If you visit the wrong file unintentionally by typing its name incorrectly, type C-x C-v (find-alternate-file) to visit the file you really wanted. C-x C-v is similar to C-x C-f, but it kills the current buffer (after first offering to save it if it is modified). When C-x C-v reads the file name to visit, it inserts the entire default file name in the buffer, with point just after the directory part; this is convenient if you made a slight error in typing the name.

If you visit a file that is actually a directory, Emacs invokes Dired, the Emacs directory browser. See Dired, the Directory Editor. You can disable this behavior by setting the variable find-file-run-dired to nil; in that case, it is an error to try to visit a directory.

Files which are actually collections of other files, or file archives, are visited in special modes which invoke a Dired-like environment to allow operations on archive members. See File Archives, for more about these features.

If you visit a file that the operating system won’t let you modify, or that is marked read-only, Emacs makes the buffer read-only too, so that you won’t go ahead and make changes that you’ll have trouble saving afterward. You can make the buffer writable with C-x C-q (read-only-mode). See Miscellaneous Buffer Operations.

If you want to visit a file as read-only in order to protect yourself from entering changes accidentally, visit it with the command C-x C-r (find-file-read-only) instead of C-x C-f.

C-x 4 f (find-file-other-window) is like C-x C-f except that the buffer containing the specified file is selected in another window. The window that was selected before C-x 4 f continues to show the same buffer it was already showing. If this command is used when only one window is being displayed, that window is split in two, with one window showing the same buffer as before, and the other one showing the newly requested file. See Multiple Windows.

C-x 5 f (find-file-other-frame) is similar, but opens a new frame, or selects any existing frame showing the specified file. See Frames and Graphical Displays.

On graphical displays, there are two additional methods for visiting files. Firstly, when Emacs is built with a suitable GUI toolkit, commands invoked with the mouse (by clicking on the menu bar or tool bar) use the toolkit’s standard file selection dialog instead of prompting for the file name in the minibuffer. On GNU/Linux and Unix platforms, Emacs does this when built with GTK+, LessTif, and Motif toolkits; on MS-Windows and Mac, the GUI version does that by default. For information on how to customize this, see Using Dialog Boxes.

Secondly, Emacs supports drag and drop: dropping a file into an ordinary Emacs window visits the file using that window. As an exception, dropping a file into a window displaying a Dired buffer moves or copies the file into the displayed directory. For details, see Drag and Drop, and Other Dired Features.

On text-mode terminals and on graphical displays when Emacs was built without a GUI toolkit, you can visit files via the menu-bar ‘File’ menu, which has the ‘Visit New File’ and the ‘Open File’ items.

Each time you visit a file, Emacs automatically scans its contents to detect what character encoding and end-of-line convention it uses, and converts these to Emacs’s internal encoding and end-of-line convention within the buffer. When you save the buffer, Emacs performs the inverse conversion, writing the file to disk with its original encoding and end-of-line convention. See Coding Systems.

If you wish to edit a file as a sequence of ASCII characters with no special encoding or conversion, use the M-x find-file-literally command. This visits a file, like C-x C-f, but does not do format conversion (see Format Conversion in the Emacs Lisp Reference Manual), character code conversion (see Coding Systems), or automatic uncompression (see Accessing Compressed Files), and does not add a final newline because of require-final-newline (see Customizing Saving of Files). If you have already visited the same file in the usual (non-literal) manner, this command asks you whether to visit it literally instead.

Files are sometimes (loosely) tied to other files, and you could call these files sibling files. For instance, when editing C files, if you have a file called ‘"foo.c"’, you often also have a file called ‘"foo.h"’, and that could be its sibling file. Or you may have different versions of a file, for instance ‘"src/emacs/emacs-27/lisp/allout.el"’ and ‘"src/emacs/emacs-28/lisp/allout.el"’ might be considered siblings. Emacs provides the find-sibling-file command to jump between sibling files, but it’s impossible to guess at which files a user might want to be considered siblings, so Emacs lets you configure this freely by altering the find-sibling-rules user option. This is a list of match/expansion elements.

For instance, to do the ‘".c"’ to ‘".h"’ mapping, you could say:

(setq find-sibling-rules
      '(("\\([^/]+\\)\\.c\\'" "\\1.h")))

(ff-find-related-file offers similar functionality especially geared towards C files, see Other Commands for C Mode.)

Or, if you want to consider all files under ‘"src/emacs/DIR/file-name"’ to be siblings of other dirs, you could say:

(setq find-sibling-rules
      '(("src/emacs/[^/]+/\\(.*\\)\\'" "src/emacs/.*/\\1")))

As you can see, this is a list of (MATCH EXPANSION...) elements. The match is a regular expression that matches the visited file name, and each expansion may refer to match groups by using ‘\\1’ and so on. The resulting expansion string is then applied to the file system to see if any files match this expansion (interpreted as a regexp).

Two special hook variables allow extensions to modify the operation of visiting files. Visiting a file that does not exist runs the functions in find-file-not-found-functions; this variable holds a list of functions, which are called one by one (with no arguments) until one of them returns non-nil. This is not a normal hook, and the name ends in ‘-functions’ rather than ‘-hook’ to indicate that fact.

Successful visiting of any file, whether existing or not, calls the functions in find-file-hook, with no arguments. This variable is a normal hook. In the case of a nonexistent file, the find-file-not-found-functions are run first. See Hooks.

There are several ways to specify automatically the major mode for editing the file (see Choosing File Modes), and to specify local variables defined for that file (see Local Variables in Files).


19.3 Saving Files

Saving a buffer in Emacs means writing its contents back into the file that was visited in the buffer.


19.3.1 Commands for Saving Files

These are the commands that relate to saving and writing files.

C-x C-s

Save the current buffer to its file (save-buffer).

C-x s

Save any or all buffers to their files (save-some-buffers).

M-~

Forget that the current buffer has been changed (not-modified). With prefix argument (C-u), mark the current buffer as changed.

C-x C-w

Save the current buffer with a specified file name (write-file).

M-x set-visited-file-name

Change the file name under which the current buffer will be saved.

M-x rename-visited-file

The same as M-x set-visited-file-name, but also rename the file the buffer is visiting (if any).

When you wish to save the file and make your changes permanent, type C-x C-s (save-buffer). After saving is finished, C-x C-s displays a message like this:

Wrote /u/rms/gnu/gnu.tasks

If the current buffer is not modified (no changes have been made in it since the buffer was created or last saved), saving is not really done, because it would have no effect. Instead, C-x C-s displays a message like this in the echo area:

(No changes need to be saved)

With a prefix argument, C-u C-x C-s, Emacs also marks the buffer to be backed up when the next save is done. See Backup Files.

The command C-x s (save-some-buffers) offers to save any or all modified buffers. It asks you what to do with each buffer. The possible responses are analogous to those of query-replace:

y
SPC

Save this buffer and ask about the rest of the buffers.

n
DEL

Don’t save this buffer, but ask about the rest of the buffers.

!

Save this buffer and all the rest with no more questions.

q
RET

Terminate save-some-buffers without any more saving.

.

Save this buffer, then exit save-some-buffers without even asking about other buffers.

C-r

View the buffer that you are currently being asked about. When you exit View mode, you get back to save-some-buffers, which asks the question again.

C-f

Exit save-some-buffers and visit the buffer that you are currently being asked about.

d

Diff the buffer against its corresponding file, so you can see what changes you would be saving. This calls the command diff-buffer-with-file (see Comparing Files).

C-h

Display a help message about these options.

You can customize the value of save-some-buffers-default-predicate to control which buffers Emacs will ask about.

C-x C-c, the key sequence to exit Emacs, invokes save-some-buffers and therefore asks the same questions.

If you have changed a buffer but do not wish to save the changes, you should take some action to prevent it. Otherwise, each time you use C-x s or C-x C-c, you are liable to save this buffer by mistake. One thing you can do is type M-~ (not-modified), which clears out the indication that the buffer is modified. If you do this, none of the save commands will believe that the buffer needs to be saved. (‘~’ is often used as a mathematical symbol for “not”; thus M-~ is “not”, metafied.) Alternatively, you can cancel all the changes made since the file was visited or saved, by reading the text from the file again. This is called reverting. See Reverting a Buffer. (You could also undo all the changes by repeating the undo command C-x u until you have undone all the changes; but reverting is easier.)

M-x set-visited-file-name alters the name of the file that the current buffer is visiting. It reads the new file name using the minibuffer. Then it marks the buffer as visiting that file name, and changes the buffer name correspondingly. set-visited-file-name does not save the buffer in the newly visited file; it just alters the records inside Emacs in case you do save later. It also marks the buffer as modified so that C-x C-s in that buffer will save.

If you wish to mark the buffer as visiting a different file and save it right away, use C-x C-w (write-file). This is equivalent to set-visited-file-name followed by C-x C-s, except that C-x C-w asks for confirmation if the file exists. C-x C-s used on a buffer that is not visiting a file has the same effect as C-x C-w; that is, it reads a file name, marks the buffer as visiting that file, and saves it there. The default file name in a buffer that is not visiting a file is made by combining the buffer name with the buffer’s default directory (see File Names).

If the new file name implies a major mode, then C-x C-w switches to that major mode, in most cases. The command set-visited-file-name also does this. See Choosing File Modes.

If you wish to save the current buffer to a different file without visiting that file, use mark-whole-buffer (C-x h), then M-x write-region (see Miscellaneous File Operations).

If Emacs is about to save a file and sees that the date of the latest version on disk does not match what Emacs last read or wrote, Emacs notifies you of this fact, because it probably indicates a problem caused by simultaneous editing and requires your immediate attention. See Simultaneous Editing.


19.3.2 Backup Files

On most operating systems, rewriting a file automatically destroys all record of what the file used to contain. Thus, saving a file from Emacs throws away the old contents of the file—or it would, except that Emacs carefully copies the old contents to another file, called the backup file, before actually saving.

Emacs makes a backup for a file only the first time the file is saved from a buffer. No matter how many times you subsequently save the file, its backup remains unchanged. However, if you kill the buffer and then visit the file again, a new backup file will be made.

For most files, the variable make-backup-files determines whether to make backup files. On most operating systems, its default value is t, so that Emacs does write backup files.

For files managed by a version control system (see Version Control), the variable vc-make-backup-files determines whether to make backup files. By default it is nil, since backup files are redundant when you store all the previous versions in a version control system. See General Options.

At your option, Emacs can keep either a single backup for each file, or make a series of numbered backup files for each file that you edit. See Single or Numbered Backups.

The default value of the backup-enable-predicate variable prevents backup files being written for files in the directories used for temporary files, specified by temporary-file-directory or small-temporary-file-directory.

You can explicitly tell Emacs to make another backup file from a buffer, even though that buffer has been saved before. If you save the buffer with C-u C-x C-s, the version thus saved will be made into a backup file if you save the buffer again. C-u C-u C-x C-s saves the buffer, but first makes the previous file contents into a new backup file. C-u C-u C-u C-x C-s does both things: it makes a backup from the previous contents, and arranges to make another from the newly saved contents if you save again.

You can customize the variable backup-directory-alist to specify that files matching certain patterns should be backed up in specific directories. A typical use is to add an element ("." . dir) to make all backups in the directory with absolute name dir. Emacs modifies the backup file names to avoid clashes between files with the same names originating in different directories. Alternatively, adding, ("." . ".~") would make backups in the invisible subdirectory .~ of the original file’s directory. Emacs creates the directory, if necessary, to make the backup.


19.3.2.1 Single or Numbered Backups

When Emacs makes a backup file, its name is normally constructed by appending ‘~’ to the file name being edited; thus, the backup file for eval.c would be eval.c~.

If access control stops Emacs from writing backup files under the usual names, it writes the backup file as ~/.emacs.d/%backup%~. Only one such file can exist, so only the most recently made such backup is available.

Emacs can also make numbered backup files. Numbered backup file names contain ‘.~’, the number, and another ‘~’ after the original file name. Thus, the backup files of eval.c would be called eval.c.~1~, eval.c.~2~, and so on, all the way through names like eval.c.~259~ and beyond.

The variable version-control determines whether to make single backup files or multiple numbered backup files. Its possible values are:

nil

Make numbered backups for files that have numbered backups already. Otherwise, make single backups. This is the default.

t

Make numbered backups.

never

Never make numbered backups; always make single backups.

The usual way to set this variable is globally, through your init file or the customization buffer. However, you can set version-control locally in an individual buffer to control the making of backups for that buffer’s file (see Local Variables). Some modes, such as Rmail mode, set this variable. You can also have Emacs set version-control locally whenever you visit a given file (see Local Variables in Files).

If you set the environment variable VERSION_CONTROL, to tell various GNU utilities what to do with backup files, Emacs also obeys the environment variable by setting the Lisp variable version-control accordingly at startup. If the environment variable’s value is ‘t’ or ‘numbered’, then version-control becomes t; if the value is ‘nil’ or ‘existing’, then version-control becomes nil; if it is ‘never’ or ‘simple’, then version-control becomes never.

If you set the variable make-backup-file-name-function to a suitable Lisp function, you can override the usual way Emacs constructs backup file names.


19.3.2.2 Automatic Deletion of Backups

To prevent excessive consumption of disk space, Emacs can delete numbered backup versions automatically. Generally Emacs keeps the first few backups and the latest few backups, deleting any in between. This happens every time a new backup is made.

The two variables kept-old-versions and kept-new-versions control this deletion. Their values are, respectively, the number of oldest (lowest-numbered) backups to keep and the number of newest (highest-numbered) ones to keep, each time a new backup is made. The backups in the middle (excluding those oldest and newest) are the excess middle versions—those backups are deleted. These variables’ values are used when it is time to delete excess versions, just after a new backup version is made; the newly made backup is included in the count in kept-new-versions. By default, both variables are 2.

If delete-old-versions is t, Emacs deletes the excess backup files silently. If it is nil, the default, Emacs asks you whether it should delete the excess backup versions. If it has any other value, then Emacs never automatically deletes backups.

Dired’s . (Period) command can also be used to delete old versions. See Flagging Many Files at Once.


19.3.2.3 Copying vs. Renaming

Backup files can be made by copying the old file or by renaming it. This makes a difference when the old file has multiple names (hard links). If the old file is renamed into the backup file, then the alternate names become names for the backup file. If the old file is copied instead, then the alternate names remain names for the file that you are editing, and the contents accessed by those names will be the new contents.

The method of making a backup file may also affect the file’s owner and group. If copying is used, these do not change. If renaming is used, you become the file’s owner, and the file’s group becomes the default (different operating systems have different defaults for the group).

The choice of renaming or copying is made as follows:

  • If the variable backup-by-copying is non-nil (the default is nil), use copying.
  • Otherwise, if the variable backup-by-copying-when-linked is non-nil (the default is nil), and the file has multiple names, use copying.
  • Otherwise, if the variable backup-by-copying-when-mismatch is non-nil (the default is t), and renaming would change the file’s owner or group, use copying.

    If you change backup-by-copying-when-mismatch to nil, Emacs checks the numeric user-id of the file’s owner and the numeric group-id of the file’s group. If either is no greater than backup-by-copying-when-privileged-mismatch, then it behaves as though backup-by-copying-when-mismatch is non-nil anyway.

  • Otherwise, renaming is the default choice.

When a file is managed with a version control system (see Version Control), Emacs does not normally make backups in the usual way for that file. But committing (a.k.a. checking in, see Concepts of Version Control) new versions of files is similar in some ways to making backups. One unfortunate similarity is that these operations typically break hard links, disconnecting the file name you visited from any alternate names for the same file. This has nothing to do with Emacs—the version control system does it.


19.3.3 Customizing Saving of Files

If the value of the variable require-final-newline is t, saving or writing a file silently puts a newline at the end if there isn’t already one there. If the value is visit, Emacs adds a newline at the end of any file that doesn’t have one, just after it visits the file. (This marks the buffer as modified, and you can undo it.) If the value is visit-save, Emacs adds such newlines both on visiting and on saving. If the value is nil, Emacs leaves the end of the file unchanged; any other non-nil value means Emacs asks you whether to add a newline. The default is nil.

Some major modes are designed for specific kinds of files that are always supposed to end in newlines. Such major modes set the variable require-final-newline to the value of mode-require-final-newline, which defaults to t. By setting the latter variable, you can control how these modes handle final newlines.

If this option is non-nil and you’re visiting a file via a symbolic link, Emacs will break the symbolic link upon saving the buffer, and will write the buffer to a file with the same name as the symbolic link, if the value of file-precious-flag is non-nil (see file-precious-flag in The Emacs Lisp Reference Manual). If you want Emacs to save the buffer to the file the symbolic link points to (thereby preserving the link) in these cases, customize the variable file-preserve-symlinks-on-save to t.

Normally, when a program writes a file, the operating system briefly caches the file’s data in main memory before committing the data to disk. This can greatly improve performance; for example, when running on laptops, it can avoid a disk spin-up each time a file is written. However, it risks data loss if the operating system crashes before committing the cache to disk.

To lessen this risk, Emacs can invoke the fsync system call after saving a file. Using fsync does not eliminate the risk of data loss, partly because many systems do not implement fsync properly, and partly because Emacs’s file-saving procedure typically relies also on directory updates that might not survive a crash even if fsync works properly.

The write-region-inhibit-fsync variable controls whether Emacs invokes fsync after saving a file. The variable’s default value is nil when Emacs is interactive, and t when Emacs runs in batch mode (see Batch Mode).

Emacs never uses fsync when writing auto-save files, as these files might lose data anyway.


19.3.4 Protection against Simultaneous Editing

Simultaneous editing occurs when two users visit the same file, both make changes, and then both save them. If nobody is informed that this is happening, whichever user saves first would later find that their changes were lost.

On some systems, Emacs notices immediately when the second user starts to change the file, and issues an immediate warning. On all systems, Emacs checks when you save the file, and warns if you are about to overwrite another user’s changes. You can prevent loss of the other user’s work by taking the proper corrective action instead of saving the file.

When you make the first modification in an Emacs buffer that is visiting a file, Emacs records that the file is locked by you. (It does this by creating a specially-named symbolic link7 with special contents in the same directory. See (elisp)File Locks, for more details.) Emacs removes the lock when you save the changes. The idea is that the file is locked whenever an Emacs buffer visiting it has unsaved changes.

You can prevent the creation of lock files by setting the variable create-lockfiles to nil. Caution: by doing so you will lose the benefits that this feature provides. You can also control where lock files are written by using the lock-file-name-transforms variable.

If you begin to modify the buffer while the visited file is locked by someone else, this constitutes a collision. When Emacs detects a collision, it asks you what to do, by calling the Lisp function ask-user-about-lock. You can redefine this function for the sake of customization. The standard definition of this function asks you a question and accepts three possible answers:

s

Steal the lock. Whoever was already changing the file loses the lock, and you gain the lock.

p

Proceed. Go ahead and edit the file despite its being locked by someone else.

q

Quit. This causes an error (file-locked), and the buffer contents remain unchanged—the modification you were trying to make does not actually take place.

If Emacs or the operating system crashes, this may leave behind lock files which are stale, so you may occasionally get warnings about spurious collisions. When you determine that the collision is spurious, just use p to tell Emacs to go ahead anyway.

Note that locking works on the basis of a file name; if a file has multiple names, Emacs does not prevent two users from editing it simultaneously under different names.

A lock file cannot be written in some circumstances, e.g., if Emacs lacks the system permissions or cannot create lock files for some other reason. In these cases, Emacs can still detect the collision when you try to save a file, by checking the file’s last-modification date. If the file has changed since the last time Emacs visited or saved it, that implies that changes have been made in some other way, and will be lost if Emacs proceeds with saving. Emacs then displays a warning message and asks for confirmation before saving; answer yes to save, and no or C-g cancel the save.

If you are notified that simultaneous editing has already taken place, one way to compare the buffer to its file is the M-x diff-buffer-with-file command. See Comparing Files.

You can prevent the creation of remote lock files by setting the variable remote-file-name-inhibit-locks to t.

The minor mode lock-file-mode, called interactively, toggles the local value of create-lockfiles in the current buffer.


19.3.5 Shadowing Files

You can arrange to keep identical shadow copies of certain files in more than one place—possibly on different machines. To do this, first you must set up a shadow file group, which is a set of identically-named files shared between a list of sites. The file group is permanent and applies to further Emacs sessions as well as the current one. Once the group is set up, every time you exit Emacs, it will copy the file you edited to the other files in its group. You can also do the copying without exiting Emacs, by typing M-x shadow-copy-files.

A shadow cluster is a group of hosts that share directories, so that copying to or from one of them is sufficient to update the file on all of them. Each shadow cluster has a name, and specifies the network address of a primary host (the one we copy files to), and a regular expression that matches the host names of all the other hosts in the cluster. You can define a shadow cluster with M-x shadow-define-cluster.

M-x shadow-initialize

Set up file shadowing.

M-x shadow-define-literal-group

Declare a single file to be shared between sites.

M-x shadow-define-regexp-group

Make all files that match each of a group of files be shared between hosts.

M-x shadow-define-cluster RET name RET

Define a shadow file cluster name.

M-x shadow-copy-files

Copy all pending shadow files.

M-x shadow-cancel

Cancel the instruction to shadow some files.

To set up a shadow file group, use M-x shadow-define-literal-group or M-x shadow-define-regexp-group. See their documentation strings for further information.

Before copying a file to its shadows, Emacs asks for confirmation. You can answer “no” to bypass copying of this file, this time. If you want to cancel the shadowing permanently for a certain file, use M-x shadow-cancel to eliminate or change the shadow file group.

File Shadowing is not available on MS Windows.


19.3.6 Updating Time Stamps Automatically

You can arrange to put a time stamp in a file, so that it is updated automatically each time you edit and save the file. The time stamp must be in the first eight lines of the file, and you should insert it like this:

Time-stamp: <>

or like this:

Time-stamp: " "

Then add the function time-stamp to the hook before-save-hook (see Hooks). When you save the file, this function then automatically updates the time stamp with the current date and time. You can also use the command M-x time-stamp to update the time stamp manually. By default the time stamp is formatted according to your locale setting (see Environment Variables) and time zone (see Time of Day in The Emacs Lisp Reference Manual). For customizations, see the Custom group time-stamp.


19.4 Reverting a Buffer

If you have made extensive changes to a file-visiting buffer and then change your mind, you can revert the changes and go back to the saved version of the file. To do this, type C-x x g. Since reverting unintentionally could lose a lot of work, Emacs asks for confirmation first if the buffer is modified.

The revert-buffer command tries to position point in such a way that, if the file was edited only slightly, you will be at approximately the same part of the text as before. But if you have made major changes, point may end up in a totally different location.

Reverting marks the buffer as not modified. However, it adds the reverted changes as a single modification to the buffer’s undo history (see Undo). Thus, after reverting, you can type C-/ or its aliases to bring the reverted changes back, if you happen to change your mind.

To revert a buffer more conservatively, you can use the command revert-buffer-with-fine-grain. This command acts like revert-buffer, but it tries to be as non-destructive as possible, making an effort to preserve all markers, properties and overlays in the buffer. Since reverting this way can be very slow when you have made a large number of changes, you can modify the variable revert-buffer-with-fine-grain-max-seconds to specify a maximum amount of seconds that replacing the buffer contents this way should take. Note that it is not ensured that the whole execution of revert-buffer-with-fine-grain won’t take longer than this.

Some kinds of buffers that are not associated with files, such as Dired buffers, can also be reverted. For them, reverting means recalculating their contents. Buffers created explicitly with C-x b cannot be reverted; revert-buffer reports an error if you try.

When you edit a file that changes automatically and frequently—for example, a log of output from a process that continues to run—it may be useful for Emacs to revert the file without querying you. To request this behavior, set the variable revert-without-query to a list of regular expressions. When a file name matches one of these regular expressions, find-file and revert-buffer will revert it automatically if it has changed—provided the buffer itself is not modified. (If you have edited the text, it would be wrong to discard your changes.)

The C-x x g keystroke is bound to the revert-buffer-quick command. This is like the revert-buffer command, but prompts less. Unlike revert-buffer, it will not prompt if the current buffer visits a file, and the buffer is not modified. It also respects the revert-buffer-quick-short-answers user option. If this option is non-nil, use a shorter y/n query instead of a longer yes/no query.

You can also tell Emacs to revert buffers automatically when their visited files change on disk; see Auto Revert: Keeping buffers automatically up-to-date.


19.5 Auto Revert: Keeping buffers automatically up-to-date

A buffer can get out of sync with respect to its visited file on disk if that file is changed by another program. To keep it up to date, you can enable Auto Revert mode by typing M-x auto-revert-mode. This automatically reverts the buffer when its visited file changes on disk. To do the same for all file buffers, type M-x global-auto-revert-mode to enable Global Auto Revert mode.

Auto Revert will not revert a buffer if it has unsaved changes, or if its file on disk is deleted or renamed.

One use of Auto Revert mode is to “tail” a file such as a system log, so that changes made to that file by other programs are continuously displayed. To do this, just move the point to the end of the buffer, and it will stay there as the file contents change. However, if you are sure that the file will only change by growing at the end, use Auto Revert Tail mode instead (auto-revert-tail-mode). It is more efficient for this. Auto Revert Tail mode also works for remote files.

When a buffer is auto-reverted, a message is generated. This can be suppressed by setting auto-revert-verbose to nil.

The Auto Revert modes do not check or revert remote files, because that is usually too slow. This behavior can be changed by setting the variable auto-revert-remote-files to non-nil.

By default, Auto Revert mode works using file notifications, whereby changes in the filesystem are reported to Emacs by the OS. You can disable use of file notifications by customizing the variable auto-revert-use-notify to a nil value, then Emacs will check for file changes by polling every five seconds. You can change the polling interval through the variable auto-revert-interval.

Not all systems support file notifications; where they are not supported, auto-revert-use-notify will be nil by default.

By default, Auto Revert mode will poll files for changes periodically even when file notifications are used. Polling is unnecessary in many cases, and turning it off may save power by relying on notifications only. To do so, set the variable auto-revert-avoid-polling to non-nil. However, notification is ineffective on certain file systems; mainly network file system on Unix-like machines, where files can be altered from other machines. For such file systems, polling may be necessary. To force polling when auto-revert-avoid-polling is non-nil, set auto-revert-notify-exclude-dir-regexp to match files that should be excluded from using notification.

In Dired buffers (see Dired, the Directory Editor), Auto Revert mode refreshes the buffer when a file is created or deleted in the buffer’s directory.

See Undoing Version Control Actions, for commands to revert to earlier versions of files under version control. See Version Control and the Mode Line, for Auto Revert peculiarities when visiting files under version control.


19.5.1 Auto Reverting Non-File Buffers

Global Auto Revert Mode normally only reverts file buffers. There are two ways to auto-revert certain non-file buffers: by enabling Auto Revert Mode in those buffers (using M-x auto-revert-mode); and by setting global-auto-revert-non-file-buffers to a non-nil value. The latter enables Auto Reverting for all types of buffers for which it is implemented (listed in the menu below).

Like file buffers, non-file buffers should normally not revert while you are working on them, or while they contain information that might get lost after reverting. Therefore, they do not revert if they are modified. This can get tricky, because deciding when a non-file buffer should be marked modified is usually more difficult than for file buffers.

Another tricky detail is that, for efficiency reasons, Auto Revert often does not try to detect all possible changes in the buffer, only changes that are major or easy to detect. Hence, enabling auto-reverting for a non-file buffer does not always guarantee that all information in the buffer is up-to-date, and does not necessarily make manual reverts useless.

At the other extreme, certain buffers automatically revert every auto-revert-interval seconds. (This currently only applies to the Buffer Menu.) In this case, Auto Revert does not print any messages while reverting, even when auto-revert-verbose is non-nil.

Some non-file buffers can be updated reliably by file notification on their default directory; Dired buffers is an example. The major mode can indicate this by setting buffer-auto-revert-by-notification to a non-nil value in that buffer, allowing Auto Revert to avoid periodic polling. Such notification does not include changes to files in that directory, only to the directory itself.

The details depend on the particular types of buffers and are explained in the corresponding sections.


19.5.1.1 Auto Reverting the Buffer Menu

If auto-reverting of non-file buffers is enabled, the Buffer Menu (see Operating on Several Buffers) automatically reverts every auto-revert-interval seconds, whether there is a need for it or not. (It would probably take longer to check whether there is a need than to actually revert.)

If the Buffer Menu inappropriately gets marked modified, just revert it manually using g and auto-reverting will resume. However, if you marked certain buffers to get deleted or to be displayed, you have to be careful, because reverting erases all marks. The fact that adding marks sets the buffer’s modified flag prevents Auto Revert from automatically erasing the marks.


19.5.1.2 Auto Reverting Dired buffers

Dired buffers only auto-revert when the file list of the buffer’s main directory changes (e.g., when a new file is added or deleted). They do not auto-revert when information about a particular file changes (e.g., when the size changes) or when inserted subdirectories change. To be sure that all listed information is up to date, you have to manually revert using g, even if auto-reverting is enabled in the Dired buffer. Sometimes, you might get the impression that modifying or saving files listed in the main directory actually does cause auto-reverting. This is because making changes to a file, or saving it, very often causes changes in the directory itself; for instance, through backup files or auto-save files. However, this is not guaranteed.

If the Dired buffer is marked modified and there are no changes you want to protect, then most of the time you can make auto-reverting resume by manually reverting the buffer using g. There is one exception. If you flag or mark files, you can safely revert the buffer. This will not erase the flags or marks (unless the marked file has been deleted, of course). However, the buffer will stay modified, even after reverting, and auto-reverting will not resume. This is because, if you flag or mark files, you may be working on the buffer and you might not want the buffer to change without warning. If you want auto-reverting to resume in the presence of marks and flags, mark the buffer non-modified using M-~. However, adding, deleting or changing marks or flags will mark it modified again.

Remote Dired buffers are currently not auto-reverted. Neither are Dired buffers for which you used shell wildcards or file arguments to list only some of the files. *Find* and *Locate* buffers do not auto-revert either.

Note that auto-reverting Dired buffers may not work satisfactorily on some systems.


19.6 Auto-Saving: Protection Against Disasters

From time to time, Emacs automatically saves each visited file in a separate file, without altering the file you actually use. This is called auto-saving. It prevents you from losing more than a limited amount of work if the system crashes.

When Emacs determines that it is time for auto-saving, it considers each buffer, and each is auto-saved if auto-saving is enabled for it and it has been changed since the last time it was auto-saved. When the auto-save-no-message variable is set to nil (the default), the message ‘Auto-saving...’ is displayed in the echo area during auto-saving, if any files are actually auto-saved; to disable these messages, customize the variable to a non-nil value. Errors occurring during auto-saving are caught so that they do not interfere with the execution of commands you have been typing.


19.6.1 Auto-Save Files

Auto-saving does not normally save in the files that you visited, because it can be very undesirable to save a change that you did not want to make permanent. Instead, auto-saving is done in a different file called the auto-save file, and the visited file is changed only when you request saving explicitly (such as with C-x C-s).

Normally, the auto-save file name is made by appending ‘#’ to the front and rear of the visited file name. Thus, a buffer visiting file foo.c is auto-saved in a file #foo.c#. Most buffers that are not visiting files are auto-saved only if you request it explicitly; when they are auto-saved, the auto-save file name is made by appending ‘#’ to the front and rear of buffer name, then adding digits and letters at the end for uniqueness. For example, the *mail* buffer in which you compose messages to be sent might be auto-saved in a file named #*mail*#704juu. Auto-save file names are made this way unless you reprogram parts of Emacs to do something different (the functions make-auto-save-file-name and auto-save-file-name-p). The file name to be used for auto-saving in a buffer is calculated when auto-saving is turned on in that buffer.

The variable auto-save-file-name-transforms allows a degree of control over the auto-save file name. It lets you specify a series of regular expressions and replacements to transform the auto save file name. The default value puts the auto-save files for remote files (see Remote Files) into the temporary file directory on the local machine.

When you delete a substantial part of the text in a large buffer, auto save turns off temporarily in that buffer. This is because if you deleted the text unintentionally, you might find the auto-save file more useful if it contains the deleted text. To reenable auto-saving after this happens, save the buffer with C-x C-s, or use C-u 1 M-x auto-save-mode.

If you want auto-saving to be done in the visited file rather than in a separate auto-save file, enable the global minor mode auto-save-visited-mode. In this mode, auto-saving is identical to explicit saving. Note that this mode is orthogonal to the auto-save mode described above; you can enable both at the same time. However, if auto-save mode is active in some buffer and the obsolete auto-save-visited-file-name variable is set to a non-nil value, that buffer won’t be affected by auto-save-visited-mode.

You can use the variable auto-save-visited-interval to customize the interval between auto-save operations in auto-save-visited-mode; by default it’s five seconds. auto-save-interval and auto-save-timeout have no effect on auto-save-visited-mode. See Controlling Auto-Saving, for details on these variables.

A buffer’s auto-save file is deleted when you save the buffer in its visited file. (You can inhibit this by setting the variable delete-auto-save-files to nil.) Changing the visited file name with C-x C-w or set-visited-file-name renames any auto-save file to go with the new visited name.

Killing a buffer, by default, doesn’t remove the buffer’s auto-save file. If kill-buffer-delete-auto-save-files is non-nil, killing a buffer that has an auto-save file will make Emacs prompt the user for whether the auto-save file should be deleted. (This is inhibited if delete-auto-save-files is nil.)


19.6.2 Controlling Auto-Saving

Each time you visit a file, auto-saving is turned on for that file’s buffer if the variable auto-save-default is non-nil (but not in batch mode; see Initial Options). The default for this variable is t, so auto-saving is the usual practice for file-visiting buffers. To toggle auto-saving in the current buffer, type M-x auto-save-mode. Auto Save mode acts as a buffer-local minor mode (see Minor Modes).

Emacs auto-saves periodically based on how many characters you have typed since the last auto-save. The variable auto-save-interval specifies how many characters there are between auto-saves. By default, it is 300. Emacs doesn’t accept values that are too small: if you customize auto-save-interval to a value less than 20, Emacs will behave as if the value is 20.

Auto-saving also takes place when you stop typing for a while. By default, it does this after 30 seconds of idleness (at this time, Emacs may also perform garbage collection; see Garbage Collection in The Emacs Lisp Reference Manual). To change this interval, customize the variable auto-save-timeout. The actual time period is longer if the current buffer is long; this is a heuristic which aims to keep out of your way when you are editing long buffers, in which auto-save takes an appreciable amount of time. Auto-saving during idle periods accomplishes two things: first, it makes sure all your work is saved if you go away from the terminal for a while; second, it may avoid some auto-saving while you are actually typing.

When auto-save-visited-mode is enabled, Emacs will auto-save file-visiting buffers after five seconds of idle time. You can customize the variable auto-save-visited-interval to change the idle time interval.

Emacs also does auto-saving whenever it gets a fatal error. This includes killing the Emacs job with a shell command such as ‘kill %emacs’, or disconnecting a phone line or network connection.

You can perform an auto-save explicitly with the command M-x do-auto-save.


19.6.3 Recovering Data from Auto-Saves

You can use the contents of an auto-save file to recover from a loss of data with the command M-x recover-file RET file RET. This visits file and then (after your confirmation) restores the contents from its auto-save file #file#. You can then save with C-x C-s to put the recovered text into file itself. For example, to recover file foo.c from its auto-save file #foo.c#, do:

M-x recover-file RET foo.c RET
yes RET
C-x C-s

Before asking for confirmation, M-x recover-file displays a directory listing describing the specified file and the auto-save file, so you can compare their sizes and dates. If the auto-save file is older, M-x recover-file does not offer to read it.

If Emacs or the computer crashes, you can recover all the files you were editing from their auto save files with the command M-x recover-session. This first shows you a list of recorded interrupted sessions. Move point to the one you choose, and type C-c C-c.

Then recover-session asks about each of the files that were being edited during that session, asking whether to recover that file. If you answer y, it calls recover-file, which works in its normal fashion. It shows the dates of the original file and its auto-save file, and asks once again whether to recover that file.

When recover-session is done, the files you’ve chosen to recover are present in Emacs buffers. You should then save them. Only this—saving them—updates the files themselves.

Emacs records information about interrupted sessions in files named .saves-pid-hostname~ in the directory ~/.emacs.d/auto-save-list/. This directory is determined by the variable auto-save-list-file-prefix. If you set auto-save-list-file-prefix to nil, sessions are not recorded for recovery.


19.7 File Name Aliases

Symbolic links and hard links both make it possible for several file names to refer to the same file. Hard links are alternate names that refer directly to the file; all the names are equally valid, and no one of them is preferred. By contrast, a symbolic link is a kind of defined alias: when foo is a symbolic link to bar, you can use either name to refer to the file, but bar is the real name, while foo is just an alias. More complex cases occur when symbolic links point to directories.

Normally, if you visit a file which Emacs is already visiting under a different name, Emacs displays a message in the echo area and uses the existing buffer visiting that file. This can happen on systems that support hard or symbolic links, or if you use a long file name on a system that truncates long file names, or on a case-insensitive file system. You can suppress the message by setting the variable find-file-suppress-same-file-warnings to a non-nil value. You can disable this feature entirely by setting the variable find-file-existing-other-name to nil: then if you visit the same file under two different names, you get a separate buffer for each file name.

If the variable find-file-visit-truename is non-nil, then the file name recorded for a buffer is the file’s truename (made by replacing all symbolic links with their target names), rather than the name you specify. Setting find-file-visit-truename also implies the effect of find-file-existing-other-name.

Sometimes, a directory is ordinarily accessed through a symbolic link, and you may want Emacs to preferentially show its linked name. To do this, customize directory-abbrev-alist. Each element in this list should have the form (from . to), which means to replace from with to whenever from appears in a directory name. The from string is a regular expression (see Syntax of Regular Expressions). It is matched against directory names anchored at the first character, and should start with ‘\`’ (to support directory names with embedded newlines, which would defeat ‘^’). The to string should be an ordinary absolute directory name pointing to the same directory. Do not use ‘~’ to stand for a home directory in the to string; Emacs performs these substitutions separately. Here’s an example, from a system on which /home/fsf is normally accessed through a symbolic link named /fsf:

(("\\`/home/fsf" . "/fsf"))

19.8 File Directories

The file system groups files into directories. A directory listing is a list of all the files in a directory. Emacs provides commands to create and delete directories, and to make directory listings in brief format (file names only) and verbose format (sizes, dates, and other attributes included). Emacs also includes a directory browser feature called Dired, which you can invoke with C-x d; see Dired, the Directory Editor.

C-x C-d dir-or-pattern RET

Display a brief directory listing (list-directory).

C-u C-x C-d dir-or-pattern RET

Display a verbose directory listing.

M-x make-directory RET dirname RET

Create a new directory named dirname.

M-x delete-directory RET dirname RET

Delete the directory named dirname. If it isn’t empty, you will be asked whether you want to delete it recursively.

The command to display a directory listing is C-x C-d (list-directory). It reads using the minibuffer a file name which is either a directory to be listed or a wildcard-containing pattern for the files to be listed. For example,

C-x C-d /u2/emacs/etc RET

lists all the files in directory /u2/emacs/etc. Here is an example of specifying a file name pattern:

C-x C-d /u2/emacs/src/*.c RET

Normally, C-x C-d displays a brief directory listing containing just file names. A numeric argument (regardless of value) tells it to make a verbose listing including sizes, dates, and owners (like ‘ls -l’).

The text of a directory listing is mostly obtained by running ls in an inferior process. Two Emacs variables control the switches passed to ls: list-directory-brief-switches is a string giving the switches to use in brief listings ("-CF" by default), and list-directory-verbose-switches is a string giving the switches to use in a verbose listing ("-l" by default).

In verbose directory listings, Emacs adds information about the amount of free space on the disk that contains the directory.

The command M-x delete-directory prompts for a directory’s name using the minibuffer, and deletes the directory if it is empty. If the directory is not empty, you will be asked whether you want to delete it recursively. On systems that have a “Trash” (or “Recycle Bin”) feature, you can make this command move the specified directory to the Trash instead of deleting it outright, by changing the variable delete-by-moving-to-trash to t. See Miscellaneous File Operations, for more information about using the Trash.


19.9 Comparing Files

The command M-x diff prompts for two file names, using the minibuffer, and displays the differences between the two files in a buffer named *diff*. This works by running the diff program, using options taken from the variable diff-switches. The value of diff-switches should be a string; the default is "-u" to specify a unified context diff. See Diff in Comparing and Merging Files, for more information about the diff program.

The output of the diff command is shown using a major mode called Diff mode. See Diff Mode.

A (much more sophisticated) alternative is M-x ediff (see Ediff in The Ediff Manual).

The command M-x diff-backup compares a specified file with its most recent backup. If you specify the name of a backup file, diff-backup compares it with the source file that it is a backup of. In all other respects, this behaves like M-x diff.

The command M-x diff-buffer-with-file compares a specified buffer with its corresponding file. This shows you what changes you would make to the file if you save the buffer.

The command M-x diff-buffers compares the contents of two specified buffers.

The command M-x compare-windows compares the text in the current window with that in the window that was the selected window before you selected the current one. (For more information about windows in Emacs, see Multiple Windows.) Comparison starts at point in each window, after pushing each initial point value on the mark ring (see The Mark Ring) in its respective buffer. Then it moves point forward in each window, one character at a time, until it reaches characters that don’t match. Then the command exits.

If point in the two windows is followed by non-matching text when the command starts, M-x compare-windows tries heuristically to advance up to matching text in the two windows, and then exits. So if you use M-x compare-windows repeatedly (see Repeating a Command), each time it either skips one matching range or finds the start of another.

With a numeric argument, compare-windows ignores changes in whitespace. If the variable compare-ignore-case is non-nil, the comparison ignores differences in case as well. If the variable compare-ignore-whitespace is non-nil, compare-windows by default ignores changes in whitespace, but a prefix argument turns that off for that single invocation of the command.

You can use M-x smerge-mode to turn on Smerge mode, a minor mode for editing output from the diff3 program. This is typically the result of a failed merge from a version control system update outside VC, due to conflicting changes to a file. Smerge mode provides commands to resolve conflicts by selecting specific changes.

See Merging Files with Emerge, for the Emerge facility, which provides a powerful interface for merging files.


19.10 Diff Mode

Diff mode is a major mode used for the output of M-x diff and other similar commands. This kind of output is called a patch, because it can be passed to the patch command to automatically apply the specified changes. To select Diff mode manually, type M-x diff-mode.

The changes specified in a patch are grouped into hunks, which are contiguous chunks of text that contain one or more changed lines. Hunks usually also include unchanged lines to provide context for the changes. Each hunk is preceded by a hunk header, which specifies the old and new line numbers where the hunk’s changes occur. Diff mode highlights each hunk header, to distinguish it from the actual contents of the hunk.

The first hunk in a patch is preceded by a file header, which shows the names of the new and the old versions of the file, and their time stamps. If a patch shows changes for more than one file, each file has such a header before the first hunk of that file’s changes.

You can edit a Diff mode buffer like any other buffer. (If it is read-only, you need to make it writable first; see Miscellaneous Buffer Operations.) Whenever you edit a hunk, Diff mode attempts to automatically correct the line numbers in the hunk headers, to ensure that the patch remains correct, and could still be applied by patch. To disable automatic line number correction, change the variable diff-update-on-the-fly to nil.

Diff mode arranges for hunks to be treated as compiler error messages by M-g M-n and other commands that handle error messages (see Compilation Mode). Thus, you can use the compilation-mode commands to visit the corresponding source locations.

In addition, Diff mode provides the following commands to navigate, manipulate and apply parts of patches:

M-n

Move to the next hunk-start (diff-hunk-next). With prefix argument n, move forward to the nth next hunk.

By default, Diff mode refines hunks as Emacs displays them, highlighting their changes with better granularity. Alternatively, if you set diff-refine to the symbol navigation, Diff mode only refines the hunk you move to with this command or with diff-hunk-prev.

M-p

Move to the previous hunk-start (diff-hunk-prev). With prefix argument n, move back to the nth previous hunk. Like M-n, this command refines the hunk you move to if you set diff-refine to the symbol navigation.

M-}

Move to the next file-start, in a multi-file patch (diff-file-next). With prefix argument n, move forward to the start of the nth next file.

M-{

Move to the previous file-start, in a multi-file patch (diff-file-prev). With prefix argument n, move back to the start of the nth previous file.

M-k

Kill the hunk at point (diff-hunk-kill).

M-K

In a multi-file patch, kill the current file part. (diff-file-kill).

C-c C-a

Apply this hunk to its target file (diff-apply-hunk). With a prefix argument of C-u, revert this hunk, i.e. apply the reverse of the hunk, which changes the “new” version into the “old” version. If diff-jump-to-old-file is non-nil, apply the hunk to the “old” version of the file instead.

C-c C-b

Highlight the changes of the hunk at point with a finer granularity (diff-refine-hunk). This allows you to see exactly which parts of each changed line were actually changed.

By default, Diff mode refines hunks as Emacs displays them, so you may find this command useful if you customize diff-refine to a non-default value.

C-c C-c

Go to the source file and line corresponding to this hunk (diff-goto-source). By default, this jumps to the “new” version of the file, the one shown first on the file header. With a prefix argument, jump to the “old” version instead. If diff-jump-to-old-file is non-nil, this command by default jumps to the “old” file, and the meaning of the prefix argument is reversed. If the prefix argument is a number greater than 8 (e.g., if you type C-u C-u C-c C-c), then this command also sets diff-jump-to-old-file for the next invocation. If the source file is under version control (see Version Control), this jumps to the work file by default. With a prefix argument, jump to the “old” revision of the file (see Examining And Comparing Old Revisions), when point is on the old line, or otherwise jump to the “new” revision.

C-c C-e

Start an Ediff session with the patch (diff-ediff-patch). See Ediff in The Ediff Manual.

C-c C-n

Restrict the view to the current hunk (diff-restrict-view). See Narrowing. With a prefix argument, restrict the view to the current file of a multiple-file patch. To widen again, use C-x n w (widen).

C-c C-r

Reverse the direction of comparison for the entire buffer (diff-reverse-direction). With a prefix argument, reverse the direction only inside the current region (see The Mark and the Region). Reversing the direction means changing the hunks and the file-start headers to produce a patch that would change the “new” version into the “old” one.

C-c C-s

Split the hunk at point (diff-split-hunk) into two separate hunks. This inserts a hunk header and modifies the header of the current hunk. This command is useful for manually editing patches, and only works with the unified diff format produced by the -u or --unified options to the diff program. If you need to split a hunk in the context diff format produced by the -c or --context options to diff, first convert the buffer to the unified diff format with C-c C-u.

C-c C-d

Convert the entire buffer to the context diff format (diff-unified->context). With a prefix argument, convert only the hunks within the region.

C-c C-u

Convert the entire buffer to unified diff format (diff-context->unified). With a prefix argument, convert unified format to context format. When the mark is active, convert only the hunks within the region.

C-c C-l

Re-generate the current hunk (diff-refresh-hunk).

C-c C-w

Re-generate the current hunk, disregarding changes in whitespace (diff-ignore-whitespace-hunk).

C-x 4 A

Generate a ChangeLog entry, like C-x 4 a does (see Change Logs), for each one of the hunks (diff-add-change-log-entries-other-window). This creates a skeleton of the log of changes that you can later fill with the actual descriptions of the changes. C-x 4 a itself in Diff mode operates on behalf of the current hunk’s file, but gets the function name from the patch itself. This is useful for making log entries for functions that are deleted by the patch.

Patches sometimes include trailing whitespace on modified lines, as an unintentional and undesired change. There are two ways to deal with this problem. Firstly, if you enable Whitespace mode in a Diff buffer (see Useless Whitespace), it automatically highlights trailing whitespace in modified lines. Secondly, you can use the command M-x diff-delete-trailing-whitespace, which searches for trailing whitespace in the lines modified by the patch, and removes that whitespace in both the patch and the patched source file(s). This command does not save the modifications that it makes, so you can decide whether to save the changes (the list of modified files is displayed in the echo area). With a prefix argument, it tries to modify the original (“old”) source files rather than the patched (“new”) source files.

If diff-font-lock-syntax is non-nil, fragments of source in hunks are highlighted according to the appropriate major mode.


19.11 Copying, Naming and Renaming Files

Emacs has several commands for copying, naming, and renaming files. All of them read two file names, old (or target) and new, using the minibuffer, and then copy or adjust a file’s name accordingly; they do not accept wildcard file names.

In all these commands, if the argument new is just a directory name (see Directory Names in the Emacs Lisp Reference Manual), the real new name is in that directory, with the same non-directory component as old. For example, the command M-x rename-file RET ~/foo RET /tmp/ RET renames ~/foo to /tmp/foo. On GNU and other POSIX-like systems, directory names end in ‘/’.

All these commands ask for confirmation when the new file name already exists.

M-x copy-file copies the contents of the file old to the file new.

M-x copy-directory copies directories, similar to the cp -r shell command. If new is a directory name, it creates a copy of the old directory and puts it in new. Otherwise it copies all the contents of old into a new directory named new. If copy-directory-create-symlink is non-nil and old is a symbolic link, this command will copy the symbolic link. If nil, this command will follow the link and copy the contents instead. (This is the default.)

M-x rename-file renames file old as new. If the file name new already exists, you must confirm with yes or renaming is not done; this is because renaming causes the old meaning of the name new to be lost. If old and new are on different file systems, the file old is copied and deleted.

If a file is under version control (see Version Control), you should rename it using M-x vc-rename-file instead of M-x rename-file. See Deleting and Renaming Version-Controlled Files.

M-x add-name-to-file adds an additional name to an existing file without removing the old name. The new name is created as a hard link to the existing file. The new name must belong on the same file system that the file is on. On MS-Windows, this command works only if the file resides in an NTFS file system. On MS-DOS, and some remote system types, it works by copying the file.

M-x make-symbolic-link creates a symbolic link named new, which points at target. The effect is that future attempts to open file new will refer to whatever file is named target at the time the opening is done, or will get an error if the name target is nonexistent at that time. This command does not expand the argument target, so that it allows you to specify a relative name as the target of the link. However, this command does expand leading ‘~’ in target so that you can easily specify home directories, and strips leading ‘/:’ so that you can specify relative names beginning with literal ‘~’ or ‘/:’. See Quoted File Names. On MS-Windows, this command works only on MS Windows Vista and later. When new is remote, it works depending on the system type.


19.12 Miscellaneous File Operations

Emacs has commands for performing many other operations on files. All operate on one file; they do not accept wildcard file names.

M-x delete-file prompts for a file and deletes it. If you are deleting many files in one directory, it may be more convenient to use Dired rather than delete-file. See Deleting Files with Dired.

M-x move-file-to-trash moves a file into the system Trash (or Recycle Bin). This is a facility available on most operating systems; files that are moved into the Trash can be brought back later if you change your mind. (The way to restore trashed files is system-dependent.)

By default, Emacs deletion commands do not use the Trash. To use the Trash (when it is available) for common deletion commands, change the variable delete-by-moving-to-trash to t. This affects the commands M-x delete-file and M-x delete-directory (see File Directories), as well as the deletion commands in Dired (see Deleting Files with Dired). Supplying a prefix argument to M-x delete-file or M-x delete-directory makes them delete outright, instead of using the Trash, regardless of delete-by-moving-to-trash.

If you have delete-by-moving-to-trash set, and you want to delete files manually in Emacs from the Trash directory, using commands like D (dired-do-delete) doesn’t work well in the Trash directory (it’ll just give the file a new name, but won’t delete anything). If you want to be able to do this, you should create a .dir-locals.el file containing something like the following in the Trash directory:

((dired-mode . ((delete-by-moving-to-trash . nil))))

Note, however, if you use the system “empty trash” command, it’s liable to also delete this .dir-locals.el file, so this should only be done if you delete files from the Trash directory manually.

If a file is under version control (see Version Control), you should delete it using M-x vc-delete-file instead of M-x delete-file. See Deleting and Renaming Version-Controlled Files.

M-x insert-file (also C-x i) inserts a copy of the contents of the specified file into the current buffer at point, leaving point unchanged before the contents. The position after the inserted contents is added to the mark ring, without activating the mark (see The Mark Ring).

M-x insert-file-literally is like M-x insert-file, except the file is inserted literally: it is treated as a sequence of ASCII characters with no special encoding or conversion, similar to the M-x find-file-literally command (see Visiting Files).

M-x write-region is the inverse of M-x insert-file; it copies the contents of the region into the specified file. M-x append-to-file adds the text of the region to the end of the specified file. See Accumulating Text. The variable write-region-inhibit-fsync applies to these commands, as well as saving files; see Customizing Saving of Files.

M-x set-file-modes reads a file name followed by a file mode, and applies that file mode to the specified file. File modes, also called file permissions, determine whether a file can be read, written to, or executed, and by whom. This command reads file modes using the same symbolic or octal format accepted by the chmod command; for instance, ‘u+x’ means to add execution permission for the user who owns the file. It has no effect on operating systems that do not support file modes. chmod is a convenience alias for this function.


19.13 Accessing Compressed Files

Emacs automatically uncompresses compressed files when you visit them, and automatically recompresses them if you alter them and save them. Emacs recognizes compressed files by their file names. File names ending in ‘.gz’ indicate a file compressed with gzip. Other endings indicate other compression programs.

Automatic uncompression and compression apply to all the operations in which Emacs uses the contents of a file. This includes visiting it, saving it, inserting its contents into a buffer, loading it, and byte compiling it.

To disable this feature, type the command M-x auto-compression-mode. You can disable it permanently by customizing the variable auto-compression-mode.


19.14 File Archives

A file whose name ends in ‘.tar’ is normally an archive made by the tar program. Emacs views these files in a special mode called Tar mode which provides a Dired-like list of the contents (see Dired, the Directory Editor). You can move around through the list just as you would in Dired, and visit the subfiles contained in the archive. However, not all Dired commands are available in Tar mode.

If Auto Compression mode is enabled (see Accessing Compressed Files), then Tar mode is used also for compressed archives—files with extensions ‘.tgz’, .tar.Z and .tar.gz.

The keys e, f and RET all extract a component file into its own buffer. You can edit it there, and if you save the buffer, the edited version will replace the version in the Tar buffer. Clicking with the mouse on the file name in the Tar buffer does likewise. v extracts a file into a buffer in View mode (see View Mode). o extracts the file and displays it in another window, so you could edit the file and operate on the archive simultaneously.

The I key adds a new (regular) file to the archive. The file is initially empty, but can readily be edited using the commands above. The command inserts the new file before the current one, so that using it on the topmost line of the Tar buffer makes the new file the first one in the archive, and using it at the end of the buffer makes it the last one.

d marks a file for deletion when you later use x, and u unmarks a file, as in Dired. C copies a file from the archive to disk and R renames a file within the archive. g reverts the buffer from the archive on disk. The keys M, G, and O change the file’s permission bits, group, and owner, respectively.

Saving the Tar buffer writes a new version of the archive to disk with the changes you made to the components.

You don’t need the tar program to use Tar mode—Emacs reads the archives directly. However, accessing compressed archives requires the appropriate uncompression program.

A separate but similar Archive mode is used for arc, jar, lzh, zip, rar, 7z, and zoo archives, as well as exe files that are self-extracting executables.

The key bindings of Archive mode are similar to those in Tar mode, with the addition of the m key which marks a file for subsequent operations, and M-DEL which unmarks all the marked files. Also, the a key toggles the display of detailed file information, for those archive types where it won’t fit in a single line. Operations such as renaming a subfile, or changing its mode or owner, are supported only for some of the archive formats.

Unlike Tar mode, Archive mode runs the archiving programs to unpack and repack archives. However, you don’t need these programs to look at the archive table of contents, only to extract or manipulate the subfiles in the archive. Details of the program names and their options can be set in the ‘Archive’ Customize group (see Customization Groups).


19.15 Remote Files

You can refer to files on other machines using a special file name syntax:

/method:host:filename
/method:user@host:filename
/method:user@host#port:filename

To carry out this request, Emacs uses a remote-login program such as ssh. You must always specify in the file name which method to use—for example, /ssh:user@host:filename uses ssh. When you specify the pseudo method ‘-’ in the file name, Emacs chooses the method as follows:

  1. If the host name starts with ‘ftp.’ (with dot), Emacs uses FTP.
  2. If the user name is ‘ftp’ or ‘anonymous’, Emacs uses FTP.
  3. If the variable tramp-default-method is set to ‘ftp’, Emacs uses FTP.
  4. If ssh-agent is running, Emacs uses scp.
  5. Otherwise, Emacs uses ssh.

You can entirely turn off the remote file name feature by setting the variable tramp-mode to nil. You can turn off the feature in individual cases by quoting the file name with ‘/:’ (see Quoted File Names).

Remote file access through FTP is handled by the Ange-FTP package, which is documented in the following. Remote file access through the other methods is handled by the Tramp package, which has its own manual. See The Tramp Manual in The Tramp Manual.

When the Ange-FTP package is used, Emacs logs in through FTP using the name user, if that is specified in the remote file name. If user is unspecified, Emacs logs in using your user name on the local system; but if you set the variable ange-ftp-default-user to a string, that string is used instead. When logging in, Emacs may also ask for a password.

For performance reasons, Emacs does not make backup files for files accessed via FTP by default. To make it do so, change the variable ange-ftp-make-backup-files to a non-nil value.

By default, auto-save files for remote files are made in the temporary file directory on the local machine, as specified by the variable auto-save-file-name-transforms. See Auto-Save Files.

To visit files accessible by anonymous FTP, you use special user names ‘anonymous’ or ‘ftp’. Passwords for these user names are handled specially. The variable ange-ftp-generate-anonymous-password controls what happens: if the value of this variable is a string, then that string is used as the password; if non-nil (the default), then the value of user-mail-address is used; if nil, then Emacs prompts you for a password as usual (see Entering passwords).

Sometimes you may be unable to access files on a remote machine because a firewall in between blocks the connection for security reasons. If you can log in on a gateway machine from which the target files are accessible, and whose FTP server supports gatewaying features, you can still use remote file names; all you have to do is specify the name of the gateway machine by setting the variable ange-ftp-gateway-host, and set ange-ftp-smart-gateway to t. Otherwise you may be able to make remote file names work, but the procedure is complex. You can read the instructions by typing M-x finder-commentary RET ange-ftp RET.


19.16 Quoted File Names

You can quote an absolute file name to prevent special characters and syntax in it from having their special effects. The way to do this is to add ‘/:’ at the beginning.

For example, you can quote a local file name which appears remote, to prevent it from being treated as a remote file name. Thus, if you have a directory named /foo: and a file named bar in it, you can refer to that file in Emacs as ‘/:/foo:/bar’.

If you want to quote only special characters in the local part of a remote file name, you can quote just the local part. ‘/ssh:baz:/:/foo:/bar’ refers to the file bar of directory /foo: on the host baz.

/:’ can also prevent ‘~’ from being treated as a special character for a user’s home directory. For example, /:/tmp/~hack refers to a file whose name is ~hack in directory /tmp.

Quoting with ‘/:’ is also a way to enter in the minibuffer a file name that contains ‘$’. In order for this to work, the ‘/:’ must be at the beginning of the minibuffer contents. (You can also double each ‘$’; see File Names with $.)

You can also quote wildcard characters with ‘/:’, for visiting. For example, /:/tmp/foo*bar visits the file /tmp/foo*bar.

Another method of getting the same result is to enter /tmp/foo[*]bar, which is a wildcard specification that matches only /tmp/foo*bar. However, in many cases there is no need to quote the wildcard characters because even unquoted they give the right result. For example, if the only file name in /tmp that starts with ‘foo’ and ends with ‘bar’ is foo*bar, then specifying /tmp/foo*bar will visit only /tmp/foo*bar.


19.17 File Name Cache

You can use the file name cache to make it easy to locate a file by name, without having to remember exactly where it is located. When typing a file name in the minibuffer, C-TAB (file-cache-minibuffer-complete) completes it using the file name cache. If you repeat C-TAB, that cycles through the possible completions of what you had originally typed. (However, note that the C-TAB character cannot be typed on most text terminals.)

The file name cache does not fill up automatically. Instead, you load file names into the cache using these commands:

M-x file-cache-add-directory RET directory RET

Add each file name in directory to the file name cache.

M-x file-cache-add-directory-using-find RET directory RET

Add each file name in directory and all of its nested subdirectories to the file name cache.

M-x file-cache-add-directory-using-locate RET directory RET

Add each file name in directory and all of its nested subdirectories to the file name cache, using locate to find them all.

M-x file-cache-add-directory-list RET variable RET

Add each file name in each directory listed in variable to the file name cache. variable should be a Lisp variable whose value is a list of directories, like load-path.

M-x file-cache-clear-cache RET

Clear the cache; that is, remove all file names from it.

The file name cache is not persistent: it is kept and maintained only for the duration of the Emacs session. You can view the contents of the cache with the file-cache-display command.


19.18 Convenience Features for Finding Files

In this section, we introduce some convenient facilities for finding recently-opened files, reading file names from a buffer.

If you enable Recentf mode, with M-x recentf-mode, Emacs maintains a list of recently opened files. To open a file from this list, use the M-x recentf-open command. When this mode is enabled, the ‘File’ menu will include a submenu that you can use to visit one of these files. M-x recentf-save-list saves the current recentf-list to a file, and M-x recentf-edit-list edits it.

The M-x ffap command generalizes find-file with more powerful heuristic defaults (see Finding Files and URLs at Point), often based on the text at point. Partial Completion mode offers other features extending find-file, which can be used with ffap. See Completion Options.


19.19 Viewing Image Files

Visiting image files automatically selects Image mode. In this major mode, you can type C-c C-c (image-toggle-display) to toggle between displaying the file as an image in the Emacs buffer, and displaying its underlying text (or raw byte) representation. Additionally you can type C-c C-x (image-toggle-hex-display) to toggle between displaying the file as an image in the Emacs buffer, and displaying it in hex representation. Displaying the file as an image works only if Emacs is compiled with support for displaying such images.

If the displayed image is wider or taller than the window in which it is displayed, the usual point motion keys (C-f, C-p, and so forth) cause different parts of the image to be displayed. However, by default images are resized automatically to fit the window, so this is only necessary if you customize the default behavior by using the options image-auto-resize and image-auto-resize-on-window-resize.

To resize the image manually you can use the command image-transform-fit-to-window bound to s w that fits the image to both the window height and width. To scale the image to a percentage of its original size, use the command image-transform-set-percent bound to s p. To scale the image specifying a scale factor, use the command image-transform-set-scale bound to s s. To reset all transformations to the initial state, use image-transform-reset-to-initial bound to s 0, or image-transform-reset-to-original bound to s o.

You can press n (image-next-file) and p (image-previous-file) to visit the next image file and the previous image file in the same directory, respectively. These commands will consult the “parent” dired buffer to determine what the next/previous image file is. These commands also work when opening a file from archive files (like zip or tar files), and will then instead consult the archive mode buffer. If neither an archive nor a dired “parent” buffer can be found, a dired buffer is opened.

When looking through images, it’s sometimes convenient to be able to mark the files for later processing (for instance, if you want to select a group of images to copy somewhere else). The m (image-mode-mark-file) command will mark the current file in any Dired buffer(s) that display the current file’s directory. If no such buffer is open, the directory is opened in a new buffer. To unmark files, use the u (image-mode-mark-file) command. Finally, if you just want to copy the current buffers file name to the kill ring, you can use the w (image-mode-copy-file-name-as-kill) command.

If the image can be animated, the command RET (image-toggle-animation) starts or stops the animation. Animation plays once, unless the option image-animate-loop is non-nil. With f (image-next-frame) and b (image-previous-frame) you can step through the individual frames. Both commands accept a numeric prefix to step through several frames at once. You can go to a specific frame with F (image-goto-frame). Frames are indexed from 1. Typing a + (image-increase-speed) increases the speed of the animation, a - (image-decrease-speed) decreases it, and a r (image-reverse-speed) reverses it. The command a 0 (image-reset-speed) resets the speed to the original value.

In addition to the above key bindings, which are specific to Image mode, images shown in any Emacs buffer have special key bindings when point is at or inside the image:

i +

Increase the image size (image-increase-size) by 20%. Prefix numeric argument controls the increment; the value of n means to multiply the size by the factor of 1 + n / 10, so C-u 5 i + means to increase the size by 50%.

i -

Decrease the image size (image-increase-size) by 20%. Prefix numeric argument controls the decrement; the value of n means to multiply the size by the factor of - n / 10, so C-u 3 i - means to decrease the size by 30%.

i r

Rotate the image by 90 degrees clockwise (image-rotate). With the prefix argument, rotate by 90 degrees counter-clockwise instead. Note that this command is not available for sliced images.

i h

Flip the image horizontally (image-flip-horizontally). This presents the image as if reflected in a vertical mirror. Note that this command is not available for sliced images.

i v

Flip the image vertically (image-flip-vertically). This presents the image as if reflected in a horizontal mirror. Note that this command is not available for sliced images.

i o

Save the image to a file (image-save). This command prompts you for the name of the file to save the image.

i c

Crop the image (image-crop). This command is available only if your system has an external program installed that can be used for cropping and cutting of images; the user option image-crop-crop-command determines what program to use, and defaults to the ImageMagick’s convert program. The command displays the image with a rectangular frame superimposed on it, and lets you use the mouse to move and resize the frame. Type m to cause mouse movements to move the frame instead of resizing it; type s to move a square frame instead. When you are satisfied with the position and size of the cropping frame, type RET to actually crop the part under the frame; or type q to exit without cropping. You can then save the cropped image using i o or M-x image-save.

i x

Cut a rectangle from the image (image-cut). This works the same as image-crop (and also requires an external program, defined by the variable image-crop-cut-command, to perform the image cut), but instead of cropping the image, it removes the part inside the frame and fills that part with the color specified by image-cut-color. With prefix argument, the command prompts for the color to use.

The size and rotation commands are “repeating”, which means that you can continue adjusting the image without using the i prefix.

If Emacs was compiled with support for the ImageMagick library, it can use ImageMagick to render a wide variety of images. The variable imagemagick-enabled-types lists the image types that Emacs may render using ImageMagick; each element in the list should be an internal ImageMagick name for an image type, as a symbol or an equivalent string (e.g., BMP for .bmp images). To enable ImageMagick for all possible image types, change imagemagick-enabled-types to t. The variable imagemagick-types-inhibit lists the image types which should never be rendered using ImageMagick, regardless of the value of imagemagick-enabled-types (the default list includes types like C and HTML, which ImageMagick can render as an image but Emacs should not). To disable ImageMagick entirely, change imagemagick-types-inhibit to t.

If Emacs doesn’t have native support for the image format in question, and image-use-external-converter is non-nil, Emacs will try to determine whether there are external utilities that can be used to transform the image in question to PNG before displaying. GraphicsMagick, ImageMagick and ffmpeg are currently supported for image conversions.

In addition, you may wish to add special handlers for certain image formats. These can be added with the image-converter-add-handler function. For instance, to allow viewing Krita files as simple images, you could say something like:

(image-converter-add-handler
 "kra"
 (lambda (file data-p)
   (if data-p
       (error "Can't decode non-files")
     (call-process "unzip" nil t nil
                   "-qq" "-c" "-x" file "mergedimage.png"))))

The function takes two parameters, where the first is a file name suffix, and the second is a function to do the “conversion”. This function takes two parameters, where the first is the file name or a string with the data, and the second says whether the first parameter is data or not, and should output an image in image-convert-to-format format in the current buffer.

The Image-Dired package can also be used to view images as thumbnails. See Viewing Image Thumbnails in Dired.


19.20 Filesets

If you regularly edit a certain group of files, you can define them as a fileset. This lets you perform certain operations, such as visiting, query-replace, and shell commands on all the files at once. To make use of filesets, you must first add the expression (filesets-init) to your init file (see The Emacs Initialization File). This adds a ‘Filesets’ sub-menu to the menu bar’s ‘File’ menu.

The simplest way to define a fileset is by adding files to it one at a time. To add a file to fileset name, visit the file and type M-x filesets-add-buffer RET name RET. If there is no fileset name, this creates a new one, which initially contains only the current file. The command M-x filesets-remove-buffer removes the current file from a fileset.

You can also edit the list of filesets directly, with M-x filesets-edit (or by choosing ‘Edit Filesets’ from the ‘Filesets’ menu). The editing is performed in a Customize buffer (see Easy Customization Interface). Normally, a fileset is a simple list of files, but you can also define a fileset as a regular expression matching file names. Some examples of these more complicated filesets are shown in the Customize buffer. Remember to select ‘Save for future sessions’ if you want to use the same filesets in future Emacs sessions.

You can use the command M-x filesets-open to visit all the files in a fileset, and M-x filesets-close to close them. Use M-x filesets-run-cmd to run a shell command on all the files in a fileset. These commands are also available from the ‘Filesets’ menu, where each existing fileset is represented by a submenu.

See Version Control, for a different concept of filesets: groups of files bundled together for version control operations. Filesets of that type are unnamed, and do not persist across Emacs sessions.


20 Using Multiple Buffers

The text you are editing in Emacs resides in an object called a buffer. Each time you visit a file, a buffer is used to hold the file’s text. Each time you invoke Dired, a buffer is used to hold the directory listing. If you send a message with C-x m, a buffer is used to hold the text of the message. When you ask for a command’s documentation, that appears in a buffer named *Help*.

Buffers exist as long as they are in use, and are deleted (“killed”) when no longer needed, either by you (see Killing Buffers) or by Emacs (e.g., when you exit Emacs, see Exiting Emacs).

Each buffer has a unique name, which can be of any length. When a buffer is displayed in a window, its name is shown in the mode line (see The Mode Line). The distinction between upper and lower case matters in buffer names. Most buffers are made by visiting files, and their names are derived from the files’ names; however, you can also create an empty buffer with any name you want. A newly started Emacs has several buffers, including one named *scratch*, which can be used for evaluating Lisp expressions and is not associated with any file (see Lisp Interaction Buffers).

At any time, one and only one buffer is selected; we call it the current buffer. We sometimes say that a command operates on “the buffer”; this really means that it operates on the current buffer. When there is only one Emacs window, the buffer displayed in that window is current. When there are multiple windows, the buffer displayed in the selected window is current. See Multiple Windows.

A buffer’s contents consist of a series of characters, each of which optionally carries a set of text properties (see Text properties) that can specify more information about that character.

Aside from its textual contents, each buffer records several pieces of information, such as what file it is visiting (if any), whether it is modified, and what major mode and minor modes are in effect (see Major and Minor Modes). These are stored in buffer-local variables—variables that can have a different value in each buffer. See Local Variables.

A buffer’s size cannot be larger than some maximum, which is defined by the largest buffer position representable by Emacs integers. This is because Emacs tracks buffer positions using that data type. For typical 64-bit machines, this maximum buffer size is 2^{61} - 2 bytes, or about 2 EiB. For typical 32-bit machines, the maximum is usually 2^{29} - 2 bytes, or about 512 MiB. Buffer sizes are also limited by the amount of memory in the system.


20.1 Creating and Selecting Buffers

C-x b buffer RET

Select or create a buffer named buffer (switch-to-buffer).

C-x 4 b buffer RET

Similar, but select buffer in another window (switch-to-buffer-other-window).

C-x 5 b buffer RET

Similar, but select buffer in a separate frame (switch-to-buffer-other-frame).

C-x LEFT

Select the previous buffer in the buffer list (previous-buffer).

C-x RIGHT

Select the next buffer in the buffer list (next-buffer).

C-u M-g M-g
C-u M-g g

Read a number n and move to line n in the most recently selected buffer other than the current buffer, in another window.

The C-x b (switch-to-buffer) command reads a buffer name using the minibuffer. Then it makes that buffer current, and displays it in the currently-selected window. An empty input specifies the buffer that was current most recently among those not now displayed in any window.

While entering the buffer name, you can use the usual completion and history commands (see The Minibuffer). Note that C-x b, and related commands, use permissive completion with confirmation for minibuffer completion: if you type RET when the minibuffer text names a nonexistent buffer, Emacs prints ‘[Confirm]’ and you must type a second RET to submit that buffer name. See Completion Exit, for details. For other completion options and features, see Completion Options.

If you specify a buffer that does not exist, C-x b creates a new, empty buffer that is not visiting any file, and selects it for editing. The default value of the variable major-mode determines the new buffer’s major mode; the default value is Fundamental mode. See Major Modes. One reason to create a new buffer is to use it for making temporary notes. If you try to save it, Emacs asks for the file name to use, and the buffer’s major mode is re-established taking that file name into account (see Choosing File Modes).

For conveniently switching between a few buffers, use the commands C-x LEFT and C-x RIGHT. C-x LEFT (previous-buffer) selects the previous buffer (following the order of most recent selection in the current frame), while C-x RIGHT (next-buffer) moves through buffers in the reverse direction. Both commands support a numeric prefix argument that serves as a repeat count.

To select a buffer in a window other than the current one (see Multiple Windows), type C-x 4 b (switch-to-buffer-other-window). This prompts for a buffer name using the minibuffer, displays that buffer in another window, and selects that window.

Similarly, C-x 5 b (switch-to-buffer-other-frame) prompts for a buffer name, displays that buffer in another frame (see Frames and Graphical Displays), and selects that frame. If the buffer is already being shown in a window on another frame, Emacs selects that window and frame instead of creating a new frame.

See Displaying a Buffer in a Window, for how the C-x 4 b and C-x 5 b commands get the window and/or frame to display in.

In addition, C-x C-f, and any other command for visiting a file, can also be used to switch to an existing file-visiting buffer. See Visiting Files.

C-u M-g M-g, that is goto-line with a plain prefix argument, reads a number n using the minibuffer, selects the most recently selected buffer other than the current buffer in another window, and then moves point to the beginning of line number n in that buffer. This is mainly useful in a buffer that refers to line numbers in another buffer: if point is on or just after a number, goto-line uses that number as the default for n. Note that prefix arguments other than just C-u behave differently. C-u 4 M-g M-g goes to line 4 in the current buffer, without reading a number from the minibuffer. (Remember that M-g M-g without prefix argument reads a number n and then moves to line number n in the current buffer. See Changing the Location of Point.)

Emacs uses buffer names that start with a space for internal purposes. It treats these buffers specially in minor ways—for example, by default they do not record undo information. It is best to avoid using such buffer names yourself.


20.2 Listing Existing Buffers

C-x C-b

List the existing buffers (list-buffers).

To display a list of existing buffers, type C-x C-b. This pops up a buffer menu in a buffer named *Buffer List*. Each line in the list shows one buffer’s name, size, major mode and visited file. The buffers are listed in the order that they were current; the buffers that were current most recently come first. This section describes how the list of buffers is displayed and how to interpret the various indications in the list; see Operating on Several Buffers, for description of the special mode in the *Buffer List* buffer and the commands available there.

.’ in the first field of a line indicates that the buffer is current. ‘%’ indicates a read-only buffer. ‘*’ indicates that the buffer is modified. If several buffers are modified, it may be time to save some with C-x s (see Commands for Saving Files). Here is an example of a buffer list:

CRM Buffer                Size  Mode              File
. * .emacs                3294  Emacs-Lisp        ~/.emacs
 %  *Help*                 101  Help
    search.c             86055  C                 ~/cvs/emacs/src/search.c
 %  src                  20959  Dired by name     ~/cvs/emacs/src/
  * *mail*                  42  Mail
 %  HELLO                 1607  Fundamental       ~/cvs/emacs/etc/HELLO
 %  NEWS                481184  Outline           ~/cvs/emacs/etc/NEWS
    *scratch*              191  Lisp Interaction
  * *Messages*            1554  Messages

The buffer *Help* was made by a help request (see Help); it is not visiting any file. The buffer src was made by Dired on the directory ~/cvs/emacs/src/. You can list only buffers that are visiting files by giving the command a prefix argument, as in C-u C-x C-b.

list-buffers omits buffers whose names begin with a space, unless they visit files: such buffers are used internally by Emacs.


20.3 Miscellaneous Buffer Operations

C-x C-q

Toggle read-only status of buffer (read-only-mode).

C-x x r RET buffer RET

Change the name of the current buffer.

C-x x u

Rename the current buffer by adding ‘<number>’ to the end.

M-x view-buffer RET buffer RET

Scroll through buffer buffer. See View Mode.

A buffer can be read-only, which means that commands to insert or delete its text are not allowed. (However, other commands, like C-x RET f, can still mark it as modified, see Specifying a Coding System for File Text). The mode line indicates read-only buffers with ‘%%’ or ‘%*’ near the left margin. See The Mode Line. Read-only buffers are usually made by subsystems such as Dired and Rmail that have special commands to operate on the text. Visiting a file whose access control says you cannot write it also makes the buffer read-only.

The command C-x C-q (read-only-mode) makes a read-only buffer writable, and makes a writable buffer read-only. This works by setting the variable buffer-read-only, which has a local value in each buffer and makes the buffer read-only if its value is non-nil. If you change the option view-read-only to a non-nil value, making the buffer read-only with C-x C-q also enables View mode in the buffer (see View Mode).

C-x x r (rename-buffer changes the name of the current buffer. You specify the new name as a minibuffer argument; there is no default. If you specify a name that is in use for some other buffer, an error happens and no renaming is done.

C-x x u (rename-uniquely) renames the current buffer to a similar name with a numeric suffix added to make it both different and unique. This command does not need an argument. It is useful for creating multiple shell buffers: if you rename the *shell* buffer, then do M-x shell again, it makes a new shell buffer named *shell*; meanwhile, the old shell buffer continues to exist under its new name. This method is also good for mail buffers, compilation buffers, and most Emacs features that create special buffers with particular names. (With some of these features, such as M-x compile, M-x grep, you need to switch to some other buffer before using the command again, otherwise it will reuse the current buffer despite the name change.)

The commands M-x append-to-buffer and C-x x i (insert-buffer) can also be used to copy text from one buffer to another. See Accumulating Text.


20.4 Killing Buffers

If you continue an Emacs session for a while, you may accumulate a large number of buffers. You may then find it convenient to kill the buffers you no longer need. (Some other editors call this operation close, and talk about “closing the buffer” or “closing the file” visited in the buffer.) On most operating systems, killing a buffer releases the memory Emacs used for the buffer back to the operating system so that other programs can use it. Here are some commands for killing buffers:

C-x k buffer RET

Kill buffer buffer (kill-buffer).

M-x kill-some-buffers

Offer to kill each buffer, one by one.

M-x kill-matching-buffers

Offer to kill all buffers matching a regular expression.

C-x k (kill-buffer) kills one buffer, whose name you specify in the minibuffer. The default, used if you type just RET in the minibuffer, is to kill the current buffer. If you kill the current buffer, another buffer becomes current: one that was current in the recent past but is not displayed in any window now. If you ask to kill a file-visiting buffer that is modified, then you must confirm with yes before the buffer is killed.

The command M-x kill-some-buffers asks about each buffer, one by one. An answer of yes means to kill the buffer, just like kill-buffer. This command ignores buffers whose names begin with a space, which are used internally by Emacs.

The command M-x kill-matching-buffers prompts for a regular expression and kills all buffers whose names match that expression. See Syntax of Regular Expressions. Like kill-some-buffers, it asks for confirmation before each kill. This command normally ignores buffers whose names begin with a space, which are used internally by Emacs. To kill internal buffers as well, call kill-matching-buffers with a prefix argument.

The Buffer Menu feature is also convenient for killing various buffers. See Operating on Several Buffers.

If you want to do something special every time a buffer is killed, you can add hook functions to the hook kill-buffer-hook (see Hooks).

If you run one Emacs session for a period of days, as many people do, it can fill up with buffers that you used several days ago. The command M-x clean-buffer-list is a convenient way to purge them; it kills all the unmodified buffers that you have not used for a long time. An ordinary buffer is killed if it has not been displayed for three days; however, you can specify certain buffers that should never be killed automatically, and others that should be killed if they have been unused for a mere hour. These defaults, and other aspects of this command’s behavior, can be controlled by customizing several options described in the doc string of clean-buffer-list.

You can also have this buffer purging done for you, once a day, by enabling Midnight mode. Midnight mode operates each day at midnight; at that time, it runs clean-buffer-list, or whichever functions you have placed in the normal hook midnight-hook (see Hooks). To enable Midnight mode, use the Customization buffer to set the variable midnight-mode to t. See Easy Customization Interface.


20.5 Operating on Several Buffers

M-x buffer-menu

Begin editing a buffer listing all Emacs buffers.

M-x buffer-menu-other-window

Similar, but do it in another window.

The Buffer Menu opened by C-x C-b (see Listing Existing Buffers) does not merely list buffers. It also allows you to perform various operations on buffers, through an interface similar to Dired (see Dired, the Directory Editor). You can save buffers, kill them (here called deleting them, for consistency with Dired), or display them.

To use the Buffer Menu, type C-x C-b and switch to the window displaying the *Buffer List* buffer. You can also type M-x buffer-menu to open the Buffer Menu in the selected window. Alternatively, the command M-x buffer-menu-other-window opens the Buffer Menu in another window, and selects that window.

The Buffer Menu is a read-only buffer, and can be changed only through the special commands described in this section. The usual cursor motion commands can be used in this buffer. The following commands apply to the buffer described on the current line:

d

Flag the buffer for deletion (killing), then move point to the next line (Buffer-menu-delete). The deletion flag is indicated by the character ‘D’ on the line, before the buffer name. The deletion occurs only when you type the x command (see below).

C-d

Like d, but move point up instead of down (Buffer-menu-delete-backwards).

s

Flag the buffer for saving (Buffer-menu-save). The save flag is indicated by the character ‘S’ on the line, before the buffer name. The saving occurs only when you type x. You may request both saving and deletion for the same buffer.

x

Perform all flagged deletions and saves (Buffer-menu-execute).

u

Remove all flags from the current line, and move down (Buffer-menu-unmark). With a prefix argument, moves up after removing the flags.

DEL

Move to the previous line and remove all flags on that line (Buffer-menu-backup-unmark).

M-DEL

Remove a particular flag from all lines (Buffer-menu-unmark-all-buffers). This asks for a single character, and unmarks buffers marked with that character; typing RET removes all marks.

U

Remove all flags from all the lines (Buffer-menu-unmark-all).

The commands for removing flags, d and C-d, accept a numeric argument as a repeat count.

The following commands operate immediately on the buffer listed on the current line. They also accept a numeric argument as a repeat count.

~

Mark the buffer as unmodified (Buffer-menu-not-modified). See Commands for Saving Files.

%

Toggle the buffer’s read-only status (Buffer-menu-toggle-read-only). See Miscellaneous Buffer Operations.

t

Visit the buffer as a tags table (Buffer-menu-visit-tags-table). See Selecting a Tags Table.

The following commands are used to select another buffer or buffers:

q

Quit the Buffer Menu (quit-window). The most recent formerly visible buffer is displayed in its place.

RET
f

Select this line’s buffer, replacing the *Buffer List* buffer in its window (Buffer-menu-this-window).

o

Select this line’s buffer in another window, as if by C-x 4 b, leaving *Buffer List* visible (Buffer-menu-other-window).

C-o

Display this line’s buffer in another window, without selecting it (Buffer-menu-switch-other-window).

1

Select this line’s buffer in a full-frame window (Buffer-menu-1-window).

2

Set up two windows on the current frame, with this line’s buffer selected in one, and a previously current buffer (aside from *Buffer List*) in the other (Buffer-menu-2-window).

b

Bury this line’s buffer (Buffer-menu-bury) (i.e., move it to the end of the buffer list).

m

Mark this line’s buffer to be displayed in another window if you exit with the v command (Buffer-menu-mark). The display flag is indicated by the character ‘>’ at the beginning of the line. (A single buffer may not have both deletion and display flags.)

v

Select this line’s buffer, and also display in other windows any buffers flagged with the m command (Buffer-menu-select). If you have not flagged any buffers, this command is equivalent to 1.

The following commands affect the entire buffer list:

S

Sort the Buffer Menu entries according to their values in the column at point. With a numeric prefix argument n, sort according to the n-th column (tabulated-list-sort).

}

Widen the current column width by n (the prefix numeric argument) characters.

{

Narrow the current column width by n (the prefix numeric argument) characters.

T

Delete, or reinsert, lines for non-file buffers (Buffer-menu-toggle-files-only). This command toggles the inclusion of such buffers in the buffer list.

Normally, the buffer *Buffer List* is not updated automatically when buffers are created and killed; its contents are just text. If you have created, deleted or renamed buffers, the way to update *Buffer List* to show what you have done is to type g (revert-buffer). You can make this happen regularly every auto-revert-interval seconds if you enable Auto Revert mode in this buffer, as long as it is not marked modified. Global Auto Revert mode applies to the *Buffer List* buffer only if global-auto-revert-non-file-buffers is non-nil. See global-auto-revert-non-file-buffers, for details.


20.6 Indirect Buffers

An indirect buffer shares the text of some other buffer, which is called the base buffer of the indirect buffer. In some ways it is a buffer analogue of a symbolic link between files.

M-x make-indirect-buffer RET base-buffer RET indirect-name RET

Create an indirect buffer named indirect-name with base buffer base-buffer.

M-x clone-indirect-buffer RET

Create an indirect buffer that is a twin copy of the current buffer.

C-x 4 c

Create an indirect buffer that is a twin copy of the current buffer, and select it in another window (clone-indirect-buffer-other-window).

The text of the indirect buffer is always identical to the text of its base buffer; changes made by editing either one are visible immediately in the other. “Text” here includes both the characters and their text properties. But in all other respects, the indirect buffer and its base buffer are completely separate. They can have different names, different values of point, different narrowing, different markers, different overlays, different major modes, and different local variables.

An indirect buffer cannot visit a file, but its base buffer can. If you try to save the indirect buffer, that actually works by saving the base buffer. Killing the base buffer effectively kills the indirect buffer, but killing an indirect buffer has no effect on its base buffer.

One way to use indirect buffers is to display multiple views of an outline. See Viewing One Outline in Multiple Views.

A quick and handy way to make an indirect buffer is with the command C-x 4 c (clone-indirect-buffer-other-window). It creates and selects an indirect buffer whose base buffer is the current buffer. With a numeric argument, it prompts for the name of the indirect buffer; otherwise it uses the name of the current buffer, with a ‘<n>’ suffix added.

The more general way to make an indirect buffer is with the command M-x make-indirect-buffer. It creates an indirect buffer named indirect-name from a buffer base-buffer, prompting for both using the minibuffer.

The functions that create indirect buffers run the hook clone-indirect-buffer-hook after creating the indirect buffer. When this hook runs, the newly created indirect buffer is the current buffer.

Note: When a modification is made to the text of a buffer, the modification hooks are run only in the base buffer, because most of the functions on those hooks are not prepared to work correctly in indirect buffers. So if you need a modification hook function in an indirect buffer, you need to manually add that function to the hook in the base buffer and then make the function operate in the desired indirect buffer.


20.7 Convenience Features and Customization of Buffer Handling

This section describes several modes and features that make it more convenient to switch between buffers.


20.7.1 Making Buffer Names Unique

When several buffers visit identically-named files, Emacs must give the buffers distinct names. The default method adds a suffix based on the names of the directories that contain the files. For example, if you visit files /foo/bar/mumble/name and /baz/quux/mumble/name at the same time, their buffers will be named ‘name<bar/mumble>’ and ‘name<quux/mumble>’, respectively. Emacs adds as many directory parts as are needed to make a unique name.

You can choose from several different styles for constructing unique buffer names, by customizing the option uniquify-buffer-name-style.

The forward naming method includes part of the file’s directory name at the beginning of the buffer name; using this method, buffers visiting the files /u/rms/tmp/Makefile and /usr/projects/zaphod/Makefile would be named ‘tmp/Makefile’ and ‘zaphod/Makefile’.

In contrast, the post-forward naming method would call the buffers ‘Makefile|tmp’ and ‘Makefile|zaphod’. The default method post-forward-angle-brackets is like post-forward, except that it encloses the unique path in angle brackets. The reverse naming method would call them ‘Makefile\tmp’ and ‘Makefile\zaphod’. The nontrivial difference between post-forward and reverse occurs when just one directory name is not enough to distinguish two files; then reverse puts the directory names in reverse order, so that /top/middle/file becomes ‘file\middle\top’, while post-forward puts them in forward order after the file name, as in ‘file|top/middle’. If uniquify-buffer-name-style is set to nil, the buffer names simply get ‘<2>’, ‘<3>’, etc. appended.

The value of uniquify-buffer-name-style can be set to a customized function with two arguments base and extra-strings where base is a string and extra-strings is a list of strings. For example the current implementation for post-forward-angle-brackets could be:

(defun my-post-forward-angle-brackets (base extra-string)
  (concat base \"<\" (mapconcat #'identity extra-string \"/\") \">\"))

Which rule to follow for putting the directory names in the buffer name is not very important if you are going to look at the buffer names before you type one. But as an experienced user, if you know the rule, you won’t have to look. And then you may find that one rule or another is easier for you to remember and apply quickly.


20.7.2 Fast minibuffer selection

Icomplete global minor mode provides a convenient way to quickly select an element among the possible completions in a minibuffer. When enabled, typing in the minibuffer continuously displays a list of possible completions that match the string you have typed.

At any time, you can type C-j to select the first completion in the list. So the way to select a particular completion is to make it the first in the list. There are two ways to do this. You can type more of the completion name and thus narrow down the list, excluding unwanted completions above the desired one. Alternatively, you can use C-. and C-, to rotate the list until the desired buffer is first.

M-TAB will select the first completion in the list, like C-j but without exiting the minibuffer, so you can edit it further. This is typically used when entering a file name, where M-TAB can be used a few times to descend in the hierarchy of directories.

To enable Icomplete mode, type M-x icomplete-mode, or customize the variable icomplete-mode to t (see Easy Customization Interface).

An alternative to Icomplete mode is Fido mode. This is very similar to Icomplete mode, but retains some functionality from a popular extension called Ido mode (in fact the name is derived from “Fake Ido”). Among other things, in Fido mode, C-s and C-r are also used to rotate the completions list, C-k can be used to delete files and kill buffers in-list. Another noteworthy aspect is that flex is used as the default completion style (see How Completion Alternatives Are Chosen). To change this, add the following to your initialization file (see The Emacs Initialization File):

(defun my-icomplete-styles ()
  (setq-local completion-styles '(initials flex)))
(add-hook 'icomplete-minibuffer-setup-hook 'my-icomplete-styles)

To enable Fido mode, type M-x fido-mode, or customize the variable fido-mode to t (see Easy Customization Interface).

Icomplete mode and Fido mode display the possible completions on the same line as the prompt by default. To display the completion candidates vertically under the prompt, type M-x icomplete-vertical-mode, or customize the variable icomplete-vertical-mode to t (see Easy Customization Interface).


20.7.3 Customizing Buffer Menus

M-x bs-show

Make a list of buffers similarly to M-x list-buffers but customizable.

M-x ibuffer

Make a list of buffers and operate on them in Dired-like fashion.

M-x bs-show pops up a buffer list similar to the one normally displayed by C-x C-b, but whose display you can customize in a more flexible fashion. For example, you can specify the list of buffer attributes to show, the minimum and maximum width of buffer name column, a regexp for names of buffers that will never be shown and those which will always be shown, etc. If you prefer this to the usual buffer list, you can bind this command to C-x C-b. To customize this buffer list, use the bs Custom group (see Easy Customization Interface), or invoke bs-customize.

MSB global minor mode (“MSB” stands for “mouse select buffer”) provides a different and customizable mouse buffer menu which you may prefer. It replaces the mouse-buffer-menu commands, normally bound to C-Down-mouse-1 and C-F10, with its own commands, and also modifies the menu-bar buffer menu. You can customize the menu in the msb Custom group.

IBuffer is a major mode for viewing a list of buffers and operating on them in a way analogous to that of Dired (see Dired, the Directory Editor), including filtering, marking, sorting in various ways, and acting on buffers.


21 Multiple Windows

Emacs can split a frame into two or many windows. Multiple windows can display parts of different buffers, or different parts of one buffer. Multiple frames always imply multiple windows, because each frame has its own set of windows. Each window belongs to one and only one frame.


21.1 Concepts of Emacs Windows

Each Emacs window displays one Emacs buffer at any time. A single buffer may appear in more than one window; if it does, any changes in its text are displayed in all the windows where it appears. But these windows can show different parts of the buffer, because each window has its own value of point.

At any time, one Emacs window is the selected window; the buffer this window is displaying is the current buffer. On graphical displays, the point is indicated by a solid blinking cursor in the selected window, and by a hollow box in non-selected windows. On text terminals, the cursor is drawn only in the selected window. See Displaying the Cursor.

Commands to move point affect the value of point for the selected Emacs window only. They do not change the value of point in other Emacs windows, even those showing the same buffer. The same is true for buffer-switching commands such as C-x b; they do not affect other windows at all. However, there are other commands such as C-x 4 b that select a different window and switch buffers in it. Also, all commands that display information in a window, including (for example) C-h f (describe-function) and C-x C-b (list-buffers), usually work by displaying buffers in a nonselected window without affecting the selected window.

When multiple windows show the same buffer, they can have different regions, because they can have different values of point. However, they all have the same value for the mark, because each buffer has only one mark position.

Each window has its own mode line, which displays the buffer name, modification status and major and minor modes of the buffer that is displayed in the window. The selected window’s mode line appears in a different color. See The Mode Line, for details.


21.2 Splitting Windows

C-x 2

Split the selected window into two windows, one above the other (split-window-below).

C-x 3

Split the selected window into two windows, positioned side by side (split-window-right).

C-mouse-2

In the mode line of a window, split that window.

C-x 2 (split-window-below) splits the selected window into two windows, one above the other. After splitting, the selected window is the upper one, and the newly split-off window is below. Both windows have the same value of point as before, and display the same portion of the buffer (or as close to it as possible). If necessary, the windows are scrolled to keep point on-screen. By default, the two windows each get half the height of the original window. A positive numeric argument specifies how many lines to give to the top window; a negative numeric argument specifies how many lines to give to the bottom window.

If you change the variable split-window-keep-point to nil, C-x 2 instead adjusts the portion of the buffer displayed by the two windows, as well as the value of point in each window, in order to keep the text on the screen as close as possible to what it was before; furthermore, if point was in the lower half of the original window, the bottom window is selected instead of the upper one.

C-x 3 (split-window-right) splits the selected window into two side-by-side windows. The left window is the selected one; the right window displays the same portion of the same buffer, and has the same value of point. A positive numeric argument specifies how many columns to give the left window; a negative numeric argument specifies how many columns to give the right window.

When you split a window with C-x 3, each resulting window occupies less than the full width of the frame. If it becomes too narrow, the buffer may be difficult to read if continuation lines are in use (see Continuation Lines). Therefore, Emacs automatically switches to line truncation if the window width becomes narrower than 50 columns. This truncation occurs regardless of the value of the variable truncate-lines (see Line Truncation); it is instead controlled by the variable truncate-partial-width-windows. If the value of this variable is a positive integer (the default is 50), that specifies the minimum total width for a partial-width window before automatic line truncation occurs; if the value is nil, automatic line truncation is disabled; and for any other non-nil value, Emacs truncates lines in every partial-width window regardless of its width. The total width of a window is in column units as reported by window-total-width (see Window Sizes in The Emacs Lisp Reference Manual), it includes the fringes, the continuation and truncation glyphs, the margins, and the scroll bar.

On text terminals, side-by-side windows are separated by a vertical divider which is drawn using the vertical-border face.

If you click C-mouse-2 in the mode line of a window, that splits the window, putting a vertical divider where you click. Depending on how Emacs is compiled, you can also split a window by clicking C-mouse-2 in the scroll bar, which puts a horizontal divider where you click (this feature does not work when Emacs uses GTK+ scroll bars).

By default, when you split a window, Emacs gives each of the resulting windows dimensions that are an integral multiple of the default font size of the frame. That might subdivide the screen estate unevenly between the resulting windows. If you set the variable window-resize-pixelwise to a non-nil value, Emacs will give each window the same number of pixels (give or take one pixel if the initial dimension was an odd number of pixels). Note that when a frame’s pixel size is not a multiple of the frame’s character size, at least one window may get resized pixelwise even if this option is nil.


21.3 Using Other Windows

C-x o

Select another window (other-window).

C-M-v

Scroll the next window upward (scroll-other-window).

C-M-S-v

Scroll the next window downward (scroll-other-window-down).

C-M-S-l

Recenter the next window (recenter-other-window).

mouse-1

mouse-1, in the text area of a window, selects the window and moves point to the position clicked. Clicking in the mode line selects the window without moving point in it.

With the keyboard, you can switch windows by typing C-x o (other-window). That is an o, for “other”, not a zero. When there are more than two windows, this command moves through all the windows in a cyclic order, generally top to bottom and left to right. After the rightmost and bottommost window, it goes back to the one at the upper left corner. A numeric argument means to move several steps in the cyclic order of windows. A negative argument moves around the cycle in the opposite order. When the minibuffer is active, the minibuffer window is the last window in the cycle; you can switch from the minibuffer window to one of the other windows, and later switch back and finish supplying the minibuffer argument that is requested. See Editing in the Minibuffer.

The other-window command will normally only switch to the next window in the current frame (unless otherwise configured). If you work in a multi-frame environment and you want windows in all frames to be part of the cycle, you can rebind C-x o to the next-window-any-frame command. (See Changing Key Bindings Interactively, for how to rebind a command.)

The usual scrolling commands (see Controlling the Display) apply to the selected window only, but there are also commands to scroll the next window. C-M-v (scroll-other-window) scrolls the window that C-x o would select. In other respects, the command behaves like C-v; both move the buffer text upward relative to the window, and take positive and negative arguments. (In the minibuffer, C-M-v scrolls the help window associated with the minibuffer, if any, rather than the next window in the standard cyclic order; see Editing in the Minibuffer.) C-M-S-v (scroll-other-window-down) scrolls the next window downward in a similar way. Likewise, C-M-S-l (recenter-other-window) behaves like C-l (recenter-top-bottom) in the next window.

If you set mouse-autoselect-window to a non-nil value, moving the mouse over a different window selects that window. This feature is off by default.


21.4 Displaying in Another Window

C-x 4 is a prefix key for a variety of commands that switch to a buffer in a different window—either another existing window, or a new window created by splitting the selected window. See How display-buffer works, for how Emacs picks or creates the window to use.

C-x 4 b bufname RET

Select buffer bufname in another window (switch-to-buffer-other-window). See Creating and Selecting Buffers.

C-x 4 C-o bufname RET

Display buffer bufname in some window, without trying to select it (display-buffer). See Displaying a Buffer in a Window, for details about how the window is chosen.

C-x 4 f filename RET

Visit file filename and select its buffer in another window (find-file-other-window). See Visiting Files.

C-x 4 d directory RET

Select a Dired buffer for directory directory in another window (dired-other-window). See Dired, the Directory Editor.

C-x 4 m

Start composing a mail message, similar to C-x m (see Sending Mail), but in another window (compose-mail-other-window).

C-x 4 .

Find the definition of an identifier, similar to M-. (see Find Identifier References), but in another window (xref-find-definitions-other-window).

C-x 4 r filename RET

Visit file filename read-only, and select its buffer in another window (find-file-read-only-other-window). See Visiting Files.

C-x 4 4

A more general prefix command affects the buffer displayed by the next command invoked immediately after this prefix command. It requests the buffer of the next command to be displayed in another window.

C-x 4 1

This general prefix command requests the buffer of the next command to be displayed in the same window.


21.5 Deleting and Resizing Windows

C-x 0

Delete the selected window (delete-window).

C-x 1

Delete all windows in the selected frame except the selected window (delete-other-windows).

C-x 4 0

Delete the selected window and kill the buffer that was showing in it (kill-buffer-and-window). The last character in this key sequence is a zero.

C-x w 0 RET buffer RET

Delete windows showing the specified buffer.

C-x ^

Make selected window taller (enlarge-window).

C-x }

Make selected window wider (enlarge-window-horizontally).

C-x {

Make selected window narrower (shrink-window-horizontally).

C-x -

Shrink this window if its buffer doesn’t need so many lines (shrink-window-if-larger-than-buffer).

C-x +

Make all windows the same height (balance-windows).

To delete the selected window, type C-x 0 (delete-window). (That is a zero.) Once a window is deleted, the space that it occupied is given to an adjacent window (but not the minibuffer window, even if that is active at the time). Deleting the window has no effect on the buffer it used to display; the buffer continues to exist, and you can still switch to it with C-x b. The option delete-window-choose-selected controls which window is chosen as the new selected window instead (see Deleting Windows in The Emacs Lisp Reference Manual).

C-x 4 0 (kill-buffer-and-window) is a stronger command than C-x 0; it kills the current buffer and then deletes the selected window.

C-x 1 (delete-other-windows) deletes all the windows, except the selected one; the selected window expands to use the whole frame. (This command cannot be used while the minibuffer window is active; attempting to do so signals an error.)

M-x delete-windows-on deletes windows that show a specific buffer. It prompts for the buffer, defaulting to the current buffer. With prefix argument of zero, C-u 0, this command deletes windows only on the current display’s frames.

The command C-x ^ (enlarge-window) makes the selected window one line taller, taking space from a vertically adjacent window without changing the height of the frame. With a positive numeric argument, this command increases the window height by that many lines; with a negative argument, it reduces the height by that many lines. If there are no vertically adjacent windows (i.e., the window is at the full frame height), that signals an error. The command also signals an error if you attempt to reduce the height of any window below a certain minimum number of lines, specified by the variable window-min-height (the default is 4).

Similarly, C-x } (enlarge-window-horizontally) makes the selected window wider, and C-x { (shrink-window-horizontally) makes it narrower. These commands signal an error if you attempt to reduce the width of any window below a certain minimum number of columns, specified by the variable window-min-width (the default is 10).

Mouse clicks on the mode line (see Mode Line Mouse Commands) or on window dividers (see Window Dividers) provide another way to change window heights and to split or delete windows.

C-x - (shrink-window-if-larger-than-buffer) reduces the height of the selected window, if it is taller than necessary to show the whole text of the buffer it is displaying. It gives the extra lines to other windows in the frame.

You can also use C-x + (balance-windows) to even out the heights of all the windows in the selected frame.


21.6 Displaying a Buffer in a Window

It is a common Emacs operation to display or pop up some buffer in response to a user command. There are several different ways in which commands do this.

Many commands, like C-x C-f (find-file), by default display the buffer by “taking over” the selected window, expecting that the user’s attention will be diverted to that buffer.

Some commands try to display intelligently, trying not to take over the selected window, e.g., by splitting off a new window and displaying the desired buffer there. Such commands, which include the various help commands (see Help), work by calling display-buffer internally. See How display-buffer works, for details.

Other commands do the same as display-buffer, and additionally select the displaying window so that you can begin editing its buffer. The command M-g M-n (next-error) is one example (see Compilation Mode). Such commands work by calling the function pop-to-buffer internally. See Switching to a Buffer in a Window in The Emacs Lisp Reference Manual.

Commands with names ending in -other-window behave like display-buffer, except that they never display in the selected window. Several of these commands are bound in the C-x 4 prefix key (see Displaying in Another Window).

Commands with names ending in -other-frame behave like display-buffer, except that they (i) never display in the selected window and (ii) prefer to either create a new frame or use a window on some other frame to display the desired buffer. Several of these commands are bound in the C-x 5 prefix key.


21.6.1 How display-buffer works

The display-buffer command (as well as commands that call it internally) chooses a window to display by following the steps given below. See Choosing a Window for Displaying a Buffer in The Emacs Lisp Reference Manual, for details about how to alter this sequence of steps.

  • If the buffer should be displayed in the selected window regardless of other considerations, reuse the selected window. By default, this step is skipped, but you can tell Emacs not to skip it by adding a regular expression matching the buffer’s name together with a reference to the display-buffer-same-window action function (see Action Functions for Buffer Display in The Emacs Lisp Reference Manual) to the option display-buffer-alist (see Choosing a Window for Displaying a Buffer in The Emacs Lisp Reference Manual). For example, to display the buffer *scratch* preferably in the selected window write:
    (setopt
     display-buffer-alist
     '(("\\*scratch\\*" (display-buffer-same-window))))
    

    By default, display-buffer-alist is nil.

  • Otherwise, if the buffer is already displayed in an existing window, reuse that window. Normally, only windows on the selected frame are considered, but windows on other frames are also reusable if you use the corresponding reusable-frames action alist entry (see Action Alists for Buffer Display in The Emacs Lisp Reference Manual). See the next step for an example of how to do that.
  • Otherwise, optionally create a new frame and display the buffer there. By default, this step is skipped. To enable it, change the value of the option display-buffer-base-action (see Choosing a Window for Displaying a Buffer in The Emacs Lisp Reference Manual) as follows:
    (setopt
     display-buffer-base-action
     '((display-buffer-reuse-window display-buffer-pop-up-frame)
       (reusable-frames . 0)))
    

    This customization will also try to make the preceding step search for a reusable window on all visible or iconified frames.

  • Otherwise, try to create a new window by splitting a window on the selected frame, and display the buffer in that new window.

    The split can be either vertical or horizontal, depending on the variables split-height-threshold and split-width-threshold. These variables should have integer values. If split-height-threshold is smaller than the chosen window’s height, the split puts the new window below. Otherwise, if split-width-threshold is smaller than the window’s width, the split puts the new window on the right. If neither condition holds, Emacs tries to split so that the new window is below—but only if the window was not split before (to avoid excessive splitting).

  • Otherwise, display the buffer in a window previously showing it. Normally, only windows on the selected frame are considered, but with a suitable reusable-frames action alist entry (see above) the window may be also on another frame.
  • Otherwise, display the buffer in an existing window on the selected frame.
  • If all the above methods fail for whatever reason, create a new frame and display the buffer there.

21.6.2 Displaying non-editable buffers.

Some buffers are shown in windows for perusal rather than for editing. Help commands (see Help) typically use a buffer called *Help* for that purpose, minibuffer completion (see Completion) uses a buffer called *Completions*, etc. Such buffers are usually displayed only for a short period of time.

Normally, Emacs chooses the window for such temporary displays via display-buffer, as described in the previous subsection. The *Completions* buffer, on the other hand, is normally displayed in a window at the bottom of the selected frame, regardless of the number of windows already shown on that frame.

If you prefer Emacs to display a temporary buffer in a different fashion, customize the variable display-buffer-alist (see Choosing a Window for Displaying a Buffer in The Emacs Lisp Reference Manual) appropriately. For example, to display *Completions* always below the selected window, use the following form in your initialization file (see The Emacs Initialization File):

(setopt
 display-buffer-alist
 '(("\\*Completions\\*" display-buffer-below-selected)))

The *Completions* buffer is also special in the sense that Emacs usually tries to make its window just as large as necessary to display all of its contents. To resize windows showing other temporary displays, like, for example, the *Help* buffer, turn on the minor mode (see Minor Modes) temp-buffer-resize-mode (see Temporary Displays in The Emacs Lisp Reference Manual).

The maximum size of windows resized by temp-buffer-resize-mode can be controlled by customizing the options temp-buffer-max-height and temp-buffer-max-width (see Temporary Displays in The Emacs Lisp Reference Manual), and cannot exceed the size of the containing frame.


21.7 Convenience Features for Window Handling

Winner mode is a global minor mode that records the changes in the window configuration (i.e., how the frames are partitioned into windows), so that you can undo them. You can toggle Winner mode with M-x winner-mode, or by customizing the variable winner-mode. When the mode is enabled, C-c left (winner-undo) undoes the last window configuration change. If you change your mind while undoing, you can redo the changes you had undone using C-c right (M-x winner-redo). To prevent Winner mode from binding C-c left and C-c right, you can customize the variable winner-dont-bind-my-keys to a non-nil value. By default, Winner mode stores a maximum of 200 window configurations per frame, but you can change that by modifying the variable winner-ring-size. If there are some buffers whose windows you wouldn’t want Winner mode to restore, add their names to the list variable winner-boring-buffers or to the regexp winner-boring-buffers-regexp.

Follow mode (M-x follow-mode) synchronizes several windows on the same buffer so that they always display adjacent sections of that buffer. See Follow Mode.

The Windmove package defines commands for moving directionally between neighboring windows in a frame. M-x windmove-right selects the window immediately to the right of the currently selected one, and similarly for the left, up, and down counterparts. windmove-default-keybindings binds these commands to S-right etc.; doing so disables shift selection for those keys (see Shift Selection). In the same way as key bindings can be defined for commands that select windows directionally, you can use windmove-display-default-keybindings to define keybindings for commands that specify in what direction to display the window for the buffer that the next command is going to display. Also there is windmove-delete-default-keybindings to define keybindings for commands that delete windows directionally, and windmove-swap-states-default-keybindings that defines key bindings for commands that swap the window contents of the selected window with the window in the specified direction.

The command M-x compare-windows lets you compare the text shown in different windows. See Comparing Files.

Scroll All mode (M-x scroll-all-mode) is a global minor mode that causes scrolling commands and point motion commands to apply to every single window.


21.8 Window Tab Line

The command global-tab-line-mode toggles the display of a tab line on the top screen line of each window. The Tab Line shows special buttons (“tabs”) for each buffer that was displayed in a window, and allows switching to any of these buffers by clicking the corresponding button. Clicking on the + icon adds a new buffer to the window-local tab line of buffers, and clicking on the x icon of a tab deletes it. The mouse wheel on the tab line scrolls the tabs horizontally.

Selecting the previous window-local tab is the same as typing C-x LEFT (previous-buffer), selecting the next tab is the same as C-x RIGHT (next-buffer). Both commands support a numeric prefix argument as a repeat count.

You can customize the variable tab-line-tabs-function to define the preferred contents of the tab line. By default, it displays all buffers previously visited in the window, as described above. But you can also set it to display a list of buffers with the same major mode as the current buffer, or to display buffers grouped by their major mode, where clicking on the mode name in the first tab displays a list of all major modes where you can select another group of buffers.

Note that the Tab Line is different from the Tab Bar (see Tab Bars). Whereas tabs on the Tab Bar at the top of each frame are used to switch between window configurations containing several windows with buffers, tabs on the Tab Line at the top of each window are used to switch between buffers in the window.


22 Frames and Graphical Displays

When Emacs is started on a graphical display, e.g., on the X Window System, it occupies a graphical system-level display region. In this manual, we call this a frame, reserving the word “window” for the part of the frame used for displaying a buffer. A frame initially contains one window, but it can be subdivided into multiple windows (see Multiple Windows). A frame normally also contains a menu bar, tool bar, and echo area.

You can also create additional frames (see Creating Frames). All frames created in the same Emacs session have access to the same underlying buffers and other data. For instance, if a buffer is being shown in more than one frame, any changes made to it in one frame show up immediately in the other frames too.

Typing C-x C-c closes all the frames on the current display, and ends the Emacs session if it has no frames open on any other displays (see Exiting Emacs). To close just the selected frame, type C-x 5 0 (that is zero, not o).

This chapter describes Emacs features specific to graphical displays (particularly mouse commands), and features for managing multiple frames. On text terminals, many of these features are unavailable. However, it is still possible to create multiple frames on text terminals; such frames are displayed one at a time, filling the entire terminal screen (see Text Terminals). It is also possible to use the mouse on some text terminals (see Using a Mouse in Text Terminals, for doing so on GNU and Unix systems; and see Mouse Usage on MS-DOS, for doing so on MS-DOS). Menus are supported on all text terminals.


22.1 Mouse Commands for Editing

mouse-1

Move point to where you click (mouse-set-point).

Drag-mouse-1

Activate the region around the text selected by dragging, and put the text in the primary selection (mouse-set-region).

mouse-2

Move point to where you click, and insert the contents of the primary selection there (mouse-yank-primary).

mouse-3

If the region is active, move the nearer end of the region to the click position; otherwise, set mark at the current value of point and point at the click position. Save the resulting region in the kill ring; on a second click, kill it (mouse-save-then-kill).

C-M-mouse-1

Activate a rectangular region around the text selected by dragging. See Rectangles.

The most basic mouse command is mouse-set-point, which is invoked by clicking with the left mouse button, mouse-1, in the text area of a window. This moves point to the position where you clicked. If that window was not the selected window, it becomes the selected window. You can also activate a region by double-clicking mouse-1 (see Mouse Commands for Words and Lines).

Normally, if the frame you clicked in was not the selected frame, it is made the selected frame, in addition to selecting the window and setting the cursor. On the X Window System, you can change this by setting the variable x-mouse-click-focus-ignore-position to t. In that case, the initial click on an unselected frame just selects the frame, without doing anything else; clicking again selects the window and sets the cursor position.

Holding down mouse-1 and dragging the mouse over a stretch of text activates the region around that text (mouse-set-region), placing the mark where you started holding down the mouse button, and point where you release it (see The Mark and the Region). In addition, the text in the region becomes the primary selection (see Cut and Paste with Other Window Applications).

If you change the variable mouse-drag-copy-region to a non-nil value, dragging the mouse over a stretch of text also adds the text to the kill ring. The default is nil.

If this variable is non-empty, only copy to the kill ring if the region is non-empty. For instance, if you mouse drag an area that is less than a half a character, you’d normally get the empty string in your kill ring, but with non-empty, this short mouse drag won’t affect the kill ring.

If you move the mouse off the top or bottom of the window while dragging, the window scrolls at a steady rate until you move the mouse back into the window. This way, you can select regions that don’t fit entirely on the screen. The number of lines scrolled per step depends on how far away from the window edge the mouse has gone; the variable mouse-scroll-min-lines specifies a minimum step size.

If you enable the option mouse-drag-mode-line-buffer and dragging files is supported by the window system, then dragging the mouse on the buffer name portion of the mode line will drag that buffer’s file to another program or frame.

Clicking with the middle mouse button, mouse-2, moves point to the position where you clicked and inserts the contents of the primary selection (mouse-yank-primary). See Cut and Paste with Other Window Applications. This behavior is consistent with other X applications. Alternatively, you can rebind mouse-2 to mouse-yank-at-click, which performs a yank at the position you click.

If you change the variable mouse-yank-at-point to a non-nil value, mouse-2 does not move point; it inserts the text at point, regardless of where you clicked or even which of the frame’s windows you clicked on. This variable affects both mouse-yank-primary and mouse-yank-at-click.

Clicking with the right mouse button, mouse-3, runs the command mouse-save-then-kill. This performs several actions depending on where you click and the status of the region:

  • If no region is active, clicking mouse-3 activates the region, placing the mark where point was and point at the clicked position.
  • If a region is active, clicking mouse-3 adjusts the nearer end of the region by moving it to the clicked position. The adjusted region’s text is copied to the kill ring; if the text in the original region was already on the kill ring, it replaces it there.
  • If you originally specified the region using a double or triple mouse-1, so that the region is defined to consist of entire words or lines (see Mouse Commands for Words and Lines), then adjusting the region with mouse-3 also proceeds by entire words or lines.
  • If you use mouse-3 a second time consecutively, at the same place, that kills the region already selected. Thus, the simplest way to kill text with the mouse is to click mouse-1 at one end, then click mouse-3 twice at the other end. To copy the text into the kill ring without deleting it from the buffer, press mouse-3 just once—or just drag across the text with mouse-1. Then you can copy it elsewhere by yanking it.

The mouse-save-then-kill command also obeys the variable mouse-drag-copy-region (described above). If the value is non-nil, then whenever the command sets or adjusts the active region, the text in the region is also added to the kill ring. If the latest kill ring entry had been added the same way, that entry is replaced rather than making a new entry.

Whenever you set the region using any of the mouse commands described above, the mark will be deactivated by any subsequent unshifted cursor motion command, in addition to the usual ways of deactivating the mark. See Shift Selection.

Some mice have a “wheel” which can be used for scrolling. Emacs supports scrolling windows with the mouse wheel, by default, on most graphical displays. To toggle this feature, use M-x mouse-wheel-mode. The variables mouse-wheel-follow-mouse and mouse-wheel-scroll-amount determine where and by how much buffers are scrolled. The variable mouse-wheel-progressive-speed determines whether the scroll speed is linked to how fast you move the wheel. This mode also supports increasing or decreasing the font size, by default bound to scrolling with the Ctrl modifier. When this mode is enabled, mouse wheel produces special events like wheel-up and wheel-down. (Some older systems report them as mouse-4 and mouse-5.) If the mouse has a horizontal scroll wheel, it produces wheel-left and wheel-right events as well.

Emacs also supports horizontal scrolling with the Shift modifier. Typing a numeric prefix arg (e.g., M-5) before starting horizontal scrolling changes its step value defined by the user option mouse-wheel-scroll-amount-horizontal.

If your mouse’s wheel can be tilted, or if your touchpad supports it, then you can also enable horizontal scrolling by customizing the variable mouse-wheel-tilt-scroll to a non-nil value. By default, tilting the mouse wheel scrolls the window’s view horizontally in the direction of the tilt: e.g., tilting to the right scrolls the window to the right, so that the text displayed in the window moves horizontally to the left. If you’d like to reverse the direction of horizontal scrolling, customize the variable mouse-wheel-flip-direction to a non-nil value.

When the mouse pointer is over an image in Image mode, see Viewing Image Files, scrolling the mouse wheel with the Ctrl modifier scales the image under the mouse pointer, and scrolling the mouse wheel with the Shift modifier scrolls the image horizontally.


22.2 Mouse Commands for Words and Lines

These variants of mouse-1 select entire words or lines at a time. Emacs activates the region around the selected text, which is also copied to the kill ring.

Double-mouse-1

Select the text around the word or character which you click on.

Double-clicking on a character with symbol syntax (such as underscore, in C mode) selects the symbol surrounding that character. Double-clicking on a character with open- or close-parenthesis syntax selects the parenthetical grouping which that character starts or ends. Double-clicking on a character with string-delimiter syntax (such as a single-quote or double-quote in C) selects the string constant (Emacs uses heuristics to figure out whether that character is the beginning or the end of it).

Double-clicking on the beginning of a parenthetical grouping or beginning string-delimiter moves point to the end of the region, scrolling the buffer display forward if necessary to show the new location of point. Double-clicking on the end of a parenthetical grouping or end string-delimiter keeps point at the end of the region by default, so the beginning of the region will not be visible if it is above the top of the window; setting the user option mouse-select-region-move-to-beginning to non-nil changes this to move point to the beginning of the region, scrolling the display backward if necessary.

Double-Drag-mouse-1

Select the text you drag across, in units of whole words.

Triple-mouse-1

Select the line you click on.

Triple-Drag-mouse-1

Select the text you drag across, in units of whole lines.


22.3 Following References with the Mouse

Some Emacs buffers include buttons, or hyperlinks: pieces of text that perform some action (e.g., following a reference) when activated (e.g., by clicking on them). Usually, a button’s text is visually highlighted: it is underlined, or a box is drawn around it. If you move the mouse over a button, the shape of the mouse cursor changes and the button lights up. If you change the variable mouse-highlight to nil, Emacs disables this highlighting.

You can activate a button by moving point to it and typing RET, or by clicking either mouse-1 or mouse-2 on the button. For example, in a Dired buffer, each file name is a button; activating it causes Emacs to visit that file (see Dired, the Directory Editor). In a *Compilation* buffer, each error message is a button, and activating it visits the source code for that error (see Running Compilations under Emacs).

Although clicking mouse-1 on a button usually activates the button, if you hold the mouse button down for a period of time before releasing it (specifically, for more than 450 milliseconds), then Emacs moves point where you clicked, without activating the button. In this way, you can use the mouse to move point over a button without activating it. Dragging the mouse over or onto a button has its usual behavior of setting the region, and does not activate the button.

You can change how mouse-1 applies to buttons by customizing the variable mouse-1-click-follows-link. If the value is a positive integer, that determines how long you need to hold the mouse button down for, in milliseconds, to cancel button activation; the default is 450, as described in the previous paragraph. If the value is nil, mouse-1 just sets point where you clicked, and does not activate buttons. If the value is double, double clicks activate buttons but single clicks just set point.

Normally, mouse-1 on a button activates the button even if it is in a non-selected window. If you change the variable mouse-1-click-in-non-selected-windows to nil, mouse-1 on a button in an unselected window moves point to the clicked position and selects that window, without activating the button.


22.5 Mode Line Mouse Commands

You can use mouse clicks on window mode lines to select and manipulate windows.

Some areas of the mode line, such as the buffer name, and major and minor mode names, have their own special mouse bindings. These areas are highlighted when you hold the mouse over them, and information about the special bindings will be displayed (see Tooltips). This section’s commands do not apply in those areas.

mouse-1

mouse-1 on a mode line selects the window it belongs to. By dragging mouse-1 on the mode line, you can move it, thus changing the height of the windows above and below. Changing heights with the mouse in this way never deletes windows, it just refuses to make any window smaller than the minimum height.

mouse-2

mouse-2 on a mode line expands that window to fill its frame.

mouse-3

mouse-3 on a mode line deletes the window it belongs to. If the frame has only one window, it does nothing.

C-mouse-2

C-mouse-2 on a mode line splits that window, producing two side-by-side windows with the boundary running through the click position (see Splitting Windows).

Furthermore, by clicking and dragging mouse-1 on the divider between two side-by-side mode lines, you can move the vertical boundary to the left or right.

Note that resizing windows is affected by the value of window-resize-pixelwise, see Splitting Windows.


22.6 Creating Frames

The prefix key C-x 5 is analogous to C-x 4. Whereas each C-x 4 command pops up a buffer in a different window in the selected frame (see Displaying in Another Window), the C-x 5 commands use a different frame. If an existing visible or iconified (a.k.a. “minimized”, see Visibility of Frames in The Emacs Lisp Reference Manual) frame already displays the requested buffer, that frame is raised and deiconified (“un-minimized”); otherwise, a new frame is created on the current display terminal.

The various C-x 5 commands differ in how they find or create the buffer to select:

C-x 5 2

Create a new frame using the default frame parameters (make-frame-command).

C-x 5 c

Create a new frame using the window configuration and frame parameters of the current frame (clone-frame).

C-x 5 b bufname RET

Select buffer bufname in another frame. This runs switch-to-buffer-other-frame.

C-x 5 f filename RET

Visit file filename and select its buffer in another frame. This runs find-file-other-frame. See Visiting Files.

C-x 5 d directory RET

Select a Dired buffer for directory directory in another frame. This runs dired-other-frame. See Dired, the Directory Editor.

C-x 5 m

Start composing a mail message in another frame. This runs compose-mail-other-frame. It is the other-frame variant of C-x m. See Sending Mail.

C-x 5 .

Find the definition of an identifier in another frame. This runs xref-find-definitions-other-frame, the multiple-frame variant of M-.. See Find Identifier References.

C-x 5 r filename RET

Visit file filename read-only, and select its buffer in another frame. This runs find-file-read-only-other-frame. See Visiting Files.

C-x 5 5

A more general prefix command that affects the buffer displayed by the next command invoked immediately after this prefix command (other-frame-prefix). It requests the buffer of the next command to be displayed in another frame.

You can control the appearance and behavior of the newly-created frames by specifying frame parameters. See Frame Parameters.


22.7 Frame Commands

The following commands are used to delete and operate on frames:

C-x 5 0

Delete the selected frame (delete-frame). This signals an error if there is only one frame.

C-x 5 u

When undelete-frame-mode is enabled, undelete one of the 16 most recently deleted frames. Without a prefix argument, undelete the most recently deleted frame. With a numerical prefix argument between 1 and 16, where 1 is the most recently deleted frame, undelete the corresponding deleted frame.

C-z

Minimize (or iconify) the selected Emacs frame (suspend-frame). See Exiting Emacs.

C-x 5 o

Select another frame, and raise it. If you repeat this command, it cycles through all the frames on your terminal.

C-x 5 1

Delete all frames on the current terminal, except the selected one.

M-F10

Toggle the maximization state of the current frame. When a frame is maximized, it fills the screen.

F11

Toggle full-screen mode for the current frame. (The difference between full-screen and maximized is normally that the former hides window manager decorations, giving slightly more screen space to Emacs itself.)

Note that with some window managers you may have to customize the variable frame-resize-pixelwise to a non-nil value in order to make a frame truly maximized or full-screen. This variable, when set to a non-nil value, in general allows resizing frames at pixel resolution, rather than in integral multiples of lines and columns.

The C-x 5 0 (delete-frame) command deletes the selected frame. However, it will refuse to delete the last frame in an Emacs session, to prevent you from losing the ability to interact with the Emacs session. Note that when Emacs is run as a daemon (see Using Emacs as a Server), there is always a virtual frame that remains after all the ordinary, interactive frames are deleted. In this case, C-x 5 0 can delete the last interactive frame; you can use emacsclient to reconnect to the Emacs session.

The C-x 5 1 (delete-other-frames) command deletes all other frames on the current terminal (this terminal refers to either a graphical display, or a text terminal; see Text Terminals). If the Emacs session has frames open on other graphical displays or text terminals, those are not deleted.

The C-x 5 o (other-frame) command selects the next frame on the current terminal. If you are using Emacs on the X Window System with a window manager that selects (or gives focus to) whatever frame the mouse cursor is over, you have to change the variable focus-follows-mouse to t in order for this command to work properly. Then invoking C-x 5 o will also warp the mouse cursor to the chosen frame.


22.8 Fonts

By default, Emacs displays text on graphical displays using a 10-point monospace font, and the font size can be changed interactively (see Text Scale).

There are several different ways to specify a different font:

  • Click on ‘Set Default Font’ in the ‘Options’ menu. This makes the selected font the default on all existing graphical frames. To save this for future sessions, click on ‘Save Options’ in the ‘Options’ menu.
  • Add a line to your init file, modifying the variable default-frame-alist to specify the font parameter (see Frame Parameters), like this:
    (add-to-list 'default-frame-alist
                 '(font . "DejaVu Sans Mono-10"))
    

    This makes the font the default on all graphical frames created after restarting Emacs with that init file.

  • Add an ‘emacs.font’ X resource setting to your X resource file, like this:
    emacs.font: DejaVu Sans Mono-12
    

    You must restart X, or use the xrdb command, for the X resources file to take effect. See X Resources. Do not quote font names in X resource files.

  • If you are running Emacs on the GNOME desktop or Haiku, you can tell Emacs to adjust the frame’s default font along with changes to the default system font by setting the variable font-use-system-font to t (the default is nil). For this to work, Emacs must have been compiled with support for Gsettings (or the older Gconf). (To be specific, the Gsettings configuration names used are ‘org.gnome.desktop.interface monospace-font-name’ and ‘org.gnome.desktop.interface font-name’.)
  • Use the command line option ‘-fn’ (or ‘--font’). See Font Specification Options.

To check what font you’re currently using, the C-u C-x = command can be helpful. It describes the character at point, and names the font that it’s rendered in.

There are four different ways to express a font name. The first is to use a Fontconfig pattern. Fontconfig patterns have the following form:

fontname[-fontsize][:name1=values1][:name2=values2]...

Within this format, any of the elements in brackets may be omitted. Here, fontname is the family name of the font, such as ‘Monospace’ or ‘DejaVu Sans Mono’; fontsize is the point size of the font (one printer’s point is about 1/72 of an inch); and the ‘name=values’ entries specify settings such as the slant and weight of the font. Each values may be a single value, or a list of values separated by commas. In addition, some property values are valid with only one kind of property name, in which case the ‘name=’ part may be omitted.

Here is a list of common font properties:

slant

One of ‘italic’, ‘oblique’, or ‘roman’.

weight

One of ‘light’, ‘medium’, ‘demibold’, ‘bold’ or ‘black’.

style

Some fonts define special styles which are a combination of slant and weight. For instance, ‘Dejavu Sans’ defines the ‘book’ style, which overrides the slant and weight properties.

width

One of ‘condensed’, ‘normal’, or ‘expanded’.

spacing

One of ‘monospace’, ‘proportional’, ‘dual-width’, or ‘charcell’.

Here are some examples of Fontconfig patterns:

Monospace
Monospace-12
Monospace-12:bold
DejaVu Sans Mono:bold:italic
Monospace-12:weight=bold:slant=italic

For a more detailed description of Fontconfig patterns, see the Fontconfig manual, which is distributed with Fontconfig and available online at https://fontconfig.org/fontconfig-user.html.

On MS-Windows, only the subset of the form fontname[-fontsize] is supported for all fonts; the full Fontconfig pattern might not work for all of them.

The second way to specify a font is to use a GTK font pattern. These have the syntax

fontname [properties] [fontsize]

where fontname is the family name, properties is a list of property values separated by spaces, and fontsize is the point size. The properties that you may specify for GTK font patterns are as follows:

  • Slant properties: ‘Italic’ or ‘Oblique’. If omitted, the default (roman) slant is implied.
  • Weight properties: ‘Bold’, ‘Book’, ‘Light’, ‘Medium’, ‘Semi-bold’, or ‘Ultra-light’. If omitted, ‘Medium’ weight is implied.
  • Width properties: ‘Semi-Condensed’ or ‘Condensed’. If omitted, a default width is used.

Here are some examples of GTK font patterns:

Monospace 12
Monospace Bold Italic 12

On MS-Windows, only the subset fontname is supported.

The third way to specify a font is to use an XLFD (X Logical Font Description). This is the traditional method for specifying fonts under X, and is also supported on MS-Windows. Each XLFD consists of fourteen words or numbers, separated by dashes, like this:

-misc-fixed-medium-r-semicondensed--13-*-*-*-c-60-iso8859-1

A wildcard character (‘*’) in an XLFD matches any sequence of characters (including none), and ‘?’ matches any single character. However, matching is implementation-dependent, and can be inaccurate when wildcards match dashes in a long name. For reliable results, supply all 14 dashes and use wildcards only within a field. Case is insignificant in an XLFD. The syntax for an XLFD is as follows:

-maker-family-weight-slant-widthtype-style…
…-pixels-height-horiz-vert-spacing-width-registry-encoding

The entries have the following meanings:

maker

The name of the font manufacturer.

family

The name of the font family (e.g., ‘courier’).

weight

The font weight—normally either ‘bold’, ‘medium’ or ‘light’. Some font names support other values.

slant

The font slant—normally ‘r’ (roman), ‘i’ (italic), ‘o’ (oblique), ‘ri’ (reverse italic), or ‘ot’ (other). Some font names support other values.

widthtype

The font width—normally ‘normal’, ‘condensed’, ‘semicondensed’, or ‘extended’. Some font names support other values.

style

An optional additional style name. Usually it is empty—most XLFDs have two hyphens in a row at this point. The style name can also specify a two-letter ISO-639 language name, like ‘ja’ or ‘ko’; some fonts that support CJK scripts have that spelled out in the style name part.

pixels

The font height, in pixels.

height

The font height on the screen, measured in tenths of a printer’s point. This is the point size of the font, times ten. For a given vertical resolution, height and pixels are proportional; therefore, it is common to specify just one of them and use ‘*’ for the other.

horiz

The horizontal resolution, in pixels per inch, of the screen for which the font is intended.

vert

The vertical resolution, in pixels per inch, of the screen for which the font is intended. Normally the resolution of the fonts on your system is the right value for your screen; therefore, you normally specify ‘*’ for this and horiz.

spacing

This is ‘m’ (monospace), ‘p’ (proportional) or ‘c’ (character cell).

width

The average character width, in pixels, multiplied by ten.

registry
encoding

The X font character set that the font depicts. (X font character sets are not the same as Emacs character sets, but they are similar.) You can use the xfontsel program to check which choices you have. Normally you should use ‘iso8859’ for registry and ‘1’ for encoding.

The fourth and final method of specifying a font is to use a font nickname. Certain fonts have shorter nicknames, which you can use instead of a normal font specification. For instance, ‘6x13’ is equivalent to

-misc-fixed-medium-r-semicondensed--13-*-*-*-c-60-iso8859-1

This form is not supported on MS-Windows.

On X, Emacs recognizes two types of fonts: client-side fonts, which are provided by the Xft and Fontconfig libraries, and server-side fonts, which are provided by the X server itself. Most client-side fonts support advanced font features such as antialiasing and subpixel hinting, while server-side fonts do not. Fontconfig and GTK patterns match only client-side fonts.

You will probably want to use a fixed-width default font—that is, a font in which all characters have the same width. For Xft and Fontconfig fonts, you can use the fc-list command to list the available fixed-width fonts, like this:

fc-list :spacing=mono
fc-list :spacing=charcell

For server-side X fonts, you can use the xlsfonts program to list the available fixed-width fonts, like this:

xlsfonts -fn '*x*' | grep -E '^[0-9]+x[0-9]+'
xlsfonts -fn '*-*-*-*-*-*-*-*-*-*-*-m*'
xlsfonts -fn '*-*-*-*-*-*-*-*-*-*-*-c*'

Any font with ‘m’ or ‘c’ in the spacing field of the XLFD is a fixed-width font. To see what a particular font looks like, use the xfd command. For example:

xfd -fn 6x13

displays the entire font ‘6x13’.

While running Emacs, you can also set the font of a specific kind of text (see Text Faces), or a particular frame (see Frame Parameters).


22.9 Speedbar Frames

The speedbar is a special frame for conveniently navigating in or operating on another frame. The speedbar, when it exists, is always associated with a specific frame, called its attached frame; all speedbar operations act on that frame.

Type M-x speedbar to create the speedbar and associate it with the current frame. To dismiss the speedbar, type M-x speedbar again, or select the speedbar and type q. (You can also delete the speedbar frame like any other Emacs frame.) If you wish to associate the speedbar with a different frame, dismiss it and call M-x speedbar from that frame.

The speedbar can operate in various modes. Its default mode is File Display mode, which shows the files in the current directory of the selected window of the attached frame, one file per line. Clicking on a non-directory visits that file in the selected window of the attached frame, and clicking on a directory shows that directory in the speedbar (see Following References with the Mouse). Each line also has a box, ‘[+]’ or ‘<+>’, that you can click on to expand the contents of that item. Expanding a directory adds the contents of that directory to the speedbar display, underneath the directory’s own line. Expanding an ordinary file adds a list of the tags in that file to the speedbar display; you can click on a tag name to jump to that tag in the selected window of the attached frame. When a file or directory is expanded, the ‘[+]’ changes to ‘[-]’; you can click on that box to contract the item, hiding its contents.

You navigate through the speedbar using the keyboard, too. Typing RET while point is on a line in the speedbar is equivalent to clicking the item on the current line, and SPC expands or contracts the item. U displays the parent directory of the current directory. To copy, delete, or rename the file on the current line, type C, D, and R respectively. To create a new directory, type M.

Another general-purpose speedbar mode is Buffer Display mode; in this mode, the speedbar displays a list of Emacs buffers. To switch to this mode, type b in the speedbar. To return to File Display mode, type f. You can also change the display mode by clicking mouse-3 anywhere in the speedbar window (or mouse-1 on the mode-line) and selecting ‘Displays’ in the pop-up menu.

Some major modes, including Rmail mode, Info, and GUD, have specialized ways of putting useful items into the speedbar for you to select. For example, in Rmail mode, the speedbar shows a list of Rmail files, and lets you move the current message to another Rmail file by clicking on its ‘<M>’ box.

For more details on using and programming the speedbar, See Speedbar in Speedbar Manual.


22.10 Multiple Displays

A single Emacs can talk to more than one X display. Initially, Emacs uses just one display—the one specified with the DISPLAY environment variable or with the ‘--display’ option (see Initial Options). To connect to another display, use the command make-frame-on-display:

M-x make-frame-on-display RET display RET

Create a new frame on display display.

A single X server can handle more than one screen. When you open frames on two screens belonging to one server, Emacs knows they share a single keyboard, and it treats all the commands arriving from these screens as a single stream of input.

When you open frames on different X servers, Emacs makes a separate input stream for each server. Each server also has its own selected frame. The commands you enter with a particular X server apply to that server’s selected frame.

On multi-monitor displays it is possible to use the command make-frame-on-monitor:

M-x make-frame-on-monitor RET monitor RET

Create a new frame on monitor monitor whose screen area is a part of the current display.


22.11 Frame Parameters

You can control the default appearance and behavior of all frames by specifying a default list of frame parameters in the variable default-frame-alist. Its value should be a list of entries, each specifying a parameter name and a value for that parameter. These entries take effect whenever Emacs creates a new frame, including the initial frame.

For example, you can add the following lines to your init file (see The Emacs Initialization File) to set the default frame width to 90 character columns, the default frame height to 40 character rows, and the default font to ‘Monospace-10’:

(add-to-list 'default-frame-alist '(width  . 90))
(add-to-list 'default-frame-alist '(height . 40))
(add-to-list 'default-frame-alist '(font . "Monospace-10"))

For a list of frame parameters and their effects, see Frame Parameters in The Emacs Lisp Reference Manual.

You can also specify a list of frame parameters which apply to just the initial frame, by customizing the variable initial-frame-alist.

If Emacs is compiled to use an X toolkit, frame parameters that specify colors and fonts don’t affect menus and the menu bar, since those are drawn by the toolkit and not directly by Emacs.

Frame appearance and behavior can also be customized through X resources (see X Options and Resources); these override the parameters of the initial frame specified in your init file.

Note that if you are using the desktop library to save and restore your sessions, the frames to be restored are recorded in the desktop file, together with their parameters. When these frames are restored, the recorded parameters take precedence over the frame parameters specified by default-frame-alist and initial-frame-alist in your init file. See Saving Emacs Sessions, for how to avoid that.


22.12 Scroll Bars

On graphical displays, there is a vertical scroll bar on the side of each Emacs window. Clicking mouse-1 on the scroll bar’s up and down buttons scrolls the window by one line at a time (but some toolkits allow you to customize the scroll bars to not have those buttons). Clicking mouse-1 above or below the scroll bar’s inner box scrolls the window by nearly the entire height of the window, like M-v and C-v respectively (see Changing the Location of Point). (This, too, can behave differently with some toolkits.) Dragging the inner box scrolls continuously.

If Emacs is compiled on the X Window System without X toolkit support, the scroll bar behaves differently. Clicking mouse-1 anywhere on the scroll bar scrolls forward like C-v, while mouse-3 scrolls backward like M-v. Clicking mouse-2 in the scroll bar lets you drag the inner box up and down.

To toggle the use of vertical scroll bars, type M-x scroll-bar-mode. This command applies to all frames, including frames yet to be created. To toggle vertical scroll bars for just the selected frame, use the command M-x toggle-scroll-bar.

To control the use of vertical scroll bars at startup, customize the variable scroll-bar-mode (see Customization). Its value should be either right (put scroll bars on the right side of windows), left (put them on the left), or nil (disable vertical scroll bars). By default, Emacs puts scroll bars on the right if it was compiled with GTK+ support on the X Window System, and on MS-Windows or macOS; Emacs puts scroll bars on the left if compiled on the X Window System without GTK+ support (following the old convention for X applications).

You can also use the X resource ‘verticalScrollBars’ to enable or disable the scroll bars (see X Resources). To control the scroll bar width, change the scroll-bar-width frame parameter (see Frame Parameters in The Emacs Lisp Reference Manual).

If you’re using Emacs on X (with GTK+ or Motif), you can customize the variable scroll-bar-adjust-thumb-portion to control overscrolling of the scroll bar, i.e., dragging the thumb down even when the end of the buffer is visible. If its value is non-nil, the scroll bar can be dragged downwards even if the end of the buffer is shown; if nil, the thumb will be at the bottom when the end of the buffer is shown. You cannot over-scroll when the entire buffer is visible.

The visual appearance of the scroll bars is controlled by the scroll-bar face. (Some toolkits, such as GTK+ and MS-Windows, ignore this face; the scroll-bar appearance there can only be customized system-wide, for GTK+ see GTK+ resources).

On graphical frames, vertical scroll bars implicitly serve to separate side-by-side windows visually. When vertical scroll bars are disabled, Emacs by default separates such windows with the help of a one-pixel wide vertical border. That border occupies the first pixel column of the window on the right and may thus overdraw the leftmost pixels of any glyph displayed there. If these pixels convey important information, you can make them visible by enabling window dividers, see Window Dividers. To replicate the look of vertical borders, set the right-divider-width parameter of frames to one and have the window-divider face inherit from that of vertical-border, Window Dividers in The Emacs Lisp Reference Manual.

On graphical displays with toolkit support, Emacs may also supply a horizontal scroll bar on the bottom of each window. Clicking mouse-1 on that scroll bar’s left and right buttons scrolls the window horizontally by one column at a time. (Note that some toolkits allow customizations of the scroll bar that cause these buttons not to be shown.) Clicking mouse-1 on the left or right of the scroll bar’s inner box scrolls the window by four columns. Dragging the inner box scrolls the window continuously.

Note that such horizontal scrolling can make the window’s position of point disappear on the left or the right. Typing a character to insert text or moving point with a keyboard command will usually bring it back into view.

To toggle the use of horizontal scroll bars, type M-x horizontal-scroll-bar-mode. This command applies to all frames, including frames yet to be created. To toggle horizontal scroll bars for just the selected frame, use the command M-x toggle-horizontal-scroll-bar.

To control the use of horizontal scroll bars at startup, customize the variable horizontal-scroll-bar-mode.

You can also use the X resource ‘horizontalScrollBars’ to enable or disable horizontal scroll bars (see X Resources). To control the scroll bar height, change the scroll-bar-height frame parameter (see Frame Parameters in The Emacs Lisp Reference Manual).


22.13 Window Dividers

On graphical displays, you can use window dividers in order to separate windows visually. Window dividers are bars that can be dragged with the mouse, thus allowing you to easily resize adjacent windows.

To toggle the display of window dividers, use the command M-x window-divider-mode.

To customize where dividers should appear, use the option window-divider-default-places. Its value should be either bottom-only (to show dividers only on the bottom of windows), right-only (to show dividers only on the right of windows), or t (to show them on the bottom and on the right).

To adjust the width of window dividers displayed by this mode customize the options window-divider-default-bottom-width and window-divider-default-right-width.

When vertical scroll bars are disabled, dividers can be also useful to make the first pixel column of a window visible, which would be otherwise covered by the vertical border used to separate side-by-side windows (see Scroll Bars).

For more details about window dividers see Window Dividers in The Emacs Lisp Reference Manual.


22.14 Drag and Drop

In most graphical desktop environments, Emacs has basic support for drag and drop operations. For instance, dropping text onto an Emacs frame inserts the text where it is dropped. Dropping a file onto an Emacs frame visits that file. As a special case, dropping the file on a Dired buffer moves or copies the file (according to the conventions of the application it came from) into the directory displayed in that buffer.

Dropping a file normally visits it in the window you drop it on. If you prefer to visit the file in a new window in such cases, customize the variable dnd-open-file-other-window.

The XDND and Motif drag and drop protocols, and the old KDE 1.x protocol, are currently supported.

It can be difficult to scroll a window or determine where dropped text will be inserted while dragging text onto an Emacs window. Setting the option dnd-indicate-insertion-point to a non-nil value makes point move to the location any dropped text will be inserted when the mouse moves in a window during drag, and setting dnd-scroll-margin to an integer value causes a window to be scrolled if the mouse moves within that many lines of the top or bottom of the window during drag.

Emacs can also optionally drag the region with the mouse into another portion of this or another buffer. To enable that, customize the variable mouse-drag-and-drop-region to a non-nil value. Normally, the text is moved, i.e. cut and pasted, when the destination is the same buffer as the origin; dropping the region on another buffer copies the text instead. If the value of this variable names a modifier key, such as ‘shift’, ‘control’ or ‘alt’, then pressing that modifier key when dropping the text will copy it instead of cutting it, even if you drop on the same buffer as the one from which the text came.

In order to cut text even when source and destination buffers differ, set the option mouse-drag-and-drop-region-cut-when-buffers-differ to a non-nil value. By default, on a graphic display the selected text is shown in a tooltip and point moves together with the mouse cursor during dragging. To suppress such behavior, set the options mouse-drag-and-drop-region-show-tooltip and/or mouse-drag-and-drop-region-show-cursor to nil.

To drag text from Emacs to other programs, set the option mouse-drag-and-drop-region-cross-program to a non-nil value.

On the X window system, some programs can drop files on Emacs, expecting Emacs to save them. Normally, Emacs will prompt for a file name under which the file will be saved, and then open the file, but that behavior can be changed by changing the variable x-dnd-direct-save-function. See Drag and Drop in The Emacs Lisp Reference Manual.


22.16 Tool Bars

On graphical displays, Emacs puts a tool bar at the top of each frame, just below the menu bar. This is a row of icons which you can click on with the mouse to invoke various commands.

The global (default) tool bar contains general commands. Some major modes define their own tool bars; whenever a buffer with such a major mode is current, the mode’s tool bar replaces the global tool bar.

To toggle the use of tool bars, type M-x tool-bar-mode. This command applies to all frames, including frames yet to be created. To control the use of tool bars at startup, customize the variable tool-bar-mode.

When Emacs is compiled with GTK+ support, each tool bar item can consist of an image, or a text label, or both. By default, Emacs follows the Gnome desktop’s tool bar style setting; if none is defined, it displays tool bar items as just images. To impose a specific tool bar style, customize the variable tool-bar-style.

You can also control the placement of the tool bar for the GTK+ tool bar with the frame parameter tool-bar-position. See Frame Parameters in The Emacs Lisp Reference Manual.

NS builds consider the tool bar to be a window decoration, and therefore do not display it when a window is undecorated. See Frame Parameters in The Emacs Lisp Reference Manual. On macOS the tool bar is hidden when the frame is put into fullscreen, but can be displayed by moving the mouse pointer to the top of the screen.


22.17 Tab Bars

On graphical displays and on text terminals, Emacs can optionally display a Tab Bar at the top of each frame, just below the menu bar (see Menu Bars) and above or below the tool bar (see Tool Bars) depending on the variable tab-bar-position. The Tab Bar is a row of tabs—buttons that you can click to switch between window configurations.

Each tab on the Tab Bar represents a named persistent window configuration of its frame, i.e., how that frame is partitioned into windows and which buffer is displayed in each window. The tab’s name is composed from the list of names of buffers shown in windows of that window configuration. Clicking on the tab switches to the window configuration recorded by the tab; it is a configuration of windows and buffers which was previously used in the frame when that tab was the current tab.

If you are using the desktop library to save and restore your sessions (see Saving Emacs Sessions), the tabs from the Tab Bar are recorded in the desktop file, together with their associated window configurations, and will be available after restoring the session.

Note that the Tab Bar is different from the Tab Line (see Window Tab Line). Whereas tabs on the Tab Line at the top of each window are used to switch between buffers in the window, tabs on the Tab Bar at the top of each frame are used to switch between window configurations containing several windows showing one or more buffers.

To toggle the use of Tab Bars, type M-x tab-bar-mode. This command applies to all frames, including frames yet to be created. To control the use of tab bars at startup, customize the variable tab-bar-mode and save your customization.

The variable tab-bar-show controls whether the Tab Bar mode is turned on automatically. If the value is t, then tab-bar-mode is enabled when using the commands that create new tabs. The value 1 hides the tab bar when it has only one tab, and shows it again when more tabs are created. More generally, a value that is a non-negative integer causes the Tab Bar to be displayed only if the number of tabs is greater than that integer. The value nil always keeps the Tab Bar hidden; in this case it’s still possible to switch between named window configurations without displaying the Tab Bar by using M-x tab-next, M-x tab-switcher, and other commands that provide completion on tab names. Also it’s possible to create and close tabs without the Tab Bar by using commands M-x tab-new, M-x tab-close, etc.

Note that a numerical value of tab-bar-show can cause the Tab Bar to be displayed on some frames, but not on others, depending on the number of tabs created on each frame.

To toggle the use of the Tab Bar only on the selected frame, type M-x toggle-frame-tab-bar. This command allows to enable the display of the Tab Bar on some frames and disable it on others, regardless of the values of tab-bar-mode and tab-bar-show.

The prefix key C-x t is analogous to C-x 5. Whereas each C-x 5 command pops up a buffer in a different frame (see Creating Frames), the C-x t commands use a different tab with a different window configuration in the selected frame.

The various C-x t commands differ in how they find or create the buffer to select. The following commands can be used to select a buffer in a new tab:

C-x t 2

Add a new tab (tab-new). You can control the choice of the buffer displayed in a new tab by customizing the variable tab-bar-new-tab-choice. You can control the names given by default to new tabs by customizing the variable tab-bar-tab-name-function.

C-x t b bufname RET

Select buffer bufname in another tab. This runs switch-to-buffer-other-tab.

C-x t f filename RET

Visit the file filename (see Visiting Files) and select its buffer in another tab. This runs find-file-other-tab.

C-x t d directory RET

Edit the specified directory (see Dired, the Directory Editor) in another tab. This runs dired-other-tab.

C-x t t

This is a prefix command (other-tab-prefix) that affects the next command invoked immediately after this prefix command. It requests the buffer displayed by the next command to be shown in another tab.

By default, a new tab starts with the buffer that was current before calling the command that adds a new tab. To start a new tab with other buffers, customize the variable tab-bar-new-tab-choice.

The variable tab-bar-new-tab-to defines where to place a new tab. By default, a new tab is added on the right side of the current tab.

The following commands can be used to delete tabs:

C-x t 0

Close the selected tab (tab-close). This has no effect if there is only one tab, unless the variable tab-bar-close-last-tab-choice is customized to a non-default value.

C-x t 1

Close all tabs, except the selected tab, on the selected frame.

The variable tab-bar-close-tab-select defines what tab to select after closing the current tab. By default, it selects a recently used tab.

The command tab-undo restores the last closed tab.

The following commands can be used to switch between tabs:

C-x t o
C-TAB

Switch to the next tab (tab-next). If you repeat this command, it cycles through all the tabs on the selected frame. With a positive numeric argument n, it switches to the nth next tab; with a negative argument −n, it switches back to the nth previous tab.

S-C-TAB

Switch to the previous tab (tab-previous). With a positive numeric argument n, it switches to the nth previous tab; with a negative argument −n, it switches to the nth next tab.

C-x t RET tabname RET

Switch to the tab by its name (tab-switch), with completion on all tab names. The default value and the “future history” of tab names is sorted by recency, so you can use M-n (next-history-element) to get the name of the last visited tab, the second last, and so on.

modifier-tab-number

Switch to the tab by its number tab-number (tab-select). After customizing the variable tab-bar-select-tab-modifiers to specify one or more modifier keys, you can select a tab by its ordinal number using one of the specified modifiers in combination with the tab number to select. The number 9 can be used to select the last tab. You can select any modifiers supported by Emacs, see Modifier Keys. To display the tab number alongside the tab name, you can customize another variable tab-bar-tab-hints. This will help you decide which numerical key to press to select the tab by its number.

modifier-9

Switch to the last tab (tab-last). The key combination is the modifier key defined by tab-bar-select-tab-modifiers and the key 9. With a numeric argument n, switch to the nth last tab.

modifier-0

Switch to the recent tab (tab-recent). The key combination is the modifier key defined by tab-bar-select-tab-modifiers and the key 0. With a numeric argument n, switch to the nth recent tab.

The following commands can be used to operate on tabs:

C-x t r tabname RET

Rename the current tab to tabname (tab-rename).

C-x t m

Move the current tab one position to the right (tab-move). With a positive numeric argument n, move it that many positions to the right; with a negative argument −n, move it n positions to the left.

You can use the mouse to operate on tabs. Clicking mouse-2 closes the tab. Clicking mouse-3 pops up the context menu with the items that operate on the clicked tab. Dragging the tab with mouse-1 moves it to another position on the tab bar. Mouse wheel scrolling switches to the next or previous tab. Holding down the SHIFT key during scrolling moves the tab to the left or right.

You can enable tab-bar-history-mode to remember window configurations used in every tab, and later restore them.

M-x tab-bar-history-back

Restore a previous window configuration used in the current tab. This navigates back in the history of window configurations.

M-x tab-bar-history-forward

Cancel restoration of the previous window configuration. This moves forward in the history of window configurations.

It’s possible to customize the items displayed on the tab bar by the user option tab-bar-format.


22.18 Using Dialog Boxes

A dialog box is a special kind of menu for asking you a yes-or-no question or some other special question. Many Emacs commands use a dialog box to ask a yes-or-no question, if you used the mouse to invoke the command that led to the question.

To disable the use of dialog boxes, change the variable use-dialog-box to nil. In that case, Emacs always performs yes-or-no prompts using the echo area and keyboard input. This variable also controls whether to use file selection windows (but those are not supported on all platforms).

A file selection window is a special kind of dialog box for asking for file names. You can customize the variable use-file-dialog to suppress the use of file selection windows, even if you still want other kinds of dialogs. This variable has no effect if you have suppressed all dialog boxes with the variable use-dialog-box.

When Emacs is compiled with GTK+ support, it uses the GTK+ file chooser dialog. Emacs adds an additional toggle button to this dialog, which you can use to enable or disable the display of hidden files (files starting with a dot) in that dialog. If you want this toggle to be activated by default, change the variable x-gtk-show-hidden-files to t. In addition, Emacs adds help text to the GTK+ file chooser dialog; to disable this help text, change the variable x-gtk-file-dialog-help-text to nil.


22.19 Tooltips

Tooltips are small special frames that display text information at the current mouse position. They activate when there is a pause in mouse movement over some significant piece of text in a window, or the mode line, or some other part of the Emacs frame such as a tool bar button or menu item.

You can toggle the use of tooltips with the command M-x tooltip-mode. When Tooltip mode is disabled, the help text is displayed in the echo area instead. To control the use of tooltips at startup, customize the variable tooltip-mode.

The following variables provide customization options for tooltip display:

tooltip-delay

This variable specifies how long Emacs should wait before displaying the first tooltip. The value is in seconds.

tooltip-short-delay

This variable specifies how long Emacs should wait before displaying subsequent tooltips on different items, having already displayed the first tooltip. The value is in seconds.

tooltip-hide-delay

The number of seconds since displaying a tooltip to hide it, if the mouse doesn’t move.

tooltip-x-offset
tooltip-y-offset

The X and Y offsets, in pixels, of the left top corner of the tooltip from the mouse pointer position. Note that these are ignored if tooltip-frame-parameters was customized to include, respectively, the left and top parameters. The values of the offsets should be chosen so that the tooltip doesn’t cover the mouse pointer’s hot spot, or it might interfere with clicking the mouse.

tooltip-frame-parameters

The frame parameters used for displaying tooltips. See Frame Parameters in The Emacs Lisp Reference Manual, and also Tooltips in The Emacs Lisp Reference Manual.

For additional customization options for displaying tooltips, use M-x customize-group RET tooltip RET.

If Emacs is built with the GTK+ toolkit, Nextstep windowing, or Haiku windowing support, it displays tooltips via the toolkit, using the default appearance of the toolkit’s tooltips.8 To disable this, change the variable use-system-tooltips to nil. If you do this, or if Emacs is built without the appropriate windowing support, most attributes of the tooltip text are specified by the tooltip face, and by X resources (see X Options and Resources).

GUD tooltips are special tooltips that show the values of variables when debugging a program with GUD. See Debugger Operation.


22.20 Mouse Avoidance

On graphical terminals, the mouse pointer may obscure the text in the Emacs frame. Emacs provides two methods to avoid this problem.

Firstly, Emacs hides the mouse pointer each time you type a self-inserting character, if the pointer lies inside an Emacs frame; moving the mouse pointer makes it visible again. To disable this feature, set the variable make-pointer-invisible to nil. See Customization of Display.

Secondly, you can use Mouse Avoidance mode, a minor mode, to keep the mouse pointer away from point. To use Mouse Avoidance mode, customize the variable mouse-avoidance-mode. You can set this to various values to move the mouse in several ways:

banish

Move the pointer to a corner of the frame on any key-press. You can customize the variable mouse-avoidance-banish-position to specify where the pointer goes when it is banished.

exile

Banish the pointer only if the cursor gets too close, and allow it to return once the cursor is out of the way.

jump

If the cursor gets too close to the pointer, displace the pointer by a random distance and direction.

animate

As jump, but shows steps along the way for illusion of motion.

cat-and-mouse

The same as animate.

proteus

As animate, but changes the shape of the mouse pointer too.

You can also use the command M-x mouse-avoidance-mode to enable the mode. Whenever Mouse Avoidance mode moves the mouse, it also raises the frame.


22.21 Text Terminals

On a text terminal, Emacs can display only one Emacs frame at a time. However, you can still create multiple Emacs frames, and switch between them. Switching frames on these terminals is much like switching between different window configurations.

Use C-x 5 2 to create a new frame and switch to it; use C-x 5 o to cycle through the existing frames; use C-x 5 0 to delete the current frame.

Each frame has a number to distinguish it. If your terminal can display only one frame at a time, the selected frame’s number n appears near the beginning of the mode line, in the form ‘Fn’.

Fn’ is in fact the frame’s initial name. You can give frames more meaningful names if you wish, and you can select a frame by its name. Use the command M-x set-frame-name RET name RET to specify a new name for the selected frame, and use M-x select-frame-by-name RET name RET to select a frame according to its name. The name you specify appears in the mode line when the frame is selected.


22.22 Using a Mouse in Text Terminals

Some text terminals support mouse clicks in the terminal window.

In a terminal emulator which is compatible with xterm, you can use M-x xterm-mouse-mode to give Emacs control over simple uses of the mouse—basically, only non-modified single clicks are supported. Newer versions of xterm also support mouse-tracking. The normal xterm mouse functionality for such clicks is still available by holding down the SHIFT key when you press the mouse button. Xterm Mouse mode is a global minor mode (see Minor Modes). Repeating the command turns the mode off again.

In the console on GNU/Linux, you can use M-x gpm-mouse-mode to enable mouse support. You must have the gpm server installed and running on your system in order for this to work. Note that when this mode is enabled, you cannot use the mouse to transfer text between Emacs and other programs which use GPM. This is due to limitations in GPM and the Linux kernel.

See Mouse Usage on MS-DOS, for information about mouse support on MS-DOS.


23 International Character Set Support

Emacs supports a wide variety of international character sets, including European and Vietnamese variants of the Latin alphabet, as well as Arabic scripts, Brahmic scripts (for languages such as Bengali, Hindi, and Thai), Cyrillic, Ethiopic, Georgian, Greek, Han (for Chinese and Japanese), Hangul (for Korean), Hebrew and IPA. Emacs also supports various encodings of these characters that are used by other internationalized software, such as word processors and mailers.

Emacs allows editing text with international characters by supporting all the related activities:

The rest of this chapter describes these issues in detail.


23.1 Introduction to International Character Sets

The users of international character sets and scripts have established many more-or-less standard coding systems for storing files. These coding systems are typically multibyte, meaning that sequences of two or more bytes are used to represent individual non-ASCII characters.

Internally, Emacs uses its own multibyte character encoding, which is a superset of the Unicode standard. This internal encoding allows characters from almost every known script to be intermixed in a single buffer or string. Emacs translates between the multibyte character encoding and various other coding systems when reading and writing files, and when exchanging data with subprocesses.

The command C-h h (view-hello-file) displays the file etc/HELLO, which illustrates various scripts by showing how to say “hello” in many languages. If some characters can’t be displayed on your terminal, they appear as ‘?’ or as hollow boxes (see Undisplayable Characters).

Keyboards, even in the countries where these character sets are used, generally don’t have keys for all the characters in them. You can insert characters that your keyboard does not support, using C-x 8 RET (insert-char). See Inserting Text. Shorthands are available for some common characters; for example, you can insert a left single quotation mark by typing C-x 8 [, or in Electric Quote mode, usually by simply typing `. See Quotation Marks. Emacs also supports various input methods, typically one for each script or language, which make it easier to type characters in the script. See Input Methods.

The prefix key C-x RET is used for commands that pertain to multibyte characters, coding systems, and input methods.

The command C-x = (what-cursor-position) shows information about the character at point. In addition to the character position, which was described in Cursor Position Information, this command displays how the character is encoded. For instance, it displays the following line in the echo area for the character ‘c’:

Char: c (99, #o143, #x63) point=28062 of 36168 (78%) column=53

The four values after ‘Char:’ describe the character that follows point, first by showing it and then by giving its character code in decimal, octal and hex. For a non-ASCII multibyte character, these are followed by ‘file’ and the character’s representation, in hex, in the buffer’s coding system, if that coding system encodes the character safely and with a single byte (see Coding Systems). If the character’s encoding is longer than one byte, Emacs shows ‘file ...’.

On rare occasions, Emacs encounters raw bytes: single bytes whose values are in the range 128 (0200 octal) through 255 (0377 octal), which Emacs cannot interpret as part of a known encoding of some non-ASCII character. Such raw bytes are treated as if they belonged to a special character set eight-bit; Emacs displays them as escaped octal codes (this can be customized; see Customization of Display). In this case, C-x = shows ‘raw-byte’ instead of ‘file’. In addition, C-x = shows the character codes of raw bytes as if they were in the range #x3FFF80..#x3FFFFF, which is where Emacs maps them to distinguish them from Unicode characters in the range #x0080..#x00FF.

With a prefix argument (C-u C-x =), this command additionally calls the command describe-char, which displays a detailed description of the character:

  • The character set name, and the codes that identify the character within that character set; ASCII characters are identified as belonging to the ascii character set.
  • The character’s script, syntax and categories.
  • What keys to type to input the character in the current input method (if it supports the character).
  • The character’s encodings, both internally in the buffer, and externally if you were to save the buffer to a file.
  • If you are running Emacs on a graphical display, the font name and glyph code for the character. If you are running Emacs on a text terminal, the code(s) sent to the terminal.
  • If the character was composed on display with any following characters to form one or more grapheme clusters, the composition information: the font glyphs if the frame is on a graphical display, and the characters that were composed.
  • The character’s text properties (see Text Properties in the Emacs Lisp Reference Manual), including any non-default faces used to display the character, and any overlays containing it (see Overlays in the same manual).

Here’s an example, with some lines folded to fit into this manual:

             position: 1 of 1 (0%), column: 0
            character: ê (displayed as ê) (codepoint 234, #o352, #xea)
    preferred charset: unicode (Unicode (ISO10646))
code point in charset: 0xEA
               script: latin
               syntax: w        which means: word
             category: .:Base, L:Left-to-right (strong), c:Chinese,
                       j:Japanese, l:Latin, v:Viet
             to input: type "C-x 8 RET ea" or
                       "C-x 8 RET LATIN SMALL LETTER E WITH CIRCUMFLEX"
          buffer code: #xC3 #xAA
            file code: #xC3 #xAA (encoded by coding system utf-8-unix)
              display: by this font (glyph code)
    xft:-PfEd-DejaVu Sans Mono-normal-normal-
        normal-*-15-*-*-*-m-0-iso10646-1 (#xAC)

Character code properties: customize what to show
  name: LATIN SMALL LETTER E WITH CIRCUMFLEX
  old-name: LATIN SMALL LETTER E CIRCUMFLEX
  general-category: Ll (Letter, Lowercase)
  decomposition: (101 770) ('e' '^')

23.2 Language Environments

All supported character sets are supported in Emacs buffers whenever multibyte characters are enabled; there is no need to select a particular language in order to display its characters. However, it is important to select a language environment in order to set various defaults. Roughly speaking, the language environment represents a choice of preferred script rather than a choice of language.

The language environment controls which coding systems to recognize when reading text (see Recognizing Coding Systems). This applies to files, incoming mail, and any other text you read into Emacs. It may also specify the default coding system to use when you create a file. Each language environment also specifies a default input method.

To select a language environment, customize current-language-environment or use the command M-x set-language-environment. It makes no difference which buffer is current when you use this command, because the effects apply globally to the Emacs session. See the variable language-info-alist for the list of supported language environments, and use the command C-h L lang-env RET (describe-language-environment) for more information about the language environment lang-env. Supported language environments include:

ASCII, Arabic, Belarusian, Bengali, Brazilian Portuguese, Bulgarian, Burmese, Cham, Chinese-BIG5, Chinese-CNS, Chinese-EUC-TW, Chinese-GB, Chinese-GB18030, Chinese-GBK, Croatian, Cyrillic-ALT, Cyrillic-ISO, Cyrillic-KOI8, Czech, Devanagari, Dutch, English, Esperanto, Ethiopic, French, Georgian, German, Greek, Gujarati, Hebrew, IPA, Italian, Japanese, Kannada, Khmer, Korean, Lao, Latin-1, Latin-2, Latin-3, Latin-4, Latin-5, Latin-6, Latin-7, Latin-8, Latin-9, Latvian, Lithuanian, Malayalam, Oriya, Persian, Polish, Punjabi, Romanian, Russian, Sinhala, Slovak, Slovenian, Spanish, Swedish, TaiViet, Tajik, Tamil, Telugu, Thai, Tibetan, Turkish, UTF-8, Ukrainian, Vietnamese, Welsh, and Windows-1255.

To display the script(s) used by your language environment on a graphical display, you need to have suitable fonts. See Fontsets, for more details about setting up your fonts.

Some operating systems let you specify the character-set locale you are using by setting the locale environment variables LC_ALL, LC_CTYPE, or LANG. (If more than one of these is set, the first one that is nonempty specifies your locale for this purpose.) During startup, Emacs looks up your character-set locale’s name in the system locale alias table, matches its canonical name against entries in the value of the variables locale-charset-language-names and locale-language-names (the former overrides the latter), and selects the corresponding language environment if a match is found. It also adjusts the display table and terminal coding system, the locale coding system, the preferred coding system as needed for the locale, and—last but not least—the way Emacs decodes non-ASCII characters sent by your keyboard.

If you modify the LC_ALL, LC_CTYPE, or LANG environment variables while running Emacs (by using M-x setenv), you may want to invoke the set-locale-environment command afterwards to readjust the language environment from the new locale.

The set-locale-environment function normally uses the preferred coding system established by the language environment to decode system messages. But if your locale matches an entry in the variable locale-preferred-coding-systems, Emacs uses the corresponding coding system instead. For example, if the locale ‘ja_JP.PCK’ matches japanese-shift-jis in locale-preferred-coding-systems, Emacs uses that encoding even though it might normally use utf-8.

You can override the language environment chosen at startup with explicit use of the command set-language-environment, or with customization of current-language-environment in your init file.

To display information about the effects of a certain language environment lang-env, use the command C-h L lang-env RET (describe-language-environment). This tells you which languages this language environment is useful for, and lists the character sets, coding systems, and input methods that go with it. It also shows some sample text to illustrate scripts used in this language environment. If you give an empty input for lang-env, this command describes the chosen language environment.

You can customize any language environment with the normal hook set-language-environment-hook. The command set-language-environment runs that hook after setting up the new language environment. The hook functions can test for a specific language environment by checking the variable current-language-environment. This hook is where you should put non-default settings for specific language environments, such as coding systems for keyboard input and terminal output, the default input method, etc.

Before it starts to set up the new language environment, set-language-environment first runs the hook exit-language-environment-hook. This hook is useful for undoing customizations that were made with set-language-environment-hook. For instance, if you set up a special key binding in a specific language environment using set-language-environment-hook, you should set up exit-language-environment-hook to restore the normal binding for that key.


23.3 Input Methods

An input method is a kind of character conversion designed specifically for interactive input. This section describes input methods that come with Emacs; for native input methods provided by the underlying OS, see Unibyte Editing Mode.

In Emacs, typically each language has its own input method; sometimes several languages that use the same characters can share one input method. A few languages support several input methods.

The simplest kind of input method works by mapping ASCII letters into another alphabet; this allows you to use one other alphabet instead of ASCII. The Greek and Russian input methods work this way.

A more powerful technique is composition: converting sequences of characters into one letter. Many European input methods use composition to produce a single non-ASCII letter from a sequence that consists of a letter followed by accent characters (or vice versa). For example, some methods convert the sequence o ^ into a single accented letter. These input methods have no special commands of their own; all they do is compose sequences of printing characters.

The input methods for syllabic scripts typically use mapping followed by composition. The input methods for Thai and Korean work this way. First, letters are mapped into symbols for particular sounds or tone marks; then, sequences of these that make up a whole syllable are mapped into one syllable sign.

Chinese and Japanese require more complex methods. In Chinese input methods, first you enter the phonetic spelling of a Chinese word (in input method chinese-py, among others), or a sequence of portions of the character (input methods chinese-4corner and chinese-sw, and others). One input sequence typically corresponds to many possible Chinese characters. You select the one you mean using keys such as C-f, C-b, C-n, C-p (or the arrow keys), and digits, which have special meanings in this situation.

The possible characters are conceptually arranged in several rows, with each row holding up to 10 alternatives. Normally, Emacs displays just one row at a time, in the echo area; (i/j) appears at the beginning, to indicate that this is the ith row out of a total of j rows. Type C-n or C-p to display the next row or the previous row.

Type C-f and C-b to move forward and backward among the alternatives in the current row. As you do this, Emacs highlights the current alternative with a special color; type C-SPC to select the current alternative and use it as input. The alternatives in the row are also numbered; the number appears before the alternative. Typing a number selects the associated alternative of the current row and uses it as input.

TAB in these Chinese input methods displays a buffer showing all the possible characters at once; then clicking mouse-2 on one of them selects that alternative. The keys C-f, C-b, C-n, C-p, and digits continue to work as usual, but they do the highlighting in the buffer showing the possible characters, rather than in the echo area.

To enter characters according to the pīnyīn transliteration method instead, use the chinese-sisheng input method. This is a composition based method, where e.g. pi1 results in ‘’.

In Japanese input methods, first you input a whole word using phonetic spelling; then, after the word is in the buffer, Emacs converts it into one or more characters using a large dictionary. One phonetic spelling corresponds to a number of different Japanese words; to select one of them, use C-n and C-p to cycle through the alternatives.

Sometimes it is useful to cut off input method processing so that the characters you have just entered will not combine with subsequent characters. For example, in input method latin-1-postfix, the sequence o ^ combines to form an ‘o’ with an accent. What if you want to enter them as separate characters?

One way is to type the accent twice; this is a special feature for entering the separate letter and accent. For example, o ^ ^ gives you the two characters ‘o^’. Another way is to type another letter after the o—something that won’t combine with that—and immediately delete it. For example, you could type o o DEL ^ to get separate ‘o’ and ‘^’. Another method, more general but not quite as easy to type, is to use C-\ C-\ between two characters to stop them from combining. This is the command C-\ (toggle-input-method) used twice. See Selecting an Input Method.

C-\ C-\ is especially useful inside an incremental search, because it stops waiting for more characters to combine, and starts searching for what you have already entered.

To find out how to input the character after point using the current input method, type C-u C-x =. See Cursor Position Information.

The variables input-method-highlight-flag and input-method-verbose-flag control how input methods explain what is happening. If input-method-highlight-flag is non-nil, the partial sequence is highlighted in the buffer (for most input methods—some disable this feature). If input-method-verbose-flag is non-nil, the list of possible characters to type next is displayed in the echo area (but not when you are in the minibuffer).

You can modify how an input method works by making your changes in a function that you add to the hook variable quail-activate-hook. See Hooks. For example, you can redefine some of the input method’s keys by defining key bindings in the keymap returned by the function quail-translation-keymap, using define-key. See Rebinding Keys in Your Init File.

Input methods are inhibited when the text in the buffer is read-only for some reason. This is so single-character key bindings work in modes that make buffer text or parts of it read-only, such as read-only-mode and image-mode, even when an input method is active.

Another facility for typing characters not on your keyboard is by using C-x 8 RET (insert-char) to insert a single character based on its Unicode name or code-point; see Inserting Text.

There are specialized commands for inserting Emoji, and these can be found on the C-x 8 e keymap. C-x 8 e e (emoji-insert) will let you navigate through different Emoji categories and then choose one. C-x 8 e l (emoji-list) will pop up a new buffer and list all the Emoji; clicking (or using RET) on an emoji character will insert it in the current buffer. Finally, C-x 8 e s (emoji-search) will allow you to search for Emoji based on their names.

describe-char displays a lot of information about the character/glyphs under point (including emojis). It’s sometimes useful to get a quick description of the name, and you can use the C-x 8 e d (emoji-describe) command to do that. It’s meant primarily to help distinguish between different Emoji variants (which can look very similar), but it will also tell you the names of non-Emoji characters.


23.4 Selecting an Input Method

C-\

Enable or disable use of the selected input method (toggle-input-method).

C-x RET C-\ method RET

Select a new input method for the current buffer (set-input-method).

C-x \ method RET

Temporarily enable the selected transient input method ; it will be automatically disabled after inserting a single character (activate-transient-input-method).

C-h I method RET
C-h C-\ method RET

Describe the input method method (describe-input-method). By default, it describes the current input method (if any). This description should give you the full details of how to use any particular input method.

M-x list-input-methods

Display a list of all the supported input methods.

To choose an input method for the current buffer, use C-x RET C-\ (set-input-method). This command reads the input method name from the minibuffer; the name normally starts with the language environment that it is meant to be used with. The variable current-input-method records which input method is selected.

Input methods use various sequences of ASCII characters to stand for non-ASCII characters. Sometimes it is useful to turn off the input method temporarily. To do this, type C-\ (toggle-input-method). To reenable the input method, type C-\ again.

If you type C-\ and you have not yet selected an input method, it prompts you to specify one. This has the same effect as using C-x RET C-\ to specify an input method.

When invoked with a numeric argument, as in C-u C-\, toggle-input-method always prompts you for an input method, suggesting the most recently selected one as the default.

Selecting a language environment specifies a default input method for use in various buffers. When you have a default input method, you can select it in the current buffer by typing C-\. The variable default-input-method specifies the default input method (nil means there is none).

In some language environments, which support several different input methods, you might want to use an input method different from the default chosen by set-language-environment. You can instruct Emacs to select a different default input method for a certain language environment, if you wish, by using set-language-environment-hook (see set-language-environment-hook). For example:

(defun my-chinese-setup ()
  "Set up my private Chinese environment."
  (if (equal current-language-environment "Chinese-GB")
      (setq default-input-method "chinese-tonepy")))
(add-hook 'set-language-environment-hook 'my-chinese-setup)

This sets the default input method to be chinese-tonepy whenever you choose a Chinese-GB language environment.

You can instruct Emacs to activate a certain input method automatically. For example:

(add-hook 'text-mode-hook
  (lambda () (set-input-method "german-prefix")))

This automatically activates the input method german-prefix in Text mode.

Some input methods for alphabetic scripts work by (in effect) remapping the keyboard to emulate various keyboard layouts commonly used for those scripts. How to do this remapping properly depends on your actual keyboard layout. To specify which layout your keyboard has, use the command M-x quail-set-keyboard-layout.

You can use the command M-x quail-show-key to show what key (or key sequence) to type in order to input the character following point, using the selected keyboard layout. The command C-u C-x = also shows that information, in addition to other information about the character.

M-x list-input-methods displays a list of all the supported input methods. The list gives information about each input method, including the string that stands for it in the mode line.

Sometimes it can be convenient to enable an input method transiently, for inserting only a single character. Typing C-x \ (activate-transient-input-method) will temporarily enable an input method, let you insert a single character using the input method rules, and then automatically disable the input method. If no transient input method was selected yet, C-x \ will prompt you for an input method; subsequent invocations of this command will enable the selected transient input method. To select a different transient input method, type C-u C-x \. You can select a transient method that is different from the input method which you selected using C-u C-\.


23.5 Coding Systems

Users of various languages have established many more-or-less standard coding systems for representing them. Emacs does not use these coding systems internally; instead, it converts from various coding systems to its own system when reading data, and converts the internal coding system to other coding systems when writing data. Conversion is possible in reading or writing files, in sending or receiving from the terminal, and in exchanging data with subprocesses.

Emacs assigns a name to each coding system. Most coding systems are used for one language, and the name of the coding system starts with the language name. Some coding systems are used for several languages; their names usually start with ‘iso’. There are also special coding systems, such as no-conversion, raw-text, and emacs-internal.

A special class of coding systems, collectively known as codepages, is designed to support text encoded by MS-Windows and MS-DOS software. The names of these coding systems are cpnnnn, where nnnn is a 3- or 4-digit number of the codepage. You can use these encodings just like any other coding system; for example, to visit a file encoded in codepage 850, type C-x RET c cp850 RET C-x C-f filename RET.

In addition to converting various representations of non-ASCII characters, a coding system can perform end-of-line conversion. Emacs handles three different conventions for how to separate lines in a file: newline (Unix), carriage return followed by linefeed (DOS), and just carriage return (Mac).

C-h C coding RET

Describe coding system coding (describe-coding-system).

C-h C RET

Describe the coding systems currently in use (describe-coding-system).

M-x list-coding-systems

Display a list of all the supported coding systems.

The command C-h C (describe-coding-system) displays information about particular coding systems, including the end-of-line conversion specified by those coding systems. You can specify a coding system name as the argument; alternatively, with an empty argument, it describes the coding systems currently selected for various purposes, both in the current buffer and as the defaults, and the priority list for recognizing coding systems (see Recognizing Coding Systems).

To display a list of all the supported coding systems, type M-x list-coding-systems. The list gives information about each coding system, including the letter that stands for it in the mode line (see The Mode Line).

Each of the coding systems that appear in this list—except for no-conversion, which means no conversion of any kind—specifies how and whether to convert printing characters, but leaves the choice of end-of-line conversion to be decided based on the contents of each file. For example, if the file appears to use the sequence carriage return and linefeed to separate lines, DOS end-of-line conversion will be used.

Each of the listed coding systems has three variants, which specify exactly what to do for end-of-line conversion:

…-unix

Don’t do any end-of-line conversion; assume the file uses newline to separate lines. (This is the convention normally used on Unix and GNU systems, and macOS.)

…-dos

Assume the file uses carriage return followed by linefeed to separate lines, and do the appropriate conversion. (This is the convention normally used on Microsoft systems.9)

…-mac

Assume the file uses carriage return to separate lines, and do the appropriate conversion. (This was the convention used in Classic Mac OS.)

These variant coding systems are omitted from the list-coding-systems display for brevity, since they are entirely predictable. For example, the coding system iso-latin-1 has variants iso-latin-1-unix, iso-latin-1-dos and iso-latin-1-mac.

The coding systems unix, dos, and mac are aliases for undecided-unix, undecided-dos, and undecided-mac, respectively. These coding systems specify only the end-of-line conversion, and leave the character code conversion to be deduced from the text itself.

The coding system raw-text is good for a file which is mainly ASCII text, but may contain byte values above 127 that are not meant to encode non-ASCII characters. With raw-text, Emacs copies those byte values unchanged, and sets enable-multibyte-characters to nil in the current buffer so that they will be interpreted properly. raw-text handles end-of-line conversion in the usual way, based on the data encountered, and has the usual three variants to specify the kind of end-of-line conversion to use.

In contrast, the coding system no-conversion specifies no character code conversion at all—none for non-ASCII byte values and none for end of line. This is useful for reading or writing binary files, tar files, and other files that must be examined verbatim. It, too, sets enable-multibyte-characters to nil.

The easiest way to edit a file with no conversion of any kind is with the M-x find-file-literally command. This uses no-conversion, and also suppresses other Emacs features that might convert the file contents before you see them. See Visiting Files.

The coding system emacs-internal (or utf-8-emacs, which is equivalent) means that the file contains non-ASCII characters stored with the internal Emacs encoding. This coding system handles end-of-line conversion based on the data encountered, and has the usual three variants to specify the kind of end-of-line conversion.


23.6 Recognizing Coding Systems

Whenever Emacs reads a given piece of text, it tries to recognize which coding system to use. This applies to files being read, output from subprocesses, text from X selections, etc. Emacs can select the right coding system automatically most of the time—once you have specified your preferences.

Some coding systems can be recognized or distinguished by which byte sequences appear in the data. However, there are coding systems that cannot be distinguished, not even potentially. For example, there is no way to distinguish between Latin-1 and Latin-2; they use the same byte values with different meanings.

Emacs handles this situation by means of a priority list of coding systems. Whenever Emacs reads a file, if you do not specify the coding system to use, Emacs checks the data against each coding system, starting with the first in priority and working down the list, until it finds a coding system that fits the data. Then it converts the file contents assuming that they are represented in this coding system.

The priority list of coding systems depends on the selected language environment (see Language Environments). For example, if you use French, you probably want Emacs to prefer Latin-1 to Latin-2; if you use Czech, you probably want Latin-2 to be preferred. This is one of the reasons to specify a language environment.

However, you can alter the coding system priority list in detail with the command M-x prefer-coding-system. This command reads the name of a coding system from the minibuffer, and adds it to the front of the priority list, so that it is preferred to all others. If you use this command several times, each use adds one element to the front of the priority list.

If you use a coding system that specifies the end-of-line conversion type, such as iso-8859-1-dos, what this means is that Emacs should attempt to recognize iso-8859-1 with priority, and should use DOS end-of-line conversion when it does recognize iso-8859-1.

Sometimes a file name indicates which coding system to use for the file. The variable file-coding-system-alist specifies this correspondence. There is a special function modify-coding-system-alist for adding elements to this list. For example, to read and write all ‘.txt’ files using the coding system chinese-iso-8bit, you can execute this Lisp expression:

(modify-coding-system-alist 'file "\\.txt\\'" 'chinese-iso-8bit)

The first argument should be file, the second argument should be a regular expression that determines which files this applies to, and the third argument says which coding system to use for these files.

Emacs recognizes which kind of end-of-line conversion to use based on the contents of the file: if it sees only carriage returns, or only carriage return followed by linefeed sequences, then it chooses the end-of-line conversion accordingly. You can inhibit the automatic use of end-of-line conversion by setting the variable inhibit-eol-conversion to non-nil. If you do that, DOS-style files will be displayed with the ‘^M’ characters visible in the buffer; some people prefer this to the more subtle ‘(DOS)’ end-of-line type indication near the left edge of the mode line (see eol-mnemonic).

By default, the automatic detection of the coding system is sensitive to escape sequences. If Emacs sees a sequence of characters that begin with an escape character, and the sequence is valid as an ISO-2022 code, that tells Emacs to use one of the ISO-2022 encodings to decode the file.

However, there may be cases that you want to read escape sequences in a file as is. In such a case, you can set the variable inhibit-iso-escape-detection to non-nil. Then the code detection ignores any escape sequences, and never uses an ISO-2022 encoding. The result is that all escape sequences become visible in the buffer.

The default value of inhibit-iso-escape-detection is nil. We recommend that you not change it permanently, only for one specific operation. That’s because some Emacs Lisp source files in the Emacs distribution contain non-ASCII characters encoded in the coding system iso-2022-7bit, and they won’t be decoded correctly when you visit those files if you suppress the escape sequence detection.

The variables auto-coding-alist and auto-coding-regexp-alist are the strongest way to specify the coding system for certain patterns of file names, or for files containing certain patterns, respectively. These variables even override ‘-*-coding:-*-’ tags in the file itself (see Specifying a File’s Coding System). For example, Emacs uses auto-coding-alist for tar and archive files, to prevent it from being confused by a ‘-*-coding:-*-’ tag in a member of the archive and thinking it applies to the archive file as a whole.

Another way to specify a coding system is with the variable auto-coding-functions. For example, one of the builtin auto-coding-functions detects the encoding for XML files. Unlike the previous two, this variable does not override any ‘-*-coding:-*-’ tag.


23.7 Specifying a File’s Coding System

If Emacs recognizes the encoding of a file incorrectly, you can reread the file using the correct coding system with C-x RET r (revert-buffer-with-coding-system). This command prompts for the coding system to use. To see what coding system Emacs actually used to decode the file, look at the coding system mnemonic letter near the left edge of the mode line (see The Mode Line), or type C-h C (describe-coding-system).

You can specify the coding system for a particular file in the file itself, using the ‘-*--*- construct at the beginning, or a local variables list at the end (see Local Variables in Files). You do this by defining a value for the “variable” named coding. Emacs does not really have a variable coding; instead of setting a variable, this uses the specified coding system for the file. For example, ‘-*-mode: C; coding: latin-1; -*- specifies use of the Latin-1 coding system, as well as C mode. When you specify the coding explicitly in the file, that overrides file-coding-system-alist.


23.8 Choosing Coding Systems for Output

Once Emacs has chosen a coding system for a buffer, it stores that coding system in buffer-file-coding-system. That makes it the default for operations that write from this buffer into a file, such as save-buffer and write-region. You can specify a different coding system for further file output from the buffer using set-buffer-file-coding-system (see Specifying a Coding System for File Text).

You can insert any character Emacs supports into any Emacs buffer, but most coding systems can only handle a subset of these characters. Therefore, it’s possible that the characters you insert cannot be encoded with the coding system that will be used to save the buffer. For example, you could visit a text file in Polish, encoded in iso-8859-2, and add some Russian words to it. When you save that buffer, Emacs cannot use the current value of buffer-file-coding-system, because the characters you added cannot be encoded by that coding system.

When that happens, Emacs tries the most-preferred coding system (set by M-x prefer-coding-system or M-x set-language-environment). If that coding system can safely encode all of the characters in the buffer, Emacs uses it, and stores its value in buffer-file-coding-system. Otherwise, Emacs displays a list of coding systems suitable for encoding the buffer’s contents, and asks you to choose one of those coding systems.

If you insert the unsuitable characters in a mail message, Emacs behaves a bit differently. It additionally checks whether the most-preferred coding system is recommended for use in MIME messages; if not, it informs you of this fact and prompts you for another coding system. This is so you won’t inadvertently send a message encoded in a way that your recipient’s mail software will have difficulty decoding. (You can still use an unsuitable coding system if you enter its name at the prompt.)

When you send a mail message (see Sending Mail), Emacs has four different ways to determine the coding system to use for encoding the message text. It first tries the buffer’s own value of buffer-file-coding-system, if that is non-nil. Otherwise, it uses the value of sendmail-coding-system, if that is non-nil. Thirdly, it uses the value of default-sendmail-coding-system. If all of these three values are nil, Emacs encodes outgoing mail using the default coding system for new files (i.e., the default value of buffer-file-coding-system), which is controlled by your choice of language environment.


23.9 Specifying a Coding System for File Text

In cases where Emacs does not automatically choose the right coding system for a file’s contents, you can use these commands to specify one:

C-x RET f coding RET

Use coding system coding to save or revisit the file in the current buffer (set-buffer-file-coding-system).

C-x RET c coding RET

Specify coding system coding for the immediately following command (universal-coding-system-argument).

C-x RET r coding RET

Revisit the current file using the coding system coding (revert-buffer-with-coding-system).

M-x recode-region RET right RET wrong RET

Convert a region that was decoded using coding system wrong, decoding it using coding system right instead.

The command C-x RET f (set-buffer-file-coding-system) sets the file coding system for the current buffer (i.e., the coding system to use when saving or reverting the file). You specify which coding system using the minibuffer. You can also invoke this command by clicking with mouse-3 on the coding system indicator in the mode line (see The Mode Line).

If you specify a coding system that cannot handle all the characters in the buffer, Emacs will warn you about the troublesome characters, and ask you to choose another coding system, when you try to save the buffer (see Choosing Coding Systems for Output).

You can also use this command to specify the end-of-line conversion (see end-of-line conversion) for encoding the current buffer. For example, C-x RET f dos RET will cause Emacs to save the current buffer’s text with DOS-style carriage return followed by linefeed line endings.

Another way to specify the coding system for a file is when you visit the file. First use the command C-x RET c (universal-coding-system-argument); this command uses the minibuffer to read a coding system name. After you exit the minibuffer, the specified coding system is used for the immediately following command.

So if the immediately following command is C-x C-f, for example, it reads the file using that coding system (and records the coding system for when you later save the file). Or if the immediately following command is C-x C-w, it writes the file using that coding system. When you specify the coding system for saving in this way, instead of with C-x RET f, there is no warning if the buffer contains characters that the coding system cannot handle.

Other file commands affected by a specified coding system include C-x i and C-x C-v, as well as the other-window variants of C-x C-f. C-x RET c also affects commands that start subprocesses, including M-x shell (see Running Shell Commands from Emacs). If the immediately following command does not use the coding system, then C-x RET c ultimately has no effect.

An easy way to visit a file with no conversion is with the M-x find-file-literally command. See Visiting Files.

The default value of the variable buffer-file-coding-system specifies the choice of coding system to use when you create a new file. It applies when you find a new file, and when you create a buffer and then save it in a file. Selecting a language environment typically sets this variable to a good choice of default coding system for that language environment.

If you visit a file with a wrong coding system, you can correct this with C-x RET r (revert-buffer-with-coding-system). This visits the current file again, using a coding system you specify.

If a piece of text has already been inserted into a buffer using the wrong coding system, you can redo the decoding of it using M-x recode-region. This prompts you for the proper coding system, then for the wrong coding system that was actually used, and does the conversion. It first encodes the region using the wrong coding system, then decodes it again using the proper coding system.


23.10 Coding Systems for Interprocess Communication

This section explains how to specify coding systems for use in communication with other processes.

C-x RET x coding RET

Use coding system coding for transferring selections to and from other graphical applications (set-selection-coding-system).

C-x RET X coding RET

Use coding system coding for transferring one selection—the next one—to or from another graphical application (set-next-selection-coding-system).

C-x RET p input-coding RET output-coding RET

Use coding systems input-coding and output-coding for subprocess input and output in the current buffer (set-buffer-process-coding-system).

The command C-x RET x (set-selection-coding-system) specifies the coding system for sending selected text to other windowing applications, and for receiving the text of selections made in other applications. This command applies to all subsequent selections, until you override it by using the command again. The command C-x RET X (set-next-selection-coding-system) specifies the coding system for the next selection made in Emacs or read by Emacs.

The variable x-select-request-type specifies the data type to request from the X Window System for receiving text selections from other applications. If the value is nil (the default), Emacs tries UTF8_STRING and COMPOUND_TEXT, in this order, and uses various heuristics to choose the more appropriate of the two results; if none of these succeed, Emacs falls back on STRING. If the value of x-select-request-type is one of the symbols COMPOUND_TEXT, UTF8_STRING, STRING, or TEXT, Emacs uses only that request type. If the value is a list of some of these symbols, Emacs tries only the request types in the list, in order, until one of them succeeds, or until the list is exhausted.

The command C-x RET p (set-buffer-process-coding-system) specifies the coding system for input and output to a subprocess. This command applies to the current buffer; normally, each subprocess has its own buffer, and thus you can use this command to specify translation to and from a particular subprocess by giving the command in the corresponding buffer.

You can also use C-x RET c (universal-coding-system-argument) just before the command that runs or starts a subprocess, to specify the coding system for communicating with that subprocess. See Specifying a Coding System for File Text.

The default for translation of process input and output depends on the current language environment.

The variable locale-coding-system specifies a coding system to use when encoding and decoding system strings such as system error messages and format-time-string formats and time stamps. That coding system might also be used for decoding non-ASCII keyboard input on the X Window System and will also be used to encode text sent to the standard output and error streams in batch mode. You should choose a coding system that is compatible with the underlying system’s text representation, which is normally specified by one of the environment variables LC_ALL, LC_CTYPE, and LANG. (The first one, in the order specified above, whose value is nonempty is the one that determines the text representation.)


23.11 Coding Systems for File Names

C-x RET F coding RET

Use coding system coding for encoding and decoding file names (set-file-name-coding-system).

The command C-x RET F (set-file-name-coding-system) specifies a coding system to use for encoding file names. It has no effect on reading and writing the contents of files.

In fact, all this command does is set the value of the variable file-name-coding-system. If you set the variable to a coding system name (as a Lisp symbol or a string), Emacs encodes file names using that coding system for all file operations. This makes it possible to use non-ASCII characters in file names—or, at least, those non-ASCII characters that the specified coding system can encode.

If file-name-coding-system is nil, Emacs uses a default coding system determined by the selected language environment, and stored in the default-file-name-coding-system variable (normally UTF-8).

When Emacs runs on MS-Windows versions that are descendants of the NT family (Windows 2000, XP, and all the later versions), the value of file-name-coding-system is largely ignored, as Emacs by default uses APIs that allow passing Unicode file names directly. By contrast, on Windows 9X, file names are encoded using file-name-coding-system, which should be set to the codepage (see codepage) pertinent for the current system locale. The value of the variable w32-unicode-filenames controls whether Emacs uses the Unicode APIs when it calls OS functions that accept file names. This variable is set by the startup code to nil on Windows 9X, and to t on newer versions of MS-Windows.

Warning: if you change file-name-coding-system (or the language environment) in the middle of an Emacs session, problems can result if you have already visited files whose names were encoded using the earlier coding system and cannot be encoded (or are encoded differently) under the new coding system. If you try to save one of these buffers under the visited file name, saving may use the wrong file name, or it may encounter an error. If such a problem happens, use C-x C-w to specify a new file name for that buffer.

If a mistake occurs when encoding a file name, use the command M-x recode-file-name to change the file name’s coding system. This prompts for an existing file name, its old coding system, and the coding system to which you wish to convert.


23.12 Coding Systems for X Keyboard Input

Input methods under the X Window System specify their own coding systems that must be used to decode keyboard input. By default, Emacs determines the coding system used for each input method automatically upon establishing the connection to the input method server, and uses that specific coding system to decode keyboard input. However, that determination can sometimes fail; in that situation, the locale coding system (see Coding Systems for Interprocess Communication) is used instead.

If the input method does not correctly announce the coding system it uses to encode text, then the coding system used by Emacs to decode text from input methods must be manually specified. The value of the variable x-input-coding-system, when set to a symbol, is unconditionally used as the coding system used to decode keyboard input from input methods.


23.13 Coding Systems for Terminal I/O

C-x RET t coding RET

Use coding system coding for terminal output (set-terminal-coding-system).

C-x RET k coding RET

Use coding system coding for keyboard input (set-keyboard-coding-system).

The command C-x RET t (set-terminal-coding-system) specifies the coding system for terminal output. If you specify a character code for terminal output, all characters output to the terminal are translated into that coding system.

This feature is useful for certain character-only terminals built to support specific languages or character sets—for example, European terminals that support one of the ISO Latin character sets. You need to specify the terminal coding system when using multibyte text, so that Emacs knows which characters the terminal can actually handle.

By default, output to the terminal is not translated at all, unless Emacs can deduce the proper coding system from your terminal type or your locale specification (see Language Environments).

The command C-x RET k (set-keyboard-coding-system), or the variable keyboard-coding-system, specifies the coding system for keyboard input. Character-code translation of keyboard input is useful for terminals with keys that send non-ASCII graphic characters—for example, some terminals designed for ISO Latin-1 or subsets of it.

By default, keyboard input is translated based on your system locale setting. If your terminal does not really support the encoding implied by your locale (for example, if you find it inserts a non-ASCII character if you type M-i), you will need to set keyboard-coding-system to nil to turn off encoding. You can do this by putting

(set-keyboard-coding-system nil)

in your init file.

Setting keyboard-coding-system has no effect on MS-Windows, except on old Windows 9X systems, in which case the encoding must match the current codepage of the MS-Windows console, which can be changed by calling w32-set-console-codepage.

There is a similarity between using a coding system translation for keyboard input, and using an input method: both define sequences of keyboard input that translate into single characters. However, input methods are designed to be convenient for interactive use by humans, and the sequences that are translated are typically sequences of ASCII printing characters. Coding systems typically translate sequences of non-graphic characters.


23.14 Fontsets

A font typically defines shapes for a single alphabet or script. Therefore, displaying the entire range of scripts that Emacs supports requires a collection of many fonts. In Emacs, such a collection is called a fontset. A fontset is defined by a list of font specifications, each assigned to handle a range of character codes, and may fall back on another fontset for characters that are not covered by the fonts it specifies.

Each fontset has a name, like a font. However, while fonts are stored in the system and the available font names are defined by the system, fontsets are defined within Emacs itself. Once you have defined a fontset, you can use it within Emacs by specifying its name, anywhere that you could use a single font. Of course, Emacs fontsets can use only the fonts that your system supports. If some characters appear on the screen as empty boxes or hex codes, this means that the fontset in use for them has no font for those characters. In this case, or if the characters are shown, but not as well as you would like, you may need to install extra fonts or modify the fontset to use specific fonts already installed on your system (see below). Your operating system may have optional fonts that you can install; or you can install the GNU Intlfonts package, which includes fonts for most supported scripts.10

Emacs creates three fontsets automatically: the standard fontset, the startup fontset and the default fontset. The default fontset is most likely to have fonts for a wide variety of non-ASCII characters, and is the default fallback for the other two fontsets, and if you set a default font rather than fontset. However, it does not specify font family names, so results can be somewhat random if you use it directly. You can specify a particular fontset by starting Emacs with the ‘-fn’ option. For example,

emacs -fn fontset-standard

You can also specify a fontset with the ‘Font’ resource (see X Options and Resources).

If no fontset is specified for use, then Emacs uses an ASCII font, with ‘fontset-default’ as a fallback for characters the font does not cover. The standard fontset is only used if explicitly requested, despite its name.

To show the information about a specific fontset, use the M-x describe-fontset command. It prompts for a fontset name, defaulting to the one used by the current frame, and then displays all the subranges of characters and the fonts assigned to them in that fontset. To see which fonts Emacs is using in a session started without a specific fontset (which is what happens normally), type fontset-default RET at the prompt, or just RET to describe the fontset used by the current frame.

A fontset does not necessarily specify a font for every character code. If a fontset specifies no font for a certain character, or if it specifies a font that does not exist on your system, then it cannot display that character properly. It will display that character as a hex code or thin space or an empty box instead. (See glyphless characters, for details.) Or a fontset might specify a font for some range of characters, but you may not like their visual appearance. If this happens, you may wish to modify your fontset; see Modifying Fontsets, for how to do that.


23.15 Defining Fontsets

When running on X, Emacs creates a standard fontset automatically according to the value of standard-fontset-spec. This fontset’s name is

-*-fixed-medium-r-normal-*-16-*-*-*-*-*-fontset-standard

or just ‘fontset-standard’ for short.

On GNUstep and macOS, the standard fontset is created using the value of ns-standard-fontset-spec, and on MS Windows it is created using the value of w32-standard-fontset-spec.

Bold, italic, and bold-italic variants of the standard fontset are created automatically. Their names have ‘bold’ instead of ‘medium’, or ‘i’ instead of ‘r’, or both.

Emacs generates a fontset automatically, based on any default ASCII font that you specify with the ‘Font’ resource or the ‘-fn’ argument, or the default font that Emacs found when it started. This is the startup fontset and its name is fontset-startup. Emacs generates this fontset by replacing the charset_registry field with ‘fontset’, and replacing the charset_encoding field with ‘startup’, then using the resulting string to specify a fontset.

For instance, if you start Emacs with a font of this form,

emacs -fn "*courier-medium-r-normal--14-140-*-iso8859-1"

Emacs generates the following fontset and uses it for the initial X window frame:

-*-courier-medium-r-normal-*-14-140-*-*-*-*-fontset-startup

The startup fontset will use the font that you specify, or a variant with a different registry and encoding, for all the characters that are supported by that font, and fallback on ‘fontset-default’ for other characters.

With the X resource ‘Emacs.Font’, you can specify a fontset name just like an actual font name. But be careful not to specify a fontset name in a wildcard resource like ‘Emacs*Font’—that wildcard specification matches various other resources, such as for menus, and menus cannot handle fontsets. See X Options and Resources.

You can specify additional fontsets using X resources named ‘Fontset-n’, where n is an integer starting from 0. The resource value should have this form:

fontpattern, [charset:font]…

where fontpattern should have the form of a standard X font name (see the previous fontset-startup example), except for the last two fields. They should have the form ‘fontset-alias’.

Each fontset has two names, one long and one short. The long name is fontpattern. The short name is ‘fontset-alias’, the last 2 fields of the long name (e.g., ‘fontset-startup’ for the fontset automatically created at startup). You can refer to the fontset by either name.

The construct ‘charset:font’ specifies which font to use (in this fontset) for one particular character set. Here, charset is the name of a character set, and font is the font to use for that character set. You can use this construct any number of times in defining one fontset.

For the other character sets, Emacs chooses a font based on fontpattern. It replaces ‘fontset-alias’ with values that describe the character set. For the ASCII character font, ‘fontset-alias’ is replaced with ‘ISO8859-1’.

In addition, when several consecutive fields are wildcards, Emacs collapses them into a single wildcard. This is to prevent use of auto-scaled fonts. Fonts made by scaling larger fonts are not usable for editing, and scaling a smaller font is also not useful, because it is better to use the smaller font in its own size, which is what Emacs does.

Thus if fontpattern is this,

-*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24

the font specification for ASCII characters would be this:

-*-fixed-medium-r-normal-*-24-*-ISO8859-1

and the font specification for Chinese GB2312 characters would be this:

-*-fixed-medium-r-normal-*-24-*-gb2312*-*

You may not have any Chinese font matching the above font specification. Most X distributions include only Chinese fonts that have ‘song ti’ or ‘fangsong ti’ in the family field. In such a case, ‘Fontset-n’ can be specified as:

Emacs.Fontset-0: -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24,\
        chinese-gb2312:-*-*-medium-r-normal-*-24-*-gb2312*-*

Then, the font specifications for all but Chinese GB2312 characters have ‘fixed’ in the family field, and the font specification for Chinese GB2312 characters has a wild card ‘*’ in the family field.

The function that processes the fontset resource value to create the fontset is called create-fontset-from-fontset-spec. You can also call this function explicitly to create a fontset.

See Fonts, for more information about font naming.


23.16 Modifying Fontsets

Fontsets do not always have to be created from scratch. If only minor changes are required it may be easier to modify an existing fontset, usually ‘fontset-default’. Modifying ‘fontset-default’ will also affect other fontsets that use it as a fallback, so can be an effective way of fixing problems with the fonts that Emacs chooses for a particular script.

Fontsets can be modified using the function set-fontset-font, specifying a character, a charset, a script, or a range of characters to modify the font for, and a font specification for the font to be used. Some examples are:

;; Prefer a big5 font for han characters.
(set-fontset-font "fontset-default"
                  'han (font-spec :registry "big5")
                  nil 'prepend)

;; Use MyPrivateFont for the Unicode private use area.
(set-fontset-font "fontset-default"  '(#xe000 . #xf8ff)
                  "MyPrivateFont")

;; Use Liberation Mono for latin-3 charset.
(set-fontset-font "fontset-default" 'iso-8859-3
                  "Liberation Mono")

;; Use DejaVu Sans Mono as a fallback in fontset-startup
;; before resorting to fontset-default.
(set-fontset-font "fontset-startup" nil "DejaVu Sans Mono"
                  nil 'append)

See Fontsets in GNU Emacs Lisp Reference Manual, for more details about using the set-fontset-font function.

If you don’t know the character’s codepoint or the script to which it belongs, you can ask Emacs. With point at the character, type C-u C-x = (what-cursor-position), and this information, together with much more, will be displayed in the *Help* buffer that Emacs pops up. See Cursor Position Information. For example, Japanese characters belong to the ‘kana’ script, but Japanese text also mixes them with Chinese characters so the following uses the ‘han’ script to set up Emacs to use the ‘Kochi Gothic’ font for Japanese text:

(set-fontset-font "fontset-default" 'han "Kochi Gothic")

(For convenience, the ‘han’ script in Emacs is set up to support all of the Chinese, Japanese, and Korean, a.k.a. CJK, characters, not just Chinese characters.)

For the list of known scripts, see the variable script-representative-chars.

Fontset settings like those above only affect characters that the default font doesn’t support, so if the ‘Kochi Gothic’ font covers Latin characters, it will not be used for displaying Latin scripts, since the default font used by Emacs usually covers Basic Latin.

Some fonts installed on your system might be broken, or produce unpleasant results for characters for which they are used, and you may wish to instruct Emacs to completely ignore them while searching for a suitable font required to display a character. You can do that by adding the offending fonts to the value of the variable face-ignored-fonts, which is a list. Here’s an example to put in your ~/.emacs:

(add-to-list 'face-ignored-fonts "Some Bad Font")

23.17 Undisplayable Characters

There may be some non-ASCII characters that your terminal cannot display. Most text terminals support just a single character set (use the variable default-terminal-coding-system to tell Emacs which one, Coding Systems for Terminal I/O); characters that can’t be encoded in that coding system are displayed as ‘?’ by default.

Graphical displays can display a broader range of characters, but you may not have fonts installed for all of them; characters that have no font appear as a hollow box.

If you use Latin-1 characters but your terminal can’t display Latin-1, you can arrange to display mnemonic ASCII sequences instead, e.g., ‘"o’ for o-umlaut. Load the library iso-ascii to do this.

If your terminal can display Latin-1, you can display characters from other European character sets using a mixture of equivalent Latin-1 characters and ASCII mnemonics. Customize the variable latin1-display to enable this. The mnemonic ASCII sequences mostly correspond to those of the prefix input methods.


23.18 Unibyte Editing Mode

The ISO 8859 Latin-n character sets define character codes in the range 0240 to 0377 octal (160 to 255 decimal) to handle the accented letters and punctuation needed by various European languages (and some non-European ones). Note that Emacs considers bytes with codes in this range as raw bytes, not as characters, even in a unibyte buffer, i.e., if you disable multibyte characters. However, Emacs can still handle these character codes as if they belonged to one of the single-byte character sets at a time. To specify which of these codes to use, invoke M-x set-language-environment and specify a suitable language environment such as ‘Latin-n’. See Disabling Multibyte Characters in GNU Emacs Lisp Reference Manual.

Emacs can also display bytes in the range 160 to 255 as readable characters, provided the terminal or font in use supports them. This works automatically. On a graphical display, Emacs can also display single-byte characters through fontsets, in effect by displaying the equivalent multibyte characters according to the current language environment. To request this, set the variable unibyte-display-via-language-environment to a non-nil value. Note that setting this only affects how these bytes are displayed, but does not change the fundamental fact that Emacs treats them as raw bytes, not as characters.

If your terminal does not support display of the Latin-1 character set, Emacs can display these characters as ASCII sequences which at least give you a clear idea of what the characters are. To do this, load the library iso-ascii. Similar libraries for other Latin-n character sets could be implemented, but have not been so far.

Normally non-ISO-8859 characters (decimal codes between 128 and 159 inclusive) are displayed as octal escapes. You can change this for non-standard extended versions of ISO-8859 character sets by using the function standard-display-8bit in the disp-table library.

There are two ways to input single-byte non-ASCII characters:

  • You can use an input method for the selected language environment. See Input Methods. When you use an input method in a unibyte buffer, the non-ASCII character you specify with it is converted to unibyte.
  • If your keyboard can generate character codes 128 (decimal) and up, representing non-ASCII characters, you can type those character codes directly.

    On a graphical display, you should not need to do anything special to use these keys; they should simply work. On a text terminal, you should use the command M-x set-keyboard-coding-system or customize the variable keyboard-coding-system to specify which coding system your keyboard uses (see Coding Systems for Terminal I/O). Enabling this feature will probably require you to use ESC to type Meta characters; however, on a console terminal or a terminal emulator such as xterm, you can arrange for Meta to be converted to ESC and still be able to type 8-bit characters present directly on the keyboard or using Compose or AltGr keys. See Kinds of User Input.

    Many modern systems provide native input methods for many languages whose characters don’t have keyboard keys assigned to them. If Emacs was built with support for these native input methods, you can activate such an input method and type the characters they support. How to activate and use these input methods depends on the system and the input method, and will not be described here; see your system documentation. Here we describe some Emacs facilities to control the use of the native input methods.

    In Emacs built with the GTK toolkit, the variable x-gtk-use-native-input controls whether Emacs should receive characters produced by GTK input methods. If the value is nil, the default, Emacs uses the X input methods (XIM), otherwise it uses the GTK input methods. The useXIM X resource controls whether to use XIM, and inputStyle X resource controls the display on X of preview text generated by the native input methods; see Table of X Resources for Emacs.

    On MS-Windows, Emacs supports native inputs methods provided by IMM, the Input Method Manager, but that can be turned off if needed; see Keyboard Usage on MS-Windows.

  • You can use the key C-x 8 as a compose-character prefix for entry of non-ASCII Latin-1 and other printing characters. C-x 8 is good for insertion (in the minibuffer as well as other buffers), for searching, and in any other context where a key sequence is allowed.

    C-x 8 works by loading the iso-transl library. Once that library is loaded, the Alt modifier key, if the keyboard has one, serves the same purpose as C-x 8: use Alt together with an accent character to modify the following letter. In addition, if the keyboard has keys for the Latin-1 dead accent characters, they too are defined to compose with the following character, once iso-transl is loaded.

    Use C-x 8 C-h to list all the available C-x 8 translations.


23.19 Charsets

In Emacs, charset is short for “character set”. Emacs supports most popular charsets (such as ascii, iso-8859-1, cp1250, big5, and unicode), in addition to some charsets of its own (such as emacs, unicode-bmp, and eight-bit). All supported characters belong to one or more charsets.

Emacs normally does the right thing with respect to charsets, so that you don’t have to worry about them. However, it is sometimes helpful to know some of the underlying details about charsets.

One example is font selection (see Fonts). Each language environment (see Language Environments) defines a priority list for the various charsets. When searching for a font, Emacs initially attempts to find one that can display the highest-priority charsets. For instance, in the Japanese language environment, the charset japanese-jisx0208 has the highest priority, so Emacs tries to use a font whose registry property is ‘JISX0208.1983-0’.

There are two commands that can be used to obtain information about charsets. The command M-x list-charset-chars prompts for a charset name, and displays all the characters in that character set. The command M-x describe-character-set prompts for a charset name, and displays information about that charset, including its internal representation within Emacs.

M-x list-character-sets displays a list of all supported charsets. The list gives the names of charsets and additional information to identity each charset; for more details, see the ISO International Register of Coded Character Sets to be Used with Escape Sequences (ISO-IR) maintained by the Information Processing Society of Japan/Information Technology Standards Commission of Japan (IPSJ/ITSCJ). In this list, charsets are divided into two categories: normal charsets are listed first, followed by supplementary charsets. A supplementary charset is one that is used to define another charset (as a parent or a subset), or to provide backward-compatibility for older Emacs versions.

To find out which charset a character in the buffer belongs to, put point before it and type C-u C-x = (see Introduction to International Character Sets).


23.20 Bidirectional Editing

Emacs supports editing text written in scripts, such as Arabic, Farsi, and Hebrew, whose natural ordering of horizontal text for display is from right to left. However, digits and Latin text embedded in these scripts are still displayed left to right. It is also not uncommon to have small portions of text in Arabic or Hebrew embedded in an otherwise Latin document; e.g., as comments and strings in a program source file. For these reasons, text that uses these scripts is actually bidirectional: a mixture of runs of left-to-right and right-to-left characters.

This section describes the facilities and options provided by Emacs for editing bidirectional text.

Emacs stores right-to-left and bidirectional text in the so-called logical (or reading) order: the buffer or string position of the first character you read precedes that of the next character. Reordering of bidirectional text into the visual order happens at display time. As a result, character positions no longer increase monotonically with their positions on display. Emacs implements the Unicode Bidirectional Algorithm (UBA) described in the Unicode Standard Annex #9, for reordering of bidirectional text for display. It deviates from the UBA only in how continuation lines are displayed when text direction is opposite to the base paragraph direction, e.g., when a long line of English text appears in a right-to-left paragraph.

The buffer-local variable bidi-display-reordering controls whether text in the buffer is reordered for display. If its value is non-nil, Emacs reorders characters that have right-to-left directionality when they are displayed. The default value is t.

Each paragraph of bidirectional text can have its own base direction, either right-to-left or left-to-right. Text in left-to-right paragraphs begins on the screen at the left margin of the window and is truncated or continued when it reaches the right margin. By contrast, text in right-to-left paragraphs is displayed starting at the right margin and is continued or truncated at the left margin. By default, paragraph boundaries are empty lines, i.e., lines consisting entirely of whitespace characters. To change that, you can customize the two variables bidi-paragraph-start-re and bidi-paragraph-separate-re, whose values should be regular expressions (strings); e.g., to have a single newline start a new paragraph, set both of these variables to "^". These two variables are buffer-local (see Local Variables).

Emacs determines the base direction of each paragraph dynamically, based on the text at the beginning of the paragraph. However, sometimes a buffer may need to force a certain base direction for its paragraphs. The variable bidi-paragraph-direction, if non-nil, disables the dynamic determination of the base direction, and instead forces all paragraphs in the buffer to have the direction specified by its buffer-local value. The value can be either right-to-left or left-to-right. Any other value is interpreted as nil.

Alternatively, you can control the base direction of a paragraph by inserting special formatting characters in front of the paragraph. The special character RIGHT-TO-LEFT MARK, or RLM, forces the right-to-left direction on the following paragraph, while LEFT-TO-RIGHT MARK, or LRM forces the left-to-right direction. (You can use C-x 8 RET to insert these characters.) In a GUI session, the LRM and RLM characters display as very thin blank characters; on text terminals they display as blanks.

Because characters are reordered for display, Emacs commands that operate in the logical order or on stretches of buffer positions may produce unusual effects. For example, the commands C-f and C-b move point in the logical order, so the cursor will sometimes jump when point traverses reordered bidirectional text. Similarly, a highlighted region covering a contiguous range of character positions may look discontinuous if the region spans reordered text. This is normal and similar to the behavior of other programs that support bidirectional text.

Cursor motion commands bound to arrow keys, such as LEFT and C-RIGHT, are sensitive to the base direction of the current paragraph. In a left-to-right paragraph, commands bound to RIGHT with or without modifiers move forward through buffer text, but in a right-to-left paragraph they move backward instead. This reflects the fact that in a right-to-left paragraph buffer positions predominantly increase when moving to the left on display.

When you move out of a paragraph, the meaning of the arrow keys might change if the base direction of the preceding or the following paragraph is different from the paragraph out of which you moved. When that happens, you need to adjust the arrow key you press to the new base direction.

By default, LEFT and RIGHT move in the logical order, but if visual-order-cursor-movement is non-nil, these commands move to the character that is, correspondingly, to the left or right of the current screen position, moving to the next or previous screen line as appropriate. Note that this might potentially move point many buffer positions away, depending on the surrounding bidirectional context.

Bidirectional text sometimes uses special formatting characters to affect the reordering of text for display. The LRM and RLM characters, mentioned above, are two such characters, but there are more of them. They are by default displayed as thin space glyphs on GUI frames, and as simple spaces on text-mode frames. If you want to be aware of these special control characters, so that their effect on display does not come as a surprise, you can turn on the glyphless-display-mode (see How Text Is Displayed). This minor mode will cause these formatting characters to be displayed as acronyms inside a small box, so that they stand out on display, and make their effect easier to understand.


24 Major and Minor Modes

Emacs contains many editing modes that alter its basic behavior in useful ways. These are divided into major modes and minor modes.

Major modes provide specialized facilities for working on a particular file type, such as a C source file (see Editing Programs), or a particular type of non-file buffer, such as a shell buffer (see Running Shell Commands from Emacs). Major modes are mutually exclusive; each buffer has one and only one major mode at any time.

Minor modes are optional features which you can turn on or off, not necessarily specific to a type of file or buffer. For example, Auto Fill mode is a minor mode in which SPC breaks lines between words as you type (see Auto Fill Mode). Minor modes are independent of one another, and of the selected major mode.


24.1 Major Modes

Every buffer possesses a major mode, which determines the editing behavior of Emacs while that buffer is current. The mode line normally shows the name of the current major mode, in parentheses (see The Mode Line).

The least specialized major mode is called Fundamental mode. This mode has no mode-specific redefinitions or variable settings, so that each Emacs command behaves in its most general manner, and each user option variable is in its default state.

For editing text of a specific type that Emacs knows about, such as Lisp code or English text, you typically use a more specialized major mode, such as Lisp mode or Text mode. Most major modes fall into three major groups. The first group contains modes for normal text, either plain or with mark-up. It includes Text mode, HTML mode, SGML mode, TeX mode and Outline mode. The second group contains modes for specific programming languages. These include Lisp mode (which has several variants), C mode, Fortran mode, and others. The third group consists of major modes that are not associated directly with files; they are used in buffers created for specific purposes by Emacs. Examples include Dired mode for buffers made by Dired (see Dired, the Directory Editor), Message mode for buffers made by C-x m (see Sending Mail), and Shell mode for buffers used to communicate with an inferior shell process (see Interactive Subshell).

Usually, the major mode is automatically set by Emacs, when you first visit a file or create a buffer (see Choosing File Modes). You can explicitly select a new major mode by using an M-x command. Take the name of the mode and add -mode to get the name of the command to select that mode (e.g., M-x lisp-mode enters Lisp mode). Since every buffer has exactly one major mode, there is no way to “turn off” a major mode; instead you must switch to a different one.

The value of the buffer-local variable major-mode is a symbol with the same name as the major mode command (e.g., lisp-mode). This variable is set automatically; you should not change it yourself.

The default value of major-mode determines the major mode to use for files that do not specify a major mode, and for new buffers created with C-x b. Normally, this default value is the symbol fundamental-mode, which specifies Fundamental mode. You can change this default value via the Customization interface (see Easy Customization Interface), or by adding a line like this to your init file (see The Emacs Initialization File):

(setq-default major-mode 'text-mode)

If the default value of major-mode is nil, the major mode is taken from the previously current buffer.

Specialized major modes often change the meanings of certain keys to do something more suitable for the mode. For instance, programming language modes bind TAB to indent the current line according to the rules of the language (see Indentation). The keys that are commonly changed are TAB, DEL, and C-j. Many modes also define special commands of their own, usually bound to key sequences whose prefix key is C-c (see Keys). Major modes can also alter user options and variables; for instance, programming language modes typically set a buffer-local value for the variable comment-start, which determines how source code comments are delimited (see Manipulating Comments).

To view the documentation for the current major mode, including a list of its key bindings, type C-h m (describe-mode). See Other Help Commands.

Every major mode, apart from Fundamental mode, defines a mode hook, a customizable list of Lisp functions to run each time the mode is enabled in a buffer. See Hooks, for more information about hooks. Each mode hook is named after its major mode, e.g., Fortran mode has fortran-mode-hook. Furthermore, all text-based major modes run text-mode-hook, and many programming language modes 11 (including all those distributed with Emacs) run prog-mode-hook, prior to running their own mode hooks. Hook functions can look at the value of the variable major-mode to see which mode is actually being entered.

Mode hooks are commonly used to enable minor modes (see Minor Modes). For example, you can put the following lines in your init file to enable Flyspell minor mode in all text-based major modes (see Checking and Correcting Spelling), and ElDoc minor mode in Emacs Lisp mode (see Programming Language Documentation Lookup):

(add-hook 'text-mode-hook 'flyspell-mode)
(add-hook 'emacs-lisp-mode-hook 'eldoc-mode)

24.2 Minor Modes

A minor mode is an optional editing mode that alters the behavior of Emacs in some well-defined way. Unlike major modes, any number of minor modes can be in effect at any time. Some minor modes are buffer-local, and can be turned on (enabled) in certain buffers and off (disabled) in others. Other minor modes are global: while enabled, they affect everything you do in the Emacs session, in all buffers. Most minor modes are disabled by default, but a few are enabled by default.

Most buffer-local minor modes say in the mode line when they are enabled, just after the major mode indicator. For example, ‘Fill’ in the mode line means that Auto Fill mode is enabled. See The Mode Line.

Like major modes, each minor mode is associated with a mode command, whose name consists of the mode name followed by ‘-mode’. For instance, the mode command for Auto Fill mode is auto-fill-mode. But unlike a major mode command, which simply enables the mode, the mode command for a minor mode can either enable or disable it:

  • If you invoke the mode command directly with no prefix argument (either via M-x, or by binding it to a key and typing that key; see Customizing Key Bindings), that toggles the minor mode. The minor mode is turned on if it was off, and turned off if it was on.
  • If you invoke the mode command with a prefix argument, the minor mode is unconditionally turned off if that argument is zero or negative; otherwise, it is unconditionally turned on.
  • If the mode command is called via Lisp, the minor mode is unconditionally turned on if the argument is omitted or nil. This makes it easy to turn on a minor mode from a major mode’s mode hook (see Major Modes). A non-nil argument is handled like an interactive prefix argument, as described above.

Most minor modes also have a mode variable, with the same name as the mode command. Its value is non-nil if the mode is enabled, and nil if it is disabled. In general, you should not try to enable or disable the mode by changing the value of the mode variable directly in Lisp; you should run the mode command instead. However, setting the mode variable through the Customize interface (see Easy Customization Interface) will always properly enable or disable the mode, since Customize automatically runs the mode command for you.

The following is a list of some buffer-local minor modes:

  • Abbrev mode automatically expands text based on pre-defined abbreviation definitions. See Abbrevs.
  • Auto Fill mode inserts newlines as you type to prevent lines from becoming too long. See Filling Text.
  • Auto Save mode saves the buffer contents periodically to reduce the amount of work you can lose in case of a crash. See Auto-Saving: Protection Against Disasters.
  • Electric Quote mode automatically converts quotation marks. For example, it requotes text typed `like this' to text ‘like this’. You can control what kind of text it operates in, and you can disable it entirely in individual buffers. See Quotation Marks.
  • Enriched mode enables editing and saving of formatted text. See Enriched Text.
  • Flyspell mode automatically highlights misspelled words. See Checking and Correcting Spelling.
  • Font-Lock mode automatically highlights certain textual units found in programs. It is enabled globally by default, but you can disable it in individual buffers. See Text Faces.
  • Display Line Numbers mode is a convenience wrapper around display-line-numbers, setting it using the value of display-line-numbers-type. See Customization of Display.
  • Outline minor mode provides similar facilities to the major mode called Outline mode. See Outline Mode.
  • Overwrite mode causes ordinary printing characters to replace existing text instead of shoving it to the right. For example, if point is in front of the ‘B’ in ‘FOOBAR’, then in Overwrite mode typing a G changes it to ‘FOOGAR’, instead of producing ‘FOOGBAR’ as usual. In Overwrite mode, the command C-q inserts the next character whatever it may be, even if it is a digit—this gives you a way to insert a character instead of replacing an existing character. The mode command, overwrite-mode, is bound to the Insert key.
  • Binary Overwrite mode is a variant of Overwrite mode for editing binary files; it treats newlines and tabs like other characters, so that they overwrite other characters and can be overwritten by them. In Binary Overwrite mode, digits after C-q specify an octal character code, as usual.
  • Visual Line mode performs word wrapping, causing long lines to be wrapped at word boundaries. See Visual Line Mode.

And here are some useful global minor modes:

  • Column Number mode enables display of the current column number in the mode line. See The Mode Line.
  • Delete Selection mode causes text insertion to first delete the text in the region, if the region is active. See Operating on the Region.
  • Icomplete mode displays an indication of available completions when you are in the minibuffer and completion is active. See Fast minibuffer selection.
  • Line Number mode enables display of the current line number in the mode line. It is enabled by default. See The Mode Line.
  • Menu Bar mode gives each frame a menu bar. It is enabled by default. See Menu Bars.
  • Scroll Bar mode gives each window a scroll bar. It is enabled by default, but the scroll bar is only displayed on graphical terminals. See Scroll Bars.
  • Tool Bar mode gives each frame a tool bar. It is enabled by default, but the tool bar is only displayed on graphical terminals. See Tool Bars.
  • Tab Bar mode gives each frame a tab bar. See Tab Bars.
  • Tab Line mode gives each window a tab line. See Window Tab Line.
  • Transient Mark mode highlights the region, and makes many Emacs commands operate on the region when the mark is active. It is enabled by default. See The Mark and the Region.

24.3 Choosing File Modes

When you visit a file, Emacs chooses a major mode automatically. Normally, it makes the choice based on the file name—for example, files whose names end in ‘.c’ are normally edited in C mode—but sometimes it chooses the major mode based on special text in the file. This special text can also be used to enable buffer-local minor modes.

Here is the exact procedure:

First, Emacs checks whether the file contains file-local mode variables. See Local Variables in Files. If there is a file-local variable that specifies a major mode, then Emacs uses that major mode, ignoring all other criteria. There are several methods to specify a major mode using a file-local variable; the simplest is to put the mode name in the first nonblank line, preceded and followed by ‘-*-’. Other text may appear on the line as well. For example,

; -*-Lisp-*-

tells Emacs to use Lisp mode. Note how the semicolon is used to make Lisp treat this line as a comment. You could equivalently write

; -*- mode: Lisp;-*-

You can also use file-local variables to specify buffer-local minor modes, by using eval specifications. For example, this first nonblank line puts the buffer in Lisp mode and enables Auto-Fill mode:

; -*- mode: Lisp; eval: (auto-fill-mode 1); -*-

Note, however, that it is usually inappropriate to enable minor modes this way, since most minor modes represent individual user preferences. If you personally want to use a minor mode for a particular file type, it is better to enable the minor mode via a major mode hook (see Major Modes).

Second, Emacs checks whether the file’s extension matches an entry in any directory-local auto-mode-alist. These are found using the .dir-locals.el facility (see Per-Directory Local Variables).

Third, if there is no file variable specifying a major mode, Emacs checks whether the file’s contents begin with ‘#!’. If so, that indicates that the file can serve as an executable shell command, which works by running an interpreter named on the file’s first line (the rest of the file is used as input to the interpreter). Therefore, Emacs tries to use the interpreter name to choose a mode. For instance, a file that begins with ‘#!/usr/bin/perl’ is opened in Perl mode. The variable interpreter-mode-alist specifies the correspondence between interpreter program names and major modes.

When the first line starts with ‘#!’, you usually cannot use the ‘-*-’ feature on the first line, because the system would get confused when running the interpreter. So Emacs looks for ‘-*-’ on the second line in such files as well as on the first line. The same is true for man pages which start with the magic string ‘'\"’ to specify a list of troff preprocessors.

Fourth, Emacs tries to determine the major mode by looking at the text at the start of the buffer, based on the variable magic-mode-alist. By default, this variable is nil (an empty list), so Emacs skips this step; however, you can customize it in your init file (see The Emacs Initialization File). The value should be a list of elements of the form

(regexp . mode-function)

where regexp is a regular expression (see Syntax of Regular Expressions), and mode-function is a major mode command. If the text at the beginning of the file matches regexp, Emacs chooses the major mode specified by mode-function.

Alternatively, an element of magic-mode-alist may have the form

(match-function . mode-function)

where match-function is a Lisp function that is called at the beginning of the buffer; if the function returns non-nil, Emacs set the major mode with mode-function.

Fifth—if Emacs still hasn’t found a suitable major mode—it looks at the file’s name. The correspondence between file names and major modes is controlled by the variable auto-mode-alist. Its value is a list in which each element has this form,

(regexp . mode-function)

or this form,

(regexp mode-function flag)

For example, one element normally found in the list has the form ("\\.c\\'" . c-mode), and it is responsible for selecting C mode for files whose names end in .c. (Note that ‘\\’ is needed in Lisp syntax to include a ‘\’ in the string, which must be used to suppress the special meaning of ‘.’ in regexps.)

If the element has the form (regexp mode-function flag) and flag is non-nil, then after calling mode-function (if it is non-nil), Emacs discards the suffix that matched regexp and searches the list again for another match. This “recursive extension stripping” is used for files which have multiple extensions, and the “outer” extension hides the “inner” one that actually specifies the right mode. For example, backup files and GPG-encrypted files with .gpg extension use this feature.

On GNU/Linux and other systems with case-sensitive file names, Emacs performs a case-sensitive search through auto-mode-alist; if this search fails, it performs a second case-insensitive search through the alist. To suppress the second search, change the variable auto-mode-case-fold to nil. On systems with case-insensitive file names, such as Microsoft Windows, Emacs performs a single case-insensitive search through auto-mode-alist.

Finally, if Emacs still hasn’t found a major mode to use, it compares the text at the start of the buffer to the variable magic-fallback-mode-alist. This variable works like magic-mode-alist, described above, except that it is consulted only after auto-mode-alist. By default, magic-fallback-mode-alist contains forms that check for image files, HTML/XML/SGML files, PostScript files, and Unix style Conf files.

Once a major mode is found, Emacs does a final check to see if the mode has been remapped by major-mode-remap-alist, in which case it uses the remapped mode instead. This is used when several different major modes can be used for the same file type, so you can specify which mode you prefer.

If you have changed the major mode of a buffer, you can return to the major mode Emacs would have chosen automatically, by typing M-x normal-mode. This is the same function that find-file calls to choose the major mode. If the buffer is visiting a file, this command also processes the file’s ‘-*-’ line and file-local variables list (if any). See Local Variables in Files. If the buffer doesn’t visit a file, the command processes only the major mode specification, if any, in the ‘-*-’ line and in the file-local variables list.

The commands C-x C-w and set-visited-file-name change to a new major mode if the new file name implies a mode (see Saving Files). (C-x C-s does this too, if the buffer wasn’t visiting a file.) However, this does not happen if the buffer contents specify a major mode, and certain special major modes do not allow the mode to change. You can turn off this mode-changing feature by setting change-major-mode-with-file-name to nil.


25 Indentation

Indentation refers to inserting or adjusting whitespace characters (space and/or tab characters) at the beginning of a line of text. This chapter documents indentation commands and options which are common to Text mode and related modes, as well as programming language modes. See Indentation for Programs, for additional documentation about indenting in programming modes.

The simplest way to perform indentation is the TAB key. In most major modes, this runs the command indent-for-tab-command. (In C and related modes, TAB runs the command c-indent-line-or-region, which behaves similarly, see Commands for C Indentation).

TAB

Insert whitespace, or indent the current line, in a mode-appropriate way (indent-for-tab-command). If the region is active, indent all the lines within it.

The exact behavior of TAB depends on the major mode. In Text mode and related major modes, TAB normally inserts some combination of space and tab characters to advance point to the next tab stop (see Tab Stops). For this purpose, the position of the first non-whitespace character on the preceding line is treated as an additional tab stop, so you can use TAB to align point with the preceding line. If the region is active (see Operating on the Region), TAB acts specially: it indents each line in the region so that its first non-whitespace character is aligned with the preceding line.

In programming modes, TAB indents the current line of code in a way that makes sense given the code in the preceding lines. If the region is active, all the lines in the region are indented this way. If point was initially within the current line’s indentation, it is repositioned to the first non-whitespace character on the line.

If you just want to insert a tab character in the buffer, type C-q TAB (see Inserting Text).


25.1 Indentation Commands

Apart from the TAB (indent-for-tab-command) command, Emacs provides a variety of commands to perform indentation in other ways.

C-M-o

Split the current line at point (split-line). The text on the line after point becomes a new line, indented to the same column where point is located. This command first moves point forward over any spaces and tabs. Afterward, point is positioned before the inserted newline.

M-m

Move (forward or back) to the first non-whitespace character on the current line (back-to-indentation). If there are no non-whitespace characters on the line, move to the end of the line.

M-i

Indent whitespace at point, up to the next tab stop (tab-to-tab-stop). See Tab Stops.

M-x indent-relative

Insert whitespace at point, until point is aligned with the first non-whitespace character on the previous line (actually, the last non-blank line). If point is already farther right than that, run tab-to-tab-stop instead—unless called with a numeric argument, in which case do nothing.

M-^

Merge the previous and the current line (delete-indentation). This joins the two lines cleanly, by replacing any indentation at the front of the current line, together with the line boundary, with a single space.

As a special case (useful for Lisp code), the single space is omitted if the characters to be joined are consecutive opening and closing parentheses, or if the junction follows another newline.

If there is a fill prefix, M-^ deletes the fill prefix if it appears after the newline that is deleted. See The Fill Prefix.

With a prefix argument, join the current line to the following line. If the region is active, and no prefix argument is given, join all lines in the region instead.

C-M-\

Indent all the lines in the region, as though you had typed TAB at the beginning of each line (indent-region).

If a numeric argument is supplied, indent every line in the region to that column number.

C-x TAB

Indent all lines that begin in the region, moving the affected lines as a rigid unit (indent-rigidly).

If called with no argument, this command activates a transient mode for adjusting the indentation of the affected lines interactively. While this transient mode is active, typing LEFT or RIGHT indents leftward and rightward, respectively, by one space. You can also type S-LEFT or S-RIGHT to indent leftward or rightward to the next tab stop (see Tab Stops). Typing any other key disables the transient mode, and this key is then acted upon as normally.

If called with a prefix argument n, this command indents the lines forward by n spaces (without enabling the transient mode). Negative values of n indent backward, so you can remove all indentation from the lines in the region using a large negative argument, like this:

C-u -999 C-x TAB

25.2 Tab Stops

Emacs defines certain column numbers to be tab stops. These are used as stopping points by TAB when inserting whitespace in Text mode and related modes (see Indentation), and by commands like M-i (see Indentation Commands). The variable tab-stop-list controls these positions. The default value is nil, which means a tab stop every 8 columns. The value can also be a list of zero-based column numbers (in increasing order) at which to place tab stops. Emacs extends the list forever by repeating the difference between the last and next-to-last elements.

Instead of customizing the variable tab-stop-list directly, a convenient way to view and set tab stops is via the command M-x edit-tab-stops. This switches to a buffer containing a description of the tab stop settings, which looks like this:

        :       :       :       :       :       :
0         1         2         3         4
0123456789012345678901234567890123456789012345678
To install changes, type C-c C-c

The first line contains a colon at each tab stop. The numbers on the next two lines are present just to indicate where the colons are. If the value of tab-stop-list is nil, as it is by default, no colons are displayed initially.

You can edit this buffer to specify different tab stops by placing colons on the desired columns. The buffer uses Overwrite mode (see Minor Modes). Remember that Emacs will extend the list of tab stops forever by repeating the difference between the last two explicit stops that you place. When you are done, type C-c C-c to make the new tab stops take effect. Normally, the new tab stop settings apply to all buffers. However, if you have made the tab-stop-list variable local to the buffer where you called M-x edit-tab-stops (see Local Variables), then the new tab stop settings apply only to that buffer. To save the tab stop settings for future Emacs sessions, use the Customize interface to save the value of tab-stop-list (see Easy Customization Interface).

Note that the tab stops discussed in this section have nothing to do with how tab characters are displayed in the buffer. Tab characters are always displayed as empty spaces extending to the next display tab stop. See How Text Is Displayed.


25.3 Tabs vs. Spaces

Normally, indentation commands insert (or remove) the shortest possible series of tab and space characters so as to align to the desired column. Tab characters are displayed as a stretch of empty space extending to the next display tab stop. By default, there is one display tab stop every tab-width columns (the default is 8). See How Text Is Displayed.

If you prefer, all indentation can be made from spaces only. To request this, set the buffer-local variable indent-tabs-mode to nil. See Local Variables, for information about setting buffer-local variables. Note, however, that C-q TAB always inserts a tab character, regardless of the value of indent-tabs-mode.

One reason to set indent-tabs-mode to nil is that not all editors display tab characters in the same way. Emacs users, too, may have different customized values of tab-width. By using spaces only, you can make sure that your file always looks the same. If you only care about how it looks within Emacs, another way to tackle this problem is to set the tab-width variable in a file-local variable (see Local Variables in Files).

There are also commands to convert tabs to spaces or vice versa, always preserving the columns of all non-whitespace text. M-x tabify scans the region for sequences of spaces, and converts sequences of at least two spaces to tabs if that can be done without changing indentation. M-x untabify changes all tabs in the region to appropriate numbers of spaces.


25.4 Convenience Features for Indentation

The variable tab-always-indent tweaks the behavior of the TAB (indent-for-tab-command) command. The default value, t, gives the behavior described in Indentation. If you change the value to the symbol complete, then TAB first tries to indent the current line, and if the line was already indented, it tries to complete the text at point (see Completion for Symbol Names). If the value is nil, then TAB indents the current line only if point is at the left margin or in the line’s indentation; otherwise, it inserts a tab character.

If tab-always-indent is complete, whether to expand or indent can be further customized via the tab-first-completion variable. For instance, if that variable is eol, only complete if point is at the end of a line. See Mode-Specific Indent in The Emacs Lisp Reference Manual, for further details.

Electric Indent mode is a global minor mode that automatically indents the line after every RET you type. This mode is enabled by default. To toggle this minor mode, type M-x electric-indent-mode. To toggle the mode in a single buffer, use M-x electric-indent-local-mode.


25.5 Code Alignment

Alignment is the process of adjusting whitespace in a sequence of lines in the region such that in all lines certain parts begin at the same column. This is usually something you do to enhance readability of a piece of text or code. The classic example is aligning a series of assignments in C-like programming languages:

int a = 1;
short foo = 2;
double blah = 4;

is commonly aligned to:

int    a    = 1;
short  foo  = 2;
double blah = 4;

You can use the command M-x align to align lines in the current region. This command knows about common alignment patterns across many markup and programming languages. It encodes these patterns as a set of alignment rules, that say how to align different kinds of text in different contexts.

The user option align-rules-list says which alignment rules M-x align should consult. The value of this option is a list with elements describing alignment rules. Each element is a cons cell (title . attributes), where title is the name of the alignment rule as a symbol, and attributes is a list of rule attributes that define when the rule should apply and how it partitions and aligns lines. Each rule attribute is a cons cell (attribute . value), where attribute is the name of attribute and value is its value. The only required attribute is regexp, whose value is a regular expression with sub-expressions matching the parts of each line where M-x align should expand or contract whitespace (see Backslash in Regular Expressions). See the documentation string of align-rules-list (C-h v align-rules-list RET) for a full description of possible alignment rule attributes. By default, this option is set to a long list of alignment rules for many languages that Emacs supports. The default rules use the modes rule attribute to specify major modes in which M-x align should apply them. Major modes can also override align-rules-list by setting the buffer-local variable align-mode-rules-list to a non-nil list of alignment rules. When align-mode-rules-list is non-nil, M-x align consults it instead of align-rules-list.

Besides alignment rules, M-x align uses another kind of rules called exclusion rules. The exclusion rules say which parts in the region M-x align should not align and instead leave them intact. The user option align-exclude-rules-list specifies these exclusion rules. Similarly to align-rules-list, the value of align-exclude-rules-list is also a list of cons cells that describe the exclusion rules. By default, align-exclude-rules-list includes rules that exclude alignment in quoted strings and comments in Lisp, C and other languages. Beyond the default exclusion rules in align-exclude-rules-list, major modes can define bespoke exclusion rules by setting align-mode-exclude-rules-list to a non-nil list of rules, this overrides align-exclude-rules-list just like align-mode-rules-list overrides align-rules-list.

M-x align splits the region into a series of sections, usually sequences of non-blank lines, and aligns each section according to all matching alignment rule by expanding or contracting stretches of whitespace. M-x align consistently aligns all lines inside a single section, but it may align different sections in the region differently. The user option align-region-separate specifies how M-x align separates the region to sections. This option can be one of the symbols entire, group, or a regular expression. If align-region-separate is entire, Emacs aligns the entire region as a single section. If this option is group, Emacs aligns each group of consecutive non-blank lines in the region as a separate section. If align-region-separate is a regular expression, M-x align scans the region for matches to that regular expression and treats them as section separators. By default align-region-separate is set to a regular expression that matches blank lines and lines that contains only whitespace and a single curly brace (‘{’ or ‘}’). For special cases where regular expressions are not accurate enough, you can also set align-region-separate to a function that says how to separate the region to alignment sections. See the documentation string of align-region-separate for more details. Specific alignment rules can override the value of align-region-separate and define their own section separator by specifying the separate rule attribute.

If you call M-x align with a prefix argument (C-u), it enables more alignment rules that are often useful but may sometimes be too intrusive. For example, in a Lisp buffer with the following form:

(set-face-attribute 'mode-line-inactive nil
                    :box nil
                    :background nil
                    :underline "black")

Typing (C-u M-x align) yields:

(set-face-attribute 'mode-line-inactive nil
                    :box                nil
                    :background         nil
                    :underline          "black")

In most cases, you should try M-x align without a prefix argument first, and if that doesn’t produce the right result you can undo with C-/ and try again with C-u M-x align.

You can use the command M-x align-highlight-rule to visualize the effect of a specific alignment or exclusion rule in the current region. This command prompts you for the title of a rule and highlights the parts on the region that this rule affects. For alignment rules, this command highlights the whitespace that M-x align would expand or contract, and for exclusion this command highlights the parts that M-x align would exclude from alignment. To remove the highlighting that this command creates, type M-x align-unhighlight-rule.

The command M-x align-current is similar to M-x align, except that it operates only on the alignment section that contains point regardless of the current region. This command determines the boundaries of the current section according to the section separators that align-region-separate define. M-x align-entire is another variant of M-x align, that disregards align-region-separate and aligns the entire region as a single alignment section with consistent alignment. If you set align-region-separate to entire, M-x align behaves like M-x align-entire by default. To illustrate the effect of aligning the entire region as a single alignment section, consider the following code:

one = 1;
foobarbaz = 2;

spam = 3;
emacs = 4;

when the region covers all of these lines, typing M-x align yields:

one       = 1;
foobarbaz = 2;

spam  = 3;
emacs = 4;

On the other hand, M-x align-entire aligns all of the lines as a single section, so the ‘=’ appears at the same column in all lines:

one       = 1;
foobarbaz = 2;

spam      = 3;
emacs     = 4;

The command M-x align-regexp lets you align the current region with an alignment rule that you define ad-hoc, instead of using the predefined rules in align-rules-list. M-x align-regexp prompts you for a regular expression and uses that expression as the regexp attribute for an ad-hoc alignment rule that this command uses to align the current region. By default, this command adjusts the whitespace that matches the first sub-expression of the regular expression you specify. If you call M-x align-regexp with a prefix argument, it also prompts you for the sub-expression to use and lets you specify the amount of whitespace to use as padding, as well as whether to apply the rule repeatedly to all matches of the regular expression in each line. See Backslash in Regular Expressions, for more information about regular expressions and their sub-expressions.

If the user option align-indent-before-aligning is non-nil, Emacs indents the region before aligning it with M-x align. See Indentation. By default align-indent-before-aligning is set to nil.

The user option align-to-tab-stop says whether aligned parts should start at a tab stop (see Tab Stops). If this option is nil, M-x align uses just enough whitespace for alignment, disregarding tab stops. If this is a non-nil symbol, M-x align checks the value of that symbol, and if this value is non-nil, M-x align aligns to tab stops. By default, this option is set to indent-tabs-mode, so alignment respects tab stops in buffers that use tabs for indentation. See Tabs vs. Spaces.

The user option align-default-spacing specifies the default amount of whitespace that M-x align and its related commands use for padding between the different parts of each line when aligning it. When align-to-tab-stop is nil, the value of align-default-spacing is the number of spaces to use for padding; when align-to-tab-stop is non-nil, the value of align-default-spacing is instead the number of tab stops to use. Each alignment rule can override the default that align-default-spacing specifies with the spacing attribute rule.


26 Commands for Human Languages

This chapter describes Emacs commands that act on text, by which we mean sequences of characters in a human language (as opposed to, say, a computer programming language). These commands act in ways that take into account the syntactic and stylistic conventions of human languages: conventions involving words, sentences, paragraphs, and capital letters. There are also commands for filling, which means rearranging the lines of a paragraph to be approximately equal in length. These commands, while intended primarily for editing text, are also often useful for editing programs.

Emacs has several major modes for editing human-language text. If the file contains ordinary text, use Text mode, which customizes Emacs in small ways for the syntactic conventions of text. Outline mode provides special commands for operating on text with an outline structure. See Outline Mode.

Org mode extends Outline mode and turns Emacs into a full-fledged organizer: you can manage TODO lists, store notes and publish them in many formats. See the Org Info manual, which is distributed with Emacs.

Emacs has other major modes for text which contains embedded commands, such as TeX and LaTeX (see TeX Mode); HTML and SGML (see SGML and HTML Modes); XML (see the nXML mode Info manual, which is distributed with Emacs); and Groff and Nroff (see Nroff Mode).

If you need to edit ASCII art pictures made out of text characters, use Picture mode, a special major mode for editing such pictures. See Editing Pictures.


26.1 Words

Emacs defines several commands for moving over or operating on words:

M-f

Move forward over a word (forward-word).

M-b

Move backward over a word (backward-word).

M-d

Kill up to the end of a word (kill-word).

M-DEL

Kill back to the beginning of a word (backward-kill-word).

M-@

Set mark at the end of the next word (mark-word).

M-t

Transpose two words or drag a word across others (transpose-words).

Notice how these keys form a series that parallels the character-based C-f, C-b, C-d, DEL and C-t. M-@ is cognate to C-@, which is an alias for C-SPC.

The commands M-f (forward-word) and M-b (backward-word) move forward and backward over words. These Meta-based key sequences are analogous to the key sequences C-f and C-b, which move over single characters. The analogy extends to numeric arguments, which serve as repeat counts. M-f with a negative argument moves backward, and M-b with a negative argument moves forward. Forward motion stops right after the last letter of the word, while backward motion stops right before the first letter.

M-d (kill-word) kills the word after point. To be precise, it kills everything from point to the place M-f would move to. Thus, if point is in the middle of a word, M-d kills just the part after point. If some punctuation comes between point and the next word, it is killed along with the word. (If you wish to kill only the next word but not the punctuation before it, simply do M-f to get the end, and kill the word backwards with M-DEL.) M-d takes arguments just like M-f.

M-DEL (backward-kill-word) kills the word before point. It kills everything from point back to where M-b would move to. For instance, if point is after the space in ‘FOO, BAR, it kills ‘FOO, . If you wish to kill just ‘FOO’, and not the comma and the space, use M-b M-d instead of M-DEL.

M-t (transpose-words) exchanges the word before or containing point with the following word. The delimiter characters between the words do not move. For example, ‘FOO, BAR transposes into ‘BAR, FOO rather than ‘BAR FOO,’. See Transposing Text, for more on transposition.

To operate on words with an operation which acts on the region, use the command M-@ (mark-word). This command sets the mark where M-f would move to. See Commands to Mark Textual Objects, for more information about this command.

The word commands’ understanding of word boundaries is controlled by the syntax table. Any character can, for example, be declared to be a word delimiter. See Syntax Tables in The Emacs Lisp Reference Manual.

In addition, see Cursor Position Information for the M-= (count-words-region) and M-x count-words commands, which count and report the number of words in the region or buffer.


26.2 Sentences

The Emacs commands for manipulating sentences and paragraphs are mostly on Meta keys, like the word-handling commands.

M-a

Move back to the beginning of the sentence (backward-sentence).

M-e

Move forward to the end of the sentence (forward-sentence).

M-k

Kill forward to the end of the sentence (kill-sentence).

C-x DEL

Kill back to the beginning of the sentence (backward-kill-sentence).

The commands M-a (backward-sentence) and M-e (forward-sentence) move to the beginning and end of the current sentence, respectively. Their bindings were chosen to resemble C-a and C-e, which move to the beginning and end of a line. Unlike them, M-a and M-e move over successive sentences if repeated.

Moving backward over a sentence places point just before the first character of the sentence; moving forward places point right after the punctuation that ends the sentence. Neither one moves over the whitespace at the sentence boundary.

Just as C-a and C-e have a kill command, C-k, to go with them, M-a and M-e have a corresponding kill command: M-k (kill-sentence) kills from point to the end of the sentence. With a positive numeric argument n, it kills the next n sentences; with a negative argument −n, it kills back to the beginning of the nth preceding sentence.

The C-x DEL (backward-kill-sentence) kills back to the beginning of a sentence.

The sentence commands assume that you follow the American typist’s convention of putting two spaces at the end of a sentence. That is, a sentence ends wherever there is a ‘.’, ‘?’ or ‘!’ followed by the end of a line or two spaces, with any number of ‘)’, ‘]’, ‘'’, or ‘"’ characters allowed in between. A sentence also begins or ends wherever a paragraph begins or ends. It is useful to follow this convention, because it allows the Emacs sentence commands to distinguish between periods that end a sentence and periods that indicate abbreviations.

If you want to use just one space between sentences, you can set the variable sentence-end-double-space to nil to make the sentence commands stop for single spaces. However, this has a drawback: there is no way to distinguish between periods that end sentences and those that indicate abbreviations. For convenient and reliable editing, we therefore recommend you follow the two-space convention. The variable sentence-end-double-space also affects filling (see Explicit Fill Commands).

The variable sentence-end controls how to recognize the end of a sentence. If non-nil, its value should be a regular expression, which is used to match the last few characters of a sentence, together with the whitespace following the sentence (see Syntax of Regular Expressions). If the value is nil, the default, then Emacs computes sentence ends according to various criteria such as the value of sentence-end-double-space.

Some languages, such as Thai, do not use periods to indicate the end of a sentence. Set the variable sentence-end-without-period to t in such cases.


26.3 Paragraphs

The Emacs commands for manipulating paragraphs are also on Meta keys.

M-{

Move back to previous paragraph beginning (backward-paragraph).

M-}

Move forward to next paragraph end (forward-paragraph).

M-h

Put point and mark around this or next paragraph (mark-paragraph).

M-{ (backward-paragraph) moves to the beginning of the current or previous paragraph, depending on where point is when the command is invoked (see below for the definition of a paragraph). M-} (forward-paragraph) similarly moves to the end of the current or next paragraph. If there is a blank line before the paragraph, M-{ moves to the blank line.

When you wish to operate on a paragraph, type M-h (mark-paragraph) to set the region around it. For example, M-h C-w kills the paragraph around or after point. M-h puts point at the beginning and mark at the end of the paragraph point was in. If point is between paragraphs (in a run of blank lines, or at a boundary), M-h sets the region around the paragraph following point. If there are blank lines preceding the first line of the paragraph, one of these blank lines is included in the region. If the region is already active, the command sets the mark without changing point, and each subsequent M-h further advances the mark by one paragraph.

The definition of a paragraph depends on the major mode. In Fundamental mode, as well as Text mode and related modes, a paragraph is separated from neighboring paragraphs by one or more blank lines—lines that are either empty, or consist solely of space, tab and/or formfeed characters. In programming language modes, paragraphs are usually defined in a similar way, so that you can use the paragraph commands even though there are no paragraphs as such in a program.

Note that an indented line is not itself a paragraph break in Text mode. If you want indented lines to separate paragraphs, use Paragraph-Indent Text mode instead. See Text Mode.

If you set a fill prefix, then paragraphs are delimited by all lines which don’t start with the fill prefix. See Filling Text.

The precise definition of a paragraph boundary is controlled by the variables paragraph-separate and paragraph-start. The value of paragraph-start is a regular expression that should match lines that either start or separate paragraphs (see Syntax of Regular Expressions). The value of paragraph-separate is another regular expression that should match lines that separate paragraphs without being part of any paragraph (for example, blank lines). Lines that start a new paragraph and are contained in it must match only paragraph-start, not paragraph-separate. For example, in Fundamental mode, paragraph-start is "\f\\|[ \t]*$", and paragraph-separate is "[ \t\f]*$".

Note that paragraph-start and paragraph-separate are matched against the text at the left margin, which is not necessarily the beginning of the line, so these regexps should not use ‘^’ as an anchor, to ensure that the paragraph functions will work equally within a region of text indented by a margin setting.


26.4 Pages

Within some text files, text is divided into pages delimited by the formfeed character (ASCII code 12, also denoted as ‘control-L’), which is displayed in Emacs as the escape sequence ‘^L’ (see How Text Is Displayed). Traditionally, when such text files are printed to hardcopy, each formfeed character forces a page break. Most Emacs commands treat it just like any other character, so you can insert it with C-q C-l, delete it with DEL, etc. In addition, Emacs provides commands to move over pages and operate on them.

M-x what-page

Display the page number of point, and the line number within that page.

C-x [

Move point to previous page boundary (backward-page).

C-x ]

Move point to next page boundary (forward-page).

C-x C-p

Put point and mark around this page (or another page) (mark-page).

C-x l

Count the lines in this page (count-lines-page).

M-x what-page counts pages from the beginning of the file, and counts lines within the page, showing both numbers in the echo area.

The C-x [ (backward-page) command moves point to immediately after the previous page delimiter. If point is already right after a page delimiter, it skips that one and stops at the previous one. A numeric argument serves as a repeat count. The C-x ] (forward-page) command moves forward past the next page delimiter.

The C-x C-p command (mark-page) puts point at the beginning of the current page (after that page delimiter at the front), and the mark at the end of the page (after the page delimiter at the end).

C-x C-p C-w is a handy way to kill a page to move it elsewhere. If you move to another page delimiter with C-x [ and C-x ], then yank the killed page, all the pages will be properly delimited once again. Making sure this works as expected is the reason C-x C-p includes only the following page delimiter in the region.

A numeric argument to C-x C-p specifies which page to go to, relative to the current one. Zero means the current page, one means the next page, and −1 means the previous one.

The C-x l command (count-lines-page) is good for deciding where to break a page in two. It displays in the echo area the total number of lines in the current page, and then divides it up into those preceding the current line and those following, as in

Page has 96 (72+25) lines

Notice that the sum is off by one; this is correct if point is not at the beginning of a line.

The variable page-delimiter controls where pages begin. Its value is a regular expression that matches the beginning of a line that separates pages (see Syntax of Regular Expressions). The normal value of this variable is "^\f", which matches a formfeed character at the beginning of a line.


26.5 Quotation Marks

One common way to quote is the typewriter convention, which quotes using straight apostrophes ‘'like this'’ or double-quotes ‘"like this"’. Another common way is the curved quote convention, which uses left and right single or double quotation marks ‘like this’ or “like this”12. In text files, typewriter quotes are simple and portable; curved quotes are less ambiguous and typically look nicer.

Electric Quote mode makes it easier to type curved quotes. As you type characters it optionally converts ` to , ' to , `` to , and '' to . It’s possible to change the default quotes listed above, by customizing the variable electric-quote-chars, a list of four characters, where the items correspond to the left single quote, the right single quote, the left double quote and the right double quote, respectively, whose default value is '(?‘ ?’ ?“ ?”).

You can customize the behavior of Electric Quote mode by customizing variables that control where it is active. It is active in text paragraphs if electric-quote-paragraph is non-nil, in programming-language comments if electric-quote-comment is non-nil, and in programming-language strings if electric-quote-string is non-nil. The default is nil for electric-quote-string and t for the other variables.

You can also set the option electric-quote-replace-double to a non-nil value. Then, typing " inserts an appropriate curved double quote depending on context: at the beginning of the buffer or after a line break, whitespace, opening parenthesis, or quote character, and otherwise.

Electric Quote mode is disabled by default. To toggle it in a single buffer, use M-x electric-quote-local-mode. To toggle it globally, type M-x electric-quote-mode. To suppress it for a single use, type C-q ` or C-q ' instead of ` or '. To insert a curved quote even when Electric Quote is disabled or inactive, you can type C-x 8 [ for , C-x 8 ] for , C-x 8 { for , and C-x 8 } for . See Inserting Text. Note that the value of electric-quote-chars does not affect these key bindings, they are not key bindings of electric-quote-mode but bound in global-map.


26.6 Filling Text

Filling text means breaking it up into lines that fit a specified width. Emacs does filling in two ways. In Auto Fill mode, inserting text with self-inserting characters also automatically fills it. There are also explicit fill commands that you can use when editing text.


26.6.1 Auto Fill Mode

Auto Fill mode is a buffer-local minor mode (see Minor Modes) in which lines are broken automatically when the line becomes too wide and you type SPC or RET.

M-x auto-fill-mode

Enable or disable Auto Fill mode.

SPC
RET

In Auto Fill mode, break lines when appropriate.

The mode command M-x auto-fill-mode toggles Auto Fill mode in the current buffer. Like any other minor mode, with a positive numeric argument, it enables Auto Fill mode, and with a negative argument it disables it. To enable Auto Fill mode automatically in certain major modes, add auto-fill-mode to the mode hooks (see Major Modes). When Auto Fill mode is enabled, the mode indicator ‘Fill’ appears in the mode line (see The Mode Line).

Auto Fill mode breaks lines automatically at the appropriate places whenever lines get longer than the desired width. This line breaking occurs only when you type SPC or RET. If you wish to insert a space or newline without permitting line-breaking, type C-q SPC or C-q C-j respectively. Also, C-o inserts a newline without line breaking.

The place where Auto Fill breaks a line depends on the line’s characters. For characters from ASCII, Latin, and most other scripts Emacs breaks a line on space characters, to keep the words intact. But for CJK scripts, a line can be broken between any two characters. (If you load the kinsoku library, Emacs will avoid breaking a line between certain pairs of CJK characters, where special rules prohibit that.)

When Auto Fill mode breaks a line, it tries to obey the adaptive fill prefix: if a fill prefix can be deduced from the first and/or second line of the current paragraph, it is inserted into the new line (see Adaptive Filling). Otherwise the new line is indented, as though you had typed TAB on it (see Indentation). In a programming language mode, if a line is broken in the middle of a comment, the comment is split by inserting new comment delimiters as appropriate.

Auto Fill mode does not refill entire paragraphs; it breaks lines but does not merge lines. Therefore, editing in the middle of a paragraph can result in a paragraph that is not correctly filled. To fill it, call the explicit fill commands (see Explicit Fill Commands).

A similar feature that wraps long lines automatically at display time is Visual Line Mode (see Visual Line Mode).


26.6.2 Explicit Fill Commands

M-q

Fill current paragraph (fill-paragraph).

C-x f

Set the fill column (set-fill-column).

M-x fill-region

Fill each paragraph in the region (fill-region).

M-x fill-region-as-paragraph

Fill the region, considering it as one paragraph.

M-x center-line

Center a line.

The command M-q (fill-paragraph) fills the current paragraph. It redistributes the line breaks within the paragraph, and deletes any excess space and tab characters occurring within the paragraph, in such a way that the lines end up fitting within a certain maximum width. Like Auto Fill mode, this and other filling commands usually break lines at space characters, but for CJK characters these commands can break a line between almost any two characters, and they can also obey the kinsoku rules. See Auto Fill Mode.

Normally, M-q acts on the paragraph where point is, but if point is between paragraphs, it acts on the paragraph after point. If the region is active, it acts instead on the text in the region. You can also call M-x fill-region to specifically fill the text in the region.

M-q and fill-region use the usual Emacs criteria for finding paragraph boundaries (see Paragraphs). For more control, you can use M-x fill-region-as-paragraph, which refills everything between point and mark as a single paragraph. This command deletes any blank lines within the region, so separate blocks of text end up combined into one block.

A numeric argument to M-q tells it to justify the text as well as filling it. This means that extra spaces are inserted to make the right margin line up exactly at the fill column. To remove the extra spaces, use M-q with no argument. (Likewise for fill-region.)

The maximum line width for filling is specified by the buffer-local variable fill-column. The default value (see Local Variables) is 70. The easiest way to set fill-column in the current buffer is to use the command C-x f (set-fill-column). With a numeric argument, it uses that as the new fill column. With just C-u as argument, it sets fill-column to the current horizontal position of point. Note that, by its very nature, fill-column is measured in column units; the actual position of that column on a graphical display depends on the font being used. In particular, using variable-pitch fonts will cause the fill-column occupy different horizontal positions on display in different lines.

The command M-x center-line centers the current line within the current fill column. With an argument n, it centers n lines individually and moves past them. This binding is made by Text mode and is available only in that and related modes (see Text Mode).

By default, Emacs considers a period followed by two spaces or by a newline as the end of a sentence; a period followed by just one space indicates an abbreviation, not the end of a sentence. Accordingly, the fill commands will not break a line after a period followed by just one space. If you set the variable sentence-end-double-space to nil, the fill commands will break a line after a period followed by one space, and put just one space after each period. See Sentences, for other effects and possible drawbacks of this.

If the variable colon-double-space is non-nil, the fill commands put two spaces after a colon.

To specify additional conditions where line-breaking is not allowed, customize the abnormal hook variable fill-nobreak-predicate (see Hooks). Each function in this hook is called with no arguments, with point positioned where Emacs is considering breaking a line. If a function returns a non-nil value, Emacs will not break the line there. Functions you can use there include: fill-single-word-nobreak-p (don’t break after the first word of a sentence or before the last); fill-single-char-nobreak-p (don’t break after a one-letter word preceded by a whitespace character); fill-french-nobreak-p (don’t break after ‘(’ or before ‘)’, ‘:’ or ‘?’); and fill-polish-nobreak-p (don’t break after a one letter word, even if preceded by a non-whitespace character).

Emacs can display an indicator in the fill-column position using the Display fill column indicator mode (see display-fill-column-indicator).


26.6.3 The Fill Prefix

The fill prefix feature allows paragraphs to be filled so that each line starts with a special string of characters (such as a sequence of spaces, giving an indented paragraph). You can specify a fill prefix explicitly; otherwise, Emacs tries to deduce one automatically (see Adaptive Filling).

C-x .

Set the fill prefix (set-fill-prefix).

M-q

Fill a paragraph using current fill prefix (fill-paragraph).

M-x fill-individual-paragraphs

Fill the region, considering each change of indentation as starting a new paragraph.

M-x fill-nonuniform-paragraphs

Fill the region, considering only paragraph-separator lines as starting a new paragraph.

To specify a fill prefix for the current buffer, move to a line that starts with the desired prefix, put point at the end of the prefix, and type C-x . (set-fill-prefix). (That’s a period after the C-x.) To turn off the fill prefix, specify an empty prefix: type C-x . with point at the beginning of a line.

When a fill prefix is in effect, the fill commands remove the fill prefix from each line of the paragraph before filling, and insert it on each line after filling. (The beginning of the first line of the paragraph is left unchanged, since often that is intentionally different.) Auto Fill mode also inserts the fill prefix automatically when it makes a new line (see Auto Fill Mode). The C-o command inserts the fill prefix on new lines it creates, when you use it at the beginning of a line (see Blank Lines). Conversely, the command M-^ deletes the prefix (if it occurs) after the newline that it deletes (see Indentation).

For example, if fill-column is 40 and you set the fill prefix to ‘;; ’, then M-q in the following text

;; This is an
;; example of a paragraph
;; inside a Lisp-style comment.

produces this:

;; This is an example of a paragraph
;; inside a Lisp-style comment.

Lines that do not start with the fill prefix are considered to start paragraphs, both in M-q and the paragraph commands; this gives good results for paragraphs with hanging indentation (every line indented except the first one). Lines which are blank or indented once the prefix is removed also separate or start paragraphs; this is what you want if you are writing multi-paragraph comments with a comment delimiter on each line.

You can use M-x fill-individual-paragraphs to set the fill prefix for each paragraph automatically. This command divides the region into paragraphs, treating every change in the amount of indentation as the start of a new paragraph, and fills each of these paragraphs. Thus, all the lines in one paragraph have the same amount of indentation. That indentation serves as the fill prefix for that paragraph.

M-x fill-nonuniform-paragraphs is a similar command that divides the region into paragraphs in a different way. It considers only paragraph-separating lines (as defined by paragraph-separate) as starting a new paragraph. Since this means that the lines of one paragraph may have different amounts of indentation, the fill prefix used is the smallest amount of indentation of any of the lines of the paragraph. This gives good results with styles that indent a paragraph’s first line more or less that the rest of the paragraph.

The fill prefix is stored in the variable fill-prefix. Its value is a string, or nil when there is no fill prefix. This is a per-buffer variable; altering the variable affects only the current buffer, but there is a default value which you can change as well. See Local Variables.

The indentation text property provides another way to control the amount of indentation paragraphs receive. See Indentation in Enriched Text.


26.6.4 Adaptive Filling

The fill commands can deduce the proper fill prefix for a paragraph automatically in certain cases: either whitespace or certain punctuation characters at the beginning of a line are propagated to all lines of the paragraph.

If the paragraph has two or more lines, the fill prefix is taken from the paragraph’s second line, but only if it appears on the first line as well.

If a paragraph has just one line, fill commands may take a prefix from that line. The decision is complicated because there are three reasonable things to do in such a case:

  • Use the first line’s prefix on all the lines of the paragraph.
  • Indent subsequent lines with whitespace, so that they line up under the text that follows the prefix on the first line, but don’t actually copy the prefix from the first line.
  • Don’t do anything special with the second and following lines.

All three of these styles of formatting are commonly used. So the fill commands try to determine what you would like, based on the prefix that appears and on the major mode. Here is how.

If the prefix found on the first line matches adaptive-fill-first-line-regexp, or if it appears to be a comment-starting sequence (this depends on the major mode), then the prefix found is used for filling the paragraph, provided it would not act as a paragraph starter on subsequent lines.

Otherwise, the prefix found is converted to an equivalent number of spaces, and those spaces are used as the fill prefix for the rest of the lines, provided they would not act as a paragraph starter on subsequent lines.

In Text mode, and other modes where only blank lines and page delimiters separate paragraphs, the prefix chosen by adaptive filling never acts as a paragraph starter, so it can always be used for filling.

The variable adaptive-fill-regexp determines what kinds of line beginnings can serve as a fill prefix: any characters at the start of the line that match this regular expression are used. If you set the variable adaptive-fill-mode to nil, the fill prefix is never chosen automatically.

You can specify more complex ways of choosing a fill prefix automatically by setting the variable adaptive-fill-function to a function. This function is called with point after the left margin of a line, and it should return the appropriate fill prefix based on that line. If it returns nil, adaptive-fill-regexp gets a chance to find a prefix.


26.7 Case Conversion Commands

Emacs has commands for converting either a single word or any arbitrary range of text to upper case or to lower case.

M-l

Convert following word to lower case (downcase-word).

M-u

Convert following word to upper case (upcase-word).

M-c

Capitalize the following word (capitalize-word).

C-x C-l

Convert region to lower case (downcase-region).

C-x C-u

Convert region to upper case (upcase-region).

M-l (downcase-word) converts the word after point to lower case, moving past it. Thus, repeating M-l converts successive words. M-u (upcase-word) converts to all capitals instead, while M-c (capitalize-word) puts the first letter of the word into upper case and the rest into lower case. All these commands convert several words at once if given an argument. They are especially convenient for converting a large amount of text from all upper case to mixed case, because you can move through the text using M-l, M-u or M-c on each word as appropriate, occasionally using M-f instead to skip a word.

When given a negative argument, the word case conversion commands apply to the appropriate number of words before point, but do not move point. This is convenient when you have just typed a word in the wrong case: you can give the case conversion command and continue typing.

If a word case conversion command is given in the middle of a word, it applies only to the part of the word which follows point. (This is comparable to what M-d (kill-word) does.) With a negative argument, case conversion applies only to the part of the word before point.

The other case conversion commands are C-x C-u (upcase-region) and C-x C-l (downcase-region), which convert everything between point and mark to the specified case. Point and mark do not move.

The region case conversion commands upcase-region and downcase-region are normally disabled. This means that they ask for confirmation if you try to use them. When you confirm, you may enable the command, which means it will not ask for confirmation again. See Disabling Commands.


26.8 Text Mode

Text mode is a major mode for editing files of text in a human language. Files which have names ending in the extension .txt are usually opened in Text mode (see Choosing File Modes). To explicitly switch to Text mode, type M-x text-mode.

In Text mode, only blank lines and page delimiters separate paragraphs. As a result, paragraphs can be indented, and adaptive filling determines what indentation to use when filling a paragraph. See Adaptive Filling.

In Text mode, the TAB (indent-for-tab-command) command usually inserts whitespace up to the next tab stop, instead of indenting the current line. See Indentation, for details.

Text mode turns off the features concerned with comments except when you explicitly invoke them. It changes the syntax table so that apostrophes are considered part of words (e.g., ‘don't’ is considered one word). However, if a word starts with an apostrophe, it is treated as a prefix for the purposes of capitalization (e.g., M-c converts ‘'hello'’ into ‘'Hello'’, as expected).

If you indent the first lines of paragraphs, then you should use Paragraph-Indent Text mode (M-x paragraph-indent-text-mode) rather than Text mode. In that mode, you do not need to have blank lines between paragraphs, because the first-line indentation is sufficient to start a paragraph; however paragraphs in which every line is indented are not supported. Use M-x paragraph-indent-minor-mode to enable an equivalent minor mode for situations where you shouldn’t change the major mode—in mail composition, for instance.

Text mode binds M-TAB to ispell-complete-word. This command performs completion of the partial word in the buffer before point, using the spelling dictionary as the space of possible words. See Checking and Correcting Spelling. If your window manager defines M-TAB to switch windows, you can type ESC TAB or C-M-i instead.

Entering Text mode runs the mode hook text-mode-hook (see Major Modes).

The following sections describe several major modes that are derived from Text mode. These derivatives share most of the features of Text mode described above. In particular, derivatives of Text mode run text-mode-hook prior to running their own mode hooks.


26.9 Outline Mode

Outline mode is a major mode derived from Text mode, which is specialized for editing outlines. It provides commands to navigate between entries in the outline structure, and commands to make parts of a buffer temporarily invisible, so that the outline structure may be more easily viewed. Type M-x outline-mode to switch to Outline mode. Entering Outline mode runs the hook text-mode-hook followed by the hook outline-mode-hook (see Hooks).

When you use an Outline mode command to make a line invisible (see Outline Visibility Commands), the line disappears from the screen. An ellipsis (three periods in a row) is displayed at the end of the previous visible line, to indicate the hidden text. Multiple consecutive invisible lines produce just one ellipsis.

Editing commands that operate on lines, such as C-n and C-p, treat the text of the invisible line as part of the previous visible line. Killing the ellipsis at the end of a visible line really kills all the following invisible text associated with the ellipsis.


26.9.1 Outline Minor Mode

Outline minor mode is a buffer-local minor mode which provides the same commands as the major mode, Outline mode, but can be used in conjunction with other major modes. You can type M-x outline-minor-mode to toggle Outline minor mode in the current buffer, or use a file-local variable setting to enable it in a specific file (see Local Variables in Files).

The major mode, Outline mode, provides special key bindings on the C-c prefix. Outline minor mode provides similar bindings with C-c @ as the prefix; this is to reduce the conflicts with the major mode’s special commands. (The variable outline-minor-mode-prefix controls the prefix used.)

If outline-minor-mode-use-buttons is non-nil, Outline minor mode will use buttons at the beginning of the heading lines, in addition to ellipsis, to show that a section is hidden. Clicking the mouse on the button toggles display of the section. If the value of this variable is insert, the buttons are inserted directly into the buffer text, so RET on the button will also toggle display of the section, like a mouse click does. Using the value insert is not recommended in editable buffers because it modifies them. If the value is in-margins, Outline minor mode will use the window margins to indicate that a section is hidden. The buttons are customizable as icons (see Icons).

If the outline-minor-mode-cycle user option is non-nil, the TAB and S-TAB keys that cycle the visibility are enabled on the outline heading lines (see outline-cycle). TAB cycles hiding, showing the sub-heading, and showing all for the current section. S-TAB does the same for the entire buffer.


26.9.2 Format of Outlines

Outline mode assumes that the lines in the buffer are of two types: heading lines and body lines. A heading line represents a topic in the outline. Heading lines start with one or more asterisk (‘*’) characters; the number of asterisks determines the depth of the heading in the outline structure. Thus, a heading line with one ‘*’ is a major topic; all the heading lines with two ‘*’s between it and the next one-‘*’ heading are its subtopics; and so on. Any line that is not a heading line is a body line. Body lines belong with the preceding heading line. Here is an example:

* Food
This is the body,
which says something about the topic of food.

** Delicious Food
This is the body of the second-level header.

** Distasteful Food
This could have
a body too, with
several lines.

*** Dormitory Food

* Shelter
Another first-level topic with its header line.

A heading line together with all following body lines is called collectively an entry. A heading line together with all following deeper heading lines and their body lines is called a subtree.

You can customize the criterion for distinguishing heading lines by setting the variable outline-regexp. (The recommended ways to do this are in a major mode function or with a file local variable.) Any line whose beginning has a match for this regexp is considered a heading line. Matches that start within a line (not at the left margin) do not count.

The length of the matching text determines the level of the heading; longer matches make a more deeply nested level. Thus, for example, if a text formatter has commands ‘@chapter’, ‘@section’ and ‘@subsection’ to divide the document into chapters and sections, you could make those lines count as heading lines by setting outline-regexp to ‘"@chap\\|@\\(sub\\)*section"’. Note the trick: the two words ‘chapter’ and ‘section’ are equally long, but by defining the regexp to match only ‘chap’ we ensure that the length of the text matched on a chapter heading is shorter, so that Outline mode will know that sections are contained in chapters. This works as long as no other command starts with ‘@chap’.

You can explicitly specify a rule for calculating the level of a heading line by setting the variable outline-level. The value of outline-level should be a function that takes no arguments and returns the level of the current heading. The recommended ways to set this variable are in a major mode command or with a file local variable.


26.9.3 Outline Motion Commands

Outline mode provides special motion commands that move backward and forward to heading lines.

C-c C-n

Move point to the next visible heading line (outline-next-visible-heading).

C-c C-p

Move point to the previous visible heading line (outline-previous-visible-heading).

C-c C-f

Move point to the next visible heading line at the same level as the one point is on (outline-forward-same-level).

C-c C-b

Move point to the previous visible heading line at the same level (outline-backward-same-level).

C-c C-u

Move point up to a lower-level (more inclusive) visible heading line (outline-up-heading).

All of the above commands accept numeric arguments as repeat counts. For example, C-c C-f, when given an argument, moves forward that many visible heading lines on the same level, and C-c C-u with an argument moves out of that many nested levels.


26.9.4 Outline Visibility Commands

Outline mode provides several commands for temporarily hiding or revealing parts of the buffer, based on the outline structure. These commands are not undoable; their effects are simply not recorded by the undo mechanism, so you can undo right past them (see Undo).

Many of these commands act on the current heading line. If point is on a heading line, that is the current heading line; if point is on a body line, the current heading line is the nearest preceding header line.

C-c C-c

Make the current heading line’s body invisible (outline-hide-entry).

C-c C-e

Make the current heading line’s body visible (outline-show-entry).

C-c C-d

Make everything under the current heading invisible, not including the heading itself (outline-hide-subtree).

C-c C-s

Make everything under the current heading visible, including body, subheadings, and their bodies (outline-show-subtree).

C-c C-l

Make the body of the current heading line, and of all its subheadings, invisible (outline-hide-leaves).

C-c C-k

Make all subheadings of the current heading line, at all levels, visible (outline-show-branches).

C-c C-i

Make immediate subheadings (one level down) of the current heading line visible (outline-show-children).

C-c C-t

Make all body lines in the buffer invisible (outline-hide-body).

C-c C-a

Make all lines in the buffer visible (outline-show-all).

C-c C-q

Hide everything except the top n levels of heading lines (outline-hide-sublevels).

C-c C-o

Hide everything except for the heading or body that point is in, plus the headings leading up from there to the top level of the outline (outline-hide-other).

The simplest of these commands are C-c C-c (outline-hide-entry), which hides the body lines directly following the current heading line, and C-c C-e (outline-show-entry), which reveals them. Subheadings and their bodies are not affected.

The commands C-c C-d (outline-hide-subtree) and C-c C-s (outline-show-subtree) are more powerful. They apply to the current heading line’s subtree: its body, all of its subheadings, both direct and indirect, and all of their bodies.

The command C-c C-l (outline-hide-leaves) hides the body of the current heading line as well as all the bodies in its subtree; the subheadings themselves are left visible. The command C-c C-k (outline-show-branches) reveals the subheadings, if they had previously been hidden (e.g., by C-c C-d). The command C-c C-i (outline-show-children) is a weaker version of this; it reveals just the direct subheadings, i.e., those one level down.

The command C-c C-o (outline-hide-other) hides everything except the entry that point is in, plus its parents (the headers leading up from there to top level in the outline) and the top level headings. It also reveals body lines preceding the first heading in the buffer.

The remaining commands affect the whole buffer. C-c C-t (outline-hide-body) makes all body lines invisible, so that you see just the outline structure (as a special exception, it will not hide lines at the top of the file, preceding the first header line, even though these are technically body lines). C-c C-a (outline-show-all) makes all lines visible. C-c C-q (outline-hide-sublevels) hides all but the top level headings at and above the level of the current heading line (defaulting to 1 if point is not on a heading); with a numeric argument n, it hides everything except the top n levels of heading lines. Note that it completely reveals all the n top levels and the body lines before the first heading.

Outline also provides two convenience commands to cycle the visibility of each section and the whole buffer. Typing TAB (outline-cycle) on a heading cycles the current section between “hide all”, “subheadings”, and “show all” states. Typing S-TAB (outline-cycle-buffer) cycles the whole buffer between “only top-level headings”, “all headings and subheadings”, and “show all” states.

When incremental search finds text that is hidden by Outline mode, it makes that part of the buffer visible. If you exit the search at that position, the text remains visible. To toggle whether or not an active incremental search can match hidden text, type M-s i. To change the default for future searches, customize the option search-invisible. (This option also affects how query-replace and related functions treat hidden text, see Query Replace.) You can also automatically make text visible as you navigate in it by using Reveal mode (M-x reveal-mode), a buffer-local minor mode.

The outline-default-state variable controls what headings will be visible after Outline mode is turned on. If non-nil, some headings are initially outlined. If equal to a number, show only headings up to and including the corresponding level. If equal to outline-show-all, all text of buffer is shown. If equal to outline-show-only-headings, show only headings, whatever their level is. If equal to a lambda function or function name, this function is expected to toggle headings visibility, and will be called without arguments after the mode is enabled.


26.9.5 Viewing One Outline in Multiple Views

You can display two views of a single outline at the same time, in different windows. To do this, you must create an indirect buffer using M-x make-indirect-buffer. The first argument of this command is the existing outline buffer name, and its second argument is the name to use for the new indirect buffer. See Indirect Buffers.

Once the indirect buffer exists, you can display it in a window in the normal fashion, with C-x 4 b or other Emacs commands. The Outline mode commands to show and hide parts of the text operate on each buffer independently; as a result, each buffer can have its own view. If you want more than two views on the same outline, create additional indirect buffers.


26.9.6 Folding Editing

The Foldout package extends Outline mode and Outline minor mode with folding commands. The idea of folding is that you zoom in on a nested portion of the outline, while hiding its relatives at higher levels.

Consider an Outline mode buffer with all the text and subheadings under level-1 headings hidden. To look at what is hidden under one of these headings, you could use C-c C-e (M-x outline-show-entry) to expose the body, or C-c C-i to expose the child (level-2) headings.

With Foldout, you use C-c C-z (M-x foldout-zoom-subtree). This exposes the body and child subheadings, and narrows the buffer so that only the level-1 heading, the body and the level-2 headings are visible. Now to look under one of the level-2 headings, position the cursor on it and use C-c C-z again. This exposes the level-2 body and its level-3 child subheadings and narrows the buffer again. Zooming in on successive subheadings can be done as much as you like. A string in the mode line shows how deep you’ve gone.

When zooming in on a heading, to see only the child subheadings specify a numeric argument: C-u C-c C-z. The number of levels of children can be specified too (compare M-x outline-show-children), e.g., M-2 C-c C-z exposes two levels of child subheadings. Alternatively, the body can be specified with a negative argument: M-- C-c C-z. The whole subtree can be expanded, similarly to C-c C-s (M-x outline-show-subtree), by specifying a zero argument: M-0 C-c C-z.

While you’re zoomed in, you can still use Outline mode’s exposure and hiding functions without disturbing Foldout. Also, since the buffer is narrowed, global editing actions will only affect text under the zoomed-in heading. This is useful for restricting changes to a particular chapter or section of your document.

To unzoom (exit) a fold, use C-c C-x (M-x foldout-exit-fold). This hides all the text and subheadings under the top-level heading and returns you to the previous view of the buffer. Specifying a numeric argument exits that many levels of folds. Specifying a zero argument exits all folds.

To cancel the narrowing of a fold without hiding the text and subheadings, specify a negative argument. For example, M--2 C-c C-x exits two folds and leaves the text and subheadings exposed.

Foldout mode also provides mouse commands for entering and exiting folds, and for showing and hiding text:

C-M-mouse-1 zooms in on the heading clicked on
  • single click: expose body.
  • double click: expose subheadings.
  • triple click: expose body and subheadings.
  • quad click: expose entire subtree.
C-M-mouse-2 exposes text under the heading clicked on
  • single click: expose body.
  • double click: expose subheadings.
  • triple click: expose body and subheadings.
  • quad click: expose entire subtree.
C-M-mouse-3 hides text under the heading clicked on or exits fold
  • single click: hide subtree.
  • double click: exit fold and hide text.
  • triple click: exit fold without hiding text.
  • quad click: exit all folds and hide text.

You can specify different modifier keys (instead of Ctrl-Meta-) by setting foldout-mouse-modifiers; but if you have already loaded the foldout.el library, you must reload it in order for this to take effect.

To use the Foldout package, you can type M-x load-library RET foldout RET; or you can arrange for to do that automatically by putting the following in your init file:

(with-eval-after-load "outline"
  (require 'foldout))

26.10 Org Mode

Org mode is a variant of Outline mode for using Emacs as an organizer and/or authoring system. Files with names ending in the extension .org are opened in Org mode (see Choosing File Modes). To explicitly switch to Org mode, type M-x org-mode.

In Org mode, as in Outline mode, each entry has a heading line that starts with one or more ‘*’ characters. See Format of Outlines. In addition, any line that begins with the ‘#’ character is treated as a comment.

Org mode provides commands for easily viewing and manipulating the outline structure. The simplest of these commands is TAB (org-cycle). If invoked on a heading line, it cycles through the different visibility states of the subtree: (i) showing only that heading line, (ii) showing only the heading line and the heading lines of its direct children, if any, and (iii) showing the entire subtree. If invoked in a body line, the global binding for TAB is executed.

Typing S-TAB (org-shifttab) anywhere in an Org mode buffer cycles the visibility of the entire outline structure, between (i) showing only top-level heading lines, (ii) showing all heading lines but no body lines, and (iii) showing everything.

You can move an entire entry up or down in the buffer, including its body lines and subtree (if any), by typing M-UP (org-metaup) or M-DOWN (org-metadown) on the heading line. Similarly, you can promote or demote a heading line with M-LEFT (org-metaleft) and M-RIGHT (org-metaright). These commands execute their global bindings if invoked on a body line.

The following subsections give basic instructions for using Org mode as an organizer and as an authoring system. For details, see Introduction in The Org Manual.


26.10.1 Org as an organizer

You can tag an Org entry as a TODO item by typing C-c C-t (org-todo) anywhere in the entry. This adds the keyword ‘TODO’ to the heading line. Typing C-c C-t again switches the keyword to ‘DONE’; another C-c C-t removes the keyword entirely, and so forth. You can customize the keywords used by C-c C-t via the variable org-todo-keywords.

Apart from marking an entry as TODO, you can attach a date to it, by typing C-c C-s (org-schedule) in the entry. This prompts for a date by popping up the Emacs Calendar (see The Calendar and the Diary), and then adds the tag ‘SCHEDULED’, together with the selected date, beneath the heading line. The command C-c C-d (org-deadline) has the same effect, except that it uses the tag DEADLINE.

Once you have some TODO items planned in an Org file, you can add that file to the list of agenda files by typing C-c [ (org-agenda-file-to-front). Org mode is designed to let you easily maintain multiple agenda files, e.g., for organizing different aspects of your life. The list of agenda files is stored in the variable org-agenda-files.

To view items coming from your agenda files, type M-x org-agenda. This command prompts for what you want to see: a list of things to do this week, a list of TODO items with specific keywords, etc. See Agenda Views in The Org Manual, for details.


26.10.2 Org as an authoring system

You may want to format your Org notes nicely and to prepare them for export and publication. To export the current buffer, type C-c C-e (org-export-dispatch) anywhere in an Org buffer. This command prompts for an export format; currently supported formats include HTML, LaTeX, Texinfo, OpenDocument (.odt), iCalendar, Markdown, man-page, and PDF. Some formats, such as PDF, require certain system tools to be installed.

To export several files at once to a specific directory, either locally or over the network, you must define a list of projects through the variable org-publish-project-alist. See its documentation for details.

Org supports a simple markup scheme for applying text formatting to exported documents:

- This text is /emphasized/
- This text is *in bold*
- This text is _underlined_
- This text uses =a teletype font=

#+begin_quote
``This is a quote.''
#+end_quote

#+begin_example
This is an example.
#+end_example

For further details, Exporting in The Org Manual, and Publishing in The Org Manual.


26.11 TeX Mode

TeX is a powerful text formatter written by Donald Knuth; like GNU Emacs, it is free software. The TeX format has several variants, including LaTeX, a simplified input format for TeX; DocTeX, a special file format in which the LaTeX sources are written, combining sources with documentation; and SliTeX, an obsolete special form of LaTeX13.

Emacs provides a TeX major mode for each of these variants: Plain TeX mode, LaTeX mode, DocTeX mode, and SliTeX mode. Emacs selects the appropriate mode by looking at the contents of the buffer. (This is done by invoking the tex-mode command, which is normally called automatically when you visit a TeX-like file. See Choosing File Modes.) If the contents are insufficient to determine this, Emacs chooses the mode specified by the variable tex-default-mode; its default value is latex-mode. If Emacs does not guess right, you can select the correct variant of TeX mode using the commands plain-tex-mode, latex-mode, slitex-mode, or doctex-mode.

The following sections document the features of TeX mode and its variants. There are several other TeX-related Emacs packages, which are not documented in this manual:

  • BibTeX mode is a major mode for BibTeX files, which are commonly used for keeping bibliographic references for LaTeX documents. For more information, see the documentation string for the command bibtex-mode.
  • The RefTeX package provides a minor mode which can be used with LaTeX mode to manage bibliographic references. For more information, see the RefTeX Info manual, which is distributed with Emacs.
  • The AUCTeX package provides more advanced features for editing TeX and its related formats, including the ability to preview TeX equations within Emacs buffers. Unlike BibTeX mode and the RefTeX package, AUCTeX is not distributed with Emacs by default. It can be downloaded via the Package Menu (see Emacs Lisp Packages); once installed, see the AUCTeX manual, which is included with the package.

26.11.1 TeX Editing Commands

"

Insert, according to context, either ‘``’ or ‘"’ or ‘''’ (tex-insert-quote).

C-j

Insert a paragraph break (two newlines) and check the previous paragraph for unbalanced braces or dollar signs (tex-terminate-paragraph).

M-x tex-validate-region

Check each paragraph in the region for unbalanced braces or dollar signs.

C-c {

Insert ‘{}’ and position point between them (tex-insert-braces).

C-c }

Move forward past the next unmatched close brace (up-list).

In TeX, the character ‘"’ is not normally used; instead, quotations begin with ‘``’ and end with ‘''’. TeX mode therefore binds the " key to the tex-insert-quote command. This inserts ‘``’ after whitespace or an open brace, ‘"’ after a backslash, and ‘''’ after any other character.

As a special exception, if you type " when the text before point is either ‘``’ or ‘''’, Emacs replaces that preceding text with a single ‘"’ character. You can therefore type "" to insert ‘"’, should you ever need to do so. (You can also use C-q " to insert this character.)

In TeX mode, ‘$’ has a special syntax code which attempts to understand the way TeX math mode delimiters match. When you insert a ‘$’ that is meant to exit math mode, the position of the matching ‘$’ that entered math mode is displayed for a second. This is the same feature that displays the open brace that matches a close brace that is inserted. However, there is no way to tell whether a ‘$’ enters math mode or leaves it; so when you insert a ‘$’ that enters math mode, the previous ‘$’ position is shown as if it were a match, even though they are actually unrelated.

TeX uses braces as delimiters that must match. Some users prefer to keep braces balanced at all times, rather than inserting them singly. Use C-c { (tex-insert-braces) to insert a pair of braces. It leaves point between the two braces so you can insert the text that belongs inside. Afterward, use the command C-c } (up-list) to move forward past the close brace. You can also invoke C-c { after marking some text: then the command encloses the marked text in braces.

There are two commands for checking the matching of braces. C-j (tex-terminate-paragraph) checks the paragraph before point, and inserts two newlines to start a new paragraph. It outputs a message in the echo area if any mismatch is found. M-x tex-validate-region checks a region, paragraph by paragraph. The errors are listed in an *Occur* buffer; you can use the usual Occur mode commands in that buffer, such as C-c C-c, to visit a particular mismatch (see Other Search-and-Loop Commands).

Note that Emacs commands count square brackets and parentheses in TeX mode, not just braces. This is not strictly correct for the purpose of checking TeX syntax. However, parentheses and square brackets are likely to be used in text as matching delimiters, and it is useful for the various motion commands and automatic match display to work with them.


26.11.2 LaTeX Editing Commands

LaTeX mode provides a few extra features not applicable to plain TeX:

C-c C-o

Insert ‘\begin’ and ‘\end’ for LaTeX block and position point on a line between them (latex-insert-block).

C-c C-e

Close the innermost LaTeX block not yet closed (latex-close-block).

In LaTeX input, ‘\begin’ and ‘\end’ tags are used to group blocks of text. To insert a block, type C-c C-o (latex-insert-block). This prompts for a block type, and inserts the appropriate matching ‘\begin’ and ‘\end’ tags, leaving a blank line between the two and moving point there.

When entering the block type argument to C-c C-o, you can use the usual completion commands (see Completion). The default completion list contains the standard LaTeX block types. If you want additional block types for completion, customize the list variable latex-block-names.

In LaTeX input, ‘\begin’ and ‘\end’ tags must balance. You can use C-c C-e (latex-close-block) to insert an ‘\end’ tag which matches the last unmatched ‘\begin’. It also indents the ‘\end’ to match the corresponding ‘\begin’, and inserts a newline after the ‘\end’ tag if point is at the beginning of a line. The minor mode latex-electric-env-pair-mode automatically inserts an ‘\end’ or ‘\begin’ tag for you when you type the corresponding one.


26.11.3 TeX Printing Commands

You can invoke TeX as a subprocess of Emacs, supplying either the entire contents of the buffer or just part of it (e.g., one chapter of a larger document).

C-c C-b

Invoke TeX on the entire current buffer (tex-buffer).

C-c C-r

Invoke TeX on the current region, together with the buffer’s header (tex-region).

C-c C-f

Invoke TeX on the current file (tex-file).

C-c C-v

Preview the output from the last C-c C-b, C-c C-r, or C-c C-f command (tex-view).

C-c C-p

Print the output from the last C-c C-b, C-c C-r, or C-c C-f command (tex-print).

C-c TAB

Invoke BibTeX on the current file (tex-bibtex-file).

C-c C-l

Recenter the window showing output from TeX so that the last line can be seen (tex-recenter-output-buffer).

C-c C-k

Kill the TeX subprocess (tex-kill-job).

C-c C-c

Invoke some other compilation command on the entire current buffer (tex-compile).

To pass the current buffer through TeX, type C-c C-b (tex-buffer). The formatted output goes in a temporary file, normally a .dvi file. Afterwards, you can type C-c C-v (tex-view) to launch an external program, such as xdvi, to view this output file. You can also type C-c C-p (tex-print) to print a hardcopy of the output file.

By default, C-c C-b runs TeX in the current directory. The output of TeX is also created in this directory. To run TeX in a different directory, change the variable tex-directory to the desired directory. If your environment variable TEXINPUTS contains relative names, or if your files contain ‘\input’ commands with relative file names, then tex-directory must be "." or you will get the wrong results. Otherwise, it is safe to specify some other directory, such as "/tmp".

The buffer’s TeX variant determines what shell command C-c C-b actually runs. In Plain TeX mode, it is specified by the variable tex-run-command, which defaults to "tex". In LaTeX mode, it is specified by latex-run-command, which defaults to "latex". The shell command that C-c C-v runs to view the .dvi output is determined by the variable tex-dvi-view-command, regardless of the TeX variant. The shell command that C-c C-p runs to print the output is determined by the variable tex-dvi-print-command. The variable tex-print-file-extension can be set to the required file extension for viewing and printing TeX-compiled files. For example, you can set it to .pdf, and update tex-dvi-view-command and tex-dvi-print-command accordingly, as well as latex-run-command or tex-run-command.

Normally, Emacs automatically appends the output file name to the shell command strings described in the preceding paragraph. For example, if tex-dvi-view-command is "xdvi", C-c C-v runs xdvi output-file-name. In some cases, however, the file name needs to be embedded in the command, e.g., if you need to provide the file name as an argument to one command whose output is piped to another. You can specify where to put the file name with ‘*’ in the command string. For example,

(setq tex-dvi-print-command "dvips -f * | lpr")

The terminal output from TeX, including any error messages, appears in a buffer called *tex-shell*. If TeX gets an error, you can switch to this buffer and feed it input (this works as in Shell mode; see Interactive Subshell). Without switching to this buffer you can scroll it so that its last line is visible by typing C-c C-l.

Type C-c C-k (tex-kill-job) to kill the TeX process if you see that its output is no longer useful. Using C-c C-b or C-c C-r also kills any TeX process still running.

You can also pass an arbitrary region through TeX by typing C-c C-r (tex-region). This is tricky, however, because most files of TeX input contain commands at the beginning to set parameters and define macros, without which no later part of the file will format correctly. To solve this problem, C-c C-r allows you to designate a part of the file as containing essential commands; it is included before the specified region as part of the input to TeX. The designated part of the file is called the header.

To indicate the bounds of the header in Plain TeX mode, you insert two special strings in the file. Insert ‘%**start of header’ before the header, and ‘%**end of header’ after it. Each string must appear entirely on one line, but there may be other text on the line before or after. The lines containing the two strings are included in the header. If ‘%**start of header’ does not appear within the first 100 lines of the buffer, C-c C-r assumes that there is no header.

In LaTeX mode, the header begins with ‘\documentclass’ or ‘\documentstyle’ and ends with ‘\begin{document}’. These are commands that LaTeX requires you to use in any case, so nothing special needs to be done to identify the header.

The commands (tex-buffer) and (tex-region) do all of their work in a temporary directory, and do not have available any of the auxiliary files needed by TeX for cross-references; these commands are generally not suitable for running the final copy in which all of the cross-references need to be correct.

When you want the auxiliary files for cross references, use C-c C-f (tex-file) which runs TeX on the current buffer’s file, in that file’s directory. Before running TeX, it offers to save any modified buffers. Generally, you need to use (tex-file) twice to get the cross-references right.

The value of the variable tex-start-options specifies options for the TeX run.

The value of the variable tex-start-commands specifies TeX commands for starting TeX. The default value causes TeX to run in nonstop mode. To run TeX interactively, set the variable to "".

Large TeX documents are often split into several files—one main file, plus subfiles. Running TeX on a subfile typically does not work; you have to run it on the main file. In order to make tex-file useful when you are editing a subfile, you can set the variable tex-main-file to the name of the main file. Then tex-file runs TeX on that file.

The most convenient way to use tex-main-file is to specify it in a local variable list in each of the subfiles. See Local Variables in Files.

For LaTeX files, you can use BibTeX to process the auxiliary file for the current buffer’s file. BibTeX looks up bibliographic citations in a data base and prepares the cited references for the bibliography section. The command C-c TAB (tex-bibtex-file) runs the shell command (tex-bibtex-command) to produce a ‘.bbl’ file for the current buffer’s file. Generally, you need to do C-c C-f (tex-file) once to generate the ‘.aux’ file, then do C-c TAB (tex-bibtex-file), and then repeat C-c C-f (tex-file) twice more to get the cross-references correct.

To invoke some other compilation program on the current TeX buffer, type C-c C-c (tex-compile). This command knows how to pass arguments to many common programs, including pdflatex, yap, xdvi, and dvips. You can select your desired compilation program using the standard completion keys (see Completion).


26.11.4 TeX Mode Miscellany

Entering any variant of TeX mode runs the hooks text-mode-hook and tex-mode-hook. Then it runs either plain-tex-mode-hook, doctex-mode-hook, latex-mode-hook, or slitex-mode-hook, whichever is appropriate. Starting the TeX shell runs the hook tex-shell-hook. See Hooks.

The commands M-x iso-iso2tex, M-x iso-tex2iso, M-x iso-iso2gtex and M-x iso-gtex2iso can be used to convert between Latin-1 encoded files and TeX-encoded equivalents.


26.12 SGML and HTML Modes

The major modes for SGML and HTML provide indentation support and commands for operating on tags.

HTML consists of two modes—one, a basic mode called html-mode is a slightly customized variant of SGML mode. The other, which is used by default for HTML files, is called mhtml-mode, and attempts to properly handle Javascript enclosed in a <script> element and CSS embedded in a <style> element.

C-c C-n

Interactively specify a special character and insert the SGML ‘&’-command for that character (sgml-name-char).

C-c C-t

Interactively specify a tag and its attributes (sgml-tag). This command asks you for a tag name and for the attribute values, then inserts both the opening tag and the closing tag, leaving point between them.

With a prefix argument n, the command puts the tag around the n words already present in the buffer after point. Whenever a region is active, it puts the tag around the region (when Transient Mark mode is off, it does this when a numeric argument of −1 is supplied.)

C-c C-a

Interactively insert attribute values for the current tag (sgml-attributes).

C-c C-f

Skip across a balanced tag group (which extends from an opening tag through its corresponding closing tag) (sgml-skip-tag-forward). A numeric argument acts as a repeat count.

C-c C-b

Skip backward across a balanced tag group (which extends from an opening tag through its corresponding closing tag) (sgml-skip-tag-backward). A numeric argument acts as a repeat count.

C-c C-d

Delete the tag at or after point, and delete the matching tag too (sgml-delete-tag). If the tag at or after point is an opening tag, delete the closing tag too; if it is a closing tag, delete the opening tag too.

C-c ? tag RET

Display a description of the meaning of tag tag (sgml-tag-help). If the argument tag is empty, describe the tag at point.

C-c /

Insert a close tag for the innermost unterminated tag (sgml-close-tag). If called within a tag or a comment, close it instead of inserting a close tag.

C-c 8

Toggle a minor mode in which Latin-1 characters insert the corresponding SGML commands that stand for them, instead of the characters themselves (sgml-name-8bit-mode).

C-c C-v

Run a shell command (which you must specify) to validate the current buffer as SGML (sgml-validate). (In HTML mode this key sequence runs a different command.)

C-c TAB

Toggle the visibility of existing tags in the buffer. This can be used as a cheap preview (sgml-tags-invisible).

The major mode for editing XML documents is called nXML mode. This is a powerful major mode that can recognize many existing XML schemas and use them to provide completion of XML elements via M-TAB, as well as on-the-fly XML validation with error highlighting. To enable nXML mode in an existing buffer, type M-x nxml-mode, or, equivalently, M-x xml-mode. Emacs uses nXML mode for files which have the extension .xml. For XHTML files, which have the extension .xhtml, Emacs uses HTML mode by default; you can make it use nXML mode by customizing the variable auto-mode-alist (see Choosing File Modes). nXML mode is described in an Info manual, which is distributed with Emacs.

You may choose to use the less powerful SGML mode for editing XML, since XML is a strict subset of SGML. To enable SGML mode in an existing buffer, type M-x sgml-mode. On enabling SGML mode, Emacs examines the buffer to determine whether it is XML; if so, it sets the variable sgml-xml-mode to a non-nil value. This causes SGML mode’s tag insertion commands, described above, to always insert explicit closing tags as well.


26.13 Nroff Mode

Nroff mode, a major mode derived from Text mode, is specialized for editing nroff files (e.g., Unix man pages). Type M-x nroff-mode to enter this mode. Entering Nroff mode runs the hook text-mode-hook, then nroff-mode-hook (see Hooks).

In Nroff mode, nroff command lines are treated as paragraph separators, pages are separated by ‘.bp’ commands, and comments start with backslash-doublequote. It also defines these commands:

M-n

Move to the beginning of the next line that isn’t an nroff command (nroff-forward-text-line). An argument is a repeat count.

M-p

Like M-n but move up (nroff-backward-text-line).

M-?

Displays in the echo area the number of text lines (lines that are not nroff commands) in the region (nroff-count-text-lines).

Electric Nroff mode is a buffer-local minor mode that can be used with Nroff mode. To toggle this minor mode, type M-x nroff-electric-mode (see Minor Modes). When the mode is on, each time you type RET to end a line containing an nroff command that opens a kind of grouping, the nroff command to close that grouping is automatically inserted on the following line.

If you use Outline minor mode with Nroff mode (see Outline Mode), heading lines are lines of the form ‘.H’ followed by a number (the header level).


26.14 Enriched Text

Enriched mode is a minor mode for editing formatted text files in a WYSIWYG (What You See Is What You Get) fashion. When Enriched mode is enabled, you can apply various formatting properties to the text in the buffer, such as fonts and colors; upon saving the buffer, those properties are saved together with the text, using the MIME ‘text/enriched’ file format.

Enriched mode is typically used with Text mode (see Text Mode). It is not compatible with Font Lock mode, which is used by many major modes, including most programming language modes, for syntax highlighting (see Font Lock mode). Unlike Enriched mode, Font Lock mode assigns text properties automatically, based on the current buffer contents; those properties are not saved to disk.

The file enriched.txt in Emacs’s data-directory serves as an example of the features of Enriched mode.


26.14.1 Enriched Mode

Enriched mode is a buffer-local minor mode (see Minor Modes). When you visit a file that has been saved in the ‘text/enriched’ format, Emacs automatically enables Enriched mode, and applies the formatting information in the file to the buffer text. When you save a buffer with Enriched mode enabled, it is saved using the ‘text/enriched’ format, including the formatting information.

To create a new file of formatted text, visit the nonexistent file and type M-x enriched-mode. This command actually toggles Enriched mode. With a prefix argument, it enables Enriched mode if the argument is positive, and disables Enriched mode otherwise. If you disable Enriched mode, Emacs no longer saves the buffer using the ‘text/enriched’ format; any formatting properties that have been added to the buffer remain in the buffer, but they are not saved to disk.

Enriched mode does not save all Emacs text properties, only those specified in the variable enriched-translations. These include properties for fonts, colors, indentation, and justification.

If you visit a file and Emacs fails to recognize that it is in the ‘text/enriched’ format, type M-x format-decode-buffer. This command prompts for a file format, and re-reads the file in that format. Specifying the ‘text/enriched’ format automatically enables Enriched mode.

To view a ‘text/enriched’ file in raw form (as plain text with markup tags rather than formatted text), use M-x find-file-literally (see Visiting Files).

See Format Conversion in the Emacs Lisp Reference Manual, for details of how Emacs recognizes and converts file formats like ‘text/enriched’. See Text Properties in the Emacs Lisp Reference Manual, for more information about text properties.


26.14.2 Hard and Soft Newlines

In Enriched mode, Emacs distinguishes between two different kinds of newlines, hard newlines and soft newlines. You can also enable or disable this feature in other buffers, by typing M-x use-hard-newlines.

Hard newlines are used to separate paragraphs, or anywhere there needs to be a line break regardless of how the text is filled; soft newlines are used for filling. The RET (newline) and C-o (open-line) commands insert hard newlines. The fill commands, including Auto Fill (see Auto Fill Mode), insert only soft newlines and delete only soft newlines, leaving hard newlines alone.

Thus, when editing with Enriched mode, you should not use RET or C-o to break lines in the middle of filled paragraphs. Use Auto Fill mode or explicit fill commands (see Explicit Fill Commands) instead. Use RET or C-o where line breaks should always remain, such as in tables and lists. For such lines, you may also want to set the justification style to unfilled (see Justification in Enriched Text).


26.14.3 Editing Format Information

The easiest way to alter properties is with the ‘Text Properties’ menu. You can get to this menu from the ‘Edit’ menu in the menu bar (see The Menu Bar), or with C-mouse-2 (see Mouse Clicks for Menus). Some of the commands in the ‘Text Properties’ menu are listed below (you can also invoke them with M-x):

Remove Face Properties

Remove face properties from the region (facemenu-remove-face-props).

Remove Text Properties

Remove all text properties from the region, including face properties (facemenu-remove-all).

Describe Properties

List all text properties and other information about the character following point (describe-text-properties).

Display Faces

Display a list of defined faces (list-faces-display). See Text Faces.

Display Colors

Display a list of defined colors (list-colors-display). See Colors for Faces.

The other menu entries are described in the following sections.


26.14.4 Faces in Enriched Text

The following commands can be used to add or remove faces (see Text Faces). Each applies to the text in the region if the mark is active, and to the next self-inserting character if the mark is inactive. With a prefix argument, each command applies to the next self-inserting character even if the region is active.

M-o d

Remove all face properties (facemenu-set-default).

M-o b

Apply the bold face (facemenu-set-bold).

M-o i

Apply the italic face (facemenu-set-italic).

M-o l

Apply the bold-italic face (facemenu-set-bold-italic).

M-o u

Apply the underline face (facemenu-set-underline).

M-o o face RET

Apply the face face (facemenu-set-face).

M-x facemenu-set-foreground

Prompt for a color (see Colors for Faces), and apply it as a foreground color.

M-x facemenu-set-background

Prompt for a color, and apply it as a background color.

These commands are also available via the Text Properties menu.

A self-inserting character normally inherits the face properties (and most other text properties) from the preceding character in the buffer. If you use one of the above commands to specify the face for the next self-inserting character, that character will not inherit the faces properties from the preceding character, but it will still inherit other text properties.

Enriched mode defines two additional faces: excerpt and fixed. These correspond to codes used in the text/enriched file format. The excerpt face is intended for quotations; by default, it appears the same as italic. The fixed face specifies fixed-width text; by default, it appears the same as bold.


26.14.5 Indentation in Enriched Text

In Enriched mode, you can specify different amounts of indentation for the right or left margin of a paragraph or a part of a paragraph. These margins also affect fill commands such as M-q (see Filling Text).

The Indentation submenu of Text Properties offers commands for specifying indentation:

Indent More

Indent the region by 4 columns (increase-left-margin). In Enriched mode, this command is also available on C-x TAB; if you supply a numeric argument, that says how many columns to add to the margin (a negative argument reduces the number of columns).

Indent Less

Remove 4 columns of indentation from the region.

Indent Right More

Make the text narrower by indenting 4 columns at the right margin.

Indent Right Less

Remove 4 columns of indentation from the right margin.

The variable standard-indent specifies how many columns these commands should add to or subtract from the indentation. The default value is 4. The default right margin for Enriched mode is controlled by the variable fill-column, as usual.

You can also type C-c [ (set-left-margin) and C-c ] (set-right-margin) to set the left and right margins. You can specify the margin width with a numeric argument; otherwise these commands prompt for a value via the minibuffer.

The fill prefix, if any, works in addition to the specified paragraph indentation: C-x . does not include the specified indentation’s whitespace in the new value for the fill prefix, and the fill commands look for the fill prefix after the indentation on each line. See The Fill Prefix.


26.14.6 Justification in Enriched Text

In Enriched mode, you can use the following commands to specify various justification styles for filling. These commands apply to the paragraph containing point, or, if the region is active, to all paragraphs overlapping the region.

M-j l

Align lines to the left margin (set-justification-left).

M-j r

Align lines to the right margin (set-justification-right).

M-j b

Align lines to both margins, inserting spaces in the middle of the line to achieve this (set-justification-full).

M-j c
M-S

Center lines between the margins (set-justification-center).

M-j u

Turn off filling entirely (set-justification-none). The fill commands do nothing on text with this setting. You can, however, still indent the left margin.

You can also specify justification styles using the Justification submenu in the Text Properties menu. The default justification style is specified by the per-buffer variable default-justification. Its value should be one of the symbols left, right, full, center, or none; their meanings correspond to the commands above.


26.14.7 Setting Other Text Properties

The Special Properties submenu of Text Properties has entries for adding or removing four other text properties: read-only, (which disallows alteration of the text), invisible (which hides text), intangible (which disallows moving point within the text), and charset (which is important for selecting a proper font to display a character). The ‘Remove Special’ menu item removes all of these special properties from the text in the region.

The invisible and intangible properties are not saved.

Enriched mode also supports saving and restoring display properties (see Display Property in the Emacs Lisp Reference Manual), which affect how text is displayed on the screen, and also allow displaying images and strings that come from sources other than buffer text. The display properties also support execution of arbitrary Lisp forms as part of processing the property for display, thus providing a means to dynamically tailor the display to some conditions that can only be known at display time. Since execution of arbitrary Lisp opens Emacs to potential attacks, especially when the source of enriched text is outside of Emacs or even outside of your system (e.g., if it was received in an email message), such execution is by default disabled in Enriched mode. You can enable it by customizing the variable enriched-allow-eval-in-display-props to a non-nil value.


26.15 Editing Text-based Tables

The table package provides commands to easily edit text-based tables. Here is an example of what such a table looks like:

+-----------------+--------------------------------+-----------------+
|     Command     |          Description           |   Key Binding   |
+-----------------+--------------------------------+-----------------+
|  forward-char   |Move point right N characters   |       C-f       |
|                 |(left if N is negative).        |                 |
|                 |                                |                 |
+-----------------+--------------------------------+-----------------+
|  backward-char  |Move point left N characters    |       C-b       |
|                 |(right if N is negative).       |                 |
|                 |                                |                 |
+-----------------+--------------------------------+-----------------+

When Emacs recognizes such a stretch of text as a table (see Table Recognition), editing the contents of each table cell will automatically resize the table, whenever the contents become too large to fit in the cell. You can use the commands defined in the following sections for navigating and editing the table layout.

Type M-x table-fixed-width-mode to toggle the automatic table resizing feature.


26.15.1 What is a Text-based Table?

A table consists of a rectangular text area which is divided into cells. Each cell must be at least one character wide and one character high, not counting its border lines. A cell can be subdivided into more cells, but they cannot overlap.

Cell border lines are drawn with three special characters, specified by the following variables:

table-cell-vertical-char

The character used for vertical lines. The default is ‘|’.

table-cell-horizontal-chars

The characters used for horizontal lines. The default is ‘"-="’.

table-cell-intersection-char

The character used for the intersection of horizontal and vertical lines. The default is ‘+’.

The following are examples of invalid tables:

   +-----+       +--+    +-++--+
   |     |       |  |    | ||  |
   |     |       |  |    | ||  |
   +--+  |    +--+--+    +-++--+
   |  |  |    |  |  |    +-++--+
   |  |  |    |  |  |    | ||  |
   +--+--+    +--+--+    +-++--+
      a          b          c

From left to right:

  1. Overlapped cells or non-rectangular cells are not allowed.
  2. The border must be rectangular.
  3. Cells must have a minimum width/height of one character.

26.15.2 Creating a Table

To create a text-based table from scratch, type M-x table-insert. This command prompts for the number of table columns, the number of table rows, cell width and cell height. The cell width and cell height do not include the cell borders; each can be specified as a single integer (which means each cell is given the same width/height), or as a sequence of integers separated by spaces or commas (which specify the width/height of the individual table columns/rows, counting from left to right for table columns and from top to bottom for table rows). The specified table is then inserted at point.

The table inserted by M-x table-insert contains special text properties, which tell Emacs to treat it specially as a text-based table. If you save the buffer to a file and visit it again later, those properties are lost, and the table appears to Emacs as an ordinary piece of text. See the next section, for how to convert it back into a table.


26.15.3 Table Recognition

Existing text-based tables in a buffer, which lack the special text properties applied by M-x table-insert, are not treated specially as tables. To apply those text properties, type M-x table-recognize. This command scans the current buffer, recognizes valid table cells, and applies the relevant text properties. Conversely, type M-x table-unrecognize to unrecognize all tables in the current buffer, removing the special text properties and converting tables back to plain text.

You can also use the following commands to selectively recognize or unrecognize tables:

M-x table-recognize-region

Recognize tables within the current region.

M-x table-unrecognize-region

Unrecognize tables within the current region.

M-x table-recognize-table

Recognize the table at point and activate it.

M-x table-unrecognize-table

Deactivate the table at point.

M-x table-recognize-cell

Recognize the cell at point and activate it.

M-x table-unrecognize-cell

Deactivate the cell at point.

See Converting Between Plain Text and Tables, for another way to recognize a table.


26.15.4 Commands for Table Cells

The commands M-x table-forward-cell and M-x table-backward-cell move point from the current cell to an adjacent cell. The order is cyclic: when point is in the last cell of a table, M-x table-forward-cell moves to the first cell. Likewise, when point is on the first cell, M-x table-backward-cell moves to the last cell.

M-x table-span-cell prompts for a direction—right, left, above, or below—and merges the current cell with the adjacent cell in that direction. This command signals an error if the merge would result in an illegitimate cell layout.

M-x table-split-cell splits the current cell vertically or horizontally, prompting for the direction with the minibuffer. To split in a specific direction, use M-x table-split-cell-vertically and M-x table-split-cell-horizontally. When splitting vertically, the old cell contents are automatically split between the two new cells. When splitting horizontally, you are prompted for how to divide the cell contents, if the cell is non-empty; the options are ‘split’ (divide the contents at point), ‘left’ (put all the contents in the left cell), and ‘right’ (put all the contents in the right cell).

The following commands enlarge or shrink a cell. By default, they resize by one row or column; if a numeric argument is supplied, that specifies the number of rows or columns to resize by.

M-x table-heighten-cell

Enlarge the current cell vertically.

M-x table-shorten-cell

Shrink the current cell vertically.

M-x table-widen-cell

Enlarge the current cell horizontally.

M-x table-narrow-cell

Shrink the current cell horizontally.


26.15.5 Cell Justification

The command M-x table-justify imposes justification on one or more cells in a text-based table. Justification determines how the text in the cell is aligned, relative to the edges of the cell. Each cell in a table can be separately justified.

M-x table-justify first prompts for what to justify; the options are ‘cell’ (just the current cell), ‘column’ (all cells in the current table column) and ‘row’ (all cells in the current table row). The command then prompts for the justification style; the options are left, center, right, top, middle, bottom, or none (meaning no vertical justification).

Horizontal and vertical justification styles are specified independently, and both types can be in effect simultaneously; for instance, you can call M-x table-justify twice, once to specify right justification and once to specify bottom justification, to align the contents of a cell to the bottom right.

The justification style is stored in the buffer as a text property, and is lost when you kill the buffer or exit Emacs. However, the table recognition commands, such as M-x table-recognize (see Table Recognition), attempt to determine and re-apply each cell’s justification style, by examining its contents. To disable this feature, change the variable table-detect-cell-alignment to nil.


26.15.6 Table Rows and Columns

M-x table-insert-row inserts a row of cells before the current table row. The current row, together with point, is pushed down past the new row. To insert a row after the last row at the bottom of a table, invoke this command with point below the table, just below the bottom edge. You can insert more than one row at a time by using a numeric prefix argument.

Similarly, M-x table-insert-column inserts a column of cells to the left of the current table column. To insert a column to the right side of the rightmost column, invoke this command with point to the right of the rightmost column, outside the table. A numeric prefix argument specifies the number of columns to insert.

M-x table-delete-column deletes the column of cells at point. Similarly, M-x table-delete-row deletes the row of cells at point. A numeric prefix argument to either command specifies the number of columns or rows to delete.


26.15.7 Converting Between Plain Text and Tables

The command M-x table-capture captures plain text in a region and turns it into a table. Unlike M-x table-recognize (see Table Recognition), the original text does not need to have a table appearance; it only needs to have a logical table-like structure.

For example, suppose we have the following numbers, which are divided into three lines and separated horizontally by commas:

1, 2, 3, 4
5, 6, 7, 8
, 9, 10

Invoking M-x table-capture on that text produces this table:

+-----+-----+-----+-----+
|1    |2    |3    |4    |
+-----+-----+-----+-----+
|5    |6    |7    |8    |
+-----+-----+-----+-----+
|     |9    |10   |     |
+-----+-----+-----+-----+

M-x table-release does the opposite: it converts a table back to plain text, removing its cell borders.

One application of this pair of commands is to edit a text in layout. Look at the following three paragraphs:

table-capture is a powerful command.
Here are some things it can do:

Parse Cell Items   Using row and column delimiter regexps,
                   it parses the specified text area and
                   extracts cell items into a table.

Applying table-capture to a region containing the above text, with empty strings for the column and row delimiter regexps, creates a table with a single cell like the following one.

+----------------------------------------------------------+
|table-capture is a powerful command.                      |
|Here are some things it can do:                           |
|                                                          |
|Parse Cell Items   Using row and column delimiter regexps,|
|                   it parses the specified text area and  |
|                   extracts cell items into a table.      |
+----------------------------------------------------------+

We can then use the cell splitting commands (see Commands for Table Cells) to subdivide the table so that each paragraph occupies a cell:

+----------------------------------------------------------+
|table-capture is a powerful command.                      |
|Here are some things it can do:                           |
+-----------------+----------------------------------------+
|Parse Cell Items | Using row and column delimiter regexps,|
|                 | it parses the specified text area and  |
|                 | extracts cell items into a table.      |
+-----------------+----------------------------------------+

Each cell can now be edited independently without affecting the layout of other cells. When finished, we can invoke M-x table-release to convert the table back to plain text.


26.15.8 Table Miscellany

The command table-query-dimension reports the layout of the table and table cell at point. Here is an example of its output:

Cell: (21w, 6h), Table: (67w, 16h), Dim: (2c, 3r), Total Cells: 5

This indicates that the current cell is 21 characters wide and 6 lines high, the table is 67 characters wide and 16 lines high with 2 columns and 3 rows, and a total of 5 cells.

M-x table-insert-sequence traverses the cells of a table inserting a sequence of text strings into each cell as it goes. It asks for the base string of the sequence, and then produces the sequence by “incrementing” the base string, either numerically (if the base string ends in numerical characters) or in the ASCII order. In addition to the base string, the command prompts for the number of elements in the sequence, the increment, the cell interval, and the justification of the text in each cell.

M-x table-generate-source generates a table formatted for a specific markup language. It asks for a language (which must be one of html, latex, cals, wiki or mediawiki), a destination buffer in which to put the result, and a table caption, and then inserts the generated table into the specified buffer. The default destination buffer is table.lang, where lang is the language you specified.


26.16 Two-Column Editing

Two-column mode lets you conveniently edit two side-by-side columns of text. It uses two side-by-side windows, each showing its own buffer. There are three ways to enter two-column mode:

F2 2 or C-x 6 2

Enter two-column mode with the current buffer on the left, and on the right, a buffer whose name is based on the current buffer’s name (2C-two-columns). If the right-hand buffer doesn’t already exist, it starts out empty; the current buffer’s contents are not changed.

This command is appropriate when the current buffer is empty or contains just one column and you want to add another column.

F2 s or C-x 6 s

Split the current buffer, which contains two-column text, into two buffers, and display them side by side (2C-split). The current buffer becomes the left-hand buffer, but the text in the right-hand column is moved into the right-hand buffer. The current column specifies the split point. Splitting starts with the current line and continues to the end of the buffer.

This command is appropriate when you have a buffer that already contains two-column text, and you wish to separate the columns temporarily.

F2 b buffer RET
C-x 6 b buffer RET

Enter two-column mode using the current buffer as the left-hand buffer, and using buffer buffer as the right-hand buffer (2C-associate-buffer).

F2 s or C-x 6 s looks for a column separator, which is a string that appears on each line between the two columns. You can specify the width of the separator with a numeric argument to F2 s; that many characters, before point, constitute the separator string. By default, the width is 1, so the column separator is the character before point.

When a line has the separator at the proper place, F2 s puts the text after the separator into the right-hand buffer, and deletes the separator. Lines that don’t have the column separator at the proper place remain unsplit; they stay in the left-hand buffer, and the right-hand buffer gets an empty line to correspond. (This is the way to write a line that spans both columns while in two-column mode: write it in the left-hand buffer, and put an empty line in the right-hand buffer.)

The command F2 RET or C-x 6 RET (2C-newline) inserts a newline in each of the two buffers at corresponding positions. This is the easiest way to add a new line to the two-column text while editing it in split buffers.

When you have edited both buffers as you wish, merge them with F2 1 or C-x 6 1 (2C-merge). This copies the text from the right-hand buffer as a second column in the other buffer. To go back to two-column editing, use F2 s.

Use F2 d or C-x 6 d to dissociate the two buffers, leaving each as it stands (2C-dissociate). If the other buffer, the one not current when you type F2 d, is empty, F2 d kills it.


27 Editing Programs

This chapter describes Emacs features for facilitating editing programs. Some of the things these features can do are:


27.1 Major Modes for Programming Languages

Emacs has specialized major modes (see Major Modes) for many programming languages. A programming language mode typically specifies the syntax of expressions, the customary rules for indentation, how to do syntax highlighting for the language, and how to find the beginning or end of a function definition. It often has features for compiling and debugging programs as well. The major mode for each language is named after the language; for instance, the major mode for the C programming language is c-mode.

Emacs has programming language modes for Lisp, Scheme, the Scheme-based DSSSL expression language, Ada, ASM, AWK, C, C++, C#, Fortran, Icon, IDL (CORBA), IDLWAVE, Java, Javascript, M4, Makefiles, Metafont (TeX’s companion for font creation), Modula2, Object Pascal, Objective-C, Octave, Pascal, Perl, Pike, PostScript, Prolog, Python, Ruby, Simula, SQL, Tcl, TypeScript, Verilog, and VHDL. An alternative mode for Perl is called CPerl mode. Modes are also available for the scripting languages of the common GNU and Unix shells, and MS-DOS/MS-Windows ‘BAT’ files, JSON, DNS master files, CSS (Cascading Style Sheets), Dockerfiles, CMake files, and various sorts of configuration files.

Ideally, Emacs should have a major mode for each programming language that you might want to edit. If it doesn’t have a mode for your favorite language, the mode might be implemented in a package not distributed with Emacs (see Emacs Lisp Packages); or you can contribute one.

If Emacs has been compiled with the ‘tree-sitter’ library, it offers several optional editing modes based on that library, which utilize the incremental parsing capabilities provided by ‘tree-sitter’. These modes have ‘-ts-’ in their names; for example c-ts-mode, python-ts-mode, etc.

In most programming languages, indentation should vary from line to line to illustrate the structure of the program. Therefore, in most programming language modes, typing TAB updates the indentation of the current line (see Indentation for Programs). Furthermore, DEL is usually bound to backward-delete-char-untabify, which deletes backward treating each tab as if it were the equivalent number of spaces, so that you can delete one column of indentation without worrying whether the whitespace consists of spaces or tabs.

Entering a programming language mode runs the custom Lisp functions specified in the hook variable prog-mode-hook, followed by those specified in the mode’s own mode hook (see Major Modes). For instance, entering C mode runs the hooks prog-mode-hook and c-mode-hook. See Hooks, for information about hooks.

Separate manuals are available for the modes for Ada (see Ada Mode in Ada Mode), C/C++/Objective C/Java/Corba IDL/Pike/AWK (see CC Mode in CC Mode), Octave, VHDL, and IDLWAVE (see IDLWAVE in IDLWAVE User Manual).


27.2 Top-Level Definitions, or Defuns

In Emacs, a major definition at the top level in the buffer, such as a function, is called a defun. The name comes from Lisp, but in Emacs we use it for all languages.


27.2.1 Left Margin Convention

Many programming-language modes have traditionally assumed that any opening parenthesis or brace found at the left margin is the start of a top-level definition, or defun. So, by default, commands which seek the beginning of a defun accept such a delimiter as signifying that position.

If you want to override this convention, you can do so by setting the user option open-paren-in-column-0-is-defun-start to nil. If this option is set to t (the default), commands seeking the start of a defun will stop at opening parentheses or braces at column zero which aren’t in a comment or string. When it is nil, defuns are found by searching for parens or braces at the outermost level. Since low-level Emacs routines no longer depend on this convention, you usually won’t need to change open-paren-in-column-0-is-defun-start from its default.


27.2.2 Moving by Defuns

These commands move point or set up the region based on top-level major definitions, also called defuns.

C-M-a

Move to beginning of current or preceding defun (beginning-of-defun).

C-M-e

Move to end of current or following defun (end-of-defun).

C-M-h

Put region around whole current or following defun (mark-defun).

The commands to move to the beginning and end of the current defun are C-M-a (beginning-of-defun) and C-M-e (end-of-defun). If you repeat one of these commands, or use a positive numeric argument, each repetition moves to the next defun in the direction of motion.

C-M-a with a negative argument −n moves forward n times to the next beginning of a defun. This is not exactly the same place that C-M-e with argument n would move to; the end of this defun is not usually exactly the same place as the beginning of the following defun. (Whitespace, comments, and perhaps declarations can separate them.) Likewise, C-M-e with a negative argument moves back to an end of a defun, which is not quite the same as C-M-a with a positive argument.

To operate on the current defun, use C-M-h (mark-defun), which sets the mark at the end of the current defun and puts point at its beginning. See Commands to Mark Textual Objects. This is the easiest way to get ready to kill the defun in order to move it to a different place in the file. If the defun is directly preceded by comments (with no intervening blank lines), they are marked, too. If you use the command while point is between defuns, it uses the following defun. If you use the command while the mark is already active, it extends the end of the region to include one more defun. With a prefix argument, it marks that many defuns or extends the region by the appropriate number of defuns. With negative prefix argument it marks defuns in the opposite direction and also changes the direction of selecting for subsequent uses of mark-defun.

In C mode, C-M-h runs the function c-mark-function, which is almost the same as mark-defun; the difference is that it backs up over the argument declarations, function name and returned data type so that the entire C function is inside the region. This is an example of how major modes adjust the standard key bindings so that they do their standard jobs in a way better fitting a particular language. Other major modes may replace any or all of these key bindings for that purpose.

Some programming languages supported nested defuns, whereby a defun (such as a function or a method or a class) can be defined inside (i.e., as part of the body) of another defun. The commands described above by default find the beginning and the end of the innermost defun around point. Major modes based on the tree-sitter library provide control of this behavior: if the variable treesit-defun-tactic is set to the value top-level, the defun commands will find the outermost defuns instead.


27.2.3 Imenu

The Imenu facility offers a way to find the major definitions in a file by name. It is also useful in text formatter major modes, where it treats each chapter, section, etc., as a definition. (See Find Identifier References, for a more powerful feature that handles multiple files together.)

If you type M-g i (imenu), it reads the name of a definition using the minibuffer, then moves point to that definition. You can use completion to specify the name; the command always displays the whole list of valid names.

Alternatively, you can bind the command imenu to a mouse click. Then it displays mouse menus for you to select a definition name. You can also add the buffer’s index to the menu bar by calling imenu-add-menubar-index. If you want to have this menu bar item available for all buffers in a certain major mode, you can do this by adding imenu-add-menubar-index to its mode hook. But if you have done that, you will have to wait a little while each time you visit a file in that mode, while Emacs finds all the definitions in that buffer.

When you change the contents of a buffer, if you add or delete definitions, you can update the buffer’s index based on the new contents by invoking the ‘*Rescan*’ item in the menu. Rescanning happens automatically if you set imenu-auto-rescan to a non-nil value. There is no need to rescan because of small changes in the text.

imenu-auto-rescan will be disabled in buffers that are larger than imenu-auto-rescan-maxout in bytes, and scanning is stopped if it takes more than imenu-max-index-time seconds.

You can customize the way the menus are sorted by setting the variable imenu-sort-function. By default, names are ordered as they occur in the buffer; if you want alphabetic sorting, use the symbol imenu--sort-by-name as the value. You can also define your own comparison function by writing Lisp code.

If Eglot is activated for the current buffer’s project (see Working with Projects) and the current buffer’s major mode, Eglot provides its own facility for producing the buffer’s index based on the analysis of the program source by the language-server which manages the current buffer. See Eglot Features in Eglot: The Emacs LSP Client.

Imenu provides the information to guide Which Function mode (see Which Function Mode). The Speedbar can also use it (see Speedbar Frames).


27.2.4 Which Function Mode

Which Function mode is a global minor mode (see Minor Modes) which displays the current function name in the mode line, updating it as you move around in a buffer.

To either enable or disable Which Function mode, use the command M-x which-function-mode. Which Function mode is a global minor mode. By default, it takes effect in all major modes that know how to support it (i.e., all the major modes that support Imenu). You can restrict it to a specific list of major modes by changing the value of the variable which-func-modes from t (which means to support all available major modes) to a list of major mode names.


27.3 Indentation for Programs

The best way to keep a program properly indented is to use Emacs to reindent it as you change it. Emacs has commands to indent either a single line, a specified number of lines, or all of the lines inside a single parenthetical grouping.

See Indentation, for general information about indentation. This section describes indentation features specific to programming language modes.

Emacs also provides a Lisp pretty-printer in the pp package, which reformats Lisp objects with nice-looking indentation. See pp in The Emacs Lisp Reference Manual.


27.3.1 Basic Program Indentation Commands

TAB

Adjust indentation of current line (indent-for-tab-command).

RET

Insert a newline, then adjust indentation of following line (newline).

The basic indentation command is TAB (indent-for-tab-command), which was documented in Indentation. In programming language modes, TAB indents the current line, based on the indentation and syntactic content of the preceding lines; if the region is active, TAB indents each line within the region, not just the current line.

The command RET (newline), which was documented in Inserting Text, does the same as C-j followed by TAB: it inserts a new line, then adjusts the line’s indentation.

When indenting a line that starts within a parenthetical grouping, Emacs usually places the start of the line under the preceding line within the group, or under the text after the parenthesis. If you manually give one of these lines a nonstandard indentation (e.g., for aesthetic purposes), the lines below will follow it.

The indentation commands for most programming language modes assume that an open-parenthesis, open-brace or other opening delimiter at the left margin is the start of a function. If the code you are editing violates this assumption—even if the delimiters occur in strings or comments—you must set open-paren-in-column-0-is-defun-start to nil for indentation to work properly. See Left Margin Convention.


27.3.2 Indenting Several Lines

Sometimes, you may want to reindent several lines of code at a time. One way to do this is to use the mark; when the mark is active and the region is non-empty, TAB indents every line in the region. Alternatively, the command C-M-\ (indent-region) indents every line in the region, whether or not the mark is active (see Indentation Commands).

In addition, Emacs provides the following commands for indenting large chunks of code:

C-M-q

Reindent all the lines within one parenthetical grouping.

C-u TAB

Shift an entire parenthetical grouping rigidly sideways so that its first line is properly indented.

M-x indent-code-rigidly

Shift all the lines in the region rigidly sideways, but do not alter lines that start inside comments and strings.

To reindent the contents of a single parenthetical grouping, position point before the beginning of the grouping and type C-M-q. This changes the relative indentation within the grouping, without affecting its overall indentation (i.e., the indentation of the line where the grouping starts). The function that C-M-q runs depends on the major mode; it is indent-pp-sexp in Lisp mode, c-indent-exp in C mode, etc. To correct the overall indentation as well, type TAB first.

If you like the relative indentation within a grouping but not the indentation of its first line, move point to that first line and type C-u TAB. In Lisp, C, and some other major modes, TAB with a numeric argument reindents the current line as usual, then reindents by the same amount all the lines in the parenthetical grouping starting on the current line. It is clever, though, and does not alter lines that start inside strings. Neither does it alter C preprocessor lines when in C mode, but it does reindent any continuation lines that may be attached to them.

The command M-x indent-code-rigidly rigidly shifts all the lines in the region sideways, like indent-rigidly does (see Indentation Commands). It doesn’t alter the indentation of lines that start inside a string, unless the region also starts inside that string. The prefix arg specifies the number of columns to indent.


27.3.3 Customizing Lisp Indentation

The indentation pattern for a Lisp expression can depend on the function called by the expression. For each Lisp function, you can choose among several predefined patterns of indentation, or define an arbitrary one with a Lisp program.

The standard pattern of indentation is as follows: the second line of the expression is indented under the first argument, if that is on the same line as the beginning of the expression; otherwise, the second line is indented underneath the function name. Each following line is indented under the previous line whose nesting depth is the same.

If the variable lisp-indent-offset is non-nil, it overrides the usual indentation pattern for the second line of an expression, so that such lines are always indented lisp-indent-offset more columns than the containing list.

Certain functions override the standard pattern. Functions whose names start with def treat the second lines as the start of a body, by indenting the second line lisp-body-indent additional columns beyond the open-parenthesis that starts the expression.

You can override the standard pattern in various ways for individual functions, according to the lisp-indent-function property of the function name. This is normally done for macro definitions, using the declare construct. See Defining Macros in The Emacs Lisp Reference Manual.

In Emacs Lisp, lists are usually indented as if they are function-like forms:

(setq foo '(bar zot
                gazonk))

However, if you add a space after the opening parenthesis, this tells Emacs that it’s a data list instead of a piece of code, and Emacs will then indent it like this:

(setq foo '( bar zot
             gazonk))

27.3.4 Commands for C Indentation

Here are special features for indentation in C mode and related modes:

C-c C-q

Reindent the current top-level function definition or aggregate type declaration (c-indent-defun in CC mode, c-ts-mode-indent-defun in c-ts-mode based on tree-sitter).

C-M-q

Reindent each line in the balanced expression (see Expressions with Balanced Parentheses), also known as “sexp”, that follows point. In CC mode, this invokes c-indent-exp; in tree-sitter based c-ts-mode this invokes a more general prog-indent-sexp. A prefix argument inhibits warning messages about invalid syntax.

TAB

Reindent the current line, active region, or block starting on this line (c-indent-line-or-region). With prefix argument, rigidly reindent the balanced expression which starts on the current line, if the current line needs reindentation.

If c-tab-always-indent is t, this command always reindents the current line and does nothing else. This is the default.

If that variable is nil, this command reindents the current line only if point is at the left margin or in the line’s indentation; otherwise, it inserts a tab (or the equivalent number of spaces, if indent-tabs-mode is nil).

Any other value (not nil or t) means always reindent the line, and also insert a tab if within a comment or a string.

To reindent the whole current buffer, type C-x h C-M-\. This first selects the whole buffer as the region, then reindents that region.

To reindent the current block, use C-M-u C-M-q. This moves to the front of the block and then reindents it all.


27.3.5 Customizing C Indentation

C mode and related modes use a flexible mechanism for customizing indentation. C mode indents a source line in two steps: first it classifies the line syntactically according to its contents and context; second, it determines the indentation offset associated by your selected style with the syntactic construct and adds this onto the indentation of the anchor statement.

C-c . style RET

Select a predefined style style (c-set-style in CC mode, c-ts-mode-set-style in c-ts-mode based on tree-sitter).

A style is a named collection of customizations that can be used in C mode and the related modes. Styles in The CC Mode Manual, for a complete description. Emacs comes with several predefined styles, including gnu, k&r, bsd, stroustrup, linux, python, java, whitesmith, ellemtel, and awk. Some of these styles are primarily intended for one language, but any of them can be used with any of the languages supported by these modes. To find out what a style looks like, select it and reindent some code, e.g., by typing C-M-q at the start of a function definition.

To choose a style for the current buffer, use the command C-c .. Specify a style name as an argument (case is not significant). This command affects the current buffer only, and it affects only future invocations of the indentation commands; it does not reindent the code already in the buffer. To reindent the whole buffer in the new style, you can type C-x h C-M-\.

When using CC mode, you can also set the variable c-default-style to specify the default style for various major modes. Its value should be either the style’s name (a string) or an alist, in which each element specifies one major mode and which indentation style to use for it. For example,

(setq c-default-style
      '((java-mode . "java")
        (awk-mode . "awk")
        (other . "gnu")))

specifies explicit choices for Java and AWK modes, and the default ‘gnu’ style for the other C-like modes. (These settings are actually the defaults.) This variable takes effect when you select one of the C-like major modes; thus, if you specify a new default style for Java mode, you can make it take effect in an existing Java mode buffer by typing M-x java-mode there.

When using the tree-sitter based c-ts-mode, you can set the default indentation style by customizing the variable c-ts-mode-indent-style.

The gnu style specifies the formatting recommended by the GNU Project for C; it is the default, so as to encourage use of our recommended style.

See Indentation Engine Basics in the CC Mode Manual, and Customizing Indentation in the CC Mode Manual, for more information on customizing indentation for C and related modes, including how to override parts of an existing style and how to define your own styles.

As an alternative to specifying a style, you can tell Emacs to guess a style by typing M-x c-guess in a sample code buffer. You can then apply the guessed style to other buffers with M-x c-guess-install. See Guessing the Style in the CC Mode Manual, for details.


27.4 Commands for Editing with Parentheses

This section describes the commands and features that take advantage of the parenthesis structure in a program, or help you keep it balanced.

When talking about these facilities, the term “parenthesis” also includes braces, brackets, or whatever delimiters are defined to match in pairs. The major mode controls which delimiters are significant, through the syntax table (see Syntax Tables in The Emacs Lisp Reference Manual). In Lisp, only parentheses count; in C, these commands apply to braces and brackets too.

You can use M-x check-parens to find any unbalanced parentheses and unbalanced string quotes in the buffer.


27.4.1 Expressions with Balanced Parentheses

Each programming language mode has its own definition of a balanced expression. Balanced expressions typically include individual symbols, numbers, and string constants, as well as pieces of code enclosed in a matching pair of delimiters. The following commands deal with balanced expressions (in Emacs, such expressions are referred to internally as sexps14).

C-M-f

Move forward over a balanced expression (forward-sexp).

C-M-b

Move backward over a balanced expression (backward-sexp).

C-M-k

Kill balanced expression forward (kill-sexp).

C-M-t

Transpose expressions (transpose-sexps).

C-M-@
C-M-SPC

Put mark after following expression (mark-sexp).

To move forward over a balanced expression, use C-M-f (forward-sexp). If the first significant character after point is an opening delimiter (e.g., ‘(’, ‘[’ or ‘{’ in C), this command moves past the matching closing delimiter. If the character begins a symbol, string, or number, the command moves over that.

The command C-M-b (backward-sexp) moves backward over a balanced expression—like C-M-f, but in the reverse direction. If the expression is preceded by any prefix characters (single-quote, backquote and comma, in Lisp), the command moves back over them as well.

C-M-f or C-M-b with an argument repeats that operation the specified number of times; with a negative argument means to move in the opposite direction. In most modes, these two commands move across comments as if they were whitespace. Note that their keys, C-M-f and C-M-b, are analogous to C-f and C-b, which move by characters (see Changing the Location of Point), and M-f and M-b, which move by words (see Words).

To kill a whole balanced expression, type C-M-k (kill-sexp). This kills the text that C-M-f would move over.

C-M-t (transpose-sexps) switches the positions of the previous balanced expression and the next one. It is analogous to the C-t command, which transposes characters (see Transposing Text). An argument to C-M-t serves as a repeat count, moving the previous expression over that many following ones. A negative argument moves the previous balanced expression backwards across those before it. An argument of zero, rather than doing nothing, transposes the balanced expressions ending at or after point and the mark.

To operate on balanced expressions with a command which acts on the region, type C-M-SPC (mark-sexp). This sets the mark where C-M-f would move to. While the mark is active, each successive call to this command extends the region by shifting the mark by one expression. Positive or negative numeric arguments move the mark forward or backward by the specified number of expressions. The alias C-M-@ is equivalent to C-M-SPC. See Commands to Mark Textual Objects, for more information about this and related commands.

In languages that use infix operators, such as C, it is not possible to recognize all balanced expressions because there can be multiple possibilities at a given position. For example, C mode does not treat ‘foo + bar’ as a single expression, even though it is one C expression; instead, it recognizes ‘foo’ as one expression and ‘bar’ as another, with the ‘+’ as punctuation between them. However, C mode recognizes ‘(foo + bar)’ as a single expression, because of the parentheses.


27.4.2 Moving in the Parenthesis Structure

The following commands move over groupings delimited by parentheses (or whatever else serves as delimiters in the language you are working with). They ignore strings and comments, including any parentheses within them, and also ignore parentheses that are quoted with an escape character. These commands are mainly intended for editing programs, but can be useful for editing any text containing parentheses. They are referred to internally as “list commands” because in Lisp these groupings are lists.

These commands assume that the starting point is not inside a string or a comment. If you invoke them from inside a string or comment, the results are unreliable.

C-M-n

Move forward over a parenthetical group (forward-list).

C-M-p

Move backward over a parenthetical group (backward-list).

C-M-u

Move up in parenthesis structure (backward-up-list).

C-M-d

Move down in parenthesis structure (down-list).

The list commands C-M-n (forward-list) and C-M-p (backward-list) move forward or backward over one (or n) parenthetical groupings.

C-M-n and C-M-p try to stay at the same level in the parenthesis structure. To move up one (or n) levels, use C-M-u (backward-up-list). C-M-u moves backward up past one unmatched opening delimiter. A positive argument serves as a repeat count; a negative argument reverses the direction of motion, so that the command moves forward and up one or more levels.

To move down in the parenthesis structure, use C-M-d (down-list). In Lisp mode, where ‘(’ is the only opening delimiter, this is nearly the same as searching for a ‘(’. An argument specifies the number of levels to go down.


27.4.3 Matching Parentheses

Emacs has a number of parenthesis matching features, which make it easy to see how and whether parentheses (or other delimiters) match up.

Whenever you type a self-inserting character that is a closing delimiter, Emacs briefly indicates the location of the matching opening delimiter, provided that is on the screen. If it is not on the screen, Emacs displays some of the text near it in the echo area. Either way, you can tell which grouping you are closing off. If the opening delimiter and closing delimiter are mismatched—such as in ‘[x)’—a warning message is displayed in the echo area.

Three variables control the display of matching parentheses:

  • blink-matching-paren turns the feature on or off: nil disables it, but the default is t to enable it. Set it to jump to make indication work by momentarily moving the cursor to the matching opening delimiter. Set it to jump-offscreen to make the cursor jump, even if the opening delimiter is off screen.
  • blink-matching-delay says how many seconds to keep indicating the matching opening delimiter. This may be an integer or floating-point number; the default is 1.
  • blink-matching-paren-distance specifies how many characters back to search to find the matching opening delimiter. If the match is not found in that distance, Emacs stops scanning and nothing is displayed. The default is 102400.

Show Paren mode is a minor mode that provides a more powerful kind of automatic matching. Whenever point is before an opening delimiter or after a closing delimiter, the delimiter, its matching delimiter, and optionally the text between them are highlighted. To toggle Show Paren mode globally, type M-x show-paren-mode. To toggle it only in the current buffer, type M-x show-paren-local-mode.

By default, this mode is switched on in all buffers that are meant for editing, but is not enabled in buffers that show data. This is controlled by the show-paren-predicate user option.

To customize the mode, type M-x customize-group RET paren-showing. The customizable options which control the operation of this mode include:

  • show-paren-highlight-openparen controls whether to highlight an open paren when point is just before it, and hence its position is marked by the cursor anyway. The default is non-nil (yes).
  • show-paren-style controls whether just the two parens, or also the text between them get highlighted. The valid options here are parenthesis (show the matching paren), expression (highlight the entire expression enclosed by the parens), and mixed (highlight the matching paren if it is visible in the window, the expression otherwise).
  • show-paren-when-point-inside-paren, when non-nil, causes highlighting also when point is inside of the parentheses. The default is nil.
  • show-paren-when-point-in-periphery, when non-nil, causes highlighting also when point is in whitespace at the beginning of a line and there is a paren at the first or last non-whitespace position on the line, or when point is at the end of a line and there is a paren at the last non-whitespace position on the line.
  • show-paren-context-when-offscreen, when non-nil, shows some context in the echo area when point is in a closing delimiter and the opening delimiter is offscreen. The context is usually the line that contains the opening delimiter, except if the opening delimiter is on its own line, in which case the context includes the previous nonblank line.

Electric Pair mode, a global minor mode, provides a way to easily insert matching delimiters: parentheses, braces, brackets, etc. Whenever you insert an opening delimiter, the matching closing delimiter is automatically inserted as well, leaving point between the two. Conversely, when you insert a closing delimiter over an existing one, no insertion takes places, and that position is simply skipped over. If the region is active (see The Mark and the Region), insertion of a delimiter operates on the region: the characters in the region are enclosed in a pair of matching delimiters, leaving point after the delimiter you typed.

These variables control additional features of Electric Pair mode:

  • electric-pair-preserve-balance, when non-nil, makes the default pairing logic balance out the number of opening and closing delimiters.
  • electric-pair-delete-adjacent-pairs, when non-nil, makes backspacing between two adjacent delimiters also automatically delete the closing delimiter.
  • electric-pair-open-newline-between-pairs, when non-nil, makes inserting a newline between two adjacent pairs also automatically open an extra newline after point.
  • electric-pair-skip-whitespace, when non-nil, causes the minor mode to skip whitespace forward before deciding whether to skip over the closing delimiter.

To toggle Electric Pair mode, type M-x electric-pair-mode. To toggle the mode in a single buffer, use M-x electric-pair-local-mode.


27.5 Manipulating Comments

Because comments are such an important part of programming, Emacs provides special commands for editing and inserting comments. It can also do spell checking on comments with Flyspell Prog mode (see Checking and Correcting Spelling).

Some major modes have special rules for indenting different kinds of comments. For example, in Lisp code, comments starting with two semicolons are indented as if they were lines of code, while those starting with three semicolons are supposed to be aligned to the left margin and are often used for sectioning purposes. Emacs understands these conventions; for instance, typing TAB on a comment line will indent the comment to the appropriate position.

;; This function is just an example.
;;; Here either two or three semicolons are appropriate.
(defun foo (x)
;;;  And now, the first part of the function:
  ;; The following line adds one.
  (1+ x))           ; This line adds one.

27.5.1 Comment Commands

The following commands operate on comments:

M-;

Insert or realign comment on current line; if the region is active, comment or uncomment the region instead (comment-dwim).

C-x C-;

Comment or uncomment the current line (comment-line). If the region is active, comment or uncomment the lines in the region instead.

C-u M-;

Kill comment on current line (comment-kill).

C-x ;

Set comment column (comment-set-column).

C-M-j
M-j

Like RET followed by inserting and aligning a comment (default-indent-new-line). See Multiple Lines of Comments.

M-x comment-region
C-c C-c (in C-like modes)

Add comment delimiters to all the lines in the region.

The command to create or align a comment is M-; (comment-dwim). The word “dwim” is an acronym for “Do What I Mean”; it indicates that this command can be used for many different jobs relating to comments, depending on the situation where you use it.

When a region is active (see The Mark and the Region), M-; either adds comment delimiters to the region, or removes them. If every line in the region is already a comment, it uncomments each of those lines by removing their comment delimiters. Otherwise, it adds comment delimiters to enclose the text in the region.

If you supply a prefix argument to M-; when a region is active, that specifies the number of comment delimiters to add or delete. A positive argument n adds n delimiters, while a negative argument −n removes n delimiters.

If the region is not active, and there is no existing comment on the current line, M-; adds a new comment to the current line. If the line is blank (i.e., empty or containing only whitespace characters), the comment is indented to the same position where TAB would indent to (see Basic Program Indentation Commands). If the line is non-blank, the comment is placed after the last non-whitespace character on the line. Emacs tries to fit the comment between the columns specified by the variables comment-column and comment-fill-column (see Options Controlling Comments), if possible. Otherwise, it will choose some other suitable position, usually separated from the non-comment text by at least one space. In each case, Emacs places point after the comment’s starting delimiter, so that you can start typing the comment text right away.

You can also use M-; to align an existing comment. If a line already contains the comment-start string, M-; realigns it to the conventional alignment and moves point after the comment’s starting delimiter. As an exception, comments starting in column 0 are not moved. Even when an existing comment is properly aligned, M-; is still useful for moving directly to the start of the comment text.

C-x C-; (comment-line) comments or uncomments complete lines. When a region is active (see The Mark and the Region), C-x C-; either comments or uncomments the lines in the region. If the region is not active, this command comments or uncomments the line point is on. With a positive prefix argument n, it operates on n lines starting with the current one; with a negative argument −n, it affects n preceding lines. After invoking this command with a negative argument, successive invocations with a positive argument will operate on preceding lines as if the argument were negated.

C-u M-; (comment-dwim with a prefix argument) when the region is not active kills any comment on the current line, along with the whitespace before it. Since the comment is saved to the kill ring, you can reinsert it on another line by moving to the end of that line, doing C-y, and then M-; to realign the comment. You can achieve the same effect as C-u M-; by typing M-x comment-kill (comment-dwim actually calls comment-kill as a subroutine when it is given a prefix argument). Invoking comment-dwim with a prefix numeric argument, as in C-u n M-;, when there’s no active region, tells comment-kill to kill comments on n lines.

The command M-x comment-region is equivalent to calling M-; on an active region, except that it always acts on the region, even if the mark is inactive. In C mode and related modes, this command is bound to C-c C-c. The command M-x uncomment-region uncomments each line in the region; a numeric prefix argument specifies the number of comment delimiters to remove (negative arguments specify the number of comment delimiters to add).

For C-like modes, you can configure the exact effect of M-; by setting the variables c-indent-comment-alist and c-indent-comments-syntactically-p. For example, on a line ending in a closing brace, M-; puts the comment one space after the brace rather than at comment-column. For full details see Comment Commands in The CC Mode Manual.


27.5.2 Multiple Lines of Comments

If you are typing a comment and wish to continue it to another line, type M-j or C-M-j (default-indent-new-line). This breaks the current line, and inserts the necessary comment delimiters and indentation to continue the comment.

For languages with closing comment delimiters (e.g., ‘*/’ in C), the exact behavior of M-j depends on the value of the variable comment-multi-line. If the value is nil, the command closes the comment on the old line and starts a new comment on the new line. Otherwise, it opens a new line within the current comment delimiters.

When Auto Fill mode is on, going past the fill column while typing a comment also continues the comment, in the same way as an explicit invocation of M-j.

To turn existing lines into comment lines, use M-; with the region active, or use M-x comment-region as described in the preceding section.

You can configure C Mode such that when you type a ‘/’ at the start of a line in a multi-line block comment, this closes the comment. Enable the comment-close-slash clean-up for this. See Clean-ups in The CC Mode Manual.


27.5.3 Options Controlling Comments

As mentioned in Comment Commands, when the M-j command adds a comment to a line, it tries to place the comment between the columns specified by the buffer-local variables comment-column and comment-fill-column (or if that is nil, then the value of fill-column, see Explicit Fill Commands). You can set either the local value or the default value of these buffer-local variables in the usual way (see Local Variables). Alternatively, you can type C-x ; (comment-set-column) to set the value of comment-column in the current buffer to the column where point is currently located. C-u C-x ; sets the comment column to match the last comment before point in the buffer, and then does a M-; to align the current line’s comment under the previous one.

The comment commands recognize comments based on the regular expression that is the value of the variable comment-start-skip. Make sure this regexp does not match the null string. It may match more than the comment starting delimiter in the strictest sense of the word; for example, in C mode the value of the variable could be "/\\*+[ \t]*\\|//+[ \t]*", which matches extra stars and spaces after the ‘/*’ itself, and accepts C++ style (‘//’) comments also. (Note that ‘\\’ is needed in Lisp syntax to include a ‘\’ in the string, which is needed to deny the first star its special meaning in regexp syntax. See Backslash in Regular Expressions.)

When a comment command makes a new comment, it inserts the value of comment-start as an opening comment delimiter. It also inserts the value of comment-end after point, as a closing comment delimiter. For example, in Lisp mode, comment-start is ‘";"’ and comment-end is "" (the empty string). In C mode, comment-start is "/* " and comment-end is " */".

The variable comment-padding specifies a string that the commenting commands should insert between the comment delimiter(s) and the comment text. The default, ‘" "’, specifies a single space. Alternatively, the value can be a number, which specifies that number of spaces, or nil, which means no spaces at all.

The variable comment-multi-line controls how M-j and Auto Fill mode continue comments over multiple lines. See Multiple Lines of Comments.

The variable comment-indent-function should contain a function that will be called to compute the alignment for a newly inserted comment or for aligning an existing comment. It is set differently by various major modes. The function is called with no arguments, but with point at the beginning of the comment, or at the end of a line if a new comment is to be inserted. It should return the column in which the comment ought to start. For example, the default function bases its decision on how many comment characters begin an existing comment.

Emacs also tries to align comments on adjacent lines. To override this, the function may return a cons of two (possibly equal) integers to indicate an acceptable range of indentation.


27.6 Documentation Lookup

Emacs provides several features you can use to look up the documentation of functions, variables and commands that you plan to use in your program.


27.6.1 Info Documentation Lookup

For major modes that apply to languages which have documentation in Info, you can use C-h S (info-lookup-symbol) to view the Info documentation for a symbol used in the program. You specify the symbol with the minibuffer; the default is the symbol appearing in the buffer at point. For example, in C mode this looks for the symbol in the C Library Manual. The command only works if the appropriate manual’s Info files are installed.

Emacs determines where to look for documentation for the symbol—which Info files to look in, and which indices to search—based on the major mode. You can also use M-x info-lookup-file to look for documentation for a file name.

If you use C-h S in a major mode that does not support it, it asks you to specify the symbol help mode. You should enter a command such as c-mode that would select a major mode which C-h S does support.


27.6.2 Man Page Lookup

On Unix, the main form of on-line documentation was the manual page or man page. In the GNU operating system, we aim to replace man pages with better-organized manuals that you can browse with Info (see Other Help Commands). This process is not finished, so it is still useful to read manual pages.

You can read the man page for an operating system command, library function, or system call, with the M-x man command. This prompts for a topic, with completion (see Completion), and runs the man program to format the corresponding man page. If the system permits, it runs man asynchronously, so that you can keep on editing while the page is being formatted. The result goes in a buffer named *Man topic*. These buffers use a special major mode, Man mode, that facilitates scrolling and jumping to other manual pages. For details, type C-h m while in a Man mode buffer.

Each man page belongs to one of ten or more sections, each named by a digit or by a digit and a letter. Sometimes there are man pages with the same name in different sections. To read a man page from a specific section, type ‘topic(section)’ or ‘section topic’ when M-x man prompts for the topic. For example, the man page for the C library function chmod is in section 2, but there is a shell command of the same name, whose man page is in section 1; to view the former, type M-x man RET chmod(2) RET.

If you do not specify a section, M-x man normally displays only the first man page found. On some systems, the man program accepts a ‘-a’ command-line option, which tells it to display all the man pages for the specified topic. To make use of this, change the value of the variable Man-switches to ‘"-a"’. Then, in the Man mode buffer, you can type M-n and M-p to switch between man pages in different sections. The mode line shows how many manual pages are available.

An alternative way of reading manual pages is the M-x woman command. Unlike M-x man, it does not run any external programs to format and display the man pages; the formatting is done by Emacs, so it works on systems such as MS-Windows where the man program may be unavailable. It prompts for a man page, and displays it in a buffer named *WoMan section topic.

M-x woman computes the completion list for manpages the first time you invoke the command. With a numeric argument, it recomputes this list; this is useful if you add or delete manual pages.

If you type a name of a manual page and M-x woman finds that several manual pages by the same name exist in different sections, it pops up a window with possible candidates asking you to choose one of them.

Note that M-x woman doesn’t yet support the latest features of modern man pages, so we recommend using M-x man if that is available on your system.

For more information about setting up and using M-x woman, see the WoMan Info manual, which is distributed with Emacs.


27.6.3 Programming Language Documentation Lookup

When editing Emacs Lisp code, you can use the commands C-h f (describe-function) and C-h v (describe-variable) to view the built-in documentation for the Lisp functions and variables that you want to use. See Help by Command or Variable Name.

ElDoc15 is a buffer-local minor mode that helps with looking up documentation of symbols (functions, methods, classes, variables, etc.) in your program. When this mode is enabled, the echo area displays useful information whenever there is a documented symbol at point. For example, in buffers under the Emacs Lisp mode, it shows the argument list of a function at point, and for a Lisp variable it shows the first line of the variable’s documentation string.

To toggle ElDoc mode, type M-x eldoc-mode. There’s also a Global ElDoc mode, which is turned on by default, and turns on the ElDoc mode in buffers whose major mode sets the variables described below. Use M-x global-eldoc-mode to turn it off globally.

Various major modes configure the Global ElDoc mode to use their documentation functions. Examples include Emacs Lisp mode, Python mode, and Cfengine mode. In addition, Emacs features that provide support for several major modes configure ElDoc to use their facilities for retrieving the documentation. Examples include Eglot (see Eglot Features in Eglot: The Emacs LSP Client), which provides documentation based on information from language servers; Semantic’s Idle Summary mode (see Idle Summary Mode in Semantic Manual); and Flymake, which uses ElDoc to show diagnostics at point (see Finding diagnostics in GNU Flymake manual).

The ElDoc mode works by scheduling the display of the available documentation for the symbol at point after Emacs has been idle for some short time. This avoids annoying flickering of documentation messages in the echo area or the mode line when you type quickly and without delay.

You can also trigger the display of documentation for a symbol at point by using the command M-x eldoc-print-current-symbol-info.

The following variables can be used to configure ElDoc mode:

eldoc-idle-delay

The value of this user option controls the amount of idle time before the at-point documentation is displayed. It should be set to the number of seconds to wait; the value of zero means to display without any delay. The default is 0.5 sec.

eldoc-print-after-edit

If this user option is non-nil, ElDoc will show documentation only after some editing command, like inserting or deleting some text. This comes in handy if you want Emacs to display documentation only about symbols that you type, but not about symbols that are already in the buffer (so just reading the source code will not show documentation). The default value is nil. If you change the value, you need to toggle eldoc-mode off and on again.

eldoc-echo-area-use-multiline-p

This user option controls whether and how to truncate documentation text if it is longer than the echo-area can display as a single screen line. If the value is a positive number, it specifies the number of screen lines that ElDoc is allowed to display in the echo area without truncating the documentation. A positive integer specifies the absolute maximum number of screen lines to use; a floating-point number specifies the number of screen lines as a fraction of the frame’s height. The value of t means never truncate the documentation (the echo-area will be resized up to the height allowed by max-mini-window-height, see Editing in the Minibuffer), whereas the value of nil means truncate if the documentation is longer than a single screen line. Finally, the special value truncate-sym-name-if-fit (the default) means to truncate the part of the documentation that represents a symbol’s name if doing that will allow the documentation to fit on a single screen line.

eldoc-echo-area-display-truncation-message

If non-nil (the default), and documentation shown in the echo area is truncated because it’s too long, follow the documentation by instructions about how to view the complete documentation text. If nil, just indicate with ‘’ that the documentation was truncated.

eldoc-echo-area-prefer-doc-buffer

If the value of this user option is t, ElDoc will not show the documentation in the echo area if the ElDoc buffer with the documentation is already displayed in some window. (You can use the command M-x eldoc-doc-buffer any time to show the ElDoc buffer.) If the value of this option is the symbol maybe, the documentation will not be displayed in the echo area if the ElDoc buffer is shown in some window, and the documentation text has to be truncated if displayed in the echo area. Finally, the value of nil (the default) means always show the documentation in the echo area.

eldoc-documentation-strategy

This customizable variable’s value is the function which is used to retrieve and display documentation for the symbol at point. The documentation is produced by the functions in the hook eldoc-documentation-functions. The default value of eldoc-documentation-strategy specifies that ElDoc should display the first documentation text produced by functions in the eldoc-documentation-functions hook, but you can customize eldoc-documentation-strategy to work in other ways, such as displaying all of the documentation texts concatenated together.

eldoc-documentation-functions

This abnormal hook’s value is a list of functions that can produce documentation for the symbol at point as appropriate for the current buffer’s major-mode. These functions act as a collection of backends for ElDoc. Major modes register their documentation lookup functions with ElDoc by adding their functions to the buffer-local value of this variable.


27.7 Hideshow minor mode

Hideshow mode is a buffer-local minor mode that allows you to selectively display portions of a program, which are referred to as blocks. Type M-x hs-minor-mode to toggle this minor mode (see Minor Modes).

When you use Hideshow mode to hide a block, the block disappears from the screen, to be replaced by an ellipsis (three periods in a row). Just what constitutes a block depends on the major mode. In C mode and related modes, blocks are delimited by braces, while in Lisp mode they are delimited by parentheses. Multi-line comments also count as blocks.

Hideshow mode provides the following commands:

C-c @ C-h
C-c @ C-d

Hide the current block (hs-hide-block).

C-c @ C-s

Show the current block (hs-show-block).

C-c @ C-c
C-c @ C-e
S-mouse-2

Either hide or show the current block (hs-toggle-hiding).

C-c @ C-M-h
C-c @ C-t

Hide all top-level blocks (hs-hide-all).

C-c @ C-M-s
C-c @ C-a

Show all blocks in the buffer (hs-show-all).

C-u n C-c @ C-l

Hide all blocks n levels below this block (hs-hide-level).

These variables can be used to customize Hideshow mode:

hs-hide-comments-when-hiding-all

If non-nil, C-c @ C-M-h (hs-hide-all) hides comments too.

hs-isearch-open

This variable specifies the conditions under which incremental search should unhide a hidden block when matching text occurs within the block. Its value should be either code (unhide only code blocks), comment (unhide only comments), t (unhide both code blocks and comments), or nil (unhide neither code blocks nor comments). The default value is code.


27.8 Completion for Symbol Names

Completion is normally done in the minibuffer (see Completion), but you can also complete symbol names in ordinary Emacs buffers.

In most programming language modes, C-M-i (or M-TAB16) invokes the command completion-at-point, which generates the list of possible completions for the symbol at point. This command uses the available support facilities to come up with the completion candidates:

  • If Eglot is activated for the current buffer’s project (see Working with Projects) and the current buffer’s major mode, the command tries to use the corresponding language server for producing the list of completion candidates. See Eglot Features in Eglot: The Emacs LSP Client.
  • If Semantic mode is enabled (see Semantic), the command tries to use the Semantic parser data for completion.
  • If Semantic mode is not enabled or fails at performing completion, the command tries to complete using the selected tags table (see Tags Tables); you need to visit the tags table with M-x visit-tags-table for that to work.
  • In Emacs Lisp mode, the command performs completion using the function, variable, or property names defined in the current Emacs session.

In all other respects, in-buffer symbol completion behaves like minibuffer completion. For instance, if Emacs cannot complete to a unique symbol, it displays a list of completion alternatives in another window. Then you can use the keys M-DOWN and M-UP to navigate through the completions displayed in the completions buffer without leaving the original buffer, and the key M-RET to insert the currently highlighted completion to the buffer. See Completion.

In Text mode and related modes, M-TAB completes words based on the spell-checker’s dictionary. See Checking and Correcting Spelling.


27.9 MixedCase Words

Some programming styles make use of mixed-case (or “CamelCase”) symbols like ‘unReadableSymbol’. (In the GNU project, we recommend using underscores to separate words within an identifier, rather than using case distinctions.) Emacs has various features to make it easier to deal with such symbols.

Glasses mode is a buffer-local minor mode that makes it easier to read such symbols, by altering how they are displayed. By default, it displays extra underscores between each lower-case letter and the following capital letter. This does not alter the buffer text, only how it is displayed.

To toggle Glasses mode, type M-x glasses-mode (see Minor Modes). When Glasses mode is enabled, the minor mode indicator ‘o^o’ appears in the mode line. For more information about Glasses mode, type C-h P glasses RET.

Subword mode is another buffer-local minor mode. In subword mode, Emacs’s word commands recognize upper case letters in ‘StudlyCapsIdentifiers’ as word boundaries. When Subword mode is enabled, the minor mode indicator ‘,’ appears in the mode line. See also the similar superword-mode (see Other Features Useful for Editing Programs).


27.10 Semantic

Semantic is a package that provides language-aware editing commands based on source code parsers. This section provides a brief description of Semantic; for full details, see Semantic in Semantic.

Most of the language-aware features in Emacs, such as Font Lock mode (see Font Lock mode), rely on rules of thumb17 that usually give good results but are never completely exact. In contrast, the parsers used by Semantic have an exact understanding of programming language syntax. This allows Semantic to provide search, navigation, and completion commands that are powerful and precise.

To begin using Semantic, type M-x semantic-mode or click on the menu item named ‘Source Code Parsers (Semantic)’ in the ‘Tools’ menu. This enables Semantic mode, a global minor mode.

When Semantic mode is enabled, Emacs automatically attempts to parse each file you visit. Currently, Semantic understands C, C++, HTML, Java, Javascript, Make, Python, Scheme, SRecode, and Texinfo. Within each parsed buffer, the following commands are available:

C-c , j

Prompt for the name of a function defined in the current file, and move point there (semantic-complete-jump-local).

C-c , J

Prompt for the name of a function defined in any file Emacs has parsed, and move point there (semantic-complete-jump).

C-c , SPC

Display a list of possible completions for the symbol at point (semantic-complete-analyze-inline). This also activates a set of special key bindings for choosing a completion: RET accepts the current completion, M-n and M-p cycle through possible completions, TAB completes as far as possible and then cycles, and C-g or any other key aborts completion.

C-c , l

Display a list of the possible completions of the symbol at point, in another window (semantic-analyze-possible-completions).

In addition to the above commands, the Semantic package provides a variety of other ways to make use of parser information. For instance, you can use it to display a list of completions when Emacs is idle. See Semantic in Semantic, for details.


27.11 Other Features Useful for Editing Programs

Some Emacs commands that aren’t designed specifically for editing programs are useful for that nonetheless.

The Emacs commands that operate on words, sentences and paragraphs are useful for editing code. Most symbol names contain words (see Words), while sentences can be found in strings and comments (see Sentences). As for paragraphs, they are defined in most programming language modes to begin and end at blank lines (see Paragraphs). Therefore, judicious use of blank lines to make the program clearer will also provide useful chunks of text for the paragraph commands to work on. Auto Fill mode, if enabled in a programming language major mode, indents the new lines which it creates.

Superword mode is a buffer-local minor mode that causes editing and motion commands to treat symbols (e.g., ‘this_is_a_symbol’) as words. When Superword mode is enabled, the minor mode indicator ‘²’ appears in the mode line. See also the similar subword-mode (see MixedCase Words).

Electric Layout mode (M-x electric-layout-mode) is a global minor mode that automatically inserts newlines when you type certain characters; for example, ‘{’, ‘}’ and ‘;’ in Javascript mode.

Apart from Hideshow mode (see Hideshow minor mode), another way to selectively display parts of a program is to use the selective display feature (see Selective Display). Programming modes often also support Outline minor mode (see Outline Mode), which can be used with the Foldout package (see Folding Editing).

Prettify Symbols mode is a buffer-local minor mode that replaces certain strings with more attractive versions for display purposes. For example, in Emacs Lisp mode, it replaces the string ‘lambda’ with the Greek lambda character ‘λ’. In a TeX buffer, it will replace ‘\alpha’ … ‘\omega’ and other math macros with their Unicode characters. You may wish to use this in non-programming modes as well. You can customize the mode by adding more entries to prettify-symbols-alist. More elaborate customization is available via customizing prettify-symbols-compose-predicate if its default value prettify-symbols-default-compose-p is not appropriate. There is also a global version, global-prettify-symbols-mode, which enables the mode in all buffers that support it.

The symbol at point can be shown in its original form. This is controlled by the variable prettify-symbols-unprettify-at-point: if non-nil, the original form of symbol at point will be restored for as long as point is at it.


This section gives a brief description of the special features available in C, C++, Objective-C, Java, CORBA IDL, Pike and AWK modes. (These are called “C mode and related modes”.) For more details, see the CC mode Info manual, which is distributed with Emacs.


27.12.1 C Mode Motion Commands

This section describes commands for moving point, in C mode and related modes.

C-M-a
C-M-e

Move point to the beginning or end of the current function or top-level definition. In languages with enclosing scopes (such as C++’s classes) the current function is the immediate one, possibly inside a scope. Otherwise it is the one defined by the least enclosing braces. (By contrast, beginning-of-defun and end-of-defun search for braces in column zero.) See Moving by Defuns.

C-c C-u

Move point back to the containing preprocessor conditional, leaving the mark behind. A prefix argument acts as a repeat count. With a negative argument, move point forward to the end of the containing preprocessor conditional.

#elif’ is equivalent to ‘#else’ followed by ‘#if’, so the function will stop at a ‘#elif’ when going backward, but not when going forward.

C-c C-p

Move point back over a preprocessor conditional, leaving the mark behind. A prefix argument acts as a repeat count. With a negative argument, move forward.

C-c C-n

Move point forward across a preprocessor conditional, leaving the mark behind. A prefix argument acts as a repeat count. With a negative argument, move backward.

M-a

Move point to the beginning of the innermost C statement (c-beginning-of-statement). If point is already at the beginning of a statement, move to the beginning of the preceding statement. With prefix argument n, move back n − 1 statements.

In comments or in strings which span more than one line, this command moves by sentences instead of statements.

M-e

Move point to the end of the innermost C statement or sentence; like M-a except that it moves in the other direction (c-end-of-statement).


27.12.2 Electric C Characters

In C mode and related modes, certain printing characters are electric—in addition to inserting themselves, they also reindent the current line, and optionally also insert newlines. The electric characters are {, }, :, #, ;, ,, <, >, /, *, (, and ).

You might find electric indentation inconvenient if you are editing chaotically indented code. If you are new to CC Mode, you might find it disconcerting. You can toggle electric action with the command C-c C-l; when it is enabled, ‘/cl’ appears in the mode line after the mode name (where c, if present, is ‘*’ or ‘/’, depending on whether the comment style is block or line). See Minor Modes in The CC Mode Manual, for more about mode-line indicators in CC Mode.

C-c C-l

Toggle electric action (c-toggle-electric-state). With a positive prefix argument, this command enables electric action, with a negative one it disables it.

Electric characters insert newlines only when, in addition to the electric state, the auto-newline feature is enabled (indicated by ‘/cla’ in the mode line after the mode name). You can turn this feature on or off with the command C-c C-a:

C-c C-a

Toggle the auto-newline feature (c-toggle-auto-newline). With a prefix argument, this command turns the auto-newline feature on if the argument is positive, and off if it is negative.

Usually the CC Mode style configures the exact circumstances in which Emacs inserts auto-newlines. You can also configure this directly. See Custom Auto-newlines in The CC Mode Manual.


27.12.3 Hungry Delete Feature in C

If you want to delete an entire block of whitespace at point, you can use hungry deletion. This deletes all the contiguous whitespace either before point or after point in a single operation. Whitespace here includes tabs and newlines, but not comments or preprocessor commands.

C-c C-DEL
C-c DEL

Delete the entire block of whitespace preceding point (c-hungry-delete-backwards).

C-c C-d
C-c C-Delete
C-c Delete

Delete the entire block of whitespace after point (c-hungry-delete-forward).

As an alternative to the above commands, you can enable hungry delete mode. When this feature is enabled (indicated by ‘h’ after a ‘/’ in the mode line after the mode name), a single DEL deletes all preceding whitespace, not just one space, and a single C-d (but not plain Delete) deletes all following whitespace.

M-x c-toggle-hungry-state

Toggle the hungry-delete feature (c-toggle-hungry-state). With a prefix argument, this command turns the hungry-delete feature on if the argument is positive, and off if it is negative.

The variable c-hungry-delete-key controls whether the hungry-delete feature is enabled.


27.12.4 Other Commands for C Mode

M-x c-context-line-break

This command inserts a line break and indents the new line in a manner appropriate to the context. In normal code, it does the work of RET (newline), in a C preprocessor line it additionally inserts a ‘\’ at the line break, and within comments it’s like M-j (c-indent-new-comment-line).

c-context-line-break isn’t bound to a key by default, but it needs a binding to be useful. The following code will bind it to RET. We use c-initialization-hook here to make sure the keymap is loaded before we try to change it.

(defun my-bind-clb ()
  (keymap-set c-mode-base-map "RET"
              'c-context-line-break))
(add-hook 'c-initialization-hook 'my-bind-clb)
C-M-h

Put mark at the end of a function definition, and put point at the beginning (c-mark-function).

M-q

Fill a paragraph, handling C and C++ comments (c-fill-paragraph). If any part of the current line is a comment or within a comment, this command fills the comment or the paragraph of it that point is in, preserving the comment indentation and comment delimiters.

C-c C-e

Run the C preprocessor on the text in the region, and show the result, which includes the expansion of all the macro calls (c-macro-expand). The buffer text before the region is also included in preprocessing, for the sake of macros defined there, but the output from this part isn’t shown.

When you are debugging C code that uses macros, sometimes it is hard to figure out precisely how the macros expand. With this command, you don’t have to figure it out; you can see the expansions.

C-c C-\

Insert or align ‘\’ characters at the ends of the lines of the region (c-backslash-region). This is useful after writing or editing a C macro definition.

If a line already ends in ‘\’, this command adjusts the amount of whitespace before it. Otherwise, it inserts a new ‘\’. However, the last line in the region is treated specially; no ‘\’ is inserted on that line, and any ‘\’ there is deleted.

M-x cpp-highlight-buffer

Highlight parts of the text according to its preprocessor conditionals. This command displays another buffer named *CPP Edit*, which serves as a graphic menu for selecting how to display particular kinds of conditionals and their contents. After changing various settings, click on ‘[A]pply these settings’ (or go to that buffer and type a) to rehighlight the C mode buffer accordingly.

C-c C-s

Display the syntactic information about the current source line (c-show-syntactic-information). This information directs how the line is indented.

M-x cwarn-mode
M-x global-cwarn-mode

CWarn minor mode highlights certain suspicious C and C++ constructions:

  • Assignments inside expressions.
  • Semicolon following immediately after ‘if’, ‘for’, and ‘while’ (except after a ‘do … while’ statement);
  • C++ functions with reference parameters.

You can enable the mode for one buffer with the command M-x cwarn-mode, or for all suitable buffers with the command M-x global-cwarn-mode or by customizing the variable global-cwarn-mode. You must also enable Font Lock mode to make it work.

M-x hide-ifdef-mode

Hide-ifdef minor mode hides selected code within ‘#if’ and ‘#ifdef’ preprocessor blocks. If you change the variable hide-ifdef-shadow to t, Hide-ifdef minor mode shadows preprocessor blocks by displaying them with a less prominent face, instead of hiding them entirely. See the documentation string of hide-ifdef-mode for more information.

Find a file related in a special way to the file visited by the current buffer. Typically this will be the header file corresponding to a C/C++ source file, or vice versa. The variable ff-related-file-alist specifies how to compute related file names.


27.13 Asm Mode

Asm mode is a major mode for editing files of assembler code. It defines these commands:

TAB

tab-to-tab-stop.

C-j

Insert a newline and then indent using tab-to-tab-stop.

:

Insert a colon and then remove the indentation from before the label preceding colon. Then do tab-to-tab-stop.

;

Insert or align a comment.

The variable asm-comment-char specifies which character starts comments in assembler syntax.


27.14 Fortran Mode

Fortran mode is meant for editing fixed form (and also tab format) source code (normally Fortran 77). For editing more modern free-form source code (Fortran 90, 95, 2003, 2008), use F90 mode (f90-mode). Emacs normally uses Fortran mode for files with extension ‘.f’, ‘.F’ or ‘.for’, and F90 mode for the extensions ‘.f90’, ‘.f95’, ‘.f03’ and ‘.f08’. Customize auto-mode-alist to add more extensions. GNU Fortran supports both free and fixed form. This manual mainly documents Fortran mode, but the corresponding F90 mode features are mentioned when relevant.

Fortran mode provides special motion commands for Fortran statements and subprograms, and indentation commands that understand Fortran conventions of nesting, line numbers and continuation statements. Fortran mode has support for Auto Fill mode that breaks long lines into proper Fortran continuation lines. Fortran mode also supports Hideshow minor mode (see Hideshow minor mode), and Imenu (see Imenu).

Special commands for comments are provided because Fortran comments are unlike those of other languages. Built-in abbrevs optionally save typing when you insert Fortran keywords.

Use M-x fortran-mode to switch to this major mode. This command runs the hook fortran-mode-hook. See Hooks.


27.14.1 Motion Commands

In addition to the normal commands for moving by and operating on defuns (Fortran subprograms—functions and subroutines, as well as modules for F90 mode, using the commands fortran-end-of-subprogram and fortran-beginning-of-subprogram), Fortran mode provides special commands to move by statements and other program units.

C-c C-n

Move to the beginning of the next statement (fortran-next-statement/f90-next-statement).

C-c C-p

Move to the beginning of the previous statement (fortran-previous-statement/f90-previous-statement). If there is no previous statement (i.e., if called from the first statement in the buffer), move to the start of the buffer.

C-c C-e

Move point forward to the start of the next code block, or the end of the current one, whichever comes first (f90-next-block). A code block is a subroutine, ifendif statement, and so forth. This command exists for F90 mode only, not Fortran mode. With a numeric argument, it moves forward that many blocks.

C-c C-a

Move point backward to the previous block (f90-previous-block). This is like f90-next-block, but moves backwards.

C-M-n

Move to the end of the current code block (fortran-end-of-block/f90-end-of-block). With a numeric argument, move forward that number of blocks. The mark is set before moving point. The F90 mode version of this command checks for consistency of block types and labels (if present), but it does not check the outermost block since that may be incomplete.

C-M-p

Move to the start of the current code block (fortran-beginning-of-block/f90-beginning-of-block). This is like fortran-end-of-block, but moves backwards.

The commands fortran-beginning-of-subprogram and fortran-end-of-subprogram move to the start or end of the current subprogram, respectively. The commands fortran-mark-do and fortran-mark-if mark the end of the current do or if block, and move point to the start.


27.14.2 Fortran Indentation

Special commands and features are needed for indenting fixed (or tab) form Fortran code in order to make sure various syntactic entities (line numbers, comment line indicators and continuation line flags) appear in the required columns.


27.14.2.1 Fortran Indentation and Filling Commands

C-M-j

Break the current line at point and set up a continuation line (fortran-split-line).

M-^

Join this line to the previous line (fortran-join-line).

C-M-q

Indent all the lines of the subprogram that point is in (fortran-indent-subprogram).

M-q

Fill a comment block or statement (using fortran-fill-paragraph or fortran-fill-statement).

The key C-M-q runs fortran-indent-subprogram, a command to reindent all the lines of the Fortran subprogram (function or subroutine) containing point.

The key C-M-j runs fortran-split-line, which splits a line in the appropriate fashion for Fortran. In a non-comment line, the second half becomes a continuation line and is indented accordingly. In a comment line, both halves become separate comment lines.

M-^ or C-c C-d run the command fortran-join-line, which joins a continuation line back to the previous line, roughly as the inverse of fortran-split-line. The point must be on a continuation line when this command is invoked.

M-q in Fortran mode fills the comment block or statement that point is in. This removes any excess statement continuations.


27.14.2.2 Continuation Lines

Most Fortran 77 compilers allow two ways of writing continuation lines. If the first non-space character on a line is in column 5, then that line is a continuation of the previous line. We call this fixed form. (In GNU Emacs we always count columns from 0; but note that the Fortran standard counts from 1. You can customize the variable column-number-indicator-zero-based to make the column display Fortran-like; see Optional Mode Line Features.) The variable fortran-continuation-string specifies what character to put in column 5. A line that starts with a tab character followed by any digit except ‘0’ is also a continuation line. We call this style of continuation tab format. (Fortran 90 introduced free-form continuation lines.)

Fortran mode can use either style of continuation line. When you enter Fortran mode, it tries to deduce the proper continuation style automatically from the buffer contents. It does this by scanning up to fortran-analyze-depth (default 100) lines from the start of the buffer. The first line that begins with either a tab character or six spaces determines the choice. If the scan fails (for example, if the buffer is new and therefore empty), the value of fortran-tab-mode-default (nil for fixed form, and non-nil for tab format) is used. ‘/t’ (fortran-tab-mode-string) in the mode line indicates tab format is selected. Fortran mode sets the value of indent-tabs-mode accordingly.

If the text on a line starts with the Fortran continuation marker ‘$’, or if it begins with any non-whitespace character in column 5, Fortran mode treats it as a continuation line. When you indent a continuation line with TAB, it converts the line to the current continuation style. When you split a Fortran statement with C-M-j, the continuation marker on the newline is created according to the continuation style.

The setting of continuation style affects several other aspects of editing in Fortran mode. In fixed form mode, the minimum column number for the body of a statement is 6. Lines inside of Fortran blocks that are indented to larger column numbers must use only the space character for whitespace. In tab format mode, the minimum column number for the statement body is 8, and the whitespace before column 8 must consist of one tab character.


27.14.2.3 Line Numbers

If a number is the first non-whitespace in the line, Fortran indentation assumes it is a line number and moves it to columns 0 through 4. (Columns always count from 0 in Emacs, but setting column-number-indicator-zero-based to nil can change that, see Optional Mode Line Features.)

Line numbers of four digits or less are normally indented one space. The variable fortran-line-number-indent controls this; it specifies the maximum indentation a line number can have. The default value of the variable is 1. Fortran mode tries to prevent line number digits passing column 4, reducing the indentation below the specified maximum if necessary. If fortran-line-number-indent has the value 5, line numbers are right-justified to end in column 4.

Simply inserting a line number is enough to indent it according to these rules. As each digit is inserted, the indentation is recomputed. To turn off this feature, set the variable fortran-electric-line-number to nil.


27.14.2.4 Syntactic Conventions

Fortran mode assumes that you follow certain conventions that simplify the task of understanding a Fortran program well enough to indent it properly:

  • Two nested ‘do’ loops never share a ‘continue’ statement.
  • Fortran keywords such as ‘if’, ‘else’, ‘then’, ‘do’ and others are written without embedded whitespace or line breaks.

    Fortran compilers generally ignore whitespace outside of string constants, but Fortran mode does not recognize these keywords if they are not contiguous. Constructs such as ‘else if’ or ‘end do’ are acceptable, but the second word should be on the same line as the first and not on a continuation line.

If you fail to follow these conventions, the indentation commands may indent some lines unaesthetically. However, a correct Fortran program retains its meaning when reindented even if the conventions are not followed.


27.14.2.5 Variables for Fortran Indentation

Several additional variables control how Fortran indentation works:

fortran-do-indent

Extra indentation within each level of ‘do’ statement (default 3).

fortran-if-indent

Extra indentation within each level of ‘if’, ‘select case’, or ‘where’ statements (default 3).

fortran-structure-indent

Extra indentation within each level of ‘structure’, ‘union’, ‘map’, or ‘interface’ statements (default 3).

fortran-continuation-indent

Extra indentation for bodies of continuation lines (default 5).

fortran-check-all-num-for-matching-do

In Fortran 77, a numbered ‘do’ statement is terminated by any statement with a matching line number. It is common (but not compulsory) to use a ‘continue’ statement for this purpose. If this variable has a non-nil value, indenting any numbered statement must check for a ‘do’ that ends there. If you always end ‘do’ statements with a ‘continue’ line (or if you use the more modern ‘enddo’), then you can speed up indentation by setting this variable to nil (the default).

fortran-blink-matching-if

If this is t, indenting an ‘endif’ (or ‘enddo’) statement moves the cursor momentarily to the matching ‘if’ (or ‘do’) statement to show where it is. The default is nil.

fortran-minimum-statement-indent-fixed

Minimum indentation for Fortran statements when using fixed form continuation line style. Statement bodies are never indented by less than this. The default is 6.

fortran-minimum-statement-indent-tab

Minimum indentation for Fortran statements for tab format continuation line style. Statement bodies are never indented by less than this. The default is 8.

The following section describes the variables controlling the indentation of comments.


27.14.3 Fortran Comments

The usual Emacs comment commands assume that a comment can follow a line of code. In Fortran 77, the standard comment syntax requires an entire line to be just a comment. Therefore, Fortran mode replaces the standard Emacs comment commands and defines some new variables.

Fortran mode can also handle the Fortran 90 comment syntax where comments start with ‘!’ and can follow other text. Because only some Fortran 77 compilers accept this syntax, Fortran mode will not insert such comments unless you have said in advance to do so. To do this, set the variable fortran-comment-line-start to ‘"!"’. If you use an unusual value, you may need to change fortran-comment-line-start-skip.

M-;

Align comment or insert new comment (comment-dwim).

C-x ;

Applies to nonstandard ‘!’ comments only (comment-set-column).

C-c ;

Turn all lines of the region into comments, or (with argument) turn them back into real code (fortran-comment-region).

M-; in Fortran mode runs the standard comment-dwim. This recognizes any kind of existing comment and aligns its text appropriately; if there is no existing comment, a comment is inserted and aligned. Inserting and aligning comments are not the same in Fortran mode as in other modes.

When a new comment must be inserted, if the current line is blank, a full-line comment is inserted. On a non-blank line, a nonstandard ‘!’ comment is inserted if you have said you want to use them. Otherwise, a full-line comment is inserted on a new line before the current line.

Nonstandard ‘!’ comments are aligned like comments in other languages, but full-line comments are different. In a standard full-line comment, the comment delimiter itself must always appear in column zero. What can be aligned is the text within the comment. You can choose from three styles of alignment by setting the variable fortran-comment-indent-style to one of these values:

fixed

Align the text at a fixed column, which is the sum of fortran-comment-line-extra-indent and the minimum statement indentation. This is the default.

The minimum indentation is fortran-minimum-statement-indent-tab for tab format continuation line style and fortran-minimum-statement-indent-fixed for fixed form style.

relative

Align the text as if it were a line of code, but with an additional fortran-comment-line-extra-indent columns of indentation.

nil

Don’t move text in full-line comments automatically.

In addition, you can specify the character to be used to indent within full-line comments by setting the variable fortran-comment-indent-char to the single-character string you want to use.

Compiler directive lines, or preprocessor lines, have much the same appearance as comment lines. It is important, though, that such lines never be indented at all, no matter what the value of fortran-comment-indent-style. The variable fortran-directive-re is a regular expression that specifies which lines are directives. Matching lines are never indented, and receive distinctive font-locking.

The normal Emacs comment command C-x ; (comment-set-column) has not been redefined. If you use ‘!’ comments, this command can be used with them. Otherwise, it is useless in Fortran mode.

The command C-c ; (fortran-comment-region) turns all the lines of the region into comments by inserting the string ‘c$$$’ at the front of each one. With a numeric argument, it turns the region back into live code by deleting ‘c$$$’ from the front of each line in it. The string used for these comments can be controlled by setting the variable fortran-comment-region. Note that here we have an example of a command and a variable with the same name; these two uses of the name never conflict because in Lisp and in Emacs it is always clear from the context which one is meant.


27.14.4 Auto Fill in Fortran Mode

Fortran mode has specialized support for Auto Fill mode, which is a minor mode that automatically splits statements as you insert them when they become too wide. Splitting a statement involves making continuation lines using fortran-continuation-string (see Continuation Lines). This splitting happens when you type SPC, RET, or TAB, and also in the Fortran indentation commands. You activate Auto Fill in Fortran mode in the normal way. See Auto Fill Mode.

Auto Fill breaks lines at spaces or delimiters when the lines get longer than the desired width (the value of fill-column). The delimiters (besides whitespace) that Auto Fill can break at are ‘+’, ‘-’, ‘/’, ‘*’, ‘=’, ‘<’, ‘>’, and ‘,’. The line break comes after the delimiter if the variable fortran-break-before-delimiters is nil. Otherwise (and by default), the break comes before the delimiter.

To enable Auto Fill in all Fortran buffers, add auto-fill-mode to fortran-mode-hook. See Hooks.


27.14.5 Checking Columns in Fortran

In standard Fortran 77, anything beyond column 72 is ignored. Most compilers provide an option to change this (for example, ‘-ffixed-line-length-N’ in gfortran). Customize the variable fortran-line-length to change the line length in Fortran mode. Anything beyond this point is font-locked as a comment. (Unless it is inside a string: strings that extend beyond fortran-line-length will confuse font-lock.)

C-c C-r

Display a column ruler momentarily above the current line (fortran-column-ruler).

C-c C-w

Split the current window horizontally temporarily so that it is fortran-line-length columns wide (fortran-window-create-momentarily). This may help you avoid making lines longer than the limit imposed by your Fortran compiler.

C-u C-c C-w

Split the current window horizontally so that it is fortran-line-length columns wide (fortran-window-create). You can then continue editing.

M-x fortran-strip-sequence-nos

Delete all text in column fortran-line-length and beyond.

The command C-c C-r (fortran-column-ruler) shows a column ruler momentarily above the current line. The comment ruler is two lines of text that show you the locations of columns with special significance in Fortran programs. Square brackets show the limits of the columns for line numbers, and curly brackets show the limits of the columns for the statement body. Column numbers appear above them.

Note that the column numbers count from zero, as always in GNU Emacs (but customizing column-number-indicator-zero-based can change column display to match that of Fortran; see Optional Mode Line Features.) As a result, the numbers may be one less than those you are familiar with; but the positions they indicate in the line are standard for Fortran.

The text used to display the column ruler depends on the value of the variable indent-tabs-mode. If indent-tabs-mode is nil, then the value of the variable fortran-column-ruler-fixed is used as the column ruler. Otherwise, the value of the variable fortran-column-ruler-tab is displayed. By changing these variables, you can change the column ruler display.

C-c C-w (fortran-window-create-momentarily) temporarily splits the current window horizontally, making a window fortran-line-length columns wide, so you can see any lines that are too long. Type a space to restore the normal width.

You can also split the window horizontally and continue editing with the split in place. To do this, use C-u C-c C-w (M-x fortran-window-create). By editing in this window you can immediately see when you make a line too wide to be correct Fortran.

The command M-x fortran-strip-sequence-nos deletes all text in column fortran-line-length and beyond, on all lines in the current buffer. This is the easiest way to get rid of old sequence numbers.


27.14.6 Fortran Keyword Abbrevs

Fortran mode provides many built-in abbrevs for common keywords and declarations. These are the same sort of abbrev that you can define yourself. To use them, you must turn on Abbrev mode. See Abbrevs.

The built-in abbrevs are unusual in one way: they all start with a semicolon. For example, one built-in Fortran abbrev is ‘;c’ for ‘continue’. If you insert ‘;c’ and then insert a punctuation character such as a space or a newline, the ‘;c’ expands automatically to ‘continue’, provided Abbrev mode is enabled.

Type ‘;?’ or ‘;C-h’ to display a list of all the built-in Fortran abbrevs and what they stand for.


28 Compiling and Testing Programs

The previous chapter discusses the Emacs commands that are useful for making changes in programs. This chapter deals with commands that assist in the process of compiling and testing programs.


28.1 Running Compilations under Emacs

Emacs can run compilers for languages such as C and Fortran, feeding the compilation log into an Emacs buffer. It can also parse the error messages and show you where the errors occurred.

M-x compile

Run a compiler asynchronously under Emacs, with error messages going to the *compilation* buffer.

M-x recompile
g (Compilation mode)

Invoke a compiler with the same command as in the last invocation of M-x compile.

M-x kill-compilation

Kill the running compilation subprocess.

To run make or another compilation command, type M-x compile. This reads a shell command line using the minibuffer, and then executes the command by running a shell as a subprocess (or inferior process) of Emacs. The output is inserted in a buffer named *compilation*. The current buffer’s default directory is used as the working directory for the execution of the command, so by default compilation takes place in that directory.

The default compilation command is ‘make -k’, which is usually correct for programs compiled using the make utility (the ‘-k’ flag tells make to continue compiling as much as possible after an error). See Make in GNU Make Manual. If you have done M-x compile before, the command that you specified is automatically stored in the variable compile-command; this is used as the default the next time you type M-x compile. A file can also specify a file-local value for compile-command (see Local Variables in Files).

Starting a compilation displays the *compilation* buffer in another window but does not select it. While the compilation is running, the word ‘run’ is shown in the major mode indicator for the *compilation* buffer, and the word ‘Compiling’ appears in all mode lines. You do not have to keep the *compilation* buffer visible while compilation is running; it continues in any case. When the compilation ends, for whatever reason, the mode line of the *compilation* buffer changes to say ‘exit’ (followed by the exit code: ‘[0]’ for a normal exit), or ‘signal’ (if a signal terminated the process).

If you want to watch the compilation transcript as it appears, switch to the *compilation* buffer and move point to the end of the buffer. When point is at the end, new compilation output is inserted above point, which remains at the end. Otherwise, point remains fixed while compilation output is added at the end of the buffer.

While compilation proceeds, the mode line shows the number of errors, warnings, and informational messages emitted by the compiler so far.

If you change the variable compilation-scroll-output to a non-nil value, the *compilation* buffer scrolls automatically to follow the output. If the value is first-error, scrolling stops when the first error appears, leaving point at that error. For any other non-nil value, scrolling continues until there is no more output.

To rerun the last compilation with the same command, type M-x recompile. This reuses the compilation command from the last invocation of M-x compile. It also reuses the *compilation* buffer and starts the compilation in its default directory, which is the directory in which the previous compilation was started. In *compilation* buffers this command is bound to g.

Starting a new compilation also kills any compilation already running in *compilation*, as the buffer can only handle one compilation at any time. However, M-x compile and M-x recompile ask for confirmation before actually killing a compilation that is running; to always automatically kill the compilation without asking, change the variable compilation-always-kill to t. You can also kill a compilation process with the command M-x kill-compilation.

To run two compilations at once, start the first one, then rename the *compilation* buffer (perhaps using rename-uniquely; see Miscellaneous Buffer Operations), then switch buffers and start the other compilation. This will create a new *compilation* buffer.

You can control the environment passed to the compilation command with the variable compilation-environment. Its value is a list of environment variable settings; each element should be a string of the form "envvarname=value". These environment variable settings override the usual ones.

Displaying extremely long lines in compilation output can slow Emacs down. Lines that are longer than compilation-max-output-line-length will have the portion that’s exceeds that limit hidden behind a button that can be clicked on to reveal the hidden portion. Set this variable to nil to never hide anything.


28.2 Compilation Mode

The *compilation* buffer uses a major mode called Compilation mode. Compilation mode turns each error message in the buffer into a hyperlink; you can move point to it and type RET, or click on it with the mouse (see Following References with the Mouse), to visit the locus of the error message in a separate window. The locus is the specific position in a file where that error occurred.

The appearance of the *compilation* buffer can be controlled by customizing the faces which are used to highlight parts of the *compilation* buffer, e.g., compilation-error or compilation-warning, for error and warning messages respectively. Note that since those faces inherit from the error and warning faces, it is also possible to customize the parent face directly instead.

Use M-x customize-group RET compilation to see the entire list of customization variables and faces.

If you change the variable compilation-auto-jump-to-first-error to a non-nil value, Emacs automatically visits the locus of the first error message that appears in the *compilation* buffer. (This variable can also have the values if-location-known and first-known, which modify the conditions for automatically visiting the error locus.)

Compilation mode provides the following additional commands. These commands can also be used in *grep* buffers, where the hyperlinks are search matches rather than error messages (see Searching with Grep under Emacs).

M-g M-n
M-g n
C-x `

Visit the locus of the next error message or match (next-error).

M-g M-p
M-g p

Visit the locus of the previous error message or match (previous-error).

M-n

Move point to the next error message or match, without visiting its locus (compilation-next-error).

M-p

Move point to the previous error message or match, without visiting its locus (compilation-previous-error).

M-}

Move point to the next error message or match occurring in a different file (compilation-next-file).

M-{

Move point to the previous error message or match occurring in a different file (compilation-previous-file).

C-c C-f

Toggle Next Error Follow minor mode, which makes cursor motion in the compilation buffer produce automatic source display.

g

Re-run the last command whose output is shown in the *compilation* buffer.

M-x next-error-select-buffer

Select a buffer to be used by next invocation of next-error and previous-error.

To visit errors sequentially, type C-x ` (next-error), or equivalently M-g M-n or M-g n. This command can be invoked from any buffer, not just a Compilation mode buffer. The first time you invoke it after a compilation, it visits the locus of the first error message. Each subsequent M-g M-n visits the next error, in a similar fashion. If you visit a specific error with RET or a mouse click in the *compilation* buffer, subsequent M-g M-n commands advance from there. When M-g M-n finds no more error messages to visit, it signals an error. C-u M-g M-n starts again from the beginning of the compilation buffer, and visits the first locus.

M-g M-p or M-g p (previous-error) iterates through errors in the opposite direction.

The next-error and previous-error commands don’t just act on the errors or matches listed in *compilation* and *grep* buffers; they also know how to iterate through error or match lists produced by other commands, such as M-x occur (see Other Search-and-Loop Commands). If the current buffer contains error messages or matches, these commands will iterate through them; otherwise, Emacs looks for a buffer containing error messages or matches amongst the windows of the selected frame (if the variable next-error-find-buffer-function is customized to the value next-error-buffer-on-selected-frame), then for a buffer used previously by next-error or previous-error, and finally all other buffers. Any buffer these commands iterate through that is not currently displayed in a window will be displayed. You can use the next-error-select-buffer command to switch to a different buffer to be used by the subsequent invocation of next-error.

By default, the next-error and previous-error commands skip less important messages. The variable compilation-skip-threshold controls this. The default value, 1, means to skip anything less important than a warning. A value of 2 means to skip anything less important than an error, while 0 means not to skip any messages.

When Emacs visits the locus of an error message, it momentarily highlights the relevant source line. The duration of this highlight is determined by the variable next-error-highlight for the locus in the selected buffer, and next-error-highlight-no-select for the locus in non-selected buffers. Also you can customize the variable next-error-message-highlight that defines how to highlight the current error message in the buffer that contains messages.

If the *compilation* buffer is shown in a window with a left fringe (see Window Fringes), the locus-visiting commands put an arrow in the fringe, pointing to the current error message. If the window has no left fringe, such as on a text terminal, these commands scroll the window so that the current message is at the top of the window. If you change the variable compilation-context-lines to t, a visible arrow is inserted before column zero instead. If you change the variable to an integer value n, these commands scroll the window so that the current error message is n lines from the top, whether or not there is a fringe; the default value, nil, gives the behavior described above.

Compilation output can sometimes be very verbose, and much of it isn’t of particular interest to a user. The compilation-hidden-output user option should either be a regexp or a list of regexps, and output that matches will be made invisible. For instance, to hide the verbose output from recursive makefiles, you can say something like:

(setq compilation-hidden-output
      '("^make[^\n]+\n"))

To parse messages from the compiler, Compilation mode uses the variable compilation-error-regexp-alist which lists various error message formats and tells Emacs how to extract the locus from each. A similar variable, grep-regexp-alist, tells Emacs how to parse output from a grep command (see Searching with Grep under Emacs).

Compilation mode also defines the keys SPC and DEL to scroll by screenfuls; M-n (compilation-next-error) and M-p (compilation-previous-error) to move to the next or previous error message; and M-{ (compilation-next-file) and M-} (compilation-previous-file) to move to the next or previous error message for a different source file.

You can type C-c C-f to toggle Next Error Follow mode. In this minor mode, ordinary cursor motion in the compilation buffer automatically updates the source buffer, i.e., moving the cursor over an error message causes the locus of that error to be displayed.

The features of Compilation mode are also available in a minor mode called Compilation Minor mode. This lets you parse error messages in any buffer, not just a normal compilation output buffer. Type M-x compilation-minor-mode to enable the minor mode. For instance, in an Rlogin buffer (see Remote Host Shell), Compilation minor mode automatically accesses remote source files by FTP (see File Names).


28.3 Subshells for Compilation

This section includes various techniques and advice for using a shell and its features in compilation buffers. This material is specific to local compilations, and will most probably not work in (or be irrelevant to) compilation buffers whose default directory is on remote hosts.

The M-x compile command uses a shell to run the compilation command, but specifies the option for a noninteractive shell. This means, in particular, that the shell should start with no prompt. If you find your usual shell prompt making an unsightly appearance in the *compilation* buffer, it means you have made a mistake in your shell’s init file by setting the prompt unconditionally. (This init file may be named .bashrc, .profile, .cshrc, .shrc, etc., depending on what shell you use.) The shell init file should set the prompt only if there already is a prompt. Here’s how to do it in bash:

if [ "${PS1+set}" = set ]
then PS1=…
fi

And here’s how to do it in csh:

if ($?prompt) set prompt = …

If you want to customize the value of the TERM environment variable passed to the compilation subshell, customize the variable comint-terminfo-terminal (see Shell Mode Options).

Emacs does not expect a compiler process to launch asynchronous subprocesses; if it does, and they keep running after the main compiler process has terminated, Emacs may kill them or their output may not arrive in Emacs. To avoid this problem, make the main compilation process wait for its subprocesses to finish. In a shell script, you can do this using ‘$!’ and ‘wait’, like this:

(sleep 10; echo 2nd)& pid=$!  # Record pid of subprocess
echo first message
wait $pid                     # Wait for subprocess

If the background process does not output to the compilation buffer, so you only need to prevent it from being killed when the main compilation process terminates, this is sufficient:

nohup command; sleep 1

On MS-DOS, asynchronous subprocesses are not supported, so M-x compile runs the compilation command synchronously (i.e., you must wait until the command finishes before you can do anything else in Emacs). See Emacs and MS-DOS.


28.4 Searching with Grep under Emacs

Just as you can run a compiler from Emacs and then visit the lines with compilation errors, you can also run grep and then visit the lines on which matches were found. This works by treating the matches reported by grep as if they were errors. The output buffer uses Grep mode, which is a variant of Compilation mode (see Compilation Mode).

M-x grep
M-x lgrep

Run grep asynchronously under Emacs, listing matching lines in the buffer named *grep*.

M-x grep-find
M-x find-grep
M-x rgrep

Run grep via find, and collect output in the *grep* buffer.

M-x zrgrep

Run zgrep and collect output in the *grep* buffer.

M-x kill-grep

Kill the running grep subprocess.

To run grep, type M-x grep, then enter a command line that specifies how to run grep. Use the same arguments you would give grep when running it normally: a grep-style regexp (usually in single-quotes to quote the shell’s special characters) followed by file names, which may use wildcards. If you specify a prefix argument for M-x grep, it finds the identifier (see Find Identifier References) in the buffer around point, and puts that into the default grep command.

Your command need not simply run grep; you can use any shell command that produces output in the same format. For instance, you can chain grep commands, like this:

grep -nH -e foo *.el | grep bar | grep toto

The output from grep goes in the *grep* buffer. You can find the corresponding lines in the original files using M-g M-n, RET, and so forth, just like compilation errors. See Compilation Mode, for detailed description of commands and key bindings available in the *grep* buffer.

Some grep programs accept a ‘--color’ option to output special markers around matches for the purpose of highlighting. You can make use of this feature by setting grep-highlight-matches to t. When displaying a match in the source buffer, the exact match will be highlighted, instead of the entire source line. Highlighting is provided via matching the ANSI escape sequences emitted by grep. The matching of the sequences is controlled by grep-match-regexp, which can be customized to accommodate different grep programs.

As with compilation commands (see Running Compilations under Emacs), while the grep command runs, the mode line shows the running number of matches found and highlighted so far.

The grep commands will offer to save buffers before running. This is controlled by the grep-save-buffers variable. The possible values are either nil (don’t save), ask (ask before saving), or a function which will be used as a predicate (and is called with the file name as the parameter and should return non-nil if the buffer is to be saved). Any other non-nil value means that all buffers should be saved without asking. The default is ask.

The command M-x grep-find (also available as M-x find-grep) is similar to M-x grep, but it supplies a different initial default for the command—one that runs both find and grep, so as to search every file in a directory tree. See also the find-grep-dired command, in Dired and find.

The commands M-x lgrep (local grep) and M-x rgrep (recursive grep) are more user-friendly versions of grep and grep-find, which prompt separately for the regular expression to match, the files to search, and the base directory for the search. Case sensitivity of the search is controlled by the current value of case-fold-search. The command M-x zrgrep is similar to M-x rgrep, but it calls zgrep instead of grep to search the contents of gzipped files.

These commands build the shell commands based on the variables grep-template (for lgrep) and grep-find-template (for rgrep). The files to search can use aliases defined in the variable grep-files-aliases.

Directories listed in the variable grep-find-ignored-directories are automatically skipped by M-x rgrep. The default value includes the data directories used by various version control systems.

By default, the shell commands constructed for lgrep, rgrep, and zgrep are abbreviated for display by concealing the part that contains a long list of files and directories to ignore. You can reveal the concealed part by clicking on the button with ellipsis, which represents them. You can also interactively toggle viewing the concealed part by typing M-x grep-find-toggle-abbreviation. To disable this abbreviation of the shell commands, customize the option grep-find-abbreviate to a nil value.


28.5 Finding Syntax Errors On The Fly

Flymake mode is a minor mode that performs on-the-fly syntax checking for many programming and markup languages, including C, C++, Perl, HTML, and TeX/LaTeX. It is somewhat analogous to Flyspell mode, which performs spell checking for ordinary human languages in a similar fashion (see Checking and Correcting Spelling). As you edit a file, Flymake mode runs an appropriate syntax checking tool in the background, using a temporary copy of the buffer. It then parses the error and warning messages, and highlights the erroneous lines in the buffer. The syntax checking tool used depends on the language; for example, for C/C++ files this is usually the C compiler. Flymake can also use build tools such as make for checking complicated projects.

To enable Flymake mode, type M-x flymake-mode. You can jump to the errors that it finds by using M-x flymake-goto-next-error and M-x flymake-goto-prev-error. To display a detailed overview of the diagnostics for the current buffer, use the command M-x flymake-show-buffer-diagnostics; to display a similar overview of diagnostics for the entire project (see Working with Projects), use M-x flymake-show-project-diagnostics.

For more details about using Flymake, see Flymake in The Flymake Manual.


28.6 Running Debuggers Under Emacs

The GUD (Grand Unified Debugger) library provides an Emacs interface to a wide variety of symbolic debuggers. It can run the GNU Debugger (GDB), as well as DBX, SDB, XDB, Guile REPL debug commands, Perl’s debugging mode, the Python debugger PDB, and the Java Debugger JDB.

Emacs provides a special interface to GDB, which uses extra Emacs windows to display the state of the debugged program. See GDB Graphical Interface.

Emacs also has a built-in debugger for Emacs Lisp programs. See The Lisp Debugger in the Emacs Lisp Reference Manual.


28.6.1 Starting GUD

There are several commands for starting a debugger subprocess, each corresponding to a particular debugger program.

M-x gdb

Run GDB as a subprocess, and interact with it via an IDE-like Emacs interface. See GDB Graphical Interface, for more information about this command.

M-x gud-gdb

Run GDB, using a GUD interaction buffer for input and output to the GDB subprocess (see Debugger Operation). If such a buffer already exists, switch to it; otherwise, create the buffer and switch to it.

The other commands in this list do the same, for other debugger programs.

M-x perldb

Run the Perl interpreter in debug mode.

M-x jdb

Run the Java debugger.

M-x pdb

Run the Python debugger.

M-x guiler

Run Guile REPL for debugging Guile Scheme programs.

M-x dbx

Run the DBX debugger.

M-x xdb

Run the XDB debugger.

M-x sdb

Run the SDB debugger.

Each of these commands reads a command line to invoke the debugger, using the minibuffer. The minibuffer’s initial contents contain the standard executable name and options for the debugger, and sometimes also a guess for the name of the executable file you want to debug. Shell wildcards and variables are not allowed in this command line. Emacs assumes that the first command argument which does not start with a ‘-’ is the executable file name.

Tramp provides a facility for remote debugging, whereby both the debugger and the program being debugged are on the same remote host. See Running a debugger on a remote host in The Tramp Manual, for details. This is separate from GDB’s remote debugging feature, where the program and the debugger run on different machines (see Debugging Remote Programs in The GNU debugger).


28.6.2 Debugger Operation

The GUD interaction buffer is an Emacs buffer which is used to send text commands to a debugger subprocess, and record its output. This is the basic interface for interacting with a debugger, used by M-x gud-gdb and other commands listed in Starting GUD. The M-x gdb command extends this interface with additional specialized buffers for controlling breakpoints, stack frames, and other aspects of the debugger state (see GDB Graphical Interface).

The GUD interaction buffer uses a variant of Shell mode, so the Emacs commands defined by Shell mode are available (see Shell Mode). Completion is available for most debugger commands (see Completion), and you can use the usual Shell mode history commands to repeat them. See Commands of GUD, for special commands that can be used in the GUD interaction buffer.

As you debug a program, Emacs displays the relevant source files by visiting them in Emacs buffers, with an arrow in the left fringe indicating the current execution line. (On a text terminal, the arrow appears as ‘=>’, overlaid on the first two text columns.) Moving point in such a buffer does not move the arrow. You are free to edit these source files, but note that inserting or deleting lines will throw off the arrow’s positioning, as Emacs has no way to figure out which edited source line corresponds to the line reported by the debugger subprocess. To update this information, you typically have to recompile and restart the program.

GUD Tooltip mode is a global minor mode that adds tooltip support to GUD. To toggle this mode, type M-x gud-tooltip-mode. It is disabled by default. If enabled, you can move the mouse pointer over a variable, a function, or a macro (collectively called identifiers) to show their values in tooltips (see Tooltips). If just placing the mouse pointer over an expression doesn’t show the value of the expression you had in mind, you can tell Emacs more explicitly what expression to evaluate by dragging the mouse over the expression, then leaving the mouse inside the marked area. The GUD Tooltip mode takes effect in the GUD interaction buffer, and in all source buffers with major modes listed in the variable gud-tooltip-modes. If you turned off the tooltip mode, values are shown in the echo area instead of a tooltip.

When using GUD Tooltip mode with M-x gud-gdb, displaying an expression’s value in GDB can sometimes expand a macro, potentially causing side effects in the debugged program. For that reason, using tooltips in gud-gdb is disabled. If you use the M-x gdb interface, this problem does not occur, as there is special code to avoid side-effects; furthermore, you can display macro definitions associated with an identifier when the program is not executing.


28.6.3 Commands of GUD

GUD provides commands for setting and clearing breakpoints, selecting stack frames, and stepping through the program.

C-x C-a C-b

Set a breakpoint on the source line that point is on.

C-x C-a C-b (gud-break), when called in a source buffer, sets a debugger breakpoint on the current source line. This command is available only after starting GUD. If you call it in a buffer that is not associated with any debugger subprocess, it signals an error.

The following commands are available both in the GUD interaction buffer and globally, but with different key bindings. The keys starting with C-c are available only in the GUD interaction buffer, while those starting with C-x C-a are available globally. Some of these commands are also available via the tool bar; some are not supported by certain debuggers.

C-c C-l
C-x C-a C-l

Display, in another window, the last source line referred to in the GUD interaction buffer (gud-refresh).

C-c C-s
C-x C-a C-s

Execute the next single line of code (gud-step). If the line contains a function call, execution stops after entering the called function.

C-c C-n
C-x C-a C-n

Execute the next single line of code, stepping across function calls without stopping inside the functions (gud-next).

C-c C-i
C-x C-a C-i

Execute a single machine instruction (gud-stepi).

C-c C-p
C-x C-a C-p

Evaluate the expression at point (gud-print). If Emacs does not print the exact expression that you want, mark it as a region first.

C-c C-r
C-x C-a C-r

Continue execution without specifying any stopping point. The program will run until it hits a breakpoint, terminates, or gets a signal that the debugger is checking for (gud-cont).

C-c C-d
C-x C-a C-d

Delete the breakpoint(s) on the current source line, if any (gud-remove). If you use this command in the GUD interaction buffer, it applies to the line where the program last stopped.

C-c C-t
C-x C-a C-t

Set a temporary breakpoint on the current source line, if any (gud-tbreak). If you use this command in the GUD interaction buffer, it applies to the line where the program last stopped.

C-c <
C-x C-a <

Select the next enclosing stack frame (gud-up). This is equivalent to the GDB command ‘up’.

C-c >
C-x C-a >

Select the next inner stack frame (gud-down). This is equivalent to the GDB command ‘down’.

C-c C-u
C-x C-a C-u

Continue execution to the current line (gud-until). The program will run until it hits a breakpoint, terminates, gets a signal that the debugger is checking for, or reaches the line on which the cursor currently sits.

C-c C-f
C-x C-a C-f

Run the program until the selected stack frame returns or stops for some other reason (gud-finish).

If you are using GDB, these additional key bindings are available:

C-x C-a C-j

Only useful in a source buffer, gud-jump transfers the program’s execution point to the current line. In other words, the next line that the program executes will be the one where you gave the command. If the new execution line is in a different function from the previously one, GDB prompts for confirmation since the results may be bizarre. See the GDB manual entry regarding jump for details.

TAB

With GDB, complete a symbol name (gud-gdb-complete-command). This key is available only in the GUD interaction buffer.

These commands interpret a numeric argument as a repeat count, when that makes sense.

Because TAB serves as a completion command, you can’t use it to enter a tab as input to the program you are debugging with GDB. Instead, type C-q TAB to enter a tab.


28.6.4 GUD Customization

On startup, GUD runs one of the following hooks: gdb-mode-hook, if you are using GDB; dbx-mode-hook, if you are using DBX; sdb-mode-hook, if you are using SDB; xdb-mode-hook, if you are using XDB; guiler-mode-hook for Guile REPL debugging; perldb-mode-hook, for Perl debugging mode; pdb-mode-hook, for PDB; jdb-mode-hook, for JDB. See Hooks.

The gud-def Lisp macro (see Defining Macros in the Emacs Lisp Reference Manual) provides a convenient way to define an Emacs command that sends a particular command string to the debugger, and set up a key binding for in the GUD interaction buffer:

(gud-def function cmdstring binding docstring)

This defines a command named function which sends cmdstring to the debugger process, and gives it the documentation string docstring. You can then use the command function in any buffer. If binding is non-nil, gud-def also binds the command to C-c binding in the GUD buffer’s mode and to C-x C-a binding generally.

The command string cmdstring may contain certain ‘%’-sequences that stand for data to be filled in at the time function is called:

%f

The name of the current source file. If the current buffer is the GUD buffer, then the current source file is the file that the program stopped in.

%l

The number of the current source line. If the current buffer is the GUD buffer, then the current source line is the line that the program stopped in.

%e

In transient-mark-mode the text in the region, if it is active. Otherwise the text of the C lvalue or function-call expression at or adjacent to point.

%a

The text of the hexadecimal address at or adjacent to point.

%p

The numeric argument of the called function, as a decimal number. If the command is used without a numeric argument, ‘%p’ stands for the empty string.

If you don’t use ‘%p’ in the command string, the command you define ignores any numeric argument.

%d

The name of the directory of the current source file.

%c

Fully qualified class name derived from the expression surrounding point (jdb only).


28.6.5 GDB Graphical Interface

The command M-x gdb starts GDB in an IDE-like interface, with specialized buffers for controlling breakpoints, stack frames, and other aspects of the debugger state. It also provides additional ways to control the debugging session with the mouse, such as clicking in the fringe of a source buffer to set a breakpoint there.

To run GDB using just the GUD interaction buffer interface, without these additional features, use M-x gud-gdb (see Starting GUD).

Internally, M-x gdb informs GDB that its screen size is unlimited; for correct operation, you must not change GDB’s screen height and width values during the debugging session.


28.6.5.1 GDB User Interface Layout

If the variable gdb-many-windows is nil (the default), M-x gdb normally displays only the GUD interaction buffer. However, if the variable gdb-show-main is also non-nil, it starts with two windows: one displaying the GUD interaction buffer, and the other showing the source for the main function of the program you are debugging.

If gdb-many-windows is non-nil, then M-x gdb displays the following frame layout:

+--------------------------------+--------------------------------+
|   GUD interaction buffer       |   Locals/Registers buffer      |
|--------------------------------+--------------------------------+
|   Primary Source buffer        |   I/O buffer for debugged pgm  |
|--------------------------------+--------------------------------+
|   Stack buffer                 |   Breakpoints/Threads buffer   |
+--------------------------------+--------------------------------+

You can customize the window layout based on the one above and save that layout to a file using gdb-save-window-configuration. Then you can later load this layout back using gdb-load-window-configuration. (Internally, Emacs uses the term window configuration instead of window layout.) You can set your custom layout as the default one used by gdb-many-windows by customizing gdb-default-window-configuration-file. If it is not an absolute file name, GDB looks under gdb-window-configuration-directory for the file. gdb-window-configuration-directory defaults to user-emacs-directory (see How Emacs Finds Your Init File).

If you ever change the window layout, you can restore the default layout by typing M-x gdb-restore-windows. To toggle between the many windows layout and a simple layout with just the GUD interaction buffer and a source file, type M-x gdb-many-windows.

If you have an elaborate window setup, and don’t want gdb-many-windows to disrupt that, it is better to invoke M-x gdb in a separate frame to begin with, then the arrangement of windows on your original frame will not be affected. A separate frame for GDB sessions can come in especially handy if you work on a text-mode terminal, where the screen estate for windows could be at a premium. If you choose to start GDB in the same frame, consider setting gdb-restore-window-configuration-after-quit to a non-nil value. Your original layout will then be restored after GDB quits. Use t to always restore; use if-gdb-many-windows to restore only when gdb-many-windows is non-nil; use if-gdb-show-main to restore only when gdb-show-main is non-nil.

You may also specify additional GDB-related buffers to display, either in the same frame or a different one. Select the buffers you want by typing M-x gdb-display-buffertype-buffer or M-x gdb-frame-buffertype-buffer, where buffertype is the relevant buffer type, such as ‘breakpoints’ or ‘io’. You can do the same from the menu bar, with the ‘GDB-Windows’ and ‘GDB-Frames’ sub-menus of the ‘GUD’ menu.

By default, GDB uses at most one window to display the source file. You can make it use more windows by customizing gdb-max-source-window-count. You can also customize gdb-display-source-buffer-action to control how GDB displays source files.

When you finish debugging, kill the GUD interaction buffer with C-x k, which will also kill all the buffers associated with the session. However you need not do this if, after editing and re-compiling your source code within Emacs, you wish to continue debugging. When you restart execution, GDB automatically finds the new executable. Keeping the GUD interaction buffer has the advantage of keeping the shell history as well as GDB’s breakpoints. You do need to check that the breakpoints in recently edited source files are still in the right places.


28.6.5.2 Source Buffers

mouse-1 (in fringe)

Set or clear a breakpoint on that line (gdb-mouse-set-clear-breakpoint).

C-mouse-1 (in fringe)

Enable or disable a breakpoint on that line (gdb-mouse-toggle-breakpoint-margin).

mouse-3 (in fringe)

Continue execution to that line (gdb-mouse-until).

C-mouse-3 (in fringe)

Jump to that line (gdb-mouse-jump).

On a graphical display, you can click mouse-1 in the fringe of a source buffer, to set a breakpoint on that line (see Window Fringes). A red dot appears in the fringe, where you clicked. If a breakpoint already exists there, the click removes it. A C-mouse-1 click enables or disables an existing breakpoint; a breakpoint that is disabled, but not unset, is indicated by a gray dot.

On a text terminal, or when fringes are disabled, enabled breakpoints are indicated with a ‘B’ character in the left margin of the window. Disabled breakpoints are indicated with ‘b’. (The margin is only displayed if a breakpoint is present.)

A solid arrow in the left fringe of a source buffer indicates the line of the innermost frame where the debugged program has stopped. A hollow arrow indicates the current execution line of a higher-level frame. If you drag the arrow in the fringe with mouse-1, that causes execution to advance to the line where you release the button. Alternatively, you can click mouse-3 in the fringe to advance to that line. You can click C-mouse-3 in the fringe to jump to that line without executing the intermediate lines. This command allows you to go backwards, which can be useful for running through code that has already executed, in order to examine its execution in more detail.

By default, source file names and non-ASCII strings in the program being debugged are decoded using the default coding-system. If you prefer a different decoding, perhaps because the program being debugged uses a different character encoding, set the variable gdb-mi-decode-strings to the appropriate coding-system, or to nil to leave non-ASCII characters as undecoded octal escapes.


28.6.5.3 Breakpoints Buffer

The GDB Breakpoints buffer shows the breakpoints, watchpoints and catchpoints in the debugger session. See Breakpoints in The GNU debugger. It provides the following commands, which mostly apply to the current breakpoint (the breakpoint which point is on):

SPC

Enable/disable current breakpoint (gdb-toggle-breakpoint). On a graphical display, this changes the color of the dot in the fringe of the source buffer at that line. The dot is red when the breakpoint is enabled, and gray when it is disabled.

D

Delete the current breakpoint (gdb-delete-breakpoint).

RET

Visit the source line for the current breakpoint (gdb-goto-breakpoint).

mouse-2

Visit the source line for the breakpoint you click on (gdb-goto-breakpoint).

When gdb-many-windows is non-nil, the GDB Breakpoints buffer shares its window with the GDB Threads buffer. To switch from one to the other click with mouse-1 on the relevant button in the header line. If gdb-show-threads-by-default is non-nil, the GDB Threads buffer is the one shown by default.


28.6.5.4 Threads Buffer

The GDB Threads buffer displays a summary of the threads in the debugged program. See Debugging programs with multiple threads in The GNU debugger. To select a thread, move point there and press RET (gdb-select-thread), or click on it with mouse-2. This also displays the associated source buffer, and updates the contents of the other GDB buffers.

You can customize variables in the gdb-buffers group to select fields included in GDB Threads buffer.

gdb-thread-buffer-verbose-names

Show long thread names like ‘Thread 0x4e2ab70 (LWP 1983)’.

gdb-thread-buffer-arguments

Show arguments of thread top frames.

gdb-thread-buffer-locations

Show file information or library names.

gdb-thread-buffer-addresses

Show addresses for thread frames in threads buffer.

To view information for several threads simultaneously, use the following commands from the GDB Threads buffer.

d

Display disassembly buffer for the thread at current line (gdb-display-disassembly-for-thread).

f

Display the GDB Stack buffer for the thread at current line (gdb-display-stack-for-thread).

l

Display the GDB Locals buffer for the thread at current line (gdb-display-locals-for-thread).

r

Display the GDB Registers buffer for the thread at current line (gdb-display-registers-for-thread).

Their upper-case counterparts, D, F ,L and R, display the corresponding buffer in a new frame.

When you create a buffer showing information about some specific thread, it becomes bound to that thread and keeps showing actual information while you debug your program. The mode indicator for each GDB buffer shows the number of the thread whose information that buffer displays. The thread number is also included in the name of each bound buffer.

Further commands are available in the GDB Threads buffer which depend on the mode of GDB that is used for controlling execution of your program. See Multithreaded Debugging.


28.6.5.5 Stack Buffer

The GDB Stack buffer displays a call stack, with one line for each of the nested subroutine calls (stack frames) in the debugger session. See Backtraces in The GNU debugger.

On graphical displays, the selected stack frame is indicated by an arrow in the fringe. On text terminals, or when fringes are disabled, the selected stack frame is displayed in reverse contrast. To select a stack frame, move point in its line and type RET (gdb-frames-select), or click mouse-2 on it. Doing so also updates the Locals buffer (see Other GDB Buffers).

If you want the frame address to be shown each stack frame, customize the variable gdb-stack-buffer-addresses to a non-nil value.


28.6.5.6 Other GDB Buffers

Other buffers provided by M-x gdb whose display you can optionally request include:

Locals Buffer

This buffer displays the values of local variables of the current stack frame for simple data types (see Information on a frame in The GNU debugger). Press RET or click mouse-2 on the value if you want to edit it.

Arrays and structures display their type only. With GDB 6.4 or later, you can examine the value of the local variable at point by typing RET, or with a mouse-2 click. With earlier versions of GDB, use RET or mouse-2 on the type description (‘[struct/union]’ or ‘[array]’). See Watch Expressions.

To display the Locals buffer, type M-x gdb-display-locals-buffer.

I/O Buffer

If the program you are debugging uses standard input and output streams for interaction with the user, or emits a significant amount of output to its standard output, you may wish to separate its I/O from interaction with GDB. Use the command M-x gdb-display-io-buffer to show a window with a buffer to which Emacs redirects the input and output from the program you are debugging.

Registers Buffer

This buffer displays the values held by the registers (see Registers in The GNU debugger). Request the display of this buffer with the command M-x gdb-display-registers-buffer. Press RET or click mouse-2 on a register if you want to edit its value. With GDB 6.4 or later, recently changed register values display with font-lock-warning-face.

Assembler Buffer

The assembler buffer displays the current frame as machine code. An arrow points to the current instruction, and you can set and remove breakpoints as in a source buffer. Breakpoint icons also appear in the fringe or margin. To request the display of this buffer, use M-x gdb-display-disassembly-buffer.

Memory Buffer

The memory buffer lets you examine sections of program memory (see Examining memory in The GNU debugger). Click mouse-1 on the appropriate part of the header line to change the starting address or number of data items that the buffer displays. Alternatively, use S or N respectively. Click mouse-3 on the header line to select the display format or unit size for these data items. Use M-x gdb-display-memory-buffer to request display of this buffer.

When gdb-many-windows is non-nil, the locals buffer shares its window with the registers buffer, just like breakpoints and threads buffers. To switch from one to the other, click with mouse-1 on the relevant button in the header line.


28.6.5.7 Watch Expressions

If you want to see how a variable changes each time your program stops, move point into the variable name and click on the watch icon in the tool bar (gud-watch) or type C-x C-a C-w. If you specify a prefix argument, you can enter the variable name in the minibuffer.

Each watch expression is displayed in the speedbar (see Speedbar Frames). Complex data types, such as arrays, structures and unions are represented in a tree format. Leaves and simple data types show the name of the expression and its value and, when the speedbar frame is selected, display the type as a tooltip. Higher levels show the name, type and address value for pointers and just the name and type otherwise. Root expressions also display the frame address as a tooltip to help identify the frame in which they were defined.

To expand or contract a complex data type, click mouse-2 or press SPC on the tag to the left of the expression. Emacs asks for confirmation before expanding the expression if its number of immediate children exceeds the value of the variable gdb-max-children.

To delete a complex watch expression, move point to the root expression in the speedbar and type D (gdb-var-delete).

To edit a variable with a simple data type, or a simple element of a complex data type, move point there in the speedbar and type RET (gdb-edit-value). Or you can click mouse-2 on a value to edit it. Either way, this reads the new value using the minibuffer.

If you set the variable gdb-show-changed-values to non-nil (the default value), Emacs uses font-lock-warning-face to highlight values that have recently changed and shadow face to make variables which have gone out of scope less noticeable. When a variable goes out of scope you can’t edit its value.

If the variable gdb-delete-out-of-scope is non-nil (the default value), Emacs automatically deletes watch expressions which go out of scope. Sometimes, when your program re-enters the same function many times, it may be useful to set this value to nil so that you don’t need to recreate the watch expression.

If the variable gdb-use-colon-colon-notation is non-nil, Emacs uses the ‘function::variable’ format. This allows the user to display watch expressions which share the same variable name. The default value is nil.

To automatically raise the speedbar every time the display of watch expressions updates, set gdb-speedbar-auto-raise to non-nil. This can be useful if you are debugging with a full screen Emacs frame.


28.6.5.8 Multithreaded Debugging

In GDB’s all-stop mode, whenever your program stops, all execution threads stop. Likewise, whenever you restart the program, all threads start executing. See All-Stop Mode in The GNU debugger. For some multi-threaded targets, GDB supports a further mode of operation, called non-stop mode, in which you can examine stopped program threads in the debugger while other threads continue to execute freely. See Non-Stop Mode in The GNU debugger. Versions of GDB prior to 7.0 do not support non-stop mode, and it does not work on all targets.

The variable gdb-non-stop-setting determines whether Emacs runs GDB in all-stop mode or non-stop mode. The default is t, which means it tries to use non-stop mode if that is available. If you change the value to nil, or if non-stop mode is unavailable, Emacs runs GDB in all-stop mode. The variable takes effect when Emacs begins a debugging session; if you change its value, you should restart any active debugging session.

When a thread stops in non-stop mode, Emacs usually switches to that thread. If you don’t want Emacs to do this switch if another stopped thread is already selected, change the variable gdb-switch-when-another-stopped to nil.

Emacs can decide whether or not to switch to the stopped thread depending on the reason which caused the stop. Customize the variable gdb-switch-reasons to select the stop reasons which will cause a thread switch.

The variable gdb-stopped-functions allows you to execute your functions whenever some thread stops.

In non-stop mode, you can switch between different modes for GUD execution control commands.

Non-stop/A

When gdb-gud-control-all-threads is t (the default value), interruption and continuation commands apply to all threads, so you can halt or continue all your threads with one command using gud-stop-subjob and gud-cont, respectively. The ‘Go’ button is shown on the tool bar when at least one thread is stopped, whereas ‘Stop’ button is shown when at least one thread is running.

Non-stop/T

When gdb-gud-control-all-threads is nil, only the current thread is stopped/continued. ‘Go’ and ‘Stop’ buttons on the GUD tool bar are shown depending on the state of current thread.

You can change the current value of gdb-gud-control-all-threads from the tool bar or from ‘GUD->GDB-MI’ menu.

Stepping commands always apply to the current thread.

In non-stop mode, you can interrupt/continue your threads without selecting them. Hitting i in threads buffer interrupts thread under point, c continues it, s steps through. More such commands may be added in the future.

Note that when you interrupt a thread, it stops with the ‘signal received’ reason. If that reason is included in your gdb-switch-reasons (it is by default), Emacs will switch to that thread.


28.7 Executing Lisp Expressions

Emacs has major modes for several variants of Lisp. They use the same editing commands as other programming language modes (see Editing Programs). In addition, they provide special commands for executing Lisp expressions.

Emacs Lisp mode

The mode for editing Emacs Lisp source files. It defines C-M-x to evaluate the current top-level Lisp expression. See Evaluating Emacs Lisp Expressions.

Lisp Interaction mode

The mode for an interactive Emacs Lisp session. It defines C-j to evaluate the expression before point and insert its value in the buffer. See Lisp Interaction Buffers.

Lisp mode

The mode for editing source files of programs that run in Lisps other than Emacs Lisp. It defines C-M-x to evaluate the current top-level expression in an external Lisp. See Running an External Lisp.

Inferior Lisp mode

The mode for an interactive session with an external Lisp which is being run as a subprocess (or inferior process) of Emacs. See Running an External Lisp.

Scheme mode

Like Lisp mode, but for Scheme programs.

Inferior Scheme mode

Like Inferior Lisp mode, but for Scheme.


28.8 Libraries of Lisp Code for Emacs

Emacs Lisp code is stored in files whose names conventionally end in .el. Such files are automatically visited in Emacs Lisp mode.

Emacs Lisp code can be compiled into byte-code, which loads faster, takes up less space, and executes faster. By convention, compiled Emacs Lisp code goes in a separate file whose name ends in ‘.elc’. For example, the compiled code for foo.el goes in foo.elc. See Byte Compilation in the Emacs Lisp Reference Manual.

Emacs Lisp code can also be compiled into native code: machine code not unlike the one produced by a C or Fortran compiler. Native code runs even faster than byte-code. Natively-compiled Emacs Lisp code is stored in files whose names end in ‘.eln’. See Native Compilation in the Emacs Lisp Reference Manual.

To load an Emacs Lisp file, type M-x load-file. This command reads a file name using the minibuffer, and executes the contents of that file as Emacs Lisp code. It is not necessary to visit the file first; this command reads the file directly from disk, not from an existing Emacs buffer.

If an Emacs Lisp file is installed in the Emacs Lisp load path (defined below), you can load it by typing M-x load-library, instead of using M-x load-file. The M-x load-library command prompts for a library name rather than a file name; it searches through each directory in the Emacs Lisp load path, trying to find a file matching that library name. If the library name is ‘foo’, it tries looking for files named foo.elc, foo.el, and foo. (If Emacs was built with native compilation enabled, load-library looks for a ‘.eln’ file that corresponds to foo.el and loads it instead of foo.elc.) The default behavior is to load the first file found. This command prefers .eln files over .elc files, and prefers .elc files over .el files, because compiled files load and run faster. If it finds that lib.el is newer than lib.elc, it issues a warning, in case someone made changes to the .el file and forgot to recompile it, but loads the .elc file anyway. (Due to this behavior, you can save unfinished edits to Emacs Lisp source files, and not recompile until your changes are ready for use.) If you set the option load-prefer-newer to a non-nil value, however, then rather than the procedure described above, Emacs loads whichever version of the file is newest. If Emacs was built with native compilation, and it cannot find the ‘.eln’ file corresponding to lib.el, it will load a lib.elc and start native compilation of lib.el in the background, then load the ‘.eln’ file when it finishes compilation.

Emacs Lisp programs usually load Emacs Lisp files using the load function. This is similar to load-library, but is lower-level and accepts additional arguments. See How Programs Do Loading in the Emacs Lisp Reference Manual.

The Emacs Lisp load path is specified by the variable load-path. Its value should be a list of directories (strings). These directories are searched, in the specified order, by the M-x load-library command, the lower-level load function, and other Emacs functions that find Emacs Lisp libraries. An entry in load-path can also have the special value nil, which stands for the current default directory, but it is almost always a bad idea to use this, because its meaning will depend on the buffer that is current when load-path is used by Emacs. (If you find yourself wishing that nil were in the list, most likely what you really want is to use M-x load-file.)

The default value of load-path is a list of directories where the Lisp code for Emacs itself is stored. If you have libraries of your own in another directory, you can add that directory to the load path. Unlike most other variables described in this manual, load-path cannot be changed via the Customize interface (see Easy Customization Interface), but you can add a directory to it by putting a line like this in your init file (see The Emacs Initialization File):

(add-to-list 'load-path "/path/to/my/lisp/library")

It is customary to put locally installed libraries in the site-lisp directory that is already in the default value of load-path, or in some subdirectory of site-lisp. This way, you don’t need to modify the default value of load-path.

Similarly to load-path, the list of directories where Emacs looks for *.eln files with natively-compiled Lisp code is specified by the variable native-comp-eln-load-path.

Some commands are autoloaded; when you run them, Emacs automatically loads the associated library first. For instance, the M-x compile command (see Running Compilations under Emacs) is autoloaded; if you call it, Emacs automatically loads the compile library first. In contrast, the command M-x recompile is not autoloaded, so it is unavailable until you load the compile library.

Automatic loading can also occur when you look up the documentation of an autoloaded command (see Help by Command or Variable Name), if the documentation refers to other functions and variables in its library (loading the library lets Emacs properly set up the hyperlinks in the *Help* buffer). To disable this feature, change the variable help-enable-autoload to nil.

Automatic loading also occurs when completing names for describe-variable and describe-function, based on the prefix being completed. To disable this feature, change the variable help-enable-completion-autoload to nil.

Once you put your library in a directory where Emacs can find and load it, you may wish to make it available at startup. This is useful when the library defines features that should be available automatically on demand, and manually loading the library is thus inconvenient. In these cases, make sure the library will be loaded by adding suitable forms to your init file: either load or require (if you always need to load the library at startup), or autoload if you need Emacs to load the library when some command or function is invoked. For example:

 ;; Loads my-shining-package.elc unconditionally.
 (require 'my-shining-package)
 ;; Will load my-shining-package.elc when my-func is invoked.
 (autoload 'my-func "my-shining-package")

Note that installing a package using package-install (see Package Installation) takes care of placing the package’s Lisp files in a directory where Emacs will find it, and also writes the necessary initialization code into your init files, making the above manual customizations unnecessary.


28.9 Evaluating Emacs Lisp Expressions

Emacs Lisp mode is the major mode for editing Emacs Lisp. Its mode command is M-x emacs-lisp-mode.

Emacs provides several commands for evaluating Emacs Lisp expressions. You can use these commands in Emacs Lisp mode, to test your Emacs Lisp code as it is being written. For example, after re-writing a function, you can evaluate the function definition to make it take effect for subsequent function calls. These commands are also available globally, and can be used outside Emacs Lisp mode.

M-:

Read a single Emacs Lisp expression in the minibuffer, evaluate it, and print the value in the echo area (eval-expression).

C-x C-e

Evaluate the Emacs Lisp expression before point, and print the value in the echo area (eval-last-sexp).

C-M-x (in Emacs Lisp mode)
M-x eval-defun

Evaluate the defun containing or after point, and print the value in the echo area (eval-defun).

M-x eval-region

Evaluate all the Emacs Lisp expressions in the region.

M-x eval-buffer

Evaluate all the Emacs Lisp expressions in the buffer.

M-: (eval-expression) reads an expression using the minibuffer, and evaluates it. (Before evaluating the expression, the current buffer switches back to the buffer that was current when you typed M-:, not the minibuffer into which you typed the expression.)

The command C-x C-e (eval-last-sexp) evaluates the Emacs Lisp expression preceding point in the buffer, and displays the value in the echo area. When the result of an evaluation is an integer, it is displayed together with the value in other formats (octal, hexadecimal, and character if eval-expression-print-maximum-character, described below, allows it).

If M-: or C-x C-e is given a prefix argument, it inserts the value into the current buffer at point, rather than displaying it in the echo area. If the prefix argument is zero, any integer output is inserted together with its value in other formats (octal, hexadecimal, and character). Such a prefix argument also prevents abbreviation of the output according to the variables eval-expression-print-level and eval-expression-print-length (see below). Similarly, a prefix argument of -1 overrides the effect of eval-expression-print-length.

C-x C-e (eval-last-sexp) treats defvar expressions specially. Normally, evaluating a defvar expression does nothing if the variable it defines already has a value. But this command unconditionally resets the variable to the initial value specified by the defvar; this is convenient for debugging Emacs Lisp programs. defcustom and defface expressions are treated similarly. Note the other commands documented in this section, except eval-defun, do not have this special feature.

The eval-defun command is bound to C-M-x in Emacs Lisp mode. It evaluates the top-level Lisp expression containing or following point, and prints the value in the echo area. In this context, a top-level expression is referred to as a “defun”, but it need not be an actual defun (function definition).

This command handles defvar/defcustom/defface forms the same way that eval-last-sexp does.

With a prefix argument, C-M-x instruments the function definition for Edebug, the Emacs Lisp Debugger. See Instrumenting for Edebug in the Emacs Lisp Reference Manual.

The command M-x eval-region parses the text of the region as one or more Lisp expressions, evaluating them one by one. M-x eval-buffer is similar but evaluates the entire buffer.

The options eval-expression-print-level and eval-expression-print-length control the maximum depth and length of lists to print in the result of the evaluation commands before abbreviating them. Supplying a zero prefix argument to eval-expression or eval-last-sexp causes lists to be printed in full. eval-expression-debug-on-error controls whether evaluation errors invoke the debugger when these commands are used; its default is t. eval-expression-print-maximum-character prevents integers which are larger than it from being displayed as characters.


28.10 Lisp Interaction Buffers

When Emacs starts up, it contains a buffer named *scratch*, which is provided for evaluating Emacs Lisp expressions interactively. Its major mode is Lisp Interaction mode. You can also enable Lisp Interaction mode by typing M-x lisp-interaction-mode.

If you kill the *scratch* buffer, you can recreate it with the M-x scratch-buffer command.

In the *scratch* buffer, and other Lisp Interaction mode buffers, C-j (eval-print-last-sexp) evaluates the Lisp expression before point, and inserts the value at point. Thus, as you type expressions into the buffer followed by C-j after each expression, the buffer records a transcript of the evaluated expressions and their values. All other commands in Lisp Interaction mode are the same as in Emacs Lisp mode.

At startup, the *scratch* buffer contains a short message, in the form of a Lisp comment, that explains what it is for. This message is controlled by the variable initial-scratch-message, which should be either a documentation string, or nil (which means to suppress the message).

An alternative way of evaluating Emacs Lisp expressions interactively is to use Inferior Emacs Lisp mode, which provides an interface rather like Shell mode (see Shell Mode) for evaluating Emacs Lisp expressions. Type M-x ielm to create an *ielm* buffer which uses this mode. For more information, see that command’s documentation.


28.11 Running an External Lisp

Lisp mode is the major mode for editing programs written in general-purpose Lisp dialects, such as Common Lisp. Its mode command is M-x lisp-mode. Emacs uses Lisp mode automatically for files whose names end in .l, .lsp, or .lisp.

You can run an external Lisp session as a subprocess or inferior process of Emacs, and pass expressions to it to be evaluated. To begin an external Lisp session, type M-x run-lisp. This runs the program named lisp, and sets it up so that both input and output go through an Emacs buffer named *inferior-lisp*. To change the name of the Lisp program run by M-x run-lisp, change the variable inferior-lisp-program.

The major mode for the *lisp* buffer is Inferior Lisp mode, which combines the characteristics of Lisp mode and Shell mode (see Shell Mode). To send input to the Lisp session, go to the end of the *lisp* buffer and type the input, followed by RET. Terminal output from the Lisp session is automatically inserted in the buffer.

When you edit a Lisp program in Lisp mode, you can type C-M-x (lisp-eval-defun) to send an expression from the Lisp mode buffer to a Lisp session that you had started with M-x run-lisp. The expression sent is the top-level Lisp expression at or following point. The resulting value goes as usual into the *inferior-lisp* buffer. Note that the effect of C-M-x in Lisp mode is thus very similar to its effect in Emacs Lisp mode (see Evaluating Emacs Lisp Expressions), except that the expression is sent to a different Lisp environment instead of being evaluated in Emacs.

The facilities for editing Scheme code, and for sending expressions to a Scheme subprocess, are very similar. Scheme source files are edited in Scheme mode, which can be explicitly enabled with M-x scheme-mode. You can initiate a Scheme session by typing M-x run-scheme (the buffer for interacting with Scheme is named *scheme*), and send expressions to it by typing C-M-x.


29 Maintaining Large Programs

This chapter describes Emacs features for maintaining medium- to large-size programs and packages. These features include:

If you are maintaining a large Lisp program, then in addition to the features described here, you may find the Emacs Lisp Regression Testing (ERT) library useful (see ERT in Emacs Lisp Regression Testing).


29.1 Version Control

A version control system is a program that can record multiple versions of a source file, storing information such as the creation time of each version, who made it, and a description of what was changed.

The Emacs version control interface is called VC. VC commands work with several different version control systems; currently, it supports Bazaar, CVS, Git, Mercurial, Monotone, RCS, SRC, SCCS/CSSC, and Subversion. Of these, the GNU project distributes CVS, RCS, and Bazaar.

VC is enabled automatically whenever you visit a file governed by a version control system. To disable VC entirely, set the customizable variable vc-handled-backends to nil (see Customizing VC).

To update the VC state information for the file visited in the current buffer, use the command vc-refresh-state. This command is useful when you perform version control commands outside Emacs (e.g., from the shell prompt), or if you put the buffer’s file under a different version control system, or remove it from version control entirely.

VC is also enabled automatically in Dired buffers (see Dired, the Directory Editor) showing directories whose files are controlled by a VCS. All VC commands described in this section can be invoked from any Dired buffer showing a directory with VC-controlled files; any files that are marked in a Dired buffer (see Dired Marks vs. Flags) are considered to belong to the current fileset, and VC commands operate on the files in this fileset. This allows you to construct VC filesets including any files you want, regardless of their VC state. (If no files are marked when a VC command is invoked from a Dired buffer, the file shown on the current line in the buffer is considered the only file in the fileset.)


29.1.1 Introduction to Version Control

VC allows you to use a version control system from within Emacs, integrating the version control operations smoothly with editing. It provides a uniform interface for common operations in many version control operations.

Some uncommon or intricate version control operations, such as altering repository settings, are not supported in VC. You should perform such tasks outside VC, e.g., via the command line.

This section provides a general overview of version control, and describes the version control systems that VC supports. You can skip this section if you are already familiar with the version control system you want to use.


29.1.1.1 Understanding the Problems it Addresses

Version control systems provide you with three important capabilities:

  • Reversibility: the ability to back up to a previous state if you discover that some modification you did was a mistake or a bad idea.
  • Concurrency: the ability to have many people modifying the same collection of files knowing that conflicting modifications can be detected and resolved.
  • History: the ability to attach historical data to your data, such as explanatory comments about the intention behind each change. Even for a programmer working solo, change histories are an important aid to memory; for a multi-person project, they are a vitally important form of communication among developers.

29.1.1.2 Supported Version Control Systems

VC currently works with many different version control systems, which it refers to as back ends:

  • Git is a decentralized version control system originally invented by Linus Torvalds to support development of Linux (his kernel). VC supports many common Git operations, but others, such as repository syncing, must be done from the command line.
  • CVS is the free version control system that was, until circa 2008, used by the majority of free software projects. Since then, it has been superseded by newer systems. CVS allows concurrent multi-user development either locally or over the network. Unlike newer systems, it lacks support for atomic commits and file moving/renaming. VC supports all basic editing operations under CVS.
  • Subversion (svn) is a free version control system designed to be similar to CVS but without its problems (e.g., it supports atomic commits of filesets, and versioning of directories, symbolic links, meta-data, renames, copies, and deletes).
  • SCCS was the first version control system ever built, and was long ago superseded by more advanced ones. VC compensates for certain features missing in SCCS (e.g., tag names for releases) by implementing them itself. Other VC features, such as multiple branches, are simply unavailable. Since SCCS is non-free, we recommend avoiding it.
  • CSSC is a free replacement for SCCS. You should use CSSC only if, for some reason, you cannot use a more recent and better-designed version control system.
  • RCS is the free version control system around which VC was initially built. It is relatively primitive: it cannot be used over the network, and works at the level of individual files. Almost everything you can do with RCS can be done through VC.
  • Mercurial (hg) is a decentralized version control system broadly resembling Git. VC supports most Mercurial commands, with the exception of repository sync operations.
  • Bazaar (bzr) is a decentralized version control system that supports both repository-based and decentralized versioning. VC supports most basic editing operations under Bazaar.
  • SRC (src) is RCS, reloaded—a specialized version-control system designed for single-file projects worked on by only one person. It allows multiple files with independent version-control histories to exist in one directory, and is thus particularly well suited for maintaining small documents, scripts, and dotfiles. While it uses RCS for revision storage, it presents a modern user interface featuring lockless operation and integer sequential version numbers. VC supports almost all SRC operations.

29.1.1.3 Concepts of Version Control

When a file is under version control, we say that it is registered in the version control system. The system has a repository which stores both the file’s present state and its change history—enough to reconstruct the current version or any earlier version. The repository also contains other information, such as log entries that describe the changes made to each file.

The copy of a version-controlled file that you actually edit is called the work file. You can change each work file as you would an ordinary file. After you are done with a set of changes, you may commit (or check in) the changes; this records the changes in the repository, along with a descriptive log entry.

A directory tree of work files is called a working tree.

Each commit creates a new revision in the repository. The version control system keeps track of all past revisions and the changes that were made in each revision. Each revision is named by a revision ID, whose format depends on the version control system; in the simplest case, it is just an integer.

To go beyond these basic concepts, you will need to understand three aspects in which version control systems differ. As explained in the next three sections, they can be lock-based or merge-based; file-based or changeset-based; and centralized or decentralized. VC handles all these modes of operation, but it cannot hide the differences.


29.1.1.4 Merge-based vs Lock-based Version Control

A version control system typically has some mechanism to coordinate between users who want to change the same file. There are two ways to do this: merging and locking.

In a version control system that uses merging, each user may modify a work file at any time. The system lets you merge your work file, which may contain changes that have not been committed, with the latest changes that others have committed.

Older version control systems use a locking scheme instead. Here, work files are normally read-only. To edit a file, you ask the version control system to make it writable for you by locking it; only one user can lock a given file at any given time. This procedure is analogous to, but different from, the locking that Emacs uses to detect simultaneous editing of ordinary files (see Protection against Simultaneous Editing). When you commit your changes, that unlocks the file, and the work file becomes read-only again. Other users may then lock the file to make their own changes.

Both locking and merging systems can have problems when multiple users try to modify the same file at the same time. Locking systems have lock conflicts; a user may try to check a file out and be unable to because it is locked. In merging systems, merge conflicts happen when you commit a change to a file that conflicts with a change committed by someone else after your checkout. Both kinds of conflict have to be resolved by human judgment and communication. Experience has shown that merging is superior to locking, both in convenience to developers and in minimizing the number and severity of conflicts that actually occur.

SCCS always uses locking. RCS is lock-based by default but can be told to operate in a merging style. CVS and Subversion are merge-based by default but can be told to operate in a locking mode. Decentralized version control systems, such as Git and Mercurial, are exclusively merging-based.

VC mode supports both locking and merging version control. The terms “commit” and “update” are used in newer version control systems; older lock-based systems use the terms “check in” and “check out”. VC hides the differences between them as much as possible.


29.1.1.5 Changeset-based vs File-based Version Control

On SCCS, RCS, CVS, and other early version control systems (and also in SRC), version control operations are file-based: each file has its own comment and revision history separate from that of all other files. Newer systems, beginning with Subversion, are changeset-based: a commit may include changes to several files, and the entire set of changes is handled as a unit. Any comment associated with the change does not belong to a single file, but to the changeset itself.

Changeset-based version control is more flexible and powerful than file-based version control; usually, when a change to multiple files has to be reversed, it’s good to be able to easily identify and remove all of it.


29.1.1.6 Decentralized vs Centralized Repositories

Early version control systems were designed around a centralized model in which each project has only one repository used by all developers. SCCS, RCS, CVS, Subversion, and SRC share this kind of model. One of its drawbacks is that the repository is a choke point for reliability and efficiency.

GNU Arch pioneered the concept of distributed or decentralized version control, later implemented in Git, Mercurial, and Bazaar. A project may have several different repositories, and these systems support a sort of super-merge between repositories that tries to reconcile their change histories. In effect, there is one repository for each developer, and repository merges take the place of commit operations.

VC helps you manage the traffic between your personal workfiles and a repository. Whether the repository is a single master, or one of a network of peer repositories, is not something VC has to care about.


29.1.1.7 Types of Log File

Projects that use a version control system can have two types of log for changes. One is the log maintained by the version control system: each time you commit a change, you fill out a log entry for the change (see Features of the Log Entry Buffer). This is called the version control log.

The other kind of log is the file ChangeLog (see Change Logs). It provides a chronological record of all changes to a large portion of a program—typically one directory and its subdirectories. A small program would use one ChangeLog file; a large program may have a ChangeLog file in each major directory. See Change Logs. Programmers have used change logs since long before version control systems.

Changeset-based version systems typically maintain a changeset-based modification log for the entire system, which makes change log files somewhat redundant. One advantage that they retain is that it is sometimes useful to be able to view the transaction history of a single directory separately from those of other directories. Another advantage is that commit logs can’t be fixed in many version control systems.

A project maintained with version control can use just the version control log, or it can use both kinds of logs. It can handle some files one way and some files the other way. Each project has its policy, which you should follow.

When the policy is to use both, you typically want to write an entry for each change just once, then put it into both logs. You can write the entry in ChangeLog, then copy it to the log buffer with C-c C-a when committing the change (see Features of the Log Entry Buffer). Or you can write the entry in the log buffer while committing the change (with the help of C-c C-w), and later use the C-x v a command to copy it to ChangeLog (see Change Logs and VC).


29.1.2 Version Control and the Mode Line

When you visit a file that is under version control, Emacs indicates this on the mode line. For example, ‘Bzr-1223’ says that Bazaar is used for that file, and the current revision ID is 1223.

The character between the back-end name and the revision ID indicates the version control status of the work file. In a merge-based version control system, a ‘-’ character indicates that the work file is unmodified, and ‘:’ indicates that it has been modified. ‘!’ indicates that the file contains conflicts as result of a recent merge operation (see Merging Branches), or that the file was removed from the version control. Finally, ‘?’ means that the file is under version control, but is missing from the working tree.

In a lock-based system, ‘-’ indicates an unlocked file, and ‘:’ a locked file; if the file is locked by another user (for instance, ‘jim’), that is displayed as ‘RCS:jim:1.3’. ‘@’ means that the file was locally added, but not yet committed to the master repository.

On a graphical display, you can move the mouse over this mode line indicator to pop up a tool-tip, which displays a more verbose description of the version control status. Pressing mouse-1 over the indicator pops up a menu of VC commands, identical to ‘Tools / Version Control’ on the menu bar.

When Auto Revert mode (see Reverting a Buffer) reverts a buffer that is under version control, it updates the version control information in the mode line. However, Auto Revert mode may not properly update this information if the version control status changes without changes to the work file, from outside the current Emacs session. If you set auto-revert-check-vc-info to t, Auto Revert mode updates the version control status information every auto-revert-interval seconds, even if the work file itself is unchanged. The resulting CPU usage depends on the version control system, but is usually not excessive.


29.1.3 Basic Editing under Version Control

Most VC commands operate on VC filesets. A VC fileset is a collection of one or more files that a VC operation acts upon. When you type VC commands in a buffer visiting a version-controlled file, the VC fileset is simply that one file. When you type them in a VC Directory buffer, and some files in it are marked, the VC fileset consists of the marked files (see VC Directory Mode). Likewise, when you invoke a VC command from a Dired buffer, the VC fileset consists of the marked files (see Dired Marks vs. Flags), defaulting to the file shown on the current line if no files are marked.

With modern changeset-based version control systems (see Changeset-based vs File-based Version Control), such as Git, Mercurial, and Bazaar, VC commands handle multi-file VC filesets as a group. For example, committing a multi-file VC fileset generates a single revision, containing the changes to all those files. On older file-based version control systems like CVS, each file in a multi-file VC fileset is handled individually; thus, committing a fileset generates one revision for each changed file in the fileset.

C-x v v

Perform the next appropriate version control operation on the current VC fileset.

The principal VC command is a multi-purpose command, C-x v v (vc-next-action), which performs the most appropriate action on the current VC fileset: either registering it with a version control system, or committing it, or unlocking it, or merging changes into it. The precise actions for each situation are described in detail in the following subsections. You can use C-x v v either in a file-visiting buffer, in a Dired buffer, or in a VC Directory buffer; in the latter two cases the command operates on the fileset consisting of the marked files. You can also use C-x v v, in a buffer with patches under Diff Mode (see Diff Mode), in which case the command operates on the files whose diffs are shown in the buffer.

Note that VC filesets are distinct from the named filesets used for viewing and visiting files in functional groups (see Filesets). Unlike named filesets, VC filesets are not named and don’t persist across sessions.


29.1.3.1 Basic Version Control with Merging

With a modern merging-based version control system (such as Git and Hg; see Merge-based vs Lock-based Version Control), C-x v v does the following when invoked from a buffer that visits a version-controlled file or a VC Directory or Dired buffer:

  • If there is more than one file in the VC fileset and the files have inconsistent version control statuses, signal an error. (Note, however, that a fileset is allowed to include both newly-added files and modified files; see Registering a File for Version Control.) Also signal an error if the files in the fileset are missing (removed from the filesystem, but still tracked by version control), or are ignored by version control.
  • If every file in the VC fileset is registered and unchanged with respect to the last revision, do nothing.
  • If none of the files in the VC fileset are registered with a version control system, register the newly-added files in the VC fileset, i.e., place them under version control. See Registering a File for Version Control. If Emacs cannot find a system to register under, it prompts for a repository type, creates a new repository, and registers the VC fileset with it. You can also specify the system explicitly, see Advanced Control in C-x v v. Note that registering the files doesn’t commit them; you must invoke C-x v v again to commit, see below.
  • If every file in the VC fileset has been either newly-added or modified, commit the changed files. To do this, Emacs pops up a *vc-log* buffer; type the desired log entry for the changes, followed by C-c C-c to commit. See Features of the Log Entry Buffer.

    With modern decentralized version control systems (Git, Mercurial, etc.), the changes are committed locally and not automatically propagated to the upstream repository (which is usually on a remote host). In these cases, if the repository has been changed since your last update, the commit may fail. In that case, you must update from upstream and then try again. Use C-x v + (see Pulling/Pushing Changes into/from a Branch) or C-x v m (see Merging Branches) for that.

    With a centralized version control system, if the commit fails due to upstream changes, type C-x v v again to merge in the upstream repository changes.

  • Finally, if you are using a centralized version control system, if any file in the VC fileset is outdated with respect to the upstream repository, offer to update the fileset from the repository.

These rules also apply when you use RCS in its non-locking mode, except that changes are not automatically merged from the repository. Nothing informs you if another user has committed changes in the same file since you began editing it; when you commit your revision, that other user’s changes are removed (however, they remain in the repository and are thus not irrevocably lost). Therefore, you must verify that the current revision is unchanged before committing your changes. In addition, locking is possible with RCS even in this mode: C-x v v with an unmodified file locks the file, just as it does with RCS in its normal locking mode (see Basic Version Control with Locking).

If C-x v v is invoked from a buffer under Diff Mode, the command assumes the buffer holds a set of patches for one or more files. It then applies the changes to the respective files and commits the changes after popping up the *vc-log* buffer to allow you to type a suitable commit log message.


29.1.3.2 Basic Version Control with Locking

With a locking-based version control system (such as SCCS, and RCS in its default mode), C-x v v does the following:

  • If there is more than one file in the VC fileset and the files have inconsistent version control statuses, signal an error. Also signal an error if the files in the fileset are missing (removed from the filesystem, but still tracked by version control).
  • If each file in the VC fileset is not registered with a version control system, register the newly-added files in the fileset. See Registering a File for Version Control. If Emacs cannot find a system to register under, it prompts for a repository type, creates a new repository, and registers the VC fileset with it. You can also specify the system explicitly, see Advanced Control in C-x v v.
  • If each file is registered and unlocked, check the files out: lock each one and make it writable, so that you can begin to edit it.
  • If each file is locked by you and contains changes, commit (a.k.a. “check-in”) the changes. To do this, Emacs pops up a *vc-log* buffer; type the desired log entry for the new revision, followed by C-c C-c to commit (see Features of the Log Entry Buffer).
  • If each file is locked by you, but you have not changed it, release the lock and make the file read-only again. This undoes previous check-out operation for files that were not changed since the checkout.
  • If each file is locked by another user, ask whether you want to steal the lock. If you say yes, the file becomes locked by you, and a warning message is sent to the user who had formerly locked the file.
  • If files in the fileset are unlocked, but have changes with respect to their last revision, offer to claim the lock for each such file or to revert the file to the last checked-in revision. (This situation is exceptional and should not normally happen.)

These rules also apply when you use CVS in locking mode, except that CVS does not support stealing locks.


29.1.3.3 Advanced Control in C-x v v

When you give a prefix argument to vc-next-action (C-u C-x v v), it still performs the next logical version control operation, but accepts additional arguments to specify precisely how to do the operation.

  • You can specify the name of a version control system. This is useful if the fileset can be managed by more than one version control system, and Emacs fails to detect the correct one.
  • Otherwise, if using CVS, RCS or SRC, you can specify a revision ID.

    If the fileset is modified (or locked), this makes Emacs commit the files with that revision ID. You can create a new branch by supplying an appropriate revision ID (see Version Control Branches).

    If the fileset is unmodified (and unlocked), this checks out the specified revision into the working tree. You can also specify a revision on another branch by giving its revision or branch ID (see Switching between Branches). An empty argument (i.e., C-u C-x v v RET) checks out the latest (a.k.a. “head”) revision on the current branch.

    Specifying revision ID in this manner is silently ignored by a decentralized version control system. Those systems do not let you specify your own revision IDs, nor do they use the concept of checking out individual files.


29.1.4 Features of the Log Entry Buffer

When you tell VC to commit a change, it pops up a buffer named *vc-log*. In this buffer, you should write a log entry describing the changes you have made (see Understanding the Problems it Addresses). After you are done, type C-c C-c (log-edit-done) to exit the buffer and commit the change, together with your log entry.

The major mode for the *vc-log* buffer is Log Edit mode, a variant of Text mode (see Text Mode). On entering Log Edit mode, Emacs runs the hooks text-mode-hook and vc-log-mode-hook (see Hooks).

In the *vc-log* buffer, you can write one or more header lines, specifying additional information to be supplied to the version control system. Each header line must occupy a single line at the top of the buffer; the first line that is not a header line is treated as the start of the log entry. For example, the following header line states that the present change was not written by you, but by another developer:

Author: J. R. Hacker <jrh@example.com>

Apart from the ‘Author’ header, Emacs recognizes the headers ‘Summary’ (a one-line summary of the changeset), ‘Date’ (a manually-specified commit time), and ‘Fixes’ (a reference to a bug fixed by the change). Not all version control systems recognize all headers. If you specify a header for a system that does not support it, the header is treated as part of the log entry.

While in the *vc-log* buffer, the current VC fileset is considered to be the fileset that will be committed if you type C-c C-c. To view a list of the files in the VC fileset, type C-c C-f (log-edit-show-files). To view a diff of changes between the VC fileset and the version from which you started editing (see Examining And Comparing Old Revisions), type C-c C-d (log-edit-show-diff).

To help generate ChangeLog entries, type C-c C-w (log-edit-generate-changelog-from-diff), to generate skeleton ChangeLog entries, listing all changed file and function names based on the diff of the VC fileset. Consecutive entries left empty will be combined by M-q (fill-paragraph). By default the skeleton will just include the file name, without any leading directories. If you wish to prepend the leading directories up to the VC root, customize diff-add-log-use-relative-names.

If the VC fileset includes one or more ChangeLog files (see Change Logs), type C-c C-a (log-edit-insert-changelog) to pull the relevant entries into the *vc-log* buffer. If the topmost item in each ChangeLog was made under your user name on the current date, this command searches that item for entries matching the file(s) to be committed, and inserts them. If you are using CVS or RCS, see Change Logs and VC, for the opposite way of working—generating ChangeLog entries from the Log Edit buffer.

To abort a commit, just don’t type C-c C-c in that buffer. You can switch buffers and do other editing. As long as you don’t try to make another commit, the entry you were editing remains in the *vc-log* buffer, and you can go back to that buffer at any time to complete the commit.

You can also browse the history of previous log entries to duplicate a commit comment. This can be useful when you want to make several commits with similar comments. The commands M-n, M-p, M-s and M-r for doing this work just like the minibuffer history commands (see Minibuffer History), except that they are used outside the minibuffer.


29.1.5 Registering a File for Version Control

C-x v i

Register the visited file for version control.

The command C-x v i (vc-register) registers each file in the current VC fileset, placing it under version control. This is essentially equivalent to the action of C-x v v on an unregistered VC fileset (see Basic Editing under Version Control), except that if the VC fileset is already registered, C-x v i signals an error whereas C-x v v performs some other action.

To register a file, Emacs must choose a version control system. For a multi-file VC fileset, the VC Directory buffer specifies the system to use (see VC Directory Mode). For a single-file VC fileset, if the file’s directory already contains files registered in a version control system, or if the directory is part of a directory tree controlled by a version control system, Emacs chooses that system. In the event that more than one version control system is applicable, Emacs uses the one that appears first in the variable vc-handled-backends (see Customizing VC). If Emacs cannot find a version control system to register the file under, it prompts for a repository type, creates a new repository, and registers the file into that repository.

With most version control systems, registering a file with C-x v i or C-x v v adds it to the working tree, but does not commit it, i.e., doesn’t add it to the repository. Such files are labeled as added in the VC Directory buffer, and the mode line of the buffers visiting such files shows a revision ID of ‘@@’. To make the registration take effect in the repository, you must commit the newly-added files (see Basic Editing under Version Control). Note that a single commit can include both file additions and edits to files already known to the VCS.

With a locking-based version control system (see Merge-based vs Lock-based Version Control), registering a file leaves it unlocked and read-only. Type C-x v v to check-out the file and start editing it.


29.1.6 Examining And Comparing Old Revisions

C-x v =

Compare the work files in the current VC fileset with the versions you started from (vc-diff). With a prefix argument, prompt for two revisions of the current VC fileset and compare them. You can also call this command from a Dired buffer (see Dired, the Directory Editor).

M-x vc-ediff

Like C-x v =, but using Ediff. See Ediff in The Ediff Manual.

C-x v D

Compare the entire working tree to the revision you started from (vc-root-diff). With a prefix argument, prompt for two revisions and compare their trees.

C-x v ~

Prompt for a revision of the current file, and visit it in a separate buffer (vc-revision-other-window).

C-x v g

Display an annotated version of the current file: for each line, show the latest revision in which it was modified (vc-annotate).

C-x v = (vc-diff) displays a diff which compares each work file in the current VC fileset to the version(s) from which you started editing. The diff is displayed in another window, in a Diff mode buffer (see Diff Mode) named *vc-diff*. The usual Diff mode commands are available in this buffer. In particular, the g (revert-buffer) command performs the file comparison again, generating a new diff.

To compare two arbitrary revisions of the current VC fileset, call vc-diff with a prefix argument: C-u C-x v =. This prompts for two revision IDs (see Concepts of Version Control), and displays a diff between those versions of the fileset. This will not work reliably for multi-file VC filesets, if the version control system is file-based rather than changeset-based (e.g., CVS), since then revision IDs for different files would not be related in any meaningful way.

Instead of the revision ID, some version control systems let you specify revisions in other formats. For instance, under Bazaar you can enter ‘date:yesterday’ for the argument to C-u C-x v = (and related commands) to specify the first revision committed after yesterday. See the documentation of the version control system for details.

If you invoke C-x v = or C-u C-x v = from a Dired buffer (see Dired, the Directory Editor), the file listed on the current line is treated as the current VC fileset. The VC fileset can also include several marked files.

M-x vc-ediff works like C-x v =, except that it uses an Ediff session. See Ediff in The Ediff Manual.

C-x v D (vc-root-diff) is similar to C-x v =, but it displays the changes in the entire current working tree (i.e., the working tree containing the current VC fileset). If you invoke this command from a Dired buffer, it applies to the working tree containing the directory.

To compare two arbitrary revisions of the whole trees, call vc-root-diff with a prefix argument: C-u C-x v D. This prompts for two revision IDs (see Concepts of Version Control), and displays a diff between those versions of the entire version-controlled directory trees (RCS, SCCS, CVS, and SRC do not support this feature).

You can customize the diff options that C-x v = and C-x v D use for generating diffs. The options used are taken from the first non-nil value amongst the variables vc-backend-diff-switches, vc-diff-switches, and diff-switches (see Comparing Files), in that order. Here, backend stands for the relevant version control system, e.g., bzr for Bazaar. Since nil means to check the next variable in the sequence, either of the first two may use the value t to mean no switches at all. Most of the vc-backend-diff-switches variables default to nil, but some default to t; these are for version control systems whose diff implementations do not accept common diff options, such as Subversion.

To directly examine an older version of a file, visit the work file and type C-x v ~ revision RET (vc-revision-other-window). This retrieves the file version corresponding to revision, saves it to filename.~revision~, and visits it in a separate window.

Many version control systems allow you to view files annotated with per-line revision information, by typing C-x v g (vc-annotate). This creates a new “annotate” buffer displaying the file’s text, with each line colored to show how old it is. Red text is new, blue is old, and intermediate colors indicate intermediate ages. By default, the color is scaled over the full range of ages, such that the oldest changes are blue, and the newest changes are red. If the variable vc-annotate-background-mode is non-nil, the colors expressing the age of each line are applied to the background color, leaving the foreground at its default color.

You can customize the annotate options that C-x v g uses by customizing vc-backend-annotate-switches and vc-annotate-switches. They function similarly to vc-backend-diff-switches and vc-diff-switches, described above.

When you give a prefix argument to C-x v g, Emacs reads two arguments using the minibuffer: the revision to display and annotate (instead of the current file contents), and the time span in days the color range should cover.

From the “annotate” buffer, these and other color scaling options are available from the ‘VC-Annotate’ menu. In this buffer, you can also use the following keys to browse the annotations of past revisions, view diffs, or view log entries:

p

Annotate the previous revision, i.e., the revision before the one currently annotated. A numeric prefix argument is a repeat count, so C-u 10 p would take you back 10 revisions.

n

Annotate the next revision, i.e., the revision after the one currently annotated. A numeric prefix argument is a repeat count.

j

Annotate the revision indicated by the current line.

a

Annotate the revision before the one indicated by the current line. This is useful to see the state the file was in before the change on the current line was made.

f

Show in a buffer the file revision indicated by the current line.

d

Display the diff between the current line’s revision and the previous revision. This is useful to see what the current line’s revision actually changed in the file.

D

Display the diff between the current line’s revision and the previous revision for all files in the changeset (for VC systems that support changesets). This is useful to see what the current line’s revision actually changed in the tree.

l

Show the log of the current line’s revision. This is useful to see the author’s description of the changes in the revision on the current line.

w

Annotate the working revision—the one you are editing. If you used p and n to browse to other revisions, use this key to return to your working revision.

v

Toggle the annotation visibility. This is useful for looking just at the file contents without distraction from the annotations.


29.1.7 VC Change Log

C-x v l

Display the change history for the current fileset (vc-print-log).

C-x v L

Display the change history for the current repository (vc-print-root-log).

C-x v b l

Display the change history for another branch (vc-print-branch-log).

C-x v I

Display the changes that a “pull” operation will retrieve (vc-log-incoming).

C-x v O

Display the changes that will be sent by the next “push” operation (vc-log-outgoing).

C-x v h

Display the history of changes made in the region of file visited by the current buffer (vc-region-history).

M-x vc-log-search RET

Search the change history for a specified pattern.

C-x v l (vc-print-log) displays a buffer named *vc-change-log*, showing the history of changes made to the current fileset in the long form, including who made the changes, the dates, and the log entry for each change (these are the same log entries you would enter via the *vc-log* buffer; see Features of the Log Entry Buffer). When invoked from a buffer visiting a file, the current fileset consists of that single file, and point in the displayed *vc-change-log* buffer is centered at the revision of that file. When invoked from a VC Directory buffer (see VC Directory Mode) or from a Dired buffer (see Dired, the Directory Editor), the fileset consists of all the marked files, defaulting to the file shown on the current line in the directory buffer if no file is marked.

If the fileset includes one or more directories, the resulting *vc-change-log* buffer shows a short log of changes (one line for each change), if the VC backend supports that; otherwise it shows the log in the long form.

With a prefix argument, the command prompts for the revision to center on in the *vc-change-log* buffer and for the maximum number of revisions to display.

C-x v L (vc-print-root-log) displays a *vc-change-log* buffer showing the history of the entire version-controlled directory tree (RCS, SCCS, CVS, and SRC do not support this feature). With a prefix argument, the command prompts for the maximum number of revisions to display. A numeric prefix argument specifies the maximum number of revisions without prompting. When the numeric prefix argument is 1, as in C-1 C-x v L or C-u 1 C-x v L, the command prompts for the revision ID, and displays the log entry of that revision together with the changes (diffs) it introduced. (Some less capable version control systems, such as RCS and CVS, don’t have commands to show a revision log with its diffs; for them the command displays only the log entry, and you can request to show the diffs by typing d or D, see below.)

The C-x v L history is shown in a compact form, usually showing only the first line of each log entry. However, you can type RET (log-view-toggle-entry-display) in the *vc-change-log* buffer to reveal the entire log entry for the revision at point. A second RET hides it again.

C-x v b l branch-name RET (vc-print-branch-log) displays a *vc-change-log* buffer showing the history of the version-controlled directory tree, like vc-print-root-log does, but it shows the history of a branch other than the current one; it prompts for the branch whose history to display.

On a decentralized version control system, the C-x v I (vc-log-incoming) command displays a log buffer showing the changes that will be applied, the next time you run the version control system’s pull command to get new revisions from another remote location (see Pulling/Pushing Changes into/from a Branch). This other remote location is the default one from which changes are pulled, as defined by the version control system; with a prefix argument, vc-log-incoming prompts for a specific remote location. Similarly, C-x v O (vc-log-outgoing) shows the changes that will be sent to another remote location, the next time you run the push command; with a prefix argument, it prompts for a specific destination that in case of some version control system can be a branch name.

In the *vc-change-log* buffer, you can use the following keys to move between the logs of revisions and of files, and to examine and compare past revisions (see Examining And Comparing Old Revisions):

p

Move to the previous revision entry. (Revision entries in the log buffer are usually in reverse-chronological order, so the previous revision-item usually corresponds to a newer revision.) A numeric prefix argument is a repeat count.

n

Move to the next revision entry. A numeric prefix argument is a repeat count.

a

Annotate the revision on the current line (see Examining And Comparing Old Revisions).

e

Modify the change comment displayed at point. Note that not all VC systems support modifying change comments.

f

Visit the revision indicated at the current line.

d

Display a diff between the revision at point and the next earlier revision, for the specific file.

D

Display the changeset diff between the revision at point and the next earlier revision. This shows the changes to all files made in that revision.

RET

In a compact-style log buffer (e.g., the one created by C-x v L), toggle between showing and hiding the full log entry for the revision at point.

Because fetching many log entries can be slow, the *vc-change-log* buffer displays no more than 2000 revisions by default. The variable vc-log-show-limit specifies this limit; if you set the value to zero, that removes the limit. You can also increase the number of revisions shown in an existing *vc-change-log* buffer by clicking on the ‘Show 2X entries’ or ‘Show unlimited entries’ buttons at the end of the buffer. However, RCS, SCCS, CVS, and SRC do not support this feature.

A useful variant of examining history of changes is provided by the command vc-region-history (by default bound to C-x v h), which shows a *VC-history* buffer with the history of changes made in the region of the current buffer’s file between point and the mark (see The Mark and the Region). The history of changes includes the commit log messages and also the changes themselves in the Diff format.

Invoke this command after marking in the current buffer the region in whose changes you are interested. In the *VC-history* buffer it pops up, you can use all of the commands available in the *vc-change-log* buffer described above, and also the commands defined by Diff mode (see Diff Mode).

This command is currently available only with Git and Mercurial (hg).

The command vc-log-search allows searching for a pattern in the log of changes. It prompts for a pattern (a regular expression), and displays all entries in the change history whose log messages match the pattern. When invoked with a prefix argument, the command will also prompt for a specific VCS shell command to run for this purpose.


29.1.8 Undoing Version Control Actions

C-x v u

Revert the work file(s) in the current VC fileset to the last revision (vc-revert).

If you want to discard all the changes you have made to the current VC fileset, type C-x v u (vc-revert). This will ask you for confirmation before discarding the changes. If you agree, the fileset is reverted.

If vc-revert-show-diff is non-nil, this command will show you a diff between the work file(s) and the revision from which you started editing. Afterwards, the diff buffer will either be killed (if this variable is kill), or the buffer will be buried (any other non-nil value). If you don’t want C-x v u to show a diff, set this variable to nil (you can still view the diff directly with C-x v =; see Examining And Comparing Old Revisions).

On locking-based version control systems, C-x v u leaves files unlocked; you must lock again to resume editing. You can also use C-x v u to unlock a file if you lock it and then decide not to change it.


29.1.9 Ignore Version Control Files

C-x v G

Ignore a file under current version control system. (vc-ignore).

Many source trees contain some files that do not need to be versioned, such as editor backups, object or bytecode files, and built programs. You can simply not add them, but then they’ll always crop up as unknown files. You can also tell the version control system to ignore these files by adding them to the ignore file at the top of the tree. C-x v G (vc-ignore) can help you do this. When called with a prefix argument, you can remove a file from the ignored file list.


29.1.10 VC Directory Mode

The VC Directory buffer is a specialized buffer for viewing the version control statuses of the files in a directory tree, and performing version control operations on those files. In particular, it is used to specify multi-file VC filesets for commands like C-x v v to act on (see VC Directory Commands).

To use the VC Directory buffer, type C-x v d (vc-dir). This reads a directory’s name using the minibuffer, and switches to a VC Directory buffer for that directory. By default, the buffer is named *vc-dir*. Its contents are described in The VC Directory Buffer.

The vc-dir command automatically detects the version control system to be used in the specified directory. In the event that more than one system is being used in the directory, you should invoke the command with a prefix argument, C-u C-x v d; this prompts for the version control system which the VC Directory buffer should use.

In addition to the VC Directory buffer, Emacs has a similar facility called PCL-CVS which is specialized for CVS. See About PCL-CVS in PCL-CVS—The Emacs Front-End to CVS.

You can also invoke VC commands from Dired buffers (see Dired, the Directory Editor). In that case, any VC command you invoke considers the marked files as the current fileset (see Basic Editing under Version Control), defaulting to the file on the current line if no files are marked.


29.1.10.1 The VC Directory Buffer

The VC Directory buffer contains a list of version-controlled files and their version control statuses. It lists files in the current directory (the one specified when you called C-x v d) and its subdirectories, but only those with a noteworthy status. Files that are up-to-date (i.e., the same as in the repository) are omitted. If all the files in a subdirectory are up-to-date, the subdirectory is not listed either. As an exception, if a file has become up-to-date as a direct result of a VC command, it is listed.

Here is an example of a VC Directory buffer listing:

                     ./
    edited           configure.ac
*   added            README
    unregistered     temp.txt
                     src/
*   edited           src/main.c

Two work files have been modified but not committed: configure.ac in the current directory, and main.c in the src/ subdirectory. The file named README has been added but is not yet committed, while temp.txt is not under version control (see Registering a File for Version Control).

The ‘*’ characters next to the entries for README and src/main.c indicate that the user has marked these files as the current VC fileset (see VC Directory Commands).

The above example is typical for a decentralized version control system like Bazaar, Git, or Mercurial. Other systems can show other statuses. For instance, CVS shows the ‘needs-update’ status if the repository has changes that have not been applied to the work file. RCS and SCCS show the name of the user locking a file as its status.

On CVS, the vc-dir command normally contacts the repository, which may be on a remote machine, to check for updates. If you change the variable vc-cvs-stay-local to nil (see Options specific for CVS), then Emacs avoids contacting a remote repository when generating the VC Directory buffer (it will still contact it when necessary, e.g., when doing a commit). This may be desirable if you are working offline or the network is slow.

The VC Directory buffer omits subdirectories listed in the variable vc-directory-exclusion-list. Its default value contains directories that are used internally by version control systems.


29.1.10.2 VC Directory Commands

Emacs provides several commands for navigating the VC Directory buffer, and for marking files as belonging to the current VC fileset.

n
SPC

Move point to the next entry (vc-dir-next-line).

p

Move point to the previous entry (vc-dir-previous-line).

TAB

Move to the next directory entry (vc-dir-next-directory).

S-TAB

Move to the previous directory entry (vc-dir-previous-directory).

RET
f

Visit the file or directory listed on the current line (vc-dir-find-file).

o

Visit the file or directory on the current line, in a separate window (vc-dir-find-file-other-window).

m

Mark the file or directory on the current line (vc-dir-mark), putting it in the current VC fileset. If the region is active, mark all files in the region.

A file cannot be marked with this command if it is already in a marked directory, or one of its subdirectories. Similarly, a directory cannot be marked with this command if any file in its tree is marked.

M

If point is on a file entry, mark all files with the same status; if point is on a directory entry, mark all files in that directory tree (vc-dir-mark-all-files). With a prefix argument, mark all listed files and directories.

% m
* %

You can use this command to mark files by regexp (vc-dir-mark-by-regexp). If given a prefix, unmark files instead.

* r

You can use this command to mark files that are in one of registered states, including edited, added or removed. (vc-dir-mark-registered-files).

G

Add the file under point to the list of files that the VC should ignore (vc-dir-ignore). For instance, if the VC is Git, it will append this file to the .gitignore file. If given a prefix, do this with all the marked files.

q

Quit the VC Directory buffer, and bury it (quit-window).

u

Unmark the file or directory on the current line. If the region is active, unmark all the files in the region (vc-dir-unmark).

U

If point is on a file entry, unmark all files with the same status; if point is on a directory entry, unmark all files in that directory tree (vc-dir-unmark-all-files). With a prefix argument, unmark all files and directories.

x

Hide files with ‘up-to-date’ or ‘ignored’ status (vc-dir-hide-up-to-date). With a prefix argument, hide items whose state is that of the item at point.

While in the VC Directory buffer, all the files that you mark with m (vc-dir-mark) or M (vc-dir-mark-all-files) are in the current VC fileset. If you mark a directory entry with m, all the listed files in that directory tree are in the current VC fileset. The files and directories that belong to the current VC fileset are indicated with a ‘*’ character in the VC Directory buffer, next to their VC status. In this way, you can set up a multi-file VC fileset to be acted on by VC commands like C-x v v (see Basic Editing under Version Control), C-x v = (see Examining And Comparing Old Revisions), and C-x v u (see Undoing Version Control Actions).

The VC Directory buffer also defines some single-key shortcuts for VC commands with the C-x v prefix: =, +, l, i, D, L, G, I, O, and v.

For example, you can commit a set of edited files by opening a VC Directory buffer, where the files are listed with the ‘edited’ status; marking the files; and typing v or C-x v v (vc-next-action). If the version control system is changeset-based, Emacs will commit the files in a single revision.

While in the VC Directory buffer, you can also perform search and replace on the current VC fileset, with the following commands:

S

Search the fileset (vc-dir-search).

Q

Do a regular expression query replace on the fileset (vc-dir-query-replace-regexp).

M-s a C-s

Do an incremental search on the fileset (vc-dir-isearch).

M-s a C-M-s

Do an incremental regular expression search on the fileset (vc-dir-isearch-regexp).

Apart from acting on multiple files, these commands behave much like their single-buffer counterparts (see Searching and Replacement).

The VC Directory buffer additionally defines some branch-related commands starting with the prefix b:

b c

Create a new branch (vc-create-branch). See Creating New Branches.

b l

Prompt for the name of a branch and display the change history of that branch (vc-print-branch-log).

b s

Switch to a branch (vc-switch-branch). See Switching between Branches.

d

Delete the marked files, or the current file if no marks (vc-dir-clean-delete). The files will not be marked as deleted in the version control system, so this function is mostly useful for unregistered files.

The above commands are also available via the menu bar, and via a context menu invoked by mouse-2. Furthermore, some VC backends use the menu to provide extra backend-specific commands. For example, Git and Bazaar allow you to manipulate stashes and shelves (which are a way to temporarily put aside uncommitted changes, and bring them back at a later time).


29.1.11 Version Control Branches

One use of version control is to support multiple independent lines of development, which are called branches. Amongst other things, branches can be used for maintaining separate stable and development versions of a program, and for developing unrelated features in isolation from one another.

VC’s support for branch operations is currently fairly limited. For decentralized version control systems, it provides commands for updating one branch with the contents of another, and for merging the changes made to two different branches (see Merging Branches). For centralized version control systems, it supports checking out different branches and committing into new or different branches.


29.1.11.1 Switching between Branches

The various version control systems differ in how branches are implemented, and these differences cannot be entirely concealed by VC.

On some decentralized version control systems, including Bazaar and Mercurial in its normal mode of operation, each branch has its own working directory tree, so switching between branches just involves switching directories. On Git, branches are normally co-located in the same directory, and switching between branches is done using the git checkout command, which changes the contents of the working tree to match the branch you switch to. Bazaar also supports co-located branches, in which case the bzr switch command will switch branches in the current directory. With Subversion, you switch to another branch using the svn switch command. With Mercurial, command hg update is used to switch to another branch.

The VC command to switch to another branch in the current directory is C-x v b s branch-name RET (vc-switch-branch).

On centralized version control systems, you can also switch between branches by typing C-u C-x v v in an up-to-date work file (see Advanced Control in C-x v v), and entering the revision ID for a revision on another branch. On CVS, for instance, revisions on the trunk (the main line of development) normally have IDs of the form 1.1, 1.2, 1.3, …, while the first branch created from (say) revision 1.2 has revision IDs 1.2.1.1, 1.2.1.2, …, the second branch created from revision 1.2 has revision IDs 1.2.2.1, 1.2.2.2, …, and so forth. You can also specify the branch ID, which is a branch revision ID omitting its final component (e.g., 1.2.1), to switch to the latest revision on that branch.

On a locking-based system, switching to a different branch also unlocks (write-protects) the working tree.

Once you have switched to a branch, VC commands will apply to that branch until you switch away; for instance, any VC filesets that you commit will be committed to that specific branch.


29.1.11.2 Pulling/Pushing Changes into/from a Branch

C-x v P

With a decentralized version control system, update another repository with locally-committed changes from the current branch (a.k.a. push changes). This concept does not exist for centralized version control systems

C-x v +

With a decentralized version control system, update the current branch of the local repository by pulling in changes from another repository.

With a centralized version control system, update the current VC fileset from the repository.

On a decentralized version control system, the command C-x v P (vc-push) updates another location, commonly known as the upstream repository, with locally-committed changes from the current branch. With a prefix argument, it prompts for the exact version control command to run, which lets you specify where to push changes; the default is bzr push with Bazaar, git push with Git, and hg push with Mercurial. The default commands always push to the repository in the default location determined by the version control system from your branch configuration.

Prior to pushing, you can use C-x v O (vc-log-outgoing) to view a log buffer of the changes to be sent upstream. See VC Change Log.

This command is currently supported only by Bazaar, Git, and Mercurial. The concept of “pushing” does not exist for centralized version control systems, where this operation is a part of committing a changeset, so invoking this command on a centralized VCS signals an error. This command also signals an error when attempted in a Bazaar bound branch, where committing a changeset automatically pushes the changes to the remote repository to which the local branch is bound.

With a decentralized version control system, the command C-x v + (vc-pull) updates the current branch of the local repository and it working tree with changes made in the upstream repository. It is typically used to update a copy (a.k.a. clone) of a remote branch. If you supply a prefix argument, the command prompts for the exact version control command to use, which lets you specify where to pull changes from. Otherwise, it pulls from the repository in the default location determined by the version control system from your branch configuration.

Amongst decentralized version control systems, C-x v + is currently supported only by Bazaar, Git, and Mercurial. With Bazaar, it calls bzr pull for ordinary branches (to pull from a master branch into a mirroring branch), and bzr update for a bound branch (to pull from a central repository). With Git, it calls git pull to fetch changes from a remote repository and merge it into the current branch. With Mercurial, it calls hg pull -u to fetch changesets from the default remote repository and update the working directory.

Prior to pulling, you can use C-x v I (vc-log-incoming) to view a log buffer of the changes to be applied. See VC Change Log.

With a centralized version control system like CVS, C-x v + updates the current VC fileset from the repository.


29.1.11.3 Merging Branches

C-x v m

With a decentralized version control system, merge changes from another branch into the current one.

With a centralized version control system, merge changes from another branch into the current VC fileset.

While developing a branch, you may sometimes need to merge in changes that have already been made in another branch. This is not a trivial operation, as overlapping and conflicting changes may have been made to the two branches.

With a decentralized version control system, you merge changes with the command C-x v m (vc-merge). With Bazaar, this prompts for the exact arguments to pass to the bzr merge command, offering a sensible default if possible. With Git, this prompts for the name of a branch to merge from, with completion (based on the branch names known to the current repository). With Mercurial, this prompts for argument to pass to hg merge. The output from running the merge command is shown in a separate buffer.

With a centralized version control system like CVS, C-x v m prompts for a branch ID, or a pair of revision IDs (see Switching between Branches); then it finds the changes from that branch, or the changes between the two revisions you specified, and merges those changes into the current VC fileset. If you just type RET at the prompt, Emacs simply merges any changes that were made on the same branch since you checked the file out.

Immediately after performing a merge, only the working tree is modified, and you can review the changes produced by the merge with C-x v D and related commands (see Examining And Comparing Old Revisions). If the two branches contained overlapping changes, merging produces a conflict; a warning appears in the output of the merge command, and conflict markers are inserted into each affected work file, surrounding the two sets of conflicting changes. You must then resolve the conflict by editing the conflicted files; by default, Emacs will place buffers with VC conflicts in the special Smerge mode, which provides special commands for resolving the merge conflicts. Once you are done with resolving the conflicts and have saved the files with resolved conflicts, those files must be committed in the usual way for the merge to take effect (see Basic Editing under Version Control).


29.1.11.4 Creating New Branches

On centralized version control systems like CVS, Emacs supports creating new branches as part of a commit operation. When committing a modified VC fileset, type C-u C-x v v (vc-next-action with a prefix argument; see Advanced Control in C-x v v). Then Emacs prompts for a revision ID for the new revision. You should specify a suitable branch ID for a branch starting at the current revision. For example, if the current revision is 2.5, the branch ID should be 2.5.1, 2.5.2, and so on, depending on the number of existing branches at that point.

This procedure will not work for distributed version control systems like git or Mercurial. For those systems you should use the command vc-create-branch (C-x v b c branch-name RET) instead.

To create a new branch at an older revision (one that is no longer the head of a branch), first select that revision (see Switching between Branches). Your procedure will then differ depending on whether you are using a locking or merging-based VCS.

On a locking VCS, you will need to lock the old revision branch with C-x v v. You’ll be asked to confirm, when you lock the old revision, that you really mean to create a new branch—if you say no, you’ll be offered a chance to lock the latest revision instead. On a merging-based VCS you will skip this step.

Then make your changes and type C-x v v again to commit a new revision. This creates a new branch starting from the selected revision.

After the branch is created, subsequent commits create new revisions on that branch. To leave the branch, you must explicitly select a different revision with C-u C-x v v.


29.1.12 Miscellaneous Commands and Features of VC

This section explains the less-frequently-used features of VC.


29.1.12.1 Change Logs and VC

If you use RCS or CVS for a program with a ChangeLog file (see Change Logs), you can generate change log entries from the version control log entries of previous commits.

Note that this only works with RCS or CVS. This procedure would be particularly incorrect on a modern changeset-based version control system, where changes to the ChangeLog file would normally be committed as part of a changeset. In that case, you should write the change log entries first, then pull them into the ‘*vc-log*’ buffer when you commit (see Features of the Log Entry Buffer).

C-x v a

Visit the current directory’s ChangeLog file and, for registered files in that directory, create new entries for versions committed since the most recent change log entry (vc-update-change-log).

C-u C-x v a

As above, but only find entries for the current buffer’s file.

For example, suppose the first line of ChangeLog is dated 1999-04-10, and that the only check-in since then was by Nathaniel Bowditch to rcs2log on 1999-05-22 with log entry ‘Ignore log messages that start with '#'.’. Then C-x v a inserts this ChangeLog entry:

1999-05-22  Nathaniel Bowditch  <nat@apn.org>

        * rcs2log: Ignore log messages that start with '#'.

If the version control log entry specifies a function name (in parenthesis at the beginning of a line), that is reflected in the ChangeLog entry. For example, if a log entry for vc.el is ‘(vc-do-command): Check call-process status.’, the ChangeLog entry is:

1999-05-06  Nathaniel Bowditch  <nat@apn.org>

        * vc.el (vc-do-command): Check call-process status.

When C-x v a adds several change log entries at once, it groups related log entries together if they all are checked in by the same author at nearly the same time. If the log entries for several such files all have the same text, it coalesces them into a single entry.


29.1.12.2 Deleting and Renaming Version-Controlled Files

M-x vc-delete-file

Prompt for a file name, delete the file from the working tree, and schedule the deletion for committing.

M-x vc-rename-file

Prompt for two file names, old and new, rename them in the working tree, and schedule the renaming for committing. The old file defaults to the current buffer’s file name if it is under VC.

If you wish to delete a version-controlled file, use the command M-x vc-delete-file. This prompts for the file name, and deletes it via the version control system. The file is removed from the working tree, and in the VC Directory buffer (see VC Directory Mode), it is displayed with the ‘removed’ status. When you commit it, the deletion takes effect in the repository.

To rename a version-controlled file, type M-x vc-rename-file. This prompts for two arguments: the name of the file you wish to rename, and the new name; then it performs the renaming via the version control system. The renaming takes effect immediately in the working tree, and takes effect in the repository when you commit the renamed file.

On modern version control systems that have built-in support for renaming, the renamed file retains the full change history of the original file. On CVS and older version control systems, the vc-rename-file command actually works by creating a copy of the old file under the new name, registering it, and deleting the old file. In this case, the change history is not preserved.


29.1.12.3 Revision Tags

Most version control systems allow you to apply a revision tag to a specific version of a version-controlled tree. On modern changeset-based version control systems, a revision tag is simply a symbolic name for a particular revision. On older file-based systems like CVS, each tag is added to the entire set of version-controlled files, allowing them to be handled as a unit. Revision tags are commonly used to identify releases that are distributed to users.

There are two basic commands for tags; one makes a tag with a given name, the other retrieves a named tag.

C-x v s name RET

Define the working revision of every registered file in or under the current directory as a tag named name (vc-create-tag).

C-x v r name RET

For all registered files at or below the current directory level, retrieve the tagged revision name. This command will switch to a branch if name is a branch name and your VCS distinguishes branches from tags. (vc-retrieve-tag).

This command reports an error if any files are locked at or below the current directory, without changing anything; this is to avoid overwriting work in progress.

You can give a tag or branch name as an argument to C-x v = or C-x v ~ (see Examining And Comparing Old Revisions). Thus, you can use it to compare a tagged version against the current files, or two tagged versions against each other.

On SCCS, VC implements tags itself; these tags are visible only through VC. Most later systems (including CVS, Subversion, bzr, git, and hg) have a native tag facility, and VC uses it where available; those tags will be visible even when you bypass VC.

In file-based version control systems, when you rename a registered file you need to rename its master along with it; the command vc-rename-file will do this automatically (see Deleting and Renaming Version-Controlled Files). If you are using SCCS, you must also update the records of the tag, to mention the file by its new name (vc-rename-file does this, too). An old tag that refers to a master file that no longer exists under the recorded name is invalid; VC can no longer retrieve it. It would be beyond the scope of this manual to explain enough about RCS and SCCS to explain how to update the tags by hand. Using vc-rename-file makes the tag remain valid for retrieval, but it does not solve all problems. For example, some of the files in your program probably refer to others by name. At the very least, the makefile probably mentions the file that you renamed. If you retrieve an old tag, the renamed file is retrieved under its new name, which is not the name that the makefile expects. So the program won’t really work as retrieved.


29.1.12.4 Inserting Version Control Headers

On Subversion, CVS, RCS, and SCCS, you can put certain special strings called version headers into a work file. When the file is committed, the version control system automatically puts the revision number, the name of the user who made the commit, and other relevant information into the version header.

VC does not normally use the information in the version headers. As an exception, when using RCS, Emacs uses the version header, if there is one, to determine the file version, since it is often more reliable than the RCS master file. To inhibit using the version header this way, change the variable vc-consult-headers to nil. VC then always uses the file permissions (if it is supposed to trust them), or else checks the master file.

To insert a suitable header string into the current buffer, use the command M-x vc-insert-headers. This command works only on Subversion, CVS, RCS, and SCCS. The variable vc-backend-header contains the list of keywords to insert into the version header; for instance, CVS uses vc-cvs-header, whose default value is '("\$Id\$"). (The extra backslashes prevent the string constant from being interpreted as a header, if the Emacs Lisp file defining it is maintained with version control.) The vc-insert-headers command inserts each keyword in the list on a new line at point, surrounded by tabs, and inside comment delimiters if necessary.

The variable vc-static-header-alist specifies further strings to add based on the name of the buffer. Its value should be a list of elements of the form (regexp . format). Whenever regexp matches the buffer name, format is also inserted as part of the version header. A ‘%s’ in format is replaced with the file’s version control type.


29.1.12.5 Editing VC Commands

You can use the C-x v ! (vc-edit-next-command) prefix command to edit the shell command line that VC is about to run. This is primarily intended to make it possible to add optional command-line arguments to VCS commands without unnecessary complications of the VC command set and its interfaces with the backend.

For example, Git can produce logs of more than one branch, but C-x v b l (vc-print-branch-log) prompts for the name of just one branch. To obtain a log of more than one branch, you can type C-x v ! C-x v b l and then append the names of additional branches to the end of the ‘git log’ command that VC is about to run.


29.1.12.6 Preparing Patches

When collaborating on projects it is common to send patches via email, to share changes. You can do this using VC with the vc-prepare-patch command. This will prompt you for the revisions you wish to share, and which destination email address(es) to use. Separate the revisions using the value of crm-separator, commas by default. The command will then prepare those revisions using your MUA (Mail User Agent) for you to review and send.

When invoked interactively in a Log View buffer with marked revisions, those marked revisions will be used.

Depending on the value of the user option vc-prepare-patches-separately, vc-prepare-patch will generate one or more messages. The default value t means prepare and display a message for each revision, one after another. A value of nil means to generate a single message with all patches attached in the body.

If you expect to contribute patches on a regular basis, you can set the user option vc-default-patch-addressee to the address(es) you wish to use. This will be used as the default value when invoking vc-prepare-patch. Project maintainers may consider setting this as a directory local variable (see Per-Directory Local Variables).


29.1.13 Customizing VC

The variable vc-handled-backends determines which version control systems VC should handle. The default value is (RCS CVS SVN SCCS SRC Bzr Git Hg), so it contains all the version systems that are currently supported. If you want VC to ignore one or more of these systems, exclude its name from the list. To disable VC entirely, set this variable to nil.

The order of systems in the list is significant: when you visit a file registered in more than one system, VC uses the system that comes first in vc-handled-backends by default. The order is also significant when you register a file for the first time (see Registering a File for Version Control).


29.1.13.1 General Options

Emacs normally does not save backup files for source files that are maintained with version control. If you want to make backup files even for files that use version control, set the variable vc-make-backup-files to a non-nil value.

Editing a version-controlled file through a symbolic link may cause unexpected results, if you are unaware that the underlying file is version-controlled. The variable vc-follow-symlinks controls what Emacs does if you try to visit a symbolic link pointing to a version-controlled file. If the value is ask (the default), Emacs asks for confirmation. If it is nil, Emacs just displays a warning message. If it is t, Emacs automatically follows the link and visits the real file instead.

If vc-suppress-confirm is non-nil, then C-x v v and C-x v i can save the current buffer without asking, and C-x v u also operates without asking for confirmation.

VC mode does much of its work by running the shell commands for the appropriate version control system. If vc-command-messages is non-nil, VC displays messages to indicate which shell commands it runs, and additional messages when the commands finish.


29.1.13.2 Options for RCS and SCCS

By default, RCS uses locking to coordinate the activities of several users, but there is a mode called non-strict locking in which you can check-in changes without locking the file first. Use ‘rcs -U’ to switch to non-strict locking for a particular file, see the rcs manual page for details.

When deducing the version control state of an RCS file, VC first looks for an RCS version header string in the file (see Inserting Version Control Headers). If there is no header string, VC normally looks at the file permissions of the work file; this is fast. But there might be situations when the file permissions cannot be trusted. In this case the master file has to be consulted, which is rather expensive. Also the master file can only tell you if there’s any lock on the file, but not whether your work file really contains that locked version.

You can tell VC not to use version headers to determine the file status by setting vc-consult-headers to nil. VC then always uses the file permissions (if it is supposed to trust them), or else checks the master file.

VC determines the version control state of files under SCCS much as with RCS. It does not consider SCCS version headers, though. Thus, the variable vc-consult-headers does not affect SCCS use.


29.1.13.3 Options specific for CVS

You can specify additional command line options to pass to all CVS operations in the variable vc-cvs-global-switches. These switches are inserted immediately after the cvs command, before the name of the operation to invoke.

When using a CVS repository on a remote machine, VC can try keeping network interactions to a minimum. This is controlled by the variable vc-cvs-stay-local. If vc-cvs-stay-local is only-file (the default), VC determines the version control status of each file using only the entry in the local CVS subdirectory and the information returned by previous CVS commands. As a consequence, if you have modified a file and somebody else has checked in other changes, you will not be notified of the conflict until you try to commit.

If you change vc-cvs-stay-local to nil, VC queries the remote repository before it decides what to do in vc-next-action (C-x v v), just as it does for local repositories.

You can also set vc-cvs-stay-local to a regular expression that is matched against the repository host name; VC then stays local only for repositories from hosts that match the pattern.

When using a remote repository, Emacs normally makes automatic version backups of the original versions of each edited file. These local backups are made whenever you save the first changes to a file, and they are removed after you commit your changes to the repository. (Note that these are not the same as ordinary Emacs backup files; see Backup Files.) Commands like C-x v = and C-x v u make use of automatic version backups, if possible, to avoid having to access the network.

Setting vc-cvs-stay-local to nil disables the making of automatic version backups.

Automatic version backups have names of the form file.~version.~. This is similar to the name that C-x v ~ saves old versions to (see Examining And Comparing Old Revisions), except for the additional dot (‘.’) after the version. The relevant VC commands can use both kinds of version backups. The main difference is that the manual version backups made by C-x v ~ are not deleted automatically when you commit.

CVS does not use locking by default, but there are ways to enable locking-like behavior using its CVSREAD or watch feature; see the CVS documentation for details. If that case, you can use C-x v v in Emacs to toggle locking, as you would for a locking-based version control system (see Basic Version Control with Locking).


29.2 Working with Projects

A project is a collection of files used for producing one or more programs. Files that belong to a project are typically stored in a hierarchy of directories; the top-level directory of the hierarchy is known as the project root.

Whether a given directory is a root of some project is determined by the project-specific infrastructure, known as project back-end. Emacs currently supports two such back-ends: VC-aware (see Version Control), whereby a VCS repository is considered a project; and EDE (see Emacs Development Environment). This is expected to be extended in the future to support additional types of projects.

Which files do or don’t belong to a project is also determined by the project back-end. For example, the VC-aware back-end doesn’t consider “ignored” files (see Ignore Version Control Files) to be part of the project. Also, the VC-aware Project back-end considers “untracked” files by default. That behavior is controllable with the variable project-vc-include-untracked.


29.2.1 Project Commands That Operate on Files

C-x p f

Visit a file that belongs to the current project (project-find-file).

C-x p g

Find matches for a regexp in all files that belong to the current project (project-find-regexp).

M-x project-search

Interactively search for regexp matches in all files that belong to the current project.

C-x p r

Perform query-replace for a regexp in all files that belong to the current project (project-query-replace-regexp).

C-x p d

Run Dired in the current project’s root directory (project-dired).

C-x p v

Run vc-dir in the current project’s root directory (project-vc-dir).

C-x p s

Start an inferior shell in the current project’s root directory (project-shell).

C-x p e

Start Eshell in the current project’s root directory (project-eshell).

C-x p c

Run compilation in the current project’s root directory (project-compile).

C-x p !

Run shell command in the current project’s root directory (project-shell-command).

C-x p &

Run shell command asynchronously in the current project’s root directory (project-async-shell-command).

Emacs provides commands for handling project files conveniently. This subsection describes these commands.

All of the commands described here share the notion of the current project. The current project is determined by the default-directory (see File Names) of the buffer that is the current buffer when the command is invoked. If that directory doesn’t seem to belong to a recognizable project, these commands prompt you for the project directory.

The command C-x p f (project-find-file) is a convenient way of visiting files (see Visiting Files) that belong to the current project. Unlike C-x C-f, this command doesn’t require to type the full file name of the file to visit, you can type only the file’s base name (i.e., omit the leading directories). In addition, the completion candidates considered by the command include only the files belonging to the current project, and nothing else. If there’s a file name at point, this command offers that file as the first element of the “future history”. If given a prefix, include all files under the project root, except for VCS directories listed in vc-directory-exclusion-list.

The command C-x p g (project-find-regexp) is similar to rgrep (see Searching with Grep under Emacs), but it searches only the files that belong to the current project. The command prompts for the regular expression to search, and pops up an Xref mode buffer with the search results, where you can select a match using the Xref mode commands (see Commands Available in the *xref* Buffer). When invoked with a prefix argument, this command additionally prompts for the base directory from which to start the search; this allows, for example, to limit the search only to project files under a certain subdirectory of the project root. The way this command displays the matches is affected by the value of xref-auto-jump-to-first-xref (see Searching and Replacing with Identifiers).

M-x project-search is a sequential variant of project-find-regexp. It prompts for a regular expression to search in the current project’s files, but instead of finding all the matches and displaying them, it stops when it finds a match and visits the matched file at the locus of the match, allowing you to edit the matched file. To find the rest of the matches, type M-x fileloop-continue RET.

C-x p r (project-query-replace-regexp) is similar to project-search, but it prompts you for whether to replace each match it finds, like query-replace does (see Query Replace), and continues to the next match after you respond. If your response causes Emacs to exit the query-replace loop, you can later continue with M-x fileloop-continue RET.

The command C-x p d (project-find-dir) prompts you to choose a directory inside the current project, with completion. And opens a Dired buffer (see Dired, the Directory Editor) listing the files in it.

The command C-x p D (project-dired) opens a Dired buffer (see Dired, the Directory Editor) listing the files in the current project’s root directory.

The command C-x p v (project-vc-dir) opens a VC Directory buffer (see VC Directory Mode) listing the version control statuses of the files in a directory tree under the current project’s root directory.

The command C-x p s (project-shell) starts a shell session (see Running Shell Commands from Emacs) in a new buffer with the current project’s root as the working directory.

The command C-x p e (project-eshell) starts an Eshell session in a new buffer with the current project’s root as the working directory. See Eshell in Eshell: The Emacs Shell.

The command C-x p c (project-compile) runs compilation (see Running Compilations under Emacs) in the current project’s root directory.

The command C-x p ! (project-shell-command) runs shell-command in the current project’s root directory.

The command C-x p & (project-async-shell-command) runs async-shell-command in the current project’s root directory.


29.2.2 Project Commands That Operate on Buffers

C-x p b

Switch to another buffer belonging to the current project (project-switch-to-buffer).

C-x p C-b

List the project buffers (project-list-buffers).

C-x p k

Kill all live buffers that belong to the current project (project-kill-buffers).

Working on a project could potentially involve having many buffers visiting files that belong to the project, and also buffers that belong to the project, but don’t visit any files (like the *compilation* buffer created by project-compile). The command C-x p b (project-switch-to-buffer) helps you switch between buffers that belong to the current project by prompting for a buffer to switch and considering only the current project’s buffers as candidates for completion.

Like the command list-buffers (see Listing Existing Buffers), the command C-x p C-b (project-list-buffers) displays a list of existing buffers, but only belonging to the current project.

When you finish working on the project, you may wish to kill all the buffers that belong to the project, to keep your Emacs session smaller. The command C-x p k (project-kill-buffers) accomplishes that: it kills all the buffers that belong to the current project that satisfy any of project-kill-buffer-conditions. If project-kill-buffers-display-buffer-list is non-nil, the buffers to be killed will be displayed first.


29.2.3 Switching Projects

C-x p p

Run an Emacs command for another project (project-switch-project).

Commands that operate on project files (see Project Commands That Operate on Files) will conveniently prompt you for a project directory when no project is current. When you are inside some project, but you want to operate on a different project, use the C-x p p command (project-switch-project). This command prompts you to choose a directory among known project roots, and then displays the menu of available commands to operate on the project you choose. The variable project-switch-commands controls which commands are available in the menu, and which key invokes each command.

The variable project-list-file names the file in which Emacs records the list of known projects. It defaults to the file projects in user-emacs-directory (see How Emacs Finds Your Init File).


29.2.4 Managing the Project List File

M-x project-forget-project

Remove a known project from the project-list-file.

Normally Emacs automatically adds and removes projects to and from the project-list-file, but sometimes you may want to manually edit the available projects. M-x project-forget-project prompts you to choose one of the available projects, and then removes it from the file.


29.3 Change Logs

Many software projects keep a change log. This is a file, normally named ChangeLog, containing a chronological record of when and how the program was changed. Sometimes, these files are automatically generated from the change log entries stored in version control systems, or are used to generate these change log entries. Sometimes, there are several change log files, each recording the changes in one directory or directory tree.


29.3.1 Change Log Commands

The Emacs command C-x 4 a adds a new entry to the change log file for the file you are editing (add-change-log-entry-other-window). If that file is actually a backup file, it makes an entry appropriate for the file’s parent—that is useful for making log entries for functions that have been deleted in the current version.

C-x 4 a visits the change log file and creates a new entry unless the most recent entry is for today’s date and your name. It also creates a new item for the current file. For many languages, it can even guess the name of the function or other object that was changed.

To find the change log file, Emacs searches up the directory tree from the file you are editing. By default, it stops if it finds a directory that seems to be the root of a version-control repository. To change this, customize change-log-directory-files.

When the variable add-log-keep-changes-together is non-nil, C-x 4 a adds to any existing item for the file, rather than starting a new item.

You can combine multiple changes of the same nature. If you don’t enter any text after the initial C-x 4 a, any subsequent C-x 4 a adds another symbol to the change log entry.

If add-log-always-start-new-record is non-nil, C-x 4 a always makes a new entry, even if the last entry was made by you and on the same date.

If the value of the variable change-log-version-info-enabled is non-nil, C-x 4 a adds the file’s version number to the change log entry. It finds the version number by searching the first ten percent of the file, using regular expressions from the variable change-log-version-number-regexp-list.

The change log file is visited in Change Log mode. In this major mode, each bunch of grouped items counts as one paragraph, and each entry is considered a page. This facilitates editing the entries. C-j and auto-fill indent each new line like the previous line; this is convenient for entering the contents of an entry.

You can use the command change-log-goto-source (by default bound to C-c C-c) to go to the source location of the change log entry near point, when Change Log mode is on. Then subsequent invocations of the next-error command (by default bound to M-g M-n and C-x `) will move between entries in the change log. You will jump to the actual site in the file that was changed, not just to the next change log entry. You can also use previous-error to move back through the change log entries.

You can use the command M-x change-log-merge to merge other log files into a buffer in Change Log Mode, preserving the date ordering of entries.

Version control systems are another way to keep track of changes in your program and keep a change log. Many projects that use a VCS don’t keep a separate versioned change log file nowadays, so you may wish to avoid having such a file in the repository. If the value of add-log-dont-create-changelog-file is non-nil, commands like C-x 4 a (add-change-log-entry-other-window) will record changes in a suitably named temporary buffer instead of a file, if such a file does not already exist.

Whether you have a change log file or use a temporary buffer for change logs, you can type C-c C-a (log-edit-insert-changelog) in the VC Log buffer to insert the relevant change log entries, if they exist. See Features of the Log Entry Buffer.


29.3.2 Format of ChangeLog

A change log entry starts with a header line that contains the current date, your name (taken from the variable add-log-full-name), and your email address (taken from the variable add-log-mailing-address). Aside from these header lines, every line in the change log starts with a space or a tab. The bulk of the entry consists of items, each of which starts with a line starting with whitespace and a star. Here are two entries, both dated in May 1993, with two items and one item respectively.

1993-05-25  Richard Stallman  <rms@gnu.org>

        * man.el: Rename symbols 'man-*' to 'Man-*'.
        (manual-entry): Make prompt string clearer.

        * simple.el (blink-matching-paren-distance):
        Change default to 12,000.

1993-05-24  Richard Stallman  <rms@gnu.org>

        * vc.el (minor-mode-map-alist): Don't use it if it's void.
        (vc-cancel-version): Doc fix.

One entry can describe several changes; each change should have its own item, or its own line in an item. Normally there should be a blank line between items. When items are related (parts of the same change, in different places), group them by leaving no blank line between them.

You should put a copyright notice and permission notice at the end of the change log file. Here is an example:

Copyright 1997, 1998 Free Software Foundation, Inc.
Copying and distribution of this file, with or without modification, are
permitted provided the copyright notice and this notice are preserved.

Of course, you should substitute the proper years and copyright holder.


29.4 Find Identifier References

An identifier is a name of a syntactical subunit of the program: a function, a subroutine, a method, a class, a data type, a macro, etc. In a programming language, each identifier is a symbol in the language’s syntax. Identifiers are also known as tags.

Program development and maintenance requires capabilities to quickly find where each identifier was defined and referenced, to rename identifiers across the entire project, etc. These capabilities are also useful for finding references in major modes other than those defined to support programming languages. For example, chapters, sections, appendices, etc. of a text or a TeX document can be treated as subunits as well, and their names can be used as identifiers. In this chapter, we use the term “identifiers” to collectively refer to the names of any kind of subunits, in program source and in other kinds of text alike.

Emacs provides a unified interface to these capabilities, called ‘xref’.

To do its job, xref needs to make use of information and to employ methods specific to the major mode. What files to search for identifiers, how to find references to identifiers, how to complete on identifiers—all this and more is mode-specific knowledge. xref delegates the mode-specific parts of its job to a backend provided by the mode; it also includes defaults for some of its commands, for those modes that don’t provide their own.

A backend can implement its capabilities in a variety of ways. Here are a few examples:

  1. Some major modes provide built-in means for looking up the language symbols. For example, Emacs Lisp symbols can be identified by searching the package load history, maintained by the Emacs Lisp interpreter, and by consulting the built-in documentation strings; the Emacs Lisp mode uses these facilities in its backend to allow finding definitions of symbols. (One disadvantage of this kind of backend is that it only knows about subunits that were loaded into the interpreter.)
  2. If Eglot is activated for the current buffer’s project (see Working with Projects) and the current buffer’s major mode, Eglot consults an external language server program and provides the data supplied by the server regarding the definitions of the identifiers in the project. See Eglot Features in Eglot: The Emacs LSP Client.
  3. An external program can extract references by scanning the relevant files, and build a database of these references. A backend can then access this database whenever it needs to list or look up references. The Emacs distribution includes etags, a command for tagging identifier definitions in programs, which supports many programming languages and other major modes, such as HTML, by extracting references into tags tables. See Creating Tags Tables. Major modes for languages supported by etags can use tags tables as basis for their backend. (One disadvantage of this kind of backend is that tags tables need to be kept reasonably up to date, by rebuilding them from time to time.)

29.4.1 Find Identifiers

This subsection describes the commands that find references to identifiers and perform various queries about identifiers. Each such reference could define an identifier, e.g., provide the implementation of a program subunit or the text of a document section; or it could use the identifier, e.g., call a function or a method, assign a value to a variable, mention a chapter in a cross-reference, etc.


29.4.1.1 Looking Up Identifiers

The most important thing that xref enables you to do is to find the definition of a specific identifier.

M-.

Find definitions of an identifier (xref-find-definitions).

C-M-. pattern RET

Find all identifiers whose name matches pattern (xref-find-apropos).

C-x 4 . RET

Find definitions of identifier, but display it in another window (xref-find-definitions-other-window).

C-x 5 . RET

Find definition of identifier, and display it in a new frame (xref-find-definitions-other-frame).

M-x xref-find-definitions-at-mouse

Find definition of identifier at mouse click.

M-,

Go back to where you previously invoked M-. and friends (xref-go-back).

C-M-,

Go forward to where you previously invoked M-, (xref-go-forward).

M-x xref-etags-mode

Switch xref to use the etags backend.

M-. (xref-find-definitions) shows the definition of the identifier at point. With a prefix argument, or if there’s no identifier at point, it prompts for the identifier. (If you want it to always prompt, customize xref-prompt-for-identifier to t.)

When entering the identifier argument to M-., you can use the usual minibuffer completion commands (see Completion), with the known identifier names being the completion candidates.

Like most commands that can switch buffers, xref-find-definitions has a variant that displays the new buffer in another window, and one that makes a new frame for it. The former is C-x 4 . (xref-find-definitions-other-window), and the latter is C-x 5 . (xref-find-definitions-other-frame).

The command xref-find-definitions-at-mouse works like xref-find-definitions, but it looks for the identifier name at or around the place of a mouse event. This command is intended to be bound to a mouse event, such as C-M-mouse-1, for example.

The command C-M-. (xref-find-apropos) is like apropos for tags (see Apropos). It displays a list of identifiers in the selected tags table whose names match the specified regexp. This is just like M-., except that it does regexp matching of identifiers instead of matching symbol names as fixed strings. By default, the command pops up the *xref* buffer, like M-., but you can display additional output by customizing the variable tags-apropos-additional-actions; see its documentation for details.

If any of the above commands finds more than one matching definition, it by default pops up the *xref* buffer showing the matching candidates. (C-M-. always pops up the *xref* buffer if it finds at least one match.) The candidates are normally shown in that buffer as the name of a file and the matching identifier(s) in that file. In that buffer, you can select any of the candidates for display, and you have several additional commands, described in Commands Available in the *xref* Buffer. However, if the value of the variable xref-auto-jump-to-first-definition is move, the first of these candidates is automatically selected in the *xref* buffer, and if it’s t or show, the first candidate is automatically shown in its own window; t also selects the window showing the first candidate. The default value is nil, which just shows the candidates in the *xref* buffer, but doesn’t select any of them.

To go back to places from where you’ve displayed the definition, use M-, (xref-go-back). It jumps back to the point of the last invocation of M-.. Thus you can find and examine the definition of something with M-. and then return to where you were with M-,. M-, allows you to retrace the steps you made forward in the history of places, all the way to the first place in history, where you first invoked M-., or to any place in-between.

If you previously went back too far with M-,, or want to re-examine a place from which you went back, you can use C-M-, (xref-go-forward) to go forward again. This is similar to using M-., except that you don’t need on each step to move point to the identifier whose definition you want to look up. C-M-, allows you to retrace all the steps you made back in the history of places, all the way to the last place in history, where you invoked M-,, or to any place in-between.

Some major modes install xref support facilities that might sometimes fail to find certain identifiers. For example, in Emacs Lisp mode (see Evaluating Emacs Lisp Expressions) M-. will by default find only functions and variables from Lisp packages which are loaded into the current Emacs session or are auto-loaded (see Autoload in The Emacs Lisp Reference Manual). If M-. fails to find some identifiers, you can try forcing xref to use the etags backend (see Find Identifier References). To this end, turn on the Xref Etags minor mode with M-x xref-etags-mode, then invoke M-. again. (For this to work, be sure to run etags to create the tags table in the directory tree of the source files, see Creating Tags Tables.)


29.4.1.2 Commands Available in the *xref* Buffer

The following commands are provided in the *xref* buffer by the special XREF mode:

RET
mouse-1

Display the reference on the current line (xref-goto-xref). With prefix argument, also bury the *xref* buffer.

mouse-2

The same as mouse-1, but make the window displaying the *xref* buffer the selected window (xref-select-and-show-xref).

n
.

Move to the next reference and display it in the other window (xref-next-line).

N

Move to the first reference of the next reference group and display it in the other window (xref-next-group).

p
,

Move to the previous reference and display it in the other window (xref-prev-line).

P

Move to the first reference of the previous reference group and display it in the other window (xref-prev-group).

C-o

Display the reference on the current line in the other window (xref-show-location-at-point).

r pattern RET replacement RET

Perform interactive query-replace on references that match pattern (xref-query-replace-in-results), replacing the match with replacement. This command can only be used in *xref* buffers that show all the matches for an identifier in all the relevant files. See Searching and Replacing with Identifiers.

g

Refresh the contents of the *xref* buffer (xref-revert-buffer).

M-,

Quit the window showing the *xref* buffer, and then jump to the previous Xref stack location (xref-quit-and-pop-marker-stack).

q

Quit the window showing the *xref* buffer (xref-quit).

In addition, the usual navigation commands, such as the arrow keys, C-n, and C-p are available for moving around the buffer without displaying the references.


29.4.1.4 Identifier Inquiries

C-M-i
M-TAB

Perform completion on the text around point, possibly using the selected tags table if one is loaded (completion-at-point).

M-x list-tags RET file RET

Display a list of the identifiers defined in the program file file.

C-M-. regexp RET

Display a list of all identifiers matching regexp (xref-find-apropos). See Looking Up Identifiers.

M-x tags-next-file

Visit files recorded in the selected tags table.

In most programming language modes, you can type C-M-i or M-TAB (completion-at-point) to complete the symbol at point. Some modes provide specialized completion for this command tailored to the mode; for those that don’t, if there is a tags table loaded, this command can use it to generate completion candidates. See Completion for Symbol Names.

M-x list-tags reads the name of one of the files covered by the selected tags table, and displays a list of tags defined in that file. Do not include a directory as part of the file name unless the file name recorded in the tags table includes a directory. This command works only with the etags backend, and requires a tags table for the project to be available. See Tags Tables. If used interactively, the default tag is file name of the current buffer if used interactively.

M-x tags-next-file visits files covered by the selected tags table. The first time it is called, it visits the first file covered by the table. Each subsequent call visits the next covered file, unless a prefix argument is supplied, in which case it returns to the first file. This command requires a tags table to be selected.


29.4.2 Tags Tables

A tags table records the tags18 extracted by scanning the source code of a certain program or a certain document. Tags extracted from generated files reference the original files, rather than the generated files that were scanned during tag extraction. Examples of generated files include C files generated from Cweb source files, from a Yacc parser, or from Lex scanner definitions; .i preprocessed C files; and Fortran files produced by preprocessing .fpp source files.

To produce a tags table, you run the etags shell command on a document or the source code file. The ‘etags’ program writes the tags to a tags table file, or tags file in short. The conventional name for a tags file is TAGS. See Creating Tags Tables. (It is also possible to create a tags table by using one of the commands from other packages that can produce such tables in the same format.)

Emacs uses the tags tables via the etags package as one of the supported backends for xref. Because tags tables are produced by the etags command that is part of an Emacs distribution, we describe tags tables in more detail here.

The Ebrowse facility is similar to etags but specifically tailored for C++. See Ebrowse in Ebrowse User’s Manual. The Semantic package provides another way to generate and use tags, separate from the etags facility. See Semantic.


29.4.2.1 Source File Tag Syntax

Here is how tag syntax is defined for the most popular languages:

  • In C code, any C function or typedef is a tag, and so are definitions of struct, union and enum. #define macro definitions, #undef and enum constants are also tags, unless you specify ‘--no-defines’ when making the tags table. Similarly, global variables are tags, unless you specify ‘--no-globals’, and so are struct members, unless you specify ‘--no-members’. Use of ‘--no-globals’, ‘--no-defines’ and ‘--no-members’ can make the tags table file much smaller.

    You can tag function declarations and external variables in addition to function definitions by giving the ‘--declarations’ option to etags.

  • In C++ code, in addition to all the tag constructs of C code, member functions are also recognized; member variables are also recognized, unless you use the ‘--no-members’ option. operator definitions have tag names like ‘operator+’. If you specify the ‘--class-qualify’ option, tags for variables and functions in classes are named ‘class::variable’ and ‘class::function’. By default, class methods and members are not class-qualified, which allows to identify their names in the sources more accurately.
  • In Java code, tags include all the constructs recognized in C++, plus the interface, extends and implements constructs. Tags for variables and functions in classes are named ‘class.variable’ and ‘class.function’.
  • In LaTeX documents, the arguments for \chapter, \section, \subsection, \subsubsection, \eqno, \label, \ref, \cite, \bibitem, \part, \appendix, \entry, \index, \def, \newcommand, \renewcommand, \newenvironment and \renewenvironment are tags.

    Other commands can make tags as well, if you specify them in the environment variable TEXTAGS before invoking etags. The value of this environment variable should be a colon-separated list of command names. For example,

    TEXTAGS="mycommand:myothercommand"
    export TEXTAGS
    

    specifies (using Bourne shell syntax) that the commands ‘\mycommand’ and ‘\myothercommand’ also define tags.

  • In Lisp code, any function defined with defun, any variable defined with defvar or defconst, and in general the first argument of any expression that starts with ‘(def’ in column zero is a tag. As an exception, expressions of the form (defvar foo) are treated as declarations, and are only tagged if the ‘--declarations’ option is given.
  • In Scheme code, tags include anything defined with def or with a construct whose name starts with ‘def’. They also include variables set with set! at top level in the file.

Several other languages are also supported:

  • In Ada code, functions, procedures, packages, tasks and types are tags. Use the ‘--packages-only’ option to create tags for packages only.

    In Ada, the same name can be used for different kinds of entity (e.g., for a procedure and for a function). Also, for things like packages, procedures and functions, there is the spec (i.e., the interface) and the body (i.e., the implementation). To make it easier to pick the definition you want, Ada tag names have suffixes indicating the type of entity:

    /b

    package body.

    /f

    function.

    /k

    task.

    /p

    procedure.

    /s

    package spec.

    /t

    type.

    Thus, M-x find-tag RET bidule/b RET will go directly to the body of the package bidule, while M-x find-tag RET bidule RET will just search for any tag bidule.

  • In assembler code, labels appearing at the start of a line, followed by a colon, are tags.
  • In Bison or Yacc input files, each rule defines as a tag the nonterminal it constructs. The portions of the file that contain C code are parsed as C code.
  • In Cobol code, tags are paragraph names; that is, any word starting in column 8 and followed by a period.
  • In Erlang code, the tags are the functions, records and macros defined in the file.
  • In Fortran code, functions, subroutines and block data are tags.
  • In Go code, packages, functions, and types are tags.
  • In HTML input files, the tags are the title and the h1, h2, h3 headers. Also, tags are name= in anchors and all occurrences of id=.
  • In Lua input files, all functions are tags.
  • In makefiles, targets are tags; additionally, variables are tags unless you specify ‘--no-globals’.
  • In Objective C code, tags include Objective C definitions for classes, class categories, methods and protocols. Tags for variables and functions in classes are named ‘class::variable’ and ‘class::function’.
  • In Pascal code, the tags are the functions and procedures defined in the file.
  • In Perl code, the tags are the packages, subroutines and variables defined by the package, sub, use constant, my, and local keywords. Use ‘--globals’ if you want to tag global variables. Tags for subroutines are named ‘package::sub’. The name for subroutines defined in the default package is ‘main::sub’.
  • In PHP code, tags are functions, classes and defines. Vars are tags too, unless you use the ‘--no-members’ option.
  • In PostScript code, the tags are the functions.
  • In Prolog code, tags are predicates and rules at the beginning of line.
  • In Python code, def or class at the beginning of a line generate a tag.
  • In Ruby code, def or class or module at the beginning of a line generate a tag. Constants also generate tags.
  • In Rust code, tags anything defined with fn, enum, struct or macro_rules!.

You can also generate tags based on regexp matching (see Etags Regexps) to handle other formats and languages.


29.4.2.2 Creating Tags Tables

The etags program is used to create a tags table file. It knows the syntax of several languages, as described in Source File Tag Syntax. Here is how to run etags:

etags inputfiles

The etags program reads the specified files, and writes a tags table named TAGS in the current working directory. You can optionally specify a different file name for the tags table by using the ‘--output=file’ option; specifying - as a file name prints the tags table to standard output. You can also append the newly created tags table to an existing file by using the ‘--append’ option.

If the specified files don’t exist, etags looks for compressed versions of them and uncompresses them to read them. Under MS-DOS, etags also looks for file names like mycode.cgz if it is given ‘mycode.c’ on the command line and mycode.c does not exist.

If the tags table becomes outdated due to changes in the files described in it, you can update it by running the etags program again. If the tags table does not record a tag, or records it for the wrong file, then Emacs will not be able to find that definition until you update the tags table. But if the position recorded in the tags table becomes a little bit wrong (due to other editing), Emacs will still be able to find the right position, with a slight delay.

Thus, there is no need to update the tags table after each edit. You should update a tags table when you define new tags that you want to have listed, or when you move tag definitions from one file to another, or when changes become substantial.

You can make a tags table include another tags table, by passing the ‘--include=file’ option to etags. It then covers all the files covered by the included tags file, as well as its own.

If you specify the source files with relative file names when you run etags, the tags file will contain file names relative to the directory where the tags file was initially written. This way, you can move an entire directory tree containing both the tags file and the source files, and the tags file will still refer correctly to the source files. If the tags file is - or is in the /dev directory, however, the file names are made relative to the current working directory. This is useful, for example, when writing the tags to the standard output.

When using a relative file name, it should not be a symbolic link pointing to a tags file in a different directory, because this would generally render the file names invalid.

If you specify absolute file names as arguments to etags, then the tags file will contain absolute file names. This way, the tags file will still refer to the same files even if you move it, as long as the source files remain in the same place. Absolute file names start with ‘/’, or with ‘device:/’ on MS-DOS and MS-Windows.

When you want to make a tags table from a great number of files, you may have problems listing them on the command line, because some systems have a limit on its length. You can circumvent this limit by telling etags to read the file names from its standard input, by typing a dash in place of the file names, like this:

find . -name "*.[chCH]" -print | etags -

etags recognizes the language used in an input file based on its file name and contents. It first tries to match the file’s name and extension to the ones commonly used with certain languages. Some languages have interpreters with known names (e.g., perl for Perl or pl for Prolog), so etags next looks for an interpreter specification of the form ‘#!interp’ on the first line of an input file, and matches that against known interpreters. If none of that works, or if you want to override the automatic detection of the language, you can specify the language explicitly with the ‘--language=name’ option. You can intermix these options with file names; each one applies to the file names that follow it. Specify ‘--language=auto’ to tell etags to resume guessing the language from the file names and file contents. Specify ‘--language=none’ to turn off language-specific processing entirely; then etags recognizes tags by regexp matching alone (see Etags Regexps). This comes in handy when an input file uses a language not yet supported by etags, and you want to avoid having etags fall back on Fortran and C as the default languages.

The option ‘--parse-stdin=file’ is mostly useful when calling etags from programs. It can be used (only once) in place of a file name on the command line. etags will read from standard input and mark the produced tags as belonging to the file file.

For C and C++, if the source files don’t observe the GNU Coding Standards’ convention if having braces (‘{’ and ‘}’) in column zero only for top-level definitions, like functions and struct definitions, we advise that you use the ‘--ignore-indentation’ option, to prevent etags from incorrectly interpreting closing braces in column zero.

etags --help’ outputs the list of the languages etags knows, and the file name rules for guessing the language. It also prints a list of all the available etags options, together with a short explanation. If followed by one or more ‘--language=lang’ options, it outputs detailed information about how tags are generated for lang.


29.4.2.3 Etags Regexps

The ‘--regex’ option to etags allows tags to be recognized by regular expression matching. You can intermix this option with file names; each one applies to the source files that follow it. If you specify multiple ‘--regex’ options, all of them are used in parallel. The syntax is:

--regex=[{language}]/tagregexp/[nameregexp/]modifiers

The essential part of the option value is tagregexp, the regexp for matching tags. It is always used anchored, that is, it only matches at the beginning of a line. If you want to allow indented tags, use a regexp that matches initial whitespace; start it with ‘[ \t]*’.

In these regular expressions, ‘\’ quotes the next character, and all the C character escape sequences are supported: ‘\a’ for bell, ‘\b’ for back space, ‘\e’ for escape, ‘\f’ for formfeed, ‘\n’ for newline, ‘\r’ for carriage return, ‘\t’ for tab, and ‘\v’ for vertical tab. In addition, ‘\d’ stands for the DEL character.

Ideally, tagregexp should not match more characters than are needed to recognize what you want to tag. If the syntax requires you to write tagregexp so it matches more characters beyond the tag itself, you should add a nameregexp, to pick out just the tag. This will enable Emacs to find tags more accurately and to do completion on tag names more reliably. In nameregexp, it is frequently convenient to use “back references” (see Backslash in Regular Expressions) to parenthesized groupings ‘\( … \) in tagregexp. For example, ‘\1’ refers to the first such parenthesized grouping. You can find some examples of this below.

The modifiers are a sequence of zero or more characters that modify the way etags does the matching. A regexp with no modifiers is applied sequentially to each line of the input file, in a case-sensitive way. The modifiers and their meanings are:

i

Ignore case when matching this regexp.

m

Match this regular expression against the whole file, so that multi-line matches are possible.

s

Match this regular expression against the whole file, and allow ‘.’ in tagregexp to match newlines.

The ‘-R’ option cancels all the regexps defined by preceding ‘--regex’ options. It too applies to the file names following it. Here’s an example:

etags --regex=/reg1/i voo.doo --regex=/reg2/m \
    bar.ber -R --lang=lisp los.er

Here etags chooses the parsing language for voo.doo and bar.ber according to their contents. etags also uses reg1 to recognize additional tags in voo.doo, and both reg1 and reg2 to recognize additional tags in bar.ber. reg1 is checked against each line of voo.doo and bar.ber, in a case-insensitive way, while reg2 is checked against the whole bar.ber file, permitting multi-line matches, in a case-sensitive way. etags uses only the Lisp tags rules, with no user-specified regexp matching, to recognize tags in los.er.

You can restrict a ‘--regex’ option to match only files of a given language by using the optional prefix {language}. (‘etags --help’ prints the list of languages recognized by etags.) This is particularly useful when storing many predefined regular expressions for etags in a file. The following example tags the DEFVAR macros in the Emacs source files, for the C language only:

--regex='{c}/[ \t]*DEFVAR_[A-Z_ \t(]+"\([^"]+\)"/\1/'

When you have complex regular expressions, you can store the list of them in a file. The following option syntax instructs etags to read two files of regular expressions. The regular expressions contained in the second file are matched without regard to case.

--regex=@case-sensitive-file --ignore-case-regex=@ignore-case-file

A regex file for etags contains one regular expression per line. Empty lines, and lines beginning with space or tab are ignored. When the first character in a line is ‘@’, etags assumes that the rest of the line is the name of another file of regular expressions; thus, one such file can include another file. All the other lines are taken to be regular expressions. If the first non-whitespace text on the line is ‘--’, that line is a comment.

For example, we can create a file called ‘emacs.tags’ with the following contents:

        -- This is for GNU Emacs C source files
{c}/[ \t]*DEFVAR_[A-Z_ \t(]+"\([^"]+\)"/\1/

and then use it like this:

etags --regex=@emacs.tags *.[ch] */*.[ch]

Here are some more examples. The regexps are quoted to protect them from shell interpretation.

  • Tag Octave files:
    etags --language=none \
          --regex='/[ \t]*function.*=[ \t]*\([^ \t]*\)[ \t]*(/\1/' \
          --regex='/###key \(.*\)/\1/' \
          --regex='/[ \t]*global[ \t].*/' \
          *.m
    

    Note that tags are not generated for scripts, so that you have to add a line by yourself of the form ‘###key scriptname’ if you want to jump to it.

  • Tag Tcl files:
    etags --language=none --regex='/proc[ \t]+\([^ \t]+\)/\1/' *.tcl
    
  • Tag VHDL files:
    etags --language=none \
      --regex='/[ \t]*\(ARCHITECTURE\|CONFIGURATION\) +[^ ]* +OF/' \
      --regex='/[ \t]*\(ATTRIBUTE\|ENTITY\|FUNCTION\|PACKAGE\
      \( BODY\)?\|PROCEDURE\|PROCESS\|TYPE\)[ \t]+\([^ \t(]+\)/\3/'
    

29.4.3 Selecting a Tags Table

Emacs has at any time at most one selected tags table. All the commands for working with tags tables use the selected one first. To select a tags table, type M-x visit-tags-table, which reads the tags table file name as an argument, with TAGS defaulting to the first directory that contains a file named TAGS encountered when recursively searching upward from the default directory.

Emacs does not actually read in the tags table contents until you try to use them; all visit-tags-table does is store the file name in the variable tags-file-name, and not much more. The variable’s initial value is nil; that value tells all the commands for working with tags tables that they must ask for a tags table file name to use.

In addition to the selected tags table, Emacs maintains the list of several tags tables that you use together. For example, if you are working on a program that uses a library, you may wish to have the tags tables of both the program and the library available, so that Emacs could easily find identifiers from both. If the selected tags table doesn’t have the identifier or doesn’t mention the source file a tags command needs, the command will try using all the other tags tables in the current list of tags tables.

Using visit-tags-table to load a new tags table when another tags table is already loaded gives you a choice: you can add the new tags table to the current list of tags tables, or discard the current list and start a new list. If you start a new list, the new tags table is used instead of others. If you add the new table to the current list, it is used as well as the others.

You can specify a precise list of tags tables by setting the variable tags-table-list to a list of directory names, like this:

(setq tags-table-list
      '("~/.emacs.d" "/usr/local/lib/emacs/src"))

This tells the tags commands to look at the TAGS files in your ~/.emacs.d directory and in the /usr/local/lib/emacs/src directory. The order depends on which file you are in and which tags table mentions that file.

Do not set both tags-file-name and tags-table-list.


29.5 Emacs Development Environment

EDE (Emacs Development Environment) is a package that simplifies the task of creating, building, and debugging large programs with Emacs. It provides some of the features of an IDE, or Integrated Development Environment, in Emacs.

This section provides a brief description of EDE usage. For full details, see EDE in Emacs Development Environment.

EDE is implemented as a global minor mode (see Minor Modes). To enable it, type M-x global-ede-mode or click on the ‘Project Support (EDE)’ item in the ‘Tools’ menu. You can also enable EDE each time you start Emacs, by adding the following line to your initialization file:

(global-ede-mode t)

Activating EDE adds a menu named ‘Development’ to the menu bar. Many EDE commands, including the ones described below, can be invoked from this menu.

EDE organizes files into projects, which correspond to directory trees. The project root is the topmost directory of a project. To define a new project, visit a file in the desired project root and type M-x ede-new. This command prompts for a project type, which refers to the underlying method that EDE will use to manage the project (see EDE in Emacs Development Environment). The most common project types are ‘Make’, which uses Makefiles, and ‘Automake’, which uses GNU Automake (see Automake in Automake). In both cases, EDE also creates a file named Project.ede, which stores information about the project.

A project may contain one or more targets. A target can be an object file, executable program, or some other type of file, which is built from one or more of the files in the project.

To add a new target to a project, type C-c . t (M-x ede-new-target). This command also asks if you wish to add the current file to that target, which means that the target is to be built from that file. After you have defined a target, you can add more files to it by typing C-c . a (ede-add-file).

To build a target, type C-c . c (ede-compile-target). To build all the targets in the project, type C-c . C (ede-compile-project). EDE uses the file types to guess how the target should be built.


29.6 Merging Files with Emerge

It’s not unusual for programmers to get their signals crossed and modify the same program in two different directions. To recover from this confusion, you need to merge the two versions. Emerge makes this easier. For other ways to compare files, see Comparing Files, and Ediff in The Ediff Manual.


29.6.1 Overview of Emerge

To start Emerge, run one of these four commands:

M-x emerge-files

Merge two specified files.

M-x emerge-files-with-ancestor

Merge two specified files, with reference to a common ancestor.

M-x emerge-buffers

Merge two buffers.

M-x emerge-buffers-with-ancestor

Merge two buffers with reference to a common ancestor in a third buffer.

The Emerge commands compare two files or buffers, and display the comparison in three buffers: one for each input text (the A buffer and the B buffer), and one (the merge buffer) where merging takes place. The merge buffer shows the full merged text, not just the differences. Wherever the two input texts differ, you can choose which one of them to include in the merge buffer.

The Emerge commands that take input from existing buffers use only the accessible portions of those buffers, if they are narrowed. See Narrowing.

If a common ancestor version is available, from which the two texts to be merged were both derived, Emerge can use it to guess which alternative is right. Wherever one current version agrees with the ancestor, Emerge presumes that the other current version is a deliberate change which should be kept in the merged version. Use the ‘with-ancestor’ commands if you want to specify a common ancestor text. These commands read three file or buffer names—variant A, variant B, and the common ancestor.

After the comparison is done and the buffers are prepared, the interactive merging starts. You control the merging by typing special merge commands in the merge buffer (see Merge Commands). For each run of differences between the input texts, you can choose which one of them to keep, or edit them both together.

The merge buffer uses a special major mode, Emerge mode, with commands for making these choices. But you can also edit the buffer with ordinary Emacs commands.

At any given time, the attention of Emerge is focused on one particular difference, called the selected difference. This difference is marked off in the three buffers like this:

vvvvvvvvvvvvvvvvvvvv
text that differs
^^^^^^^^^^^^^^^^^^^^

Emerge numbers all the differences sequentially and the mode line always shows the number of the selected difference.

Normally, the merge buffer starts out with the A version of the text. But when the A version of a difference agrees with the common ancestor, then the B version is initially preferred for that difference.

Emerge leaves the merged text in the merge buffer when you exit. At that point, you can save it in a file with C-x C-w. If you give a numeric argument to emerge-files or emerge-files-with-ancestor, it reads the name of the output file using the minibuffer. (This is the last file name those commands read.) Then exiting from Emerge saves the merged text in the output file.

Normally, Emerge commands save the output buffer in its file when you exit. If you abort Emerge with C-], the Emerge command does not save the output buffer, but you can save it yourself if you wish.


29.6.2 Submodes of Emerge

You can choose between two modes for giving merge commands: Fast mode and Edit mode. In Fast mode, basic merge commands are single characters, but ordinary Emacs commands are disabled. This is convenient if you use only merge commands. In Edit mode, all merge commands start with the prefix key C-c C-c, and the normal Emacs commands are also available. This allows editing the merge buffer, but slows down Emerge operations.

Use e to switch to Edit mode, and C-c C-c f to switch to Fast mode. The mode line indicates Edit and Fast modes with ‘E’ and ‘F’.

Emerge has two additional submodes that affect how particular merge commands work: Auto Advance mode and Skip Prefers mode.

If Auto Advance mode is in effect, the a and b commands advance to the next difference. This lets you go through the merge faster as long as you simply choose one of the alternatives from the input. The mode line indicates Auto Advance mode with ‘A’.

If Skip Prefers mode is in effect, the n and p commands skip over differences in states “prefer-A” and “prefer-B” (see State of a Difference). Thus you see only differences for which neither version is presumed correct. The mode line indicates Skip Prefers mode with ‘S’. This mode is only relevant when there is an ancestor.

Use the command s a (emerge-auto-advance) to set or clear Auto Advance mode. Use s s (emerge-skip-prefers) to set or clear Skip Prefers mode. These commands turn on the mode with a positive argument, turn it off with a negative or zero argument, and toggle the mode with no argument.


29.6.3 State of a Difference

In the merge buffer, a difference is marked with lines of ‘v’ and ‘^’ characters. Each difference has one of these seven states:

A

The difference is showing the A version. The a command always produces this state; the mode line indicates it with ‘A’.

B

The difference is showing the B version. The b command always produces this state; the mode line indicates it with ‘B’.

default-A
default-B

The difference is showing the A or the B state by default, because you haven’t made a choice. All differences start in the default-A state (and thus the merge buffer is a copy of the A buffer), except those for which one alternative is preferred (see below).

When you select a difference, its state changes from default-A or default-B to plain A or B. Thus, the selected difference never has state default-A or default-B, and these states are never displayed in the mode line.

The command d a chooses default-A as the default state, and d b chooses default-B. This chosen default applies to all differences that you have never selected and for which no alternative is preferred. If you are moving through the merge sequentially, the differences you haven’t selected are those following the selected one. Thus, while moving sequentially, you can effectively make the A version the default for some sections of the merge buffer and the B version the default for others by using d a and d b between sections.

prefer-A
prefer-B

The difference is showing the A or B state because it is preferred. This means that you haven’t made an explicit choice, but one alternative seems likely to be right because the other alternative agrees with the common ancestor. Thus, where the A buffer agrees with the common ancestor, the B version is preferred, because chances are it is the one that was actually changed.

These two states are displayed in the mode line as ‘A*’ and ‘B*’.

combined

The difference is showing a combination of the A and B states, as a result of the x c or x C commands.

Once a difference is in this state, the a and b commands don’t do anything to it unless you give them a numeric argument.

The mode line displays this state as ‘comb’.


29.6.4 Merge Commands

Here are the Merge commands for Fast mode; in Edit mode, precede them with C-c C-c:

p

Select the previous difference.

n

Select the next difference.

a

Choose the A version of this difference.

b

Choose the B version of this difference.

C-u n j

Select difference number n.

.

Select the difference containing point.

q

Quit—finish the merge.

C-]

Abort—exit merging and do not save the output.

f

Go into Fast mode. (In Edit mode, this is actually C-c C-c f.)

e

Go into Edit mode.

l

Recenter (like C-l) all three windows. With an argument, reestablish the default three-window display.

-

Specify part of a prefix numeric argument.

digit

Also specify part of a prefix numeric argument.

d a

Choose the A version as the default from here down in the merge buffer.

d b

Choose the B version as the default from here down in the merge buffer.

c a

Copy the A version of this difference into the kill ring.

c b

Copy the B version of this difference into the kill ring.

i a

Insert the A version of this difference at point.

i b

Insert the B version of this difference at point.

m

Put point and mark around the difference.

^

Scroll all three windows down (like M-v).

v

Scroll all three windows up (like C-v).

<

Scroll all three windows left (like C-x <).

>

Scroll all three windows right (like C-x >).

|

Reset horizontal scroll on all three windows.

x 1

Shrink the merge window to one line. (Use C-u l to restore it to full size.)

x c

Combine the two versions of this difference (see Combining the Two Versions).

x f

Show the names of the files/buffers Emerge is operating on, in a Help window. (Use C-u l to restore windows.)

x j

Join this difference with the following one. (C-u x j joins this difference with the previous one.)

x s

Split this difference into two differences. Before you use this command, position point in each of the three buffers at the place where you want to split the difference.

x t

Trim identical lines off the top and bottom of the difference. Such lines occur when the A and B versions are identical but differ from the ancestor version.


29.6.5 Exiting Emerge

The q command (emerge-quit) finishes the merge, storing the results into the output file if you specified one. It restores the A and B buffers to their proper contents, or kills them if they were created by Emerge and you haven’t changed them. It also disables the Emerge commands in the merge buffer, since executing them later could damage the contents of the various buffers.

C-] aborts the merge. This means exiting without writing the output file. If you didn’t specify an output file, then there is no real difference between aborting and finishing the merge.

If the Emerge command was called from another Lisp program, then its return value is t for successful completion, or nil if you abort.


29.6.6 Combining the Two Versions

Sometimes you want to keep both alternatives for a particular difference. To do this, use x c, which edits the merge buffer like this:

#ifdef NEW
version from B buffer
#else /* not NEW */
version from A buffer
#endif /* not NEW */

While this example shows C preprocessor conditionals delimiting the two alternative versions, you can specify the strings to use by setting the variable emerge-combine-versions-template to a string of your choice. In the string, ‘%a’ says where to put version A, and ‘%b’ says where to put version B. The default setting, which produces the results shown above, looks like this:

"#ifdef NEW\n%b#else /* not NEW */\n%a#endif /* not NEW */\n"

29.6.7 Fine Points of Emerge

During the merge, you mustn’t try to edit the A and B buffers yourself. Emerge modifies them temporarily, but ultimately puts them back the way they were.

You can have any number of merges going at once—just don’t use any one buffer as input to more than one merge at once, since the temporary changes made in these buffers would get in each other’s way.

Starting Emerge can take a long time because it needs to compare the files fully. Emacs can’t do anything else until diff finishes. Perhaps in the future someone will change Emerge to do the comparison in the background when the input files are large—then you could keep on doing other things with Emacs until Emerge is ready to accept commands.

After setting up the merge, Emerge runs the hook emerge-startup-hook. See Hooks.


29.7 Bug Reference

Most projects with a certain amount of users track bug reports in some issue tracking software which assigns each report a unique and short number or identifier. Those are used to reference a given bug, e.g., in a source code comment above the code fixing some bug, in documentation files, or in discussions on some mailing list or IRC channel.

The minor modes bug-reference-mode and bug-reference-prog-mode highlight such bug references and make it possible to follow them to the corresponding bug report on the project’s issue tracker. bug-reference-prog-mode is a variant of bug-reference-mode which highlights bug references only inside source code comments and strings.

For its working, bug reference mode needs to know the syntax of bug references (bug-reference-bug-regexp), and the URL of the tracker where bug reports can be looked up (bug-reference-url-format). Since those are typically different from project to project, it makes sense to specify them in see Per-Directory Local Variables or see Local Variables in Files.

For example, let’s assume in our project, we usually write references to bug reports as bug#1234, or Bug-1234 and that this bug’s page on the issue tracker is https://project.org/issues/1234, then these local variables section would do.

;; Local Variables:
;; bug-reference-bug-regexp: "\\([Bb]ug[#-]\\([0-9]+\\)\\)"
;; bug-reference-url-format: "https://project.org/issues/%s"
;; End:

The string captured by the first regexp group defines the bounds of the overlay bug-reference creates, i.e., the part which is highlighted and made clickable.

The string captured by the second regexp group in bug-reference-bug-regexp is used to replace the %s template in the bug-reference-url-format.

Note that bug-reference-url-format may also be a function in order to cater for more complex scenarios, e.g., when different parts of the bug reference have to be used to distinguish between issues and merge requests resulting in different URLs.

Automatic Setup

If bug-reference-mode is activated, bug-reference-mode-hook has been run and still bug-reference-bug-regexp, and bug-reference-url-format aren’t both set, it’ll try to setup suitable values for these two variables itself by calling the functions in bug-reference-auto-setup-functions one after the other until one is able to set the variables.

Right now, there are three types of setup functions.

  1. Setup for version-controlled files configurable by the variables bug-reference-forge-alist, and bug-reference-setup-from-vc-alist. The defaults are able to setup GNU projects where https://debbugs.gnu.org is used as issue tracker and issues are usually referenced as bug#13 (but many different notations are considered, too), and several kinds of modern software forges such as GitLab, Gitea, SourceHut, or GitHub. If you deploy a self-hosted instance of such a forge, the easiest way to tell bug-reference about it is through bug-reference-forge-alist.
  2. Setup for email guessing from mail folder/mbox names, and mail header values configurable by the variable bug-reference-setup-from-mail-alist. The built-in news- and mailreader Email and Usenet News with Gnus and Reading Mail with Rmail are supported.
  3. Setup for IRC channels configurable by the variable bug-reference-setup-from-irc-alist. The built-in IRC clients Rcirc, See Rcirc in The Rcirc Manual, and ERC, See ERC in The ERC Manual, are supported.

For almost all of those modes, it’s enough to simply enable bug-reference-mode, only Rmail requires a slightly different setup.

;; Use VC-based setup if file is under version control.
(add-hook 'prog-mode-hook #'bug-reference-prog-mode)

;; Gnus (summary & article buffers)
(add-hook 'gnus-mode-hook #'bug-reference-mode)

;; Rmail
(add-hook 'rmail-show-message-hook #'bug-reference-mode-force-auto-setup)

;; Rcirc
(add-hook 'rcirc-mode-hook #'bug-reference-mode)

;; ERC
(add-hook 'erc-mode-hook #'bug-reference-mode)

In the Rmail case, instead of the mode hook, the rmail-show-message-hook has to be used in combination with the function bug-reference-mode-force-auto-setup which activates bug-reference-mode and forces auto-setup. The reason is that with Rmail all messages reside in the same buffer but the setup needs to be performed whenever another messages is displayed.

Adding support for third-party packages

Adding support for bug-reference’ auto-setup is usually quite straight-forward: write a setup function of zero arguments which gathers the required information (e.g., List-Id/To/From/Cc mail header values in the case of a MUA), and then calls one of the following helper functions:

  • bug-reference-maybe-setup-from-vc which does the setup according to bug-reference-setup-from-vc-alist,
  • bug-reference-maybe-setup-from-mail which does the setup according to bug-reference-setup-from-mail-alist,
  • and bug-reference-maybe-setup-from-irc which does the setup according to bug-reference-setup-from-irc-alist.

A setup function should return non-nil if it could setup bug-reference mode which is the case if the last thing the function does is calling one of the helper functions above.

Finally, the setup function has to be added to bug-reference-auto-setup-functions.

Note that these auto-setup functions should check as a first step if they are applicable, e.g., by checking the major-mode value.

Integration with the debbugs package

If your project’s issues are tracked on the server https://debbugs.gnu.org, you can browse and reply to reports directly in Emacs using the debbugs package, which can be downloaded via the Package Menu (see Emacs Lisp Packages). This package adds the minor mode debbugs-browse-mode, which can be activated on top of bug-reference-mode and bug-reference-prog-mode as follows:

(add-hook 'bug-reference-mode-hook 'debbugs-browse-mode)
(add-hook 'bug-reference-prog-mode-hook 'debbugs-browse-mode)

30 Abbrevs

A defined abbrev is a word which expands, if you insert it, into some different text. Abbrevs are defined by the user to expand in specific ways. For example, you might define ‘foo’ as an abbrev expanding to ‘find outer otter’. Then you could insert ‘find outer otter ’ into the buffer by typing f o o SPC.

A second kind of abbreviation facility is called dynamic abbrev expansion. You use dynamic abbrev expansion with an explicit command to expand the letters in the buffer before point by looking for other words in the buffer that start with those letters. See Dynamic Abbrev Expansion.

A third kind, hippie expansion, generalizes abbreviation expansion. See Hippie Expansion in Features for Automatic Typing.


30.1 Abbrev Concepts

An abbrev is a word that has been defined to expand into a specified expansion. When you insert a word-separator character following the abbrev, that expands the abbrev—replacing the abbrev with its expansion. For example, if ‘foo’ is defined as an abbrev expanding to ‘find outer otter’, then typing f o o . will insert ‘find outer otter.’.

Abbrevs expand only when Abbrev mode, a buffer-local minor mode, is enabled. Disabling Abbrev mode does not cause abbrev definitions to be forgotten, but they do not expand until Abbrev mode is enabled again. The command M-x abbrev-mode toggles Abbrev mode; with a numeric argument, it turns Abbrev mode on if the argument is positive, off otherwise. See Minor Modes.

Abbrevs can have mode-specific definitions, active only in one major mode. Abbrevs can also have global definitions that are active in all major modes. The same abbrev can have a global definition and various mode-specific definitions for different major modes. A mode-specific definition for the current major mode overrides a global definition.

You can define abbrevs interactively during the editing session, irrespective of whether Abbrev mode is enabled. You can also save lists of abbrev definitions in files, which you can then reload for use in later sessions.


30.2 Defining Abbrevs

C-x a g

Define an abbrev, using one or more words before point as its expansion (add-global-abbrev).

C-x a l

Similar, but define an abbrev specific to the current major mode (add-mode-abbrev).

C-x a i g

Define a word in the buffer as an abbrev (inverse-add-global-abbrev).

C-x a i l

Define a word in the buffer as a mode-specific abbrev (inverse-add-mode-abbrev).

M-x define-global-abbrev RET abbrev RET exp RET

Define abbrev as an abbrev expanding into exp.

M-x define-mode-abbrev RET abbrev RET exp RET

Define abbrev as a mode-specific abbrev expanding into exp.

M-x kill-all-abbrevs

Discard all abbrev definitions, leaving a blank slate.

The usual way to define an abbrev is to enter the text you want the abbrev to expand to, position point after it, and type C-x a g (add-global-abbrev). This reads the abbrev itself using the minibuffer, and then defines it as an abbrev for one or more words before point. Use a numeric argument to say how many words before point should be taken as the expansion. For example, to define the abbrev ‘foo’ as mentioned above, insert the text ‘find outer otter’ and then type C-u 3 C-x a g f o o RET.

If you’re using transient-mark-mode (which is the default), the active region will be used as the expansion of the abbrev being defined. If not, an argument of zero to C-x a g means to use the contents of the region.

The command C-x a l (add-mode-abbrev) is similar, but defines a mode-specific abbrev for the current major mode. The arguments work the same as for C-x a g.

C-x a i g (inverse-add-global-abbrev) and C-x a i l (inverse-add-mode-abbrev) perform the opposite task: if the abbrev text is already in the buffer, you use these commands to define an abbrev by specifying the expansion in the minibuffer. These commands will expand the abbrev text used for the definition.

You can define an abbrev without inserting either the abbrev or its expansion in the buffer using the command define-global-abbrev. It reads two arguments—the abbrev, and its expansion. The command define-mode-abbrev does likewise for a mode-specific abbrev.

To change the definition of an abbrev, just make a new definition. When an abbrev has a prior definition, the abbrev definition commands ask for confirmation before replacing it.

To remove an abbrev definition, give a negative argument to the abbrev definition command: C-u - C-x a g or C-u - C-x a l. The former removes a global definition, while the latter removes a mode-specific definition. M-x kill-all-abbrevs removes all abbrev definitions, both global and local.


30.3 Controlling Abbrev Expansion

When Abbrev mode is enabled, an abbrev expands whenever it is present in the buffer just before point and you type a self-inserting whitespace or punctuation character (SPC, comma, etc.). More precisely, any character that is not a word constituent expands an abbrev, and any word-constituent character can be part of an abbrev. The most common way to use an abbrev is to insert it and then insert a punctuation or whitespace character to expand it.

Abbrev expansion preserves case: ‘foo’ expands to ‘find outer otter’, and ‘Foo’ to ‘Find outer otter’. ‘FOO’ expands to ‘Find Outer Otter’ by default, but if you change the variable abbrev-all-caps to a non-nil value, it expands to ‘FIND OUTER OTTER’.

These commands are used to control abbrev expansion:

M-'

Separate a prefix from a following abbrev to be expanded (abbrev-prefix-mark).

C-x a e

Expand the abbrev before point (expand-abbrev). This is effective even when Abbrev mode is not enabled.

M-x unexpand-abbrev

Undo the expansion of the last expanded abbrev.

M-x expand-region-abbrevs

Expand some or all abbrevs found in the region.

You may wish to expand an abbrev and attach a prefix to the expansion; for example, if ‘cnst’ expands into ‘construction’, you might want to use it to enter ‘reconstruction’. It does not work to type recnst, because that is not necessarily a defined abbrev. What you can do is use the command M-' (abbrev-prefix-mark) in between the prefix ‘re’ and the abbrev ‘cnst’. First, insert ‘re’. Then type M-'; this inserts a hyphen in the buffer to indicate that it has done its work. Then insert the abbrev ‘cnst’; the buffer now contains ‘re-cnst’. Now insert a non-word character to expand the abbrev ‘cnst’ into ‘construction’. This expansion step also deletes the hyphen that indicated M-' had been used. The result is the desired ‘reconstruction’.

If you actually want the text of the abbrev in the buffer, rather than its expansion, you can accomplish this by inserting the following punctuation with C-q. Thus, foo C-q , leaves ‘foo,’ in the buffer, not expanding it.

If you expand an abbrev by mistake, you can undo the expansion by typing C-/ (undo). See Undo. This undoes the insertion of the abbrev expansion and brings back the abbrev text. If the result you want is the terminating non-word character plus the unexpanded abbrev, you must reinsert the terminating character, quoting it with C-q. You can also use the command M-x unexpand-abbrev to cancel the last expansion without deleting the terminating character.

M-x expand-region-abbrevs searches through the region for defined abbrevs, and for each one found offers to replace it with its expansion. This command is useful if you have typed in text using abbrevs but forgot to turn on Abbrev mode first. It may also be useful together with a special set of abbrev definitions for making several global replacements at once. This command is effective even if Abbrev mode is not enabled.

The function expand-abbrev performs the expansion by calling the function that abbrev-expand-function specifies. By changing this function you can make arbitrary changes to the abbrev expansion. See Abbrev Expansion in The Emacs Lisp Reference Manual.


30.4 Abbrevs Suggestions

You can get abbrev suggestions when you manually type text for which there is currently an active defined abbrev. For example, if there is an abbrev ‘foo’ with the expansion ‘find outer otter’, and you manually type ‘find outer otter’, Emacs can notice this and show a hint in the echo area when you have stopped typing.

To enable the abbrev suggestion feature, customize the option abbrev-suggest to a non-nil value.

The variable abbrev-suggest-hint-threshold controls when to suggest an abbrev to the user. This variable defines the minimum savings (in terms of the number of characters the user will not have to type) required for Emacs to suggest using an abbrev. For example, if the user types ‘foo bar’ (seven characters) and there is an abbrev ‘fubar’ defined (five characters), the user will not get any suggestion unless the threshold is set to the number 2 or lower. With the default value 3, the user would not get any suggestion in this example, because the savings in using the abbrev are below the threshold. If you always want to get abbrev suggestions, set this variable’s value to zero.

The command abbrev-suggest-show-report displays a buffer with all the abbrev suggestions shown during the current editing session. This can be useful if you get several abbrev suggestions and don’t remember them all.


30.5 Examining and Editing Abbrevs

M-x list-abbrevs

Display a list of all abbrev definitions. With a numeric argument, list only local abbrevs.

M-x edit-abbrevs

Edit a list of abbrevs; you can add, alter or remove definitions.

The output from M-x list-abbrevs looks like this:

various other tables…
(python-mode-skeleton-abbrev-table)
"class" (sys)	    0 "" python-skeleton-class
(lisp-mode-abbrev-table)
"ks"          0    "keymap-set"
(global-abbrev-table)
"dfn"         0    "definition"

(Some blank lines of no semantic significance, and some other abbrev tables, have been omitted.)

A line containing a name in parentheses is the header for abbrevs in a particular abbrev table; global-abbrev-table contains all the global abbrevs, and the other abbrev tables that are named after major modes contain the mode-specific abbrevs.

Within each abbrev table, each nonblank line defines one abbrev. The word at the beginning of the line is the abbrev. The number that follows is the number of times the abbrev has been expanded. Emacs keeps track of this to help you see which abbrevs you actually use, so that you can eliminate those that you don’t use often. The string at the end of the line is the expansion.

Some abbrevs are marked with ‘(sys)’. These system abbrevs (see Abbrevs in The Emacs Lisp Reference Manual) are pre-defined by various modes, and are not saved to your abbrev file. To disable a system abbrev, define an abbrev of the same name that expands to itself, and save it to your abbrev file. The system abbrevs have an associated hook function, which is called to perform the abbrev expansion; the name of that function follows the abbrev expansion in the buffer shown by list-abbrevs.

M-x edit-abbrevs allows you to add, change or kill abbrev definitions by editing a list of them in an Emacs buffer. The list has the same format described above. The buffer of abbrevs is called *Abbrevs*, and is in Edit-Abbrevs mode. Type C-c C-c in this buffer to install the abbrev definitions as specified in the buffer—and delete any abbrev definitions not listed.

The command edit-abbrevs is actually the same as list-abbrevs except that it selects the buffer *Abbrevs* whereas list-abbrevs merely displays it in another window.


30.6 Saving Abbrevs

These commands allow you to keep abbrev definitions between editing sessions.

M-x write-abbrev-file RET file RET

Write a file file describing all defined abbrevs.

M-x read-abbrev-file RET file RET

Read the file file and define abbrevs as specified therein.

M-x define-abbrevs

Define abbrevs from definitions in current buffer.

M-x insert-abbrevs

Insert all abbrevs and their expansions into current buffer.

M-x write-abbrev-file reads a file name using the minibuffer and then writes a description of all current abbrev definitions into that file. This is used to save abbrev definitions for use in a later session. The text stored in the file is a series of Lisp expressions that, when executed, define the same abbrevs that you currently have.

M-x read-abbrev-file reads a file name using the minibuffer and then reads the file, defining abbrevs according to the contents of the file. The function quietly-read-abbrev-file is similar except that it does not display a message in the echo area; you cannot invoke it interactively, and it is used primarily in your init file (see The Emacs Initialization File). If either of these functions is called with nil as the argument, it uses the file given by the variable abbrev-file-name, which is ~/.emacs.d/abbrev_defs by default. This is your standard abbrev definition file, and Emacs loads abbrevs from it automatically when it starts up. (As an exception, Emacs does not load the abbrev file when it is started in batch mode. See Initial Options, for a description of batch mode.)

Emacs will offer to save abbrevs automatically if you have changed any of them, whenever it offers to save all files (for C-x s or C-x C-c). It saves them in the file specified by abbrev-file-name. This feature can be inhibited by setting the variable save-abbrevs to nil; setting it to silently will save the abbrevs automatically without asking.

The commands M-x insert-abbrevs and M-x define-abbrevs are similar to the previous commands but work on text in an Emacs buffer. M-x insert-abbrevs inserts text into the current buffer after point, describing all current abbrev definitions; M-x define-abbrevs parses the entire current buffer and defines abbrevs accordingly.


30.7 Dynamic Abbrev Expansion

The abbrev facility described above operates automatically as you insert text, but all abbrevs must be defined explicitly. By contrast, dynamic abbrevs allow the meanings of abbreviations to be determined automatically from the contents of the buffer, but dynamic abbrev expansion happens only when you request it explicitly.

M-/

Expand the word in the buffer before point as a dynamic abbrev, by searching for words starting with that abbreviation (dabbrev-expand).

C-M-/

Complete the word before point as a dynamic abbrev (dabbrev-completion).

For example, if the buffer contains ‘does this follow ’ and you type f o M-/, the effect is to insert ‘follow’ because that is the last word in the buffer that starts with ‘fo’. A numeric argument to M-/ says to take the second, third, etc. distinct expansion found looking backward from point. Repeating M-/ searches for an alternative expansion by looking farther back. After scanning all the text before point, it searches the text after point. The variable dabbrev-limit, if non-nil, specifies how far away in the buffer to search for an expansion.

After scanning the current buffer, M-/ normally searches other buffers. The variables dabbrev-check-all-buffers and dabbrev-check-other-buffers can be used to determine which other buffers, if any, are searched. Buffers that have major modes derived from any of the modes in dabbrev-ignored-buffer-modes are ignored.

For finer control over which buffers to scan, customize the variables dabbrev-ignored-buffer-names and dabbrev-ignored-buffer-regexps. The value of the former is a list of buffer names to skip. The value of the latter is a list of regular expressions; if a buffer’s name matches any of these regular expressions, dynamic abbrev expansion skips that buffer.

A negative argument to M-/, as in C-u - M-/, says to search first for expansions after point, then other buffers, and consider expansions before point only as a last resort. If you repeat the M-/ to look for another expansion, do not specify an argument. Repeating M-/ cycles through all the expansions after point and then the expansions before point.

After you have expanded a dynamic abbrev, you can copy additional words that follow the expansion in its original context. Simply type SPC M-/ for each additional word you want to copy. The spacing and punctuation between words is copied along with the words.

You can control the way M-/ determines the word to expand and how to expand it, see Customizing Dynamic Abbreviation.

The command C-M-/ (dabbrev-completion) performs completion of a dynamic abbrev. Instead of trying the possible expansions one by one, it finds all of them, then inserts the text that they have in common. If they have nothing in common, C-M-/ displays a list of completions, from which you can select a choice in the usual manner. See Completion.

Dynamic abbrev expansion is completely independent of Abbrev mode; the expansion of a word with M-/ is completely independent of whether it has a definition as an ordinary abbrev.


30.8 Customizing Dynamic Abbreviation

Normally, dynamic abbrev expansion ignores case when searching for expansions. That is, the expansion need not agree in case with the word you are expanding.

This feature is controlled by the variable dabbrev-case-fold-search. If it is t, case is ignored in this search; if it is nil, the word and the expansion must match in case. If the value is case-fold-search (the default), then the variable case-fold-search controls whether to ignore case while searching for expansions (see Lax Matching During Searching).

Normally, dynamic abbrev expansion preserves the case pattern of the dynamic abbrev you are expanding, by converting the expansion to that case pattern.

The variable dabbrev-case-replace controls whether to preserve the case pattern of the dynamic abbrev. If it is t, the dynamic abbrev’s case pattern is preserved in most cases; if it is nil, the expansion is always copied verbatim. If the value is case-replace (the default), then the variable case-replace controls whether to copy the expansion verbatim (see Replace Commands and Lax Matches).

However, if the expansion contains a complex mixed case pattern, and the dynamic abbrev matches this pattern as far as it goes, then the expansion is always copied verbatim, regardless of those variables. Thus, for example, if the buffer contains variableWithSillyCasePattern, and you type v a M-/, it copies the expansion verbatim including its case pattern.

The variable dabbrev-abbrev-char-regexp, if non-nil, controls which characters are considered part of a word, for dynamic expansion purposes. The regular expression must match just one character, never two or more. The same regular expression also determines which characters are part of an expansion. The (default) value nil has a special meaning: dynamic abbrevs (i.e. the word at point) are made of word characters, but their expansions are looked for as sequences of word and symbol characters. This is generally appropriate for expanding symbols in a program source and also for human-readable text in many languages, but may not be what you want in a text buffer that includes unusual punctuation characters; in that case, the value "\\sw" might produce better results.

In shell scripts and makefiles, a variable name is sometimes prefixed with ‘$’ and sometimes not. Major modes for this kind of text can customize dynamic abbrev expansion to handle optional prefixes by setting the variable dabbrev-abbrev-skip-leading-regexp. Its value should be a regular expression that matches the optional prefix that dynamic abbrev expression should ignore. The default is nil, which means no characters should be skipped.


31 Dired, the Directory Editor

Dired makes an Emacs buffer containing a listing of a directory, and optionally some of its subdirectories as well. You can use the normal Emacs commands to move around in this buffer, and special Dired commands to operate on the listed files. Dired works with both local and remote directories.

The Dired buffer is normally read-only, and inserting text in it is not allowed (however, the Wdired mode allows that, see Editing the Dired Buffer). Ordinary printing characters such as d and x are redefined for special Dired commands. Some Dired commands mark or flag the current file (that is, the file on the current line); other commands operate on the marked files or on the flagged files. You first mark certain files in order to operate on all of them with one command.

The Dired-X package provides various extra features for Dired mode. See Dired-X in Dired Extra User’s Manual.

You can also view a list of files in a directory with C-x C-d (list-directory). Unlike Dired, this command does not allow you to operate on the listed files. See File Directories.


31.1 Entering Dired

To invoke Dired, type C-x d (dired). This reads a directory’s name using the minibuffer, and opens a Dired buffer listing the files in that directory. You can also supply a wildcard file name pattern as the minibuffer argument, in which case the Dired buffer lists all files matching that pattern. A wildcard may appear in the directory part as well. For instance,

C-x d  ~/foo/*.el  RET
C-x d  ~/foo/*/*.el  RET

The former lists all the files with extension ‘.el’ in directory ‘foo’. The latter lists the files with extension ‘.el’ in all the subdirectories of ‘foo’.

On Posix systems, when the system shell supports globstar, a recursive globbing feature, and that support is enabled, you can use recursive globbing in Dired:

C-x d  ~/foo/**/*.el  RET

This command produces a directory listing with all the files with extension ‘.el’, descending recursively in all the subdirectories of ‘foo’. Note that there are small differences in the implementation of globstar between different shells. Check your shell manual to know the expected behavior.

If the shell supports globstar, but that support is disabled by default, you can still let Dired use this feature by customizing dired-maybe-use-globstar to a non-nil value; then Dired will enable globstar for those shells for which it knows how (see dired-enable-globstar-in-shell for the list of those shells).

The usual history and completion commands can be used in the minibuffer; in particular, M-n puts the name of the visited file (if any) in the minibuffer (see Minibuffer History).

You can also invoke Dired by giving C-x C-f (find-file) a directory’s name.

You can ask Emacs to invoke Dired on the default-directory (see default-directory) of any buffer, by typing C-x C-j (dired-jump). If the buffer visits a file, this command will move point to that file’s line in the Dired buffer it shows; otherwise, point will end up on the first file in the directory listing. As an exception, if you type C-x C-j in a Dired buffer, Emacs displays the directory listing of the parent directory and places point on the line that corresponds to the directory where you invoked dired-jump. Typing C-x 4 C-j (dired-jump-other-window) has the same effect, but displays the Dired buffer in a new window.

The variable dired-listing-switches specifies the options to give to ls for listing the directory; this string must contain ‘-l’. If you use a prefix argument with the dired command, you can specify the ls switches with the minibuffer before you enter the directory specification. No matter how they are specified, the ls switches can include short options (that is, single characters) requiring no arguments, and long options (starting with ‘--’) whose arguments are specified with ‘=’.

Dired does not handle files that have names with embedded newline characters well. If you have many such files, you may consider adding ‘-b’ to dired-listing-switches. This will quote all special characters and allow Dired to handle them better. (You can also use the C-u C-x d command to add ‘-b’ temporarily.)

Dired displays in the mode line an indication of what were the switches used to invoke ls. By default, Dired will try to determine whether the switches indicate sorting by name or date, and will say so in the mode line. If the dired-switches-in-mode-line variable is as-is, the switches will be shown verbatim. If this variable’s value is an integer, the switch display will be truncated to that length. This variable can also be a function, which will be called with dired-actual-switches as the only parameter, and should return a string to display in the mode line.

If your ls program supports the ‘--dired’ option, Dired automatically passes it that option; this causes ls to emit special escape sequences for certain unusual file names, without which Dired will not be able to parse those names. The first time you run Dired in an Emacs session, it checks whether ls supports the ‘--dired’ option by calling it once with that option. If the exit code is 0, Dired will subsequently use the ‘--dired’ option; otherwise it will not. You can inhibit this check by customizing the variable dired-use-ls-dired. The value unspecified (the default) means to perform the check; any other non-nil value means to use the ‘--dired’ option; and nil means not to use the ‘--dired’ option.

On MS-Windows and MS-DOS systems, and also on some remote systems, Emacs emulates ls. See Emulation of ls on MS-Windows, for options and peculiarities of this emulation.

To display the Dired buffer in another window, use C-x 4 d (dired-other-window). C-x 5 d (dired-other-frame) displays the Dired buffer in a separate frame.

Typing q (quit-window) buries the Dired buffer, and deletes its window if the window was created just for that buffer.


All the usual Emacs cursor motion commands are available in Dired buffers. The keys C-n and C-p are redefined to run dired-next-line and dired-previous-line, respectively, and they put the cursor at the beginning of the file name on the line, rather than at the beginning of the line.

For extra convenience, SPC and n in Dired are equivalent to C-n. p is equivalent to C-p. (Moving by lines is so common in Dired that it deserves to be easy to type.) DEL (move up and unflag) is also often useful simply for moving up (see Deleting Files with Dired).

j (dired-goto-file) prompts for a file name using the minibuffer, and moves point to the line in the Dired buffer describing that file.

M-s f C-s (dired-isearch-filenames) performs a forward incremental search in the Dired buffer, looking for matches only amongst the file names and ignoring the rest of the text in the buffer. M-s f M-C-s (dired-isearch-filenames-regexp) does the same, using a regular expression search. If you change the variable dired-isearch-filenames to t, then the usual search commands also limit themselves to the file names; for instance, C-s behaves like M-s f C-s. If the value is dwim, then search commands match the file names only when point was on a file name initially. See Searching and Replacement, for information about incremental search.

Some additional navigation commands are available when the Dired buffer includes several directories. See Moving Over Subdirectories.


31.3 Deleting Files with Dired

One of the most frequent uses of Dired is to first flag files for deletion, then delete the files that were flagged.

d

Flag this file for deletion (dired-flag-file-deletion).

u

Remove the deletion flag (dired-unmark).

DEL

Move point to previous line and remove the deletion flag on that line (dired-unmark-backward).

x

Delete files flagged for deletion (dired-do-flagged-delete).

You can flag a file for deletion by moving to the line describing the file and typing d (dired-flag-file-deletion). The deletion flag is visible as a ‘D’ at the beginning of the line. This command moves point to the next line, so that repeated d commands flag successive files. A numeric prefix argument serves as a repeat count; a negative count means to flag preceding files.

If the region is active, the d command flags all files in the region for deletion; in this case, the command does not move point, and ignores any prefix argument.

The reason for flagging files for deletion, rather than deleting files immediately, is to reduce the danger of deleting a file accidentally. Until you direct Dired to delete the flagged files, you can remove deletion flags using the commands u and DEL. u (dired-unmark) works just like d, but removes flags rather than making flags. DEL (dired-unmark-backward) moves upward, removing flags; it is like u with argument −1. A numeric prefix argument to either command serves as a repeat count, with a negative count meaning to unflag in the opposite direction. If the region is active, these commands instead unflag all files in the region, without moving point.

To delete flagged files, type x (dired-do-flagged-delete). This command displays a list of all the file names flagged for deletion, and requests confirmation with yes. If you confirm, Dired deletes the flagged files, then deletes their lines from the text of the Dired buffer. The Dired buffer, with somewhat fewer lines, remains selected.

If you answer no or quit with C-g when asked to confirm, you return immediately to Dired, with the deletion flags still present in the buffer, and no files actually deleted.

You can delete empty directories just like other files, but normally Dired cannot delete directories that are nonempty. However, if the variable dired-recursive-deletes is non-nil, then Dired is allowed to delete nonempty directories including all their contents. That can be somewhat risky. If the value of the variable is always, Dired will delete nonempty directories recursively, which is even more risky.

Even if you have set dired-recursive-deletes to nil, you might want sometimes to delete directories recursively without being asked for confirmation for all of them. For example, you may want that when you have marked many directories for deletion and you are very sure that all of them can safely be deleted. For every nonempty directory you are asked for confirmation to delete, if you answer all, then all the remaining directories will be deleted without any further questions.

If you change the variable delete-by-moving-to-trash to t, the above deletion commands will move the affected files or directories into the operating system’s Trash, instead of deleting them outright. See Miscellaneous File Operations.

An alternative way of deleting files is to mark them with m and delete with D, see Operating on Files.


31.4 Flagging Many Files at Once

The #, ~, ., % &, and % d commands flag many files for deletion, based on their file names:

#

Flag all auto-save files (files whose names start and end with ‘#’) for deletion (see Auto-Saving: Protection Against Disasters).

~

Flag all backup files (files whose names end with ‘~’) for deletion (see Backup Files).

. (Period)

Flag excess numeric backup files for deletion. The oldest and newest few backup files of any one file are exempt; the middle ones are flagged.

% &

Flag for deletion all files with certain kinds of names which suggest you could easily create those files again.

% d regexp RET

Flag for deletion all files whose names match the regular expression regexp.

# (dired-flag-auto-save-files) flags all files whose names look like auto-save files—that is, files whose names begin and end with ‘#’. See Auto-Saving: Protection Against Disasters.

~ (dired-flag-backup-files) flags all files whose names say they are backup files—that is, files whose names end in ‘~’. See Backup Files.

. (period, dired-clean-directory) flags just some of the backup files for deletion: all but the oldest few and newest few backups of any one file. Normally, the number of newest versions kept for each file is given by the variable dired-kept-versions (not kept-new-versions; that applies only when saving). The number of oldest versions to keep is given by the variable kept-old-versions.

Period with a positive numeric argument, as in C-u 3 ., specifies the number of newest versions to keep, overriding dired-kept-versions. A negative numeric argument overrides kept-old-versions, using minus the value of the argument to specify the number of oldest versions of each file to keep.

% & (dired-flag-garbage-files) flags files whose names match the regular expression specified by the variable dired-garbage-files-regexp. By default, this matches certain files produced by TeX, ‘.bak’ files, and the ‘.orig’ and ‘.rej’ files produced by patch.

% d flags all files whose names match a specified regular expression (dired-flag-files-regexp). Only the non-directory part of the file name is used in matching. You can use ‘^’ and ‘$’ to anchor matches. You can exclude certain subdirectories from marking by hiding them while you use % d. See Hiding Subdirectories.


31.5 Visiting Files in Dired

There are several Dired commands for visiting or examining the files listed in the Dired buffer. All of them apply to the current line’s file; if that file is really a directory, these commands invoke Dired on that subdirectory (making a separate Dired buffer).

f

Visit the file described on the current line, like typing C-x C-f and supplying that file name (dired-find-file). See Visiting Files.

RET
e

Equivalent to f.

o

Like f, but uses another window to display the file’s buffer (dired-find-file-other-window). The Dired buffer remains visible in the first window. This is like using C-x 4 C-f to visit the file. See Multiple Windows.

C-o

Visit the file described on the current line, and display the buffer in another window, but do not select that window (dired-display-file).

mouse-1
mouse-2

Visit the file whose name you clicked on (dired-mouse-find-file-other-window). This uses another window to display the file, like the o command.

v

View the file described on the current line, with View mode (dired-view-file). View mode provides convenient commands to navigate the buffer but forbids changing it; See View Mode.

^

Visit the parent directory of the current directory (dired-up-directory). This is equivalent to moving to the line for .. and typing f there.

User Option: dired-kill-when-opening-new-dired-buffer

When visiting a new sub-directory in Dired, Emacs will (by default) open a new buffer to display this new directory, and leave the old Dired buffer as is. If this user option is non-nil, the old Dired buffer will be killed after selecting the new directory. This means that if you’re traversing a directory structure in Dired, you won’t end up with more than a single Dired buffer.


31.6 Dired Marks vs. Flags

Instead of flagging a file with ‘D’, you can mark the file with some other character (usually ‘*’). Most Dired commands to operate on files use the files marked with ‘*’. The only command that operates on flagged files is x, which deletes them.

Here are some commands for marking with ‘*’, for unmarking, and for operating on marks. (See Deleting Files with Dired, for commands to flag and unflag files.)

m
* m

Mark the current file with ‘*’ (dired-mark). If the region is active, mark all files in the region instead; otherwise, if a numeric argument n is supplied, mark the next n files instead, starting with the current file (if n is negative, mark the previous −n files). If invoked on a subdirectory header line (see Subdirectories in Dired), this command marks all the files in that subdirectory.

* N

Report what the number and size of the marked files are (dired-number-of-marked-files).

* *

Mark all executable files with ‘*’ (dired-mark-executables). With a numeric argument, unmark all those files.

* @

Mark all symbolic links with ‘*’ (dired-mark-symlinks). With a numeric argument, unmark all those files.

* /

Mark with ‘*’ all files which are directories, except for . and .. (dired-mark-directories). With a numeric argument, unmark all those files.

* s

Mark all the files in the current subdirectory, aside from . and .. (dired-mark-subdir-files).

u
* u

Remove any mark on this line (dired-unmark). If the region is active, unmark all files in the region instead; otherwise, if a numeric argument n is supplied, unmark the next n files instead, starting with the current file (if n is negative, unmark the previous −n files).

DEL
* DEL

Move point to previous line and remove any mark on that line (dired-unmark-backward). If the region is active, unmark all files in the region instead; otherwise, if a numeric argument n is supplied, unmark the n preceding files instead, starting with the current file (if n is negative, unmark the next −n files).

* !
U

Remove all marks from all the files in this Dired buffer (dired-unmark-all-marks).

* ? markchar
M-DEL

Remove all marks that use the character markchar (dired-unmark-all-files). If invoked with M-DEL, the command prompts for markchar. That markchar is a single character—do not use RET to terminate it. See the description of the * c command below, which lets you replace one mark character with another.

With a numeric argument, this command queries about each marked file, asking whether to remove its mark. You can answer y meaning yes, n meaning no, or ! to remove the marks from the remaining files without asking about them.

* C-n
M-}

Move down to the next marked file (dired-next-marked-file). A file is “marked” if it has any kind of mark.

* C-p
M-{

Move up to the previous marked file (dired-prev-marked-file).

t
* t

Toggle all marks (dired-toggle-marks): files marked with ‘*’ become unmarked, and unmarked files are marked with ‘*’. Files marked in any other way are not affected.

* c old-markchar new-markchar

Replace all marks that use the character old-markchar with marks that use the character new-markchar (dired-change-marks). This command is the primary way to create or use marks other than ‘*’ or ‘D’. The arguments are single characters—do not use RET to terminate them.

You can use almost any character as a mark character by means of this command, to distinguish various classes of files. If old-markchar is a space (‘ ’), then the command operates on all unmarked files; if new-markchar is a space, then the command unmarks the files it acts on.

To illustrate the power of this command, here is how to put ‘D’ flags on all the files that have no marks, while unflagging all those that already have ‘D’ flags:

* c D t  * c SPC D  * c t SPC

This assumes that no files were already marked with ‘t’.

% m regexp RET
* % regexp RET

Mark (with ‘*’) all files whose names match the regular expression regexp (dired-mark-files-regexp). This command is like % d, except that it marks files with ‘*’ instead of flagging with ‘D’.

Only the non-directory part of the file name is used in matching. Use ‘^’ and ‘$’ to anchor matches. You can exclude subdirectories by temporarily hiding them (see Hiding Subdirectories).

% g regexp RET

Mark (with ‘*’) all files whose contents contain a match for the regular expression regexp (dired-mark-files-containing-regexp). This command is like % m, except that it searches the file contents instead of the file name. Note that if a file is visited in an Emacs buffer, and dired-always-read-filesystem is nil (the default), this command will look in the buffer without revisiting the file, so the results might be inconsistent with the file on disk if its contents have changed since it was last visited. If you don’t want this, you may wish to revert the files you have visited in your buffers, or to turn on Auto-Revert mode in those buffers, before invoking this command. See Reverting a Buffer. If you prefer that this command should always revisit the file, without you having to revert the file or enable Auto-Revert mode, you might want to set dired-always-read-filesystem to non-nil.

C-/
C-x u
C-_

Undo changes in the Dired buffer, such as adding or removing marks (dired-undo). This command does not revert the actual file operations, nor recover lost files! It just undoes changes in the buffer itself.

In some cases, using this after commands that operate on files can cause trouble. For example, after renaming one or more files, dired-undo restores the original names in the Dired buffer, which gets the Dired buffer out of sync with the actual contents of the directory.


31.7 Operating on Files

This section describes the basic Dired commands to operate on one file or several files. All of these commands are capital letters; all of them use the minibuffer, either to read an argument or to ask for confirmation, before they act. All of them let you specify the files to manipulate in these ways:

  • If you give the command a numeric prefix argument n, it operates on the next n files, starting with the current file. (If n is negative, the command operates on the −n files preceding the current line.)
  • Otherwise, if some files are marked with ‘*’, the command operates on all those files.
  • Otherwise, the command operates on the current file only.

Certain other Dired commands, such as ! and the ‘%’ commands, use the same conventions to decide which files to work on.

In addition to Dired commands described here, you can also invoke Version Control (VC) commands on one or more files shown in a Dired buffer. See Version Control.

Commands which ask for a destination directory, such as those which copy and rename files or create links for them, try to guess the default target directory for the operation. Normally, they suggest the Dired buffer’s default directory, but if the option dired-dwim-target is non-nil, and if there is another Dired buffer displayed in some window, that other buffer’s directory is suggested instead. You can customize dired-dwim-target to prefer either the next window with a Dired buffer, or the most recently used window with a Dired buffer, or to use any other function. When the value is a function, it will be called with no arguments and is expected to return a list of directories which will be used as defaults (i.e. default target and “future history”).

Here are the file-manipulating Dired commands that operate on files.

C new RET

Copy the specified files (dired-do-copy). The argument new is the directory to copy into, or (if copying a single file) the new name. This is like the shell command cp.

The option dired-create-destination-dirs controls whether Dired should create non-existent directories in the destination while copying/renaming files. The default value nil means Dired never creates such missing directories; the value always, means Dired automatically creates them; the value ask means Dired asks you for confirmation before creating them.

If the option dired-create-destination-dirs-on-trailing-dirsep is non-nil in addition to dired-create-destination-dirs, a trailing directory separator at the destination directory is treated specially. In that case, when copying to ‘test/’ and no directory ‘test’ exists already, it will be created and the specified source files or directories are copied into the newly created directory.

If dired-copy-preserve-time is non-nil, then copying with this command preserves the modification time of the old file in the copy, like ‘cp -p’.

The variable dired-recursive-copies controls whether to copy directories recursively (like ‘cp -r’). The default is top, which means to ask before recursively copying a directory.

The variable dired-copy-dereference controls whether to copy symbolic links as links or after dereferencing (like ‘cp -L’). The default is nil, which means that the symbolic links are copied by creating new ones.

The dired-keep-marker-copy user option controls how this command handles file marking. The default is to mark all new copies of files with a ‘C’ mark.

D

Delete the specified files (dired-do-delete). This is like the shell command rm.

Like the other commands in this section, this command operates on the marked files, or the next n files. By contrast, x (dired-do-flagged-delete) deletes all flagged files.

R new RET

Rename the specified files (dired-do-rename). If you rename a single file, the argument new is the new name of the file. If you rename several files, the argument new is the directory into which to move the files (this is like the shell command mv).

The option dired-create-destination-dirs controls whether Dired should create non-existent directories in new.

The option dired-create-destination-dirs-on-trailing-dirsep, when set in addition to dired-create-destination-dirs, controls whether a trailing directory separator at the destination is treated specially. In that case, when renaming a directory ‘old’ to ‘new/’ and no directory ‘new’ exists already, it will be created and ‘old’ is moved into the newly created directory. Otherwise, ‘old’ is renamed to ‘new’.

Dired automatically changes the visited file name of buffers associated with renamed files so that they refer to the new names.

If the value of the variable dired-vc-rename-file is non-nil, files are renamed using the commands of the underlying VCS, via vc-rename-file (see Deleting and Renaming Version-Controlled Files).

H new RET

Make hard links to the specified files (dired-do-hardlink). This is like the shell command ln. The argument new is the directory to make the links in, or (if making just one link) the name to give the link.

S new RET

Make symbolic links to the specified files (dired-do-symlink). This is like ‘ln -s’. The argument new is the directory to make the links in, or (if making just one link) the name to give the link.

Y new RET

Make relative symbolic links to the specified files (dired-do-relsymlink). The argument new is the directory to make the links in, or (if making just one link) the name to give the link. This is like dired-do-symlink but creates relative symbolic links. For example:

    foo -> ../bar/foo

It does not create absolute ones like:

    foo -> /path/that/may/change/any/day/bar/foo
M modespec RET

Change the mode (also called permission bits) of the specified files (dired-do-chmod). modespec can be in octal or symbolic notation, like arguments handled by the chmod program. This command does not follow symbolic links, so it reports an error if you try to change the mode of a symbolic link on a platform where such modes are immutable.

G newgroup RET

Change the group of the specified files to newgroup (dired-do-chgrp).

O newowner RET

Change the owner of the specified files to newowner (dired-do-chown). (On most systems, only the superuser can do this.)

The variable dired-chown-program specifies the name of the program to use to do the work. (This variable is necessary because different systems put chown in different places).

T timestamp RET

Touch the specified files (dired-do-touch). This means updating their modification times to timestamp, which defaults to the present time. This is like the shell command touch.

P command RET

Print the specified files (dired-do-print). You must specify the command to print them with, but the minibuffer starts out with a suitable guess made using the variables lpr-command and lpr-switches (the same variables that lpr-buffer uses; see Printing Hard Copies).

Z

Compress the specified files (dired-do-compress). If the file appears to be a compressed file already, uncompress it instead. Each marked file is compressed into its own archive; this uses the gzip program if it is available, otherwise it uses compress.

On a directory name, this command produces a compressed archive depending on the dired-compress-directory-default-suffix user option. The default is a .tar.gz archive containing all of the directory’s files, by running the tar command with output piped to gzip. To allow decompression of compressed directories, typing Z on a .tar.gz or .tgz archive file unpacks all the files in the archive into a directory whose name is the archive name with the extension removed.

c

Compress the specified files (dired-do-compress-to) into a single archive anywhere on the file system. The default archive is controlled by the dired-compress-directory-default-suffix user option. Also see dired-compress-files-alist.

:d

Decrypt the specified files (epa-dired-do-decrypt). See Dired integration in EasyPG Assistant User’s Manual.

:v

Verify digital signatures on the specified files (epa-dired-do-verify). See Dired integration in EasyPG Assistant User’s Manual.

:s

Digitally sign the specified files (epa-dired-do-sign). See Dired integration in EasyPG Assistant User’s Manual.

:e

Encrypt the specified files (epa-dired-do-encrypt). See Dired integration in EasyPG Assistant User’s Manual.

L

Load the specified Emacs Lisp files (dired-do-load). See Libraries of Lisp Code for Emacs.

B

Byte compile the specified Emacs Lisp files (dired-do-byte-compile). See Byte Compilation in The Emacs Lisp Reference Manual.

I

Run Info on this file (assumed to be a file in Info format).

N

Run man on this file (assumed to be a file in nroff format).

A regexp RET

Search all the specified files for the regular expression regexp (dired-do-find-regexp).

This command is a variant of xref-find-references (see Searching and Replacing with Identifiers), it displays the *xref* buffer, where you can navigate between matches and display them as needed using the commands described in Commands Available in the *xref* Buffer.

If any of the marked files are directories, then this command searches all of the files in those directories, and any of their subdirectories, recursively, except files whose names match grep-find-ignored-files and subdirectories whose names match grep-find-ignored-directories.

Q regexp RET to RET

Perform query-replace-regexp on each of the specified files, replacing matches for regexp with the string to (dired-do-find-regexp-and-replace).

This command is a variant of xref-query-replace-in-results. It presents an *xref* buffer that lists all the matches of regexp, and you can use the special commands in that buffer (see Commands Available in the *xref* Buffer). In particular, if you exit the query replace loop, you can use r in that buffer to replace more matches. See Searching and Replacing with Identifiers.

Like with dired-do-find-regexp, if any of the marked files are directories, this command performs replacements in all of the files in those directories, and in any of their subdirectories, recursively, except for files whose names match grep-find-ignored-files and subdirectories whose names match grep-find-ignored-directories.


31.8 Shell Commands in Dired

The Dired command ! (dired-do-shell-command) reads a shell command string in the minibuffer, and runs that shell command on one or more files. The files that the shell command operates on are determined in the usual way for Dired commands (see Operating on Files). The command X is a synonym for !.

The command & (dired-do-async-shell-command) does the same, except that it runs the shell command asynchronously. (You can also do this with !, by appending a ‘&’ character to the end of the shell command.) When the command operates on more than one file, it runs multiple parallel copies of the specified shell command, one for each file. As an exception, if the specified shell command ends in ‘;’ or ‘;&’, the shell command is run in the background on each file sequentially; Emacs waits for each invoked shell command to terminate before running the next one.

For both ! and &, the working directory for the shell command is the top-level directory of the Dired buffer.

If you tell ! or & to operate on more than one file, the shell command string determines how those files are passed to the shell command:

  • If you use ‘*’ surrounded by whitespace in the command string, then the command runs just once, with the list of file names substituted for the ‘*’. The order of file names is the order of appearance in the Dired buffer.

    Thus, ! tar cf foo.tar * RET runs tar on the entire list of file names, putting them into one tar file foo.tar.

    If you want to use ‘*’ as a shell wildcard with whitespace around it, write ‘*""’. In the shell, this is equivalent to ‘*’; but since the ‘*’ is not surrounded by whitespace, Dired does not treat it specially. Emacs will prompt for confirmation if you do this, unless dired-confirm-shell-command is nil.

  • Otherwise, if the command string contains ‘?’ surrounded by whitespace or ‘`?`’, Emacs runs the shell command once for each file, substituting the current file name for ‘?’ and ‘`?`’ each time. You can use both ‘?’ and ‘`?`’ more than once in the command; the same file name replaces each occurrence. If you mix them with ‘*’ the command signals an error.
  • If the command string contains neither ‘*’ nor ‘?’ nor ‘`?`’, Emacs runs the shell command once for each file, adding the file name at the end. For example, ! uudecode RET runs uudecode on each file.

To iterate over the file names in a more complicated fashion, you might prefer to use an explicit shell loop. For example, here is how to uuencode each file, making the output file name by appending ‘.uu’ to the input file name:

for file in * ; do uuencode "$file" "$file" >"$file".uu; done

The same example with ‘`?`’ notation:

uuencode ? ? > `?`.uu

The ! and & commands do not attempt to update the Dired buffer to show new or modified files, because they don’t know what files will be changed. Use the g command to update the Dired buffer (see Updating the Dired Buffer).

See Single Shell Commands, for information about running shell commands outside Dired.


31.9 Shell Command Guessing

Based upon the name of a file, Dired tries to guess what shell command you might want to apply to it. For example, if you have point on a file named foo.tar and you press !, Dired will guess that you want to run ‘tar xvf’, and suggest that as the default shell command.

You can type M-n to get the default into the minibuffer for editing. If there are several commands for a given file, type M-n several times to see each matching command in order.

Dired only tries to guess a command for a single file, never for a list of marked files.

Variable: dired-guess-shell-alist-default

This variable specifies the predefined rules for guessing shell commands suitable for certain files. Set this to nil to turn guessing off. The elements of dired-guess-shell-alist-user (defined by the user) will override these rules.

Variable: dired-guess-shell-alist-user

If non-nil, this variable specifies the user-defined alist of file regexps and their suggested commands. These rules take precedence over the predefined rules in the variable dired-guess-shell-alist-default when dired-do-shell-command is run). The default is nil.

Each element of the alist looks like

(regexp command…)

where each command can either be a string or a Lisp expression that evaluates to a string. If several commands are given, all of them will temporarily be pushed onto the history.

A ‘*’ in the shell command stands for the file name that matched regexp. When Emacs invokes the command, it replaces each instance of ‘*’ with the matched file name.

To add rules for ‘.foo’ and ‘.bar’ file extensions, add this to your Init file:

(setq dired-guess-shell-alist-user
      (list
       (list "\\.foo$" "foo-command")  ; fixed rule
       ;; possibly more rules...
       (list "\\.bar$"  ; rule with condition test
             '(if condition
                  "bar-command-1"
                "bar-command-2"))))

This will override any predefined rules for the same extensions.

You can find more user options with M-x customize-group RET dired-guess RET.


31.10 Transforming File Names in Dired

This section describes Dired commands which alter file names in a systematic way. Each command operates on some or all of the marked files, using a new name made by transforming the existing name.

Like the basic Dired file-manipulation commands (see Operating on Files), the commands described here operate either on the next n files, or on all files marked with ‘*’, or on the current file. (To mark files, use the commands described in Dired Marks vs. Flags.)

All of the commands described in this section work interactively: they ask you to confirm the operation for each candidate file. Thus, you can select more files than you actually need to operate on (e.g., with a regexp that matches many files), and then filter the selected names by typing y or n when the command prompts for confirmation.

% u

Rename each of the selected files to an upper-case name (dired-upcase). If the old file names are Foo and bar, the new names are FOO and BAR.

% l

Rename each of the selected files to a lower-case name (dired-downcase). If the old file names are Foo and bar, the new names are foo and bar.

% R from RET to RET
% C from RET to RET
% H from RET to RET
% S from RET to RET
% Y from RET to RET

These five commands rename, copy, make hard links, make soft links, and make relative soft links, in each case computing the new name by regular-expression substitution from the name of the old file.

The four regular-expression substitution commands effectively perform a search-and-replace on the selected file names. They read two arguments: a regular expression from, and a substitution pattern to; they match each old file name against from, and then replace the matching part with to. You can use ‘\&’ and ‘\digit’ in to to refer to all or part of what the pattern matched in the old file name, as in replace-regexp (see Regexp Replacement). If the regular expression matches more than once in a file name, only the first match is replaced.

For example, % R ^.*$ RET x-\& RET renames each selected file by prepending ‘x-’ to its name. The inverse of this, removing ‘x-’ from the front of each file name, is also possible: one method is % R ^x-\(.*\)$ RET \1 RET; another is % R ^x- RET RET. (Use ‘^’ and ‘$’ to anchor matches that should span the whole file name.)

Normally, the replacement process does not consider the files’ directory names; it operates on the file name within the directory. If you specify a numeric argument of zero, then replacement affects the entire absolute file name including directory name. (A non-zero argument specifies the number of files to operate on.)

You may want to select the set of files to operate on using the same regexp from that you will use to operate on them. To do this, mark those files with % m from RET, then use the same regular expression in the command to operate on the files. To make this more convenient, the % commands to operate on files use the last regular expression specified in any % command as a default.


31.11 File Comparison with Dired

The = (dired-diff) command compares the current file (the file at point) with another file (read using the minibuffer) using the diff program. The file specified with the minibuffer is the first argument of diff, and file at point is the second argument. The output of the diff program is shown in a buffer using Diff mode (see Comparing Files).

If the region is active, the default for the file read using the minibuffer is the file at the mark (i.e., the ordinary Emacs mark, not a Dired mark; see Setting the Mark). Otherwise, if the file at point has a backup file (see Backup Files), that is the default.

You could also compare files using ediff-files, see Major Entry Points in Ediff User’s Manual.


31.12 Subdirectories in Dired

A Dired buffer usually displays just one directory, but you can optionally include its subdirectories as well.

The simplest way to include multiple directories in one Dired buffer is to specify the options ‘-lR’ for running ls. (If you give a numeric argument when you run Dired, then you can specify these options in the minibuffer.) That produces a recursive directory listing showing all subdirectories at all levels.

More often, you will want to show only specific subdirectories. You can do this with i (dired-maybe-insert-subdir):

i

Insert the contents of a subdirectory later in the buffer.

If you use this command on a line that describes a file which is a directory, it inserts the contents of that directory into the same Dired buffer, and moves there. Inserted subdirectory contents follow the top-level directory of the Dired buffer, just as they do in ‘ls -lR’ output.

If the subdirectory’s contents are already present in the buffer, the i command just moves to it.

In either case, i sets the Emacs mark before moving, so C-u C-SPC returns to your previous position in the Dired buffer (see Setting the Mark). You can also use ‘^’ to return to the parent directory in the same Dired buffer (see Visiting Files in Dired).

Use the l command (dired-do-redisplay) to update the subdirectory’s contents, and use C-u k on the subdirectory header line to remove the subdirectory listing (see Updating the Dired Buffer). You can also hide and show inserted subdirectories (see Hiding Subdirectories).


31.13 Subdirectory Switches in Dired

You can insert subdirectories with specified ls switches in Dired buffers using C-u i. You can change the ls switches of an already inserted subdirectory at point using C-u l.

Dired preserves the switches if you revert the buffer. Deleting a subdirectory forgets about its switches.

Using dired-undo (see Dired Marks vs. Flags) to reinsert or delete subdirectories that were inserted with explicit switches can bypass Dired’s machinery for remembering (or forgetting) switches. Deleting a subdirectory using dired-undo does not forget its switches. When later reinserted using i, it will be reinserted using its old switches. Using dired-undo to reinsert a subdirectory that was deleted using the regular Dired commands (not dired-undo) will originally insert it with its old switches. Reverting the buffer, however, will relist it using the buffer’s default switches. If any of this yields problems, you can easily correct the situation using C-u i or C-u l.

Dired does not remember the R switch. Inserting a subdirectory with switches that include the R switch is equivalent to inserting each of its subdirectories using all remaining switches. For instance, updating or killing a subdirectory that was inserted with the R switch will not update or kill its subdirectories.

The buffer’s default switches do not affect subdirectories that were inserted using explicitly specified switches. In particular, commands such as s that change the buffer’s switches do not affect such subdirectories. (They do, however, affect subdirectories without explicitly assigned switches.)

You can make Dired forget about all subdirectory switches and relist all subdirectories with the buffer’s default switches using M-x dired-reset-subdir-switches. This also reverts the Dired buffer.


31.14 Moving Over Subdirectories

When a Dired buffer lists subdirectories, you can use the page motion commands C-x [ and C-x ] to move by entire directories (see Pages).

The following commands move across, up and down in the tree of directories within one Dired buffer. They move to directory header lines, which are the lines that give a directory’s name, at the beginning of the directory’s contents.

C-M-n

Go to next subdirectory header line, regardless of level (dired-next-subdir).

C-M-p

Go to previous subdirectory header line, regardless of level (dired-prev-subdir).

C-M-u

Go up to the parent directory’s header line (dired-tree-up).

C-M-d

Go down in the directory tree, to the first subdirectory’s header line (dired-tree-down).

<

Move up to the previous directory-file line (dired-prev-dirline). These lines are the ones that describe a directory as a file in its parent directory.

>

Move down to the next directory-file line (dired-next-dirline).

M-G

Prompt for a directory and move to its directory-file line (dired-goto-subdir).


31.15 Hiding Subdirectories

Hiding a subdirectory means to make it invisible, except for its header line.

$

Hide or show the subdirectory that point is in, and move point to the next subdirectory (dired-hide-subdir). This is a toggle. A numeric argument serves as a repeat count.

M-$

Hide all subdirectories in this Dired buffer, leaving only their header lines (dired-hide-all). Or, if any subdirectory is currently hidden, make all subdirectories visible again. You can use this command to get an overview in very deep directory trees or to move quickly to subdirectories far away.

Ordinary Dired commands never consider files inside a hidden subdirectory. For example, the commands to operate on marked files ignore files in hidden directories even if they are marked. Thus you can use hiding to temporarily exclude subdirectories from operations without having to remove the Dired marks on files in those subdirectories.

See Subdirectories in Dired, for how to insert a subdirectory listing, and see Updating the Dired Buffer, for how to delete it.


31.16 Updating the Dired Buffer

This section describes commands to update the Dired buffer to reflect outside (non-Dired) changes in the directories and files, and to delete part of the Dired buffer.

g

Update the entire contents of the Dired buffer (revert-buffer).

l

Update the specified files (dired-do-redisplay). You specify the files for l in the same way as for file operations.

k

Delete the specified file lines—not the files, just the lines (dired-do-kill-lines).

s

Toggle between alphabetical order and date/time order (dired-sort-toggle-or-edit).

C-u s switches RET

Refresh the Dired buffer using switches as dired-listing-switches.

Type g (revert-buffer) to update the contents of the Dired buffer, based on changes in the files and directories listed. This preserves all marks except for those on files that have vanished. Hidden subdirectories are updated but remain hidden.

To update only some of the files, type l (dired-do-redisplay). Like the Dired file-operating commands, this command operates on the next n files (or previous −n files), or on the marked files if any, or on the current file. Updating the files means reading their current status, then updating their lines in the buffer to indicate that status.

If you use l on a subdirectory header line, it updates the contents of the corresponding subdirectory.

If you use C-x d or some other Dired command to visit a directory that is already being shown in a Dired buffer, Dired switches to that buffer but does not update it. If the buffer is not up-to-date, Dired displays a warning telling you to type g to update it. You can also tell Emacs to revert each Dired buffer automatically when you revisit it, by setting the variable dired-auto-revert-buffer to a non-nil value.

To delete file lines from the buffer—without actually deleting the files—type k (dired-do-kill-lines). Like the file-operating commands, this command operates on the next n files, or on the marked files if any. However, it does not operate on the current file, since otherwise mistyping k could be annoying.

If you use k to kill the line for a directory file which you had inserted in the Dired buffer as a subdirectory (see Subdirectories in Dired), it removes the subdirectory listing as well. Typing C-u k on the header line for a subdirectory also removes the subdirectory line from the Dired buffer.

The g command brings back any individual lines that you have killed in this way, but not subdirectories—you must use i to reinsert a subdirectory.

The files in a Dired buffers are normally listed in alphabetical order by file names. Alternatively Dired can sort them by date/time. The Dired command s (dired-sort-toggle-or-edit) switches between these two sorting modes. The mode line in a Dired buffer indicates which way it is currently sorted—by name, or by date.

C-u s switches RET lets you specify a new value for dired-listing-switches.


31.17 Dired and find

You can select a set of files for display in a Dired buffer more flexibly by using the find utility to choose the files.

To search for files with names matching a wildcard pattern use M-x find-name-dired. It reads arguments directory and pattern, and chooses all the files in directory or its subdirectories whose individual names match pattern.

The files thus chosen are displayed in a Dired buffer, in which the ordinary Dired commands are available.

If you want to test the contents of files, rather than their names, use M-x find-grep-dired. This command reads two minibuffer arguments, directory and regexp; it chooses all the files in directory or its subdirectories that contain a match for regexp. It works by running the programs find and grep. See also M-x grep-find, in Searching with Grep under Emacs. Remember to write the regular expression for grep, not for Emacs. (An alternative method of showing files whose contents match a given regexp is the % g regexp command, see Dired Marks vs. Flags.)

The most general command in this series is M-x find-dired, which lets you specify any condition that find can test. It takes two minibuffer arguments, directory and find-args; it runs find in directory, passing find-args to tell find what condition to test. To use this command, you need to know how to use find.

The format of listing produced by these commands is controlled by the variable find-ls-option. This is a pair of options; the first specifying how to call find to produce the file listing, and the second telling Dired to parse the output.

The command M-x locate provides a similar interface to the locate program. M-x locate-with-filter is similar, but keeps only files whose names match a given regular expression.

These buffers don’t work entirely like ordinary Dired buffers: file operations work, but do not always automatically update the buffer. Reverting the buffer with g deletes all inserted subdirectories, and erases all flags and marks.


31.18 Editing the Dired Buffer

Wdired is a special mode that allows you to perform file operations by editing the Dired buffer directly (the “W” in “Wdired” stands for “writable”). To enter Wdired mode, type C-x C-q (dired-toggle-read-only) while in a Dired buffer. Alternatively, use the ‘Immediate / Edit File Names’ menu item.

While in Wdired mode, you can rename files by editing the file names displayed in the Dired buffer. All the ordinary Emacs editing commands, including rectangle operations and query-replace, are available for this. Once you are done editing, type C-c C-c (wdired-finish-edit). This applies your changes and switches back to ordinary Dired mode.

Apart from simply renaming files, you can move a file to another directory by typing in the new file name (either absolute or relative). To mark a file for deletion, delete the entire file name. To change the target of a symbolic link, edit the link target name which appears next to the link name.

If you edit the file names to create a new subdirectory, Wdired will automatically create these new directories. To inhibit this behavior, set wdired-create-parent-directories to nil.

The rest of the text in the buffer, such as the file sizes and modification dates, is marked read-only, so you can’t edit it. However, if you set wdired-allow-to-change-permissions to t, you can edit the file permissions. For example, you can change ‘-rw-r--r--’ to ‘-rw-rw-rw-’ to make a file world-writable. These changes also take effect when you type C-c C-c.


31.19 Viewing Image Thumbnails in Dired

Image-Dired is a facility for browsing image files. It provides viewing the images either as thumbnails or in full size, either inside Emacs or through an external viewer. This is different from Image mode (see Viewing Image Files) for visiting an image file in the Emacs buffer.

To enter Image-Dired, mark the image files you want to look at in the Dired buffer, using m as usual. Then type C-t d (image-dired-display-thumbs). This creates and switches to a buffer containing Image-Dired, corresponding to the marked files.

You can also enter Image-Dired directly by typing M-x image-dired. This prompts for a directory; specify one that has image files. This creates thumbnails for all the images in that directory, and displays them all in the thumbnail buffer. The thumbnails are generated in the background and are loaded as they become available.

With point in the thumbnail buffer, you can type RET (image-dired-display-this) to display the image in another window. Use the standard Emacs movement key bindings or the arrow keys to move around in the thumbnail buffer. For easy browsing, use SPC (image-dired-display-next) to advance and display the next image. Typing DEL (image-dired-display-previous) backs up to the previous thumbnail and displays that instead.

Type C-RET (image-dired-thumbnail-display-external) to display the image in an external viewer. You must first configure image-dired-external-viewer.

You can delete images through Image-Dired also. Type d (image-dired-flag-thumb-original-file) to flag the image file for deletion in the Dired buffer. Alternatively, you can remove an image’s thumbnail from the thumbnail buffer without flagging the image for deletion, by typing C-d (image-dired-delete-char).

You could also use Image-Dired for “inline” operations (i.e., right into the Dired buffer). Type C-t C-t, and the thumbnails of the selected images in Dired will appear in front of their names (image-dired-dired-toggle-marked-thumbs). C-t i and C-t x will display the image under the point in Emacs or with the external viewer, respectively.

More advanced features include image tags, which are metadata used to categorize image files. The tags are stored in a plain text file configured by image-dired-tags-db-file.

To tag image files, mark them in the Dired buffer (you can also mark files in Dired from the thumbnail buffer by typing m) and type C-t t (image-dired-tag-files). This reads the tag name in the minibuffer. To mark files having a certain tag, type C-t f (image-dired-mark-tagged-files). After marking image files with a certain tag, you can use C-t d to view them.

You can also tag a file directly from the thumbnail buffer by typing t t, and you can remove a tag by typing t r. There is also a special tag called “comment” for each file (it is not a tag in the exact same sense as the other tags, it is handled slightly differently). That is used to enter a comment or description about the image. You comment a file from the thumbnail buffer by typing c. You will be prompted for a comment. Type C-t c to add a comment from Dired (image-dired-dired-comment-files). C-t e will bring a buffer to edit comment and tags (image-dired-dired-edit-comment-and-tags).

Files that are marked in Dired will also be marked in Image-Dired if image-dired-thumb-visible-marks is non-nil (which is the default).

Image-Dired also provides simple image manipulation. In the thumbnail buffer, type L to rotate the original image 90 degrees anti clockwise, and R to rotate it 90 degrees clockwise. This rotation is lossless, and uses an external utility called jpegtran, which you need to install first.


31.20 Other Dired Features

By default, Dired displays the available space on the directory’s disk on the first line of that directory’s listing, following the directory name. You can control this display by customizing the variable dired-free-space. Its default value is first, which produces the available space after the directory name. If you customize it to the value separate instead, Dired will display the disk space information on a separate line, following the line with the directory name, and will include in that line the space used by the files in the current directory as well as the available disk space. If you set this to nil, the available disk space information will not be displayed at all.

The command + (dired-create-directory) reads a directory’s name, and creates that directory. It signals an error if the directory already exists.

The command (dired-create-empty-file) reads a file name, and creates that file. It signals an error if the file already exists.

The command M-s a C-s (dired-do-isearch) begins a multi-file incremental search on the marked files. If a search fails at the end of a file, typing C-s advances to the next marked file and repeats the search; at the end of the last marked file, the search wraps around to the first marked file. The command M-s a M-C-s (dired-do-isearch-regexp) does the same with a regular expression search. See Repeating Incremental Search, for information about search repetition.

The command w (dired-copy-filename-as-kill) puts the names of the marked (or next n) files into the kill ring, as if you had killed them with C-w. The names are separated by a space.

With a zero prefix argument, this uses the absolute file name of each marked file. With just C-u as the prefix argument, it uses file names relative to the Dired buffer’s default directory. (This can still contain slashes if in a subdirectory.) As a special case, if point is on a directory header line, w gives you the absolute name of that directory. Any prefix argument or marked files are ignored in this case.

The main purpose of this command is so that you can yank the file names into arguments for other Emacs commands. It also displays what it added to the kill ring, so you can use it to display the list of currently marked files in the echo area.

If you have an HTML file in the file listing, it can be useful to view that file with a browser. The W (browse-url-of-dired-file) command will use the standard configured browser to view that file.

The command ( (dired-hide-details-mode) toggles whether details, such as ownership or file permissions, are visible in the current Dired buffer. By default, it also hides the targets of symbolic links, and all lines other than the header line and file/directory listings. To change this, customize the options dired-hide-details-hide-symlink-targets and dired-hide-details-hide-information-lines, respectively.

If the directory you are visiting is under version control (see Version Control), then the normal VC diff and log commands will operate on the selected files.

The command M-x dired-compare-directories is used to compare the current Dired buffer with another directory. It marks all the files that differ between the two directories. It puts these marks in all Dired buffers where these files are listed, which of course includes the current buffer.

The default comparison method (used if you type RET at the prompt) is to compare just the file names—file names differ if they do not appear in the other directory. You can specify more stringent comparisons by entering a Lisp expression, which can refer to the variables size1 and size2, the respective file sizes; mtime1 and mtime2, the last modification times in seconds, as floating point numbers; and fa1 and fa2, the respective file attribute lists (as returned by the function file-attributes). This expression is evaluated for each pair of like-named files, and files differ if the expression’s value is non-nil.

For instance, the sequence M-x dired-compare-directories RET (> mtime1 mtime2) RET marks files newer in this directory than in the other, and marks files older in the other directory than in this one. It also marks files with no counterpart, in both directories, as always.

On the X Window System, Emacs supports the drag and drop protocol. You can drag a file object from another program, and drop it onto a Dired buffer; this either moves, copies, or creates a link to the file in that directory. Precisely which action is taken is determined by the originating program. Dragging files out of a Dired buffer is also supported, by enabling the user option dired-mouse-drag-files, the mouse can be used to drag files onto other programs. When set to link, it will make the other program (typically a file manager) create a symbolic link to the file; when set to move, it will make the other program move the file to a new location, and setting it to any other non-nil value will make the other program open or create a copy of the file. The keyboard modifiers pressed during the drag-and-drop operation can also control what action the other program takes towards the file.


32 The Calendar and the Diary

Emacs provides the functions of a desk calendar, with a diary of planned or past events. It also has facilities for managing your appointments, and keeping track of how much time you spend working on certain projects.

To enter the calendar, type M-x calendar. This displays a three-month calendar centered on the current month, with point on the current date. With a numeric argument, as in C-u M-x calendar, it prompts you for the month and year to be the center of the three-month calendar. The calendar uses its own buffer, whose major mode is Calendar mode.

mouse-3 in the calendar brings up a menu of operations on a particular date; mouse-2 brings up a menu of commonly used calendar features that are independent of any particular date. To exit the calendar, type q.


32.1 Movement in the Calendar

Calendar mode provides commands to move through the calendar in logical units of time such as days, weeks, months, and years. If you move outside the three months originally displayed, the calendar display scrolls automatically through time to make the selected date visible. Moving to a date lets you view its holidays or diary entries, or convert it to other calendars; moving by long time periods is also useful simply to scroll the calendar.


32.1.1 Motion by Standard Lengths of Time

The commands for movement in the calendar buffer parallel the commands for movement in text. You can move forward and backward by days, weeks, months, and years.

C-f

Move point one day forward (calendar-forward-day).

C-b

Move point one day backward (calendar-backward-day).

C-n

Move point one week forward (calendar-forward-week).

C-p

Move point one week backward (calendar-backward-week).

M-}

Move point one month forward (calendar-forward-month).

M-{

Move point one month backward (calendar-backward-month).

C-x ]

Move point one year forward (calendar-forward-year).

C-x [

Move point one year backward (calendar-backward-year).

The day and week commands are natural analogues of the usual Emacs commands for moving by characters and by lines. Just as C-n usually moves to the same column in the following line, in Calendar mode it moves to the same day in the following week. And C-p moves to the same day in the previous week.

The arrow keys are equivalent to C-f, C-b, C-n and C-p, just as they normally are in other modes.

The commands for motion by months and years work like those for weeks, but move a larger distance. The month commands M-} and M-{ move forward or backward by an entire month. The year commands C-x ] and C-x [ move forward or backward a whole year.

The easiest way to remember these commands is to consider months and years analogous to paragraphs and pages of text, respectively. But the calendar movement commands themselves do not quite parallel those for movement through text: the ordinary Emacs paragraph commands move to the beginning or end of a paragraph, whereas these month and year commands move by an entire month or an entire year, keeping the same date within the month or year.

All these commands accept a numeric argument as a repeat count. For convenience, the digit keys and the minus sign specify numeric arguments in Calendar mode even without the Meta modifier. For example, 100 C-f moves point 100 days forward from its present location.


32.1.2 Beginning or End of Week, Month or Year

A week (or month, or year) is not just a quantity of days; we think of weeks (months, years) as starting on particular dates. So Calendar mode provides commands to move to the start or end of a week, month or year:

C-a

Move point to start of week (calendar-beginning-of-week).

C-e

Move point to end of week (calendar-end-of-week).

M-a

Move point to start of month (calendar-beginning-of-month).

M-e

Move point to end of month (calendar-end-of-month).

M-<

Move point to start of year (calendar-beginning-of-year).

M->

Move point to end of year (calendar-end-of-year).

These commands also take numeric arguments as repeat counts, with the repeat count indicating how many weeks, months, or years to move backward or forward.

By default, weeks begin on Sunday. To make them begin on Monday instead, set the variable calendar-week-start-day to 1. To change which day headers are highlighted as weekend days, set the variable calendar-weekend-days.


32.1.3 Specified Dates

Calendar mode provides commands for moving to a particular date specified in various ways.

g d

Move point to specified date (calendar-goto-date).

g D

Move point to specified day of year (calendar-goto-day-of-year).

g w

Move point to specified week of year (calendar-iso-goto-week).

o

Center calendar around specified month (calendar-other-month).

.

Move point to today’s date (calendar-goto-today).

g d (calendar-goto-date) prompts for a year, a month, and a day of the month, and then moves to that date. Because the calendar includes all dates from the beginning of the current era, you must type the year in its entirety; that is, type ‘2010’, not ‘10’.

g D (calendar-goto-day-of-year) prompts for a year and day number, and moves to that date. Negative day numbers count backward from the end of the year. g w (calendar-iso-goto-week) prompts for a year and week number, and moves to that week.

o (calendar-other-month) prompts for a month and year, then centers the three-month calendar around that month.

You can return to today’s date with . (calendar-goto-today).


32.2 Scrolling in the Calendar

The calendar display scrolls automatically through time when you move out of the visible portion. You can also scroll it manually. Imagine that the calendar window contains a long strip of paper with the months on it. Scrolling the calendar means moving the strip horizontally, so that new months become visible in the window.

>

Scroll calendar one month forward (calendar-scroll-left).

<

Scroll calendar one month backward (calendar-scroll-right).

C-v
PageDown
next

Scroll forward by three months (calendar-scroll-left-three-months).

M-v
PageUp
prior

Scroll backward by three months (calendar-scroll-right-three-months).

The most basic calendar scroll commands scroll by one month at a time. This means that there are two months of overlap between the display before the command and the display after. > scrolls the calendar contents one month forward in time. < scrolls the contents one month backwards in time.

The commands C-v and M-v scroll the calendar by an entire screenful—three months—in analogy with the usual meaning of these commands. C-v makes later dates visible and M-v makes earlier dates visible. These commands take a numeric argument as a repeat count; in particular, since C-u multiplies the next command by four, typing C-u C-v scrolls the calendar forward by a year and typing C-u M-v scrolls the calendar backward by a year.

The function keys PageDown (or next) and PageUp (or prior) are equivalent to C-v and M-v, just as they are in other modes.


32.3 Counting Days

M-=

Display the number of days in the current region (calendar-count-days-region).

To determine the number of days in a range, set the mark on one date using C-SPC, move point to another date, and type M-= (calendar-count-days-region). The numbers of days shown is inclusive; that is, it includes the days specified by mark and point.


32.4 Miscellaneous Calendar Commands

p d

Display day-in-year (calendar-print-day-of-year).

C-c C-l

Regenerate the calendar window (calendar-redraw).

SPC

Scroll the next window up (scroll-other-window).

DEL
S-SPC

Scroll the next window down (scroll-other-window-down).

q

Exit from calendar (calendar-exit).

To display the number of days elapsed since the start of the year, or the number of days remaining in the year, type the p d command (calendar-print-day-of-year). This displays both of those numbers in the echo area. The count of days elapsed includes the selected date. The count of days remaining does not include that date.

If the calendar window text gets corrupted, type C-c C-l (calendar-redraw) to redraw it. (This can only happen if you use non-Calendar-mode editing commands.)

In Calendar mode, you can use SPC (scroll-other-window) and DEL (scroll-other-window-down) to scroll the other window (if there is one) up or down, respectively. This is handy when you display a list of holidays or diary entries in another window.

To exit from the calendar, type q (calendar-exit). This buries all buffers related to the calendar, selecting other buffers. (If a frame contains a dedicated calendar window, exiting from the calendar deletes or iconifies that frame depending on the value of calendar-remove-frame-by-deleting.)


32.5 Writing Calendar Files

You can write calendars and diary entries to HTML and LaTeX files.

The Calendar HTML commands produce files of HTML code that contain calendar, holiday, and diary entries. Each file applies to one month, and has a name of the format yyyy-mm.html, where yyyy and mm are the four-digit year and two-digit month, respectively. The variable cal-html-directory specifies the default output directory for the HTML files. To prevent holidays from being shown, customize cal-html-holidays.

Diary entries enclosed by < and > are interpreted as HTML tags (for example: this is a diary entry with <font color=”red”>some red text</font>). You can change the overall appearance of the displayed HTML pages (for example, the color of various page elements, header styles) via a stylesheet cal.css in the directory containing the HTML files (see the value of the variable cal-html-css-default for relevant style settings).

H m

Generate a one-month calendar (cal-html-cursor-month).

H y

Generate a calendar file for each month of a year, as well as an index page (cal-html-cursor-year). By default, this command writes files to a yyyy subdirectory—if this is altered some hyperlinks between years will not work.

If the variable cal-html-print-day-number-flag is non-nil, then the monthly calendars show the day-of-the-year number. The variable cal-html-year-index-cols specifies the number of columns in the yearly index page.

The Calendar LaTeX commands produce a buffer of LaTeX code that prints as a calendar. Depending on the command you use, the printed calendar covers the day, week, month or year that point is in.

t m

Generate a one-month calendar (cal-tex-cursor-month).

t M

Generate a sideways-printing one-month calendar (cal-tex-cursor-month-landscape).

t d

Generate a one-day calendar (cal-tex-cursor-day).

t w 1

Generate a one-page calendar for one week, with hours (cal-tex-cursor-week).

t w 2

Generate a two-page calendar for one week, with hours (cal-tex-cursor-week2).

t w 3

Generate an ISO-style calendar for one week, without hours (cal-tex-cursor-week-iso).

t w 4

Generate a calendar for one Monday-starting week, with hours (cal-tex-cursor-week-monday).

t w W

Generate a two-page calendar for one week, without hours (cal-tex-cursor-week2-summary).

t f w

Generate a Filofax-style two-weeks-at-a-glance calendar (cal-tex-cursor-filofax-2week).

t f W

Generate a Filofax-style one-week-at-a-glance calendar (cal-tex-cursor-filofax-week).

t y

Generate a calendar for one year (cal-tex-cursor-year).

t Y

Generate a sideways-printing calendar for one year (cal-tex-cursor-year-landscape).

t f y

Generate a Filofax-style calendar for one year (cal-tex-cursor-filofax-year).

Some of these commands print the calendar sideways (in landscape mode), so it can be wider than it is long. Some of them use Filofax paper size (3.75in x 6.75in). All of these commands accept a prefix argument, which specifies how many days, weeks, months or years to print (starting always with the selected one).

If the variable cal-tex-holidays is non-nil (the default), then the printed calendars show the holidays in calendar-holidays. If the variable cal-tex-diary is non-nil (the default is nil), diary entries are included also (in monthly, Filofax, and iso-week calendars only). If the variable cal-tex-rules is non-nil (the default is nil), the calendar displays ruled pages in styles that have sufficient room. Consult the documentation of the individual cal-tex functions to see which calendars support which features.

You can use the variable cal-tex-preamble-extra to insert extra LaTeX commands in the preamble of the generated document if you need to.


32.6 Holidays

The Emacs calendar knows about many major and minor holidays, and can display them. You can add your own holidays to the default list.

mouse-3 Holidays
h

Display holidays for the selected date (calendar-cursor-holidays).

x

Mark holidays in the calendar window (calendar-mark-holidays).

u

Unmark calendar window (calendar-unmark).

a

List all holidays for the displayed three months in another window (calendar-list-holidays).

M-x holidays

List all holidays for three months around today’s date in another window.

M-x list-holidays

List holidays in another window for a specified range of years.

To see if any holidays fall on a given date, position point on that date in the calendar window and use the h command. Alternatively, click on that date with mouse-3 and then choose Holidays from the menu that appears. Either way, this displays the holidays for that date, in the echo area if they fit there, otherwise in a separate window.

To view the distribution of holidays for all the dates shown in the calendar, use the x command. This displays the dates that are holidays in a different face. See calendar-holiday-marker. The command applies both to the currently visible months and to other months that subsequently become visible by scrolling. To turn marking off and erase the current marks, type u, which also erases any diary marks (see The Diary). If the variable calendar-mark-holidays-flag is non-nil, creating or updating the calendar marks holidays automatically.

To get even more detailed information, use the a command, which displays a separate buffer containing a list of all holidays in the current three-month range. You can use SPC and DEL in the calendar window to scroll that list up and down, respectively.

The command M-x holidays displays the list of holidays for the current month and the preceding and succeeding months; this works even if you don’t have a calendar window. If the variable calendar-view-holidays-initially-flag is non-nil, creating the calendar displays holidays in this way. If you want the list of holidays centered around a different month, use C-u M-x holidays, which prompts for the month and year.

The holidays known to Emacs include United States holidays and the major Bahá’í, Chinese, Christian, Islamic, and Jewish holidays; also the solstices and equinoxes.

The command M-x holiday-list displays the list of holidays for a range of years. This function asks you for the starting and stopping years, and allows you to choose all the holidays or one of several categories of holidays. You can use this command even if you don’t have a calendar window.

The dates used by Emacs for holidays are based on current practice, not historical fact. For example Veteran’s Day began in 1919, but is shown in earlier years.


32.7 Times of Sunrise and Sunset

Special calendar commands can tell you, to within a minute or two, the times of sunrise and sunset for any date.

mouse-3 Sunrise/sunset
S

Display times of sunrise and sunset for the selected date (calendar-sunrise-sunset).

M-x sunrise-sunset

Display times of sunrise and sunset for today’s date.

C-u M-x sunrise-sunset

Display times of sunrise and sunset for a specified date.

M-x calendar-sunrise-sunset-month

Display times of sunrise and sunset for the selected month.

Within the calendar, to display the local times of sunrise and sunset in the echo area, move point to the date you want, and type S. Alternatively, click mouse-3 on the date, then choose ‘Sunrise/sunset’ from the menu that appears. The command M-x sunrise-sunset is available outside the calendar to display this information for today’s date or a specified date. To specify a date other than today, use C-u M-x sunrise-sunset, which prompts for the year, month, and day.

You can display the times of sunrise and sunset for any location and any date with C-u C-u M-x sunrise-sunset. This asks you for a longitude, latitude, number of minutes difference from Coordinated Universal Time, and date, and then tells you the times of sunrise and sunset for that location on that date.

Because the times of sunrise and sunset depend on the location on earth, you need to tell Emacs your latitude, longitude, and location name before using these commands. Here is an example of what to set:

(setq calendar-latitude 40.1)
(setq calendar-longitude -88.2)
(setq calendar-location-name "Urbana, IL")

Use one decimal place in the values of calendar-latitude and calendar-longitude.

Your time zone also affects the local time of sunrise and sunset. Emacs usually gets time zone information from the operating system, but if these values are not what you want (or if the operating system does not supply them), you must set them yourself. Here is an example:

(setq calendar-time-zone -360)
(setq calendar-standard-time-zone-name "CST")
(setq calendar-daylight-time-zone-name "CDT")

The value of calendar-time-zone is the number of minutes difference between your local standard time and Coordinated Universal Time (Greenwich time). The values of calendar-standard-time-zone-name and calendar-daylight-time-zone-name are the abbreviations used in your time zone. Emacs displays the times of sunrise and sunset corrected for daylight saving time. See Daylight Saving Time, for how daylight saving time is determined.

If you want to display numerical time zones (like ‘"+0100"’) instead of symbolic ones (like ‘"CET"’), set this to numeric.

As a user, you might find it convenient to set the calendar location variables for your usual physical location in your .emacs file. If you are a system administrator, you may want to set these variables for all users in a default.el file. See The Emacs Initialization File.


32.8 Phases of the Moon

These calendar commands display the dates and times of the phases of the moon (new moon, first quarter, full moon, last quarter). This feature is useful for debugging problems that depend on the phase of the moon.

M

Display the dates and times for all the quarters of the moon for the three-month period shown (calendar-lunar-phases).

M-x lunar-phases

Display dates and times of the quarters of the moon for three months around today’s date.

Within the calendar, use the M command to display a separate buffer of the phases of the moon for the current three-month range. The dates and times listed are accurate to within a few minutes.

Outside the calendar, use the command M-x lunar-phases to display the list of the phases of the moon for the current month and the preceding and succeeding months. For information about a different month, use C-u M-x lunar-phases, which prompts for the month and year.

The dates and times given for the phases of the moon are given in local time (corrected for daylight saving, when appropriate). See the discussion in the previous section. See Times of Sunrise and Sunset.


32.9 Conversion To and From Other Calendars

The Emacs calendar displayed is always the Gregorian calendar, sometimes called the New Style calendar, which is used in most of the world today. However, this calendar did not exist before the sixteenth century and was not widely used before the eighteenth century; it did not fully displace the Julian calendar and gain universal acceptance until the early twentieth century. The Emacs calendar can display any month since January, year 1 of the current era, but the calendar displayed is always the Gregorian, even for a date at which the Gregorian calendar did not exist.

While Emacs cannot display other calendars, it can convert dates to and from several other calendars.


32.9.1 Supported Calendar Systems

The ISO commercial calendar is often used in business.

The Julian calendar, named after Julius Caesar, was the one used in Europe throughout medieval times, and in many countries up until the nineteenth century.

Astronomers use a simple counting of days elapsed since noon, Monday, January 1, 4713 BC on the Julian calendar. The number of days elapsed is called the Julian day number or the Astronomical day number.

The Hebrew calendar is used by tradition in the Jewish religion. The Emacs calendar program uses the Hebrew calendar to determine the dates of Jewish holidays. Hebrew calendar dates begin and end at sunset.

The Islamic calendar is used in many predominantly Islamic countries. Emacs uses it to determine the dates of Islamic holidays. There is no universal agreement in the Islamic world about the calendar; Emacs uses a widely accepted version, but the precise dates of Islamic holidays often depend on proclamation by religious authorities, not on calculations. As a consequence, the actual dates of observance can vary slightly from the dates computed by Emacs. Islamic calendar dates begin and end at sunset.

The French Revolutionary calendar was created by the Jacobins after the 1789 revolution, to represent a more secular and nature-based view of the annual cycle, and to install a 10-day week in a rationalization measure similar to the metric system. The French government officially abandoned this calendar at the end of 1805.

The Maya of Central America used three separate, overlapping calendar systems, the long count, the tzolkin, and the haab. Emacs knows about all three of these calendars. Experts dispute the exact correlation between the Mayan calendar and our calendar; Emacs uses the Goodman-Martinez-Thompson correlation in its calculations.

The Copts use a calendar based on the ancient Egyptian solar calendar. Their calendar consists of twelve 30-day months followed by an extra five-day period. Once every fourth year they add a leap day to this extra period to make it six days. The Ethiopic calendar is identical in structure, but has different year numbers and month names.

The Persians use a solar calendar based on a design of Omar Khayyam. Their calendar consists of twelve months of which the first six have 31 days, the next five have 30 days, and the last has 29 in ordinary years and 30 in leap years. Leap years occur in a complicated pattern every four or five years. The calendar implemented here is the arithmetical Persian calendar championed by Birashk, based on a 2,820-year cycle. It differs from the astronomical Persian calendar, which is based on astronomical events. As of this writing the first future discrepancy is projected to occur on March 20, 2025. It is currently not clear what the official calendar of Iran will be at that time.

The Chinese calendar is a complicated system of lunar months arranged into solar years. The years go in cycles of sixty, each year containing either twelve months in an ordinary year or thirteen months in a leap year; each month has either 29 or 30 days. Years, ordinary months, and days are named by combining one of ten celestial stems with one of twelve terrestrial branches for a total of sixty names that are repeated in a cycle of sixty.

The Bahá’í calendar system is based on a solar cycle of 19 months with 19 days each. The four remaining intercalary days are placed between the 18th and 19th months.


32.9.2 Converting To Other Calendars

The following commands describe the selected date (the date at point) in various other calendar systems:

mouse-3 Other calendars
p o

Display the selected date in various other calendars. (calendar-print-other-dates).

p c

Display ISO commercial calendar equivalent for selected day (calendar-iso-print-date).

p j

Display Julian date for selected day (calendar-julian-print-date).

p a

Display astronomical (Julian) day number for selected day (calendar-astro-print-day-number).

p h

Display Hebrew date for selected day (calendar-hebrew-print-date).

p i

Display Islamic date for selected day (calendar-islamic-print-date).

p f

Display French Revolutionary date for selected day (calendar-french-print-date).

p b

Display Bahá’í date for selected day (calendar-bahai-print-date).

p C

Display Chinese date for selected day (calendar-chinese-print-date).

p k

Display Coptic date for selected day (calendar-coptic-print-date).

p e

Display Ethiopic date for selected day (calendar-ethiopic-print-date).

p p

Display Persian date for selected day (calendar-persian-print-date).

p m

Display Mayan date for selected day (calendar-mayan-print-date).

Otherwise, move point to the date you want to convert, then type the appropriate command starting with p from the table above. The prefix p is a mnemonic for “print”, since Emacs “prints” the equivalent date in the echo area. p o displays the date in all forms known to Emacs. You can also use mouse-3 and then choose Other calendars from the menu that appears. This displays the equivalent forms of the date in all the calendars Emacs understands, in the form of a menu. (Choosing an alternative from this menu doesn’t actually do anything—the menu is used only for display.)


32.9.3 Converting From Other Calendars

You can use the other supported calendars to specify a date to move to. This section describes the commands for doing this using calendars other than Mayan; for the Mayan calendar, see the following section.

g c

Move to a date specified in the ISO commercial calendar (calendar-iso-goto-date).

g w

Move to a week specified in the ISO commercial calendar (calendar-iso-goto-week).

g j

Move to a date specified in the Julian calendar (calendar-julian-goto-date).

g a

Move to a date specified with an astronomical (Julian) day number (calendar-astro-goto-day-number).

g b

Move to a date specified in the Bahá’í calendar (calendar-bahai-goto-date).

g h

Move to a date specified in the Hebrew calendar (calendar-hebrew-goto-date).

g i

Move to a date specified in the Islamic calendar (calendar-islamic-goto-date).

g f

Move to a date specified in the French Revolutionary calendar (calendar-french-goto-date).

g C

Move to a date specified in the Chinese calendar (calendar-chinese-goto-date).

g p

Move to a date specified in the Persian calendar (calendar-persian-goto-date).

g k

Move to a date specified in the Coptic calendar (calendar-coptic-goto-date).

g e

Move to a date specified in the Ethiopic calendar (calendar-ethiopic-goto-date).

These commands ask you for a date on the other calendar, move point to the Gregorian calendar date equivalent to that date, and display the other calendar’s date in the echo area. Emacs uses strict completion (see Completion Exit) whenever it asks you to type a month name, so you don’t have to worry about the spelling of Hebrew, Islamic, or French names.

One common issue concerning the Hebrew calendar is the computation of the anniversary of a date of death, called a yahrzeit. The Emacs calendar includes a facility for such calculations. If you are in the calendar, the command M-x calendar-hebrew-list-yahrzeits asks you for a range of years and then displays a list of the yahrzeit dates for those years for the date given by point. If you are not in the calendar, this command first asks you for the date of death and the range of years, and then displays the list of yahrzeit dates.


32.10 The Diary

The Emacs diary keeps track of appointments or other events on a daily basis, in conjunction with the calendar. To use the diary feature, you must first create a diary file containing a list of events and their dates. Then Emacs can automatically pick out and display the events for today, for the immediate future, or for any specified date.

Although you probably will start by creating a diary manually, Emacs provides a number of commands to let you view, add, and change diary entries.


32.10.1 The Diary File

Your diary file is a file that records events associated with particular dates. The name of the diary file is specified by the variable diary-file. The default is ~/.emacs.d/diary, though for compatibility with older versions Emacs will use ~/diary if it exists.

Each entry in the diary file describes one event and consists of one or more lines. An entry always begins with a date specification at the left margin. The rest of the entry is simply text to describe the event. If the entry has more than one line, then the lines after the first must begin with whitespace to indicate they continue a previous entry. Lines that do not begin with valid dates and do not continue a preceding entry are ignored. Here’s an example:

12/22/2015  Twentieth wedding anniversary!
10/22       Ruth's birthday.
* 21, *:    Payday
Tuesday--weekly meeting with grad students at 10am
         Supowit, Shen, Bitner, and Kapoor to attend.
1/13/89     Friday the thirteenth!!
thu 4pm     squash game with Lloyd.
mar 16      Dad's birthday
April 15, 2016 Income tax due.
* 15        time cards due.

This example uses extra spaces to align the event descriptions of most of the entries. Such formatting is purely a matter of taste.

You can also use a format where the first line of a diary entry consists only of the date or day name (with no following blanks or punctuation). For example:

02/11/2012
      Bill B. visits Princeton today
      2pm Cognitive Studies Committee meeting
      2:30-5:30 Liz at Lawrenceville
      4:00pm Dentist appt
      7:30pm Dinner at George's
      8:00-10:00pm concert

This entry will have a different appearance if you use the simple diary display (see Diary Display). The simple diary display omits the date line at the beginning; only the continuation lines appear. This style of entry looks neater when you display just a single day’s entries, but can cause confusion if you ask for more than one day’s entries.


32.10.2 Displaying the Diary

Once you have created a diary file, you can use the calendar to view it. You can also view today’s events outside of Calendar mode. In the following, key bindings refer to the Calendar buffer.

mouse-3 Diary
d

Display all diary entries for the selected date (diary-view-entries).

s

Display the entire diary file (diary-show-all-entries).

m

Mark all visible dates that have diary entries (diary-mark-entries).

u

Unmark the calendar window (calendar-unmark).

M-x diary-print-entries

Print hard copy of the diary display as it appears.

M-x diary

Display all diary entries for today’s date.

M-x diary-mail-entries

Mail yourself email reminders about upcoming diary entries.

Displaying the diary entries with d shows in a separate buffer the diary entries for the selected date in the calendar. The mode line of the new buffer shows the date of the diary entries. Holidays are shown either in the buffer or in the mode line, depending on the display method you choose (see Diary Display). If you specify a numeric argument with d, it shows all the diary entries for that many successive days. Thus, 2 d displays all the entries for the selected date and for the following day.

Another way to display the diary entries for a date is to click mouse-3 on the date, and then choose Diary entries from the menu that appears. If the variable calendar-view-diary-initially-flag is non-nil, creating the calendar lists the diary entries for the current date (provided the current date is visible).

To get a broader view of which days are mentioned in the diary, use the m command. This marks the dates that have diary entries in a different face. See diary-entry-marker.

This command applies both to the months that are currently visible and to those that subsequently become visible after scrolling. To turn marking off and erase the current marks, type u, which also turns off holiday marks (see Holidays). If the variable calendar-mark-diary-entries-flag is non-nil, creating or updating the calendar marks diary dates automatically.

To prevent an individual diary entry from being marked in the calendar, insert the string that diary-nonmarking-symbol specifies (the default is ‘&’) at the beginning of the entry, before the date. This has no effect on display of the entry in the diary buffer; it only affects marks on dates in the calendar. Nonmarking entries can be useful for generic entries that would otherwise mark many different dates.

To see the full diary file, rather than just some of the entries, use the s command.

The command M-x diary displays the diary entries for the current date, independently of the calendar display, and optionally for the next few days as well; the variable diary-number-of-entries specifies how many days to include. See diary-number-of-entries.

If you put (diary) in your .emacs file, this automatically displays a window with the day’s diary entries when you start Emacs.

Some people like to receive email notifications of events in their diary. To send such mail to yourself, use the command M-x diary-mail-entries. A prefix argument specifies how many days (starting with today) to check; otherwise, the variable diary-mail-days says how many days.


32.10.3 Date Formats

Here are some sample diary entries, illustrating different ways of formatting a date. The examples all show dates in American order (month, day, year), but Calendar mode supports European order (day, month, year) and ISO order (year, month, day) as options.

4/20/12  Switch-over to new tabulation system
apr. 25  Start tabulating annual results
4/30  Results for April are due
*/25  Monthly cycle finishes
Friday  Don't leave without backing up files

The first entry appears only once, on April 20, 2012. The second and third appear every year on the specified dates, and the fourth uses a wildcard (asterisk) for the month, so it appears on the 25th of every month. The final entry appears every week on Friday.

You can use just numbers to express a date, as in ‘month/day’ or ‘month/day/year’. This must be followed by a nondigit. In the date itself, month and day are numbers of one or two digits. The optional year is also a number, and may be abbreviated to the last two digits; that is, you can use ‘11/12/2012’ or ‘11/12/12’.

Dates can also have the form ‘monthname day’ or ‘monthname day, year’, where the month’s name can be spelled in full or abbreviated (with or without a period). The preferred abbreviations for month and day names can be set using the variables calendar-abbrev-length, calendar-month-abbrev-array, and calendar-day-abbrev-array. The default is to use the first three letters of a name as its abbreviation. Case is not significant.

A date may be generic; that is, partially unspecified. Then the entry applies to all dates that match the specification. If the date does not contain a year, it is generic and applies to any year. Alternatively, month, day, or year can be ‘*’; this matches any month, day, or year, respectively. Thus, a diary entry ‘3/*/*’ matches any day in March of any year; so does ‘march *’.

If you prefer the European style of writing dates (in which the day comes before the month), or the ISO style (in which the order is year, month, day), type M-x calendar-set-date-style while in the calendar, or customize the variable calendar-date-style. This affects how diary dates are interpreted, date display, and the order in which some commands expect their arguments to be given.

You can use the name of a day of the week as a generic date which applies to any date falling on that day of the week. You can abbreviate the day of the week as described above, or spell it in full; case is not significant.


32.10.4 Commands to Add to the Diary

While in the calendar, there are several commands to create diary entries. The basic commands are listed here; more sophisticated commands are in the next section (see Special Diary Entries). Entries can also be based on non-Gregorian calendars. See Diary Entries Using non-Gregorian Calendars.

i d

Add a diary entry for the selected date (diary-insert-entry).

i w

Add a diary entry for the selected day of the week (diary-insert-weekly-entry).

i m

Add a diary entry for the selected day of the month (diary-insert-monthly-entry).

i y

Add a diary entry for the selected day of the year (diary-insert-yearly-entry).

You can make a diary entry for a specific date by selecting that date in the calendar window and typing the i d command. This command displays the end of your diary file in another window and inserts the date; you can then type the rest of the diary entry.

If you want to make a diary entry that applies to a specific day of the week, select that day of the week (any occurrence will do) and type i w. This inserts the day-of-week as a generic date; you can then type the rest of the diary entry. You can make a monthly diary entry in the same fashion: select the day of the month, use the i m command, and type the rest of the entry. Similarly, you can insert a yearly diary entry with the i y command.

All of the above commands make marking diary entries by default. To make a nonmarking diary entry, give a prefix argument to the command. For example, C-u i w makes a nonmarking weekly diary entry.

When you modify the diary file, be sure to save the file before exiting Emacs. Saving the diary file after using any of the above insertion commands will automatically update the diary marks in the calendar window, if appropriate. You can use the command calendar-redraw to force an update at any time.


32.10.5 Special Diary Entries

In addition to entries based on calendar dates, the diary file can contain sexp entries for regular events such as anniversaries. These entries are based on Lisp expressions (sexps) that Emacs evaluates as it scans the diary file. Instead of a date, a sexp entry contains ‘%%’ followed by a Lisp expression which must begin and end with parentheses. The Lisp expression determines which dates the entry applies to.

Calendar mode provides commands to insert certain commonly used sexp entries:

i a

Add an anniversary diary entry for the selected date (diary-insert-anniversary-entry).

i b

Add a block diary entry for the current region (diary-insert-block-entry).

i c

Add a cyclic diary entry starting at the date (diary-insert-cyclic-entry).

If you want to make a diary entry that applies to the anniversary of a specific date, move point to that date and use the i a command. This displays the end of your diary file in another window and inserts the anniversary description; you can then type the rest of the diary entry. The entry looks like this:

%%(diary-anniversary 10 31 1988) Arthur's birthday

This entry applies to October 31 in any year after 1988; ‘10 31 1988’ specifies the date. (If you are using the European or ISO calendar style, the input order of month, day and year is different.) The reason this expression requires a beginning year is that advanced diary functions can use it to calculate the number of elapsed years.

A block diary entry applies to a specified range of consecutive dates. Here is a block diary entry that applies to all dates from June 24, 2012 through July 10, 2012:

%%(diary-block 6 24 2012 7 10 2012) Vacation

The ‘6 24 2012’ indicates the starting date and the ‘7 10 2012’ indicates the stopping date. (Again, if you are using the European or ISO calendar style, the input order of month, day and year is different.)

To insert a block entry, place point and the mark on the two dates that begin and end the range, and type i b. This command displays the end of your diary file in another window and inserts the block description; you can then type the diary entry.

Cyclic diary entries repeat after a fixed interval of days. To create one, select the starting date and use the i c command. The command prompts for the length of interval, then inserts the entry, which looks like this:

%%(diary-cyclic 50 3 1 2012) Renew medication

This entry applies to March 1, 2012 and every 50th day following; ‘3 1 2012’ specifies the starting date. (If you are using the European or ISO calendar style, the input order of month, day and year is different.)

All three of these commands make marking diary entries. To insert a nonmarking entry, give a prefix argument to the command. For example, C-u i a makes a nonmarking anniversary diary entry.

Marking sexp diary entries in the calendar can be time-consuming, since every date visible in the calendar window must be individually checked. So it’s a good idea to make sexp diary entries nonmarking (with ‘&’) when possible.

Another sophisticated kind of sexp entry, a floating diary entry, specifies a regularly occurring event by offsets specified in days, weeks, and months. It is comparable to a crontab entry interpreted by the cron utility. Here is a nonmarking, floating diary entry that applies to the fourth Thursday in November:

&%%(diary-float 11 4 4) American Thanksgiving

The 11 specifies November (the eleventh month), the 4 specifies Thursday (the fourth day of the week, where Sunday is numbered zero), and the second 4 specifies the fourth Thursday (1 would mean “first”, 2 would mean “second”, −2 would mean “second-to-last”, and so on). The month can be a single month or a list of months. Thus you could change the 11 above to ‘'(1 2 3)’ and have the entry apply to the last Thursday of January, February, and March. If the month is t, the entry applies to all months of the year.

%%(diary-offset '(diary-float t 3 4) 2) Monthly committee meeting

This entry applies to the Saturday after the third Thursday of each month. The 2 specifies number of days after when the sexp '(diary-float t 3 4) would evaluate to t. This is useful when for example your organization has a committee meeting two days after every monthly meeting which takes place on the third Thursday, or if you would like to attend a virtual meeting scheduled in a different timezone causing a difference in the date.

Each of the standard sexp diary entries takes an optional parameter specifying the name of a face or a single-character string to use when marking the entry in the calendar. Most generally, sexp diary entries can perform arbitrary computations to determine when they apply. See Sexp Entries and the Fancy Diary Display.


32.10.6 Appointments

If you have a diary entry for an appointment, and that diary entry begins with a recognizable time of day, Emacs can warn you in advance that an appointment is pending. Emacs alerts you to the appointment by displaying a message in your chosen format, as specified by the variable appt-display-format. If the value of appt-audible is non-nil, the warning includes an audible reminder. In addition, if appt-display-mode-line is non-nil, Emacs displays the number of minutes to the appointment on the mode line.

If appt-display-format has the value window, then the variable appt-display-duration controls how long the reminder window is visible for; and the variables appt-disp-window-function and appt-delete-window-function give the names of functions used to create and destroy the window, respectively.

To enable appointment notification, type M-x appt-activate. With a positive argument, it enables notification; with a negative argument, it disables notification; with no argument, it toggles. Enabling notification also sets up an appointment list for today from the diary file, giving all diary entries found with recognizable times of day, and reminds you just before each of them.

For example, suppose the diary file contains these lines:

Monday
  9:30am Coffee break
 12:00pm Lunch

Then on Mondays, you will be reminded at around 9:20am about your coffee break and at around 11:50am about lunch. The variable appt-message-warning-time specifies how many minutes (default 12) in advance to warn you. This is a default warning time. Each appointment can specify a different warning time by adding a piece matching appt-warning-time-regexp (see that variable’s documentation for details).

You can write times in am/pm style (with ‘12:00am’ standing for midnight and ‘12:00pm’ standing for noon), or 24-hour European/military style. You need not be consistent; your diary file can have a mixture of the two styles. Times must be at the beginning of diary entries if they are to be recognized.

Emacs updates the appointments list from the diary file automatically just after midnight. You can force an update at any time by re-enabling appointment notification. Both these actions also display the day’s diary buffer, unless you set appt-display-diary to nil. The appointments list is also updated whenever the diary file (or a file it includes; see Fancy Diary Display) is saved. If you use the Org Mode and keep appointments in your Org agenda files, you can add those appointments to the list using the org-agenda-to-appt command. See Appointment reminders in The Org Manual, for more about that command.

You can also use the appointment notification facility like an alarm clock. The command M-x appt-add adds entries to the appointment list without affecting your diary file. You delete entries from the appointment list with M-x appt-delete.


32.10.7 Importing and Exporting Diary Entries

You can transfer diary entries between Emacs diary files and a variety of other formats.

You can import diary entries from Outlook-generated appointment messages. While viewing such a message in Rmail or Gnus, do M-x diary-from-outlook to import the entry. You can make this command recognize additional appointment message formats by customizing the variable diary-outlook-formats. Other mail clients can set diary-from-outlook-function to an appropriate value.

The icalendar package allows you to transfer data between your Emacs diary file and iCalendar files, which are defined in RFC 2445—Internet Calendaring and Scheduling Core Object Specification (iCalendar) (as well as the earlier vCalendar format).

The command icalendar-import-buffer extracts iCalendar data from the current buffer and adds it to your diary file. This function is also suitable for automatic extraction of iCalendar data; for example with the Rmail mail client one could use:

(add-hook 'rmail-show-message-hook 'icalendar-import-buffer)

The command icalendar-import-file imports an iCalendar file and adds the results to an Emacs diary file. For example:

(icalendar-import-file "/here/is/calendar.ics"
                       "/there/goes/ical-diary")

You can use an #include directive to add the import file contents to the main diary file, if these are different files. See Fancy Diary Display.

Use icalendar-export-file to interactively export an entire Emacs diary file to iCalendar format. To export only a part of a diary file, mark the relevant area, and call icalendar-export-region. In both cases, Emacs appends the result to the target file.


32.11 Daylight Saving Time

Emacs understands the difference between standard time and daylight saving time—the times given for sunrise, sunset, solstices, equinoxes, and the phases of the moon take that into account. The rules for daylight saving time vary from place to place and have also varied historically from year to year. To do the job properly, Emacs needs to know which rules to use.

Some operating systems keep track of the rules that apply to the place where you are; on these systems, Emacs gets the information it needs from the system automatically. If some or all of this information is missing, Emacs fills in the gaps with the rules currently used in Cambridge, Massachusetts. If the resulting rules are not what you want, you can tell Emacs the rules to use by setting certain variables: calendar-daylight-savings-starts and calendar-daylight-savings-ends.

These values should be Lisp expressions that refer to the variable year, and evaluate to the Gregorian date on which daylight saving time starts or (respectively) ends, in the form of a list (month day year). The values should be nil if your area does not use daylight saving time.

Emacs uses these expressions to determine the starting date of daylight saving time for the holiday list and for correcting times of day in the solar and lunar calculations.

The values for Cambridge, Massachusetts are as follows:

(calendar-nth-named-day 2 0 3 year)
(calendar-nth-named-day 1 0 11 year)

That is, the second 0th day (Sunday) of the third month (March) in the year specified by year, and the first Sunday of the eleventh month (November) of that year. If daylight saving time were changed to start on October 1, you would set calendar-daylight-savings-starts to this:

(list 10 1 year)

If there is no daylight saving time at your location, or if you want all times in standard time, set calendar-daylight-savings-starts and calendar-daylight-savings-ends to nil.

The variable calendar-daylight-time-offset specifies the difference between daylight saving time and standard time, measured in minutes. The value for Cambridge, Massachusetts is 60.

Finally, the two variables calendar-daylight-savings-starts-time and calendar-daylight-savings-ends-time specify the number of minutes after midnight local time when the transition to and from daylight saving time should occur. For Cambridge, Massachusetts both variables’ values are 120.


32.12 Summing Time Intervals

The timeclock package adds up time intervals, so you can (for instance) keep track of how much time you spend working on particular projects. (A more advanced alternative is to use the Org Mode’s facilities for clocking time, see Clocking Work Time in The Org Manual).

Use the M-x timeclock-in command when you start working on a project, and M-x timeclock-out command when you’re done. Each time you do this, it adds one time interval to the record of the project. You can change to working on a different project with M-x timeclock-change.

Once you’ve collected data from a number of time intervals, you can use M-x timeclock-workday-remaining to see how much time is left to work today (assuming a typical average of 8 hours a day), and M-x timeclock-when-to-leave which will calculate when you’re done.

If you want Emacs to display the amount of time left of your workday in the mode line, either customize the timeclock-mode-line-display variable and set its value to t, or invoke the M-x timeclock-mode-line-display command.

Terminating the current Emacs session might or might not mean that you have stopped working on the project and, by default, Emacs asks you. You can, however, customize the value of the variable timeclock-ask-before-exiting to nil to avoid the question; then, only an explicit M-x timeclock-out or M-x timeclock-change will tell Emacs that the current interval is over.

The timeclock functions work by accumulating the data in a file called ~/.emacs.d/timelog. You can specify a different name for this file by customizing the variable timeclock-file. If you edit the timeclock file manually, or if you change the value of any of timeclock’s customizable variables, you should run the command M-x timeclock-reread-log to update the data in Emacs from the file.


32.13 More advanced features of the Calendar and Diary

This section describes some of the more advanced/specialized features of the calendar and diary. It starts with some of the many ways in which you can customize the calendar and diary to suit your personal tastes.


32.13.1 Customizing the Calendar

The calendar display unfortunately cannot be changed from three months, but you can customize the whitespace used by setting the variables: calendar-left-margin, calendar-day-header-width, calendar-day-digit-width, calendar-column-width, and calendar-intermonth-spacing. To display text between the months, for example week numbers, customize the variables calendar-intermonth-header and calendar-intermonth-text as described in their documentation.

The variable calendar-month-header controls the text that appears above each month in the calendar. By default, it shows the month and year. The variable calendar-day-header-array controls the text that appears above each day’s column in every month. By default, it shows the first two letters of each day’s name.

The variable calendar-holiday-marker specifies how to mark a date that is a holiday. Its value may be a single-character string to insert next to the date, or a face name to use for displaying the date. Likewise, the variable diary-entry-marker specifies how to mark a date that has diary entries. The function calendar-mark-today uses calendar-today-marker to mark today’s date. By default, the calendar uses faces named holiday, diary, and calendar-today for these purposes.

Starting the calendar runs the normal hook calendar-initial-window-hook. Recomputation of the calendar display does not run this hook. But if you leave the calendar with the q command and reenter it, the hook runs again.

The variable calendar-today-visible-hook is a normal hook run after the calendar buffer has been prepared with the calendar, when the current date is visible in the window. One use of this hook is to mark today’s date; to do that use either of the functions calendar-mark-today or calendar-star-date:

(add-hook 'calendar-today-visible-hook 'calendar-mark-today)

A similar normal hook, calendar-today-invisible-hook is run if the current date is not visible in the window.

Each of the calendar cursor motion commands runs the hook calendar-move-hook after it moves the cursor.


32.13.2 Customizing the Holidays

There are several variables listing the default holidays that Emacs knows about. These are: holiday-general-holidays, holiday-local-holidays, holiday-solar-holidays, holiday-bahai-holidays, holiday-christian-holidays, holiday-hebrew-holidays, holiday-islamic-holidays, holiday-oriental-holidays, and holiday-other-holidays. The names should be self-explanatory; e.g., holiday-solar-holidays lists sun- and moon-related holidays.

You can customize these lists of holidays to your own needs, deleting or adding holidays as described below. Set any of them to nil to not show the associated holidays.

The general holidays are, by default, holidays common throughout the United States. In contrast, holiday-local-holidays and holiday-other-holidays are both empty by default. These are intended for system-wide settings and your individual use, respectively.

By default, Emacs does not include all the holidays of the religions that it knows, only those commonly found in secular calendars. For a more extensive collection of religious holidays, you can set any (or all) of the variables calendar-bahai-all-holidays-flag, calendar-christian-all-holidays-flag, calendar-hebrew-all-holidays-flag, or calendar-islamic-all-holidays-flag to t.

Each of the holiday variables is a list of holiday forms, each form describing a holiday (or sometimes a list of holidays). Here is a table of the possible kinds of holiday form. Day numbers and month numbers count starting from 1, but dayname numbers count Sunday as 0. The argument string is always the description of the holiday, as a string.

(holiday-fixed month day string)

A fixed date on the Gregorian calendar.

(holiday-float month dayname k string

&optional day) The kth dayname (dayname=0 for Sunday, and so on) after or before Gregorian date month, day. Negative k means count back from the end of the month. Optional day defaults to 1 if k is positive, and the last day of month otherwise.

(holiday-chinese month day string)

A fixed date on the Chinese calendar.

(holiday-hebrew month day string)

A fixed date on the Hebrew calendar.

(holiday-islamic month day string)

A fixed date on the Islamic calendar.

(holiday-julian month day string)

A fixed date on the Julian calendar.

(holiday-sexp sexp string)

A date calculated by the Lisp expression sexp. The expression should use the variable year to compute and return the date of a holiday in the form of a list (month day year), or nil if the holiday doesn’t happen this year.

(if condition holiday-form)

A holiday that happens only if condition is true.

(function [args])

A list of dates calculated by the function function, called with arguments args.

For example, suppose you want to add Bastille Day, celebrated in France on July 14 (i.e., the fourteenth day of the seventh month). You can do this as follows:

(setq holiday-other-holidays '((holiday-fixed 7 14 "Bastille Day")))

Many holidays occur on a specific day of the week, at a specific time of month. Here is a holiday form describing Hurricane Supplication Day, celebrated in the Virgin Islands on the fourth Monday in July:

(holiday-float 7 1 4 "Hurricane Supplication Day")

Here the 7 specifies July, the 1 specifies Monday (Sunday is 0, Tuesday is 2, and so on), and the 4 specifies the fourth occurrence in the month (1 specifies the first occurrence, 2 the second occurrence, −1 the last occurrence, −2 the second-to-last occurrence, and so on).

You can specify holidays that occur on fixed days of the Bahá’í, Chinese, Hebrew, Islamic, and Julian calendars too. For example,

(setq holiday-other-holidays
      '((holiday-hebrew 10 2 "Last day of Hanukkah")
        (holiday-islamic 3 12 "Mohammed's Birthday")
        (holiday-julian 4 2 "Jefferson's Birthday")))

adds the last day of Hanukkah (since the Hebrew months are numbered with 1 starting from Nisan), the Islamic feast celebrating Mohammed’s birthday (since the Islamic months are numbered from 1 starting with Muharram), and Thomas Jefferson’s birthday, which is 2 April 1743 on the Julian calendar.

To include a holiday conditionally, use either Emacs Lisp’s if or the holiday-sexp form. For example, American presidential elections occur on the first Tuesday after the first Monday in November of years divisible by 4:

(holiday-sexp '(if (zerop (% year 4))
                   (calendar-gregorian-from-absolute
                    (1+ (calendar-dayname-on-or-before
                          1 (+ 6 (calendar-absolute-from-gregorian
                                  (list 11 1 year)))))))
              "US Presidential Election")

or

(if (zerop (% displayed-year 4))
    (holiday-fixed 11
           (calendar-extract-day
             (calendar-gregorian-from-absolute
               (1+ (calendar-dayname-on-or-before
                     1 (+ 6 (calendar-absolute-from-gregorian
                              (list 11 1 displayed-year)))))))
           "US Presidential Election"))

Some holidays just don’t fit into any of these forms because special calculations are involved in their determination. In such cases you must write a Lisp function to do the calculation. To include eclipses, for example, add (eclipses) to holiday-other-holidays and write an Emacs Lisp function eclipses that returns a (possibly empty) list of the relevant Gregorian dates among the range visible in the calendar window, with descriptive strings, like this:

(((6 4 2012) "Lunar Eclipse") ((11 13 2012) "Solar Eclipse") ... )

32.13.3 Converting from the Mayan Calendar

Here are the commands to select dates based on the Mayan calendar:

g m l

Move to a date specified by the long count calendar (calendar-mayan-goto-long-count-date).

g m n t

Move to the next occurrence of a place in the tzolkin calendar (calendar-mayan-next-tzolkin-date).

g m p t

Move to the previous occurrence of a place in the tzolkin calendar (calendar-mayan-previous-tzolkin-date).

g m n h

Move to the next occurrence of a place in the haab calendar (calendar-mayan-next-haab-date).

g m p h

Move to the previous occurrence of a place in the haab calendar (calendar-mayan-previous-haab-date).

g m n c

Move to the next occurrence of a place in the calendar round (calendar-mayan-next-calendar-round-date).

g m p c

Move to the previous occurrence of a place in the calendar round (calendar-mayan-previous-calendar-round-date).

To understand these commands, you need to understand the Mayan calendars. The long count is a counting of days with these units:

1 kin = 1 day   1 uinal = 20 kin   1 tun = 18 uinal
1 katun = 20 tun   1 baktun = 20 katun

Thus, the long count date 12.16.11.16.6 means 12 baktun, 16 katun, 11 tun, 16 uinal, and 6 kin. The Emacs calendar can handle Mayan long count dates as early as 7.17.18.13.3, but no earlier. When you use the g m l command, type the Mayan long count date with the baktun, katun, tun, uinal, and kin separated by periods.

The Mayan tzolkin calendar is a cycle of 260 days formed by a pair of independent cycles of 13 and 20 days. Since this cycle repeats endlessly, Emacs provides commands to move backward and forward to the previous or next point in the cycle. Type g m p t to go to the previous tzolkin date; Emacs asks you for a tzolkin date and moves point to the previous occurrence of that date. Similarly, type g m n t to go to the next occurrence of a tzolkin date.

The Mayan haab calendar is a cycle of 365 days arranged as 18 months of 20 days each, followed by a 5-day monthless period. Like the tzolkin cycle, this cycle repeats endlessly, and there are commands to move backward and forward to the previous or next point in the cycle. Type g m p h to go to the previous haab date; Emacs asks you for a haab date and moves point to the previous occurrence of that date. Similarly, type g m n h to go to the next occurrence of a haab date.

The Maya also used the combination of the tzolkin date and the haab date. This combination is a cycle of about 52 years called a calendar round. If you type g m p c, Emacs asks you for both a haab and a tzolkin date and then moves point to the previous occurrence of that combination. Use g m n c to move point to the next occurrence of a combination. These commands signal an error if the haab/tzolkin date combination you have typed is impossible.

Emacs uses strict completion (see Completion Exit) whenever it asks you to type a Mayan name, so you don’t have to worry about spelling.


32.13.4 Date Display Format

You can customize the way dates are displayed in the diary, mode lines, and messages by setting calendar-date-display-form. This variable holds a list of expressions that can involve the variables month, day, and year, which are all numbers in string form, and monthname and dayname, which are both alphabetic strings. In the American style, the default value of this list is as follows:

((if dayname (concat dayname ", ")) monthname " " day ", " year)

while in the European style this value is the default:

((if dayname (concat dayname ", ")) day " " monthname " " year)

The default ISO date representation is:

((format "%s-%.2d-%.2d" year (string-to-number month)
         (string-to-number day)))

Another typical American format is:

(month "/" day "/" (substring year -2))

32.13.5 Time Display Format

The calendar and diary by default display times of day in the conventional American style with the hours from 1 through 12, minutes, and either ‘am’ or ‘pm’. If you prefer the European style, also known in the US as military, in which the hours go from 00 to 23, you can alter the variable calendar-time-display-form. This variable is a list of expressions that can involve the variables 12-hours, 24-hours, and minutes, which are all numbers in string form, and am-pm and time-zone, which are both alphabetic strings. The default value is:

(12-hours ":" minutes am-pm
          (if time-zone " (") time-zone (if time-zone ")"))

Here is a value that provides European style times:

(24-hours ":" minutes
          (if time-zone " (") time-zone (if time-zone ")"))

Note that few calendar functions return a time of day (at present, only solar functions).


32.13.6 Customizing the Diary

Ordinarily, the diary window indicates any holidays that fall on the date of the diary entries, either in the mode line or the buffer itself. The process of checking for holidays can be slow, depending on the defined holidays. In that case, setting diary-show-holidays-flag to nil will speed up the diary display.

The variable diary-number-of-entries controls the number of days of diary entries to be displayed at one time. It affects the initial display when calendar-view-diary-initially-flag is t, as well as the command M-x diary. For example, a value of 1 (the default) displays only the current day’s diary entries, whereas a value of 2 will also show the next day’s entries. The value can also be a vector of seven integers: for example, if the value is [0 2 2 2 2 4 1] then no diary entries appear on Sunday, the current date’s and the next day’s diary entries appear Monday through Thursday, Friday through Monday’s entries appear on Friday, while on Saturday only that day’s entries appear.

You can customize the form of dates in your diary file by setting the variable diary-date-forms. This variable is a list of patterns for recognizing a date. Each date pattern is a list whose elements may be regular expressions (see Regular Expressions in the Emacs Lisp Reference Manual) or the symbols month, day, year, monthname, and dayname. All these elements serve as patterns that match certain kinds of text in the diary file. In order for the date pattern as a whole to match, all of its elements must match consecutively.

A regular expression in a date pattern matches in its usual fashion, using the standard syntax table altered so that ‘*’ is a word constituent.

The symbols month, day, year, monthname, and dayname match the month number, day number, year number, month name, and day name of the date being considered. The symbols that match numbers allow leading zeros; those that match names allow capitalization and abbreviation (as specified by calendar-month-abbrev-array and calendar-day-abbrev-array). All the symbols can match ‘*’; since ‘*’ in a diary entry means “any day”, “any month”, and so on, it should match regardless of the date being considered.

The default value of diary-date-forms in the American style is provided by diary-american-date-forms:

((month "/" day "[^/0-9]")
 (month "/" day "/" year "[^0-9]")
 (monthname " *" day "[^,0-9]")
 (monthname " *" day ", *" year "[^0-9]")
 (dayname "\\W"))

The variables diary-european-date-forms and diary-iso-date-forms provide other default styles.

The date patterns in the list must be mutually exclusive and must not match any portion of the diary entry itself, just the date and one character of whitespace. If, to be mutually exclusive, the pattern must match a portion of the diary entry text—beyond the whitespace that ends the date—then the first element of the date pattern must be backup. This causes the date recognizer to back up to the beginning of the current word of the diary entry, after finishing the match. Even if you use backup, the date pattern must absolutely not match more than a portion of the first word of the diary entry. For example, the default value of diary-european-date-forms is:

((day "/" month "[^/0-9]")
 (day "/" month "/" year "[^0-9]")
 (backup day " *" monthname "\\W+\\<\\([^*0-9]\\|\\([0-9]+[:aApP]\\)\\)")
 (day " *" monthname " *" year "[^0-9]")
 (dayname "\\W"))

Notice the use of backup in the third pattern, because it needs to match part of a word beyond the date itself to distinguish it from the fourth pattern.


32.13.7 Diary Entries Using non-Gregorian Calendars

As well as entries based on the standard Gregorian calendar, your diary can have entries based on Bahá’í, Chinese, Hebrew, or Islamic dates. Recognition of such entries can be time-consuming, however, and since most people don’t use them, you must explicitly enable their use. If you want the diary to recognize Hebrew-date diary entries, for example, you must do this:

(add-hook 'diary-nongregorian-listing-hook 'diary-hebrew-list-entries)
(add-hook 'diary-nongregorian-marking-hook 'diary-hebrew-mark-entries)

Similarly, for Islamic, Bahá’í and Chinese entries, add diary-islamic-list-entries and diary-islamic-mark-entries, diary-bahai-list-entries and diary-bahai-mark-entries, or diary-chinese-list-entries and diary-chinese-mark-entries.

These diary entries have the same formats as Gregorian-date diary entries; except that diary-bahai-entry-symbol (default ‘B’) must precede a Bahá’í date, diary-chinese-entry-symbol (default ‘C’) a Chinese date, diary-hebrew-entry-symbol (default ‘H’) a Hebrew date, and diary-islamic-entry-symbol (default ‘I’) an Islamic date. Moreover, non-Gregorian month names may not be abbreviated (because the first three letters are often not unique). (Note also that you must use “Adar I” if you want Adar of a common Hebrew year.) For example, a diary entry for the Hebrew date Heshvan 25 could look like this:

HHeshvan 25 Happy Hebrew birthday!

and would appear in the diary for any date that corresponds to Heshvan 25 on the Hebrew calendar. And here is an Islamic-date diary entry that matches Dhu al-Qada 25:

IDhu al-Qada 25 Happy Islamic birthday!

As with Gregorian-date diary entries, non-Gregorian entries are nonmarking if preceded by diary-nonmarking-symbol (default ‘&’).

Here is a table of commands used in the calendar to create diary entries that match the selected date and other dates that are similar in the Bahá’í, Chinese, Hebrew, or Islamic calendars:

i h d

diary-hebrew-insert-entry

i h m

diary-hebrew-insert-monthly-entry

i h y

diary-hebrew-insert-yearly-entry

i i d

diary-islamic-insert-entry

i i m

diary-islamic-insert-monthly-entry

i i y

diary-islamic-insert-yearly-entry

i B d

diary-bahai-insert-entry

i B m

diary-bahai-insert-monthly-entry

i B y

diary-bahai-insert-yearly-entry

i C d

diary-chinese-insert-entry

i C m

diary-chinese-insert-monthly-entry

i C y

diary-chinese-insert-yearly-entry

i C a

diary-chinese-insert-anniversary-entry

These commands work much like the corresponding commands for ordinary diary entries: they apply to the date that point is on in the calendar window, and what they do is insert just the date portion of a diary entry at the end of your diary file. You must then insert the rest of the diary entry. The basic commands add an entry for the specific non-Gregorian date, the ‘monthly’ commands for the given non-Gregorian day-within-month in every month, and the ‘yearly’ commands for the given non-Gregorian day and month in every year.


32.13.8 Diary Display

Diary display works by preparing the list of diary entries and then running the function specified by the variable diary-display-function. The default value diary-fancy-display displays diary entries and holidays by copying them into a special buffer that exists only for the sake of display. Copying diary entries to a separate buffer provides an opportunity to change the displayed text to make it prettier—for example, to sort the entries by the dates they apply to.

Ordinarily, the fancy diary buffer does not show days for which there are no diary entries, even if that day is a holiday. If you want such days to be shown in the fancy diary buffer, set the variable diary-list-include-blanks to t.

The fancy diary buffer enables View mode (see View Mode).

The alternative display method diary-simple-display shows the actual diary buffer, and uses invisible text to hide entries that don’t apply. Holidays are shown in the mode line. The advantage of this method is that you can edit the buffer and save your changes directly to the diary file. This method is not as flexible as the fancy method, however. For example, it cannot sort entries. Another disadvantage is that invisible text can be confusing. For example, if you copy a region of text in order to paste it elsewhere, invisible text may be included. Similarly, since the diary buffer as you see it is an illusion, simply printing the buffer may not print what you see on your screen.

For this reason, there is a special command to print hard copy of the diary buffer as it appears; this command is M-x diary-print-entries. It works with either display method, although with the fancy display you can also print the buffer like any other. To print a hard copy of a day-by-day diary for a week, position point on the first day of the week, type 7 d, and then do M-x diary-print-entries. As usual, the inclusion of the holidays slows down the display slightly; you can speed things up by setting the variable diary-show-holidays-flag to nil.

This command prepares a temporary buffer that contains only the diary entries currently visible in the diary buffer. Unlike with the simple display, the other irrelevant entries are really absent, not just hidden. After preparing the buffer, it runs the hook diary-print-entries-hook. The default value of this hook sends the data directly to the printer with the command lpr-buffer (see Printing Hard Copies). If you want to use a different command to do the printing, just change the value of this hook. Other uses might include, for example, rearranging the lines into order by day and time.

You can edit the diary entries as they appear in the simple diary window, but it is important to remember that the buffer displayed contains the entire diary file, with portions of it concealed from view. This means, for instance, that the C-f (forward-char) command can put point at what appears to be the end of the line, but what is in reality the middle of some concealed line.

Be careful when editing the diary entries in the simple display! Inserting additional lines or adding/deleting characters in the middle of a visible line cannot cause problems, but editing at the end of a line may not do what you expect. Deleting a line may delete other invisible entries that follow it. Before editing the simple diary buffer, it is best to display the entire file with s (diary-show-all-entries).


32.13.9 Fancy Diary Display

The following features only work with the fancy diary display.

You can use the normal hook diary-list-entries-hook to sort each day’s diary entries by their time of day. Here’s how:

(add-hook 'diary-list-entries-hook 'diary-sort-entries t)

For each day, this sorts diary entries that begin with a recognizable time of day according to their times. Diary entries without times come first within each day. Note how the sort command is placed at the end of the hook list, in case earlier members of the list change the order of the diary entries, or add items.

You can write ‘comments’ in diary entries, by setting the variables diary-comment-start and diary-comment-end to strings that delimit comments. The fancy display does not print comments. You might want to put meta-data for the use of other packages (e.g., the appointment package, see Appointments) inside comments.

Your main diary file can include other files. This permits a group of people to share a diary file for events that apply to all of them. Lines in the diary file starting with diary-include-string:

#include "filename"

include the diary entries from the file filename in the fancy diary buffer. The include mechanism is recursive, so that included files can include other files, and so on (you must be careful not to have a cycle of inclusions, of course). Here is how to enable the include facility:

(add-hook 'diary-list-entries-hook 'diary-include-other-diary-files)
(add-hook 'diary-mark-entries-hook 'diary-mark-included-diary-files)

The include mechanism works only with the fancy diary display, because simple diary display shows the entries directly from your diary file.


32.13.10 Sexp Entries and the Fancy Diary Display

Sexp diary entries allow you to do more than just have complicated conditions under which a diary entry applies. Sexp entries should be preceded by diary-sexp-entry-symbol (default ‘%%’) in the diary file. With the fancy diary display, sexp entries can generate the text of the entry depending on the date itself.

For example, an anniversary diary entry can insert the number of years since the anniversary date into the text of the diary entry. Thus the ‘%d’ in this diary entry:

%%(diary-anniversary 10 31 1948) Arthur's birthday (%d years old)

gets replaced by the age, so on October 31, 1990 the entry appears in the fancy diary buffer like this:

Arthur's birthday (42 years old)

If the diary file instead contains this entry:

%%(diary-anniversary 10 31 1948) Arthur's %d%s birthday

the entry in the fancy diary buffer for October 31, 1990 appears like this:

Arthur's 42nd birthday

Similarly, cyclic diary entries can interpolate the number of repetitions that have occurred:

%%(diary-cyclic 50 1 1 2012) Renew medication (%d%s time)

looks like this:

Renew medication (5th time)

in the fancy diary display on September 7, 2012.

There is an early-reminder diary sexp that includes its entry in the diary not only on the date of occurrence, but also on earlier dates. For example, if you want a reminder a week before your anniversary, you can use

%%(diary-remind '(diary-anniversary 12 22 1968) 7) Ed's anniversary

and the fancy diary will show ‘Ed's anniversary’ both on December 15 and on December 22.

The function diary-date applies to dates described by a month, day, year combination, each of which can be an integer, a list of integers, or t (meaning all values). For example,

%%(diary-date '(10 11 12) 22 t) Rake leaves

causes the fancy diary to show

Rake leaves

on October 22, November 22, and December 22 of every year.

The function diary-float allows you to describe diary entries that apply to dates like the third Friday of November, or the last Tuesday in April. The parameters are the month, dayname, and an index n. The entry appears on the nth dayname after the first day of month, where dayname=0 means Sunday, 1 means Monday, and so on. If n is negative it counts backward from the end of month. The value of month can be a list of months, a single month, or t to specify all months. You can also use an optional parameter day to specify the nth dayname on or after/before day of month; the value of day defaults to 1 if n is positive and to the last day of month if n is negative. For example,

%%(diary-float t 1 -1) Pay rent

causes the fancy diary to show

Pay rent

on the last Monday of every month.

The generality of sexp diary entries lets you specify any diary entry that you can describe algorithmically. A sexp diary entry contains an expression that computes whether the entry applies to any given date. If its value is non-nil, the entry applies to that date; otherwise, it does not. The expression can use the variable date to find the date being considered; its value is a list (month day year) that refers to the Gregorian calendar.

The sexp diary entry applies to a date when the expression’s value is non-nil, but some values have more specific meanings. If the value is a string, that string is a description of the event which occurs on that date. The value can also have the form (mark . string); then mark specifies how to mark the date in the calendar, and string is the description of the event. If mark is a single-character string, that character appears next to the date in the calendar. If mark is a face name, the date is displayed in that face. If mark is nil, that specifies no particular highlighting for the date.

Suppose you get paid on the 21st of the month if it is a weekday, and on the Friday before if the 21st is on a weekend. Here is how to write a sexp diary entry that matches those dates:

&%%(let ((dayname (calendar-day-of-week date))
         (day (cadr date)))
      (or (and (= day 21) (memq dayname '(1 2 3 4 5)))
          (and (memq day '(19 20)) (= dayname 5)))
         ) Pay check deposited

The following sexp diary entries take advantage of the ability (in the fancy diary display) to concoct diary entries whose text varies based on the date:

%%(diary-sunrise-sunset)

Make a diary entry for today’s local times of sunrise and sunset.

%%(diary-lunar-phases)

Make a diary entry for the phases (quarters) of the moon.

%%(diary-day-of-year)

Make a diary entry with today’s day number in the current year and the number of days remaining in the current year.

%%(diary-iso-date)

Make a diary entry with today’s equivalent ISO commercial date.

%%(diary-julian-date)

Make a diary entry with today’s equivalent Julian calendar date.

%%(diary-astro-day-number)

Make a diary entry with today’s equivalent astronomical (Julian) day number.

%%(diary-bahai-date)

Make a diary entry with today’s equivalent Bahá’í calendar date.

%%(diary-chinese-date)

Make a diary entry with today’s equivalent Chinese calendar date.

%%(diary-coptic-date)

Make a diary entry with today’s equivalent Coptic calendar date.

%%(diary-ethiopic-date)

Make a diary entry with today’s equivalent Ethiopic calendar date.

%%(diary-french-date)

Make a diary entry with today’s equivalent date on the French Revolutionary calendar.

%%(diary-hebrew-date)

Make a diary entry with today’s equivalent Hebrew calendar date.

%%(diary-islamic-date)

Make a diary entry with today’s equivalent Islamic calendar date.

%%(diary-mayan-date)

Make a diary entry with today’s equivalent Mayan calendar date.

%%(diary-persian-date)

Make a diary entry with today’s equivalent Persian calendar date.

For example, including the diary entry

&%%(diary-hebrew-date)

causes every day’s diary display to contain the equivalent date on the Hebrew calendar, if you are using the fancy diary display. (With simple diary display, the literal line ‘&%%(diary-hebrew-date)’ appears in the diary for any date.)

This function has been used to construct certain standard Hebrew sexp diary entries:

%%(diary-hebrew-rosh-hodesh)

Make a diary entry that tells the occurrence and ritual announcement of each new Hebrew month.

%%(diary-hebrew-parasha)

Make a Saturday diary entry that tells the weekly synagogue scripture reading.

%%(diary-hebrew-sabbath-candles)

Make a Friday diary entry that tells the local time of Sabbath candle lighting.

%%(diary-hebrew-omer)

Make a diary entry that gives the omer count, when appropriate.

%%(diary-hebrew-yahrzeit month day year) name

Make a diary entry marking the anniversary of a date of death. The date is the Gregorian (civil) date of death. The diary entry appears on the proper Hebrew calendar anniversary and on the day before. (The order of the parameters changes according to the calendar date style; for example in the European style to day, month, year.)

%%(diary-hebrew-birthday month day year)

Make a diary entry for a birthday on the Hebrew calendar.

All the functions documented above take an optional argument mark which specifies how to mark the date in the calendar display. If one of these functions decides that it applies to a certain date, it returns a value that contains mark, as described above.


33 Sending Mail

To send an email message from Emacs, type C-x m. This switches to a buffer named *unsent mail*, where you can edit the text and headers of the message. When done, type C-c C-s or C-c C-c to send it.

C-x m

Begin composing mail (compose-mail).

C-x 4 m

Likewise, in another window (compose-mail-other-window).

C-x 5 m

Likewise, but in a new frame (compose-mail-other-frame).

C-c C-s

In the mail buffer, send the message (message-send).

C-c C-c

In the mail buffer, send the message and bury the buffer (message-send-and-exit).

The mail buffer is an ordinary Emacs buffer, so you can switch to other buffers while composing the mail. If you want to send another message before finishing the current one, type C-x m again to open a new mail buffer whose name has a different numeric suffix (see Miscellaneous Buffer Operations). (This only works if you use the default Message mode to compose email; see Mail Commands.) If you know that you’d like to continue composing the unsent message you were editing, invoke this command with a prefix argument, C-u C-x m, and Emacs will switch to the last mail buffer you used and let you pick up editing the message where you left off.

The command C-x 4 m (compose-mail-other-window) does the same as C-x m, except it displays the mail buffer in a different window. The command C-x 5 m (compose-mail-other-frame) does it in a new frame.

When you type C-c C-c or C-c C-s to send the mail, Emacs may ask you how it should deliver the mail—either directly via SMTP, or using some other method. See Mail Sending, for details.


33.1 The Format of the Mail Buffer

Here is an example of the contents of a mail buffer:

To: subotai@example.org
CC: mongol.soldier@example.net, rms@gnu.org
Subject: Re: What is best in life?
From: conan@example.org
--text follows this line--
To crush your enemies, see them driven before you, and to
hear the lamentation of their women.

At the top of the mail buffer is a set of header fields, which are used for specifying information about the email’s recipient(s), subject, and so on. The above buffer contains header fields for ‘To’, ‘CC’, ‘Subject’, and ‘From’. Some header fields are automatically pre-initialized in the mail buffer, when appropriate.

The line that says ‘--text follows this line--’ separates the header fields from the body (or text) of the message. Everything above that line is treated as part of the headers; everything below it is treated as the body. The delimiter line itself does not appear in the message actually sent.

You can insert and edit header fields using ordinary editing commands. See Mail Header Editing, for commands specific to editing header fields. Certain headers, such as ‘Date’ and ‘Message-Id’, are normally omitted from the mail buffer and are created automatically when the message is sent.


33.2 Mail Header Fields

A header field in the mail buffer starts with a field name at the beginning of a line, terminated by a colon. Upper and lower case are equivalent in field names. After the colon and optional whitespace comes the contents of the field.

You can use any name you like for a header field, but normally people use only standard field names with accepted meanings.

The ‘From’ header field identifies the person sending the email (i.e., you). This should be a valid mailing address, as replies are normally sent there. The default contents of this header field are computed from the variables user-full-name (which specifies your full name) and user-mail-address (your email address). On some operating systems, Emacs initializes these two variables using environment variables (see General Variables). If this information is unavailable or wrong, you should customize the variables yourself (see Easy Customization Interface).

Apart from ‘From’, here is a table of commonly-used fields:

To

The mailing address(es) to which the message is addressed. To list more than one address, use commas to separate them.

Subject

The subject of the message.

CC

Additional mailing address(es) to send the message to. This is like ‘To’, except that these readers should not regard the message as directed at them.

BCC

Additional mailing address(es) to send the message to, which should not appear in the header of the message actually sent. ‘BCC’ stands for blind carbon copies.

FCC

The name of a file, to which a copy of the sent message should be appended. Emacs writes the message in mbox format, unless the file is in Babyl format (used by Rmail before Emacs 23), in which case Emacs writes in Babyl format. If an Rmail buffer is visiting the file, Emacs updates it accordingly. To specify more than one file, use several ‘FCC’ fields, with one file name in each field.

Reply-To

An address to which replies should be sent, instead of ‘From’. This is used if, for some reason, your ‘From’ address cannot receive replies.

Mail-Reply-To

This field takes precedence over ‘Reply-To’. It is used because some mailing lists set the ‘Reply-To’ field for their own purposes (a somewhat controversial practice).

Mail-Followup-To

One of more address(es) to use as default recipient(s) for follow-up messages. This is typically used when you reply to a message from a mailing list that you are subscribed to, and want replies to go to the list without sending an extra copy to you.

In-Reply-To

An identifier for the message you are replying to. Most mail readers use this information to group related messages together. Normally, this header is filled in automatically when you reply to a message in any mail program built into Emacs.

References

Identifiers for previous related messages. Like ‘In-Reply-To’, this is normally filled in automatically for you.

The ‘To’, ‘CC’, and ‘BCC’ fields can appear any number of times, and each such header field can contain multiple addresses, separated by commas. This way, you can specify any number of places to send the message. These fields can also have continuation lines: one or more lines starting with whitespace, following the starting line of the field, are considered part of the field. Here’s an example of a ‘To’ field with a continuation line:

To: foo@example.net, this@example.net,
  bob@example.com

You can direct Emacs to insert certain default headers into the mail buffer by setting the variable mail-default-headers to a string. Then C-x m inserts this string into the message headers. For example, here is how to add a ‘Reply-To’ and ‘FCC’ header to each message:

(setq mail-default-headers
      "Reply-To: foo@example.com\nFCC: ~/Mail/sent")

If the default header fields are not appropriate for a particular message, edit them as necessary before sending the message.


33.3 Mail Aliases

You can define mail aliases, which are short mnemonic names that stand for one or more mailing addresses. By default, mail aliases are defined in the file ~/.mailrc. You can specify a different file name to use, by setting the variable mail-personal-alias-file.

To define an alias in ~/.mailrc, write a line like this:

alias nick fulladdresses

This means that nick should expand into fulladdresses, where fulladdresses can be either a single address, or multiple addresses separated with spaces. For instance, to make maingnu stand for gnu@gnu.org plus a local address of your own, put in this line:

alias maingnu gnu@gnu.org local-gnu

If an address contains a space, quote the whole address with a pair of double quotes, like this:

alias jsmith "John Q. Smith <none@example.com>"

Note that you need not include double quotes around individual parts of the address, such as the person’s full name. Emacs puts them in if they are needed. For instance, it inserts the above address as ‘"John Q. Smith" <none@example.com>’.

After editing the ~/.mailrc file, or if the file was modified outside of Emacs, you can update the mail aliases used by a running Emacs session with M-x rebuild-mail-abbrevs RET. This prompts for the name of the file to use, the default being the value of mail-personal-alias-file. A similar command merge-mail-abbrevs prompts for a file with mail aliases, then merges the aliases in that file with the existing ones.

Alternatively, you can use Emacs commands to define mail aliases. The command define-mail-abbrev prompts for the alias and the full address, and defines the alias to expand to the full address. Emacs will save the added aliases whenever it offers to save all files (for C-x s or C-x C-c), like it does with other abbrevs (see Saving Abbrevs).

Emacs also recognizes include commands in ~/.mailrc. They look like this:

source filename

The ~/.mailrc file is not unique to Emacs; many other mail-reading programs use it for mail aliases, and it can contain various other commands. However, Emacs ignores everything except alias definitions and include commands.

Mail aliases expand as abbrevs—that is to say, as soon as you type a word-separator character after an alias (see Abbrevs). This expansion takes place only within the ‘To’, ‘From’, ‘CC’, ‘BCC’, and ‘Reply-To’ header fields (plus their ‘Resent-’ variants); it does not take place in other header fields, such as ‘Subject’.

You can also insert an aliased address directly, using the command M-x mail-abbrev-insert-alias. This reads an alias name, with completion, and inserts its definition at point.

The command mail-abbrev-complete-alias completes on the mail alias preceding point.


33.4 Mail Commands

The default major mode for the *mail* buffer is called Message mode. It behaves like Text mode in many ways, but provides several additional commands on the C-c prefix, which make editing a message more convenient.

In this section, we will describe some of the most commonly-used commands available in Message mode. Message mode also has its own manual, where its features are described in greater detail. See Message in Message.


33.4.1 Mail Sending

C-c C-c

Send the message, and bury the mail buffer (message-send-and-exit).

C-c C-s

Send the message, and leave the mail buffer selected (message-send).

The usual command to send a message is C-c C-c (message-send-and-exit). This sends the message and then buries the mail buffer, putting it at the lowest priority for reselection. If you want it to kill the mail buffer instead, change the variable message-kill-buffer-on-exit to t.

The command C-c C-s (message-send) sends the message and leaves the buffer selected. Use this command if you want to modify the message (perhaps with new recipients) and send it again.

Sending a message runs the hook message-send-hook. It also marks the mail buffer as unmodified, except if the mail buffer is also a file-visiting buffer (in that case, only saving the file does that, and you don’t get a warning if you try to send the same message twice).

The variable message-send-mail-function controls how the message is delivered (send-mail-function is used for Mail mode). The value of send-mail-function should be one of the following functions:

sendmail-query-once

Query for a delivery method (one of the other entries in this list), and use that method for this message; then save the method to send-mail-function, so that it is used for future deliveries. This is the default, unless you have already set the variables for sending mail via smtpmail-send-it (see below).

smtpmail-send-it

Send mail through an external mail host, such as your Internet service provider’s outgoing SMTP mail server. If you have not told Emacs how to contact the SMTP server, it prompts for this information, which is saved in the smtpmail-smtp-server variable and the file ~/.authinfo. See Emacs SMTP Library in Sending mail via SMTP.

sendmail-send-it

Send mail using the system’s default sendmail program, or equivalent. This requires the system to be set up for delivering mail directly via SMTP.

mailclient-send-it

Pass the mail buffer on to the system’s designated mail client. See the commentary section in the file mailclient.el for details.

feedmail-send-it

This is similar to sendmail-send-it, but allows you to queue messages for later sending. See the commentary section in the file feedmail.el for details.

When you send a message containing non-ASCII characters, they need to be encoded with a coding system (see Coding Systems). Usually the coding system is specified automatically by your chosen language environment (see Language Environments). You can explicitly specify the coding system for outgoing mail by setting the variable sendmail-coding-system (see Recognizing Coding Systems). If the coding system thus determined does not handle the characters in a particular message, Emacs asks you to select the coding system to use, showing a list of possible coding systems. See Choosing Coding Systems for Output.


33.4.2 Mail Header Editing

Message mode provides the following special commands to move to particular header fields and to complete addresses in headers.

C-c C-f C-t

Move to the ‘To’ header (message-goto-to).

C-c C-f C-s

Move to the ‘Subject’ header (message-goto-subject).

C-c C-f C-c

Move to the ‘CC’ header (message-goto-cc).

C-c C-f C-b

Move to the ‘BCC’ header (message-goto-bcc).

C-c C-f C-r

Move to the ‘Reply-To’ header (message-goto-reply-to).

C-c C-f C-f

Move to the ‘Mail-Followup-To’ header field (message-goto-followup-to).

C-c C-f C-w

Add a new ‘FCC’ header field, with file-name completion (message-goto-fcc).

C-c C-b

Move to the start of the message body (message-goto-body).

TAB

Complete a mailing address (message-tab).

The commands to move point to particular header fields are all based on the prefix C-c C-f (‘C-f’ is for “field”). If the field in question does not exist, the command creates one (the exception is mail-fcc, which creates a new field each time).

The command C-c C-b (message-goto-body) moves point to just after the header separator line—that is, to the beginning of the body.

While editing a header field that contains addresses, such as ‘To:’, ‘CC:’ and ‘BCC:’, you can complete an address by typing TAB (message-tab). This attempts to insert the full name corresponding to the address based on a couple of methods, including EUDC, a library that recognizes a number of directory server protocols (see EUDC in The Emacs Unified Directory Client). Failing that, it attempts to expand the address as a mail alias (see Mail Aliases). If point is on a header field that does not take addresses, or if it is in the message body, then TAB just inserts a tab character.


33.4.3 Citing Mail

C-c C-y

Yank the selected message from the mail reader, as a citation (message-yank-original).

C-c C-q

Fill each paragraph cited from another message (message-fill-yanked-message).

You can use the command C-c C-y (message-yank-original) to cite a message that you are replying to. This inserts the text of that message into the mail buffer. This command works only if the mail buffer is invoked from a mail reader running in Emacs, such as Rmail.

By default, Emacs inserts the string ‘>’ in front of each line of the cited text; this prefix string is specified by the variable message-yank-prefix. If you call message-yank-original with a prefix argument, the citation prefix is not inserted.

After using C-c C-y, you can type C-c C-q (message-fill-yanked-message) to fill the paragraphs of the cited message. One use of C-c C-q fills all such paragraphs, each one individually. To fill a single paragraph of the quoted message, use M-q. If filling does not automatically handle the type of citation prefix you use, try setting the fill prefix explicitly. See Filling Text.

You can customize mail citation through the hook mail-citation-hook. For example, you can use the Supercite package, which provides more flexible citation (see Introduction in Supercite).


33.4.4 Mail Miscellany

You can attach a file to an outgoing message by typing C-c C-a (mml-attach-file) in the mail buffer. Attaching is done using the Multipurpose Internet Mail Extensions (MIME) standard.

The mml-attach-file command prompts for the name of the file, and for the attachment’s content type, description, and disposition. The content type is normally detected automatically; just type RET to accept the default. The description is a single line of text that the recipient will see next to the attachment; you may also choose to leave this empty. The disposition is either ‘inline’, which means the recipient will see a link to the attachment within the message body, or ‘attachment’, which means the link will be separate from the body.

The mml-attach-file command is specific to Message mode; in Mail mode use mail-add-attachment instead. It will prompt only for the name of the file, and will determine the content type and the disposition automatically. If you want to include some description of the attached file, type that in the message body.

The actual contents of the attached file are not inserted into the mail buffer. Instead, some placeholder text is inserted into the mail buffer, like this:

<#part type="text/plain" filename="~/foo.txt" disposition=inline>
<#/part>

When you type C-c C-c or C-c C-s to send the message, the attached file will be delivered with it.

While composing a message, you can do spelling correction on the message text by typing M-x ispell-message. If you have yanked an incoming message into the outgoing draft, this command skips what was yanked, but it checks the text that you yourself inserted (it looks for indentation or mail-yank-prefix to distinguish the cited lines from your input). See Checking and Correcting Spelling.

Turning on Message mode (which C-x m does automatically) runs the normal hooks text-mode-hook and message-mode-hook. Initializing a new outgoing message runs the normal hook message-setup-hook; you can use this hook if you want to make changes to the appearance of the mail buffer. See Hooks.

The main difference between these hooks is just when they are invoked. Whenever you type C-x m, message-mode-hook runs as soon as the mail buffer is created. Then the message-setup function inserts the default contents of the buffer. After these default contents are inserted, message-setup-hook runs.

If you use C-x m to continue an existing composition, message-mode-hook runs immediately after switching to the mail buffer. If the buffer is unmodified, or if you decide to erase it and start again, message-setup-hook runs after the default contents are inserted.


33.5 Mail Signature

You can add a standard piece of text—your mail signature—to the end of every message. This signature may contain information such as your telephone number or your physical location. The variable message-signature determines how Emacs handles the mail signature.

The default value of message-signature is t; this means to look for your mail signature in the file ~/.signature. If this file exists, its contents are automatically inserted into the end of the mail buffer. You can change the signature file via the variable message-signature-file.

If you change message-signature to a string, that specifies the text of the signature directly.

If you change message-signature to nil, Emacs will not insert your mail signature automatically. You can insert your mail signature by typing C-c C-w (message-insert-signature) in the mail buffer. Emacs will look for your signature in the signature file.

If you use Mail mode rather than Message mode for composing your mail, the corresponding variables that determine how your signature is sent are mail-signature and mail-signature-file instead.

By convention, a mail signature should be marked by a line whose contents are ‘-- ’. If your signature lacks this prefix, it is added for you. The remainder of your signature should be no more than four lines.


33.6 Mail Amusements

M-x spook adds a line of randomly chosen keywords to an outgoing mail message. The keywords are chosen from a list of words that suggest you are discussing something subversive.

The idea behind this feature is the suspicion that the NSA19 and other intelligence agencies snoop on all electronic mail messages that contain keywords suggesting they might find them interesting. (The agencies say that they don’t, but that’s what they would say.) The idea is that if lots of people add suspicious words to their messages, the agencies will get so busy with spurious input that they will have to give up reading it all. Whether or not this is true, it at least amuses some people.

You can use the fortune program to put a fortune cookie message into outgoing mail. To do this, add fortune-to-signature to mail-setup-hook:

(add-hook 'mail-setup-hook 'fortune-to-signature)

You will probably need to set the variable fortune-file before using this.


33.7 Mail-Composition Methods

In this chapter we have described the usual Emacs mode for editing and sending mail—Message mode. This is only one of several available modes. Prior to Emacs 23.2, the default mode was Mail mode, which is similar to Message mode in many respects but lacks features such as MIME support. Another available mode is MH-E (see MH-E in The Emacs Interface to MH).

You can choose any of these mail user agents as your preferred method for editing and sending mail. The commands C-x m, C-x 4 m and C-x 5 m use whichever agent you have specified; so do various other parts of Emacs that send mail, such as the bug reporter (see Reporting Bugs). To specify a mail user agent, customize the variable mail-user-agent. Currently, legitimate values include message-user-agent (Message mode) sendmail-user-agent (Mail mode), gnus-user-agent, and mh-e-user-agent. Additional options may be available; check in the manual of your mail user agent package for details. You may also define another mail user agent using define-mail-user-agent.

If you select a different mail-composition method, the information in this chapter about the mail buffer and Message mode does not apply; the other methods use a different format of text in a different buffer, and their commands are different as well.

Similarly, to specify your preferred method for reading mail, customize the variable read-mail-command. The default is rmail (see Reading Mail with Rmail).


34 Reading Mail with Rmail

Rmail is an Emacs subsystem for reading and disposing of mail that you receive. Rmail stores mail messages in files called Rmail files. Reading the messages in an Rmail file is done in a special major mode, Rmail mode, which redefines most letters to run commands for managing mail.

Emacs also comes with a much more sophisticated and flexible subsystem for reading mail, called Gnus. Gnus is a very large package, and is therefore described in its own manual, see The Gnus Newsreader.


34.1 Basic Concepts of Rmail

Using Rmail in the simplest fashion, you have one Rmail file ~/RMAIL in which all of your mail is saved. It is called your primary Rmail file. The command M-x rmail reads your primary Rmail file, merges new mail in from your inboxes, displays the first message you haven’t read yet, and lets you begin reading. The variable rmail-file-name specifies the name of the primary Rmail file.

Rmail displays only one message in the Rmail file at a time. The message that is shown is called the current message. Rmail mode’s special commands can do such things as delete the current message, copy it into another file, send a reply, or move to another message. You can also create multiple Rmail files (see File Handling) and use Rmail to move messages between them (see Copying Messages Out to Files).

Within the Rmail file, messages are normally arranged sequentially in order of receipt; you can specify other ways to sort them (see Sorting the Rmail File). Messages are identified by consecutive integers which are their message numbers. The number of the current message is displayed in Rmail’s mode line, followed by the total number of messages in the file. You can move to a message by specifying its message number with the j key (see Moving Among Messages).

Following the usual conventions of Emacs, changes in an Rmail file become permanent only when you save the file. You can save it with s (rmail-expunge-and-save), which also expunges deleted messages from the file first (see Deleting Messages). To save the file without expunging, use C-x C-s. Rmail automatically saves the Rmail file after merging new mail from an inbox file (see Rmail Files and Inboxes).

You can exit Rmail with q (rmail-quit); this expunges and saves the Rmail file, then buries the Rmail buffer as well as its summary buffer, if present (see Summaries). But there is no need to exit formally. If you switch from Rmail to editing in other buffers, and never switch back, you have exited. Just make sure to save the Rmail file eventually (like any other file you have changed). C-x s is a suitable way to do this (see Commands for Saving Files). The Rmail command b, rmail-bury, buries the Rmail buffer and its summary without expunging and saving the Rmail file.


34.2 Scrolling Within a Message

When Rmail displays a message that does not fit on the screen, you must scroll through it to read the rest. You could do this with the usual scrolling commands: C-v, M-v and M-< (see Scrolling), but in Rmail scrolling is so frequent that it deserves to be easier.

SPC

Scroll forward (scroll-up-command).

DEL
S-SPC

Scroll backward (scroll-down-command).

.

Scroll to start of message (rmail-beginning-of-message).

/

Scroll to end of message (rmail-end-of-message).

Since the most common thing to do while reading a message is to scroll through it by screenfuls, Rmail makes SPC and DEL (or S-SPC) do the same as C-v (scroll-up-command) and M-v (scroll-down-command) respectively.

The command . (rmail-beginning-of-message) scrolls back to the beginning of the selected message. This is not quite the same as M-<: for one thing, it does not set the mark; for another, it resets the buffer boundaries of the current message if you have changed them (e.g., by editing, see Editing Within a Message). Similarly, the command / (rmail-end-of-message) scrolls forward to the end of the selected message.


34.3 Moving Among Messages

The most basic thing to do with a message is to read it. The way to do this in Rmail is to make the message current. The usual practice is to move sequentially through the file, since this is the order of receipt of messages. When you enter Rmail, you are positioned at the first message that you have not yet made current (that is, the first one that has the ‘unseen’ attribute; see Rmail Attributes). Move forward to see the other new messages; move backward to re-examine old messages.

n

Move to the next nondeleted message, skipping any intervening deleted messages (rmail-next-undeleted-message).

p

Move to the previous nondeleted message (rmail-previous-undeleted-message).

M-n

Move to the next message, including deleted messages (rmail-next-message).

M-p

Move to the previous message, including deleted messages (rmail-previous-message).

C-c C-n

Move to the next message with the same subject as the current one (rmail-next-same-subject).

C-c C-p

Move to the previous message with the same subject as the current one (rmail-previous-same-subject).

j

Move to the first message. With argument n, move to message number n (rmail-show-message).

>

Move to the last message (rmail-last-message).

<

Move to the first message (rmail-first-message).

M-s regexp RET

Move to the next message containing a match for regexp (rmail-search).

- M-s regexp RET

Move to the previous message containing a match for regexp. (This is M-s with a negative argument.)

n and p are the usual way of moving among messages in Rmail. They move through the messages sequentially, but skip over deleted messages, which is usually what you want to do. Their command definitions are named rmail-next-undeleted-message and rmail-previous-undeleted-message. If you do not want to skip deleted messages—for example, if you want to move to a message to undelete it—use the variants M-n and M-p (rmail-next-message and rmail-previous-message). A numeric argument to any of these commands serves as a repeat count.

In Rmail, you can specify a numeric argument by typing just the digits. You don’t need to type C-u first. You can also specify a negative argument by typing just -.

The M-s (rmail-search) command is Rmail’s version of search. The usual incremental search command C-s works in Rmail, but it searches only within the current message. The purpose of M-s is to search for another message. It reads a regular expression (see Syntax of Regular Expressions) nonincrementally, then searches starting at the beginning of the following message for a match. It then selects that message. If regexp is empty, M-s reuses the regexp used the previous time.

To search backward in the file for another message, give M-s a negative argument. In Rmail you can do this with - M-s. This begins searching from the end of the previous message.

It is also possible to search for a message based on labels. See Labels.

The C-c C-n (rmail-next-same-subject) command moves to the next message with the same subject as the current one. A prefix argument serves as a repeat count. With a negative argument, this command moves backward, acting like C-c C-p (rmail-previous-same-subject). When comparing subjects, these commands ignore the prefixes typically added to the subjects of replies. These commands are useful for reading all of the messages pertaining to the same subject, a.k.a. thread.

To move to a message specified by absolute message number, use j (rmail-show-message) with the message number as argument. With no argument, j selects the first message. < (rmail-first-message) also selects the first message. > (rmail-last-message) selects the last message.


34.4 Deleting Messages

When you no longer need to keep a message, you can delete it. This flags it as ignorable, and some Rmail commands pretend it is no longer present; but it still has its place in the Rmail file, and still has its message number.

Expunging the Rmail file actually removes the deleted messages. The remaining messages are renumbered consecutively.

d

Delete the current message, and move to the next nondeleted message (rmail-delete-forward).

C-d

Delete the current message, and move to the previous nondeleted message (rmail-delete-backward).

u

Undelete the current message, or move back to the previous deleted message and undelete it (rmail-undelete-previous-message).

x

Expunge the Rmail file (rmail-expunge).

There are two Rmail commands for deleting messages. Both delete the current message and select another. d (rmail-delete-forward) moves to the following message, skipping messages already deleted, while C-d (rmail-delete-backward) moves to the previous nondeleted message. If there is no nondeleted message to move to in the specified direction, the message that was just deleted remains current. A numeric prefix argument serves as a repeat count, to allow deletion of several messages in a single command. A negative argument reverses the meaning of d and C-d.

Whenever Rmail deletes a message, it runs the hook rmail-delete-message-hook. When the hook functions are invoked, the message has been marked deleted, but it is still the current message in the Rmail buffer.

To make all the deleted messages finally vanish from the Rmail file, type x (rmail-expunge). Until you do this, you can still undelete the deleted messages. The undeletion command, u (rmail-undelete-previous-message), is designed to cancel the effect of a d command in most cases. It undeletes the current message if the current message is deleted. Otherwise it moves backward to previous messages until a deleted message is found, and undeletes that message. A numeric prefix argument serves as a repeat count, to allow undeletion of several messages in a single command.

You can usually undo a d with a u because the u moves back to and undeletes the message that the d deleted. But this does not work when the d skips a few already-deleted messages that follow the message being deleted; then the u command undeletes the last of the messages that were skipped. There is no clean way to avoid this problem. However, by repeating the u command, you can eventually get back to the message that you intend to undelete. You can also select a particular deleted message with the M-p command, then type u to undelete it.

A deleted message has the ‘deleted’ attribute, and as a result ‘deleted’ appears in the mode line when the current message is deleted. In fact, deleting or undeleting a message is nothing more than adding or removing this attribute. See Rmail Attributes.


34.5 Rmail Files and Inboxes

When you receive mail locally, the operating system places incoming mail for you in a file that we call your inbox. When you start up Rmail, it runs a C program called movemail to copy the new messages from your inbox into your primary Rmail file, which also contains other messages saved from previous Rmail sessions. It is in this file that you actually read the mail with Rmail. This operation is called getting new mail. You can get new mail at any time in Rmail by typing g.

The variable rmail-primary-inbox-list contains a list of the files that are inboxes for your primary Rmail file. If you don’t set this variable explicitly, Rmail uses the MAIL environment variable, or, as a last resort, a default inbox based on rmail-spool-directory. The default inbox file depends on your operating system; often it is /var/mail/username, /var/spool/mail/username, or /usr/spool/mail/username.

You can specify the inbox file(s) for any Rmail file for the current session with the command set-rmail-inbox-list; see Multiple Rmail Files.

There are two reasons for having separate Rmail files and inboxes.

  1. The inbox file format varies between operating systems and according to the other mail software in use. Only one part of Rmail needs to know about the alternatives, and it need only understand how to convert all of them to Rmail’s own format.
  2. It is very cumbersome to access an inbox file without danger of losing mail, because it is necessary to interlock with mail delivery. Moreover, different operating systems use different interlocking techniques. The strategy of moving mail out of the inbox once and for all into a separate Rmail file avoids the need for interlocking in all the rest of Rmail, since only Rmail operates on the Rmail file.

Rmail uses the standard ‘mbox’ format, introduced by Unix and GNU systems for inbox files, as its internal format of Rmail files. (In fact, there are a few slightly different mbox formats. The differences are not very important, but you can set the variable rmail-mbox-format to tell Rmail which form your system uses. See that variable’s documentation for more details.)

When getting new mail, Rmail first copies the new mail from the inbox file to the Rmail file; then it saves the Rmail file; then it clears out the inbox file. This way, a system crash may cause duplication of mail between the inbox and the Rmail file, but cannot lose mail. If rmail-preserve-inbox is non-nil, then Rmail does not clear out the inbox file when it gets new mail. You may wish to set this, for example, on a portable computer you use to check your mail via POP while traveling, so that your mail will remain on the server and you can save it later on your main desktop workstation.

In some cases, Rmail copies the new mail from the inbox file indirectly. First it runs the movemail program to move the mail from the inbox to an intermediate file called .newmail-inboxname, in the same directory as the Rmail file. Then Rmail merges the new mail from that file, saves the Rmail file, and only then deletes the intermediate file. If there is a crash at the wrong time, this file continues to exist, and Rmail will use it again the next time it gets new mail from that inbox.

If Rmail is unable to convert the data in .newmail-inboxname into mbox format, it renames the file to RMAILOSE.n (n is an integer chosen to make the name unique) so that Rmail will not have trouble with the data again. You should look at the file, find whatever message confuses Rmail (probably one that includes the control-underscore character, octal code 037), and delete it. Then you can use 1 g to get new mail from the corrected file.


34.6 Multiple Rmail Files

Rmail operates by default on your primary Rmail file, which is named ~/RMAIL and receives your incoming mail from your system inbox file. But you can also have other Rmail files and edit them with Rmail. These files can receive mail through their own inboxes, or you can move messages into them with explicit Rmail commands (see Copying Messages Out to Files).

i file RET

Read file into Emacs and run Rmail on it (rmail-input).

g

Merge new mail from current Rmail file’s inboxes (rmail-get-new-mail).

C-u g file RET

Merge new mail from inbox file file.

To run Rmail on a file other than your primary Rmail file, you can use the i (rmail-input) command in Rmail. This visits the file in Rmail mode. You can use M-x rmail-input even when not in Rmail, but it is easier to type C-u M-x rmail, which does the same thing.

The file you read with i should normally be a valid mbox file. If it is not, Rmail tries to convert its text to mbox format, and visits the converted text in the buffer. If you save the buffer, that converts the file.

If you specify a file name that doesn’t exist, i initializes a new buffer for creating a new Rmail file.

You can also select an Rmail file from a menu. In the Classify menu, choose the Input Rmail File item; then choose the Rmail file you want. The variables rmail-secondary-file-directory and rmail-secondary-file-regexp specify which files to offer in the menu: the first variable says which directory to find them in; the second says which files in that directory to offer (all those that match the regular expression). If no files match, you cannot select this menu item. These variables also apply to choosing a file for output (see Copying Messages Out to Files).

The inbox files to use are specified by the variable rmail-inbox-list, which is buffer-local in Rmail mode. As a special exception, if you have specified no inbox files for your primary Rmail file, it uses the MAIL environment variable, or your standard system inbox.

The g command (rmail-get-new-mail) merges mail into the current Rmail file from its inboxes. If the Rmail file has no inboxes, g does nothing. The command M-x rmail also merges new mail into your primary Rmail file.

To merge mail from a file that is not the usual inbox, give the g key a numeric argument, as in C-u g. Then it reads a file name and merges mail from that file. The inbox file is not deleted or changed in any way when g with an argument is used. This is, therefore, a general way of merging one file of messages into another.


34.7 Copying Messages Out to Files

These commands copy messages from an Rmail file into another file.

o file RET

Append a full copy of the current message to the file file (rmail-output).

C-o file RET

Append a copy of the current message, as displayed, to the file file (rmail-output-as-seen).

w file RET

Output just the message body to the file file, taking the default file name from the message ‘Subject’ header.

The commands o and C-o copy the current message into a specified file, adding it at the end. A positive prefix argument serves as a repeat count: that many consecutive messages will be copied to the specified file, starting with the current one and ignoring deleted messages.

The two commands differ mainly in how much to copy: o copies the full message headers, even if they are not all visible, while C-o copies exactly the headers currently displayed and no more. See Display of Messages. In addition, o converts the message to Babyl format (used by Rmail in Emacs version 22 and before) if the file is in Babyl format; C-o cannot output to Babyl files at all.

If the output file is currently visited in an Emacs buffer, the output commands append the message to that buffer. It is up to you to save the buffer eventually in its file.

Sometimes you may receive a message whose body holds the contents of a file. You can save the body to a file (excluding the message header) with the w command (rmail-output-body-to-file). Often these messages contain the intended file name in the ‘Subject’ field, so the w command uses the ‘Subject’ field as the default for the output file name (after replacing some characters that cannot be portably used in file names). However, the file name is read using the minibuffer, so you can specify a different name if you wish.

You can also output a message to an Rmail file chosen with a menu. In the Classify menu, choose the Output Rmail File menu item; then choose the Rmail file you want. This outputs the current message to that file, like the o command. The variables rmail-secondary-file-directory and rmail-secondary-file-regexp specify which files to offer in the menu: the first variable says which directory to find them in; the second says which files in that directory to offer (all those that match the regular expression). If no files match, you cannot select this menu item.

Copying a message with o or C-o gives the original copy of the message the ‘filed’ attribute, so that ‘filed’ appears in the mode line when such a message is current.

If you like to keep just a single copy of every mail message, set the variable rmail-delete-after-output to t; then the o, C-o and w commands delete the original message after copying it. (You can undelete it afterward if you wish, see Deleting Messages.)

By default, o will leave the deleted status of a message it outputs as it was on the original message; thus, a message deleted before it was output will appear as deleted in the output file. Setting the variable rmail-output-reset-deleted-flag to a non-nil value countermands that: the copy of the message will have its deleted status reset, so the message will appear as undeleted in the output file. In addition, when this variable is non-nil, specifying a positive argument to o will not ignore deleted messages when looking for consecutive messages to output.

The variable rmail-output-file-alist lets you specify intelligent defaults for the output file, based on the contents of the current message. The value should be a list whose elements have this form:

(regexp . name-exp)

If there’s a match for regexp in the current message, then the default file name for output is name-exp. If multiple elements match the message, the first matching element decides the default file name. The subexpression name-exp may be a string constant giving the file name to use, or more generally it may be any Lisp expression that yields a file name as a string. rmail-output-file-alist applies to both o and C-o.

Rmail can automatically save messages from your primary Rmail file (the one that rmail-file-name specifies) to other files, based on the value of the variable rmail-automatic-folder-directives. This variable is a list of elements (‘directives’) that say which messages to save where. Each directive is a list consisting of an output file, followed by one or more pairs of a header name and a regular expression. If a message has a header matching the specified regular expression, that message is saved to the given file. If the directive has more than one header entry, all must match. Rmail checks directives when it shows a message from the file rmail-file-name, and applies the first that matches (if any). If the output file is nil, the message is deleted, not saved. For example, you can use this feature to save messages from a particular address, or with a particular subject, to a dedicated file.


34.8 Labels

Each message can have various labels assigned to it as a means of classification. Each label has a name; different names are different labels. Any given label is either present or absent on a particular message. A few label names have standard meanings and are given to messages automatically by Rmail when appropriate; these special labels are called attributes. (See Rmail Attributes.) All other labels are assigned only by users.

a label RET

Assign the label label to the current message (rmail-add-label).

k label RET

Remove the label label from the current message (rmail-kill-label).

C-M-n labels RET

Move to the next message that has one of the labels labels (rmail-next-labeled-message).

C-M-p labels RET

Move to the previous message that has one of the labels labels (rmail-previous-labeled-message).

l labels RET
C-M-l labels RET

Make a summary of all messages containing any of the labels labels (rmail-summary-by-labels).

The a (rmail-add-label) and k (rmail-kill-label) commands allow you to assign or remove any label on the current message. If the label argument is empty, it means to assign or remove the label most recently assigned or removed.

Once you have given messages labels to classify them as you wish, there are three ways to use the labels: in moving, in summaries, and in sorting.

C-M-n labels RET (rmail-next-labeled-message) moves to the next message that has one of the labels labels. The argument labels specifies one or more label names, separated by commas. C-M-p (rmail-previous-labeled-message) is similar, but moves backwards to previous messages. A numeric argument to either command serves as a repeat count.

The command C-M-l labels RET (rmail-summary-by-labels) displays a summary containing only the messages that have at least one of a specified set of labels. The argument labels is one or more label names, separated by commas. See Summaries, for information on summaries.

If the labels argument to C-M-n, C-M-p or C-M-l is empty, it means to use the last set of labels specified for any of these commands.

See Sorting the Rmail File, for information on sorting messages with labels.


34.9 Rmail Attributes

Some labels such as ‘deleted’ and ‘filed’ have built-in meanings, and Rmail assigns them to messages automatically at appropriate times; these labels are called attributes. Here is a list of Rmail attributes:

unseen

Means the message has never been current. Assigned to messages when they come from an inbox file, and removed when a message is made current. When you start Rmail, it initially shows the first message that has this attribute.

deleted

Means the message is deleted. Assigned by deletion commands and removed by undeletion commands (see Deleting Messages).

filed

Means the message has been copied to some other file. Assigned by the o and C-o file output commands (see Copying Messages Out to Files).

answered

Means you have mailed an answer to the message. Assigned by the r command (rmail-reply). See Sending Replies.

forwarded

Means you have forwarded the message. Assigned by the f command (rmail-forward). See Sending Replies.

edited

Means you have edited the text of the message within Rmail. See Editing Within a Message.

resent

Means you have resent the message. Assigned by the command M-x rmail-resend. See Sending Replies.

retried

Means you have retried a failed outgoing message. Assigned by the command M-x rmail-retry-failure. See Sending Replies.

All other labels are assigned or removed only by users, and have no standard meaning.


34.10 Sending Replies

Rmail has several commands to send outgoing mail. See Sending Mail, for information on using Message mode, including certain features meant to work with Rmail. What this section documents are the special commands of Rmail for entering the mail buffer used to compose the outgoing message. Note that the usual keys for sending mail—C-x m, C-x 4 m, and C-x 5 m—also work normally in Rmail mode.

m

Send a message (rmail-mail).

c

Continue editing the already started outgoing message (rmail-continue).

r

Send a reply to the current Rmail message (rmail-reply).

f

Forward the current message to other users (rmail-forward).

C-u f

Resend the current message to other users (rmail-resend).

M-m

Try sending a bounced message a second time (rmail-retry-failure).

The most common reason to send a message while in Rmail is to reply to the message you are reading. To do this, type r (rmail-reply). This displays a mail composition buffer in another window, much like C-x 4 m, but preinitializes the ‘Subject’, ‘To’, ‘CC’, ‘In-Reply-To’ and ‘References’ header fields based on the message you are replying to. The ‘To’ field starts out as the address of the person who sent the message you received, and the ‘CC’ field starts out with all the other recipients of that message.

You can exclude certain recipients from being included automatically in replies, using the variable mail-dont-reply-to-names. Its value should be a regular expression; any recipients that match are excluded from the ‘CC’ field. They are also excluded from the ‘To’ field, unless this would leave the field empty. If this variable is nil, then the first time you compose a reply it is initialized to a default value that matches your own address.

To reply only to the sender of the original message, enter the reply command with a numeric argument: C-u r or 1 r. This omits the ‘CC’ field completely for a particular reply.

Once the mail composition buffer has been initialized, editing and sending the mail goes as usual (see Sending Mail). You can edit the presupplied header fields if they are not what you want. You can also use commands such as C-c C-y, which yanks in the message that you are replying to (see Mail Commands). You can also switch to the Rmail buffer, select a different message there, switch back, and yank the new current message.

Sometimes a message does not reach its destination. Mailers usually send the failed message back to you, enclosed in a failure message. The Rmail command M-m (rmail-retry-failure) prepares to send the same message a second time: it sets up a mail composition buffer with the same text and header fields as before. If you type C-c C-c right away, you send the message again exactly the same as the first time. Alternatively, you can edit the text or headers and then send it. The variable rmail-retry-ignored-headers, in the same format as rmail-ignored-headers (see Display of Messages), controls which headers are stripped from the failed message when retrying it.

Another frequent reason to send mail in Rmail is to forward the current message to other users. f (rmail-forward) makes this easy by preinitializing the mail composition buffer with the current message as the text, and a subject of the form [from: subject], where from and subject are the sender and subject of the original message. All you have to do is fill in the recipients and send. When you forward a message, recipients get a message which is from you, and which has the original message in its contents.

Rmail offers two formats for forwarded messages. The default is to use the MIME format (see Display of Messages). This includes the original message as a separate part. You can use a simpler format if you prefer, by setting the variable rmail-enable-mime-composing to nil. In this case, Rmail just includes the original message enclosed between two delimiter lines. It also modifies every line that starts with a dash, by inserting ‘-  at the start of the line. When you receive a forwarded message in this format, if it contains something besides ordinary text—for example, program source code—you might find it useful to undo that transformation. You can do this by selecting the forwarded message and typing M-x unforward-rmail-message. This command extracts the original forwarded message, deleting the inserted ‘-  strings, and inserts it into the Rmail file as a separate message immediately following the current one.

Resending is an alternative similar to forwarding; the difference is that resending sends a message that is from the original sender, just as it reached you—with a few added header fields (‘Resent-From’ and ‘Resent-To’) to indicate that it came via you. To resend a message in Rmail, use C-u f. (f runs rmail-forward, which invokes rmail-resend if you provide a numeric argument.)

Use the m (rmail-mail) command to start editing an outgoing message that is not a reply. It leaves the header fields empty. Its only difference from C-x 4 m is that it makes the Rmail buffer accessible for C-c C-y, just as r does.

The c (rmail-continue) command resumes editing the mail composition buffer, to finish editing an outgoing message you were already composing, or to alter a message you have sent.

If you set the variable rmail-mail-new-frame to a non-nil value, then all the Rmail commands to start sending a message create a new frame to edit it in. This frame is deleted when you send the message.

All the Rmail commands to send a message use the mail-composition method that you have chosen (see Mail-Composition Methods).


34.11 Summaries

A summary is a buffer containing one line per message to give you an overview of the mail in an Rmail file. Each line shows the message number and date, the sender, the line count, the labels, and the subject. Moving point in the summary buffer selects messages as you move to their summary lines. Almost all Rmail commands are valid in the summary buffer also; when used there, they apply to the message described by the current line of the summary.

A summary buffer applies to a single Rmail file only; if you are editing multiple Rmail files, each one can have its own summary buffer. The summary buffer name is made by appending ‘-summary’ to the Rmail buffer’s name. Normally only one summary buffer is displayed at a time.


34.11.1 Making Summaries

Here are the commands to create a summary for the current Rmail buffer. Once the Rmail buffer has a summary, changes in the Rmail buffer (such as deleting or expunging messages, and getting new mail) automatically update the summary.

h
C-M-h

Summarize all messages (rmail-summary).

l labels RET
C-M-l labels RET

Summarize messages that have one or more of the specified labels (rmail-summary-by-labels).

C-M-r rcpts RET

Summarize messages that match the specified recipients (rmail-summary-by-recipients).

C-M-t topic RET

Summarize messages that have a match for the specified regexp topic in their subjects (rmail-summary-by-topic).

C-M-s regexp RET

Summarize messages whose headers match the specified regular expression regexp (rmail-summary-by-regexp).

C-M-f senders RET

Summarize messages that match the specified senders. (rmail-summary-by-senders).

The h or C-M-h (rmail-summary) command fills the summary buffer for the current Rmail buffer with a summary of all the messages in the buffer. It then displays and selects the summary buffer in another window.

C-M-l labels RET (rmail-summary-by-labels) makes a partial summary mentioning only the messages that have one or more of the labels labels. labels should contain label names separated by commas.

C-M-r rcpts RET (rmail-summary-by-recipients) makes a partial summary mentioning only the messages that have one or more recipients matching the regular expression rcpts. This is matched against the ‘To’, ‘From’, and ‘CC’ headers (supply a prefix argument to exclude the ‘CC’ header).

C-M-t topic RET (rmail-summary-by-topic) makes a partial summary mentioning only the messages whose subjects have a match for the regular expression topic. With a prefix argument, the match is against the whole message, not just the subject.

C-M-s regexp RET (rmail-summary-by-regexp) makes a partial summary that mentions only the messages whose headers (including the date and the subject lines) match the regular expression regexp.

C-M-f senders RET (rmail-summary-by-senders) makes a partial summary that mentions only the messages whose ‘From’ fields match the regular expression senders.

Note that there is only one summary buffer for any Rmail buffer; making any kind of summary discards any previous summary.

The variable rmail-summary-window-size says how many lines to use for the summary window. The variable rmail-summary-line-count-flag controls whether the summary line for a message should include the line count of the message. Setting this option to nil might speed up the generation of summaries.


34.11.2 Editing in Summaries

You can use the Rmail summary buffer to do almost anything you can do in the Rmail buffer itself. In fact, once you have a summary buffer, there’s no need to switch back to the Rmail buffer.

You can select and display various messages in the Rmail buffer, from the summary buffer, just by moving point in the summary buffer to different lines. It doesn’t matter what Emacs command you use to move point; whichever line point is on at the end of the command, that message is selected in the Rmail buffer.

Almost all Rmail commands work in the summary buffer as well as in the Rmail buffer. Thus, d in the summary buffer deletes the current message, u undeletes, and x expunges. (However, in the summary buffer, if there are no more undeleted messages in the relevant direction, the delete commands go to the first or last message, rather than staying on the current message.) o and C-o output the current message to a FILE; r starts a reply to it; etc. You can scroll the current message while remaining in the summary buffer using SPC and DEL. However, in the summary buffer scrolling past the end or the beginning of a message with SPC or DEL goes, respectively, to the next or previous undeleted message. Customize the rmail-summary-scroll-between-messages option to nil to disable scrolling to next/previous messages.

M-u (rmail-summary-undelete-many) undeletes all deleted messages in the summary. A prefix argument means to undelete that many of the previous deleted messages.

The Rmail commands to move between messages also work in the summary buffer, but with a twist: they move through the set of messages included in the summary. They also ensure the Rmail buffer appears on the screen (unlike cursor motion commands, which update the contents of the Rmail buffer but don’t display it in a window unless it already appears). Here is a list of these commands:

n

Move to next line, skipping lines saying “deleted”, and select its message (rmail-summary-next-msg).

p

Move to previous line, skipping lines saying “deleted”, and select its message (rmail-summary-previous-msg).

M-n

Move to next line and select its message (rmail-summary-next-all).

M-p

Move to previous line and select its message (rmail-summary-previous-all).

>

Move to the last line, and select its message (rmail-summary-last-message).

<

Move to the first line, and select its message (rmail-summary-first-message).

j
RET

Select the message on the current line (ensuring that the Rmail buffer appears on the screen; rmail-summary-goto-msg). With argument n, select message number n and move to its line in the summary buffer; this signals an error if the message is not listed in the summary buffer.

M-s pattern RET

Search through messages for pattern starting with the current message; select the message found, and move point in the summary buffer to that message’s line (rmail-summary-search). A prefix argument acts as a repeat count; a negative argument means search backward (equivalent to rmail-summary-search-backward.)

C-M-n labels RET

Move to the next message with at least one of the specified labels (rmail-summary-next-labeled-message). labels is a comma-separated list of labels. A prefix argument acts as a repeat count.

C-M-p labels RET

Move to the previous message with at least one of the specified labels (rmail-summary-previous-labeled-message).

C-c C-n RET

Move to the next message with the same subject as the current message (rmail-summary-next-same-subject). A prefix argument acts as a repeat count.

C-c C-p RET

Move to the previous message with the same subject as the current message (rmail-summary-previous-same-subject).

Deletion, undeletion, and getting new mail, and even selection of a different message all update the summary buffer when you do them in the Rmail buffer. If the variable rmail-redisplay-summary is non-nil, these actions also bring the summary buffer back onto the screen.

When you are finished using the summary, type Q (rmail-summary-wipe) to delete the summary buffer’s window. You can also exit Rmail while in the summary: q (rmail-summary-quit) deletes the summary window, then exits from Rmail by saving the Rmail file and switching to another buffer. Alternatively, b (rmail-summary-bury) simply buries the Rmail summary and buffer.


34.12 Sorting the Rmail File

C-c C-s C-d
M-x rmail-sort-by-date

Sort messages of current Rmail buffer by date.

C-c C-s C-s
M-x rmail-sort-by-subject

Sort messages of current Rmail buffer by subject.

C-c C-s C-a
M-x rmail-sort-by-author

Sort messages of current Rmail buffer by author’s name.

C-c C-s C-r
M-x rmail-sort-by-recipient

Sort messages of current Rmail buffer by recipient’s name.

C-c C-s C-c
M-x rmail-sort-by-correspondent

Sort messages of current Rmail buffer by the name of the other correspondent.

C-c C-s C-l
M-x rmail-sort-by-lines

Sort messages of current Rmail buffer by number of lines.

C-c C-s C-k RET labels RET
M-x rmail-sort-by-labels RET labels RET

Sort messages of current Rmail buffer by labels. The argument labels should be a comma-separated list of labels. The order of these labels specifies the order of messages; messages with the first label come first, messages with the second label come second, and so on. Messages that have none of these labels come last.

The Rmail sort commands perform a stable sort: if there is no reason to prefer either one of two messages, their order remains unchanged. You can use this to sort by more than one criterion. For example, if you use rmail-sort-by-date and then rmail-sort-by-author, messages from the same author appear in order by date.

With a prefix argument, all these commands reverse the order of comparison. This means they sort messages from newest to oldest, from biggest to smallest, or in reverse alphabetical order.

The same keys in the summary buffer run similar functions; for example, C-c C-s C-l runs rmail-summary-sort-by-lines. These commands always sort the whole Rmail buffer, even if the summary is only showing a subset of messages.

Note that you cannot undo a sort, so you may wish to save the Rmail buffer before sorting it.


34.13 Display of Messages

This section describes how Rmail displays mail headers, MIME sections and attachments, URLs, and encrypted messages.

t

Toggle display of complete header (rmail-toggle-header).

Before displaying each message for the first time, Rmail reformats its header, hiding uninteresting header fields to reduce clutter. The t (rmail-toggle-header) command toggles this, switching between showing the reformatted header fields and showing the complete, original header. With a positive prefix argument, the command shows the reformatted header; with a zero or negative prefix argument, it shows the full header. Selecting the message again also reformats it if necessary.

The variable rmail-ignored-headers holds a regular expression specifying the header fields to hide; any matching header line will be hidden. The variable rmail-nonignored-headers overrides this: any header field matching that regular expression is shown even if it matches rmail-ignored-headers too. The variable rmail-displayed-headers is an alternative to these two variables; if non-nil, this should be a regular expression specifying which headers to display (the default is nil).

Rmail highlights certain header fields that are especially interesting—by default, the ‘From’ and ‘Subject’ fields. This highlighting uses the rmail-highlight face. The variable rmail-highlighted-headers holds a regular expression specifying the header fields to highlight; if it matches the beginning of a header field, that whole field is highlighted. To disable this feature, set rmail-highlighted-headers to nil.

If a message is in MIME (Multipurpose Internet Mail Extensions) format and contains multiple parts (MIME entities), Rmail displays each part with a tagline. The tagline summarizes the part’s index, size, and content type. Depending on the content type, it may also contain one or more buttons; these perform actions such as saving the part into a file.

RET

Hide or show the MIME part at point (rmail-mime-toggle-hidden).

TAB

Move point to the next MIME tagline button. (rmail-mime-next-item).

S-TAB

Move point to the previous MIME part (rmail-mime-previous-item).

v

Toggle between MIME display and raw message (rmail-mime).

Each plain-text MIME part is initially displayed immediately after its tagline, as part of the Rmail buffer (unless the message has an HTML part, see below), while MIME parts of other types are represented only by their taglines, with their actual contents hidden. In either case, you can toggle a MIME part between its displayed and hidden states by typing RET anywhere in the part—or anywhere in its tagline (except for buttons for other actions, if there are any). Type RET (or click with the mouse) to activate a tagline button, and TAB to cycle point between tagline buttons.

The v (rmail-mime) command toggles between the default MIME display described above, and a raw display showing the undecoded MIME data. With a prefix argument, this command toggles the display of only an entity at point.

If the message has an HTML MIME part, Rmail displays it in preference to the plain-text part, if Emacs can render HTML20. To prevent that, and have the plain-text part displayed instead, customize the variable rmail-mime-prefer-html to a nil value.

To prevent Rmail from handling MIME decoded messages, change the variable rmail-enable-mime to nil. When this is the case, the v (rmail-mime) command instead creates a temporary buffer to display the current MIME message.

If the current message is an encrypted one, use the command C-c C-d (rmail-epa-decrypt) to decrypt it, using the EasyPG library (see EasyPG in EasyPG Assistant User’s Manual).

You can highlight and activate URLs in the Rmail buffer using Goto Address mode:

(add-hook 'rmail-show-message-hook 'goto-address-mode)

Then you can browse these URLs by clicking on them with mouse-2 (or mouse-1 quickly) or by moving to one and typing C-c RET. See Activating URLs.


34.14 Rmail and Coding Systems

Rmail automatically decodes messages which contain non-ASCII characters, just as Emacs does with files you visit and with subprocess output. Rmail uses the standard ‘charset=charset’ header in the message, if any, to determine how the message was encoded by the sender. It maps charset into the corresponding Emacs coding system (see Coding Systems), and uses that coding system to decode message text. If the message header doesn’t have the ‘charset’ specification, or if charset is not recognized, Rmail chooses the coding system with the usual Emacs heuristics and defaults (see Recognizing Coding Systems).

Occasionally, a message is decoded incorrectly, either because Emacs guessed the wrong coding system in the absence of the ‘charset’ specification, or because the specification was inaccurate. For example, a misconfigured mailer could send a message with a ‘charset=iso-8859-1’ header when the message is actually encoded in koi8-r. When you see the message text garbled, or some of its characters displayed as hex codes or empty boxes, this may have happened.

You can correct the problem by decoding the message again using the right coding system, if you can figure out or guess which one is right. To do this, invoke the M-x rmail-redecode-body command. It reads the name of a coding system, and then redecodes the message using the coding system you specified. If you specified the right coding system, the result should be readable.

When you get new mail in Rmail, each message is translated automatically from the coding system it is written in, as if it were a separate file. This uses the priority list of coding systems that you have specified. If a MIME message specifies a character set, Rmail obeys that specification. For reading and saving Rmail files themselves, Emacs uses the coding system specified by the variable rmail-file-coding-system. The default value is nil, which means that Rmail files are not translated (they are read and written in the Emacs internal character code).


34.15 Editing Within a Message

Most of the usual Emacs key bindings are available in Rmail mode, though a few, such as C-M-n and C-M-h, are redefined by Rmail for other purposes. However, the Rmail buffer is normally read only, and most of the letters are redefined as Rmail commands. If you want to edit the text of a message, you must use the Rmail command e.

e

Edit the current message as ordinary text.

The e command (rmail-edit-current-message) switches from Rmail mode into Rmail Edit mode, another major mode which is nearly the same as Text mode. The mode line indicates this change.

In Rmail Edit mode, letters insert themselves as usual and the Rmail commands are not available. You can edit the message body and header fields. When you are finished editing the message, type C-c C-c (rmail-cease-edit) to switch back to Rmail mode. Alternatively, you can return to Rmail mode but cancel any editing that you have done, by typing C-c C-] (rmail-abort-edit).

Entering Rmail Edit mode runs the hook text-mode-hook; then it runs the hook rmail-edit-mode-hook (see Hooks). Returning to ordinary Rmail mode adds the attribute ‘edited’ to the message, if you have made any changes in it (see Rmail Attributes).


34.16 Digest Messages

A digest message is a message which exists to contain and carry several other messages. Digests are used on some mailing lists; all the messages that arrive for the list during a period of time such as one day are put inside a single digest which is then sent to the subscribers. Transmitting the single digest uses less computer time than transmitting the individual messages even though the total size is the same, because of the per-message overhead in network mail transmission.

When you receive a digest message, the most convenient way to read it is to undigestify it: to turn it back into many individual messages. Then you can read and delete the individual messages as it suits you. To do this, select the digest message and type the command M-x undigestify-rmail-message. This extracts the submessages as separate Rmail messages, and inserts them following the digest. The digest message itself is flagged as deleted.


34.17 Reading Rot13 Messages

Mailing list messages that might offend or annoy some readers are sometimes encoded in a simple code called rot13—so named because it rotates the alphabet by 13 letters. This code is not for secrecy, as it provides none; rather, it enables those who wish to avoid seeing the real text of the message. For example, a review of a film might use rot13 to hide important plot points.

To view a buffer that uses the rot13 code, use the command M-x rot13-other-window. This displays the current buffer in another window which applies the code when displaying the text.

If you are only interested in a region, the command M-x rot13-region might be preferable. This will encrypt/decrypt the active region in-place. If the buffer is read-only, it will attempt to display the plain text in the echo area. If the text is too long for the echo area, the command will pop up a temporary buffer with the encrypted/decrypted text.


34.18 movemail program

Rmail uses the movemail program to move mail from your inbox to your Rmail file (see Rmail Files and Inboxes). When loaded for the first time, Rmail attempts to locate the movemail program and determine its version. There are two versions of the movemail program: the GNU Mailutils version (see movemail in GNU mailutils), and an Emacs-specific version that is built and installed unless Emacs was configured --with-mailutils in effect. The two movemail versions support the same command line syntax and the same basic subset of options. However, the Mailutils version offers additional features and is more secure.

The Emacs version of movemail can retrieve mail from the usual Unix mailbox formats. Warning: Although it can also use the POP3 protocol, this is not recommended because it does not support POP3 via encrypted TLS channels.

The Mailutils version is able to handle a wide set of mailbox formats, such as plain Unix mailboxes, maildir and MH mailboxes, etc. It is able to access remote mailboxes using the POP3 or IMAP4 protocol, and can retrieve mail from them using a TLS encrypted channel. It also accepts mailbox arguments in URL form. The detailed description of mailbox URLs can be found in URL in Mailbox URL Formats. In short, a URL is:

proto://[user[:password]@]host-or-file-name[:port]

where square brackets denote optional elements.

proto

Specifies the mailbox protocol, or format to use. The exact semantics of the rest of URL elements depends on the actual value of proto (see below).

user

User name to access the remote mailbox.

password

User password to access the remote mailbox.

host-or-file-name

Hostname of the remote server for remote mailboxes or file name of a local mailbox.

port

Optional port number, if not the default for that protocol.

proto can be one of:

mbox

Usual Unix mailbox format. In this case, user, pass and port are not used, and host-or-file-name denotes the file name of the mailbox file, e.g., mbox:///var/spool/mail/smith.

mh

A local mailbox in the MH format. user, pass and port are not used. host-or-file-name denotes the name of MH folder, e.g., mh:///Mail/inbox.

maildir

A local mailbox in the maildir format. user, pass and port are not used, and host-or-file-name denotes the name of maildir mailbox, e.g., maildir:///mail/inbox.

file

Any local file in mailbox format. Its actual format is detected automatically by movemail.

pop
pops

A remote mailbox to be accessed via POP3 protocol. user specifies the remote user name to use, pass may be used to specify the user password, host-or-file-name is the name or IP address of the remote mail server to connect to, and port is the port number; e.g., pop://smith:guessme@remote.server.net:995. If the server supports it, movemail tries to use an encrypted connection—use the ‘pops’ form to require one.

imap
imaps

A remote mailbox to be accessed via IMAP4 protocol. user specifies the remote user name to use, pass may be used to specify the user password, host-or-file-name is the name or IP address of the remote mail server to connect to, and port is the port number; e.g., imap://smith:guessme@remote.server.net:993. If the server supports it, movemail tries to use an encrypted connection—use the ‘imaps’ form to require one.

Alternatively, you can specify the file name of the mailbox to use. This is equivalent to specifying the ‘file’ protocol:

/var/spool/mail/user ≡ file:///var/spool/mail/user

The variable rmail-movemail-program controls which version of movemail to use. If that is a string, it specifies the absolute file name of the movemail executable. If it is nil, Rmail searches for movemail in the directories listed in rmail-movemail-search-path, then in exec-path (see Running Shell Commands from Emacs), then in exec-directory.


34.19 Retrieving Mail from Remote Mailboxes

Some sites use a method called POP3 for accessing users’ inbox data instead of storing the data in inbox files. The Mailutils movemail by default supports POP3 with TLS encryption. Warning: Although the Emacs movemail supports POP3, its use for this is not recommended since it does not support encrypted connections—the Mailutils version does. Both versions of movemail work only with POP3, not with older versions of POP.

You can specify a POP3 inbox by using a POP3 URL (see movemail program). A POP3 URL is of the form ‘pop://username@hostname:port’, where hostname and port are the host name (or IP address) and port number of the remote mail server and username is the user name on that server. Additionally, you may specify the password in the mailbox URL: ‘pop://username:password@hostname:port’. In this case, password takes preference over the one set by rmail-remote-password (see below). This is especially useful if you have several remote mailboxes with different passwords. If using Mailutils movemail, you may wish to use ‘pops’ in place of ‘pop’.

For backward compatibility, Rmail also supports an alternative way of specifying remote POP3 mailboxes. Specifying an inbox name in the form ‘po:username:hostname:port’ is equivalent to ‘pop://username@hostname:port’. If you omit the :hostname part, the MAILHOST environment variable specifies the machine on which to look for the POP3 server.

Another method for accessing remote mailboxes is IMAP. This method is supported only by the Mailutils movemail. To specify an IMAP mailbox in the inbox list, use the following mailbox URL: ‘imap://username[:password]@hostname:port’. The password part is optional, as described above. You may wish to use ‘imaps’ in place of ‘imap’.

Accessing a remote mailbox may require a password. Rmail uses the following algorithm to retrieve it:

  1. If a password is present in the mailbox URL (see above), it is used.
  2. If the variable rmail-remote-password-required is nil, Rmail assumes no password is required.
  3. If the variable rmail-remote-password is non-nil, its value is used.
  4. Otherwise, Rmail will ask you for the password to use.

On some mail servers the usernames include domain information, which can mean they contain the ‘@’ character. The inbox specifier string uses ‘@’ to signal the start of the mailserver name. This creates confusion for movemail. If your username contains ‘@’ and you’re using Mailutils movemail then you can fix this: Replace @ in the user name with its URL encoding ‘%40’.

If you need to pass additional command-line flags to movemail, set the variable rmail-movemail-flags a list of the flags you wish to use. Do not use this variable to pass the ‘-p’ flag to preserve your inbox contents; use rmail-preserve-inbox instead.

The movemail program installed at your site may support Kerberos authentication. If it is supported, it is used by default whenever you attempt to retrieve POP3 mail when rmail-remote-password and rmail-remote-password-required are unset.

Some POP3 servers store messages in reverse order. If your server does this, and you would rather read your mail in the order in which it was received, you can tell movemail to reverse the order of downloaded messages by adding the ‘-r’ flag to rmail-movemail-flags.

Mailutils movemail supports TLS encryption. If you wish to use it, add the ‘--tls’ flag to rmail-movemail-flags.


34.20 Retrieving Mail from Local Mailboxes in Various Formats

If your incoming mail is stored on a local machine in a format other than Unix mailbox, you will need the Mailutils movemail to retrieve it. See movemail program, for the detailed description of movemail versions. For example, to access mail from an inbox in maildir format located in /var/spool/mail/in, you would include the following in the Rmail inbox list:

maildir:///var/spool/mail/in

35 Email and Usenet News with Gnus

Gnus is an Emacs package primarily designed for reading and posting Usenet news. It can also be used to read and respond to messages from a number of other sources—email, remote directories, digests, and so on. Here we introduce Gnus and describe several basic features. For full details, see Gnus in The Gnus Manual.


35.1 Gnus Buffers

Gnus uses several buffers to display information and to receive commands. The three most commonly-used Gnus buffers are the group buffer, the summary buffer and the article buffer.

The group buffer contains a list of article sources (e.g., newsgroups and email inboxes), which are collectively referred to as groups. This is the first buffer Gnus displays when it starts up. It normally displays only the groups to which you subscribe and that contain unread articles. From this buffer, you can select a group to read.

The summary buffer lists the articles in a single group, showing one article per line. By default, it displays each article’s author, subject, and line number, but this is customizable; See Summary Buffer Format in The Gnus Manual. The summary buffer is created when you select a group in the group buffer, and is killed when you exit the group.

From the summary buffer, you can choose an article to view. The article is displayed in the article buffer. In normal Gnus usage, you view this buffer but do not select it—all useful Gnus commands can be invoked from the summary buffer. But you can select the article buffer, and execute Gnus commands from it, if you wish.


35.2 When Gnus Starts Up

If your system has been set up for reading Usenet news, getting started with Gnus is easy—just type M-x gnus.

On starting up, Gnus reads your news initialization file: a file named .newsrc in your home directory which lists your Usenet newsgroups and subscriptions (this file is not unique to Gnus; it is used by many other newsreader programs). It then tries to contact the system’s default news server, which is typically specified by the NNTPSERVER environment variable.

If your system does not have a default news server, or if you wish to use Gnus for reading email, then before invoking M-x gnus you need to tell Gnus where to get news and/or mail. To do this, customize the variables gnus-select-method and/or gnus-secondary-select-methods. See Finding the News in The Gnus Manual.

Once Gnus has started up, it displays the group buffer. By default, the group buffer shows only a small number of subscribed groups. Groups with other statuses—unsubscribed, killed, or zombie—are hidden. The first time you start Gnus, any group to which you are not subscribed is made into a killed group; any group that subsequently appears on the news server becomes a zombie group.

To proceed, you must select a group in the group buffer to open the summary buffer for that group; then, select an article in the summary buffer to view its article buffer in a separate window. The following sections explain how to use the group and summary buffers to do this.

To quit Gnus, type q in the group buffer. This automatically records your group statuses in the files .newsrc and .newsrc.eld, so that they take effect in subsequent Gnus sessions.


35.3 Using the Gnus Group Buffer

The following commands are available in the Gnus group buffer:

SPC

Switch to the summary buffer for the group on the current line (gnus-group-read-group).

l
A s

In the group buffer, list only the groups to which you subscribe and which contain unread articles (gnus-group-list-groups; this is the default listing).

L
A u

List all subscribed and unsubscribed groups, but not killed or zombie groups (gnus-group-list-all-groups).

A k

List killed groups (gnus-group-list-killed).

A z

List zombie groups (gnus-group-list-zombies).

u

Toggle the subscription status of the group (gnus-group-toggle-subscription-at-point) on the current line. Invoking this on a killed or zombie group turns it into an unsubscribed group.

C-k

Kill the group on the current line (gnus-group-kill-group). Killed groups are not recorded in the .newsrc file, and they are not shown in the l or L listings.

DEL

Move point to the previous group containing unread articles (gnus-group-prev-unread-group).

n

Move point to the next unread group (gnus-group-next-unread-group).

p

Move point to the previous unread group (gnus-group-prev-unread-group).

q

Update your Gnus settings, and quit Gnus (gnus-group-exit).


35.4 Using the Gnus Summary Buffer

The following commands are available in the Gnus summary buffer:

SPC

If there is no article selected, select the article on the current line and display its article buffer. Otherwise, try scrolling the selected article buffer in its window; on reaching the end of the buffer, select the next unread article (gnus-summary-next-page).

Thus, you can read through all articles by repeatedly typing SPC.

DEL

Scroll the text of the article backwards (gnus-summary-prev-page).

n

Select the next unread article (gnus-summary-next-unread-article).

p

Select the previous unread article (gnus-summary-prev-unread-article).

s

Do an incremental search on the selected article buffer (gnus-summary-isearch-article), as if you switched to the buffer and typed C-s (see Incremental Search).

M-s M-s regexp RET

Search forward for articles containing a match for regexp (gnus-summary-search-article-forward).

M-r regexp RET

Search back for articles containing a match for regexp (gnus-summary-search-article-backward).

q

Exit the summary buffer and return to the group buffer (gnus-summary-exit).


36 Host Security

Emacs runs inside an operating system such as GNU/Linux, and relies on the operating system to check security constraints such as accesses to files. The default settings for Emacs are designed for typical use; they may require some tailoring in environments where security is more of a concern, or less of a concern, than usual. For example, file-local variables can be risky, and you can set the variable enable-local-variables to :safe or (even more conservatively) to nil; conversely, if your files can all be trusted and the default checking for these variables is irritating, you can set enable-local-variables to :all. See Safety of File Variables.

See Security Considerations in The Emacs Lisp Reference Manual, for more information about security considerations when using Emacs as part of a larger application.


37 Network Security

Whenever Emacs establishes any network connection, it passes the established connection to the Network Security Manager (NSM). NSM is responsible for enforcing the network security under your control. Currently, this works by using the Transport Layer Security (TLS) features.

The network-security-level variable determines the security level that NSM enforces. If its value is low, no security checks are performed. This is not recommended, and will basically mean that your network connections can’t be trusted. However, the setting can be useful in limited circumstances, as when testing network issues.

If this variable is medium (which is the default), a number of checks will be performed. If as result NSM determines that the network connection might not be trustworthy, it will make you aware of that, and will ask you what to do about the network connection.

You can decide to register a permanent security exception for an unverified connection, a temporary exception, or refuse the connection entirely.

In addition to the basic certificate correctness checks, several TLS algorithm checks are available. Some encryption technologies that were previously thought to be secure have shown themselves to be fragile, so Emacs (by default) warns you about some of these problems.

The protocol network checks is controlled via the network-security-protocol-checks variable.

It’s an alist where the first element of each association is the name of the check, and the second element is the security level where the check should be used.

An element like (rc4 medium) will result in the function nsm-protocol-check--rc4 being called like thus: (nsm-protocol-check--rc4 host port status settings). The function should return non-nil if the connection should proceed and nil otherwise.

Below is a list of the checks done on the default medium level.

unable to verify a TLS certificate

If the connection is a TLS, SSL or STARTTLS connection, NSM will check whether the certificate used to establish the identity of the server we’re connecting to can be verified.

While an invalid certificate is often the cause for concern (there could be a Man-in-the-Middle hijacking your network connection and stealing your password), there may be valid reasons for going ahead with the connection anyway. For instance, the server may be using a self-signed certificate, or the certificate may have expired. It’s up to you to determine whether it’s acceptable to continue with the connection.

a self-signed certificate has changed

If you’ve previously accepted a self-signed certificate, but it has now changed, that could mean that the server has just changed the certificate, but it might also mean that the network connection has been hijacked.

previously encrypted connection now unencrypted

If the connection is unencrypted, but it was encrypted in previous sessions, this might mean that there is a proxy between you and the server that strips away STARTTLS announcements, leaving the connection unencrypted. This is usually very suspicious.

talking to an unencrypted service when sending a password

When connecting to an IMAP or POP3 server, these should usually be encrypted, because it’s common to send passwords over these connections. Similarly, if you’re sending email via SMTP that requires a password, you usually want that connection to be encrypted. If the connection isn’t encrypted, NSM will warn you.

Diffie-Hellman low prime bits

When doing the public key exchange, the number of prime bits should be high enough to ensure that the channel can’t be eavesdropped on by third parties. If this number is too low, Emacs will warn you. (This is the diffie-hellman-prime-bits check in network-security-protocol-checks).

RC4 stream cipher

The RC4 stream cipher is believed to be of low quality and may allow eavesdropping by third parties. (This is the rc4 check in network-security-protocol-checks).

SHA1 in the host certificate or in intermediate certificates

It is believed that if an intermediate certificate uses the SHA1 hashing algorithm, then third parties can issue certificates pretending to be that issuing instance. These connections are therefore vulnerable to man-in-the-middle attacks. (These are the signature-sha1 and intermediate-sha1 checks in network-security-protocol-checks).

SSL1, SSL2 and SSL3

The protocols older than TLS1.0 are believed to be vulnerable to a variety of attacks, and you may want to avoid using these if what you’re doing requires higher security. (This is the ssl check in network-security-protocol-checks).

If network-security-level is high, the following checks will be made, in addition to the above:

3DES cipher

The 3DES stream cipher provides at most 112 bits of effective security, which is considered to be towards the low end. (This is the 3des check in network-security-protocol-checks).

a validated certificate changes the public key

Servers change their keys occasionally, and that is normally nothing to be concerned about. However, if you are worried that your network connections are being hijacked by agencies who have access to pliable Certificate Authorities which issue new certificates for third-party services, you may want to keep track of these changes.

Finally, if network-security-level is paranoid, you will also be notified the first time NSM sees any new certificate. This will allow you to inspect all the certificates from all the connections that Emacs makes.

The following additional variables can be used to control details of NSM operation:

nsm-settings-file

This is the file where NSM stores details about connections. It defaults to ~/.emacs.d/network-security.data.

nsm-save-host-names

By default, host names will not be saved for non-STARTTLS connections. Instead a host/port hash is used to identify connections. This means that one can’t casually read the settings file to see what servers the user has connected to. If this variable is t, NSM will also save host names in the nsm-settings-file.


38 Document Viewing

DocView mode is a major mode for viewing DVI, PostScript (PS), PDF, OpenDocument, Microsoft Office, EPUB, CBZ, FB2, XPS and OXPS documents. It provides features such as slicing, zooming, and searching inside documents. It works by converting the document to a set of images using the gs (GhostScript) or pdfdraw/mutool draw (MuPDF) commands and other external tools, and then displays those converted images.

When you visit a document file that can be displayed with DocView mode, Emacs automatically uses that mode 21. As an exception, when you visit a PostScript file, Emacs switches to PS mode, a major mode for editing PostScript files as text; however, it also enables DocView minor mode, so you can type C-c C-c to view the document with DocView. In either DocView mode or DocView minor mode, repeating C-c C-c (doc-view-toggle-display) toggles between DocView and the underlying file contents.

When you visit a file which would normally be handled by DocView mode but some requirement is not met (e.g., you operate in a terminal frame or Emacs has no PNG support), you are queried if you want to view the document’s contents as plain text. If you confirm, the buffer is put in text mode and DocView minor mode is activated. Thus, by typing C-c C-c you switch to the fallback mode. With another C-c C-c you return to DocView mode. The plain text contents can also be displayed from within DocView mode by typing C-c C-t (doc-view-open-text).

You can explicitly enable DocView mode with the command M-x doc-view-mode. You can toggle DocView minor mode with M-x doc-view-minor-mode.

When DocView mode starts, it displays a welcome screen and begins formatting the file, page by page. It displays the first page once that has been formatted.

To kill the DocView buffer, type k (doc-view-kill-proc-and-buffer). To bury it, type q (quit-window).


38.1 DocView Navigation

In DocView mode, you can scroll the current page using the usual Emacs movement keys: C-p, C-n, C-b, C-f, and the arrow keys.

By default, the line-motion keys C-p and C-n stop scrolling at the beginning and end of the current page, respectively. However, if you change the variable doc-view-continuous to a non-nil value, then C-p displays the previous page if you are already at the beginning of the current page, and C-n displays the next page if you are at the end of the current page.

You can also display the next page by typing n, PageDown, next or C-x ] (doc-view-next-page). To display the previous page, type p, PageUp, prior or C-x [ (doc-view-previous-page).

SPC (doc-view-scroll-up-or-next-page) is a convenient way to advance through the document. It scrolls within the current page or advances to the next. DEL moves backwards in a similar way (doc-view-scroll-down-or-previous-page).

To go to the first page, type M-< (doc-view-first-page); to go to the last one, type M-> (doc-view-last-page). To jump to a page by its number, type M-g M-g or M-g g (doc-view-goto-page).

You can enlarge or shrink the document with + (doc-view-enlarge) and - (doc-view-shrink). By default, these commands just rescale the already-rendered image. If you instead want the image to be re-rendered at the new size, set doc-view-scale-internally to nil. To specify the default size for DocView, customize the variable doc-view-resolution.

When the mutool program is available, DocView will use it to generate entries for an outline menu, making it accessible via the imenu facility (see Imenu). To disable this functionality even when mutool can be found on your system, customize the variable doc-view-imenu-enabled to the nil value. You can further customize how imenu items are formatted and displayed using the variables doc-view-imenu-format and doc-view-flatten.


38.2 DocView Searching

In DocView mode, you can search the file’s text for a regular expression (see Syntax of Regular Expressions). The interface for searching is inspired by isearch (see Incremental Search).

To begin a search, type C-s (doc-view-search) or C-r (doc-view-search-backward). This reads a regular expression using a minibuffer, then echoes the number of matches found within the document. You can move forward and back among the matches by typing C-s and C-r. DocView mode has no way to show the match inside the page image; instead, it displays a tooltip (at the mouse position) listing all matching lines in the current page. To force display of this tooltip, type C-t (doc-view-show-tooltip).

To start a new search, use the search command with a prefix argument; i.e., C-u C-s for a forward search or C-u C-r for a backward search.


38.3 DocView Slicing

Documents often have wide margins for printing. They are annoying when reading the document on the screen, because they use up screen space and can cause inconvenient scrolling.

With DocView you can hide these margins by selecting a slice of pages to display. A slice is a rectangle within the page area; once you specify a slice in DocView, it applies to whichever page you look at.

To specify the slice numerically, type c s (doc-view-set-slice); then enter the top left pixel position and the slice’s width and height.

A more convenient graphical way to specify the slice is with c m (doc-view-set-slice-using-mouse), where you use the mouse to select the slice. Simply press and hold the left mouse button at the upper-left corner of the region you want to have in the slice, then move the mouse pointer to the lower-right corner and release the button.

The most convenient way is to set the optimal slice by using BoundingBox information automatically determined from the document by typing c b (doc-view-set-slice-from-bounding-box).

To cancel the selected slice, type c r (doc-view-reset-slice). Then DocView shows the entire page including its entire margins.


38.4 DocView Conversion

For efficiency, DocView caches the images produced by gs. The name of the directory where it caches images is given by the variable doc-view-cache-directory. You can clear the cache directory by typing M-x doc-view-clear-cache.

To force reconversion of the currently viewed document, type r or g (revert-buffer). To kill the converter process associated with the current buffer, type K (doc-view-kill-proc). The command k (doc-view-kill-proc-and-buffer) kills the converter process and the DocView buffer.


39 Running Shell Commands from Emacs

Emacs has commands for passing single command lines to shell subprocesses, and for running a shell interactively with input and output to an Emacs buffer, and for running a shell in a terminal emulator window.

M-! cmd RET

Run the shell command cmd and display the output (shell-command).

M-| cmd RET

Run the shell command cmd with region contents as input; optionally replace the region with the output (shell-command-on-region).

M-& cmd RET

Run the shell command cmd asynchronously, and display the output (async-shell-command).

M-x shell

Run a subshell with input and output through an Emacs buffer. You can then give commands interactively.

M-x term

Run a subshell with input and output through an Emacs buffer. You can then give commands interactively. Full terminal emulation is available.

Whenever you specify a relative file name for an executable program (either in the cmd argument to one of the above commands, or in other contexts), Emacs searches for the program in the directories specified by the variable exec-path. The value of this variable must be a list of directories; the default value is initialized from the environment variable PATH when Emacs is started (see General Variables).

M-x eshell invokes a shell implemented entirely in Emacs. It is documented in its own manual. See Eshell in Eshell: The Emacs Shell.


39.1 Single Shell Commands

M-! (shell-command) reads a line of text using the minibuffer and executes it as a shell command, in a subshell made just for that command. Standard input for the command comes from the null device. If the shell command produces any output, the output appears either in the echo area (if it is short), or in the ‘"*Shell Command Output*"’ (shell-command-buffer-name) buffer (if the output is long). The variables resize-mini-windows and max-mini-window-height (see Editing in the Minibuffer) control when Emacs should consider the output to be too long for the echo area. Note that customizing shell-command-dont-erase-buffer, described below, can affect what is displayed in the echo area.

For instance, one way to decompress a file named foo.gz is to type M-! gunzip foo.gz RET. That shell command normally creates the file foo and produces no terminal output.

A numeric argument to shell-command, e.g., M-1 M-!, causes it to insert terminal output into the current buffer instead of a separate buffer. By default, it puts point before the output, and sets the mark after the output (but a non-default value of shell-command-dont-erase-buffer can change that, see below). For instance, M-1 M-! gunzip < foo.gz RET would insert the uncompressed form of the file foo.gz into the current buffer.

Provided the specified shell command does not end with ‘&’, it runs synchronously, and you must wait for it to exit before continuing to use Emacs. To stop waiting, type C-g to quit; this sends a SIGINT signal to terminate the shell command (this is the same signal that C-c normally generates in the shell). Emacs then waits until the command actually terminates. If the shell command doesn’t stop (because it ignores the SIGINT signal), type C-g again; this sends the command a SIGKILL signal, which is impossible to ignore.

A shell command that ends in ‘&’ is executed asynchronously, and you can continue to use Emacs as it runs. You can also type M-& (async-shell-command) to execute a shell command asynchronously; this is exactly like calling M-! with a trailing ‘&’, except that you do not need the ‘&’. The output from asynchronous shell commands, by default, goes into the ‘"*Async Shell Command*"’ buffer (shell-command-buffer-name-async). Emacs inserts the output into this buffer as it comes in, whether or not the buffer is visible in a window.

If you want to run more than one asynchronous shell command at the same time, they could end up competing for the output buffer. The option async-shell-command-buffer specifies what to do about this; e.g., whether to rename the pre-existing output buffer, or to use a different buffer for the new command. Consult the variable’s documentation for more possibilities.

If you want the output buffer for asynchronous shell commands to be displayed only when the command generates output, set async-shell-command-display-buffer to nil.

The option async-shell-command-width defines the number of display columns available for output of asynchronous shell commands. A positive integer tells the shell to use that number of columns for command output. The default value is nil that means to use the same number of columns as provided by the shell.

To make the above commands show the current directory in their prompts, customize the variable shell-command-prompt-show-cwd to a non-nil value.

M-| (shell-command-on-region) is like M-!, but passes the contents of the region as the standard input to the shell command, instead of no input. With a numeric argument, it deletes the old region and replaces it with the output from the shell command.

For example, you can use M-| with the gpg program to see what keys are in the buffer. If the buffer contains a GnuPG key, type C-x h M-| gpg RET to feed the entire buffer contents to gpg. This will output the list of keys to the buffer whose name is the value of shell-command-buffer-name.

The above commands use the shell specified by the variable shell-file-name. Its default value is determined by the SHELL environment variable when Emacs is started. If the file name is relative, Emacs searches the directories listed in exec-path (see Running Shell Commands from Emacs).

If the default directory is remote (see Remote Files), the default value is /bin/sh. This can be changed by declaring shell-file-name connection-local (see Per-Connection Local Variables).

To specify a coding system for M-! or M-|, use the command C-x RET c immediately beforehand. See Coding Systems for Interprocess Communication.

By default, error output is intermixed with the regular output in the output buffer. But if you change the value of the variable shell-command-default-error-buffer to a string, error output is inserted into a buffer of that name.

By default, the output buffer is erased between shell commands, except when the output goes to the current buffer. If you change the value of the option shell-command-dont-erase-buffer to erase, then the output buffer is always erased. Other non-nil values prevent erasing of the output buffer, and—if the output buffer is not the current buffer—also control where to put point after inserting the output of the shell command:

beg-last-out

Puts point at the beginning of the last shell-command output.

end-last-out

Puts point at the end of the last shell-command output, i.e. at the end of the output buffer.

save-point

Restores the position of point as it was before inserting the shell-command output.

Note that if this option is non-nil, the output shown in the echo area could be from more than just the last command, since the echo area just displays a portion of the output buffer.

In case the output buffer is not the current buffer, shell command output is appended at the end of this buffer.


39.2 Interactive Subshell

To run a subshell interactively, type M-x shell. This creates (or reuses) a buffer named *shell*, and runs a shell subprocess with input coming from and output going to that buffer. That is to say, any terminal output from the subshell goes into the buffer, advancing point, and any terminal input for the subshell comes from text in the buffer. To give input to the subshell, go to the end of the buffer and type the input, terminated by RET.

By default, when the subshell is invoked interactively, the *shell* buffer is displayed in a new window, unless the current window already shows the *shell* buffer. This behavior can be customized via display-buffer-alist (see How display-buffer works).

While the subshell is waiting or running a command, you can switch windows or buffers and perform other editing in Emacs. Emacs inserts the output from the subshell into the Shell buffer whenever it has time to process it (e.g., while waiting for keyboard input).

In the Shell buffer, prompts are displayed with the face comint-highlight-prompt, and submitted input lines are displayed with the face comint-highlight-input. This makes it easier to distinguish input lines from the shell output. See Text Faces.

To make multiple subshells, invoke M-x shell with a prefix argument (e.g., C-u M-x shell). Then the command will read a buffer name, and create (or reuse) a subshell in that buffer. You can also rename the *shell* buffer using M-x rename-uniquely, then create a new *shell* buffer using plain M-x shell. Subshells in different buffers run independently and in parallel.

Emacs attempts to keep track of what the current directory is by looking at the commands you enter, looking for ‘cd’ commands and the like. This is an error-prone solution, since there are many ways to change the current directory, so Emacs also looks for special OSC (Operating System Commands) escape codes that are designed to convey this information in a more reliable fashion. You should arrange for your shell to print the appropriate escape sequence at each prompt, for instance with the following command:

printf "\e]7;file://%s%s\e\\" "$HOSTNAME" "$PWD"

To specify the shell file name used by M-x shell, customize the variable explicit-shell-file-name. If this is nil (the default), Emacs uses the environment variable ESHELL if it exists. Otherwise, it usually uses the variable shell-file-name (see Single Shell Commands); but if the default directory is remote (see Remote Files), it prompts you for the shell file name. See Minibuffers for File Names, for hints how to type remote file names effectively.

Emacs sends the new shell the contents of the file ~/.emacs_shellname as input, if it exists, where shellname is the name of the file that the shell was loaded from. For example, if you use bash, the file sent to it is ~/.emacs_bash. If this file is not found, Emacs tries with ~/.emacs.d/init_shellname.sh.

To specify a coding system for the shell, you can use the command C-x RET c immediately before M-x shell. You can also change the coding system for a running subshell by typing C-x RET p in the shell buffer. See Coding Systems for Interprocess Communication.

Emacs sets the environment variable INSIDE_EMACS in the subshell to ‘version,comint’, where version is the Emacs version (e.g., ‘28.1’). Programs can check this variable to determine whether they are running inside an Emacs subshell.


39.3 Shell Mode

The major mode for Shell buffers is Shell mode. Many of its special commands are bound to the C-c prefix, and resemble the usual editing and job control characters present in ordinary shells, except that you must type C-c first. Here is a list of Shell mode commands:

RET

Send the current line as input to the subshell (comint-send-input). Any shell prompt at the beginning of the line is omitted (see Shell Prompts). If point is at the end of buffer, this is like submitting the command line in an ordinary interactive shell. However, you can also invoke RET elsewhere in the shell buffer to submit the current line as input.

TAB

Complete the command name or file name before point in the shell buffer (completion-at-point). This uses the usual Emacs completion rules (see Completion), with the completion alternatives being file names, environment variable names, the shell command history, and history references (see Shell History References). For options controlling the completion, see Shell Mode Options.

M-?

Display temporarily a list of the possible completions of the file name before point (comint-dynamic-list-filename-completions).

C-d

Either delete a character or send EOF (comint-delchar-or-maybe-eof). Typed at the end of the shell buffer, this sends EOF to the subshell. Typed at any other position in the buffer, this deletes a character as usual.

C-c C-a

Move to the beginning of the line, but after the prompt if any (comint-bol-or-process-mark). If you repeat this command twice in a row, the second time it moves back to the process mark, which is the beginning of the input that you have not yet sent to the subshell. (Normally that is the same place—the end of the prompt on this line—but after C-c SPC the process mark may be in a previous line.)

C-c SPC

Accumulate multiple lines of input, then send them together (comint-accumulate). This command inserts a newline before point, but does not send the preceding text as input to the subshell—at least, not yet. Both lines, the one before this newline and the one after, will be sent together (along with the newline that separates them), when you type RET.

C-c C-u

Kill all text pending at end of buffer to be sent as input (comint-kill-input). If point is not at end of buffer, this only kills the part of this text that precedes point.

C-c C-w

Kill a word before point (backward-kill-word).

C-c C-c

Interrupt the shell or its current subjob if any (comint-interrupt-subjob). This command also kills any shell input pending in the shell buffer and not yet sent.

C-c C-z

Stop the shell or its current subjob if any (comint-stop-subjob). This command also kills any shell input pending in the shell buffer and not yet sent.

C-c C-\

Send quit signal to the shell or its current subjob if any (comint-quit-subjob). This command also kills any shell input pending in the shell buffer and not yet sent.

C-c C-o

Delete the last batch of output from a shell command (comint-delete-output). This is useful if a shell command spews out lots of output that just gets in the way. With a prefix argument, this command saves the deleted text in the kill-ring (see The Kill Ring), so that you could later yank it (see Yanking) elsewhere.

C-c C-s

Write the last batch of output from a shell command to a file (comint-write-output). With a prefix argument, the file is appended to instead. Any prompt at the end of the output is not written.

C-c C-r
C-M-l

Scroll to display the beginning of the last batch of output at the top of the window; also move the cursor there (comint-show-output).

C-c C-e

Scroll to put the last line of the buffer at the bottom of the window (comint-show-maximum-output).

C-c C-f

Move forward across one shell command, but not beyond the current line (shell-forward-command). The variable shell-command-regexp specifies how to recognize the end of a command.

C-c C-b

Move backward across one shell command, but not beyond the current line (shell-backward-command).

M-x dirs

Ask the shell for its working directory, and update the Shell buffer’s default directory. See Directory Tracking.

M-x comint-send-invisible RET text RET

Send text as input to the shell, after reading it without echoing. This is useful when a shell command runs a program that asks for a password.

Please note that Emacs will not echo passwords by default. If you really want them to be echoed, evaluate (see Evaluating Emacs Lisp Expressions) the following Lisp expression:

(remove-hook 'comint-output-filter-functions
             'comint-watch-for-password-prompt)
M-x comint-continue-subjob

Continue the shell process. This is useful if you accidentally suspend the shell process.22

M-x comint-strip-ctrl-m

Discard all control-M characters from the current group of shell output. The most convenient way to use this command is to make it run automatically when you get output from the subshell. To do that, evaluate this Lisp expression:

(add-hook 'comint-output-filter-functions
          'comint-strip-ctrl-m)
M-x comint-truncate-buffer

This command truncates the shell buffer to a certain maximum number of lines, specified by the variable comint-buffer-maximum-size. Here’s how to do this automatically each time you get output from the subshell:

(add-hook 'comint-output-filter-functions
          'comint-truncate-buffer)

By default, Shell mode handles common ANSI escape codes (for instance, for changing the color of text). Emacs also optionally supports some extend escape codes, like some of the OSC (Operating System Codes) if you put the following in your init file:

(add-hook 'comint-output-filter-functions 'comint-osc-process-output)

With this enabled, the output from, for instance, ls --hyperlink will be made into clickable buttons in the Shell mode buffer.

Shell mode is a derivative of Comint mode, a general-purpose mode for communicating with interactive subprocesses. Most of the features of Shell mode actually come from Comint mode, as you can see from the command names listed above. The special features of Shell mode include the directory tracking feature, and a few user commands.

Other Emacs features that use variants of Comint mode include GUD (see Running Debuggers Under Emacs) and M-x run-lisp (see Running an External Lisp).

You can use M-x comint-run to execute any program of your choice in a subprocess using unmodified Comint mode—without the specializations of Shell mode. To pass arguments to the program, use C-u M-x comint-run.


39.4 Shell Prompts

A prompt is text output by a program to show that it is ready to accept new user input. Normally, Comint mode (and thus Shell mode) automatically figures out which part of the buffer is a prompt, based on the output of the subprocess. (Specifically, it assumes that any received output line which doesn’t end with a newline is a prompt.)

Comint mode divides the buffer into two types of fields: input fields (where user input is typed) and output fields (everywhere else). Prompts are part of the output fields. Most Emacs motion commands do not cross field boundaries, unless they move over multiple lines. For instance, when point is in the input field on a shell command line, C-a puts point at the beginning of the input field, after the prompt. Internally, the fields are implemented using the field text property (see Text Properties in the Emacs Lisp Reference Manual).

If you change the variable comint-use-prompt-regexp to a non-nil value, then Comint mode will recognize prompts using a regular expression (see Syntax of Regular Expressions). In Shell mode, the regular expression is specified by the variable shell-prompt-pattern. The default value of comint-use-prompt-regexp is nil, because this method for recognizing prompts is unreliable, but you may want to set it to a non-nil value in unusual circumstances. In that case, Emacs does not divide the Comint buffer into fields, so the general motion commands behave as they normally do in buffers without special text properties. However, you can use the paragraph motion commands to conveniently navigate the buffer (see Paragraphs); in Shell mode, Emacs uses shell-prompt-pattern as paragraph boundaries.


39.5 Shell Command History

Shell buffers support three ways of repeating earlier commands. You can use keys like those used for the minibuffer history; these work much as they do in the minibuffer, inserting text from prior commands while point remains always at the end of the buffer. You can move through the buffer to previous inputs in their original place, then resubmit them or copy them to the end. Or you can use a ‘!’-style history reference.


39.5.1 Shell History Ring

M-p
C-UP

Fetch the next earlier old shell command (comint-previous-input).

M-n
C-DOWN

Fetch the next later old shell command (comint-next-input).

M-r

Begin an incremental regexp search of old shell commands (comint-history-isearch-backward-regexp).

C-c C-x

Fetch the next subsequent command from the history (comint-get-next-from-history).

C-c .

Fetch one argument from an old shell command (comint-input-previous-argument).

C-c C-l

Display the buffer’s history of shell commands in another window (comint-dynamic-list-input-ring).

Shell buffers provide a history of previously entered shell commands. To reuse shell commands from the history, use the editing commands M-p, M-n, and M-r. These work similar to the minibuffer history commands (see Minibuffer History), except that they operate within the Shell buffer rather than the minibuffer, and M-r in a Shell buffer invokes incremental search through shell command history.

M-p fetches an earlier shell command to the end of the shell buffer. Successive use of M-p fetches successively earlier shell commands, each replacing any text that was already present as potential shell input. M-n does likewise except that it finds successively more recent shell commands from the buffer. C-UP works like M-p, and C-DOWN like M-n.

The history search command M-r begins an incremental regular expression search of previous shell commands. After typing M-r, start typing the desired string or regular expression; the last matching shell command will be displayed in the current line. Incremental search commands have their usual effects—for instance, C-s and C-r search forward and backward for the next match (see Incremental Search). When you find the desired input, type RET to terminate the search. This puts the input in the command line. Any partial input you were composing before navigating the history list is restored when you go to the beginning or end of the history ring.

Often it is useful to reexecute several successive shell commands that were previously executed in sequence. To do this, first find and reexecute the first command of the sequence. Then type C-c C-x; that will fetch the following command—the one that follows the command you just repeated. Then type RET to reexecute this command. You can reexecute several successive commands by typing C-c C-x RET over and over.

The command C-c . (comint-insert-previous-argument) copies an individual argument from a previous command, like ESC . in Bash and zsh. The simplest use copies the last argument from the previous shell command. With a prefix argument n, it copies the nth argument instead. Repeating C-c . copies from an earlier shell commands, always using the same value of n (don’t give a prefix argument when you repeat the C-c . command).

If you set comint-insert-previous-argument-from-end to a non-nil value, C-c . will instead copy the nth argument counting from the last one; this emulates ESC . in zsh.

These commands get the text of previous shell commands from a special history list, not from the shell buffer itself. Thus, editing the shell buffer, or even killing large parts of it, does not affect the history that these commands access.

Some shells store their command histories in files so that you can refer to commands from previous shell sessions. Emacs reads the command history file for your chosen shell, to initialize its own command history. The file name is ~/.bash_history for bash, ~/.sh_history for ksh, and ~/.history for other shells.

If you run the shell on a remote host, this setting might be overwritten by the variable tramp-histfile-override. It is recommended to set this variable to nil.


39.5.2 Shell History Copying

C-c C-p

Move point to the previous prompt (comint-previous-prompt).

C-c C-n

Move point to the following prompt (comint-next-prompt).

C-c RET

Copy the input command at point, inserting the copy at the end of the buffer (comint-copy-old-input). This is useful if you move point back to a previous command. After you copy the command, you can submit the copy as input with RET. If you wish, you can edit the copy before resubmitting it. If you use this command on an output line, it copies that line to the end of the buffer.

mouse-2

If comint-use-prompt-regexp is nil (the default), copy the old input command that you click on, inserting the copy at the end of the buffer (comint-insert-input). If comint-use-prompt-regexp is non-nil, or if the click is not over old input, just yank as usual.

Moving to a previous input and then copying it with C-c RET or mouse-2 produces the same results—the same buffer contents—that you would get by using M-p enough times to fetch that previous input from the history list. However, C-c RET copies the text from the buffer, which can be different from what is in the history list if you edit the input text in the buffer after it has been sent.


39.5.3 Shell History References

Various shells, including csh and bash, support history references that begin with ‘!’ and ‘^’. Shell mode recognizes these constructs, and can perform the history substitution for you.

If you insert a history reference and type TAB, this searches the input history for a matching command, performs substitution if necessary, and places the result in the buffer in place of the history reference. For example, you can fetch the most recent command beginning with ‘mv’ with ! m v TAB. You can edit the command if you wish, and then resubmit the command to the shell by typing RET.

Shell mode can optionally expand history references in the buffer when you send them to the shell. To request this, set the variable comint-input-autoexpand to input. You can make SPC perform history expansion by binding SPC to the command comint-magic-space. See Changing Key Bindings Interactively.

Shell mode recognizes history references when they follow a prompt. See Shell Prompts, for how Shell mode recognizes prompts.


39.6 Directory Tracking

Shell mode keeps track of ‘cd’, ‘pushd’ and ‘popd’ commands given to the subshell, in order to keep the Shell buffer’s default directory (see File Names) the same as the shell’s working directory. It recognizes these commands by examining lines of input that you send.

If you use aliases for these commands, you can tell Emacs to recognize them also, by setting the variables shell-pushd-regexp, shell-popd-regexp, and shell-cd-regexp to the appropriate regular expressions (see Syntax of Regular Expressions). For example, if shell-pushd-regexp matches the beginning of a shell command line, that line is regarded as a pushd command. These commands are recognized only at the beginning of a shell command line.

If Emacs gets confused about changes in the working directory of the subshell, type M-x dirs. This command asks the shell for its working directory and updates the default directory accordingly. It works for shells that support the most common command syntax, but may not work for unusual shells.

You can also use Dirtrack mode, a buffer-local minor mode that implements an alternative method of tracking the shell’s working directory. To use this method, your shell prompt must contain the working directory at all times, and you must supply a regular expression for recognizing which part of the prompt contains the working directory; see the documentation of the variable dirtrack-list for details. To use Dirtrack mode, type M-x dirtrack-mode in the Shell buffer, or add dirtrack-mode to shell-mode-hook (see Hooks).


39.7 Shell Mode Options

If the variable comint-scroll-to-bottom-on-input is non-nil, insertion and yank commands scroll the selected window to the bottom before inserting. The default is nil.

If comint-scroll-show-maximum-output is non-nil, then arrival of output when point is at the end tries to scroll the last line of text to the bottom line of the window, showing as much useful text as possible. (This mimics the scrolling behavior of most terminals.) The default is t.

By setting comint-move-point-for-output, you can opt for having point jump to the end of the buffer whenever output arrives—no matter where in the buffer point was before. If the value is this, point jumps in the selected window. If the value is all, point jumps in each window that shows the Comint buffer. If the value is other, point jumps in all nonselected windows that show the current buffer. The default value is nil, which means point does not jump to the end.

If you set comint-prompt-read-only, the prompts in the Comint buffer are read-only.

The variable comint-input-ignoredups controls whether successive identical inputs are stored in the input history. A non-nil value means to omit an input that is the same as the previous input. The default is nil, which means to store each input even if it is equal to the previous input.

Three variables customize file name completion. The variable comint-completion-addsuffix controls whether completion inserts a space or a slash to indicate a fully completed file or directory name (non-nil means do insert a space or slash). comint-completion-recexact, if non-nil, directs TAB to choose the shortest possible completion if the usual Emacs completion algorithm cannot add even a single character. comint-completion-autolist, if non-nil, says to list all the possible completions whenever completion is not exact.

Command completion normally considers only executable files. If you set shell-completion-execonly to nil, it considers nonexecutable files as well.

The variable shell-completion-fignore specifies a list of file name extensions to ignore in Shell mode completion. The default setting is nil, but some users prefer ("~" "#" "%") to ignore file names ending in ‘~’, ‘#’ or ‘%’. Other related Comint modes use the variable comint-completion-fignore instead.

Some implementation details of the shell command completion may also be found in the lisp documentation of the shell-dynamic-complete-command function.

You can configure the behavior of ‘pushd’. Variables control whether ‘pushd’ behaves like ‘cd’ if no argument is given (shell-pushd-tohome), pop rather than rotate with a numeric argument (shell-pushd-dextract), and only add directories to the directory stack if they are not already on it (shell-pushd-dunique). The values you choose should match the underlying shell, of course.

Comint mode sets the TERM environment variable to a safe default value, but this value disables some useful features. For example, color is disabled in applications that use TERM to determine if color is supported. Therefore, Emacs provides an option comint-terminfo-terminal to let you choose a terminal with more advanced features, as defined in your system’s terminfo database. Emacs will use this option as the value for TERM so long as system-uses-terminfo is non-nil.

Both comint-terminfo-terminal and system-uses-terminfo can be declared as connection-local variables to adjust these options to match what a remote system expects (see Per-Connection Local Variables).


39.8 Emacs Terminal Emulator

To run a subshell in a text terminal emulator, use M-x term. This creates (or reuses) a buffer named *terminal*, and runs a subshell with input coming from your keyboard, and output going to that buffer.

The terminal emulator uses Term mode, which has two input modes. In line mode, Term basically acts like Shell mode (see Shell Mode). In char mode, each character is sent directly to the subshell, as terminal input; the sole exception is the terminal escape character, which by default is C-c (see Term Mode). Any echoing of your input is the responsibility of the subshell; any terminal output from the subshell goes into the buffer, advancing point.

Some programs (such as Emacs itself) need to control the appearance of the terminal screen in detail. They do this by emitting special control codes. Term mode recognizes and handles ANSI-standard VT100-style escape sequences, which are accepted by most modern terminals, including xterm. (Hence, you can actually run Emacs inside an Emacs Term window.)

The term face specifies the default appearance of text in the terminal emulator (the default is the same appearance as the default face). When terminal control codes are used to change the appearance of text, these are represented in the terminal emulator by the faces term-color-black, term-color-red, term-color-green, term-color-yellow term-color-blue, term-color-magenta, term-color-cyan, term-color-white, term-color-underline, and term-color-bold. See Text Faces.

You can also use Term mode to communicate with a device connected to a serial port. See Serial Terminal.

The file name used to load the subshell is determined the same way as for Shell mode. To make multiple terminal emulators, rename the buffer *terminal* to something different using M-x rename-uniquely, just as with Shell mode.

Unlike Shell mode, Term mode does not track the current directory by examining your input. But some shells can tell Term what the current directory is. This is done automatically by bash version 1.15 and later.


39.9 Term Mode

To switch between line and char mode in Term mode, use these commands:

C-c C-j

Switch to line mode (term-line-mode). Do nothing if already in line mode.

C-c C-k

Switch to char mode (term-char-mode). Do nothing if already in char mode.

The following commands are only available in char mode:

C-c C-c

Send a literal C-c to the sub-shell (term-interrupt-subjob).

C-c char

This is equivalent to C-x char in normal Emacs. For example, C-c o invokes the global binding of C-x o, which is normally ‘other-window’.

Term mode has a page-at-a-time feature. When enabled, it makes output pause at the end of each screenful:

C-c C-q

Toggle the page-at-a-time feature (term-pager-toggle). This command works in both line and char modes. When the feature is enabled, the mode-line displays the word ‘page’, and each time Term receives more than a screenful of output, it pauses and displays ‘**MORE**’ in the mode-line. Type SPC to display the next screenful of output, or ? to see your other options. The interface is similar to the more program.


39.10 Remote Host Shell

You can login to a remote computer, using whatever commands you would from a regular terminal (e.g., the ssh command), from a Term window.

A program that asks you for a password will normally suppress echoing of the password, so the password will not show up in the buffer. This will happen just as if you were using a real terminal, if the buffer is in char mode. If it is in line mode, the password is temporarily visible, but will be erased when you hit return. (This happens automatically; there is no special password processing.)

When you log in to a different machine, you need to specify the type of terminal you’re using, by setting the TERM environment variable in the environment for the remote login command. (If you use bash, you do that by writing the variable assignment before the remote login command, without a separating comma.) Terminal types ‘ansi’ or ‘vt100’ will work on most systems.


39.11 Serial Terminal

If you have a device connected to a serial port of your computer, you can communicate with it by typing M-x serial-term. This command asks for a serial port name and speed, and switches to a new Term mode buffer. Emacs communicates with the serial device through this buffer just like it does with a terminal in ordinary Term mode.

The speed of the serial port is measured in bits per second. The most common speed is 9600 bits per second. You can change the speed interactively by clicking on the mode line.

A serial port can be configured even more by clicking on ‘8N1’ in the mode line. By default, a serial port is configured as ‘8N1’, which means that each byte consists of 8 data bits, No parity check bit, and 1 stopbit.

If the speed or the configuration is wrong, you cannot communicate with your device and will probably only see garbage output in the window.


40 Using Emacs as a Server

Various programs can invoke your choice of editor to edit a particular piece of text. For instance, version control programs invoke an editor to enter version control logs (see Version Control), and the Unix mail utility invokes an editor to enter a message to send. By convention, your choice of editor is specified by the environment variable EDITOR. If you set EDITOR to ‘emacs’, Emacs would be invoked, but in an inconvenient way—by starting a new Emacs process. This is inconvenient because the new Emacs process doesn’t share buffers, a command history, or other kinds of information with any existing Emacs process.

You can solve this problem by setting up Emacs as an edit server, so that it “listens” for external edit requests and acts accordingly. There are various ways to start an Emacs server:

Once an Emacs server is started, you can use a shell command called emacsclient to connect to the Emacs process and tell it to visit a file. You can then set the EDITOR environment variable to ‘emacsclient’, so that external programs will use the existing Emacs process for editing.23

You can run multiple Emacs servers on the same machine by giving each one a unique server name, using the variable server-name. For example, M-x set-variable RET server-name RET "foo" RET sets the server name to ‘foo’. The emacsclient program can specify a server by name, using the ‘-s’ or the ‘-f’ option (see emacsclient Options), depending on whether or not the server uses a TCP socket (see TCP Emacs server).

If you want to run multiple Emacs daemons (see Initial Options), you can give each daemon its own server name like this:

  emacs --daemon=foo

The Emacs server can optionally be stopped automatically when certain conditions are met. To do this, call the function server-stop-automatically in your init file (see The Emacs Initialization File), with one of the following arguments:

If you have defined a server by a unique server name, it is possible to connect to the server from another Emacs instance and evaluate Lisp expressions on the server, using the server-eval-at function. For instance, (server-eval-at "foo" '(+ 1 2)) evaluates the expression (+ 1 2) on the ‘foo’ server, and returns 3. (If there is no server with that name, an error is signaled.) Currently, this feature is mainly useful for developers.

If your operating system’s desktop environment is freedesktop.org-compatible (which is true of most GNU/Linux and other recent Unix-like GUIs), you may use the ‘Emacs (Client)’ menu entry to connect to an Emacs server with emacsclient. The daemon starts if not already running.


40.1 TCP Emacs server

An Emacs server usually listens to connections on a local Unix domain socket. Some operating systems, such as MS-Windows, do not support local sockets; in that case, the server uses TCP sockets instead. In some cases it is useful to have the server listen on a TCP socket even if local sockets are supported, e.g., if you need to contact the Emacs server from a remote machine. You can set server-use-tcp to non-nil to have Emacs listen on a TCP socket instead of a local socket. This is the default if your OS does not support local sockets.

If the Emacs server is set to use TCP, it will by default listen on a random port on the localhost interface. This can be changed to another interface and/or a fixed port using the variables server-host and server-port.

A TCP socket is not subject to file system permissions. To retain some control over which users can talk to an Emacs server over TCP sockets, the emacsclient program must send an authorization key to the server. This key is normally randomly generated by the Emacs server. This is the recommended mode of operation.

If needed, you can set the authorization key to a static value by setting the server-auth-key variable. The key must consist of 64 ASCII printable characters except for space (this means characters from ‘!’ to ‘~’, or from decimal code 33 to 126). You can use M-x server-generate-key to get a random key.

When you start a TCP Emacs server, Emacs creates a server file containing the TCP information to be used by emacsclient to connect to the server. The variable server-auth-dir specifies the default directory containing the server file; by default, this is ~/.emacs.d/server/. In the absence of a local socket with file permissions, the permissions of this directory determine which users can have their emacsclient processes talk to the Emacs server. If server-name is an absolute file name, the server file is created where specified by that file name.

To tell emacsclient to connect to the server over TCP with a specific server file, use the ‘-f’ or ‘--server-file’ option, or set the EMACS_SERVER_FILE environment variable (see emacsclient Options). If server-auth-dir is set to a non-standard value, or if server-name is set to an absolute file name, emacsclient needs an absolute file name to the server file, as the default server-auth-dir is hard-coded in emacsclient to be used as the directory for resolving relative filenames.


40.2 Invoking emacsclient

The simplest way to use the emacsclient program is to run the shell command ‘emacsclient file’, where file is a file name. This connects to an Emacs server, and tells that Emacs process to visit file in one of its existing frames—either a graphical frame, or one in a text terminal (see Frames and Graphical Displays). You can then select that frame to begin editing.

If there is no Emacs server, the emacsclient program halts with an error message (you can prevent this from happening by using the ‘--alternate-editor=""’ option to emacsclient, see emacsclient Options). If the Emacs process has no existing frame—which can happen if it was started as a daemon (see Using Emacs as a Server)—then Emacs opens a frame on the terminal in which you called emacsclient.

You can also force emacsclient to open a new frame on a graphical display using the ‘-c’ option, or on a text terminal using the ‘-t’ option. See emacsclient Options.

If you are running on a single text terminal, you can switch between emacsclient’s shell and the Emacs server using one of two methods: (i) run the Emacs server and emacsclient on different virtual terminals, and switch to the Emacs server’s virtual terminal after calling emacsclient; or (ii) call emacsclient from within the Emacs server itself, using Shell mode (see Interactive Subshell) or Term mode (see Term Mode); emacsclient blocks only the subshell under Emacs, and you can still use Emacs to edit the file.

When you finish editing file in the Emacs server, type C-x # (server-edit) in its buffer. This saves the file and sends a message back to the emacsclient program, telling it to exit. Programs that use EDITOR usually wait for the editor—in this case emacsclient—to exit before doing something else.

If you want to abandon the edit instead, use the M-x server-edit-abort command. This sends a message back to the emacsclient program, telling it to exit with abnormal exit status, and doesn’t save any buffers.

You can also call emacsclient with multiple file name arguments: ‘emacsclient file1 file2 ...’ tells the Emacs server to visit file1, file2, and so forth. Emacs selects the buffer visiting file1, and buries the other buffers at the bottom of the buffer list (see Using Multiple Buffers). The emacsclient program exits once all the specified files are finished (i.e., once you have typed C-x # in each server buffer).

Finishing with a server buffer also kills the buffer, unless it already existed in the Emacs session before the server was asked to create it. However, if you set server-kill-new-buffers to nil, then a different criterion is used: finishing with a server buffer kills it if the file name matches the regular expression server-temp-file-regexp. This is set up to distinguish certain temporary files.

Each C-x # checks for other pending external requests to edit various files, and selects the next such file. You can switch to a server buffer manually if you wish; you don’t have to arrive at it with C-x #. But C-x # is the way to tell emacsclient that you are finished.

If you set the value of the variable server-window to a window or a frame, C-x # always displays the next server buffer in that window or in that frame.

When emacsclient connects, the server will normally output a message that says how to exit the client frame. If server-client-instructions is set to nil, this message is inhibited.


40.3 emacsclient Options

You can pass some optional arguments to the emacsclient program, such as:

emacsclient -c +12 file1 +4:3 file2

The ‘+line’ or ‘+line:column’ arguments specify line numbers, or line and column numbers, for the next file argument. These behave like the command line arguments for Emacs itself. See Action Arguments.

The other optional arguments recognized by emacsclient are listed below:

-a command
--alternate-editor=command

Specify a shell command to run if emacsclient fails to contact Emacs. This is useful when running emacsclient in a script. The command may include arguments, which may be quoted "like this". Currently, escaping of quotes is not supported.

As a special exception, if command is the empty string, then emacsclient starts Emacs in daemon mode (as ‘emacs --daemon’) and then tries connecting again.

The environment variable ALTERNATE_EDITOR has the same effect as the ‘-a’ option. If both are present, the latter takes precedence.

-c
--create-frame

Create a new graphical client frame, instead of using an existing Emacs frame. See below for the special behavior of C-x C-c in a client frame. If Emacs cannot create a new graphical frame (e.g., if it cannot connect to the X server), it tries to create a text terminal client frame, as though you had supplied the ‘-t’ option instead.

On MS-Windows, a single Emacs session cannot display frames on both graphical and text terminals, nor on multiple text terminals. Thus, if the Emacs server is running on a text terminal, the ‘-c’ option, like the ‘-t’ option, creates a new frame in the server’s current text terminal. See How to Start Emacs on MS-Windows.

If you omit a filename argument while supplying the ‘-c’ option, the new frame displays the *scratch* buffer by default. You can customize this behavior with the variable initial-buffer-choice (see Entering Emacs).

-r
--reuse-frame

Create a new graphical client frame if none exists, otherwise use an existing Emacs frame.

-F alist
--frame-parameters=alist

Set the parameters for a newly-created graphical frame (see Frame Parameters).

-d display
--display=display

Tell Emacs to open the given files on the X display display (assuming there is more than one X display available).

-e
--eval

Tell Emacs to evaluate some Emacs Lisp code, instead of visiting some files. When this option is given, the arguments to emacsclient are interpreted as a list of expressions to evaluate, not as a list of files to visit.

-f server-file
--server-file=server-file

Specify a server file (see TCP Emacs server) for connecting to an Emacs server via TCP. Alternatively, you can set the EMACS_SERVER_FILE environment variable to point to the server file. (The command-line option overrides the environment variable.)

An Emacs server usually uses a local socket to listen for connections, but also supports connections over TCP. To connect to a TCP Emacs server, emacsclient needs to read a server file containing the connection details of the Emacs server. The name of this file is specified with this option, either as a file name relative to ~/.emacs.d/server or as an absolute file name. See TCP Emacs server.

-n
--no-wait

Let emacsclient exit immediately, instead of waiting until all server buffers are finished. You can take as long as you like to edit the server buffers within Emacs, and they are not killed when you type C-x # in them.

-w
--timeout=N

Wait for a response from Emacs for N seconds before giving up. If there is no response within that time, emacsclient will display a warning and exit. The default is ‘0’, which means to wait forever.

--parent-id=id

Open an emacsclient frame as a client frame in the parent X window with id id, via the XEmbed protocol. Currently, this option is mainly useful for developers.

-q
--quiet

Do not let emacsclient display messages about waiting for Emacs or connecting to remote server sockets.

-u
--suppress-output

Do not let emacsclient display results returned from the server. Mostly useful in combination with ‘-e’ when the evaluation performed is for side-effect rather than result.

-s server-name
--socket-name=server-name

Connect to the Emacs server named server-name. (This option is not supported on MS-Windows.) The server name is given by the variable server-name on the Emacs server. If this option is omitted, emacsclient connects to the default socket. If you set server-name of the Emacs server to an absolute file name, give the same absolute file name as server-name to this option to instruct emacsclient to connect to that server. You need to use this option if you started Emacs as daemon (see Initial Options) and specified the name for the server started by the daemon.

Alternatively, you can set the EMACS_SOCKET_NAME environment variable to point to the server socket. (The command-line option overrides the environment variable.)

-t
--tty
-nw

Create a new client frame on the current text terminal, instead of using an existing Emacs frame. This behaves just like the ‘-c’ option, described above, except that it creates a text terminal frame (see Text Terminals).

On MS-Windows, ‘-t’ behaves just like ‘-c’ if the Emacs server is using the graphical display, but if the Emacs server is running on a text terminal, it creates a new frame in the current text terminal.

-T tramp-prefix
--tramp-prefix=tramp-prefix

Set the prefix to add to filenames for Emacs to locate files on remote machines (see Remote Files) using TRAMP (see The Tramp Manual in The Tramp Manual). This is mostly useful in combination with using the Emacs server over TCP (see TCP Emacs server). By ssh-forwarding the listening port and making the server-file available on a remote machine, programs on the remote machine can use emacsclient as the value for the EDITOR and similar environment variables, but instead of talking to an Emacs server on the remote machine, the files will be visited in the local Emacs session using TRAMP.

Setting the environment variable EMACSCLIENT_TRAMP has the same effect as using the ‘-T’ option. If both are specified, the command-line option takes precedence.

For example, assume two hosts, ‘local’ and ‘remote’, and that the local Emacs listens on tcp port 12345. Assume further that /home is on a shared file system, so that the server file ~/.emacs.d/server/server is readable on both hosts.

local$ ssh -R12345:localhost:12345 remote
remote$ export EDITOR="emacsclient \
        --server-file=server \
        --tramp=/ssh:remote:"
remote$ $EDITOR /tmp/foo.txt #Should open in local emacs.

The new graphical or text terminal frames created by the ‘-c’ or ‘-t’ options are considered client frames. Any new frame that you create from a client frame is also considered a client frame. If you type C-x C-c (save-buffers-kill-terminal) in a client frame, that command does not kill the Emacs session as it normally does (see Exiting Emacs). Instead, Emacs deletes the client frame; furthermore, if the client frame has an emacsclient waiting to regain control (i.e., if you did not supply the ‘-n’ option), Emacs deletes all other frames of the same client, and marks the client’s server buffers as finished, as though you had typed C-x # in all of them. If it so happens that there are no remaining frames after the client frame(s) are deleted, the Emacs session exits.

As an exception, when Emacs is started as a daemon, all frames are considered client frames, and C-x C-c never kills Emacs. To kill a daemon session, type M-x kill-emacs.

Note that the ‘-t’ and ‘-n’ options are contradictory: ‘-t’ says to take control of the current text terminal to create a new client frame, while ‘-n’ says not to take control of the text terminal. If you supply both options, Emacs visits the specified files(s) in an existing frame rather than a new client frame, negating the effect of ‘-t’.


41 Printing Hard Copies

Emacs provides commands for printing hardcopies of either an entire buffer or part of one. You can invoke the printing commands directly, as detailed below, or using the ‘File’ menu on the menu bar.

Aside from the commands described in this section, you can also print hardcopies from Dired (see Operating on Files) and the diary (see Displaying the Diary). You can also “print” an Emacs buffer to HTML with the command M-x htmlfontify-buffer, which converts the current buffer to a HTML file, replacing Emacs faces with CSS-based markup. Furthermore, Org mode allows you to print Org files to a variety of formats, such as PDF (see Org Mode).

M-x print-buffer

Print hardcopy of current buffer with page headings containing the file name and page number.

M-x lpr-buffer

Print hardcopy of current buffer without page headings.

M-x print-region

Like print-buffer but print only the current region.

M-x lpr-region

Like lpr-buffer but print only the current region.

On most operating systems, the above hardcopy commands submit files for printing by calling the lpr program. To change the printer program, customize the variable lpr-command. To specify extra switches to give the printer program, customize the list variable lpr-switches. Its value should be a list of option strings, each of which should start with ‘-’ (e.g., the option string "-w80" specifies a line width of 80 columns). The default is the empty list, nil.

To specify the printer to use, set the variable printer-name. The default, nil, specifies the default printer. If you set it to a printer name (a string), that name is passed to lpr with the ‘-P’ switch; if you are not using lpr, you should specify the switch with lpr-printer-switch.

The variable lpr-headers-switches similarly specifies the extra switches to use to make page headers. The variable lpr-add-switches controls whether to supply ‘-T’ and ‘-J’ options (suitable for lpr) to the printer program: nil means don’t add them (this should be the value if your printer program is not compatible with lpr).


41.1 PostScript Hardcopy

These commands convert buffer contents to PostScript, either printing it or leaving it in another Emacs buffer.

M-x ps-print-buffer

Print hardcopy of the current buffer in PostScript form.

M-x ps-print-region

Print hardcopy of the current region in PostScript form.

M-x ps-print-buffer-with-faces

Print hardcopy of the current buffer in PostScript form, showing the faces used in the text by means of PostScript features.

M-x ps-print-region-with-faces

Print hardcopy of the current region in PostScript form, showing the faces used in the text.

M-x ps-spool-buffer

Generate and spool a PostScript image for the current buffer text.

M-x ps-spool-region

Generate and spool a PostScript image for the current region.

M-x ps-spool-buffer-with-faces

Generate and spool a PostScript image for the current buffer, showing the faces used.

M-x ps-spool-region-with-faces

Generate and spool a PostScript image for the current region, showing the faces used.

M-x ps-despool

Send the spooled PostScript to the printer.

M-x handwrite

Generate/print PostScript for the current buffer as if handwritten.

The ps-print-buffer and ps-print-region commands print buffer contents in PostScript form. One command prints the entire buffer; the other, just the region. The commands ps-print-buffer-with-faces and ps-print-region-with-faces behave similarly, but use PostScript features to show the faces (fonts and colors) of the buffer text.

Interactively, when you use a prefix argument (C-u), these commands prompt the user for a file name, and save the PostScript image in that file instead of sending it to the printer.

The commands whose names have ‘spool’ instead of ‘print’, generate the PostScript output in an Emacs buffer instead of sending it to the printer.

Use the command ps-despool to send the spooled images to the printer. This command sends the PostScript generated by ‘-spool-’ commands (see commands above) to the printer. With a prefix argument (C-u), it prompts for a file name, and saves the spooled PostScript image in that file instead of sending it to the printer.

M-x handwrite is more frivolous. It generates a PostScript rendition of the current buffer as a cursive handwritten document. It can be customized in group handwrite. This function only supports ISO 8859-1 characters.


41.2 Variables for PostScript Hardcopy

All the PostScript hardcopy commands use the variables ps-lpr-command and ps-lpr-switches to specify how to print the output. ps-lpr-command specifies the command name to run, ps-lpr-switches specifies command line options to use, and ps-printer-name specifies the printer. If you don’t set the first two variables yourself, they take their initial values from lpr-command and lpr-switches. If ps-printer-name is nil, printer-name is used.

The variable ps-print-header controls whether these commands add header lines to each page—set it to nil to turn headers off.

If your printer doesn’t support colors, you should turn off color processing by setting ps-print-color-p to nil. By default, if the display supports colors, Emacs produces hardcopy output with color information; on black-and-white printers, colors are emulated with shades of gray. This might produce barely-readable or even illegible output, even if your screen colors only use shades of gray.

Alternatively, you can set ps-print-color-p to black-white to have colors display better on black/white printers. This works by using information in ps-black-white-faces to express colors by customizable list of shades of gray, augmented by bold and italic face attributes.

By default, PostScript printing ignores the background colors of the faces, unless the variable ps-use-face-background is non-nil. This is to avoid unwanted interference with the zebra stripes and background image/text.

The variable ps-paper-type specifies which size of paper to format for; legitimate values include a4, a3, a4small, b4, b5, executive, ledger, legal, letter, letter-small, statement, tabloid. The default is letter. You can define additional paper sizes by changing the variable ps-page-dimensions-database.

The variable ps-landscape-mode specifies the orientation of printing on the page. The default is nil, which stands for portrait mode. Any non-nil value specifies landscape mode.

The variable ps-number-of-columns specifies the number of columns; it takes effect in both landscape and portrait mode. The default is 1.

The variable ps-font-family specifies which font family to use for printing ordinary text. Legitimate values include Courier, Helvetica, NewCenturySchlbk, Palatino and Times. The variable ps-font-size specifies the size of the font for ordinary text and defaults to 8.5 points. The value of ps-font-size can also be a cons of 2 floats: one for landscape mode, the other for portrait mode.

Emacs supports more scripts and characters than a typical PostScript printer. Thus, some of the characters in your buffer might not be printable using the fonts built into your printer. You can augment the fonts supplied with the printer with those from the GNU Intlfonts package, or you can instruct Emacs to use Intlfonts exclusively. The variable ps-multibyte-buffer controls this: the default value, nil, is appropriate for printing ASCII and Latin-1 characters; a value of non-latin-printer is for printers which have the fonts for ASCII, Latin-1, Japanese, and Korean characters built into them. A value of bdf-font arranges for the BDF fonts from the Intlfonts package to be used for all characters. Finally, a value of bdf-font-except-latin instructs the printer to use built-in fonts for ASCII and Latin-1 characters, and Intlfonts BDF fonts for the rest.

To be able to use the BDF fonts, Emacs needs to know where to find them. The variable bdf-directory-list holds the list of directories where Emacs should look for the fonts; the default value includes a single directory /usr/local/share/emacs/fonts/bdf.

Many other customization variables for these commands are defined and described in the Lisp files ps-print.el and ps-mule.el.


41.3 Printing Package

The basic Emacs facilities for printing hardcopy can be extended using the Printing package. This provides an easy-to-use interface for choosing what to print, previewing PostScript files before printing, and setting various printing options such as print headers, landscape or portrait modes, duplex modes, and so forth. On GNU/Linux or Unix systems, the Printing package relies on the gs and gv utilities, which are distributed as part of the GhostScript program. On MS-Windows, the gstools port of Ghostscript can be used.

To use the Printing package, add (require 'printing) to your init file (see The Emacs Initialization File), followed by (pr-update-menus). This function replaces the usual printing commands in the menu bar with a ‘Printing’ submenu that contains various printing options. You can also type M-x pr-interface RET; this creates a *Printing Interface* buffer, similar to a customization buffer, where you can set the printing options. After selecting what and how to print, you start the print job using the ‘Print’ button (click mouse-2 on it, or move point over it and type RET). For further information on the various options, use the ‘Interface Help’ button.


42 Sorting Text

Emacs provides several commands for sorting text in the buffer. All operate on the contents of the region. They divide the text of the region into many sort records, identify a sort key for each record, and then reorder the records into the order determined by the sort keys. The records are ordered so that their keys are in alphabetical order, or, for numeric sorting, in numeric order. In alphabetic sorting, all upper-case letters ‘A’ through ‘Z’ come before lower-case ‘a’, in accordance with the ASCII character sequence (but sort-fold-case, described below, can change that).

The various sort commands differ in how they divide the text into sort records and in which part of each record is used as the sort key. Most of the commands make each line a separate sort record, but some commands use paragraphs or pages as sort records. Most of the sort commands use each entire sort record as its own sort key, but some use only a portion of the record as the sort key.

M-x sort-lines

Divide the region into lines, and sort by comparing the entire text of a line. A numeric argument means sort into descending order.

M-x sort-paragraphs

Divide the region into paragraphs, and sort by comparing the entire text of a paragraph (except for leading blank lines). A numeric argument means sort into descending order.

M-x sort-pages

Divide the region into pages, and sort by comparing the entire text of a page (except for leading blank lines). A numeric argument means sort into descending order.

M-x sort-fields

Divide the region into lines, and sort by comparing the contents of one field in each line. Fields are defined as separated by whitespace, so the first run of consecutive non-whitespace characters in a line constitutes field 1, the second such run constitutes field 2, etc.

Specify which field to sort by with a numeric argument: 1 to sort by field 1, etc.; the default is 1. A negative argument means count fields from the right instead of from the left; thus, minus 1 means sort by the last field. If several lines have identical contents in the field being sorted, they keep the same relative order that they had in the original buffer.

M-x sort-numeric-fields

Like M-x sort-fields except the specified field is converted to an integer for each line, and the numbers are compared. ‘10’ comes before ‘2’ when considered as text, but after it when considered as a number. By default, numbers are interpreted according to sort-numeric-base, but numbers beginning with ‘0x’ or ‘0’ are interpreted as hexadecimal and octal, respectively.

M-x sort-columns

Like M-x sort-fields except that the text within each line used for comparison comes from a fixed range of columns. With a prefix argument, sort in reverse order. See below for more details on this command.

M-x reverse-region

Reverse the order of the lines in the region. This is useful for sorting into descending order by fields, since those sort commands do not have a feature for doing that.

For example, if the buffer contains this:

On systems where clash detection (locking of files being edited) is
implemented, Emacs also checks the first time you modify a buffer
whether the file has changed on disk since it was last visited or
saved.  If it has, you are asked to confirm that you want to change
the buffer.

applying M-x sort-lines to the entire buffer produces this:

On systems where clash detection (locking of files being edited) is
implemented, Emacs also checks the first time you modify a buffer
saved.  If it has, you are asked to confirm that you want to change
the buffer.
whether the file has changed on disk since it was last visited or

where the upper-case ‘O’ sorts before all lower-case letters. If you use C-u 2 M-x sort-fields instead, you get this:

implemented, Emacs also checks the first time you modify a buffer
saved.  If it has, you are asked to confirm that you want to change
the buffer.
On systems where clash detection (locking of files being edited) is
whether the file has changed on disk since it was last visited or

where the sort keys were ‘Emacs’, ‘If’, ‘buffer’, ‘systems’ and ‘the’.

M-x sort-columns requires more explanation. You specify the columns by putting point at one of the columns and the mark at the other column. Because this means you cannot put point or the mark at the beginning of the first line of the text you want to sort, this command uses an unusual definition of “region”: all of the line point is in is considered part of the region, and so is all of the line the mark is in, as well as all the lines in between.

For example, to sort a table by information found in columns 10 to 15, you could put the mark on column 10 in the first line of the table, and point on column 15 in the last line of the table, and then run sort-columns. Equivalently, you could run it with the mark on column 15 in the first line and point on column 10 in the last line.

This can be thought of as sorting the rectangle specified by point and the mark, except that the text on each line to the left or right of the rectangle moves along with the text inside the rectangle. See Rectangles.

Many of the sort commands ignore case differences when comparing, if sort-fold-case is non-nil.


43 Editing Pictures

To edit a picture made out of text characters (for example, a picture of the division of a register into fields, as a comment in a program), use the command M-x picture-mode to enter Picture mode.

In Picture mode, editing is based on the quarter-plane model of text, according to which the text characters lie studded on an area that stretches infinitely far to the right and downward. The concept of the end of a line does not exist in this model; the most you can say is where the last nonblank character on the line is found.

Of course, Emacs really always considers text as a sequence of characters, and lines really do have ends. But Picture mode replaces the most frequently-used commands with variants that simulate the quarter-plane model of text. They do this by inserting spaces or by converting tabs to spaces.

Most of the basic editing commands of Emacs are redefined by Picture mode to do essentially the same thing but in a quarter-plane way. In addition, Picture mode defines various keys starting with the C-c prefix to run special picture editing commands.

One of these keys, C-c C-c, is particularly important. Often a picture is part of a larger file that is usually edited in some other major mode. Picture mode records the name of the previous major mode so you can use the C-c C-c command (picture-mode-exit) later to go back to that mode. C-c C-c also deletes spaces from the ends of lines, unless given a numeric argument.

The special commands of Picture mode all work in other modes (provided the picture library is loaded), but are not bound to keys except in Picture mode. The descriptions below talk of moving “one column” and so on, but all the picture mode commands handle numeric arguments as their normal equivalents do.

Turning on Picture mode runs the hook picture-mode-hook. Additional extensions to Picture mode can be found in artist.el.


43.1 Basic Editing in Picture Mode

Most keys do the same thing in Picture mode that they usually do, but do it in a quarter-plane style. For example, C-f is rebound to run picture-forward-column, a command which moves point one column to the right, inserting a space if necessary so that the actual end of the line makes no difference. C-b is rebound to run picture-backward-column, which always moves point left one column, converting a tab to multiple spaces if necessary. C-n and C-p are rebound to run picture-move-down and picture-move-up, which can either insert spaces or convert tabs as necessary to make sure that point stays in exactly the same column. C-e runs picture-end-of-line, which moves to after the last nonblank character on the line. C-a runs picture-beginning-of-line. (The choice of screen model does not affect beginnings of lines; the only extra thing this command does is update the current picture column to 0.)

Insertion of text is adapted to the quarter-plane screen model through the use of Overwrite mode (see Minor Modes.) Self-inserting characters replace existing text, column by column, rather than pushing existing text to the right. RET runs picture-newline, which just moves to the beginning of the following line so that new text will replace that line.

In Picture mode, the commands that normally delete or kill text, instead erase text (replacing it with spaces). DEL (picture-backward-clear-column) replaces the preceding character with a space rather than removing it; this moves point backwards. C-d (picture-clear-column) replaces the next character or characters with spaces, but does not move point. (If you want to clear characters to spaces and move forward over them, use SPC.) C-k (picture-clear-line) really kills the contents of lines, but does not delete the newlines from the buffer.

To do actual insertion, you must use special commands. C-o (picture-open-line) creates a blank line after the current line; it never splits a line. C-M-o (split-line) makes sense in Picture mode, so it is not changed. C-j (picture-duplicate-line) inserts another line with the same contents below the current line.

To do actual deletion in Picture mode, use C-w, C-c C-d (which is defined as delete-char, as C-d is in other modes), or one of the picture rectangle commands (see Picture Mode Rectangle Commands).


43.2 Controlling Motion after Insert

Since self-inserting characters in Picture mode overwrite and move point, there is no essential restriction on how point should be moved. Normally point moves right, but you can specify any of the eight orthogonal or diagonal directions for motion after a self-inserting character. This is useful for drawing lines in the buffer.

C-c <
C-c LEFT

Move left after insertion (picture-movement-left).

C-c >
C-c RIGHT

Move right after insertion (picture-movement-right).

C-c ^
C-c UP

Move up after insertion (picture-movement-up).

C-c .
C-c DOWN

Move down after insertion (picture-movement-down).

C-c `
C-c Home

Move up and left (“northwest”) after insertion (picture-movement-nw).

C-c '
C-c PageUp
C-c prior

Move up and right (“northeast”) after insertion (picture-movement-ne).

C-c /
C-c End

Move down and left (“southwest”) after insertion
(picture-movement-sw).

C-c \
C-c PageDown
C-c next

Move down and right (“southeast”) after insertion
(picture-movement-se).

Two motion commands move based on the current Picture insertion direction. The command C-c C-f (picture-motion) moves in the same direction as motion after insertion currently does, while C-c C-b (picture-motion-reverse) moves in the opposite direction.


43.3 Picture Mode Tabs

Two kinds of tab-like action are provided in Picture mode. Use M-TAB (picture-tab-search) for context-based tabbing. With no argument, it moves to a point underneath the next “interesting” character that follows whitespace in the previous nonblank line. “Next” here means “appearing at a horizontal position greater than the one point starts out at”. With prefix argument, as in C-u M-TAB, this command moves to the next such interesting character in the current line. M-TAB does not change the text; it only moves point. “Interesting” characters are defined by the variable picture-tab-chars, which should define a set of characters. The syntax for this variable is like the syntax used inside of ‘[…]’ in a regular expression—but without the ‘[’ and the ‘]’. Its default value is "!-~".

TAB itself runs picture-tab, which operates based on the current tab stop settings; it is the Picture mode equivalent of tab-to-tab-stop. Normally it just moves point, but with a numeric argument it clears the text that it moves over.

The context-based and tab-stop-based forms of tabbing are brought together by the command C-c TAB (picture-set-tab-stops). This command sets the tab stops to the positions which M-TAB would consider significant in the current line. The use of this command, together with TAB, can get the effect of context-based tabbing. But M-TAB is more convenient in the cases where it is sufficient.

It may be convenient to prevent use of actual tab characters in pictures. For example, this prevents C-x TAB from messing up the picture. You can do this by setting the variable indent-tabs-mode to nil.


43.4 Picture Mode Rectangle Commands

Picture mode defines commands for working on rectangular pieces of the text in ways that fit with the quarter-plane model. The standard rectangle commands may also be useful. See Rectangles.

C-c C-k

Clear out the region-rectangle with spaces (picture-clear-rectangle). With a prefix argument, delete the text.

C-c C-w r

Similar, but save rectangle contents in register r first (picture-clear-rectangle-to-register). See Registers.

C-c C-y

Copy last killed rectangle into the buffer by overwriting, with upper left corner at point (picture-yank-rectangle). With argument, insert instead.

C-c C-x r

Similar, but use the rectangle in register r (picture-yank-rectangle-from-register).

The picture rectangle commands C-c C-k (picture-clear-rectangle) and C-c C-w (picture-clear-rectangle-to-register) differ from the standard rectangle commands in that they normally clear the rectangle instead of deleting it; this is analogous with the way C-d is changed in Picture mode.

However, deletion of rectangles can be useful in Picture mode, so these commands delete the rectangle if given a numeric argument. C-c C-k either with or without a numeric argument saves the rectangle for C-c C-y.

The Picture mode commands for yanking rectangles differ from the standard ones in that they overwrite instead of inserting. This is the same way that Picture mode insertion of other text differs from other modes. C-c C-y (picture-yank-rectangle) inserts (by overwriting) the rectangle that was most recently killed, while C-c C-x (picture-yank-rectangle-from-register) does likewise for the rectangle found in a specified register.


44 Editing Binary Files

There is a special major mode for editing binary files: Hexl mode. To use it, use M-x hexl-find-file instead of C-x C-f to visit the file. This command converts the file’s contents to hexadecimal and lets you edit the translation. When you save the file, it is converted automatically back to binary.

You can also use M-x hexl-mode to translate an existing buffer into hex. This is useful if you visit a file normally and then discover it is a binary file.

Inserting text always overwrites in Hexl mode. This is to reduce the risk of accidentally spoiling the alignment of data in the file. Ordinary text characters insert themselves (i.e., overwrite with themselves). There are commands for insertion of special characters by their code. Most cursor motion keys, as well as C-x C-s, are bound in Hexl mode to commands that produce the same effect. Here is a list of other important commands special to Hexl mode:

C-M-d

Insert a byte with a code typed in decimal.

C-M-o

Insert a byte with a code typed in octal.

C-M-x

Insert a byte with a code typed in hex.

C-M-a

Move to the beginning of a 512-byte page.

C-M-e

Move to the end of a 512-byte page.

C-x [

Move to the beginning of a 1k-byte page.

C-x ]

Move to the end of a 1k-byte page.

M-g

Move to an address specified in hex.

M-j

Move to an address specified in decimal.

C-c C-c

Leave Hexl mode, going back to the major mode this buffer had before you invoked hexl-mode.

Other Hexl commands let you insert strings (sequences) of binary bytes, move by shorts or ints, etc.; type C-h a hexl- TAB for details.

Hexl mode can also be used for editing text files. This could come in handy if the text file includes unusual characters or uses unusual encoding (see Coding Systems). For this purpose, Hexl commands that insert bytes can also insert ASCII and non-ASCII characters, including multibyte characters. To edit a text file with Hexl, visit the file as usual, and then type M-x hexl-mode RET to switch to Hexl mode. You can now insert text characters by typing them. However, inserting multibyte characters requires special care, to avoid the danger of creating invalid multibyte sequences: you should start typing such characters when point is on the first byte of a multibyte sequence in the file.


45 Saving Emacs Sessions

You can use the desktop library to save the state of Emacs from one session to another. The saved Emacs desktop configuration includes the buffers, their file names, major modes, buffer positions, window and frame configuration, and some important global variables.

To enable this feature, use the Customization buffer (see Easy Customization Interface) to set desktop-save-mode to t for future sessions, or add this line in your init file (see The Emacs Initialization File):

(desktop-save-mode 1)

If you turn on desktop-save-mode in your init file, then when Emacs starts, it looks for a saved desktop in desktop-path (which defaults to user-emacs-directory and then your home directory) and uses the first desktop it finds. While Emacs runs with desktop-save-mode turned on, it by default auto-saves the desktop whenever any of the desktop configuration changes. The variable desktop-auto-save-timeout determines how frequently Emacs checks for modifications to your desktop. The desktop is also saved when you exit Emacs.

Specify the option ‘--no-desktop’ on the Emacs command line when you don’t want it to reload any saved desktop configurations. This turns off desktop-save-mode for the current session. Starting Emacs with the ‘--no-init-file’ option also disables desktop reloading, since it bypasses the init file, where desktop-save-mode is usually turned on.

You can have separate saved desktop configurations in different directories; starting Emacs from a directory where you have a saved desktop configuration will restore that configuration, provided that you customize desktop-path to prepend . (the current directory) to the other directories there. You can save the current desktop and reload the one saved in another directory by typing M-x desktop-change-dir. Typing M-x desktop-revert reverts to the previously reloaded desktop.

The file in which Emacs saves the desktop is locked while the session runs, to avoid inadvertently overwriting it from another Emacs session. That lock is normally removed when Emacs exits, but if Emacs or your system crashes, the lock stays, and when you restart Emacs, it will by default ask you whether to use the locked desktop file. You can avoid the question by customizing the variable desktop-load-locked-desktop to either nil, which means never load the desktop in this case, or t, which means load the desktop without asking. You can also customize the variable to the special value check-pid, which means to load the file if the Emacs process that has locked the desktop is not running on the local machine. This should not be used in circumstances where the locking Emacs might still be running on another machine, which could be the case in multi-user environments where your home directory is mounted remotely using NFS or similar.

When Emacs starts in daemon mode, it cannot ask you any questions, so if it finds the desktop file locked, it will not load it, unless desktop-load-locked-desktop is t. Note that restoring the desktop in daemon mode is somewhat problematic for other reasons: e.g., the daemon cannot use GUI features, so parameters such as frame position, size, and decorations cannot be restored. For that reason, you may wish to delay restoring the desktop in daemon mode until the first client connects, by calling desktop-read (see below) in a hook function that you add to server-after-make-frame-hook (see Creating Frames in The Emacs Lisp Reference Manual).

Whenever you want, you can use the command M-x desktop-save to force immediate saving of the current desktop. This is useful either if you do not want to use the automatic desktop restoration, and thus don’t turn on desktop-save-mode, or when you have made significant changes to the desktop, and want to make sure the configuration doesn’t get lost if Emacs or your system crashes. You can use M-x desktop-read to restore a previously-saved desktop if the current Emacs session didn’t load any desktop yet.

By default, the desktop tries to save and restore the frame and window configuration. To disable this, set desktop-restore-frames to nil. (See that variable’s documentation for some related options that you can customize to fine-tune this behavior.)

When the desktop restores the frame and window configuration, it uses the recorded values of frame parameters, disregarding any settings for those parameters you have in your init file (see The Emacs Initialization File). This means that frame parameters such as fonts and faces for the restored frames will come from the desktop file, where they were saved when you exited your previous Emacs session; any settings for those parameters in your init file will be ignored. To disable this, customize the value of frameset-filter-alist to filter out the frame parameters you don’t want to be restored; they will then be set according to your customizations in the init file.

Information about buffers visiting remote files is not saved by default. Customize the variable desktop-files-not-to-save to change this.

By default, all the buffers in the desktop are restored in one go. However, this may be slow if there are a lot of buffers in the desktop. You can specify the maximum number of buffers to restore immediately with the variable desktop-restore-eager; the remaining buffers are restored lazily, when Emacs is idle.

Type M-x desktop-clear to empty the Emacs desktop; this can be useful, for example, if you want to switch to another desktop by invoking M-x desktop-read next. The desktop-clear command kills all buffers except for internal ones, and clears the global variables listed in desktop-globals-to-clear. If you want it to preserve certain buffers, customize the variable desktop-clear-preserve-buffers-regexp, whose value is a regular expression matching the names of buffers not to kill.

If you want to save minibuffer history from one session to another, use the savehist library. You can also save selected minibuffer-history variables as part of desktop-save-mode if you add those variables to the value of desktop-globals-to-save.


46 Recursive Editing Levels

A recursive edit is a situation in which you are using Emacs commands to perform arbitrary editing while in the middle of another Emacs command. For example, when you type C-r inside of a query-replace, you enter a recursive edit in which you can change the current buffer. On exiting from the recursive edit, you go back to the query-replace. See Query Replace.

Exiting the recursive edit means returning to the unfinished command, which continues execution. The command to exit is C-M-c (exit-recursive-edit).

You can also abort the recursive edit. This is like exiting, but also quits the unfinished command immediately. Use the command C-] (abort-recursive-edit) to do this. See Quitting and Aborting.

The mode line shows you when you are in a recursive edit by displaying square brackets around the parentheses that always surround the major and minor mode names. Every window’s mode line shows this in the same way, since being in a recursive edit is true of Emacs as a whole rather than any particular window or buffer.

It is possible to be in recursive edits within recursive edits. For example, after typing C-r in a query-replace, you may type a command that enters the debugger. This begins a recursive editing level for the debugger, within the recursive editing level for C-r. Mode lines display a pair of square brackets for each recursive editing level currently in progress.

Exiting the inner recursive edit (such as with the debugger c command) resumes the command running in the next level up. When that command finishes, you can then use C-M-c to exit another recursive editing level, and so on. Exiting applies to the innermost level only. Aborting also gets out of only one level of recursive edit; it returns immediately to the command level of the previous recursive edit. If you wish, you can then abort the next recursive editing level.

Alternatively, the command M-x top-level aborts all levels of recursive edits, returning immediately to the top-level command reader. It also exits the minibuffer, if it is active.

The text being edited inside the recursive edit need not be the same text that you were editing at top level. It depends on what the recursive edit is for. If the command that invokes the recursive edit selects a different buffer first, that is the buffer you will edit recursively. In any case, you can switch buffers within the recursive edit in the normal manner (as long as the buffer-switching keys have not been rebound). You could probably do all the rest of your editing inside the recursive edit, visiting files and all. But this could have surprising effects (such as stack overflow) from time to time. So remember to exit or abort the recursive edit when you no longer need it.

In general, we try to minimize the use of recursive editing levels in GNU Emacs. This is because they constrain you to go back in a particular order—from the innermost level toward the top level. When possible, we present different activities in separate buffers so that you can switch between them as you please. Some commands switch to a new major mode which provides a command to switch back. These approaches give you more flexibility to go back to unfinished tasks in the order you choose.


47 Hyperlinking and Web Navigation Features

The following subsections describe convenience features for handling URLs and other types of links occurring in Emacs buffer text.


47.1 Web Browsing with EWW

EWW, the Emacs Web Wowser, is a web browser package for Emacs. It allows browsing URLs within an Emacs buffer. The command M-x eww will open a URL or search the web. You can open a file using the command M-x eww-open-file. You can use EWW as the web browser for browse-url, see Following URLs. For full details, see EWW in The Emacs Web Wowser Manual.


47.2 Embedded WebKit Widgets

If Emacs was compiled with the appropriate support packages, it is able to show browser widgets in its buffers. The command M-x xwidget-webkit-browse-url asks for a URL to display in the browser widget. The URL normally defaults to the URL at or before point, but if there is an active region (see The Mark and the Region), the default URL comes from the region instead, after removing any whitespace from it. The command then creates a new buffer with the embedded browser showing the specified URL. The buffer is put in the Xwidget-WebKit mode (similar to Image mode, see Viewing Image Files), which provides one-key commands for scrolling the widget, changing its size, and reloading it. Type C-h b in that buffer to see the key bindings.

By default, typing a self-inserting character inside an xwidget webkit buffer will do nothing, or trigger some special action. To make those characters and other common editing keys insert themselves when pressed, you can enable xwidget-webkit-edit-mode, which redefines them to be passed through to the WebKit xwidget.

You can also enable xwidget-webkit-edit-mode by typing e inside the xwidget webkit buffer.

xwidget-webkit-isearch-mode is a minor mode that behaves similarly to incremental search (see Incremental Search), but operates on the contents of a WebKit widget instead of the current buffer. It is bound to C-s and C-r inside xwidget-webkit buffers. When it is invoked by C-r, the initial search will be performed in reverse direction.

Typing any self-inserting character will cause the character to be inserted into the current search query. Typing C-s will cause the WebKit widget to display the next search result, while typing C-r will cause it to display the previous one.

To leave incremental search, you can type C-g.

The command xwidget-webkit-browse-history displays a buffer containing a list of pages previously loaded by the current WebKit buffer, and lets you navigate to those pages by hitting RET.

It is bound to H.


47.3 Following URLs

M-x browse-url RET url RET

Load a URL into a Web browser.

The Browse-URL package allows you to easily follow URLs from within Emacs. Most URLs are followed by invoking a web browser; ‘mailto:’ URLs are followed by invoking the compose-mail Emacs command to send mail to the specified address (see Sending Mail).

The command M-x browse-url prompts for a URL, and follows it. If point is located near a plausible URL, that URL is offered as the default. The Browse-URL package also provides other commands which you might like to bind to keys, such as browse-url-at-point and browse-url-at-mouse.

You can customize Browse-URL’s behavior via various options in the browse-url Customize group. In particular, the option browse-url-mailto-function lets you define how to follow ‘mailto:’ URLs, while browse-url-browser-function specifies your default browser.

You can define that certain URLs are browsed with other functions by customizing browse-url-handlers, an alist of regular expressions or predicates paired with functions to browse matching URLs.

For more information, view the package commentary by typing C-h P browse-url RET.

Emacs also has a minor mode that has some support for handling URLs as if they were files. url-handler-mode is a global minor mode that affects most of the Emacs commands and primitives that deal with file names. After switching on this mode, you can say, for instance, C-x C-f https://www.gnu.org/ RET to see the HTML for that web page, and you can then edit it and save it to a local file, for instance.


47.4 Activating URLs

M-x goto-address-mode

Activate URLs and e-mail addresses in the current buffer.

M-x global-goto-address-mode

Activate goto-address-mode in all buffers.

You can make Emacs mark out URLs specially in the current buffer, by typing M-x goto-address-mode. When this buffer-local minor mode is enabled, it finds all the URLs in the buffer, highlights them, and turns them into clickable buttons. You can follow the URL by typing C-c RET (goto-address-at-point) while point is on its text; or by clicking with mouse-2, or by clicking mouse-1 quickly (see Following References with the Mouse). Following a URL is done by calling browse-url as a subroutine (see Following URLs).

It can be useful to add goto-address-mode to mode hooks and hooks for displaying an incoming message (e.g., rmail-show-message-hook for Rmail). This is not needed for Gnus or MH-E, which have similar features of their own.


47.5 Finding Files and URLs at Point

The FFAP package replaces certain key bindings for finding files, such as C-x C-f, with commands that provide more sensible defaults. These commands behave like the ordinary ones when given a prefix argument. Otherwise, they get the default file name or URL from the text around point. If what is found in the buffer has the form of a URL rather than a file name, the commands use browse-url to view it (see Following URLs).

This feature is useful for following references in mail or news buffers, README files, MANIFEST files, and so on. For more information, view the package commentary by typing C-h P ffap RET.

To enable FFAP, type M-x ffap-bindings. This makes the following key bindings, and also installs hooks for additional FFAP functionality in Rmail, Gnus and VM article buffers.

C-x C-f filename RET

Find filename, guessing a default from text around point (find-file-at-point).

C-x C-r filename RET

ffap-read-only, analogous to find-file-read-only.

C-x C-v filename RET

ffap-alternate-file, analogous to find-alternate-file.

C-x d directory RET

Start Dired on directory, defaulting to the directory at point (dired-at-point).

C-x C-d directory RET

ffap-list-directory, analogous to list-directory.

C-x 4 f filename RET

ffap-other-window, analogous to find-file-other-window.

C-x 4 r filename RET

ffap-read-only-other-window, analogous to find-file-read-only-other-window.

C-x 4 d directory RET

ffap-dired-other-window, like dired-other-window.

C-x 5 f filename RET

ffap-other-frame, analogous to find-file-other-frame.

C-x 5 r filename RET

ffap-read-only-other-frame, analogous to find-file-read-only-other-frame.

C-x 5 d directory RET

ffap-dired-other-frame, analogous to dired-other-frame.

C-x t C-f filename return

ffap-other-tab, analogous to find-file-other-tab.

C-x t C-r filename return

ffap-read-only-other-tab, analogous to find-file-read-only-other-tab.

M-x ffap-next

Search buffer for next file name or URL, then find that file or URL.

S-mouse-3

ffap-at-mouse finds the file guessed from text around the position of a mouse click.

C-S-mouse-3

Display a menu of files and URLs mentioned in current buffer, then find the one you select (ffap-menu).


48 Games and Other Amusements

The animate package makes text dance (e.g., M-x animate-birthday-present).

M-x blackbox, M-x mpuz and M-x 5x5 are puzzles. blackbox challenges you to determine the location of objects inside a box by tomography. mpuz displays a multiplication puzzle with letters standing for digits in a code that you must guess—to guess a value, type a letter and then the digit you think it stands for. The aim of 5x5 is to fill in all the squares.

M-x bubbles is a game in which the object is to remove as many bubbles as you can in the smallest number of moves.

M-x decipher helps you to cryptanalyze a buffer which is encrypted in a simple monoalphabetic substitution cipher.

M-x dissociated-press scrambles the text in the current Emacs buffer, word by word or character by character, writing its output to a buffer named *Dissociation*. A positive argument tells it to operate character by character, and specifies the number of overlap characters. A negative argument tells it to operate word by word, and specifies the number of overlap words. Dissociated Press produces results fairly like those of a Markov chain, but is however, an independent, ignoriginal invention; it techniquitously copies several consecutive characters from the sample text between random jumps, unlike a Markov chain which would jump randomly after each word or character. Keep dissociwords out of your documentation, if you want it to be well userenced and properbose.

M-x dunnet runs a text-based adventure game.

If you want a little more personal involvement, try M-x gomoku, which plays the game Go Moku with you.

If you are a little bit bored, you can try M-x hanoi. If you are considerably bored, give it a numeric argument. If you are very, very bored, try an argument of 9. Sit back and watch.

M-x life runs Conway’s Game of Life cellular automaton.

M-x morse-region converts the text in the region to Morse code; M-x unmorse-region converts it back. M-x nato-region converts the text in the region to NATO phonetic alphabet; M-x denato-region converts it back.

M-x pong, M-x snake and M-x tetris are implementations of the well-known Pong, Snake and Tetris games.

M-x solitaire plays a game of solitaire in which you jump pegs across other pegs.

The command M-x zone plays games with the display when Emacs is idle.

“Real Programmers” deploy M-x butterfly, which uses butterflies to flip a bit on the drive platter, see https://xkcd.com/378.

Finally, if you find yourself frustrated, try describing your problems to the famous psychotherapist Eliza. Just do M-x doctor. End each input by typing RET twice.


49 Emacs Lisp Packages

Emacs is extended by implementing additional features in packages, which are Emacs Lisp libraries. These could be written by you or provided by someone else. If you want to install such a package so it is available in your future Emacs session, you need to compile it and put it in a directory where Emacs looks for Lisp libraries. See Libraries of Lisp Code for Emacs, for more details about this manual installation method. Many packages provide installation and usage instructions in the large commentary near the beginning of the Lisp file; you can use those instructions for installing and fine-tuning your use of the package.

Packages can also be provided by package archives, which are large collections of Emacs Lisp packages. Each package is a separate Emacs Lisp program, sometimes including other components such as an Info manual. Emacs includes a facility that lets you easily download and install packages from such archives. The rest of this chapter describes this facility.

To list the packages available for installation from package archives, type M-x list-packages RET. It brings up a buffer named *Packages* with a list of all packages. You can install or uninstall packages via this buffer. See The Package Menu Buffer.

The command C-h P (describe-package) prompts for the name of a package, and displays a help buffer describing the attributes of the package and the features that it implements.

By default, Emacs downloads packages from a package archive maintained by the Emacs developers and hosted by the GNU project. Optionally, you can also download packages from archives maintained by third parties. See Package Installation.

For information about turning an Emacs Lisp program into an installable package, See Packaging in The Emacs Lisp Reference Manual.


49.1 The Package Menu Buffer

The command M-x list-packages brings up the package menu. This is a buffer listing all the packages that Emacs knows about, one on each line, with the following information:

  • The package name (e.g., ‘auctex’).
  • The package’s version number (e.g., ‘11.86’).
  • The package’s status—normally one of ‘available’ (can be downloaded from the package archive), ‘installed’, or ‘built-in’ (included in Emacs by default). See Package Statuses.
  • Which package archive this package is from, if you have more than one package archive enabled.
  • A short description of the package.

The list-packages command accesses the network, to retrieve the list of available packages from package archive servers. If the network is unavailable, it falls back on the most recently retrieved list.

The main command to use in the package list buffer is the x command. If the package under point isn’t installed already, this command will install it. If the package under point is already installed, this command will delete it.

The following commands are available in the package menu:

h

Print a short message summarizing how to use the package menu (package-menu-quick-help).

?
RET

Display a help buffer for the package on the current line (package-menu-describe-package), similar to the help window displayed by the C-h P command (see Emacs Lisp Packages).

i

Mark the package on the current line for installation (package-menu-mark-install). If the package status is ‘available’, this adds an ‘I’ character to the start of the line; typing x (see below) will download and install the package.

d

Mark the package on the current line for deletion (package-menu-mark-delete). If the package status is ‘installed’, this adds a ‘D’ character to the start of the line; typing x (see below) will delete the package. See Package Files and Directory Layout, for information about what package deletion entails.

w

Open the package website on the current line in a browser (package-browse-url). browse-url is used to open the browser.

~

Mark all obsolete packages for deletion (package-menu-mark-obsolete-for-deletion). This marks for deletion all the packages whose status is ‘obsolete’.

u
DEL

Remove any installation or deletion mark previously added to the current line by an i or d command (package-menu-mark-unmark).

U

Mark all package with a newer available version for upgrading (package-menu-mark-upgrades). This places an installation mark on the new available versions, and a deletion mark on the old installed versions (marked with status ‘obsolete’). By default, this won’t mark built-in packages for which a newer version is available, but customizing package-install-upgrade-built-in can change that. See Package Installation. If you customize package-install-upgrade-built-in to a non-nil value, be sure to review all the built-in packages the U command marks, to avoid updating built-in packages you don’t want to overwrite.

x

Download and install all packages marked with i, and their dependencies; also, delete all packages marked with d (package-menu-execute). This also removes the marks. If no packages are marked, this command will install the package under point (if it isn’t installed already), or delete the package under point (if it’s already installed).

g
r

Refresh the package list (revert-buffer). This fetches the list of available packages from the package archive again, and redisplays the package list.

H

Hide packages whose names match a regexp (package-menu-hide-package). This prompts for a regexp, and then hides the packages with matching names. The default value of the regexp will hide only the package whose name is at point, so just pressing RET to the prompt will hide the current package.

(

Toggle visibility of old versions of packages and also of versions from lower-priority archives (package-menu-toggle-hiding).

/ a

Filter package list by archive (package-menu-filter-by-archive). This prompts for a package archive (e.g., ‘gnu’), then shows only packages from that archive. You can specify several archives by typing their names separated by commas.

/ d

Filter package list by description (package-menu-filter-by-description). This prompts for a regular expression, then shows only packages with descriptions matching that regexp.

/ k

Filter package list by keyword (package-menu-filter-by-keyword). This prompts for a keyword (e.g., ‘games’), then shows only packages with that keyword. You can specify several keywords by typing them separated by commas.

/ N

Filter package list by name or description (package-menu-filter-by-name-or-description). This prompts for a regular expression, then shows only packages with a name or description matching that regexp.

/ n

Filter package list by name (package-menu-filter-by-name). This prompts for a regular expression, then shows only packages with names matching that regexp.

/ s

Filter package list by status (package-menu-filter-by-status). This prompts for one or more statuses (e.g., ‘available’, see Package Statuses), then shows only packages with matching status. You can specify several status values by typing them separated by commas.

/ v

Filter package list by version (package-menu-filter-by-version). This prompts first for one of the comparison symbols ‘<’, ‘>’ or ‘=’ and for a version string, and then shows packages whose versions are correspondingly lower, equal or higher than the version you typed.

/ m

Filter package list by non-empty mark (package-menu-filter-marked). This shows only the packages that have been marked to be installed or deleted.

/ u

Filter package list to show only packages for which there are available upgrades (package-menu-filter-upgradable). By default, this filter excludes the built-in packages for which a newer version is available, but customizing package-install-upgrade-built-in can change that. See Package Installation.

/ /

Clear filter currently applied to the package list (package-menu-filter-clear).

For example, you can install a package by typing i on the line listing that package, followed by x.


49.2 Package Statuses

A package can have one of the following statuses:

available

The package is not installed, but can be downloaded and installed from the package archive.

avail-obso

The package is available for installation, but a newer version is also available. Packages with this status are hidden by default.

built-in

The package is included in Emacs by default. It cannot be deleted through the package menu, and by default is not considered for upgrading (but you can change that by customizing package-install-upgrade-built-in, see Package Installation).

dependency

The package was installed automatically to satisfy a dependency of another package.

disabled

The package has been disabled using the package-load-list variable.

external

The package is not built-in and not from the directory specified by package-user-dir (see Package Files and Directory Layout). External packages are treated much like ‘built-in’ packages and cannot be deleted.

held

The package is held, See Package Installation.

incompat

The package cannot be installed for some reason, for example because it depends on uninstallable packages.

installed

The package is installed.

new

Equivalent to ‘available’, except that the package became newly available on the package archive after your last invocation of M-x list-packages.

obsolete

The package is an outdated installed version; in addition to this version of the package, a newer version is also installed.


49.3 Package Installation

Packages are most conveniently installed using the package menu (see The Package Menu Buffer), but you can also use the command M-x package-install. This prompts for the name of a package with the ‘available’ status, then downloads and installs it. Similarly, if you want to upgrade a package, you can use the M-x package-upgrade command, and if you want to upgrade all the packages, you can use the M-x package-upgrade-all command.

By default, package-install doesn’t consider built-in packages for which new versions are available from the archives. (A package is built-in if it is included in the Emacs distribution.) In particular, it will not show built-in packages in the list of completion candidates when you type at its prompt. But if you invoke package-install with a prefix argument, it will also consider built-in packages that can be upgraded. You can make this behavior the default by customizing the variable package-install-upgrade-built-in: if its value is non-nil, package-install will consider built-in packages even when invoked without a prefix argument. Note that the package-menu commands (see The Package Menu Buffer) are also affected by package-install-upgrade-built-in.

By contrast, package-upgrade and package-upgrade-all never consider built-in packages. If you want to use these commands for upgrading some built-in packages, you need to upgrade each of those packages, once, either via C-u M-x package-install RET, or by customizing package-install-upgrade-built-in to a non-nil value, and then upgrading the package once via the package menu or by package-install.

If you customize package-install-upgrade-built-in to a non-nil value, be very careful when using commands that update many packages at once, like package-upgrade-all and U in the package menu: those might overwrite built-in packages that you didn’t intent to replace with newer versions from the archives. Don’t use these bulk commands if you want to update only a small number of built-in packages.

A package may require certain other packages to be installed, because it relies on functionality provided by them. When Emacs installs such a package, it also automatically downloads and installs any required package that is not already installed. (If a required package is somehow unavailable, Emacs signals an error and stops installation.) A package’s requirements list is shown in its help buffer.

By default, packages are downloaded from a single package archive maintained by the Emacs developers. This is controlled by the variable package-archives, whose value is a list of package archives known to Emacs. Each list element must have the form (id . location), where id is the name of a package archive and location is the URL or name of the package archive directory. You can alter this list if you wish to use third party package archives—but do so at your own risk, and use only third parties that you think you can trust!

The maintainers of package archives can increase the trust that you can have in their packages by signing them. They generate a private/public pair of cryptographic keys, and use the private key to create a signature file for each package. With the public key, you can use the signature files to verify the package creator and make sure the package has not been tampered with. Signature verification uses the GnuPG package via the EasyPG interface (see EasyPG in Emacs EasyPG Assistant Manual). A valid signature is not a cast-iron guarantee that a package is not malicious, so you should still exercise caution. Package archives should provide instructions on how you can obtain their public key. One way is to download the key from a server such as https://pgp.mit.edu/. Use M-x package-import-keyring to import the key into Emacs. Emacs stores package keys in the directory specified by the variable package-gnupghome-dir, by default in the gnupg subdirectory of package-user-dir, which causes Emacs to invoke GnuPG with the option ‘--homedir’ when verifying signatures. If package-gnupghome-dir is nil, GnuPG’s option ‘--homedir’ is omitted. The public key for the GNU package archive is distributed with Emacs, in the etc/package-keyring.gpg. Emacs uses it automatically.

If the user option package-check-signature is non-nil, Emacs attempts to verify signatures when you install packages. If the option has the value allow-unsigned, and a usable OpenPGP configuration is found, signed packages will be checked, but you can still install a package that is not signed. If you use some archives that do not sign their packages, you can add them to the list package-unsigned-archives. (If the value is allow-unsigned and no usable OpenPGP is found, this option is treated as if its value was nil.) If the value is t, at least one signature must be valid; if the value is all, all of them must be valid.

For more information on cryptographic keys and signing, see GnuPG in The GNU Privacy Guard Manual. Emacs comes with an interface to GNU Privacy Guard, see EasyPG in Emacs EasyPG Assistant Manual.

If you have more than one package archive enabled, and some of them offer different versions of the same package, you may find the option package-pinned-packages useful. You can add package/archive pairs to this list, to ensure that the specified package is only ever downloaded from the specified archive.

Another option that is useful when you have several package archives enabled is package-archive-priorities. It specifies the priority of each archive (higher numbers specify higher priority archives). By default, archives have the priority of zero, unless specified otherwise by this option’s value. Packages from lower-priority archives will not be shown in the menu, if the same package is available from a higher-priority archive. (This is controlled by the value of package-menu-hide-low-priority.)

Once a package is downloaded, byte-compiled and installed, it is made available to the current Emacs session. Making a package available adds its directory to load-path and loads its autoloads. The effect of a package’s autoloads varies from package to package. Most packages just make some new commands available, while others have more wide-ranging effects on the Emacs session. For such information, consult the package’s help buffer.

Installed packages are automatically made available by Emacs in all subsequent sessions. This happens at startup, before processing the init file but after processing the early init file (see The Early Init File). As an exception, Emacs does not make packages available at startup if invoked with the ‘-q’ or ‘--no-init-file’ options (see Initial Options).

To keep Emacs from automatically making packages available at startup, change the variable package-enable-at-startup to nil. You must do this in the early init file, as the variable is read before loading the regular init file. Currently this variable cannot be set via Customize.

If you have many packages installed, you can improve startup times by setting the user option package-quickstart to t. Setting this option will make Emacs precompute many things instead of re-computing them on every Emacs startup. However, if you do this, then you have to manually run the command package-quickstart-refresh when the activations need to be changed, such as when you change the value of package-load-list.

If you have set package-enable-at-startup to nil, you can still make packages available either during or after startup. To make installed packages available during startup, call the function package-activate-all in your init file. To make installed packages available after startup, invoke the command M-: (package-activate-all) RET.

For finer control over which packages are made available at startup, you can use the variable package-load-list. Its value should be a list. A list element of the form (name version) tells Emacs to make available version version of the package named name. Here, version should be a version string (corresponding to a specific version of the package), or t (which means to make available any installed version), or nil (which means no version; this disables the package, preventing it from being made available). A list element can also be the symbol all, which means to make available the latest installed version of any package not named by the other list elements. The default value is just '(all).

For example, if you set package-load-list to '((muse "3.20") all), then Emacs only makes available version 3.20 of the ‘muse’ package, plus any installed version of packages other than ‘muse’. Any other version of ‘muse’ that happens to be installed will be ignored. The ‘muse’ package will be listed in the package menu with the ‘held’ status.

Emacs byte code is quite stable, but it’s possible for byte code to become outdated, or for the compiled files to rely on macros that have changed in new versions of Emacs. You can use the command M-x package-recompile to recompile a particular package, or M-x package-recompile-all to recompile all the packages. (The latter command might take quite a while to run if you have many installed packages.)


49.4 Package Files and Directory Layout

Each package is downloaded from the package archive in the form of a single package file—either an Emacs Lisp source file, or a tar file containing multiple Emacs Lisp source and other files. Package files are automatically retrieved, processed, and disposed of by the Emacs commands that install packages. Normally, you will not need to deal directly with them, unless you are making a package (see Packaging in The Emacs Lisp Reference Manual). Should you ever need to install a package directly from a package file, use the command M-x package-install-file.

Once installed, the contents of a package are placed in a subdirectory of ~/.emacs.d/elpa/ (you can change the name of that directory by changing the variable package-user-dir). The package subdirectory is named name-version, where name is the package name and version is its version string.

In addition to package-user-dir, Emacs looks for installed packages in the directories listed in package-directory-list. These directories are meant for system administrators to make Emacs packages available system-wide; Emacs itself never installs packages there. The package subdirectories for package-directory-list are laid out in the same way as in package-user-dir.

Deleting a package (see The Package Menu Buffer) involves deleting the corresponding package subdirectory. This only works for packages installed in package-user-dir; if told to act on a package in a system-wide package directory, the deletion command signals an error.


49.5 Fetching Package Sources

By default package-install downloads a Tarball from a package archive and installs its files. This might be inadequate if you wish to hack on the package sources and share your changes with others. In that case, you may prefer to directly fetch and work on the upstream source. This often makes it easier to develop patches and report bugs.

One way to do this is to use package-vc-install, to fetch the source code for a package directly from source. The command will also automatically ensure that all files are byte-compiled and auto-loaded, just like with a regular package. Packages installed this way behave just like any other package. You can upgrade them using package-upgrade or package-upgrade-all and delete them again using package-delete. They are even displayed in the regular package listing. If you just wish to clone the source of a package, without adding it to the package list, use package-vc-checkout.

With the source checkout, you might want to reproduce a bug against the current development head or implement a new feature to scratch an itch. If the package metadata indicates how to contact the maintainer, you can use the command package-report-bug to report a bug via Email. This report will include all the user options that you have customized. If you have made a change you wish to share with the maintainers, first commit your changes then use the command package-vc-prepare-patch to share it. See Preparing Patches.

If you maintain your own packages you might want to use a local checkout instead of cloning a remote repository. You can do this by using package-vc-install-from-checkout, which creates a symbolic link from the package directory (see Package Files and Directory Layout) to your checkout and initializes the code. Note that you might have to use package-vc-rebuild to repeat the initialization and update the autoloads.

49.5.1 Specifying Package Sources

To install a package from source, Emacs must know where to get the package’s source code (such as a code repository) and basic information about the structure of the code (such as the main file in a multi-file package). A package specification describes these properties.

When supported by a package archive (see Package Archives in The Emacs Lisp Reference Manual), Emacs can automatically download a package’s specification from said archive. If the first argument passed to package-vc-install is a symbol naming a package, then Emacs will use the specification provided by the archive for that package.

;; Emacs will download BBDB's specification from GNU ELPA:
(package-vc-install 'bbdb)

The first argument to package-vc-install may also be a package specification. This allows you to install source packages from locations other than the known archives listed in the user option package-archives. A package specification is a list of the form (name . spec), in which spec should be a property list using any of the keys in the table below.

For definitions of basic terms for working with code repositories and version control systems, see VCS Concepts in The GNU Emacs Manual.

:url

A string providing the URL that specifies the repository from which to fetch the package’s source code.

:branch

A string providing the revision of the code to install. Do not confuse this with a package’s version number.

:lisp-dir

A string providing the repository-relative name of the directory to use for loading the Lisp sources, which defaults to the root directory of the repository.

:main-file

A string providing the main file of the project, from which to gather package metadata. If not given, the default is the package name with ".el" appended to it.

:doc

A string providing the repository-relative name of the documentation file from which to build an Info file. This can be a Texinfo file or an Org file.

:vc-backend

A symbol naming the VC backend to use for downloading a copy of the package’s repository (see Version Control Systems in The GNU Emacs Manual). If omitted, Emacs will attempt to make a guess based on the provided URL, or, failing that, the process will fall back onto the value of package-vc-default-backend.

;; Specifying information manually:
(package-vc-install
  '(bbdb :url "https://git.savannah.nongnu.org/git/bbdb.git"
         :lisp-dir "lisp"
         :doc "doc/bbdb.texi"))

50 Customization

This chapter describes some simple methods to customize the behavior of Emacs.

Apart from the methods described here, see X Options and Resources for information about using X resources to customize Emacs, and see Keyboard Macros for information about recording and replaying keyboard macros. Making more far-reaching and open-ended changes involves writing Emacs Lisp code; see Emacs Lisp in The Emacs Lisp Reference Manual.


50.1 Easy Customization Interface

Emacs has many settings which you can change. Most settings are customizable variables (see Variables), which are also called user options. There is a huge number of customizable variables, controlling numerous aspects of Emacs behavior; the variables documented in this manual are listed in Variable Index. A separate class of settings are the faces, which determine the fonts, colors, and other attributes of text (see Text Faces).

To browse and alter settings (both variables and faces), type M-x customize. This creates a customization buffer, which lets you navigate through a logically organized list of settings, edit and set their values, and save them permanently.


50.1.1 Customization Groups

Customization settings are organized into customization groups. These groups are collected into bigger groups, all the way up to a master group called Emacs.

M-x customize creates a customization buffer that shows the top-level Emacs group. It looks like this, in part:

For help using this buffer, see [Easy Customization] in the [Emacs manual].

________________________________________ [ Search ]

 Operate on all settings in this buffer:
 [ Revert... ] [ Apply ] [ Apply and Save ]


Emacs group: Customization of the One True Editor.
      [State]: visible group members are all at standard values.
      See also [Manual].

[Editing]      Basic text editing facilities.
[Convenience]  Convenience features for faster editing.

...more second-level groups...

The main part of this buffer shows the ‘Emacs’ customization group, which contains several other groups (‘Editing’, ‘Convenience’, etc.). The contents of those groups are not listed here, only one line of documentation each.

The state of the group indicates whether setting in that group has been edited, set, or saved. See Changing a Variable.

Most of the customization buffer is read-only, but it includes some editable fields that you can edit. For example, at the top of the customization buffer is an editable field for searching for settings (see Browsing and Searching for Settings). There are also buttons and links, which you can activate by either clicking with the mouse, or moving point there and typing RET. For example, the group names like ‘[Editing]’ are links; activating one of these links brings up the customization buffer for that group.

In the customization buffer, you can type TAB (widget-forward) to move forward to the next button or editable field. S-TAB (widget-backward) moves back to the previous button or editable field.


50.1.2 Browsing and Searching for Settings

From the top-level customization buffer created by M-x customize, you can follow the links to the subgroups of the ‘Emacs’ customization group. These subgroups may contain settings for you to customize; they may also contain further subgroups, dealing with yet more specialized subsystems of Emacs. As you navigate the hierarchy of customization groups, you should find some settings that you want to customize.

If you are interested in customizing a particular setting or customization group, you can go straight there with the commands M-x customize-option, M-x customize-face, or M-x customize-group. See Customizing Specific Items.

If you don’t know exactly what groups or settings you want to customize, you can search for them using the editable search field at the top of each customization buffer. Here, you can type in a search term—either one or more words separated by spaces, or a regular expression (see Syntax of Regular Expressions). Then type RET in the field, or activate the ‘Search’ button next to it, to switch to a customization buffer containing groups and settings that match those terms. Note, however, that this feature only finds groups and settings that are loaded in the current Emacs session.

If you don’t want customization buffers to show the search field, change the variable custom-search-field to nil.

The command M-x customize-apropos is similar to using the search field, except that it reads the search term(s) using the minibuffer. See Customizing Specific Items.

M-x customize-browse is another way to browse the available settings. This command creates a special customization buffer, which shows only the names of groups and settings, in a structured layout. You can show the contents of a group, in the same buffer, by invoking the ‘[+]’ button next to the group name. When the group contents are shown, the button changes to ‘[-]’; invoking that hides the group contents again. Each group or setting in this buffer has a link which says ‘[Group]’, ‘[Option]’ or ‘[Face]’. Invoking this link creates an ordinary customization buffer showing just that group, option, or face; this is the way to change settings that you find with M-x customize-browse.


50.1.3 Changing a Variable

Here is an example of what a variable, or user option, looks like in the customization buffer:

[Hide] Kill Ring Max: Integer (positive or zero): 120
   [State]: STANDARD.
   Maximum length of kill ring before oldest elements are thrown away.

The first line shows that the variable is named kill-ring-max, formatted as ‘Kill Ring Max’ for easier viewing, and also shows its expected type: a positive integer or zero. The default value is ‘120’. The button labeled ‘[Hide]’, if activated, hides the variable’s value and state; this is useful to avoid cluttering up the customization buffer with very long values (for this reason, variables that have very long values may start out hidden). If you use the ‘[Hide]’ button, it changes to ‘[Show Value]’, which you can activate to reveal the value and state. On a graphical display, the ‘[Hide]’ and ‘[Show Value]’ buttons are replaced with graphical triangles pointing downwards and rightwards respectively.

The line after the variable name indicates the customization state of the variable: in this example, ‘STANDARD’ means you have not changed the variable, so its value is the default one. The ‘[State]’ button gives a menu of operations for customizing the variable.

Below the customization state is the documentation for the variable. This is the same documentation that would be shown by the C-h v command (see Examining and Setting Variables). If the documentation is more than one line long, only one line may be shown. If so, that line ends with a ‘[More]’ button; activate this to see the full documentation.

To enter a new value for ‘Kill Ring Max’, just move point to the value and edit it. For example, type M-d to delete the ‘60’ and type in another number. As you begin to alter the text, the ‘[State]’ line will change:

[State]: EDITED, shown value does not take effect until you
         set or save it.

Editing the value does not make it take effect right away. To do that, you must set the variable by activating the ‘[State]’ button and choosing ‘Set for Current Session’. Then the variable’s state becomes:

[State]: SET for current session only.

You don’t have to worry about specifying a value that is not valid; the ‘Set for Current Session’ operation checks for validity and will not install an unacceptable value.

While editing certain kinds of values, such as file names, directory names, and Emacs command names, you can perform completion with C-M-i (widget-complete), or the equivalent keys M-TAB or ESC TAB. This behaves much like minibuffer completion (see Completion).

Typing RET on an editable value field moves point forward to the next field or button, like TAB. You can thus type RET when you are finished editing a field, to move on to the next button or field. To insert a newline within an editable field, use C-o or C-q C-j.

For some variables, there is only a fixed set of legitimate values, and you are not allowed to edit the value directly. Instead, a ‘[Value Menu]’ button appears before the value; activating this button presents a choice of values. For a boolean “on or off” value, the button says ‘[Toggle]’, and flips the value. After using the ‘[Value Menu]’ or ‘[Toggle]’ button, you must again set the variable to make the chosen value take effect.

Some variables have values with complex structure. For example, the value of minibuffer-frame-alist is an association list. Here is how it appears in the customization buffer:

[Hide] Minibuffer Frame Alist:
[INS] [DEL] Parameter: width
            Value: 80
[INS] [DEL] Parameter: height
            Value: 2
[INS]
   [ State ]: STANDARD.
   Alist of parameters for the initial minibuffer frame. [Hide]
   […more lines of documentation…]

In this case, each association in the list consists of two items, one labeled ‘Parameter’ and one labeled ‘Value’; both are editable fields. You can delete an association from the list with the ‘[DEL]’ button next to it. To add an association, use the ‘[INS]’ button at the position where you want to insert it; the very last ‘[INS]’ button inserts at the end of the list.

When you set a variable, the new value takes effect only in the current Emacs session. To save the value for future sessions, use the ‘[State]’ button and select the ‘Save for Future Sessions’ operation. See Saving Customizations.

You can also restore the variable to its standard value by using the ‘[State]’ button and selecting the ‘Erase Customization’ operation. There are actually four reset operations:

Undo Edits

If you have modified but not yet set the variable, this restores the text in the customization buffer to match the actual value.

Revert This Session's Customizations

This restores the value of the variable to the last saved value, if there was one. Otherwise it restores the standard value. It updates the text accordingly.

Erase Customization

This sets the variable to its standard value. Any saved value that you have is also eliminated.

Set to Backup Value

This sets the variable to a previous value that was set in the customization buffer in this session. If you customize a variable and then reset it, which discards the customized value, you can get the discarded value back again with this operation.

Sometimes it is useful to record a comment about a specific customization. Use the ‘Add Comment’ item from the ‘[State]’ menu to create a field for entering the comment.

Near the top of the customization buffer are two lines of buttons:

 Operate on all settings in this buffer:
 [Revert...] [Apply] [Apply and Save]

The ‘[Revert...]’ button drops a menu with the first 3 reset operations described above. The ‘[Apply]’ button applies the settings for the current session. The ‘[Apply and Save]’ button applies the settings and saves them for future sessions; this button does not appear if Emacs was started with the -q or -Q option (see Initial Options).

The command C-c C-c (Custom-set) is equivalent to using the ‘[Set for Current Session]’ button. The command C-x C-s (Custom-save) is like using the ‘[Save for Future Sessions]’ button.

The ‘[Exit]’ button switches out of the customization buffer, and buries the buffer at the bottom of the buffer list. To make it kill the customization buffer instead, change the variable custom-buffer-done-kill to t.


50.1.4 Saving Customizations

In the customization buffer, you can save a customization setting by choosing the ‘Save for Future Sessions’ choice from its ‘[State]’ button. The C-x C-s (Custom-save) command, or the ‘[Apply and Save]’ button at the top of the customization buffer, saves all applicable settings in the buffer.

Saving works by writing code to a file, usually your initialization file (see The Emacs Initialization File). Future Emacs sessions automatically read this file at startup, which sets up the customizations again.

You can choose to save customizations somewhere other than your initialization file. To make this work, you must add a couple of lines of code to your initialization file, to set the variable custom-file to the name of the desired file, and to load that file. For example:

(setq custom-file "~/.config/emacs-custom.el")
(load custom-file)

You can even specify different customization files for different Emacs versions, like this:

(cond ((< emacs-major-version 28)
       ;; Emacs 27 customization.
       (setq custom-file "~/.config/custom-27.el"))
      ((and (= emacs-major-version 26)
            (< emacs-minor-version 3))
       ;; Emacs 26 customization, before version 26.3.
       (setq custom-file "~/.config/custom-26.el"))
      (t
       ;; Emacs version 28.1 or later.
       (setq custom-file "~/.config/emacs-custom.el")))

(load custom-file)

If Emacs was invoked with the -q or --no-init-file options (see Initial Options), it will not let you save your customizations in your initialization file. This is because saving customizations from such a session would wipe out all the other customizations you might have on your initialization file.

Please note that any customizations you have not chosen to save for future sessions will be lost when you terminate Emacs. If you’d like to be prompted about unsaved customizations at termination time, add the following to your initialization file:

(add-hook 'kill-emacs-query-functions
          'custom-prompt-customize-unsaved-options)

50.1.5 Customizing Faces

You can customize faces (see Text Faces), which determine how Emacs displays different types of text. Customization groups can contain both variables and faces.

For example, in programming language modes, source code comments are shown with font-lock-comment-face (see Font Lock mode). In a customization buffer, that face appears like this, after you click on the ‘[Show All Attributes]’ link:

[Hide] Font Lock Comment Face:[sample]
   [State] : STANDARD.
   Font Lock mode face used to highlight comments.
   [ ] Font Family: --
   [ ] Font Foundry: --
   [ ] Width: --
   [ ] Height: --
   [ ] Weight: --
   [ ] Slant: --
   [ ] Underline: --
   [ ] Overline: --
   [ ] Strike-through: --
   [ ] Box around text: --
   [ ] Inverse-video: --
   [X] Foreground: Firebrick     [Choose]  (sample)
   [ ] Background: --
   [ ] Stipple: --
   [ ] Inherit: --
   [Hide Unused Attributes]

The first three lines show the name, ‘[State]’ button, and documentation for the face. Below that is a list of face attributes. In front of each attribute is a checkbox. A filled checkbox, ‘[X]’, means that the face specifies a value for this attribute; an empty checkbox, ‘[ ]’, means that the face does not specify any special value for the attribute. You can activate a checkbox to specify or unspecify its attribute.

A face does not have to specify every single attribute; in fact, most faces only specify a few attributes. In the above example, font-lock-comment-face only specifies the foreground color. Any unspecified attribute is taken from the special face named default, whose attributes are all specified. The default face is the face used to display any text that does not have an explicitly-assigned face; furthermore, its background color attribute serves as the background color of the frame.

The ‘[Hide Unused Attributes]’ button, at the end of the attribute list, hides the unspecified attributes of the face. When attributes are being hidden, the button changes to ‘[Show All Attributes]’, which reveals the entire attribute list. The customization buffer may start out with unspecified attributes hidden, to avoid cluttering the interface.

When an attribute is specified, you can change its value in the usual ways.

Foreground and background colors can be specified using either color names or RGB triplets (see Colors for Faces). You can also use the ‘[Choose]’ button to switch to a list of color names; select a color with RET in that buffer to put the color name in the value field.

Setting, saving and resetting a face work like the same operations for variables (see Changing a Variable).

A face can specify different appearances for different types of displays. For example, a face can make text red on a color display, but use a bold font on a monochrome display. To specify multiple appearances for a face, select ‘For All Kinds of Displays’ in the menu you get from invoking ‘[State]’.


50.1.6 Customizing Specific Items

M-x customize-option RET option RET
M-x customize-variable RET option RET

Set up a customization buffer for just one user option, option.

M-x customize-face RET face RET

Set up a customization buffer for just one face, face.

M-x customize-icon RET face RET

Set up a customization buffer for just one icon, icon.

M-x customize-group RET group RET

Set up a customization buffer for just one group, group.

M-x customize-apropos RET regexp RET

Set up a customization buffer for all the settings and groups that match regexp.

M-x customize-changed RET version RET

Set up a customization buffer with all the user options, faces and groups whose meaning has changed since (or been added after) Emacs version version.

M-x customize-saved

Set up a customization buffer containing all settings that you have saved with customization buffers.

M-x customize-unsaved

Set up a customization buffer containing all settings that you have set but not saved.

If you want to customize a particular user option, type M-x customize-option. This reads the variable name, and sets up the customization buffer with just that one user option. When entering the variable name into the minibuffer, completion is available, but only for the names of variables that have been loaded into Emacs.

Likewise, you can customize a specific face using M-x customize-face. You can set up a customization buffer for a specific customization group using M-x customize-group.

M-x customize-apropos prompts for a search term—either one or more words separated by spaces, or a regular expression—and sets up a customization buffer for all loaded settings and groups with matching names. This is like using the search field at the top of the customization buffer (see Customization Groups).

When you upgrade to a new Emacs version, you might want to consider customizing new settings, and settings whose meanings or default values have changed. To do this, use M-x customize-changed and specify a previous Emacs version number using the minibuffer. It creates a customization buffer which shows all the settings and groups whose definitions have been changed since the specified version, loading them if necessary.

If you change settings and then decide the change was a mistake, you can use two commands to revisit your changes. Use M-x customize-saved to customize settings that you have saved. Use M-x customize-unsaved to customize settings that you have set but not saved.


50.1.7 Custom Themes

Custom themes are collections of settings that can be enabled or disabled as a unit. You can use Custom themes to switch easily between various collections of settings, and to transfer such collections from one computer to another.

A Custom theme is stored as an Emacs Lisp source file. If the name of the Custom theme is name, the theme file is named name-theme.el. See Creating Custom Themes, for the format of a theme file and how to make one.

Type M-x customize-themes to switch to a buffer named *Custom Themes*, which lists the Custom themes that Emacs knows about. By default, Emacs looks for theme files in two locations: the directory specified by the variable custom-theme-directory (which defaults to ~/.emacs.d/), and a directory named etc/themes in your Emacs installation (see the variable data-directory). The latter contains several Custom themes distributed with Emacs that customize Emacs’s faces to fit various color schemes. (Note, however, that Custom themes need not be restricted to this purpose; they can be used to customize variables too.)

If you want Emacs to look for Custom themes in some other directory, add the directory to the list variable custom-theme-load-path. Its default value is (custom-theme-directory t); here, the symbol custom-theme-directory has the special meaning of the value of the variable custom-theme-directory, while t stands for the built-in theme directory etc/themes. The themes listed in the *Custom Themes* buffer are those found in the directories specified by custom-theme-load-path.

In the *Custom Themes* buffer, you can activate the checkbox next to a Custom theme to enable or disable the theme for the current Emacs session. When a Custom theme is enabled, all of its settings (variables and faces) take effect in the Emacs session. To apply the choice of theme(s) to future Emacs sessions, type C-x C-s (custom-theme-save) or use the ‘[Save Theme Settings]’ button.

When you first enable a Custom theme, Emacs displays the contents of the theme file and asks if you really want to load it. Because loading a Custom theme can execute arbitrary Lisp code, you should only say yes if you know that the theme is safe; in that case, Emacs offers to remember in the future that the theme is safe (this is done by saving the theme file’s SHA-256 hash to the variable custom-safe-themes; if you want to treat all themes as safe, change its value to t). Themes that come with Emacs (in the etc/themes directory) are exempt from this check, and are always considered safe.

Setting or saving Custom themes actually works by customizing the variable custom-enabled-themes. The value of this variable is a list of Custom theme names (as Lisp symbols, e.g., tango). Instead of using the *Custom Themes* buffer to set custom-enabled-themes, you can customize the variable using the usual customization interface, e.g., with M-x customize-option. Note that Custom themes are not allowed to set custom-enabled-themes themselves.

Any customizations that you make through the customization buffer take precedence over theme settings. This lets you easily override individual theme settings that you disagree with. If settings from two different themes overlap, the theme occurring earlier in custom-enabled-themes takes precedence. In the customization buffer, if a setting has been changed from its default by a Custom theme, its ‘State’ display shows ‘THEMED’ instead of ‘STANDARD’.

You can enable a specific Custom theme in the current Emacs session by typing M-x load-theme. This prompts for a theme name, loads the theme from the theme file, and enables it. If a theme file has been loaded before, you can enable the theme without loading its file by typing M-x enable-theme. To disable a Custom theme, type M-x disable-theme.

To see a description of a Custom theme, type ? on its line in the *Custom Themes* buffer; or type M-x describe-theme anywhere in Emacs and enter the theme name.

Some themes have variants (most often just two: light and dark). You can switch to another variant using M-x theme-choose-variant. If the currently active theme has only one other variant, it will be selected; if there are more variants, the command will prompt you which one to switch to.

Note that theme-choose-variant only works if a single theme is active.


50.1.8 Creating Custom Themes

You can define a Custom theme using an interface similar to the customization buffer, by typing M-x customize-create-theme. This switches to a buffer named *Custom Theme*. It also offers to insert some common Emacs faces into the theme (a convenience, since Custom themes are often used to customize faces). If you answer no, the theme will initially contain no settings.

Near the top of the *Custom Theme* buffer, there are editable fields where you can enter the theme’s name and description. The name can be anything except ‘user’. The description is the one that will be shown when you invoke M-x describe-theme for the theme. Its first line should be a brief one-sentence summary; in the buffer made by M-x customize-themes, this sentence is displayed next to the theme name.

To add a new setting to the theme, use the ‘[Insert Additional Face]’ or ‘[Insert Additional Variable]’ buttons. Each button reads a face or variable name using the minibuffer, with completion, and inserts a customization entry for the face or variable. You can edit the variable values or face attributes in the same way as in a normal customization buffer. To remove a face or variable from the theme, uncheck the checkbox next to its name.

After specifying the Custom theme’s faces and variables, type C-x C-s (custom-theme-write) or use the buffer’s ‘[Save Theme]’ button. This saves the theme file, named name-theme.el where name is the theme name, in the directory named by custom-theme-directory.

From the *Custom Theme* buffer, you can view and edit an existing Custom theme by activating the ‘[Visit Theme]’ button and specifying the theme name. You can also add the settings of another theme into the buffer, using the ‘[Merge Theme]’ button. You can import your non-theme settings into a Custom theme by using the ‘[Merge Theme]’ button and specifying the special theme named ‘user’.

A theme file is simply an Emacs Lisp source file, and loading the Custom theme works by loading the Lisp file. Therefore, you can edit a theme file directly instead of using the *Custom Theme* buffer. See Custom Themes in The Emacs Lisp Reference Manual, for details.


50.2 Variables

A variable is a Lisp symbol which has a value. The symbol’s name is also called the variable name. A variable name can contain any characters that can appear in a file, but most variable names consist of ordinary words separated by hyphens.

The name of the variable serves as a compact description of its role. Most variables also have a documentation string, which describes what the variable’s purpose is, what kind of value it should have, and how the value will be used. You can view this documentation using the help command C-h v (describe-variable). See Examining and Setting Variables.

Emacs uses many Lisp variables for internal record keeping, but the most interesting variables for a non-programmer user are those meant for users to change—these are called customizable variables or user options (see Easy Customization Interface). In the following sections, we will describe other aspects of Emacs variables, such as how to set them outside Customize.

Emacs Lisp allows any variable (with a few exceptions) to have any kind of value. However, many variables are meaningful only if assigned values of a certain type. For example, only numbers are meaningful values for kill-ring-max, which specifies the maximum length of the kill ring (see Yanking Earlier Kills); if you give kill-ring-max a string value, commands such as C-y (yank) will signal an error. On the other hand, some variables don’t care about type; for instance, if a variable has one effect for nil values and another effect for non-nil values, then any value that is not the symbol nil induces the second effect, regardless of its type (by convention, we usually use the value t—a symbol which stands for “true”—to specify a non-nil value). If you set a variable using the customization buffer, you need not worry about giving it an invalid type: the customization buffer usually only allows you to enter meaningful values. When in doubt, use C-h v (describe-variable) to check the variable’s documentation string to see what kind of value it expects (see Examining and Setting Variables).


50.2.1 Examining and Setting Variables

C-h v var RET

Display the value and documentation of variable var (describe-variable).

M-x set-variable RET var RET value RET

Change the value of variable var to value.

To examine the value of a variable, use C-h v (describe-variable). This reads a variable name using the minibuffer, with completion, and displays both the value and the documentation of the variable. For example,

C-h v fill-column RET

displays something like this:

fill-column is a variable defined in ‘C source code’.
Its value is 70

  Automatically becomes buffer-local when set.
  This variable is safe as a file local variable if its value
  satisfies the predicate ‘integerp’.
  Probably introduced at or before Emacs version 18.

Documentation:
Column beyond which automatic line-wrapping should happen.
Interactively, you can set the buffer local value using C-x f.

You can customize this variable.

The line that says ‘You can customize the variable’ indicates that this variable is a user option. C-h v is not restricted to user options; it allows non-customizable variables too.

The most convenient way to set a specific customizable variable is with M-x set-variable. This reads the variable name with the minibuffer (with completion), and then reads a Lisp expression for the new value using the minibuffer a second time (you can insert the old value into the minibuffer for editing via M-n). For example,

M-x set-variable RET fill-column RET 75 RET

sets fill-column to 75.

M-x set-variable is limited to customizable variables, but you can set any variable with a Lisp expression like this:

(setq fill-column 75)

To execute such an expression, type M-: (eval-expression) and enter the expression in the minibuffer (see Evaluating Emacs Lisp Expressions). Alternatively, go to the *scratch* buffer, type in the expression, and then type C-j (see Lisp Interaction Buffers).

Setting variables, like all means of customizing Emacs except where otherwise stated, affects only the current Emacs session. The only way to alter the variable in future sessions is to put something in your initialization file (see The Emacs Initialization File).

If you’re setting a customizable variable in your initialization file, and you don’t want to use the Customize interface, you can use the setopt macro. For instance:

(setopt fill-column 75)

This works the same as setq, but if the variable has any special setter functions, they will be run automatically when using setopt. You can also use setopt on other, non-customizable variables, but this is less efficient than using setq.


50.2.2 Hooks

Hooks are an important mechanism for customizing Emacs. A hook is a Lisp variable which holds a list of functions, to be called on some well-defined occasion. (This is called running the hook.) The individual functions in the list are called the hook functions of the hook. For example, the hook kill-emacs-hook runs just before exiting Emacs (see Exiting Emacs).

Most hooks are normal hooks. This means that when Emacs runs the hook, it calls each hook function in turn, with no arguments. We have made an effort to keep most hooks normal, so that you can use them in a uniform way. Every variable whose name ends in ‘-hook’ is a normal hook.

A few hooks are abnormal hooks. Their names end in ‘-functions’, instead of ‘-hook’ (some old code may also use the deprecated suffix ‘-hooks’). What makes these hooks abnormal is the way its functions are called—perhaps they are given arguments, or perhaps the values they return are used in some way. For example, find-file-not-found-functions is abnormal because as soon as one hook function returns a non-nil value, the rest are not called at all (see Visiting Files). The documentation of each abnormal hook variable explains how its functions are used.

You can set a hook variable with setq like any other Lisp variable, but the recommended way to add a function to a hook (either normal or abnormal) is to use add-hook, as shown by the following examples. See Hooks in The Emacs Lisp Reference Manual, for details.

Most major modes run one or more mode hooks as the last step of initialization. Mode hooks are a convenient way to customize the behavior of individual modes; they are always normal. For example, here’s how to set up a hook to turn on Auto Fill mode in Text mode and other modes based on Text mode:

(add-hook 'text-mode-hook 'auto-fill-mode)

This works by calling auto-fill-mode, which enables the minor mode when no argument is supplied (see Minor Modes). Next, suppose you don’t want Auto Fill mode turned on in LaTeX mode, which is one of the modes based on Text mode. You can do this with the following additional line:

(add-hook 'latex-mode-hook (lambda () (auto-fill-mode -1)))

Here we have used the special macro lambda to construct an anonymous function (see Lambda Expressions in The Emacs Lisp Reference Manual), which calls auto-fill-mode with an argument of -1 to disable the minor mode. Because LaTeX mode runs latex-mode-hook after running text-mode-hook, the result leaves Auto Fill mode disabled.

Here is a more complex example, showing how to use a hook to customize the indentation of C code:

(setq my-c-style
  '((c-comment-only-line-offset . 4)
    (c-cleanup-list . (scope-operator
                       empty-defun-braces
                       defun-close-semi))))

(add-hook 'c-mode-common-hook
  (lambda () (c-add-style "my-style" my-c-style t)))

Major mode hooks also apply to other major modes derived from the original mode (see Derived Modes in The Emacs Lisp Reference Manual). For instance, HTML mode is derived from Text mode (see SGML and HTML Modes); when HTML mode is enabled, it runs text-mode-hook before running html-mode-hook. This provides a convenient way to use a single hook to affect several related modes. In particular, if you want to apply a hook function to any programming language mode, add it to prog-mode-hook; Prog mode is a major mode that does little else than to let other major modes inherit from it, exactly for this purpose.

It is best to design your hook functions so that the order in which they are executed does not matter. Any dependence on the order is asking for trouble. However, the order is predictable: the hook functions are executed in the order they appear in the hook.

If you play with adding various different versions of a hook function by calling add-hook over and over, remember that all the versions you added will remain in the hook variable together. You can clear out individual functions by calling remove-hook, or do (setq hook-variable nil) to remove everything.

If the hook variable is buffer-local, the buffer-local variable will be used instead of the global variable. However, if the buffer-local variable contains the element t, the global hook variable will be run as well.


50.2.3 Local Variables

M-x make-local-variable RET var RET

Make variable var have a local value in the current buffer.

M-x kill-local-variable RET var RET

Make variable var use its global value in the current buffer.

M-x make-variable-buffer-local RET var RET

Mark variable var so that setting it will make it local to the buffer that is current at that time.

Almost any variable can be made local to a specific Emacs buffer. This means that its value in that buffer is independent of its value in other buffers. A few variables are always local in every buffer. Every other Emacs variable has a global value which is in effect in all buffers that have not made the variable local.

M-x make-local-variable reads the name of a variable and makes it local to the current buffer. Changing its value subsequently in this buffer will not affect others, and changes in its global value will not affect this buffer.

M-x make-variable-buffer-local marks a variable so it will become local automatically whenever it is set. More precisely, once a variable has been marked in this way, the usual ways of setting the variable automatically do make-local-variable first. We call such variables per-buffer variables. Many variables in Emacs are normally per-buffer; the variable’s document string tells you when this is so. A per-buffer variable’s global value is normally never effective in any buffer, but it still has a meaning: it is the initial value of the variable for each new buffer.

Major modes (see Major Modes) always make variables local to the buffer before setting the variables. This is why changing major modes in one buffer has no effect on other buffers. Minor modes also work by setting variables—normally, each minor mode has one controlling variable which is non-nil when the mode is enabled (see Minor Modes). For many minor modes, the controlling variable is per buffer, and thus always buffer-local. Otherwise, you can make it local in a specific buffer like any other variable.

A few variables cannot be local to a buffer because they are always local to each display instead (see Multiple Displays). If you try to make one of these variables buffer-local, you’ll get an error message.

M-x kill-local-variable makes a specified variable cease to be local to the current buffer. The global value of the variable henceforth is in effect in this buffer. Setting the major mode kills all the local variables of the buffer except for a few variables specially marked as permanent locals.

To set the global value of a variable, regardless of whether the variable has a local value in the current buffer, you can use the Lisp construct setq-default. This construct is used just like setq, but it sets variables’ global values instead of their local values (if any). When the current buffer does have a local value, the new global value may not be visible until you switch to another buffer. Here is an example:

(setq-default fill-column 75)

setq-default is the only way to set the global value of a variable that has been marked with make-variable-buffer-local.

Lisp programs can use default-value to look at a variable’s default value. This function takes a symbol as argument and returns its default value. The argument is evaluated; usually you must quote it explicitly. For example, here’s how to obtain the default value of fill-column:

(default-value 'fill-column)

50.2.4 Local Variables in Files

A file can specify local variable values to use when editing the file with Emacs. Visiting the file or setting a major mode checks for local variable specifications; it automatically makes these variables local to the buffer, and sets them to the values specified in the file.

File local variables override directory local variables (see Per-Directory Local Variables), if any are specified for a file’s directory.


50.2.4.1 Specifying File Variables

There are two ways to specify file local variable values: in the first line, or with a local variables list. Here’s how to specify them in the first line:

-*- mode: modename; var: value; … -*-

You can specify any number of variable/value pairs in this way, each pair with a colon and semicolon. The special variable/value pair mode: modename;, if present, specifies a major mode (without the “-mode” suffix). The values are used literally, and not evaluated.

You can use M-x add-file-local-variable-prop-line instead of adding entries by hand. This command prompts for a variable and value, and adds them to the first line in the appropriate way. M-x delete-file-local-variable-prop-line prompts for a variable, and deletes its entry from the line. The command M-x copy-dir-locals-to-file-locals-prop-line copies the current directory-local variables to the first line (see Per-Directory Local Variables).

Here is an example first line that specifies Lisp mode and sets two variables with numeric values:

;; -*- mode: Lisp; fill-column: 75; comment-column: 50; -*-

Aside from mode, other keywords that have special meanings as file variables are coding, unibyte, and eval. These are described below.

In shell scripts, the first line is used to identify the script interpreter, so you cannot put any local variables there. To accommodate this, Emacs looks for local variable specifications in the second line if the first line specifies an interpreter. The same is true for man pages which start with the magic string ‘'\"’ to specify a list of troff preprocessors (not all do, however).

Apart from using a ‘-*-’ line, you can define file local variables using a local variables list near the end of the file. The start of the local variables list should be no more than 3000 characters from the end of the file, and must be on the last page if the file is divided into pages.

If a file has both a local variables list and a ‘-*-’ line, Emacs processes everything in the ‘-*-’ line first, and everything in the local variables list afterward. The exception to this is a major mode specification. Emacs applies this first, wherever it appears, since most major modes kill all local variables as part of their initialization.

A local variables list starts with a line containing the string ‘Local Variables:’, and ends with a line containing the string ‘End:’. In between come the variable names and values, one set per line, like this:

/* Local Variables:  */
/* mode: c           */
/* comment-column: 0 */
/* End:              */

In this example, each line starts with the prefix ‘/*’ and ends with the suffix ‘*/’. Emacs recognizes the prefix and suffix by finding them surrounding the magic string ‘Local Variables:’, on the first line of the list; it then automatically discards them from the other lines of the list. The usual reason for using a prefix and/or suffix is to embed the local variables list in a comment, so it won’t confuse other programs that the file is intended for. The example above is for the C programming language, where comments start with ‘/*’ and end with ‘*/’.

If some unrelated text might look to Emacs as a local variables list, you can countermand that by inserting a form-feed character (a page delimiter, see Pages) after that text. Emacs only looks for file-local variables in the last page of a file, after the last page delimiter.

Instead of typing in the local variables list directly, you can use the command M-x add-file-local-variable. This prompts for a variable and value, and adds them to the list, adding the ‘Local Variables:’ string and start and end markers as necessary. The command M-x delete-file-local-variable deletes a variable from the list. M-x copy-dir-locals-to-file-locals copies directory-local variables to the list (see Per-Directory Local Variables).

As with the ‘-*-’ line, the variables in a local variables list are used literally, and are not evaluated first. If you want to split a long string value across multiple lines of the file, you can use backslash-newline, which is ignored in Lisp string constants; you should put the prefix and suffix on each line, even lines that start or end within the string, as they will be stripped off when processing the list. Here is an example:

# Local Variables:
# compile-command: "cc foo.c -Dfoo=bar -Dhack=whatever \
#   -Dmumble=blaah"
# End:

Some names have special meanings in a local variables list:

  • mode enables the specified major mode.
  • eval evaluates the specified Lisp expression (the value returned by that expression is ignored).
  • coding specifies the coding system for character code conversion of this file. See Coding Systems.
  • unibyte says to load or compile a file of Emacs Lisp in unibyte mode, if the value is t. See Disabling Multibyte Characters in GNU Emacs Lisp Reference Manual.

These four keywords are not really variables; setting them in any other context has no special meaning.

If you’re editing a file across Emacs versions, and a new mode has been introduced to handle a file in a newer Emacs version, you can use several mode entries to use the new mode (called my-new-mode) in the new Emacs, and fall back to the old mode (called my-old-mode) in older Emacs versions. If you’re enabling the modes in the first line of the file, can say:

-*- mode: my-old; mode: my-new -*-

Emacs will use the final defined mode it finds, so in older Emacs versions it will ignore my-new-mode, while in Emacs versions where my-new-mode is defined, it’ll ignore my-old-mode. Similarly, in a local variable block at the end of the file:

Local variables:
mode: my-old
mode: my-new

Do not use the mode keyword for minor modes. To enable or disable a minor mode in a local variables list, use the eval keyword with a Lisp expression that runs the mode command (see Minor Modes). For example, the following local variables list enables ElDoc mode (see Programming Language Documentation Lookup) by calling eldoc-mode with no argument (calling it with an argument of 1 would do the same), and disables Font Lock mode (see Font Lock mode) by calling font-lock-mode with an argument of −1.

;; Local Variables:
;; eval: (eldoc-mode)
;; eval: (font-lock-mode -1)
;; End:

Note, however, that it is often a mistake to specify minor modes this way. Minor modes represent individual user preferences, and it may be inappropriate to impose your preferences on another user who might edit the file. If you wish to automatically enable or disable a minor mode in a situation-dependent way, it is often better to do it in a major mode hook (see Hooks).

Use the command M-x normal-mode to reset the local variables and major mode of a buffer according to the file name and contents, including the local variables list if any. See Choosing File Modes.


50.2.4.2 Safety of File Variables

File-local variables can be dangerous; when you visit someone else’s file, there’s no telling what its local variables list could do to your Emacs. Improper values of the eval “variable”, and other variables such as load-path, could execute Lisp code you didn’t intend to run.

Therefore, whenever Emacs encounters file local variable values that are not known to be safe, it displays the file’s entire local variables list, and asks you for confirmation before setting them. You can type y or SPC to put the local variables list into effect, or n to ignore it. When Emacs is run in batch mode (see Initial Options), it can’t really ask you, so it assumes the answer n.

Emacs normally recognizes certain variable/value pairs as safe. For instance, it is safe to give comment-column or fill-column any integer value. If a file specifies only known-safe variable/value pairs, Emacs does not ask for confirmation before setting them. Otherwise, you can tell Emacs to record all the variable/value pairs in this file as safe, by typing ! at the confirmation prompt. When Emacs encounters these variable/value pairs subsequently, in the same file or others, it will assume they are safe.

You can also tell Emacs to permanently ignore all the variable/value pairs in the file, by typing i at the confirmation prompt – these pairs will thereafter be ignored in this file and in all other files.

Some variables, such as load-path, are considered particularly risky: there is seldom any reason to specify them as local variables, and changing them can be dangerous. If a file contains only risky local variables, Emacs neither offers nor accepts ! as input at the confirmation prompt. If some of the local variables in a file are risky, and some are only potentially unsafe, you can enter ! at the prompt. It applies all the variables, but only marks the non-risky ones as safe for the future. If you really want to record safe values for risky variables, do it directly by customizing ‘safe-local-variable-values’ (see Easy Customization Interface). Similarly, if you want to record values of risky variables that should be permanently ignored, customize ignored-local-variable-values.

The variable enable-local-variables allows you to change the way Emacs processes local variables. Its default value is t, which specifies the behavior described above. If it is nil, Emacs simply ignores all file local variables. :safe means use only the safe values and ignore the rest. :all instructs Emacs to set all file local variables regardless of whether their value is safe or not (we advise not to use this permanently). Any other value says to query you about each file that has local variables, without trying to determine whether the values are known to be safe.

The variable enable-local-eval controls whether Emacs processes eval variables. The three possibilities for the variable’s value are t, nil, and anything else, just as for enable-local-variables. The default is maybe, which is neither t nor nil, so normally Emacs does ask for confirmation about processing eval variables.

As an exception, Emacs never asks for confirmation to evaluate any eval form if that form occurs within the variable safe-local-eval-forms.


50.2.5 Per-Directory Local Variables

Sometimes, you may wish to define the same set of local variables to all the files in a certain directory and its subdirectories, such as the directory tree of a large software project. This can be accomplished with directory-local variables. File local variables override directory local variables, so if some of the files in a directory need specialized settings, you can specify the settings for the majority of the directory’s files in directory variables, and then define file local variables in a few files which need the general settings overridden.

The usual way to define directory-local variables is to put a file named .dir-locals.el24 in a directory. Whenever Emacs visits any file in that directory or any of its subdirectories, it will apply the directory-local variables specified in .dir-locals.el, as though they had been defined as file-local variables for that file (see Local Variables in Files). Emacs searches for .dir-locals.el starting in the directory of the visited file, and moving up the directory tree. To avoid slowdown, this search is skipped for remote files. If needed, the search can be extended for remote files by setting the variable enable-remote-dir-locals to t.

You can also use .dir-locals-2.el; if found, Emacs loads it in addition to .dir-locals.el. This is useful when .dir-locals.el is under version control in a shared repository and can’t be used for personal customizations.

The .dir-locals.el file should hold a specially-constructed list, which maps major mode names (symbols) to alists (see Association Lists in The Emacs Lisp Reference Manual). Each alist entry consists of a variable name and the directory-local value to assign to that variable, when the specified major mode is enabled. Instead of a mode name, you can specify ‘nil’, which means that the alist applies to any mode; or you can specify a subdirectory (a string), in which case the alist applies to all files in that subdirectory.

Here’s an example of a .dir-locals.el file:

((nil . ((indent-tabs-mode . t)
         (fill-column . 80)
         (mode . auto-fill)))
 (c-mode . ((c-file-style . "BSD")
            (subdirs . nil)))
 ("src/imported"
  . ((nil . ((change-log-default-name
              . "ChangeLog.local"))))))

This sets the variables ‘indent-tabs-mode’ and fill-column for any file in the directory tree, and the indentation style for any C source file. The special mode element specifies the minor mode to be enabled. So (mode . auto-fill) specifies that the minor mode auto-fill-mode needs to be enabled. The special subdirs element is not a variable, but a special keyword which indicates that the C mode settings are only to be applied in the current directory, not in any subdirectories. Finally, it specifies a different ChangeLog file name for any file in the src/imported subdirectory.

If the .dir-locals.el file contains multiple different values for a variable using different mode names or directories, the values will be applied in an order such that the values for more specific modes take priority over more generic modes. Values specified under a directory have even more priority. For example:

((nil . ((fill-column . 40)))
 (c-mode . ((fill-column . 50)))
 (prog-mode . ((fill-column . 60)))
 ("narrow-files" . ((nil . ((fill-column . 20))))))

Files that use c-mode also match prog-mode because the former inherits from the latter. The value used for fill-column in C files will however be 50 because the mode name is more specific than prog-mode. Files using other modes inheriting from prog-mode will use 60. Any file under the directory narrow-files will use the value 20 even if they use c-mode because directory entries have priority over mode entries.

You can specify the variables mode, eval, and unibyte in your .dir-locals.el, and they have the same meanings as they would have in file local variables. coding cannot be specified as a directory local variable. See Local Variables in Files.

The special key auto-mode-alist in a .dir-locals.el lets you set a file’s major mode. It works much like the variable auto-mode-alist (see Choosing File Modes). For example, here is how you can tell Emacs that .def source files in this directory should be in C mode:

((auto-mode-alist . (("\\.def\\'" . c-mode))))

Instead of editing the .dir-locals.el file by hand, you can use the command M-x add-dir-local-variable. This prompts for a mode or subdirectory, and for variable and value, and adds the entry defining the directory-local variable. M-x delete-dir-local-variable deletes an entry. M-x copy-file-locals-to-dir-locals copies the file-local variables in the current file into .dir-locals.el.

Another method of specifying directory-local variables is to define a group of variables/value pairs in a directory class, using the dir-locals-set-class-variables function; then, tell Emacs which directories correspond to the class by using the dir-locals-set-directory-class function. These function calls normally go in your initialization file (see The Emacs Initialization File). This method is useful when you can’t put .dir-locals.el in a directory for some reason. For example, you could apply settings to an unwritable directory this way:

(dir-locals-set-class-variables 'unwritable-directory
   '((nil . ((some-useful-setting . value)))))

(dir-locals-set-directory-class
   "/usr/include/" 'unwritable-directory)

If a variable has both a directory-local and file-local value specified, the file-local value takes effect. Unsafe directory-local variables are handled in the same way as unsafe file-local variables (see Safety of File Variables).

Directory-local variables also take effect in certain buffers that do not visit a file directly but perform work within a directory, such as Dired buffers (see Dired, the Directory Editor).


50.2.6 Per-Connection Local Variables

Most of the variables reflect the situation on the local machine. Often, they must use a different value when you operate in buffers with a remote default directory. Think about the behavior when calling shell – on your local machine, you might use /bin/bash and rely on termcap, but on a remote machine, it may be /bin/ksh and terminfo.

This can be accomplished with connection-local variables. Directory and file local variables override connection-local variables. Unsafe connection-local variables are handled in the same way as unsafe file-local variables (see Safety of File Variables).

Connection-local variables are declared as a group of variables/value pairs in a profile, using the connection-local-set-profile-variables function. The function connection-local-set-profiles activates profiles for a given criteria, identifying a remote machine:

(connection-local-set-profile-variables 'remote-terminfo
   '((system-uses-terminfo . t)
     (comint-terminfo-terminal . "dumb-emacs-ansi")))

(connection-local-set-profile-variables 'remote-ksh
   '((shell-file-name . "/bin/ksh")
     (shell-command-switch . "-c")))

(connection-local-set-profile-variables 'remote-bash
   '((shell-file-name . "/bin/bash")
     (shell-command-switch . "-c")))

(connection-local-set-profiles
   '(:application tramp :machine "remotemachine")
   'remote-terminfo 'remote-ksh)

This code declares three different profiles, remote-terminfo, remote-ksh, and remote-bash. The profiles remote-terminfo and remote-ksh are applied to all buffers which have a remote default directory matching the regexp "remotemachine" as host name. Such a criteria can also discriminate for the properties :protocol (this is the Tramp method) or :user (a remote user name). The nil criteria matches all buffers with a remote default directory.

Be careful when declaring different profiles with the same variable, and setting these profiles to criteria which could match in parallel. It is unspecified which variable value is used then.


50.3 Customizing Key Bindings

This section describes key bindings, which map keys to commands, and keymaps, which record key bindings. It also explains how to customize key bindings, which is done by editing your init file (see Rebinding Keys in Your Init File).

Since most modes define their own key bindings, activating a mode might override your custom key bindings. A small number of keys are reserved for user-defined bindings, and should not be used by modes, so key bindings using those keys are safer in this regard. The reserved key sequences are those consisting of C-c followed by a letter (either upper or lower case), and function keys F5 through F9 without modifiers (see Modifier Keys).


50.3.1 Keymaps

As described in Keys and Commands, each Emacs command is a Lisp function whose definition provides for interactive use. Like every Lisp function, a command has a function name, which usually consists of lower-case letters and hyphens.

A key sequence (key, for short) is a sequence of input events that have a meaning as a unit. Input events include characters, function keys, and mouse buttons—all the inputs that you can send to the computer. A key sequence gets its meaning from its binding, which says what command it runs.

The bindings between key sequences and command functions are recorded in data structures called keymaps. Emacs has many of these, each used on particular occasions.

The global keymap is the most important keymap because it is always in effect. The global keymap defines keys for Fundamental mode (see Major Modes); most of these definitions are common to most or all major modes. Each major or minor mode can have its own keymap which overrides the global definitions of some keys.

For example, a self-inserting character such as g is self-inserting because the global keymap binds it to the command self-insert-command. The standard Emacs editing characters such as C-a also get their standard meanings from the global keymap. Commands to rebind keys, such as M-x keymap-global-set, work by storing the new binding in the proper place in the global map (see Changing Key Bindings Interactively). To view the current key bindings, use the C-h b command.

Most modern keyboards have function keys as well as character keys. Function keys send input events just as character keys do, and keymaps can have bindings for them. Key sequences can mix function keys and characters. For example, if your keyboard has a Home function key, Emacs can recognize key sequences like C-x Home. You can even mix mouse events with keyboard events, such as S-down-mouse-1.

On text terminals, typing a function key actually sends the computer a sequence of characters; the precise details of the sequence depend on the function key and on the terminal type. (Often the sequence starts with ESC [.) If Emacs understands your terminal type properly, it automatically handles such sequences as single input events.

Key sequences that consist of C-c followed by a letter (upper or lower case; ASCII or non-ASCII) are reserved for users. Emacs itself will never bind those key sequences, and Emacs extensions should avoid binding them. In other words, users can bind key sequences like C-c a or C-c ç and rely on these never being shadowed by other Emacs bindings.


50.3.2 Prefix Keymaps

Internally, Emacs records only single events in each keymap. Interpreting a key sequence of multiple events involves a chain of keymaps: the first keymap gives a definition for the first event, which is another keymap, which is used to look up the second event in the sequence, and so on. Thus, a prefix key such as C-x or ESC has its own keymap, which holds the definition for the event that immediately follows that prefix.

The definition of a prefix key is usually the keymap to use for looking up the following event. The definition can also be a Lisp symbol whose function definition is the following keymap; the effect is the same, but it provides a command name for the prefix key that can be used as a description of what the prefix key is for. Thus, the binding of C-x is the symbol Control-X-prefix, whose function definition is the keymap for C-x commands. The definitions of C-c, C-x, C-h, and ESC as prefix keys appear in the global map, so these prefix keys are always available.

Aside from ordinary prefix keys, there is a fictitious “prefix key” which represents the menu bar; see Menu Bar in The Emacs Lisp Reference Manual, for special information about menu bar key bindings. Mouse button events that invoke pop-up menus are also prefix keys; see Menu Keymaps in The Emacs Lisp Reference Manual, for more details.

Some prefix keymaps are stored in variables with names:

  • ctl-x-map is the variable name for the map used for characters that follow C-x.
  • help-map is for characters that follow C-h.
  • esc-map is for characters that follow ESC. Thus, all Meta characters are actually defined by this map.
  • ctl-x-4-map is for characters that follow C-x 4.
  • mode-specific-map is for characters that follow C-c.
  • project-prefix-map is for characters that follow C-x p, used for project-related commands (see Working with Projects).

50.3.3 Local Keymaps

So far, we have explained the ins and outs of the global map. Major modes customize Emacs by providing their own key bindings in local keymaps. For example, C mode overrides TAB to make it indent the current line for C code. Minor modes can also have local keymaps; whenever a minor mode is in effect, the definitions in its keymap override both the major mode’s local keymap and the global keymap. In addition, portions of text in the buffer can specify their own keymaps, which override all other keymaps.

A local keymap can redefine a key as a prefix key by defining it as a prefix keymap. If the key is also defined globally as a prefix, its local and global definitions (both keymaps) effectively combine: both definitions are used to look up the event that follows the prefix key. For example, if a local keymap defines C-c as a prefix keymap, and that keymap defines C-z as a command, this provides a local meaning for C-c C-z. This does not affect other sequences that start with C-c; if those sequences don’t have their own local bindings, their global bindings remain in effect.

Another way to think of this is that Emacs handles a multi-event key sequence by looking in several keymaps, one by one, for a binding of the whole key sequence. First it checks the minor mode keymaps for minor modes that are enabled, then it checks the major mode’s keymap, and then it checks the global keymap. This is not precisely how key lookup works, but it’s good enough for understanding the results in ordinary circumstances.


50.3.4 Minibuffer Keymaps

The minibuffer has its own set of local keymaps; they contain various completion and exit commands.

  • minibuffer-local-map is used for ordinary input (no completion).
  • minibuffer-local-ns-map is similar, except that SPC exits just like RET.
  • minibuffer-local-completion-map is for permissive completion.
  • minibuffer-local-must-match-map is for strict completion and for cautious completion.
  • minibuffer-local-filename-completion-map is like the two previous ones, but specifically for file name completion. It does not bind SPC.

By default, TAB, SPC and ? do completion in minibuffer-local-completion-map. If you commonly complete over collections that have elements with space or question mark characters in them, it may be convenient to disable completion on those keys by putting this in your init file:

(keymap-set minibuffer-local-completion-map "SPC" 'self-insert-command)
(keymap-set minibuffer-local-completion-map "?" 'self-insert-command)

50.3.5 Changing Key Bindings Interactively

The way to redefine an Emacs key is to change its entry in a keymap. You can change the global keymap, in which case the change is effective in all major modes (except those that have their own overriding local bindings for the same key). Or you can change a local keymap, which affects all buffers using the same major mode.

In this section, we describe how to rebind keys for the present Emacs session. See Rebinding Keys in Your Init File, for a description of how to make key rebindings affect future Emacs sessions.

M-x keymap-global-set RET key cmd RET

Define key globally to run cmd.

M-x keymap-local-set RET key cmd RET

Define key locally (in the major mode now in effect) to run cmd.

M-x keymap-global-unset RET key

Make key undefined in the global map.

M-x keymap-local-unset RET key

Make key undefined locally (in the major mode now in effect).

For example, the following binds C-z to the shell command (see Interactive Subshell), replacing the normal global definition of C-z:

M-x keymap-global-set RET C-z shell RET

The keymap-global-set command reads the command name after the key. After you press the key, a message like this appears so that you can confirm that you are binding the key you want:

Set key C-z to command:

You can redefine function keys and mouse events in the same way; just type the function key or click the mouse when it’s time to specify the key to rebind.

You can rebind a key that contains more than one event in the same way. Emacs keeps reading the key to rebind until it is a complete key (that is, not a prefix key). Thus, if you type C-f for key, that’s the end; it enters the minibuffer immediately to read cmd. But if you type C-x, since that’s a prefix, it reads another character; if that is 4, another prefix character, it reads one more character, and so on. For example,

M-x keymap-global-set RET C-x 4 $ spell-other-window RET

redefines C-x 4 $ to run the (fictitious) command spell-other-window.

You can remove the global definition of a key with keymap-global-unset. This makes the key undefined; if you type it, Emacs will just beep. Similarly, keymap-local-unset makes a key undefined in the current major mode keymap, which makes the global definition (or lack of one) come back into effect in that major mode.

If you have redefined (or undefined) a key and you subsequently wish to retract the change, undefining the key will not do the job—you need to redefine the key with its standard definition. To find the name of the standard definition of a key, go to a Fundamental mode buffer in a fresh Emacs and use C-h c. The documentation of keys in this manual also lists their command names.

If you want to prevent yourself from invoking a command by mistake, it is better to disable the command than to undefine the key. A disabled command is less work to invoke when you really want to. See Disabling Commands.


50.3.6 Rebinding Keys in Your Init File

If you have a set of key bindings that you like to use all the time, you can specify them in your initialization file by writing Lisp code. See The Emacs Initialization File, for a description of the initialization file.

The recommended way to write a key binding using Lisp is to use either the keymap-global-set or the keymap-set functions. For example, here’s how to bind C-z to the shell command in the global keymap (see Interactive Subshell):

(keymap-global-set "C-z" 'shell)

The first argument to keymap-global-set describes the key sequence. It is a string made of a series of characters separated by spaces, with each character corresponding to a key. Keys with modifiers can be specified by prepending the modifier, such as ‘C-’ for Control, or ‘M-’ for Meta. Special keys, such as TAB and RET, can be specified within angle brackets as in TAB and RET.

The single-quote before the command name that is being bound to the key sequence, shell in the above example, marks it as a constant symbol rather than a variable. If you omit the quote, Emacs would try to evaluate shell as a variable. This will probably cause an error; it certainly isn’t what you want.

Here are some additional examples, including binding function keys and mouse events:

(keymap-global-set "C-c y" 'clipboard-yank)
(keymap-global-set "C-M-q" 'query-replace)
(keymap-global-set "<f5>" 'flyspell-mode)
(keymap-global-set "C-<f5>" 'display-line-numbers-mode)
(keymap-global-set "C-<right>" 'forward-sentence)
(keymap-global-set "<mouse-2>" 'mouse-save-then-kill)

Language and coding systems may cause problems with key bindings for non-ASCII characters. See Non-ASCII Characters in Init Files.

Alternatively, you can use the low level functions define-key and global-set-key. For example, to bind C-z to the shell command, as in the above example, using these low-level functions, use:

(global-set-key (kbd "C-z") 'shell)

There are various ways to specify the key sequence but the simplest is to use the function kbd as shown in the example above. kbd takes a single string argument that is a textual representation of a key sequence, and converts it into a form suitable for low-level functions such as global-set-key. For more details about binding keys using Lisp, see Keymaps in The Emacs Lisp Reference Manual.

As described in Local Keymaps, major modes and minor modes can define local keymaps. These keymaps are constructed when the mode is loaded for the first time in a session. The function keymap-set can be used to make changes in a specific keymap. To remove a key binding, use keymap-unset.

Since a mode’s keymaps are not constructed until it has been loaded, you must delay running code which modifies them, e.g., by putting it on a mode hook (see Hooks). For example, Texinfo mode runs the hook texinfo-mode-hook. Here’s how you can use the hook to add local bindings for C-c n and C-c p, and remove the one for C-c C-x x in Texinfo mode:

(add-hook 'texinfo-mode-hook
          (lambda ()
            (keymap-set texinfo-mode-map "C-c p"
                        'backward-paragraph)
            (keymap-set texinfo-mode-map "C-c n"
                        'forward-paragraph)
            (keymap-set texinfo-mode-map "C-c C-x x" nil)))

50.3.7 Modifier Keys

The default key bindings in Emacs are set up so that modified alphabetical characters are case-insensitive. In other words, C-A does the same thing as C-a, and M-A does the same thing as M-a. This concerns only alphabetical characters, and does not apply to shifted versions of other keys; for instance, C-@ is not the same as C-2.

A Control-modified alphabetical character is generally considered case-insensitive: Emacs always treats C-A as C-a, C-B as C-b, and so forth. The reason for this is historical: In non-graphical environments there is no distinction between those keystrokes. However, you can bind shifted Control alphabetical keystrokes in GUI frames:

(keymap-global-set "C-S-n" #'previous-line)

For all other modifiers, you can make the modified alphabetical characters case-sensitive (even on non-graphical frames) when you customize Emacs. For instance, you could make M-a and M-A run different commands.

Although only the Control and Meta modifier keys are commonly used, Emacs supports three other modifier keys. These are called Super, Hyper, and Alt. Few terminals provide ways to use these modifiers; the key labeled Alt on most keyboards usually issues the Meta modifier, not Alt. The standard key bindings in Emacs do not include any characters with the Super and Hyper modifiers, and only a small number of standard key bindings use Alt. However, you can customize Emacs to assign meanings to key bindings that use these modifiers. The modifier bits are labeled as ‘s-’, ‘H-’ and ‘A-’ respectively.

Even if your keyboard lacks these additional modifier keys, you can enter them using C-x @: C-x @ h adds the Hyper flag to the next character, C-x @ s adds the Super flag, and C-x @ a adds the Alt flag. For instance, C-x @ h C-a is a way to enter Hyper-Control-a. (Unfortunately, there is no way to add two modifiers by using C-x @ twice for the same character, because the first one goes to work on the C-x.) You can similarly enter the Shift, Control, and Meta modifiers by using C-x @ S, C-x @ c, and C-x @ m, respectively, although this is rarely needed.


50.3.8 Rebinding Function Keys

Key sequences can contain function keys as well as ordinary characters. Just as Lisp characters (actually integers) represent keyboard characters, Lisp symbols represent function keys. If the function key has a word as its label, then that word is also the name of the corresponding Lisp symbol. Here are the conventional Lisp names for common function keys:

left, up, right, down

Cursor arrow keys.

begin, end, home, next, prior

Other cursor repositioning keys.

select, print, execute, backtab
insert, undo, redo, clearline
insertline, deleteline, insertchar, deletechar

Miscellaneous function keys.

f1, f2, … f35

Numbered function keys (across the top of the keyboard).

kp-add, kp-subtract, kp-multiply, kp-divide
kp-backtab, kp-space, kp-tab, kp-enter
kp-separator, kp-decimal, kp-equal
kp-prior, kp-next, kp-end, kp-home
kp-left, kp-up, kp-right, kp-down
kp-insert , kp-delete

Keypad keys (to the right of the regular keyboard), with names or punctuation.

kp-0, kp-1, … kp-9

Keypad keys with digits.

kp-f1, kp-f2, kp-f3, kp-f4

Keypad PF keys.

These names are conventional, but some systems (especially when using X) may use different names. To make certain what symbol is used for a given function key on your terminal, type C-h c followed by that key.

See Rebinding Keys in Your Init File, for examples of binding function keys.

Many keyboards have a numeric keypad on the right-hand side. The numeric keys in the keypad double up as cursor motion keys, toggled by a key labeled ‘Num Lock’. By default, Emacs translates these keys to the corresponding keys on the main keyboard. For example, when ‘Num Lock’ is on, the key labeled ‘8’ on the numeric keypad produces kp-8, which is translated to 8; when ‘Num Lock’ is off, the same key produces kp-up, which is translated to UP. If you rebind a key such as 8 or UP, it affects the equivalent keypad key too. However, if you rebind a ‘kp-’ key directly, that won’t affect its non-keypad equivalent. Note that the modified keys are not translated: for instance, if you hold down the Meta key while pressing the ‘8’ key on the numeric keypad, that generates M-kp-8.

Emacs provides a convenient method for binding the numeric keypad keys, using the variables keypad-setup, keypad-numlock-setup, keypad-shifted-setup, and keypad-numlock-shifted-setup. These can be found in the ‘keyboard’ customization group (see Easy Customization Interface). You can rebind the keys to perform other tasks, such as issuing numeric prefix arguments.


50.3.9 Named ASCII Control Characters

TAB, RET, BS, LFD, ESC, and DEL started out as names for certain ASCII control characters, used so often that they have special keys of their own. For instance, TAB was another name for C-i. Later, users found it convenient to distinguish in Emacs between these keys and the corresponding control characters typed with the Ctrl key. Therefore, on most modern terminals, they are no longer the same: TAB is different from C-i.

Emacs can distinguish these two kinds of input if the keyboard does. It treats the special keys as function keys named tab, return, backspace, linefeed, escape, and delete. These function keys translate automatically into the corresponding ASCII characters if they have no bindings of their own. As a result, neither users nor Lisp programs need to pay attention to the distinction unless they care to.

If you do not want to distinguish between (for example) TAB and C-i, make just one binding, for the ASCII character TAB (octal code 011). If you do want to distinguish, make one binding for this ASCII character, and another for the function key tab.

With an ordinary ASCII terminal, there is no way to distinguish between TAB and C-i (and likewise for other such pairs), because the terminal sends the same character in both cases.


50.3.10 Rebinding Mouse Buttons

Emacs uses Lisp symbols to designate mouse buttons, too. The ordinary mouse events in Emacs are click events; these happen when you press a button and release it without moving the mouse. You can also get drag events, when you move the mouse while holding the button down. Drag events happen when you finally let go of the button.

The symbols for basic click events are mouse-1 for the leftmost button, mouse-2 for the next, and so on. Here is how you can redefine the second mouse button to split the current window:

(keymap-global-set "<mouse-2>" 'split-window-below)

The symbols for drag events are similar, but have the prefix ‘drag-’ before the word ‘mouse’. For example, dragging the first button generates a drag-mouse-1 event.

You can also define bindings for events that occur when a mouse button is pressed down. These events start with ‘down-’ instead of ‘drag-’. Such events are generated only if they have key bindings. When you get a button-down event, a corresponding click or drag event will always follow.

If you wish, you can distinguish single, double, and triple clicks. A double click means clicking a mouse button twice in approximately the same place. The first click generates an ordinary click event. The second click, if it comes soon enough, generates a double-click event instead. The event type for a double-click event starts with ‘double-’: for example, double-mouse-3.

This means that you can give a special meaning to the second click at the same place, but it must act on the assumption that the ordinary single click definition has run when the first click was received.

This constrains what you can do with double clicks, but user interface designers say that this constraint ought to be followed in any case. A double click should do something similar to the single click, only more so. The command for the double-click event should perform the extra work for the double click.

If a double-click event has no binding, it changes to the corresponding single-click event. Thus, if you don’t define a particular double click specially, it executes the single-click command twice.

Emacs also supports triple-click events whose names start with ‘triple-’. Emacs does not distinguish quadruple clicks as event types; clicks beyond the third generate additional triple-click events. However, the full number of clicks is recorded in the event list, so if you know Emacs Lisp you can distinguish if you really want to (see Click Events in The Emacs Lisp Reference Manual). We don’t recommend distinct meanings for more than three clicks, but sometimes it is useful for subsequent clicks to cycle through the same set of three meanings, so that four clicks are equivalent to one click, five are equivalent to two, and six are equivalent to three.

Emacs also records multiple presses in drag and button-down events. For example, when you press a button twice, then move the mouse while holding the button, Emacs gets a ‘double-drag-’ event. And at the moment when you press it down for the second time, Emacs gets a ‘double-down-’ event (which is ignored, like all button-down events, if it has no binding).

The variable double-click-time specifies how much time can elapse between clicks and still allow them to be grouped as a multiple click. Its value is in units of milliseconds. If the value is nil, double clicks are not detected at all. If the value is t, then there is no time limit. The default is 500.

The variable double-click-fuzz specifies how much the mouse can move between clicks and still allow them to be grouped as a multiple click. Its value is in units of pixels on windowed displays and in units of 1/8 of a character cell on text-mode terminals; the default is 3.

The symbols for mouse events also indicate the status of the modifier keys, with the usual prefixes ‘C-’, ‘M-’, ‘H-’, ‘s-’, ‘A-’, and ‘S-’. These always precede ‘double-’ or ‘triple-’, which always precede ‘drag-’ or ‘down-’.

A frame includes areas that don’t show text from the buffer, such as the mode line and the scroll bar. You can tell whether a mouse button comes from a special area of the screen by means of dummy prefix keys. For example, if you click the mouse in the mode line, you get the prefix key mode-line before the ordinary mouse-button symbol. Thus, here is how to define the command for clicking the first button in a mode line to run scroll-up-command:

(keymap-global-set "<mode-line> <mouse-1>" 'scroll-up-command)

Here is the complete list of these dummy prefix keys and their meanings:

mode-line

The mouse was in the mode line of a window.

vertical-line

The mouse was in the vertical line separating side-by-side windows. (If you use scroll bars, they appear in place of these vertical lines.)

vertical-scroll-bar

The mouse was in a vertical scroll bar. (This is the only kind of scroll bar Emacs currently supports.)

menu-bar

The mouse was in the menu bar.

tab-bar

The mouse was in a tab bar.

tab-line

The mouse was in a tab line.

header-line

The mouse was in a header line.

You can put more than one mouse button in a key sequence, but it isn’t usual to do so.


50.3.11 Disabling Commands

Disabling a command means that invoking it interactively asks for confirmation from the user. The purpose of disabling a command is to prevent users from executing it by accident; we do this for commands that might be confusing to the uninitiated.

Attempting to invoke a disabled command interactively in Emacs displays a window containing the command’s name, its documentation, and some instructions on what to do immediately; then Emacs asks for input saying whether to execute the command as requested, enable it and execute it, or cancel. If you decide to enable the command, you must then answer another question—whether to do this permanently, or just for the current session. (Enabling permanently works by automatically editing your initialization file.) You can also type ! to enable all commands, for the current session only.

The direct mechanism for disabling a command is to put a non-nil disabled property on the Lisp symbol for the command. Here is the Lisp program to do this:

(put 'delete-region 'disabled t)

If the value of the disabled property is a string, that string is included in the message displayed when the command is used:

(put 'delete-region 'disabled
     "It's better to use `kill-region' instead.\n")

As a less heavy-handed alternative to disabling commands, you may want to be queried before executing a command. For instance, to be queried before executing the M-> (end-of-buffer) command, you could put something like the following in your init file:

(command-query
 'end-of-buffer
 "Do you really want to go to the end of the buffer?")

By default, you’ll be queried with a y/n question, but if you give a non-nil value to the third, optional argument, you’ll be queried with yes/no instead.

You can make a command disabled either by editing the initialization file directly, or with the command M-x disable-command, which edits the initialization file for you. Likewise, M-x enable-command edits the initialization file to enable a command permanently. See The Emacs Initialization File.

If Emacs was invoked with the -q or --no-init-file options (see Initial Options), it will not edit your initialization file. Doing so could lose information because Emacs has not read your initialization file.

Whether a command is disabled is independent of what key is used to invoke it; disabling also applies if the command is invoked using M-x. However, disabling a command has no effect on calling it as a function from Lisp programs.


50.4 The Emacs Initialization File

When Emacs is started, it normally tries to load a Lisp program from an initialization file, or init file for short. This file, if it exists, specifies how to initialize Emacs for you. Traditionally, file ~/.emacs is used as the init file, although Emacs also looks at ~/.emacs.el, ~/.emacs.d/init.el, ~/.config/emacs/init.el, or other locations. See How Emacs Finds Your Init File.

You may find it convenient to have all your Emacs configuration in one directory, in which case you should use ~/.emacs.d/init.el or the XDG-compatible ~/.config/emacs/init.el.

You can use the command line switch ‘-q’ to prevent loading your init file, and ‘-u’ (or ‘--user’) to specify a different user’s init file (see Initial Options).

There can also be a default init file, which is the library named default.el, found via the standard search path for libraries. The Emacs distribution contains no such library; your site may create one for local customizations. If this library exists, it is loaded whenever you start Emacs (except when you specify ‘-q’). But your init file, if any, is loaded first; if it sets inhibit-default-init non-nil, then default is not loaded.

Your site may also have a site startup file; this is named site-start.el, if it exists. Like default.el, Emacs finds this file via the standard search path for Lisp libraries. Emacs loads this library before it loads your init file. To inhibit loading of this library, use the option ‘--no-site-file’. See Initial Options. We recommend against using site-start.el for changes that some users may not like. It is better to put them in default.el, so that users can more easily override them.

You can place default.el and site-start.el in any of the directories which Emacs searches for Lisp libraries. The variable load-path (see Libraries of Lisp Code for Emacs) specifies these directories. Many sites put these files in a subdirectory named site-lisp in the Emacs installation directory, such as /usr/local/share/emacs/site-lisp.

Byte-compiling your init file is not recommended (see Byte Compilation in the Emacs Lisp Reference Manual). It generally does not speed up startup very much, and often leads to problems when you forget to recompile the file. A better solution is to use the Emacs server to reduce the number of times you have to start Emacs (see Using Emacs as a Server). If your init file defines many functions, consider moving them to a separate (byte-compiled) file that you load in your init file.

If you are going to write actual Emacs Lisp programs that go beyond minor customization, you should read the Emacs Lisp Reference Manual. See Emacs Lisp in the Emacs Lisp Reference Manual.


50.4.1 Init File Syntax

The init file contains one or more Lisp expressions. Each of these consists of a function name followed by arguments, all surrounded by parentheses. For example, (setq fill-column 60) calls the function setq to set the variable fill-column (see Filling Text) to 60.

You can set any Lisp variable with setq, but with certain variables setq won’t do what you probably want in the init file. Some variables automatically become buffer-local when set with setq; what you want in the init file is to set the default value, using setq-default. (The following section has examples of both of these methods.)

Some customizable minor mode variables do special things to enable the mode when you set them with Customize, but ordinary setq won’t do that; to enable the mode in your init file, call the minor mode command. Finally, a few customizable user options are initialized in complex ways, and these have to be set either via the customize interface (see Customization), or by using customize-set-variable/setopt (see Examining and Setting Variables).

The second argument to setq is an expression for the new value of the variable. This can be a constant, a variable, or a function call expression. In the init file, constants are used most of the time. They can be:

Numbers:

Numbers are written in decimal, with an optional initial minus sign.

Strings:

Lisp string syntax is the same as C string syntax with a few extra features. Use a double-quote character to begin and end a string constant.

In a string, you can include newlines and special characters literally. But often it is cleaner to use backslash sequences for them: ‘\n’ for newline, ‘\b’ for backspace, ‘\r’ for carriage return, ‘\t’ for tab, ‘\f’ for formfeed (control-L), ‘\e’ for escape, ‘\\’ for a backslash, ‘\"’ for a double-quote, or ‘\ooo’ for the character whose octal code is ooo. Backslash and double-quote are the only characters for which backslash sequences are mandatory.

\C-’ can be used as a prefix for a control character, as in ‘\C-s’ for ASCII control-S, and ‘\M-’ can be used as a prefix for a Meta character, as in ‘\M-a’ for Meta-A or ‘\M-\C-a’ for Ctrl-Meta-A.

See Non-ASCII Characters in Init Files, for information about including non-ASCII in your init file.

Characters:

Lisp character constant syntax consists of a ‘?’ followed by either a character or an escape sequence starting with ‘\’. Examples: ?x, ?\n, ?\", ?\). Note that strings and characters are not interchangeable in Lisp; some contexts require one and some contexts require the other.

See Non-ASCII Characters in Init Files, for information about binding commands to keys which send non-ASCII characters.

True:

t stands for “true”.

False:

nil stands for “false”.

Other Lisp objects:

Write a single-quote (') followed by the Lisp object you want.

For more information on the Emacs Lisp syntax, see Introduction in The Emacs Lisp Reference Manual.


50.4.2 Init File Examples

Here are some examples of doing certain commonly desired things with Lisp expressions:

  • Add a directory to the variable load-path. You can then put Lisp libraries that are not included with Emacs in this directory, and load them with M-x load-library. See Libraries of Lisp Code for Emacs.
    (add-to-list 'load-path "/path/to/lisp/libraries")
    
  • Make TAB in C mode just insert a tab if point is in the middle of a line.
    (setq c-tab-always-indent nil)
    

    Here we have a variable whose value is normally t for “true” and the alternative is nil for “false”.

  • Make searches case sensitive by default (in all buffers that do not override this).
    (setq-default case-fold-search nil)
    

    This sets the default value, which is effective in all buffers that do not have local values for the variable (see Local Variables). Setting case-fold-search with setq affects only the current buffer’s local value, which is probably not what you want to do in an init file.

  • Specify your own email address, if Emacs can’t figure it out correctly.
    (setq user-mail-address "cheney@torture.gov")
    

    Various Emacs packages, such as Message mode, consult user-mail-address when they need to know your email address. See Mail Header Fields.

  • Make Text mode the default mode for new buffers.
    (setq-default major-mode 'text-mode)
    

    Note that text-mode is used because it is the command for entering Text mode. The single-quote before it makes the symbol a constant; otherwise, text-mode would be treated as a variable name.

  • Set up defaults for the Latin-1 character set, which supports most of the languages of Western Europe.
    (set-language-environment "Latin-1")
    
  • Turn off Line Number mode, a global minor mode.
    (line-number-mode 0)
    
  • Turn on Auto Fill mode automatically in Text mode and related modes (see Hooks).
    (add-hook 'text-mode-hook 'auto-fill-mode)
    
  • Change the coding system used when using the clipboard (see Coding Systems for Interprocess Communication).
    (setopt selection-coding-system 'utf-8)
    
  • Load the installed Lisp library named foo (actually a file foo.elc or foo.el in a standard Emacs directory).
    (load "foo")
    

    When the argument to load is a relative file name, not starting with ‘/’ or ‘~’, load searches the directories in load-path (see Libraries of Lisp Code for Emacs).

  • Load the compiled Lisp file foo.elc from your home directory.
    (load "~/foo.elc")
    

    Here a full file name is used, so no searching is done.

  • Tell Emacs to find the definition for the function myfunction by loading a Lisp library named mypackage (i.e., a file mypackage.elc or mypackage.el):
    (autoload 'myfunction "mypackage" "Do what I say." t)
    

    Here the string "Do what I say." is the function’s documentation string. You specify it in the autoload definition so it will be available for help commands even when the package is not loaded. The last argument, t, indicates that this function is interactive; that is, it can be invoked interactively by typing M-x myfunction RET or by binding it to a key. If the function is not interactive, omit the t or use nil.

  • Rebind the key C-x l to run the function make-symbolic-link (see Rebinding Keys in Your Init File).
    (keymap-global-set "C-x l" 'make-symbolic-link)
    

    or

    (keymap-set global-map "C-x l" 'make-symbolic-link)
    

    Note once again the single-quote used to refer to the symbol make-symbolic-link instead of its value as a variable.

  • Do the same thing for Lisp mode only.
    (keymap-set lisp-mode-map "C-x l" 'make-symbolic-link)
    
  • Redefine all keys which now run next-line in Fundamental mode so that they run forward-line instead.
    (keymap-substitute global-map 'next-line 'forward-line)
    
  • Make C-x C-v undefined.
    (keymap-global-unset "C-x C-v")
    

    One reason to undefine a key is so that you can make it a prefix. Simply defining C-x C-v anything will make C-x C-v a prefix, but C-x C-v must first be freed of its usual non-prefix definition.

  • Make ‘$’ have the syntax of punctuation in Text mode. Note the use of a character constant for ‘$’.
    (modify-syntax-entry ?\$ "." text-mode-syntax-table)
    
  • Enable the use of the command narrow-to-region without confirmation.
    (put 'narrow-to-region 'disabled nil)
    
  • Adjusting the configuration to various platforms and Emacs versions.

    Users typically want Emacs to behave the same on all systems, so the same init file is right for all platforms. However, sometimes it happens that a function you use for customizing Emacs is not available on some platforms or in older Emacs versions. To deal with that situation, put the customization inside a conditional that tests whether the function or facility is available, like this:

    (if (fboundp 'blink-cursor-mode)
        (blink-cursor-mode 0))
    
    (if (boundp 'coding-category-utf-8)
        (set-coding-priority '(coding-category-utf-8)))
    

    You can also simply disregard the errors that occur if the function is not defined.

    (ignore-errors (set-face-background 'region "grey75"))
    

    A setq on a variable which does not exist is generally harmless, so those do not need a conditional.

  • Using use-package to automatically load and configure a package.
    (use-package hi-lock
      :defer t
      :init (add-hook 'some-hook 'hi-lock-mode)
      :config (use-package my-hi-lock)
      :bind (("M-o l" . highlight-lines-matching-regexp)
             ("M-o r" . highlight-regexp)
             ("M-o w" . highlight-phrase)))
    

    This will load hi-lock when some of its commands or variables are first used, bind 3 keys to its commands, and additionally load the my-hi-lock package (presumably further customizing hi-lock) after loading hi-lock. The use-package facility is fully documented in its own manual, see use-package User manual.


50.4.3 Terminal-specific Initialization

Each terminal type can have a Lisp library to be loaded into Emacs when it is run on that type of terminal. For a terminal type named termtype, the library is called term/termtype. (If there is an entry of the form (termtype . alias) in the term-file-aliases association list, Emacs uses alias in place of termtype.) The library is found by searching the directories load-path as usual and trying the suffixes ‘.elc’ and ‘.el’. Normally it appears in the subdirectory term of the directory where most Emacs libraries are kept.

The usual purpose of the terminal-specific library is to map the escape sequences used by the terminal’s function keys onto more meaningful names, using input-decode-map. See the file term/lk201.el for an example of how this is done. Many function keys are mapped automatically according to the information in the Termcap data base; the terminal-specific library needs to map only the function keys that Termcap does not specify.

When the terminal type contains a hyphen, only the part of the name before the first hyphen is significant in choosing the library name. Thus, terminal types ‘aaa-48’ and ‘aaa-30-rv’ both use the library term/aaa. The code in the library can use (getenv "TERM") to find the full terminal type name.

The library’s name is constructed by concatenating the value of the variable term-file-prefix and the terminal type. Your .emacs file can prevent the loading of the terminal-specific library by setting term-file-prefix to nil.

Emacs runs the hook tty-setup-hook at the end of initialization, after both your .emacs file and any terminal-specific library have been read in. Add hook functions to this hook if you wish to override part of any of the terminal-specific libraries and to define initializations for terminals that do not have a library. See Hooks.


50.4.4 How Emacs Finds Your Init File

Emacs normally finds your init file in a location under your home directory25. See The Emacs Initialization File.

Emacs looks for your init file using the filenames ~/.emacs.el, ~/.emacs, or ~/.emacs.d/init.el in that order; you can choose to use any one of these names. (Note that only the locations directly in your home directory have a leading dot in the location’s basename.)

Emacs can also look in an XDG-compatible location for init.el, the default is the directory ~/.config/emacs. This can be overridden by setting XDG_CONFIG_HOME in your environment, its value replaces ~/.config in the name of the default XDG init file. However ~/.emacs.d, ~/.emacs, and ~/.emacs.el are always preferred if they exist, which means that you must delete or rename them in order to use the XDG location.

Note also that if neither the XDG location nor ~/.emacs.d exist, then Emacs will create ~/.emacs.d (and therefore use it during subsequent invocations).

Emacs will set user-emacs-directory to the directory it decides to use.

Although this is backward-compatible with older Emacs versions, modern POSIX platforms prefer putting your initialization files under ~/.config so that troubleshooting a problem that might be due to a bad init file, or archiving a collection of init files, can be done by renaming that directory. To help older Emacs versions find configuration files in their current default locations, you can execute the following Emacs Lisp code:

(make-symbolic-link ".config/emacs" "~/.emacs.d")

However, if you run Emacs from a shell started by su and XDG_CONFIG_HOME is not set in your environment, Emacs tries to find your own initialization files, not that of the user you are currently pretending to be. The idea is that you should get your own editor customizations even if you are running as the super user.

More precisely, Emacs first determines which user’s init file to use. It gets your user name from the environment variables LOGNAME and USER; if neither of those exists, it uses the effective user-ID. If that user name matches the real user-ID, then Emacs uses HOME; otherwise, it looks up the home directory corresponding to that user name in the system’s data base of users.

For brevity the rest of the Emacs documentation generally uses just the current default location ~/.emacs.d/init.el for the init file.


50.4.5 Non-ASCII Characters in Init Files

Language and coding systems may cause problems if your init file contains non-ASCII characters, such as accented letters, in strings or key bindings.

If you want to use non-ASCII characters in your init file, you should put a ‘-*-coding: coding-system-*- tag on the first line of the init file, and specify a coding system that supports the character(s) in question. See Recognizing Coding Systems. This is because the defaults for decoding non-ASCII text might not yet be set up by the time Emacs reads those parts of your init file which use such strings, possibly leading Emacs to decode those strings incorrectly. You should then avoid adding Emacs Lisp code that modifies the coding system in other ways, such as calls to set-language-environment.

An alternative to using non-ASCII characters directly is to use one of the character escape syntaxes described in see General Escape Syntax in The Emacs Lisp Reference Manual, as they allow all Unicode codepoints to be specified using only ASCII characters.

To bind non-ASCII keys, you must use a vector (see Rebinding Keys in Your Init File). The string syntax cannot be used, since the non-ASCII characters will be interpreted as meta keys. For instance:

(global-set-key [?char] 'some-function)

Type C-q, followed by the key you want to bind, to insert char.


50.4.6 The Early Init File

Most customizations for Emacs should be put in the normal init file. See The Emacs Initialization File. However, it is sometimes necessary to have customizations take effect during Emacs startup earlier than the normal init file is processed. Such customizations can be put in the early init file, ~/.config/emacs/early-init.el or ~/.emacs.d/early-init.el. This file is loaded before the package system and GUI is initialized, so in it you can customize variables that affect the package initialization process, such as package-enable-at-startup, package-load-list, and package-user-dir. Note that variables like package-archives which only affect the installation of new packages, and not the process of making already-installed packages available, may be customized in the regular init file. See Package Installation.

We do not recommend that you move into early-init.el customizations that can be left in the normal init files. That is because the early init file is read before the GUI is initialized, so customizations related to GUI features will not work reliably in early-init.el. By contrast, the normal init files are read after the GUI is initialized. If you must have customizations in the early init file that rely on GUI features, make them run off hooks provided by the Emacs startup, such as window-setup-hook or tty-setup-hook. See Hooks.

For more information on the early init file, see Init File in The Emacs Lisp Reference Manual.


50.5 Keeping Persistent Authentication Information

Some Emacs packages, which connect to other services, require authentication (see Entering passwords), e.g., see Gnus in The Gnus Manual, or Tramp in The Tramp Manual. Because it might be annoying to provide the same user name and password again and again, Emacs offers to keep this information persistent via the auth-source library.

By default, the authentication information is taken from the file ~/.authinfo or ~/.authinfo.gpg or ~/.netrc. These files have a syntax similar to netrc files as known from the ftp program, like this:

machine mymachine login myloginname password mypassword port myport

Similarly, the auth-source library supports multiple storage backend, currently either the classic netrc backend, JSON files, the Secret Service API, and pass, the standard unix password manager.

All these alternatives can be customized via the user option auth-sources, see Emacs auth-source in Emacs auth-source.

When a password is entered interactively, which is not found via the configured backend, some of the backends offer to save it persistently. This can be changed by customizing the user option auth-source-save-behavior.


51 Quitting and Aborting

C-g
C-Break (MS-DOS only)

Quit: cancel running or partially typed command.

C-]

Abort innermost recursive editing level and cancel the command which invoked it (abort-recursive-edit).

ESC ESC ESC

Either quit or abort, whichever makes sense (keyboard-escape-quit).

M-x top-level

Abort all recursive editing levels that are currently executing.

C-/
C-x u
C-_

Cancel a previously made change in the buffer contents (undo).

There are two ways of canceling a command before it has finished: quitting with C-g, and aborting with C-] or M-x top-level. Quitting cancels a partially typed command, or one which is still running. Aborting exits a recursive editing level and cancels the command that invoked the recursive edit (see Recursive Editing Levels).

Quitting with C-g is the way to get rid of a partially typed command, or a numeric argument that you don’t want. Furthermore, if you are in the middle of a command that is running, C-g stops the command in a relatively safe way. For example, if you quit out of a kill command that is taking a long time, either your text will all still be in the buffer, or it will all be in the kill ring, or maybe both. If the region is active, C-g deactivates the mark, unless Transient Mark mode is off (see Disabling Transient Mark Mode). If you are in the middle of an incremental search, C-g behaves specially; it may take two successive C-g characters to get out of a search. See Incremental Search, for details.

If you type C-g in a minibuffer, this quits the command that opened that minibuffer, closing it. If that minibuffer is not the most recently opened one (which can happen when minibuffer-follows-selected-frame is nil (see Using the Minibuffer)), C-g also closes the more recently opened ones, quitting their associated commands, after asking you for confirmation.

On MS-DOS, the character C-Break serves as a quit character like C-g. The reason is that it is not feasible, on MS-DOS, to recognize C-g while a command is running, between interactions with the user. By contrast, it is feasible to recognize C-Break at all times. See Keyboard Usage on MS-DOS.

C-g works by setting the variable quit-flag to t the instant C-g is typed; Emacs Lisp checks this variable frequently, and quits if it is non-nil. C-g is only actually executed as a command if you type it while Emacs is waiting for input. In that case, the command it runs is keyboard-quit.

On a text terminal, if you quit with C-g a second time before the first C-g is recognized, you activate the emergency-escape feature and return to the shell. See Emergency Escape.

There are some situations where you cannot quit. When Emacs is waiting for the operating system to do something, quitting is impossible unless special pains are taken for the particular system call within Emacs where the waiting occurs. We have done this for the system calls that users are likely to want to quit from, but it’s possible you will encounter a case not handled. In one very common case—waiting for file input or output using NFS—Emacs itself knows how to quit, but many NFS implementations simply do not allow user programs to stop waiting for NFS when the NFS server is hung.

Aborting with C-] (abort-recursive-edit) is used to get out of a recursive editing level and cancel the command which invoked it. Quitting with C-g does not do this, and could not do this, because it is used to cancel a partially typed command within the recursive editing level. Both operations are useful. For example, if you are in a recursive edit and type C-u 8 to enter a numeric argument, you can cancel that argument with C-g and remain in the recursive edit.

The sequence ESC ESC ESC (keyboard-escape-quit) can either quit or abort. (We defined it this way because ESC means “get out” in many PC programs.) It can cancel a prefix argument, clear a selected region, or get out of a Query Replace, like C-g. It can get out of the minibuffer or a recursive edit, like C-]. It can also get out of splitting the frame into multiple windows, as with C-x 1. One thing it cannot do, however, is stop a command that is running. That’s because it executes as an ordinary command, and Emacs doesn’t notice it until it is ready for the next command.

The command M-x top-level is equivalent to enough C-] commands to get you out of all the levels of recursive edits that you are in; it also exits the minibuffer if it is active. C-] gets you out one level at a time, but M-x top-level goes out all levels at once. Both C-] and M-x top-level are like all other commands, and unlike C-g, in that they take effect only when Emacs is ready for a command. C-] is an ordinary key and has its meaning only because of its binding in the keymap. See Recursive Editing Levels.

C-/ (undo) is not strictly speaking a way of canceling a command, but you can think of it as canceling a command that already finished executing. See Undo, for more information about the undo facility.


52 Dealing with Emacs Trouble

This section describes how to recognize and deal with situations in which Emacs does not work as you expect, such as keyboard code mixups, garbled displays, running out of memory, and crashes and hangs.

See Reporting Bugs, for what to do when you think you have found a bug in Emacs.


52.1 Recursive Editing Levels

Recursive editing levels are important and useful features of Emacs, but they can seem like malfunctions if you do not understand them.

If the mode line has square brackets ‘[…]’ around the parentheses that contain the names of the major and minor modes, you have entered a recursive editing level. If you did not do this on purpose, or if you don’t understand what that means, you should just get out of the recursive editing level. To do so, type M-x top-level. See Recursive Editing Levels.


52.2 Garbage on the Screen

If the text on a text terminal looks wrong, the first thing to do is see whether it is wrong in the buffer. Type C-l (recenter-top-bottom) to redisplay the entire screen. If the screen appears correct after this, the problem was entirely in the previous screen update. (Otherwise, see the following section.)

Display updating problems often result from an incorrect terminfo entry for the terminal you are using. The file etc/TERMS in the Emacs distribution gives the fixes for known problems of this sort. INSTALL contains general advice for these problems in one of its sections. If you seem to be using the right terminfo entry, it is possible that there is a bug in the terminfo entry, or a bug in Emacs that appears for certain terminal types.


52.3 Garbage in the Text

If C-l shows that the text is wrong, first type C-h l (view-lossage) to see what commands you typed to produce the observed results. Then try undoing the changes step by step using C-x u (undo), until it gets back to a state you consider correct.

If a large portion of text appears to be missing at the beginning or end of the buffer, check for the word ‘Narrow’ in the mode line. If it appears, the text you don’t see is probably still present, but temporarily off-limits. To make it accessible again, type C-x n w (widen). See Narrowing.


52.4 Running out of Memory

If you get the error message ‘Virtual memory exceeded’, save your modified buffers with C-x s (save-some-buffers). This method of saving them has the smallest need for additional memory. Emacs keeps a reserve of memory which it makes available when this error happens; that should be enough to enable C-x s to complete its work. When the reserve has been used, ‘!MEM FULL!’ appears at the beginning of the mode line, indicating there is no more reserve.

Once you have saved your modified buffers, you can exit this Emacs session and start another, or you can use M-x kill-some-buffers to free space in the current Emacs job. If this frees up sufficient space, Emacs will refill its memory reserve, and ‘!MEM FULL!’ will disappear from the mode line. That means you can safely go on editing in the same Emacs session.

Do not use M-x buffer-menu to save or kill buffers when you run out of memory, because the Buffer Menu needs a fair amount of memory itself, and the reserve supply may not be enough.

On GNU/Linux systems, Emacs does not normally get notified about out-of-memory situations; instead, the OS can kill the Emacs process when it runs out of memory. This feature is known as the out-of-memory killer, or OOM killer. When this behavior is in effect, Emacs is unable to detect the out-of-memory situation in time, and won’t be able to let you save your buffer as described above. However, it is possible to turn off this behavior of the OS, and thus allow Emacs a chance to handle the out-of-memory situation in a more useful manner, before it is killed. To do that, become the super user, edit the file /etc/sysctl.conf to contain the lines shown below, and then invoke the command sysctl -p from the shell prompt:

vm.overcommit_memory=2
vm.overcommit_ratio=0

Please note that the above setting affects all the processes on the system, and in general the behavior of the system under memory pressure, not just the Emacs process alone.


52.5 When Emacs Crashes

Emacs is not supposed to crash, but if it does, it produces a crash report prior to exiting. The crash report is printed to the standard error stream. If Emacs was started from a graphical desktop on a GNU or Unix system, the standard error stream is commonly redirected to a file such as ~/.xsession-errors, so you can look for the crash report there. On MS-Windows, the crash report is written to a file named emacs_backtrace.txt in the current directory of the Emacs process, in addition to the standard error stream.

The format of the crash report depends on the platform. On some platforms, such as those using the GNU C Library, the crash report includes a backtrace describing the execution state prior to crashing, which can be used to help debug the crash. Here is an example for a GNU system:

Fatal error 11: Segmentation fault
Backtrace:
emacs[0x5094e4]
emacs[0x4ed3e6]
emacs[0x4ed504]
/lib64/libpthread.so.0[0x375220efe0]
/lib64/libpthread.so.0(read+0xe)[0x375220e08e]
emacs[0x509af6]
emacs[0x5acc26]
…

The number ‘11’ is the system signal number corresponding to the crash—in this case a segmentation fault. The hexadecimal numbers are program addresses, which can be associated with source code lines using a debugging tool. For example, the GDB command ‘list *0x509af6’ prints the source-code lines corresponding to the ‘emacs[0x509af6]’ entry. If your system has the addr2line utility, the following shell command outputs a backtrace with source-code line numbers:

sed -n 's/.*\[\(.*\)]$/\1/p' backtrace |
  addr2line -C -f -i -p -e bindir/emacs-binary

On MS-Windows, the backtrace looks somewhat differently, for example:

Backtrace:
00007ff61166a12e
00007ff611538be1
00007ff611559601
00007ff6116ce84a
00007ff9b7977ff0
…

Therefore, the filtering via sed is not required, and the command to show the source-code line number is

 addr2line -C -f -i -p -e bindir/emacs-binary < backtrace

Here, backtrace is the name of a text file containing a copy of the backtrace (on MS-Windows, emacs_backtrace.txt in the directory where Emacs was started), bindir is the name of the directory that contains the Emacs executable, and emacs-binary is the name of the Emacs executable file, normally emacs on GNU and Unix systems and emacs.exe on MS-Windows and MS-DOS. Omit the -p option if your version of addr2line is too old to have it.

Optionally, Emacs can generate a core dump when it crashes, on systems that support core files. A core dump is a file containing voluminous data about the state of the program prior to the crash, usually examined by loading it into a debugger such as GDB. On many platforms, core dumps are disabled by default, and you must explicitly enable them by running the shell command ‘ulimit -c unlimited’ (e.g., in your shell startup script).


52.6 Recovery After a Crash

If Emacs or the computer crashes, you can recover the files you were editing at the time of the crash from their auto-save files. To do this, start Emacs again and type the command M-x recover-session.

This command initially displays a buffer which lists interrupted session files, each with its date. You must choose which session to recover from. Typically the one you want is the most recent one. Move point to the one you choose, and type C-c C-c.

Then recover-session considers each of the files that you were editing during that session; for each such file, it asks whether to recover that file. If you answer y for a file, it shows the dates of that file and its auto-save file, then asks once again whether to recover that file. For the second question, you must confirm with yes. If you do, Emacs visits the file but gets the text from the auto-save file.

When recover-session is done, the files you’ve chosen to recover are present in Emacs buffers. You should then save them. Only this—saving them—updates the files themselves.

As a last resort, if you had buffers with content which were not associated with any files, or if the autosave was not recent enough to have recorded important changes, you can use the etc/emacs-buffer.gdb script with GDB (the GNU Debugger) to retrieve them from a core dump—provided that a core dump was saved, and that the Emacs executable was not stripped of its debugging symbols.

As soon as you get the core dump, rename it to another name such as core.emacs, so that another crash won’t overwrite it.

To use this script, run gdb with the file name of your Emacs executable and the file name of the core dump, e.g., ‘gdb /usr/bin/emacs core.emacs’. At the (gdb) prompt, load the recovery script: ‘source /usr/src/emacs/etc/emacs-buffer.gdb’. Then type the command ybuffer-list to see which buffers are available. For each buffer, it lists a buffer number. To save a buffer, use ysave-buffer; you specify the buffer number, and the file name to write that buffer into. You should use a file name which does not already exist; if the file does exist, the script does not make a backup of its old contents.


52.7 Emergency Escape

On text terminals, the emergency escape feature suspends Emacs immediately if you type C-g a second time before Emacs can actually respond to the first one by quitting. This is so you can always get out of GNU Emacs no matter how badly it might be hung. When things are working properly, Emacs recognizes and handles the first C-g so fast that the second one won’t trigger emergency escape. However, if some problem prevents Emacs from handling the first C-g properly, then the second one will get you back to the shell.

When you resume Emacs after a suspension caused by emergency escape, it reports the resumption and asks a question or two before going back to what it had been doing:

Emacs is resuming after an emergency escape.
Auto-save? (y or n)
Abort (and dump core)? (y or n)

Answer each question with y or n followed by RET.

Saying y to ‘Auto-save?’ causes immediate auto-saving of all modified buffers in which auto-saving is enabled. Saying n skips this. This question is omitted if Emacs is in a state where auto-saving cannot be done safely.

Saying y to ‘Abort (and dump core)?’ causes Emacs to crash, dumping core. This is to enable a wizard to figure out why Emacs was failing to quit in the first place. Execution does not continue after a core dump.

If you answer this question n, Emacs execution resumes. With luck, Emacs will ultimately do the requested quit. If not, each subsequent C-g invokes emergency escape again.

If Emacs is not really hung, just slow, you may invoke the double C-g feature without really meaning to. Then just resume and answer n to both questions, and you will get back to the former state. The quit you requested will happen by and by.

Emergency escape is active only for text terminals. On graphical displays, you can use the mouse to kill Emacs or switch to another program.

On MS-DOS, you must type C-Break (twice) to cause emergency escape—but there are cases where it won’t work, when a system call hangs or when Emacs is stuck in a tight loop in C code.


52.8 If DEL Fails to Delete

Every keyboard has a large key, usually labeled BACKSPACE, which is ordinarily used to erase the last character that you typed. In Emacs, this key is supposed to be equivalent to DEL.

When Emacs starts up on a graphical display, it determines automatically which key should be DEL. In some unusual cases, Emacs gets the wrong information from the system, and BACKSPACE ends up deleting forwards instead of backwards.

Some keyboards also have a Delete key, which is ordinarily used to delete forwards. If this key deletes backward in Emacs, that too suggests Emacs got the wrong information—but in the opposite sense.

On a text terminal, if you find that BACKSPACE prompts for a Help command, like Control-h, instead of deleting a character, it means that key is actually sending the ‘BS’ character. Emacs ought to be treating BS as DEL, but it isn’t.

In all of those cases, the immediate remedy is the same: use the command M-x normal-erase-is-backspace-mode. This toggles between the two modes that Emacs supports for handling DEL, so if Emacs starts in the wrong mode, this should switch to the right mode. On a text terminal, if you want to ask for help when BS is treated as DEL, use F1 instead of C-h; C-? may also work, if it sends character code 127.

To fix the problem in every Emacs session, put one of the following lines into your initialization file (see The Emacs Initialization File). For the first case above, where BACKSPACE deletes forwards instead of backwards, use this line to make BACKSPACE act as DEL:

(normal-erase-is-backspace-mode 0)

For the other two cases, use this line:

(normal-erase-is-backspace-mode 1)

Another way to fix the problem for every Emacs session is to customize the variable normal-erase-is-backspace: the value t specifies the mode where BS or BACKSPACE is DEL, and nil specifies the other mode. See Easy Customization Interface.


53 Reporting Bugs

If you think you have found a bug in Emacs, please report it. We cannot promise to fix it, or always to agree that it is a bug, but we certainly want to hear about it. The same applies for new features you would like to see added. This section will help you to determine whether you found a bug, and if so, construct an effective bug report.

The general procedure when you find something that could be a bug is as follows:


53.1 Reading Existing Bug Reports and Known Problems

Before reporting a bug, if at all possible, please check to see if we already know about it. Indeed, it may already have been fixed in a later release of Emacs, or in the development version. Here is a list of the main places you can read about known issues:

  • The etc/PROBLEMS file; type C-h C-p to read it. This file contains a list of particularly well-known issues that have been encountered in compiling, installing and running Emacs, with special emphasis on issues caused by other software that cannot be easily solved in Emacs. Often, you will find there suggestions for workarounds and solutions.
  • The GNU Bug Tracker at https://debbugs.gnu.org. Emacs bugs and issues are filed in the tracker under the ‘emacs’ package. The tracker records information about the status of each bug, the initial bug report, and the follow-up messages by the bug reporter and Emacs developers who participate in discussing and fixing the bug. You can search for bugs by subject, severity, and other criteria. For more complex search criteria, use https://debbugs.gnu.org/cgi/search.cgi.

    Instead of browsing the bug tracker as a web page, you can browse it from Emacs using the debbugs package, which can be downloaded via the Package Menu (see Emacs Lisp Packages). This package provides the command M-x debbugs-gnu to list bugs, and M-x debbugs-gnu-search to search for a specific bug. User tags, applied by the Emacs maintainers, are shown by M-x debbugs-gnu-usertags.

  • The ‘bug-gnu-emacs’ mailing list (also available as the newsgroup ‘gnu.emacs.bug’). You can read the list archives at https://lists.gnu.org/mailman/listinfo/bug-gnu-emacs. This list works as a mirror of the Emacs bug reports and follow-up messages which are sent to the bug tracker. It also contains old bug reports from before the bug tracker was introduced (in early 2008).

    If you like, you can subscribe to the list. Be aware that its purpose is to provide the Emacs maintainers with information about bugs and feature requests, so reports may contain fairly large amounts of data; spectators should not complain about this.

  • The ‘emacs-pretest-bug’ mailing list. This list is no longer used, and is mainly of historical interest. At one time, it was used for bug reports in development (i.e., not yet released) versions of Emacs. You can read the archives for 2003 to mid 2007 at https://lists.gnu.org/r/emacs-pretest-bug/. Nowadays, email messages sent to this list are redirected to ‘bug-gnu-emacs’.
  • The ‘emacs-devel’ mailing list. Sometimes people report bugs to this mailing list. This is not the main purpose of the list, however, and it is much better to send bug reports to the bug list. You should not feel obliged to read this list before reporting a bug.

53.2 When Is There a Bug

If Emacs accesses an invalid memory location (a.k.a. “segmentation fault”) or exits with an operating system error message that indicates a problem in the program (as opposed to something like “disk full”), then it is certainly a bug.

If the Emacs display does not correspond properly to the contents of the buffer, then it is a bug. But you should check that features like buffer narrowing (see Narrowing), which can hide parts of the buffer or change how it is displayed, are not responsible.

Taking forever to complete a command can be a bug, but you must make sure that it is really Emacs’s fault. Some commands simply take a long time. Type C-g (C-Break on MS-DOS) and then C-h l to see whether the input Emacs received was what you intended to type; if the input was such that you know it should have been processed quickly, report a bug. If you don’t know whether the command should take a long time, find out by looking in the manual or by asking for assistance.

If a command you are familiar with causes an Emacs error message in a case where its usual definition ought to be reasonable, it is probably a bug.

If a command does the wrong thing, that is a bug. But be sure you know for certain what it ought to have done. If you aren’t familiar with the command, it might actually be working right. If in doubt, read the command’s documentation (see Help by Command or Variable Name).

A command’s intended definition may not be the best possible definition for editing with. This is a very important sort of problem, but it is also a matter of judgment. Also, it is easy to come to such a conclusion out of ignorance of some of the existing features. It is probably best not to complain about such a problem until you have checked the documentation in the usual ways, feel confident that you understand it, and know for certain that what you want is not available. Ask other Emacs users, too. If you are not sure what the command is supposed to do after a careful reading of the manual, check the index and glossary for any terms that may be unclear.

If after careful rereading of the manual you still do not understand what the command should do, that indicates a bug in the manual, which you should report. The manual’s job is to make everything clear to people who are not Emacs experts—including you. It is just as important to report documentation bugs as program bugs.

If the built-in documentation for a function or variable disagrees with the manual, one of them must be wrong; that is a bug.

For problems with packages that are not part of Emacs, it is better to begin by reporting them to the package developers.


53.3 Understanding Bug Reporting

When you decide that there is a bug, it is important to report it, and to report it in a way which is useful. What is most useful is an exact description of what commands you type, starting with the shell command to run Emacs, until the problem happens, and the effects produced by typing those commands.

The most important principle in reporting a bug is to report facts. Hypotheses and verbal descriptions are no substitute for the detailed raw data. Reporting the facts is straightforward, but many people strain to posit explanations and report them instead of the facts. If the explanations are based on guesses about how Emacs is implemented, they might not be useful; meanwhile, lacking the facts, we will have no real information about the bug. If you want to actually debug the problem, and report explanations that are more than guesses, that is useful—but please include the raw facts as well.

For example, suppose that you type C-x C-f /glorp/baz.ugh RET, visiting a file which (you know) happens to be rather large, and Emacs displays ‘I feel pretty today’. The bug report would need to provide all that information. You should not assume that the problem is due to the size of the file and say, “I visited a large file, and Emacs displayed ‘I feel pretty today’.” This is what we mean by “guessing explanations”. The problem might be due to the fact that there is a ‘z’ in the file name. If this is so, then when we got your report, we would try out the problem with some large file, probably with no ‘z’ in its name, and not see any problem. There is no way we could guess that we should try visiting a file with a ‘z’ in its name.

You should not even say “visit a file” instead of C-x C-f. That’s because a file can be visited in more than one way, and there’s no certainty that all of them reproduce the problem. Similarly, rather than saying “if I have three characters on the line”, say “after I type RET A B C RET C-p”, if that is the way you entered the text—that is, tell us about the text which in your case produced the problem.

If possible, try quickly to reproduce the bug by invoking Emacs with emacs -Q (so that Emacs starts with no initial customizations; see Initial Options), and repeating the steps that you took to trigger the bug. If you can reproduce the bug this way, that rules out bugs in your personal customizations and makes the bug much easier to reproduce. Then your bug report should begin by stating that you started Emacs with emacs -Q, followed by the exact sequence of steps for reproducing the bug. If possible, inform us of the exact contents of any file that is needed to reproduce the bug.

Some bugs are not reproducible from emacs -Q; some are not easily reproducible at all. In that case, you should report what you have—but, as before, please stick to the raw facts about what you did to trigger the bug the first time.

If you have multiple issues that you want to report, please make a separate bug report for each.


53.4 Checklist for Bug Reports

Before reporting a bug, first try to see if the problem has already been reported (see Reading Existing Bug Reports and Known Problems).

If you are able to, try the latest release of Emacs to see if the problem has already been fixed. Even better is to try the latest development version. We recognize that this is not easy for some people, so do not feel that you absolutely must do this before making a report.

The best way to write a bug report for Emacs is to use the command M-x report-emacs-bug. This sets up a mail buffer (see Sending Mail) and automatically inserts some of the essential information. However, it cannot supply all the necessary information; you should still read and follow the guidelines below, so you can enter the other crucial information by hand before you send the message. You may feel that some of the information inserted by M-x report-emacs-bug is not relevant, but unless you are absolutely sure, it is best to leave it, so that the developers can decide for themselves.

When you have finished writing your report, type C-c C-c and it will be sent to the Emacs maintainers at bug-gnu-emacs. If you cannot send mail from inside Emacs, you can copy the text of your report to your normal mail client (if your system supports it, you can type C-c M-i to have Emacs do this for you) and send it to that address. Or you can simply send an email to that address describing the problem, including the necessary information mentioned below.

If you want to submit code to Emacs (to fix a problem or implement a new feature), the easiest way to do this is to send a patch to the Emacs issue tracker. Use the M-x submit-emacs-patch command for that, which works much the same as when reporting bugs; see Sending Patches for GNU Emacs.

In any case, your report will be sent to the ‘bug-gnu-emacs’ mailing list, and stored in the GNU Bug Tracker at https://debbugs.gnu.org. Please include a valid reply email address, in case we need to ask you for more information about your report. Submissions are moderated, so there may be a delay before your report actually appears on the tracker.

You do not need to know how the GNU Bug Tracker works in order to report a bug, but if you want to, you can read the tracker’s online documentation to see the various features you can use.

All mail sent to the ‘bug-gnu-emacs’ mailing list is also gatewayed to the ‘gnu.emacs.bug’ newsgroup. The reverse is also true, but we ask you not to post bug reports (or replies) via the newsgroup. It can make it much harder to contact you if we need to ask for more information, and it does not integrate well with the bug tracker.

If your data is more than 500,000 bytes, please don’t include it directly in the bug report; instead, offer to send it on request, or make it available online and say where. Large attachments are best sent compressed.

The GNU Bug Tracker will assign a bug number to your report; please use it in the following discussions, keeping the bug address in the list of recipients, so that the bug discussion is recorded by the tracker. The bug address will look like ‘nnnnn@debbugs.gnu.org’, where nnnnn is the bug number.

To enable maintainers to investigate a bug, your report should include all these things:

  • A description of what behavior you observe that you believe is incorrect. For example, “The Emacs process gets a fatal signal”, or, “The resulting text is as follows, which I think is wrong.”

    Of course, if the bug is that Emacs gets a fatal signal, then one can’t miss it. But if the bug is incorrect text, the maintainer might fail to notice what is wrong. Why leave it to chance?

    Even if the problem you experience is a fatal signal, you should still say so explicitly. Suppose something strange is going on, such as, your copy of the source is out of sync, or you have encountered a bug in the C library on your system. (This has happened!) Your copy might crash and the copy here might not. If you said to expect a crash, then when Emacs here fails to crash, we would know that the bug was not happening. If you don’t say to expect a crash, then we would not know whether the bug was happening—we would not be able to draw any conclusion from our observations.

    Usually, description of the behavior and of the way to reproduce the problem needs to specify one or more of the following aspects:

    • The complete text of any files needed to reproduce the bug.

      If you can tell us a way to cause the problem without visiting any files, please do so. This makes it much easier to debug. If you do need files, make sure you arrange for us to see their exact contents. For example, it can matter whether there are spaces at the ends of lines, or a newline after the last line in the buffer (nothing ought to care whether the last line is terminated, but try telling the bugs that).

    • The precise commands we need to type to reproduce the bug. If at all possible, give a full recipe for an Emacs started with the ‘-Q’ option (see Initial Options). This bypasses your personal customizations.

      One way to record the input to Emacs precisely is to write a dribble file. To start the file, use the command M-x open-dribble-file. From then on, Emacs copies all your input to the specified dribble file until the Emacs process is killed. Be aware that sensitive information (such as passwords) may end up recorded in the dribble file.

    • If the bug is that the Emacs Manual or the Emacs Lisp Reference Manual fails to describe the actual behavior of Emacs, or that the text is confusing, copy in the text from the manual which you think is at fault. If the section is small, just the section name is enough.
    • If the manifestation of the bug is an Emacs error message, it is important to report the precise text of the error message, and a backtrace showing how the Lisp program in Emacs arrived at the error.

      To get the error message text accurately, copy it from the *Messages* buffer into the bug report. Copy all of it, not just part.

    • Check whether any programs you have loaded into the Lisp world, including your initialization file, set any variables that may affect the functioning of Emacs. Also, see whether the problem happens in a freshly started Emacs without loading your initialization file (start Emacs with the -Q switch to prevent loading the init files). If the problem does not occur then, you must report the precise contents of any programs that you must load into the Lisp world in order to cause the problem to occur.
    • If the problem does depend on an init file or other Lisp programs that are not part of the standard Emacs system, then you should make sure it is not a bug in those programs by complaining to their maintainers first. After they verify that they are using Emacs in a way that is supposed to work, they should report the bug.
    • If you wish to mention something in the GNU Emacs source, show the line of code with a few lines of context. Don’t just give a line number.

      The line numbers in the development sources don’t match those in your sources. It would take extra work for the maintainers to determine what code is in your version at a given line number, and we could not be certain.

    • For possible display bugs on text-mode terminals, the terminal type (the value of environment variable TERM), the complete termcap entry for the terminal from /etc/termcap (since that file is not identical on all machines), and the output that Emacs actually sent to the terminal.

      The way to collect the terminal output is to invoke the command M-x open-termscript just after starting Emacs; it will prompt you for the name of the file where to record all terminal output until the Emacs process is killed. If the problem happens when Emacs starts up, put the Lisp expression

      (open-termscript "~/termscript")
      

      into your Emacs initialization file so that the termscript file will be open when Emacs displays the screen for the first time.

      Be warned: it is often difficult, and sometimes impossible, to fix a terminal-dependent bug without access to a terminal of the type that stimulates the bug.

  • The version number of Emacs. Without this, we won’t know whether there is any point in looking for the bug in the current version of GNU Emacs.

    M-x report-emacs-bug includes this information automatically, but if you are not using that command for your report you can get the version number by typing M-x emacs-version RET. If that command does not work, you probably have something other than GNU Emacs, so you will have to report the bug somewhere else.

  • The type of machine you are using, and the operating system name and version number (again, automatically included by M-x report-emacs-bug). M-x emacs-version RET provides this information too. Copy its output from the *Messages* buffer, so that you get it all and get it accurately, or use C-u M-x emacs-version RET to insert the version information into the current buffer.
  • The command-line arguments given to the configure command when Emacs was built (automatically included by M-x report-emacs-bug).
  • A complete list of any modifications you have made to the Emacs source. (We may not have time to investigate the bug unless it happens in an unmodified Emacs. But if you’ve made modifications and you don’t tell us, you are sending us on a wild goose chase.)

    Be precise about these changes. A description in English is not enough—send a unified context diff for them.

    Adding files of your own, or porting to another machine, is a modification of the source.

  • Details of any other deviations from the standard procedure for installing GNU Emacs.
  • If non-ASCII text or internationalization is relevant, the locale that was current when you started Emacs. This is automatically included by M-x report-emacs-bug; alternatively, on GNU/Linux and Unix systems, or if you use a POSIX-style shell such as Bash, you can use this shell command to view the relevant values:
    echo LC_ALL=$LC_ALL LC_COLLATE=$LC_COLLATE LC_CTYPE=$LC_CTYPE \
      LC_MESSAGES=$LC_MESSAGES LC_TIME=$LC_TIME LANG=$LANG
    

    You can also use the locale command, if your system has it, to display your locale settings.

Here are some things that are not necessary in a bug report:

  • A description of the envelope of the bug—this is not necessary for a reproducible bug.

    Often people who encounter a bug spend a lot of time investigating which changes to the input file will make the bug go away and which changes will not affect it.

    This is often time-consuming and not very useful, because the way we will find the bug is by running a single example under the debugger with breakpoints, not by pure deduction from a series of examples. You might as well save time by not searching for additional examples. It is better to send the bug report right away, go back to editing, and find another bug to report.

    Of course, if you can find a simpler example to report instead of the original one, that is a convenience. Errors in the output will be easier to spot, running under the debugger will take less time, etc.

    However, simplification is not vital; if you can’t do this or don’t have time to try, please report the bug with your original test case.

  • A core dump file.

    Debugging the core dump might be useful, but it can only be done on your machine, with your Emacs executable. Therefore, sending the core dump file to the Emacs maintainers won’t be useful. Above all, don’t include the core file in an email bug report! Such a large message can be extremely inconvenient.

  • A system-call trace of Emacs execution.

    System-call traces are very useful for certain special kinds of debugging, but in most cases they give little useful information. It is therefore strange that many people seem to think that the way to report information about a crash is to send a system-call trace. Perhaps this is a habit formed from experience debugging programs that don’t have source code or debugging symbols.

    In most programs, a backtrace is normally far, far more informative than a system-call trace. Even in Emacs, a simple backtrace is generally more informative, though to give full information you should supplement the backtrace by displaying variable values and printing them as Lisp objects with pr (see above).

  • A patch for the bug.

    A patch for the bug is useful if it is a good one. But don’t omit the other information that a bug report needs, such as the test case, on the assumption that a patch is sufficient. We might see problems with your patch and decide to fix the problem another way, or we might not understand it at all. And if we can’t understand what bug you are trying to fix, or why your patch should be an improvement, we mustn’t install it. See Sending Patches for GNU Emacs, for guidelines on how to make it easy for us to understand and install your patches.

  • A guess about what the bug is or what it depends on.

    Such guesses are usually wrong. Even experts can’t guess right about such things without first using the debugger to find the facts.

If you are willing to debug Emacs and provide additional information about the bug, here is some useful advice:

  • If the bug manifests itself as an error message, try providing a Lisp backtrace for the error. To make a backtrace for the error, use M-x toggle-debug-on-error before the error happens (that is to say, you must give that command and then make the bug happen). This causes the error to start the Lisp debugger, which shows you a backtrace. Copy the text of the debugger’s backtrace into the bug report. (The backtrace is more detailed if you load the relevant Lisp *.el source files before triggering the error, so do that if you know how to find and load those files.)

    To debug the error, we suggest using Edebug. See Edebug in the Emacs Lisp Reference Manual, for information on debugging Emacs Lisp programs with the Edebug package.

    This use of the debugger is possible only if you know how to make the bug happen again. If you can’t make it happen again, at least copy the whole error message.

  • If Emacs appears to be stuck in an infinite loop or in a very long operation, typing C-g with the variable debug-on-quit non-nil will start the Lisp debugger and show a backtrace. This backtrace is useful for debugging such long loops, so if you can produce it, copy it into the bug report.

    If you cannot get Emacs to respond to C-g (e.g., because inhibit-quit is set), then you can try sending the signal specified by debug-on-event (default SIGUSR2) from outside Emacs to cause it to enter the debugger.

  • Additional information from a C debugger such as GDB might enable someone to find a problem on a machine which he does not have available. If you don’t know how to use GDB, please read the GDB manual—it is not very long, and using GDB is easy. You can find the GDB distribution, including the GDB manual in online form, in most of the same places you can find the Emacs distribution. To run Emacs under GDB, you should switch to the src subdirectory in which Emacs was compiled, then type gdb ./emacs. It is important for the directory src to be current so that GDB will read the .gdbinit file in this directory. (You can also tell GDB to read that file from inside GDB, by typing source ./.gdbinit.)

    However, you need to think when you collect the additional information if you want it to show what causes the bug.

    For example, many people send just a C-level backtrace, but that is not very useful by itself. A simple backtrace with arguments often conveys little about what is happening inside GNU Emacs, because most of the arguments listed in the backtrace are pointers to Lisp objects. The numeric values of these pointers have no significance whatever; all that matters is the contents of the objects they point to (and most of the contents are themselves pointers).

    To provide useful information, you need to show the values of Lisp objects in Lisp notation. Do this for each variable which is a Lisp object, in several stack frames near the bottom of the stack. Look at the source to see which variables are Lisp objects, because the debugger thinks of them as integers.

    To show a variable’s value in Lisp syntax, first print its value, then use the user-defined GDB command pr to print the Lisp object in Lisp syntax. (If you must use another debugger, call the function debug_print with the object as an argument.) The pr command is defined by the file .gdbinit, and it works only if you are debugging a running process (not with a core dump).

    To make Lisp errors stop Emacs and return to GDB, put a breakpoint at Fsignal.

    For a backtrace of Lisp functions running, type the GDB command xbacktrace.

    The file .gdbinit defines several other commands that are useful for examining the data types and contents of Lisp objects. Their names begin with ‘x’. These commands work at a lower level than pr, and are less convenient, but they may work even when pr does not, such as when debugging a core dump or when Emacs has had a fatal signal.

    More detailed advice and other useful techniques for debugging Emacs are available in the file etc/DEBUG in the Emacs distribution. That file also includes instructions for investigating problems whereby Emacs stops responding (many people assume that Emacs is “hung”, whereas in fact it might be in an infinite loop).

    To find the file etc/DEBUG in your Emacs installation, use the directory name stored in the variable data-directory.


53.5 Sending Patches for GNU Emacs

If you would like to write bug fixes or improvements for GNU Emacs, that is very helpful. When you send your changes, please follow these guidelines to make it easy for the maintainers to use them. If you don’t follow these guidelines, your information might still be useful, but using it will take extra work. Maintaining GNU Emacs is a lot of work in the best of circumstances, and we can’t keep up unless you do your best to help.

Every patch must have several pieces of information before we can properly evaluate it. They are described below.

When you have all these pieces, use the M-x submit-emacs-patch command to send the patch. The command will prompt you for the Subject of the patch and a patch file. It will then create and display a Message mode buffer with the patch file as an attachment, display the buffer, and let you explain more about the patch and add any other information as requested below. When you are done, type C-c C-c to send the patch via email to the developers. It will be sent to the GNU Bug Tracker at https://debbugs.gnu.org. The tracker will assign a number to your submission, just like it does with bug reports. The developers will usually respond, perhaps asking you for more details or any additional information, so be sure to include a valid reply email address.

Here’s what we ask you to provide as part of your patch submissions:

  • An explanation of what problem you are fixing or what improvement will the patches bring about:
    • For a fix for an existing bug, it is best to reply to the relevant discussion on the ‘bug-gnu-emacs’ list, or the bug entry in the GNU Bug Tracker at https://debbugs.gnu.org. Explain why your change fixes the bug.
    • For a new feature, include a description of the feature and your implementation.
    • For a new bug, include a proper bug report for the problem you think you have fixed; see Checklist for Bug Reports. We need to convince ourselves that the change is right before installing it. Even if it is correct, we might have trouble understanding it if we don’t have a way to reproduce the problem it tries to fix.
  • Include in your code changes all the comments that are appropriate to help people reading the source in the future understand why this change was needed.
  • Don’t mix together changes made for different reasons. Send them individually.

    If you make two changes for separate reasons, then we might not want to install them both. We might want to install just one, or install each one in a different versions of Emacs. If you send them all jumbled together in a single set of diffs, we have to do extra work to disentangle them—to figure out which parts of the change serve which purpose. If we don’t have time for this, we might have to postpone inclusion of your patches for a long time.

    If you send each change as soon as you have written it, with its own explanation, then two changes never get tangled up, and we can consider each one properly without any extra work to disentangle them.

  • Send each change as soon as that change is finished. Sometimes people think they are helping us by accumulating many changes to send them all together. As explained above, this is absolutely the worst thing you could do.

    Since you should send each change separately, you might as well send it right away. That gives us the option of installing it immediately if it is important.

  • The patch itself. This can be produced in one of the following ways:
    • If you are using the Emacs repository, make sure your copy is up-to-date (e.g., with git pull). You can commit your changes to a private branch and generate a patch from the master version by using git format-patch master. (This is the preferred method, as it makes our job of applying the patch easier.) Or you can leave your changes uncommitted and use git diff, as described below.
    • Use diff -u to make your diffs. If you have GNU diff, use diff -u -F'^[_a-zA-Z0-9$]\+ *(' when making diffs of C code. This shows the name of the function that each change occurs in.

      When producing the diffs, avoid any ambiguity as to which is the old version and which is the new. Please make the old version the first argument to diff, and the new version the second argument. And please give one version or the other a name that indicates whether it is the old version or your new changed one.

  • Write the commit log entries for your changes. This is both to save us the extra work of writing them, and to help explain your changes so we can understand them.

    The purpose of the commit log is to explain the rationale of the changes, the way the modified code solves whatever problems your patch is trying to fix, and also show people where to find what was changed. So you need to be specific about what functions you changed and why. For the details about our style and requirements for good commit log messages, please see the “Commit messages” section of the file CONTRIBUTE in the Emacs source tree.

    Please also look at the commit log entries of recent commits to see what sorts of information to put in, and to learn the style that we use. Note that, unlike some other projects, we do require commit logs for documentation, i.e., Texinfo files. See Change Logs, see https://www.gnu.org/prep/standards/html_node/Change-Log-Concepts.html, See Change Log Concepts in GNU Coding Standards.

  • When you write the fix, keep in mind that we can’t install a change that would break other systems. Please think about what effect your change will have if compiled and/or used on another type of system.

    Sometimes people send fixes that might be an improvement in general—but it is hard to be sure of this. It’s hard to install such changes because we have to study them very carefully. Of course, a good explanation of the reasoning by which you concluded the change was correct can help convince us.

    The safest changes are changes to the files or portions of files that are only used for a particular machine or a particular system. These are safe because they can’t create new bugs on other machines or systems.

    Please help us keep up with the workload by designing the patch in a form that is clearly safe to install.


54 Contributing to Emacs Development

Emacs is a collaborative project and we encourage contributions from anyone and everyone.

There are many ways to contribute to Emacs:

If you would like to work on improving Emacs, please contact the maintainers at the emacs-devel mailing list. You can ask for suggested projects or suggest your own ideas.

If you have a feature request or a suggestion for how to improve Emacs, the best place to send it is to bug-gnu-emacs . Please explain as clearly as possible what change you would like to see, and why and how you think it would improve Emacs.

If you have already written an improvement, please tell us about it. If you have not yet started work, it is useful to contact emacs-devel before you start; it might be possible to suggest ways to make your extension fit in better with the rest of Emacs.

When implementing a feature, please follow the Emacs coding standards; see Coding Standards. In addition, substantial contributions require a copyright assignment to the FSF; see Copyright Assignment.

The development version of Emacs can be downloaded from the repository where it is actively maintained by a group of developers. See the Emacs project page https://savannah.gnu.org/projects/emacs/ for access details.

It is important to write your patches based on the current working version. If you start from an older version, your patch may be outdated (so that maintainers will have a hard time applying it), or changes in Emacs may have made your patch unnecessary. After you have downloaded the repository source, you should read the file INSTALL.REPO for build instructions (they differ to some extent from a normal build).

If you would like to make more extensive contributions, see the CONTRIBUTE file in the Emacs source tree for information on how to be an Emacs developer. That file is distributed as part of the source tarball of every released Emacs version, and can also be found on-line in the Emacs on-line source repository. If you cloned the Emacs repository, per the instructions in https://savannah.gnu.org/projects/emacs/, you will find this file in the top directory of the source Emacs tree.

For documentation on Emacs (to understand how to implement your desired change), refer to:


54.1 Coding Standards

Contributed code should follow the GNU Coding Standards https://www.gnu.org/prep/standards/. This may also be available in info on your system.

If it doesn’t, we’ll need to find someone to fix the code before we can use it.

Emacs has additional style and coding conventions:

  • the “Tips and Conventions” Appendix in the Emacs Lisp Reference https://www.gnu.org/software/emacs/manual/html_node/elisp/Tips.html.
  • Avoid using defadvice or with-eval-after-load for Lisp code to be included in Emacs.
  • Remove all trailing whitespace in all source and text files.
  • Use ?\s instead of ? in Lisp code for a space character.

55 How To Get Help with GNU Emacs

If you need help installing, using or changing GNU Emacs, there are two ways to find it:


Appendix A GNU GENERAL PUBLIC LICENSE

Version 3, 29 June 2007
Copyright © 2007 Free Software Foundation, Inc. https://fsf.org/

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.

Preamble

The GNU General Public License is a free, copyleft license for software and other kinds of works.

The licenses for most software and other practical works are designed to take away your freedom to share and change the works. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change all versions of a program—to make sure it remains free software for all its users. We, the Free Software Foundation, use the GNU General Public License for most of our software; it applies also to any other work released this way by its authors. You can apply it to your programs, too.

When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for them if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs, and that you know you can do these things.

To protect your rights, we need to prevent others from denying you these rights or asking you to surrender the rights. Therefore, you have certain responsibilities if you distribute copies of the software, or if you modify it: responsibilities to respect the freedom of others.

For example, if you distribute copies of such a program, whether gratis or for a fee, you must pass on to the recipients the same freedoms that you received. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.

Developers that use the GNU GPL protect your rights with two steps: (1) assert copyright on the software, and (2) offer you this License giving you legal permission to copy, distribute and/or modify it.

For the developers’ and authors’ protection, the GPL clearly explains that there is no warranty for this free software. For both users’ and authors’ sake, the GPL requires that modified versions be marked as changed, so that their problems will not be attributed erroneously to authors of previous versions.

Some devices are designed to deny users access to install or run modified versions of the software inside them, although the manufacturer can do so. This is fundamentally incompatible with the aim of protecting users’ freedom to change the software. The systematic pattern of such abuse occurs in the area of products for individuals to use, which is precisely where it is most unacceptable. Therefore, we have designed this version of the GPL to prohibit the practice for those products. If such problems arise substantially in other domains, we stand ready to extend this provision to those domains in future versions of the GPL, as needed to protect the freedom of users.

Finally, every program is threatened constantly by software patents. States should not allow patents to restrict development and use of software on general-purpose computers, but in those that do, we wish to avoid the special danger that patents applied to a free program could make it effectively proprietary. To prevent this, the GPL assures that patents cannot be used to render the program non-free.

The precise terms and conditions for copying, distribution and modification follow.

TERMS AND CONDITIONS

  1. Definitions.

    “This License” refers to version 3 of the GNU General Public License.

    “Copyright” also means copyright-like laws that apply to other kinds of works, such as semiconductor masks.

    “The Program” refers to any copyrightable work licensed under this License. Each licensee is addressed as “you”. “Licensees” and “recipients” may be individuals or organizations.

    To “modify” a work means to copy from or adapt all or part of the work in a fashion requiring copyright permission, other than the making of an exact copy. The resulting work is called a “modified version” of the earlier work or a work “based on” the earlier work.

    A “covered work” means either the unmodified Program or a work based on the Program.

    To “propagate” a work means to do anything with it that, without permission, would make you directly or secondarily liable for infringement under applicable copyright law, except executing it on a computer or modifying a private copy. Propagation includes copying, distribution (with or without modification), making available to the public, and in some countries other activities as well.

    To “convey” a work means any kind of propagation that enables other parties to make or receive copies. Mere interaction with a user through a computer network, with no transfer of a copy, is not conveying.

    An interactive user interface displays “Appropriate Legal Notices” to the extent that it includes a convenient and prominently visible feature that (1) displays an appropriate copyright notice, and (2) tells the user that there is no warranty for the work (except to the extent that warranties are provided), that licensees may convey the work under this License, and how to view a copy of this License. If the interface presents a list of user commands or options, such as a menu, a prominent item in the list meets this criterion.

  2. Source Code.

    The “source code” for a work means the preferred form of the work for making modifications to it. “Object code” means any non-source form of a work.

    A “Standard Interface” means an interface that either is an official standard defined by a recognized standards body, or, in the case of interfaces specified for a particular programming language, one that is widely used among developers working in that language.

    The “System Libraries” of an executable work include anything, other than the work as a whole, that (a) is included in the normal form of packaging a Major Component, but which is not part of that Major Component, and (b) serves only to enable use of the work with that Major Component, or to implement a Standard Interface for which an implementation is available to the public in source code form. A “Major Component”, in this context, means a major essential component (kernel, window system, and so on) of the specific operating system (if any) on which the executable work runs, or a compiler used to produce the work, or an object code interpreter used to run it.

    The “Corresponding Source” for a work in object code form means all the source code needed to generate, install, and (for an executable work) run the object code and to modify the work, including scripts to control those activities. However, it does not include the work’s System Libraries, or general-purpose tools or generally available free programs which are used unmodified in performing those activities but which are not part of the work. For example, Corresponding Source includes interface definition files associated with source files for the work, and the source code for shared libraries and dynamically linked subprograms that the work is specifically designed to require, such as by intimate data communication or control flow between those subprograms and other parts of the work.

    The Corresponding Source need not include anything that users can regenerate automatically from other parts of the Corresponding Source.

    The Corresponding Source for a work in source code form is that same work.

  3. Basic Permissions.

    All rights granted under this License are granted for the term of copyright on the Program, and are irrevocable provided the stated conditions are met. This License explicitly affirms your unlimited permission to run the unmodified Program. The output from running a covered work is covered by this License only if the output, given its content, constitutes a covered work. This License acknowledges your rights of fair use or other equivalent, as provided by copyright law.

    You may make, run and propagate covered works that you do not convey, without conditions so long as your license otherwise remains in force. You may convey covered works to others for the sole purpose of having them make modifications exclusively for you, or provide you with facilities for running those works, provided that you comply with the terms of this License in conveying all material for which you do not control copyright. Those thus making or running the covered works for you must do so exclusively on your behalf, under your direction and control, on terms that prohibit them from making any copies of your copyrighted material outside their relationship with you.

    Conveying under any other circumstances is permitted solely under the conditions stated below. Sublicensing is not allowed; section 10 makes it unnecessary.

  4. Protecting Users’ Legal Rights From Anti-Circumvention Law.

    No covered work shall be deemed part of an effective technological measure under any applicable law fulfilling obligations under article 11 of the WIPO copyright treaty adopted on 20 December 1996, or similar laws prohibiting or restricting circumvention of such measures.

    When you convey a covered work, you waive any legal power to forbid circumvention of technological measures to the extent such circumvention is effected by exercising rights under this License with respect to the covered work, and you disclaim any intention to limit operation or modification of the work as a means of enforcing, against the work’s users, your or third parties’ legal rights to forbid circumvention of technological measures.

  5. Conveying Verbatim Copies.

    You may convey verbatim copies of the Program’s source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice; keep intact all notices stating that this License and any non-permissive terms added in accord with section 7 apply to the code; keep intact all notices of the absence of any warranty; and give all recipients a copy of this License along with the Program.

    You may charge any price or no price for each copy that you convey, and you may offer support or warranty protection for a fee.

  6. Conveying Modified Source Versions.

    You may convey a work based on the Program, or the modifications to produce it from the Program, in the form of source code under the terms of section 4, provided that you also meet all of these conditions:

    1. The work must carry prominent notices stating that you modified it, and giving a relevant date.
    2. The work must carry prominent notices stating that it is released under this License and any conditions added under section 7. This requirement modifies the requirement in section 4 to “keep intact all notices”.
    3. You must license the entire work, as a whole, under this License to anyone who comes into possession of a copy. This License will therefore apply, along with any applicable section 7 additional terms, to the whole of the work, and all its parts, regardless of how they are packaged. This License gives no permission to license the work in any other way, but it does not invalidate such permission if you have separately received it.
    4. If the work has interactive user interfaces, each must display Appropriate Legal Notices; however, if the Program has interactive interfaces that do not display Appropriate Legal Notices, your work need not make them do so.

    A compilation of a covered work with other separate and independent works, which are not by their nature extensions of the covered work, and which are not combined with it such as to form a larger program, in or on a volume of a storage or distribution medium, is called an “aggregate” if the compilation and its resulting copyright are not used to limit the access or legal rights of the compilation’s users beyond what the individual works permit. Inclusion of a covered work in an aggregate does not cause this License to apply to the other parts of the aggregate.

  7. Conveying Non-Source Forms.

    You may convey a covered work in object code form under the terms of sections 4 and 5, provided that you also convey the machine-readable Corresponding Source under the terms of this License, in one of these ways:

    1. Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by the Corresponding Source fixed on a durable physical medium customarily used for software interchange.
    2. Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by a written offer, valid for at least three years and valid for as long as you offer spare parts or customer support for that product model, to give anyone who possesses the object code either (1) a copy of the Corresponding Source for all the software in the product that is covered by this License, on a durable physical medium customarily used for software interchange, for a price no more than your reasonable cost of physically performing this conveying of source, or (2) access to copy the Corresponding Source from a network server at no charge.
    3. Convey individual copies of the object code with a copy of the written offer to provide the Corresponding Source. This alternative is allowed only occasionally and noncommercially, and only if you received the object code with such an offer, in accord with subsection 6b.
    4. Convey the object code by offering access from a designated place (gratis or for a charge), and offer equivalent access to the Corresponding Source in the same way through the same place at no further charge. You need not require recipients to copy the Corresponding Source along with the object code. If the place to copy the object code is a network server, the Corresponding Source may be on a different server (operated by you or a third party) that supports equivalent copying facilities, provided you maintain clear directions next to the object code saying where to find the Corresponding Source. Regardless of what server hosts the Corresponding Source, you remain obligated to ensure that it is available for as long as needed to satisfy these requirements.
    5. Convey the object code using peer-to-peer transmission, provided you inform other peers where the object code and Corresponding Source of the work are being offered to the general public at no charge under subsection 6d.

    A separable portion of the object code, whose source code is excluded from the Corresponding Source as a System Library, need not be included in conveying the object code work.

    A “User Product” is either (1) a “consumer product”, which means any tangible personal property which is normally used for personal, family, or household purposes, or (2) anything designed or sold for incorporation into a dwelling. In determining whether a product is a consumer product, doubtful cases shall be resolved in favor of coverage. For a particular product received by a particular user, “normally used” refers to a typical or common use of that class of product, regardless of the status of the particular user or of the way in which the particular user actually uses, or expects or is expected to use, the product. A product is a consumer product regardless of whether the product has substantial commercial, industrial or non-consumer uses, unless such uses represent the only significant mode of use of the product.

    “Installation Information” for a User Product means any methods, procedures, authorization keys, or other information required to install and execute modified versions of a covered work in that User Product from a modified version of its Corresponding Source. The information must suffice to ensure that the continued functioning of the modified object code is in no case prevented or interfered with solely because modification has been made.

    If you convey an object code work under this section in, or with, or specifically for use in, a User Product, and the conveying occurs as part of a transaction in which the right of possession and use of the User Product is transferred to the recipient in perpetuity or for a fixed term (regardless of how the transaction is characterized), the Corresponding Source conveyed under this section must be accompanied by the Installation Information. But this requirement does not apply if neither you nor any third party retains the ability to install modified object code on the User Product (for example, the work has been installed in ROM).

    The requirement to provide Installation Information does not include a requirement to continue to provide support service, warranty, or updates for a work that has been modified or installed by the recipient, or for the User Product in which it has been modified or installed. Access to a network may be denied when the modification itself materially and adversely affects the operation of the network or violates the rules and protocols for communication across the network.

    Corresponding Source conveyed, and Installation Information provided, in accord with this section must be in a format that is publicly documented (and with an implementation available to the public in source code form), and must require no special password or key for unpacking, reading or copying.

  8. Additional Terms.

    “Additional permissions” are terms that supplement the terms of this License by making exceptions from one or more of its conditions. Additional permissions that are applicable to the entire Program shall be treated as though they were included in this License, to the extent that they are valid under applicable law. If additional permissions apply only to part of the Program, that part may be used separately under those permissions, but the entire Program remains governed by this License without regard to the additional permissions.

    When you convey a copy of a covered work, you may at your option remove any additional permissions from that copy, or from any part of it. (Additional permissions may be written to require their own removal in certain cases when you modify the work.) You may place additional permissions on material, added by you to a covered work, for which you have or can give appropriate copyright permission.

    Notwithstanding any other provision of this License, for material you add to a covered work, you may (if authorized by the copyright holders of that material) supplement the terms of this License with terms:

    1. Disclaiming warranty or limiting liability differently from the terms of sections 15 and 16 of this License; or
    2. Requiring preservation of specified reasonable legal notices or author attributions in that material or in the Appropriate Legal Notices displayed by works containing it; or
    3. Prohibiting misrepresentation of the origin of that material, or requiring that modified versions of such material be marked in reasonable ways as different from the original version; or
    4. Limiting the use for publicity purposes of names of licensors or authors of the material; or
    5. Declining to grant rights under trademark law for use of some trade names, trademarks, or service marks; or
    6. Requiring indemnification of licensors and authors of that material by anyone who conveys the material (or modified versions of it) with contractual assumptions of liability to the recipient, for any liability that these contractual assumptions directly impose on those licensors and authors.

    All other non-permissive additional terms are considered “further restrictions” within the meaning of section 10. If the Program as you received it, or any part of it, contains a notice stating that it is governed by this License along with a term that is a further restriction, you may remove that term. If a license document contains a further restriction but permits relicensing or conveying under this License, you may add to a covered work material governed by the terms of that license document, provided that the further restriction does not survive such relicensing or conveying.

    If you add terms to a covered work in accord with this section, you must place, in the relevant source files, a statement of the additional terms that apply to those files, or a notice indicating where to find the applicable terms.

    Additional terms, permissive or non-permissive, may be stated in the form of a separately written license, or stated as exceptions; the above requirements apply either way.

  9. Termination.

    You may not propagate or modify a covered work except as expressly provided under this License. Any attempt otherwise to propagate or modify it is void, and will automatically terminate your rights under this License (including any patent licenses granted under the third paragraph of section 11).

    However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

    Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

    Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, you do not qualify to receive new licenses for the same material under section 10.

  10. Acceptance Not Required for Having Copies.

    You are not required to accept this License in order to receive or run a copy of the Program. Ancillary propagation of a covered work occurring solely as a consequence of using peer-to-peer transmission to receive a copy likewise does not require acceptance. However, nothing other than this License grants you permission to propagate or modify any covered work. These actions infringe copyright if you do not accept this License. Therefore, by modifying or propagating a covered work, you indicate your acceptance of this License to do so.

  11. Automatic Licensing of Downstream Recipients.

    Each time you convey a covered work, the recipient automatically receives a license from the original licensors, to run, modify and propagate that work, subject to this License. You are not responsible for enforcing compliance by third parties with this License.

    An “entity transaction” is a transaction transferring control of an organization, or substantially all assets of one, or subdividing an organization, or merging organizations. If propagation of a covered work results from an entity transaction, each party to that transaction who receives a copy of the work also receives whatever licenses to the work the party’s predecessor in interest had or could give under the previous paragraph, plus a right to possession of the Corresponding Source of the work from the predecessor in interest, if the predecessor has it or can get it with reasonable efforts.

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  12. Patents.

    A “contributor” is a copyright holder who authorizes use under this License of the Program or a work on which the Program is based. The work thus licensed is called the contributor’s “contributor version”.

    A contributor’s “essential patent claims” are all patent claims owned or controlled by the contributor, whether already acquired or hereafter acquired, that would be infringed by some manner, permitted by this License, of making, using, or selling its contributor version, but do not include claims that would be infringed only as a consequence of further modification of the contributor version. For purposes of this definition, “control” includes the right to grant patent sublicenses in a manner consistent with the requirements of this License.

    Each contributor grants you a non-exclusive, worldwide, royalty-free patent license under the contributor’s essential patent claims, to make, use, sell, offer for sale, import and otherwise run, modify and propagate the contents of its contributor version.

    In the following three paragraphs, a “patent license” is any express agreement or commitment, however denominated, not to enforce a patent (such as an express permission to practice a patent or covenant not to sue for patent infringement). To “grant” such a patent license to a party means to make such an agreement or commitment not to enforce a patent against the party.

    If you convey a covered work, knowingly relying on a patent license, and the Corresponding Source of the work is not available for anyone to copy, free of charge and under the terms of this License, through a publicly available network server or other readily accessible means, then you must either (1) cause the Corresponding Source to be so available, or (2) arrange to deprive yourself of the benefit of the patent license for this particular work, or (3) arrange, in a manner consistent with the requirements of this License, to extend the patent license to downstream recipients. “Knowingly relying” means you have actual knowledge that, but for the patent license, your conveying the covered work in a country, or your recipient’s use of the covered work in a country, would infringe one or more identifiable patents in that country that you have reason to believe are valid.

    If, pursuant to or in connection with a single transaction or arrangement, you convey, or propagate by procuring conveyance of, a covered work, and grant a patent license to some of the parties receiving the covered work authorizing them to use, propagate, modify or convey a specific copy of the covered work, then the patent license you grant is automatically extended to all recipients of the covered work and works based on it.

    A patent license is “discriminatory” if it does not include within the scope of its coverage, prohibits the exercise of, or is conditioned on the non-exercise of one or more of the rights that are specifically granted under this License. You may not convey a covered work if you are a party to an arrangement with a third party that is in the business of distributing software, under which you make payment to the third party based on the extent of your activity of conveying the work, and under which the third party grants, to any of the parties who would receive the covered work from you, a discriminatory patent license (a) in connection with copies of the covered work conveyed by you (or copies made from those copies), or (b) primarily for and in connection with specific products or compilations that contain the covered work, unless you entered into that arrangement, or that patent license was granted, prior to 28 March 2007.

    Nothing in this License shall be construed as excluding or limiting any implied license or other defenses to infringement that may otherwise be available to you under applicable patent law.

  13. No Surrender of Others’ Freedom.

    If conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot convey a covered work so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not convey it at all. For example, if you agree to terms that obligate you to collect a royalty for further conveying from those to whom you convey the Program, the only way you could satisfy both those terms and this License would be to refrain entirely from conveying the Program.

  14. Use with the GNU Affero General Public License.

    Notwithstanding any other provision of this License, you have permission to link or combine any covered work with a work licensed under version 3 of the GNU Affero General Public License into a single combined work, and to convey the resulting work. The terms of this License will continue to apply to the part which is the covered work, but the special requirements of the GNU Affero General Public License, section 13, concerning interaction through a network will apply to the combination as such.

  15. Revised Versions of this License.

    The Free Software Foundation may publish revised and/or new versions of the GNU General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

    Each version is given a distinguishing version number. If the Program specifies that a certain numbered version of the GNU General Public License “or any later version” applies to it, you have the option of following the terms and conditions either of that numbered version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of the GNU General Public License, you may choose any version ever published by the Free Software Foundation.

    If the Program specifies that a proxy can decide which future versions of the GNU General Public License can be used, that proxy’s public statement of acceptance of a version permanently authorizes you to choose that version for the Program.

    Later license versions may give you additional or different permissions. However, no additional obligations are imposed on any author or copyright holder as a result of your choosing to follow a later version.

  16. Disclaimer of Warranty.

    THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

  17. Limitation of Liability.

    IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

  18. Interpretation of Sections 15 and 16.

    If the disclaimer of warranty and limitation of liability provided above cannot be given local legal effect according to their terms, reviewing courts shall apply local law that most closely approximates an absolute waiver of all civil liability in connection with the Program, unless a warranty or assumption of liability accompanies a copy of the Program in return for a fee.

END OF TERMS AND CONDITIONS

How to Apply These Terms to Your New Programs

If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.

To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively state the exclusion of warranty; and each file should have at least the “copyright” line and a pointer to where the full notice is found.

one line to give the program's name and a brief idea of what it does.
Copyright (C) year name of author

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see https://www.gnu.org/licenses/.

Also add information on how to contact you by electronic and paper mail.

If the program does terminal interaction, make it output a short notice like this when it starts in an interactive mode:

program Copyright (C) year name of author
This program comes with ABSOLUTELY NO WARRANTY; for details type ‘show w’.
This is free software, and you are welcome to redistribute it
under certain conditions; type ‘show c’ for details.

The hypothetical commands ‘show w’ and ‘show c’ should show the appropriate parts of the General Public License. Of course, your program’s commands might be different; for a GUI interface, you would use an “about box”.

You should also get your employer (if you work as a programmer) or school, if any, to sign a “copyright disclaimer” for the program, if necessary. For more information on this, and how to apply and follow the GNU GPL, see https://www.gnu.org/licenses/.

The GNU General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Lesser General Public License instead of this License. But first, please read https://www.gnu.org/licenses/why-not-lgpl.html.


Appendix B GNU Free Documentation License

Version 1.3, 3 November 2008
Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
https://fsf.org/

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
  1. PREAMBLE

    The purpose of this License is to make a manual, textbook, or other functional and useful document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

    This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

    We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

  2. APPLICABILITY AND DEFINITIONS

    This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

    A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

    A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document’s overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

    The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

    The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

    A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.

    Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.

    The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work’s title, preceding the beginning of the body of the text.

    The “publisher” means any person or entity that distributes copies of the Document to the public.

    A section “Entitled XYZ” means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) To “Preserve the Title” of such a section when you modify the Document means that it remains a section “Entitled XYZ” according to this definition.

    The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.

  3. VERBATIM COPYING

    You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

    You may also lend copies, under the same conditions stated above, and you may publicly display copies.

  4. COPYING IN QUANTITY

    If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document’s license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

    If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

    If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

    It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

  5. MODIFICATIONS

    You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

    1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
    2. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.
    3. State on the Title page the name of the publisher of the Modified Version, as the publisher.
    4. Preserve all the copyright notices of the Document.
    5. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
    6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
    7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document’s license notice.
    8. Include an unaltered copy of this License.
    9. Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
    10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the “History” section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
    11. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
    12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
    13. Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version.
    14. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title with any Invariant Section.
    15. Preserve any Warranty Disclaimers.

    If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version’s license notice. These titles must be distinct from any other section titles.

    You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties—for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

    You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

    The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

  6. COMBINING DOCUMENTS

    You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

    The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

    In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements.”

  7. COLLECTIONS OF DOCUMENTS

    You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

    You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

  8. AGGREGATION WITH INDEPENDENT WORKS

    A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation’s users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

    If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document’s Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

  9. TRANSLATION

    Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

    If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

  10. TERMINATION

    You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.

    However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

    Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

    Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it.

  11. FUTURE REVISIONS OF THIS LICENSE

    The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See https://www.gnu.org/licenses/.

    Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy’s public statement of acceptance of a version permanently authorizes you to choose that version for the Document.

  12. RELICENSING

    “Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A “Massive Multiauthor Collaboration” (or “MMC”) contained in the site means any set of copyrightable works thus published on the MMC site.

    “CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization.

    “Incorporate” means to publish or republish a Document, in whole or in part, as part of another Document.

    An MMC is “eligible for relicensing” if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.

    The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

  Copyright (C)  year  your name.
  Permission is granted to copy, distribute and/or modify this document
  under the terms of the GNU Free Documentation License, Version 1.3
  or any later version published by the Free Software Foundation;
  with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
  Texts.  A copy of the license is included in the section entitled ``GNU
  Free Documentation License''.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with…Texts.” line with this:

    with the Invariant Sections being list their titles, with
    the Front-Cover Texts being list, and with the Back-Cover Texts
    being list.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.


Appendix C Command Line Arguments for Emacs Invocation

Emacs supports command line arguments to request various actions when invoking Emacs. These are for compatibility with other editors and for sophisticated activities. We don’t recommend using them for ordinary editing (See Using Emacs as a Server, for a way to access an existing Emacs job from the command line).

Arguments starting with ‘-’ are options, and so is ‘+linenum’. All other arguments specify files to visit. Emacs visits the specified files while it starts up. The last file specified on the command line becomes the current buffer; the other files are also visited in other buffers. As with most programs, the special argument ‘--’ says that all subsequent arguments are file names, not options, even if they start with ‘-’.

Emacs command options can specify many things, such as the size and position of the X window Emacs uses, its colors, and so on. A few options support advanced usage, such as running Lisp functions on files in batch mode. The sections of this chapter describe the available options, arranged according to their purpose.

There are two ways of writing options: the short forms that start with a single ‘-’, and the long forms that start with ‘--’. For example, ‘-d’ is a short form and ‘--display’ is the corresponding long form.

The long forms with ‘--’ are easier to remember, but longer to type. However, you don’t have to spell out the whole option name; any unambiguous abbreviation is enough. When a long option requires an argument, you can use either a space or an equal sign to separate the option name and the argument. Thus, for the option ‘--display’, you can write either ‘--display sugar-bombs:0.0’ or ‘--display=sugar-bombs:0.0’. We recommend an equal sign because it makes the relationship clearer, and the tables below always show an equal sign.

Most options specify how to initialize Emacs, or set parameters for the Emacs session. We call them initial options. A few options specify things to do, such as loading libraries or calling Lisp functions. These are called action options. These and file names together are called action arguments. The action arguments are stored as a list of strings in the variable command-line-args. (Actually, when Emacs starts up, command-line-args contains all the arguments passed from the command line; during initialization, the initial arguments are removed from this list when they are processed, leaving only the action arguments.)


C.1 Action Arguments

Here is a table of action arguments:

file
--file=file
--find-file=file
--visit=file

Visit the specified file. See Visiting Files.

When Emacs starts up, it displays the startup buffer in one window, and the buffer visiting file in another window (see Multiple Windows). If you supply more than one file argument, the displayed file is the last one specified on the command line; the other files are visited but their buffers are not shown.

If the startup buffer is disabled (see Entering Emacs), then starting Emacs with one file argument displays the buffer visiting file in a single window. With two file arguments, Emacs displays the files in two different windows. With more than two file arguments, Emacs displays the last file specified in one window, plus another window with a Buffer Menu showing all the other files (see Operating on Several Buffers). To inhibit using the Buffer Menu for this, change the variable inhibit-startup-buffer-menu to t.

+linenum file

Visit the specified file, then go to line number linenum in it.

+linenum:columnnum file

Visit the specified file, then go to line number linenum and put point at column number columnnum.

-l file
--load=file

Load a Lisp library named file with the function load. If file is not an absolute file name, Emacs first looks for it in the current directory, then in the directories listed in load-path (see Libraries of Lisp Code for Emacs).

Warning: If previous command-line arguments have visited files, the current directory is the directory of the last file visited.

-L dir
--directory=dir

Prepend directory dir to the variable load-path. If you specify multiple ‘-L’ options, Emacs preserves the relative order; i.e., using ‘-L /foo -L /bar’ results in a load-path of the form ("/foo" "/bar" …). If dir begins with ‘:’, Emacs removes the ‘:’ and appends (rather than prepends) the remainder to load-path. (On MS Windows, use ‘;’ instead of ‘:’; i.e., use the value of path-separator.)

-f function
--funcall=function

Call Lisp function function. If it is an interactive function (a command), it reads the arguments interactively just as if you had called the same function with a key sequence. Otherwise, it calls the function with no arguments.

--eval=expression
--execute=expression

Evaluate Lisp expression expression.

--insert=file

Insert the contents of file into the buffer that is current when this command-line argument is processed. Usually, this is the *scratch* buffer (see Lisp Interaction Buffers), but if arguments earlier on the command line visit files or switch buffers, that might be a different buffer. The effect of this command-line argument is like what M-x insert-file does (see Miscellaneous File Operations).

--kill

Exit from Emacs without asking for confirmation.

--help

Print a usage message listing all available options, then exit successfully.

--version

Print Emacs version, then exit successfully.

--fingerprint

Print the Emacs “fingerprint”, which is used to uniquely identify the compiled version of Emacs.


C.2 Initial Options

The initial options specify parameters for the Emacs session. This section describes the more general initial options; some other options specifically related to the X Window System appear in the following sections.

Some initial options affect the loading of the initialization file. Normally, Emacs first loads site-start.el if it exists, then your own initialization file if it exists, and finally the default initialization file default.el if it exists (see The Emacs Initialization File). Certain options prevent loading of some of these files or substitute other files for them.

-chdir directory
--chdir=directory

Change to directory before doing anything else. This is mainly used by session management in X so that Emacs starts in the same directory as it stopped. This makes desktop saving and restoring easier.

-t device
--terminal=device

Use device as the device for terminal input and output. This option implies ‘--no-window-system’.

-d display
--display=display

Use the X Window System and use the display named display to open the initial Emacs frame. See Specifying the Display Name, for more details.

-nw
--no-window-system

Don’t communicate directly with the window system, disregarding the DISPLAY environment variable even if it is set. This means that Emacs uses the terminal from which it was launched for all its display and input.

-batch
--batch

Run Emacs in batch mode. Batch mode is used for running programs written in Emacs Lisp from shell scripts, makefiles, and so on. To invoke a Lisp program, use the ‘-batch’ option in conjunction with one or more of ‘-l’, ‘-f’ or ‘--eval’ (see Action Arguments). See Command Argument Example, for an example.

In batch mode, Emacs does not display the text being edited, and the standard terminal interrupt characters such as C-z and C-c have their usual effect. Emacs functions that normally print a message in the echo area will print to either the standard output stream (stdout) or the standard error stream (stderr) instead. (To be precise, functions like prin1, princ and print print to stdout, while message and error print to stderr.) Functions that normally read keyboard input from the minibuffer take their input from the terminal’s standard input stream (stdin) instead.

--batch’ implies ‘-q’ (do not load an initialization file), but site-start.el is loaded nonetheless. It also causes Emacs to exit after processing all the command options. In addition, it disables auto-saving except in buffers for which auto-saving is explicitly requested, and when saving files it omits the fsync system call unless otherwise requested.

Errors that occur when running a ‘--batch’ Emacs will result in an Emacs Lisp backtrace being printed. To disable this behavior, set backtrace-on-error-noninteractive to nil.

--script file

Run Emacs in batch mode, like ‘--batch’, and then read and execute the Lisp code in file.

The normal use of this option is in executable script files that run Emacs. They can start with this text on the first line

#!/usr/bin/emacs --script

which will invoke Emacs with ‘--script’ and supply the name of the script file as file. Emacs Lisp then treats the ‘#!’ on this first line as a comment delimiter.

-x

This option can only be used in executable script files, and should be invoked like this:

#!/usr/bin/emacs -x

This is like ‘--script’, but suppresses loading the init files (like --quick), and can’t be used on a normal command line (since it doesn’t specify the script to load). In addition, when it reaches the end of the script, it exits Emacs and uses the value of the final form as the exit value from the script (if the final value is numerical). Otherwise, it will always exit with a zero value. Note that when Emacs reads the Lisp code in this case, it ignores any file-local variables (see Specifying File Variables), both in the first line and in a local-variables section near the end of the file.

--no-build-details

Omit details like system name and build time from the Emacs executable, so that builds are more deterministic. This switch is not meant for regular (or interactive) use, since it makes commands like system-name return nil.

-q
--no-init-file

Do not load any initialization file (see The Emacs Initialization File). When Emacs is invoked with this option, the Customize facility does not allow options to be saved (see Easy Customization Interface). This option does not disable loading site-start.el.

--no-site-file
-nsl

Do not load site-start.el (see The Emacs Initialization File). The ‘-Q’ option does this too, but other options like ‘-q’ do not.

--no-site-lisp

Do not include the site-lisp directories in load-path (see The Emacs Initialization File). The ‘-Q’ option does this too.

--init-directory

Specify the directory to use when looking for the Emacs init files.

--no-splash

Do not display a startup screen. You can also achieve this effect by setting the variable inhibit-startup-screen to non-nil in your initialization file (see Entering Emacs).

--no-x-resources

Do not load X resources. You can also achieve this effect by setting the variable inhibit-x-resources to t in your initialization file (see X Resources).

-Q
--quick

Start Emacs with minimum customizations. This is similar to using ‘-q’, ‘--no-site-file’, ‘--no-site-lisp’, ‘--no-x-resources’, and ‘--no-splash’ together.

-daemon
--daemon[=name]
--bg-daemon[=name]
--fg-daemon[=name]

Start Emacs as a daemon: after Emacs starts up, it starts the Emacs server without opening any frames. You can then use the emacsclient command to connect to Emacs for editing. (Optionally, you can specify an explicit name for the server; if you do, you will need to specify the same name when you invoke emacsclient, via its --socket-name option, see emacsclient Options.) See Using Emacs as a Server, for information about using Emacs as a daemon. A “background” daemon disconnects from the terminal and runs in the background (‘--daemon’ is an alias for ‘--bg-daemon’).

--no-desktop

Do not reload any saved desktop. See Saving Emacs Sessions.

-u user
--user=user

Load user’s initialization file instead of your own26.

--debug-init

Enable the Emacs Lisp debugger for errors in the init file. See Entering the Debugger on an Error in The GNU Emacs Lisp Reference Manual.

--module-assertions

Enable expensive correctness checks when dealing with dynamically loadable modules. This is intended for module authors that wish to verify that their module conforms to the module API requirements. The option makes Emacs abort if a module-related assertion triggers. See Writing Dynamically-Loaded Modules in The GNU Emacs Lisp Reference Manual.

--dump-file=file

Load the dumped Emacs state from the named file. By default, an installed Emacs will look for its dump state in a file named emacs.pdmp in the directory where the Emacs installation puts the architecture-dependent files; the variable exec-directory holds the name of that directory. emacs is the name of the Emacs executable file, normally just emacs. (When you invoke Emacs from the src directory where it was built without installing it, it will look for the dump file in the directory of the executable.) If you rename or move the dump file to a different place, you can use this option to tell Emacs where to find that file.


C.3 Command Argument Example

Here is an example of using Emacs with arguments and options. It assumes you have a Lisp program file called hack-c.el which, when loaded, performs some useful operation on the current buffer, expected to be a C program.

emacs --batch foo.c -l hack-c -f save-buffer >& log

This says to visit foo.c, load hack-c.el (which makes changes in the visited file), save foo.c (note that save-buffer is the function that C-x C-s is bound to), and then exit back to the shell (because of ‘--batch’). ‘--batch’ also guarantees there will be no problem redirecting output to log, because Emacs will not assume that it has a display terminal to work with.


C.4 Environment Variables

The environment is a feature of the operating system; it consists of a collection of variables with names and values. Each variable is called an environment variable; environment variable names are case-sensitive, and it is conventional to use upper case letters only. The values are all text strings.

What makes the environment useful is that subprocesses inherit the environment automatically from their parent process. This means you can set up an environment variable in your login shell, and all the programs you run (including Emacs) will automatically see it. Subprocesses of Emacs (such as shells, compilers, and version control programs) inherit the environment from Emacs, too.

Inside Emacs, the command M-x getenv reads the name of an environment variable, and prints its value in the echo area. M-x setenv sets a variable in the Emacs environment, and C-u M-x setenv removes a variable. (Environment variable substitutions with ‘$’ work in the value just as in file names; see File Names with $.) The variable initial-environment stores the initial environment inherited by Emacs.

The way to set environment variables outside of Emacs depends on the operating system, and especially the shell that you are using. For example, here’s how to set the environment variable ORGANIZATION to ‘not very much’ using Bash:

export ORGANIZATION="not very much"

and here’s how to do it in csh or tcsh:

setenv ORGANIZATION "not very much"

When Emacs is using the X Window System, various environment variables that control X work for Emacs as well. See the X documentation for more information.


C.4.1 General Variables

Here is an alphabetical list of environment variables that have special meanings in Emacs. Most of these variables are also used by some other programs. Emacs does not require any of these environment variables to be set, but it uses their values if they are set.

CDPATH

Used by the cd command to search for the directory you specify, when you specify a relative directory.

COLORTERM

If this variable is set to the value ‘truecolor’, it tells Emacs to use 24-bit true color on text-mode displays even if the terminfo database is not installed. Emacs will use built-in commands to request true color by RGB values instead of the missing terminfo information.

DBUS_SESSION_BUS_ADDRESS

Used by D-Bus when Emacs is compiled with it. Usually, there is no need to change it. Setting it to a dummy address, like ‘unix:path=/dev/null’, suppresses connections to the D-Bus session bus as well as autolaunching the D-Bus session bus if not running yet.

EMACSDATA

Directory for the architecture-independent files that come with Emacs. This is used to initialize the variable data-directory.

EMACSDOC

Directory for the documentation string file, which is used to initialize the Lisp variable doc-directory.

EMACSLOADPATH

A colon-separated list of directories27 to search for Emacs Lisp files. If set, it modifies the usual initial value of the load-path variable (see Libraries of Lisp Code for Emacs). An empty element stands for the default value of load-path; e.g., using ‘EMACSLOADPATH="/tmp:"’ adds /tmp to the front of the default load-path. To specify an empty element in the middle of the list, use 2 colons in a row, as in ‘EMACSLOADPATH="/tmp::/foo"’.

EMACSPATH

A colon-separated list of directories to search for executable files. If set, Emacs uses this in addition to PATH (see below) when initializing the variable exec-path (see Running Shell Commands from Emacs).

EMAIL

Your email address; used to initialize the Lisp variable user-mail-address, which the Emacs mail interface puts into the ‘From’ header of outgoing messages (see Mail Header Fields).

ESHELL

Used for shell-mode to override the SHELL environment variable (see Interactive Subshell).

HISTFILE

The name of the file that shell commands are saved in between logins. This variable defaults to ~/.bash_history if you use Bash, to ~/.sh_history if you use ksh, and to ~/.history otherwise.

HOME

The location of your files in the directory tree; used for expansion of file names starting with a tilde (~). If set, it should be set to an absolute file name. (If set to a relative file name, Emacs interprets it relative to the directory where Emacs was started, but we don’t recommend to use this feature.) If unset, HOME normally defaults to the home directory of the user given by LOGNAME, USER or your user ID, or to / if all else fails. On MS-DOS, it defaults to the directory from which Emacs was started, with ‘/bin’ removed from the end if it was present. On Windows, the default value of HOME is the Application Data subdirectory of the user profile directory (normally, this is C:/Documents and Settings/username/Application Data, where username is your user name), though for backwards compatibility C:/ will be used instead if a .emacs file is found there.

HOSTNAME

The name of the machine that Emacs is running on.

INFOPATH

A colon-separated list of directories in which to search for Info files.

LC_ALL
LC_COLLATE
LC_CTYPE
LC_MESSAGES
LC_MONETARY
LC_NUMERIC
LC_TIME
LANG

The user’s preferred locale. The locale has six categories, specified by the environment variables LC_COLLATE for sorting, LC_CTYPE for character encoding, LC_MESSAGES for system messages, LC_MONETARY for monetary formats, LC_NUMERIC for numbers, and LC_TIME for dates and times. If one of these variables is not set, the category defaults to the value of the LANG environment variable, or to the default ‘C’ locale if LANG is not set. But if LC_ALL is specified, it overrides the settings of all the other locale environment variables.

On MS-Windows and macOS, if LANG is not already set in the environment, Emacs sets it based on the system-wide default. You can set this in the “Regional Settings” Control Panel on some versions of MS-Windows, and in the “Language and Region” System Preference on macOS.

The value of the LC_CTYPE category is matched against entries in locale-language-names, locale-charset-language-names, and locale-preferred-coding-systems, to select a default language environment and coding system. See Language Environments.

LOGNAME

The user’s login name. See also USER.

MAIL

The name of your system mail inbox.

MH

Name of setup file for the mh system. See MH-E in The Emacs Interface to MH.

NAME

Your real-world name. This is used to initialize the variable user-full-name (see Mail Header Fields).

NNTPSERVER

The name of the news server. Used by the mh and Gnus packages.

ORGANIZATION

The name of the organization to which you belong. Used for setting the ‘Organization:’ header in your posts from the Gnus package.

PATH

A colon-separated list of directories containing executable files. This is used to initialize the variable exec-path (see Running Shell Commands from Emacs).

PWD

If set, this should be the default directory when Emacs was started.

REPLYTO

If set, this specifies an initial value for the variable mail-default-reply-to (see Mail Header Fields).

SAVEDIR

The name of a directory in which news articles are saved by default. Used by the Gnus package.

SHELL

The name of an interpreter used to parse and execute programs run from inside Emacs. This is used to initialize the variable shell-file-name (see Single Shell Commands).

SMTPSERVER

The name of the outgoing mail server. This is used to initialize the variable smtpmail-smtp-server (see Mail Sending).

TERM

The type of the terminal that Emacs is using. This variable must be set unless Emacs is run in batch mode. On MS-DOS, it defaults to ‘internal’, which specifies a built-in terminal emulation that handles the machine’s own display.

TERMCAP

The name of the termcap library file describing how to program the terminal specified by TERM. This defaults to /etc/termcap.

TMPDIR
TMP
TEMP

These environment variables are used to initialize the variable temporary-file-directory, which specifies a directory in which to put temporary files (see Backup Files). Emacs tries to use TMPDIR first. If that is unset, Emacs normally falls back on /tmp, but on MS-Windows and MS-DOS it instead falls back on TMP, then TEMP, and finally c:/temp.

TZ

This specifies the default time zone and possibly also daylight saving time information. See Time Zone Rules in The GNU Emacs Lisp Reference Manual. On MS-DOS, if TZ is not set in the environment when Emacs starts, Emacs defines a default value as appropriate for the country code returned by DOS. On MS-Windows, Emacs does not use TZ at all.

USER

The user’s login name. See also LOGNAME. On MS-DOS, this defaults to ‘root’.

VERSION_CONTROL

Used to initialize the version-control variable (see Single or Numbered Backups).


C.4.2 Miscellaneous Variables

These variables are used only on particular configurations:

COMSPEC

On MS-DOS and MS-Windows, the name of the command interpreter to use when invoking batch files and commands internal to the shell. On MS-DOS this is also used to make a default value for the SHELL environment variable.

NAME

On MS-DOS, this variable defaults to the value of the USER variable.

EMACSTEST

On MS-DOS, this specifies a file to use to log the operation of the internal terminal emulator. This feature is useful for submitting bug reports.

EMACSCOLORS

On MS-DOS, this specifies the screen colors. It is useful to set them this way, since otherwise Emacs would display the default colors momentarily when it starts up.

The value of this variable should be the two-character encoding of the foreground (the first character) and the background (the second character) colors of the default face. Each character should be the hexadecimal code for the desired color on a standard PC text-mode display. For example, to get blue text on a light gray background, specify ‘EMACSCOLORS=17’, since 1 is the code of the blue color and 7 is the code of the light gray color.

The PC display usually supports only eight background colors. However, Emacs switches the DOS display to a mode where all 16 colors can be used for the background, so all four bits of the background color are actually used.

PRELOAD_WINSOCK

On MS-Windows, if you set this variable, Emacs will load and initialize the network library at startup, instead of waiting until the first time it is required.

WAYLAND_DISPLAY

Pgtk Emacs (built with --with-pgtk) can run on Wayland natively. WAYLAND_DISPLAY specifies the connection to the compositor.

emacs_dir

On MS-Windows, emacs_dir is a special environment variable, which indicates the full path of the directory in which Emacs is installed. If Emacs is installed in the standard directory structure, it calculates this value automatically. It is not much use setting this variable yourself unless your installation is non-standard, since unlike other environment variables, it will be overridden by Emacs at startup. When setting other environment variables, such as EMACSLOADPATH, you may find it useful to use emacs_dir rather than hard-coding an absolute path. This allows multiple versions of Emacs to share the same environment variable settings, and it allows you to move the Emacs installation directory, without changing any environment or registry settings.


C.4.3 The MS-Windows System Registry

On MS-Windows, the environment variables emacs_dir, EMACSLOADPATH, EMACSDATA, EMACSPATH, EMACSDOC, SHELL, TERM, HOME, LANG, and PRELOAD_WINSOCK can also be set in the HKEY_CURRENT_USER or the HKEY_LOCAL_MACHINE section of the system registry, under the /Software/GNU/Emacs key. When Emacs starts, as well as checking the environment, it also checks the system registry for those variables.

To determine the value of those variables, Emacs goes through the following procedure. First, it checks the environment. If the variable is not found there, Emacs looks for a registry key by the name of the variable under /Software/GNU/Emacs; first in the HKEY_CURRENT_USER section of the registry, and if not found there, in the HKEY_LOCAL_MACHINE section. Finally, if Emacs still cannot determine the values, it uses the compiled-in defaults.

Note that the registry settings have global system-wide effect: they will affect all Emacs sessions run on the system. Thus, if you run different Emacs versions, or use both installed and un-installed Emacs executables, or build newer versions of Emacs, the settings in the registry will cause all of them to use the same directories, which is probably not what you want. For this reason, we recommend against setting these variables in the registry. If you have such settings in the registry, we recommend that you remove them.

If you run the Emacs MS-Windows installation program addpm.exe, it will update any existing registry settings of the emacs_dir, EMACSLOADPATH, EMACSDATA, EMACSPATH, EMACSDOC, SHELL, and TERM variables to have the values suitable for the installed Emacs version with which addpm.exe came. Note that addpm.exe will not create any registry setting that didn’t exist, it will only update existing settings, which are most probably inherited from an old Emacs installation, so that they are compatible with the newly installed Emacs version. Running addpm.exe is no longer necessary when installing recent versions of Emacs, so we only recommend doing that if you are upgrading from an older version, and cannot remove these settings from the registry for some reason.

In addition to the environment variables above, you can also add settings to the /Software/GNU/Emacs registry key to specify X resources (see X Options and Resources). Most of the settings you can specify in your .Xdefaults file can be set from that registry key.


C.5 Specifying the Display Name

The environment variable DISPLAY tells all X clients, including Emacs, where to display their windows. Its value is set by default in ordinary circumstances, when you start an X server and run jobs locally. You can specify the display yourself; one reason to do this is if you want to log into another system and run Emacs there, and have the window displayed at your local terminal.

DISPLAY has the syntax ‘host:display.screen’, where host is the host name of the X Window System server machine, display is an arbitrarily-assigned number that distinguishes your server (X terminal) from other servers on the same machine, and screen is a field that allows an X server to control multiple terminal screens. The period and the screen field are optional. If included, screen is usually zero.

For example, if your host is named ‘glasperle’ and your server is the first (or perhaps the only) server listed in the configuration, your DISPLAY is ‘glasperle:0.0’.

You can specify the display name explicitly when you run Emacs, either by changing the DISPLAY variable, or with the option ‘-d display’ or ‘--display=display’. Here is an example:

emacs --display=glasperle:0 &

You can inhibit the use of the X window system with the ‘-nw’ option. Then Emacs uses its controlling text terminal for display. See Initial Options.

Sometimes, security arrangements prevent a program on a remote system from displaying on your local system. In this case, trying to run Emacs produces messages like this:

Xlib:  connection to "glasperle:0.0" refused by server

You might be able to overcome this problem by using the xhost command on the local system to give permission for access from your remote machine.


C.6 Font Specification Options

You can use the command line option ‘-fn font’ (or ‘--font’, which is an alias for ‘-fn’) to specify a default font:

-fn font
--font=font

Use font as the default font.

When passing a font name to Emacs on the command line, you may need to quote it, by enclosing it in quotation marks, if it contains characters that the shell treats specially (e.g., spaces). For example:

emacs -fn "DejaVu Sans Mono-12"

See Fonts, for details about font names and other ways to specify the default font.


C.7 Window Color Options

You can use the following command-line options to specify the colors to use for various parts of the Emacs display. Colors may be specified using either color names or RGB triplets (see Colors for Faces).

-fg color
--foreground-color=color

Specify the foreground color, overriding the color specified by the default face (see Text Faces).

-bg color
--background-color=color

Specify the background color, overriding the color specified by the default face.

-bd color
--border-color=color

Specify the color of the border of the X window. This has no effect if Emacs is compiled with GTK+ support.

-cr color
--cursor-color=color

Specify the color of the Emacs cursor which indicates where point is.

-ms color
--mouse-color=color

Specify the color for the mouse cursor when the mouse is in the Emacs window.

-r
-rv
--reverse-video

Reverse video: swap the foreground and background colors.

--color=mode

Set the color support mode when Emacs is run on a text terminal. This option overrides the number of supported colors that the character terminal advertises in its termcap or terminfo database. The parameter mode can be one of the following:

never
no

Don’t use colors even if the terminal’s capabilities specify color support.

default
auto

Same as when --color is not used at all: Emacs detects at startup whether the terminal supports colors, and if it does, turns on colored display.

always
yes
ansi8

Turn on the color support unconditionally, and use color commands specified by the ANSI escape sequences for the 8 standard colors.

num

Use color mode for num colors. If num is −1, turn off color support (equivalent to ‘never’); if it is 0, use the default color support for this terminal (equivalent to ‘auto’); otherwise use an appropriate standard mode for num colors. Depending on your terminal’s capabilities, Emacs might be able to turn on a color mode for 8, 16, 88, or 256 as the value of num. If there is no mode that supports num colors, Emacs acts as if num were 0, i.e., it uses the terminal’s default color support mode.

If mode is omitted, it defaults to ansi8.

For example, to use a coral mouse cursor and a slate blue text cursor, enter:

emacs -ms coral -cr 'slate blue' &

You can reverse the foreground and background colors through the ‘-rv’ option or with the X resource ‘reverseVideo’.

The ‘-fg’, ‘-bg’, and ‘-rv’ options function on text terminals as well as on graphical displays.


C.8 Options for Window Size and Position

Here is a list of the command-line options for specifying size and position of the initial Emacs frame:

-g widthxheight[{+-}xoffset{+-}yoffset]]
--geometry=widthxheight[{+-}xoffset{+-}yoffset]]

Specify the size width and height (measured in character columns and lines), and positions xoffset and yoffset (measured in pixels). The width and height parameters apply to all frames, whereas xoffset and yoffset only to the initial frame.

-fs
--fullscreen

Specify that width and height should be that of the screen. Normally no window manager decorations are shown. (After starting Emacs, you can toggle this state using F11, toggle-frame-fullscreen.)

-mm
--maximized

Specify that the Emacs frame should be maximized. This normally means that the frame has window manager decorations. (After starting Emacs, you can toggle this state using M-F10, toggle-frame-maximized.)

-fh
--fullheight

Specify that the height should be the height of the screen.

-fw
--fullwidth

Specify that the width should be the width of the screen.

In the ‘--geometry’ option, {+-} means either a plus sign or a minus sign. A plus sign before xoffset means it is the distance from the left side of the screen; a minus sign means it counts from the right side. A plus sign before yoffset means it is the distance from the top of the screen, and a minus sign there indicates the distance from the bottom. The values xoffset and yoffset may themselves be positive or negative, but that doesn’t change their meaning, only their direction.

Emacs uses the same units as xterm does to interpret the geometry. The width and height are measured in characters, so a large font creates a larger frame than a small font. (If you specify a proportional font, Emacs uses its maximum bounds width as the width unit.) The xoffset and yoffset are measured in pixels.

You do not have to specify all of the fields in the geometry specification. If you omit both xoffset and yoffset, the window manager decides where to put the Emacs frame, possibly by letting you place it with the mouse. For example, ‘164x55’ specifies a window 164 columns wide, enough for two ordinary width windows side by side, and 55 lines tall.

The default frame width is 80 characters and the default height is between 35 and 40 lines, depending on the OS and the window manager. You can omit either the width or the height or both. If you start the geometry with an integer, Emacs interprets it as the width. If you start with an ‘x’ followed by an integer, Emacs interprets it as the height. Thus, ‘81’ specifies just the width; ‘x45’ specifies just the height.

If you start the geometry with ‘+’ or ‘-’, that introduces an offset, which means both sizes are omitted. Thus, ‘-3’ specifies the xoffset only. (If you give just one offset, it is always xoffset.) ‘+3-3’ specifies both the xoffset and the yoffset, placing the frame near the bottom left of the screen.

You can specify a default for any or all of the fields in your X resource file (see X Resources), and then override selected fields with a ‘--geometry’ option.

Since the mode line and the echo area occupy the last 2 lines of the frame, the height of the initial text window is 2 less than the height specified in your geometry. In non-X-toolkit versions of Emacs, the menu bar also takes one line of the specified number. But in the X toolkit version, the menu bar is additional and does not count against the specified height. The tool bar, if present, is also additional.

Enabling or disabling the menu bar or tool bar alters the amount of space available for ordinary text. Therefore, if Emacs starts up with a tool bar (which is the default), and handles the geometry specification assuming there is a tool bar, and then your initialization file disables the tool bar, you will end up with a frame geometry different from what you asked for. To get the intended size with no tool bar, use an X resource to specify “no tool bar” (see Table of X Resources for Emacs); then Emacs will already know there’s no tool bar when it processes the specified geometry.

When using one of ‘--fullscreen’, ‘--maximized’, ‘--fullwidth’ or ‘--fullheight’, some window managers require you to set the variable frame-resize-pixelwise to a non-nil value to make a frame appear truly maximized or full-screen.

Some window managers have options that can make them ignore both program-specified and user-specified positions. If these are set, Emacs fails to position the window correctly.


C.9 Internal and Outer Borders

An Emacs frame has an internal border and an outer border. The internal border is an extra strip of the background color around the text portion of the frame. Emacs itself draws the internal border. The outer border is drawn by X outside the tool and menu bars of the frame. There is also an external border which is drawn by the window manager. The size of the external border cannot be set from within Emacs.

-ib width
--internal-border=width

Specify width as the width of the internal border (around the frame’s text area), in pixels.

-bw width
--border-width=width

Specify width as the width of the outer border, in pixels.

When you specify the size of the frame, that does not count the borders. The frame’s position is measured from the outside edge of the external border.

Use the ‘-ib n’ option to specify an internal border n pixels wide. The default is 1. Use ‘-bw n’ to specify the width of the outer border (though the window manager may not pay attention to what you specify). The default width of the outer border is 2.


C.10 Frame Titles

Each Emacs frame always has a title, which appears in window decorations and icons as the name of the frame. The default title is of the form ‘invocation-name@machine’ (if there is only one frame) or shows the selected window’s buffer name (if there is more than one frame).

You can specify a non-default title for the initial Emacs frame with a command line option:

-T title
--title=title

Specify title as the title for the initial Emacs frame.

The ‘--name’ option (see X Resources) also specifies the title for the initial Emacs frame.


C.11 Icons

-iconic
--iconic

Start Emacs in an iconified state.

-nbi
--no-bitmap-icon

Disable the use of the Emacs icon.

Most window managers allow you to iconify (or “minimize”) an Emacs frame, hiding it from sight. Some window managers replace iconified windows with tiny icons, while others remove them entirely from sight. The ‘-iconic’ option tells Emacs to begin running in an iconified state, rather than showing a frame right away. The text frame doesn’t appear until you deiconify (or “un-minimize”) it.

By default, Emacs uses an icon containing the Emacs logo. On desktop environments such as Gnome, this icon is also displayed in other contexts, e.g., when switching into an Emacs frame. The ‘-nbi’ or ‘--no-bitmap-icon’ option tells Emacs to let the window manager choose what sort of icon to use—usually just a small rectangle containing the frame’s title.


C.12 Other Display Options

--parent-id id

Open Emacs as a client X window via the XEmbed protocol, with id as the parent X window id. Currently, this option is mainly useful for developers.

-vb
--vertical-scroll-bars

Enable vertical scroll bars.

-lsp pixels
--line-spacing=pixels

Specify pixels as additional space to put between lines, in pixels.

-nbc
--no-blinking-cursor

Disable the blinking cursor on graphical displays.

-D
--basic-display

Disable the menu-bar, the tool-bar, the scroll-bars, tool tips, and turn off font-lock-mode and the blinking cursor. This can be useful for making a test case that simplifies debugging of display problems.

The ‘--xrm’ option (see X Resources) specifies additional X resource values.


Appendix D X Options and Resources

You can customize some X-related aspects of Emacs behavior using X resources, as is usual for programs that use X.

When Emacs is compiled with GTK+ support, the appearance of various graphical widgets, such as the menu-bar, scroll-bar, and dialog boxes, is determined by GTK+ resources, which we will also describe. When Emacs is built without GTK+ support, the appearance of these widgets is determined by additional X resources.

On MS-Windows, you can customize some of the same aspects using the system registry (see The MS-Windows System Registry).


D.1 X Resources

Programs running under the X Window System organize their user options under a hierarchy of classes and resources. You can specify default values for these options in your X resource file, usually named ~/.Xdefaults or ~/.Xresources. Changes in this file do not take effect immediately, because the X server stores its own list of resources; to update it, use the command xrdb—for instance, ‘xrdb ~/.Xdefaults’.

Settings specified via X resources in general override the equivalent settings in Emacs init files (see The Emacs Initialization File), in particular for parameters of the initial frame (see Frame Parameters).

(MS-Windows systems do not support X resource files; on such systems, Emacs looks for X resources in the Windows Registry, first under the key ‘HKEY_CURRENT_USER\SOFTWARE\GNU\Emacs’, which affects only the current user and override the system-wide settings, and then under the key ‘HKEY_LOCAL_MACHINE\SOFTWARE\GNU\Emacs’, which affects all users of the system. The menu and scroll bars are native widgets on MS-Windows, so they are only customizable via the system-wide settings in the Display Control Panel. You can also set resources using the ‘-xrm’ command line option, as explained below.)

Each line in the X resource file specifies a value for one option or for a collection of related options. The order in which the lines appear in the file does not matter. Each resource specification consists of a program name and a resource name. Case distinctions are significant in each of these names. Here is an example:

emacs.cursorColor: dark green

The program name is the name of the executable file to which the resource applies. For Emacs, this is normally ‘emacs’. To specify a definition that applies to all instances of Emacs, regardless of the name of the Emacs executable, use ‘Emacs’.

The resource name is the name of a program setting. For instance, Emacs recognizes a ‘cursorColor’ resource that controls the color of the text cursor.

Resources are grouped into named classes. For instance, the ‘Foreground’ class contains the ‘cursorColor’, ‘foreground’ and ‘pointerColor’ resources (see Table of X Resources for Emacs). Instead of using a resource name, you can use a class name to specify the default value for all resources in that class, like this:

emacs.Foreground: dark green

Emacs does not process X resources at all if you set the variable inhibit-x-resources to a non-nil value. If you invoke Emacs with the ‘-Q’ (or ‘--quick’) command-line option, inhibit-x-resources is automatically set to t (see Initial Options).

In addition, you can use the following command-line options to override the X resources file:

-name name
--name=name

This option sets the program name of the initial Emacs frame to name. It also sets the title of the initial frame to name. This option does not affect subsequent frames.

If you don’t specify this option, the default is to use the Emacs executable’s name as the program name.

For consistency, ‘-name’ also specifies the name to use for other resource values that do not belong to any particular frame.

The resources that name Emacs invocations also belong to a class, named ‘Emacs’. If you write ‘Emacs’ instead of ‘emacs’, the resource applies to all frames in all Emacs jobs, regardless of frame titles and regardless of the name of the executable file.

-xrm resource-value
--xrm=resource-value

This option specifies X resource values for the present Emacs job.

resource-value should have the same format that you would use inside a file of X resources. Several ‘-xrm’ options are possible to include multiple resource specifications. You can also use ‘#include "filename"’ as resource-value to include a file full of resource specifications. Resource values specified with ‘-xrm’ take precedence over all other resource specifications.


D.2 Table of X Resources for Emacs

The table below lists the X resource names that Emacs recognizes. Note that some of the resources have no effect in Emacs compiled with various X toolkits (GTK+, Lucid, etc.)—we indicate below when this is the case.

alpha (class Alpha)

Sets the ‘alpha’ frame parameter, determining frame transparency (see Frame Parameters in The Emacs Lisp Reference Manual).

alphaBackground (class AlphaBackground)

Sets the ‘alpha-background’ frame parameter, determining background transparency (see Frame Parameters in The Emacs Lisp Reference Manual).

background (class Background)

Background color (see Colors for Faces).

bitmapIcon (class BitmapIcon)

Tell the window manager to display the Emacs icon if ‘on’; don’t do so if ‘off’. See Icons, for a description of the icon.

borderColor (class BorderColor)

Color of the frame’s external border. This has no effect if Emacs is compiled with GTK+ support.

borderWidth (class BorderWidth)

Width of the frame’s external border, in pixels. This has no effect if Emacs is compiled with GTK+ support.

cursorBlink (class CursorBlink)

If the value of this resource is ‘off’ or ‘false’ or ‘0’ at startup, Emacs disables Blink Cursor mode (see Displaying the Cursor).

cursorColor (class Foreground)

Text cursor color. If this resource is specified when Emacs starts up, Emacs sets its value as the background color of the cursor face (see Text Faces).

font (class Font)

Font name for the default face (see Fonts). You can also specify a fontset name (see Fontsets).

fontBackend (class FontBackend)

Comma-delimited list of backend(s) to use for drawing fonts, in order of precedence. For instance, the value ‘x,xft’ tells Emacs to draw fonts using the X core font driver, falling back on the Xft font driver if that fails. Normally, you should leave this resource unset, in which case Emacs tries using all available font backends.

foreground (class Foreground)

Default foreground color for text.

fullscreen (class Fullscreen)

The desired fullscreen size. The value can be one of fullboth, maximized, fullwidth or fullheight, which correspond to the command-line options ‘-fs’, ‘-mm’, ‘-fw’, and ‘-fh’ (see Options for Window Size and Position). Note that this applies to the initial frame only.

geometry (class Geometry)

Window size and position. The value should be a size and position specification, of the same form as in the ‘-g’ or ‘--geometry’ command-line option (see Options for Window Size and Position).

The size applies to all frames in the Emacs session, but the position applies only to the initial Emacs frame (or, in the case of a resource for a specific frame name, only that frame).

Be careful not to specify this resource as ‘emacs*geometry’, as that may affect individual menus as well as the main Emacs frame.

horizontalScrollBars (class ScrollBars)

If the value of this resource is ‘off’ or ‘false’ or ‘0’, Emacs disables Horizontal Scroll Bar mode at startup (see Scroll Bars).

iconName (class Title)

Name to display in the icon.

internalBorder (class BorderWidth)

Width of the internal frame border, in pixels.

lineSpacing (class LineSpacing)

Additional space between lines, in pixels.

menuBackground (class Background)

The background color of the menus in non-toolkit versions of Emacs. (For toolkit versions, see Lucid Menu And Dialog X Resources, also see Motif Menu X Resources, and see GTK+ resources.)

menuBar (class MenuBar)

If the value of this resource is ‘off’ or ‘false’ or ‘0’, Emacs disables Menu Bar mode at startup (see Menu Bars).

minibuffer (class Minibuffer)

If ‘none’, Emacs will not make a minibuffer in this frame; it will use a separate minibuffer frame instead.

paneFont (class Font)

Font name for menu pane titles, in non-toolkit versions of Emacs. (For toolkit versions, see Lucid Menu And Dialog X Resources, also see Motif Menu X Resources, and see GTK+ resources.)

paneForeground (class Foreground)

Foreground color for menu pane titles, in non-toolkit versions of Emacs. (For toolkit versions, see Lucid Menu And Dialog X Resources, also see Motif Menu X Resources, and see GTK+ resources.)

pointerColor (class Foreground)

Color of the mouse cursor. This has no effect in many graphical desktop environments, as they do not let Emacs change the mouse cursor this way.

privateColormap (class PrivateColormap)

If ‘on’, use a private color map, in the case where the default visual of class PseudoColor and Emacs is using it.

reverseVideo (class ReverseVideo)

Switch foreground and background default colors if ‘on’, use colors as specified if ‘off’.

screenGamma (class ScreenGamma)

Gamma correction for colors, equivalent to the frame parameter screen-gamma.

scrollBar (class ScrollBar)

If the value of this resource is ‘off’ or ‘false’ or ‘0’, Emacs disables Scroll Bar mode at startup (see Scroll Bars).

scrollBarWidth (class ScrollBarWidth)

The scroll bar width in pixels, equivalent to the frame parameter scroll-bar-width. Do not set this resource if Emacs is compiled with GTK+ support.

selectionFont (class SelectionFont)

Font name for pop-up menu items, in non-toolkit versions of Emacs. (For toolkit versions, see Lucid Menu And Dialog X Resources, also see Motif Menu X Resources, and see GTK+ resources.)

selectionForeground (class SelectionForeground)

Foreground color for pop-up menu items, in non-toolkit versions of Emacs. (For toolkit versions, see Lucid Menu And Dialog X Resources, also see Motif Menu X Resources, and see GTK+ resources.)

selectionTimeout (class SelectionTimeout)

Number of milliseconds to wait for a selection reply. If the selection owner doesn’t reply in this time, we give up. A value of 0 means wait as long as necessary.

synchronous (class Synchronous)

Run Emacs in synchronous mode if ‘on’. Synchronous mode is useful for debugging X problems.

title (class Title)

Name to display in the title bar of the initial Emacs frame.

toolBar (class ToolBar)

If the value of this resource is ‘off’ or ‘false’ or ‘0’, Emacs disables Tool Bar mode at startup (see Tool Bars).

tabBar (class TabBar)

If the value of this resource is ‘on’ or ‘yes’ or ‘1’, Emacs enables Tab Bar mode at startup (see Tab Bars).

useXIM (class UseXIM)

Disable use of X input methods (XIM) if ‘false’ or ‘off’. This is only relevant if your Emacs is built with XIM support. It might be useful to turn off XIM on slow X client/server links.

inputStyle (class InputStyle)

This resource controls how preview text generated by X input methods is displayed. Its value can be on of the following:

callback

Display the contents of the preview text in the current buffer.

offthespot

Display the preview text inside a separate area of the display provided by Emacs.

overthespot

Display the preview text inside a popup window at the location of point in the current window.

none

Let the input method decide how to display itself. This is usually equivalent to ‘overthespot’, but it might work with more input methods.

native

Use the toolkit for handling input methods. This is currently implemented only on GTK.

root

Use some location on display specific to the input method for displaying the preview text.

synchronizeResize (class SynchronizeResize)

If ‘off’ or ‘false’, Emacs will not try to tell the window manager when it has finished redrawing the display in response to a frame being resized. Otherwise, the window manager will postpone drawing a frame that was just resized until its contents are updated, which prevents blank areas of a frame that have not yet been painted from being displayed. If set to ‘extended’, it will enable use of an alternative frame synchronization protocol, which might be supported by some compositing window managers that don’t support the protocol Emacs uses by default, and causes Emacs to synchronize display with the monitor refresh rate when a compatible compositing window manager is in use.

verticalScrollBars (class ScrollBars)

Give frames scroll bars on the left if ‘left’, on the right if ‘right’; don’t have scroll bars if ‘off’ (see Scroll Bars).

visualClass (class VisualClass)

The visual class for X color display. If specified, the value should start with one of ‘TrueColor’, ‘PseudoColor’, ‘DirectColor’, ‘StaticColor’, ‘GrayScale’, and ‘StaticGray’, followed by ‘-depth’, where depth is the number of color planes.

You can also use X resources to customize individual Emacs faces (see Text Faces). For example, setting the resource ‘face.attributeForeground’ is equivalent to customizing the ‘foreground’ attribute of the face face. However, we recommend customizing faces from within Emacs, instead of using X resources. See Customizing Faces.


D.3 Lucid Menu And Dialog X Resources

If Emacs is compiled with the X toolkit support using Lucid widgets, you can use X resources to customize the appearance of the menu bar (see The Menu Bar), pop-up menus, and dialog boxes (see Using Dialog Boxes). The resources for the menu bar fall in the ‘pane.menubar’ class (following, as always, either the name of the Emacs executable or ‘Emacs’ for all Emacs invocations). The resources for the pop-up menu are in the ‘menu*’ class. The resources for dialog boxes are in the ‘dialog*’ class.

For example, to display menu bar entries with the ‘Courier-12’ font (see Fonts), write this:

Emacs.pane.menubar.font: Courier-12

Lucid widgets can display multilingual text in your locale. To enable this, specify a fontSet resource instead of a font resource. See Fontsets. If both font and fontSet resources are specified, the fontSet resource is used.

Here is a list of resources for menu bars, pop-up menus, and dialogs:

font

Font for menu item text.

fontSet

Fontset for menu item text.

background

Background color.

buttonForeground

Foreground color for a selected item.

foreground

Foreground color.

disabledForeground

Foreground color for a disabled menu item.

highlightForeground

Foreground color for a menu item highlighted by the mouse or key navigation.

highlightBackground

Background color for a menu item highlighted by the mouse or key navigation.

horizontalSpacing

Horizontal spacing in pixels between items. Default is 3.

verticalSpacing

Vertical spacing in pixels between items. Default is 2.

arrowSpacing

Horizontal spacing between the arrow (which indicates a submenu) and the associated text. Default is 10.

shadowThickness

Thickness of shadow lines for 3D buttons, arrows, and other graphical elements. Default is 1.

borderThickness

Thickness of the external borders of the menu bars and pop-up menus. Default is 1.

cursor

Name of the cursor to use in the menu bars and pop-up menus. Default is "right_ptr".

margin

Margin of the menu bar, in characters. Default is 1.


D.4 Motif Menu X Resources

If Emacs is compiled with the X toolkit support using Motif or LessTif widgets, you can use X resources to customize the appearance of the menu bar (see The Menu Bar), pop-up menus, and dialog boxes (see Using Dialog Boxes). However, the resources are organized differently from Lucid widgets.

The resource names for the menu bar are in the ‘pane.menubar’ class, and they must be specified in this form:

Emacs.pane.menubar.subwidget.resource: value

For pop-up menus, the resources are in the ‘menu*’ class, instead of ‘pane.menubar’. For dialog boxes, they are in ‘dialog’. In each case, each individual menu string is a subwidget; the subwidget’s name is the same as the menu item string. For example, the ‘File’ menu in the menu bar is a subwidget named ‘emacs.pane.menubar.File’.

Typically, you want to specify the same resources for the whole menu bar. To do this, use ‘*’ instead of a specific subwidget name. For example, to specify the font ‘8x16’ for all menu bar items, including submenus, write this:

Emacs.pane.menubar.*.fontList: 8x16

Each item in a submenu also has its own name for X resources; for example, the ‘File’ submenu has an item named ‘Save (current buffer)’. A resource specification for a submenu item looks like this:

Emacs.pane.menubar.popup_*.menu.item.resource: value

For example, here’s how to specify the font for the ‘Save (current buffer)’ item:

Emacs.pane.menubar.popup_*.File.Save (current buffer).fontList: 8x16

For an item in a second-level submenu, such as ‘Complete Word’ under ‘Spell Checking’ under ‘Tools’, the resource fits this template:

Emacs.pane.menubar.popup_*.popup_*.menu.resource: value

For example,

Emacs.pane.menubar.popup_*.popup_*.Spell Checking.Complete Word: value

(This should be one long line.)

If you want the submenu items to look different from the menu bar itself, you must first specify the resource for all of them, then override the value for submenus alone. Here is an example:

Emacs.pane.menubar.*.fontList: 9x18
Emacs.pane.menubar.popup_*.fontList: 8x16

To specify resources for the LessTif file-selection box, use ‘fsb*’, like this:

Emacs.fsb*.fontList: 8x16

Here is a list of resources for LessTif menu bars and pop-up menus:

armColor

The color to show in an armed button.

fontList

The font to use.

marginBottom
marginHeight
marginLeft
marginRight
marginTop
marginWidth

Amount of space to leave around the item, within the border.

borderWidth

The width of the border around the menu item, on all sides.

shadowThickness

The width of the border shadow.

bottomShadowColor

The color for the border shadow, on the bottom and the right.

topShadowColor

The color for the border shadow, on the top and the left.


D.5 GTK+ resources

If Emacs is compiled with GTK+ toolkit support, the simplest way to customize its GTK+ widgets (e.g., menus, dialogs, tool bars and scroll bars) is to choose an appropriate GTK+ theme, for example with the GNOME theme selector.

In GTK+ version 2, you can also use GTK+ resources to customize the appearance of GTK+ widgets used by Emacs. These resources are specified in either the file ~/.emacs.d/gtkrc (for Emacs-specific GTK+ resources), or ~/.gtkrc-2.0 (for general GTK+ resources). We recommend using ~/.emacs.d/gtkrc, since GTK+ seems to ignore ~/.gtkrc-2.0 when running GConf with GNOME. Note, however, that some GTK+ themes may override customizations in ~/.emacs.d/gtkrc; there is nothing we can do about this. GTK+ resources do not affect aspects of Emacs unrelated to GTK+ widgets, such as fonts and colors in the main Emacs window; those are governed by normal X resources (see X Resources).

The following sections describe how to customize GTK+ resources for Emacs. For details about GTK+ resources, see the GTK+ API document at https://developer-old.gnome.org/gtk2/stable/gtk2-Resource-Files.html.

In GTK+ version 3, GTK+ resources have been replaced by a completely different system. The appearance of GTK+ widgets is now determined by CSS-like style files: gtk-3.0/gtk.css in the GTK+ installation directory, and ~/.themes/theme/gtk-3.0/gtk.css for local style settings (where theme is the name of the current GTK+ theme). Therefore, the description of GTK+ resources in this section does not apply to GTK+ 3. For details about the GTK+ 3 styling system, see https://developer-old.gnome.org/gtk3/3.0/GtkCssProvider.html.


D.5.1 GTK+ Resource Basics

In a GTK+ 2 resource file (usually ~/.emacs.d/gtkrc), the simplest kind of a resource setting simply assigns a value to a variable. For example, putting the following line in the resource file changes the font on all GTK+ widgets to ‘courier-12’:

gtk-font-name = "courier 12"

Note that in this case the font name must be supplied as a GTK font pattern (also called a Pango font name), not as a Fontconfig-style font name or XLFD. See Fonts.

To customize widgets you first define a style, and then apply the style to the widgets. Here is an example that sets the font for menus (‘#’ characters indicate comments):

# Define the style ‘my_style’.
style "my_style"
{
  font_name = "helvetica bold 14"
}

# Specify that widget type ‘*emacs-menuitem*’ uses ‘my_style’.
widget "*emacs-menuitem*" style "my_style"

The widget name in this example contains wildcards, so the style is applied to all widgets matching ‘*emacs-menuitem*’. The widgets are named by the way they are contained, from the outer widget to the inner widget. Here is another example that applies ‘my_style’ specifically to the Emacs menu bar:

widget "Emacs.pane.menubar.*" style "my_style"

Here is a more elaborate example, showing how to change the parts of the scroll bar:

style "scroll"
{
  fg[NORMAL] = "red"     # Arrow color.
  bg[NORMAL] = "yellow"  # Thumb and background around arrow.
  bg[ACTIVE] = "blue"    # Trough color.
  bg[PRELIGHT] = "white" # Thumb color when the mouse is over it.
}

widget "*verticalScrollBar*" style "scroll"

D.5.2 GTK+ widget names

A GTK+ widget is specified by a widget name and a widget class. The widget name refers to a specific widget (e.g., ‘emacs-menuitem’), while the widget class refers to a collection of similar widgets (e.g., ‘GtkMenuItem’). A widget always has a class, but need not have a name.

Absolute names are sequences of widget names or widget classes, corresponding to hierarchies of widgets embedded within other widgets. For example, if a GtkWindow named top contains a GtkVBox named box, which in turn contains a GtkMenuBar called menubar, the absolute class name of the menu-bar widget is GtkWindow.GtkVBox.GtkMenuBar, and its absolute widget name is top.box.menubar.

GTK+ resource files can contain two types of commands for specifying widget appearances:

widget

specifies a style for widgets based on the class name, or just the class.

widget_class

specifies a style for widgets based on the class name.

See the previous subsection for examples of using the widget command; the widget_class command is used similarly. Note that the widget name/class and the style must be enclosed in double-quotes, and these commands must be at the top level in the GTK+ resource file.

As previously noted, you may specify a widget name or class with shell wildcard syntax: ‘*’ matches zero or more characters and ‘?’ matches one character. This example assigns a style to all widgets:

widget "*" style "my_style"

D.5.3 GTK+ Widget Names in Emacs

The GTK+ widgets used by an Emacs frame are listed below:

Emacs (class GtkWindow)
pane (class GtkVBox)
menubar (class GtkMenuBar)
[menu item widgets]
[unnamed widget] (class GtkHandleBox)
emacs-toolbar (class GtkToolbar)
[tool bar item widgets]
emacs (class GtkFixed)
verticalScrollBar (class GtkVScrollbar)

The contents of Emacs windows are drawn in the emacs widget. Note that even if there are multiple Emacs windows, each scroll bar widget is named verticalScrollBar.

For example, here are two different ways to set the menu bar style:

widget "Emacs.pane.menubar.*" style "my_style"
widget_class "GtkWindow.GtkVBox.GtkMenuBar.*" style "my_style"

For GTK+ dialogs, Emacs uses a widget named emacs-dialog, of class GtkDialog. For file selection, Emacs uses a widget named emacs-filedialog, of class GtkFileSelection.

Because the widgets for pop-up menus and dialogs are free-standing windows and not contained in the Emacs widget, their GTK+ absolute names do not start with ‘Emacs’. To customize these widgets, use wildcards like this:

widget "*emacs-dialog*" style "my_dialog_style"
widget "*emacs-filedialog* style "my_file_style"
widget "*emacs-menuitem* style "my_menu_style"

If you want to apply a style to all menus in Emacs, use this:

widget_class "*Menu*" style "my_menu_style"

D.5.4 GTK+ styles

Here is an example of two GTK+ style declarations:

pixmap_path "/usr/share/pixmaps:/usr/include/X11/pixmaps"

style "default"
{
  font_name = "helvetica 12"

  bg[NORMAL] = { 0.83, 0.80, 0.73 }
  bg[SELECTED] = { 0.0, 0.55, 0.55 }
  bg[INSENSITIVE] = { 0.77, 0.77, 0.66 }
  bg[ACTIVE] = { 0.0, 0.55, 0.55 }
  bg[PRELIGHT] = { 0.0, 0.55, 0.55 }

  fg[NORMAL] = "black"
  fg[SELECTED] = { 0.9, 0.9, 0.9 }
  fg[ACTIVE] = "black"
  fg[PRELIGHT] = { 0.9, 0.9, 0.9 }

  base[INSENSITIVE] = "#777766"
  text[INSENSITIVE] = { 0.60, 0.65, 0.57 }

  bg_pixmap[NORMAL] = "background.xpm"
  bg_pixmap[INSENSITIVE] = "background.xpm"
  bg_pixmap[ACTIVE] = "background.xpm"
  bg_pixmap[PRELIGHT] = "<none>"

}

style "ruler" = "default"
{
  font_name = "helvetica 8"
}

The style ‘ruler’ inherits from ‘default’. This way you can build on existing styles. The syntax for fonts and colors is described below.

As this example shows, it is possible to specify several values for foreground and background depending on the widget’s state. The possible states are:

NORMAL

This is the default state for widgets.

ACTIVE

This is the state for a widget that is ready to do something. It is also for the trough of a scroll bar, i.e., bg[ACTIVE] = "red" sets the scroll bar trough to red. Buttons that have been armed (pressed but not released yet) are in this state.

PRELIGHT

This is the state for a widget that can be manipulated, when the mouse pointer is over it—for example when the mouse is over the thumb in the scroll bar or over a menu item. When the mouse is over a button that is not pressed, the button is in this state.

SELECTED

This is the state for data that has been selected by the user. It can be selected text or items selected in a list. This state is not used in Emacs.

INSENSITIVE

This is the state for widgets that are visible, but they cannot be manipulated in the usual way—for example, buttons that can’t be pressed, and disabled menu items. To display disabled menu items in yellow, use fg[INSENSITIVE] = "yellow".

Here are the things that can go in a style declaration:

bg[state] = color

This specifies the background color for the widget. Note that editable text doesn’t use bg; it uses base instead.

base[state] = color

This specifies the background color for editable text. In Emacs, this color is used for the background of the text fields in the file dialog.

bg_pixmap[state] = "pixmap"

This specifies an image background (instead of a background color). pixmap should be the image file name. GTK+ can use a number of image file formats, including XPM, XBM, GIF, JPEG and PNG. If you want a widget to use the same image as its parent, use ‘<parent>’. If you don’t want any image, use ‘<none>’. ‘<none>’ is the way to cancel a background image inherited from a parent style.

You can’t specify the file by its absolute file name. GTK+ looks for the pixmap file in directories specified in pixmap_path. pixmap_path is a colon-separated list of directories within double quotes, specified at the top level in a gtkrc file (i.e., not inside a style definition; see example above):

pixmap_path "/usr/share/pixmaps:/usr/include/X11/pixmaps"
fg[state] = color

This specifies the foreground color for widgets to use. It is the color of text in menus and buttons, and the color for the arrows in the scroll bar. For editable text, use text.

text[state] = color

This is the color for editable text. In Emacs, this color is used for the text fields in the file dialog.

font_name = "font"

This specifies the font for text in the widget. font is a GTK-style (or Pango) font name, like ‘Sans Italic 10’. See Fonts. The names are case insensitive.

There are three ways to specify a color: a color name, an RGB triplet, or a GTK-style RGB triplet. See Colors for Faces, for a description of color names and RGB triplets. Color names should be enclosed with double quotes, e.g., ‘"red"’. RGB triplets should be written without double quotes, e.g., ‘#ff0000’. GTK-style RGB triplets have the form rgb }, where r, g and b are either integers in the range 0–65535 or floats in the range 0.0–1.0.


Appendix E Emacs 28 Antinews

For those users who live backwards in time, here is information about downgrading to Emacs version 28.2. We hope you will enjoy the greater simplicity that results from the absence of many Emacs 29.2 features.


Appendix F Emacs and macOS / GNUstep

This section describes the peculiarities of using Emacs built with the GNUstep libraries on GNU/Linux or other operating systems, or on macOS with native window system support. On macOS, Emacs can be built either without window system support, with X11, or with the Cocoa interface; this section only applies to the Cocoa build. This does not support versions before macOS 10.6.

GNUstep is free software; macOS is not. Because it is a non-free operating system, macOS denies its users the freedom that every computer user deserves. That is an injustice. For your freedom’s sake, we urge you to switch to a free operating system.

We support GNU Emacs on proprietary operating systems because we hope this taste of freedom will inspire users to escape from them.

For various historical and technical reasons, Emacs uses the term ‘Nextstep’ internally, instead of “Cocoa” or “macOS”; for instance, most of the commands and variables described in this section begin with ‘ns-’, which is short for ‘Nextstep’. NeXTstep was an application interface released by NeXT Inc. during the 1980s, of which Cocoa is a direct descendant. Apart from Cocoa, there is another NeXTstep-style system: GNUstep, which is free software. As of this writing, Emacs GNUstep support is in alpha status (see GNUstep Support), but we hope to improve it in the future.


F.1 Basic Emacs usage under macOS and GNUstep

By default, the Alt and Option keys are the same as Meta. The Mac Cmd key is the same as Super, and Emacs provides a set of key bindings using this modifier key that mimic other Mac / GNUstep applications (see Windowing System Events under macOS / GNUstep). You can change these bindings in the usual way (see Customizing Key Bindings). The modifiers themselves can be customized; see Mac / GNUstep Customization.

S-mouse-1 adjusts the region to the click position, just like mouse-3 (mouse-save-then-kill); it does not pop up a menu for changing the default face, as S-mouse-1 normally does (see Text Scale). This change makes Emacs behave more like other Mac / GNUstep applications.

When you open or save files using the menus, or using the Cmd-o and Cmd-S bindings, Emacs uses graphical file dialogs to read file names. However, if you use the regular Emacs key sequences, such as C-x C-f, Emacs uses the minibuffer to read file names.

On GNUstep, in an X-windows environment you need to use Cmd-c instead of one of the C-w or M-w commands to transfer text to the X primary selection; otherwise, Emacs will use the clipboard selection. Likewise, Cmd-y (instead of C-y) yanks from the X primary selection instead of the kill-ring or clipboard.

F.1.1 Grabbing environment variables

Many programs which may run under Emacs, like latex or man, depend on the settings of environment variables. If Emacs is launched from the shell, it will automatically inherit these environment variables and its subprocesses will inherit them from it. But if Emacs is launched from the Finder it is not a descendant of any shell, so its environment variables haven’t been set, which often causes the subprocesses it launches to behave differently than they would when launched from the shell.

For the PATH and MANPATH variables, a system-wide method of setting PATH is recommended on macOS, using the /etc/paths files and the /etc/paths.d directory.


F.2 Mac / GNUstep Customization

There are a few customization options that are specific to the Nextstep port. For example, they affect things such as the modifier keys and the fullscreen behavior. To see all such options, use M-x customize-group RET ns RET.

F.2.1 Modifier keys

The following variables control the behavior of the actual modifier keys:

ns-alternate-modifier
ns-right-alternate-modifier

The left and right Option or Alt keys.

ns-command-modifier
ns-right-command-modifier

The left and right Command keys.

ns-control-modifier
ns-right-control-modifier

The left and right Control keys.

ns-function-modifier

The Function (fn) key.

The value of each variable is either a symbol, describing the key for any purpose, or a list of the form (:ordinary symbol :function symbol :mouse symbol), which describes the modifier when used with ordinary keys, function keys (that do not produce a character, such as arrow keys), and mouse clicks.

If the symbol is one of control, meta, alt, super or hyper, this describes the Emacs modifier it represents. If symbol is none, Emacs does not use the key, which retains its standard behavior. For instance, the Option key in macOS is then used for composing additional characters.

The variables for right-hand keys, like ns-right-alternate-modifier, may also be set to left, which means to use the same behavior as the corresponding left-hand key.

F.2.2 Frame Variables

ns-use-proxy-icon

This variable specifies whether to display the proxy icon in the titlebar. The proxy icon can be used to drag the file associated with the current buffer to other applications, a printer, the desktop, etc., in the same way you can from Finder. You might have to disable tool-bar-mode to see the proxy icon.

ns-confirm-quit

This variable specifies whether to display a graphical confirmation dialog on quitting.

ns-auto-hide-menu-bar

This variable specifies whether the macOS menu bar is hidden when an Emacs frame is selected. If non-nil the menu bar is not shown unless the mouse pointer is moved near to the top of the screen.

ns-use-native-fullscreen

This variable controls whether to use native, or non-native fullscreen. Native fullscreen is only available on macOS 10.7 and above.

F.2.3 macOS Trackpad/Mousewheel Variables

These variables only apply to macOS 10.7 (Lion) and above.

ns-use-mwheel-acceleration

This variable controls whether Emacs ignores the system mousewheel acceleration. When nil each ‘click’ of the mousewheel will correspond exactly with one mousewheel event. When non-nil, the default, each ‘click’ may correspond with more than one mousewheel event, depending on the user’s input.

ns-use-mwheel-momentum

This variable controls whether Emacs ignores the system ‘momentum’ when scrolling using a trackpad. When non-nil, the default, scrolling rapidly may result in the buffer continuing to scroll for a short while after the user has lifted their fingers off the trackpad.

ns-mwheel-line-height

This variable controls the sensitivity of scrolling with the trackpad. Apple trackpads scroll by pixels, not lines, so Emacs converts the system’s pixel values into lines. When set to a number, this variable sets the number of pixels Emacs will consider as one line. When nil or a non-number the default line height is used.

Setting a lower number makes the trackpad more sensitive, and a higher number makes the trackpad less sensitive.


F.3 Windowing System Events under macOS / GNUstep

Nextstep applications receive a number of special events which have no X equivalent. These are sent as specially defined key events, which do not correspond to any sequence of keystrokes. Under Emacs, these key events can be bound to functions just like ordinary keystrokes. Here is a list of these events.

ns-open-file

This event occurs when another Nextstep application requests that Emacs open a file. A typical reason for this would be a user double-clicking a file in the Finder application. By default, Emacs responds to this event by opening a new frame and visiting the file in that frame (ns-find-file). As an exception, if the selected buffer is the *scratch* buffer, Emacs visits the file in the selected frame.

You can change how Emacs responds to a ns-open-file event by changing the variable ns-pop-up-frames. Its default value, ‘fresh’, is what we have just described. A value of t means to always visit the file in a new frame. A value of nil means to always visit the file in the selected frame.

ns-open-temp-file

This event occurs when another application requests that Emacs open a temporary file. By default, this is handled by just generating a ns-open-file event, the results of which are described above.

ns-open-file-line

Some applications, such as ProjectBuilder and gdb, request not only a particular file, but also a particular line or sequence of lines in the file. Emacs handles this by visiting that file and highlighting the requested line (ns-open-file-select-line).

ns-power-off

This event occurs when the user logs out and Emacs is still running, or when “Quit Emacs” is chosen from the application menu. The default behavior is to save all file-visiting buffers.

ns-show-prefs

This event occurs when the user selects “Preferences” from the application menu. By default, it is bound to the command customize.

Emacs also allows users to make use of Nextstep services, via a set of commands whose names begin with ‘ns-service-’ and end with the name of the service. Type M-x ns-service- TAB to see a list of these commands. These functions either operate on marked text (replacing it with the result) or take a string argument and return the result as a string. You can also use the Lisp function ns-perform-service to pass arbitrary strings to arbitrary services and receive the results back. Note that you may need to restart Emacs to access newly-available services.


F.4 GNUstep Support

Emacs can be built and run under GNUstep, but there are still issues to be addressed. Interested developers should contact the emacs-devel mailing list.


Appendix G Emacs and Haiku

Haiku is a Unix-like operating system that originated as a re-implementation of the operating system BeOS.

This section describes the peculiarities of using Emacs built with the Application Kit, the windowing system native to Haiku. The oddities described here do not apply to using Emacs on Haiku built without windowing support, or built with X11.


G.1 Installation and usage peculiarities under Haiku

Emacs installs two separate executables under Haiku; it is up to the user to decide which one suits him best: A regular executable, with the lowercase name emacs, and a binary containing Haiku-specific application metadata, with the name Emacs.

If you are launching Emacs from the Tracker, or want to make the Tracker open files using Emacs, you should use the binary named Emacs; if you are going to use Emacs in the terminal, or wish to launch separate instances of Emacs, or do not care for the aforementioned system integration features, use the binary named emacs instead.

On Haiku, unusual modifier keys such as the Hyper key are unsupported. By default, the super key corresponds with the option key defined by the operating system, the meta key with the command key, the control key with the system control key, and the shift key with the system shift key. On a standard PC keyboard, Haiku should map these keys to positions familiar to those using a GNU system, but this may require some adjustment to your system’s configuration to work.

It is impossible to type accented characters using the system super key map.

You can customize the correspondence between modifier keys known to the system, and those known to Emacs. The variables that allow for that are described below.

haiku-meta-keysym

The system modifier key that will be treated as the Meta key by Emacs. It defaults to command.

haiku-control-keysym

The system modifier key that will be treated as the Control key by Emacs. It defaults to control.

haiku-super-keysym

The system modifier key that will be treated as the Super key by Emacs. It defaults to option.

haiku-shift-keysym

The system modifier key that will be treated as the Shift key by Emacs. It defaults to shift.

The value of each variable can be one of the symbols command, control, option, shift, or nil. nil or any other value will cause the default value to be used instead.

On Haiku, Emacs defaults to using the system tooltip mechanism. This usually leads to more responsive tooltips, but the tooltips will not be able to display text properties or faces. If you need those features, customize the variable use-system-tooltips to the nil value, and Emacs will use its own implementation of tooltips.

Unlike the X window system, Haiku does not have a system-wide resource database. Since many important options are specified via X resources (see X Options and Resources), an emulation is provided: upon startup, Emacs will load a file named GNU Emacs inside the user configuration directory (normally /boot/home/config/settings), which should be a flattened system message where keys and values are both strings, and correspond to attributes and their values respectively.

You can create such a file with the xmlbmessage tool.

G.1.1 What to do when Emacs crashes

If the variable haiku-debug-on-fatal-error is non-nil, Emacs will launch the system debugger when a fatal signal is received. It defaults to t. If GDB cannot be used on your system, please attach the report generated by the system debugger when reporting a bug.


G.2 Font and font backend selection on Haiku

Emacs, when built with Haiku windowing support, can be built with several different font backends. You can specify font backends by specifying -xrm Emacs.fontBackend:BACKEND on the command line used to invoke Emacs, where BACKEND is one of the backends specified below, or on a per-frame basis by changing the font-backend frame parameter.

Two of these backends, ftcr and ftcrhb are identical to their counterparts on the X Window System. There is also a Haiku-specific backend named haiku, that uses the App Server to draw fonts, but does not at present support display of color font and emoji.


Appendix H Emacs and Microsoft Windows/MS-DOS

This section describes peculiarities of using Emacs on Microsoft Windows. Some of these peculiarities are also relevant to Microsoft’s older MS-DOS operating system. However, Emacs features that are relevant only to MS-DOS are described in a separate section (see Emacs and MS-DOS).

MS-Windows is a non-free operating system; that means it denies its users the freedom that every computer user deserves. That is an injustice. For your freedom’s sake, we urge you to switch to a free operating system.

We support GNU Emacs on proprietary operating systems because we hope this taste of freedom will inspire users to escape from them.

The behavior of Emacs on MS-Windows is reasonably similar to what is documented in the rest of the manual, including support for long file names, multiple frames, scroll bars, mouse menus, and subprocesses. However, a few special considerations apply, and they are described here.


H.1 How to Start Emacs on MS-Windows

There are several ways of starting Emacs on MS-Windows:

  1. From the desktop shortcut icon: either double-click the left mouse button on the icon, or click once, then press RET. The desktop shortcut should specify as its “Target” (in the “Properties” of the shortcut) the full absolute file name of runemacs.exe, not of emacs.exe. This is because runemacs.exe hides the console window that would have been created if the target of the shortcut were emacs.exe (which is a console program, as far as Windows is concerned). If you use this method, Emacs starts in the directory specified by the shortcut. To control where that is, right-click on the shortcut, select “Properties”, and in the “Shortcut” tab modify the “Start in” field to your liking.
  2. From a task-bar shortcut icon, by clicking once the left mouse button. Windows versions since Vista allow you to create such shortcuts by pinning the icon of a running program that appears in the task bar. You can do that with Emacs, but afterwards you will have to change the properties of the pinned shortcut to run runemacs.exe, not of emacs.exe. You can also pin Emacs to the task bar by clicking the right mouse button on its icon in the Start menu, then selecting ‘Pin to taskbar’. Once again, be sure to specify runemacs.exe as the program to run. You can control where Emacs starts by setting the “Start in” field of the shortcut’s Properties.
  3. From the Command Prompt window, by typing emacs RET at the prompt. The Command Prompt window where you did that will not be available for invoking other commands until Emacs exits. In this case, Emacs will start in the current directory of the Windows shell.
  4. From the Command Prompt window, by typing runemacs RET at the prompt. The Command Prompt window where you did that will be immediately available for invoking other commands. In this case, Emacs will start in the current directory of the Windows shell.
  5. From the Windows Run dialog (normally reached by clicking the Start button). Typing runemacs RET into the dialog will start Emacs in the parent directory of the Windows equivalent of your user’s HOME directory, see HOME and Startup Directories on MS-Windows.
  6. Via emacsclient.exe or emacsclientw.exe, which allow you to invoke Emacs from other programs, and to reuse a running Emacs process for serving editing jobs required by other programs. See Using Emacs as a Server. The difference between emacsclient.exe and emacsclientw.exe is that the former is a console program, while the latter is a Windows GUI program. Both programs wait for Emacs to signal that the editing job is finished, before they exit and return control to the program that invoked them. Which one of them to use in each case depends on the expectations of the program that needs editing services. If that program is itself a console (text-mode) program, you should use emacsclient.exe, so that any of its messages and prompts appear in the same command window as those of the invoking program. By contrast, if the invoking program is a GUI program, you will be better off using emacsclientw.exe, because emacsclient.exe will pop up a command window if it is invoked from a GUI program. A notable situation where you would want emacsclientw.exe is when you right-click on a file in the Windows Explorer and select “Open With” from the pop-up menu. Use the ‘--alternate-editor=’ or ‘-a’ options if Emacs might not be running (or not running as a server) when emacsclient is invoked—that will always give you an editor. When invoked via emacsclient, Emacs will start in the current directory of the program that invoked emacsclient.

Note that, due to limitations of MS-Windows, Emacs cannot have both GUI and text-mode frames in the same session. It also cannot open text-mode frames on more than a single Command Prompt window, because each Windows program can have only one console at any given time. For these reasons, if you invoke emacsclient with the -c option, and the Emacs server runs in a text-mode session, Emacs will always create a new text-mode frame in the same Command Prompt window where it was started; a GUI frame will be created only if the server runs in a GUI session. Similarly, if you invoke emacsclient with the -t option, Emacs will create a GUI frame if the server runs in a GUI session, or a text-mode frame when the session runs in text mode in a Command Prompt window. See emacsclient Options.


H.2 Text Files and Binary Files

GNU Emacs uses newline characters to separate text lines. This is the convention used on GNU, Unix, and other POSIX-compliant systems.

By contrast, MS-DOS and MS-Windows normally use carriage return followed by linefeed, a two-character sequence, to separate text lines. (Linefeed is the same character as newline.) Therefore, convenient editing of typical files with Emacs requires conversion of these end-of-line (EOL) sequences. And that is what Emacs normally does: it converts carriage return followed by linefeed into newline when reading files, and converts newline into carriage return followed by linefeed when writing files. The same mechanism that handles conversion of international character codes does this conversion also (see Coding Systems).

One consequence of this special format-conversion of most files is that character positions as reported by Emacs (see Cursor Position Information) do not agree with the file size information known to the operating system.

In addition, if Emacs recognizes from a file’s contents that it uses newline rather than carriage return followed by linefeed as its line separator, it does not perform EOL conversion when reading or writing that file. Thus, you can read and edit files from GNU and Unix systems on MS-DOS with no special effort, and they will retain their Unix-style end-of-line convention after you edit them.

The mode line indicates whether end-of-line translation was used for the current buffer. If MS-DOS end-of-line translation is in use for the buffer, the MS-Windows build of Emacs displays a backslash ‘\’ after the coding system mnemonic near the beginning of the mode line (see The Mode Line). If no EOL translation was performed, the string ‘(Unix)’ is displayed instead of the backslash, to alert you that the file’s EOL format is not the usual carriage return followed by linefeed.

To visit a file and specify whether it uses DOS-style or Unix-style end-of-line, specify a coding system (see Specifying a Coding System for File Text). For example, C-x RET c unix RET C-x C-f foobar.txt visits the file foobar.txt without converting the EOLs; if some line ends with a carriage return followed by linefeed pair, Emacs will display ‘^M’ at the end of that line. Similarly, you can direct Emacs to save a buffer in a specified EOL format with the C-x RET f command. For example, to save a buffer with Unix EOL format, type C-x RET f unix RET C-x C-s. If you visit a file with DOS EOL conversion, then save it with Unix EOL format, that effectively converts the file to Unix EOL style, like the dos2unix program.

When you use NFS, Samba, or some other similar method to access file systems that reside on computers using GNU or Unix systems, Emacs should not perform end-of-line translation on any files in these file systems—not even when you create a new file. To request this, designate these file systems as untranslated file systems by calling the function w32-add-untranslated-filesystem. It takes one argument: the file system name, including a drive letter and optionally a directory. For example,

(w32-add-untranslated-filesystem "Z:")

designates drive Z as an untranslated file system, and

(w32-add-untranslated-filesystem "Z:\\foo")

designates directory \foo on drive Z as an untranslated file system.

Most often you would use w32-add-untranslated-filesystem in your .emacs or init.el init file, or in site-start.el so that all the users at your site get the benefit of it.

To countermand the effect of w32-add-untranslated-filesystem, use the function w32-remove-untranslated-filesystem. This function takes one argument, which should be a string just like the one that was used previously with w32-add-untranslated-filesystem.

Designating a file system as untranslated does not affect character set conversion, only end-of-line conversion. Essentially, it directs Emacs to default to creating new files with the Unix-style convention of using newline at the end of a line. See Coding Systems.


H.3 File Names on MS-Windows

MS-Windows and MS-DOS normally use a backslash, ‘\’, to separate name units within a file name, instead of the slash used on other systems. Emacs on MS-DOS/MS-Windows permits use of either slash or backslash, and also knows about drive letters in file names.

On MS-DOS/MS-Windows, file names are case-insensitive, so Emacs by default ignores letter-case in file names during completion. To this end, the default value of read-file-name-completion-ignore-case is non-nil on MS-DOS/MS-Windows. See Completion Options.

The variable w32-get-true-file-attributes controls whether Emacs should issue additional system calls to determine more accurately file attributes in primitives like file-attributes and directory-files-and-attributes. These additional calls are needed to report correct file ownership, link counts and file types for special files such as pipes. Without these system calls, file ownership will be attributed to the current user, link counts will be always reported as 1, and special files will be reported as regular files.

If the value of this variable is local (the default), Emacs will issue these additional system calls only for files on local fixed drives. Any other non-nil value means do this even for removable and remote volumes, where this could potentially slow down Dired and other related features. The value of nil means never issue those system calls. Non-nil values are more useful on NTFS volumes, which support hard links and file security, than on FAT, FAT32, and exFAT volumes.

Unlike Unix, MS-Windows file systems restrict the set of characters that can be used in a file name. The following characters are not allowed:

  • Shell redirection symbols ‘<’, ‘>’, and ‘|’.
  • Colon ‘:’ (except after the drive letter).
  • Forward slash ‘/’ and backslash ‘\’ (except as directory separators).
  • Wildcard characters ‘*’ and ‘?’.
  • Control characters whose codepoints are 1 through 31 decimal. In particular, newlines in file names are not allowed.
  • The null character, whose codepoint is zero (this limitation exists on Unix filesystems as well).

In addition, referencing any file whose name matches a DOS character device, such as NUL or LPT1 or PRN or CON, with or without any file-name extension, will always resolve to those character devices, in any directory. Therefore, only use such file names when you want to use the corresponding character device.


H.4 Emulation of ls on MS-Windows

Dired normally uses the external program ls to produce the directory listing displayed in Dired buffers (see Dired, the Directory Editor). However, MS-Windows and MS-DOS systems don’t come with such a program, although several ports of GNU ls are available. Therefore, Emacs on those systems emulates ls in Lisp, by using the ls-lisp.el package. While ls-lisp.el provides a reasonably full emulation of ls, there are some options and features peculiar to that emulation; they are described in this section.

The ls emulation supports many of the ls switches, but it doesn’t support all of them. Here’s the list of the switches it does support: -A, -a, -B, -C, -c, -G, -g, -h, -i, -n, -R, -r, -S, -s, -t, -U, -u, -v, and -X. The -F switch is partially supported (it appends the character that classifies the file, but does not prevent symlink following).

On MS-Windows and MS-DOS, ls-lisp.el is preloaded when Emacs is built, so the Lisp emulation of ls is always used on those platforms. If you have a ported ls, setting ls-lisp-use-insert-directory-program to a non-nil value will revert to using an external program named by the variable insert-directory-program.

The order in which ls-lisp.el sorts files depends on several customizable options described below.

The default sorting order follows locale-specific rules derived from your system locale. You can make the order locale-independent by customizing ls-lisp-use-string-collate to a nil value.

On GNU and Unix systems, when the locale’s encoding is UTF-8, the collation order follows the Unicode Collation Algorithm (UCA). To have a similar effect on MS-Windows, the variable ls-lisp-UCA-like-collation should have a non-nil value (this is the default). The resulting sorting order ignores punctuation, symbol characters, and whitespace characters, so .foobar, foobar and foo bar will appear together rather than far apart.

By default, ls-lisp.el uses a case-sensitive sort order for the directory listing it produces; this is so the listing looks the same as on other platforms. If you wish that the files be sorted in case-insensitive order, set the variable ls-lisp-ignore-case to a non-nil value.

By default, files and subdirectories are sorted together, to emulate the behavior of ls. However, native MS-Windows/MS-DOS file managers list the directories before the files; if you want that behavior, customize the option ls-lisp-dirs-first to a non-nil value.

The variable ls-lisp-verbosity controls the file attributes that ls-lisp.el displays. The value should be either nil or a list that contains one or more of the symbols links, uid, and gid. links means display the count of different file names that are associated with (a.k.a. links to) the file’s data; this is only useful on NTFS volumes. uid means display the numerical identifier of the user who owns the file. gid means display the numerical identifier of the file owner’s group. The default value is (links uid gid) i.e., all the 3 optional attributes are displayed. The value nil means not to display any of these attributes.

The variable ls-lisp-emulation controls the flavor of the ls emulation by setting the defaults for the 3 options described above: ls-lisp-ignore-case, ls-lisp-dirs-first, and ls-lisp-verbosity. The value of this option can be one of the following symbols:

GNU
nil

Emulate GNU systems; this is the default. This sets ls-lisp-ignore-case and ls-lisp-dirs-first to nil, and ls-lisp-verbosity to (links uid gid).

UNIX

Emulate Unix systems. Like GNU, but sets ls-lisp-verbosity to (links uid).

MacOS

Emulate macOS. Sets ls-lisp-ignore-case to t, and ls-lisp-dirs-first and ls-lisp-verbosity to nil.

MS-Windows

Emulate MS-Windows. Sets ls-lisp-ignore-case and ls-lisp-dirs-first to t, and ls-lisp-verbosity to nil on Windows 9X and to t on modern versions of Windows. Note that the default emulation is not MS-Windows, even on Windows, since many users of Emacs on those platforms prefer the GNU defaults.

Any other value of ls-lisp-emulation means the same as GNU. Customizing this option calls the function ls-lisp-set-options to update the 3 dependent options as needed. If you change the value of this variable without using customize after ls-lisp.el is loaded (note that it is preloaded on MS-Windows and MS-DOS), you can call that function manually for the same result.

The variable ls-lisp-support-shell-wildcards controls how file-name patterns are supported: if it is non-nil (the default), they are treated as shell-style wildcards; otherwise they are treated as Emacs regular expressions.

The variable ls-lisp-format-time-list defines how to format the date and time of files. The value of this variable is ignored, unless Emacs cannot determine the current locale. (However, if the value of ls-lisp-use-localized-time-format is non-nil, Emacs obeys ls-lisp-format-time-list even if the current locale is available; see below.)

The value of ls-lisp-format-time-list is a list of 2 strings. The first string is used if the file was modified within the current year, while the second string is used for older files. In each of these two strings you can use ‘%’-sequences to substitute parts of the time. For example:

("%b %e %H:%M" "%b %e  %Y")

Note that the strings substituted for these ‘%’-sequences depend on the current locale. See Time Parsing in The Emacs Lisp Reference Manual, for more about format time specs.

Normally, Emacs formats the file time stamps in either traditional or ISO-style time format. However, if the value of the variable ls-lisp-use-localized-time-format is non-nil, Emacs formats file time stamps according to what ls-lisp-format-time-list specifies. The ‘%’-sequences in ls-lisp-format-time-list produce locale-dependent month and day names, which might cause misalignment of columns in Dired display. The default value of ls-lisp-use-localized-time-format is nil.


H.5 HOME and Startup Directories on MS-Windows

The Windows equivalent of HOME is the user-specific application data directory. The actual location depends on the Windows version; typical values are C:\Documents and Settings\username\Application Data on Windows 2000 up to XP, C:\Users\username\AppData\Roaming on Windows Vista and later, and either C:\WINDOWS\Application Data or C:\WINDOWS\Profiles\username\Application Data on Windows 9X/ME. If this directory does not exist or cannot be accessed, Emacs falls back to C:\ as the default value of HOME.

You can override this default value of HOME by explicitly setting the environment variable HOME to point to any directory on your system. HOME can be set either from the command shell prompt or from ‘Properties’ dialog of ‘My Computer’. HOME can also be set in the system registry, see The MS-Windows System Registry.

For compatibility with older versions of Emacs28, if there is a file named .emacs in C:\, the root directory of drive C:, and HOME is set neither in the environment nor in the Registry, Emacs will treat C:\ as the default HOME location, and will not look in the application data directory, even if it exists. Note that only .emacs is looked for in C:\; the older name _emacs (see below) is not. This use of C:\.emacs to define HOME is deprecated; Emacs will display a warning about its use during startup.

Whatever the final place is, Emacs sets the internal value of the HOME environment variable to point to it, and it will use that location for other files and directories it normally looks for or creates in your home directory.

You can always find out what Emacs thinks is your home directory’s location by typing C-x d ~/ RET. This should present the list of files in the home directory, and show its full name on the first line. Likewise, to visit your init file, type C-x C-f ~/.emacs RET (assuming the file’s name is .emacs).

Your init file can have any name mentioned in The Emacs Initialization File.

Because MS-DOS does not allow file names with leading dots, and older Windows systems made it hard to create files with such names, the Windows port of Emacs supports an init file name _emacs, if such a file exists in the home directory and .emacs does not. This name is considered obsolete, so Emacs will display a warning if it is used.


H.6 Keyboard Usage on MS-Windows

This section describes the Windows-specific features related to keyboard input in Emacs.

Many key combinations (known as “keyboard shortcuts”) that have conventional uses in MS-Windows programs conflict with traditional Emacs key bindings. (These Emacs key bindings were established years before Microsoft was founded.) Examples of conflicts include C-c, C-x, C-z, and C-a. You can redefine some of them with meanings more like the MS-Windows meanings by enabling CUA Mode (see CUA Bindings). Another optional feature which will make Emacs behave like other Windows applications is Delete Selection mode (see Operating on the Region).

By default, the key labeled Alt is mapped as the Meta key. If you wish it to produce the Alt modifier instead, set the variable w32-alt-is-meta to a nil value.

MS-Windows reserves certain key combinations, such as Alt-TAB and a number of Windows key combinations, for its own use. These key combinations are intercepted by the system before Emacs can see them. Also, on Windows 10, all Windows key combinations are reserved by the system in such a way that they are never propagated to applications, even if the system does not currently define a hotkey on the specific combination. You can use the w32-register-hot-key function to allow a key sequence to be seen by Emacs instead of being grabbed by Windows. When registered as a hot key, the key combination is pulled out of the system’s input queue before it is handled by Windows, effectively overriding the special meaning of that key sequence for Windows. The override is only effective when Emacs is active; with other applications on the foreground the keys behave normally.

The argument to w32-register-hot-key must be a single key with a single modifier, in vector form that would be acceptable to define-key. The control and shift modifiers have no effect on the argument. The meta modifier is interpreted as the Alt key if w32-alt-is-meta is t (the default), and the super and hyper modifiers are interpreted according to the bindings of w32-lwindow-modifier and w32-rwindow-modifier. Additionally, a modifier with the trailing dash but with no key indicates that all Windows defined hotkeys for that modifier are to be overridden in the favor of Emacs.

For example, (w32-register-hot-key [M-tab]) lets you use M-TAB normally in Emacs; for instance, to complete the word or symbol at point at top level, or to complete the current search string against previously sought strings during incremental search. (w32-register-hot-key [s-]) with w32-lwindow-modifier bound to super disables all the Windows’ own Windows key based shortcuts.29

Note that w32-register-hot-key checks the w32-[lr]window-modifier values at the time of the function call. Thus, you can set w32-lwindow-modifier as super, then call (w32-register-hot-key [s-r]), and finally set w32-rwindow-modifier as super as well. The result is that the left Windows key together with R invokes whichever function you have bound for the combination in Emacs, and the right Windows key and R opens the Windows Run dialog.

The hotkey registrations always also include all the shift and control modifier combinations for the given hotkey; that is, registering s-a as a hotkey gives you S-s-a, C-s-a and C-S-s-a as well.

On Windows 98 and ME, the hotkey registration is more restricted. The desired hotkey must always be fully specified, and w32-phantom-key-code can be customized to achieve desired results.

The function w32-unregister-hot-key reverses the effect of w32-register-hot-key for its argument key sequence.

By default, the CapsLock key only affects normal character keys (it converts lower-case characters to their upper-case variants). However, if you set the variable w32-capslock-is-shiftlock to a non-nil value, the CapsLock key will affect non-character keys as well, as if you pressed the SHIFT key while typing the non-character key.

If the variable w32-enable-caps-lock is set to a nil value, the CapsLock key produces the symbol capslock instead of the shifted version of typed keys. The default value is t.

Similarly, if w32-enable-num-lock is nil, the NumLock key will produce the symbol kp-numlock. The default is t, which causes NumLock to work as expected: toggle the meaning of the keys on the numeric keypad.

The variable w32-apps-modifier controls the effect of the Apps key (usually located between the right Alt and the right Ctrl keys). Its value can be one of the symbols hyper, super, meta, alt, control, or shift for the respective modifier, or nil to appear as the key apps. The default is nil.

The variable w32-lwindow-modifier determines the effect of the left Windows key (usually labeled with start and the Windows logo). If its value is nil (the default), the key will produce the symbol lwindow. Setting it to one of the symbols hyper, super, meta, alt, control, or shift will produce the respective modifier. A similar variable w32-rwindow-modifier controls the effect of the right Windows key, and w32-scroll-lock-modifier does the same for the ScrLock key. If these variables are set to nil, the right Windows key produces the symbol rwindow and ScrLock produces the symbol scroll. If you want ScrLock to produce the same effect as in other applications, i.e. toggle the Scroll Lock LED indication on the keyboard, set w32-scroll-lock-modifier to t or any non-nil value other than the above modifier symbols.

Emacs compiled as a native Windows application normally turns off the Windows feature that tapping the Alt key invokes the Windows menu. The reason is that the Alt serves as Meta in Emacs. When using Emacs, users often press the Meta key temporarily and then change their minds; if this has the effect of bringing up the Windows menu, it alters the meaning of subsequent commands. Many users find this frustrating.

You can re-enable Windows’s default handling of tapping the Alt key by setting w32-pass-alt-to-system to a non-nil value.

The variables w32-pass-lwindow-to-system and w32-pass-rwindow-to-system determine whether the respective keys are passed to Windows or swallowed by Emacs. If the value is nil, the respective key is silently swallowed by Emacs, otherwise it is passed to Windows. The default is t for both of these variables. Passing each of these keys to Windows produces its normal effect: for example, Lwindow opens the Start menu, etc.

The variable w32-recognize-altgr controls whether the AltGr key (if it exists on your keyboard), or its equivalent, the combination of the right Alt and left Ctrl keys pressed together, is recognized as the AltGr key. The default is t, which means these keys produce AltGr; setting it to nil causes AltGr or the equivalent key combination to be interpreted as the combination of Ctrl and Meta modifiers.

Some versions of MS-Windows, typically East Asian localized Windows, enable the Input Method Manager (IMM) that allows applications to communicate with the Input Method Editor (IME), the native Windows input method service. Emacs uses the IME when available to allow users to input East Asian non-ASCII characters, similarly to Emacs’s built-in input methods (see Input Methods). However, in some situations the IME can get in the way if it interprets simple ASCII keys you input as part of a key sequence that designates a non-ASCII character. The IME can be temporarily turned off and then on again by using the w32-set-ime-open-status function.


H.7 Mouse Usage on MS-Windows

This section describes the Windows-specific variables related to the mouse.

The variable w32-mouse-button-tolerance specifies the time interval, in milliseconds, for faking middle mouse button press on 2-button mice. If both mouse buttons are depressed within this time interval, Emacs generates a middle mouse button click event instead of a double click on one of the buttons.

If the variable w32-pass-extra-mouse-buttons-to-system is non-nil, Emacs passes the fourth and fifth mouse buttons to Windows.

The variable w32-swap-mouse-buttons controls which of the 3 mouse buttons generates the mouse-2 events. When it is nil (the default), the middle button generates mouse-2 and the right button generates mouse-3 events. If this variable is non-nil, the roles of these two buttons are reversed.


H.8 Subprocesses on Windows 9X/ME and Windows NT/2K/XP/Vista/7/8/10

Emacs compiled as a native Windows application (as opposed to the DOS version) includes full support for asynchronous subprocesses. In the Windows version, synchronous and asynchronous subprocesses work fine on all versions of MS-Windows, as long as you run only 32-bit or 64-bit Windows applications. However, when you run a DOS application in a subprocess, you may encounter problems or be unable to run the application at all; and if you run two DOS applications at the same time in two subprocesses, you may have to reboot your system.

Since the standard command interpreter (and most command line utilities) on Windows 9X are DOS applications, these problems are significant when using that system. But there’s nothing we can do about them; only Microsoft can fix them.

If you run just one DOS application subprocess, the subprocess should work as expected as long as it is “well-behaved” and does not perform direct screen access or other unusual actions. If you have a CPU monitor application, your machine will appear to be 100% busy even when the DOS application is idle, but this is only an artifact of the way CPU monitors measure processor load.

You must terminate the DOS application before you start any other DOS application in a different subprocess. Emacs is unable to interrupt or terminate a DOS subprocess. The only way you can terminate such a subprocess is by giving it a command that tells its program to exit.

If you attempt to run two DOS applications at the same time in separate subprocesses, the second one that is started will be suspended until the first one finishes, even if either or both of them are asynchronous.

If you can go to the first subprocess, and tell it to exit, the second subprocess should continue normally. However, if the second subprocess is synchronous, Emacs itself will be hung until the first subprocess finishes. If it will not finish without user input, then you have no choice but to reboot if you are running on Windows 9X. If you are running on Windows NT and later, you can use a process viewer application to kill the appropriate instance of NTVDM instead (this will terminate both DOS subprocesses).

If you have to reboot Windows 9X in this situation, do not use the Shutdown command on the Start menu; that usually hangs the system. Instead, type Ctrl-Alt-DEL and then choose Shutdown. That usually works, although it may take a few minutes to do its job.

The variable w32-quote-process-args controls how Emacs quotes the process arguments. Non-nil means quote with the " character. If the value is a character, Emacs uses that character to escape any quote characters that appear; otherwise it chooses a suitable escape character based on the type of the program.

The variable w32-pipe-buffer-size controls the size of the buffer Emacs requests from the system when it creates pipes for communications with subprocesses. The default value is zero, which lets the OS choose the size. Any valid positive value will request a buffer of that size in bytes. This can be used to tailor communications with subprocesses to programs that exhibit unusual behavior with respect to buffering pipe I/O.

If you need to invoke MS-DOS programs as Emacs subprocesses, you may see low rate of reading data from such programs. Setting the variable w32-pipe-read-delay to a non-zero value may improve throughput in these cases; we suggest the value of 50 for such situations. The default is zero.

The function w32-shell-execute can be useful for writing customized commands that run MS-Windows applications registered to handle a certain standard Windows operation for a specific type of document or file. This function is a wrapper around the Windows ShellExecute API. See the MS-Windows API documentation for more details.


H.9 Printing and MS-Windows

Printing commands, such as lpr-buffer (see Printing Hard Copies) and ps-print-buffer (see PostScript Hardcopy) work in MS-DOS and MS-Windows by sending the output to one of the printer ports, if a POSIX-style lpr program is unavailable. The same Emacs variables control printing on all systems, but in some cases they have different default values on MS-DOS and MS-Windows.

Emacs on MS Windows attempts to determine your default printer automatically (using the function default-printer-name). But in some rare cases this can fail, or you may wish to use a different printer from within Emacs. The rest of this section explains how to tell Emacs which printer to use.

If you want to use your local printer, then set the Lisp variable lpr-command to "" (its default value on Windows) and printer-name to the name of the printer port—for example, "PRN", the usual local printer port, or "LPT2", or "COM1" for a serial printer. You can also set printer-name to a file name, in which case “printed” output is actually appended to that file. If you set printer-name to "NUL", printed output is silently discarded (sent to the system null device).

You can also use a printer shared by another machine by setting printer-name to the UNC share name for that printer—for example, "//joes_pc/hp4si". (It doesn’t matter whether you use forward slashes or backslashes here.) To find out the names of shared printers, run the command ‘net view’ from the command prompt to obtain a list of servers, and ‘net view server-name’ to see the names of printers (and directories) shared by that server. Alternatively, click the ‘Network Neighborhood’ icon on your desktop, and look for machines that share their printers via the network.

If the printer doesn’t appear in the output of ‘net view’, or if setting printer-name to the UNC share name doesn’t produce a hardcopy on that printer, you can use the ‘net use’ command to connect a local print port such as "LPT2" to the networked printer. For example, typing net use LPT2: \\joes_pc\hp4si30 causes Windows to capture the LPT2 port and redirect the printed material to the printer connected to the machine joes_pc. After this command, setting printer-name to "LPT2" should produce the hardcopy on the networked printer.

With some varieties of Windows network software, you can instruct Windows to capture a specific printer port such as "LPT2", and redirect it to a networked printer via the Control Panel->Printers applet instead of ‘net use’.

If you set printer-name to a file name, it’s best to use an absolute file name. Emacs changes the working directory according to the default directory of the current buffer, so if the file name in printer-name is relative, you will end up with several such files, each one in the directory of the buffer from which the printing was done.

If the value of printer-name is correct, but printing does not produce the hardcopy on your printer, it is possible that your printer does not support printing plain text (some cheap printers omit this functionality). In that case, try the PostScript print commands, described below.

The commands print-buffer and print-region call the pr program, or use special switches to the lpr program, to produce headers on each printed page. MS-DOS and MS-Windows don’t normally have these programs, so by default, the variable lpr-headers-switches is set so that the requests to print page headers are silently ignored. Thus, print-buffer and print-region produce the same output as lpr-buffer and lpr-region, respectively. If you do have a suitable pr program (for example, from GNU Coreutils), set lpr-headers-switches to nil; Emacs will then call pr to produce the page headers, and print the resulting output as specified by printer-name.

Finally, if you do have an lpr work-alike, you can set the variable lpr-command to "lpr". Then Emacs will use lpr for printing, as on other systems. (If the name of the program isn’t lpr, set lpr-command to the appropriate value.) The variable lpr-switches has its standard meaning when lpr-command is not "". If the variable printer-name has a string value, it is used as the value for the -P option to lpr, as on Unix.

A parallel set of variables, ps-lpr-command, ps-lpr-switches, and ps-printer-name (see Variables for PostScript Hardcopy), defines how PostScript files should be printed. These variables are used in the same way as the corresponding variables described above for non-PostScript printing. Thus, the value of ps-printer-name is used as the name of the device (or file) to which PostScript output is sent, just as printer-name is used for non-PostScript printing. (There are two distinct sets of variables in case you have two printers attached to two different ports, and only one of them is a PostScript printer.)

The default value of the variable ps-lpr-command is "", which causes PostScript output to be sent to the printer port specified by ps-printer-name; but ps-lpr-command can also be set to the name of a program which will accept PostScript files. Thus, if you have a non-PostScript printer, you can set this variable to the name of a PostScript interpreter program (such as Ghostscript). Any switches that need to be passed to the interpreter program are specified using ps-lpr-switches. (If the value of ps-printer-name is a string, it will be added to the list of switches as the value for the -P option. This is probably only useful if you are using lpr, so when using an interpreter typically you would set ps-printer-name to something other than a string so it is ignored.)

For example, to use Ghostscript for printing on the system’s default printer, put this in your .emacs file:

(setq ps-printer-name t)
(setq ps-lpr-command "D:/gs6.01/bin/gswin32c.exe")
(setq ps-lpr-switches '("-q" "-dNOPAUSE" "-dBATCH"
                        "-sDEVICE=mswinpr2"
                        "-sPAPERSIZE=a4"))

(This assumes that Ghostscript is installed in the D:/gs6.01 directory.)


H.10 Specifying Fonts on MS-Windows

Fonts are specified by their name, size and optional properties. The format for specifying fonts comes from the fontconfig library used in modern Free desktops:

  [Family[-PointSize]][:Option1=Value1[:Option2=Value2[...]]]

The old XLFD based format is also supported for backwards compatibility.

Emacs on MS-Windows supports a number of font backends. Currently, the gdi, uniscribe, and harfbuzz backends are available. The gdi font backend is available on all versions of Windows, and supports all fonts that are natively supported by Windows. The uniscribe font backend is available on Windows 2000 and later, and supports TrueType and OpenType fonts. The harfbuzz font backend is available if Emacs was built with HarfBuzz support, and if the HarfBuzz DLL is installed on your system; like uniscribe, this backend supports only TrueType and OpenType fonts. Some languages requiring complex layout can only be properly supported by the Uniscribe or HarfBuzz backends. By default, two backends are enabled for each frame: gdi and either harfbuzz or uniscribe, depending on which one is available (if both are available, only harfbuzz is enabled by default). The harfbuzz and uniscribe backends take priority over gdi when Emacs looks for a suitable font. To override that and use the GDI backend even if Uniscribe is available, invoke Emacs with the -xrm Emacs.fontBackend:gdi command-line argument, or add a Emacs.fontBackend resource with the value gdi in the Registry under either the ‘HKEY_CURRENT_USER\SOFTWARE\GNU\Emacs’ or the ‘HKEY_LOCAL_MACHINE\SOFTWARE\GNU\Emacs’ key (see X Resources). Similarly, to use the Uniscribe backend even if HarfBuzz is available, use -xrm Emacs.fontBackend:uniscribe on the command line that invokes Emacs. You can also request all the 3 backends via the font-backend frame parameter, but be warned that in that case font searches for characters for which no fonts are available on the system will take longer.

Alternatively, you could specify a font backend for a frame via the font-backend frame parameter, using modify-frame-parameters (see Parameter Access in The Emacs Lisp Reference Manual). You can also request specific font backend(s) for all your frames via default-frame-alist and initial-frame-alist (see Frame Parameters). Note that the value of the font-backend parameter should be a list of symbols, as in (uniscribe) or (harfbuzz uniscribe gdi).

Optional font properties supported on MS-Windows are:

weight

Specifies the weight of the font. Special values light, medium, demibold, bold, and black can be specified without weight= (e.g., Courier New-12:bold). Otherwise, the weight should be a numeric value between 100 and 900, or one of the named weights in font-weight-table. If unspecified, a regular font is assumed.

slant

Specifies whether the font is italic. Special values roman, italic and oblique can be specified without slant= (e.g., Courier New-12:italic). Otherwise, the slant should be a numeric value, or one of the named slants in font-slant-table. On Windows, any slant above 150 is treated as italics, and anything below as roman.

family

Specifies the font family, but normally this will be specified at the start of the font name.

pixelsize

Specifies the font size in pixels. This can be used instead of the point size specified after the family name.

adstyle

Specifies additional style information for the font. On MS-Windows, the values mono, sans, serif, script and decorative are recognized. These are most useful as a fallback with the font family left unspecified.

registry

Specifies the character set registry that the font is expected to cover. Most TrueType and OpenType fonts will be Unicode fonts that cover several national character sets, but you can narrow down the selection of fonts to those that support a particular character set by using a specific registry from w32-charset-info-alist here.

spacing

Specifies how the font is spaced. The p spacing specifies a proportional font, and m or c specify a monospaced font.

foundry

Not used on Windows, but for informational purposes and to prevent problems with code that expects it to be set, is set internally to raster for bitmapped fonts, outline for scalable fonts, or unknown if the type cannot be determined as one of those.

script

Specifies a Unicode subrange the font should support.

All the scripts known to Emacs (which generally means all the scripts defined by the latest Unicode Standard) are recognized on MS-Windows. However, GDI fonts support only a subset of the known scripts: greek, hangul, kana, kanbun, bopomofo, tibetan, yi, mongolian, hebrew, arabic, and thai.

antialias

Specifies the antialiasing method. The value none means no antialiasing, standard means use standard antialiasing, subpixel means use subpixel antialiasing (known as Cleartype on Windows), and natural means use subpixel antialiasing with adjusted spacing between letters. If unspecified, the font will use the system default antialiasing.

The method used by Emacs on MS-Windows to look for fonts suitable for displaying a given non-ASCII character might fail for some rare scripts, specifically those added by Unicode relatively recently, even if you have fonts installed on your system that support those scripts. That is because these scripts have no Unicode Subrange Bits (USBs) defined for them in the information used by Emacs on MS-Windows to look for fonts. You can use the w32-find-non-USB-fonts function to overcome these problems. It needs to be run once at the beginning of the Emacs session, and again if you install new fonts. You can add the following line to your init file to have this function run every time you start Emacs:

(w32-find-non-USB-fonts)

Alternatively, you can run this function manually via M-: (see Evaluating Emacs Lisp Expressions) at any time. On a system that has many fonts installed, running w32-find-non-USB-fonts might take a couple of seconds; if you consider that to be too long to be run during startup, and if you install new fonts only rarely, run this function once via M-:, and then assign the value it returns, if non-nil, to the variable w32-non-USB-fonts in your init file. (If the function returns nil, you have no fonts installed that can display characters from the scripts which need this facility.)

The variable w32-use-w32-font-dialog controls the way fonts can be selected via S-mouse-1 (mouse-appearance-menu). If the value is t, the default, Emacs uses the standard Windows font selection dialog. If the value is nil, Emacs instead pops a menu of a fixed set of fonts. The fonts to appear in the menu are determined by w32-fixed-font-alist.


H.11 Miscellaneous Windows-specific features

This section describes Windows-specific features that don’t fit anywhere else.

The variable w32-use-visible-system-caret is a flag that determines whether to make the system caret visible. The default when no screen reader software is in use is nil, which means Emacs draws its own cursor to indicate the position of point. A non-nil value means Emacs will indicate point location with the system caret; this facilitates use of screen reader software, and is the default when such software is detected when running Emacs. When this variable is non-nil, other variables affecting the cursor display have no effect.

The variable w32-grab-focus-on-raise, if set to a non-nil value causes a frame to grab focus when it is raised. The default is t, which fits well with the Windows default click-to-focus policy.

On Windows 10 (version 1809 and higher) and Windows 11, Emacs title bars and scroll bars will follow the system’s Light or Dark mode, similar to other programs such as Explorer and Command Prompt. To change the color mode, select Personalization from Windows Settings, then Colors->Choose your color (or Choose your default app mode); then restart Emacs.


H.12 Emacs and MS-DOS

This section briefly describes the peculiarities of using Emacs on MS-DOS. Information about peculiarities common to MS-DOS and Microsoft’s current operating systems Windows is in Emacs and Microsoft Windows/MS-DOS.

If you build Emacs for MS-DOS, the binary will also run on Windows 3.X, Windows NT, Windows 9X/ME, or Windows 2000/XP as a DOS application; all of this chapter applies for all of those systems, if you use an Emacs that was built for MS-DOS.

See Text Files and Binary Files, for information about Emacs’s special handling of text files under MS-DOS (and Windows).


H.12.1 Keyboard Usage on MS-DOS

The key that is called DEL in Emacs (because that’s how it is designated on most workstations) is known as BS (backspace) on a PC. That is why the PC-specific terminal initialization remaps the BS key to act as DEL; the Delete key is remapped to act as C-d for the same reasons.

Emacs built for MS-DOS recognizes C-Break as a quit character, just like C-g. This is because Emacs cannot detect that you have typed C-g until it is ready for more input. As a consequence, you cannot use C-g to stop a running command (see Quitting and Aborting). By contrast, C-Break is detected as soon as you type it (as C-g is on other systems), so it can be used to stop a running command and for emergency escape (see Emergency Escape).

The PC keyboard maps use the left Alt key as the Meta key. You have two choices for emulating the SUPER and Hyper keys: choose either the right Ctrl key or the right Alt key by setting the variables dos-hyper-key and dos-super-key to 1 or 2 respectively. If neither dos-super-key nor dos-hyper-key is 1, then by default the right Alt key is also mapped to the Meta key. However, if the MS-DOS international keyboard support program KEYB.COM is installed, Emacs will not map the right Alt to Meta, since it is used for accessing characters like ~ and @ on non-US keyboard layouts; in this case, you may only use the left Alt as Meta key.

The variable dos-keypad-mode is a flag variable that controls what key codes are returned by keys in the numeric keypad. You can also define the keypad ENTER key to act like C-j, by putting the following line into your _emacs file:

;; Make the ENTER key from the numeric keypad act as C-j.
(keymap-set function-key-map "<kp-enter>" "C-j")

H.12.2 Mouse Usage on MS-DOS

Emacs on MS-DOS supports a mouse (on the default terminal only). The mouse commands work as documented, including those that use menus and the menu bar (see The Menu Bar). Scroll bars don’t work in MS-DOS Emacs. PC mice usually have only two buttons; these act as mouse-1 and mouse-2, but if you press both of them together, that has the effect of mouse-3. If the mouse does have 3 buttons, Emacs detects that at startup, and all the 3 buttons function normally, as on X.

Help strings for menu-bar and pop-up menus are displayed in the echo area when the mouse pointer moves across the menu items. Highlighting of mouse-sensitive text (see Following References with the Mouse) is also supported.

Some versions of mouse drivers don’t report the number of mouse buttons correctly. For example, mice with a wheel report that they have 3 buttons, but only 2 of them are passed to Emacs; the clicks on the wheel, which serves as the middle button, are not passed. In these cases, you can use the M-x msdos-set-mouse-buttons command to tell Emacs how many mouse buttons to expect. You could make such a setting permanent by adding this fragment to your _emacs init file:

;; Treat the mouse like a 2-button mouse.
(msdos-set-mouse-buttons 2)

Emacs built for MS-DOS supports clipboard operations when it runs on Windows. Commands that put text on the kill ring, or yank text from the ring, check the Windows clipboard first, just as Emacs does on the X Window System (see Mouse Commands for Editing). Only the primary selection and the cut buffer are supported by MS-DOS Emacs on Windows; the secondary selection always appears as empty.

Due to the way clipboard access is implemented by Windows, the length of text you can put into the clipboard is limited by the amount of free DOS memory that is available to Emacs. Usually, up to 620KB of text can be put into the clipboard, but this limit depends on the system configuration and is lower if you run Emacs as a subprocess of another program. If the killed text does not fit, Emacs outputs a message saying so, and does not put the text into the clipboard.

Null characters also cannot be put into the Windows clipboard. If the killed text includes null characters, Emacs does not put such text into the clipboard, and displays in the echo area a message to that effect.

The variable dos-display-scancodes, when non-nil, directs Emacs to display the ASCII value and the keyboard scan code of each keystroke; this feature serves as a complement to the view-lossage command, for debugging.


H.12.3 Display on MS-DOS

Display on MS-DOS cannot use font variants, like bold or italic, but it does support multiple faces, each of which can specify a foreground and a background color. Therefore, you can get the full functionality of Emacs packages that use fonts (such as font-lock, Enriched Text mode, and others) by defining the relevant faces to use different colors. Use the list-colors-display command (see Colors for Faces) and the list-faces-display command (see Text Faces) to see what colors and faces are available and what they look like.

See International Support on MS-DOS, later in this chapter, for information on how Emacs displays glyphs and characters that aren’t supported by the native font built into the DOS display.

When Emacs starts, it changes the cursor shape to a solid box. This is for compatibility with other systems, where the box cursor is the default in Emacs. This default shape can be changed to a bar by specifying the cursor-type parameter in the variable default-frame-alist (see Creating Frames). The MS-DOS terminal doesn’t support a vertical-bar cursor, so the bar cursor is horizontal, and the width parameter, if specified by the frame parameters, actually determines its height. For this reason, the bar and hbar cursor types produce the same effect on MS-DOS. As an extension, the bar cursor specification can include the starting scan line of the cursor as well as its width, like this:

 '(cursor-type bar width . start)

In addition, if the width parameter is negative, the cursor bar begins at the top of the character cell.

The MS-DOS terminal can only display a single frame at a time. The Emacs frame facilities work on MS-DOS much as they do on text terminals (see Frames and Graphical Displays). When you run Emacs from a DOS window on MS-Windows, you can make the visible frame smaller than the full screen, but Emacs still cannot display more than a single frame at a time.

The dos-mode4350 command switches the display to 43 or 50 lines, depending on your hardware; the dos-mode25 command switches to the default 80x25 screen size.

By default, Emacs only knows how to set screen sizes of 80 columns by 25, 28, 35, 40, 43 or 50 rows. However, if your video adapter has special video modes that will switch the display to other sizes, you can have Emacs support those too. When you ask Emacs to switch the frame to n rows by m columns dimensions, it checks if there is a variable called screen-dimensions-nxm, and if so, uses its value (which must be an integer) as the video mode to switch to. (Emacs switches to that video mode by calling the BIOS Set Video Mode function with the value of screen-dimensions-nxm in the AL register.) For example, suppose your adapter will switch to 66x80 dimensions when put into video mode 85. Then you can make Emacs support this screen size by putting the following into your _emacs file:

(setq screen-dimensions-66x80 85)

Since Emacs on MS-DOS can only set the frame size to specific supported dimensions, it cannot honor every possible frame resizing request. When an unsupported size is requested, Emacs chooses the next larger supported size beyond the specified size. For example, if you ask for 36x80 frame, you will get 40x80 instead.

The variables screen-dimensions-nxm are used only when they exactly match the specified size; the search for the next larger supported size ignores them. In the above example, even if your VGA supports 38x80 dimensions and you define a variable screen-dimensions-38x80 with a suitable value, you will still get 40x80 screen when you ask for a 36x80 frame. If you want to get the 38x80 size in this case, you can do it by setting the variable named screen-dimensions-36x80 with the same video mode value as screen-dimensions-38x80.

Changing frame dimensions on MS-DOS has the effect of changing all the other frames to the new dimensions.


H.12.4 File Names on MS-DOS

On MS-DOS, file names are case-insensitive and limited to eight characters, plus optionally a period and three more characters. Emacs knows enough about these limitations to handle file names that were meant for other operating systems. For instance, leading dots ‘.’ in file names are invalid in MS-DOS, so Emacs transparently converts them to underscores ‘_’; thus your default init file (see The Emacs Initialization File) is called _emacs on MS-DOS. Excess characters before or after the period are generally ignored by MS-DOS itself; thus, if you visit the file LongFileName.EvenLongerExtension, you will silently get longfile.eve, but Emacs will still display the long file name on the mode line. Other than that, it’s up to you to specify file names which are valid under MS-DOS; the transparent conversion as described above only works on file names built into Emacs.

The above restrictions on the file names on MS-DOS make it almost impossible to construct the name of a backup file (see Single or Numbered Backups) without losing some of the original file name characters. For example, the name of a backup file for docs.txt is docs.tx~ even if single backup is used.

If you run Emacs as a DOS application under Windows 9X, Windows ME, or Windows 2000/XP, you can turn on support for long file names. If you do that, Emacs doesn’t truncate file names or convert them to lower case; instead, it uses the file names that you specify, verbatim. To enable long file name support, set the environment variable LFN to ‘y’ before starting Emacs. Unfortunately, Windows NT doesn’t allow DOS programs to access long file names, so Emacs built for MS-DOS will only see their short 8+3 aliases.

MS-DOS has no notion of home directory, so Emacs on MS-DOS pretends that the directory where it is installed is the value of the HOME environment variable. That is, if your Emacs binary, emacs.exe, is in the directory c:/utils/emacs/bin, then Emacs acts as if HOME were set to ‘c:/utils/emacs’. In particular, that is where Emacs looks for the init file _emacs. With this in mind, you can use ‘~’ in file names as an alias for the home directory, as you would on GNU or Unix. You can also set HOME variable in the environment before starting Emacs; its value will then override the above default behavior.

Emacs on MS-DOS handles the name /dev specially, because of a feature in the emulator libraries of DJGPP that pretends I/O devices have names in that directory. We recommend that you avoid using an actual directory named /dev on any disk.


H.12.5 Printing and MS-DOS

Printing commands, such as lpr-buffer (see Printing Hard Copies) and ps-print-buffer (see PostScript Hardcopy) can work on MS-DOS by sending the output to one of the printer ports, if a POSIX-style lpr program is unavailable. The same Emacs variables control printing on all systems, but in some cases they have different default values on MS-DOS.

See Printing and MS-Windows, for details about setting up printing to a networked printer.

Some printers expect DOS codepage encoding of non-ASCII text, even though they are connected to a Windows machine that uses a different encoding for the same locale. For example, in the Latin-1 locale, DOS uses codepage 850 whereas Windows uses codepage 1252. See International Support on MS-DOS. When you print to such printers from Windows, you can use the C-x RET c (universal-coding-system-argument) command before M-x lpr-buffer; Emacs will then convert the text to the DOS codepage that you specify. For example, C-x RET c cp850-dos RET M-x lpr-region RET will print the region while converting it to the codepage 850 encoding.

For backwards compatibility, the value of dos-printer (dos-ps-printer), if it has a value, overrides the value of printer-name (ps-printer-name), on MS-DOS.


H.12.6 International Support on MS-DOS

Emacs on MS-DOS supports the same international character sets as it does on GNU, Unix and other platforms (see International Character Set Support), including coding systems for converting between the different character sets. However, due to incompatibilities between MS-DOS/MS-Windows and other systems, there are several DOS-specific aspects of this support that you should be aware of. This section describes these aspects.

The description below is largely specific to the MS-DOS port of Emacs, especially where it talks about practical implications for Emacs users.

M-x dos-codepage-setup

Set up Emacs display and coding systems as appropriate for the current DOS codepage.

MS-DOS is designed to support one character set of 256 characters at any given time, but gives you a variety of character sets to choose from. The alternative character sets are known as DOS codepages. Each codepage includes all 128 ASCII characters, but the other 128 characters (codes 128 through 255) vary from one codepage to another. Each DOS codepage is identified by a 3-digit number, such as 850, 862, etc.

In contrast to X, which lets you use several fonts at the same time, MS-DOS normally doesn’t allow use of several codepages in a single session. MS-DOS was designed to load a single codepage at system startup, and require you to reboot in order to change it31. Much the same limitation applies when you run DOS executables on other systems such as MS-Windows.

For multibyte operation on MS-DOS, Emacs needs to know which characters the chosen DOS codepage can display. So it queries the system shortly after startup to get the chosen codepage number, and stores the number in the variable dos-codepage. Some systems return the default value 437 for the current codepage, even though the actual codepage is different. (This typically happens when you use the codepage built into the display hardware.) You can specify a different codepage for Emacs to use by setting the variable dos-codepage in your init file.

Multibyte Emacs supports only certain DOS codepages: those which can display Far-Eastern scripts, like the Japanese codepage 932, and those that encode a single ISO 8859 character set.

The Far-Eastern codepages can directly display one of the MULE character sets for these countries, so Emacs simply sets up to use the appropriate terminal coding system that is supported by the codepage. The special features described in the rest of this section mostly pertain to codepages that encode ISO 8859 character sets.

For the codepages that correspond to one of the ISO character sets, Emacs knows the character set based on the codepage number. Emacs automatically creates a coding system to support reading and writing files that use the current codepage, and uses this coding system by default. The name of this coding system is cpnnn, where nnn is the codepage number.32

All the cpnnn coding systems use the letter ‘D’ (for “DOS”) as their mode-line mnemonic. Since both the terminal coding system and the default coding system for file I/O are set to the proper cpnnn coding system at startup, it is normal for the mode line on MS-DOS to begin with ‘-DD\-’. See The Mode Line. Far-Eastern DOS terminals do not use the cpnnn coding systems, and thus their initial mode line looks like the Emacs default.

Since the codepage number also indicates which script you are using, Emacs automatically runs set-language-environment to select the language environment for that script (see Language Environments).

If a buffer contains a character belonging to some other ISO 8859 character set, not the one that the chosen DOS codepage supports, Emacs displays it using a sequence of ASCII characters. For example, if the current codepage doesn’t have a glyph for the letter ‘ò’ (small ‘o’ with a grave accent), it is displayed as ‘{`o}’, where the braces serve as a visual indication that this is a single character. (This may look awkward for some non-Latin characters, such as those from Greek or Hebrew alphabets, but it is still readable by a person who knows the language.) Even though the character may occupy several columns on the screen, it is really still just a single character, and all Emacs commands treat it as one.

MS-Windows provides its own codepages, which are different from the DOS codepages for the same locale. For example, DOS codepage 850 supports the same character set as Windows codepage 1252; DOS codepage 855 supports the same character set as Windows codepage 1251, etc. The MS-Windows version of Emacs uses the current codepage for display when invoked with the ‘-nw’ option.


H.12.7 Subprocesses on MS-DOS

Because MS-DOS is a single-process “operating system”, asynchronous subprocesses are not available. In particular, Shell mode and its variants do not work. Most Emacs features that use asynchronous subprocesses also don’t work on MS-DOS, including Shell mode and GUD. When in doubt, try and see; commands that don’t work output an error message saying that asynchronous processes aren’t supported.

Compilation under Emacs with M-x compile, searching files with M-x grep and displaying differences between files with M-x diff do work, by running the inferior processes synchronously. This means you cannot do any more editing until the inferior process finishes.

Spell checking also works, by means of special support for synchronous invocation of the ispell program. This is slower than the asynchronous invocation on other platforms.

Instead of the Shell mode, which doesn’t work on MS-DOS, you can use the M-x eshell command. This invokes the Eshell package that implements a POSIX-like shell entirely in Emacs Lisp.

By contrast, Emacs compiled as a native Windows application does support asynchronous subprocesses. See Subprocesses on Windows 9X/ME and Windows NT/2K/XP/Vista/7/8/10.

Printing commands, such as lpr-buffer (see Printing Hard Copies) and ps-print-buffer (see PostScript Hardcopy), work in MS-DOS by sending the output to one of the printer ports. See Printing and MS-DOS.

When you run a subprocess synchronously on MS-DOS, make sure the program terminates and does not try to read keyboard input. If the program does not terminate on its own, you will be unable to terminate it, because MS-DOS provides no general way to terminate a process. Pressing C-c or C-Break might sometimes help in these cases.

Accessing files on other machines is not supported on MS-DOS. Other network-oriented commands such as sending mail, Web browsing, remote login, etc., don’t work either, unless network access is built into MS-DOS with some network redirector.

Dired on MS-DOS uses the ls-lisp package (see Emulation of ls on MS-Windows). Therefore, Dired on MS-DOS supports only some of the possible options you can mention in the dired-listing-switches variable. The options that work are ‘-A’, ‘-a’, ‘-c’, ‘-i’, ‘-r’, ‘-S’, ‘-s’, ‘-t’, and ‘-u’.


The GNU Manifesto

The GNU Manifesto which appears below was written by Richard Stallman at the beginning of the GNU project, to ask for participation and support. For the first few years, it was updated in minor ways to account for developments, but now it seems best to leave it unchanged as most people have seen it.

Since that time, we have learned about certain common misunderstandings that different wording could help avoid. Footnotes added in 1993 help clarify these points.

For up-to-date information about available GNU software, please see our web site, https://www.gnu.org. For software tasks and other ways to contribute, see https://www.gnu.org/help.

What’s GNU? Gnu’s Not Unix!

GNU, which stands for Gnu’s Not Unix, is the name for the complete Unix-compatible software system which I am writing so that I can give it away free to everyone who can use it.33 Several other volunteers are helping me. Contributions of time, money, programs and equipment are greatly needed.

So far we have an Emacs text editor with Lisp for writing editor commands, a source level debugger, a yacc-compatible parser generator, a linker, and around 35 utilities. A shell (command interpreter) is nearly completed. A new portable optimizing C compiler has compiled itself and may be released this year. An initial kernel exists but many more features are needed to emulate Unix. When the kernel and compiler are finished, it will be possible to distribute a GNU system suitable for program development. We will use TeX as our text formatter, but an nroff is being worked on. We will use the free, portable X window system as well. After this we will add a portable Common Lisp, an Empire game, a spreadsheet, and hundreds of other things, plus on-line documentation. We hope to supply, eventually, everything useful that normally comes with a Unix system, and more.

GNU will be able to run Unix programs, but will not be identical to Unix. We will make all improvements that are convenient, based on our experience with other operating systems. In particular, we plan to have longer file names, file version numbers, a crashproof file system, file name completion perhaps, terminal-independent display support, and perhaps eventually a Lisp-based window system through which several Lisp programs and ordinary Unix programs can share a screen. Both C and Lisp will be available as system programming languages. We will try to support UUCP, MIT Chaosnet, and Internet protocols for communication.

GNU is aimed initially at machines in the 68000/16000 class with virtual memory, because they are the easiest machines to make it run on. The extra effort to make it run on smaller machines will be left to someone who wants to use it on them.

To avoid horrible confusion, please pronounce the “G” in the word “GNU” when it is the name of this project.

Why I Must Write GNU

I consider that the golden rule requires that if I like a program I must share it with other people who like it. Software sellers want to divide the users and conquer them, making each user agree not to share with others. I refuse to break solidarity with other users in this way. I cannot in good conscience sign a nondisclosure agreement or a software license agreement. For years I worked within the Artificial Intelligence Lab to resist such tendencies and other inhospitalities, but eventually they had gone too far: I could not remain in an institution where such things are done for me against my will.

So that I can continue to use computers without dishonor, I have decided to put together a sufficient body of free software so that I will be able to get along without any software that is not free. I have resigned from the AI lab to deny MIT any legal excuse to prevent me from giving GNU away.

Why GNU Will Be Compatible with Unix

Unix is not my ideal system, but it is not too bad. The essential features of Unix seem to be good ones, and I think I can fill in what Unix lacks without spoiling them. And a system compatible with Unix would be convenient for many other people to adopt.

How GNU Will Be Available

GNU is not in the public domain. Everyone will be permitted to modify and redistribute GNU, but no distributor will be allowed to restrict its further redistribution. That is to say, proprietary modifications will not be allowed. I want to make sure that all versions of GNU remain free.

Why Many Other Programmers Want to Help

I have found many other programmers who are excited about GNU and want to help.

Many programmers are unhappy about the commercialization of system software. It may enable them to make more money, but it requires them to feel in conflict with other programmers in general rather than feel as comrades. The fundamental act of friendship among programmers is the sharing of programs; marketing arrangements now typically used essentially forbid programmers to treat others as friends. The purchaser of software must choose between friendship and obeying the law. Naturally, many decide that friendship is more important. But those who believe in law often do not feel at ease with either choice. They become cynical and think that programming is just a way of making money.

By working on and using GNU rather than proprietary programs, we can be hospitable to everyone and obey the law. In addition, GNU serves as an example to inspire and a banner to rally others to join us in sharing. This can give us a feeling of harmony which is impossible if we use software that is not free. For about half the programmers I talk to, this is an important happiness that money cannot replace.

How You Can Contribute

I am asking computer manufacturers for donations of machines and money. I’m asking individuals for donations of programs and work.

One consequence you can expect if you donate machines is that GNU will run on them at an early date. The machines should be complete, ready to use systems, approved for use in a residential area, and not in need of sophisticated cooling or power.

I have found very many programmers eager to contribute part-time work for GNU. For most projects, such part-time distributed work would be very hard to coordinate; the independently-written parts would not work together. But for the particular task of replacing Unix, this problem is absent. A complete Unix system contains hundreds of utility programs, each of which is documented separately. Most interface specifications are fixed by Unix compatibility. If each contributor can write a compatible replacement for a single Unix utility, and make it work properly in place of the original on a Unix system, then these utilities will work right when put together. Even allowing for Murphy to create a few unexpected problems, assembling these components will be a feasible task. (The kernel will require closer communication and will be worked on by a small, tight group.)

If I get donations of money, I may be able to hire a few people full or part time. The salary won’t be high by programmers’ standards, but I’m looking for people for whom building community spirit is as important as making money. I view this as a way of enabling dedicated people to devote their full energies to working on GNU by sparing them the need to make a living in another way.

Why All Computer Users Will Benefit

Once GNU is written, everyone will be able to obtain good system software free, just like air.34

This means much more than just saving everyone the price of a Unix license. It means that much wasteful duplication of system programming effort will be avoided. This effort can go instead into advancing the state of the art.

Complete system sources will be available to everyone. As a result, a user who needs changes in the system will always be free to make them himself, or hire any available programmer or company to make them for him. Users will no longer be at the mercy of one programmer or company which owns the sources and is in sole position to make changes.

Schools will be able to provide a much more educational environment by encouraging all students to study and improve the system code. Harvard’s computer lab used to have the policy that no program could be installed on the system if its sources were not on public display, and upheld it by actually refusing to install certain programs. I was very much inspired by this.

Finally, the overhead of considering who owns the system software and what one is or is not entitled to do with it will be lifted.

Arrangements to make people pay for using a program, including licensing of copies, always incur a tremendous cost to society through the cumbersome mechanisms necessary to figure out how much (that is, which programs) a person must pay for. And only a police state can force everyone to obey them. Consider a space station where air must be manufactured at great cost: charging each breather per liter of air may be fair, but wearing the metered gas mask all day and all night is intolerable even if everyone can afford to pay the air bill. And the TV cameras everywhere to see if you ever take the mask off are outrageous. It’s better to support the air plant with a head tax and chuck the masks.

Copying all or parts of a program is as natural to a programmer as breathing, and as productive. It ought to be as free.

Some Easily Rebutted Objections to GNU’s Goals

“Nobody will use it if it is free, because that means they can’t rely on any support.”

“You have to charge for the program to pay for providing the support.”

If people would rather pay for GNU plus service than get GNU free without service, a company to provide just service to people who have obtained GNU free ought to be profitable.35

We must distinguish between support in the form of real programming work and mere handholding. The former is something one cannot rely on from a software vendor. If your problem is not shared by enough people, the vendor will tell you to get lost.

If your business needs to be able to rely on support, the only way is to have all the necessary sources and tools. Then you can hire any available person to fix your problem; you are not at the mercy of any individual. With Unix, the price of sources puts this out of consideration for most businesses. With GNU this will be easy. It is still possible for there to be no available competent person, but this problem cannot be blamed on distribution arrangements. GNU does not eliminate all the world’s problems, only some of them.

Meanwhile, the users who know nothing about computers need handholding: doing things for them which they could easily do themselves but don’t know how.

Such services could be provided by companies that sell just hand-holding and repair service. If it is true that users would rather spend money and get a product with service, they will also be willing to buy the service having got the product free. The service companies will compete in quality and price; users will not be tied to any particular one. Meanwhile, those of us who don’t need the service should be able to use the program without paying for the service.

“You cannot reach many people without advertising, and you must charge for the program to support that.”

“It’s no use advertising a program people can get free.”

There are various forms of free or very cheap publicity that can be used to inform numbers of computer users about something like GNU. But it may be true that one can reach more microcomputer users with advertising. If this is really so, a business which advertises the service of copying and mailing GNU for a fee ought to be successful enough to pay for its advertising and more. This way, only the users who benefit from the advertising pay for it.

On the other hand, if many people get GNU from their friends, and such companies don’t succeed, this will show that advertising was not really necessary to spread GNU. Why is it that free market advocates don’t want to let the free market decide this?36

“My company needs a proprietary operating system to get a competitive edge.”

GNU will remove operating system software from the realm of competition. You will not be able to get an edge in this area, but neither will your competitors be able to get an edge over you. You and they will compete in other areas, while benefiting mutually in this one. If your business is selling an operating system, you will not like GNU, but that’s tough on you. If your business is something else, GNU can save you from being pushed into the expensive business of selling operating systems.

I would like to see GNU development supported by gifts from many manufacturers and users, reducing the cost to each.37

“Don’t programmers deserve a reward for their creativity?”

If anything deserves a reward, it is social contribution. Creativity can be a social contribution, but only in so far as society is free to use the results. If programmers deserve to be rewarded for creating innovative programs, by the same token they deserve to be punished if they restrict the use of these programs.

“Shouldn’t a programmer be able to ask for a reward for his creativity?”

There is nothing wrong with wanting pay for work, or seeking to maximize one’s income, as long as one does not use means that are destructive. But the means customary in the field of software today are based on destruction.

Extracting money from users of a program by restricting their use of it is destructive because the restrictions reduce the amount and the ways that the program can be used. This reduces the amount of wealth that humanity derives from the program. When there is a deliberate choice to restrict, the harmful consequences are deliberate destruction.

The reason a good citizen does not use such destructive means to become wealthier is that, if everyone did so, we would all become poorer from the mutual destructiveness. This is Kantian ethics; or, the Golden Rule. Since I do not like the consequences that result if everyone hoards information, I am required to consider it wrong for one to do so. Specifically, the desire to be rewarded for one’s creativity does not justify depriving the world in general of all or part of that creativity.

“Won’t programmers starve?”

I could answer that nobody is forced to be a programmer. Most of us cannot manage to get any money for standing on the street and making faces. But we are not, as a result, condemned to spend our lives standing on the street making faces, and starving. We do something else.

But that is the wrong answer because it accepts the questioner’s implicit assumption: that without ownership of software, programmers cannot possibly be paid a cent. Supposedly it is all or nothing.

The real reason programmers will not starve is that it will still be possible for them to get paid for programming; just not paid as much as now.

Restricting copying is not the only basis for business in software. It is the most common basis because it brings in the most money. If it were prohibited, or rejected by the customer, software business would move to other bases of organization which are now used less often. There are always numerous ways to organize any kind of business.

Probably programming will not be as lucrative on the new basis as it is now. But that is not an argument against the change. It is not considered an injustice that sales clerks make the salaries that they now do. If programmers made the same, that would not be an injustice either. (In practice they would still make considerably more than that.)

“Don’t people have a right to control how their creativity is used?”

“Control over the use of one’s ideas” really constitutes control over other people’s lives; and it is usually used to make their lives more difficult.

People who have studied the issue of intellectual property rights38 carefully (such as lawyers) say that there is no intrinsic right to intellectual property. The kinds of supposed intellectual property rights that the government recognizes were created by specific acts of legislation for specific purposes.

For example, the patent system was established to encourage inventors to disclose the details of their inventions. Its purpose was to help society rather than to help inventors. At the time, the life span of 17 years for a patent was short compared with the rate of advance of the state of the art. Since patents are an issue only among manufacturers, for whom the cost and effort of a license agreement are small compared with setting up production, the patents often do not do much harm. They do not obstruct most individuals who use patented products.

The idea of copyright did not exist in ancient times, when authors frequently copied other authors at length in works of non-fiction. This practice was useful, and is the only way many authors’ works have survived even in part. The copyright system was created expressly for the purpose of encouraging authorship. In the domain for which it was invented—books, which could be copied economically only on a printing press—it did little harm, and did not obstruct most of the individuals who read the books.

All intellectual property rights are just licenses granted by society because it was thought, rightly or wrongly, that society as a whole would benefit by granting them. But in any particular situation, we have to ask: are we really better off granting such license? What kind of act are we licensing a person to do?

The case of programs today is very different from that of books a hundred years ago. The fact that the easiest way to copy a program is from one neighbor to another, the fact that a program has both source code and object code which are distinct, and the fact that a program is used rather than read and enjoyed, combine to create a situation in which a person who enforces a copyright is harming society as a whole both materially and spiritually; in which a person should not do so regardless of whether the law enables him to.

“Competition makes things get done better.”

The paradigm of competition is a race: by rewarding the winner, we encourage everyone to run faster. When capitalism really works this way, it does a good job; but its defenders are wrong in assuming it always works this way. If the runners forget why the reward is offered and become intent on winning, no matter how, they may find other strategies—such as, attacking other runners. If the runners get into a fist fight, they will all finish late.

Proprietary and secret software is the moral equivalent of runners in a fist fight. Sad to say, the only referee we’ve got does not seem to object to fights; he just regulates them (“For every ten yards you run, you can fire one shot”). He really ought to break them up, and penalize runners for even trying to fight.

“Won’t everyone stop programming without a monetary incentive?”

Actually, many people will program with absolutely no monetary incentive. Programming has an irresistible fascination for some people, usually the people who are best at it. There is no shortage of professional musicians who keep at it even though they have no hope of making a living that way.

But really this question, though commonly asked, is not appropriate to the situation. Pay for programmers will not disappear, only become less. So the right question is, will anyone program with a reduced monetary incentive? My experience shows that they will.

For more than ten years, many of the world’s best programmers worked at the Artificial Intelligence Lab for far less money than they could have had anywhere else. They got many kinds of non-monetary rewards: fame and appreciation, for example. And creativity is also fun, a reward in itself.

Then most of them left when offered a chance to do the same interesting work for a lot of money.

What the facts show is that people will program for reasons other than riches; but if given a chance to make a lot of money as well, they will come to expect and demand it. Low-paying organizations do poorly in competition with high-paying ones, but they do not have to do badly if the high-paying ones are banned.

“We need the programmers desperately. If they demand that we stop helping our neighbors, we have to obey.”

You’re never so desperate that you have to obey this sort of demand. Remember: millions for defense, but not a cent for tribute!

“Programmers need to make a living somehow.”

In the short run, this is true. However, there are plenty of ways that programmers could make a living without selling the right to use a program. This way is customary now because it brings programmers and businessmen the most money, not because it is the only way to make a living. It is easy to find other ways if you want to find them. Here are a number of examples.

A manufacturer introducing a new computer will pay for the porting of operating systems onto the new hardware.

The sale of teaching, hand-holding and maintenance services could also employ programmers.

People with new ideas could distribute programs as freeware39, asking for donations from satisfied users, or selling hand-holding services. I have met people who are already working this way successfully.

Users with related needs can form users’ groups, and pay dues. A group would contract with programming companies to write programs that the group’s members would like to use.

All sorts of development can be funded with a Software Tax:

Suppose everyone who buys a computer has to pay x percent of the price as a software tax. The government gives this to an agency like the NSF to spend on software development.

But if the computer buyer makes a donation to software development himself, he can take a credit against the tax. He can donate to the project of his own choosing—often, chosen because he hopes to use the results when it is done. He can take a credit for any amount of donation up to the total tax he had to pay.

The total tax rate could be decided by a vote of the payers of the tax, weighted according to the amount they will be taxed on.

The consequences:

  • The computer-using community supports software development.
  • This community decides what level of support is needed.
  • Users who care which projects their share is spent on can choose this for themselves.

In the long run, making programs free is a step toward the post-scarcity world, where nobody will have to work very hard just to make a living. People will be free to devote themselves to activities that are fun, such as programming, after spending the necessary ten hours a week on required tasks such as legislation, family counseling, robot repair and asteroid prospecting. There will be no need to be able to make a living from programming.

We have already greatly reduced the amount of work that the whole society must do for its actual productivity, but only a little of this has translated itself into leisure for workers because much nonproductive activity is required to accompany productive activity. The main causes of this are bureaucracy and isometric struggles against competition. Free software will greatly reduce these drains in the area of software production. We must do this, in order for technical gains in productivity to translate into less work for us.


Glossary

Abbrev

An abbrev is a text string that expands into a different text string when present in the buffer. For example, you might define a few letters as an abbrev for a long phrase that you want to insert frequently. See Abbrevs.

Aborting

Aborting means getting out of a recursive edit (q.v.). The commands C-] and M-x top-level are used for this. See Quitting and Aborting.

Active Region

Setting the mark (q.v.) at a position in the text also activates it. When the mark is active, we call the region an active region. See The Mark and the Region.

Alt

Alt is the name of a modifier bit that a keyboard input character may have. To make a character Alt, type it while holding down the Alt key. Such characters are given names that start with Alt- (usually written A- for short). (Note that many terminals have a key labeled Alt that is really a Meta key.) See Alt.

Argument

See Glossary---Numeric Argument.

ASCII character

An ASCII character is either an ASCII control character or an ASCII printing character. See Kinds of User Input.

ASCII control character

An ASCII control character is the Control version of an upper-case letter, or the Control version of one of the characters ‘@[\]^_?’.

ASCII printing character

ASCII letters, digits, space, and the following punctuation characters: ‘!@#$%^&*()_-+=|\~`{}[]:;"'<>,.?/’.

Auto Fill Mode

Auto Fill mode is a minor mode (q.v.) in which text that you insert is automatically broken into lines of a given maximum width. See Filling Text.

Auto Saving

Auto saving is the practice of periodically saving the contents of an Emacs buffer in a specially-named file, so that the information will be preserved if the buffer is lost due to a system error or user error. See Auto-Saving: Protection Against Disasters.

Autoloading

Emacs can automatically load Lisp libraries when a Lisp program requests a function from those libraries. This is called “autoloading”. See Libraries of Lisp Code for Emacs.

Backtrace

A backtrace is a trace of a series of function calls showing how a program arrived at a certain point. It is used mainly for finding and correcting bugs (q.v.). Emacs can display a backtrace when it signals an error or when you type C-g (see Glossary---Quitting). See Checklist for Bug Reports.

Backup File

A backup file records the contents that a file had before the current editing session. Emacs makes backup files automatically to help you track down or cancel changes you later regret making. See Backup Files.

Balancing Parentheses

Emacs can balance parentheses (or other matching delimiters) either manually or automatically. You do manual balancing with the commands to move over parenthetical groupings (see Moving in the Parenthesis Structure). Automatic balancing works by blinking or highlighting the delimiter that matches the one you just inserted, or inserting the matching delimiter for you (see Matching Parens).

Balanced Expressions

A balanced expression is a syntactically recognizable expression, such as a symbol (q.v.), number, string constant, block, or parenthesized expression in C. See Balanced Expressions.

Balloon Help

See Glossary---Tooltips.

Base Buffer

A base buffer is a buffer whose text is shared by an indirect buffer (q.v.).

Bidirectional Text

Some human languages, such as English, are written from left to right. Others, such as Arabic, are written from right to left. Emacs supports both of these forms, as well as any mixture of them—this is “bidirectional text”. See Bidirectional Editing.

Bind

To bind a key sequence means to give it a binding (q.v.). See Changing Key Bindings Interactively.

Binding

A key sequence gets its meaning in Emacs by having a binding, which is a command (q.v.)—a Lisp function that is run when you type that sequence. See Binding. Customization often involves rebinding a character to a different command function. The bindings of all key sequences are recorded in the keymaps (q.v.). See Keymaps.

Blank Lines

Blank lines are lines that contain only whitespace. Emacs has several commands for operating on the blank lines in the buffer. See Blank Lines.

Bookmark

Bookmarks are akin to registers (q.v.) in that they record positions in buffers to which you can return later. Unlike registers, bookmarks persist between Emacs sessions. See Bookmarks.

Border

A border is a thin space along the edge of the frame, used just for spacing, not for displaying anything. An Emacs frame has an ordinary external border, outside of everything including the menu bar, plus an internal border that surrounds the text windows, their scroll bars and fringes, and separates them from the menu bar and tool bar. You can customize both borders with options and resources (see Internal and Outer Borders). Borders are not the same as fringes (q.v.).

Buffer

The buffer is the basic editing unit; one buffer corresponds to one text being edited. You normally have several buffers, but at any time you are editing only one, the current buffer, though several can be visible when you are using multiple windows or frames (q.v.). Most buffers are visiting (q.v.) some file. See Using Multiple Buffers.

Buffer Selection History

Emacs keeps a buffer selection history that records how recently each Emacs buffer has been selected. This is used for choosing which buffer to select. See Using Multiple Buffers.

Bug

A bug is an incorrect or unreasonable behavior of a program, or inaccurate or confusing documentation. Emacs developers treat bug reports, both in Emacs code and its documentation, very seriously and ask you to report any bugs you find. See Reporting Bugs.

Button Down Event

A button down event is the kind of input event (q.v.) generated right away when you press down on a mouse button. See Rebinding Mouse Buttons.

By Default

See Glossary---Default.

Byte Compilation

See Glossary---Compilation.

cf.
c.f.

Short for “confer” in Latin, which means “compare with” or “compare to”. The second variant, “c.f.”, is a widespread misspelling.

C-

C- in the name of a character is an abbreviation for Control. See C-.

C-M-

C-M- in the name of a character is an abbreviation for Control-Meta. If your terminal lacks a real Meta key, you type a Control-Meta character by typing ESC and then typing the corresponding Control character. See C-M-.

Case Conversion

Case conversion means changing text from upper case to lower case or vice versa. See Case Conversion Commands.

Case Folding

Case folding means ignoring the differences between case variants of the same letter: upper-case, lower-case, and title-case. Emacs performs case folding by default in text search. See Lax Matching During Searching.

Character

Characters form the contents of an Emacs buffer. Also, key sequences (q.v.) are usually made up of characters (though they may include other input events as well). See Kinds of User Input.

Character Folding

Character folding means ignoring differences between similarly looking characters, such as between a, and ä and á. Emacs performs character folding by default in text search. See Lax Matching During Searching.

Character Set

Emacs supports a number of character sets, each of which represents a particular alphabet or script. See International Character Set Support.

Character Terminal

See Glossary---Text Terminal.

Click Event

A click event is the kind of input event (q.v.) generated when you press a mouse button and release it without moving the mouse. See Rebinding Mouse Buttons.

Client

See Glossary---Server.

Clipboard

A clipboard is a buffer provided by the window system for transferring text between applications. On the X Window System, the clipboard is provided in addition to the primary selection (q.v.); on MS-Windows and Mac, the clipboard is used instead of the primary selection. See Using the Clipboard.

Coding System

A coding system is a way to encode text characters in a file or in a stream of information. Emacs has the ability to convert text to or from a variety of coding systems when reading or writing it. See Coding Systems.

Command

A command is a Lisp function specially defined to be able to serve as a key binding in Emacs or to be invoked by its name (see Glossary---Command Name). (Another term for command is interactive function—they are used interchangeably.) When you type a key sequence (q.v.), its binding (q.v.) is looked up in the relevant keymaps (q.v.) to find the command to run. See Keys and Commands.

Command History

See Glossary---Minibuffer History.

Command Name

A command name is the name of a Lisp symbol (q.v.) that is a command (see Keys and Commands). You can invoke any command by its name using M-x (see Running Commands by Name).

Comment

A comment is text in a program which is intended only for humans reading the program, and which is specially marked so that it will be ignored when the program is loaded or compiled. Emacs offers special commands for creating, aligning and killing comments. See Manipulating Comments.

Common Lisp

Common Lisp is a dialect of Lisp (q.v.) much larger and more powerful than Emacs Lisp. Emacs provides a subset of Common Lisp in the CL package. See Overview in Common Lisp Extensions.

Compilation

Compilation is the process of creating an executable program from source code. Emacs has commands for compiling files of Emacs Lisp code (see Byte Compilation in the Emacs Lisp Reference Manual) and programs in C and other languages (see Running Compilations under Emacs). Byte-compiled Emacs Lisp code loads and executes faster.

Complete Key

A complete key is a key sequence that fully specifies one action to be performed by Emacs. For example, X and C-f and C-x m are complete keys. Complete keys derive their meanings from being bound (see Glossary---Bind) to commands (q.v.). Thus, X is conventionally bound to a command to insert ‘X’ in the buffer; C-x m is conventionally bound to a command to begin composing a mail message. See Keys.

Completion

Completion is what Emacs does when it automatically expands an abbreviation for a name into the entire name. Completion is done for minibuffer (q.v.) arguments when the set of possible valid inputs is known; for example, on command names, buffer names, and file names. Completion usually occurs when TAB, SPC or RET is typed. See Completion.

Continuation Line

When a line of text is longer than the width of the window, it normally takes up more than one screen line when displayed (but see Glossary---Truncation). We say that the text line is continued, and all screen lines used for it after the first are called continuation lines. See Continuation Lines. A related Emacs feature is filling (q.v.).

Control Character

A control character is a character that you type by holding down the Ctrl key. Some control characters also have their own keys, so that you can type them without using Ctrl. For example, RET, TAB, ESC and DEL are all control characters. See Kinds of User Input.

Copyleft

A copyleft is a notice giving the public legal permission to redistribute and modify a program or other work of art, but requiring modified versions to carry similar permission. Copyright is normally used to keep users divided and helpless; with copyleft we turn that around to empower users and encourage them to cooperate.

The particular form of copyleft used by the GNU project is called the GNU General Public License. See GNU GENERAL PUBLIC LICENSE.

Ctrl

The Ctrl or control key is what you hold down in order to enter a control character (q.v.). See Glossary---C-.

Current Buffer

The current buffer in Emacs is the Emacs buffer on which most editing commands operate. You can select any Emacs buffer as the current one. See Using Multiple Buffers.

Current Line

The current line is the line that point is on (see Point).

Current Paragraph

The current paragraph is the paragraph that point is in. If point is between two paragraphs, the current paragraph is the one that follows point. See Paragraphs.

Current Defun

The current defun is the defun (q.v.) that point is in. If point is between defuns, the current defun is the one that follows point. See Top-Level Definitions, or Defuns.

Cursor

The cursor is the rectangle on the screen which indicates the position (called point; q.v.) at which insertion and deletion takes place. The cursor is on or under the character that follows point. Often people speak of “the cursor” when, strictly speaking, they mean “point”. See Cursor.

Customization

Customization is making minor changes in the way Emacs works, to reflect your preferences or needs. It is often done by setting variables (see Variables) or faces (see Customizing Faces), or by rebinding key sequences (see Keymaps).

Cut and Paste

See Glossary---Killing, and Glossary---Yanking.

Daemon

A daemon is a standard term for a system-level process that runs in the background. Daemons are often started when the system first starts up. When Emacs runs in daemon-mode, it does not open a display. You connect to it with the emacsclient program. See Using Emacs as a Server.

Default Argument

The default for an argument is the value that will be assumed if you do not specify one. When the minibuffer is used to read an argument, the default argument is used if you just type RET. See The Minibuffer.

Default

A default is the value that is used for a certain purpose when you do not explicitly specify a value to use.

Default Directory

When you specify a file name that does not start with ‘/’ or ‘~’, it is interpreted relative to the current buffer’s default directory. (On MS systems, file names that start with a drive letter ‘x:’ are treated as absolute, not relative.) See Default Directory.

Defun

A defun is a major definition at the top level in a program. The name “defun” comes from Lisp, where most such definitions use the construct defun. See Top-Level Definitions, or Defuns.

DEL

DEL is a character that runs the command to delete one character of text before the cursor. It is typically either the Delete key or the BACKSPACE key, whichever one is easy to type. See DEL.

Deletion

Deletion means erasing text without copying it into the kill ring (q.v.). The alternative is killing (q.v.). See Deletion.

Deletion of Files

Deleting a file means erasing it from the file system. (Note that some systems use the concept of a trash can, or recycle bin, to allow you to undelete files.) See Miscellaneous File Operations.

Deletion of Messages

Deleting a message (in Rmail, and other mail clients) means flagging it to be eliminated from your mail file. Until you expunge (q.v.) the Rmail file, you can still undelete the messages you have deleted. See Deleting Messages.

Deletion of Windows

Deleting a window means eliminating it from the screen. Other windows expand to use up the space. The text that was in the window is not lost, and you can create a new window with the same dimensions as the old if you wish. See Multiple Windows.

Directory

File directories are named collections in the file system, within which you can place individual files or subdirectories. They are sometimes referred to as “folders”. See File Directories.

Directory Local Variable

A directory local variable is a local variable (q.v.) that applies to all the files within a certain directory. See Per-Directory Local Variables.

Directory Name

On GNU and other Unix-like systems, directory names are strings that end in ‘/’. For example, /no-such-dir/ is a directory name whereas /tmp is not, even though /tmp names a file that happens to be a directory. On MS-Windows the relationship is more complicated. See Directory Names in the Emacs Lisp Reference Manual.

Dired

Dired is the Emacs facility that displays the contents of a file directory and allows you to “edit the directory”, performing operations on the files in the directory. See Dired, the Directory Editor.

Disabled Command

A disabled command is one that you may not run without special confirmation. The usual reason for disabling a command is that it is confusing for beginning users. See Disabling Commands.

Down Event

Short for “button down event” (q.v.).

Drag Event

A drag event is the kind of input event (q.v.) generated when you press a mouse button, move the mouse, and then release the button. See Rebinding Mouse Buttons.

Dribble File

A dribble file is a file into which Emacs writes all the characters that you type on the keyboard. Dribble files can be used to make a record for debugging Emacs bugs. Emacs does not make a dribble file unless you tell it to. See Reporting Bugs.

e.g.

Short for “exempli gratia” in Latin, which means “for example”.

Echo Area

The echo area is the bottom line of the screen, used for echoing the arguments to commands, for asking questions, and showing brief messages (including error messages). The messages are stored in the buffer *Messages* so you can review them later. See The Echo Area.

Echoing

Echoing is acknowledging the receipt of input events by displaying them (in the echo area). Emacs never echoes single-character key sequences; longer key sequences echo only if you pause while typing them.

Electric

We say that a character is electric if it is normally self-inserting (q.v.), but the current major mode (q.v.) redefines it to do something else as well. For example, some programming language major modes define particular delimiter characters to reindent the line, or insert one or more newlines in addition to self-insertion.

End Of Line

End of line is a character or a sequence of characters that indicate the end of a text line. On GNU and Unix systems, this is a newline (q.v.), but other systems have other conventions. See end-of-line. Emacs can recognize several end-of-line conventions in files and convert between them.

Environment Variable

An environment variable is one of a collection of variables stored by the operating system, each one having a name and a value. Emacs can access environment variables set by its parent shell, and it can set variables in the environment it passes to programs it invokes. See Environment Variables.

EOL

See Glossary---End Of Line.

Error

An error occurs when an Emacs command cannot execute in the current circumstances. When an error occurs, execution of the command stops (unless the command has been programmed to do otherwise) and Emacs reports the error by displaying an error message (q.v.).

Error Message

An error message is output displayed by Emacs when you ask it to do something impossible (such as, killing text forward when point is at the end of the buffer), or when a command malfunctions in some way. Such messages appear in the echo area, accompanied by a beep.

ESC

ESC is a character used as a prefix for typing Meta characters on keyboards lacking a Meta key. Unlike the Meta key (which, like the SHIFT key, is held down while another character is typed), you press the ESC key as you would press a letter key, and it applies to the next character you type.

etc.

Short for “et cetera” in Latin, which means “and so on”.

Expression

See Glossary---Balanced Expression.

Expunging

Expunging an Rmail, Gnus newsgroup, or Dired buffer is an operation that truly discards the messages or files you have previously flagged for deletion.

Face

A face is a style of displaying characters. It specifies attributes such as font family and size, foreground and background colors, underline and strike-through, background stipple, etc. Emacs provides features to associate specific faces with portions of buffer text, in order to display that text as specified by the face attributes. See Text Faces.

File Local Variable

A file local variable is a local variable (q.v.) specified in a given file. See Local Variables in Files, and Glossary---Directory Local Variable.

File Locking

Emacs uses file locking to notice when two different users start to edit one file at the same time. See Protection against Simultaneous Editing.

File Name

A file name is a name that refers to a file. File names may be relative or absolute; the meaning of a relative file name depends on the current directory, but an absolute file name refers to the same file regardless of which directory is current. On GNU and Unix systems, an absolute file name starts with a slash (the root directory) or with ‘~/’ or ‘~user/’ (a home directory). On MS-Windows/MS-DOS, an absolute file name can also start with a drive letter and a colon, e.g., ‘d:’.

Some people use the term “pathname” for file names, but we do not; we use the word “path” only in the term “search path” (q.v.).

File-Name Component

A file-name component names a file directly within a particular directory. On GNU and Unix systems, a file name is a sequence of file-name components, separated by slashes. For example, foo/bar is a file name containing two components, ‘foo’ and ‘bar’; it refers to the file named ‘bar’ in the directory named ‘foo’ in the current directory. MS-DOS/MS-Windows file names can also use backslashes to separate components, as in foo\bar.

Fill Prefix

The fill prefix is a string that should be expected at the beginning of each line when filling is done. It is not regarded as part of the text to be filled. See Filling Text.

Filling

Filling text means adjusting the position of line-breaks to shift text between consecutive lines, so that all the lines are approximately the same length. See Filling Text. Some other editors call this feature “line wrapping”.

Font Lock

Font Lock is a mode that highlights parts of buffer text in different faces, according to the syntax. Some other editors refer to this as “syntax highlighting”. For example, all comments (q.v.) might be colored red. See Font Lock mode.

Fontset

A fontset is a named collection of fonts. A fontset specification lists character sets and which font to use to display each of them. Fontsets make it easy to change several fonts at once by specifying the name of a fontset, rather than changing each font separately. See Fontsets.

Formfeed Character

See Glossary---Page.

Frame

A frame is a rectangular cluster of Emacs windows. Emacs starts out with one frame, but you can create more. You can subdivide each frame into Emacs windows (q.v.). When you are using a window system (q.v.), more than one frame can be visible at the same time. See Frames and Graphical Displays. Some other editors use the term “window” for this, but in Emacs a window means something else.

Free Software

Free software is software that gives you the freedom to share, study and modify it. Emacs is free software, part of the GNU project (q.v.), and distributed under a copyleft (q.v.) license called the GNU General Public License. See GNU GENERAL PUBLIC LICENSE.

Free Software Foundation

The Free Software Foundation (FSF) is a charitable foundation dedicated to promoting the development of free software (q.v.). For more information, see the FSF website.

Fringe

On a graphical display (q.v.), there’s a narrow portion of the frame (q.v.) between the text area and the window’s border. These “fringes” are used to display symbols that provide information about the buffer text (see Window Fringes). Emacs displays the fringe using a special face (q.v.) called fringe. See fringe.

FSF

See Glossary---Free Software Foundation.

FTP

FTP is an acronym for File Transfer Protocol. This is one standard method for retrieving remote files (q.v.).

Function Key

A function key is a key on the keyboard that sends input but does not correspond to any character. See Rebinding Function Keys.

Global

Global means “independent of the current environment; in effect throughout Emacs”. It is the opposite of local (q.v.). Particular examples of the use of “global” appear below.

Global Abbrev

A global definition of an abbrev (q.v.) is effective in all major modes that do not have local (q.v.) definitions for the same abbrev. See Abbrevs.

Global Keymap

The global keymap (q.v.) contains key bindings that are in effect everywhere, except when overridden by local key bindings in a major mode’s local keymap (q.v.). See Keymaps.

Global Mark Ring

The global mark ring records the series of buffers you have recently set a mark (q.v.) in. In many cases you can use this to backtrack through buffers you have been editing, or in which you have found tags (see Glossary---Tags Table). See The Global Mark Ring.

Global Substitution

Global substitution means replacing each occurrence of one string by another string throughout a large amount of text. See Replacement Commands.

Global Variable

The global value of a variable (q.v.) takes effect in all buffers that do not have their own local (q.v.) values for the variable. See Variables.

GNU

GNU is a recursive acronym for GNU’s Not Unix, and it refers to a Unix-compatible operating system which is free software (q.v.). See The GNU Manifesto. GNU is normally used with Linux as the kernel since Linux works better than the GNU kernel. For more information, see the GNU website.

Graphic Character

Graphic characters are those assigned pictorial images rather than just names. All the non-Meta (q.v.) characters except for the Control (q.v.) characters are graphic characters. These include letters, digits, punctuation, and spaces; they do not include RET or ESC. In Emacs, typing a graphic character inserts that character (in ordinary editing modes). See Inserting Text.

Graphical Display

A graphical display is one that can display images and multiple fonts. Usually it also has a window system (q.v.).

Highlighting

Highlighting text means displaying it with a different foreground and/or background color to make it stand out from the rest of the text in the buffer.

Emacs uses highlighting in several ways. It highlights the region whenever it is active (see The Mark and the Region). Incremental search also highlights matches (see Incremental Search). See Glossary---Font Lock.

Hardcopy

Hardcopy means printed output. Emacs has various commands for printing the contents of Emacs buffers. See Printing Hard Copies.

HELP

HELP is the Emacs name for C-h or F1. You can type HELP at any time to ask what options you have, or to ask what a command does. See Help.

Help Echo

Help echo is a short message displayed in the echo area (q.v.) when the mouse pointer is located on portions of display that require some explanations. Emacs displays help echo for menu items, parts of the mode line, tool-bar buttons, etc. On graphical displays, the messages can be displayed as tooltips (q.v.). See Tooltips.

Home Directory

Your home directory contains your personal files. On a multi-user GNU or Unix system, each user has his or her own home directory. When you start a new login session, your home directory is the default directory in which to start. A standard shorthand for your home directory is ‘~’. Similarly, ‘~user’ represents the home directory of some other user.

Hook

A hook is a list of functions to be called on specific occasions, such as saving a buffer in a file, major mode activation, etc. By customizing the various hooks, you can modify Emacs’s behavior without changing any of its code. See Hooks.

Hyper

Hyper is the name of a modifier bit that a keyboard input character may have. To make a character Hyper, type it while holding down the Hyper key. Such characters are given names that start with Hyper- (usually written H- for short). See Modifier Keys.

i.e.

Short for “id est” in Latin, which means “that is”.

Iff

“Iff” means “if and only if”. This terminology comes from mathematics. Try to avoid using this term in documentation, since many are unfamiliar with it and mistake it for a typo.

Inbox

An inbox is a file in which mail is delivered by the operating system. Rmail transfers mail from inboxes to Rmail files in which the mail is then stored permanently or until explicitly deleted. See Rmail Files and Inboxes.

Incremental Search

Emacs provides an incremental search facility, whereby Emacs begins searching for a string as soon as you type the first character. As you type more characters, it refines the search. See Incremental Search.

Indentation

Indentation means blank space at the beginning of a line. Most programming languages have conventions for using indentation to illuminate the structure of the program, and Emacs has special commands to adjust indentation. See Indentation.

Indirect Buffer

An indirect buffer is a buffer that shares the text of another buffer, called its base buffer (q.v.). See Indirect Buffers.

Info

Info is the hypertext format used by the GNU project for writing documentation.

Input Event

An input event represents, within Emacs, one action taken by the user on the terminal. Input events include typing characters, typing function keys, pressing or releasing mouse buttons, and switching between Emacs frames. See Kinds of User Input.

Input Method

An input method is a system for entering non-ASCII text characters by typing sequences of ASCII characters (q.v.). See Input Methods.

Insertion

Insertion means adding text into the buffer, either from the keyboard or from some other place in Emacs.

Interactive Function

A different term for command (q.v.).

Interactive Invocation

A function can be called from Lisp code, or called as a user level command (via M-x, a key binding or a menu). In the latter case, the function is said to be called interactively.

Interlocking

See Glossary---File Locking.

Isearch

See Glossary---Incremental Search.

Justification

Justification means adding extra spaces within lines of text in order to adjust the position of the text edges. See Explicit Fill Commands.

Key Binding

See Glossary---Binding.

Keyboard Macro

Keyboard macros are a way of defining new Emacs commands from sequences of existing ones, with no need to write a Lisp program. You can use a macro to record a sequence of commands, then play them back as many times as you like. See Keyboard Macros.

Keyboard Shortcut

A keyboard shortcut is a key sequence (q.v.) that invokes a command. What some programs call “assigning a keyboard shortcut”, Emacs calls “binding a key sequence”. See Glossary---Binding.

Key Sequence

A key sequence (key, for short) is a sequence of input events (q.v.) that are meaningful as a single unit. If the key sequence is enough to specify one action, it is a complete key (q.v.); if it is not enough, it is a prefix key (q.v.). See Keys.

Keymap

The keymap is the data structure that records the bindings (q.v.) of key sequences to the commands that they run. For example, the global keymap binds the character C-n to the command function next-line. See Keymaps.

Keyboard Translation Table

The keyboard translation table is an array that translates the character codes that come from the terminal into the character codes that make up key sequences.

Kill Ring

The kill ring is where all text you have killed (see Glossary---Killing) recently is saved. You can reinsert any of the killed text still in the ring; this is called yanking (q.v.). See Yanking.

Killing

Killing means erasing text and saving it on the kill ring so it can be yanked (q.v.) later. Some other systems call this “cutting”. Most Emacs commands that erase text perform killing, as opposed to deletion (q.v.). See Killing and Moving Text.

Killing a Job

Killing a job (such as, an invocation of Emacs) means making it cease to exist. Any data within it, if not saved in a file, is lost. See Exiting Emacs.

Language Environment

Your choice of language environment specifies defaults for the input method (q.v.) and coding system (q.v.). See Language Environments. These defaults are relevant if you edit non-ASCII text (see International Character Set Support).

Line Wrapping

See Glossary---Filling.

Lisp

Lisp is a programming language. Most of Emacs is written in a dialect of Lisp, called Emacs Lisp, which is extended with special features that make it especially suitable for text editing tasks.

List

A list is, approximately, a text string beginning with an open parenthesis and ending with the matching close parenthesis. In C mode and other non-Lisp modes, groupings surrounded by other kinds of matched delimiters appropriate to the language, such as braces, are also considered lists. Emacs has special commands for many operations on lists. See Moving in the Parenthesis Structure.

Local

Local means “in effect only in a particular context”; the relevant kind of context is a particular function execution, a particular buffer, or a particular major mode. It is the opposite of “global” (q.v.). Specific uses of “local” in Emacs terminology appear below.

Local Abbrev

A local abbrev definition is effective only if a particular major mode is selected. In that major mode, it overrides any global definition for the same abbrev. See Abbrevs.

Local Keymap

A local keymap is used in a particular major mode; the key bindings (q.v.) in the current local keymap override global bindings of the same key sequences. See Keymaps.

Local Variable

A local value of a variable (q.v.) applies to only one buffer. See Local Variables.

M-

M- in the name of a character is an abbreviation for Meta, one of the modifier keys that can accompany any character. See M-.

M-C-

M-C- in the name of a character is an abbreviation for Control-Meta; it means the same thing as C-M- (q.v.).

M-x

M-x is the key sequence that is used to call an Emacs command by name. This is how you run commands that are not bound to key sequences. See Running Commands by Name.

Mail

Mail means messages sent from one user to another through the computer system, to be read at the recipient’s convenience. Emacs has commands for composing and sending mail, and for reading and editing the mail you have received. See Sending Mail. See Reading Mail with Rmail, for one way to read mail with Emacs.

Mail Composition Method

A mail composition method is a program runnable within Emacs for editing and sending a mail message. Emacs lets you select from several alternative mail composition methods. See Mail-Composition Methods.

Major Mode

The Emacs major modes are a mutually exclusive set of options, each of which configures Emacs for editing a certain sort of text. Ideally, each programming language has its own major mode. See Major Modes.

Margin

The space between the usable part of a window (including the fringe) and the window edge.

Mark

The mark points to a position in the text. It specifies one end of the region (q.v.), point being the other end. Many commands operate on all the text from point to the mark. Each buffer has its own mark. See The Mark and the Region.

Mark Ring

The mark ring is used to hold several recent previous locations of the mark, in case you want to move back to them. Each buffer has its own mark ring; in addition, there is a single global mark ring (q.v.). See The Mark Ring.

Menu Bar

The menu bar is a line at the top of an Emacs frame. It contains words you can click on with the mouse to bring up menus, or you can use a keyboard interface to navigate it. See Menu Bars.

Message

See Glossary---Mail.

Meta

Meta is the name of a modifier bit which you can use in a command character. To enter a meta character, you hold down the Meta key while typing the character. We refer to such characters with names that start with Meta- (usually written M- for short). For example, M-< is typed by holding down Meta and at the same time typing < (which itself is done, on most terminals, by holding down SHIFT and typing ,). See Meta.

On some terminals, the Meta key is actually labeled Alt or Edit.

Meta Character

A Meta character is one whose character code includes the Meta bit.

Minibuffer

The minibuffer is the window that appears when necessary inside the echo area (q.v.), used for reading arguments to commands. See The Minibuffer.

Minibuffer History

The minibuffer history records the text you have specified in the past for minibuffer arguments, so you can conveniently use the same text again. See Minibuffer History.

Minor Mode

A minor mode is an optional feature of Emacs, which can be switched on or off independently of all other features. Each minor mode has a command to turn it on or off. Some minor modes are global (q.v.), and some are local (q.v.). See Minor Modes.

Minor Mode Keymap

A minor mode keymap is a keymap that belongs to a minor mode and is active when that mode is enabled. Minor mode keymaps take precedence over the buffer’s local keymap, just as the local keymap takes precedence over the global keymap. See Keymaps.

Mode Line

The mode line is the line at the bottom of each window (q.v.), giving status information on the buffer displayed in that window. See The Mode Line.

Modified Buffer

A buffer (q.v.) is modified if its text has been changed since the last time the buffer was saved (or since it was created, if it has never been saved). See Saving Files.

Moving Text

Moving text means erasing it from one place and inserting it in another. The usual way to move text is by killing (q.v.) it and then yanking (q.v.) it. See Killing and Moving Text.

MULE

Prior to Emacs 23, MULE was the name of a software package which provided a MULtilingual Enhancement to Emacs, by adding support for multiple character sets (q.v.). MULE was later integrated into Emacs, and much of it was replaced when Emacs gained internal Unicode support in version 23.

Some parts of Emacs that deal with character set support still use the MULE name. See International Character Set Support.

Multibyte Character

A multibyte character is a character that takes up several bytes in a buffer. Emacs uses multibyte characters to represent non-ASCII text, since the number of non-ASCII characters is much more than 256. See International Characters.

Named Mark

A named mark is a register (q.v.), in its role of recording a location in text so that you can move point to that location. See Registers.

Narrowing

Narrowing means creating a restriction (q.v.) that limits editing in the current buffer to only a part of the text. Text outside that part is inaccessible for editing (or viewing) until the boundaries are widened again, but it is still there, and saving the file saves it all. See Narrowing.

Newline

Control-J characters in the buffer terminate lines of text and are therefore also called newlines. See Glossary---End Of Line.

nil

nil is a value usually interpreted as a logical “false”. Its opposite is t, interpreted as “true”.

Numeric Argument

A numeric argument is a number, specified before a command, to change the effect of the command. Often the numeric argument serves as a repeat count. See Numeric Arguments.

Overwrite Mode

Overwrite mode is a minor mode. When it is enabled, ordinary text characters replace the existing text after point rather than pushing it to one side. See Minor Modes.

Package

A package is a collection of Lisp code that you download and automatically install from within Emacs. Packages provide a convenient way to add new features. See Emacs Lisp Packages.

Page

A page is a unit of text, delimited by formfeed characters (ASCII control-L, code 014) at the beginning of a line. Some Emacs commands are provided for moving over and operating on pages. See Pages.

Paragraph

Paragraphs are the medium-size unit of human-language text. There are special Emacs commands for moving over and operating on paragraphs. See Paragraphs.

Parsing

We say that certain Emacs commands parse words or expressions in the text being edited. Really, all they know how to do is find the other end of a word or expression.

Point

Point is the place in the buffer at which insertion and deletion occur. Point is considered to be between two characters, not at one character. The terminal’s cursor (q.v.) indicates the location of point. See Point.

Prefix Argument

See Glossary---Numeric Argument.

Prefix Key

A prefix key is a key sequence (q.v.) whose sole function is to introduce a set of longer key sequences. C-x is an example of prefix key; any two-character sequence starting with C-x is therefore a legitimate key sequence. See Keys.

Primary Selection

The primary selection is one particular X selection (q.v.); it is the selection that most X applications use for transferring text to and from other applications.

The Emacs commands that mark or select text set the primary selection, and clicking the mouse inserts text from the primary selection when appropriate. See Shift Selection.

Prompt

A prompt is text used to ask you for input. Displaying a prompt is called prompting. Emacs prompts always appear in the echo area (q.v.). One kind of prompting happens when the minibuffer is used to read an argument (see The Minibuffer); the echoing that happens when you pause in the middle of typing a multi-character key sequence is also a kind of prompting (see The Echo Area).

q.v.

Short for “quod vide” in Latin, which means “which see”.

Query-Replace

Query-replace is an interactive string replacement feature provided by Emacs. See Query Replace.

Quitting

Quitting means canceling a partially typed command or a running command, using C-g (or C-Break on MS-DOS). See Quitting and Aborting.

Quoting

Quoting means depriving a character of its usual special significance. The most common kind of quoting in Emacs is with C-q. What constitutes special significance depends on the context and on convention. For example, an ordinary character as an Emacs command inserts itself; so in this context, a special character is any character that does not normally insert itself (such as DEL, for example), and quoting it makes it insert itself as if it were not special. Not all contexts allow quoting. See Quoting.

Quoting File Names

Quoting a file name turns off the special significance of constructs such as ‘$’, ‘~’ and ‘:’. See Quoted File Names.

Read-Only Buffer

A read-only buffer is one whose text you are not allowed to change. Normally Emacs makes buffers read-only when they contain text which has a special significance to Emacs; for example, Dired buffers. Visiting a file that is write-protected also makes a read-only buffer. See Using Multiple Buffers.

Rectangle

A rectangle consists of the text in a given range of columns on a given range of lines. Normally you specify a rectangle by putting point at one corner and putting the mark at the diagonally opposite corner. See Rectangles.

Recursive Editing Level

A recursive editing level is a state in which part of the execution of a command involves asking you to edit some text. This text may or may not be the same as the text to which the command was applied. The mode line (q.v.) indicates recursive editing levels with square brackets (‘[’ and ‘]’). See Recursive Editing Levels.

Redisplay

Redisplay is the process of correcting the image on the screen to correspond to changes that have been made in the text being edited. See Redisplay.

Regexp

See Glossary---Regular Expression.

Region

The region is the text between point (q.v.) and the mark (q.v.). Many commands operate on the text of the region. See Region.

Register

Registers are named slots in which text, buffer positions, or rectangles can be saved for later use. See Registers. A related Emacs feature is bookmarks (q.v.).

Regular Expression

A regular expression is a pattern that can match various text strings; for example, ‘a[0-9]+’ matches ‘a’ followed by one or more digits. See Syntax of Regular Expressions.

Remote File

A remote file is a file that is stored on a system other than your own. Emacs can access files on other computers provided that they are reachable from your machine over the network, and (obviously) that you have a supported method to gain access to those files. See Remote Files.

Repeat Count

See Glossary---Numeric Argument.

Replacement

See Glossary---Global Substitution.

Restriction

A buffer’s restriction is the amount of text, at the beginning or the end of the buffer, that is temporarily inaccessible. Giving a buffer a nonzero amount of restriction is called narrowing (q.v.); removing a restriction is called widening (q.v.). See Narrowing.

RET

RET is a character that in Emacs runs the command to insert a newline into the text. It is also used to terminate most arguments read in the minibuffer (q.v.). See Return.

Reverting

Reverting means returning to the original state. For example, Emacs lets you revert a buffer by re-reading its file from disk. See Reverting a Buffer.

Saving

Saving a buffer means copying its text into the file that was visited (q.v.) in that buffer. This is the way text in files actually gets changed by your Emacs editing. See Saving Files.

Scroll Bar

A scroll bar is a tall thin hollow box that appears at the side of a window. You can use mouse commands in the scroll bar to scroll the window. The scroll bar feature is supported only under windowing systems. See Scroll Bars.

Scrolling

Scrolling means shifting the text in the Emacs window so as to see a different part of the buffer. See Scrolling.

Searching

Searching means moving point to the next occurrence of a specified string or the next match for a specified regular expression. See Searching and Replacement.

Search Path

A search path is a list of directories, to be used for searching for files for certain purposes. For example, the variable load-path holds a search path for finding Lisp library files. See Libraries of Lisp Code for Emacs.

Secondary Selection

The secondary selection is one particular X selection (q.v.); some X applications can use it for transferring text to and from other applications. Emacs has special mouse commands for transferring text using the secondary selection. See Secondary Selection.

Selected Frame

The selected frame is the one your input currently operates on. See Frames and Graphical Displays.

Selected Window

The selected window is the one your input currently operates on. See Concepts of Emacs Windows.

Selecting a Buffer

Selecting a buffer means making it the current (q.v.) buffer. See Creating and Selecting Buffers.

Selection

Windowing systems allow an application program to specify selections whose values are text. A program can also read the selections that other programs have set up. This is the principal way of transferring text between window applications. Emacs has commands to work with the primary (q.v.) selection and the secondary (q.v.) selection, and also with the clipboard (q.v.).

Self-Documentation

Self-documentation is the feature of Emacs that can tell you what any command does, or give you a list of all commands related to a topic you specify. You ask for self-documentation with the help character, C-h. See Help.

Self-Inserting Character

A character is self-inserting if typing that character inserts that character in the buffer. Ordinary printing and whitespace characters are self-inserting in Emacs, except in certain special major modes.

Sentences

Emacs has commands for moving by or killing by sentences. See Sentences.

Server

Within Emacs, you can start a “server” process, which listens for connections from “clients”. This offers a faster alternative to starting several Emacs instances. See Using Emacs as a Server, and Glossary---Daemon.

Sexp

A sexp (short for “s-expression”) is the basic syntactic unit of Lisp in its textual form: either a list, or Lisp atom. Sexps are also the balanced expressions (q.v.) of the Lisp language; this is why the commands for editing balanced expressions have ‘sexp’ in their name. See Sexps.

Simultaneous Editing

Simultaneous editing means two users modifying the same file at once. Simultaneous editing, if not detected, can cause one user to lose his or her work. Emacs detects all cases of simultaneous editing, and warns one of the users to investigate. See Simultaneous Editing.

SPC

SPC is the space character, which you enter by pressing the space bar.

Speedbar

The speedbar is a special tall frame that provides fast access to Emacs buffers, functions within those buffers, Info nodes, and other interesting parts of text within Emacs. See Speedbar Frames.

Spell Checking

Spell checking means checking correctness of the written form of each one of the words in a text. Emacs can use various external spelling-checker programs to check the spelling of parts of a buffer via a convenient user interface. See Checking and Correcting Spelling.

String

A string is a kind of Lisp data object that contains a sequence of characters. Many Emacs variables are intended to have strings as values. The Lisp syntax for a string consists of the characters in the string with a ‘"’ before and another ‘"’ after. A ‘"’ that is part of the string must be written as ‘\"’ and a ‘\’ that is part of the string must be written as ‘\\’. All other characters, including newline, can be included just by writing them inside the string; however, backslash sequences as in C, such as ‘\n’ for newline or ‘\241’ using an octal character code, are allowed as well.

String Substitution

See Glossary---Global Substitution.

Symbol

A symbol in Emacs Lisp is an object with a name. The object can be a variable (q.v.), a function or command (q.v.), or a face (q.v.). The symbol’s name serves as the printed representation of the symbol. See Symbol Type in The Emacs Lisp Reference Manual.

Syntax Highlighting

See Glossary---Font Lock.

Syntax Table

The syntax table tells Emacs which characters are part of a word, which characters balance each other like parentheses, etc. See Syntax Tables in The Emacs Lisp Reference Manual.

Super

Super is the name of a modifier bit that a keyboard input character may have. To make a character Super, type it while holding down the SUPER key. Such characters are given names that start with Super- (usually written s- for short). See Modifier Keys.

Suspending

Suspending Emacs means stopping it temporarily and returning control to its parent process, which is usually a shell. Unlike killing a job (q.v.), you can later resume the suspended Emacs job without losing your buffers, unsaved edits, undo history, etc. See Exiting Emacs.

TAB

TAB is the tab character. In Emacs it is typically used for indentation or completion.

Tab Bar

The tab bar is a row of tabs at the top of an Emacs frame. Clicking on one of these tabs switches named persistent window configurations. See Tab Bars.

Tab Line

The tab line is a line of tabs at the top of an Emacs window. Clicking on one of these tabs switches window buffers. See Window Tab Line.

Tag

A tag is an identifier in a program source. See Find Identifier References.

Tags Table

A tags table is a file that serves as an index to identifiers: definitions of functions, macros, data structures, etc., in one or more other files. See Tags Tables.

Termscript File

A termscript file contains a record of all characters sent by Emacs to the terminal. It is used for tracking down bugs in Emacs redisplay. Emacs does not make a termscript file unless you tell it to. See Reporting Bugs.

Text

“Text” has two meanings (see Commands for Human Languages):

  • Data consisting of a sequence of characters, as opposed to binary numbers, executable programs, and the like. The basic contents of an Emacs buffer (aside from the text properties, q.v.) are always text in this sense.
  • Data consisting of written human language (as opposed to programs), or following the stylistic conventions of human language.
Text Terminal

A text terminal, or character terminal, is a display that is limited to displaying text in character units. Such a terminal cannot control individual pixels it displays. Emacs supports a subset of display features on text terminals.

Text Properties

Text properties are annotations recorded for particular characters in the buffer. Images in the buffer are recorded as text properties; they also specify formatting information. See Editing Format Information.

Theme

A theme is a set of customizations (q.v.) that give Emacs a particular appearance or behavior. For example, you might use a theme for your favorite set of faces (q.v.).

Tool Bar

The tool bar is a line (sometimes multiple lines) of icons at the top of an Emacs frame. Clicking on one of these icons executes a command. You can think of this as a graphical relative of the menu bar (q.v.). See Tool Bars.

Tooltips

Tooltips are small windows displaying a help echo (q.v.) text, which explains parts of the display, lists useful options available via mouse clicks, etc. See Tooltips.

Top Level

Top level is the normal state of Emacs, in which you are editing the text of the file you have visited. You are at top level whenever you are not in a recursive editing level (q.v.) or the minibuffer (q.v.), and not in the middle of a command. You can get back to top level by aborting (q.v.) and quitting (q.v.). See Quitting and Aborting.

Transient Mark Mode

The default behavior of the mark (q.v.) and region (q.v.), in which setting the mark activates it and highlights the region, is called Transient Mark mode. It is enabled by default. See Disabling Transient Mark Mode.

Transposition

Transposing two units of text means putting each one into the place formerly occupied by the other. There are Emacs commands to transpose two adjacent characters, words, balanced expressions (q.v.) or lines (see Transposing Text).

Trash Can

See Glossary---Deletion of Files.

Truncation

Truncating text lines in the display means leaving out any text on a line that does not fit within the right margin of the window displaying it. See Truncation, and Glossary---Continuation Line.

TTY

See Glossary---Text Terminal.

Undoing

Undoing means making your previous editing go in reverse, bringing back the text that existed earlier in the editing session. See Undo.

Unix

Unix is a class of multi-user computer operating systems with a long history. There are several implementations today. The GNU project (q.v.) aims to develop a complete Unix-like operating system that is free software (q.v.).

User Option

A user option is a face (q.v.) or a variable (q.v.) that exists so that you can customize Emacs by setting it to a new value. See Easy Customization Interface.

Variable

A variable is an object in Lisp that can store an arbitrary value. Emacs uses some variables for internal purposes, and has others (known as “user options”; q.v.) just so that you can set their values to control the behavior of Emacs. The variables used in Emacs that you are likely to be interested in are listed in the Variables Index in this manual (see Variable Index). See Variables, for information on variables.

Version Control

Version control systems keep track of multiple versions of a source file. They provide a more powerful alternative to keeping backup files (q.v.). See Version Control.

Visiting

Visiting a file means loading its contents into a buffer (q.v.) where they can be edited. See Visiting Files.

Whitespace

Whitespace is any run of consecutive formatting characters (space, tab, newline, backspace, etc.).

Widening

Widening is removing any restriction (q.v.) on the current buffer; it is the opposite of narrowing (q.v.). See Narrowing.

Window

Emacs divides a frame (q.v.) into one or more windows, each of which can display the contents of one buffer (q.v.) at any time. See The Organization of the Screen, for basic information on how Emacs uses the screen. See Multiple Windows, for commands to control the use of windows. Some other editors use the term “window” for what we call a “frame” in Emacs.

Window System

A window system is software that operates on a graphical display (q.v.), to subdivide the screen so that multiple applications can have their own windows at the same time. All modern operating systems include a window system.

Word Abbrev

See Glossary---Abbrev.

Word Search

Word search is searching for a sequence of words, considering the punctuation between them as insignificant. See Word Search.

Yanking

Yanking means reinserting text previously killed (q.v.). It can be used to undo a mistaken kill, or for copying or moving text. Some other systems call this “pasting”. See Yanking.


Acknowledgments

Many people have contributed code included in the Free Software Foundation’s distribution of GNU Emacs. To show our appreciation for their public spirit, we list here in alphabetical order those who have written substantial portions. Others too numerous to mention have reported and fixed bugs, and added features to many parts of Emacs. We thank them for their generosity as well.

This list is intended to mention every contributor of a major package or feature; if you know of someone we have omitted, please make a bug report. More comprehensive information is available in the ChangeLog files, summarized in the file etc/AUTHORS in the distribution.


Key (Character) Index

Jump to:   !   "   #   $   %   (   *   +   -   .   /   1   2   :   <   =   >   ?   ^   {   }   ~  
A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z  
Index Entry  Section

!
! (Dired): Shell Commands in Dired

"
" (TeX mode): TeX Editing

#
# (Dired): Flagging Many Files

$
$ (Dired): Hiding Subdirectories

%
% & (Dired): Flagging Many Files
% (Buffer Menu): Several Buffers
% C (Dired): Transforming File Names
% d (Dired): Flagging Many Files
% g (Dired): Marks vs Flags
% H (Dired): Transforming File Names
% l (Dired): Transforming File Names
% m (Dired): Marks vs Flags
% R (Dired): Transforming File Names
% S (Dired): Transforming File Names
% u (Dired): Transforming File Names
% Y (Dired): Transforming File Names

(
( (Dired): Misc Dired Features
( (Package Menu): Package Menu

*
* ! (Dired): Marks vs Flags
* % (Dired): Marks vs Flags
* * (Dired): Marks vs Flags
* / (Dired): Marks vs Flags
* ? (Dired): Marks vs Flags
* @ (Dired): Marks vs Flags
* c (Dired): Marks vs Flags
* C-n (Dired): Marks vs Flags
* C-p (Dired): Marks vs Flags
* DEL (Dired): Marks vs Flags
* m (Dired): Marks vs Flags
* N (Dired): Marks vs Flags
* s (Dired): Marks vs Flags
* t (Dired): Marks vs Flags
* u (Dired): Marks vs Flags

+
+ (Dired): Misc Dired Features
+ (DocView mode): DocView Navigation

-
- (DocView mode): DocView Navigation

.
. (Calendar mode): Specified Dates
. (Dired): Flagging Many Files
. (Rmail): Rmail Scrolling

/
/ (Rmail): Rmail Scrolling
/ / (Package Menu): Package Menu
/ a (Package Menu): Package Menu
/ d (Package Menu): Package Menu
/ k (Package Menu): Package Menu
/ m (Package Menu): Package Menu
/ N (Package Menu): Package Menu
/ n (Package Menu): Package Menu
/ s (Package Menu): Package Menu
/ u (Package Menu): Package Menu
/ v (Package Menu): Package Menu

1
1 (Buffer Menu): Several Buffers

2
2 (Buffer Menu): Several Buffers

:
:d (Dired): Operating on Files
:e (Dired): Operating on Files
:s (Dired): Operating on Files
:v (Dired): Operating on Files

<
< (Calendar mode): Scroll Calendar
< (Dired): Subdirectory Motion
< (Rmail): Rmail Motion

=
= (Dired): Comparison in Dired

>
> (Calendar mode): Scroll Calendar
> (Dired): Subdirectory Motion
> (Rmail): Rmail Motion

?
? (completion): Completion Commands
? (Package Menu): Package Menu

^
^ (Dired): Dired Visiting

{
{ (Buffer Menu): Several Buffers

}
} (Buffer Menu): Several Buffers

~
~ (Buffer Menu): Several Buffers
~ (Dired): Flagging Many Files
~ (Package Menu): Package Menu

A
a (Calendar mode): Holidays
A (Dired): Operating on Files
a (Rmail): Rmail Labels
A k (Gnus Group mode): Gnus Group Buffer
A s (Gnus Group mode): Gnus Group Buffer
A u (Gnus Group mode): Gnus Group Buffer
A z (Gnus Group mode): Gnus Group Buffer
AltGr (MS-Windows): Windows Keyboard

B
b (Buffer Menu): Several Buffers
B (Dired): Operating on Files
b (Rmail summary): Rmail Summary Edit
b (Rmail): Rmail Basics
BS (MS-DOS): MS-DOS Keyboard

C
C (Dired): Operating on Files
c (Dired): Operating on Files
c (Rmail): Rmail Reply
C-/: Undo
C-0, tab bar: Tab Bars
C-1, tab bar: Tab Bars
C-9, tab bar: Tab Bars
C-@: Setting Mark
C-a: Moving Point
C-a (Calendar mode): Move to Beginning or End
C-b: Moving Point
C-b (Calendar mode): Calendar Unit Motion
C-b, when using input methods: Input Methods
C-Break (MS-DOS): MS-DOS Keyboard
C-c ' (Picture mode): Insert in Picture
C-c , j: Semantic
C-c , J: Semantic
C-c , l: Semantic
C-c , SPC: Semantic
C-c . (C mode): Custom C Indent
C-c . (Picture mode): Insert in Picture
C-c . (Shell mode): Shell Ring
C-c / (Picture mode): Insert in Picture
C-c / (SGML mode): HTML Mode
C-c 8 (SGML mode): HTML Mode
C-c ; (Fortran mode): Fortran Comments
C-c < (GUD): Commands of GUD
C-c < (Picture mode): Insert in Picture
C-c > (GUD): Commands of GUD
C-c > (Picture mode): Insert in Picture
C-c ? (SGML mode): HTML Mode
C-c @ (Outline minor mode): Outline Minor Mode
C-c @ C-c: Hideshow
C-c @ C-h: Hideshow
C-c @ C-l: Hideshow
C-c @ C-M-h: Hideshow
C-c @ C-M-s: Hideshow
C-c @ C-r: Hideshow
C-c @ C-s: Hideshow
C-c C-a (C mode): Electric C
C-c C-a (F90 mode): Fortran Motion
C-c C-a (Log Edit mode): Log Buffer
C-c C-a (Message mode): Mail Misc
C-c C-a (Outline mode): Outline Visibility
C-c C-a (SGML mode): HTML Mode
C-c C-a (Shell mode): Shell Mode
C-c C-b (Help mode): Help Mode
C-c C-b (Message mode): Header Editing
C-c C-b (Outline mode): Outline Motion
C-c C-b (Picture mode): Insert in Picture
C-c C-b (SGML mode): HTML Mode
C-c C-b (Shell mode): Shell Mode
C-c C-b (TeX mode): TeX Print
C-c C-c (C mode): Comment Commands
C-c C-c (customization buffer): Changing a Variable
C-c C-c (Edit Abbrevs): Editing Abbrevs
C-c C-c (Edit Tab Stops): Tab Stops
C-c C-c (Log Edit mode): Log Buffer
C-c C-c (Message mode): Mail Sending
C-c C-c (Outline mode): Outline Visibility
C-c C-c (Shell mode): Shell Mode
C-c C-c (TeX mode): TeX Print
C-c C-d (C Mode): Hungry Delete
C-c C-d (Fortran mode): ForIndent Commands
C-c C-d (GUD): Commands of GUD
C-c C-d (Log Edit mode): Log Buffer
C-c C-d (Org Mode): Org Organizer
C-c C-d (Outline mode): Outline Visibility
C-c C-d (Picture mode): Basic Picture
C-c C-d (SGML mode): HTML Mode
C-c C-DEL (C Mode): Hungry Delete
C-c C-Delete (C Mode): Hungry Delete
C-c C-e (C mode): Other C Commands
C-c C-e (F90 mode): Fortran Motion
C-c C-e (LaTeX mode): LaTeX Editing
C-c C-e (Org mode): Org Authoring
C-c C-e (Outline mode): Outline Visibility
C-c C-e (Shell mode): Shell Mode
C-c C-f (GUD): Commands of GUD
C-c C-f (Help mode): Help Mode
C-c C-f (Log Edit mode): Log Buffer
C-c C-f (Outline mode): Outline Motion
C-c C-f (Picture mode): Insert in Picture
C-c C-f (SGML mode): HTML Mode
C-c C-f (Shell mode): Shell Mode
C-c C-f (TeX mode): TeX Print
C-c C-f C-b (Message mode): Header Editing
C-c C-f C-c (Message mode): Header Editing
C-c C-f C-f (Message mode): Header Editing
C-c C-f C-r (Message mode): Header Editing
C-c C-f C-s (Message mode): Header Editing
C-c C-f C-t (Message mode): Header Editing
C-c C-f C-w (Message mode): Header Editing
C-c C-i (GUD): Commands of GUD
C-c C-i (Outline mode): Outline Visibility
C-c C-j (Term mode): Term Mode
C-c C-k (Outline mode): Outline Visibility
C-c C-k (Picture mode): Rectangles in Picture
C-c C-k (Term mode): Term Mode
C-c C-k (TeX mode): TeX Print
C-c C-l (C mode): Electric C
C-c C-l (Calendar mode): General Calendar
C-c C-l (GUD): Commands of GUD
C-c C-l (Outline mode): Outline Visibility
C-c C-l (Shell mode): Shell Ring
C-c C-l (TeX mode): TeX Print
C-c C-n (C mode): Motion in C
C-c C-n (Fortran mode): Fortran Motion
C-c C-n (GUD): Commands of GUD
C-c C-n (Outline mode): Outline Motion
C-c C-n (Rmail): Rmail Motion
C-c C-n (SGML mode): HTML Mode
C-c C-n (Shell mode): Shell History Copying
C-c C-o (LaTeX mode): LaTeX Editing
C-c C-o (Outline mode): Outline Visibility
C-c C-o (Shell mode): Shell Mode
C-c C-p (C mode): Motion in C
C-c C-p (Fortran mode): Fortran Motion
C-c C-p (GUD): Commands of GUD
C-c C-p (Outline mode): Outline Motion
C-c C-p (Rmail): Rmail Motion
C-c C-p (Shell mode): Shell History Copying
C-c C-p (TeX mode): TeX Print
C-c C-q (C mode): C Indent
C-c C-q (Message mode): Citing Mail
C-c C-q (Outline mode): Outline Visibility
C-c C-q (Term mode): Term Mode
C-c C-r (Fortran mode): Fortran Columns
C-c C-r (GUD): Commands of GUD
C-c C-r (Shell mode): Shell Mode
C-c C-r (TeX mode): TeX Print
C-c C-s (C mode): Other C Commands
C-c C-s (GUD): Commands of GUD
C-c C-s (Message mode): Mail Sending
C-c C-s (Org Mode): Org Organizer
C-c C-s (Outline mode): Outline Visibility
C-c C-s (Shell mode): Shell Mode
C-c C-t (GUD): Commands of GUD
C-c C-t (Org Mode): Org Organizer
C-c C-t (Outline mode): Outline Visibility
C-c C-t (SGML mode): HTML Mode
C-c C-u (C mode): Motion in C
C-c C-u (GUD): Commands of GUD
C-c C-u (Outline mode): Outline Motion
C-c C-u (Shell mode): Shell Mode
C-c C-v (SGML mode): HTML Mode
C-c C-v (TeX mode): TeX Print
C-c C-w (Fortran mode): Fortran Columns
C-c C-w (Log Edit mode): Log Buffer
C-c C-w (Message mode): Mail Signature
C-c C-w (Picture mode): Rectangles in Picture
C-c C-w (Shell mode): Shell Mode
C-c C-x: Foldout
C-c C-x (Picture mode): Rectangles in Picture
C-c C-x (Shell mode): Shell Ring
C-c C-y (Message mode): Citing Mail
C-c C-y (Picture mode): Rectangles in Picture
C-c C-z: Foldout
C-c C-z (Shell mode): Shell Mode
C-c C-\ (C mode): Other C Commands
C-c C-\ (Shell mode): Shell Mode
C-c DEL (C Mode): Hungry Delete
C-c Delete (C Mode): Hungry Delete
C-c DOWN (Picture mode): Insert in Picture
C-c End (Picture mode): Insert in Picture
C-c Home (Picture mode): Insert in Picture
C-c LEFT (Picture mode): Insert in Picture
C-c next (Picture mode): Insert in Picture
C-c PageDown (Picture mode): Insert in Picture
C-c PageUp (Picture mode): Insert in Picture
C-c prior (Picture mode): Insert in Picture
C-c RET (Goto Address mode): Goto Address mode
C-c RET (Shell mode): Shell History Copying
C-c RIGHT (Picture mode): Insert in Picture
C-c TAB (Picture mode): Tabs in Picture
C-c TAB (SGML mode): HTML Mode
C-c TAB (TeX mode): TeX Print
C-c UP (Picture mode): Insert in Picture
C-c [ (Enriched mode): Enriched Indentation
C-c [ (Org Mode): Org Organizer
C-c \ (Picture mode): Insert in Picture
C-c ] (Enriched mode): Enriched Indentation
C-c ^ (Picture mode): Insert in Picture
C-c ` (Picture mode): Insert in Picture
C-c { (TeX mode): TeX Editing
C-c } (TeX mode): TeX Editing
C-d (Buffer Menu): Several Buffers
C-d (Rmail): Rmail Deletion
C-d (Shell mode): Shell Mode
C-Down-mouse-1: Buffer Menus
C-e: Moving Point
C-e (Calendar mode): Move to Beginning or End
C-END: Moving Point
C-f: Moving Point
C-f (Calendar mode): Calendar Unit Motion
C-f, when using input methods: Input Methods
C-g: Quitting
C-g (Incremental search): Error in Isearch
C-g (MS-DOS): MS-DOS Keyboard
C-g C-g (Incremental Search): Basic Isearch
C-h: Help
C-h .: Help Echo
C-h 4 i: Misc Help
C-h a: Apropos
C-h b: Misc Help
C-h c: Key Help
C-h C: Coding Systems
C-h C-c: Help Files
C-h C-d: Help Files
C-h C-e: Help Files
C-h C-f: Help Files
C-h C-h: Help
C-h C-h (Incremental Search): Special Isearch
C-h C-m: Help Files
C-h C-n: Help Files
C-h C-o: Help Files
C-h C-p: Help Files
C-h C-q: Misc Help
C-h C-t: Help Files
C-h C-w: Help Files
C-h C-\: Select Input Method
C-h d: Apropos
C-h e: Misc Help
C-h f: Name Help
C-h F: Name Help
C-h g: Help Files
C-h h: International Chars
C-h i: Misc Help
C-h I: Select Input Method
C-h k: Key Help
C-h K: Key Help
C-h l: Misc Help
C-h L: Language Environments
C-h m: Misc Help
C-h o: Name Help
C-h p: Package Keywords
C-h P: Package Keywords
C-h S: Misc Help
C-h s: Misc Help
C-h t: Basic
C-h v: Name Help
C-h w: Key Help
C-h x: Name Help
C-j: Inserting Text
C-j (and major modes): Major Modes
C-j (Lisp Interaction mode): Lisp Interaction
C-j (MS-DOS): MS-DOS Keyboard
C-j (TeX mode): TeX Editing
C-k: Killing by Lines
C-k (Gnus Group mode): Gnus Group Buffer
C-l: Recentering
C-LEFT: Moving Point
C-M-%: Query Replace
C-M-% (Incremental search): Special Isearch
C-M-,: Looking Up Identifiers
C-M-.: Looking Up Identifiers
C-M-/: Dynamic Abbrevs
C-M-@: Marking Objects
C-M-a: Moving by Defuns
C-M-b: Expressions
C-M-c: Recursive Edit
C-M-d: Moving by Parens
C-M-d (Dired): Subdirectory Motion
C-M-d (Incremental search): Isearch Yank
C-M-e: Moving by Defuns
C-M-f: Expressions
C-M-f (Rmail): Rmail Make Summary
C-M-h: Moving by Defuns
C-M-h (C mode): Moving by Defuns
C-M-i: Symbol Completion
C-M-i (customization buffer): Changing a Variable
C-M-j: Multi-Line Comments
C-M-j (Fortran mode): ForIndent Commands
C-M-k: Expressions
C-M-l: Recentering
C-M-l (Rmail): Rmail Make Summary
C-M-l (Shell mode): Shell Mode
C-M-n: Moving by Parens
C-M-n (Dired): Subdirectory Motion
C-M-n (Fortran mode): Fortran Motion
C-M-n (Rmail): Rmail Labels
C-M-o: Indentation Commands
C-M-p: Moving by Parens
C-M-p (Dired): Subdirectory Motion
C-M-p (Fortran mode): Fortran Motion
C-M-p (Rmail): Rmail Labels
C-M-q: Multi-line Indent
C-M-q (C mode): C Indent
C-M-q (Fortran mode): ForIndent Commands
C-M-r: Regexp Search
C-M-r (Rmail): Rmail Make Summary
C-M-s: Regexp Search
C-M-s (Rmail): Rmail Make Summary
C-M-S-l: Other Window
C-M-S-v: Other Window
C-M-SPC: Expressions
C-M-t: Expressions
C-M-t (Rmail): Rmail Make Summary
C-M-u: Moving by Parens
C-M-u (Dired): Subdirectory Motion
C-M-v: Other Window
C-M-w: Appending Kills
C-M-w (Incremental search): Isearch Yank
C-M-wheel-down: Text Scale
C-M-wheel-up: Text Scale
C-M-x (Emacs Lisp mode): Lisp Eval
C-M-x (Lisp mode): External Lisp
C-M-x (Scheme mode): External Lisp
C-M-y (Incremental search): Isearch Yank
C-M-z (Incremental search): Isearch Yank
C-M-\: Indentation Commands
C-mouse-1: Menu Mouse Clicks
C-mouse-2: Menu Mouse Clicks
C-mouse-2 (mode line): Split Window
C-mouse-2 (scroll bar): Split Window
C-mouse-3: Menu Mouse Clicks
C-mouse-3 (when menu bar is disabled): Menu Bars
C-n: Moving Point
C-n (Calendar mode): Calendar Unit Motion
C-n (Dired): Dired Navigation
C-n, when using input methods: Input Methods
C-o: Blank Lines
C-o (Buffer Menu): Several Buffers
C-o (Dired): Dired Visiting
C-o (Occur mode): Other Repeating Search
C-o (Rmail): Rmail Output
C-p: Moving Point
C-p (Calendar mode): Calendar Unit Motion
C-p (Dired): Dired Navigation
C-p, when using input methods: Input Methods
C-q: Inserting Text
C-q (Incremental Search): Special Isearch
C-r: Basic Isearch
C-r (Incremental Search): Repeat Isearch
C-RIGHT: Moving Point
C-s: Basic Isearch
C-s (Incremental Search): Repeat Isearch
C-S-backspace: Killing by Lines
C-S-mouse-3 (FFAP): FFAP
C-SPC: Setting Mark
C-SPC C-SPC: Mark Ring
C-SPC C-SPC, enabling Transient Mark mode temporarily: Disabled Transient Mark
C-t: Transpose
C-t d (Image-Dired): Image-Dired
C-TAB: File Name Cache
C-TAB: Tab Bars
C-u: Arguments
C-u C-/: Undo
C-u C-c C-w (Fortran mode): Fortran Columns
C-u C-SPC: Mark Ring
C-u C-x C-x: Disabled Transient Mark
C-u C-x v =: Old Revisions
C-u C-x v D: Old Revisions
C-u M-;: Comment Commands
C-u TAB: Multi-line Indent
C-v: Moving Point
C-v: Scrolling
C-v (Calendar mode): Scroll Calendar
C-w: Other Kill Commands
C-w (Incremental search): Isearch Yank
C-wheel-down: Text Scale
C-wheel-up: Text Scale
C-x #: Invoking emacsclient
C-x $: Selective Display
C-x (: Basic Keyboard Macro
C-x ): Basic Keyboard Macro
C-x +: Change Window
C-x -: Change Window
C-x .: Fill Prefix
C-x 0: Change Window
C-x 1: Change Window
C-x 2: Split Window
C-x 3: Split Window
C-x 4: Pop Up Window
C-x 4 .: Looking Up Identifiers
C-x 4 0: Change Window
C-x 4 a: Change Log Commands
C-x 4 b: Select Buffer
C-x 4 c: Indirect Buffers
C-x 4 C-j: Dired Enter
C-x 4 C-o: Pop Up Window
C-x 4 d: Dired Enter
C-x 4 f: Visiting
C-x 4 f (FFAP): FFAP
C-x 4 m: Sending Mail
C-x 5: Creating Frames
C-x 5 .: Looking Up Identifiers
C-x 5 0: Frame Commands
C-x 5 1: Frame Commands
C-x 5 2: Creating Frames
C-x 5 b: Select Buffer
C-x 5 c: Creating Frames
C-x 5 d: Dired Enter
C-x 5 f: Visiting
C-x 5 f (FFAP): FFAP
C-x 5 m: Sending Mail
C-x 5 o: Frame Commands
C-x 5 r: Creating Frames
C-x 5 u: Frame Commands
C-x 6 1: Two-Column
C-x 6 2: Two-Column
C-x 6 b: Two-Column
C-x 6 d: Two-Column
C-x 6 RET: Two-Column
C-x 6 s: Two-Column
C-x 8: Inserting Text
C-x 8 e: Input Methods
C-x 8 e RET (Incremental Search): Special Isearch
C-x 8 RET: Input Methods
C-x 8 RET (Incremental Search): Special Isearch
C-x ;: Options for Comments
C-x <: Horizontal Scrolling
C-x =: Position Info
C-x =, and international characters: International Chars
C-x >: Horizontal Scrolling
C-x a g: Defining Abbrevs
C-x a i g: Defining Abbrevs
C-x a i l: Defining Abbrevs
C-x a l: Defining Abbrevs
C-x b: Select Buffer
C-x C-+: Text Scale
C-x C--: Text Scale
C-x C-0: Text Scale
C-x C-;: Comment Commands
C-x C-=: Text Scale
C-x C-a (GUD): Commands of GUD
C-x C-a C-b: Commands of GUD
C-x C-a C-j (GUD): Commands of GUD
C-x C-a C-w (GUD): Watch Expressions
C-x C-b: List Buffers
C-x C-c: Exiting
C-x C-c (customization buffer): Changing a Variable
C-x C-d: Directories
C-x C-e: Lisp Eval
C-x C-f: Visiting
C-x C-f (FFAP): FFAP
C-x C-j: Dired Enter
C-x C-k b: Save Keyboard Macro
C-x C-k C-a: Keyboard Macro Counter
C-x C-k C-c: Keyboard Macro Counter
C-x C-k C-e: Edit Keyboard Macro
C-x C-k C-f: Keyboard Macro Counter
C-x C-k C-i: Keyboard Macro Counter
C-x C-k C-k: Keyboard Macro Ring
C-x C-k C-n: Keyboard Macro Ring
C-x C-k C-p: Keyboard Macro Ring
C-x C-k d: Basic Keyboard Macro
C-x C-k e: Edit Keyboard Macro
C-x C-k l: Edit Keyboard Macro
C-x C-k n: Save Keyboard Macro
C-x C-k r: Basic Keyboard Macro
C-x C-k RET: Edit Keyboard Macro
C-x C-k SPC: Keyboard Macro Step-Edit
C-x C-k x: Keyboard Macro Registers
C-x C-l: Case
C-x C-M-+: Text Scale
C-x C-M--: Text Scale
C-x C-M-0: Text Scale
C-x C-M-=: Text Scale
C-x C-n: Moving Point
C-x C-o: Blank Lines
C-x C-p: Pages
C-x C-q: Misc Buffer
C-x C-r: Visiting
C-x C-r (FFAP): FFAP
C-x C-s: Save Commands
C-x C-s (Custom Themes buffer): Custom Themes
C-x C-SPC: Global Mark Ring
C-x C-t: Transpose
C-x C-u: Case
C-x C-v: Visiting
C-x C-v (FFAP): FFAP
C-x C-w: Save Commands
C-x C-x: Setting Mark
C-x C-x, in rectangle-mark-mode: Rectangles
C-x C-z: External Lisp
C-x d: Dired Enter
C-x d (FFAP): FFAP
C-x DEL: Sentences
C-x e: Basic Keyboard Macro
C-x ESC ESC: Repetition
C-x f: Fill Commands
C-x h: Marking Objects
C-x i: Misc File Ops
C-x k: Kill Buffer
C-x l: Pages
C-x LEFT: Select Buffer
C-x m: Sending Mail
C-x n d: Narrowing
C-x n n: Narrowing
C-x n p: Narrowing
C-x n w: Narrowing
C-x o: Other Window
C-x q: Keyboard Macro Query
C-x r +: Number Registers
C-x r b: Bookmarks
C-x r c: Rectangles
C-x r d: Rectangles
C-x r f: Configuration Registers
C-x r i: Text Registers
C-x r j: Position Registers
C-x r k: Rectangles
C-x r l: Bookmarks
C-x r m: Bookmarks
C-x r M: Bookmarks
C-x r M-w: Rectangles
C-x r N: Rectangles
C-x r n: Number Registers
C-x r o: Rectangles
C-x r r: Rectangle Registers
C-x r s: Text Registers
C-x r SPC: Position Registers
C-x r t: Rectangles
C-x r w: Configuration Registers
C-x r y: Rectangles
C-x RET: International Chars
C-x RET c: Text Coding
C-x RET C-\: Select Input Method
C-x RET f: Text Coding
C-x RET F: File Name Coding
C-x RET k: Terminal Coding
C-x RET p: Communication Coding
C-x RET r: Text Coding
C-x RET t: Terminal Coding
C-x RET x: Communication Coding
C-x RET X: Communication Coding
C-x RIGHT: Select Buffer
C-x s: Save Commands
C-x t: Tab Bars
C-x t 0: Tab Bars
C-x t 1: Tab Bars
C-x t 2: Tab Bars
C-x t b: Tab Bars
C-x t C-f (FFAP): FFAP
C-x t d: Tab Bars
C-x t f: Tab Bars
C-x t m: Tab Bars
C-x t o: Tab Bars
C-x t r: Tab Bars
C-x t RET: Tab Bars
C-x t t: Tab Bars
C-x TAB: Indentation Commands
C-x TAB (Enriched mode): Enriched Indentation
C-x u: Undo
C-x v !: Editing VC Commands
C-x v +: Pulling / Pushing
C-x v =: Old Revisions
C-x v a: Change Logs and VC
C-x v b c: Creating Branches
C-x v b l: VC Change Log
C-x v b s: Switching Branches
C-x v D: Old Revisions
C-x v d: VC Directory Mode
C-x v g: Old Revisions
C-x v G: VC Ignore
C-x v h: VC Change Log
C-x v i: Registering
C-x v I: VC Change Log
C-x v l: VC Change Log
C-x v L: VC Change Log
C-x v O: VC Change Log
C-x v P: Pulling / Pushing
C-x v r: Revision Tags
C-x v s: Revision Tags
C-x v u: VC Undo
C-x v v: Basic VC Editing
C-x v ~: Old Revisions
C-x w .: Highlight Interactively
C-x w b: Highlight Interactively
C-x w h: Highlight Interactively
C-x w i: Highlight Interactively
C-x w l: Highlight Interactively
C-x w p: Highlight Interactively
C-x w r: Highlight Interactively
C-x x g: Reverting
C-x x i: Misc Buffer
C-x x r: Misc Buffer
C-x x t: Line Truncation
C-x x u: Misc Buffer
C-x z: Repeating
C-x [: Pages
C-x [ (Calendar mode): Calendar Unit Motion
C-x [ (DocView mode): DocView Navigation
C-x \: Select Input Method
C-x ]: Pages
C-x ] (Calendar mode): Calendar Unit Motion
C-x ] (DocView mode): DocView Navigation
C-x ^: Change Window
C-x `: Compilation Mode
C-x }: Change Window
C-y: Yanking
C-y (Incremental search): Isearch Yank
C-z: Exiting
C-z (X windows): Frame Commands
C-\: Select Input Method
C-]: Quitting
C-^ (Incremental Search): Special Isearch
C-_: Undo
C-_ (Dired): Marks vs Flags

D
d (Buffer Menu): Several Buffers
d (Calendar mode): Displaying the Diary
d (Dired): Dired Deletion
D (Dired): Operating on Files
D (GDB Breakpoints buffer): Breakpoints Buffer
D (GDB speedbar): Watch Expressions
d (GDB threads buffer): Threads Buffer
d (Package Menu): Package Menu
d (Rmail): Rmail Deletion
DEL (and major modes): Major Modes
DEL (Buffer Menu): Several Buffers
DEL (Dired): Dired Deletion
DEL (DocView mode): DocView Navigation
DEL (Gnus Group mode): Gnus Group Buffer
DEL (Gnus Summary mode): Gnus Summary Buffer
DEL (Incremental search): Basic Isearch
DEL (MS-DOS): MS-DOS Keyboard
DEL (programming modes): Program Modes
DEL (Rmail): Rmail Scrolling
DEL (View mode): View Mode
DOWN: Moving Point
DOWN (minibuffer history): Minibuffer History
Down-mouse-3: Menu Mouse Clicks

E
e (Dired): Dired Visiting
e (Rmail): Rmail Editing
e (View mode): View Mode
END: Moving Point
ESC ESC ESC: Quitting
ESC ESC ESC (Incremental Search): Basic Isearch

F
f (Buffer Menu): Several Buffers
f (Dired): Dired Visiting
f (GDB threads buffer): Threads Buffer
f (Rmail): Rmail Reply
F1: Help
F10: Menu Bar
F11: Frame Commands
F2 1: Two-Column
F2 2: Two-Column
F2 b: Two-Column
F2 d: Two-Column
F2 RET: Two-Column
F2 s: Two-Column
F3: Basic Keyboard Macro
F4: Basic Keyboard Macro

G
G (Dired): Operating on Files
g (Dired): Dired Updating
g (Package Menu): Package Menu
g (Rmail): Rmail Files
g char (Calendar mode): From Other Calendar
g d (Calendar mode): Specified Dates
g D (Calendar mode): Specified Dates
g m (Calendar mode): Mayan Calendar
g w (Calendar mode): Specified Dates

H
H (Calendar mode): Writing Calendar Files
h (Calendar mode): Holidays
H (Dired): Operating on Files
h (Package Menu): Package Menu
H (Package Menu): Package Menu
h (Rmail): Rmail Make Summary
HOME: Moving Point

I
I (Dired): Operating on Files
i (Dired): Subdirectories in Dired
i (Package Menu): Package Menu
i (Rmail): Rmail Files
i + (Image mode): Image Mode
i - (Image mode): Image Mode
i a (Calendar mode): Special Diary Entries
i b (Calendar mode): Special Diary Entries
i c (Calendar mode): Special Diary Entries
i c (Image mode): Image Mode
i d (Calendar mode): Adding to Diary
i h (Image mode): Image Mode
i m (Calendar mode): Adding to Diary
i o (Image mode): Image Mode
i r (Image mode): Image Mode
i v (Image mode): Image Mode
i w (Calendar mode): Adding to Diary
i x (Image mode): Image Mode
i y (Calendar mode): Adding to Diary
INSERT: Minor Modes

J
j (Dired): Dired Navigation
j (Rmail): Rmail Motion

K
k (Dired): Dired Updating
k (Rmail): Rmail Labels

L
L (Dired): Operating on Files
l (Dired): Dired Updating
l (GDB threads buffer): Threads Buffer
l (Gnus Group mode): Gnus Group Buffer
L (Gnus Group mode): Gnus Group Buffer
l (Help mode): Help Mode
l (Rmail): Rmail Make Summary
LEFT: Moving Point
LEFT, and bidirectional text: Bidirectional Editing

M
m (Buffer Menu): Several Buffers
M (Calendar mode): Lunar Phases
m (Calendar mode): Displaying the Diary
m (Dired): Marks vs Flags
M (Dired): Operating on Files
m (Rmail): Rmail Reply
M-!: Single Shell
M-$: Spelling
M-$ (Dired): Hiding Subdirectories
M-%: Query Replace
M-% (Incremental search): Special Isearch
M-&: Single Shell
M-': Expanding Abbrevs
M-,: Looking Up Identifiers
M--: Arguments
M-- M-c: Fixing Case
M-- M-l: Fixing Case
M-- M-u: Fixing Case
M-.: Looking Up Identifiers
M-/: Dynamic Abbrevs
M-0, tab bar: Tab Bars
M-1: Arguments
M-1, tab bar: Tab Bars
M-9, tab bar: Tab Bars
M-:: Lisp Eval
M-;: Comment Commands
M-<: Moving Point
M-< (Calendar mode): Move to Beginning or End
M-< (DocView mode): DocView Navigation
M-=: Position Info
M-= (Calendar mode): Counting Days
M->: Moving Point
M-> (Calendar mode): Move to Beginning or End
M-> (DocView mode): DocView Navigation
M-?: Identifier Search
M-? (Nroff mode): Nroff Mode
M-? (Shell mode): Shell Mode
M-@: Marking Objects
M-@: Words
M-a: Sentences
M-a (C mode): Motion in C
M-a (Calendar mode): Move to Beginning or End
M-b: Words
M-c: Case
M-c (Incremental search): Lax Search
M-d: Words
M-DEL: Words
M-DEL (Buffer Menu): Several Buffers
M-DEL (Dired): Marks vs Flags
M-DOWN: Completion Commands
M-DOWN (Org Mode): Org Mode
M-Drag-mouse-1: Secondary Selection
M-e: Sentences
M-e (C mode): Motion in C
M-e (Calendar mode): Move to Beginning or End
M-e (Incremental search): Repeat Isearch
M-f: Words
M-F10: Frame Commands
M-G (Dired): Subdirectory Motion
M-g c: Moving Point
M-g g: Moving Point
M-g M-g: Moving Point
M-g M-n: Compilation Mode
M-g n: Compilation Mode
M-g TAB: Moving Point
M-h: Paragraphs
M-i: Indentation Commands
M-j: Multi-Line Comments
M-j b (Enriched mode): Enriched Justification
M-j c (Enriched mode): Enriched Justification
M-j l (Enriched mode): Enriched Justification
M-j r (Enriched mode): Enriched Justification
M-j u (Enriched mode): Enriched Justification
M-k: Sentences
M-l: Case
M-LEFT: Moving Point
M-LEFT (Org Mode): Org Mode
M-m: Indentation Commands
M-m (Rmail): Rmail Reply
M-mouse-1: Secondary Selection
M-mouse-2: Secondary Selection
M-mouse-3: Secondary Selection
M-n (Incremental search): Repeat Isearch
M-n (Log Edit mode): Log Buffer
M-n (Man mode): Man Page
M-n (minibuffer history): Minibuffer History
M-n (Nroff mode): Nroff Mode
M-n (Rmail): Rmail Motion
M-n (Shell mode): Shell Ring
M-o b (Enriched mode): Enriched Faces
M-o d (Enriched mode): Enriched Faces
M-o i (Enriched mode): Enriched Faces
M-o l (Enriched mode): Enriched Faces
M-o o (Enriched mode): Enriched Faces
M-o u (Enriched mode): Enriched Faces
M-p (Incremental search): Repeat Isearch
M-p (Log Edit mode): Log Buffer
M-p (Man mode): Man Page
M-p (minibuffer history): Minibuffer History
M-p (Nroff mode): Nroff Mode
M-p (Rmail): Rmail Motion
M-p (Shell mode): Shell Ring
M-q: Fill Commands
M-q (C mode): Other C Commands
M-q (Fortran mode): ForIndent Commands
M-r: Moving Point
M-r (Incremental Search): Special Isearch
M-r (Log Edit mode): Log Buffer
M-r (minibuffer history): Minibuffer History
M-r (Shell mode): Shell Ring
M-RET: Completion Commands
M-RIGHT: Moving Point
M-RIGHT (Org Mode): Org Mode
M-s ' (Incremental Search): Lax Search
M-S (Enriched mode): Enriched Justification
M-s (Log Edit mode): Log Buffer
M-s (minibuffer history): Minibuffer History
M-s (Rmail): Rmail Motion
M-s .: Symbol Search
M-s a C-s (Dired): Misc Dired Features
M-s a M-C-s (Dired): Misc Dired Features
M-s c (Incremental search): Lax Search
M-s C-e (Incremental search): Isearch Yank
M-s f C-s (Dired): Dired Navigation
M-s f M-C-s (Dired): Dired Navigation
M-s h .: Highlight Interactively
M-s h f: Highlight Interactively
M-s h l: Highlight Interactively
M-s h l (Incremental Search): Special Isearch
M-s h p: Highlight Interactively
M-s h r: Highlight Interactively
M-s h r (Incremental Search): Special Isearch
M-s h u: Highlight Interactively
M-s h w: Highlight Interactively
M-s i (Incremental search): Special Isearch
M-s M-.: Isearch Yank
M-s M-<: Special Isearch
M-s M->: Special Isearch
M-s M-r (Gnus Summary mode): Gnus Summary Buffer
M-s M-s (Gnus Summary mode): Gnus Summary Buffer
M-s M-w: Word Search
M-s o: Other Repeating Search
M-s o (Incremental Search): Special Isearch
M-s r (Incremental Search): Special Isearch
M-s SPC (Incremental search): Lax Search
M-s w: Word Search
M-s _: Symbol Search
M-S-x: M-x
M-SPC: Deletion
M-t: Transpose
M-TAB: Symbol Completion
M-TAB (customization buffer): Changing a Variable
M-TAB (Incremental search): Special Isearch
M-TAB (Picture mode): Tabs in Picture
M-TAB (Text mode): Text Mode
M-TAB, (MS-Windows): Windows Keyboard
M-u: Case
M-UP: Completion Commands
M-UP (Org Mode): Org Mode
M-v: Moving Point
M-v: Scrolling
M-v (Calendar mode): Scroll Calendar
M-w: Other Kill Commands
M-x: M-x
M-X: M-x
M-y: Earlier Kills
M-y (Incremental search): Isearch Yank
M-z: Other Kill Commands
M-\: Deletion
M-^: Indentation Commands
M-^ (Fortran mode): ForIndent Commands
M-`: Menu Bar
M-{: Paragraphs
M-{ (Calendar mode): Calendar Unit Motion
M-{ (Dired): Marks vs Flags
M-|: Single Shell
M-}: Paragraphs
M-} (Calendar mode): Calendar Unit Motion
M-} (Dired): Marks vs Flags
M-~: Save Commands
mouse-1: Mouse Commands
mouse-1 (mode line): Mode Line Mouse
mouse-1 (on buttons): Mouse References
mouse-1 (scroll bar): Mode Line Mouse
mouse-1 in the minibuffer (Incremental Search): Repeat Isearch
mouse-2: Mouse Commands
mouse-2 (GDB Breakpoints buffer): Breakpoints Buffer
mouse-2 (mode line): Mode Line Mouse
mouse-2 (on buttons): Mouse References
mouse-2 in the minibuffer (Incremental search): Isearch Yank
mouse-3: Mouse Commands
mouse-3 (mode line): Mode Line Mouse

N
N (Dired): Operating on Files
n (DocView mode): DocView Navigation
n (Gnus Group mode): Gnus Group Buffer
n (Gnus Summary mode): Gnus Summary Buffer
n (Help mode): Help Mode
n (Rmail): Rmail Motion
next: Moving Point
next: Scrolling
next (Calendar mode): Scroll Calendar
next (DocView mode): DocView Navigation

O
o (Buffer Menu): Several Buffers
o (Calendar mode): Specified Dates
o (Dired): Dired Visiting
O (Dired): Operating on Files
o (Occur mode): Other Repeating Search
o (Rmail): Rmail Output

P
p (Calendar mode): To Other Calendar
P (Dired): Operating on Files
p (DocView mode): DocView Navigation
p (Gnus Group mode): Gnus Group Buffer
p (Gnus Summary mode): Gnus Summary Buffer
p (Help mode): Help Mode
p (Rmail): Rmail Motion
p d (Calendar mode): General Calendar
PageDown: Moving Point
PageDown: Scrolling
PageDown (Calendar mode): Scroll Calendar
PageDown (DocView mode): DocView Navigation
PageUp: Moving Point
PageUp: Scrolling
PageUp (Calendar mode): Scroll Calendar
PageUp (DocView mode): DocView Navigation
prior: Moving Point
prior: Scrolling
prior (Calendar mode): Scroll Calendar
prior (DocView mode): DocView Navigation

Q
q (Buffer Menu): Several Buffers
q (Calendar mode): General Calendar
q (Dired): Dired Enter
Q (Dired): Operating on Files
q (Gnus Group mode): Gnus Group Buffer
q (Gnus Summary mode): Gnus Summary Buffer
Q (Rmail summary): Rmail Summary Edit
q (Rmail summary): Rmail Summary Edit
q (Rmail): Rmail Basics
q (View mode): View Mode

R
R (Dired): Operating on Files
r (GDB threads buffer): Threads Buffer
r (Help mode): Help Mode
r (Package Menu): Package Menu
r (Rmail): Rmail Reply
RET: Inserting Text
RET (Buffer Menu): Several Buffers
RET (completion in minibuffer): Completion Exit
RET (Dired): Dired Visiting
RET (GDB Breakpoints buffer): Breakpoints Buffer
RET (GDB speedbar): Watch Expressions
RET (Help mode): Help Mode
RET (Incremental search): Basic Isearch
RET (Occur mode): Other Repeating Search
RET (Package Menu): Package Menu
RET (Shell mode): Shell Mode
RIGHT: Moving Point
RIGHT, and bidirectional text: Bidirectional Editing

S
s (Buffer Menu): Several Buffers
S (Buffer Menu): Several Buffers
S (Calendar mode): Sunrise/Sunset
s (Calendar mode): Displaying the Diary
S (Dired): Operating on Files
s (Dired): Dired Updating
s (Gnus Summary mode): Gnus Summary Buffer
s (Rmail): Rmail Basics
s (View mode): View Mode
s 0 (Image mode): Image Mode
s o (Image mode): Image Mode
s p (Image mode): Image Mode
s s (Image mode): Image Mode
s w (Image mode): Image Mode
S-C-TAB: Tab Bars
S-F10: Menu Mouse Clicks
S-mouse-2: Hideshow
S-mouse-3 (FFAP): FFAP
S-SPC (Rmail): Rmail Scrolling
S-TAB (customization buffer): Customization Groups
S-TAB (Help mode): Help Mode
S-TAB (Org Mode): Org Mode
SPC (Calendar mode): General Calendar
SPC (completion): Completion Commands
SPC (Dired): Dired Navigation
SPC (DocView mode): DocView Navigation
SPC (GDB Breakpoints buffer): Breakpoints Buffer
SPC (Gnus Group mode): Gnus Group Buffer
SPC (Gnus Summary mode): Gnus Summary Buffer
SPC (Incremental search): Lax Search
SPC (Rmail): Rmail Scrolling
SPC (View mode): View Mode

T
t (Buffer Menu): Several Buffers
T (Buffer Menu): Several Buffers
t (Calendar mode): Writing Calendar Files
t (Dired): Marks vs Flags
T (Dired): Operating on Files
t (Rmail): Rmail Display
TAB (and major modes): Major Modes
TAB (completion example): Completion Example
TAB (completion): Completion Commands
TAB (customization buffer): Customization Groups
TAB (GUD): Commands of GUD
TAB (Help mode): Help Mode
TAB (indentation): Indentation
TAB (Message mode): Header Editing
TAB (Org Mode): Org Mode
TAB (programming modes): Basic Indent
TAB (Shell mode): Shell Mode
TAB (Text mode): Text Mode
TAB, when using Chinese input methods: Input Methods

U
u (Buffer Menu): Several Buffers
U (Buffer Menu): Several Buffers
u (Calendar mode): Holidays
u (Dired deletion): Dired Deletion
u (Dired): Marks vs Flags
U (Dired): Marks vs Flags
u (Gnus Group mode): Gnus Group Buffer
u (Package Menu): Package Menu
U (Package Menu): Package Menu
u (Rmail): Rmail Deletion
UP: Moving Point
UP (minibuffer history): Minibuffer History

V
v (Buffer Menu): Several Buffers
v (Dired): Dired Visiting
v (Rmail): Rmail Display

W
w (Dired): Misc Dired Features
W (Dired): Misc Dired Features
w (Package Menu): Package Menu
w (Rmail): Rmail Output

X
x (Buffer Menu): Several Buffers
x (Calendar mode): Holidays
x (Dired): Dired Deletion
X (Dired): Shell Commands in Dired
x (Package Menu): Package Menu
x (Rmail): Rmail Deletion

Y
Y (Dired): Operating on Files

Z
Z (Dired): Operating on Files


Command-Line Options Index

Jump to:   +   -
Index Entry  Section

+
+linenum: Action Arguments

-
--background-color: Colors X
--basic-display: Misc X
--batch: Initial Options
--border-color: Colors X
--border-width: Borders X
--chdir: Initial Options
--color: Colors X
--cursor-color: Colors X
--daemon: Initial Options
--debug-init: Initial Options
--directory: Action Arguments
--display: Initial Options
--dump-file: Initial Options
--eval: Action Arguments
--execute: Action Arguments
--file: Action Arguments
--find-file: Action Arguments
--fingerprint: Action Arguments
--font: Font X
--foreground-color: Colors X
--fullheight: Window Size X
--fullscreen: Window Size X
--fullwidth: Window Size X
--funcall: Action Arguments
--geometry: Window Size X
--help: Action Arguments
--iconic: Icons X
--init-directory: Initial Options
--insert: Action Arguments
--internal-border: Borders X
--kill: Action Arguments
--line-spacing: Misc X
--load: Action Arguments
--maximized: Window Size X
--module-assertions: Initial Options
--mouse-color: Colors X
--name: Resources
--no-bitmap-icon: Icons X
--no-blinking-cursor: Misc X
--no-build-details: Initial Options
--no-desktop: Initial Options
--no-init-file: Initial Options
--no-site-file: Initial Options
--no-site-lisp: Initial Options
--no-splash: Initial Options
--no-window-system: Initial Options
--no-x-resources: Initial Options
--quick: Initial Options
--reverse-video: Colors X
--script: Initial Options
--terminal: Initial Options
--title: Title X
--user: Initial Options
--version: Action Arguments
--vertical-scroll-bars: Misc X
--visit: Action Arguments
--xrm: Resources
-bd: Colors X
-bg: Colors X
-bw: Borders X
-chdir: Initial Options
-cr: Colors X
-d: Initial Options
-D: Misc X
-daemon: Initial Options
-f: Action Arguments
-fg: Colors X
-fh: Window Size X
-fn: Font X
-fs: Window Size X
-fw: Window Size X
-g: Window Size X
-ib: Borders X
-l: Action Arguments
-L: Action Arguments
-lsp: Misc X
-mm: Window Size X
-ms: Colors X
-nbc: Misc X
-nbi: Icons X
-nsl: Initial Options
-nw: Initial Options
-q: Initial Options
-Q: Initial Options
-r: Colors X
-rv: Colors X
-t: Initial Options
-T: Title X
-u: Initial Options
-vb: Misc X
-x: Initial Options


Command and Function Index

Jump to:   2   5  
A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z  
Index Entry  Section

2
2C-associate-buffer: Two-Column
2C-dissociate: Two-Column
2C-merge: Two-Column
2C-newline: Two-Column
2C-split: Two-Column
2C-two-columns: Two-Column

5
5x5: Amusements

A
abbrev-mode: Abbrev Concepts
abbrev-prefix-mark: Expanding Abbrevs
abbrev-suggest-show-report: Abbrevs Suggestions
abort-recursive-edit: Quitting
activate-transient-input-method: Select Input Method
add-change-log-entry-other-window: Change Log Commands
add-change-log-entry-other-window, in Diff mode: Diff Mode
add-dir-local-variable: Directory Variables
add-file-local-variable: Specifying File Variables
add-file-local-variable-prop-line: Specifying File Variables
add-global-abbrev: Defining Abbrevs
add-hook: Hooks
add-mode-abbrev: Defining Abbrevs
add-name-to-file: Copying and Naming
align: Code Alignment
align-current: Code Alignment
align-entire: Code Alignment
align-highlight-rule: Code Alignment
align-regexp: Code Alignment
align-unhighlight-rule: Code Alignment
animate-birthday-present: Amusements
append-next-kill: Appending Kills
append-to-buffer: Accumulating Text
append-to-file: Accumulating Text
append-to-register: Text Registers
apply-macro-to-region-lines: Basic Keyboard Macro
appt-activate: Appointments
appt-add: Appointments
appt-delete: Appointments
apropos: Apropos
apropos-command: Apropos
apropos-documentation: Apropos
apropos-local-value: Apropos
apropos-local-variable: Apropos
apropos-user-option: Apropos
apropos-value: Apropos
apropos-variable: Apropos
ask-user-about-lock: Interlocking
async-shell-command: Single Shell
auto-compression-mode: Compressed Files
auto-fill-mode: Auto Fill
auto-revert-mode: Auto Revert
auto-revert-tail-mode: Auto Revert
auto-save-mode: Auto Save Control

B
back-to-indentation: Indentation Commands
backward-button: Help Mode
backward-char: Moving Point
backward-delete-char-untabify: Program Modes
backward-kill-sentence: Sentences
backward-kill-word: Words
backward-list: Moving by Parens
backward-page: Pages
backward-paragraph: Paragraphs
backward-sentence: Sentences
backward-sexp: Expressions
backward-up-list: Moving by Parens
backward-word: Words
balance-windows: Change Window
beginning-of-buffer: Moving Point
beginning-of-defun: Moving by Defuns
beginning-of-visual-line: Visual Line Mode
bibtex-mode: TeX Mode
binary-overwrite-mode: Minor Modes
blackbox: Amusements
blink-cursor-mode: Cursor Display
bookmark-delete: Bookmarks
bookmark-insert: Bookmarks
bookmark-insert-location: Bookmarks
bookmark-jump: Bookmarks
bookmark-load: Bookmarks
bookmark-save: Bookmarks
bookmark-set: Bookmarks
bookmark-set-no-overwrite: Bookmarks
bookmark-write: Bookmarks
browse-url: Browse-URL
browse-url-at-mouse: Browse-URL
browse-url-at-point: Browse-URL
browse-url-of-dired-file: Misc Dired Features
bs-customize: Buffer Menus
bs-show: Buffer Menus
bubbles: Amusements
buffer-menu: Several Buffers
Buffer-menu-1-window: Several Buffers
Buffer-menu-2-window: Several Buffers
Buffer-menu-backup-unmark: Several Buffers
Buffer-menu-bury: Several Buffers
Buffer-menu-delete: Several Buffers
Buffer-menu-delete-backwards: Several Buffers
Buffer-menu-execute: Several Buffers
Buffer-menu-mark: Several Buffers
Buffer-menu-not-modified: Several Buffers
buffer-menu-other-window: Several Buffers
Buffer-menu-other-window: Several Buffers
Buffer-menu-save: Several Buffers
Buffer-menu-select: Several Buffers
Buffer-menu-switch-other-window: Several Buffers
Buffer-menu-this-window: Several Buffers
Buffer-menu-toggle-files-only: Several Buffers
Buffer-menu-toggle-read-only: Several Buffers
Buffer-menu-unmark: Several Buffers
Buffer-menu-unmark-all: Several Buffers
Buffer-menu-unmark-all-buffers: Several Buffers
Buffer-menu-visit-tags-table: Several Buffers
bug-reference-mode: Bug Reference
bug-reference-prog-mode: Bug Reference
butterfly: Amusements
button-describe: Key Help

C
c-backslash-region: Other C Commands
c-backward-conditional: Motion in C
c-beginning-of-defun: Motion in C
c-beginning-of-statement: Motion in C
c-context-line-break: Other C Commands
c-end-of-defun: Motion in C
c-end-of-statement: Motion in C
c-fill-paragraph: Other C Commands
c-forward-conditional: Motion in C
c-guess: Custom C Indent
c-guess-install: Custom C Indent
c-hungry-delete-backwards: Hungry Delete
c-hungry-delete-forward: Hungry Delete
c-indent-defun: C Indent
c-indent-exp: C Indent
c-indent-line-or-region: C Indent
c-macro-expand: Other C Commands
c-mark-function: Moving by Defuns
c-set-style: Custom C Indent
c-show-syntactic-information: Other C Commands
c-toggle-auto-newline: Electric C
c-toggle-electric-state: Electric C
c-toggle-hungry-state: Hungry Delete
c-ts-mode-indent-defun: C Indent
c-ts-mode-set-style: Custom C Indent
c-up-conditional: Motion in C
calendar: Calendar/Diary
calendar-astro-goto-day-number: From Other Calendar
calendar-astro-print-day-number: To Other Calendar
calendar-backward-day: Calendar Unit Motion
calendar-backward-month: Calendar Unit Motion
calendar-backward-week: Calendar Unit Motion
calendar-backward-year: Calendar Unit Motion
calendar-bahai-goto-date: From Other Calendar
calendar-bahai-print-date: To Other Calendar
calendar-beginning-of-month: Move to Beginning or End
calendar-beginning-of-week: Move to Beginning or End
calendar-beginning-of-year: Move to Beginning or End
calendar-chinese-goto-date: From Other Calendar
calendar-chinese-print-date: To Other Calendar
calendar-coptic-goto-date: From Other Calendar
calendar-coptic-print-date: To Other Calendar
calendar-count-days-region: Counting Days
calendar-cursor-holidays: Holidays
calendar-end-of-month: Move to Beginning or End
calendar-end-of-week: Move to Beginning or End
calendar-end-of-year: Move to Beginning or End
calendar-ethiopic-goto-date: From Other Calendar
calendar-ethiopic-print-date: To Other Calendar
calendar-forward-day: Calendar Unit Motion
calendar-forward-month: Calendar Unit Motion
calendar-forward-week: Calendar Unit Motion
calendar-forward-year: Calendar Unit Motion
calendar-french-goto-date: From Other Calendar
calendar-french-print-date: To Other Calendar
calendar-goto-date: Specified Dates
calendar-goto-day-of-year: Specified Dates
calendar-goto-today: Specified Dates
calendar-hebrew-goto-date: From Other Calendar
calendar-hebrew-list-yahrzeits: From Other Calendar
calendar-hebrew-print-date: To Other Calendar
calendar-islamic-goto-date: From Other Calendar
calendar-islamic-print-date: To Other Calendar
calendar-iso-goto-date: From Other Calendar
calendar-iso-goto-week: Specified Dates
calendar-iso-print-date: To Other Calendar
calendar-julian-goto-date: From Other Calendar
calendar-julian-print-date: To Other Calendar
calendar-list-holidays: Holidays
calendar-lunar-phases: Lunar Phases
calendar-mark-holidays: Holidays
calendar-mark-today: Calendar Customizing
calendar-mayan-goto-long-count-date: Mayan Calendar
calendar-mayan-next-calendar-round-date: Mayan Calendar
calendar-mayan-next-haab-date: Mayan Calendar
calendar-mayan-next-tzolkin-date: Mayan Calendar
calendar-mayan-previous-haab-date: Mayan Calendar
calendar-mayan-previous-tzolkin-date: Mayan Calendar
calendar-mayan-print-date: To Other Calendar
calendar-other-month: Specified Dates
calendar-persian-goto-date: From Other Calendar
calendar-persian-print-date: To Other Calendar
calendar-print-day-of-year: General Calendar
calendar-print-other-dates: To Other Calendar
calendar-redraw: General Calendar
calendar-scroll-left: Scroll Calendar
calendar-scroll-left-three-months: Scroll Calendar
calendar-scroll-right: Scroll Calendar
calendar-scroll-right-three-months: Scroll Calendar
calendar-set-date-style: Date Formats
calendar-star-date: Calendar Customizing
calendar-sunrise-sunset: Sunrise/Sunset
calendar-unmark: Holidays
capitalize-word: Case
category-set-mnemonics: Visual Line Mode
cd: File Names
center-line: Fill Commands
change-log-goto-source: Change Log Commands
change-log-merge: Change Log Commands
change-log-mode: Change Log Commands
char-category-set: Visual Line Mode
check-parens: Parentheses
choose-completion: Completion Commands
clean-buffer-list: Kill Buffer
clear-rectangle: Rectangles
clipboard-kill-region: Clipboard
clipboard-kill-ring-save: Clipboard
clipboard-yank: Clipboard
clone-frame: Creating Frames
clone-indirect-buffer: Indirect Buffers
clone-indirect-buffer-other-window: Indirect Buffers
column-number-mode: Optional Mode Line
comint-bol-or-process-mark: Shell Mode
comint-continue-subjob: Shell Mode
comint-copy-old-input: Shell History Copying
comint-delchar-or-maybe-eof: Shell Mode
comint-delete-output: Shell Mode
comint-dynamic-list-filename…: Shell Mode
comint-dynamic-list-input-ring: Shell Ring
comint-get-next-from-history: Shell Ring
comint-history-isearch-backward-regexp: Shell Ring
comint-insert-previous-argument: Shell Ring
comint-interrupt-subjob: Shell Mode
comint-kill-input: Shell Mode
comint-magic-space: History References
comint-next-input: Shell Ring
comint-next-prompt: Shell History Copying
comint-previous-input: Shell Ring
comint-previous-prompt: Shell History Copying
comint-quit-subjob: Shell Mode
comint-run: Shell Mode
comint-send-input: Shell Mode
comint-send-invisible: Shell Mode
comint-show-maximum-output: Shell Mode
comint-show-output: Shell Mode
comint-stop-subjob: Shell Mode
comint-strip-ctrl-m: Shell Mode
comint-truncate-buffer: Shell Mode
comint-write-output: Shell Mode
command-query: Disabling
comment-dwim: Comment Commands
comment-kill: Comment Commands
comment-line: Comment Commands
comment-region: Comment Commands
comment-set-column: Options for Comments
compare-windows: Comparing Files
compilation-next-error: Compilation Mode
compilation-next-file: Compilation Mode
compilation-previous-error: Compilation Mode
compilation-previous-file: Compilation Mode
compile: Compilation
compile (MS-DOS): MS-DOS Processes
compile-goto-error: Compilation Mode
completion-at-point, in programming language modes: Symbol Completion
completion-at-point, in Shell Mode: Shell Mode
compose-mail: Sending Mail
compose-mail-other-frame: Sending Mail
compose-mail-other-window: Sending Mail
connection-local-set-profile-variables: Connection Variables
connection-local-set-profiles: Connection Variables
context-menu-mode: Menu Mouse Clicks
copy-dir-locals-to-file-locals: Specifying File Variables
copy-dir-locals-to-file-locals-prop-line: Specifying File Variables
copy-directory: Copying and Naming
copy-file: Copying and Naming
copy-file-locals-to-dir-locals: Directory Variables
copy-matching-lines: Other Repeating Search
copy-rectangle-as-kill: Rectangles
copy-rectangle-to-register: Rectangle Registers
copy-to-buffer: Accumulating Text
copy-to-register: Text Registers
count-lines-page: Pages
count-words: Position Info
count-words-region: Position Info
cpp-highlight-buffer: Other C Commands
create-fontset-from-fontset-spec: Defining Fontsets
cua-mode: CUA Bindings
custom-prompt-customize-unsaved-options: Saving Customizations
Custom-save: Changing a Variable
Custom-set: Changing a Variable
customize: Easy Customization
customize-apropos: Specific Customization
customize-browse: Browsing Custom
customize-changed: Specific Customization
customize-create-theme: Creating Custom Themes
customize-face: Specific Customization
customize-group: Specific Customization
customize-option: Specific Customization
customize-saved: Specific Customization
customize-themes: Custom Themes
customize-unsaved: Specific Customization
cwarn-mode: Other C Commands
cycle-spacing: Deletion

D
dabbrev-completion: Dynamic Abbrevs
dabbrev-expand: Dynamic Abbrevs
dbx: Starting GUD
debbugs-browse-mode: Bug Reference
debug_print: Checklist
decipher: Amusements
default-indent-new-line: Multi-Line Comments
default-value: Locals
define-abbrevs: Saving Abbrevs
define-global-abbrev: Defining Abbrevs
define-key: Init Rebinding
define-mail-abbrev: Mail Aliases
define-mail-user-agent: Mail Methods
define-mode-abbrev: Defining Abbrevs
delete-backward-char: Deletion
delete-blank-lines: Blank Lines
delete-char: Deletion
delete-dir-local-variable: Directory Variables
delete-duplicate-lines: Deletion
delete-file: Misc File Ops
delete-file-local-variable: Specifying File Variables
delete-file-local-variable-prop-line: Specifying File Variables
delete-frame: Frame Commands
delete-horizontal-space: Deletion
delete-indentation: Indentation Commands
delete-other-frames: Frame Commands
delete-other-windows: Change Window
delete-rectangle: Rectangles
delete-selection-mode: Using Region
delete-trailing-whitespace: Useless Whitespace
delete-whitespace-rectangle: Rectangles
delete-window: Change Window
describe-bindings: Misc Help
describe-categories: Regexp Backslash
describe-char: International Chars
describe-character-set: Charsets
describe-coding-system: Coding Systems
describe-command: Name Help
describe-copying: Help Files
describe-distribution: Help Files
describe-fontset: Fontsets
describe-function: Name Help
describe-gnu-project: Help Files
describe-input-method: Select Input Method
describe-key: Key Help
describe-key-briefly: Key Help
describe-keymap: Misc Help
describe-language-environment: Language Environments
describe-mode: Misc Help
describe-no-warranty: Help Files
describe-package: Package Keywords
describe-prefix-bindings: Misc Help
describe-repeat-maps: Repeating
describe-symbol: Name Help
describe-syntax: Misc Help
describe-text-properties: Editing Format Info
describe-theme: Custom Themes
describe-variable: Name Help
desktop-change-dir: Saving Emacs Sessions
desktop-clear: Saving Emacs Sessions
desktop-read: Saving Emacs Sessions
desktop-revert: Saving Emacs Sessions
desktop-save: Saving Emacs Sessions
desktop-save-mode: Saving Emacs Sessions
diary: Displaying the Diary
diary-anniversary: Special Diary Entries
diary-anniversary, and sexp diary entries: Sexp Diary Entries
diary-astro-day-number: Sexp Diary Entries
diary-bahai-date: Sexp Diary Entries
diary-bahai-insert-entry: Non-Gregorian Diary
diary-bahai-insert-monthly-entry: Non-Gregorian Diary
diary-bahai-insert-yearly-entry: Non-Gregorian Diary
diary-bahai-list-entries: Non-Gregorian Diary
diary-bahai-mark-entries: Non-Gregorian Diary
diary-block: Special Diary Entries
diary-chinese-date: Sexp Diary Entries
diary-chinese-insert-anniversary-entry: Non-Gregorian Diary
diary-chinese-insert-entry: Non-Gregorian Diary
diary-chinese-insert-monthly-entry: Non-Gregorian Diary
diary-chinese-insert-yearly-entry: Non-Gregorian Diary
diary-chinese-list-entries: Non-Gregorian Diary
diary-chinese-mark-entries: Non-Gregorian Diary
diary-coptic-date: Sexp Diary Entries
diary-cyclic: Special Diary Entries
diary-cyclic, and sexp diary entries: Sexp Diary Entries
diary-date: Sexp Diary Entries
diary-day-of-year: Sexp Diary Entries
diary-ethiopic-date: Sexp Diary Entries
diary-fancy-display: Diary Display
diary-float: Special Diary Entries
diary-float, and sexp diary entries: Sexp Diary Entries
diary-french-date: Sexp Diary Entries
diary-hebrew-birthday: Sexp Diary Entries
diary-hebrew-date: Sexp Diary Entries
diary-hebrew-insert-entry: Non-Gregorian Diary
diary-hebrew-insert-monthly-entry: Non-Gregorian Diary
diary-hebrew-insert-yearly-entry: Non-Gregorian Diary
diary-hebrew-list-entries: Non-Gregorian Diary
diary-hebrew-mark-entries: Non-Gregorian Diary
diary-hebrew-omer: Sexp Diary Entries
diary-hebrew-parasha: Sexp Diary Entries
diary-hebrew-rosh-hodesh: Sexp Diary Entries
diary-hebrew-sabbath-candles: Sexp Diary Entries
diary-hebrew-yahrzeit: Sexp Diary Entries
diary-include-other-diary-files: Fancy Diary Display
diary-insert-anniversary-entry: Special Diary Entries
diary-insert-block-entry: Special Diary Entries
diary-insert-cyclic-entry: Special Diary Entries
diary-insert-entry: Adding to Diary
diary-insert-monthly-entry: Adding to Diary
diary-insert-weekly-entry: Adding to Diary
diary-insert-yearly-entry: Adding to Diary
diary-islamic-date: Sexp Diary Entries
diary-islamic-insert-entry: Non-Gregorian Diary
diary-islamic-insert-monthly-entry: Non-Gregorian Diary
diary-islamic-insert-yearly-entry: Non-Gregorian Diary
diary-islamic-list-entries: Non-Gregorian Diary
diary-islamic-mark-entries: Non-Gregorian Diary
diary-iso-date: Sexp Diary Entries
diary-julian-date: Sexp Diary Entries
diary-lunar-phases: Sexp Diary Entries
diary-mail-entries: Displaying the Diary
diary-mark-entries: Displaying the Diary
diary-mark-included-diary-files: Fancy Diary Display
diary-mayan-date: Sexp Diary Entries
diary-offset: Special Diary Entries
diary-persian-date: Sexp Diary Entries
diary-print-entries: Diary Display
diary-remind: Sexp Diary Entries
diary-show-all-entries: Displaying the Diary
diary-simple-display: Diary Display
diary-sort-entries: Fancy Diary Display
diary-sunrise-sunset: Sexp Diary Entries
diary-view-entries: Displaying the Diary
diff: Comparing Files
diff-add-change-log-entries-other-window: Diff Mode
diff-apply-hunk: Diff Mode
diff-backup: Comparing Files
diff-buffer-with-file: Comparing Files
diff-buffers: Comparing Files
diff-context->unified: Diff Mode
diff-delete-trailing-whitespace: Diff Mode
diff-ediff-patch: Diff Mode
diff-file-kill: Diff Mode
diff-file-next: Diff Mode
diff-file-prev: Diff Mode
diff-goto-source: Diff Mode
diff-hunk-kill: Diff Mode
diff-hunk-next: Diff Mode
diff-hunk-prev: Diff Mode
diff-ignore-whitespace-hunk: Diff Mode
diff-mode: Diff Mode
diff-refine-hunk: Diff Mode
diff-refresh-hunk: Diff Mode
diff-restrict-view: Diff Mode
diff-reverse-direction: Diff Mode
diff-split-hunk: Diff Mode
diff-unified->context: Diff Mode
digit-argument: Arguments
dir-locals-set-class-variables: Directory Variables
dir-locals-set-directory-class: Directory Variables
dired: Dired Enter
dired-at-point: FFAP
dired-change-marks: Marks vs Flags
dired-clean-directory: Flagging Many Files
dired-compare-directories: Misc Dired Features
dired-copy-filename-as-kill: Misc Dired Features
dired-create-directory: Misc Dired Features
dired-create-empty-file: Misc Dired Features
dired-diff: Comparison in Dired
dired-display-file: Dired Visiting
dired-do-byte-compile: Operating on Files
dired-do-chgrp: Operating on Files
dired-do-chmod: Operating on Files
dired-do-chown: Operating on Files
dired-do-compress: Operating on Files
dired-do-compress-to: Operating on Files
dired-do-copy: Operating on Files
dired-do-copy-regexp: Transforming File Names
dired-do-delete: Operating on Files
dired-do-find-regexp: Operating on Files
dired-do-find-regexp-and-replace: Operating on Files
dired-do-flagged-delete: Dired Deletion
dired-do-hardlink: Operating on Files
dired-do-hardlink-regexp: Transforming File Names
dired-do-info: Operating on Files
dired-do-isearch: Misc Dired Features
dired-do-isearch-regexp: Misc Dired Features
dired-do-kill-lines: Dired Updating
dired-do-load: Operating on Files
dired-do-man: Operating on Files
dired-do-print: Operating on Files
dired-do-redisplay: Dired Updating
dired-do-relsymlink: Operating on Files
dired-do-relsymlink-regexp: Transforming File Names
dired-do-rename: Operating on Files
dired-do-rename-regexp: Transforming File Names
dired-do-shell-command: Shell Commands in Dired
dired-do-symlink: Operating on Files
dired-do-symlink-regexp: Transforming File Names
dired-do-touch: Operating on Files
dired-downcase: Transforming File Names
dired-find-file: Dired Visiting
dired-find-file-other-window: Dired Visiting
dired-flag-auto-save-files: Flagging Many Files
dired-flag-backup-files: Flagging Many Files
dired-flag-file-deletion: Dired Deletion
dired-flag-files-regexp: Flagging Many Files
dired-flag-garbage-files: Flagging Many Files
dired-goto-file: Dired Navigation
dired-goto-subdir: Subdirectory Motion
dired-hide-all: Hiding Subdirectories
dired-hide-details-mode: Misc Dired Features
dired-hide-subdir: Hiding Subdirectories
dired-isearch-filenames: Dired Navigation
dired-isearch-filenames-regexp: Dired Navigation
dired-jump: Dired Enter
dired-jump-other-window: Dired Enter
dired-mark: Marks vs Flags
dired-mark-directories: Marks vs Flags
dired-mark-executables: Marks vs Flags
dired-mark-files-containing-regexp: Marks vs Flags
dired-mark-files-regexp: Marks vs Flags
dired-mark-subdir-files: Marks vs Flags
dired-mark-symlinks: Marks vs Flags
dired-maybe-insert-subdir: Subdirectories in Dired
dired-mouse-find-file-other-window: Dired Visiting
dired-next-dirline: Subdirectory Motion
dired-next-line: Dired Navigation
dired-next-marked-file: Marks vs Flags
dired-next-subdir: Subdirectory Motion
dired-number-of-marked-files: Marks vs Flags
dired-other-frame: Dired Enter
dired-other-tab: Tab Bars
dired-other-window: Dired Enter
dired-prev-dirline: Subdirectory Motion
dired-prev-marked-file: Marks vs Flags
dired-prev-subdir: Subdirectory Motion
dired-previous-line: Dired Navigation
dired-sort-toggle-or-edit: Dired Updating
dired-toggle-marks: Marks vs Flags
dired-tree-down: Subdirectory Motion
dired-tree-up: Subdirectory Motion
dired-undo: Marks vs Flags
dired-unmark: Marks vs Flags
dired-unmark-all-files: Marks vs Flags
dired-unmark-all-marks: Marks vs Flags
dired-unmark-backward: Marks vs Flags
dired-up-directory: Dired Visiting
dired-upcase: Transforming File Names
dired-view-file: Dired Visiting
dirs: Directory Tracking
dirtrack-mode: Directory Tracking
disable-command: Disabling
disable-theme: Custom Themes
display-battery-mode: Optional Mode Line
display-buffer (command): Pop Up Window
display-buffer, detailed description: Window Choice
display-fill-column-indicator-mode: Displaying Boundaries
display-line-numbers-mode: Display Custom
display-local-help: Help Echo
display-time: Optional Mode Line
dissociated-press: Amusements
do-auto-save: Auto Save Control
doc-view-clear-cache: DocView Conversion
doc-view-enlarge: DocView Navigation
doc-view-first-page: DocView Navigation
doc-view-goto-page: DocView Navigation
doc-view-kill-proc: DocView Conversion
doc-view-kill-proc-and-buffer: DocView Conversion
doc-view-last-page: DocView Navigation
doc-view-minor-mode: Document View
doc-view-mode: Document View
doc-view-next-page: DocView Navigation
doc-view-open-text: Document View
doc-view-previous-page: DocView Navigation
doc-view-reset-slice: DocView Slicing
doc-view-scroll-down-or-previous-page: DocView Navigation
doc-view-scroll-up-or-next-page: DocView Navigation
doc-view-search: DocView Searching
doc-view-search-backward: DocView Searching
doc-view-set-slice: DocView Slicing
doc-view-set-slice-using-mouse: DocView Slicing
doc-view-show-tooltip: DocView Searching
doc-view-shrink: DocView Navigation
doc-view-toggle-display: Document View
doctex-mode: TeX Mode
doctor: Amusements
dos-mode25: MS-DOS Display
dos-mode4350: MS-DOS Display
down-list: Moving by Parens
downcase-region: Case
downcase-word: Case
dunnet: Amusements

E
edit-abbrevs: Editing Abbrevs
edit-kbd-macro: Edit Keyboard Macro
edit-tab-stops: Tab Stops
eldoc-doc-buffer: Programming Language Doc
eldoc-mode: Programming Language Doc
eldoc-print-current-symbol-info: Programming Language Doc
electric-indent-mode: Indent Convenience
electric-layout-mode: Misc for Programs
electric-pair-mode: Matching
electric-quote-mode: Quotation Marks
emacs-lisp-mode: Lisp Eval
emacs-version: Checklist
emerge-auto-advance: Submodes of Emerge
emerge-buffers: Overview of Emerge
emerge-buffers-with-ancestor: Overview of Emerge
emerge-files: Overview of Emerge
emerge-files-with-ancestor: Overview of Emerge
emerge-skip-prefers: Submodes of Emerge
emoji-describe: Input Methods
emoji-insert: Input Methods
emoji-list: Input Methods
emoji-search: Input Methods
enable-command: Disabling
enable-theme: Custom Themes
end-of-buffer: Moving Point
end-of-defun: Moving by Defuns
end-of-visual-line: Visual Line Mode
enlarge-window: Change Window
enlarge-window-horizontally: Change Window
enriched-mode: Enriched Mode
epa-dired-do-decrypt: Operating on Files
epa-dired-do-encrypt: Operating on Files
epa-dired-do-sign: Operating on Files
epa-dired-do-verify: Operating on Files
eval-buffer: Lisp Eval
eval-defun: Lisp Eval
eval-expression: Lisp Eval
eval-last-sexp: Lisp Eval
eval-print-last-sexp: Lisp Interaction
eval-region: Lisp Eval
eww: EWW
eww-open-file: EWW
eww-search-words: Word Search
exchange-point-and-mark: Setting Mark
exchange-point-and-mark, in rectangle-mark-mode: Rectangles
execute-extended-command: M-x
exit-calendar: General Calendar
exit-recursive-edit: Recursive Edit
expand-abbrev: Expanding Abbrevs
expand-region-abbrevs: Expanding Abbrevs

F
f90-beginning-of-block: Fortran Motion
f90-end-of-block: Fortran Motion
f90-mode: Fortran
f90-next-block: Fortran Motion
f90-next-statement: Fortran Motion
f90-previous-block: Fortran Motion
f90-previous-statement: Fortran Motion
facemenu-remove-all: Editing Format Info
facemenu-remove-face-props: Editing Format Info
facemenu-set-background: Enriched Faces
facemenu-set-bold: Enriched Faces
facemenu-set-bold-italic: Enriched Faces
facemenu-set-default: Enriched Faces
facemenu-set-face: Enriched Faces
facemenu-set-foreground: Enriched Faces
facemenu-set-italic: Enriched Faces
facemenu-set-underline: Enriched Faces
ff-find-related-file: Other C Commands
ffap: FFAP
ffap-menu: FFAP
ffap-mode: FFAP
ffap-next: FFAP
fido-mode: Icomplete
file-cache-add-directory: File Name Cache
file-cache-minibuffer-complete: File Name Cache
file-name-shadow-mode: Minibuffer File
fileloop-continue: Identifier Search
filesets-add-buffer: Filesets
filesets-init: Filesets
filesets-remove-buffer: Filesets
fill-individual-paragraphs: Fill Prefix
fill-nonuniform-paragraphs: Fill Prefix
fill-paragraph: Fill Commands
fill-region: Fill Commands
fill-region-as-paragraph: Fill Commands
find-alternate-file: Visiting
find-dired: Dired and Find
find-file: Visiting
find-file-at-point: FFAP
find-file-literally: Visiting
find-file-other-frame: Visiting
find-file-other-tab: Tab Bars
find-file-other-window: Visiting
find-file-read-only: Visiting
find-file-read-only-other-frame: Creating Frames
find-grep: Grep Searching
find-grep-dired: Dired and Find
find-name-dired: Dired and Find
find-sibling-file: Visiting
find-tag-other-window: Pop Up Window
finder-by-keyword: Package Keywords
flush-lines: Other Repeating Search
flyspell-auto-correct-word: Spelling
flyspell-correct-word: Spelling
flyspell-correct-word-before-point: Spelling
flyspell-mode: Spelling
flyspell-prog-mode: Spelling
foldout-exit-fold: Foldout
foldout-zoom-subtree: Foldout
follow-mode: Follow Mode
font-lock-add-keywords: Traditional Font Lock
font-lock-mode: Font Lock
font-lock-remove-keywords: Traditional Font Lock
format-decode-buffer: Enriched Mode
fortran-beginning-of-block: Fortran Motion
fortran-column-ruler: Fortran Columns
fortran-comment-region: Fortran Comments
fortran-end-of-block: Fortran Motion
fortran-indent-subprogram: ForIndent Commands
fortran-join-line: ForIndent Commands
fortran-mode: Fortran
fortran-next-statement: Fortran Motion
fortran-previous-statement: Fortran Motion
fortran-split-line: ForIndent Commands
fortran-strip-sequence-nos: Fortran Columns
fortran-window-create: Fortran Columns
fortran-window-create-momentarily: Fortran Columns
fortune-to-signature: Mail Amusements
forward-button: Help Mode
forward-char: Moving Point
forward-list: Moving by Parens
forward-page: Pages
forward-paragraph: Paragraphs
forward-sentence: Sentences
forward-sexp: Expressions
forward-word: Words
frameset-to-register: Configuration Registers
fringe-mode: Fringes

G
gdb: Starting GUD
gdb-delete-breakpoint: Breakpoints Buffer
gdb-display-disassembly-buffer: Other GDB Buffers
gdb-display-disassembly-for-thread: Threads Buffer
gdb-display-io-buffer: Other GDB Buffers
gdb-display-locals-buffer: Other GDB Buffers
gdb-display-locals-for-thread: Threads Buffer
gdb-display-memory-buffer: Other GDB Buffers
gdb-display-registers-buffer: Other GDB Buffers
gdb-display-registers-for-thread: Threads Buffer
gdb-display-stack-for-thread: Threads Buffer
gdb-edit-value: Watch Expressions
gdb-frames-select: Stack Buffer
gdb-goto-breakpoint: Breakpoints Buffer
gdb-load-window-configuration: GDB User Interface Layout
gdb-many-windows: GDB User Interface Layout
gdb-restore-windows: GDB User Interface Layout
gdb-save-window-configuration: GDB User Interface Layout
gdb-select-thread: Threads Buffer
gdb-toggle-breakpoint: Breakpoints Buffer
gdb-var-delete: Watch Expressions
getenv: Environment
global-auto-revert-mode: Auto Revert
global-cwarn-mode: Other C Commands
global-display-fill-column-indicator-mode: Displaying Boundaries
global-display-line-numbers-mode: Display Custom
global-eldoc-mode: Programming Language Doc
global-font-lock-mode: Font Lock
global-hl-line-mode: Cursor Display
global-set-key: Init Rebinding
global-tab-line-mode: Tab Line
global-text-scale-adjust: Text Scale
global-visual-line-mode: Visual Line Mode
global-whitespace-mode: Useless Whitespace
global-whitespace-toggle-options: Useless Whitespace
glyphless-display-mode: Text Display
gnus: Gnus Startup
gnus-group-exit: Gnus Group Buffer
gnus-group-kill-group: Gnus Group Buffer
gnus-group-list-all-groups: Gnus Group Buffer
gnus-group-list-groups: Gnus Group Buffer
gnus-group-list-killed: Gnus Group Buffer
gnus-group-list-zombies: Gnus Group Buffer
gnus-group-next-unread-group: Gnus Group Buffer
gnus-group-prev-unread-group: Gnus Group Buffer
gnus-group-read-group: Gnus Group Buffer
gnus-group-toggle-subscription-at-point: Gnus Group Buffer
gnus-summary-isearch-article: Gnus Summary Buffer
gnus-summary-next-page: Gnus Summary Buffer
gnus-summary-next-unread-article: Gnus Summary Buffer
gnus-summary-prev-page: Gnus Summary Buffer
gnus-summary-prev-unread-article: Gnus Summary Buffer
gnus-summary-search-article-backward: Gnus Summary Buffer
gnus-summary-search-article-forward: Gnus Summary Buffer
gomoku: Amusements
goto-address-at-point: Goto Address mode
goto-address-mode: Goto Address mode
goto-char: Moving Point
goto-followup-to: Header Editing
goto-line: Moving Point
goto-line, with an argument: Select Buffer
goto-line-relative: Moving Point
goto-reply-to: Header Editing
gpm-mouse-mode: Text-Only Mouse
grep: Grep Searching
grep (MS-DOS): MS-DOS Processes
grep-find: Grep Searching
grep-find-toggle-abbreviation: Grep Searching
gud-cont: Commands of GUD
gud-def: GUD Customization
gud-down: Commands of GUD
gud-finish: Commands of GUD
gud-gdb: Starting GUD
gud-gdb-complete-command: Commands of GUD
gud-jump: Commands of GUD
gud-next: Commands of GUD
gud-print: Commands of GUD
gud-refresh: Commands of GUD
gud-remove: Commands of GUD
gud-step: Commands of GUD
gud-stepi: Commands of GUD
gud-tbreak: Commands of GUD
gud-tooltip-mode: Debugger Operation
gud-until: Commands of GUD
gud-up: Commands of GUD
gud-watch: Watch Expressions
guiler: Starting GUD

H
handwrite: PostScript
hanoi: Amusements
help-command: Help
help-follow: Help Mode
help-for-help: Help
help-go-back: Help Mode
help-go-forward: Help Mode
help-goto-next-page: Help Mode
help-goto-previous-page: Help Mode
help-mode: Help Mode
help-quick: Misc Help
help-quick-toggle: Misc Help
help-with-tutorial: Basic
hi-lock-find-patterns: Highlight Interactively
hi-lock-mode: Highlight Interactively
hi-lock-write-interactive-patterns: Highlight Interactively
hide-ifdef-mode: Other C Commands
hide-sublevels: Outline Visibility
highlight-changes-mode: Highlight Interactively
highlight-lines-matching-regexp: Highlight Interactively
highlight-phrase: Highlight Interactively
highlight-regexp: Highlight Interactively
highlight-symbol-at-point: Highlight Interactively
hl-line-mode: Cursor Display
holidays: Holidays
horizontal-scroll-bar-mode: Scroll Bars
how-many: Other Repeating Search
hs-hide-all: Hideshow
hs-hide-block: Hideshow
hs-hide-level: Hideshow
hs-minor-mode: Hideshow
hs-show-all: Hideshow
hs-show-block: Hideshow
hs-show-region: Hideshow
hs-toggle-hiding: Hideshow
hs-toggle-hiding: Hideshow
html-mode: HTML Mode
htmlfontify-buffer: Printing

I
ibuffer: Buffer Menus
icalendar-export-file: Importing Diary
icalendar-export-region: Importing Diary
icalendar-import-buffer: Importing Diary
icalendar-import-file: Importing Diary
icomplete-mode: Icomplete
icomplete-vertical-mode: Icomplete
ielm: Lisp Interaction
image-converter-add-handler: Image Mode
image-crop: Image Mode
image-cut: Image Mode
image-decrease-size: Image Mode
image-decrease-speed: Image Mode
image-dired-dired-comment-files: Image-Dired
image-dired-dired-display-external: Image-Dired
image-dired-dired-display-image: Image-Dired
image-dired-dired-edit-comment-and-tags: Image-Dired
image-dired-dired-toggle-marked-thumbs: Image-Dired
image-dired-display-next: Image-Dired
image-dired-display-previous: Image-Dired
image-dired-display-this: Image-Dired
image-dired-display-thumbs: Image-Dired
image-flip-horizontally: Image Mode
image-flip-vertically: Image Mode
image-goto-frame: Image Mode
image-increase-size: Image Mode
image-increase-speed: Image Mode
image-mode: Image Mode
image-mode-copy-file-name-as-kill: Image Mode
image-mode-mark-file: Image Mode
image-mode-unmark-file: Image Mode
image-next-file: Image Mode
image-next-frame: Image Mode
image-previous-file: Image Mode
image-previous-frame: Image Mode
image-reset-speed: Image Mode
image-reverse-speed: Image Mode
image-rotate: Image Mode
image-save: Image Mode
image-toggle-animation: Image Mode
image-toggle-display: Image Mode
image-transform-fit-to-window: Image Mode
image-transform-reset-to-initial: Image Mode
image-transform-reset-to-original: Image Mode
image-transform-set-percent: Image Mode
image-transform-set-scale: Image Mode
imenu: Imenu
imenu-add-menubar-index: Imenu
increase-left-margin: Enriched Indentation
increment-register: Number Registers
indent-code-rigidly: Multi-line Indent
indent-for-tab-command: Indentation
indent-line-function: Basic Indent
indent-pp-sexp: Multi-line Indent
indent-region: Indentation Commands
indent-relative: Indentation Commands
indent-rigidly: Indentation Commands
info: Misc Help
Info-goto-emacs-command-node: Name Help
Info-goto-emacs-key-command-node: Key Help
info-lookup-file: Info Lookup
info-lookup-symbol: Misc Help
info-other-window: Misc Help
insert-abbrevs: Saving Abbrevs
insert-char: Inserting Text
insert-file: Misc File Ops
insert-file-literally: Misc File Ops
insert-kbd-macro: Save Keyboard Macro
insert-register: Text Registers
inverse-add-global-abbrev: Defining Abbrevs
inverse-add-mode-abbrev: Defining Abbrevs
isearch-abort: Basic Isearch
isearch-backward: Basic Isearch
isearch-backward-regexp: Regexp Search
isearch-cancel: Basic Isearch
isearch-char-by-name: Special Isearch
isearch-complete: Special Isearch
isearch-del-char: Isearch Yank
isearch-delete-char: Basic Isearch
isearch-edit-string: Repeat Isearch
isearch-emoji-by-name: Special Isearch
isearch-exit: Basic Isearch
isearch-forward: Basic Isearch
isearch-forward-regexp: Regexp Search
isearch-forward-symbol: Symbol Search
isearch-forward-symbol-at-point: Symbol Search
isearch-forward-thing-at-point: Isearch Yank
isearch-forward-word: Word Search
isearch-help-map: Special Isearch
isearch-highlight-lines-matching-regexp: Special Isearch
isearch-highlight-regexp: Special Isearch
isearch-occur: Special Isearch
isearch-query-replace: Special Isearch
isearch-query-replace-regexp: Special Isearch
isearch-quote-char: Special Isearch
isearch-repeat-backward: Repeat Isearch
isearch-repeat-forward: Repeat Isearch
isearch-ring-advance: Repeat Isearch
isearch-ring-retreat: Repeat Isearch
isearch-toggle-case-fold: Lax Search
isearch-toggle-char-fold: Lax Search
isearch-toggle-input-method: Special Isearch
isearch-toggle-invisible: Special Isearch
isearch-toggle-lax-whitespace: Lax Search
isearch-toggle-regexp: Special Isearch
isearch-toggle-specified-input-method: Special Isearch
isearch-toggle-symbol: Symbol Search
isearch-toggle-word: Word Search
isearch-transient-input-method: Special Isearch
isearch-yank-char: Isearch Yank
isearch-yank-kill: Isearch Yank
isearch-yank-line: Isearch Yank
isearch-yank-pop: Isearch Yank
isearch-yank-symbol-or-char: Isearch Yank
isearch-yank-until-char: Isearch Yank
isearch-yank-word-or-char: Isearch Yank
isearch-yank-x-selection: Isearch Yank
iso-gtex2iso: TeX Misc
iso-iso2gtex: TeX Misc
iso-iso2tex: TeX Misc
iso-tex2iso: TeX Misc
ispell: Spelling
ispell-buffer: Spelling
ispell-change-dictionary: Spelling
ispell-comment-or-string-at-point: Spelling
ispell-comments-and-strings: Spelling
ispell-complete-word: Spelling
ispell-continue: Spelling
ispell-kill-ispell: Spelling
ispell-message: Mail Misc
ispell-region: Spelling
ispell-word: Spelling

J
jdb: Starting GUD
jump-to-register: Position Registers
just-one-space: Deletion

K
kbd: Init Rebinding
kbd-macro-query: Keyboard Macro Query
keep-lines: Other Repeating Search
keyboard-escape-quit: Quitting
keyboard-quit: Quitting
keymap-global-set: Rebinding
keymap-global-set: Init Rebinding
keymap-global-unset: Rebinding
keymap-local-set: Rebinding
keymap-local-unset: Rebinding
keymap-set: Init Rebinding
keymap-substitute: Init Examples
keymap-unset: Init Rebinding
kill-all-abbrevs: Defining Abbrevs
kill-buffer: Kill Buffer
kill-buffer-and-window: Change Window
kill-compilation: Compilation
kill-current-buffer: Completion Commands
kill-emacs: Exiting
kill-line: Killing by Lines
kill-local-variable: Locals
kill-matching-buffers: Kill Buffer
kill-matching-lines: Other Repeating Search
kill-rectangle: Rectangles
kill-region: Other Kill Commands
kill-ring-save: Other Kill Commands
kill-sentence: Sentences
kill-sexp: Expressions
kill-some-buffers: Kill Buffer
kill-whole-line: Killing by Lines
kill-word: Words
kmacro-add-counter: Keyboard Macro Counter
kmacro-bind-to-key: Save Keyboard Macro
kmacro-cycle-ring-next: Keyboard Macro Ring
kmacro-cycle-ring-previous: Keyboard Macro Ring
kmacro-edit-lossage: Edit Keyboard Macro
kmacro-edit-macro: Edit Keyboard Macro
kmacro-end-and-call-macro: Basic Keyboard Macro
kmacro-end-macro: Basic Keyboard Macro
kmacro-end-or-call-macro: Basic Keyboard Macro
kmacro-end-or-call-macro-repeat: Keyboard Macro Ring
kmacro-insert-counter: Keyboard Macro Counter
kmacro-name-last-macro: Save Keyboard Macro
kmacro-redisplay: Basic Keyboard Macro
kmacro-set-counter: Keyboard Macro Counter
kmacro-set-format: Keyboard Macro Counter
kmacro-start-macro: Basic Keyboard Macro
kmacro-start-macro-or-insert-counter: Basic Keyboard Macro
kmacro-step-edit-macro: Keyboard Macro Step-Edit
kmacro-to-register: Keyboard Macro Registers

L
latex-close-block: LaTeX Editing
latex-electric-env-pair-mode: LaTeX Editing
latex-insert-block: LaTeX Editing
latex-mode: TeX Mode
left-char: Moving Point
left-char, and bidirectional text: Bidirectional Editing
left-word: Moving Point
lgrep: Grep Searching
life: Amusements
line-number-mode: Optional Mode Line
lisp-eval-defun: External Lisp
lisp-interaction-mode: Lisp Interaction
list-abbrevs: Editing Abbrevs
list-bookmarks: Bookmarks
list-buffers: List Buffers
list-character-sets: Charsets
list-charset-chars: Charsets
list-coding-systems: Coding Systems
list-colors-display: Colors
list-command-history: Repetition
list-directory: Directories
list-faces-display: Faces
list-holidays: Holidays
list-input-methods: Select Input Method
list-matching-lines: Other Repeating Search
list-packages: Package Menu
list-tags: List Identifiers
load: Lisp Libraries
load-file: Lisp Libraries
load-library: Lisp Libraries
load-theme: Custom Themes
locate: Dired and Find
locate-with-filter: Dired and Find
log-edit-done: Log Buffer
log-edit-generate-changelog-from-diff: Log Buffer
log-edit-insert-changelog: Log Buffer
log-edit-show-diff: Log Buffer
log-edit-show-files: Log Buffer
log-view-toggle-entry-display: VC Change Log
lossage-size: Misc Help
lpr-buffer: Printing
lpr-region: Printing
lunar-phases: Lunar Phases

M
mail-abbrev-complete-alias: Mail Aliases
mail-abbrev-insert-alias: Mail Aliases
mail-add-attachment: Mail Misc
mail-fill-yanked-message: Citing Mail
mail-text: Header Editing
make-frame-command: Creating Frames
make-frame-on-display: Multiple Displays
make-frame-on-monitor: Multiple Displays
make-indirect-buffer: Indirect Buffers
make-local-variable: Locals
make-symbolic-link: Copying and Naming
make-variable-buffer-local: Locals
man: Man Page
mark-defun: Moving by Defuns
mark-page: Pages
mark-paragraph: Paragraphs
mark-sexp: Marking Objects
mark-whole-buffer: Marking Objects
mark-word: Marking Objects
menu-bar-mode: Menu Bars
menu-bar-open: Menu Bar
merge-mail-abbrevs: Mail Aliases
message-goto-bcc: Header Editing
message-goto-cc: Header Editing
message-goto-fcc: Header Editing
message-goto-subject: Header Editing
message-goto-to: Header Editing
message-insert-signature: Mail Signature
message-send: Mail Sending
message-send-and-exit: Mail Sending
message-tab: Header Editing
message-yank-original: Citing Mail
message-yank-prefix: Citing Mail
minibuffer-choose-completion: Completion Commands
minibuffer-complete: Completion Commands
minibuffer-complete-and-exit: Completion Exit
minibuffer-complete-word: Completion Commands
minibuffer-depth-indicate-mode: Minibuffer Edit
minibuffer-electric-default-mode: Basic Minibuffer
minibuffer-inactive-mode: Minibuffer Edit
minibuffer-next-completion: Completion Commands
minibuffer-previous-completion: Completion Commands
mml-attach-file: Mail Misc
modify-category-entry: Visual Line Mode
morse-region: Amusements
mouse-avoidance-mode: Mouse Avoidance
mouse-buffer-menu: Buffer Menus
mouse-save-then-kill: Mouse Commands
mouse-secondary-save-then-kill: Secondary Selection
mouse-set-point: Mouse Commands
mouse-set-region: Mouse Commands
mouse-set-secondary: Secondary Selection
mouse-start-secondary: Secondary Selection
mouse-wheel-mode: Mouse Commands
mouse-wheel-text-scale: Text Scale
mouse-yank-at-click: Mouse Commands
mouse-yank-primary: Mouse Commands
mouse-yank-secondary: Secondary Selection
move-beginning-of-line: Moving Point
move-end-of-line: Moving Point
move-file-to-trash: Misc File Ops
move-to-column: Moving Point
move-to-window-line-top-bottom: Moving Point
mpuz: Amusements
msb-mode: Buffer Menus
msdos-set-mouse-buttons: MS-DOS Mouse
multi-isearch-buffers: Other Repeating Search
multi-isearch-buffers-regexp: Other Repeating Search
multi-isearch-files: Other Repeating Search
multi-isearch-files-regexp: Other Repeating Search
multi-occur: Other Repeating Search
multi-occur-in-matching-buffers: Other Repeating Search

N
narrow-to-defun: Narrowing
narrow-to-page: Narrowing
narrow-to-region: Narrowing
nato-region: Amusements
negative-argument: Arguments
next-buffer: Select Buffer
next-completion: Completion Commands
next-error: Compilation Mode
next-error-follow-minor-mode: Compilation Mode
next-error-select-buffer: Compilation Mode
next-history-element: Minibuffer History
next-line: Moving Point
next-line-or-history-element: Minibuffer History
next-logical-line: Visual Line Mode
next-matching-history-element: Minibuffer History
next-window-any-frame: Other Window
normal-erase-is-backspace-mode: DEL Does Not Delete
normal-mode: Choosing Modes
not-modified: Save Commands
nroff-backward-text-line: Nroff Mode
nroff-count-text-lines: Nroff Mode
nroff-electric-mode: Nroff Mode
nroff-forward-text-line: Nroff Mode
nroff-mode: Nroff Mode
number-to-register: Number Registers
nxml-mode: HTML Mode

O
occur: Other Repeating Search
open-dribble-file: Checklist
open-line: Blank Lines
open-rectangle: Rectangles
open-termscript: Checklist
org-agenda: Org Organizer
org-agenda-file-to-front: Org Organizer
org-cycle: Org Mode
org-deadline: Org Organizer
org-export-dispatch: Org Authoring
org-metadown: Org Mode
org-metaleft: Org Mode
org-metaright: Org Mode
org-metaup: Org Mode
org-mode: Org Mode
org-schedule: Org Organizer
org-shifttab: Org Mode
org-todo: Org Organizer
other-frame: Frame Commands
other-tab-prefix: Tab Bars
other-window: Other Window
outline-backward-same-level: Outline Motion
outline-cycle: Outline Visibility
outline-cycle-buffer: Outline Visibility
outline-forward-same-level: Outline Motion
outline-hide-body: Outline Visibility
outline-hide-entry: Outline Visibility
outline-hide-leaves: Outline Visibility
outline-hide-other: Outline Visibility
outline-hide-subtree: Outline Visibility
outline-minor-mode: Outline Minor Mode
outline-mode: Outline Mode
outline-next-visible-heading: Outline Motion
outline-previous-visible-heading: Outline Motion
outline-show-all: Outline Visibility
outline-show-branches: Outline Visibility
outline-show-children: Outline Visibility
outline-show-entry: Outline Visibility
outline-show-subtree: Outline Visibility
outline-up-heading: Outline Motion
overwrite-mode: Minor Modes

P
package-activate-all: Package Installation
package-browse-url: Package Menu
package-install: Package Installation
package-install-file: Package Files
package-menu-describe-package: Package Menu
package-menu-execute: Package Menu
package-menu-filter-by-archive: Package Menu
package-menu-filter-by-description: Package Menu
package-menu-filter-by-keyword: Package Menu
package-menu-filter-by-name: Package Menu
package-menu-filter-by-name-or-description: Package Menu
package-menu-filter-by-status: Package Menu
package-menu-filter-by-version: Package Menu
package-menu-filter-clear: Package Menu
package-menu-filter-marked: Package Menu
package-menu-filter-upgradable: Package Menu
package-menu-hide-package: Package Menu
package-menu-mark-delete: Package Menu
package-menu-mark-install: Package Menu
package-menu-mark-obsolete-for-deletion: Package Menu
package-menu-mark-unmark: Package Menu
package-menu-mark-upgrades: Package Menu
package-menu-quick-help: Package Menu
package-menu-toggle-hiding: Package Menu
package-quickstart-refresh: Package Installation
package-recompile: Package Installation
package-recompile-all: Package Installation
package-report-bug: Fetching Package Sources
package-upgrade: Package Installation
package-upgrade-all: Package Installation
package-vc-checkout: Fetching Package Sources
package-vc-install: Fetching Package Sources
package-vc-install-from-checkout: Fetching Package Sources
package-vc-prepare-patch: Fetching Package Sources
package-vc-rebuild: Fetching Package Sources
paragraph-indent-minor-mode: Text Mode
paragraph-indent-text-mode: Text Mode
pdb: Starting GUD
perldb: Starting GUD
picture-backward-clear-column: Basic Picture
picture-backward-column: Basic Picture
picture-clear-column: Basic Picture
picture-clear-line: Basic Picture
picture-clear-rectangle: Rectangles in Picture
picture-clear-rectangle-to-register: Rectangles in Picture
picture-forward-column: Basic Picture
picture-mode: Picture Mode
picture-motion: Insert in Picture
picture-motion-reverse: Insert in Picture
picture-move-down: Basic Picture
picture-move-up: Basic Picture
picture-movement-down: Insert in Picture
picture-movement-left: Insert in Picture
picture-movement-ne: Insert in Picture
picture-movement-nw: Insert in Picture
picture-movement-right: Insert in Picture
picture-movement-se: Insert in Picture
picture-movement-sw: Insert in Picture
picture-movement-up: Insert in Picture
picture-newline: Basic Picture
picture-open-line: Basic Picture
picture-set-tab-stops: Tabs in Picture
picture-tab: Tabs in Picture
picture-tab-search: Tabs in Picture
picture-yank-rectangle: Rectangles in Picture
picture-yank-rectangle-from-register: Rectangles in Picture
plain-tex-mode: TeX Mode
point-to-register: Position Registers
pong: Amusements
pop-global-mark: Global Mark Ring
pr-interface: Printing Package
prefer-coding-system: Recognize Coding
prepend-to-buffer: Accumulating Text
prepend-to-register: Text Registers
prettify-symbols-mode: Misc for Programs
previous-buffer: Select Buffer
previous-completion: Completion Commands
previous-history-element: Minibuffer History
previous-line: Moving Point
previous-line-or-history-element: Minibuffer History
previous-logical-line: Visual Line Mode
previous-matching-history-element: Minibuffer History
print-buffer: Printing
print-buffer (MS-DOS): Windows Printing
print-region: Printing
print-region (MS-DOS): Windows Printing
prog-indent-sexp: C Indent
project-async-shell-command: Project File Commands
project-compile: Project File Commands
project-dired: Project File Commands
project-eshell: Project File Commands
project-find-dir: Project File Commands
project-find-file: Project File Commands
project-find-regexp: Project File Commands
project-forget-project: Managing Projects
project-kill-buffers: Project Buffer Commands
project-list-buffers: Project Buffer Commands
project-query-replace-regexp: Project File Commands
project-search: Project File Commands
project-shell: Project File Commands
project-shell-command: Project File Commands
project-switch-project: Switching Projects
project-switch-to-buffer: Project Buffer Commands
project-vc-dir: Project File Commands
ps-despool: PostScript
ps-print-buffer: PostScript
ps-print-buffer (MS-DOS): Windows Printing
ps-print-buffer-with-faces: PostScript
ps-print-region: PostScript
ps-print-region-with-faces: PostScript
ps-spool-buffer: PostScript
ps-spool-buffer (MS-DOS): Windows Printing
ps-spool-buffer-with-faces: PostScript
ps-spool-region: PostScript
ps-spool-region-with-faces: PostScript
pwd: File Names

Q
quail-set-keyboard-layout: Select Input Method
quail-show-key: Select Input Method
quail-translation-keymap: Input Methods
query-replace: Query Replace
query-replace-regexp: Query Replace
quietly-read-abbrev-file: Saving Abbrevs
quit-window: Completion Commands
quit-window: Several Buffers
quit-window, in Dired buffers: Dired Enter
quoted-insert: Inserting Text

R
re-search-backward: Regexp Search
re-search-forward: Regexp Search
read-abbrev-file: Saving Abbrevs
read-only-mode: Misc Buffer
rebuild-mail-abbrevs: Mail Aliases
recenter: Recentering
recenter-other-window: Other Window
recenter-top-bottom: Recentering
recentf-edit-list: File Conveniences
recentf-mode: File Conveniences
recentf-open: File Conveniences
recentf-save-list: File Conveniences
recode-file-name: File Name Coding
recode-region: Text Coding
recompile: Compilation
recover-file: Recover
recover-session: Recover
rectangle: Rectangles
rectangle-exchange-point-and-mark: Rectangles
rectangle-mark-mode: Rectangles
remove-hook: Hooks
rename-buffer: Misc Buffer
rename-file: Copying and Naming
rename-uniquely: Misc Buffer
repeat: Repeating
repeat-complex-command: Repetition
repeat-mode: Repeating
replace-regexp: Regexp Replace
replace-string: Unconditional Replace
report-emacs-bug: Checklist
reposition-window: Recentering
reveal-mode: Outline Visibility
reverse-region: Sorting
revert-buffer: Reverting
revert-buffer (Dired): Dired Updating
revert-buffer-quick: Reverting
revert-buffer-with-coding-system: Text Coding
revert-buffer-with-fine-grain: Reverting
rgrep: Grep Searching
right-char: Moving Point
right-char, and bidirectional text: Bidirectional Editing
right-word: Moving Point
rmail: Rmail
rmail-abort-edit: Rmail Editing
rmail-add-label: Rmail Labels
rmail-beginning-of-message: Rmail Scrolling
rmail-bury: Rmail Basics
rmail-cease-edit: Rmail Editing
rmail-continue: Rmail Reply
rmail-delete-backward: Rmail Deletion
rmail-delete-forward: Rmail Deletion
rmail-edit-current-message: Rmail Editing
rmail-end-of-message: Rmail Scrolling
rmail-epa-decrypt: Rmail Display
rmail-expunge: Rmail Deletion
rmail-expunge-and-save: Rmail Basics
rmail-first-message: Rmail Motion
rmail-forward: Rmail Reply
rmail-get-new-mail: Rmail Files
rmail-input: Rmail Files
rmail-kill-label: Rmail Labels
rmail-last-message: Rmail Motion
rmail-mail: Rmail Reply
rmail-mime: Rmail Display
rmail-mime-next-item: Rmail Display
rmail-mime-previous-item: Rmail Display
rmail-mime-toggle-hidden: Rmail Display
rmail-mode: Rmail
rmail-next-labeled-message: Rmail Labels
rmail-next-message: Rmail Motion
rmail-next-same-subject: Rmail Motion
rmail-next-undeleted-message: Rmail Motion
rmail-output: Rmail Output
rmail-output-as-seen: Rmail Output
rmail-output-body-to-file: Rmail Output
rmail-previous-labeled-message: Rmail Labels
rmail-previous-message: Rmail Motion
rmail-previous-same-subject: Rmail Motion
rmail-previous-undeleted-message: Rmail Motion
rmail-quit: Rmail Basics
rmail-redecode-body: Rmail Coding
rmail-reply: Rmail Reply
rmail-resend: Rmail Reply
rmail-retry-failure: Rmail Reply
rmail-search: Rmail Motion
rmail-show-message: Rmail Motion
rmail-sort-by-author: Rmail Sorting
rmail-sort-by-correspondent: Rmail Sorting
rmail-sort-by-date: Rmail Sorting
rmail-sort-by-labels: Rmail Sorting
rmail-sort-by-lines: Rmail Sorting
rmail-sort-by-recipient: Rmail Sorting
rmail-sort-by-subject: Rmail Sorting
rmail-summary: Rmail Make Summary
rmail-summary-bury: Rmail Summary Edit
rmail-summary-by-labels: Rmail Make Summary
rmail-summary-by-recipients: Rmail Make Summary
rmail-summary-by-regexp: Rmail Make Summary
rmail-summary-by-senders: Rmail Make Summary
rmail-summary-by-topic: Rmail Make Summary
rmail-summary-quit: Rmail Summary Edit
rmail-summary-undelete-many: Rmail Summary Edit
rmail-summary-wipe: Rmail Summary Edit
rmail-toggle-header: Rmail Display
rmail-undelete-previous-message: Rmail Deletion
rot13-other-window: Rmail Rot13
rot13-region: Rmail Rot13
run-lisp: External Lisp
run-scheme: External Lisp

S
save-buffer: Save Commands
save-buffers-kill-terminal: Exiting
save-some-buffers: Save Commands
scheme-mode: External Lisp
scratch-buffer: Lisp Interaction
scroll-bar-mode: Scroll Bars
scroll-down-command: Scrolling
scroll-down-line: Scrolling
scroll-left: Horizontal Scrolling
scroll-other-window: Other Window
scroll-other-window-down: Other Window
scroll-right: Horizontal Scrolling
scroll-up-command: Scrolling
scroll-up-line: Scrolling
sdb: Starting GUD
search-backward: Nonincremental Search
search-forward: Nonincremental Search
select-frame-by-name: Text Terminals
serial-term: Serial Terminal
server-edit: Invoking emacsclient
server-edit-abort: Invoking emacsclient
server-eval-at: Emacs Server
server-generate-key: TCP Emacs server
server-start: Emacs Server
server-stop-automatically: Emacs Server
set-buffer-file-coding-system: Text Coding
set-buffer-process-coding-system: Communication Coding
set-face-background: Colors
set-face-foreground: Colors
set-file-modes: Misc File Ops
set-file-name-coding-system: File Name Coding
set-fill-column: Fill Commands
set-fill-prefix: Fill Prefix
set-fontset-font: Modifying Fontsets
set-frame-name: Text Terminals
set-fringe-style: Fringes
set-goal-column: Moving Point
set-input-method: Select Input Method
set-justification-center: Enriched Justification
set-justification-full: Enriched Justification
set-justification-left: Enriched Justification
set-justification-none: Enriched Justification
set-justification-right: Enriched Justification
set-keyboard-coding-system: Terminal Coding
set-language-environment: Language Environments
set-left-margin: Enriched Indentation
set-locale-environment: Language Environments
set-mark-command: Setting Mark
set-next-selection-coding-system: Communication Coding
set-right-margin: Enriched Indentation
set-selection-coding-system: Communication Coding
set-selective-display: Selective Display
set-terminal-coding-system: Terminal Coding
set-variable: Examining
set-visited-file-name: Save Commands
setenv: Environment
setopt: Examining
setq-default: Locals
sgml-attributes: HTML Mode
sgml-close-tag: HTML Mode
sgml-delete-tag: HTML Mode
sgml-mode: HTML Mode
sgml-name-8bit-mode: HTML Mode
sgml-name-char: HTML Mode
sgml-skip-tag-backward: HTML Mode
sgml-skip-tag-forward: HTML Mode
sgml-tag: HTML Mode
sgml-tag-help: HTML Mode
sgml-tags-invisible: HTML Mode
sgml-validate: HTML Mode
shadow-initialize: File Shadowing
shell: Interactive Shell
shell-backward-command: Shell Mode
shell-command: Single Shell
shell-command-on-region: Single Shell
shell-dynamic-complete-command: Shell Options
shell-forward-command: Shell Mode
shell-pushd-dextract: Shell Options
shell-pushd-dunique: Shell Options
shell-pushd-tohome: Shell Options
shortdoc: Name Help
show-paren-local-mode: Matching
show-paren-mode: Matching
shrink-window-horizontally: Change Window
shrink-window-if-larger-than-buffer: Change Window
size-indication-mode: Optional Mode Line
slitex-mode: TeX Mode
smerge-mode: Comparing Files
snake: Amusements
solitaire: Amusements
sort-columns: Sorting
sort-fields: Sorting
sort-lines: Sorting
sort-numeric-fields: Sorting
sort-pages: Sorting
sort-paragraphs: Sorting
split-line: Indentation Commands
split-window-below: Split Window
split-window-right: Split Window
spook: Mail Amusements
standard-display-8bit: Unibyte Mode
string-insert-rectangle: Rectangles
string-rectangle: Rectangles
subword-mode: MixedCase Words
sunrise-sunset: Sunrise/Sunset
superword-mode: Misc for Programs
suspend-frame: Exiting
switch-to-buffer: Select Buffer
switch-to-buffer-other-frame: Select Buffer
switch-to-buffer-other-tab: Tab Bars
switch-to-buffer-other-window: Select Buffer
switch-to-completions: Completion Commands

T
tab-bar-history-back: Tab Bars
tab-bar-history-forward: Tab Bars
tab-bar-history-mode: Tab Bars
tab-bar-mode: Tab Bars
tab-close: Tab Bars
tab-close-other: Tab Bars
tab-last: Tab Bars
tab-move: Tab Bars
tab-new: Tab Bars
tab-next: Tab Bars
tab-previous: Tab Bars
tab-recent: Tab Bars
tab-rename: Tab Bars
tab-select: Tab Bars
tab-switch: Tab Bars
tab-to-tab-stop: Indentation Commands
tab-undo: Tab Bars
tabify: Just Spaces
table-backward-cell: Cell Commands
table-capture: Table Conversion
table-fixed-width-mode: Text Based Tables
table-forward-cell: Cell Commands
table-generate-source: Table Misc
table-heighten-cell: Cell Commands
table-insert: Table Creation
table-insert-column: Table Rows and Columns
table-insert-row: Table Rows and Columns
table-insert-sequence: Table Misc
table-justify: Cell Justification
table-narrow-cell: Cell Commands
table-query-dimension: Table Misc
table-recognize: Table Recognition
table-recognize-cell: Table Recognition
table-recognize-region: Table Recognition
table-recognize-table: Table Recognition
table-release: Table Conversion
table-shorten-cell: Cell Commands
table-span-cell: Cell Commands
table-split-cell: Cell Commands
table-split-cell-horizontally: Cell Commands
table-split-cell-vertically: Cell Commands
table-unrecognize: Table Recognition
table-unrecognize-cell: Table Recognition
table-unrecognize-region: Table Recognition
table-unrecognize-table: Table Recognition
table-widen-cell: Cell Commands
tabulated-list-narrow-current-column: Several Buffers
tabulated-list-sort: Several Buffers
tabulated-list-widen-current-column: Several Buffers
tags-next-file: List Identifiers
tags-query-replace: Identifier Search
tags-search: Identifier Search
temp-buffer-resize-mode: Temporary Displays
term: Terminal emulator
term-char-mode: Term Mode
term-line-mode: Term Mode
term-pager-toggle: Term Mode
tetris: Amusements
tex-bibtex-file: TeX Print
tex-buffer: TeX Print
tex-compile: TeX Print
tex-file: TeX Print
tex-insert-braces: TeX Editing
tex-insert-quote: TeX Editing
tex-kill-job: TeX Print
tex-mode: TeX Mode
tex-print: TeX Print
tex-recenter-output-buffer: TeX Print
tex-region: TeX Print
tex-terminate-paragraph: TeX Editing
tex-validate-region: TeX Editing
tex-view: TeX Print
text-mode: Text Mode
text-scale-adjust: Text Scale
text-scale-decrease: Text Scale
text-scale-increase: Text Scale
text-scale-mode: Text Scale
text-scale-pinch: Text Scale
text-scale-set: Text Scale
theme-choose-variant: Custom Themes
thumbs-mode: Image Mode
time-stamp: Time Stamps
timeclock-change: Time Intervals
timeclock-in: Time Intervals
timeclock-mode-line-display: Time Intervals
timeclock-out: Time Intervals
timeclock-reread-log: Time Intervals
timeclock-when-to-leave: Time Intervals
timeclock-workday-remaining: Time Intervals
tmm-menubar: Menu Bar
toggle-debug-on-error: Checklist
toggle-frame-fullscreen: Frame Commands
toggle-frame-maximized: Frame Commands
toggle-frame-tab-bar: Tab Bars
toggle-input-method: Select Input Method
toggle-scroll-bar: Scroll Bars
toggle-truncate-lines: Line Truncation
tool-bar-mode: Tool Bars
tooltip-mode: Tooltips
top-level: Quitting
transient-mark-mode: Disabled Transient Mark
transpose-chars: Transpose
transpose-lines: Transpose
transpose-paragraphs: Transpose
transpose-regions: Transpose
transpose-sentences: Transpose
transpose-sexps: Expressions
transpose-words: Transpose
tty-suppress-bold-inverse-default-colors: Display Custom

U
uncomment-region: Comment Commands
undelete-frame: Frame Commands
undelete-frame-mode: Frame Commands
undigestify-rmail-message: Rmail Digest
undo: Undo
undo-only: Undo
undo-redo: Undo
unexpand-abbrev: Expanding Abbrevs
unforward-rmail-message: Rmail Reply
unhighlight-regexp: Highlight Interactively
universal-argument: Arguments
universal-coding-system-argument: Text Coding
unmorse-region: Amusements
untabify: Just Spaces
up-list: TeX Editing
upcase-region: Case
upcase-word: Case
url-handler-mode: Browse-URL
use-hard-newlines: Hard and Soft Newlines

V
vc-annotate: Old Revisions
vc-create-branch: Creating Branches
vc-create-tag: Revision Tags
vc-delete-file: VC Delete/Rename
vc-diff: Old Revisions
vc-dir: VC Directory Mode
vc-dir-mark: VC Directory Commands
vc-dir-mark-all-files: VC Directory Commands
vc-dir-mark-by-regexp: VC Directory Commands
vc-dir-mark-registered-files: VC Directory Commands
vc-ediff: Old Revisions
vc-edit-next-command: Editing VC Commands
vc-ignore: VC Ignore
vc-insert-headers: Version Headers
vc-log-incoming: VC Change Log
vc-log-outgoing: VC Change Log
vc-log-search: VC Change Log
vc-next-action: Basic VC Editing
vc-prepare-patch: Preparing Patches
vc-print-branch-log: VC Change Log
vc-print-log: VC Change Log
vc-print-root-log: VC Change Log
vc-pull: Pulling / Pushing
vc-push: Pulling / Pushing
vc-refresh-state: Version Control
vc-region-history: VC Change Log
vc-register: Registering
vc-rename-file: VC Delete/Rename
vc-retrieve-tag: Revision Tags
vc-revert: VC Undo
vc-revision-other-window: Old Revisions
vc-root-diff: Old Revisions
vc-root-version-diff: Old Revisions
vc-state-refresh: Version Control
vc-switch-branch: Switching Branches
vc-update-change-log: Change Logs and VC
view-buffer: View Mode
view-echo-area-messages: Misc Help
view-emacs-debugging: Help Files
view-emacs-FAQ: Help Files
view-emacs-news: Help Files
view-emacs-problems: Help Files
view-emacs-todo: Help Files
View-exit: View Mode
view-external-packages: Help Files
view-file: View Mode
view-hello-file: International Chars
view-lossage: Misc Help
view-order-manuals: Help Files
View-quit: View Mode
view-register: Registers
visit-tags-table: Select Tags Table
visual-line-mode: Visual Line Mode

W
w32-add-untranslated-filesystem: Text and Binary
w32-find-non-USB-fonts: Windows Fonts
w32-register-hot-key: Windows Keyboard
w32-remove-untranslated-filesystem: Text and Binary
w32-set-console-codepage: Terminal Coding
w32-set-ime-open-status: Windows Keyboard
w32-shell-execute: Windows Processes
w32-unregister-hot-key: Windows Keyboard
wdired-change-to-wdired-mode: Wdired
wdired-finish-edit: Wdired
what-cursor-position: Position Info
what-cursor-position, and international characters: International Chars
what-line: Position Info
what-page: Pages
where-is: Key Help
which-function-mode: Which Function
whitespace-mode: Useless Whitespace
whitespace-toggle-options: Useless Whitespace
widen: Narrowing
widget-backward: Customization Groups
widget-complete: Changing a Variable
widget-describe: Key Help
widget-forward: Customization Groups
windmove-default-keybindings: Window Convenience
windmove-delete-default-keybindings: Window Convenience
windmove-display-default-keybindings: Window Convenience
windmove-right: Window Convenience
windmove-swap-states-default-keybindings: Window Convenience
window-configuration-to-register: Configuration Registers
window-divider-mode: Window Dividers
winner-mode: Window Convenience
woman: Man Page
word-search-backward: Word Search
word-search-forward: Word Search
write-abbrev-file: Saving Abbrevs
write-file: Save Commands
write-region: Misc File Ops

X
xdb: Starting GUD
xref-etags-mode: Looking Up Identifiers
xref-find-apropos: Looking Up Identifiers
xref-find-definitions: Looking Up Identifiers
xref-find-definitions-other-frame: Looking Up Identifiers
xref-find-definitions-other-window: Looking Up Identifiers
xref-find-references: Identifier Search
xref-find-references-and-replace: Identifier Search
xref-go-back: Looking Up Identifiers
xref-go-forward: Looking Up Identifiers
xref-next-group: Xref Commands
xref-next-line: Xref Commands
xref-prev-group: Xref Commands
xref-prev-line: Xref Commands
xref-query-replace-in-results: Identifier Search
xref-quit: Xref Commands
xref-quit-and-pop-marker-stack: Xref Commands
xref-revert-buffer: Xref Commands
xref-select-and-show-xref: Xref Commands
xref-show-location-at-point: Xref Commands
xwidget-webkit-browse-history: Embedded WebKit Widgets
xwidget-webkit-browse-url: Embedded WebKit Widgets
xwidget-webkit-edit-mode: Embedded WebKit Widgets
xwidget-webkit-isearch-mode: Embedded WebKit Widgets
xwidget-webkit-mode: Embedded WebKit Widgets

Y
yank: Yanking
yank-media: Clipboard
yank-pop: Earlier Kills
yank-rectangle: Rectangles

Z
zap-to-char: Other Kill Commands
zap-up-to-char: Other Kill Commands
zone: Amusements
zrgrep: Grep Searching


Variable Index

Jump to:   A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y  
Index Entry  Section

A
abbrev-all-caps: Expanding Abbrevs
abbrev-file-name: Saving Abbrevs
abbrev-suggest: Abbrevs Suggestions
abbrev-suggest-hint-threshold: Abbrevs Suggestions
adaptive-fill-first-line-regexp: Adaptive Fill
adaptive-fill-function: Adaptive Fill
adaptive-fill-mode: Adaptive Fill
adaptive-fill-regexp: Adaptive Fill
add-log-always-start-new-record: Change Log Commands
add-log-dont-create-changelog-file: Change Log Commands
add-log-keep-changes-together: Change Log Commands
align-default-spacing: Code Alignment
align-exclude-rules-list: Code Alignment
align-indent-before-aligning: Code Alignment
align-mode-exclude-rules-list: Code Alignment
align-mode-rules-list: Code Alignment
align-region-separate: Code Alignment
align-rules-list: Code Alignment
align-to-tab-stop: Code Alignment
ange-ftp-default-user: Remote Files
ange-ftp-gateway-host: Remote Files
ange-ftp-generate-anonymous-password: Remote Files
ange-ftp-make-backup-files: Remote Files
ange-ftp-smart-gateway: Remote Files
appt-audible: Appointments
appt-delete-window-function: Appointments
appt-disp-window-function: Appointments
appt-display-diary: Appointments
appt-display-duration: Appointments
appt-display-format: Appointments
appt-display-mode-line: Appointments
appt-message-warning-time: Appointments
appt-warning-time-regexp: Appointments
apropos-do-all: Apropos
apropos-documentation-sort-by-scores: Apropos
apropos-sort-by-scores: Apropos
async-shell-command-buffer: Single Shell
async-shell-command-display-buffer: Single Shell
async-shell-command-width: Single Shell
auth-source-save-behavior: Authentication
auth-sources: Authentication
auto-coding-alist: Recognize Coding
auto-coding-functions: Recognize Coding
auto-coding-regexp-alist: Recognize Coding
auto-compression-mode: Compressed Files
auto-hscroll-mode: Horizontal Scrolling
auto-mode-alist: Choosing Modes
auto-mode-case-fold: Choosing Modes
auto-revert-avoid-polling: Auto Revert
auto-revert-check-vc-info: VC Mode Line
auto-revert-interval: Auto Revert
auto-revert-notify-exclude-dir-regexp: Auto Revert
auto-revert-remote-files: Auto Revert
auto-revert-use-notify: Auto Revert
auto-revert-verbose: Auto Revert
auto-save-default: Auto Save Control
auto-save-file-name-transforms: Auto Save Files
auto-save-interval: Auto Save Control
auto-save-list-file-prefix: Recover
auto-save-no-message: Auto Save
auto-save-timeout: Auto Save Control
auto-save-visited-interval: Auto Save Control
auto-save-visited-mode: Auto Save Files

B
backtrace-on-error-noninteractive: Initial Options
backup-by-copying: Backup Copying
backup-by-copying-when-linked: Backup Copying
backup-by-copying-when-mismatch: Backup Copying
backup-by-copying-when-privileged-mismatch: Backup Copying
backup-directory-alist: Backup
backup-enable-predicate: Backup
battery-mode-line-format: Optional Mode Line
bdf-directory-list: PostScript Variables
bidi-display-reordering: Bidirectional Editing
bidi-paragraph-direction: Bidirectional Editing
bidi-paragraph-separate-re: Bidirectional Editing
bidi-paragraph-start-re: Bidirectional Editing
blink-cursor-alist: Cursor Display
blink-cursor-blinks: Cursor Display
blink-cursor-mode: Cursor Display
blink-matching-delay: Matching
blink-matching-paren: Matching
blink-matching-paren-distance: Matching
bookmark-default-file: Bookmarks
bookmark-save-flag: Bookmarks
bookmark-search-size: Bookmarks
bookmark-use-annotations: Bookmarks
browse-url-browser-function: Browse-URL
browse-url-handlers: Browse-URL
browse-url-mailto-function: Browse-URL
buffer-auto-revert-by-notification: Non-File Buffers
buffer-file-coding-system: Output Coding
buffer-read-only: Misc Buffer
bug-reference-auto-setup-functions: Bug Reference
bug-reference-auto-setup-functions: Bug Reference
bug-reference-bug-regexp: Bug Reference
bug-reference-forge-alist: Bug Reference
bug-reference-setup-from-irc-alist: Bug Reference
bug-reference-setup-from-mail-alist: Bug Reference
bug-reference-setup-from-vc-alist: Bug Reference
bug-reference-url-format: Bug Reference

C
c-default-style: Custom C Indent
c-hungry-delete-key: Hungry Delete
c-mode-hook: Program Modes
c-tab-always-indent: C Indent
c-ts-mode-indent-style: Custom C Indent
cal-html-css-default: Writing Calendar Files
calendar-bahai-all-holidays-flag: Holiday Customizing
calendar-christian-all-holidays-flag: Holiday Customizing
calendar-date-display-form: Date Display Format
calendar-date-style: Date Formats
calendar-day-header-array: Calendar Customizing
calendar-daylight-savings-ends: Daylight Saving
calendar-daylight-savings-ends-time: Daylight Saving
calendar-daylight-savings-starts: Daylight Saving
calendar-daylight-time-offset: Daylight Saving
calendar-daylight-time-zone-name: Sunrise/Sunset
calendar-hebrew-all-holidays-flag: Holiday Customizing
calendar-holiday-marker: Calendar Customizing
calendar-holidays: Holiday Customizing
calendar-initial-window-hook: Calendar Customizing
calendar-intermonth-text: Calendar Customizing
calendar-islamic-all-holidays-flag: Holiday Customizing
calendar-latitude: Sunrise/Sunset
calendar-location-name: Sunrise/Sunset
calendar-longitude: Sunrise/Sunset
calendar-mark-diary-entries-flag: Displaying the Diary
calendar-mark-holidays-flag: Holidays
calendar-month-header: Calendar Customizing
calendar-move-hook: Calendar Customizing
calendar-remove-frame-by-deleting: General Calendar
calendar-standard-time-zone-name: Sunrise/Sunset
calendar-time-display-form: Time Display Format
calendar-time-zone: Sunrise/Sunset
calendar-time-zone-style: Sunrise/Sunset
calendar-today-invisible-hook: Calendar Customizing
calendar-today-marker: Calendar Customizing
calendar-today-visible-hook: Calendar Customizing
calendar-view-diary-initially-flag: Displaying the Diary
calendar-view-holidays-initially-flag: Holidays
calendar-week-start-day: Move to Beginning or End
calendar-weekend-days: Move to Beginning or End
case-fold-search: Lax Search
case-replace: Replacement and Lax Matches
CDPATH, environment variable: General Variables
change-log-version-info-enabled: Change Log Commands
change-log-version-number-regexp-list: Change Log Commands
change-major-mode-with-file-name: Choosing Modes
char-fold-exclude: Lax Search
char-fold-include: Lax Search
char-fold-override: Lax Search
char-fold-symmetric: Lax Search
clone-indirect-buffer-hook: Indirect Buffers
coding: Specify Coding
colon-double-space: Fill Commands
COLORTERM, environment variable: General Variables
column-number-indicator-zero-based: Optional Mode Line
comint-completion-addsuffix: Shell Options
comint-completion-autolist: Shell Options
comint-completion-fignore: Shell Options
comint-completion-recexact: Shell Options
comint-input-autoexpand: History References
comint-input-ignoredups: Shell Options
comint-input-ring-file-name: Shell Ring
comint-insert-previous-argument-from-end: Shell Ring
comint-move-point-for-output: Shell Options
comint-prompt-read-only: Shell Options
comint-scroll-show-maximum-output: Shell Options
comint-scroll-to-bottom-on-input: Shell Options
comint-terminfo-terminal: Shell Options
comint-use-prompt-regexp: Shell Prompts
command-history: Repetition
command-line-args: Emacs Invocation
comment-column: Options for Comments
comment-end: Options for Comments
comment-fill-column: Options for Comments
comment-indent-function: Options for Comments
comment-multi-line: Multi-Line Comments
comment-padding: Options for Comments
comment-start: Options for Comments
comment-start-skip: Options for Comments
compare-ignore-case: Comparing Files
compare-ignore-whitespace: Comparing Files
compilation-always-kill: Compilation
compilation-auto-jump-to-first-error: Compilation Mode
compilation-context-lines: Compilation Mode
compilation-environment: Compilation
compilation-error: Compilation Mode
compilation-error-regexp-alist: Compilation Mode
compilation-hidden-output: Compilation Mode
compilation-max-output-line-length: Compilation
compilation-scroll-output: Compilation
compilation-skip-threshold: Compilation Mode
compilation-warning: Compilation Mode
compile-command: Compilation
completion-auto-help: Completion Options
completion-auto-select: Completion Options
completion-category-overrides: Completion Styles
completion-cycle-threshold: Completion Options
completion-ignored-extensions: Completion Options
completion-styles: Completion Styles
completions-detailed: Name Help
completions-format: Completion Options
completions-header-format: Completion Options
completions-highlight-face: Completion Options
completions-max-height: Completion Options
completions-sort: Completion Options
COMSPEC: Misc Variables
confirm-kill-emacs: Exiting
confirm-kill-processes: Exiting
confirm-nonexistent-file-or-buffer: Completion Exit
context-menu-functions: Menu Mouse Clicks
copy-directory-create-symlink: Copying and Naming
create-lockfiles: Interlocking
ctl-arrow: Text Display
ctl-x-4-map: Prefix Keymaps
ctl-x-map: Prefix Keymaps
cua-enable-cua-keys: CUA Bindings
cua-mode: CUA Bindings
current-input-method: Select Input Method
current-language-environment: Language Environments
cursor-in-non-selected-windows: Cursor Display
cursor-type: Cursor Display
custom-buffer-done-kill: Changing a Variable
custom-enabled-themes: Custom Themes
custom-file: Saving Customizations
custom-safe-themes: Custom Themes
custom-search-field: Browsing Custom
custom-theme-directory: Custom Themes
custom-theme-directory, saving theme files: Creating Custom Themes
custom-theme-load-path: Custom Themes
cycle-spacing-actions: Deletion

D
dabbrev-abbrev-char-regexp: Dabbrev Customization
dabbrev-abbrev-skip-leading-regexp: Dabbrev Customization
dabbrev-case-fold-search: Dabbrev Customization
dabbrev-case-replace: Dabbrev Customization
dabbrev-check-all-buffers: Dynamic Abbrevs
dabbrev-check-other-buffers: Dynamic Abbrevs
dabbrev-ignored-buffer-modes: Dynamic Abbrevs
dabbrev-ignored-buffer-names: Dynamic Abbrevs
dabbrev-ignored-buffer-regexps: Dynamic Abbrevs
dabbrev-limit: Dynamic Abbrevs
DBUS_SESSION_BUS_ADDRESS, environment variable: General Variables
dbx-mode-hook: GUD Customization
debug-on-event: Checklist
debug-on-quit: Checklist
default-directory: File Names
default-frame-alist: Frame Parameters
default-input-method: Select Input Method
default-justification: Enriched Justification
delete-active-region: Using Region
delete-auto-save-files: Auto Save Files
delete-by-moving-to-trash: Misc File Ops
delete-by-moving-to-trash, and Dired: Dired Deletion
delete-old-versions: Backup Deletion
delete-selection-temporary-region: Using Region
delete-trailing-lines: Useless Whitespace
desktop-auto-save-timeout: Saving Emacs Sessions
desktop-clear-preserve-buffers-regexp: Saving Emacs Sessions
desktop-files-not-to-save: Saving Emacs Sessions
desktop-globals-to-clear: Saving Emacs Sessions
desktop-globals-to-save: Saving Emacs Sessions
desktop-load-locked-desktop: Saving Emacs Sessions
desktop-path: Saving Emacs Sessions
desktop-restore-eager: Saving Emacs Sessions
desktop-restore-frames: Saving Emacs Sessions
desktop-save-mode: Saving Emacs Sessions
diary-bahai-entry-symbol: Non-Gregorian Diary
diary-chinese-entry-symbol: Non-Gregorian Diary
diary-comment-start: Fancy Diary Display
diary-date-forms: Diary Customizing
diary-display-function: Diary Display
diary-entry-marker: Calendar Customizing
diary-file: Format of Diary File
diary-hebrew-entry-symbol: Non-Gregorian Diary
diary-include-string: Fancy Diary Display
diary-islamic-entry-symbol: Non-Gregorian Diary
diary-list-entries-hook: Fancy Diary Display
diary-list-include-blanks: Diary Display
diary-mail-days: Displaying the Diary
diary-mark-entries-hook: Fancy Diary Display
diary-nongregorian-listing-hook: Non-Gregorian Diary
diary-nongregorian-marking-hook: Non-Gregorian Diary
diary-nonmarking-symbol: Displaying the Diary
diary-number-of-entries: Diary Customizing
diary-outlook-formats: Importing Diary
diary-print-entries-hook: Diary Display
diary-sexp-entry-symbol: Sexp Diary Entries
diary-show-holidays-flag: Diary Customizing
diff-add-log-use-relative-names: Log Buffer
diff-font-lock-syntax: Diff Mode
diff-jump-to-old-file: Diff Mode
diff-refine: Diff Mode
diff-refine: Diff Mode
diff-switches: Comparing Files
diff-update-on-the-fly: Diff Mode
directory-abbrev-alist: File Aliases
dired-auto-revert-buffer: Dired Updating
dired-chown-program: Operating on Files
dired-confirm-shell-command: Shell Commands in Dired
dired-copy-dereference: Operating on Files
dired-copy-preserve-time: Operating on Files
dired-create-destination-dirs: Operating on Files
dired-create-destination-dirs-on-trailing-dirsep: Operating on Files
dired-dwim-target: Operating on Files
dired-enable-globstar-in-shell: Dired Enter
dired-free-space: Misc Dired Features
dired-garbage-files-regexp: Flagging Many Files
dired-guess-shell-alist-default: Shell Command Guessing
dired-guess-shell-alist-user: Shell Command Guessing
dired-hide-details-hide-information-lines: Misc Dired Features
dired-hide-details-hide-symlink-targets: Misc Dired Features
dired-isearch-filenames: Dired Navigation
dired-keep-marker-copy: Operating on Files
dired-kept-versions: Flagging Many Files
dired-kill-when-opening-new-dired-buffer: Dired Visiting
dired-listing-switches: Dired Enter
dired-listing-switches (MS-DOS): MS-DOS Processes
dired-maybe-use-globstar: Dired Enter
dired-mouse-drag-files: Misc Dired Features
dired-recursive-copies: Operating on Files
dired-recursive-deletes: Dired Deletion
dired-switches-in-mode-line: Dired Enter
dired-use-ls-dired: Dired Enter
dired-vc-rename-file: Operating on Files
dirtrack-list: Directory Tracking
display-battery-mode: Optional Mode Line
display-fill-column-indicator-character: Displaying Boundaries
display-fill-column-indicator-column: Displaying Boundaries
display-hourglass: Display Custom
display-line-numbers: Display Custom
display-line-numbers-current-absolute: Display Custom
display-line-numbers-grow-only: Display Custom
display-line-numbers-offset: Display Custom
display-line-numbers-type: Display Custom
display-line-numbers-widen: Display Custom
display-line-numbers-width: Display Custom
display-line-numbers-width-start: Display Custom
display-raw-bytes-as-hex: Display Custom
display-time-24hr-format: Optional Mode Line
display-time-mail-directory: Optional Mode Line
display-time-mail-face: Optional Mode Line
display-time-mail-file: Optional Mode Line
display-time-use-mail-icon: Optional Mode Line
dnd-indicate-insertion-point: Drag and Drop
dnd-open-file-other-window: Drag and Drop
dnd-scroll-margin: Drag and Drop
doc-view-cache-directory: DocView Conversion
doc-view-continuous: DocView Navigation
doc-view-imenu-enabled: DocView Navigation
doc-view-imenu-flatten: DocView Navigation
doc-view-imenu-format: DocView Navigation
doc-view-resolution: DocView Navigation
doc-view-scale-internally: DocView Navigation
doctex-mode-hook: TeX Misc
dos-codepage: MS-DOS and MULE
dos-display-scancodes: MS-DOS Mouse
dos-hyper-key: MS-DOS Keyboard
dos-keypad-mode: MS-DOS Keyboard
dos-printer: MS-DOS Printing
dos-ps-printer: MS-DOS Printing
dos-super-key: MS-DOS Keyboard
double-click-fuzz: Mouse Buttons
double-click-time: Mouse Buttons

E
echo-keystrokes: Display Custom
eldoc-documentation-functions: Programming Language Doc
eldoc-documentation-strategy: Programming Language Doc
eldoc-echo-area-display-truncation-message: Programming Language Doc
eldoc-echo-area-prefer-doc-buffer: Programming Language Doc
eldoc-echo-area-use-multiline-p: Programming Language Doc
eldoc-idle-delay: Programming Language Doc
eldoc-print-after-edit: Programming Language Doc
electric-pair-delete-adjacent-pairs: Matching
electric-pair-open-newline-between-pairs: Matching
electric-pair-preserve-balance: Matching
electric-pair-skip-whitespace: Matching
electric-quote-chars: Quotation Marks
electric-quote-comment: Quotation Marks
electric-quote-paragraph: Quotation Marks
electric-quote-replace-double: Quotation Marks
electric-quote-string: Quotation Marks
emacs-lisp-mode-hook: Program Modes
EMACSCLIENT_TRAMP, environment variable: emacsclient Options
EMACSCOLORS: Misc Variables
EMACSDATA, environment variable: General Variables
EMACSDOC, environment variable: General Variables
EMACSLOADPATH, environment variable: General Variables
EMACSPATH, environment variable: General Variables
EMACSTEST: Misc Variables
emacs_dir: Misc Variables
EMACS_SERVER_FILE, environment variable: TCP Emacs server
EMAIL, environment variable: General Variables
emerge-combine-versions-template: Combining in Emerge
emerge-startup-hook: Fine Points of Emerge
enable-local-eval: Safe File Variables
enable-local-variables: Safe File Variables
enable-recursive-minibuffers: Minibuffer Edit
enriched-allow-eval-in-display-props: Enriched Properties
enriched-translations: Enriched Mode
eol-mnemonic-dos: Optional Mode Line
eol-mnemonic-mac: Optional Mode Line
eol-mnemonic-undecided: Optional Mode Line
eol-mnemonic-unix: Optional Mode Line
esc-map: Prefix Keymaps
ESHELL, environment variable: General Variables
eval-expression-debug-on-error: Lisp Eval
eval-expression-print-length: Lisp Eval
eval-expression-print-level: Lisp Eval
eval-expression-print-maximum-character: Lisp Eval
eww-search-prefix: Word Search
exec-path: Shell
exit-language-environment-hook: Language Environments
explicit-shell-file-name: Interactive Shell
extended-command-suggest-shorter: M-x

F
face-ignored-fonts: Modifying Fontsets
fast-but-imprecise-scrolling: Scrolling
ff-related-file-alist: Other C Commands
file-coding-system-alist: Recognize Coding
file-name-at-point-functions: Minibuffer History
file-name-coding-system: File Name Coding
file-preserve-symlinks-on-save: Customize Save
fill-column: Fill Commands
fill-column-indicator: Displaying Boundaries
fill-nobreak-predicate: Fill Commands
fill-prefix: Fill Prefix
find-file-existing-other-name: File Aliases
find-file-hook: Visiting
find-file-not-found-functions: Visiting
find-file-run-dired: Visiting
find-file-suppress-same-file-warnings: File Aliases
find-file-visit-truename: File Aliases
find-file-wildcards: Visiting
find-ls-option: Dired and Find
find-sibling-rules: Visiting
focus-follows-mouse: Frame Commands
foldout-mouse-modifiers: Foldout
font-lock-ignore: Traditional Font Lock
font-lock-maximum-decoration: Traditional Font Lock
font-slant-table (MS-Windows): Windows Fonts
font-weight-table (MS-Windows): Windows Fonts
fortran-analyze-depth: ForIndent Cont
fortran-break-before-delimiters: Fortran Autofill
fortran-check-all-num…: ForIndent Vars
fortran-column-ruler-fixed: Fortran Columns
fortran-column-ruler-tabs: Fortran Columns
fortran-comment-indent-char: Fortran Comments
fortran-comment-indent-style: Fortran Comments
fortran-comment-line-extra-indent: Fortran Comments
fortran-comment-line-start: Fortran Comments
fortran-comment-region: Fortran Comments
fortran-continuation-indent: ForIndent Vars
fortran-continuation-string: ForIndent Cont
fortran-directive-re: Fortran Comments
fortran-do-indent: ForIndent Vars
fortran-electric-line-number: ForIndent Num
fortran-if-indent: ForIndent Vars
fortran-line-length: Fortran Columns
fortran-line-number-indent: ForIndent Num
fortran-minimum-statement-indent…: ForIndent Vars
fortran-structure-indent: ForIndent Vars
fortran-tab-mode-default: ForIndent Cont
frame-background-mode: Faces
frame-resize-pixelwise: Frame Commands
frameset-filter-alist: Saving Emacs Sessions
fringe-mode (variable): Fringes

G
gdb-default-window-configuration-file: GDB User Interface Layout
gdb-delete-out-of-scope: Watch Expressions
gdb-display-source-buffer-action: GDB User Interface Layout
gdb-gud-control-all-threads: Multithreaded Debugging
gdb-many-windows: GDB User Interface Layout
gdb-max-source-window-count: GDB User Interface Layout
gdb-mi-decode-strings: Source Buffers
gdb-mode-hook: GUD Customization
gdb-non-stop-setting: Multithreaded Debugging
gdb-restore-window-configuration-after-quit: GDB User Interface Layout
gdb-show-changed-values: Watch Expressions
gdb-show-main: GDB User Interface Layout
gdb-show-threads-by-default: Breakpoints Buffer
gdb-speedbar-auto-raise: Watch Expressions
gdb-stack-buffer-addresses: Stack Buffer
gdb-stopped-functions: Multithreaded Debugging
gdb-switch-reasons: Multithreaded Debugging
gdb-switch-when-another-stopped: Multithreaded Debugging
gdb-thread-buffer-addresses: Threads Buffer
gdb-thread-buffer-arguments: Threads Buffer
gdb-thread-buffer-locations: Threads Buffer
gdb-thread-buffer-verbose-names: Threads Buffer
gdb-use-colon-colon-notation: Watch Expressions
gdb-window-configuration-directory: GDB User Interface Layout
global-cwarn-mode: Other C Commands
global-font-lock-mode: Font Lock
global-mark-ring-max: Global Mark Ring
global-text-scale-adjust-resizes-frames: Text Scale
grep-find-abbreviate: Grep Searching
grep-find-ignored-directories: Grep Searching
grep-find-ignored-directories (Dired): Operating on Files
grep-find-ignored-files (Dired): Operating on Files
grep-match-regexp: Grep Searching
grep-regexp-alist: Compilation Mode
gud-gdb-command-name: GDB Graphical Interface
gud-xdb-directories: Starting GUD
guiler-mode-hook: GUD Customization

H
haiku-control-keysym: Haiku Basics
haiku-debug-on-fatal-error: Haiku Basics
haiku-meta-keysym: Haiku Basics
haiku-shift-keysym: Haiku Basics
haiku-super-keysym: Haiku Basics
help-at-pt-display-when-idle: Help Echo
help-clean-buttons: Help Mode
help-enable-autoload: Lisp Libraries
help-enable-completion-autoload: Lisp Libraries
help-enable-symbol-autoload: Name Help
help-map: Prefix Keymaps
help-window-keep-selected: Help
help-window-select: Help
help-window-select, and apropos commands: Apropos
hi-lock-auto-select-face: Highlight Interactively
hi-lock-exclude-modes: Highlight Interactively
hi-lock-file-patterns-policy: Highlight Interactively
hide-ifdef-shadow: Other C Commands
highlight-nonselected-windows: Mark
HISTFILE, environment variable: General Variables
history-delete-duplicates: Minibuffer History
history-length: Minibuffer History
holiday-bahai-holidays: Holiday Customizing
holiday-christian-holidays: Holiday Customizing
holiday-general-holidays: Holiday Customizing
holiday-hebrew-holidays: Holiday Customizing
holiday-islamic-holidays: Holiday Customizing
holiday-local-holidays: Holiday Customizing
holiday-oriental-holidays: Holiday Customizing
holiday-other-holidays: Holiday Customizing
holiday-solar-holidays: Holiday Customizing
HOME, environment variable: General Variables
horizontal-scroll-bar-mode: Scroll Bars
HOSTNAME, environment variable: General Variables
hourglass-delay: Display Custom
hs-hide-comments-when-hiding-all: Hideshow
hs-isearch-open: Hideshow
hs-special-modes-alist: Hideshow
hscroll-margin: Horizontal Scrolling
hscroll-step: Horizontal Scrolling

I
icon-preference: Icons
ignored-local-variable-values: Safe File Variables
image-animate-loop: Image Mode
image-auto-resize: Image Mode
image-auto-resize-on-window-resize: Image Mode
image-crop-crop-command: Image Mode
image-crop-cut-command: Image Mode
image-cut-color: Image Mode
image-dired-external-viewer: Image-Dired
image-dired-thumb-visible-marks: Image-Dired
image-use-external-converter: Image Mode
imagemagick-enabled-types: Image Mode
imagemagick-types-inhibit: Image Mode
imenu-auto-rescan: Imenu
imenu-auto-rescan-maxout: Imenu
imenu-max-index-time: Imenu
imenu-sort-function: Imenu
indent-tabs-mode: Just Spaces
indent-tabs-mode (Fortran mode): ForIndent Cont
indicate-buffer-boundaries: Displaying Boundaries
indicate-empty-lines: Useless Whitespace
inferior-lisp-program: External Lisp
INFOPATH, environment variable: General Variables
inhibit-eol-conversion: Recognize Coding
inhibit-iso-escape-detection: Recognize Coding
inhibit-startup-buffer-menu: Action Arguments
inhibit-startup-screen: Entering Emacs
initial-environment: Environment
initial-frame-alist: Frame Parameters
initial-scratch-message: Lisp Interaction
input-method-highlight-flag: Input Methods
input-method-verbose-flag: Input Methods
insert-default-directory: Minibuffer File
interpreter-mode-alist: Choosing Modes
isearch-allow-motion: Not Exiting Isearch
isearch-allow-prefix: Not Exiting Isearch
isearch-allow-scroll: Not Exiting Isearch
isearch-hide-immediately: Search Customizations
isearch-lazy-count: Search Customizations
isearch-lazy-highlight: Search Customizations
isearch-mode-map: Special Isearch
isearch-motion-changes-direction: Not Exiting Isearch
isearch-repeat-on-direction-change: Repeat Isearch
isearch-resume-in-command-history: Repetition
isearch-wrap-pause: Repeat Isearch
ispell-complete-word-dict: Spelling
ispell-dictionary: Spelling
ispell-local-dictionary: Spelling
ispell-personal-dictionary: Spelling
ispell-program-name: Spelling

J
jdb-mode-hook: GUD Customization
jit-lock-defer-time: Scrolling

K
kept-new-versions: Backup Deletion
kept-old-versions: Backup Deletion
keyboard-coding-system: Terminal Coding
kill-buffer-delete-auto-save-files: Auto Save Files
kill-buffer-hook: Kill Buffer
kill-do-not-save-duplicates: Kill Options
kill-read-only-ok: Kill Options
kill-ring: Kill Ring
kill-ring-max: Kill Ring
kill-transform-function: Kill Options
kill-whole-line: Killing by Lines
kmacro-ring-max: Keyboard Macro Ring

L
LANG, environment variable: General Variables
large-file-warning-threshold: Visiting
latex-block-names: LaTeX Editing
latex-mode-hook: TeX Misc
latex-run-command: TeX Print
latin1-display: Undisplayable Characters
lazy-count-prefix-format: Search Customizations
lazy-count-suffix-format: Search Customizations
lazy-highlight-initial-delay: Search Customizations
lazy-highlight-interval: Search Customizations
lazy-highlight-max-at-a-time: Search Customizations
lazy-highlight-no-delay-length: Search Customizations
LC_ALL, environment variable: General Variables
LC_COLLATE, environment variable: General Variables
LC_CTYPE, environment variable: General Variables
LC_MESSAGES, environment variable: General Variables
LC_MONETARY, environment variable: General Variables
LC_NUMERIC, environment variable: General Variables
LC_TIME, environment variable: General Variables
line-move-visual: Moving Point
line-number-display-limit: Optional Mode Line
line-number-display-limit-width: Optional Mode Line
lisp-body-indent: Lisp Indent
lisp-indent-offset: Lisp Indent
lisp-interaction-mode-hook: Program Modes
lisp-mode-hook: Program Modes
list-colors-sort: Colors
list-directory-brief-switches: Directories
list-directory-verbose-switches: Directories
list-matching-lines-default-context-lines: Other Repeating Search
list-matching-lines-jump-to-current-line: Other Repeating Search
load-path: Lisp Libraries
load-prefer-newer: Lisp Libraries
locale-charset-language-names: Language Environments
locale-coding-system: Communication Coding
locale-language-names: Language Environments
locale-preferred-coding-systems: Language Environments
locate-command: Dired and Find
LOGNAME, environment variable: General Variables
lpr-add-switches: Printing
lpr-command (MS-DOS): Windows Printing
lpr-commands: Printing
lpr-headers-switches: Printing
lpr-headers-switches (MS-DOS): Windows Printing
lpr-printer-switch: Printing
lpr-switches: Printing
lpr-switches (MS-DOS): Windows Printing
ls-lisp-dirs-first: ls in Lisp
ls-lisp-emulation: ls in Lisp
ls-lisp-format-time-list: ls in Lisp
ls-lisp-ignore-case: ls in Lisp
ls-lisp-support-shell-wildcards: ls in Lisp
ls-lisp-UCA-like-collation: ls in Lisp
ls-lisp-use-insert-directory-program: ls in Lisp
ls-lisp-use-localized-time-format: ls in Lisp
ls-lisp-use-string-collate: ls in Lisp
ls-lisp-verbosity: ls in Lisp

M
magic-fallback-mode-alist: Choosing Modes
magic-mode-alist: Choosing Modes
MAIL, environment variable: General Variables
mail-citation-hook: Citing Mail
mail-default-headers: Mail Headers
mail-dont-reply-to-names: Rmail Reply
mail-personal-alias-file: Mail Aliases
mail-signature: Mail Signature
mail-signature-file: Mail Signature
mail-user-agent: Mail Methods
major-mode: Major Modes
major-mode-remap-alist: Choosing Modes
make-backup-file-name-function: Backup Names
make-backup-files: Backup
make-pointer-invisible: Display Custom
Man-switches: Man Page
mark-even-if-inactive: Using Region
mark-ring-max: Mark Ring
max-mini-window-height: Minibuffer Edit
maximum-scroll-margin: Auto Scrolling
menu-bar-mode: Menu Bars
message-kill-buffer-on-exit: Mail Sending
message-log-max: Echo Area
message-mode-hook: Mail Misc
message-send-hook: Mail Sending
message-send-mail-function: Mail Sending
message-setup-hook: Mail Misc
message-signature: Mail Signature
message-signature-file: Mail Signature
MH, environment variable: General Variables
midnight-hook: Kill Buffer
midnight-mode: Kill Buffer
minibuffer-completion-auto-choose: Completion Commands
minibuffer-default-prompt-format: Basic Minibuffer
minibuffer-eldef-shorten-default: Basic Minibuffer
minibuffer-follows-selected-frame: Basic Minibuffer
minibuffer-local-completion-map: Minibuffer Maps
minibuffer-local-filename-completion-map: Minibuffer Maps
minibuffer-local-map: Minibuffer Maps
minibuffer-local-must-match-map: Minibuffer Maps
minibuffer-local-ns-map: Minibuffer Maps
minibuffer-prompt-properties: Standard Faces
mode-line-in-non-selected-windows: Optional Mode Line
mode-require-final-newline: Customize Save
mode-specific-map: Prefix Keymaps
mouse-1-click-follows-link: Mouse References
mouse-1-click-in-non-selected-windows: Mouse References
mouse-autoselect-window: Other Window
mouse-avoidance-mode: Mouse Avoidance
mouse-drag-and-drop-region: Drag and Drop
mouse-drag-and-drop-region-cross-program: Drag and Drop
mouse-drag-and-drop-region-cut-when-buffers-differ: Drag and Drop
mouse-drag-and-drop-region-show-cursor: Drag and Drop
mouse-drag-and-drop-region-show-tooltip: Drag and Drop
mouse-drag-copy-region: Mouse Commands
mouse-drag-mode-line-buffer: Mouse Commands
mouse-highlight: Mouse References
mouse-scroll-min-lines: Mouse Commands
mouse-wheel-flip-direction: Mouse Commands
mouse-wheel-follow-mouse: Mouse Commands
mouse-wheel-progressive-speed: Mouse Commands
mouse-wheel-scroll-amount: Mouse Commands
mouse-wheel-scroll-amount-horizontal: Mouse Commands
mouse-wheel-tilt-scroll: Mouse Commands
mouse-yank-at-point: Mouse Commands

N
NAME: Misc Variables
NAME, environment variable: General Variables
native-comp-eln-load-path: Lisp Libraries
network-security-level: Network Security
network-security-protocol-checks: Network Security
next-error-find-buffer-function: Compilation Mode
next-error-highlight: Compilation Mode
next-error-highlight-no-select: Compilation Mode
next-error-message-highlight: Compilation Mode
next-line-add-newlines: Moving Point
next-screen-context-lines: Scrolling
NNTPSERVER, environment variable: General Variables
nobreak-char-display: Text Display
normal-erase-is-backspace: DEL Does Not Delete
nroff-mode-hook: Nroff Mode
ns-alternate-modifier: Mac / GNUstep Customization
ns-auto-hide-menu-bar: Mac / GNUstep Customization
ns-command-modifier: Mac / GNUstep Customization
ns-confirm-quit: Mac / GNUstep Customization
ns-control-modifier: Mac / GNUstep Customization
ns-function-modifier: Mac / GNUstep Customization
ns-mwheel-line-height: Mac / GNUstep Customization
ns-pop-up-frames: Mac / GNUstep Events
ns-right-alternate-modifier: Mac / GNUstep Customization
ns-right-command-modifier: Mac / GNUstep Customization
ns-right-control-modifier: Mac / GNUstep Customization
ns-standard-fontset-spec: Defining Fontsets
ns-use-mwheel-acceleration: Mac / GNUstep Customization
ns-use-mwheel-momentum: Mac / GNUstep Customization
ns-use-native-fullscreen: Mac / GNUstep Customization
ns-use-proxy-icon: Mac / GNUstep Customization
nsm-save-host-names: Network Security
nsm-settings-file: Network Security

O
open-paren-in-column-0-is-defun-start: Left Margin Paren
org-agenda-files: Org Organizer
org-publish-project-alist: Org Authoring
org-todo-keywords: Org Organizer
ORGANIZATION, environment variable: General Variables
outline-default-state: Outline Visibility
outline-level: Outline Format
outline-minor-mode-cycle: Outline Minor Mode
outline-minor-mode-prefix: Outline Minor Mode
outline-minor-mode-use-buttons: Outline Minor Mode
outline-mode-hook: Outline Mode
outline-regexp: Outline Format
overflow-newline-into-fringe: Fringes
overline-margin: Display Custom

P
package-archive-priorities: Package Installation
package-archives: Package Installation
package-check-signature: Package Installation
package-directory-list: Package Files
package-enable-at-startup: Package Installation
package-install-upgrade-built-in: Package Installation
package-load-list: Package Installation
package-menu-async: Package Menu
package-menu-hide-low-priority: Package Installation
package-pinned-packages: Package Installation
package-quickstart: Package Installation
package-unsigned-archives: Package Installation
package-user-dir: Package Files
page-delimiter: Pages
paragraph-separate: Paragraphs
paragraph-start: Paragraphs
PATH, environment variable: General Variables
pdb-mode-hook: GUD Customization
perldb-mode-hook: GUD Customization
picture-mode-hook: Picture Mode
picture-tab-chars: Tabs in Picture
plain-tex-mode-hook: TeX Misc
PRELOAD_WINSOCK: Misc Variables
print-region-function (MS-DOS): Windows Printing
printer-name: Printing
printer-name, (MS-DOS/MS-Windows): Windows Printing
prog-mode-hook: Major Modes
project-kill-buffer-conditions: Project Buffer Commands
project-kill-buffers-display-buffer-list: Project Buffer Commands
project-list-file: Switching Projects
project-prefix-map: Prefix Keymaps
project-switch-commands: Switching Projects
ps-black-white-faces: PostScript Variables
ps-font-family: PostScript Variables
ps-font-info-database: PostScript Variables
ps-font-size: PostScript Variables
ps-landscape-mode: PostScript Variables
ps-lpr-command: PostScript Variables
ps-lpr-command (MS-DOS): Windows Printing
ps-lpr-switches: PostScript Variables
ps-lpr-switches (MS-DOS): Windows Printing
ps-multibyte-buffer: PostScript Variables
ps-number-of-columns: PostScript Variables
ps-page-dimensions-database: PostScript Variables
ps-paper-type: PostScript Variables
ps-print-color-p: PostScript Variables
ps-print-header: PostScript Variables
ps-printer-name: PostScript Variables
ps-printer-name (MS-DOS): Windows Printing
ps-use-face-background: PostScript Variables
PWD, environment variable: General Variables

Q
quail-activate-hook: Input Methods
query-about-changed-file: Visiting
query-replace-from-to-separator: Query Replace
query-replace-highlight: Query Replace
query-replace-highlight-submatches: Query Replace
query-replace-lazy-highlight: Query Replace
query-replace-show-replacement: Query Replace
query-replace-skip-read-only: Query Replace

R
read-buffer-completion-ignore-case: Completion Options
read-extended-command-predicate: M-x
read-file-name-completion-ignore-case: Completion Options
read-mail-command: Mail Methods
read-quoted-char-radix: Inserting Text
recenter-positions: Recentering
recenter-redisplay: Recentering
recentf-mode: File Conveniences
redisplay-skip-fontification-on-input: Scrolling
regexp-search-ring-max: Regexp Search
register-preview-delay: Registers
register-separator: Text Registers
remote-file-name-inhibit-locks: Interlocking
repeat-exit-key: Repeating
repeat-exit-timeout: Repeating
replace-lax-whitespace: Replacement and Lax Matches
replace-regexp-lax-whitespace: Replacement and Lax Matches
REPLYTO, environment variable: General Variables
require-final-newline: Customize Save
resize-mini-windows: Minibuffer Edit
revert-buffer-quick-short-answers: Reverting
revert-buffer-with-fine-grain-max-seconds: Reverting
revert-without-query: Reverting
rmail-automatic-folder-directives: Rmail Output
rmail-delete-after-output: Rmail Output
rmail-delete-message-hook: Rmail Deletion
rmail-displayed-headers: Rmail Display
rmail-edit-mode-hook: Rmail Editing
rmail-enable-mime: Rmail Display
rmail-enable-mime-composing: Rmail Reply
rmail-file-coding-system: Rmail Coding
rmail-file-name: Rmail Basics
rmail-highlighted-headers: Rmail Display
rmail-ignored-headers: Rmail Display
rmail-inbox-list: Rmail Files
rmail-mail-new-frame: Rmail Reply
rmail-mbox-format: Rmail Inbox
rmail-mime-prefer-html: Rmail Display
rmail-mode-hook: Rmail
rmail-movemail-flags: Remote Mailboxes
rmail-movemail-program: Movemail
rmail-movemail-search-path: Movemail
rmail-nonignored-headers: Rmail Display
rmail-output-file-alist: Rmail Output
rmail-output-reset-deleted-flag: Rmail Output
rmail-preserve-inbox: Rmail Inbox
rmail-primary-inbox-list: Rmail Inbox
rmail-redisplay-summary: Rmail Summary Edit
rmail-remote-password: Remote Mailboxes
rmail-remote-password-required: Remote Mailboxes
rmail-retry-ignored-headers: Rmail Reply
rmail-secondary-file-directory: Rmail Files
rmail-secondary-file-regexp: Rmail Files
rmail-summary-line-count-flag: Rmail Make Summary
rmail-summary-scroll-between-messages: Rmail Summary Edit
rmail-summary-window-size: Rmail Make Summary

S
safe-local-eval-forms: Safe File Variables
safe-local-variable-values: Safe File Variables
save-abbrevs: Saving Abbrevs
save-interprogram-paste-before-kill: Clipboard
save-some-buffers-default-predicate: Save Commands
SAVEDIR, environment variable: General Variables
scheme-mode-hook: Program Modes
script-representative-chars: Modifying Fontsets
scroll-all-mode: Window Convenience
scroll-bar-adjust-thumb-portion: Scroll Bars
scroll-bar-height: Scroll Bars
scroll-bar-mode: Scroll Bars
scroll-bar-width: Scroll Bars
scroll-conservatively: Auto Scrolling
scroll-down: Scrolling
scroll-down-aggressively: Auto Scrolling
scroll-error-top-bottom: Scrolling
scroll-margin: Auto Scrolling
scroll-minibuffer-conservatively: Auto Scrolling
scroll-preserve-screen-position: Scrolling
scroll-step: Auto Scrolling
scroll-up: Scrolling
scroll-up-aggressively: Auto Scrolling
sdb-mode-hook: GUD Customization
search-exit-option: Not Exiting Isearch
search-highlight: Search Customizations
search-highlight-submatches: Search Customizations
search-invisible: Outline Visibility
search-nonincremental-instead: Search Customizations
search-ring-max: Repeat Isearch
search-slow-speed: Search Customizations
search-slow-window-lines: Search Customizations
search-upper-case: Lax Search
search-whitespace-regexp: Lax Search
select-active-regions: Primary Selection
select-enable-clipboard: Clipboard
select-enable-primary: Clipboard
selective-display-ellipses: Selective Display
send-mail-function: Mail Sending
sendmail-coding-system: Output Coding
sentence-end: Sentences
sentence-end-double-space: Sentences
sentence-end-without-period: Sentences
server-auth-dir: TCP Emacs server
server-auth-key: TCP Emacs server
server-client-instructions: Invoking emacsclient
server-host: TCP Emacs server
server-kill-new-buffers: Invoking emacsclient
server-name: Emacs Server
server-port: TCP Emacs server
server-temp-file-regexp: Invoking emacsclient
server-use-tcp: TCP Emacs server
server-window: Invoking emacsclient
set-language-environment-hook: Language Environments
set-mark-command-repeat-pop: Mark Ring
sgml-xml-mode: HTML Mode
SHELL, environment variable: General Variables
shell-cd-regexp: Directory Tracking
shell-command-buffer-name: Single Shell
shell-command-buffer-name-async: Single Shell
shell-command-default-error-buffer: Single Shell
shell-command-dont-erase-buffer: Single Shell
shell-command-prompt-show-cwd: Single Shell
shell-command-regexp: Shell Mode
shell-completion-execonly: Shell Options
shell-completion-fignore: Shell Options
shell-file-name: Single Shell
shell-popd-regexp: Directory Tracking
shell-prompt-pattern: Shell Prompts
shell-pushd-regexp: Directory Tracking
shift-select-mode: Shift Selection
show-paren-context-when-offscreen: Matching
show-paren-highlight-openparen: Matching
show-paren-predicate: Matching
show-paren-style: Matching
show-paren-when-point-in-periphery: Matching
show-paren-when-point-inside-paren: Matching
show-trailing-whitespace: Useless Whitespace
slitex-mode-hook: TeX Misc
small-temporary-file-directory: Backup
SMTPSERVER, environment variable: General Variables
sort-fold-case: Sorting
sort-numeric-base: Sorting
split-height-threshold: Window Choice
split-width-threshold: Window Choice
split-window-keep-point: Split Window
standard-fontset-spec: Defining Fontsets
standard-indent: Enriched Indentation
suggest-key-bindings: M-x
system-uses-terminfo: Shell Options

T
tab-always-indent: Indent Convenience
tab-bar-close-last-tab-choice: Tab Bars
tab-bar-close-tab-select: Tab Bars
tab-bar-new-tab-choice: Tab Bars
tab-bar-new-tab-to: Tab Bars
tab-bar-select-tab-modifiers: Tab Bars
tab-bar-show: Tab Bars
tab-bar-tab-hints: Tab Bars
tab-bar-tab-name-function: Tab Bars
tab-first-completion: Indent Convenience
tab-stop-list: Tab Stops
tab-width: Text Display
table-cell-horizontal-chars: Table Definition
table-cell-intersection-char: Table Definition
table-cell-vertical-char: Table Definition
table-detect-cell-alignment: Cell Justification
tags-apropos-additional-actions: Looking Up Identifiers
tags-case-fold-search: Identifier Search
tags-file-name: Select Tags Table
tags-table-list: Select Tags Table
TEMP, environment variable: General Variables
temp-buffer-max-height: Temporary Displays
temp-buffer-max-width: Temporary Displays
temporary-file-directory: Backup
TERM, environment variable: General Variables
TERM, environment variable, and display bugs: Checklist
TERM, environment variable, in compilation mode: Compilation Shell
TERM, environment variable, in sub-shell: Shell Options
term-file-aliases: Terminal Init
term-file-prefix: Terminal Init
TERMCAP, environment variable: General Variables
tex-bibtex-command: TeX Print
tex-default-mode: TeX Mode
tex-directory: TeX Print
tex-dvi-print-command: TeX Print
tex-dvi-view-command: TeX Print
tex-main-file: TeX Print
tex-mode-hook: TeX Misc
tex-print-file-extension: TeX Print
tex-run-command: TeX Print
tex-shell-hook: TeX Misc
tex-start-commands: TeX Print
tex-start-options: TeX Print
text-mode-hook: Text Mode
timeclock-ask-before-exiting: Time Intervals
timeclock-file: Time Intervals
timeclock-mode-line-display: Time Intervals
TMP, environment variable: General Variables
TMPDIR, environment variable: General Variables
tool-bar-mode: Tool Bars
tool-bar-style: Tool Bars
tooltip-delay: Tooltips
tooltip-frame-parameters: Tooltips
tooltip-hide-delay: Tooltips
tooltip-short-delay: Tooltips
tooltip-x-offset: Tooltips
tooltip-y-offset: Tooltips
track-eol: Moving Point
tramp-histfile-override: Shell Ring
treesit-defun-tactic: Moving by Defuns
treesit-font-lock-feature-list: Parser-based Font Lock
treesit-font-lock-level: Parser-based Font Lock
treesit-max-buffer-size: Visiting
truncate-lines: Line Truncation
truncate-partial-width-windows: Split Window
tty-menu-open-use-tmm: Menu Bar
tty-setup-hook: Terminal Init
TZ, environment variable: General Variables

U
underline-minimum-offset: Display Custom
undo-limit: Undo
undo-outer-limit: Undo
undo-strong-limit: Undo
unibyte-display-via-language-environment: Unibyte Mode
uniquify-buffer-name-style: Uniquify
use-dialog-box: Dialog Boxes
use-file-dialog: Dialog Boxes
use-system-tooltips: Tooltips
USER, environment variable: General Variables
user-full-name: Mail Headers
user-mail-address: Mail Headers
user-mail-address, in init file: Init Examples
user-mail-address, initialization: General Variables

V
vc-annotate-background-mode: Old Revisions
vc-annotate-switches: Old Revisions
vc-backend-header: Version Headers
vc-command-messages: General VC Options
vc-consult-headers: Version Headers
vc-cvs-global-switches: CVS Options
vc-cvs-stay-local: CVS Options
vc-default-patch-addressee: Preparing Patches
vc-diff-switches: Old Revisions
vc-directory-exclusion-list: VC Directory Buffer
vc-directory-exclusion-list: Project File Commands
vc-follow-symlinks: General VC Options
vc-handled-backends: Customizing VC
vc-log-mode-hook: Log Buffer
vc-log-show-limit: VC Change Log
vc-make-backup-files: General VC Options
vc-prepare-patches-separately: Preparing Patches
vc-revert-show-diff: VC Undo
vc-static-header-alist: Version Headers
vc-suppress-confirm: General VC Options
version-control: Backup Names
VERSION_CONTROL, environment variable: General Variables
view-read-only: Misc Buffer
visible-bell: Display Custom
visible-cursor: Cursor Display
visual-order-cursor-movement: Bidirectional Editing

W
w32-alt-is-meta: Windows Keyboard
w32-apps-modifier: Windows Keyboard
w32-capslock-is-shiftlock: Windows Keyboard
w32-charset-info-alist: Windows Fonts
w32-enable-caps-lock: Windows Keyboard
w32-enable-num-lock: Windows Keyboard
w32-fixed-font-alist: Windows Fonts
w32-get-true-file-attributes: Windows Files
w32-grab-focus-on-raise: Windows Misc
w32-lwindow-modifier: Windows Keyboard
w32-mouse-button-tolerance: Windows Mouse
w32-non-USB-fonts: Windows Fonts
w32-pass-alt-to-system: Windows Keyboard
w32-pass-extra-mouse-buttons-to-system: Windows Mouse
w32-pass-lwindow-to-system: Windows Keyboard
w32-pass-rwindow-to-system: Windows Keyboard
w32-pipe-buffer-size: Windows Processes
w32-pipe-read-delay: Windows Processes
w32-quote-process-args: Windows Processes
w32-recognize-altgr: Windows Keyboard
w32-rwindow-modifier: Windows Keyboard
w32-scroll-lock-modifier: Windows Keyboard
w32-standard-fontset-spec: Defining Fontsets
w32-swap-mouse-buttons: Windows Mouse
w32-unicode-filenames: File Name Coding
w32-use-visible-system-caret: Windows Misc
w32-use-w32-font-dialog: Windows Fonts
WAYLAND_DISPLAY: Misc Variables
what-cursor-show-names: Position Info
which-func-modes: Which Function
whitespace-big-indent-regexp: Useless Whitespace
whitespace-line-column: Useless Whitespace
whitespace-style: Useless Whitespace
window-divider-default-bottom-width: Window Dividers
window-divider-default-places: Window Dividers
window-divider-default-right-width: Window Dividers
window-min-height: Change Window
window-min-width: Change Window
window-resize-pixelwise: Split Window
winner-boring-buffers: Window Convenience
winner-boring-buffers-regexp: Window Convenience
winner-dont-bind-my-keys: Window Convenience
winner-ring-size: Window Convenience
word-wrap-by-category: Visual Line Mode
word-wrap-whitespace-mode: Visual Line Mode
write-region-inhibit-fsync: Customize Save

X
x-gtk-file-dialog-help-text: Dialog Boxes
x-gtk-show-hidden-files: Dialog Boxes
x-gtk-use-native-input: Unibyte Mode
x-input-coding-system: X Coding
x-mouse-click-focus-ignore-position: Mouse Commands
x-select-enable-clipboard-manager: Clipboard
x-select-request-type: Communication Coding
x-stretch-cursor: Cursor Display
x-underline-at-descent-line: Display Custom
xdb-mode-hook: GUD Customization
xref-auto-jump-to-first-definition: Looking Up Identifiers
xref-auto-jump-to-first-xref: Identifier Search
xref-prompt-for-identifier: Looking Up Identifiers

Y
yank-pop-change-selection: Clipboard


Concept Index

Jump to:   #   $   (   *   -   .   /   7   8   ?   _   ~  
A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z  
Index Entry  Section

#
#, in auto-save file names: Auto Save Files

$
$ in file names: File Names

(
( in leftmost column: Left Margin Paren

*
*Messages* buffer: Echo Area

-
–/—/.-./.../.: Amusements

.
.#, lock file names: Interlocking
.dir-locals.el file: Directory Variables
.emacs file: Init File
.mailrc file: Mail Aliases
.newsrc file: Gnus Startup

/
// in file name: Minibuffer File

7
7z: File Archives

8
8-bit display: Unibyte Mode
8-bit input: Unibyte Mode

?
?’ in display: International Chars

_
_emacs init file, MS-Windows: Windows HOME

~
~, in names of backup files: Backup Names
~/.authinfo file: Authentication
~/.authinfo.gpg file: Authentication
~/.config/emacs/init.el file: Init File
~/.emacs file: Init File
~/.emacs.d/%backup%~: Backup Names
~/.emacs.d/gtkrc file: GTK resources
~/.gtkrc-2.0 file: GTK resources
~/.netrc file: Authentication
~/.Xdefaults file: Resources
~/.Xresources file: Resources

A
A and B buffers (Emerge): Overview of Emerge
A-: Modifier Keys
abbrev file: Saving Abbrevs
Abbrev mode: Abbrev Concepts
abbrevs: Abbrevs
abnormal hook: Hooks
aborting recursive edit: Quitting
accented characters: Unibyte Mode
accessible portion: Narrowing
accumulating scattered text: Accumulating Text
action options (command line): Emacs Invocation
activating the mark: Mark
active region: Mark
active text: Help Echo
adaptive filling: Adaptive Fill
added files, VC: Registering
adding to the kill ring in Dired: Misc Dired Features
addpm, MS-Windows installation program: MS-Windows Registry
adjust buffer font size: Text Scale
adjust global font size: Text Scale
aggressive scrolling: Auto Scrolling
alarm clock: Appointments
align exclusion rules: Code Alignment
aligning code: Code Alignment
alignment for comments: Comment Commands
alignment rules: Code Alignment
alignment sections: Code Alignment
Alt key (MS-Windows): Windows Keyboard
Alt key invokes menu (Windows): Windows Keyboard
Alt key, serving as Meta: User Input
Alt, modifier key: Modifier Keys
Alt-TAB vs M-TAB (MS-Windows): Windows Keyboard
ALTERNATE_EDITOR environment variable: emacsclient Options
AltGr key (MS-Windows): Windows Keyboard
ange-ftp: Remote Files
animate: Amusements
animated images: Image Mode
anonymous FTP: Remote Files
appending kills in the ring: Appending Kills
appointment notification: Appointments
apropos: Apropos
apropos search results, order by score: Apropos
Arabic: Language Environments
arc: File Archives
Archive mode: File Archives
arguments (command line): Emacs Invocation
arguments to commands: Arguments
arrow keys: Moving Point
ASCII: User Input
ASCII (language environment): Language Environments
ASCII art: Text
Asm mode: Asm Mode
assembler mode: Asm Mode
astronomical day numbers: Calendar Systems
at-point documentation for program symbols: Programming Language Doc
attached frame (of speedbar): Speedbar
attribute (Rmail): Rmail Labels
attributes of mode line, changing: Optional Mode Line
Auto Compression mode: Compressed Files
Auto Fill mode: Auto Fill
Auto Revert mode: Auto Revert
Auto Save mode: Auto Save
auto-save for remote files: Auto Save Files
autoload: Lisp Libraries
autoload Lisp libraries: Init Examples
automatic scrolling: Auto Scrolling
automatic version backups: CVS Options
avoiding mouse in the way of your typing: Mouse Avoidance
Awk mode: Program Modes
AWK mode: C Modes

B
back end (version control): Version Control Systems
back reference, in regexp: Regexp Backslash
back reference, in regexp replacement: Regexp Replace
background color: Faces
background color, command-line argument: Colors X
background for menus (X resource): Table of Resources
background mode, on xterm: General Variables
background syntax highlighting: Font Lock
BACKSPACE vs DEL: DEL Does Not Delete
backtrace: Crashing
backtrace for bug reports: Checklist
backup file: Backup
backup file names: Backup Names
backup file names on MS-DOS: MS-DOS File Names
backup files, choosing a major mode: Choosing Modes
backup, and user-id: Backup Copying
backups for remote files: Remote Files
Bahá’í calendar: Calendar Systems
balanced expression: Expressions
balloon help: Help Echo
base buffer: Indirect Buffers
base direction of paragraphs: Bidirectional Editing
basic, completion style: Completion Styles
batch mode: Initial Options
battery status (on mode line): Optional Mode Line
Bazaar: Version Control Systems
Belarusian: Language Environments
Bengali: Language Environments
bidi formatting control characters: Bidirectional Editing
bidirectional editing: Bidirectional Editing
binding: Commands
binding keyboard macros: Save Keyboard Macro
binding keys: Rebinding
blank lines: Blank Lines
blank lines in programs: Multi-Line Comments
blinking cursor: Cursor Display
blinking cursor disable, command-line argument: Misc X
body lines (Outline mode): Outline Format
bookmark annotations: Bookmarks
bookmarks: Bookmarks
border color, command-line argument: Colors X
borders (X Window System): Borders X
boredom: Amusements
bound branch (Bazaar VCS): Pulling / Pushing
brace in column zero and fontification: Traditional Font Lock
braces, moving across: Moving by Parens
branch (version control): Branches
Brazilian Portuguese: Language Environments
Browse-URL: Browse-URL
bubbles: Amusements
buffer contents: Buffers
buffer definitions index: Imenu
buffer list, customizable: Buffer Menus
Buffer Menu: Several Buffers
buffer size display: Optional Mode Line
buffer size, maximum: Buffers
buffer text garbled: Text Garbled
buffer-local hooks: Hooks
buffers: Buffers
bug criteria: Bug Criteria
bug reference: Bug Reference
bug reporting, checklist: Checklist
bug reporting, principles: Understanding Bug Reporting
bug tracker: Known Problems
bugs: Bugs
build details: Initial Options
building programs: Building
built-in package: Package Menu
built-in package: Package Statuses
Bulgarian: Language Environments
Burmese: Language Environments
butterfly: Amusements
button-down events: Mouse Buttons
buttons: Mouse References
buttons (customization buffer): Customization Groups
buttons at buffer position: Editing Format Info
bypassing init and default.el file: Initial Options
byte code: Lisp Libraries
byte-compiling several files (in Dired): Operating on Files
bzr: Version Control Systems

C
C editing: Programs
C mode: C Modes
C# mode: Program Modes
C++ class browser, tags: Tags Tables
C++ mode: C Modes
C-: User Input
cache of file names: File Name Cache
calendar: Calendar/Diary
calendar and HTML: Writing Calendar Files
calendar and LaTeX: Writing Calendar Files
calendar layout: Calendar Customizing
calendar week numbers: Calendar Customizing
calendar, first day of week: Move to Beginning or End
call Lisp functions, command-line argument: Action Arguments
camel case: MixedCase Words
candle lighting times: Sexp Diary Entries
capitalizing words: Case
case conversion: Case
case folding in replace commands: Replacement and Lax Matches
case folding in search: Lax Search
case in completion: Completion Options
case preservation in replace commands: Replacement and Lax Matches
case-sensitivity and completion: Completion Options
case-sensitivity and search: Lax Search
case-sensitivity and tags search: Identifier Search
categories of characters: Regexp Backslash
CBZ file: Document View
cells, for text-based tables: Table Definition
centering: Fill Commands
centralized version control: VCS Repositories
Cham: Language Environments
change buffers: Select Buffer
change Emacs directory: Initial Options
change log: Change Log
Change Log mode: Change Log Commands
changes, undoing: Undo
changeset-based version control: VCS Changesets
changing file group (in Dired): Operating on Files
changing file owner (in Dired): Operating on Files
changing file permissions (in Dired): Operating on Files
changing file time (in Dired): Operating on Files
char mode (terminal emulator): Terminal emulator
character classes, in regular expressions: Regexps
character equivalence in search: Lax Search
character folding in replace commands: Replacement and Lax Matches
character folding in search: Lax Search
character set (keyboard): User Input
character set of character at point: International Chars
character set, in regular expressions: Regexps
character syntax: Init Syntax
characters (in text): Text Display
characters in a certain charset: Charsets
characters which belong to a specific language: Regexp Backslash
characters with no font glyphs: Text Display
characters, inserting by name or code-point: Inserting Text
charsets: Charsets
cheat sheet of popular Emacs commands: Misc Help
checking out files: VCS Concepts
checking spelling: Spelling
checking syntax: Flymake
checklist before reporting a bug: Checklist
Chinese: Language Environments
Chinese calendar: Calendar Systems
choosing a major mode: Choosing Modes
choosing a minor mode: Choosing Modes
ciphers: Amusements
citing mail: Citing Mail
CKJ characters: Modifying Fontsets
class browser, C++: Tags Tables
Cleartype: Windows Fonts
click events: Mouse Buttons
client frame: emacsclient Options
client-side fonts: Fonts
clipboard: Clipboard
clipboard manager: Clipboard
clocking time: Time Intervals
close buffer: Kill Buffer
close file: Kill Buffer
CMake mode: Program Modes
code alignment: Code Alignment
codepage, MS-DOS: MS-DOS and MULE
codepoint of a character: Modifying Fontsets
coding standards for Emacs submissions: Coding Standards
coding systems: Coding Systems
collision: Interlocking
color emulation on black-and-white printers: PostScript Variables
color name: Colors
color of window, from command line: Colors X
color scheme: Custom Themes
Column Number mode: Optional Mode Line
columns (and rectangles): Rectangles
columns (indentation): Indentation
columns, splitting: Two-Column
Comint mode: Shell Mode
comint-highlight-input face: Interactive Shell
comint-highlight-prompt face: Interactive Shell
command: Commands
command history: Repetition
command line arguments: Emacs Invocation
commands in *xref* buffers: Xref Commands
comments: Comments
comments on customized settings: Changing a Variable
Common Lisp: External Lisp
compare files (in Dired): Comparison in Dired
comparing 3 files (diff3): Comparing Files
comparing files: Comparing Files
compilation buffer, keeping point at end: Compilation
compilation errors: Compilation
Compilation mode: Compilation Mode
compilation mode faces: Compilation Mode
compilation under MS-DOS: MS-DOS Processes
complete key: Keys
completion: Completion
completion (Lisp symbols): Symbol Completion
completion (symbol names): Symbol Completion
completion alternative: Completion
completion list: Completion Commands
completion style: Completion Styles
completion, walking through candidates: Minibuffer History
compose character: Unibyte Mode
compressing files (in Dired): Operating on Files
compression: Compressed Files
Conf mode: Program Modes
confirming in the minibuffer: Completion Exit
conflicts, VC: Merging
connecting to remote host: Remote Host
connection-local variables: Connection Variables
contents of a buffer: Buffers
context menu: Menu Mouse Clicks
continuation line: Continuation Lines
contributing to Emacs: Contributing
Control: User Input
control character: User Input
control characters on display: Text Display
converting text to upper or lower case: Case
Coptic calendar: Calendar Systems
copy: Cut and Paste
copy/paste to/from primary selection (macOS): Mac / GNUstep Basics
copying files: Copying and Naming
copying files (in Dired): Operating on Files
copying text: Yanking
copyright assignment: Copyright Assignment
CORBA IDL mode: C Modes
core dump: Crashing
correcting spelling: Spelling
CPerl mode: Program Modes
crash report: Crashing
crashes: Auto Save
crashes, Haiku: Haiku Basics
create a text-based table: Table Creation
creating files: Visiting
creating frames: Creating Frames
Croatian: Language Environments
cropping images: Image Mode
cryptanalysis: Amusements
CSS mode: Program Modes
CSSC: Version Control Systems
CUA key bindings: CUA Bindings
curly quotes: Quotation Marks
curly quotes, and terminal capabilities: Text Display
curly quotes, inserting: Inserting Text
current buffer: Buffers
current function name in mode line: Which Function
current message (Rmail): Rmail Basics
current project: Project File Commands
cursor: Point
cursor color, command-line argument: Colors X
cursor face: Faces
cursor in non-selected windows: Cursor Display
cursor location: Position Info
cursor location, on MS-DOS: Text and Binary
cursor motion: Moving Point
cursor shape on MS-DOS: MS-DOS Display
cursor, blinking: Cursor Display
cursor, visual-order motion: Bidirectional Editing
curved quotes: Quotation Marks
curved quotes, and terminal capabilities: Text Display
curved quotes, inserting: Inserting Text
custom themes: Custom Themes
custom themes, creating: Creating Custom Themes
customizable variable: Easy Customization
customization: Customization
customization buffer: Easy Customization
customization groups: Customization Groups
customization of menu face: Standard Faces
customizing faces: Face Customization
customizing Lisp indentation: Lisp Indent
customizing variables: Changing a Variable
cut: Cut and Paste
cut and paste: Glossary
cutting text: Deletion and Killing
cvs: VC Directory Mode
CVS: Version Control Systems
CVS directory mode: VC Directory Mode
CWarn mode: Other C Commands
cycle visibility, in Outline mode: Outline Visibility
Cyrillic: Language Environments
Czech: Language Environments

D
daemon, Emacs: Emacs Server
day of year: General Calendar
daylight saving time: Daylight Saving
DBX: Debuggers
deactivating the mark: Mark
dead character: Unibyte Mode
debbugs package: Known Problems
debuggers: Debuggers
debugging Emacs, tricks and techniques: Checklist
debugging X problems: Table of Resources
decentralized version control: VCS Repositories
decoding mail messages (Rmail): Rmail Coding
decoding non-ASCII keyboard input on X: Communication Coding
decrease buffer font size: Text Scale
decrypting files (in Dired): Operating on Files
default argument: Basic Minibuffer
default directory: Minibuffer File
default directory, of a buffer: File Names
default face: Faces
default file name: File Names
default search mode: Search Customizations
default.el file, not loading: Initial Options
default.el, the default init file: Init File
defining keyboard macros: Keyboard Macros
defuns: Moving by Defuns
DEL does not delete: DEL Does Not Delete
DEL vs BACKSPACE: DEL Does Not Delete
Delete Selection mode: Using Region
delete window: Change Window
deleting auto-save files: Flagging Many Files
deleting blank lines: Blank Lines
deleting characters and lines: Erasing
deleting files (in Dired): Dired Deletion
deleting rows and column in text-based tables: Table Rows and Columns
deleting some backup files: Flagging Many Files
deleting windows: Change Window
deletion: Deletion and Killing
deletion (of files): Misc File Ops
deletion (Rmail): Rmail Deletion
dereference symbolic links: Operating on Files
desktop configuration: Saving Emacs Sessions
desktop restore in daemon mode: Saving Emacs Sessions
desktop shortcut, MS-Windows: Windows Startup
deterministic build: Initial Options
Devanagari: Language Environments
device for Emacs terminal I/O: Initial Options
dialog boxes: Dialog Boxes
Dialog X Resources (Lucid widgets): Lucid Resources
diary: Diary
diary buffer: Diary Display
diary file: Format of Diary File
Diff mode: Diff Mode
digest message: Rmail Digest
directional window selection: Window Convenience
directories in buffer names: Uniquify
directory header lines: Subdirectory Motion
directory listing: Directories
directory listing on MS-DOS: MS-DOS Processes
directory name abbreviation: File Aliases
directory tracking: Directory Tracking
directory where Emacs starts on MS-Windows: Windows Startup
directory-local variables: Directory Variables
Dired: Dired
Dired and version control: Misc Dired Features
Dired sorting: Dired Updating
Dired sorting order, on MS-Windows/MS-DOS: ls in Lisp
Dired, and MS-Windows/MS-DOS: ls in Lisp
Dirtrack mode: Directory Tracking
disable restoring of desktop configuration: Saving Emacs Sessions
disable window system: Initial Options
disabled command: Disabling
disabling remote files: Remote Files
DISPLAY environment variable: Display X
display for Emacs frame: Initial Options
display line numbers: Display Custom
display name (X Window System): Display X
display of buffer size: Optional Mode Line
display of current line number: Optional Mode Line
display server: Multiple Displays
display, incorrect: Screen Garbled
distributed version control: VCS Repositories
DNS mode: Program Modes
Dockerfile mode: Program Modes
DocTeX mode: TeX Mode
document viewer (DocView): Document View
documentation for program symbols: Programming Language Doc
documentation string: Key Help
DocView mode: Document View
DOS applications, running from Emacs: Windows Processes
DOS codepages: MS-DOS and MULE
DOS-style end-of-line display: Recognize Coding
DOS-to-Unix conversion of files: Text and Binary
double clicks: Mouse Buttons
double slash in file name: Minibuffer File
down events: Mouse Buttons
downcase file names: Transforming File Names
drag and drop: Drag and Drop
drag and drop, Dired: Misc Dired Features
drag events: Mouse Buttons
drastic changes: Reverting
dribble file: Checklist
DSSSL mode: Program Modes
dunnet: Amusements
Dutch: Language Environments
DVI file: Document View

E
early init file: Early Init File
early-init.el file: Early Init File
Ebrowse: Tags Tables
echo area: Echo Area
echo area message: Echo Area
echoing: Echo Area
EDE (Emacs Development Environment): EDE
Edebug: Checklist
editable fields (customization buffer): Customization Groups
editing binary files: Editing Binary Files
editing in Picture mode: Basic Picture
editing level, recursive: Recursive Edit
EDITOR environment variable: Emacs Server
eight-bit character set: International Chars
ElDoc mode: Programming Language Doc
Electric Indent mode: Indent Convenience
Electric Pair mode: Matching
Electric Quote mode: Quotation Marks
Eliza: Amusements
Emacs as a server: Emacs Server
Emacs Development Environment: EDE
Emacs icon, a gnu: Icons X
Emacs initialization file: Init File
Emacs Lisp mode: Lisp Eval
Emacs Lisp package archive: Packages
emacs-internal, coding system: Coding Systems
emacs22, completion style: Completion Styles
emacsclient: Emacs Server
emacsclient invocation: Invoking emacsclient
emacsclient options: emacsclient Options
emacsclient, on MS-Windows: Windows Startup
emacsclient.exe: Windows Startup
emacsclientw.exe: Windows Startup
emacs_backtrace.txt file, MS-Windows: Crashing
email: Sending Mail
embedded widgets: Embedded WebKit Widgets
Emerge: Emerge
emergency escape: Emergency Escape
emoji input: Input Methods
enabling Transient Mark mode temporarily: Disabled Transient Mark
encoding of characters: International
encrypted files, choosing a major mode: Choosing Modes
encrypted mails (reading in Rmail): Rmail Display
encrypting files (in Dired): Operating on Files
encryption: Network Security
end-of-line convention, mode-line indication: Mode Line
end-of-line conversion: Coding Systems
end-of-line conversion on MS-DOS/MS-Windows: Text and Binary
English: Language Environments
Enriched mode: Enriched Text
enriched text: Enriched Text
entering Emacs: Entering Emacs
entering passwords: Passwords
environment variables: Environment
environment variables (macOS): Mac / GNUstep Basics
environment variables for subshells: Interactive Shell
environment variables in file names: File Names
EPUB file: Document View
equivalent character sequences: Lax Search
erasing characters and lines: Erasing
error log: Compilation
error message: Echo Area
errors in init file: Initial Options
ESC replacing Meta key: User Input
escape sequences in files: Recognize Coding
escape-glyph face: Text Display
ESHELL environment variable: Interactive Shell
Esperanto: Language Environments
etags: Tags Tables
etags program: Create Tags Table
Ethiopic: Language Environments
Ethiopic calendar: Calendar Systems
European character sets: Unibyte Mode
evaluate expression, command-line argument: Action Arguments
evaluation, Emacs Lisp: Lisp Eval
events on macOS: Mac / GNUstep Events
exit incremental search: Basic Isearch
exiting: Exiting
exiting recursive edit: Recursive Edit
expanding subdirectories in Dired: Subdirectories in Dired
expansion (of abbrevs): Abbrevs
expansion of C macros: Other C Commands
expansion of environment variables: File Names
expression: Expressions
expunging (Rmail): Rmail Deletion

F
face at point: International Chars
face colors, setting: Colors
faces: Faces
faces for highlighting query replace: Query Replace
faces for highlighting search matches: Basic Isearch
faces for mode lines: Standard Faces
faces for text-mode menus: Standard Faces
faces under MS-DOS: MS-DOS Display
faces, customizing: Face Customization
failed merges: Comparing Files
fallback modes: Specifying File Variables
FB2 file: Document View
Feedmail: Mail Sending
FFAP minor mode: FFAP
fido mode: Icomplete
file archives: File Archives
file comparison (in Dired): Comparison in Dired
file database (locate): Dired and Find
file dates: Interlocking
file directory: Directories
file local variables: File Variables
file locking: Interlocking
file management: Dired
file modes: Misc File Ops
file name caching: File Name Cache
file names: File Names
file names on MS-Windows: Windows Files
file names under MS-DOS: MS-DOS File Names
file names under Windows 95/NT: MS-DOS File Names
file names with non-ASCII characters: File Name Coding
file names, invalid characters on MS-Windows: Windows Files
file names, quote special characters: Quoted File Names
file notifications: Auto Revert
file ownership, and backup: Backup Copying
file permissions: Misc File Ops
file selection dialog: Visiting
file selection dialog, how to disable: Dialog Boxes
file shadows: File Shadowing
file truenames: File Aliases
file version in change log entries: Change Log Commands
file, warning when size is large: Visiting
file-based version control: VCS Changesets
file-name completion, on MS-Windows: Windows Files
file-name encoding, MS-Windows: File Name Coding
files: Files
files added to VCS: Registering
files, visiting and saving: Visiting
filesets: Filesets
filesets, VC: Basic VC Editing
filesets, VC, in Dired buffers: Version Control
fill prefix: Fill Prefix
filling text: Filling
find: File Name Cache
find and Dired: Dired and Find
find definition of symbols: Looking Up Identifiers
find Info manual by its file name: Misc Help
find references to symbols: Looking Up Identifiers
finder: Package Keywords
finding file at point: FFAP
finding files containing regexp matches (in Dired): Marks vs Flags
finding strings within text: Search
firewall, and accessing remote files: Remote Files
fixing incorrectly decoded mail messages: Rmail Coding
flagging files (in Dired): Dired Deletion
flagging many files for deletion (in Dired): Flagging Many Files
flex, completion style: Completion Styles
Flyspell mode: Spelling
folding editing: Foldout
Follow mode: Follow Mode
follow symbolic links: Operating on Files
font antialiasing (MS Windows): Windows Fonts
font backend selection (Haiku): Haiku Fonts
font backend selection (MS-Windows): Windows Fonts
font for menus (X resource): Table of Resources
Font Lock mode: Font Lock
font lookup, MS-Windows: Windows Fonts
font name (X Window System): Font X
font of character at point: International Chars
font properties (MS Windows): Windows Fonts
font scripts (MS Windows): Windows Fonts
font size of default face, increase or decrease: Text Scale
font specification (MS Windows): Windows Fonts
font Unicode subranges (MS Windows): Windows Fonts
font-lock via tree-sitter: Parser-based Font Lock
fontconfig: Fonts
fonts: Fonts
fonts and faces: Face Customization
fonts for PostScript printing: PostScript Variables
fonts for various scripts: Fontsets
fonts, emulating under MS-DOS: MS-DOS Display
fonts, how to ignore: Modifying Fontsets
fontsets: Fontsets
fontsets, modifying: Modifying Fontsets
foreground color, command-line argument: Colors X
foreground for menus (X resource): Table of Resources
formfeed character: Pages
Fortran 77 and Fortran 90, 95, 2003, 2008: Fortran
Fortran continuation lines: ForIndent Cont
Fortran fixed form and free form: Fortran
Fortran mode: Fortran
fortune cookies: Mail Amusements
forwarding a message: Rmail Reply
frame: Screen
frame focus policy, MS-Windows: Windows Misc
frame size under MS-DOS: MS-DOS Display
frame size, specifying default: Frame Parameters
frame title, command-line argument: Title X
frames: Frames
frames on MS-DOS: MS-DOS Display
frameset: Configuration Registers
frameset, saving in a register: Configuration Registers
French: Language Environments
French Revolutionary calendar: Calendar Systems
fringe face: Standard Faces
fringes: Fringes
fringes, and continuation lines: Continuation Lines
fringes, and unused line indication: Useless Whitespace
fringes, for debugging: Source Buffers
FTP: Remote Files
fullheight, command-line argument: Window Size X
fullscreen, command-line argument: Window Size X
fullwidth, command-line argument: Window Size X
function key: Keymaps
function, move to beginning or end: Moving by Defuns
future history for file names: Minibuffer History

G
games: Amusements
gamma correction (X resource): Table of Resources
garbled display: Screen Garbled
garbled text: Text Garbled
gateway, and remote file access with ange-ftp: Remote Files
GDB: Debuggers
GDB User Interface layout: GDB User Interface Layout
geometry of Emacs window: Window Size X
geometry, command-line argument: Window Size X
Georgian: Language Environments
German: Language Environments
getting help with keys: Basic Help
Ghostscript, use for PostScript printing: Windows Printing
git: Version Control Systems
git source of package: Fetching Package Sources
Glasses mode: MixedCase Words
Global Auto Revert mode: Auto Revert
global keymap: Keymaps
global mark: CUA Bindings
global mark ring: Global Mark Ring
global substitution: Replace
globstar, in Dired: Dired Enter
glossary: Glossary
glyphless characters: Text Display
glyphless-char face: Text Display
gnu.emacs.help’ newsgroup: Service
Gnus: Gnus
GNUstep: Mac OS / GNUstep
Go Moku: Amusements
Goto Address mode: Goto Address mode
graphic characters: Inserting Text
Greek: Language Environments
Gregorian calendar: Other Calendars
grouping, in regular expressions: Regexp Backslash
growing minibuffer: Minibuffer Edit
GTK font pattern: Fonts
GTK input methods: Unibyte Mode
GTK+ resources: GTK resources
GTK+ styles: GTK styles
GTK+ widget classes: GTK Names in Emacs
GTK+ widget names: GTK Widget Names
GTK+ widget names in Emacs: GTK Names in Emacs
GUD interaction buffer: Debugger Operation
GUD library: Debuggers
GUD Tooltip mode: Debugger Operation
guessing shell commands for files (in Dired): Shell Command Guessing
guillemets: Quotation Marks
Gujarati: Language Environments
gzip: Compressed Files

H
H-: Modifier Keys
Haiku: Haiku
haiku application: Haiku Basics
haiku debugger: Haiku Basics
haiku installation: Haiku Basics
haiku keymap: Haiku Basics
haiku tooltips: Haiku Basics
Han: International
handwriting: PostScript
Hangul: International
hard links (creation): Copying and Naming
hard links (in Dired): Operating on Files
hard links (visiting): File Aliases
hard newline: Hard and Soft Newlines
hardcopy: Printing
header (TeX mode): TeX Print
header line (Dired): Subdirectory Motion
header-line face: Standard Faces
header-line-highlight face: Standard Faces
headers (of mail message): Mail Headers
heading lines (Outline mode): Outline Format
Hebrew: Language Environments
Hebrew calendar: Calendar Systems
height of minibuffer: Minibuffer Edit
height of the horizontal scroll bar: Scroll Bars
help: Help
help buffer: Help
help in using Emacs: Service
help mode: Help Mode
help text, in GTK+ file chooser: Dialog Boxes
help, viewing web pages: Help Mode
help-gnu-emacs’ mailing list: Service
hex editing: Editing Binary Files
Hexl mode: Editing Binary Files
hg: Version Control Systems
Hi Lock mode: Highlight Interactively
hidden files, in GTK+ file chooser: Dialog Boxes
Hide-ifdef mode: Other C Commands
Hideshow mode: Hideshow
hiding details in Dired: Misc Dired Features
hiding subdirectories (Dired): Hiding Subdirectories
Highlight Changes mode: Highlight Interactively
highlight current line: Cursor Display
highlighting by matching: Highlight Interactively
highlighting lines of text: Highlight Interactively
highlighting matching parentheses: Matching
highlighting phrase: Highlight Interactively
highlighting region: Disabled Transient Mark
highlighting symbol at point: Highlight Interactively
Hindi: International
history of commands: Repetition
history of minibuffer input: Minibuffer History
history of webkit buffers: Embedded WebKit Widgets
history reference: History References
holiday forms: Holiday Customizing
holidays: Holidays
HOME directory on MS-Windows: Windows HOME
home directory shorthand: Minibuffer File
HOME directory under MS-DOS: MS-DOS File Names
homoglyph face: Text Display
hook: Hooks
Horizontal Scroll Bar: Scroll Bars
Horizontal Scroll Bar mode: Scroll Bars
horizontal scrolling: Horizontal Scrolling
hourglass pointer display: Display Custom
HTML mode: HTML Mode
hungry deletion (C Mode): Hungry Delete
hunk, diff: Diff Mode
Hyper (under MS-DOS): MS-DOS Keyboard
Hyper, modifier key: Modifier Keys
hyperlink: Help Mode
hyperlinks: Mouse References

I
iCalendar support: Importing Diary
Icomplete mode: Icomplete
Icomplete vertical mode: Icomplete
Icon mode: Program Modes
iconifying: Exiting
icons (X Window System): Icons X
icons, on clickable buttons: Icons
icons, toolbar: Tool Bars
identifier, finding definition of: Looking Up Identifiers
IDL mode: C Modes
IDLWAVE mode: Program Modes
ignore case: Glossary
ignore font: Modifying Fontsets
ignored file names, in completion: Completion Options
image animation: Image Mode
image resize: Image Mode
image rotation: Image Mode
image-dired: Image-Dired
image-dired mode: Image-Dired
ImageMagick support: Image Mode
images, viewing: Image Mode
IMAP mailboxes: Remote Mailboxes
IME, MS-Windows: Windows Keyboard
in-situ subdirectory (Dired): Subdirectories in Dired
inbox file: Rmail Inbox
incorrect fontification: Traditional Font Lock
increase buffer font size: Text Scale
incremental search: Incremental Search
incremental search, edit search string: Repeat Isearch
incremental search, exiting: Basic Isearch
incremental search, go to first or last occurrence: Special Isearch
incremental search, help on special keys: Special Isearch
incremental search, input method interference: Input Methods
indentation: Indentation
indentation for comments: Comment Commands
indentation for programs: Program Indent
index of buffer definitions: Imenu
indirect buffer: Indirect Buffers
indirect buffers and outlines: Outline Views
inferior process: Compilation
inferior processes under MS-DOS: MS-DOS Processes
Info: Misc Help
init file: Init File
init file .emacs on MS-Windows: Windows HOME
init file, default name under MS-DOS: MS-DOS File Names
init file, not loading: Initial Options
initial options (command line): Emacs Invocation
initials, completion style: Completion Styles
input event: User Input
input item, isearch: Basic Isearch
input method style, X: Table of Resources
input methods: Input Methods
input methods, native: Unibyte Mode
input methods, X: Table of Resources
input with the keyboard: User Input
inputStyle (X resource): Table of Resources
insert character by name or code-point: Input Methods
insert file contents, command-line argument: Action Arguments
insert Unicode character: Inserting Text
inserted subdirectory (Dired): Subdirectories in Dired
inserting blank lines: Blank Lines
inserting Emoji: Input Methods
inserting matching parentheses: Matching
inserting rows and columns in text-based tables: Table Rows and Columns
insertion: Inserting Text
INSIDE_EMACS environment variable: Interactive Shell
Integrated development environment: EDE
interactive highlighting: Highlight Interactively
interactively edit search string: Repeat Isearch
internal border width, command-line argument: Borders X
international characters in .emacs: Init Non-ASCII
international files from DOS/Windows systems: Coding Systems
international scripts: International
international support (MS-DOS): MS-DOS and MULE
Internet search: Word Search
Intlfonts for PostScript printing: PostScript Variables
Intlfonts package, installation: Fontsets
invisible lines: Outline Mode
invisible text, and query-replace: Query Replace
invisible text, searching for: Special Isearch
invocation (command line arguments): Emacs Invocation
invoking Emacs from Windows Explorer: Windows Startup
IPA: Language Environments
isearch: Incremental Search
isearch face: Basic Isearch
isearch input item: Basic Isearch
isearch multiple buffers: Other Repeating Search
isearch multiple files: Other Repeating Search
isearch-fail face: Error in Isearch
isearch-move property: Not Exiting Isearch
isearch-scroll property: Not Exiting Isearch
Islamic calendar: Calendar Systems
ISO commercial calendar: Calendar Systems
ISO Latin character sets: Unibyte Mode
iso-ascii library: Unibyte Mode
iso-transl library: Unibyte Mode
ispell program: Spelling
issue tracker: Known Problems
Italian: Language Environments

J
Japanese: Language Environments
jar: File Archives
Java class archives: File Archives
Java mode: C Modes
Javascript mode: Program Modes
JDB: Debuggers
JSON mode: Program Modes
Julian calendar: Calendar Systems
Julian day numbers: Calendar Systems
just-in-time (JIT) font-lock: Font Lock
justification: Fill Commands
justification in text-based tables: Cell Justification
justification style: Enriched Justification

K
Kannada: Language Environments
Kerberos POP3 authentication: Remote Mailboxes
key: Keys
key bindings: Key Bindings
key rebinding, permanent: Init Rebinding
key rebinding, this session: Rebinding
key sequence: Keys
key sequence syntax: Init Rebinding
keyboard input: User Input
keyboard macro: Keyboard Macros
keyboard macros, in registers: Keyboard Macro Registers
keyboard shortcuts: Glossary
keyboard, MS-Windows: Windows Keyboard
keymap: Keymaps
keypad: Function Keys
keypad keys (MS-Windows): Windows Keyboard
keys stolen by window manager: User Input
keys, reserved: Key Bindings
Khmer: Language Environments
kill DOS application: Windows Processes
kill ring: Yanking
killing buffers: Kill Buffer
killing characters and lines: Erasing
killing Emacs: Exiting
killing expressions: Expressions
killing rectangular areas of text: Rectangles
killing text: Deletion and Killing
killing unsaved buffers: Kill Buffer
kinsoku line-breaking rules: Auto Fill
known bugs and problems: Known Problems
Korean: Language Environments

L
label (Rmail): Rmail Labels
language environment, automatic selection on MS-DOS: MS-DOS and MULE
language environments: Language Environments
Lao: Language Environments
large programming projects, maintaining: Maintaining
LaTeX mode: TeX Mode
Latin: Language Environments
Latin-1 TeX encoding: TeX Misc
Latvian: Language Environments
launching Emacs from the tracker: Haiku Basics
lax search: Lax Search
lax space matching in replace commands: Replacement and Lax Matches
lax space matching in search: Lax Search
lazy highlighting customizations: Search Customizations
lazy search highlighting: Repeat Isearch
lazy-highlight face: Search Customizations
lazy-highlight face, in replace: Query Replace
leaving Emacs: Exiting
libraries: Lisp Libraries
Life: Amusements
line endings: Coding Systems
line mode (terminal emulator): Terminal emulator
line number commands: Position Info
line number display: Optional Mode Line
line spacing (X resource): Table of Resources
line spacing, command-line argument: Misc X
line truncation: Line Truncation
line truncation, and fringes: Continuation Lines
line wrapping: Continuation Lines
line-number face: Display Custom
lines, highlighting: Highlight Interactively
links: Mouse References
links (customization buffer): Customization Groups
Lisp character syntax: Init Syntax
Lisp editing: Programs
Lisp mode: External Lisp
Lisp object syntax: Init Syntax
Lisp string syntax: Init Syntax
Lisp symbol completion: Symbol Completion
lisp-indent-function property: Lisp Indent
list commands: Moving by Parens
listing current buffers: List Buffers
listing system fonts: Fonts
Lithuanian: Language Environments
load init file of another user: Initial Options
load path for Emacs Lisp: Lisp Libraries
loading Lisp code: Lisp Libraries
loading Lisp libraries automatically: Init Examples
loading Lisp libraries, command-line argument: Action Arguments
loading several files (in Dired): Operating on Files
local keymap: Local Keymaps
local variables: Locals
local variables in files: File Variables
local variables, for all files in a directory: Directory Variables
local variables, for all remote connections: Connection Variables
locale, date format: Time Stamps
locales: Language Environments
location of point: Position Info
lock-file-mode: Interlocking
locking (CVS): CVS Options
locking files: Interlocking
locking, non-strict (RCS): RCS and SCCS
locking-based version: VCS Merging
locus: Compilation Mode
Log Edit mode: Log Buffer
log File, types of: Types of Log File
logging keystrokes: Checklist
logical line: Continuation Lines
logical order: Bidirectional Editing
long file names in DOS box under Windows 95/NT: MS-DOS File Names
looking for a subject in documentation: Help
lost-selection-mode: Primary Selection
lpr usage under MS-DOS: Windows Printing
LRM: Bidirectional Editing
ls emulation: ls in Lisp
Lucid Widget X Resources: Lucid Resources
lzh: File Archives

M
M-: User Input
M-TAB vs Alt-TAB (MS-Windows): Windows Keyboard
M4 mode: Program Modes
Macintosh: Mac OS / GNUstep
Macintosh end-of-line conversion: Coding Systems
macOS: Mac OS / GNUstep
macro expansion in C: Other C Commands
mail: Sending Mail
mail (on mode line): Optional Mode Line
mail aliases: Mail Aliases
MAIL environment variable: Rmail Inbox
Mail mode: Mail Methods
mail signature: Mail Signature
mail-composition methods: Mail Methods
Mailclient: Mail Sending
MAILHOST environment variable: Remote Mailboxes
mailrc file: Mail Aliases
main border width, command-line argument: Borders X
maintaining large programs: Maintaining
major modes: Major Modes
make: Compilation
Makefile mode: Program Modes
making pictures out of text characters: Picture Mode
Malayalam: Language Environments
man page: Man Page
man pages, and local file variables: Specifying File Variables
manipulating paragraphs: Paragraphs
manipulating sentences: Sentences
manipulating text: Text
manual pages, on MS-DOS/MS-Windows: Man Page
manual version backups: CVS Options
manuals, included: Misc Help
mark: Mark
mark rectangle: Rectangles
mark ring: Mark Ring
marking executable files (in Dired): Marks vs Flags
marking many files (in Dired): Marks vs Flags
marking sections of text: Marking Objects
marking subdirectories (in Dired): Marks vs Flags
marking symbolic links (in Dired): Marks vs Flags
match (face name): Other Repeating Search
matching parentheses: Matching
matching parenthesis and braces, moving to: Moving by Parens
maximized, command-line argument: Window Size X
maximum buffer size exceeded, error message: Visiting
Mayan calendar: Mayan Calendar
Mayan calendar round: Mayan Calendar
Mayan calendars: Calendar Systems
Mayan haab calendar: Mayan Calendar
Mayan long count: Mayan Calendar
Mayan tzolkin calendar: Mayan Calendar
mbox files: Rmail Inbox
memory full: Memory Full
menu bar: Menu Bar
menu bar (X resource): Table of Resources
menu bar access using keyboard: Menu Bar
menu bar appearance: Standard Faces
menu bar mode: Menu Bars
menu face, no effect if customized: Standard Faces
Menu X Resources (Lucid widgets): Lucid Resources
Menu X Resources (Motif widgets): Motif Resources
Mercurial: Version Control Systems
merge buffer (Emerge): Overview of Emerge
merge mail from file (Rmail): Rmail Files
merges, failed: Comparing Files
merging changes: Merging
merging files: Emerge
merging-based version: VCS Merging
message: Sending Mail
Message mode: Mail Commands
Message mode for sending mail: Mail Methods
message number (Rmail): Rmail Basics
messages saved from echo area: Echo Area
META: User Input
Meta (under MS-DOS): MS-DOS Keyboard
Meta commands and words: Words
Metafont mode: Program Modes
MH mail interface: Mail Methods
Microsoft Office file: Document View
Microsoft Windows: Microsoft Windows
Midnight mode: Kill Buffer
MIME: Mail Misc
MIME messages (Rmail): Rmail Display
minibuffer: Minibuffer
minibuffer confirmation: Completion Exit
minibuffer defaults for file names: Minibuffer History
Minibuffer Electric Default mode: Basic Minibuffer
minibuffer history: Minibuffer History
minibuffer history, searching: Isearch Minibuffer
minibuffer keymaps: Minibuffer Maps
minibuffer-prompt face: Standard Faces
minimizing: Exiting
minimizing a frame at startup: Icons X
minor mode keymap: Local Keymaps
minor modes: Minor Modes
mistakes, correcting: Fixit
mode commands for minor modes: Minor Modes
mode hook: Major Modes
mode hook, and major modes: Program Modes
mode line: Mode Line
mode line (MS-DOS): MS-DOS and MULE
mode line, 3D appearance: Optional Mode Line
mode line, mouse: Mode Line Mouse
mode, Abbrev: Abbrev Concepts
mode, archive: File Archives
mode, Auto Compression: Compressed Files
mode, Auto Fill: Auto Fill
mode, Auto Revert: Auto Revert
mode, Auto Save: Auto Save
mode, AWK: C Modes
mode, C: C Modes
mode, C++: C Modes
mode, Column Number: Optional Mode Line
mode, Comint: Shell Mode
mode, Compilation: Compilation Mode
mode, CORBA IDL: C Modes
mode, Delete Selection: Using Region
mode, Dirtrack: Directory Tracking
mode, display-fill-column-indicator: Displaying Boundaries
mode, DocTeX: TeX Mode
mode, DocView: Document View
mode, Electric Indent: Indent Convenience
mode, Electric Quote: Quotation Marks
mode, Emacs Lisp: Lisp Eval
mode, Enriched: Enriched Text
mode, Flyspell: Spelling
mode, Follow: Follow Mode
mode, Font Lock: Font Lock
mode, Fortran: Fortran
mode, Glasses: MixedCase Words
mode, Global Auto Revert: Auto Revert
mode, Goto Address: Goto Address mode
mode, GUD Tooltip: Debugger Operation
mode, Hexl: Editing Binary Files
mode, Hideshow: Hideshow
mode, HTML: HTML Mode
mode, Java: C Modes
mode, LaTeX: TeX Mode
mode, Lisp: External Lisp
mode, Log Edit: Log Buffer
mode, Mail: Mail Methods
mode, major: Major Modes
mode, Menu Bar: Menu Bars
mode, Message: Mail Commands
mode, Minibuffer Electric Default: Basic Minibuffer
mode, minor: Minor Modes
mode, Mouse Wheel: Mouse Commands
mode, MSB: Buffer Menus
mode, nXML: HTML Mode
mode, Objective C: C Modes
mode, Occur: Other Repeating Search
mode, Occur Edit: Other Repeating Search
mode, Org: Org Mode
mode, Outline: Outline Mode
mode, Overwrite: Minor Modes
mode, Paragraph-Indent Text: Text Mode
mode, Pike: C Modes
mode, Scheme: External Lisp
mode, Scroll Bar: Scroll Bars
mode, Scroll-all: Window Convenience
mode, Semantic: Semantic
mode, SGML: HTML Mode
mode, Shell: Shell Mode
mode, SliTeX: TeX Mode
mode, Tab Bar: Tab Bars
mode, tar: File Archives
mode, Term: Term Mode
mode, TeX: TeX Mode
mode, Text: Text Mode
mode, Thumbs: Image Mode
mode, Tool Bar: Tool Bars
mode, Transient Mark: Disabled Transient Mark
mode, View: View Mode
mode, Visual Line: Visual Line Mode
mode, Whitespace: Useless Whitespace
mode, Window Divider: Window Dividers
mode, Winner: Window Convenience
mode, XML: HTML Mode
mode-line face: Standard Faces
mode-line-buffer-id face: Standard Faces
mode-line-highlight face: Standard Faces
mode-line-inactive face: Standard Faces
modes for editing programs: Hooks
modes for programming languages: Program Modes
modification dates: Time Stamps
modified (buffer): Visiting
modifier key customization (Haiku): Haiku Basics
modifier keys: User Input
modifier keys (macOS): Mac / GNUstep Basics
modifier keys and system keymap (Haiku): Haiku Basics
modifier keys unsupported by keyboard: Modifier Keys
modifier keys, and key rebinding: Modifier Keys
Modula2 mode: Program Modes
module verification: Initial Options
moon, phases of: Lunar Phases
Morse code: Amusements
Motif Widget X Resources: Motif Resources
motion commands, during incremental search: Not Exiting Isearch
mouse avoidance: Mouse Avoidance
mouse button events: Mouse Buttons
mouse buttons (what they do): Mouse Commands
mouse input: Mouse Input
mouse on mode line: Mode Line Mouse
mouse pointer: Display Custom
mouse pointer color, command-line argument: Colors X
mouse support: Text-Only Mouse
mouse support under MS-DOS: MS-DOS Mouse
mouse wheel: Mouse Commands
Mouse Wheel minor mode: Mouse Commands
mouse, and MS-Windows: Windows Mouse
mouse, dragging: Mouse Commands
mouse, selecting text using: Mouse Commands
mouse, set number of buttons: MS-DOS Mouse
move to beginning or end of function: Moving by Defuns
movemail: Remote Mailboxes
movemail program: Movemail
movement: Moving Point
moving files (in Dired): Operating on Files
moving inside the calendar: Calendar Motion
moving point: Moving Point
moving text: Yanking
moving the cursor: Moving Point
MS-DOS end-of-line conversion: Coding Systems
MS-DOS peculiarities: MS-DOS
MS-Windows codepages: MS-DOS and MULE
MS-Windows keyboard shortcuts: Windows Keyboard
MS-Windows, and primary selection: Primary Selection
MS-Windows, Emacs peculiarities: Microsoft Windows
MSB mode: Buffer Menus
MULE: Glossary
multibyte characters: International
multiple displays: Multiple Displays
multiple source file search and replace: Identifier Search
multiple views of outline: Outline Views
multiple windows in Emacs: Windows
multiple-buffer isearch: Other Repeating Search
multiple-file isearch: Other Repeating Search
Multipurpose Internet Mail Extensions: Mail Misc
Multithreaded debugging in GDB: Multithreaded Debugging

N
names of backup files: Backup Names
narrowing: Narrowing
narrowing, and line number display: Optional Mode Line
native compilation: Lisp Libraries
nested defuns: Moving by Defuns
net use’, and printing on MS-Windows: Windows Printing
network security manager: Network Security
networked printers (MS-Windows): Windows Printing
newline: Inserting Text
newlines, hard and soft: Hard and Soft Newlines
newsreader: Gnus
Next Error Follow mode: Compilation Mode
NFS and quitting: Quitting
nil: Glossary
no-conversion, coding system: Coding Systems
nobreak-space face: Text Display
non-ASCII characters in .emacs: Init Non-ASCII
non-ASCII keys, binding: Init Non-ASCII
non-breaking hyphen: Text Display
non-breaking space: Text Display
non-greedy regexp matching: Regexps
non-integral number of lines in a window: Optional Mode Line
non-selected windows, mode line appearance: Optional Mode Line
Non-stop debugging in GDB: Multithreaded Debugging
non-strict locking (RCS): RCS and SCCS
nonincremental search: Nonincremental Search
normal hook: Hooks
nroff: Nroff Mode
ns-open-file event: Mac / GNUstep Events
ns-open-file-line event: Mac / GNUstep Events
ns-open-temp-file event: Mac / GNUstep Events
ns-power-off event: Mac / GNUstep Events
ns-show-prefs event: Mac / GNUstep Events
NSA: Mail Amusements
NSM: Network Security
number lines in a buffer: Display Custom
numeric arguments: Arguments
nXML mode: HTML Mode

O
Objective C mode: C Modes
obsolete command: M-x
Occur Edit mode: Other Repeating Search
Occur mode: Other Repeating Search
octal escapes: Text Display
Octave mode: Program Modes
omer count: Sexp Diary Entries
OOM killer: Memory Full
OPascal mode: Program Modes
open file: Visiting
open-parenthesis in leftmost column: Left Margin Paren
OpenDocument file: Document View
operating on files in Dired: Operating on Files
operations on a marked region: Using Region
options (command line): Emacs Invocation
Org agenda: Org Organizer
Org exporting: Org Authoring
Org mode: Org Mode
organizer: Org Mode
Oriya: Language Environments
out of memory: Memory Full
out of memory killer, GNU/Linux: Memory Full
outer border width, command-line argument: Borders X
Outline mode: Outline Mode
outline with multiple views: Outline Views
overlays at character position: Editing Format Info
override character terminal color support: Colors X
overscrolling: Scroll Bars
overwrapped search: Repeat Isearch
Overwrite mode: Minor Modes
OXPS file: Document View

P
Package: Packages
Package archive: Packages
package development source: Fetching Package Sources
package directory: Package Files
package file: Package Files
package menu: Package Menu
package requirements: Package Installation
package security: Package Installation
package signing: Package Installation
package specification: Fetching Package Sources
package status: Package Statuses
pages: Pages
paging in Term mode: Term Mode
paragraph, base direction: Bidirectional Editing
Paragraph-Indent Text mode: Text Mode
paragraphs: Paragraphs
parasha, weekly: Sexp Diary Entries
parentheses, displaying matches: Matching
parentheses, moving across: Moving by Parens
parenthesis in column zero and fontification: Traditional Font Lock
parenthetical groupings: Moving by Parens
parser-based font-lock: Parser-based Font Lock
partial completion: Completion Styles
partial-completion, completion style: Completion Styles
paste: Cut and Paste
pasting: Yanking
patches, applying: Diff Mode
patches, editing: Diff Mode
patches, sending: Sending Patches
PCL-CVS: VC Directory Mode
PDB: Debuggers
PDF file: Document View
pending, in incremental search: Regexp Search
per-buffer variables: Locals
per-connection local variables: Connection Variables
per-directory local variables: Directory Variables
Perl mode: Program Modes
Perldb: Debuggers
Persian: Language Environments
Persian calendar: Calendar Systems
phases of the moon: Lunar Phases
phrase, highlighting: Highlight Interactively
Picture mode and rectangles: Rectangles in Picture
pictures: Picture Mode
Pike mode: C Modes
pinch to scale: Text Scale
pinning Emacs to Windows task bar: Windows Startup
planner: Org Mode
point: Point
point location: Position Info
point location, on MS-DOS: Text and Binary
Polish: Language Environments
Pong game: Amusements
POP3 mailboxes: Remote Mailboxes
position and size of Emacs frame: Window Size X
PostScript file: Document View
PostScript mode: Program Modes
prefix argument commands, during incremental search: Not Exiting Isearch
prefix arguments: Arguments
prefix key: Keys
preprocessor highlighting: Other C Commands
pretty-printer: Program Indent
prevent commands from exiting incremental search: Not Exiting Isearch
preview of registers: Registers
primary Rmail file: Rmail Basics
primary selection: Primary Selection
primary selection, when active region changes: Setting Mark
printing: Printing
printing character: Text Display
printing files (in Dired): Operating on Files
Printing package: Printing Package
printing under MS-DOS: MS-DOS Processes
Prog mode: Hooks
program building: Building
program editing: Programs
program functions and variables, documentation lookup: Programming Language Doc
project back-end: Projects
project root: Projects
projects: Projects
Prolog mode: Program Modes
prompt: Basic Minibuffer
prompt, shell: Shell Prompts
PS file: Document View
pull changes from upstream (VC): Pulling / Pushing
Punjabi: Language Environments
push changes to upstream (VC): Pulling / Pushing
puzzles: Amusements
Python mode: Program Modes

Q
query replace: Query Replace
query-replace face: Query Replace
quitting: Quitting
quitting (in search): Error in Isearch
quitting Emacs: Exiting
quitting on MS-DOS: MS-DOS Keyboard
Quotation marks: Quotation Marks
quoting: Inserting Text
quoting file names: Quoted File Names

R
rar: File Archives
raw bytes: International Chars
raw-text, coding system: Coding Systems
RCS: Version Control Systems
read-only buffer: Misc Buffer
read-only text, killing: Kill Options
reading mail: Rmail
rebinding keys, permanently: Init Rebinding
rebinding keys, this session: Rebinding
rebinding major mode keys: Init Rebinding
rebinding mouse buttons: Mouse Buttons
rebinding non-ASCII keys: Init Non-ASCII
recovering crashed session: After a Crash
rectangle: Rectangles
rectangle highlighting: CUA Bindings
rectangles and Picture mode: Rectangles in Picture
rectangular region: Rectangles
recursive copying: Operating on Files
recursive deletion: Dired Deletion
recursive editing level: Recursive Edit
recursive editing, cannot exit: Stuck Recursive
recycle bin: Misc File Ops
redo: Undo
refreshing displayed files: Dired Updating
regexp: Regexps
regexp search: Regexp Search
region: Mark
region highlighting: Disabled Transient Mark
region-rectangle: Rectangles
registered file: VCS Concepts
registers: Registers
registry, setting environment variables (MS-Windows): MS-Windows Registry
registry, setting resources (MS-Windows): Resources
regular expression: Regexps
related files: Other C Commands
reload files: Saving Emacs Sessions
remember editing session: Saving Emacs Sessions
remote file access: Remote Files
remote host: Remote Host
remote host, debugging on: Starting GUD
remote repositories (CVS): CVS Options
remove indentation: Indentation Commands
renaming files: Copying and Naming
renaming files (in Dired): Operating on Files
renaming version-controlled files: VC Delete/Rename
repeating a command: Repeating
replacement: Replace
reply to a message: Rmail Reply
report an Emacs bug, how to: Understanding Bug Reporting
report bugs in Emacs: Checklist
repository: VCS Concepts
reread a file: Reverting
reserved key bindings: Key Bindings
resize images: Image Mode
resize window: Change Window
resizing minibuffer: Minibuffer Edit
resizing windows: Change Window
resolving conflicts: Merging
resource files for GTK+: GTK resources
resource name, command-line argument: Resources
resource values, command-line argument: Resources
resources: Resources
restore session: Saving Emacs Sessions
restriction: Narrowing
retrying a failed message: Rmail Reply
reverse order in POP3 inboxes: Remote Mailboxes
reverse video, command-line argument: Colors X
revision: VCS Concepts
revision ID: VCS Concepts
revision ID in version control: Advanced C-x v v
revision tag: Revision Tags
RGB triplet: Colors
right-to-left text: Bidirectional Editing
risky variable: Safe File Variables
RLM: Bidirectional Editing
Rmail: Rmail
Rmail file sorting: Rmail Sorting
Romanian: Language Environments
rosh hodesh: Sexp Diary Entries
rot13 code: Rmail Rot13
rotating images: Image Mode
Ruby mode: Program Modes
runemacs.exe: Windows Startup
running a hook: Hooks
running info on files (in Dired): Operating on Files
running Lisp functions: Building
running man on files (in Dired): Operating on Files
Russian: Language Environments

S
s-: Modifier Keys
saved echo area messages: Echo Area
saving a setting: Changing a Variable
saving buffer name in a register: File and Buffer Registers
saving file name in a register: File and Buffer Registers
saving files: Visiting
saving frame configuration in a register: Configuration Registers
saving keyboard macro in a register: Keyboard Macro Registers
saving keyboard macros: Save Keyboard Macro
saving number in a register: Number Registers
saving position in a register: Position Registers
saving rectangle in a register: Rectangle Registers
saving sessions: Saving Emacs Sessions
saving text in a register: Text Registers
saving window configuration in a register: Configuration Registers
SCCS: Version Control Systems
Scheme mode: External Lisp
screen: Screen
screen display, wrong: Screen Garbled
screen line: Continuation Lines
screen reader software, MS-Windows: Windows Misc
script mode: Initial Options
script of a character: Modifying Fontsets
scroll bar (X resource): Table of Resources
Scroll Bar mode: Scroll Bars
Scroll-all mode: Window Convenience
scroll-bar face: Scroll Bars
scroll-command property: Scrolling
scroll-command property, and incremental search: Not Exiting Isearch
scrollbar width (X resource): Table of Resources
scrolling: Scrolling
scrolling commands, during incremental search: Not Exiting Isearch
scrolling in the calendar: Scroll Calendar
scrolling windows together: Window Convenience
SDB: Debuggers
search and replace in multiple files (in Dired): Operating on Files
search and replace in multiple source files: Identifier Search
search customizations: Search Customizations
search display on slow terminals: Search Customizations
search for a regular expression: Regexp Search
search Internet for keywords: Word Search
search known bugs: Known Problems
search mode, default: Search Customizations
search multiple files (in Dired): Operating on Files
search ring: Repeat Isearch
search, changing direction: Repeat Isearch
search, overwrapped: Repeat Isearch
search, wrapping around: Repeat Isearch
search-and-replace commands: Replace
searching: Search
searching Dired buffers: Dired Navigation
searching documentation efficiently: Help
searching in Rmail: Rmail Motion
searching in webkit buffers: Embedded WebKit Widgets
searching multiple files via Dired: Misc Dired Features
secondary selection: Secondary Selection
secondary-selection face: Secondary Selection
sections of manual pages: Man Page
security: Host Security
security, when displaying enriched text: Enriched Properties
select all: Marking Objects
selected buffer: Buffers
selected window: Basic Window
selecting buffers in other windows: Pop Up Window
selection, primary: Primary Selection
selective display: Selective Display
selective undo: Undo
self-documentation: Help
Semantic mode: Semantic
Semantic package: Semantic
sending mail: Sending Mail
sending patches for GNU Emacs: Sending Patches
Sendmail: Mail Sending
sentences: Sentences
server file: TCP Emacs server
server, using Emacs as: Emacs Server
server-side fonts: Fonts
set buffer font size: Text Scale
set of alternative characters, in regular expressions: Regexps
sets of files: Filesets
setting a mark: Mark
setting variables: Examining
settings: Easy Customization
settings, how to save: Changing a Variable
sexp: Expressions
sexp diary entries: Sexp Diary Entries
SGML mode: HTML Mode
shadow cluster: File Shadowing
shadow face: Standard Faces
shadow files: File Shadowing
shell commands: Shell
shell commands, Dired: Shell Commands in Dired
shell completion: Shell Mode
SHELL environment variable: Single Shell
Shell mode: Shell Mode
shell scripts, and local file variables: Specifying File Variables
Shell-script mode: Program Modes
shelves in version control: VC Directory Commands
shift-selection: Shift Selection
Show Paren mode: Matching
showing hidden subdirectories (Dired): Hiding Subdirectories
shy group, in regexp: Regexp Backslash
signing files (in Dired): Operating on Files
Simula mode: Program Modes
simulation of middle mouse button: Windows Mouse
simultaneous editing: Interlocking
Sinhala: Language Environments
site init file: Init File
site-lisp directories: Init File
site-lisp files, not loading: Initial Options
site-start.el file, not loading: Initial Options
site-start.el, the site startup file: Init File
size of file, warning when visiting: Visiting
size of minibuffer: Minibuffer Edit
slashes repeated in file name: Minibuffer File
SliTeX mode: TeX Mode
Slovak: Language Environments
Slovenian: Language Environments
Smerge mode: Comparing Files
SMTP: Mail Sending
Snake: Amusements
socket activation, systemd, Emacs: Emacs Server
soft hyphen: Text Display
soft newline: Hard and Soft Newlines
solitaire: Amusements
sorting: Sorting
sorting diary entries: Fancy Diary Display
sorting Dired buffer: Dired Updating
sorting Rmail file: Rmail Sorting
Spanish: Language Environments
specific version control system: Advanced C-x v v
specification, for source packages: Fetching Package Sources
specify default font from the command line: Font X
specify dump file: Initial Options
specify end-of-line conversion: Text Coding
specifying fullscreen for Emacs frame: Window Size X
speedbar: Speedbar
spell-checking the active region: Spelling
spelling, checking and correcting: Spelling
splash screen: Initial Options
splitting columns: Two-Column
splitting table cells: Cell Commands
SQL mode: Program Modes
SRC: Version Control Systems
src: Version Control Systems
SSH: Remote Host
SSL: Network Security
standard colors on a character terminal: Colors X
standard faces: Standard Faces
standard fontset: Defining Fontsets
start directory, MS-Windows: Windows Startup
start iconified, command-line argument: Icons X
starting Emacs: Entering Emacs
starting Emacs on MS-Windows: Windows Startup
STARTTLS: Network Security
startup (command line arguments): Emacs Invocation
startup (init file): Init File
startup fontset: Defining Fontsets
startup message: Initial Options
startup screen: Entering Emacs
stashes in version control: VC Directory Commands
string substitution: Replace
string syntax: Init Syntax
stuck in recursive editing: Stuck Recursive
style (for indentation): Custom C Indent
sub-expressions, in regular expressions: Regexp Backslash
subdirectories in Dired: Subdirectories in Dired
subprocesses on MS-Windows: Windows Processes
subscribe groups: Gnus Group Buffer
subshell: Shell
substring, completion style: Completion Styles
subtree (Outline mode): Outline Visibility
Subversion: Version Control Systems
Subword mode: MixedCase Words
summary (Rmail): Rmail Summary
summing time intervals: Time Intervals
sunrise and sunset: Sunrise/Sunset
Super (under MS-DOS): MS-DOS Keyboard
Super, modifier key: Modifier Keys
suspending: Exiting
suspicious constructions in C, C++: Other C Commands
SVN: Version Control Systems
Swedish: Language Environments
switch buffers: Select Buffer
switches (command line): Emacs Invocation
symbol search: Symbol Search
symbol, highlighting: Highlight Interactively
symbolic links (and version control): General VC Options
symbolic links (creation in Dired): Operating on Files
symbolic links (creation): Copying and Naming
symbolic links (visiting): File Aliases
synchronizing windows: Follow Mode
synchronous X mode: Table of Resources
syntax highlighting and coloring: Font Lock
syntax of regexps: Regexps
system-wide packages: Package Files
systemd unit file: Emacs Server

T
t: Glossary
tab bar (X resource): Table of Resources
tab bar mode: Tab Bars
tab line: Tab Line
tab stops: Tab Stops
tab-line face: Standard Faces
table creation: Table Creation
table dimensions: Table Misc
table for HTML and LaTeX: Table Misc
table mode: Text Based Tables
table recognition: Table Recognition
table to text: Table Conversion
tabs: Indentation
tabs, on the Tab Bar: Tab Bars
tag: Xref
tags and tag tables: Tags Tables
tags for version control: Revision Tags
tags, C++: Tags Tables
tags-based completion: Symbol Completion
TaiViet: Language Environments
Tajik: Language Environments
Tamil: Language Environments
Tar mode: File Archives
Tcl mode: Program Modes
TCP Emacs server: TCP Emacs server
Telnet: Remote Host
Telugu: Language Environments
temporary windows: Temporary Displays
Term mode: Term Mode
terminal emulators, mouse support: Text-Only Mouse
terminal, serial: Serial Terminal
termscript file: Checklist
Tetris: Amusements
TeX encoding: TeX Misc
TeX mode: TeX Mode
TEXEDIT environment variable: Emacs Server
TEXINPUTS environment variable: TeX Print
text: Text
text and binary files on MS-DOS/MS-Windows: Text and Binary
text buttons: Mouse References
text colors, from command line: Colors X
text cursor: Cursor Display
Text mode: Text Mode
text properties at point: International Chars
text properties of characters: Editing Format Info
text terminal: Text Terminals
text to table: Table Conversion
text-based tables: Text Based Tables
text-based tables, splitting cells: Cell Commands
text/enriched MIME format: Enriched Text
Thai: Language Environments
Tibetan: Language Environments
tilde (~) at end of backup file name: Backup Names
time (on mode line): Optional Mode Line
time intervals, summing: Time Intervals
time stamps: Time Stamps
timeclock: Time Intervals
timelog file: Time Intervals
TLS: Network Security
TLS encryption (Rmail): Remote Mailboxes
TODO item: Org Organizer
toggling marks (in Dired): Marks vs Flags
TOML mode: Program Modes
tool bar (X resource): Table of Resources
tool bar mode: Tool Bars
Tool Bar position: Tool Bars
Tool Bar style: Tool Bars
tooltip help: Help Echo
tooltips: Tooltips
tooltips (haiku): Haiku Basics
top level: Mode Line
touchscreen events: Mouse Input
tower of Hanoi: Amusements
traditional font-lock: Traditional Font Lock
trailing whitespace: Useless Whitespace
trailing whitespace, in patches: Diff Mode
trailing-whitespace face: Useless Whitespace
Tramp: Remote Files
Transient Mark mode: Disabled Transient Mark
Transport Layer Security: Network Security
transposition of expressions: Expressions
trash: Misc File Ops
tree-sitter library, supported major modes: Program Modes
triple clicks: Mouse Buttons
troubleshooting Emacs: Lossage
truenames of files: File Aliases
truncation: Line Truncation
tty Emacs in haiku: Haiku Basics
TTY menu faces: Standard Faces
Turkish: Language Environments
two directories (in Dired): Operating on Files
two-column editing: Two-Column
types of log file: Types of Log File
TypeScript mode: Program Modes
typos, fixing: Fixit

U
Ukrainian: Language Environments
unbalanced parentheses and quotes: Parentheses
uncompression: Compressed Files
undecided, coding system: Coding Systems
undeletion (Rmail): Rmail Deletion
undigestify: Rmail Digest
undisplayable characters: International Chars
undo: Undo
undo limit: Undo
undoing window configuration changes: Window Convenience
Unibyte operation: Unibyte Mode
Unicode: International Chars
Unicode characters, inserting: Inserting Text
Unicode Collation Algorithm (UCA), and ls-lisp.el: ls in Lisp
unique buffer names: Uniquify
unmarking files (in Dired): Marks vs Flags
unsaved buffers, killing: Kill Buffer
unsaved customizations, reminder to save: Saving Customizations
unsubscribe groups: Gnus Group Buffer
untranslated file system: Text and Binary
unused lines: Useless Whitespace
unzip archives: File Archives
upcase file names: Transforming File Names
updating Dired buffer: Dired Updating
upstream repository: Pulling / Pushing
upstream source, for packages: Fetching Package Sources
URL, viewing in help: Help Mode
URLs: Browse-URL
URLs, activating: Goto Address mode
Usenet news: Gnus
user name for remote file access: Remote Files
user option: Easy Customization
user options, changing: Changing a Variable
using Nextstep services (macOS): Mac / GNUstep Events
UTF-8: Language Environments

V
variable: Variables
variable-pitch face: Standard Faces
variables, changing: Changing a Variable
VC: Version Control
VC change log: VC Change Log
VC commands, in Dired buffers: Version Control
VC Directory buffer: VC Directory Mode
VC filesets: Basic VC Editing
VC log buffer, commands in: VC Change Log
VC mode line indicator: VC Mode Line
vc-log buffer: VC Change Log
verifying digital signatures on files (in Dired): Operating on Files
Verilog mode: Program Modes
version control: Version Control
version control log: Types of Log File
version control status: VC Mode Line
VERSION_CONTROL environment variable: Backup Names
vertical border: Scroll Bars
Vertical Scroll Bar: Scroll Bars
vertical scroll bars, command-line argument: Misc X
vertical-border face: Standard Faces
VHDL mode: Program Modes
Vietnamese: Language Environments
View mode: View Mode
viewing web pages in help: Help Mode
views of an outline: Outline Views
visiting files: Visiting
visiting files, command-line argument: Action Arguments
visual line: Continuation Lines
Visual Line mode: Visual Line Mode
visual order: Bidirectional Editing

W
Watching expressions in GDB: Watch Expressions
wdired mode: Wdired
Web: Browse-URL
web pages, viewing in help: Help Mode
webkit widgets: Embedded WebKit Widgets
weeks, which day they start on: Move to Beginning or End
Welsh: Language Environments
what constitutes an Emacs bug: Bug Criteria
wheel-down, a mouse event: Mouse Commands
wheel-left, a mouse event: Mouse Commands
wheel-right, a mouse event: Mouse Commands
wheel-up, a mouse event: Mouse Commands
whitespace character: Indentation
Whitespace mode: Useless Whitespace
whitespace, trailing: Useless Whitespace
wide block cursor: Cursor Display
widening: Narrowing
widgets at buffer position: Editing Format Info
width and height of Emacs frame: Window Size X
width of the vertical scroll bar: Scroll Bars
wildcard characters in file names: Visiting
Windmove package: Window Convenience
window configuration changes, undoing: Window Convenience
Window Divider mode: Window Dividers
window manager, keys stolen by: User Input
Windows clipboard support: MS-DOS Mouse
windows in Emacs: Windows
Windows system menu: Windows Keyboard
windows, synchronizing: Follow Mode
Windows-1255: Language Environments
Winner mode: Window Convenience
word processing: Enriched Text
word search: Word Search
word wrap: Visual Line Mode
words: Words
words, case conversion: Case
work file: VCS Concepts
working tree: VCS Concepts
World Wide Web: Browse-URL
wrapped search: Repeat Isearch
wrapping: Continuation Lines
WYSIWYG: Enriched Text

X
X cutting and pasting: Primary Selection
X defaults file: Fonts
X input method coding systems: X Coding
X input method coding systems, overriding: X Coding
X input methods (X resource): Table of Resources
X Logical Font Description: Fonts
X resources: Resources
X resources file: Fonts
X resources on Haiku: Haiku Basics
X resources, not loading: Initial Options
X selection: Primary Selection
XDB: Debuggers
XDG_CONFIG_HOME: Init File
XIM (X resource): Table of Resources
XIM, X Input Methods: Unibyte Mode
XLFD: Fonts
XML schema: HTML Mode
XPS file: Document View
xref: Xref
xref backend: Xref
XREF mode: Xref Commands
xterm: Text-Only Mouse
xwidget: Embedded WebKit Widgets
Xwidget-WebKit mode: Embedded WebKit Widgets
xwidget-webkit-edit-mode: Embedded WebKit Widgets

Y
y or n prompt: Yes or No Prompts
yahrzeits: From Other Calendar
yahrzeits, and sexp diary entries: Sexp Diary Entries
yanking: Yanking
yanking previous kills: Earlier Kills
yes or no prompt: Yes or No Prompts

Z
zip: File Archives
Zmacs mode: Disabled Transient Mark
zone: Amusements
zoo: File Archives


Footnotes

(1)

This manual is itself covered by the GNU Free Documentation License. This license is similar in spirit to the General Public License, but is more suitable for documentation. See GNU Free Documentation License.

(2)

The term “point” comes from the character ‘.’, which was the command in TECO (the language in which the original Emacs was written) for accessing the editing position.

(3)

We refer to Alt as Meta for historical reasons.

(4)

Setting inhibit-startup-screen in site-start.el doesn’t work, because the startup screen is set up before reading site-start.el. See The Emacs Initialization File, for information about site-start.el.

(5)

There is no C-SPC character in ASCII; usually, typing C-SPC on a text terminal gives the character C-@. This key is also bound to set-mark-command, so unless you are unlucky enough to have a text terminal that behaves differently, you might as well think of C-@ as C-SPC.

(6)

Aside from C-/, the undo command is also bound to C-x u because that is more straightforward for beginners to remember: ‘u’ stands for “undo”. It is also bound to C-_ because typing C-/ on some text terminals actually enters C-_.

(7)

If your file system does not support symbolic links, a regular file is used.

(8)

The foreground and background colors of toolkit-created tooltips on Nextstep can also be customized by setting the foreground and background frame parameters that are part of tooltip-frame-parameters.

(9)

It is also specified for MIME ‘text/*’ bodies and in other network transport contexts. It is different from the SGML reference syntax record-start/record-end format, which Emacs doesn’t support directly.

(10)

If you run Emacs on X, you may need to inform the X server about the location of the newly installed fonts with commands such as:

 xset fp+ /usr/local/share/emacs/fonts
 xset fp rehash
(11)

More specifically, the modes which are “derived” from prog-mode (see Derived Modes in The Emacs Lisp Reference Manual).

(12)

The curved single quote characters are U+2018 LEFT SINGLE QUOTATION MARK and U+2019 RIGHT SINGLE QUOTATION MARK; the curved double quotes are U+201C LEFT DOUBLE QUOTATION MARK and U+201D RIGHT DOUBLE QUOTATION MARK. On text terminals which cannot display these characters, the Info reader might show them as the typewriter ASCII quote characters.

(13)

It has been replaced by the ‘slides’ document class, which comes with LaTeX.

(14)

The word “sexp” is used to refer to an expression in Lisp.

(15)

The name “ElDoc” is a historical accident: this mode started by supporting Emacs Lisp buffers.

(16)

On graphical displays, the M-TAB key is usually reserved by the window manager for switching graphical windows, so you should type C-M-i or ESC TAB instead.

(17)

Regular expressions and syntax tables.

(18)

A tag is a synonym for identifier reference. Commands and features based on the etags package traditionally use “tag” with this meaning, and this subsection follows that tradition.

(19)

The US National Security Agency.

(20)

This capability requires that Emacs be built with libxml2 support or that you have the Lynx browser installed.

(21)

The needed external tools for the document type must be available, and Emacs must be running in a graphical frame and have PNG image support. If these requirements is not fulfilled, Emacs falls back to another major mode.

(22)

You should not suspend the shell process. Suspending a subjob of the shell is a completely different matter—that is normal practice, but you must use the shell to continue the subjob; this command won’t do it.

(23)

Some programs use a different environment variable; for example, to make TeX use ‘emacsclient’, set the TEXEDIT environment variable to ‘emacsclient +%d %s’.

(24)

On MS-DOS, the name of this file should be _dir-locals.el, due to limitations of the DOS filesystems. If the filesystem is limited to 8+3 file names, the name of the file will be truncated by the OS to _dir-loc.el.

(25)

On MS-Windows, there’s no single directory considered by all programs as “the home directory” of the user. Emacs uses one of the pertinent directories as the equivalent of your home directory; see HOME and Startup Directories on MS-Windows, for the details.

(26)

This option has no effect on MS-Windows.

(27)

Here and below, whenever we say “colon-separated list of directories”, it pertains to Unix and GNU/Linux systems. On MS-DOS and MS-Windows, the directories are separated by semi-colons instead, since DOS/Windows file names might include a colon after a drive letter.

(28)

Older versions of Emacs didn’t check the application data directory.

(29)

There is one known exception: The combination Windows-L that locks the workstation is handled by the system on a lower level. For this reason, w32-register-hot-key cannot override this key combination - it always locks the computer.

(30)

Note that the ‘net use’ command requires the UNC share name to be typed with the Windows-style backslashes, while the value of printer-name can be set with either forward- or backslashes.

(31)

Normally, one particular codepage is burnt into the display memory, while other codepages can be installed by modifying system configuration files, such as CONFIG.SYS, and rebooting. While there is third-party software that allows changing the codepage without rebooting, we describe here how a stock MS-DOS system behaves.

(32)

The standard Emacs coding systems for ISO 8859 are not quite right for the purpose, because typically the DOS codepage does not match the standard ISO character codes. For example, the letter ‘ç’ (‘c’ with cedilla) has code 231 in the standard Latin-1 character set, but the corresponding DOS codepage 850 uses code 135 for this glyph.

(33)

The wording here was careless. The intention was that nobody would have to pay for permission to use the GNU system. But the words don’t make this clear, and people often interpret them as saying that copies of GNU should always be distributed at little or no charge. That was never the intent; later on, the manifesto mentions the possibility of companies providing the service of distribution for a profit. Subsequently I have learned to distinguish carefully between “free” in the sense of freedom and “free” in the sense of price. Free software is software that users have the freedom to distribute and change. Some users may obtain copies at no charge, while others pay to obtain copies—and if the funds help support improving the software, so much the better. The important thing is that everyone who has a copy has the freedom to cooperate with others in using it.

(34)

This is another place I failed to distinguish carefully between the two different meanings of “free.” The statement as it stands is not false—you can get copies of GNU software at no charge, from your friends or over the net. But it does suggest the wrong idea.

(35)

Several such companies now exist.

(36)

The Free Software Foundation raises most of its funds from a distribution service, although it is a charity rather than a company. If no one chooses to obtain copies by ordering from the FSF, it will be unable to do its work. But this does not mean that proprietary restrictions are justified to force every user to pay. If a small fraction of all the users order copies from the FSF, that is sufficient to keep the FSF afloat. So we ask users to choose to support us in this way. Have you done your part?

(37)

A group of computer companies recently pooled funds to support maintenance of the GNU C Compiler.

(38)

In the 80s I had not yet realized how confusing it was to speak of “the issue” of “intellectual property.” That term is obviously biased; more subtle is the fact that it lumps together various disparate laws which raise very different issues. Nowadays I urge people to reject the term “intellectual property” entirely, lest it lead others to suppose that those laws form one coherent issue. The way to be clear is to discuss patents, copyrights, and trademarks separately. See https://www.gnu.org/philosophy/not-ipr.xhtml for more explanation of how this term spreads confusion and bias.

(39)

Subsequently we have discovered the need to distinguish between “free software” and “freeware”. The term “freeware” means software you are free to redistribute, but usually you are not free to study and change the source code, so most of it is not free software. See https://www.gnu.org/philosophy/words-to-avoid.html for more explanation.