The Emacs Editor

Emacs is the extensible, customizable, self-documenting real-time display editor. This is the Sixteenth edition of the GNU Emacs Manual, updated for Emacs version 23.3.

The homepage for GNU Emacs is at http://www.gnu.org/software/emacs/.
For information on extending Emacs, refer to the Emacs Lisp Reference Manual.
To view this manual in other formats, click here.

Copyright © 1985, 1986, 1987, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 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.”

(a) The FSF's Back-Cover Text is: “You have the freedom to copy and modify this GNU manual. Buying copies from the FSF supports it in developing GNU and promoting software freedom.”

Distrib	How to get the latest Emacs distribution.
Intro	An introduction to Emacs concepts.
Glossary	Terms used in this manual.
Indexes (each index contains a large menu)
Key Index	An item for each standard Emacs key sequence.
Option Index	An item for every command-line option.
Command Index	An item for each command name.
Variable Index	An item for each documented variable.
Concept Index	An item for each concept.
Acknowledgments	Major contributors to GNU Emacs.
Important General Concepts
Screen	How to interpret what you see on the screen.
User Input	Kinds of input events (characters, buttons, function keys).
Keys	Key sequences: what you type to request one editing action.
Commands	Named functions run by key sequences to do editing.
Entering Emacs	Starting Emacs from the shell.
Exiting	Stopping or killing Emacs.
Fundamental Editing Commands
Basic	The most basic editing commands.
Minibuffer	Entering arguments that are prompted for.
M-x	Invoking commands by their names.
Help	Commands for asking Emacs about its commands.
Important Text-Changing Commands
Mark	The mark: how to delimit a ``region'' of text.
Killing	Killing (cutting) text.
Yanking	Recovering killed text. Moving text. (Pasting.)
Accumulating Text	Other ways of copying text.
Rectangles	Operating on the text inside a rectangle on the screen.
CUA Bindings	Using C-x, C-c, C-v for copy and paste, with enhanced rectangle support.
Registers	Saving a text string or a location in the buffer.
Display	Controlling what text is displayed.
Search	Finding or replacing occurrences of a string.
Fixit	Commands especially useful for fixing typos.
Keyboard Macros	A keyboard macro records a sequence of keystrokes to be replayed with a single command.
Major Structures of Emacs
Files	All about handling files.
Buffers	Multiple buffers; editing several files at once.
Windows	Viewing two pieces of text at once.
Frames	Running the same Emacs session in multiple X windows.
International	Using non-ASCII character sets.
Advanced Features
Major Modes	Text mode vs. Lisp mode vs. C mode...
Indentation	Editing the white space at the beginnings of lines.
Text	Commands and modes for editing English.
Programs	Commands and modes for editing programs.
Building	Compiling, running and debugging programs.
Maintaining	Features for maintaining large programs.
Abbrevs	How to define text abbreviations to reduce the number of characters you must type.
Picture Mode	Editing pictures made up of characters using the quarter-plane screen model.
Sending Mail	Sending mail in Emacs.
Rmail	Reading mail in Emacs.
Dired	You can ``edit'' a directory to manage files in it.
Calendar/Diary	The calendar and diary facilities.
Document View	Viewing PDF, PS and DVI files.
Gnus	How to read netnews with Emacs.
Shell	Executing shell commands from Emacs.
Emacs Server	Using Emacs as an editing server for mail, etc.
Printing	Printing hardcopies of buffers or regions.
Sorting	Sorting lines, paragraphs or pages within Emacs.
Narrowing	Restricting display and editing to a portion of the buffer.
Two-Column	Splitting apart columns to edit them in side-by-side windows.
Editing Binary Files	Using Hexl mode to edit binary files.
Saving Emacs Sessions	Saving Emacs state from one session to the next.
Recursive Edit	A command can allow you to do editing "within the command". This is called a "recursive editing level".
Emulation	Emulating some other editors with Emacs.
Hyperlinking	Following links in buffers.
Dissociated Press	Dissociating text for fun.
Amusements	Various games and hacks.
Customization	Modifying the behavior of Emacs.
Recovery from Problems
Quitting	Quitting and aborting.
Lossage	What to do if Emacs is hung or malfunctioning.
Bugs	How and when to report a bug.
Contributing	How to contribute improvements to Emacs.
Service	How to get help for your own Emacs needs.
Appendices
Copying	The GNU General Public License gives you permission to redistribute GNU Emacs on certain terms; it also explains that there is no warranty.
GNU Free Documentation License	The license for this documentation.
Emacs Invocation	Hairy startup options.
X Resources	X resources for customizing Emacs.
Antinews	Information about Emacs version 22.
Mac OS / GNUstep	Using Emacs under Mac OS and GNUstep.
Microsoft Windows	Using Emacs on Microsoft Windows and MS-DOS.
Manifesto	What's GNU? Gnu's Not Unix!

Detailed Node Listing

Here are some other nodes which are really inferiors of the ones already listed, mentioned here so you can get to them in one step:

The Organization of the Screen
Point	The place in the text where editing commands operate.
Echo Area	Short messages appear at the bottom of the screen.
Mode Line	Interpreting the mode line.
Menu Bar	How to use the menu bar.
Basic Editing Commands
Inserting Text	Inserting text by simply typing it.
Moving Point	Moving the cursor to the place where you want to change something.
Erasing	Deleting and killing text.
Basic Undo	Undoing recent changes in the text.
Basic Files	Visiting, creating, and saving files.
Basic Help	Asking what a character does.
Blank Lines	Making and deleting blank lines.
Continuation Lines	How Emacs displays lines too wide for the screen.
Position Info	What page, line, row, or column is point on?
Arguments	Numeric arguments for repeating a command N times.
Repeating	Repeating the previous command quickly.
The Minibuffer
Minibuffer File	Entering file names with the minibuffer.
Minibuffer Edit	How to edit in the minibuffer.
Completion	An abbreviation facility for minibuffer input.
Minibuffer History	Reusing recent minibuffer arguments.
Repetition	Re-executing commands that used the minibuffer.
Passwords	Entering passwords in the echo area.
Completion
Completion Example	Examples of using completion.
Completion Commands	A list of completion commands.
Strict Completion	Different types of completion.
Completion Options	Options for completion.
Help
Help Summary	Brief list of all Help commands.
Key Help	Asking what a key does in Emacs.
Name Help	Asking about a command, variable or function name.
Apropos	Asking what pertains to a given topic.
Help Mode	Special features of Help mode and Help buffers.
Library Keywords	Finding Lisp libraries by keywords (topics).
Language Help	Help relating to international language support.
Misc Help	Other help commands.
Help Files	Commands to display pre-written help files.
Help Echo	Help on active text and tooltips (`balloon help').
The Mark and the Region
Setting Mark	Commands to set the mark.
Marking Objects	Commands to put region around textual units.
Using Region	Summary of ways to operate on contents of the region.
Mark Ring	Previous mark positions saved so you can go back there.
Global Mark Ring	Previous mark positions in various buffers.
Shift Selection	Using shifted cursor motion keys.
Persistent Mark	Keeping the mark active all the time.
Killing and Moving Text
Deletion	Commands for deleting small amounts of text and blank areas.
Killing by Lines	How to kill entire lines of text at one time.
Other Kill Commands	Commands to kill large regions of text and syntactic units such as words and sentences.
Kill Options	Options that affect killing.
Yanking
Kill Ring	Where killed text is stored. Basic yanking.
Appending Kills	Several kills in a row all yank together.
Earlier Kills	Yanking something killed some time ago.
Registers
RegPos	Saving positions in registers.
RegText	Saving text in registers.
RegRect	Saving rectangles in registers.
RegConfig	Saving window configurations in registers.
RegNumbers	Numbers in registers.
RegFiles	File names in registers.
Bookmarks	Bookmarks are like registers, but persistent.
Controlling the Display
Scrolling	Commands to move text up and down in a window.
Auto Scrolling	Redisplay scrolls text automatically when needed.
Horizontal Scrolling	Moving text left and right in a window.
Follow Mode	Follow mode lets two windows scroll as one.
Faces	How to change the display style using faces.
Standard Faces	Emacs' predefined faces.
Temporary Face Changes	Commands to temporarily modify the default text face
Font Lock	Minor mode for syntactic highlighting using faces.
Highlight Interactively	Tell Emacs what text to highlight.
Fringes	Enabling or disabling window fringes.
Displaying Boundaries	Displaying top and bottom of the buffer.
Useless Whitespace	Showing possibly-spurious trailing whitespace.
Selective Display	Hiding lines with lots of indentation.
Optional Mode Line	Optional mode line display features.
Text Display	How text characters are normally displayed.
Cursor Display	Features for displaying the cursor.
Line Truncation	Truncating lines to fit the screen width instead of continuing them to multiple screen lines.
Visual Line Mode	Word wrap and screen line-based editing.
Display Custom	Information on variables for customizing display.
Searching and Replacement
Incremental Search	Search happens as you type the string.
Nonincremental Search	Specify entire string and then search.
Word Search	Search for sequence of words.
Regexp Search	Search for match for a regexp.
Regexps	Syntax of regular expressions.
Regexp Backslash	Regular expression constructs starting with `\'.
Regexp Example	A complex regular expression explained.
Search Case	To ignore case while searching, or not.
Replace	Search, and replace some or all matches.
Other Repeating Search	Operating on all matches for some regexp.
Incremental Search
Basic Isearch	Basic incremental search commands.
Repeat Isearch	Searching for the same string again.
Error in Isearch	When your string is not found.
Special Isearch	Special input in incremental search.
Isearch Yank	Commands that grab text into the search string or else edit the search string.
Isearch Scroll	Scrolling during an incremental search.
Isearch Minibuffer	Incremental search of the minibuffer history.
Slow Isearch	Incremental search features for slow terminals.
Replacement Commands
Unconditional Replace	Replacing all matches for a string.
Regexp Replace	Replacing all matches for a regexp.
Replacement and Case	How replacements preserve case of letters.
Query Replace	How to use querying.
Commands for Fixing Typos
Undo	The Undo commands.
Transpose	Exchanging two characters, words, lines, lists...
Fixing Case	Correcting case of last word entered.
Spelling	Apply spelling checker to a word, or a whole file.
Keyboard Macros
Basic Keyboard Macro	Defining and running keyboard macros.
Keyboard Macro Ring	Where previous keyboard macros are saved.
Keyboard Macro Counter	Inserting incrementing numbers in macros.
Keyboard Macro Query	Making keyboard macros do different things each time.
Save Keyboard Macro	Giving keyboard macros names; saving them in files.
Edit Keyboard Macro	Editing keyboard macros.
Keyboard Macro Step-Edit	Interactively executing and editing a keyboard macro.
File Handling
File Names	How to type and edit file-name arguments.
Visiting	Visiting a file prepares Emacs to edit the file.
Saving	Saving makes your changes permanent.
Reverting	Reverting cancels all the changes not saved.
Autorevert	Auto Reverting non-file buffers.
Auto Save	Auto Save periodically protects against loss of data.
File Aliases	Handling multiple names for one file.
Directories	Creating, deleting, and listing file directories.
Comparing Files	Finding where two files differ.
Diff Mode	Mode for editing file differences.
Misc File Ops	Other things you can do on files.
Compressed Files	Accessing compressed files.
File Archives	Operating on tar, zip, jar etc. archive files.
Remote Files	Accessing files on other sites.
Quoted File Names	Quoting special characters in file names.
File Name Cache	Completion against a list of files you often use.
File Conveniences	Convenience Features for Finding Files.
Filesets	Handling sets of files.
Saving Files
Save Commands	Commands for saving files.
Backup	How Emacs saves the old version of your file.
Customize Save	Customizing the saving of files.
Interlocking	How Emacs protects against simultaneous editing of one file by two users.
File Shadowing	Copying files to "shadows" automatically.
Time Stamps	Emacs can update time stamps on saved files.
Backup Files
Backup Names	How backup files are named.
Backup Deletion	Emacs deletes excess numbered backups.
Backup Copying	Backups can be made by copying or renaming.
Auto Reverting Non-File Buffers
Auto Reverting the Buffer Menu	Auto Revert of the Buffer Menu.
Auto Reverting Dired	Auto Revert of Dired buffers.
Supporting additional buffers	How to add more Auto Revert support.
Auto-Saving: Protection Against Disasters
Auto Save Files	The file where auto-saved changes are actually made until you save the file.
Auto Save Control	Controlling when and how often to auto-save.
Recover	Recovering text from auto-save files.
Using Multiple Buffers
Select Buffer	Creating a new buffer or reselecting an old one.
List Buffers	Getting a list of buffers that exist.
Misc Buffer	Renaming; changing read-onlyness; copying text.
Kill Buffer	Killing buffers you no longer need.
Several Buffers	How to go through the list of all buffers and operate variously on several of them.
Indirect Buffers	An indirect buffer shares the text of another buffer.
Buffer Convenience	Convenience and customization features for buffer handling.
Convenience Features and Customization of Buffer Handling
Uniquify	Making buffer names unique with directory parts.
Iswitchb	Switching between buffers with substrings.
Buffer Menus	Configurable buffer menu.
Multiple Windows
Basic Window	Introduction to Emacs windows.
Split Window	New windows are made by splitting existing windows.
Other Window	Moving to another window or doing something to it.
Pop Up Window	Finding a file or buffer in another window.
Force Same Window	Forcing certain buffers to appear in the selected window rather than in another window.
Change Window	Deleting windows and changing their sizes.
Window Convenience	Convenience functions for window handling.
Frames and Graphical Displays
Cut and Paste	Mouse commands for cut and paste.
Mouse References	Using the mouse to select an item from a list.
Menu Mouse Clicks	Mouse clicks that bring up menus.
Mode Line Mouse	Mouse clicks on the mode line.
Creating Frames	Creating additional Emacs frames with various contents.
Frame Commands	Iconifying, deleting, and switching frames.
Fonts	Changing the frame font.
Speedbar	How to make and use a speedbar frame.
Multiple Displays	How one Emacs job can talk to several displays.
Special Buffer Frames	You can make certain buffers have their own frames.
Frame Parameters	Changing the colors and other modes of frames.
Scroll Bars	How to enable and disable scroll bars; how to use them.
Wheeled Mice	Using mouse wheels for scrolling.
Drag and Drop	Using drag and drop to open files and insert text.
Menu Bars	Enabling and disabling the menu bar.
Tool Bars	Enabling and disabling the tool bar.
Dialog Boxes	Controlling use of dialog boxes.
Tooltips	Displaying information at the current mouse position.
Mouse Avoidance	Moving the mouse pointer out of the way.
Non-Window Terminals	Multiple frames on terminals that show only one.
Text-Only Mouse	Using the mouse in text-only terminals.
Killing and Yanking on Graphical Displays
Mouse Commands	Moving, cutting, and pasting, with the mouse.
Word and Line Mouse	Mouse commands for selecting whole words or lines.
Cut/Paste Other App	Transfering text between Emacs and other apps.
Secondary Selection	Cutting without altering point and mark.
Clipboard	Using the clipboard for selections.
International Character Set Support
International Chars	Basic concepts of multibyte characters.
Enabling Multibyte	Controlling whether to use multibyte characters.
Language Environments	Setting things up for the language you use.
Input Methods	Entering text characters not on your keyboard.
Select Input Method	Specifying your choice of input methods.
Coding Systems	Character set conversion when you read and write files, and so on.
Recognize Coding	How Emacs figures out which conversion to use.
Specify Coding	Specifying a file's coding system explicitly.
Output Coding	Choosing coding systems for output.
Text Coding	Choosing conversion to use for file text.
Communication Coding	Coding systems for interprocess communication.
File Name Coding	Coding systems for file names.
Terminal Coding	Specifying coding systems for converting terminal input and output.
Fontsets	Fontsets are collections of fonts that cover the whole spectrum of characters.
Defining Fontsets	Defining a new fontset.
Modifying Fontsets	Modifying an existing fontset.
Undisplayable Characters	When characters don't display.
Unibyte Mode	You can pick one European character set to use without multibyte characters.
Charsets	How Emacs groups its internal character codes.
Major Modes
Choosing Modes	How major modes are specified or chosen.
Indentation
Indentation Commands	Various commands and techniques for indentation.
Tab Stops	You can set arbitrary "tab stops" and then indent to the next tab stop when you want to.
Just Spaces	You can request indentation using just spaces.
Commands for Human Languages
Words	Moving over and killing words.
Sentences	Moving over and killing sentences.
Paragraphs	Moving over paragraphs.
Pages	Moving over pages.
Filling	Filling or justifying text.
Case	Changing the case of text.
Text Mode	The major modes for editing text files.
Outline Mode	Editing outlines.
TeX Mode	Editing input to the formatter TeX.
HTML Mode	Editing HTML and SGML files.
Nroff Mode	Editing input to the formatter nroff.
Formatted Text	Editing formatted text directly in WYSIWYG fashion.
Text Based Tables	Editing text-based tables in WYSIWYG fashion.
Filling Text
Auto Fill	Auto Fill mode breaks long lines automatically.
Fill Commands	Commands to refill paragraphs and center lines.
Fill Prefix	Filling paragraphs that are indented or in a comment, etc.
Adaptive Fill	How Emacs can determine the fill prefix automatically.
Refill	Keeping paragraphs filled.
Longlines	Editing text with very long lines.
Outline Mode
Outline Format	What the text of an outline looks like.
Outline Motion	Special commands for moving through outlines.
Outline Visibility	Commands to control what is visible.
Outline Views	Outlines and multiple views.
Foldout	Folding means zooming in on outlines.
TeX Mode
TeX Editing	Special commands for editing in TeX mode.
LaTeX Editing	Additional commands for LaTeX input files.
TeX Print	Commands for printing part of a file with TeX.
TeX Misc	Customization of TeX mode, and related features.
Editing Formatted Text
Requesting Formatted Text	Entering and exiting Enriched mode.
Hard and Soft Newlines	There are two different kinds of newlines.
Editing Format Info	How to edit text properties.
Format Faces	Bold, italic, underline, etc.
Format Colors	Changing the color of text.
Format Indentation	Changing the left and right margins.
Format Justification	Centering, setting text flush with the left or right margin, etc.
Format Properties	The "special" text properties submenu.
Forcing Enriched Mode	How to force use of Enriched mode.
Editing Text-based Tables
Table Definition	What is a text based table.
Table Creation	How to create a table.
Table Recognition	How to activate and deactivate tables.
Cell Commands	Cell-oriented commands in a table.
Cell Justification	Justifying cell contents.
Row Commands	Manipulating rows of table cell.
Column Commands	Manipulating columns of table cell.
Fixed Width Mode	Fixing cell width.
Table Conversion	Converting between plain text and tables.
Measuring Tables	Analyzing table dimension.
Table Misc	Table miscellany.
Editing Programs
Program Modes	Major modes for editing programs.
Defuns	Commands to operate on major top-level parts of a program.
Program Indent	Adjusting indentation to show the nesting.
Parentheses	Commands that operate on parentheses.
Comments	Inserting, killing, and aligning comments.
Documentation	Getting documentation of functions you plan to call.
Hideshow	Displaying blocks selectively.
Symbol Completion	Completion on symbol names of your program or language.
Glasses	Making identifiersLikeThis more readable.
Semantic	Suite of editing tools based on source code parsing.
Misc for Programs	Other Emacs features useful for editing programs.
C Modes	Special commands of C, C++, Objective-C, Java, and Pike modes.
Asm Mode	Asm mode and its special features.
Fortran	Fortran mode and its special features.
Top-Level Definitions, or Defuns
Left Margin Paren	An open-paren or similar opening delimiter starts a defun if it is at the left margin.
Moving by Defuns	Commands to move over or mark a major definition.
Imenu	Making buffer indexes as menus.
Which Function	Which Function mode shows which function you are in.
Indentation for Programs
Basic Indent	Indenting a single line.
Multi-line Indent	Commands to reindent many lines at once.
Lisp Indent	Specifying how each Lisp function should be indented.
C Indent	Extra features for indenting C and related modes.
Custom C Indent	Controlling indentation style for C and related modes.
Commands for Editing with Parentheses
Expressions	Expressions with balanced parentheses.
Moving by Parens	Commands for moving up, down and across in the structure of parentheses.
Matching	Insertion of a close-delimiter flashes matching open.
Manipulating Comments
Comment Commands	Inserting, killing, and aligning comments.
Multi-Line Comments	Commands for adding and editing multi-line comments.
Options for Comments	Customizing the comment features.
Documentation Lookup
Info Lookup	Looking up library functions and commands in Info files.
Man Page	Looking up man pages of library functions and commands.
Lisp Doc	Looking up Emacs Lisp functions, etc.
C and Related Modes
Motion in C	Commands to move by C statements, etc.
Electric C	Colon and other chars can automatically reindent.
Hungry Delete	A more powerful DEL command.
Other C Commands	Filling comments, viewing expansion of macros, and other neat features.
Fortran Mode
Fortran Motion	Moving point by statements or subprograms.
Fortran Indent	Indentation commands for Fortran.
Fortran Comments	Inserting and aligning comments.
Fortran Autofill	Auto fill support for Fortran.
Fortran Columns	Measuring columns for valid Fortran.
Fortran Abbrev	Built-in abbrevs for Fortran keywords.
Fortran Indentation
ForIndent Commands	Commands for indenting and filling Fortran.
ForIndent Cont	How continuation lines indent.
ForIndent Num	How line numbers auto-indent.
ForIndent Conv	Conventions you must obey to avoid trouble.
ForIndent Vars	Variables controlling Fortran indent style.
Compiling and Testing Programs
Compilation	Compiling programs in languages other than Lisp (C, Pascal, etc.).
Compilation Mode	The mode for visiting compiler errors.
Compilation Shell	Customizing your shell properly for use in the compilation buffer.
Grep Searching	Searching with grep.
Flymake	Finding syntax errors on the fly.
Debuggers	Running symbolic debuggers for non-Lisp programs.
Executing Lisp	Various modes for editing Lisp programs, with different facilities for running the Lisp programs.
Lisp Libraries	Creating Lisp programs to run in Emacs.
Lisp Eval	Executing a single Lisp expression in Emacs.
Lisp Interaction	Executing Lisp in an Emacs buffer.
External Lisp	Communicating through Emacs with a separate Lisp.
Running Debuggers Under Emacs
Starting GUD	How to start a debugger subprocess.
Debugger Operation	Connection between the debugger and source buffers.
Commands of GUD	Key bindings for common commands.
GUD Customization	Defining your own commands for GUD.
GDB Graphical Interface	An enhanced mode that uses GDB features to implement a graphical debugging environment through Emacs.
GDB Graphical Interface
GDB-UI Layout	Control the number of displayed buffers.
Source Buffers	Use the mouse in the fringe/margin to control your program.
Breakpoints Buffer	A breakpoint control panel.
Stack Buffer	Select a frame from the call stack.
Other GDB-UI Buffers	Input/output, locals, registers, assembler, threads and memory buffers.
Watch Expressions	Monitor variable values in the speedbar.
Maintaining Large Programs
Version Control	Using version control systems.
Change Log	Maintaining a change history for your program.
Tags	Go directly to any function in your program in one command. Tags remembers which file it is in.
EDE	An integrated development environment for Emacs.
Emerge	A convenient way of merging two versions of a program.
Version Control
Introduction to VC	How version control works in general.
VC Mode Line	How the mode line shows version control status.
Basic VC Editing	How to edit a file under version control.
Log Buffer	Features available in log entry buffers.
Old Revisions	Examining and comparing old versions.
Secondary VC Commands	The commands used a little less frequently.
VC Directory Mode	Listing files managed by version control.
Branches	Multiple lines of development.
Remote Repositories	Efficient access to remote CVS servers.
Revision Tags	Symbolic names for revisions.
Miscellaneous VC	Various other commands and features of VC.
Customizing VC	Variables that change VC's behavior.
Introduction to Version Control
Why Version Control?	Understanding the problems it addresses.
Version Control Systems	Supported version control back-end systems.
VCS Concepts	Words and concepts related to version control.
VCS Merging	How file conflicts are handled.
VCS Changesets	Changesets in version control.
VCS Repositories	Where version control repositories are stored.
Types of Log File	The VCS log in contrast to the ChangeLog.
Basic Editing under Version Control
VC With A Merging VCS	Without locking: default mode for CVS.
VC With A Locking VCS	RCS in its default mode, SCCS, and optionally CVS.
Advanced C-x v v	Advanced features available with a prefix argument.
The Secondary Commands of VC
Registering	Putting a file under version control.
VC Change Log	Viewing the VC Change Log.
VC Undo	Canceling changes before or after check-in.
VC Directory Mode
VC Directory Buffer	What the buffer looks like and means.
VC Directory Commands	Commands to use in a VC directory buffer.
Multiple Branches of a File
Switching Branches	How to get to another existing branch.
Creating Branches	How to start a new branch.
Merging	Transferring changes between branches.
Multi-User Branching	Multiple users working at multiple branches in parallel.
Remote Repositories
Version Backups	Keeping local copies of repository versions.
Local Version Control	Using another version system for local editing.
Revision Tags
Making Revision Tags	The tag facilities.
Revision Tag Caveats	Things to be careful of when using tags.
Miscellaneous Commands and Features of VC
Change Logs and VC	Generating a change log file from log entries.
Renaming and VC	A command to rename both the source and master file correctly.
Version Headers	Inserting version control headers into working files.
Customizing VC
General VC Options	Options that apply to multiple back ends.
RCS and SCCS	Options for RCS and SCCS.
CVS Options	Options for CVS.
Change Logs
Change Log Commands	Commands for editing change log files.
Format of ChangeLog	What the change log file looks like.
Tags Tables
Tag Syntax	Tag syntax for various types of code and text files.
Create Tags Table	Creating a tags table with etags.
Etags Regexps	Create arbitrary tags using regular expressions.
Select Tags Table	How to visit a tags table.
Find Tag	Commands to find the definition of a specific tag.
Tags Search	Using a tags table for searching and replacing.
List Tags	Listing and finding tags defined in a file.
Merging Files with Emerge
Overview of Emerge	How to start Emerge. Basic concepts.
Submodes of Emerge	Fast mode vs. Edit mode. Skip Prefers mode and Auto Advance mode.
State of Difference	You do the merge by specifying state A or B for each difference.
Merge Commands	Commands for selecting a difference, changing states of differences, etc.
Exiting Emerge	What to do when you've finished the merge.
Combining in Emerge	How to keep both alternatives for a difference.
Fine Points of Emerge	Miscellaneous issues.
Abbrevs
Abbrev Concepts	Fundamentals of defined abbrevs.
Defining Abbrevs	Defining an abbrev, so it will expand when typed.
Expanding Abbrevs	Controlling expansion: prefixes, canceling expansion.
Editing Abbrevs	Viewing or editing the entire list of defined abbrevs.
Saving Abbrevs	Saving the entire list of abbrevs for another session.
Dynamic Abbrevs	Abbreviations for words already in the buffer.
Dabbrev Customization	What is a word, for dynamic abbrevs. Case handling.
Editing Pictures
Basic Picture	Basic concepts and simple commands of Picture Mode.
Insert in Picture	Controlling direction of cursor motion after "self-inserting" characters.
Tabs in Picture	Various features for tab stops and indentation.
Rectangles in Picture	Clearing and superimposing rectangles.
Sending Mail
Mail Format	Format of the mail being composed.
Mail Headers	Details of some standard mail header fields.
Mail Aliases	Abbreviating and grouping mail addresses.
Mail Commands	Special commands for editing mail being composed.
Mail Signature	Adding a signature to every message.
Mail Amusements	Distracting the NSA; adding fortune messages.
Mail Methods	Using alternative mail-composition methods.
Mail Commands
Mail Sending	Commands to send the message.
Header Editing	Commands to move to header fields and edit them.
Citing Mail	Quoting a message you are replying to.
Mail Misc	Attachments, spell checking, etc.
Reading Mail with Rmail
Rmail Basics	Basic concepts of Rmail, and simple use.
Rmail Scrolling	Scrolling through a message.
Rmail Motion	Moving to another message.
Rmail Deletion	Deleting and expunging messages.
Rmail Inbox	How mail gets into the Rmail file.
Rmail Files	Using multiple Rmail files.
Rmail Output	Copying message out to files.
Rmail Labels	Classifying messages by labeling them.
Rmail Attributes	Certain standard labels, called attributes.
Rmail Reply	Sending replies to messages you are viewing.
Rmail Summary	Summaries show brief info on many messages.
Rmail Sorting	Sorting messages in Rmail.
Rmail Display	How Rmail displays a message; customization.
Rmail Coding	How Rmail handles decoding character sets.
Rmail Editing	Editing message text and headers in Rmail.
Rmail Digest	Extracting the messages from a digest message.
Rmail Rot13	Reading messages encoded in the rot13 code.
Movemail	More details of fetching new mail.
Remote Mailboxes	Retrieving mail from remote mailboxes.
Other Mailbox Formats	Retrieving mail from local mailboxes in various formats.
Summaries
Rmail Make Summary	Making various sorts of summaries.
Rmail Summary Edit	Manipulating messages from the summary.
Dired, the Directory Editor
Dired Enter	How to invoke Dired.
Dired Navigation	Special motion commands in the Dired buffer.
Dired Deletion	Deleting files with Dired.
Flagging Many Files	Flagging files based on their names.
Dired Visiting	Other file operations through Dired.
Marks vs Flags	Flagging for deletion vs marking.
Operating on Files	How to copy, rename, print, compress, etc. either one file or several files.
Shell Commands in Dired	Running a shell command on the marked files.
Transforming File Names	Using patterns to rename multiple files.
Comparison in Dired	Running `diff' by way of Dired.
Subdirectories in Dired	Adding subdirectories to the Dired buffer.
Subdir Switches	Subdirectory switches in Dired.
Subdirectory Motion	Moving across subdirectories, and up and down.
Hiding Subdirectories	Making subdirectories visible or invisible.
Dired Updating	Discarding lines for files of no interest.
Dired and Find	Using `find' to choose the files for Dired.
Wdired	Operating on files by editing the Dired buffer.
Image-Dired	Viewing image thumbnails in Dired.
Misc Dired Features	Various other features.
The Calendar and the Diary
Calendar Motion	Moving through the calendar; selecting a date.
Scroll Calendar	Bringing earlier or later months onto the screen.
Counting Days	How many days are there between two dates?
General Calendar	Exiting or recomputing the calendar.
Writing Calendar Files	Writing calendars to files of various formats.
Holidays	Displaying dates of holidays.
Sunrise/Sunset	Displaying local times of sunrise and sunset.
Lunar Phases	Displaying phases of the moon.
Other Calendars	Converting dates to other calendar systems.
Diary	Displaying events from your diary.
Appointments	Reminders when it's time to do something.
Importing Diary	Converting diary events to/from other formats.
Daylight Saving	How to specify when daylight saving time is active.
Time Intervals	Keeping track of time intervals.
Advanced Calendar/Diary Usage	Advanced Calendar/Diary customization.
Movement in the Calendar
Calendar Unit Motion	Moving by days, weeks, months, and years.
Move to Beginning or End	Moving to start/end of weeks, months, and years.
Specified Dates	Moving to the current date or another specific date.
Conversion To and From Other Calendars
Calendar Systems	The calendars Emacs understands (aside from Gregorian).
To Other Calendar	Converting the selected date to various calendars.
From Other Calendar	Moving to a date specified in another calendar.
Mayan Calendar	Moving to a date specified in a Mayan calendar.
The Diary
Displaying the Diary	Viewing diary entries and associated calendar dates.
Format of Diary File	Entering events in your diary.
Date Formats	Various ways you can specify dates.
Adding to Diary	Commands to create diary entries.
Special Diary Entries	Anniversaries, blocks of dates, cyclic entries, etc.
Customizing the Calendar and Diary
Calendar Customizing	Calendar layout and hooks.
Holiday Customizing	Defining your own holidays.
Date Display Format	Changing the format.
Time Display Format	Changing the format.
Diary Customizing	Defaults you can set.
Non-Gregorian Diary	Diary entries based on other calendars.
Diary Display	A choice of ways to display the diary.
Fancy Diary Display	Sorting diary entries, using included diary files.
Sexp Diary Entries	More flexible diary entries.
Document Viewing
Navigation	Navigation inside DocView buffers.
Searching	Searching inside documents.
Slicing	Specifying which part of pages should be displayed.
Conversion	Influencing and triggering conversion.
Gnus
Buffers of Gnus	The group, summary, and article buffers.
Gnus Startup	What you should know about starting Gnus.
Summary of Gnus	A short description of the basic Gnus commands.
Running Shell Commands from Emacs
Single Shell	How to run one shell command and return.
Interactive Shell	Permanent shell taking input via Emacs.
Shell Mode	Special Emacs commands used with permanent shell.
Shell Prompts	Two ways to recognize shell prompts.
Shell History	Repeating previous commands in a shell buffer.
Directory Tracking	Keeping track when the subshell changes directory.
Shell Options	Options for customizing Shell mode.
Terminal emulator	An Emacs window as a terminal emulator.
Term Mode	Special Emacs commands used in Term mode.
Paging in Term	Paging in the terminal emulator.
Remote Host	Connecting to another computer.
Serial Terminal	Connecting to a serial port.
Shell Command History
Shell Ring	Fetching commands from the history list.
Shell History Copying	Moving to a command and then copying it.
History References	Expanding ‘!’-style history references.
Using Emacs as a Server
Invoking emacsclient	Connecting to the Emacs server.
emacsclient Options	Emacs client startup options.
Printing Hard Copies
PostScript	Printing buffers or regions as PostScript.
PostScript Variables	Customizing the PostScript printing commands.
Printing Package	An optional advanced printing interface.
Hyperlinking and Navigation Features
Browse-URL	Following URLs.
Goto Address mode	Activating URLs.
FFAP	Finding files etc. at point.
Customization
Minor Modes	Each minor mode is a feature you can turn on independently of any others.
Easy Customization	Convenient way to browse and change settings.
Variables	Many Emacs commands examine Emacs variables to decide what to do; by setting variables, you can control their functioning.
Key Bindings	The keymaps say what command each key runs. By changing them, you can "redefine keys".
Syntax	The syntax table controls how words and expressions are parsed.
Init File	How to write common customizations in the .emacs file.
Easy Customization Interface
Customization Groups	How settings are classified in a structure.
Browsing Custom	Browsing and searching for settings.
Changing a Variable	How to edit an option's value and set the option.
Saving Customizations	Specifying the file for saving customizations.
Face Customization	How to edit the attributes of a face.
Specific Customization	Making a customization buffer for specific variables, faces, or groups.
Custom Themes	How to define collections of customized options that can be loaded and unloaded together.
Variables
Examining	Examining or setting one variable's value.
Hooks	Hook variables let you specify programs for parts of Emacs to run on particular occasions.
Locals	Per-buffer values of variables.
File Variables	How files can specify variable values.
Directory Variables	How variable values can be specified by directory.
Local Variables in Files
Specifying File Variables	Specifying file local variables.
Safe File Variables	Making sure file local variables are safe.
Customizing Key Bindings
Keymaps	Generalities. The global keymap.
Prefix Keymaps	Keymaps for prefix keys.
Local Keymaps	Major and minor modes have their own keymaps.
Minibuffer Maps	The minibuffer uses its own local keymaps.
Rebinding	How to redefine one key's meaning conveniently.
Init Rebinding	Rebinding keys with your init file, .emacs.
Modifier Keys	Using modifier keys in key bindings.
Function Keys	Rebinding terminal function keys.
Named ASCII Chars	Distinguishing <TAB> from C-i, and so on.
Mouse Buttons	Rebinding mouse buttons in Emacs.
Disabling	Disabling a command means confirmation is required before it can be executed. This is done to protect beginners from surprises.
The Init File, ~/.emacs
Init Syntax	Syntax of constants in Emacs Lisp.
Init Examples	How to do some things with an init file.
Terminal Init	Each terminal type can have an init file.
Find Init	How Emacs finds the init file.
Init Non-ASCII	Using non-ASCII characters in an init file.
Dealing with Emacs Trouble
DEL Does Not Delete	What to do if <DEL> doesn't delete.
Stuck Recursive	`[...]' in mode line around the parentheses.
Screen Garbled	Garbage on the screen.
Text Garbled	Garbage in the text.
Memory Full	How to cope when you run out of memory.
After a Crash	Recovering editing in an Emacs session that crashed.
Emergency Escape	Emergency escape--- What to do if Emacs stops responding.
Total Frustration	When you are at your wits' end.
Reporting Bugs
Known Problems	How to read about known problems and bugs.
Bug Criteria	Have you really found a bug?
Understanding Bug Reporting	How to report a bug effectively.
Checklist	Steps to follow for a good bug report.
Sending Patches	How to send a patch for GNU Emacs.
Command Line Arguments for Emacs Invocation
Action Arguments	Arguments to visit files, load libraries, and call functions.
Initial Options	Arguments that take effect while starting Emacs.
Command Example	Examples of using command line arguments.
Resume Arguments	Specifying arguments when you resume a running Emacs.
Environment	Environment variables that Emacs uses.
Display X	Changing the default display and using remote login.
Font X	Choosing a font for text, under X.
Colors	Choosing display colors.
Window Size X	Start-up window size, under X.
Borders X	Internal and external borders, under X.
Title X	Specifying the initial frame's title.
Icons X	Choosing what sort of icon to use, under X.
Misc X	Other display options.
Environment Variables
General Variables	Environment variables that all versions of Emacs use.
Misc Variables	Certain system-specific variables.
MS-Windows Registry	An alternative to the environment on MS-Windows.
X Options and Resources
Resources	Using X resources with Emacs (in general).
Table of Resources	Table of specific X resources that affect Emacs.
Face Resources	X resources for customizing faces.
Lucid Resources	X resources for Lucid menus.
LessTif Resources	X resources for LessTif and Motif menus.
GTK resources	Resources for GTK widgets.
GTK resources
GTK widget names	How widgets in GTK are named in general.
GTK Names in Emacs	GTK widget names in Emacs.
GTK styles	What can be customized in a GTK widget.
Emacs and Mac OS / GNUstep
Mac / GNUstep Basics	Basic Emacs usage under GNUstep or Mac OS.
Mac / GNUstep Customization	Customizations under GNUstep or Mac OS.
Mac / GNUstep Events	How window system events are handled.
GNUstep Support	Details on status of GNUstep support.
Emacs and Microsoft Windows/MS-DOS
Windows Startup	How to start Emacs on Windows.
Text and Binary	Text files use CRLF to terminate lines.
Windows Files	File-name conventions on Windows.
ls in Lisp	Emulation of ls for Dired.
Windows HOME	Where Emacs looks for your .emacs.
Windows Keyboard	Windows-specific keyboard features.
Windows Mouse	Windows-specific mouse features.
Windows Processes	Running subprocesses on Windows.
Windows Printing	How to specify the printer on MS-Windows.
Windows Fonts	Specifying fonts on MS-Windows.
Windows Misc	Miscellaneous Windows features.
MS-DOS	Using Emacs on MS-DOS (otherwise known as MS-DOG).
Emacs and MS-DOS
MS-DOS Keyboard	Keyboard conventions on MS-DOS.
MS-DOS Mouse	Mouse conventions on MS-DOS.
MS-DOS Display	Fonts, frames and display size on MS-DOS.
MS-DOS File Names	File name conventions on MS-DOS.
MS-DOS Printing	Printing specifics on MS-DOS.
MS-DOS and MULE	Support for internationalization on MS-DOS.
MS-DOS Processes	Running subprocesses on MS-DOS.

Distribution

GNU Emacs is free software; this means that everyone is free to use it and free to redistribute it on 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 Copying.

One way to get a copy of GNU Emacs is from someone else who has it. You need not ask for our permission to do so, or tell any one else; just copy it. If you have access to the Internet, you can get the latest distribution version of GNU Emacs by anonymous FTP; see http://www.gnu.org/software/emacs on our website for more information.

You may also receive GNU Emacs when you buy a computer. Computer manufacturers are free to distribute copies on the same terms that apply to everyone else. These terms require them to give you the full sources, including whatever changes they may have made, and to permit you to redistribute the GNU Emacs received from them under the usual terms of the General Public License. In other words, the program must be free for you when you get it, not just free for the manufacturer.

You can also order copies of GNU Emacs from the Free Software Foundation. This is a convenient and reliable way to get a copy; it is also a good way to help fund our work. We also sell hardcopy versions of this manual and An Introduction to Programming in Emacs Lisp, by Robert J. Chassell. You can visit our online store at http://shop.fsf.org/. For further information, write to

     Free Software Foundation
     51 Franklin Street, Fifth Floor
     Boston, MA 02110-1301
     USA

The income from sales goes to support the foundation's purpose: the development of new free software, and improvements to our existing programs including GNU Emacs.

If you find GNU Emacs useful, please send a donation to the Free Software Foundation to support our work. Donations to the Free Software Foundation are tax deductible in the US. If you use GNU Emacs at your workplace, please suggest that the company make a donation. If company policy is unsympathetic to the idea of donating to charity, you might instead suggest ordering a CD-ROM from the Foundation occasionally, or subscribing to periodic updates.

Introduction

You are reading about GNU Emacs, the GNU incarnation of the advanced, self-documenting, customizable, extensible editor Emacs. (The `G' in `GNU' 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, 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 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 Emacs Lisp Intro, if you want to learn Emacs Lisp programming.

1 The Organization of the Screen

On a text-only terminal, the Emacs display occupies the entire terminal screen. On a graphical display, such as on GNU/Linux using the X Window System, Emacs creates its own windows to use. We use the term frame to mean the entire terminal screen or graphical window used by Emacs. Emacs uses both kinds of frames, in the same way, to display your editing. Emacs normally starts out with just one frame, but you can create additional frames if you wish (see Frames).

The 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 if you click on them. At the very bottom of the frame is a special echo area, where short 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. This is where Emacs displays the buffer: the text that you are editing. On a graphical display, the window possesses a scroll bar on one side, which you can use to display different parts of the buffer in the window. 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 Windows). In this manual, the word “window” refers to the initial large window if not subdivided, or any one of the multiple windows you have subdivided it into.

At any time, one window is the selected window. On graphical displays, the selected window normally shows a more prominent cursor (usually solid and blinking) while other windows show a weaker cursor (such as a hollow box). Text terminals have just one cursor, so it always appears 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.

• Point: The place in the text where editing commands operate.
• Echo Area: Short messages appear at the bottom of the screen.
• Mode Line: Interpreting the mode line.
• Menu Bar: How to use the menu bar.

1.1 Point

The active cursor shows the location at which editing commands will 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.

While the cursor appears to be on a character, you should think of point as between two characters; it points before the character that appears 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.

Sometimes people speak of “the cursor” when they mean “point,” or speak of commands that move point as “cursor motion” commands.

If you are editing several files in Emacs, each in its own buffer, each buffer has its own point location. A buffer that is not currently displayed remembers its point location in case you display it again later. When Emacs displays multiple windows, each window has its own point location. If the same buffer appears in more than one window, each window has its own point position in that buffer.

On a graphical display, Emacs shows a cursor in each window; the selected window's cursor is solid and blinking, and the other cursors are hollow. On a text-only terminal, there is just one cursor, in the selected window; even though the unselected windows have their own point positions, they do not display a cursor. See Cursor Display, for customizable variables that control cursor display.

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.

Echoing means displaying the characters that you type. Single-character commands, including most simple editing operations, are not echoed. Multi-character commands are echoed if you pause while typing them: if you pause for more than a second in the middle of a command, Emacs echoes all the characters of the command so far, to prompt you for the rest of the command. The echoed characters are displayed in the echo area. 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. See Display Custom.

If a command cannot do its job, it may display an error message. Error messages are also displayed in the echo area. They may be accompanied by beeping or by flashing the screen.

Some commands display informative messages in the echo area. Unlike error messages, these messages are not announced with a beep or flash. Sometimes the message tells you what the command has done, when this is not obvious from looking at the text being edited. Other times, the sole purpose of a command is to show you a message giving you specific information. For example, C-x = (hold down <CTRL> and type x, then let go of <CTRL> and type =) displays a message describing the character position of point in the text and its current column in the window. Commands that take a long time often display messages ending in ‘...’ while they are working, and add ‘done’ at the end when they are finished. They may also indicate progress with percentages.

Informative echo-area messages are saved in a special buffer named ‘*Messages*’. (We have not explained buffers yet; see 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.

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 (usually ending with a colon); also, 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 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, and the mode line of the selected window has a brighter color than that of unselected windows to make it stand out. On a text-only terminal, the mode line is usually drawn in inverse video.

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

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

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

cs describes the character set of the buffer (see Coding Systems). If it is a dash (‘-’), that indicates the default state of affairs: no special character set handling, except for the end-of-line translations described in the next paragraph. ‘=’ means no conversion whatsoever. Letters represent various nontrivial coding systems—for example, ‘1’ represents ISO Latin-1. On a text-only terminal, cs is preceded by two additional characters that describe the coding system for keyboard input and the coding system for terminal output. Furthermore, if you are using an input method, cs is preceded by a string that identifies the input method, which takes the form ‘i>’, ‘i+’, or ‘i@’ (see Input Methods).

The character after cs is usually a colon. However, under some circumstances a different string is displayed, which indicates a nontrivial end-of-line convention. Usually, lines of text are separated by newline characters, but two other conventions are sometimes used. The MS-DOS convention is to use 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. The Macintosh end-of-line convention is to use a “carriage-return” character instead of a newline; when editing such files, the colon indicator 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.

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 the default-directory for the current buffer is on a remote machine, ‘@’ is displayed instead (see File Names).

fr gives the selected frame name (see Frames). It appears only on text-only 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 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 it is all 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.

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.)

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, Rmail buffers display the current message number and the total number of messages. Compilation buffers and Shell buffers display the status of the subprocess.

minor is a list of some of the minor modes turned on in the buffer. Minor modes 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 through 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, not just one buffer, the square brackets appear in every window's mode line or not in any of them. See Recursive Edit.

You can change the appearance of the mode line as well as the format of its contents. See Optional Mode Line. In addition, the mode line is mouse-sensitive; clicking on different parts of the mode line performs various commands. See Mode Line Mouse.

1.4 The Menu Bar

Each Emacs frame normally has a menu bar at the top which you can use to perform common operations. There's no need to list them here, as you can more easily see them yourself.

On a graphical display, you can use the mouse to choose a command from the menu bar. A right-arrow at the end of a menu item means it leads to a subsidiary menu, or submenu. A ‘...’ at the end of a menu item means that the command invoked will prompt you for further input before it actually does anything.

Some of the commands in the menu bar have ordinary key bindings as well; if so, a key binding is shown in parentheses after the item itself. To view the full command name and documentation for a menu item, type C-h k, and then select the menu bar with the mouse in the usual way (see Key Help).

Instead of using the mouse, you can also invoke the first menu bar item by pressing <F10> (to run the command menu-bar-open). You can then navigate the menus with the arrow keys. To activate a selected menu item, press <RET>; to cancel menu navigation, press <ESC>.

On text-only terminals with no mouse, you can use the menu bar by typing M-` or <F10> (these run the command tmm-menubar). This lets you select a menu item with the keyboard. A provisional choice appears in the echo area. You can use the up and down arrow keys to move through the menu to different items, and then you can type <RET> to select the item.

Each menu item also has an assigned letter or digit which designates that item; it is usually the initial of some word in the item's name. This letter or digit is separated from the item name by ‘=>’. You can type the item's letter or digit to select the item.

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 not as efficient as using the keyboard. Therefore, this manual mainly documents how to edit with the keyboard.

Keyboard input into Emacs is based on a heavily-extended version of ASCII. The simplest characters that you can input into Emacs correspond to graphic symbols such as ‘a’, ‘B’, ‘3’, ‘=’, the space character (conventionally denoted as <SPC>), and so on. Entering these using the keyboard is straightforward. Certain characters found on non-English keyboards also fall into this category (see International).

In addition to these simple characters, Emacs recognizes control characters such as <RET>, <TAB>, <DEL>, <ESC>, <F1>, <Home>, <left>, etc. Most keyboards have special keys for entering these.

Emacs also recognizes control characters that are entered using modifier keys. Two commonly-used modifier keys are <Control> (which is usually labelled as <Ctrl>), and <Meta> (which is usually labeled as <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.

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 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-only terminals where the <Meta> key does not function reliably.

Modifier keys can apply not only to alphanumerical characters, but also to special input characters, such as the arrow keys and mouse buttons.

See Input Events, for the full Lisp-level details about keyboard and mouse input, which are collectively referred to as input events. If you are not doing Lisp programming, but simply want to redefine the meaning of some characters or non-character events, see Customization.

On graphical displays, the window manager is likely to block the character M-<TAB> before Emacs can see it. It may also block M-<SPC>, C-M-d and C-M-l. If you have these problems, we recommend that you customize your window manager to turn off those commands, or put them on key combinations that Emacs does not use.

3 Keys

Some Emacs commands are invoked by just one input event; for example, C-f moves forward one character in the buffer. But Emacs also has commands that 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 is either a complete key or a prefix key.

A prefix key combines with the following input event to make a longer key sequence, which may itself be complete or a prefix. For example, C-x is a prefix key, so C-x and the next input event combine to make a two-event key sequence. This two-event key sequence 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 a key sequence, but in practice people rarely use sequences longer than three or four input events.

You can't add input events onto a complete key. For example, the two-event sequence C-f C-k is not a key, because the C-f is a complete key in itself, so C-f C-k cannot have an independent meaning as a command. 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 v, C-x 4, C-x 5, C-x 6, <ESC>, M-g, and M-o. (<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 anything would become an invalid key sequence. See 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 displays a list of the commands starting with <ESC>.

4 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. A command also has a function definition which is a Lisp program; this is how the command does its work. In Emacs Lisp, a command is a Lisp function with special properties that make it suitable for interactive use. For more information on commands and functions, see What Is a Function.

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.

5 Entering Emacs

The usual way to invoke Emacs is with the shell command emacs. From a terminal window running in the X Window System, you can also 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.

When Emacs starts up, the initial frame displays a special buffer named ‘*GNU Emacs*’. This buffer contains some information about Emacs, and includes links to common tasks that might be useful to 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 specific 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 edit one file at a time: once you are done with that file, you exit the editor, and start it again the next time you need it.

Using Emacs in this way—starting it afresh each time you want to edit a file—is unnecessary and wasteful. Emacs can visit more than one file in a single editing session, and exiting the Emacs session loses valuable accumulated context, such as the kill ring, registers, undo history, and mark ring. These features, described later in the manual, are useful for performing edits across multiple files, or continuing edits to a single file.

The recommended way to use Emacs is to start it only once, just after you log in, and do all your editing in the same Emacs session. Each time you edit a file, visit it with the existing Emacs, which eventually has many files in it ready for editing. See Files, for more information on visiting more than one file.

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

Emacs accepts other command line arguments that tell it to load certain Lisp files, call certain functions, and so forth. These features exist mainly for advanced users. See 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. You can set the variable inhibit-startup-screen using the Customize facility (see Easy Customization), or by editing your initialization file (see Init File).⁴

You can also force Emacs to display a file or directory at startup by setting the variable initial-buffer-choice to a non-nil value. (In that case, even if you specify one or more files on the command line, Emacs opens but does not display them.) The value of initial-buffer-choice can be either the name of the desired file or directory, or t, which means to display the ‘*scratch*’ buffer.

6 Exiting Emacs

C-x C-c

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

C-z

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

Killing Emacs means terminating the Emacs program. To do this, type C-x C-c (save-buffers-kill-terminal). A two-character key 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 Shell).

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 Emacs 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.

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

You can “exit” Emacs in two other ways. On a graphical display, you can minimize (or iconify) an Emacs frame; depending on the window system, this either replaces the Emacs frame with a tiny “icon” or conceals the frame entirely (see Frames). On a text-only terminal, you can suspend Emacs; this means stopping the Emacs program temporarily, returning control to its parent process (usually a shell).

C-z runs the command suspend-frame. On a graphical display, this “minimizes” (or “iconifies”) the selected Emacs frame. On a text terminal, this suspends the Emacs process.

After minimizing or suspending Emacs, you can return to it and continue editing wherever you left off. The way to do this depends on the window system or shell. In most common shells, you can resume Emacs after suspending it with the shell command %emacs.

On very old systems that don't support suspending programs, C-z starts an inferior shell that communicates directly with the terminal, and Emacs waits until you exit the subshell. (The way to exit the subshell is usually C-d or exit.) On these systems, you can only get back to the shell from which Emacs was run (to log out, for example) when you kill Emacs. Suspending can also fail if you run Emacs under a shell that doesn't support suspending jobs, even if the system itself does support it. In this case, you can set the variable cannot-suspend to a non-nil value to force C-z to start an inferior shell.

Text-only 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).

7 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 Control-h t inside Emacs. (help-with-tutorial).

• Inserting Text: Inserting text by simply typing it.
• Moving Point: Moving the cursor to the place where you want to change something.
• Erasing: Deleting and killing text.
• Basic Undo: Undoing recent changes in the text.
• Files: Visiting, creating, and saving files.
• Help: Asking what a character does.
• Blank Lines: Making and deleting blank lines.
• Continuation Lines: How Emacs displays lines too wide for the screen.
• Position Info: What page, line, row, or column is point on?
• Arguments: Numeric arguments for repeating a command N times.
• Repeating: Repeating the previous command quickly.

7.1 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>. This key may be labeled <Return> or <Enter> on your keyboard, but we refer to it as <RET> in this manual. Pressing it inserts a newline character in the buffer. If point is at the end of the line, this creates a new blank line after it; if point is in the middle of a line, the line is split at that position.

As we explain later in this manual, you can change the way Emacs handles text insertion by turning on minor modes. For instance, if you turn on a minor mode called Auto Fill mode, Emacs can split lines automatically when they become too long (see Filling). If you turn on a minor mode called Overwrite mode, inserted characters 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>, it 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 numeric argument tells C-q how many copies of the quoted character to insert (see Arguments).

Instead of C-q, you can use C-x 8 <RET> (ucs-insert) to insert a character based on its Unicode name or code-point. This command prompts for a character to insert, using the minibuffer; you can specify the character using either (i) the character's name in the Unicode standard, or (ii) the character's code-point in the Unicode standard. If you specify the character's name, the command provides completion.

7.2 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, up and down respectively. These are equivalent to the commands <right>, <left>, <down>, and <up>, entered using the arrow keys present on many keyboards. Many Emacs users find that it is slower to use the arrow keys than the equivalent control keys. 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-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).

C-f

<right>

Move forward one character (forward-char).

C-b

<left>

Move backward one character (backward-char).

M-f

M-<right>

C-<right>

Move forward one word (forward-word).

M-b

M-<left>

C-<left>

Move backward one word (backward-word).

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.

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).

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. See Arguments, for more information on numeric arguments.

M->

Move to the end of the buffer (end-of-buffer).

C-v

<PageDown>

<next>

Scroll the display one screen forward, and move point if necessary to put it on the screen (scroll-up). If your keyboard has a <PageDown> key (sometimes labelled <next>), it does the same thing as <C-v>. Scrolling commands are described further in Scrolling.

M-v

<PageUp>

<prior>

Scroll one screen backward, and move point if necessary to put it on the screen (scroll-down). If your keyboard has a <PageUp> key (sometimes labelled <prior>), it does the same thing as M-v.

M-x goto-char

Read a number n and move point to buffer position n. Position 1 is the beginning of the buffer.

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 Select Buffer, for the behavior of M-g M-g when you give it a plain prefix argument.

C-x C-n

Use the current column of point as the semipermanent goal column for C-n and C-p (set-goal-column). When a semipermanent goal column is in effect, those commands 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. 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. Moving by logical lines was the default behavior prior to Emacs 23.1. 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 of 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.

7.3 Erasing Text

<DEL>

<Backspace>

Delete the character before point (delete-backward-char).

C-d

<Delete>

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>

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

The key <DEL> (delete-backward-char) removes the character before point, moving the cursor and all the characters after it backwards. On most keyboards, <DEL> is labelled <Backspace>, but we refer to it as <DEL> in this manual. Do not confuse <DEL> with another key, labelled <Delete>, that exists on many keyboards; we will discuss <Delete> momentarily.

Typing <DEL> when the cursor is at the beginning of a line deletes the preceding newline character, joining the line with the one before it.

On some text-only terminals, Emacs may not recognize the <DEL> key properly. If <DEL> does not do the right thing (e.g., if it deletes characters forwards), see DEL Does Not Delete.

The key C-d (delete-char) deletes the character after point, i.e., the character under the cursor. This shifts the rest of the text on the line to the left. If you type C-d at the end of a line, it joins that line with the following line. This command is also bound to the key labelled <Delete> on many keyboards.

To erase a larger amount of text, use the C-k key, which 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.

To learn more about killing text, see Killing.

7.4 Undoing Changes

C-/

Undo one entry of the undo records—usually, one command worth (undo).

C-x u

C-_

The same.

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.

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.

7.5 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. Files are named units of text which are stored by the operating system for you to retrieve later by name. To use the contents of a file in any way, including editing it with Emacs, you must specify the file name.

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 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 Files.

7.6 Help

If you forget what a key does, you can find out with the Help character, which is C-h (or <F1>, which is an alias for C-h). Type C-h k, followed by the key of interest; for example, C-h k C-n tells you what C-n does. C-h is a prefix key; C-h k is just one of its subcommands (the command describe-key). The other subcommands of C-h provide different kinds of help. Type C-h twice to get a description of all the help facilities. See Help.

7.7 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 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 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.

7.8 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. 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-only 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 Moving 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-only 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.

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.

7.9 Cursor Position Information

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

M-x what-page

Display the page number of point, and the line number within that page.

M-x what-line

Display the line number of point in the whole buffer.

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.

M-x count-lines-region

Display the number of lines in the current region. Normally bound to M-=, except in a few specialist modes. See Mark, for information about the region.

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 Cursor Display.

M-x size-indication-mode

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

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 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-x what-page counts pages from the beginning of the file, and counts lines within the page, showing both numbers in the echo area. See Pages.

Use M-x count-lines-region (normally bound to M-=) to display the number of lines in the region (see Mark). See Pages, for the command C-x l which counts the lines in the current page.

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 International Chars. 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 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.

7.10 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. Meta-- 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 “a lot” of 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, for more information on M-q.) For these commands, it is enough to 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, 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” as well as “numeric argument,” to emphasize that you type these argument before the command, and to distinguish them from minibuffer arguments that come after the command.

7.11 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 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.

8 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.

When the minibuffer is in use, it appears in the echo area, with a cursor. The minibuffer display starts with a prompt in a distinct color, usually ending with a colon. The prompt states what kind of input is expected, and how it will be used.

The simplest way to enter a minibuffer argument is to type the text, then <RET> to submit the argument and exit the minibuffer. You can cancel the minibuffer, and the command that wants the argument, by typing C-g.

Sometimes, a default argument appears in the prompt, inside parentheses before the colon. The default will be used as the argument value 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.

Since the minibuffer appears in the echo area, it can conflict with other uses of the echo area. If an error occurs while the minibuffer is active, the error message hides the minibuffer for a few seconds, or until you type something; then the minibuffer comes back. If a command such as C-x = needs to display a message in the echo area, the message hides the minibuffer for a few seconds, or until you type something; then the minibuffer comes back. While the minibuffer is in use, keystrokes do not echo.

• Minibuffer File: Entering file names with the minibuffer.
• Minibuffer Edit: How to edit in the minibuffer.
• Completion: An abbreviation facility for minibuffer input.
• Minibuffer History: Reusing recent minibuffer arguments.
• Repetition: Re-executing commands that used the minibuffer.
• Passwords: Entering passwords in the echo area.

8.1 Minibuffers for File Names

Commands such as C-x C-f (find-file) use the minibuffer to read a file name argument (see Basic 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.

You can specify the parent directory by adding ..: for example, /u2/emacs/src/../lisp/simple.el is equivalent to /u2/emacs/lisp/simple.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 Minibuffer Edit). 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

Emacs interprets a double slash as “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.)

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 Windows HOME; for MS-DOS, see HOME 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.

8.2 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 is defined to exit the minibuffer, you can't use it to insert a newline in the minibuffer. To do that, type C-o or C-q C-j. (The newline character is really the ASCII character control-J.)

Inside a minibuffer, the keys <TAB>, <SPC>, and <?> are often bound to commands that perform completion. See Completion. You can use C-q (quoted-insert) to insert a <TAB>, <SPC>, or <?> character. For example, C-q <TAB> inserts a <TAB> character. See Inserting Text.

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 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 accomodate 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 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-<prior> and M-<next> (or, equivalently, M-<PageUp> and M-<PageDown>). This is especially useful with long lists of possible completions. See Other Window.

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.

8.3 Completion

Sometimes, you can use a feature called completion to help you 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 you have typed so far.

When completion is available, certain keys (usually <TAB>, <RET>, and <SPC>) are rebound to complete the text in the minibuffer into a longer string chosen from a set of completion alternatives. The set of completion alternatives depends on the command that requested the argument, and on what you have typed so far. In addition, you can usually type ? to display a list of possible completions.

For example, 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. So, to run the command insert-buffer, you can type M-x ins <SPC> b <RET> instead of the full M-x insert-buffer <RET>.

Case is significant in completion when it is significant in the argument you are entering, such as command names. Thus, ‘insert-buffer’ is not a valid completion for ‘IN’. Completion ignores case distinctions for certain arguments in which case does not matter.

• Example: Examples of using completion.
• Commands: A list of completion commands.
• Strict Completion: Different types of completion.
• Options: Options for completion.

8.3.1 Completion Example

A concrete example may help here. If you type M-x a u <TAB>, the <TAB> looks for 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’.

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. You have been able to enter ‘auto-fill-mode’ by typing just a u <TAB> - f <TAB>.

8.3.2 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). <SPC> for completion is not available when entering a file name, since file names often include spaces.

<RET>

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

?

Display a list of possible completions of the text before point (minibuffer-completion-help).

<TAB> (minibuffer-complete) is the most fundamental completion command. It searches for all possible completion alternatives that match the existing minibuffer text, and attempts to complete as much as it can. The matching of completion alternatives to the minibuffer text is performed according to somewhat intricate rules, which are designed so that plausible completions are offered under most circumstances. A valid completion alternative must satisfy the following criteria:

• The minibuffer text before point must be the same as the beginning of the completion alternative. If there is any minibuffer text after point, it must be a substring of the remainder of the completion alternative.
• If no completion alternative satisfies the above rules, try using partial completion rules: divide the minibuffer text into words separated by hyphens or spaces, and complete each word separately. Thus, when completing command names, ‘em-l-m’ completes to ‘emacs-lisp-mode’.
• If there is still no completion alternative, try the first rule again, but ignore the minibuffer text after point (i.e., don't try matching it).

When performing these comparisons, a ‘*’ in the minibuffer text acts as a wildcard—it matches any character at the corresponding position in the completion alternative.

<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 possible completions (if there are any) in a separate window. You can choose a completion from this list using the following commands:

Mouse-1

Mouse-2

Clicking mouse button 1 or 2 on a completion possibility chooses that completion (mouse-choose-completion).

M-v

<PageUp>

<prior>

Typing M-v, while in the minibuffer, selects the window showing the completion list buffer (switch-to-completions). This paves the way for using the commands below. Typing <PageUp> or <prior> does the same, as does selecting that window in other ways.

<RET>

Typing <RET>, while in the completion list buffer, chooses the completion that point is in or next to (choose-completion). To use this command, you must first switch to the completion list window.

<Right>

Typing the right-arrow key <Right>, while in the completion list buffer, moves point to the following completion possibility (next-completion).

<Left>

Typing the left-arrow key <Left>, while in the completion list buffer, moves point to the previous completion possibility (previous-completion).

8.3.3 Strict Completion

There are three different ways that <RET> can do completion, depending on how the argument will be used.

• Strict completion accepts only known completion candidates. For example, when C-x k reads the name of a buffer to kill, only the name of an existing buffer makes sense. In strict completion, <RET> refuses to exit if the text in the minibuffer does not complete to an exact match.
• Cautious completion is similar to strict completion, except that <RET> exits only if the text is an already exact match. Otherwise, <RET> does not exit, but it does complete the text. If that completes to an exact match, a second <RET> will 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. For example, when C-x C-f reads the name of a file to visit, any file name is allowed, including nonexistent file (in case you want to create a file). In permissive completion, <RET> does not complete, it just submits the argument as you have entered it.

The completion commands display a list of all possible completions whenever they can't determine even one more character by completion. Also, typing ? explicitly requests such a list. You can scroll the list with C-M-v (see Other Window).

8.3.4 Completion 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> does the completion list buffer.

When completing file names, certain file names are usually ignored. The variable completion-ignored-extensions contains a list of strings; a file name ending in any of those strings is ignored as a completion candidate. The standard value of this variable 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 “ignored” strings, they are not ignored: in the previous example, ‘foo.e’ completes to ‘foo.elc’. Displaying a list of possible completions disregards completion-ignored-extensions; it shows them all.

If an element of completion-ignored-extensions ends in a slash (/), it's a subdirectory name; that directory and its contents are ignored. Elements of completion-ignored-extensions that do not end in a slash are ordinary file names.

When completing file names, Emacs ignores case differences 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, Emacs ignores case differences if read-buffer-completion-ignore-case is non-nil (the default value is nil).

You can customize the matching rules for completion alternatives using the variable completion-styles. Its value should be a list of symbols, each representing a completion style; valid style symbols are basic, partial-completion, emacs22, emacs21, and initials. When completing, Emacs attempts to use the first completion style in the list; if this does not return any completion alternatives, it tries the next completion style in the list, and so on. The completion rules described in Completion Commands correspond to the default value of completion-styles, which is (basic partial-completion emacs22).

Icomplete mode presents a constantly-updated display that tells you what completions are available for the text you've entered so far. The command to enable or disable this minor mode is M-x icomplete-mode.

8.4 Minibuffer History

Every argument that you enter with the minibuffer is saved in a minibuffer history list so you can easily use it again later. You can use the following arguments to quickly fetch an earlier argument into the minibuffer:

M-p

<Up>

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

M-n

<Down>

Move to the next item in the minibuffer history (next-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, typing M-p or <Up> (previous-history-element) moves up 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. Similarly, typing M-n or <Down> (next-history-element) moves back down the history list, fetching later entries into the minibuffer. You can think of these commands as “backwards” and “forwards” through the history list.

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 argument: values that you are likely to enter. You can think of this as moving through the “future list” instead of the “history list”.

The input that M-p or M-n fetches into the minibuffer entirely replaces the existing contents of the minibuffer, so you can simply type <RET> to use it as an argument. You can also edit the text before you reuse it; this does not change the history element that you “moved” to, but your new argument does go at the end of the history list in its own right.

There are also commands to search forward or backward through the history; they search for history elements that match a regular expression. M-r (previous-matching-history-element) searches older elements in the history, while M-s (next-matching-history-element) searches newer elements. These commands are unusual: they use the minibuffer to read the regular expression even though they are invoked from the minibuffer. As with incremental searching, an upper-case letter in the regular expression makes the search case-sensitive (see Search Case). You can also search through the history using an incremental search (see Isearch Minibuffer).

All uses of the minibuffer record your input on a history list, but there are separate history lists for different kinds of arguments. For example, there is a list for file names, used by all the commands that read file names. (As a special feature, this history list records the absolute file name, even if the name you entered was not absolute.)

There are several other specific history lists, including one for buffer names, one for arguments of commands like query-replace, one used by M-x for command names, and one used by compile for compilation commands. Finally, there is one “miscellaneous” history list that most minibuffer arguments use.

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 of history-length 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.

8.5 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> is used to re-execute 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 understand Lisp syntax, 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 repeated 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 minibuffer history commands (M-p, M-n, M-r, M-s; see Minibuffer History) to move through the history list of saved entire commands. After finding the desired previous command, you can edit its expression as usual and then repeat 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 which describes one command and its arguments. Lisp programs can re-execute a command by calling eval with the command-history element.

8.6 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, in a basic sense, 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 a dot (‘.’) instead of its usual form.

Most of the features and commands associated with the minibuffer can not 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). C-y inserts the current kill into the password (see Killing). 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 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 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 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.

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.

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.

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.

10 Help

Emacs provides extensive help features, all accessible through the help character, C-h. This is a prefix key that is used for commands that display documentation; the next character you type should be a help option, to ask for a particular kind of help. You can cancel the C-h command with C-g. The function key <F1> is equivalent to C-h.

C-h itself is one of the help options; C-h C-h displays a list of help options, with a brief description of each one (help-for-help). You can scroll the list with <SPC> and <DEL>, then type the help option you want. To cancel, type C-g.

C-h or <F1> means “help” in various other contexts as well. For instance, you can type them after a prefix key to display a list of the keys that can follow the prefix key. (A few prefix keys don't support C-h in this way, because they define other meanings for it, but they all support <F1> for help.)

Most help buffers use a special major mode, Help mode, which lets you scroll conveniently with <SPC> and <DEL>. You can also follow hyperlinks to URLs, and to other facilities including Info nodes and customization buffers. See Help Mode.

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.

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 Regexps). See Apropos.

C-h i d m emacs <RET> i topic <RET>

This searches for topic in the indices of the on-line Emacs manual, and displays 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. You can use the Info commands to browse it.

C-h p

This displays the available Emacs packages based on keywords. See Library Keywords.

• Help Summary: Brief list of all Help commands.
• Key Help: Asking what a key does in Emacs.
• Name Help: Asking about a command, variable or function name.
• Apropos: Asking what pertains to a given topic.
• Help Mode: Special features of Help mode and Help buffers.
• Library Keywords: Finding Lisp libraries by keywords (topics).
• Language Help: Help relating to international language support.
• Misc Help: Other help commands.
• Help Files: Commands to display pre-written help files.
• Help Echo: Help on active text and tooltips (`balloon help').

10.1 Help Summary

Here is a summary of the Emacs interactive help commands. (The character that follows C-h is the “help option.”) See Help Files, for other help commands that display fixed files of information.

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).

C-h c key

Given a key sequence key, show the name of the command that it runs (describe-key-briefly). Here c stands for “character.” For more extensive information on key, use C-h k.

C-h d topics <RET>

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

C-h e

Display the *Messages* buffer (view-echo-area-messages).

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.

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 complete Emacs manual is available on-line in Info.

C-h k key

Display the name and documentation of the command that key runs (describe-key).

C-h l

Display a description of your last 300 keystrokes (view-lossage).

C-h m

Display documentation of the current major mode (describe-mode).

C-h n

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

C-h p

Find packages by topic keyword (finder-by-keyword). For an alternative interface to the same information, try the info-finder command.

C-h r

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

C-h s

Display the current contents of the syntax table, with an explanation of what they mean (describe-syntax). See Syntax.

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).

C-h w command <RET>

Show which keys run the command named command (where-is).

C-h C coding <RET>

Describe the coding system coding (describe-coding-system).

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).

C-h I method <RET>

Describe the input method method (describe-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).

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).

C-h S symbol <RET>

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

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.)

10.2 Documentation for a Key

The help commands to get information about a key sequence are C-h c and C-h k. 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’. Since command names are chosen to describe what the commands do, this gives you a very brief description of what key does.

C-h k key is similar but gives more information: it displays the documentation string of the command as well as its name. It displays this information in a window, since it may not fit in the echo area.

To find the documentation of a key sequence key, type C-h K key. This displays the appropriate manual section which contains the documentation of 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. 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.

10.3 Help by Command or Variable Name

C-h f function <RET> (describe-function) displays the documentation of Lisp function function, in a window. Since commands are Lisp functions, you can use this method to view the documentation of any command whose name you know. For example,

     C-h f auto-fill-mode <RET>

displays the documentation of auto-fill-mode. This is the only way to 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 is also useful 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>. Because C-h f allows all function names, not just command names, you may find that some of your favorite completion abbreviations that work in M-x don't work in C-h f. An abbreviation that is unique among command names may not be unique among all function names.

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> will describe 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.

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 definition, if you have the source files installed. (See Hyperlinking.) If you know Lisp (or C), this provides the ultimate documentation. If you don't know Lisp, you should learn it. (The Introduction to Emacs Lisp Programming, available from the FSF through fsf.org, is a good way to get started.) If Emacs feels you are just using it, treating it as an object program, its feelings may be hurt. For real intimacy, read the Emacs source code.

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.

10.4 Apropos

The apropos commands answer questions like, “What are the commands for working with files?” More precisely, you specify an apropos pattern, which means either a word, a list of words, or a regular expression. Each apropos command displays a list of items that match the pattern, in a separate buffer.

C-h a pattern <RET>

Search for commands whose names match pattern.

M-x apropos <RET> pattern <RET>

Search for functions and variables whose names match pattern. Both interactive functions (commands) and noninteractive functions can be found by this command.

M-x apropos-variable <RET> pattern <RET>

Search for user-option variables whose names match pattern.

M-x apropos-value <RET> pattern <RET>

Search for functions whose definitions match pattern, and variables whose values match pattern.

C-h d pattern <RET>

Search for functions and variables whose documentation strings match pattern.

The simplest kind of apropos pattern is one word. Anything which contains that word matches the pattern. Thus, to find the 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.

The a in C-h a stands for “Apropos”; C-h a runs the command apropos-command. This command normally checks only commands (interactive functions); if you specify a prefix argument, it checks noninteractive functions as well.

For more information about a function definition, variable or symbol property listed in the 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 Regexps). 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.

Use M-x apropos instead of C-h a to list all the Lisp symbols that match an apropos pattern, not just the symbols that are commands. This command does not list key bindings by default; specify a numeric argument if you want it to list them.

Use M-x apropos-variable to list user-customizable variables that match an apropos pattern. If you specify a prefix argument, it lists all matching variables.

The apropos-documentation command is like apropos except that it searches documentation strings instead of symbol names for matches.

The apropos-value command is like apropos except that it searches variables' values for matches for the apropos pattern. With a prefix argument, it also checks symbols' function definitions and property lists.

If the variable apropos-do-all is non-nil, the apropos commands always behave as if they had been given a prefix argument.

By default, apropos lists the search results in alphabetical order. If the variable apropos-sort-by-scores is non-nil, the apropos commands try to guess the relevance of each result, and display the most relevant ones first.

By default, apropos lists the search results for apropos-documentation in order of relevance of the match. If the variable apropos-documentation-sort-by-scores is nil, apropos lists the symbols found in alphabetical order.

10.5 Help Mode Commands

Help buffers provide the same commands as View mode (see Misc File Ops), plus a few special commands of their own.

<SPC>

Scroll forward.

<DEL>

Scroll backward.

<RET>

Follow a cross reference at point.

<TAB>

Move point forward to the next cross reference.

S-<TAB>

Move point back to the previous cross reference.

Mouse-1

Mouse-2

Follow a cross reference that you click on.

C-c C-c

Show all documentation about the symbol at point.

When a function name (see Running Commands by Name), variable name (see Variables), or face name (see Faces) appears in the documentation, it normally appears inside paired single-quotes. To view the documentation of that command, variable or face, you can click on the name with Mouse-1 or Mouse-2, or move point there and type <RET>. Use C-c C-b to retrace your steps.

You can follow cross references to URLs (web pages) also. This uses the browse-url command to view the page in the browser you choose. See Browse-URL.

There are convenient commands to move point to cross references in the help text. <TAB> (help-next-ref) moves point down to the next cross reference. S-<TAB> moves up to the previous cross reference (help-previous-ref).

To view all documentation about any symbol name that appears in the text, move point to the symbol name and type C-c C-c (help-follow-symbol). This shows all available documentation about the symbol as a variable, function and/or face. As above, use C-c C-b to retrace your steps.

10.6 Keyword Search for Lisp Libraries

The C-h p command lets you search the standard Emacs Lisp libraries by topic keywords. Here is a partial list of keywords you can use:

abbrev	abbreviation handling, typing shortcuts, macros.
bib	code related to the bib bibliography processor.
c	support for the C language and related languages.
calendar	calendar and time management support.
comm	communications, networking, remote access to files.
convenience	convenience features for faster editing.
data	support for editing files of data.
docs	support for Emacs documentation.
emulations	emulations of other editors.
extensions	Emacs Lisp language extensions.
faces	support for multiple fonts.
files	support for editing and manipulating files.
frames	support for Emacs frames and window systems.
games	games, jokes and amusements.
hardware	support for interfacing with exotic hardware.
help	support for on-line help systems.
hypermedia	support for links between text or other media types.
i18n	internationalization and alternate character-set support.
internal	code for Emacs internals, build process, defaults.
languages	specialized modes for editing programming languages.
lisp	Lisp support, including Emacs Lisp.
local	code local to your site.
maint	maintenance aids for the Emacs development group.
mail	modes for electronic-mail handling.
matching	various sorts of searching and matching.
mouse	mouse support.
multimedia	images and sound support.
news	support for netnews reading and posting.
oop	support for object-oriented programming.
outlines	support for hierarchical outlining.
processes	process, subshell, compilation, and job control support.
terminals	support for terminal types.
tex	supporting code for the TeX formatter.
tools	programming tools.
unix	front-ends/assistants for, or emulators of, UNIX-like features.
wp	word processing.

10.7 Help for International Language Support

You can use the command C-h L (describe-language-environment) to get information about a specific language environment. See Language Environments. This tells you which languages this language environment supports. It also lists the character sets, coding systems, and input methods that work with this language environment, and finally shows some sample text to illustrate scripts.

The command C-h h (view-hello-file) displays the file etc/HELLO, which shows 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.

10.8 Other Help Commands

C-h i (info) runs the Info program, which browses structured documentation files. 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 300 input keystrokes. If you see commands that you don't know, you can use C-h c 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.

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 Key Bindings). C-h s displays the contents of the syntax table, with explanations of each character's syntax (see Syntax).

You can get a list of subcommands for a particular prefix key by typing C-h after the prefix key. (There are a few prefix keys for which this does not work—those that provide their own bindings for C-h. One of these is <ESC>, because <ESC> C-h is actually C-M-h, which marks a defun.)

10.9 Help Files

The Emacs help commands described above display dynamic help based on the current state within Emacs, or refer to manuals. Other help commands display pre-written, static help files.

Except for C-h g, these commands all have the form C-h C-char; that is, C-h followed by a control character.

C-h C-c

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

C-h C-d

Display how to debug Emacs problems (view-emacs-debugging).

C-h C-f

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

C-h g

Display general information about the GNU Project (describe-gnu-project).

C-h C-m

Display how to order printed copies of Emacs manuals (view-order-manuals).

C-h C-n

Display the Emacs “news” file, which lists new features in the most recent 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).

10.10 Help on Active Text and Tooltips

When text on the screen is “active”, so that it does something special in response to mouse clicks or RET, it often has associated help text. For instance, most parts of the mode line have help text. On terminals that support mouse tracking, Emacs displays the help text as a “tooltip” (sometimes known as “balloon help”) or in the echo area, whenever you leave the mouse stationary over the active text. See Tooltips.

If your terminal doesn't support mouse-tracking, you can display the help text for active buffer text using the keyboard. C-h . (display-local-help) displays any help text associated with the character after point, using the echo area. To display help text automatically whenever it is available on the character after point, set the variable help-at-pt-display-when-idle to t.

11 The Mark and the Region

Many Emacs commands operate on an arbitrary contiguous part of the current buffer. To specify the text for such a command to operate on, you set the mark at one end of it, and move point to the other end. The text between point and the mark is called the region. The region always extends between point and the mark, no matter which one comes earlier in the text; each time you move point, the region changes.

Setting the mark at a position in the text also activates it. When the mark is active, Emacs indicates the extent of the region by highlighting the text within it, using the region face (see Face Customization). 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).

This default behavior of the mark is known as Transient Mark mode. Disabling Transient Mark mode switches Emacs to an alternative behavior, in which the mark is always active, which was the default prior to Emacs 23. See Persistent Mark.

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 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.

• Setting Mark: Commands to set the mark.
• Marking Objects: Commands to put region around textual units.
• Using Region: Summary of ways to operate on contents of the region.
• Mark Ring: Previous mark positions saved so you can go back there.
• Global Mark Ring: Previous mark positions in various buffers.
• Shift Selection: Using shifted cursor motion keys.
• Persistent Mark: Keeping the mark active all the time.

11.1 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 move point where the mark was (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 motion keys’

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

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 the beginning 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.

The command C-x C-x (exchange-point-and-mark) exchanges the positions of point and the mark, keeping the region unchanged. If the mark is inactive, Emacs first reactivates the mark wherever it was last set. 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.

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 while holding down this button, 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. Using the mouse to mark a region also copies the region into the kill ring (see Kill Ring). See Mouse Commands, 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 referred to as shift-selection. This sets the mark at point before moving point, but only if there is no active mark set via shift-selection. 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.

Whenever the mark is active, you can deactivate it by typing C-g (see Quitting). The mark is also automatically deactivated after certain non-motion commands.

11.2 Commands to Mark Textual Objects

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

M-@

Set mark after end of 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) puts the mark at the end of the next word, while C-M-@ (mark-sexp) puts it at the end of the next balanced expression (see Expressions). These commands handle arguments just like M-f and C-M-f.

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) moves point to the beginning of the paragraph that surrounds or follows point, and sets the mark at the end of that paragraph (see Paragraphs). As a special exception, repeated invocations of M-h extend the region to subsequent paragraphs. This is convenient for indenting, case-converting, or killing entire paragraphs.

The M-h command accepts prefix arguments. If the argument's value is positive, M-h marks that many paragraphs starting with the one surrounding point; therefore, C-u M-h is equivalent to M-h M-h M-h M-h. If the prefix argument is −n, M-h marks n paragraphs running back from the one surrounding point; in this case, point moves forward to the end of that paragraph, and the mark goes at the start of the region.

Similarly, C-M-h (mark-defun) sets mark and point around major top-level definitions (see Moving by Defuns), and C-x C-p (mark-page) does the same for pages (see Pages). These treat repeated invocations and prefix arguments similarly to mark-paragraph.

Finally, 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. (In some programs this is called “select all.”)

11.3 Operating on the Region

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

• Kill it with C-w (see Killing).
• Copy it to the kill ring with M-w (see Yanking).
• Convert case with C-x C-l or C-x C-u (see Case).
• Undo changes within it using C-u C-/ (see Undo).
• Replace text within it using M-% (see Query Replace).
• Indent it with C-x <TAB> or C-M-\ (see Indentation).
• Fill it as text with M-x fill-region (see Filling).
• Print hardcopy with M-x print-region (see Printing).
• Evaluate it as Lisp code with M-x eval-region (see Lisp Eval).
• Save it in a register with C-x r s (see Registers).
• Save it in a buffer or a file (see Accumulating Text).

Most commands that operate on the text in the region have the word region in their names.

Some commands have a default behavior when the mark is inactive, but operate on the text in 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 region is active (see 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.

If you enable Delete Selection mode, a minor mode, then inserting text while the mark is active causes the selected text to be deleted first. This also deactivates the mark. Many graphical applications follow this convention, but Emacs does not. To toggle Delete Selection mode on or off, type M-x delete-selection-mode. Another effect of this mode is that some keys, such as <DEL> and C-d, always kill the region if one exists.

11.4 The Mark Ring

Aside from delimiting the region, the mark is also useful for remembering spots that you may want to go back to. Each buffer remembers 16 previous locations of the mark, in the mark ring. Commands that set the mark also push the old mark onto this ring.

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 Persistent Mark.)

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. 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 the variable mark-even-if-inactive is nil, commands can only use the mark and the region when it is active. This variable is non-nil by default.

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).

11.5 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, in any buffer, this is recorded in the global mark ring in addition to the current buffer's own mark ring.

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.

11.6 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, newly introduced in Emacs 23, 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 extend 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 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 this does not disable setting the mark via mouse commands.

11.7 Persistent Marks

By default, the mark is activated by setting it, and deactivated by most non-motion commands (including all commands that change the text in the buffer). This behavior is called Transient Mark mode⁶.

Turning off Transient Mark mode switches Emacs to an alternative mode of operation, which was the default prior to Emacs 23. When Transient Mark mode is off, the mark is never deactivated, but it can be set to different locations using commands such as C-<SPC>. Emacs does not highlight the region, because that would be a nuisance. As a special exception, the region is temporarily highlighted if you set it with the mouse (see Setting Mark), or with shift-selection (see Shift Selection).

To turn off Transient Mark mode, type M-x transient-mark-mode. This command toggles the mode; you can use the same command to turn it on again. You can also toggle Transient Mark mode using the ‘Active Region Highlighting’ menu item in the ‘Options’ menu.

Here are the details of how Emacs behaves when Transient Mark mode is off:

• Emacs does not show 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. Alternatively, you can check the location of the mark by using C-x C-x, which exchanges the positions of the point and the mark (see Setting Mark).
• Many commands that insert text, such as C-y (yank), position point and the mark at opposite ends of the inserted text, so that the region consists of the text just inserted. You can tell when a command sets the mark because it displays ‘Mark set’ in the echo area.
• Many commands that move point long distances, like M-< and C-s, first set the mark where point was.
• 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

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.

12 Killing and Moving Text

Killing means erasing text and copying it into the kill ring, from which you can bring it back into the buffer by yanking it. (Some applications use the terms “cutting” and “pasting” for similar operations.) This is the most common way of moving or copying text within Emacs. It is very versatile, because there are commands for killing many different types of syntactic units.

Most commands which erase text from the buffer save it in the kill ring. These are known as kill commands. The kill ring stores several recent kills, not just the last one, so killing is a very safe operation: when you make a new kill, you don't have to worry much about losing text that you previously killed.

You can yank text from the kill ring into any position in a buffer, including a position in a different buffer; the kill ring is shared by all buffers. The C-/ (undo) command can undo both kill and delete commands (see Undo); the importance of the kill ring is that you can yank the text in a different place.

Commands that erase text but do not save it in the kill ring are known as delete commands. 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. The commands' names and individual descriptions use the words ‘kill’ and ‘delete’ to say which kind of operation they perform.

You can also use the mouse to kill and yank. See Cut and Paste.

• Deletion: Commands for deleting small amounts of text and blank areas.
• Killing by Lines: How to kill entire lines of text at one time.
• Other Kill Commands: Commands to kill large regions of text and syntactic units such as words and sentences.
• Kill Options: Options that affect killing.

12.1 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.

C-d

<Delete>

Delete next character (delete-char).

<DEL>

<Backspace>

Delete previous character (delete-backward-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 C-d (delete-char) and <DEL> (delete-backward-char). See Erasing.

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. M-<SPC> (just-one-space) does likewise but leaves a single space after 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 after point.

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-^.

12.2 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. If given at the beginning of a line, it kills all the text on the line⁷, leaving it blank. When used on a blank line, it kills the whole line including its newline.

More precisely, C-k kills from point up to the end of the line, unless it is at the end of a line. In that case it kills the newline following point, thus merging the next line into the current one. Spaces and tabs at the end of the line are ignored when deciding which case applies, so as long as point is after the last visible 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.

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

12.3 Other Kill Commands

C-w

Kill region (kill-region). See Mark.

M-w

Save region as last killed text without actually killing it (kill-ring-save). Some programs call this “copying.”

M-d

Kill word (kill-word). See Words.

M-<DEL>

Kill word backwards (backward-kill-word).

C-x <DEL>

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

M-k

Kill to end of sentence (kill-sentence).

C-M-k

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

M-z char

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

Apart from C-k, the most commonly-used kill command is C-w (kill-region), which kills the text in the region (i.e., between point and mark). See Mark. If the mark is inactive when you type C-w, it first reactivates the mark where it was last set. The mark is deactivated at the end of the command.

The command M-w (kill-ring-save) copies the region into the kill ring without removing it from the buffer. This is approximately equivalent to C-w followed by C-/, except that M-w does not alter the undo history.

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); 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.

12.4 Options for Killing

Some specialized buffers contain read-only text, which cannot be modified and therefore cannot be killed. But some users like to use the kill commands to copy read-only text into the kill ring, without actually changing it. Therefore, 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, kill commands 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.

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 Yanking

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

C-y

Yank last killed text (yank).

M-y

Replace text just yanked with an earlier batch of killed text (yank-pop).

C-M-w

Append next kill to last batch of killed text (append-next-kill).

On graphical displays with window systems, if there is a current selection in some other application, and you selected it more recently than you killed any text in Emacs, C-y copies the selection instead of text killed within Emacs.

• Kill Ring: Where killed text is stored. Basic yanking.
• Appending Kills: Several kills in a row all yank together.
• Earlier Kills: Yanking something killed some time ago.

13.1 The Kill Ring

All killed text is recorded in the kill ring, a list of blocks of text that have been 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 file to another. (There are several other methods: for instance, you could store the text in a register. See Registers, for information about registers. See Accumulating Text, for some other ways to move text around.)

The command C-y (yank) reinserts the text of the most recent kill, leaving the cursor at the end of the text. It also adds the position of the beginning of the text to the mark ring, without activating the mark; this allows you to jump easily to that position with C-x C-x (see Setting Mark). With a plain prefix argument (C-u C-y), it instead leaves the cursor in front of the text, and adds the position of the end of the text to the mark ring. Using other sort of prefix argument specifies an earlier kill; for example, C-u 4 C-y reinserts the fourth most recent kill. See Earlier Kills.

The yank commands discard certain properties from the yanked text. These are properties that might lead to annoying results, such as causing the text to respond to the mouse or specifying key bindings. The list of properties to discard is stored in the variable yank-excluded-properties. Yanking of register contents and rectangles also discard these properties. See Text Properties, for more information about text properties.

13.2 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 append by first typing the command C-M-w (append-next-kill) right before it. The C-M-w tells the following command, if it is a kill command, to append the text it kills to the last killed text, instead of starting a new entry. With C-M-w, 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 Yanking Earlier Kills

To recover killed text that is no longer the most recent kill, use the M-y command (yank-pop). It takes the text previously 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. M-y is allowed only after a C-y or another M-y.

You can understand 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 moves the “last yank” pointer to a different entry, and the text in the buffer changes to match. Enough M-y commands 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.

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 it 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.

If you know how many M-y commands it would take to find the text you want, you can yank that text in one step using C-y with a numeric argument. C-y with an argument restores the text from the specified kill ring entry, counting back from the most recent as 1. Thus, C-u 2 C-y gets the next-to-the-last block of killed text—it is equivalent to C-y M-y. C-y with a numeric argument starts counting from the “last yank” pointer, and sets the “last yank” pointer to the entry that it yanks.

The length of the kill ring is controlled by the variable kill-ring-max; no more than that many blocks of killed text are saved.

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 the command C-h v kill-ring.

14 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 prependings 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 M-x 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 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.

15 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.

When you must specify a rectangle for a command to work on, you do it by putting the mark at one corner and point at the opposite corner. The rectangle thus specified is called the region-rectangle because you control it 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.

If point and the mark are in the same column, the rectangle they delimit is empty. If they are in the same line, the rectangle is one line high. This asymmetry between lines and columns comes about because point (and likewise the mark) is between two columns, but within a line.

C-x r k

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

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 rightward.

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.

The rectangle operations fall into two classes: commands for deleting and inserting rectangles, and commands for blank rectangles.

There are two ways to get rid of the text in a rectangle: you can discard the text (delete it) or save it as the “last killed” rectangle. The commands for these two ways are C-x r d (delete-rectangle) and C-x r k (kill-rectangle). In either case, the portion of each line that falls inside the rectangle's boundaries is deleted, causing any following text on the line to move left into the gap.

Note that “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 can only record 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. It is hard to define yank-popping for rectangles, so we do not try.

To yank the last killed rectangle, type C-x r y (yank-rectangle). Yanking a rectangle is the opposite of killing one. Point specifies where to put the rectangle's upper left corner. The rectangle's first line is inserted there, the rectangle's second line is inserted at the same horizontal position, but one line vertically down, and so on. The number of lines affected is determined by the height of the saved rectangle.

You can convert single-column lists into double-column lists using rectangle killing and yanking; kill the second half of the list as a rectangle and then yank it beside the first line of the list. See Two-Column, for another way to edit multi-column text.

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

There are two commands you can use for making blank rectangles: C-x r c (clear-rectangle) which blanks out existing text, and C-x r o (open-rectangle) which inserts a blank rectangle. Clearing a rectangle is equivalent to deleting it and then inserting a blank rectangle of the same size.

The command 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 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.

16 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. C-x means cut (kill), C-c copy, C-v paste (yank), and C-z undo. Standard Emacs commands like C-x C-c still work, because C-x and C-c only take effect when the mark is active (and the region is highlighted). However, if you don't want to override these bindings in Emacs at all, set cua-enable-cua-keys to nil.

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.

In CUA mode, typed text replaces the active region as in Delete-Selection mode (see Mouse Commands).

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).

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>.

17 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’.

A register can store a position, a piece of text, a rectangle, a number, a window configuration, 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.

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

• Position: Saving positions in registers.
• Text: Saving text in registers.
• Rectangle: Saving rectangles in registers.
• Configurations: Saving window configurations in registers.
• Numbers: Numbers in registers.
• Files: File names in registers.
• Bookmarks: Bookmarks are like registers, but persistent.

17.1 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, and moves point to the recorded position. 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.

17.2 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.

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 Mark. 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.

C-x r i r inserts in the buffer the text from register r. Normally it leaves point before the text and places the mark after, but with a numeric argument (C-u) it puts point after the text and the mark before.

17.3 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 numeric 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 command inserts a text string if the register contains one, and inserts a rectangle if the register contains one.

See also the command sort-columns, which you can think of as sorting a rectangle. See Sorting.

17.4 Saving Window 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 Windows, 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, in register r (frame-configuration-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.

17.5 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

Increment the number in register r by number (increment-register).

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.

17.6 Keeping File 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 in a register:

     (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.)

17.7 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 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.

The prototypical use for bookmarks is to record one current position in each of several files. So the command C-x r m, which sets a bookmark, uses 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.

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 offers to save your bookmark values in your default bookmark file, ~/.emacs.bmk, if you have changed any bookmark values. You can also save the bookmarks at any time with the M-x bookmark-save command. 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.)

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.

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.

18 Controlling the Display

Since only part of a large buffer fits in the window, Emacs tries to show a part that is likely to be interesting. Display-control commands and variables allow you to specify which part of the text you want to see, and how to display it.

• Scrolling: Commands to move text up and down in a window.
• Auto Scrolling: Redisplay scrolls text automatically when needed.
• Horizontal Scrolling: Moving text left and right in a window.
• Follow Mode: Follow mode lets two windows scroll as one.
• Faces: How to change the display style using faces.
• Standard Faces: Emacs' predefined faces.
• Temporary Face Changes: Commands to temporarily modify the default text face
• Font Lock: Minor mode for syntactic highlighting using faces.
• Highlight Interactively: Tell Emacs what text to highlight.
• Fringes: Enabling or disabling window fringes.
• Displaying Boundaries: Displaying top and bottom of the buffer.
• Useless Whitespace: Showing possibly-spurious trailing whitespace.
• Selective Display: Hiding lines with lots of indentation.
• Optional Mode Line: Optional mode line display features.
• Text Display: How text characters are normally displayed.
• Cursor Display: Features for displaying the cursor.
• Line Truncation: Truncating lines to fit the screen width instead of continuing them to multiple screen lines.
• Visual Line Mode: Word wrap and screen line-based editing.
• Display Custom: Information on variables for customizing display.

18.1 Scrolling

If a buffer contains text that is too large to fit entirely within a window that is displaying the buffer, Emacs shows a contiguous portion of the text. The portion shown always contains point.

Scrolling means moving text up or down in the window so that different parts of the text are visible. Scrolling “forward” or “up” means that text moves up, and new text appears at the bottom. Scrolling “backward” or “down” moves text down, and new text appears at the top.

Scrolling happens automatically if you move point past the bottom or top of the window. You can also scroll explicitly with these commands:

C-l

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

C-v

<next>

<PageDown>

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

M-v

<prior>

<PageUp>

Scroll backward (scroll-down).

C-M-l

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

C-l (recenter-top-bottom) is a basic scrolling command. It 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 screen 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 number 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. 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, Emacs always leaves n screen lines between point and the top or bottom of the window (see Auto Scrolling).

You can also supply C-l with a prefix argument. With a plain prefix argument, C-u C-l, Emacs simply recenters point. With a positive argument n, it scrolls to place point n lines down from the top of the window. An argument of zero puts point on the topmost line. A negative argument -n puts point n lines from the bottom of the window. For example, C-u - 1 C-l puts point on the bottom line, and C-u - 5 C-l puts it five lines from the bottom. When given an argument, C-l does not clear the screen or cycle through different screen positions.

The more primitive command recenter behaves like recenter-top-bottom, but does not cycle among screen positions. Prior to Emacs 23, C-l was bound to recenter.

If the variable recenter-redisplay has a non-nil value, Emacs clears and redisplays the screen each time C-l recenters the window; 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 Screen Garbled).

To read the buffer a windowful at a time, type C-v (scroll-up). This 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 at the new top of the window.

M-v (scroll-down) scrolls backward in a similar way.

The variable next-screen-context-lines controls the number of lines of overlap left by C-v or M-v; by default, it is 2. The function keys <next> and <prior>, or <PageDown> and <PageUp>, are equivalent to C-v and M-v respectively.

You can supply C-v or M-v with a numeric prefix argument n. This scrolls the window by n lines, while attempting 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.

The names of scroll commands are based on the direction that the text moves in the window. Thus, the command to scroll forward is called scroll-up because it moves the text upward on the screen. The keys <PageUp> and <PageDown> derive their names and customary meanings from a different convention that developed elsewhere; hence the strange result that <PageDown> runs scroll-up.

Some users like the full-screen scroll commands to keep point at the same screen position. To enable this behavior, set the variable scroll-preserve-screen-position to a non-nil value. Then, whenever a command scrolls the text around point offscreen (or within scroll-margin lines of the edge), Emacs moves point to keep it at the same vertical and horizontal position within the window. This mode is convenient for browsing through a file by scrolling by screenfuls; if you come back to the screen where you started, point goes back to the line where it started.

The C-M-l command (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.

18.2 Automatic Scrolling

Emacs performs automatic scrolling when point moves out of the visible portion of the text.

Normally, this centers point vertically within the window. However, if you set scroll-conservatively to a small number n, then if you move point just a little off the screen (less than n lines), Emacs scrolls the text just far enough to bring point back on screen. By default, scroll-conservatively is 0.

When the window does scroll by a longer distance, you can control how aggressively it scrolls by setting the variables scroll-up-aggressively and scroll-down-aggressively. The value of scroll-up-aggressively should be either nil, or a fraction f between 0 and 1. A fraction specifies where on the screen to put point when scrolling upward: when a window scrolls up because point is above the window start, the new start position is chosen to put point f parts of the window height from the top. Thus, larger f means more aggressive scrolling. The default value, nil, is equivalent to 0.5.

Likewise, scroll-down-aggressively is used for scrolling down. The value specifies how far point should be placed from the bottom of the window; thus, as with scroll-up-aggressively, a larger value is more aggressive.

The variable scroll-margin restricts how close point can come to the top or bottom of a window. 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.

18.3 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. To disable automatic horizontal scrolling, 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-mode terminals, the cursor is left at the edge instead.)

The variable hscroll-margin controls how close point can get to the window's 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 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.

18.4 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.

18.5 Faces: Controlling Text Display Style

Emacs can display text in several different styles, which are called faces. Each face can specify various face attributes, such as the font, height, weight and slant, the foreground and background color, and underlining or overlining. A face does not have to specify all of these attributes; often it inherits most of them from another face.

On a text-only terminal, not all face attributes are meaningful. Some text-only terminals support inverse video, bold, and underline attributes; some support colors. Text-only terminals generally do not support changing the height, width or font.

Most major modes assign faces to the text automatically through the work of Font Lock mode. See Font Lock, for more information about Font Lock mode and syntactic highlighting. You can print the current buffer with the highlighting that appears on your screen using the command ps-print-buffer-with-faces. See PostScript.

Enriched mode, the mode for editing formatted text, provides commands and menus for specifying faces for text in the buffer. See Format Faces.

To alter the appearance of a face, use the customization buffer. See Face Customization. You can also use X resources to specify attributes of any particular face (see Resources). When displaying a character, any attribute that isn't specified by its face is taken from the default face, whose attributes reflect the default settings of the frame itself.

You can also change the foreground and background colors of a specific 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 name, with completion, and then set that face to use the specified color. See Face Customization, for information about color names. These commands affect the face colors on all frames, both existing and those to be created in the future. These changes do not, however, persist for future Emacs sessions; to make lasting changes, use the customization buffer (see Face Customization).

You can also set foreground and background colors for the current frame only; see Frame Parameters.

Emacs can display variable-width fonts, but some of the Emacs commands that calculate width and indentation do not know how to calculate variable widths. This can sometimes lead to incorrect results when you use variable-width fonts. In particular, indentation commands can give inconsistent results, so we recommend you avoid variable-width fonts, especially for editing program source code.

18.6 Standard Faces

To see what faces are currently defined, and what they look like, type M-x list-faces-display. It's possible for a given face to look different in different frames; this command shows the appearance in the frame in which you type it. With a prefix argument, this prompts for a regular expression, and displays only faces with names matching that regular expression.

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.

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.

variable-pitch

This face forces use of a variable-width font.

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 highlighting portions of text, in various modes. For example, mouse-sensitive text is highlighted using this face.

isearch

This face is used for highlighting the current Isearch match (see Incremental Search).

query-replace

This face is used for highlighting the current Query Replace match (see Replace).

lazy-highlight

This face is used for lazy highlighting of Isearch and Query Replace matches other than the current one.

region

This face is used for displaying a selected region (see Mark).

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.

nobreak-space

The face for displaying the character “nobreak space.”

escape-glyph

The face for highlighting the ‘\’ or ‘^’ that indicates a control character. It's also used when ‘\’ indicates a nobreak space or nobreak (soft) hyphen.

These faces control the appearance of parts of the Emacs frame. They exist as faces to provide a consistent way to customize the appearance of these parts of the frame.

mode-line

This face is used for the mode line of the currently selected window, 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 non-windowed terminals.

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 portions of text on mode lines.

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.

vertical-border

This face is used for the vertical divider between windows. By default this face inherits from the mode-line-inactive face on character terminals. On graphical displays the foreground color of this face is used for the vertical line between windows without scrollbars.

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 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 Fringes.

scroll-bar

This face determines the visual appearance of the scroll bar. See Scroll Bars.

border

This face determines the color of the frame border.

cursor

This face determines the color of the cursor.

mouse

This face determines the color of the mouse pointer.

tool-bar

This face determines the color of tool bar icons. See Tool Bars.

tooltip

This face is used for tooltips. See Tooltips.

menu

This face determines the colors and font of Emacs's menus. See Menu Bars. This has no effect in Emacs built with GTK and in the MS-Windows/Mac ports; you need to use system-wide styles and options to change the appearance of GTK, Windows, or Mac menus. Setting the font of LessTif/Motif menus is currently not supported; attempts to set the font are ignored in this case.

18.7 Temporary Face Changes

The following commands change the default face within a buffer.

To increase the height 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) face height, 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.

The final key of these commands may be repeated without the leading C-x. For instance, C-x C-= C-= C-= increases the face height by three steps. Each step scales the height of the default face by the value of the variable text-scale-mode-step. As a special case, an argument of 0 removes any scaling currently active.

The commands text-scale-increase and text-scale-decrease increase or decrease the height of the default face, 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 sets the height of the default face in the current buffer to an absolute level specified by its prefix argument.

The above commands automatically enable or disable the minor mode text-scale-mode, depending on whether the current font scaling is other than 1 or not.

To temporarily change the face in the current buffer to a variable-pitch (“proportional”) font, use the command M-x variable-pitch-mode to enable or disable the Variable Pitch minor mode.

18.8 Font Lock mode

Font Lock mode is a minor mode, always local to a particular buffer, which highlights (or “fontifies”) the buffer contents according to the syntax of the text you are editing. It can recognize comments and strings in most programming languages; in several languages, it can also recognize and properly highlight various other important constructs, such as names of functions being defined or reserved keywords. Some special modes, such as Occur mode and Info mode, have completely specialized ways of assigning fonts for Font Lock mode.

Font Lock mode is turned on by default in all modes which support it. You can toggle font-lock for each buffer with the command M-x font-lock-mode. Using a positive argument unconditionally turns Font Lock mode on, and a negative or zero argument turns it off.

If you do not wish Font Lock mode to be turned on by default, customize the variable global-font-lock-mode using the Customize interface (see Easy Customization), or use the function global-font-lock-mode in your .emacs file, like this:

     (global-font-lock-mode 0)

This variable, like all the variables that control Font Lock mode, take effect whenever fontification is done; that is, potentially at any time.

If you have disabled Global Font Lock mode, you can still enable Font Lock for specific major modes by adding the function turn-on-font-lock 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 'turn-on-font-lock)

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 Face Customization.

The variable font-lock-maximum-decoration specifies the preferred level of fontification, for modes that provide multiple levels. Level 1 is the least amount of fontification; some modes support levels as high as 3. The normal default is “as high as possible.” You can specify an integer, which applies to all modes, or you can specify different numbers for particular major modes; for example, to use level 1 for C/C++ modes, and the default level otherwise, use this:

     (setq font-lock-maximum-decoration
           '((c-mode . 1) (c++-mode . 1)))

Fontification can be too slow for large buffers, so you can suppress it for buffers above a certain size. The variable font-lock-maximum-size specifies a buffer size, beyond which buffer fontification is suppressed.

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. (See Left Margin Paren.) If you don't follow this convention, Font Lock mode can misfontify the text that follows an open-parenthesis or open-brace in the leftmost column that is inside a string or comment.

The variable font-lock-beginning-of-syntax-function (always buffer-local) specifies how Font Lock mode can find a position guaranteed to be outside any comment or string. In modes which use the leftmost column parenthesis convention, the default value of the variable is beginning-of-defun—that tells Font Lock mode to use the convention. If you set this variable to nil, Font Lock no longer relies on the convention. This avoids incorrect results, but the price is that, in some cases, fontification for a changed text must rescan buffer text from the beginning of the buffer. This can considerably slow down redisplay while scrolling, particularly if you are close to the end of a large buffer.

Font Lock highlighting patterns already exist for many 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.

Fontifying large buffers can take a long time. To avoid large delays when a file is visited, Emacs 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 Specific Customization.

18.9 Interactive Highlighting

Highlight Changes mode is a minor mode that highlights the parts of the buffer 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), except that you specify explicitly the regular expressions to highlight. You control them with these commands:

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) C-x w h 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.

You can use this command multiple times, specifying various regular expressions to highlight in different ways.

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-p to show the next older expression and M-n 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.

C-x w l regexp <RET> face <RET>

Highlight entire lines containing a match for regexp, using face face (highlight-lines-matching-regexp).

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).

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.

18.10 Window Fringes

On a graphical display, 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.

The most common use of the fringes is to indicate a continuation line, when one line of text is split into multiple lines on the screen. 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.”

The fringes indicate 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 empty lines, or where a program you are debugging is executing (see Debuggers).

You can enable and disable the fringes for all frames using M-x fringe-mode. To enable and disable the fringes for the selected frame, use M-x set-fringe-style.

18.11 Displaying Boundaries

On a graphical display, Emacs can indicate the buffer boundaries in the fringes. It indicates the first line and the last line 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 up and down.

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, 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)).

18.12 Useless Whitespace

It is easy to leave unnecessary spaces at the end of a line, or empty lines at the end of a file, without realizing it. In most cases, this trailing whitespace has no effect, but there are special circumstances where it matters, and 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.

To delete all trailing whitespace within the buffer's accessible portion (see Narrowing), type M-x delete-trailing-whitespace <RET>. This command does not remove newline characters.

Emacs can indicate unused lines at the end of the window with a small image in the left fringe (see Fringes). The image appears for window lines that do not correspond to any buffer text. Blank lines at the end of the buffer then stand out because they do not have this image in the fringe.

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);. (This feature currently doesn't work on text-only terminals.)

18.13 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.

18.14 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.

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. (Use what-line command to see the line number relative to the whole file.)

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 usually appears after the buffer name, before the mode names and their parentheses. It 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 a graphical display 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 as “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.

By default, the mode line is drawn on graphics displays with 3D-style highlighting, like that of a button when it is not being pressed. If you don't like this effect, you can disable the 3D highlighting of the mode line, by customizing the attributes of the mode-line face. See Face Customization.

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.

18.15 How Text Is Displayed

ASCII printing characters (octal codes 040 through 0176) in Emacs buffers are displayed with their graphics, as are non-ASCII multibyte printing characters (octal codes above 0400).

Some ASCII control characters are displayed in special ways. The newline character (octal code 012) is displayed by starting a new line. The tab character (octal code 011) is displayed by moving to the next tab stop column (normally every 8 columns). The number of spaces per tab is controlled by the variable tab-width, which must have an integer value between 1 and 1000, inclusive, and is made buffer-local by changing it. Note that how the tab character in the buffer is displayed has nothing to do with the definition of <TAB> as a command.

Other ASCII control characters are normally displayed as a caret (‘^’) followed by the non-control version of the character; thus, control-A is displayed as ‘^A’. The caret appears in face escape-glyph.

Non-ASCII characters 0200 through 0237 (octal) are displayed with octal escape sequences; thus, character code 0230 (octal) is displayed as ‘\230’. The backslash appears in face escape-glyph.

If the variable ctl-arrow is nil, control characters in the buffer are displayed with octal escape sequences, except for newline and tab. Altering the value of ctl-arrow makes it local to the current buffer; until that time, the default value is in effect. The default is initially t.

The display of character codes 0240 through 0377 (octal) may be either as escape sequences or as graphics. They do not normally occur in multibyte buffers, but if they do, they are displayed as Latin-1 graphics. In unibyte mode, if you enable European display they are displayed using their graphics (assuming your terminal supports them), otherwise as escape sequences. See Unibyte Mode.

Some character sets define “no-break” versions of the space and hyphen characters, which are used where a line should not be broken. Emacs normally displays these characters with special faces (respectively, nobreak-space and escape-glyph) to distinguish them from ordinary spaces and hyphens. You can turn off this feature by setting the variable nobreak-char-display to nil. If you set the variable to any other value, that means to prefix these characters with an escape character.

You can customize the way any particular character code is displayed by means of a display table. See Display Tables.

18.16 Displaying the Cursor

You can customize the cursor's color, and whether it blinks, using the cursor Custom group (see Easy Customization). On a graphical display, the command M-x blink-cursor-mode enables or disables the blinking of the cursor. (On text terminals, the terminal itself blinks the cursor, and Emacs has no control over it.) You can control how the cursor appears when it blinks off by setting the variable blink-cursor-alist.

Some text terminals offer two different cursors: the normal cursor and the very visible cursor, where the latter may be e.g. bigger or blinking. 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 doesn't switch, so it uses the normal cursor.

Normally, the cursor appears in non-selected windows without blinking, with the same appearance as when the blinking cursor blinks “off.” For a box cursor, this is a hollow box; for a bar cursor, this is a thinner bar. To turn off cursors in non-selected windows, customize the variable cursor-in-non-selected-windows and assign it a nil value.

On graphical displays, Emacs can optionally draw the block cursor as wide as the character under the cursor—for example, if the cursor is on a tab character, it would cover the full width occupied by that tab character. To enable this feature, set the variable x-stretch-cursor to a non-nil value.

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.

18.17 Truncation of Lines

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-only terminals, ‘$’ appears in the first column when there is text truncated to the left, and in the last column when there is text truncated to the right.

Horizontal scrolling automatically causes line truncation (see Horizontal Scrolling). You can explicitly enable line truncation for a particular buffer with the command M-x 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 is in effect. The default value is normally nil.

If the variable truncate-partial-width-windows is non-nil, it forces truncation rather than continuation in any window less than the full width of the screen or frame, regardless of the value of truncate-lines. See also Display.

If the variable overflow-newline-into-fringe is non-nil on a graphical display, then Emacs does not continue or truncate a line which is exactly as wide as the window. Instead, the newline overflows into the right fringe, and the cursor appears in the fringe when positioned on that newline.

18.18 Visual Line Mode

Another alternative to ordinary line continuation is to use word wrap. Here, each long logical line is divided into two or more screen lines, like in ordinary line continuation. However, Emacs attempts to wrap the line at word boundaries near the right window edge. 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.

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 Init Rebinding.

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.

18.19 Customization of Display

This section describes variables (see Variables) that you can change to customize how Emacs displays. Beginning users can skip it.

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 someting to echo. See Echo Area.

The variable baud-rate holds the output speed of the terminal. Setting this variable does not change the speed of actual data transmission, but the value is used for calculations. On text-only terminals, it affects padding, and decisions about whether to scroll part of the screen or redraw it instead. It also affects the behavior of incremental search. On graphical displays, baud-rate is only used to determine how frequently to look for pending input during display updating. A higher value of baud-rate means that check for pending input will be done less frequently.

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 nil, Emacs draws the underline at the same height as the font's descent line.

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-only 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.

On a text-only terminal, when you reenter Emacs after suspending, Emacs normally clears the screen and redraws the entire display. On some terminals with more than one page of memory, it is possible to arrange the termcap entry so that the ‘ti’ and ‘te’ strings (output to the terminal when Emacs is entered and exited, respectively) switch between pages of memory so as to use one page for Emacs and another page for other output. On such terminals, you might want to set the variable no-redraw-on-reenter non-nil; this tells Emacs to assume, when resumed, that the screen page it is using still contains what Emacs last wrote there.

19 Searching and Replacement

Like other editors, Emacs has commands to search for occurrences of a string. Emacs also has commands to replace occurrences of a string with a different string. There are also commands that do the same thing, but search for patterns instead of fixed strings.

You can also search multiple files under the control of a tags table (see Tags Search) or through the Dired A command (see Operating on Files), or ask the grep program to do it (see Grep Searching).

• Incremental Search: Search happens as you type the string.
• Nonincremental Search: Specify entire string and then search.
• Word Search: Search for sequence of words.
• Regexp Search: Search for match for a regexp.
• Regexps: Syntax of regular expressions.
• Regexp Backslash: Regular expression constructs starting with `\'.
• Regexp Example: A complex regular expression explained.
• Search Case: To ignore case while searching, or not.
• Replace: Search, and replace some or all matches.
• Other Repeating Search: Operating on all matches for some regexp.

19.1 Incremental Search

The principal search command in Emacs is incremental: it begins searching as soon as you type the first character of the search string. As you type in the search string, Emacs shows you where the string (as you have typed it so far) would be found. When you have typed enough characters to identify the place you want, you can stop. Depending on what you plan to do next, you may or may not need to terminate the search explicitly with <RET>.

C-s

Incremental search forward (isearch-forward).

C-r

Incremental search backward (isearch-backward).

• Basic Isearch: Basic incremental search commands.
• Repeat Isearch: Searching for the same string again.
• Error in Isearch: When your string is not found.
• Special Isearch: Special input in incremental search.
• Isearch Yank: Commands that grab text into the search string or else edit the search string.
• Isearch Scroll: Scrolling during an incremental search.
• Isearch Minibuffer: Incremental search of the minibuffer history.
• Slow Isearch: Incremental search features for slow terminals.

19.1.1 Basics of Incremental Search

C-s

Begin incremental search (isearch-forward).

C-r

Begin reverse incremental search (isearch-backward).

C-s (isearch-forward) starts a forward incremental search. It reads characters from the keyboard, and moves point just past the end of the next occurrence of those characters in the buffer.

For instance, if you type C-s and then F, that puts the cursor after the first ‘F’ that occurs in the buffer after the starting point. Then if you then type O, the cursor moves to just after the first ‘FO’; the ‘F’ in that ‘FO’ might not be the first ‘F’ previously found. After another O, the cursor moves to just after the first ‘FOO’.

At each step, Emacs highlights the current match—the buffer text that matches the search string—using the isearch face (see Faces). The current search string is also displayed in the echo area.

If you make a mistake typing the search string, type <DEL>. Each <DEL> cancels the last character of the search string.

When you are satisfied with the place you have reached, type <RET>. This stops searching, leaving the cursor where the search brought it. Also, any command not specially meaningful in searches stops the searching and is then executed. Thus, typing C-a exits the search and then moves to the beginning of the line. <RET> is necessary only if the next command you want to type is a printing character, <DEL>, <RET>, or another character that is special within searches (C-q, C-w, C-r, C-s, C-y, M-y, M-r, M-c, M-e, and some others described below).

As a special exception, entering <RET> when the search string is empty launches nonincremental search (see Nonincremental Search).

When you exit the incremental search, it adds the original value of point to the mark ring, without activating the mark; you can thus use C-u C-<SPC> to return to where you were before beginning the search. See Mark Ring. It only does this if the mark was not already active.

To search backwards, use C-r (isearch-backward) instead of C-s to start the search. A backward search finds matches that end before the starting point, just as a forward search finds matches that begin after it.

19.1.2 Repeating Incremental Search

Suppose you search forward for ‘FOO’ and find a match, but not the one you expected to find: the ‘FOO’ you were aiming for occurs later in the buffer. In this event, type another C-s to move to the next occurrence of the search string. You can repeat this any number of times. If you overshoot, you can cancel some C-s characters with <DEL>. Similarly, each C-r in a backward incremental search repeats the backward search.

If you pause for a little while during incremental search, Emacs highlights all the other possible matches for the search string that are present on the screen. This helps you anticipate where you can get to by typing C-s or C-r to repeat the search. The other matches are highlighted differently from the current match, using the customizable face lazy-highlight (see Faces). If you don't like this feature, you can disable it by setting isearch-lazy-highlight to nil.

After exiting a search, you can search for the same string again by typing just C-s C-s. The first C-s is the key that invokes incremental search, and the second C-s means “search again.” Similarly, C-r C-r searches backward for the last search string. In determining the last search string, it doesn't matter whether the string was searched for with C-s or C-r.

If you are searching forward but you realize you were looking for something before the starting point, type C-r to switch to a backward search, leaving the search string unchanged. Similarly, C-s in a backward search switches to a forward search.

If a search is failing and you ask to repeat it by typing another C-s, it starts again from the beginning of the buffer. Repeating a failing reverse search with C-r starts again from the end. This is called wrapping around, and ‘Wrapped’ appears in the search prompt once this has happened. If you keep on going past the original starting point of the search, it changes to ‘Overwrapped’, which means that you are revisiting matches that you have already seen.

To reuse earlier search strings, use the search ring. The commands M-p and M-n move through the ring to pick a search string to reuse. These commands leave the selected search ring element in the minibuffer, where you can edit it. To edit the current search string in the minibuffer without replacing it with items from the search ring, type M-e. Type C-s or C-r to terminate editing the string and search for it.

19.1.3 Errors in Incremental Search

If your string is not found at all, the echo area says ‘Failing I-Search’. The cursor is after the place where Emacs found as much of your string as it could. Thus, if you search for ‘FOOT’, and there is no ‘FOOT’, you might see the cursor after the ‘FOO’ in ‘FOOL’. In the echo area, the part of the search string that failed to match is highlighted using the customizable face isearch-fail.

At this point, there are several things you can do. If your string was mistyped, you can use <DEL> to erase some of it and correct it. If you like the place you have found, you can type <RET> to remain there. Or you can type C-g, which removes from the search string the characters that could not be found (the ‘T’ in ‘FOOT’), leaving those that were found (the ‘FOO’ in ‘FOOT’). A second C-g at that point cancels the search entirely, returning point to where it was when the search started.

The quit command, C-g, does special things during searches; just what it does depends on the status of the search. If the search has found what you specified and is waiting for input, C-g cancels the entire search, moving the cursor back to where you started the search. If C-g is typed when there are characters in the search string that have not been found—because Emacs is still searching for them, or because it has failed to find them—then the search string characters which have not been found are discarded from the search string. With them gone, the search is now successful and waiting for more input, so a second C-g will cancel the entire search.

19.1.4 Special Input for Incremental Search

Some of the characters you type during incremental search have special effects.

If the search string you entered contains only lower-case letters, the search is case-insensitive; as long as an upper-case letter exists in the search string, the search becomes case-sensitive. If you delete the upper-case character from the search string, it ceases to have this effect. See Search Case.

To search for a newline character, type C-j.

To search for other control characters, such as <control-S>, quote it by typing C-q first (see Inserting Text). To search for non-ASCII characters, you can either use C-q and enter its octal code, or use an input method (see Input Methods). If an input method is enabled in the current buffer when you start the search, you can use it in the search string also. While typing the search string, you can toggle the input method with the command C-\ (isearch-toggle-input-method). You can also turn on a non-default input method with C-^ (isearch-toggle-specified-input-method), which prompts for the name of the input method. When an input method is active during incremental search, the search prompt includes the input method mnemonic, like this:

     I-search [im]:

where im is the mnemonic of the active input method. Any input method you enable during incremental search remains enabled in the current buffer afterwards.

Typing M-% in incremental search invokes query-replace or query-replace-regexp (depending on search mode) with the current search string used as the string to replace. See Query Replace.

Typing M-<TAB> in incremental search invokes isearch-complete, which attempts to complete the search string using the search ring as a list of completion alternatives. See Completion. In many operating systems, the M-<TAB> key sequence is captured by the window manager; you then need to rebind isearch-complete to another key sequence if you want to use it (see Rebinding).

When incremental search is active, you can type C-h C-h to access interactive help options, including a list of special keybindings. These keybindings are part of the keymap isearch-mode-map (see Keymaps).

19.1.5 Isearch Yanking

Within incremental search, you can use C-w and C-y to grab text from the buffer into the search string. This makes it convenient to search for another occurrence of text at point.

C-w copies the character or word after point and adds it to the search string, advancing point over it. (The decision, whether to copy a character or a word, is heuristic.)

C-y is similar to C-w but copies all the rest of the current line into the search string. If point is already at the end of a line, it grabs the entire next line. If the search is currently case-insensitive, both C-y and C-w convert the text they copy to lower case, so that the search remains case-insensitive.

C-M-w and C-M-y modify the search string by only one character at a time: C-M-w deletes the last character from the search string and C-M-y copies the character after point to the end of the search string. An alternative method to add the character after point into the search string is to enter the minibuffer by M-e and to type C-f at the end of the search string in the minibuffer.

The character M-y copies text from the kill ring into the search string. It uses the same text that C-y would yank. Mouse-2 in the echo area does the same. See Yanking.

19.1.6 Scrolling During Incremental Search

You can enable the use of vertical scrolling during incremental search (without exiting the search) by setting the customizable variable isearch-allow-scroll to a non-nil value. This applies to using the vertical scroll-bar and to certain keyboard commands such as <prior> (scroll-down), <next> (scroll-up) and C-l (recenter). You must run these commands via their key sequences to stay in the search—typing M-x will terminate the search. You can give prefix arguments to these commands in the usual way.

This feature won't let you scroll the current match out of visibility, however.

The feature also affects some other commands, such as C-x 2 (split-window-vertically) and C-x ^ (enlarge-window) which don't exactly scroll but do affect where the text appears on the screen. In general, it applies to any command whose name has a non-nil isearch-scroll property. So you can control which commands are affected by changing these properties.

For example, to make C-h l usable within an incremental search in all future Emacs sessions, use C-h c to find what command it runs. (You type C-h c C-h l; it says view-lossage.) Then you can put the following line in your .emacs file (see Init File):

     (put 'view-lossage 'isearch-scroll t)

This feature can be applied to any command that doesn't permanently change point, the buffer contents, the match data, the current buffer, or the selected window and frame. The command must not itself attempt an incremental search.

19.1.7 Searching the Minibuffer

If you start an incremental search while the minibuffer is active, Emacs searches the contents of the minibuffer. Unlike searching an ordinary buffer, the search string is not shown in the echo area, because that is used to display the minibuffer.

If an incremental search fails in the minibuffer, it tries searching the minibuffer history. See Minibuffer History. You can visualize the minibuffer and its history as a series of “pages”, with the earliest history element on the first page and the current minibuffer on the last page. A forward search, C-s, searches forward to later pages; a reverse search, C-r, searches backwards to earlier pages. Like in ordinary buffer search, a failing search can wrap around, going from the last page to the first page or vice versa.

When the current match is on a history element, that history element is pulled into the minibuffer. If you exit the incremental search normally (e.g. by typing <RET>), it remains in the minibuffer afterwards. Cancelling the search, with C-g, restores the contents of the minibuffer when you began the search.

19.1.8 Slow Terminal Incremental Search

Incremental search on a slow terminal uses a modified style of display that is designed to take less time. Instead of redisplaying the buffer at each place the search gets to, it creates a new single-line window and uses that to display the line that the search has found. The single-line window comes into play as soon as point moves outside of the text that is already on the screen.

When you terminate the search, the single-line window is removed. Emacs then redisplays the window in which the search was done, to show its new position of point.

The slow terminal style of display is used when the terminal baud rate is less than or equal to the value of the variable search-slow-speed, initially 1200. See also the discussion of the variable baud-rate (see Customization of Display).

The number of lines to use in slow terminal search display is controlled by the variable search-slow-window-lines. Its normal value is 1.

19.2 Nonincremental Search

Emacs also has conventional nonincremental search commands, which require you to type the entire search string before searching begins.

C-s <RET> string <RET>

Search for string.

C-r <RET> string <RET>

Search backward for string.

To start a nonincremental search, first type C-s <RET>. This enters the minibuffer to read the search string; terminate the string with <RET>, and then the search takes place. If the string is not found, the search command signals an error.

When you type C-s <RET>, the C-s invokes incremental search as usual. That command is specially programmed to invoke nonincremental search, search-forward, if the string you specify is empty. (Such an empty argument would otherwise be useless.) C-r <RET> does likewise, for a reverse incremental search.

Forward and backward nonincremental searches are implemented by the commands search-forward and search-backward. These commands may be bound to other keys in the usual manner.

19.3 Word Search

A word search finds a sequence of words without regard to the type of punctuation between them. For instance, if you enter a search string that consists of two words separated by a single space, the search matches any sequence of those two words separated by one or more spaces, newlines, or other punctuation characters. This is particularly useful for searching text documents, because you don't have to worry whether the words you are looking for are separated by newlines or spaces.

M-s w

If incremental search is active, toggle word search mode (isearch-toggle-word); otherwise, begin an incremental forward word search (isearch-forward-word).

M-s w <RET> words <RET>

Search for words, using a forward nonincremental word search.

M-s w C-r <RET> words <RET>

Search backward for words, using a nonincremental word search.

To begin a forward incremental word search, type M-s w. If incremental search is not already active, this runs the command isearch-forward-word. If incremental search is already active (whether a forward or backward search), M-s w switches to a word search while keeping the direction of the search and the current search string unchanged. You can toggle word search back off by typing M-s w again.

To begin a nonincremental word search, type M-s w <RET> for a forward search, or M-s w C-r <RET> for a backward search. These run the commands word-search-forward and word-search-backward respectively.

Incremental and nonincremental word searches differ slightly in the way they find a match. In a nonincremental word search, the last word in the search string must exactly match a whole word. In an incremental word search, the matching is more lax: the last word in the search string can match part of a word, so that the matching proceeds incrementally as you type. This additional laxity does not apply to the lazy highlight, which always matches whole words.

19.4 Regular Expression Search

A regular expression (or regexp for short) is a pattern that denotes a class of alternative strings to match. GNU Emacs provides both incremental and nonincremental ways to search for a match for a regexp. The syntax of regular expressions is explained in the following section.

C-M-s

Begin incremental regexp search (isearch-forward-regexp).

C-M-r

Begin reverse incremental regexp search (isearch-backward-regexp).

Incremental search for a regexp is done by typing C-M-s (isearch-forward-regexp), by invoking C-s with a prefix argument (whose value does not matter), or by typing M-r within a forward incremental search. This command reads a search string incrementally just like C-s, but it treats the search string as a regexp rather than looking for an exact match against the text in the buffer. Each time you add text to the search string, you make the regexp longer, and the new regexp is searched for. To search backward for a regexp, use C-M-r (isearch-backward-regexp), C-r with a prefix argument, or M-r within a backward incremental search.

All of the special key sequences in an ordinary incremental search do similar things in an incremental regexp search. For instance, typing C-s immediately after starting the search retrieves the last incremental search regexp used and searches forward for it. Incremental regexp and non-regexp searches have independent defaults. They also have separate search rings, which you can access with M-p and M-n.

If you type <SPC> in incremental regexp search, it matches any sequence of whitespace characters, including newlines. If you want to match just a space, type C-q <SPC>. You can control what a bare space matches by setting the variable search-whitespace-regexp to the desired regexp.

In some cases, adding characters to the regexp in an incremental regexp search can make the cursor move back and start again. For example, if you have searched for ‘foo’ and you add ‘\|bar’, the cursor backs up in case the first ‘bar’ precedes the first ‘foo’. See Regexps.

Forward and backward regexp search are not symmetrical, because regexp matching in Emacs always operates forward, starting with the beginning of the regexp. Thus, forward regexp search scans forward, trying a forward match at each possible starting position. Backward regexp search scans backward, trying a forward match at each possible starting position. These search methods are not mirror images.

Nonincremental search for a regexp is done by the functions re-search-forward and re-search-backward. You can invoke these with M-x, or by way of incremental regexp search with C-M-s <RET> and C-M-r <RET>.

If you use the incremental regexp search commands with a prefix argument, they perform ordinary string search, like isearch-forward and isearch-backward. See Incremental Search.

19.5 Syntax of Regular Expressions

This manual describes regular expression features that users typically use. See Regular Expressions, for additional features used mainly in Lisp programs.

Regular expressions have a syntax in which a few characters are special constructs and the rest are ordinary. An ordinary character matches that same character and nothing else. The special characters are ‘$^.*+?[\’. The character ‘]’ is special if it ends a character alternative (see later). The character ‘-’ is special inside a character alternative. Any other character appearing in a regular expression is ordinary, unless a ‘\’ precedes it. (When you use regular expressions in a Lisp program, each ‘\’ must be doubled, see the example near the end of this section.)

For example, ‘f’ is not a special character, so it is ordinary, and therefore ‘f’ is a regular expression that matches the string ‘f’ and no other string. (It does not match the string ‘ff’.) Likewise, ‘o’ is a regular expression that matches only ‘o’. (When case distinctions are being ignored, these regexps also match ‘F’ and ‘O’, but we consider this a generalization of “the same string,” rather than an exception.)

Any two regular expressions a and b can be concatenated. The result is a regular expression which matches a string if a matches some amount of the beginning of that string and b matches the rest of the string. For example, concatenating the regular expressions ‘f’ and ‘o’ gives the regular expression ‘fo’, which matches only the string ‘fo’. Still trivial. To do something nontrivial, you need to use one of the special characters. Here is a list of them.

. (Period)

is a special character that matches any single character except a newline. For example, the regular expressions ‘a.b’ matches any three-character string that begins with ‘a’ and ends with ‘b’.

*

is not a construct by itself; it is a postfix operator that means to match the preceding regular expression repetitively any number of times, as many times as possible. Thus, ‘o*’ matches any number of ‘o’s, including no ‘o’s.

‘*’ always applies to the smallest possible preceding expression. Thus, ‘fo*’ has a repeating ‘o’, not a repeating ‘fo’. It matches ‘f’, ‘fo’, ‘foo’, and so on.

The matcher processes a ‘*’ construct by matching, immediately, as many repetitions as can be found. Then it continues with the rest of the pattern. If that fails, backtracking occurs, discarding some of the matches of the ‘*’-modified construct in case that makes it possible to match the rest of the pattern. For example, in matching ‘ca*ar’ against the string ‘caaar’, the ‘a*’ first tries to match all three ‘a’s; but the rest of the pattern is ‘ar’ and there is only ‘r’ left to match, so this try fails. The next alternative is for ‘a*’ to match only two ‘a’s. With this choice, the rest of the regexp matches successfully.

+

is a postfix operator, similar to ‘*’ except that it must match the preceding expression at least once. Thus, ‘ca+r’ matches the strings ‘car’ and ‘caaaar’ but not the string ‘cr’, whereas ‘ca*r’ matches all three strings.

?

is a postfix operator, similar to ‘*’ except that it can match the preceding expression either once or not at all. Thus, ‘ca?r’ matches ‘car’ or ‘cr’, and nothing else.

*?, +?, ??

are non-greedy variants of the operators above. The normal operators ‘*’, ‘+’, ‘?’ match as much as they can, as long as the overall regexp can still match. With a following ‘?’, they will match as little as possible.

Thus, both ‘ab*’ and ‘ab*?’ can match the string ‘a’ and the string ‘abbbb’; but if you try to match them both against the text ‘abbb’, ‘ab*’ will match it all (the longest valid match), while ‘ab*?’ will match just ‘a’ (the shortest valid match).

Non-greedy operators match the shortest possible string starting at a given starting point; in a forward search, though, the earliest possible starting point for match is always the one chosen. Thus, if you search for ‘a.*?$’ against the text ‘abbab’ followed by a newline, it matches the whole string. Since it can match starting at the first ‘a’, it does.

\{n\}

is a postfix operator specifying n repetitions—that is, the preceding regular expression must match exactly n times in a row. For example, ‘x\{4\}’ matches the string ‘xxxx’ and nothing else.

\{n,m\}

is a postfix operator specifying between n and m repetitions—that is, the preceding regular expression must match at least n times, but no more than m times. If m is omitted, then there is no upper limit, but the preceding regular expression must match at least n times.
‘\{0,1\}’ is equivalent to ‘?’.
‘\{0,\}’ is equivalent to ‘*’.
‘\{1,\}’ is equivalent to ‘+’.

[ ... ]

is a character set, beginning with ‘[’ and terminated by ‘]’.

In the simplest case, the characters between the two brackets are what this set can match. Thus, ‘[ad]’ matches either one ‘a’ or one ‘d’, and ‘[ad]*’ matches any string composed of just ‘a’s and ‘d’s (including the empty string). It follows that ‘c[ad]*r’ matches ‘cr’, ‘car’, ‘cdr’, ‘caddaar’, etc.

You can also include character ranges in a character set, by writing the starting and ending characters with a ‘-’ between them. Thus, ‘[a-z]’ matches any lower-case ASCII letter. Ranges may be intermixed freely with individual characters, as in ‘[a-z$%.]’, which matches any lower-case ASCII letter or ‘$’, ‘%’ or period.

You can also include certain special character classes in a character set. A ‘[:’ and balancing ‘:]’ enclose a character class inside a character alternative. For instance, ‘[[:alnum:]]’ matches any letter or digit. See Char Classes, for a list of character classes.

To include a ‘]’ in a character set, you must make it the first character. For example, ‘[]a]’ matches ‘]’ or ‘a’. To include a ‘-’, write ‘-’ as the first or last character of the set, or put it after a range. Thus, ‘[]-]’ matches both ‘]’ and ‘-’.

To include ‘^’ in a set, put it anywhere but at the beginning of the set. (At the beginning, it complements the set—see below.)

When you use a range in case-insensitive search, you should write both ends of the range in upper case, or both in lower case, or both should be non-letters. The behavior of a mixed-case range such as ‘A-z’ is somewhat ill-defined, and it may change in future Emacs versions.

[^ ... ]

‘[^’ begins a complemented character set, which matches any character except the ones specified. Thus, ‘[^a-z0-9A-Z]’ matches all characters except ASCII letters and digits.

‘^’ is not special in a character set unless it is the first character. The character following the ‘^’ is treated as if it were first (in other words, ‘-’ and ‘]’ are not special there).

A complemented character set can match a newline, unless newline is mentioned as one of the characters not to match. This is in contrast to the handling of regexps in programs such as grep.

^

is a special character that matches the empty string, but only at the beginning of a line in the text being matched. Otherwise it fails to match anything. Thus, ‘^foo’ matches a ‘foo’ that occurs at the beginning of a line.

For historical compatibility reasons, ‘^’ can be used with this meaning only at the beginning of the regular expression, or after ‘\(’ or ‘\|’.

$

is similar to ‘^’ but matches only at the end of a line. Thus, ‘x+$’ matches a string of one ‘x’ or more at the end of a line.

For historical compatibility reasons, ‘$’ can be used with this meaning only at the end of the regular expression, or before ‘\)’ or ‘\|’.

\

has two functions: it quotes the special characters (including ‘\’), and it introduces additional special constructs.

Because ‘\’ quotes special characters, ‘\$’ is a regular expression that matches only ‘$’, and ‘\[’ is a regular expression that matches only ‘[’, and so on.

See the following section for the special constructs that begin with ‘\’.

Note: for historical compatibility, special characters are treated as ordinary ones if they are in contexts where their special meanings make no sense. For example, ‘*foo’ treats ‘*’ as ordinary since there is no preceding expression on which the ‘*’ can act. It is poor practice to depend on this behavior; it is better to quote the special character anyway, regardless of where it appears.

As a ‘\’ is not special inside a character alternative, it can never remove the special meaning of ‘-’ or ‘]’. So you should not quote these characters when they have no special meaning either. This would not clarify anything, since backslashes can legitimately precede these characters where they have special meaning, as in ‘[^\]’ ("[^\\]" for Lisp string syntax), which matches any single character except a backslash.

19.6 Backslash in Regular Expressions

For the most part, ‘\’ followed by any character matches only that character. However, there are several exceptions: two-character sequences starting with ‘\’ that have special meanings. The second character in the sequence is always an ordinary character when used on its own. Here is a table of ‘\’ constructs.

\|

specifies an alternative. Two regular expressions a and b with ‘\|’ in between form an expression that matches some text if either a matches it or b matches it. It works by trying to match a, and if that fails, by trying to match b.

Thus, ‘foo\|bar’ matches either ‘foo’ or ‘bar’ but no other string.

‘\|’ applies to the largest possible surrounding expressions. Only a surrounding ‘\( ... \)’ grouping can limit the grouping power of ‘\|’.

Full backtracking capability exists to handle multiple uses of ‘\|’.

\( ... \)

is a grouping construct that serves three purposes:

1. To enclose a set of ‘\|’ alternatives for other operations. Thus, ‘\(foo\|bar\)x’ matches either ‘foox’ or ‘barx’.
2. To enclose a complicated expression for the postfix operators ‘*’, ‘+’ and ‘?’ to operate on. Thus, ‘ba\(na\)*’ matches ‘bananana’, etc., with any (zero or more) number of ‘na’ strings.
3. To record a matched substring for future reference.

This last application is not a consequence of the idea of a parenthetical grouping; it is a separate feature that is assigned as a second meaning to the same ‘\( ... \)’ construct. In practice there is usually no conflict between the two meanings; when there is a conflict, you can use a “shy” group.

\(?: ... \)

specifies a “shy” group that does not record the matched substring; you can't refer back to it with ‘\d’. This is useful in mechanically combining regular expressions, so that you can add groups for syntactic purposes without interfering with the numbering of the groups that are meant to be referred to.

\d

matches the same text that matched the dth occurrence of a ‘\( ... \)’ construct. This is called a back reference.

After the end of a ‘\( ... \)’ construct, the matcher remembers the beginning and end of the text matched by that construct. Then, later on in the regular expression, you can use ‘\’ followed by the digit d to mean “match the same text matched the dth time by the ‘\( ... \)’ construct.”

The strings matching the first nine ‘\( ... \)’ constructs appearing in a regular expression are assigned numbers 1 through 9 in the order that the open-parentheses appear in the regular expression. So you can use ‘\1’ through ‘\9’ to refer to the text matched by the corresponding ‘\( ... \)’ constructs.

For example, ‘\(.*\)\1’ matches any newline-free string that is composed of two identical halves. The ‘\(.*\)’ matches the first half, which may be anything, but the ‘\1’ that follows must match the same exact text.

If a particular ‘\( ... \)’ construct matches more than once (which can easily happen if it is followed by ‘*’), only the last match is recorded.

\`

matches the empty string, but only at the beginning of the string or buffer (or its accessible portion) being matched against.

\'

matches the empty string, but only at the end of the string or buffer (or its accessible portion) being matched against.

\=

matches the empty string, but only at point.

\b

matches the empty string, but only at the beginning or end of a word. Thus, ‘\bfoo\b’ matches any occurrence of ‘foo’ as a separate word. ‘\bballs?\b’ matches ‘ball’ or ‘balls’ as a separate word.

‘\b’ matches at the beginning or end of the buffer regardless of what text appears next to it.

\B

matches the empty string, but not at the beginning or end of a word.

\<

matches the empty string, but only at the beginning of a word. ‘\<’ matches at the beginning of the buffer only if a word-constituent character follows.

\>

matches the empty string, but only at the end of a word. ‘\>’ matches at the end of the buffer only if the contents end with a word-constituent character.

\w

matches any word-constituent character. The syntax table determines which characters these are. See Syntax.

\W

matches any character that is not a word-constituent.

\_<

matches the empty string, but only at the beginning of a symbol. A symbol is a sequence of one or more symbol-constituent characters. A symbol-constituent character is a character whose syntax is either ‘w’ or ‘_’. ‘\_<’ matches at the beginning of the buffer only if a symbol-constituent character follows.

\_>

matches the empty string, but only at the end of a symbol. ‘\_>’ matches at the end of the buffer only if the contents end with a symbol-constituent character.

\sc

matches any character whose syntax is c. Here c is a character that designates a particular syntax class: thus, ‘w’ for word constituent, ‘-’ or ‘ ’ for whitespace, ‘.’ for ordinary punctuation, etc. See Syntax.

\Sc

matches any character whose syntax is not c.

\cc

matches any character that belongs to the category c. For example, ‘\cc’ matches Chinese characters, ‘\cg’ matches Greek characters, etc. For the description of the known categories, type M-x describe-categories <RET>.

\Cc

matches any character that does not belong to category c.

The constructs that pertain to words and syntax are controlled by the setting of the syntax table (see Syntax).

19.7 Regular Expression Example

Here is an example of a regexp—the regexp that Emacs uses, by default, to recognize the end of a sentence, not including the following space (i.e., the variable sentence-end-base):

     [.?!][]\"'””)}]*

This contains two parts in succession: a character set matching period, ‘?’, or ‘!’, and a character set matching close-brackets, quotes, or parentheses, repeated zero or more times.

19.8 Searching and Case

Searches in Emacs normally ignore the case of the text they are searching through, if you specify the text in lower case. Thus, if you specify searching for ‘foo’, then ‘Foo’ and ‘foo’ are also considered a match. Regexps, and in particular character sets, are included: ‘[ab]’ would match ‘a’ or ‘A’ or ‘b’ or ‘B’.

An upper-case letter anywhere in the incremental search string makes the search case-sensitive. Thus, searching for ‘Foo’ does not find ‘foo’ or ‘FOO’. This applies to regular expression search as well as to string search. The effect ceases if you delete the upper-case letter from the search string.

Typing M-c within an incremental search toggles the case sensitivity of that search. The effect does not extend beyond the current incremental search to the next one, but it does override the effect of adding or removing an upper-case letter in the current search.

If you set the variable case-fold-search to nil, then all letters must match exactly, including case. This is a per-buffer variable; altering the variable normally affects only the current buffer, unless you change its default value. See Locals. This variable applies to nonincremental searches also, including those performed by the replace commands (see Replace) and the minibuffer history matching commands (see Minibuffer History).

Several related variables control case-sensitivity of searching and matching for specific commands or activities. For instance, tags-case-fold-search controls case sensitivity for find-tag. To find these variables, do M-x apropos-variable <RET> case-fold-search <RET>.

19.9 Replacement Commands

Emacs provides several commands for performing search-and-replace operations. In addition to the simple M-x replace-string command, there is M-% (query-replace), which presents each occurrence of the pattern and asks you whether to replace it.

The replace commands normally operate on the text from point to the end of the buffer. When the mark is active, they operate on the region instead (see Mark). The basic replace commands replace one search string (or regexp) with one replacement string. It is possible to perform several replacements in parallel, using the command expand-region-abbrevs (see Expanding Abbrevs).

• Unconditional Replace: Replacing all matches for a string.
• Regexp Replace: Replacing all matches for a regexp.
• Replacement and Case: How replacements preserve case of letters.
• Query Replace: How to use querying.

19.9.1 Unconditional Replacement

M-x replace-string <RET> string <RET> newstring <RET>

Replace every occurrence of string with newstring.

To replace every instance of ‘foo’ after point with ‘bar’, use the command M-x replace-string with the two arguments ‘foo’ and ‘bar’. Replacement happens only in the text after point, so if you want to cover the whole buffer you must go to the beginning first. All occurrences up to the end of the buffer are replaced; to limit replacement to part of the buffer, activate the region around that part. When the region is active, replacement is limited to the region (see Mark).

When replace-string exits, it leaves point at the last occurrence replaced. It adds the prior position of point (where the replace-string command was issued) to the mark ring, without activating the mark; use C-u C-<SPC> to move back there. See Mark Ring.

A prefix argument restricts replacement to matches that are surrounded by word boundaries. The argument's value doesn't matter.

See Replacement and Case, for details about case-sensitivity in replace commands.

19.9.2 Regexp Replacement

The M-x replace-string command replaces exact matches for a single string. The similar command M-x replace-regexp replaces any match for a specified pattern.

M-x replace-regexp <RET> regexp <RET> newstring <RET>

Replace every match for regexp with newstring.

In replace-regexp, the newstring need not be constant: it can refer to all or part of what is matched by the regexp. ‘\&’ in newstring stands for the entire match being replaced. ‘\d’ in newstring, where d is a digit, stands for whatever matched the dth parenthesized grouping in regexp. (This is called a “back reference.”) ‘\#’ refers to the count of replacements already made in this command, as a decimal number. In the first replacement, ‘\#’ stands for ‘0’; in the second, for ‘1’; and so on. For example,

     M-x replace-regexp <RET> c[ad]+r <RET> \&-safe <RET>

replaces (for example) ‘cadr’ with ‘cadr-safe’ and ‘cddr’ with ‘cddr-safe’.

     M-x replace-regexp <RET> \(c[ad]+r\)-safe <RET> \1 <RET>

performs the inverse transformation. To include a ‘\’ in the text to replace with, you must enter ‘\\’.

If you want to enter part of the replacement string by hand each time, use ‘\?’ in the replacement string. Each replacement will ask you to edit the replacement string in the minibuffer, putting point where the ‘\?’ was.

The remainder of this subsection is intended for specialized tasks and requires knowledge of Lisp. Most readers can skip it.

You can use Lisp expressions to calculate parts of the replacement string. To do this, write ‘\,’ followed by the expression in the replacement string. Each replacement calculates the value of the expression and converts it to text without quoting (if it's a string, this means using the string's contents), and uses it in the replacement string in place of the expression itself. If the expression is a symbol, one space in the replacement string after the symbol name goes with the symbol name, so the value replaces them both.

Inside such an expression, you can use some special sequences. ‘\&’ and ‘\n’ refer here, as usual, to the entire match as a string, and to a submatch as a string. n may be multiple digits, and the value of ‘\n’ is nil if subexpression n did not match. You can also use ‘\#&’ and ‘\#n’ to refer to those matches as numbers (this is valid when the match or submatch has the form of a numeral). ‘\#’ here too stands for the number of already-completed replacements.

Repeating our example to exchange ‘x’ and ‘y’, we can thus do it also this way:

     M-x replace-regexp <RET> \(x\)\|y <RET>
     \,(if \1 "y" "x") <RET>

For computing replacement strings for ‘\,’, the format function is often useful (see Formatting Strings). For example, to add consecutively numbered strings like ‘ABC00042’ to columns 73 to 80 (unless they are already occupied), you can use

     M-x replace-regexp <RET> ^.\{0,72\}$ <RET>
     \,(format "%-72sABC%05d" \& \#) <RET>

19.9.3 Replace Commands and Case

If the first argument of a replace command is all lower case, the command ignores case while searching for occurrences to replace—provided case-fold-search is non-nil. If case-fold-search is set to nil, case is always significant in all searches.

In addition, when the newstring argument is all or partly lower case, replacement commands try to preserve the case pattern of each occurrence. Thus, the command

     M-x replace-string <RET> foo <RET> bar <RET>

replaces a lower case ‘foo’ with a lower case ‘bar’, an all-caps ‘FOO’ with ‘BAR’, and a capitalized ‘Foo’ with ‘Bar’. (These three alternatives—lower case, all caps, and capitalized, are the only ones that replace-string can distinguish.)

If upper-case letters are used in the replacement string, they remain upper case every time that text is inserted. If upper-case letters are used in the first argument, the second argument is always substituted exactly as given, with no case conversion. Likewise, if either case-replace or case-fold-search is set to nil, replacement is done without case conversion.

19.9.4 Query Replace

M-% string <RET> newstring <RET>

M-x query-replace <RET> string <RET> newstring <RET>

Replace some occurrences of string with newstring.

C-M-% regexp <RET> newstring <RET>

M-x query-replace-regexp <RET> regexp <RET> newstring <RET>

Replace some matches for regexp with newstring.

If you want to change only some of the occurrences of ‘foo’ to ‘bar’, not all of them, use M-% (query-replace). This command finds occurrences of ‘foo’ one by one, displays each occurrence and asks you whether to replace it. Aside from querying, query-replace works just like replace-string (see Unconditional Replace). In particular, it preserves case provided case-replace is non-nil, as it normally is (see Replacement and Case). A numeric argument means consider only occurrences that are bounded by word-delimiter characters.

C-M-% performs regexp search and replace (query-replace-regexp). It works like replace-regexp except that it queries like query-replace.

These commands highlight the current match using the face query-replace. They highlight other matches using lazy-highlight just like incremental search (see Incremental Search). By default, query-replace-regexp will show substituted replacement string for the current match in the minibuffer. If you want to keep special sequences ‘\&’ and ‘\n’ unexpanded, customize query-replace-show-replacement variable.

The characters you can type when you are shown a match for the string or regexp are:

<SPC>

to replace the occurrence with newstring.

<DEL>

to skip to the next occurrence without replacing this one.

, (Comma)

to replace this occurrence and display the result. You are then asked for another input character to say what to do next. Since the replacement has already been made, <DEL> and <SPC> are equivalent in this situation; both move to the next occurrence.

You can type C-r at this point (see below) to alter the replaced text. You can also type C-x u to undo the replacement; this exits the query-replace, so if you want to do further replacement you must use C-x <ESC> <ESC> <RET> to restart (see Repetition).

<RET>

to exit without doing any more replacements.

. (Period)

to replace this occurrence and then exit without searching for more occurrences.

!

to replace all remaining occurrences without asking again.

^

to go back to the position of the previous occurrence (or what used to be an occurrence), in case you changed it by mistake or want to reexamine it.

C-r

to enter a recursive editing level, in case the occurrence needs to be edited rather than just replaced with newstring. When you are done, exit the recursive editing level with C-M-c to proceed to the next occurrence. See Recursive Edit.

C-w

to delete the occurrence, and then enter a recursive editing level as in C-r. Use the recursive edit to insert text to replace the deleted occurrence of string. When done, exit the recursive editing level with C-M-c to proceed to the next occurrence.

e

to edit the replacement string in the minibuffer. When you exit the minibuffer by typing <RET>, the minibuffer contents replace the current occurrence of the pattern. They also become the new replacement string for any further occurrences.

C-l

to redisplay the screen. Then you must type another character to specify what to do with this occurrence.

C-h

to display a message summarizing these options. Then you must type another character to specify what to do with this occurrence.

Some other characters are aliases for the ones listed above: y, n and q are equivalent to <SPC>, <DEL> and <RET>.

Aside from this, any other character exits the query-replace, and is then reread as part of a key sequence. Thus, if you type C-k, it exits the query-replace and then kills to end of line.

To restart a query-replace once it is exited, use C-x <ESC> <ESC>, which repeats the query-replace because it used the minibuffer to read its arguments. See C-x ESC ESC.

See Operating on Files, for the Dired Q command which performs query replace on selected files. See also Transforming File Names, for Dired commands to rename, copy, or link files by replacing regexp matches in file names.

19.10 Other Search-and-Loop Commands

Here are some other commands that find matches for a regular expression. They all ignore case in matching, if the pattern contains no upper-case letters and case-fold-search is non-nil. Aside from occur and its variants, all operate on the text from point to the end of the buffer, or on the region if it is active.

M-x multi-isearch-buffers

Prompt for one or more buffer names, ending with <RET>; then, begin a multi-buffer incremental search in those buffers. (If the search fails in one buffer, the next C-s tries searching the next specified buffer, and so forth.) With a prefix argument, prompt for a regexp and begin a multi-buffer incremental search in buffers matching that regexp.

M-x multi-isearch-buffers-regexp

This command is just like multi-isearch-buffers, except it performs an incremental regexp search.

M-x occur

Prompt for a regexp, and display a list showing each line in the buffer that contains a match for it. To limit the search to part of the buffer, narrow to that part (see Narrowing). A numeric argument n specifies that n lines of context are to be displayed before and after each matching line. Currently, occur can not correctly handle multiline matches.

The buffer ‘*Occur*’ containing the output serves as a menu for finding the occurrences in their original context. Click Mouse-2 on an occurrence listed in ‘*Occur*’, or position point there and type <RET>; this switches to the buffer that was searched and moves point to the original of the chosen occurrence. o and C-o display the match in another window; C-o does not select it.

After using M-x occur, you can use next-error to visit the occurrences found, one by one. Compilation Mode.

M-s o

Run occur using the search string of the last incremental string search. You can also run M-s o when an incremental search is active; this uses the current search string.

M-x list-matching-lines

Synonym for M-x occur.

M-x multi-occur

This command is just like occur, except it is able to search through multiple buffers. It asks you to specify the buffer names one by one.

M-x multi-occur-in-matching-buffers

This command is similar to multi-occur, except the buffers to search are specified by a regular expression that matches visited file names. With a prefix argument, it uses the regular expression to match buffer names instead.

M-x how-many

Prompt for a regexp, and print the number of matches for it in the buffer after point. If the region is active, this operates on the region instead.

M-x flush-lines

Prompt for a regexp, and delete each line that contains a match for it, operating on the text after point. This command deletes the current line if it contains a match starting after point. If the region is active, it operates on the region instead; if a line partially contained in the region contains a match entirely contained in the region, it is deleted.

If a match is split across lines, flush-lines deletes all those lines. It deletes the lines before starting to look for the next match; hence, it ignores a match starting on the same line at which another match ended.

M-x keep-lines

Prompt for a regexp, and delete each line that does not contain a match for it, operating on the text after point. If point is not at the beginning of a line, this command always keeps the current line. If the region is active, the command operates on the region instead; it never deletes lines that are only partially contained in the region (a newline that ends a line counts as part of that line).

If a match is split across lines, this command keeps all those lines.

20 Commands for Fixing Typos

In this chapter we describe the commands that are especially useful when you catch a mistake in your text after you have made it, or change your mind while composing text on the fly.

The most fundamental command for correcting erroneous editing is the undo command C-/ (which is 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 self-inserting characters. 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.

• Undo: The Undo commands.
• Transpose: Exchanging two characters, words, lines, lists...
• Fixing Case: Correcting case of last word entered.
• Spelling: Apply spelling checker to a word, or a whole file.

20.1 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 as back its 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)⁸. 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, as a single set of changes. 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-/ to undo the undo command.

On the other hand, 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.

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 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.

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 Persistent Mark), 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 records for a buffer becomes too large, Emacs discards the oldest undo records from time to time (during garbage collection). You can specify how much undo records 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 80000. 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 120000.

Regardless of the values of those variables, the most recent change is never discarded unless it gets bigger than undo-outer-limit (normally 12,000,000). 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.

20.2 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).

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 are a good way of getting there. Otherwise, a reverse search (C-r) is often the best way. See Search.

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,’.

C-M-t (transpose-sexps) is a similar command for transposing two expressions (see Expressions), and C-x C-t (transpose-lines) exchanges lines. They work like M-t except as regards what 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 (word, expression, line) before or containing point across several other characters (words, expressions, 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 (word, expression, line) ending after point with the one ending after the mark.

20.3 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.

20.4 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 the spelling checker program Aspell, Ispell or Hunspell is installed. Aspell, Ispell or Hunspell are not part of Emacs, but one or the other is usually installed in GNU/Linux and other free operating systems. See Aspell.

M-$

Check and correct spelling of the active region or the word at point (ispell-word).

M-x ispell

Check and correct spelling in the active region or the entire buffer.

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-change-dictionary <RET> dict <RET>

Restart the Aspell/Ispell/Hunspell process, using dict as the dictionary.

M-x ispell-kill-ispell

Kill the Aspell/Ispell/Hunspell subprocess.

M-<TAB>

<ESC> <TAB>

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 Mark. (When Transient Mark mode is off, M-$ always acts on the word around or before point, ignoring the region. See Persistent Mark.)

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 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 Aspell or Ispell or Hunspell will consider it 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

Quit 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 Aspell/Ispell/Hunspell subprocess.

?

Show the list of options.

In Text mode and related modes, the command M-<TAB> (ispell-complete-word) shows a list of completions based on spelling correction. Insert the beginning of a word, and then type M-<TAB>; the command displays a completion list window. (If your window manager intercepts M-<TAB>, type <ESC> <TAB> or C-M-i.) To choose one of the completions listed, click Mouse-2 or Mouse-1 fast on it, or move the cursor there in the completions window and type <RET>. See Text Mode.

Once started, the Aspell or Ispell or Hunspell 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 time except when you do spelling correction.

Ispell, Aspell and Hunspell use two dictionaries together for spell checking: the standard dictionary and your private dictionary. The standard dictionary is specified by ispell-local-dictionary or, if nil, by ispell-dictionary. If both are nil the default dictionary is selected. 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. Personal dictionary is specified by ispell-personal-dictionary. If nil, default value is used.

Set variable ispell-dictionary to select a specific default dictionary for all your documents. Set variable ispell-local-dictionary in the local variables section to select a specific dictionary for a given document.

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 root and affix information. For some languages, there is a spell checking dictionary but no word completion dictionary.

Flyspell mode is a fully-automatic way to check spelling as you edit in Emacs. It operates by checking words as you change or insert them. When it finds a word that it does not recognize, it highlights that word. This does not interfere with your editing, but when you see the highlighted word, you can move to it and fix it. Type M-x flyspell-mode to enable or disable this mode in the current buffer. To enable flyspell-mode in all text mode buffers, add turn-on-flyspell to text-mode-hook.

When Flyspell mode highlights a word as misspelled, you can click on it with Mouse-2 to display a menu of possible corrections and actions. You can also correct the 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.

21 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.

• Basic Keyboard Macro: Defining and running keyboard macros.
• Keyboard Macro Ring: Where previous keyboard macros are saved.
• Keyboard Macro Counter: Inserting incrementing numbers in macros.
• Keyboard Macro Query: Making keyboard macros do different things each time.
• Save Keyboard Macro: Giving keyboard macros names; saving them in files.
• Edit Keyboard Macro: Editing keyboard macros.
• Keyboard Macro Step-Edit: Interactively executing and editing a keyboard macro.

21.1 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).

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 keybindings 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>.

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.

21.2 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.

21.3 The Keyboard Macro Counter

Each keyboard macro has an associated counter, which is initialized to 0 when you start defining the macro. This 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 incremented each time its value is inserted into the buffer.

<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 Keyboard Macro.) You can use a numeric prefix argument to specify a different increment. If you just specify a C-u prefix, that is the same as an increment of zero: it inserts the current counter value without changing it.

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). 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 RegNumbers. For most purposes, it is simpler to use a keyboard macro counter.

21.4 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 numeric 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 Edit.

21.5 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 global-set-key (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 need not 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 Lisp Libraries). If the file you save in is your init file ~/.emacs (see Init File) then the macro will be defined each time you run Emacs.

If you give insert-kbd-macro a numeric 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.

21.6 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).

21.7 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.

22 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.

• File Names: How to type and edit file-name arguments.
• Visiting: Visiting a file prepares Emacs to edit the file.
• Saving: Saving makes your changes permanent.
• Reverting: Reverting cancels all the changes not saved.
• Autorevert: Auto Reverting non-file buffers.
• Auto Save: Auto Save periodically protects against loss of data.
• File Aliases: Handling multiple names for one file.
• Directories: Creating, deleting, and listing file directories.
• Comparing Files: Finding where two files differ.
• Diff Mode: Mode for editing file differences.
• Misc File Ops: Other things you can do on files.
• Compressed Files: Accessing compressed files.
• File Archives: Operating on tar, zip, jar etc. archive files.
• Remote Files: Accessing files on other sites.
• Quoted File Names: Quoting special characters in file names.
• File Name Cache: Completion against a list of files you often use.
• File Conveniences: Convenience Features for Finding Files.
• Filesets: Handling sets of files.

22.1 File Names

Many Emacs commands that operate on a file require you to specify the file name, using the minibuffer (see Minibuffer). You can use completion to specify long file names (see Completion). Note that file name completion ignores file names whose extensions appear in the variable completion-ignored-extensions (see Completion Options).

For most operations, there is a default file name which is used if you type just <RET> to enter an empty argument. Normally, the default file name is the name of the file visited in the current buffer.

Each buffer has a default directory which is normally the same as the directory of the file visited in that buffer. For example, if the default file name is /u/rms/gnu/gnu.tasks, the default directory is normally /u/rms/gnu/. The default directory is kept in the variable default-directory, which has a separate value in every buffer. When a command reads a file name using the minibuffer, the default directory usually serves as the initial contents of the minibuffer. To inhibit the insertion of the default directory, set the variable insert-default-directory to nil.

If you enter a file name without a directory, that specifies a file in the default directory. If you specify a directory in a relative fashion, with a name that does not start with a slash, it is interpreted with respect to the default directory. For example, suppose the default directory is /u/rms/gnu/. 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 is interpreted as “ignore everything before the second slash in the pair,” and ‘~/’ is interpreted as your home directory. See Minibuffer File, for more information about these shortcuts.

The command M-x pwd displays the default directory, and the command M-x cd sets it to a value read using the minibuffer. A buffer's default directory changes only when the cd command is used. A file-visiting buffer's default directory is initialized to the directory of the file it visits. If you create a buffer with C-x b, its default directory is copied from that of the buffer that was current at the time (see Select Buffer).

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 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 if you set the variable file-name-coding-system to a non-nil value. See File Name Coding.

22.2 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.

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 append ‘<2>’, ‘<3>’, and so on, but you can select other methods. See Uniquify.

Each window's mode line shows the name of the buffer that is being displayed in that window, so you can always tell what buffer you are editing. see Mode Line.

The changes you make with editing commands are made in the Emacs buffer. They do not take effect in the file that you visited, or any permanent place, until you save the buffer (see Saving).

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.

To visit a file, type C-x C-f (find-file) and use the minibuffer to enter the name of the desired file. The usual defaulting and completion behavior is available in this minibuffer (see Minibuffer File). Note, also, that completion ignores certain file names (see Completion Options). While in the minibuffer, you can abort C-x C-f by typing C-g.

Your can tell that C-x C-f has completed successfully by the appearance of new text on the screen and a new buffer name in the mode line. If the specified file does not exist and you could not create it, or exists but you can't read it, an error message is displayed in the echo area.

If you visit a file that is already in Emacs, C-x C-f does not make another copy. It selects the existing buffer containing that file. However, before doing so, it checks whether the file itself has changed since you visited or saved it last. 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. Note, however, that Emacs cannot visit files that are larger than the maximum Emacs buffer size, which is around 512 megabytes on 32-bit machines (see Buffers). If you try, Emacs will display an error message saying that the maximum buffer size has been exceeded.

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.

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 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 Misc Dired Features.

What if you want to create a new file? Just visit it. Emacs displays ‘(New file)’ in the echo area, but in other respects behaves as if you had visited an existing empty file. If you make changes and save them, the file is created.

When <TAB> completion results in a nonexistent file name and you type <RET> immediately to visit it, Emacs asks for confirmation; this is because it's possible that you expected completion to go further and give you an existing file's name. The string ‘[Confirm]’ appears for a short time after the file name to indicate the need to confirm in this way. Type <RET> to confirm and visit the nonexistent file. The variable confirm-nonexistent-file-or-buffer controls whether Emacs asks for confirmation before visiting a new file. The default value, after-completion, gives the behavior we have just described. If the value is nil, Emacs never asks for confirmation; for any other non-nil value, Emacs always asks for confirmation. This variable also affects the switch-to-buffer command (see Select Buffer). See Completion, for more information about completion.

If you visit a nonexistent file unintentionally (because you typed the wrong file name), 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; this lets you “edit” the contents of the directory. See Dired. 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 (toggle-read-only). See Misc Buffer.

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 Windows.

C-x 5 f (find-file-other-frame) is similar, but opens a new frame, or makes visible any existing frame showing the file you seek. This feature is available only when you are using a window system. See Frames.

Emacs recognizes from the contents of a file which end-of-line convention it uses to separate lines—newline (used on GNU/Linux and on Unix), carriage-return linefeed (used on Microsoft systems), or just carriage-return (used on the Macintosh)—and automatically converts the contents to the normal Emacs convention, which is that the newline character separates lines. This is a part of the general feature of coding system conversion (see Coding Systems), and makes it possible to edit files imported from different operating systems with equal convenience. If you change the text and save the file, Emacs performs the inverse conversion, changing newlines back into carriage-return linefeed or just carriage-return if appropriate.

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 Formatted Text), character code conversion (see Coding Systems), or automatic uncompression (see Compressed Files), and does not add a final newline because of require-final-newline (see Customize Save). If you have already visited the same file in the usual (non-literal) manner, this command asks you whether to visit it literally instead.

Two special hook variables allow extensions to modify the operation of visiting files. Visiting a file that does not exist runs the functions in the list find-file-not-found-functions; this variable holds a list of functions, and the functions 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 the list 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 Modes), and to specify local variables defined for that file (see File Variables).

22.3 Saving Files

Saving a buffer in Emacs means writing its contents back into the file that was visited in the buffer.

• Save Commands: Commands for saving files.
• Backup: How Emacs saves the old version of your file.
• Customize Save: Customizing the saving of files.
• Interlocking: How Emacs protects against simultaneous editing of one file by two users.
• Shadowing: Copying files to "shadows" automatically.
• Time Stamps: Emacs can update time stamps on saved files.

22.3.1 Commands for Saving Files

These are the commands that relate to saving and writing files.

C-x C-s

Save the current buffer in its visited file on disk (save-buffer).

C-x s

Save any or all buffers in their visited 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.

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 selected 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.

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

Save this buffer and ask about the rest of the buffers.

n

Don't save this buffer, but ask about the rest of the buffers.

!

Save this buffer and all the rest with no more questions.

<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.

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.

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. (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 Modes.

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.

22.3.2 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 VC 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 Backup Names.

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.

• Names: How backup files are named.
• Deletion: Emacs deletes excess numbered backups.
• Copying: Backups can be made by copying or renaming.

22.3.2.1 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 .emacs 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 Locals). You can have Emacs set version-control locally whenever you visit a given file (see File Variables). Some modes, such as Rmail mode, set this variable.

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.

You can customize the variable backup-directory-alist to specify that files matching certain patterns should be backed up in specific directories. This variable applies to both single and numbered backups. 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.

If you define the variable make-backup-file-name-function to a suitable Lisp function, that overrides the usual way Emacs constructs backup file names.

22.3.2.2 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 Dired Deletion.

22.3.2.3 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).

Having the owner change is usually a good idea, because then the owner always shows who last edited the file. Also, the owners of the backups show who produced those versions. Occasionally there is a file whose owner should not change; it is a good idea for such files to contain local variable lists to set backup-by-copying-when-mismatch locally (see File Variables).

The choice of renaming or copying is controlled by four variables. Renaming is the default choice. If the variable backup-by-copying is non-nil, copying is used. Otherwise, if the variable backup-by-copying-when-linked is non-nil, then copying is used for files that have multiple names, but renaming may still be used when the file being edited has only one name. If the variable backup-by-copying-when-mismatch is non-nil, then copying is used if renaming would cause the file's owner or group to change. backup-by-copying-when-mismatch is t by default if you start Emacs as the superuser. The fourth variable, backup-by-copying-when-privileged-mismatch, gives the highest numeric user-id for which backup-by-copying-when-mismatch will be forced on. This is useful when low-numbered user-ids are assigned to special system users, such as root, bin, daemon, etc., which must maintain ownership of files.

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 check-in and check-out are 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.

22.3.3 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, that means to add newlines both on visiting and on saving. If the value is nil, Emacs leaves the end of the file unchanged; if it's neither nil nor t, Emacs asks you whether to add a newline. The default is nil.

Many major modes are designed for specific kinds of files that are always supposed to end in newlines. These major modes set the variable require-final-newline according to mode-require-final-newline. By setting the latter variable, you can control how these modes handle final newlines.

When Emacs saves a file, it invokes the fsync system call to force the data immediately out to disk. This is important for safety if the system crashes or in case of power outage. However, it can be disruptive on laptops using power saving, because it requires the disk to spin up each time you save a file. Setting write-region-inhibit-fsync to a non-nil value disables this synchronization. Be careful—this means increased risk of data loss.

22.3.4 Protection against Simultaneous Editing

Simultaneous editing occurs when two users visit the same file, both make changes, and then both save them. If nobody were informed that this was happening, whichever user saved first would later find that his 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 link in the same directory.) 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.

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.

Note that locking works on the basis of a file name; if a file has multiple names, Emacs does not realize that the two names are the same file and cannot prevent two users from editing it simultaneously under different names. However, basing locking on names means that Emacs can interlock the editing of new files that will not really exist until they are saved.

Some systems are not configured to allow Emacs to make locks, and there are cases where lock files cannot be written. In these cases, Emacs cannot detect trouble in advance, but it still can detect the collision when you try to save a file and overwrite someone else's changes. Every time Emacs saves a buffer, it first checks the last-modification date of the existing file on disk to verify that it has not changed since the file was last visited or saved. If the date does not match, it implies that changes were made in the file in some other way, and these changes are about to be lost if Emacs actually does save. To prevent this, Emacs displays a warning message and asks for confirmation before saving. Occasionally you will know why the file was changed and know that it does not matter; then you can answer yes and proceed. Otherwise, you should cancel the save with C-g and investigate the situation.

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.

The first thing you should do when notified that simultaneous editing has already taken place is to list the directory with C-u C-x C-d (see Directories). This shows the file's current author. You should attempt to contact him to warn him not to continue editing. Often the next step is to save the contents of your Emacs buffer under a different name, and use diff to compare the two files.

22.3.5 Shadowing Files

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.

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.

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.

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.

22.3.6 Updating Time Stamps Automatically

You can arrange to put a time stamp in a file, so that it will be updated automatically each time you edit and save the file. The time stamp has to 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 hook function time-stamp to the hook before-save-hook; that hook function will automatically update the time stamp, inserting the current date and time when you save the file. You can also use the command M-x time-stamp to update the time stamp manually. For other customizations, see the Custom group time-stamp. Note that non-numeric fields in the time stamp are formatted according to your locale setting (see Environment).

22.4 Reverting a Buffer

If you have made extensive changes to a file and then change your mind about them, you can get rid of them by reading in the previous version of the file. To do this, use M-x revert-buffer, which operates on the current buffer. Since reverting a buffer unintentionally could lose a lot of work, you must confirm this command with yes.

revert-buffer tries to position point in such a way that, if the file was edited only slightly, you will be at approximately the same piece of text after reverting as before. However, if you have made drastic changes, point may wind up in a totally different piece of text.

Reverting marks the buffer as “not modified”.

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.)

In addition, you can tell Emacs to periodically revert a buffer by typing M-x auto-revert-mode. This turns on Auto-Revert mode, a minor mode that makes Emacs automatically revert the current buffer every five seconds. You can change this interval through the variable auto-revert-interval. Typing M-x global-auto-revert-mode enables Global Auto-Revert mode, which does the same for all file buffers. Auto-Revert mode and Global Auto-Revert modes do not check or revert remote files, because that is usually too slow.

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 works also for remote files.

See VC Mode Line, for Auto Revert peculiarities in buffers that visit files under version control.

22.5 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: enabling Auto Revert Mode in those buffers (using M-x auto-revert-mode); and setting global-auto-revert-non-file-buffers non-nil. 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.

The details depend on the particular types of buffers and are explained in the corresponding sections.

• Auto Reverting the Buffer Menu: Auto Revert of the Buffer Menu.
• Auto Reverting Dired: Auto Revert of Dired buffers.
• Supporting additional buffers: How to add more Auto Revert support.

22.5.1 Auto Reverting the Buffer Menu

If auto-reverting of non-file buffers is enabled, the Buffer Menu 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.

22.5.2 Auto Reverting Dired buffers

Auto-reverting Dired buffers currently works on GNU or Unix style operating systems. It may not work satisfactorily on some other systems.

Dired buffers only auto-revert when the file list of the buffer's main directory changes (e.g. when a new file is added). 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 not auto-reverted (because it may be slow). 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.

22.5.3 Adding Support for Auto-Reverting additional Buffers.

This section is intended for Elisp programmers who would like to add support for auto-reverting new types of buffers.

To support auto-reverting the buffer must first of all have a revert-buffer-function. See Reverting.

In addition, it must have a buffer-stale-function.

Once the buffer has a revert-buffer-function and a buffer-stale-function, several problems usually remain.

The buffer will only auto-revert if it is marked unmodified. Hence, you will have to make sure that various functions mark the buffer modified if and only if either the buffer contains information that might be lost by reverting, or there is reason to believe that the user might be inconvenienced by auto-reverting, because he is actively working on the buffer. The user can always override this by manually adjusting the modified status of the buffer. To support this, calling the revert-buffer-function on a buffer that is marked unmodified should always keep the buffer marked unmodified.

It is important to assure that point does not continuously jump around as a consequence of auto-reverting. Of course, moving point might be inevitable if the buffer radically changes.

You should make sure that the revert-buffer-function does not print messages that unnecessarily duplicate Auto Revert's own messages, displayed if auto-revert-verbose is t, and effectively override a nil value for auto-revert-verbose. Hence, adapting a mode for auto-reverting often involves getting rid of such messages. This is especially important for buffers that automatically revert every auto-revert-interval seconds.

If the new auto-reverting is part of Emacs, you should mention it in the documentation string of global-auto-revert-non-file-buffers.

Similarly, you should add a section to this chapter. This section should at the very least make clear whether enabling auto-reverting for the buffer reliably assures that all information in the buffer is completely up to date (or will be after auto-revert-interval seconds).

22.6 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. The message ‘Auto-saving...’ is displayed in the echo area during auto-saving, if any files are actually auto-saved. Errors occurring during auto-saving are caught so that they do not interfere with the execution of commands you have been typing.

• Files: The file where auto-saved changes are actually made until you save the file.
• Control: Controlling when and how often to auto-save.
• Recover: Recovering text from auto-save files.

22.6.1 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, set the variable auto-save-visited-file-name to a non-nil value. In this mode, there is no real difference between auto-saving and explicit saving.

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.

22.6.2 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 Entering Emacs). The default for this variable is t, so auto-saving is the usual practice for file-visiting buffers. Auto-saving can be turned on or off for any existing buffer with the command M-x auto-save-mode. Like other minor mode commands, M-x auto-save-mode turns auto-saving on with a positive argument, off with a zero or negative argument; with no argument, it toggles.

Emacs does auto-saving periodically based on counting how many characters you have typed since the last time auto-saving was done. 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. The variable auto-save-timeout says how many seconds Emacs should wait before it does an auto save (and perhaps also a garbage collection). (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.

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 request an auto-save explicitly with the command M-x do-auto-save.

22.6.3 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 for later recovery in files named ~/.emacs.d/auto-save-list/.saves-pid-hostname. The directory used, ~/.emacs.d/auto-save-list/, is determined by the variable auto-save-list-file-prefix. You can record sessions in a different place by customizing that variable. If you set auto-save-list-file-prefix to nil in your .emacs file, sessions are not recorded for recovery.

22.7 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 Regexps). 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"))

22.8 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 authors included). Emacs also includes a directory browser feature called Dired; see Dired.

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. To do this, it runs the program specified by directory-free-space-program with arguments directory-free-space-args.

The command M-x delete-directory prompts for a directory 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 or Recycle Bin, instead of deleting it outright, by changing the variable delete-by-moving-to-trash to t. See Misc File Ops, for more information about using the Trash.

22.9 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 "-c" to specify a context diff. See Diff, for more information about diff output formats.

The output of the diff command is shown using a major mode called Diff mode. See Diff Mode.

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 compare-windows compares the text in the current window with that in the next window. (For more information about windows in Emacs, Windows.) Comparison starts at point in each window, after pushing each initial point value on 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, 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 normally ignores changes in whitespace, and a prefix argument turns that off.

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 Emerge, for the Emerge facility, which provides a powerful interface for merging files.

22.10 Diff Mode

Diff mode is a major mode used for the output of M-x diff and other similar commands, as well as the output of the diff program. 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 can 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 at which the hunk occurs. Diff mode highlights each hunk header, to distinguish it from the actual contents of the hunk.

You can edit a Diff mode buffer like any other buffer. (If it is read-only, you need to make it writable first. See Misc Buffer.) Whenever you change a hunk, Diff mode attempts to automatically correct the line numbers in the hunk headers, to ensure that the diff remains “correct”. To disable automatic line number correction, change the variable diff-update-on-the-fly to nil.

Diff mode treats each hunk as an “error message,” similar to Compilation mode. Thus, you can use commands such as C-x ' to visit the corresponding source locations. See Compilation Mode.

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).

M-p

Move to the previous hunk-start (diff-hunk-prev).

M-}

Move to the next file-start, in a multi-file patch (diff-file-next).

M-{

Move to the previous file-start, in a multi-file patch (diff-file-prev).

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.

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.

C-c C-c

Go to the source file and line corresponding to this hunk (diff-goto-source).

C-c C-e

Start an Ediff session with the patch (diff-ediff-patch). See Ediff.

C-c C-n

Restrict the view to the current hunk (diff-restrict-view). See Narrowing. With a prefix argument of C-u, 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).

C-c C-s

Split the hunk at point (diff-split-hunk). This is 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 text 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 text within the region.

C-c C-w

Refine the current hunk so that it disregards changes in whitespace (diff-refine-hunk).

C-x 4 A

Generate a ChangeLog entry, like C-x 4 a does (see Change Log), 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.

M-x diff-show-trailing-whitespaces RET

Highlight trailing whitespace characters, except for those used by the patch syntax (see Useless Whitespace).

22.11 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 view-file allows you to scan or read a file by sequential screenfuls. It reads a file name argument using the minibuffer. After reading the file into an Emacs buffer, view-file displays the beginning. You can then type <SPC> to scroll forward one windowful, or <DEL> to scroll backward. Various other commands are provided for moving around in the file, but none for changing it; type ? while viewing for a list of them. They are mostly the same as normal Emacs cursor motion commands. To exit from viewing, type q. The commands for viewing are defined by a special minor mode called View mode.

A related command, M-x view-buffer, views a buffer already present in Emacs. See Misc Buffer.

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 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).

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 Customize Save.

M-x delete-file deletes the specified file, like the rm command in the shell. If you are deleting many files in one directory, it may be more convenient to use Dired rather than delete-file. See Dired.

On some systems, there is a facility called the “Trash” (or “Recycle Bin”); “deleting” a file normally means moving it into the Trash, and you can bring the file back from the Trash if you later change your mind. By default, Emacs does not use the Trash for file deletion—when Emacs deletes a file, it is gone forever. You can tell Emacs to use the Trash by changing the variable delete-by-moving-to-trash to t. This applies to file deletion via M-x delete-file, as well as M-x delete-directory (see Directories) and file deletion in Dired (see Dired Deletion). In addition, you can explicitly move a file into the Trash with the command M-x move-file-to-trash.

M-x rename-file reads two file names old and new using the minibuffer, then 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 the argument new is just a directory name, the real new name is in that directory, with the same non-directory component as old. For example, M-x rename-file RET ~/foo RET /tmp RET renames ~/foo to /tmp/foo. The same rule applies to all the remaining commands in this section. All of them ask for confirmation when the new file name already exists, too.

The similar command M-x add-name-to-file is used to add an additional name to an existing file without removing its 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, it works by copying the file.

M-x copy-file reads the file old and writes a new file named new with the same contents. M-x copy-directory does the same for directories, by recursive copying all files and subdirectories.

M-x make-symbolic-link reads two file names target and linkname, then creates a symbolic link named linkname, which points at target. The effect is that future attempts to open file linkname 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.

Not all systems support symbolic links; on systems that don't support them, this command is not defined.

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.

22.12 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.

22.13 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). 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 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. v extracts a file into a buffer in View mode. o extracts the file and displays it in another window, so you could edit the file and operate on the archive simultaneously. 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.

If your display supports colors and the mouse, moving the mouse pointer across a file name highlights that file name, indicating that you can click on it. Clicking Mouse-2 on the highlighted file name extracts the file into a buffer and displays that buffer.

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 archives produced by the programs arc, jar, lzh, zip, rar, and zoo, which have extensions corresponding to the program names. Archive mode also works for those 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 program to unpack and repack archives. Details of the program names and their options can be set in the ‘Archive’ Customize group. 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.

22.14 Remote Files

You can refer to files on other machines using a special file name syntax:

     /host:filename
     /user@host:filename
     /user@host#port:filename
     /method:user@host:filename
     /method:user@host#port:filename

To carry out this request, Emacs uses a remote-login program such as ftp, ssh, rlogin, or telnet. You can always specify in the file name which method to use—for example, /ftp:user@host:filename uses FTP, whereas /ssh:user@host:filename uses ssh. When you don't specify a method in the file name, Emacs chooses the method as follows:

1. If the host name starts with ‘ftp.’ (with dot), then Emacs uses FTP.
2. If the user name is ‘ftp’ or ‘anonymous’, then Emacs uses FTP.
3. If the variable tramp-default-method is set to ‘ftp’, then Emacs uses FTP.
4. If ssh-agent is running, then 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.

When the Ange-FTP package is used, Emacs logs in through FTP using your user name or the name user. It may ask you for a password from time to time (see Passwords); this is used for logging in on host. The form using port allows you to access servers running on a non-default TCP port.

If you want to disable backups for remote files, set the variable ange-ftp-make-backup-files to nil.

By default, the auto-save files (see Auto Save Files) for remote files are made in the temporary file directory on the local machine. This is achieved using the variable auto-save-file-name-transforms.

Normally, if you do not specify a user name in a remote file name, that means to use your own user name. But if you set the variable ange-ftp-default-user to a string, that string is used instead.

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 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>.

22.15 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’.

‘/:’ 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.

22.16 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-only 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 such as load-path or exec-path, whose value is a list of directory names.

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.

22.17 Convenience Features for Finding Files

In this section, we introduce some convenient facilities for finding recently-opened files, reading file names from a buffer, and viewing image files.

If you enable Recentf mode, with M-x recentf-mode, the ‘File’ menu includes a submenu containing a list of recently opened files. M-x recentf-save-list saves the current recent-file-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 FFAP), 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.

Visiting image files automatically selects Image mode. This major mode allows you to toggle between displaying the file as an image in the Emacs buffer, and displaying its underlying text representation, using the command C-c C-c (image-toggle-display). This works only when Emacs can display the specific image type. If the displayed image is wider or taller than the frame, the usual point motion keys (C-f, C-p, and so forth) cause different parts of the image to be displayed.

See also the Image-Dired package (see Image-Dired) for viewing images as thumbnails.

22.18 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 .emacs file (see Init File). This adds a ‘Filesets’ menu to the menu bar.

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 creates 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). Filesets need not be a simple list of files—you can also define filesets using 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.

Emacs uses the concept of a fileset elsewhere see Version Control to describe sets of files to be treated as a group for purposes of version control operations. Those filesets are unnamed and do not persist across Emacs sessions.

23 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 created to hold the file's text. Each time you invoke Dired, a buffer is created to hold the directory listing. If you send a message with C-x m, a buffer named ‘*mail*’ is used to hold the text of the message. When you ask for a command's documentation, that appears in a buffer called ‘*Help*’.

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 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 a buffer named ‘*scratch*’, which is not associated with any file and can be used for evaluating Lisp expressions in Emacs (see Lisp Interaction).

At any time, one and only one buffer is current. This is also called the selected buffer. We often say that a command operates on “the buffer”; this really means that the command operates on the current buffer (most commands do). When there is only one Emacs window, the buffer displayed in that window is current. When there are multiple windows present, the buffer displayed in the selected window is current. See Windows.

Each buffer records individually what file it is visiting (if any), whether it is modified, and what major mode and minor modes are in effect (see Major Modes). Any Emacs variable can be made local to a particular buffer, meaning its value in that buffer can be different from the value in other buffers. See Locals.

A buffer's size cannot be larger than some maximum, which is defined by the largest buffer position representable by the Emacs integer data type. This is because Emacs tracks buffer positions using that data type. For 32-bit machines, the largest buffer size is 512 megabytes.

• Select Buffer: Creating a new buffer or reselecting an old one.
• List Buffers: Getting a list of buffers that exist.
• Misc Buffer: Renaming; changing read-onlyness; copying text.
• Kill Buffer: Killing buffers you no longer need.
• Several Buffers: How to go through the list of all buffers and operate variously on several of them.
• Indirect Buffers: An indirect buffer shares the text of another buffer.
• Buffer Convenience: Convenience and customization features for buffer handling.

23.1 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 list of existing buffers.

C-x <RIGHT>

Select the next buffer in the list of existing buffers.

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.

To select the buffer named bufname, type C-x b bufname <RET>. This runs the command switch-to-buffer with argument bufname. While entering the buffer name, you can use the usual minibuffer completion and history commands (see Minibuffer). An empty argument to C-x b specifies the buffer that was current most recently among those not now displayed in any window.

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. First, however, Emacs might prompt you for confirmation, in case you entered the wrong buffer name. Emacs asks for confirmation only if the last key you typed, before submitting the minibuffer input with <RET>, was <TAB> (minibuffer-complete). This catches a common mistake, in which one types <RET> before realizing that <TAB> did not complete far enough to yield the desired buffer name (see Completion). Emacs asks for confirmation by putting the message ‘[Confirm]’ in the minibuffer; type <RET> again to confirm and visit the buffer.

The variable confirm-nonexistent-file-or-buffer controls whether Emacs asks for confirmation before visiting a buffer that did not previously exist. The default value, after-completion, gives the behavior we have just described. If the value is nil, Emacs never asks for confirmation; for any other non-nil value, Emacs always asks for confirmation. This variable also affects the find-file command (see Visiting).

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. The default value of the variable major-mode determines the new buffer's major mode; the default value is Fundamental mode. See Major Modes.

For conveniently switching between a few buffers, use the commands C-x <LEFT> and C-x <RIGHT>. C-x <RIGHT> (previous-buffer) selects the previous buffer (following the order of most recent selection in the current frame), while C-x <LEFT> (next-buffer) moves through buffers in the reverse direction.

To select a buffer in a window other than the current one, 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. By default, if displaying the buffer causes two vertically adjacent windows to be displayed, the heights of those windows are evened out; to countermand that and preserve the window configuration, set the variable even-window-heights to nil.

Similarly, C-x 5 b (switch-to-buffer-other-frame) prompts for a buffer name, displays that buffer in another frame, and selects that frame.

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.

You can control how certain buffers are handled by these commands by customizing the variables special-display-buffer-names, special-display-regexps, same-window-buffer-names, and same-window-regexps. See Force Same Window, and Special Buffer Frames, for more about these variables. In addition, if the value of display-buffer-reuse-frames is non-nil, and the buffer you want to switch to is already displayed in some frame, Emacs will just raise that frame.

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 Moving 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.

23.2 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. Each line in the list shows one buffer's name, 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.

‘.’ 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 Save Commands). 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  Fundamental

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.

23.3 Miscellaneous Buffer Operations

C-x C-q

Toggle read-only status of buffer (toggle-read-only).

M-x rename-buffer <RET> name <RET>

Change the name of the current buffer.

M-x rename-uniquely

Rename the current buffer by adding ‘<number>’ to the end.

M-x view-buffer <RET> buffer <RET>

Scroll through buffer buffer.

A buffer can be read-only, which means that commands to change its contents are not allowed. The mode line indicates read-only buffers with ‘%%’ or ‘%*’ near the left margin. Read-only buffers are usually made by subsystems such as Dired and Rmail that have special commands to operate on the text; also by visiting a file whose access control says you cannot write it.

If you wish to make changes in a read-only buffer, use the command C-x C-q (toggle-read-only). It 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 have files under version control, you may find it convenient to bind C-x C-q to vc-toggle-read-only instead. This will guard you against an operation that will confuse most modern version-conmtrol systems. See Version Control.

M-x 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.

M-x 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 an M-x info, you need to switch to some other buffer before using the command, in order for it to make a different buffer.)

M-x view-buffer is much like M-x view-file (see Misc File Ops) except that it examines an already existing Emacs buffer. View mode provides commands for scrolling through the buffer conveniently but not for changing it. When you exit View mode with q, that switches back to the buffer (and the position) which was previously displayed in the window. Alternatively, if you exit View mode with e, the buffer and the value of point that resulted from your perusal remain in effect.

The commands M-x append-to-buffer and M-x insert-buffer can be used to copy text from one buffer to another. See Accumulating Text.

23.4 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. On most operating systems, killing a buffer releases its space back to the operating system so that other programs can use it. Here are some commands for killing buffers:

C-x k bufname <RET>

Kill buffer bufname (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 y 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 Regexps. 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 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.

You can also have this buffer purging done for you, every day at midnight, 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.

23.5 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 List Buffers) does not merely list buffers. It also allows you to perform various operations on buffers, through an interface similar to Dired (see Dired). 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 Emacs cursor motion commands can be used in this buffer. The following commands apply to the buffer described on the current line:

d

Request to delete (kill) the buffer, then move down. The request shows as a ‘D’ on the line, before the buffer name. Requested deletions take place when you type the x command.

C-d

Like d but move up afterwards instead of down.

s

Request to save the buffer. The request shows as an ‘S’ on the line. Requested saves take place when you type the x command. You may request both saving and deletion for the same buffer.

x

Perform previously requested deletions and saves.

u

Remove any request made for the current line, and move down.

<DEL>

Move to previous line and remove any request made for that line.

The d, C-d, s and u commands to add or remove flags also move down (or up) one line. They accept a numeric argument as a repeat count.

These commands operate immediately on the buffer listed on the current line:

~

Mark the buffer “unmodified.” The command ~ does this immediately when you type it.

%

Toggle the buffer's read-only flag. The command % does this immediately when you type it.

t

Visit the buffer as a tags table. See Select Tags Table.

There are also commands to select another buffer or buffers:

q

Quit the buffer menu—immediately display the most recent formerly visible buffer in its place.

<RET>

f

Immediately select this line's buffer in place of the ‘*Buffer List*’ buffer.

o

Immediately select this line's buffer in another window as if by C-x 4 b, leaving ‘*Buffer List*’ visible.

C-o

Immediately display this line's buffer in another window, but don't select the window.

1

Immediately select this line's buffer in a full-screen window.

2

Immediately set up two windows, with this line's buffer selected in one, and the previously current buffer (aside from the buffer ‘*Buffer List*’) displayed in the other.

b

Bury the buffer listed on this line.

m

Mark this line's buffer to be displayed in another window if you exit with the v command. The request shows as a ‘>’ at the beginning of the line. (A single buffer may not have both a delete request and a display request.)

v

Immediately select this line's buffer, and also display in other windows any buffers previously marked with the m command. If you have not marked any buffers, this command is equivalent to 1.

There is also a command that affects the entire buffer list:

T

Delete, or reinsert, lines for non-file buffers. This command toggles the inclusion of such buffers in the buffer list.

What buffer-menu actually does is create and switch to a suitable buffer, and turn on Buffer Menu mode in it. Everything else described above is implemented by the special commands provided in Buffer Menu mode. One consequence of this is that you can switch from the ‘*Buffer List*’ buffer to another Emacs buffer, and edit there. You can reselect the ‘*Buffer List*’ buffer later, to perform the operations already requested, or you can kill it, or pay no further attention to it.

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.

23.6 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 the analogue, for buffers, 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 whose base buffer is 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. 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 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 Outline Views.

A quick and handy way to make an indirect buffer is with the command M-x clone-indirect-buffer. 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. C-x 4 c (clone-indirect-buffer-other-window) works like M-x clone-indirect-buffer, but it selects the new buffer in another window. These functions run the hook clone-indirect-buffer-hook after creating the indirect buffer.

The more general way to make an indirect buffer is with the command M-x make-indirect-buffer. It creates an indirect buffer from buffer base-buffer, under the name indirect-name. It prompts for both base-buffer and indirect-name using the minibuffer.

23.7 Convenience Features and Customization of Buffer Handling

This section describes several modes and features that make it more convenient to switch between buffers.

• Uniquify: Making buffer names unique with directory parts.
• Iswitchb: Switching between buffers with substrings.
• Buffer Menus: Configurable buffer menu.

23.7.1 Making Buffer Names Unique

When several buffers visit identically-named files, Emacs must give the buffers distinct names. The usual method for making buffer names unique adds ‘<2>’, ‘<3>’, etc. to the end of the buffer names (all but one of them).

Other methods work by adding parts of each file's directory to the buffer name. To select one, load the library uniquify (e.g. using (require 'uniquify)), and customize the variable uniquify-buffer-name-style (see Easy Customization).

To begin with, 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’, respectively (instead of ‘Makefile’ and ‘Makefile<2>’).

In contrast, the post-forward naming method would call the buffers ‘Makefile|tmp’ and ‘Makefile|zaphod’, and 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’.

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.

23.7.2 Switching Between Buffers using Substrings

Iswitchb global minor mode provides convenient switching between buffers using substrings of their names. It replaces the normal definitions of C-x b, C-x 4 b, C-x 5 b, and C-x 4 C-o with alternative commands that are somewhat “smarter.”

When one of these commands prompts you for a buffer name, you can type in just a substring of the name you want to choose. As you enter the substring, Iswitchb mode continuously displays a list of buffers that match the substring you have typed.

At any time, you can type <RET> to select the first buffer in the list. So the way to select a particular buffer is to make it the first in the list. There are two ways to do this. You can type more of the buffer name and thus narrow down the list, excluding unwanted buffers above the desired one. Alternatively, you can use C-s and C-r to rotate the list until the desired buffer is first.

<TAB> while entering the buffer name performs completion on the string you have entered, based on the displayed list of buffers.

To enable Iswitchb mode, type M-x iswitchb-mode, or customize the variable iswitchb-mode to t (see Easy Customization).

23.7.3 Customizing Buffer Menus

M-x bs-show

Make a list of buffers similarly to M-x list-buffers but customizable.

M-x bs-show pops up a buffer list similar to the one normally displayed by C-x C-b but which you can customize. 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).

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 bindings of mouse-buffer-menu, normally on C-Down-Mouse-1, and the menu bar buffer menu. You can customize the menu in the msb Custom group.

24 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.

• Basic Window: Introduction to Emacs windows.
• Split Window: New windows are made by splitting existing windows.
• Other Window: Moving to another window or doing something to it.
• Pop Up Window: Finding a file or buffer in another window.
• Force Same Window: Forcing certain buffers to appear in the selected window rather than in another window.
• Change Window: Deleting windows and changing their sizes.
• Window Convenience: Convenience functions for window handling.

24.1 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. The terminal's cursor shows the location of point in this window. Each other window has a location of point as well. On text-only terminals, there is no way to show where those locations are, since the terminal has only one cursor. On a graphical display, the location of point in a non-selected window is indicated by a hollow box; the cursor in the selected window is blinking or solid.

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 commands such as C-x b to switch buffers in the selected window; 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), work by switching 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 Mode Line, for full details on the mode line.

24.2 Splitting Windows

C-x 2

Split the selected window into two windows, one above the other (split-window-vertically).

C-x 3

Split the selected window into two windows positioned side by side (split-window-horizontally).

C-Mouse-2

In the mode line or scroll bar of a window, split that window.

The command C-x 2 (split-window-vertically) breaks the selected window into two windows, one above the other. Both windows start out displaying the same buffer, with the same value of point. By default the two windows each get half the height of the window that was split; a numeric argument specifies how many lines to give to the top window.

C-x 3 (split-window-horizontally) breaks the selected window into two side-by-side windows. A numeric argument specifies how many columns to give the one on the left. If you are not using scrollbars, a vertical line separates the two windows. You can customize its color with the face vertical-border. Windows that are not the full width of the screen have mode lines, but they are truncated. On terminals where Emacs does not support highlighting, truncated mode lines sometimes do not appear in inverse video.

You can split a window horizontally or vertically by clicking C-Mouse-2 in the mode line or the scroll bar. The line of splitting goes through the place where you click: if you click on the mode line, the new scroll bar goes above the spot; if you click in the scroll bar, the mode line of the split window is side by side with your click.

When a window occupies less than the full width of the frame, it may become too narrow for most of the text lines in its buffer. If most of its lines are continued (see Continuation Lines), the buffer may become difficult to read. Therefore, Emacs automatically truncates lines 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 truncate-partial-width-windows is a positive integer (the default is 50), that specifies the minimum 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.

Horizontal scrolling is often used in side-by-side windows. See Horizontal Scrolling.

If split-window-keep-point is non-nil, the default, both of the windows resulting from C-x 2 inherit the value of point from the window that was split. This means that scrolling is inevitable. If this variable is nil, then C-x 2 tries to avoid scrolling the text currently visible on the screen, by putting point in each window at a position already visible in the window. It also selects whichever window contains the screen line that the cursor was previously on. Some users prefer that mode on slow terminals.

24.3 Using Other Windows

C-x o

Select another window (other-window). That is o, not zero.

C-M-v

Scroll the next window (scroll-other-window).

M-x compare-windows

Find next place where the text in the selected window does not match the text in the next window.

Mouse-1

Mouse-1, in a window's mode line, selects that window but does not move point in it (mouse-select-window).

To select a different window, click with Mouse-1 on its mode line. 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 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 Minibuffer Edit.

The usual scrolling commands (see Display) apply to the selected window only, but there is one command to scroll the next window. C-M-v (scroll-other-window) scrolls the window that C-x o would select. It takes arguments, positive and negative, like C-v. (In the minibuffer, C-M-v scrolls the window that contains the minibuffer help display, if any, rather than the next window in the standard cyclic order.)

The command M-x compare-windows lets you compare two files or buffers visible in two windows, by moving through them to the next mismatch. See Comparing Files, for details.

If you set mouse-autoselect-window to a non-nil value, moving the mouse into a different window selects that window. This feature is off by default.

24.4 Displaying in Another Window

C-x 4 is a prefix key for commands that select another window (splitting the window if there is only one) and select a buffer in that window. Different C-x 4 commands have different ways of finding the buffer to select.

C-x 4 b bufname <RET>

Select buffer bufname in another window. This runs switch-to-buffer-other-window.

C-x 4 C-o bufname <RET>

Display buffer bufname in another window, but don't select that buffer or that window. This runs display-buffer.

C-x 4 f filename <RET>

Visit file filename and select its buffer in another window. This runs find-file-other-window. See Visiting.

C-x 4 d directory <RET>

Select a Dired buffer for directory directory in another window. This runs dired-other-window. See Dired.

C-x 4 m

Start composing a mail message in another window. This runs mail-other-window; its same-window analogue is C-x m (see Sending Mail).

C-x 4 .

Find a tag in the current tags table, in another window. This runs find-tag-other-window, the multiple-window variant of M-. (see Tags).

C-x 4 r filename <RET>

Visit file filename read-only, and select its buffer in another window. This runs find-file-read-only-other-window. See Visiting.

By default, these commands split the window vertically when there is only one. You can customize the variables split-height-threshold and split-width-threshold to split the window horizontally instead.

24.5 Forcing Display in the Same Window

Certain Emacs commands switch to a specific buffer with special contents. For example, M-x shell switches to a buffer named ‘*shell*’. By convention, all these commands are written to pop up the buffer in a separate window. But you can specify that certain of these buffers should appear in the selected window.

If you add a buffer name to the list same-window-buffer-names, the effect is that such commands display that particular buffer by switching to it in the selected window. For example, if you add the element "*grep*" to the list, the grep command will display its output buffer in the selected window.

The default value of same-window-buffer-names is not nil: it specifies buffer names ‘*info*’, ‘*mail*’ and ‘*shell*’ (as well as others used by more obscure Emacs packages). This is why M-x shell normally switches to the ‘*shell*’ buffer in the selected window. If you delete this element from the value of same-window-buffer-names, the behavior of M-x shell will change—it will pop up the buffer in another window instead.

You can specify these buffers more generally with the variable same-window-regexps. Set it to a list of regular expressions; then any buffer whose name matches one of those regular expressions is displayed by switching to it in the selected window. (Once again, this applies only to buffers that normally get displayed for you in a separate window.) The default value of this variable specifies Telnet and rlogin buffers.

An analogous feature lets you specify buffers which should be displayed in their own individual frames. See Special Buffer Frames.

24.6 Deleting and Rearranging Windows

C-x 0

Delete the selected window (delete-window). The last character in this key sequence is a zero.

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 ^

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 a window, type C-x 0 (delete-window). (That is a zero.) The space occupied by the deleted window is given to an adjacent window (but not the minibuffer window, even if that is active at the time). Once a window is deleted, its attributes are forgotten; only restoring a window configuration can bring it back. Deleting the window has no effect on the buffer it used to display; the buffer continues to exist, and you can select it in any window with C-x b.

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) is more powerful in a different way; it deletes all the windows except the selected one (and the minibuffer); the selected window expands to use the whole frame except for the echo area.

To readjust the division of space among vertically adjacent windows, use C-x ^ (enlarge-window). It makes the currently selected window one line bigger, or as many lines as is specified with a numeric argument. With a negative argument, it makes the selected window smaller. C-x } (enlarge-window-horizontally) makes the selected window wider by the specified number of columns. C-x { (shrink-window-horizontally) makes the selected window narrower by the specified number of columns.

When you make a window bigger, the space comes from its peers. If this makes any window too small, it is deleted and its space is given to an adjacent window. The minimum size is specified by the variables window-min-height and window-min-width.

The command 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.

Mouse clicks on the mode line provide another way to change window heights and to delete windows. See Mode Line Mouse.

24.7 Window Handling Convenience Features and Customization

M-x 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. To undo, use C-c left (winner-undo). If you change your mind while undoing, you can redo the changes you had undone using C-c right (M-x winner-redo). Another way to enable Winner mode is by customizing the variable winner-mode.

The Windmove commands move 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. M-x windmove-default-keybindings binds these commands to S-right etc. (Not all terminals support shifted arrow keys, however.)

Follow minor 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.

M-x scroll-all-mode provides commands to scroll all visible windows together. You can also turn it on by customizing the variable scroll-all-mode. The commands provided are M-x scroll-all-scroll-down-all, M-x scroll-all-page-down-all and their corresponding “up” equivalents. To make this mode useful, you should bind these commands to appropriate keys.

25 Frames and Graphical Displays

When using a graphical display, you can create multiple system-level “windows” in a single Emacs session. We refer to these system-level windows as frames. A frame initially contains a single Emacs window; however, you can subdivide this Emacs window into smaller windows, all fitting into the same frame. Each frame normally contains its own echo area and minibuffer.

To avoid confusion, we reserve the word “window” for the subdivisions that Emacs implements, and never use it to refer to a frame.

Any editing you do in one frame affects the other frames. For instance, if you put text in the kill ring in one frame, you can yank it in another frame. If you exit Emacs through C-x C-c in one frame, it terminates all the frames. To delete just one frame, use C-x 5 0 (that is zero, not o).

Emacs compiled for MS-DOS emulates some windowing functionality, so that you can use many of the features described in this chapter. See MS-DOS Mouse.

• Cut and Paste: Mouse commands for cut and paste.
• Mouse References: Using the mouse to select an item from a list.
• Menu Mouse Clicks: Mouse clicks that bring up menus.
• Mode Line Mouse: Mouse clicks on the mode line.
• Creating Frames: Creating additional Emacs frames with various contents.
• Frame Commands: Iconifying, deleting, and switching frames.
• Fonts: Changing the frame font.
• Speedbar: How to make and use a speedbar frame.
• Multiple Displays: How one Emacs job can talk to several displays.
• Special Buffer Frames: You can make certain buffers have their own frames.
• Frame Parameters: Changing the colors and other modes of frames.
• Scroll Bars: How to enable and disable scroll bars; how to use them.
• Wheeled Mice: Using mouse wheels for scrolling.
• Drag and Drop: Using drag and drop to open files and insert text.
• Menu Bars: Enabling and disabling the menu bar.
• Tool Bars: Enabling and disabling the tool bar.
• Dialog Boxes: Controlling use of dialog boxes.
• Tooltips: Displaying information at the current mouse position.
• Mouse Avoidance: Preventing the mouse pointer from obscuring text.
• Non-Window Terminals: Multiple frames on terminals that show only one.
• Text-Only Mouse: Using the mouse in text-only terminals.

25.1 Cutting and Pasting on Graphical Displays

This section describes commands for selecting a region, cutting, and pasting using the mouse.

• Mouse Commands: Moving, cutting, and pasting, with the mouse.
• Word and Line Mouse: Mouse commands for selecting whole words or lines.
• Cut/Paste Other App: Transfering text between Emacs and other apps.
• Secondary Selection: Cutting without altering point and mark.
• Clipboard: Using the clipboard for selections.

25.1.1 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 copy it to the kill ring (mouse-set-region).

Mouse-2

Yank the last killed text at the click position (mouse-yank-at-click).

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).

The most basic mouse command is mouse-set-point, which is called 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.

Normally, Emacs does not distinguish between ordinary mouse clicks and clicks that select a frame. When you click on a frame to select it, that also changes the selected window and cursor position according to the mouse click position. On the X window system, you can change this behavior by setting the variable x-mouse-click-focus-ignore-position to t. Then the first click selects the frame, but does not affect the selected window or cursor position. If you click again in the same place, that click will be in the selected frame, so it will change the window or cursor position.

Holding down Mouse-1 and “dragging” the mouse over a stretch of text activates the region around that text (mouse-set-region). See Mark. Emacs places the mark where you started holding down the mouse button, and point where you release it. In addition, the region is copied into the kill ring (see Kill Ring). If you don't want Emacs to copy the region, change the variable mouse-drag-copy-region to nil.

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.

Clicking with the middle mouse button, Mouse-2, moves point to the position where you clicked and performs a yank (mouse-yank-at-click). See Yanking. If you change the variable mouse-yank-at-point to a non-nil value, Mouse-2 does not move point. Then it does not matter where you click, or even which of the frame's windows you click on; the yank occurs at the existing point. This variable also affects yanking the primary and secondary selections (see Cut/Paste Other App).

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. In addition, the text in the region is copied to the kill ring.
• 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, 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.

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. While the region remains active, typing <Backspace> or <Delete> deletes the text in that region and deactivates the mark; this behavior follows a convention established by other graphical programs, and it does not apply when you set the region any other way, including shift-selection (see Shift Selection).

Many graphical applications also follow the convention that insertion while text is selected deletes the selected text. You can make Emacs behave this way by enabling Delete Selection mode. See Using Region.

25.1.2 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 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 singlequote or doublequote in C) selects the string constant (Emacs uses heuristics to figure out whether that character is the beginning or the end of it).

Double-Drag-Mouse-1

Select the text you drag across, in the form of whole words.

Triple-Mouse-1

Select the line you click on.

Triple-Drag-Mouse-1

Select the text you drag across, in the form of whole lines.

25.1.3 Cut and Paste with Other Window Applications

When running Emacs under the X window system, you can easily transfer text between Emacs and other X applications using the primary selection (also called the X selection). This is not the same thing as the clipboard, which is a separate facility used on desktop environments such as Gnome, and on operating systems such as Microsoft Windows (see Clipboard).

Under X, whenever you select some text in Emacs by dragging or clicking the mouse (see Mouse Commands), it is also saved in the primary selection. You can then paste that text into any other X application, usually by clicking Mouse-2 in that application. Unlike the Emacs kill ring (see Kill Ring), the primary selection has no “memory”: each time you save something in the primary selection, either in Emacs or in another X application, the previous contents of the primary selection are lost.

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.

Whenever you kill some text using a command such as C-w (kill-region), or copy it into the kill ring using a command such as M-w (kill-ring-save), that text is also saved in the primary selection. See Killing.

If you set the region using the keyboard—for instance, by typing C-<SPC> and moving point away from the mark—the text in the region is not normally saved to the primary selection. However, if you change the variable select-active-regions to t, the region is saved to the primary selection whenever you activate the mark. Each change to the region also updates the primary selection.

If you change yank-pop-change-selection to t, rotating the kill ring with M-y (yank-pop) also saves the new yank to the primary selection (see Yanking).

If you change save-interprogram-paste-before-kill to t, each kill command first saves the existing selection onto the kill ring. This prevents you from losing the existing selection, at the risk of large memory consumption if other applications generate large selections.

Whenever Emacs saves some text to the primary selection, it may also save it to the cut buffer. The cut buffer is an obsolete predecessor to the primary selection; most modern applications do not use it. Saving text to the cut buffer is slow and inefficient, so Emacs only does it if the text is shorter than the value of x-cut-buffer-max (20000 characters by default).

You can yank the primary selection into Emacs using the usual yank commands, such as C-y (yank) and Mouse-2 (mouse-yank-at-click). These commands actually check the primary selection before referring to the kill ring; if no primary selection is available, the kill ring contents are used. To prevent yank commands from accessing the primary selection, set the variable x-select-enable-primary to nil.

The standard coding system for the primary selection is compound-text-with-extensions. You may find that the pasted text is not what you expected. In such a case, you can specify another coding system for the selection by typing C-x <RET> x or C-x <RET> X. Alternatively, you can request a different data type by modifying the variable x-select-request-type. See Communication Coding.

25.1.4 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).

This command does not alter the kill ring.

M-Mouse-1

Set one endpoint for the secondary selection (mouse-start-secondary).

M-Mouse-3

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

25.1.5 Using the Clipboard

In desktop environments such as Gnome, and operating systems such as Microsoft Windows and Mac OS X, you can transfer data (usually text) between different applications using the clipboard. The clipboard is distinct from the primary selection and secondary selection discussed earlier. You can access the clipboard through the ‘Edit’ menu of the menu bar (see Menu Bar).

The command clipboard-kill-region, which is bound to the Cut menu item, kills the region and saves it in the clipboard.

The command clipboard-kill-ring-save, which is bound to the Copy menu item, copies the region to the kill ring and saves it in the clipboard.

The Paste menu item in the Edit menu yanks the contents of the clipboard at point (clipboard-yank).

You can customize the variable x-select-enable-clipboard to make the Emacs yank functions consult the clipboard before the primary selection, and to make the kill functions to store in the clipboard as well as the primary selection. Otherwise, these commands do not access the clipboard at all. Using the clipboard is the default on MS-Windows and Mac OS, but not on other systems.

25.2 Following References with the Mouse

Some Emacs buffers include buttons. A button is a piece of text that performs some action when you activate it, such as following a reference. 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, typing <RET> or clicking on a file name in a Dired buffer visits that file (see Dired). Doing it on an error message in the ‘*Compilation*’ buffer goes to the source code for that error message (see Compilation). Doing it on a completion in the ‘*Completions*’ buffer chooses that completion (see Completion).

Although clicking Mouse-1 on a button usually activates that button, if you hold the mouse button down for a short period of time before releasing it (specifically, for more than 450 milliseconds), then Emacs moves point where you clicked instead. This behavior allows you to use the mouse to move point over a button without following it. Dragging—moving the mouse while it is held down—has its usual behavior of setting the region, even if you drag from or onto a button.

Normally, clicking Mouse-1 on a button activates the button even if it is in a nonselected window. If you change the variable mouse-1-click-in-non-selected-windows to nil, clicking Mouse-1 on a button in an un-selected window moves point to the clicked position and selects that window, without activating the button.

In Emacs versions before 22, only Mouse-2 activates buttons and Mouse-1 always sets point. If you prefer this older behavior, set the variable mouse-1-click-follows-link to nil. This variable also lets you choose various other alternatives for following links with the mouse. Type C-h v mouse-1-click-follows-link <RET> for more details.

25.3 Mouse Clicks for Menus

Several mouse clicks with the <CTRL> and <SHIFT> modifiers bring up menus.

C-Mouse-1

This menu is for selecting a buffer.

The MSB (“mouse select buffer”) global minor mode makes this menu smarter and more customizable. See Buffer Menus.

C-Mouse-2

This menu is for specifying faces and other text properties for editing formatted text. See Formatted Text.

C-Mouse-3

This menu is mode-specific. For most modes if Menu-bar mode is on, this menu has the same items as all the mode-specific menu-bar menus put together. Some modes may specify a different menu for this button.⁹ If Menu-bar mode is off, this menu contains all the items which would be present in the menu bar—not just the mode-specific ones—so that you can access them without having to display the menu bar.

S-Mouse-1

This menu is for changing the default face within the window's buffer. See Temporary Face Changes.

25.4 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 buries the current buffer instead, and switches to another buffer.

C-Mouse-2

C-Mouse-2 on a mode line splits the window above horizontally, above the place in the mode line where you click.

Using Mouse-1 on the divider between two side-by-side mode lines, you can move the vertical boundary left or right. Using C-Mouse-2 on a scroll bar splits the corresponding window vertically. See Split Window.

25.5 Creating Frames

The prefix key C-x 5 is analogous to C-x 4, with parallel subcommands. The difference is that C-x 5 commands create a new frame rather than just a new window in the selected frame (see Pop Up Window). If an existing visible or iconified (“minimized”) frame already displays the requested material, these commands use the existing frame, after raising or deiconifying (“un-minimizing”) as necessary.

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 (make-frame-command).

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.

C-x 5 d directory <RET>

Select a Dired buffer for directory directory in another frame. This runs dired-other-frame. See Dired.

C-x 5 m

Start composing a mail message in another frame. This runs mail-other-frame. It is the other-frame variant of C-x m. See Sending Mail.

C-x 5 .

Find a tag in the current tag table in another frame. This runs find-tag-other-frame, the multiple-frame variant of M-.. See Tags.

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.

You can control the appearance of new frames you create by setting the frame parameters in default-frame-alist. You can use the variable initial-frame-alist to specify parameters that affect only the initial frame. See Initial Parameters, for more information.

Here is an example of using default-frame-alist to specify the default foreground color and font:

     (add-to-list 'default-frame-alist '(font . "10x20"))
     (add-to-list 'default-frame-alist '(foreground-color . "blue"))

By putting such customizations in your init file, you can control the appearance of all the frames Emacs creates, including the initial one (see Init File). See Fonts, for other ways to set the default font.

25.6 Frame Commands

The following commands let you create, delete and operate on frames:

C-z

Minimize (or “iconify) the selected Emacs frame (suspend-frame). See Exiting.

C-x 5 0

Delete the selected frame (delete-frame). This is not allowed if there is only one frame.

C-x 5 o

Select another frame, raise it, and warp the mouse to it. If you repeat this command, it cycles through all the frames on your terminal.

C-x 5 1

Delete all frames except the selected one.

The C-x 5 0 (delete-frame) command will never delete the last frame, to prevent you from losing the ability to interact with the Emacs process. Note that when Emacs is run as a daemon (see Emacs 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.

On X, you may have to tell Emacs how the system (or the window manager) handles focus-switching between windows, in order for the command C-x 5 o (other-frame) to work properly. Unfortunately, there is no way for Emacs to detect this automatically, so you should set the variable focus-follows-mouse. If simply moving the mouse onto a window selects it and gives it focus, the variable should be t; if you have to click on the window to select it, the variable should be nil. The default is t.

The window manager that is part of MS-Windows always gives focus to a frame that raises, so this variable has no effect in the native MS-Windows build of Emacs.

25.7 Fonts

By default, Emacs displays text in X using a 12-point monospace font. There are several different ways to specify a different font:

• Click on ‘Set Default Font’ in the ‘Options’ menu. To save this for future sessions, click on ‘Save Options’ in the ‘Options’ menu.
• Add a line to your init file (see Init File), modifying the variable default-frame-alist to specify the font parameter (see Creating Frames), like this:

            (add-to-list 'default-frame-alist '(font . "DejaVu Sans Mono-12"))
  

• 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 Resources. When specifying a font in your X resources file, you should not quote it.

• If you are running Emacs on the GNOME desktop, you can tell Emacs to use the default system font by setting the variable font-use-system-font to t (the default is nil). For this to work, Emacs must be compiled with Gconf support; this is done automatically if the libraries are present at compile time.
• Use the command line option ‘-fn’ (or ‘--font’). See Font X.

On X, 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 braces may be omitted. Here, fontname is the family name of the font, such as ‘Monospace’ or ‘DejaVu Serif’; 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

See the Fontconfig manual for a more detailed description of Fontconfig patterns. This manual is located in the file fontconfig-user.html, distributed with Fontconfig. It is also available online at http://fontconfig.org/fontconfig-user.html. In particular, that manual describes additional font properties that influence how the font is hinted, antialiased, or scaled.

The second way to specify a font is to use a GTK font description. 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 are as follows:

‘style’

One of ‘roman’, ‘italic’ or ‘oblique’. If omitted, the ‘roman’ style is used.

‘weight’

One of ‘medium’, ‘ultra-light’, ‘light’, ‘semi-bold’, or ‘bold’. If omitted, ‘medium’ weight is used.

Here are some examples of GTK font descriptions:

     Monospace 12
     Monospace Bold Italic 12

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. 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 ‘condensed’, ‘extended’, ‘semicondensed’ or ‘normal’ (some font names support other values).

style

An optional additional style name. Usually it is empty—most long font names have two hyphens in a row at this point.

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

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*' | egrep "^[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 Faces), or a particular frame (see Frame Parameters).

25.8 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 file name visits that file in the selected window of the attached frame, and clicking on a directory name shows that directory in the speedbar (see Mouse References). 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.

25.9 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.

It is even possible to use this feature to let two or more users type simultaneously on the two displays, within the same Emacs job. In practice, however, the different users can easily interfere with each others' edits if they are not careful.

25.10 Special Buffer Frames

You can make certain chosen buffers, which Emacs normally displays in “another window,” appear in special frames of their own. To do this, set the variable special-display-buffer-names to a list of buffer names; any buffer whose name is in that list automatically gets a special frame, when an Emacs command wants to display it “in another window.”

For example, if you set the variable this way,

     (setq special-display-buffer-names
           '("*Completions*" "*grep*" "*tex-shell*"))

then completion lists, grep output and the TeX mode shell buffer get individual frames of their own. These frames, and the windows in them, are never automatically split or reused for any other buffers. They continue to show the buffers they were created for, unless you alter them by hand. Killing the special buffer deletes its frame automatically.

More generally, you can set special-display-regexps to a list of regular expressions; then a buffer gets its own frame if its name matches any of those regular expressions. (Once again, this applies only to buffers that normally get displayed for you in “another window.”)

The variable special-display-frame-alist specifies the frame parameters for these frames. It has a default value, so you don't need to set it.

For those who know Lisp, an element of special-display-buffer-names or special-display-regexps can also be a list. Then the first element is the buffer name or regular expression; the rest of the list specifies how to create the frame. It can be an association list specifying frame parameter values; these values take precedence over parameter values specified in special-display-frame-alist. If you specify the symbol same-window as a “frame parameter” in this list, with a non-nil value, that means to use the selected window if possible. If you use the symbol same-frame as a “frame parameter” in this list, with a non-nil value, that means to use the selected frame if possible.

Alternatively, the value can have this form:

     (function args...)

where function is a symbol. Then the frame is constructed by calling function; its first argument is the buffer, and its remaining arguments are args.

An analogous feature lets you specify buffers which should be displayed in the selected window. See Force Same Window. The same-window feature takes precedence over the special-frame feature; therefore, if you add a buffer name to special-display-buffer-names and it has no effect, check to see whether that feature is also in use for the same buffer name.

25.11 Setting Frame Parameters

These commands are available for controlling the window management behavior of the selected frame:

M-x auto-raise-mode

Toggle whether or not the selected frame should auto-raise. Auto-raise means that every time you move the mouse onto the frame, it raises the frame.

Some window managers also implement auto-raise. If you enable auto-raise for Emacs frames in your window manager, it will work, but it is beyond Emacs' control, so auto-raise-mode has no effect on it.

M-x auto-lower-mode

Toggle whether or not the selected frame should auto-lower. Auto-lower means that every time you move the mouse off the frame, the frame moves to the bottom of the stack on the screen.

The command auto-lower-mode has no effect on auto-lower implemented by the window manager. To control that, you must use the appropriate window manager features.

In Emacs versions that use an X toolkit, the color-setting and font-setting functions don't affect menus and the menu bar, since they are displayed by their own widget classes. To change the appearance of the menus and menu bar, you must use X resources (see Resources). See Colors, regarding colors. See Font X, regarding choice of font.

Colors, fonts, and other attributes of the frame's display can also be customized by setting frame parameters in the variable default-frame-alist (see Creating Frames). For a detailed description of frame parameters and customization, see Frame Parameters.

25.12 Scroll Bars

On graphical displays, Emacs normally makes a scroll bar at the left of each Emacs window, running the height of the window.¹⁰

When Emacs is compiled with GTK+ support on the X window system, or in operating systems such as Microsoft Windows or Mac OS, you can use the scroll bar as you do in other graphical applications. If you click Mouse-1 on the scroll bar's up and down buttons, that scrolls the window by one line at a time. 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 Moving Point). Dragging the inner box with Mouse-1 scrolls the window continuously.

If Emacs is compiled without GTK+ support on the X window system, the scroll bar behaves differently. The scroll bar's inner box is drawn to represent the portion of the buffer currently displayed, with the entire height of the scroll bar representing the entire length of the buffer. Mouse-1 anywhere on the scroll bar scrolls forward like C-v, and Mouse-3 scrolls backward like M-v. Clicking Mouse-2 in the scroll bar lets you move or drag the inner box up and down.

You can also click C-Mouse-2 in the scroll bar to split a window vertically. The split occurs on the line where you click.

You can toggle the use of the scroll bar with the command M-x scroll-bar-mode. With a prefix argument, this command turns use of scroll bars on if and only if the argument is positive. This command applies to all frames, including frames yet to be created. Customize the variable scroll-bar-mode to control the use of scroll bars at startup. You can use it to specify that they are placed at the right of windows if you prefer that. You have to set this variable through the ‘Customize’ interface (see Easy Customization), or it will not work properly. You can also use the X resource ‘verticalScrollBars’ to control the initial setting of Scroll Bar mode. See Resources.

To enable or disable scroll bars for just the selected frame, use the command M-x toggle-scroll-bar.

You can control the scroll bar width by changing the value of the scroll-bar-width frame parameter.

25.13 Scrolling With “Wheeled” Mice

Some mice have a “wheel” instead of a third button. You can usually click the wheel to act as either Mouse-2 or Mouse-3, depending on the setup. You can also use the wheel to scroll windows instead of using the scroll bar or keyboard commands. Mouse wheel support only works if the system generates appropriate events; whenever possible, it is turned on by default. To toggle this feature, use M-x mouse-wheel-mode.

The two 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.

25.14 Drag and Drop

Emacs supports drag and drop using the mouse. 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.

25.15 Menu Bars

You can turn display of menu bars on or off with M-x menu-bar-mode or by customizing the variable menu-bar-mode. With no argument, this command toggles Menu Bar mode, a minor mode. With an argument, the command turns Menu Bar mode on if the argument is positive, off if the argument is not positive. You can use the X resource ‘menuBar’ to control the initial setting of Menu Bar mode. See Resources.

Expert users often turn off the menu bar, especially on text-only terminals, where this makes one additional line available for text. If the menu bar is off, you can still pop up a menu of its contents with C-Mouse-3 on a display which supports pop-up menus. See Menu Mouse Clicks.

See Menu Bar, for information on how to invoke commands with the menu bar. See X Resources, for how to customize the menu bar menus' visual appearance.

25.16 Tool Bars

The tool bar is a line (or lines) of icons at the top of the Emacs window, just below the menu bar. You can click on these icons with the mouse to do various jobs.

The global tool bar contains general commands. Some major modes define their own tool bars to replace it. A few “special” modes that are not designed for ordinary editing remove some items from the global tool bar.

Tool bars work only on a graphical display. The tool bar uses colored XPM icons if Emacs was built with XPM support. Otherwise, the tool bar uses monochrome icons (PBM or XBM format).

You can turn display of tool bars on or off with M-x tool-bar-mode or by customizing the option tool-bar-mode.

25.17 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.

In GTK+ versions 2.4 through 2.10, you can choose to use an older version of the GTK+ file dialog by setting the variable x-gtk-use-old-file-dialog to a non-nil value. If Emacs is built with a GTK+ version that has only one file dialog, this variable has no effect.

25.18 Tooltips

Tooltips are small windows that display text information at the current mouse position. They activate when there is a pause in mouse movement. There are two types of tooltip: help tooltips and GUD tooltips.

Help tooltips typically display over text—including the mode line—but are also available for other parts of the Emacs frame, such as the tool bar and menu items.

You can toggle display of help tooltips (Tooltip mode) with the command M-x tooltip-mode. When Tooltip mode is disabled, the help text is displayed in the echo area instead.

GUD tooltips show values of variables. They are useful when you are debugging a program. See Debugger Operation.

The variables tooltip-delay specifies how long Emacs should wait before displaying a tooltip. For additional customization options for displaying tooltips, use M-x customize-group <RET> tooltip <RET>. See X Resources, for information on customizing the windows that display tooltips.

25.19 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.

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 mouse to the upper-right corner on any key-press;

exile

Move the mouse to the corner 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 mouse, displace the mouse a random distance & 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.

25.20 Non-Window Terminals

On a text-only 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.

25.21 Using a Mouse in Terminal Emulators

Some text-only 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 use of the mouse—basically, only non-modified single clicks are supported. 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 terminal mouse support. You must have the gpm package installed and running on your system in order for this to work.

26 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 Cyrillic, Devanagari (for Hindi and Marathi), Ethiopic, Greek, Han (for Chinese and Japanese), Hangul (for Korean), Hebrew, IPA, Kannada, Lao, Malayalam, Tamil, Thai, Tibetan, and Vietnamese scripts. Emacs also supports various encodings of these characters used by other internationalized software, such as word processors and mailers.

Emacs allows editing text with international characters by supporting all the related activities:

• You can visit files with non-ASCII characters, save non-ASCII text, and pass non-ASCII text between Emacs and programs it invokes (such as compilers, spell-checkers, and mailers). Setting your language environment (see Language Environments) takes care of setting up the coding systems and other options for a specific language or culture. Alternatively, you can specify how Emacs should encode or decode text for each command; see Text Coding.
• You can display non-ASCII characters encoded by the various scripts. This works by using appropriate fonts on graphics displays (see Defining Fontsets), and by sending special codes to text-only displays (see Terminal Coding). If some characters are displayed incorrectly, refer to Undisplayable Characters, which describes possible problems and explains how to solve them.
• You can insert non-ASCII characters or search for them. To do that, you can specify an input method (see Select Input Method) suitable for your language, or use the default input method set up when you set your language environment. If your keyboard can produce non-ASCII characters, you can select an appropriate keyboard coding system (see Terminal Coding), and Emacs will accept those characters. Latin-1 characters can also be input by using the C-x 8 prefix, see Unibyte Mode.

  On X Window systems, your locale should be set to an appropriate value to make sure Emacs interprets keyboard input correctly; see locales.

The rest of this chapter describes these issues in detail.

• International Chars: Basic concepts of multibyte characters.
• Enabling Multibyte: Controlling whether to use multibyte characters.
• Language Environments: Setting things up for the language you use.
• Input Methods: Entering text characters not on your keyboard.
• Select Input Method: Specifying your choice of input methods.
• Coding Systems: Character set conversion when you read and write files, and so on.
• Recognize Coding: How Emacs figures out which conversion to use.
• Specify Coding: Specifying a file's coding system explicitly.
• Output Coding: Choosing coding systems for output.
• Text Coding: Choosing conversion to use for file text.
• Communication Coding: Coding systems for interprocess communication.
• File Name Coding: Coding systems for file names.
• Terminal Coding: Specifying coding systems for converting terminal input and output.
• Fontsets: Fontsets are collections of fonts that cover the whole spectrum of characters.
• Defining Fontsets: Defining a new fontset.
• Modifying Fontsets: Modifying an existing fontset.
• Undisplayable Characters: When characters don't display.
• Unibyte Mode: You can pick one European character set to use without multibyte characters.
• Charsets: How Emacs groups its internal character codes.

26.1 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 shows how to say “hello” in many languages. This illustrates various scripts. 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-q (quoted-insert) or C-x 8 <RET> (ucs-insert). See Inserting Text. 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 Position Info, 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 ...’.

As a special case, if the character lies in the range 128 (0200 octal) through 159 (0237 octal), it stands for a “raw” byte that does not correspond to any specific displayable character. Such a “character” lies within the eight-bit-control character set, and is displayed as an escaped octal character code. In this case, C-x = shows ‘part of display ...’ instead of ‘file’.

With a prefix argument (C-u C-x =), this command displays a detailed description of the character in a window:

• 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 syntax and categories.
• The character's encodings, both internally in the buffer, and externally if you were to save the file.
• What keys to type to input the character in the current input method (if it supports the character).
• 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-only terminal, the code(s) sent to the terminal.
• The character's text properties (see Text Properties), including any non-default faces used to display the character, and any overlays containing it (see Overlays).

Here's an example showing the Latin-1 character A with grave accent, in a buffer whose coding system is utf-8-unix:

             character: À (192, #o300, #xc0)
     preferred charset: unicode (Unicode (ISO10646))
            code point: 0xC0
                syntax: w    which means: word
              category: j:Japanese l:Latin v:Vietnamese
           buffer code: #xC3 #x80
             file code: not encodable by coding system undecided-unix
               display: by this font (glyph code)
         xft:-unknown-DejaVu Sans Mono-normal-normal-normal-*-13-*-*-*-m-0-iso10646-1 (#x82)
     
     Character code properties: customize what to show
       name: LATIN CAPITAL LETTER A WITH GRAVE
       general-category: Lu (Letter, Uppercase)
       decomposition: (65 768) ('A' '̀')
       old-name: LATIN CAPITAL LETTER A GRAVE
     
     There are text properties here:
       auto-composed        t

26.2 Enabling Multibyte Characters

By default, Emacs starts in multibyte mode: it stores the contents of buffers and strings using an internal encoding that represents non-ASCII characters using multi-byte sequences. Multibyte mode allows you to use all the supported languages and scripts without limitations.

Under very special circumstances, you may want to disable multibyte character support, for a specific buffer. When multibyte characters are disabled in a buffer, we call that unibyte mode. In unibyte mode, each character in the buffer has a character code ranging from 0 through 255 (0377 octal); 0 through 127 (0177 octal) represent ASCII characters, and 128 (0200 octal) through 255 (0377 octal) represent non-ASCII characters.

To edit a particular file in unibyte representation, visit it using find-file-literally. See Visiting. You can convert a multibyte buffer to unibyte by saving it to a file, killing the buffer, and visiting the file again with find-file-literally. Alternatively, you can use C-x <RET> c (universal-coding-system-argument) and specify ‘raw-text’ as the coding system with which to visit or save a file. See Text Coding. Unlike find-file-literally, finding a file as ‘raw-text’ doesn't disable format conversion, uncompression, or auto mode selection.

Emacs normally loads Lisp files as multibyte. This includes the Emacs initialization file, .emacs, and the initialization files of Emacs packages such as Gnus. However, you can specify unibyte loading for a particular Lisp file, by putting ‘-*-unibyte: t;-*-’ in a comment on the first line (see File Variables). Then that file is always loaded as unibyte text. The motivation for these conventions is that it is more reliable to always load any particular Lisp file in the same way. However, you can load a Lisp file as unibyte, on any one occasion, by typing C-x <RET> c raw-text <RET> immediately before loading it.

The mode line indicates whether multibyte character support is enabled in the current buffer. If it is, there are two or more characters (most often two dashes) near the beginning of the mode line, before the indication of the visited file's end-of-line convention (colon, backslash, etc.). When multibyte characters are not enabled, nothing precedes the colon except a single dash. See Mode Line, for more details about this.

You can turn on multibyte support in a specific buffer by invoking the command toggle-enable-multibyte-characters in that buffer.

26.3 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 in an Emacs buffer. 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 Recognize Coding). 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 the variable 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. The supported language environments include:

ASCII, Belarusian, Bengali, Brazilian Portuguese, Bulgarian, Chinese-BIG5, Chinese-CNS, Chinese-EUC-TW, Chinese-GB, Chinese-GBK, Chinese-GB18030, 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 (Celtic), Latin-9 (updated Latin-1 with the Euro sign), Latvian, Lithuanian, Malayalam, Oriya, Polish, Punjabi, Romanian, Russian, Sinhala, Slovak, Slovenian, Spanish, Swedish, TaiViet, Tajik, Tamil, Telugu, Thai, Tibetan, Turkish, UTF-8 (for a setup which prefers Unicode characters and files encoded in UTF-8), Ukrainian, Vietnamese, Welsh, and Windows-1255 (for a setup which prefers Cyrillic characters and files encoded in Windows-1255).

To display the script(s) used by your language environment on a graphical display, you need to have a suitable font. If some of the characters appear as empty boxes, you should install the GNU Intlfonts package, which includes fonts for most supported scripts.¹¹ 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.¹² 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, and selects the corresponding language environment if a match is found. (The former variable overrides the latter.) 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, you may want to invoke the set-locale-environment function 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 japanese-iso-8bit.

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 environment, 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.

26.4 Input Methods

An input method is a kind of character conversion designed specifically for interactive input. In Emacs, typically each language has its own input method; sometimes several languages which 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 a' 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 which 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, 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 digit n selects the nth 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.

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 e ' combines to form an ‘e’ 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, e ' ' gives you the two characters ‘e'’. Another way is to type another letter after the e—something that won't combine with that—and immediately delete it. For example, you could type e e <DEL> ' to get separate ‘e’ 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 Select 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 Position Info.

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).

Another facility for typing characters not on your keyboard is by using the C-x 8 <RET> (ucs-insert) to insert a single character based on its Unicode name or code-point; see Inserting Text.

26.5 Selecting an Input Method

C-\

Enable or disable use of the selected input method.

C-x <RET> C-\ method <RET>

Select a new input method for the current buffer.

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 for 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 activates the input method “german-prefix” automatically in the 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 the other information about the character.

To see a list of all the supported input methods, type M-x list-input-methods. The list gives information about each input method, including the string that stands for it in the mode line.

26.6 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, carriage-return linefeed, and just carriage-return.

C-h C coding <RET>

Describe coding system coding.

C-h C <RET>

Describe the coding systems currently in use.

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 Recognize Coding).

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 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 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.)

...-dos

Assume the file uses carriage-return linefeed to separate lines, and do the appropriate conversion. (This is the convention normally used on Microsoft systems.¹³)

...-mac

Assume the file uses carriage-return to separate lines, and do the appropriate conversion. (This is the convention normally used on the Macintosh system.)

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 which 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.

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.

26.7 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 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 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 many 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, auto-coding-regexp-alist and auto-coding-functions are the strongest way to specify the coding system for certain patterns of file names, or for files containing certain patterns; these variables even override ‘-*-coding:-*-’ tags in the file itself. 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. Likewise, Emacs uses auto-coding-regexp-alist to ensure that RMAIL files, whose names in general don't match any particular pattern, are decoded correctly. One of the builtin auto-coding-functions detects the encoding for XML files.

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, unless rmail-decode-mime-charset is nil. 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).

26.8 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 by typing C-x <RET> r coding-system <RET>. 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 Mode Line), or type C-h C <RET>.

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 File Variables). 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.

26.9 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 Text Coding).

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, Emacs tells you that the most-preferred coding system is not recommended 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 type its name in response to the question.)

When you send a message with Message mode (see Sending Mail), Emacs has four different ways to determine the coding system to use for encoding the message text. It 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. The third way is to use the default coding system for new files, which is controlled by your choice of language environment, if that is non-nil. If all of these three values are nil, Emacs encodes outgoing mail using the Latin-1 coding system.

26.10 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 for saving or revisiting the visited file in the current buffer.

C-x <RET> c coding <RET>

Specify coding system coding for the immediately following command.

C-x <RET> r coding <RET>

Revisit the current file using the coding system coding.

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—in other words, it says which coding system to use when saving or reverting the visited file. You specify which coding system using the minibuffer. If you specify a coding system that cannot handle all of the characters in the buffer, Emacs warns you about the troublesome characters when you actually save the buffer.

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 CRLF 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 Shell). 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.

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.

26.11 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 window-based applications.

C-x <RET> X coding <RET>

Use coding system coding for transferring one selection—the next one—to or from another window-based application.

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.

C-x <RET> c coding <RET>

Specify coding system coding for the immediately following command.

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 COMPOUND_TEXT and UTF8_STRING, 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 just before the command that runs or starts a subprocess, to specify the coding system to use for communication with that subprocess.

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 is also used for decoding non-ASCII keyboard input on X Window systems. 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.)

The variable x-select-request-type specifies a selection data type of selection to request from the X server. The default value is nil, which means Emacs tries COMPOUND_TEXT and UTF8_STRING, and uses whichever result seems more appropriate. You can explicitly specify the data type by setting the variable to one of the symbols COMPOUND_TEXT, UTF8_STRING, STRING and TEXT.

26.12 Coding Systems for File Names

C-x <RET> F coding <RET>

Use coding system coding for encoding and decoding file names.

The variable 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.

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 which the specified coding system can encode. Use C-x <RET> F (set-file-name-coding-system) to specify this interactively.

If file-name-coding-system is nil, Emacs uses a default coding system determined by the selected language environment. In the default language environment, non-ASCII characters in file names are not encoded specially; they appear in the file system using the internal Emacs representation.

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 get 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.

26.13 Coding Systems for Terminal I/O

C-x <RET> k coding <RET>

Use coding system coding for keyboard input.

C-x <RET> t coding <RET>

Use coding system coding for terminal output.

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.

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.

26.14 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 specs, each assigned to handle a range of character codes, and may fall back on another fontset for characters which 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 the system supports; if certain characters appear on the screen as hollow boxes, this means that the fontset in use for them has no font for those characters.¹⁴

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 use of a specific fontset with the ‘-fn’ option. For example,

     emacs -fn fontset-standard

You can also specify a fontset with the ‘Font’ resource (see X 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.

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 an empty box instead.

26.15 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 Mac, fontset-standard is created using the value of ns-standard-fontset-spec, and on 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. It does this by replacing the charset_registry field with ‘fontset’, and replacing charset_encoding field with ‘startup’, then using the resulting string to specify a fontset.

For instance, if you start Emacs this way,

     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 which 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.

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]...

fontpattern should have the form of a standard X font name, except for the last two fields. They should have the form ‘fontset-alias’.

The fontset has two names, one long and one short. The long name is fontpattern. The short name is ‘fontset-alias’. 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 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 family field. In such a case, ‘Fontset-n’ can be specified as below:

     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.

26.16 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. 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-spec for the font to be used. Some examples are:

     ;; Use Liberation Mono for latin-3 charset.
     (set-fontset-font "fontset-default" 'iso-8859-3 "Liberation Mono")
     
     ;; Prefer a big5 font for han characters
     (set-fontset-font "fontset-default" 'han (font-spec :registry "big5")
                       nil 'prepend)
     
     ;; 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)
     
     ;; Use MyPrivateFont for the Unicode private use area.
     (set-fontset-font "fontset-default"  '(#xe000 . #xf8ff) "MyPrivateFont")
     

26.17 Undisplayable Characters

There may be a some non-ASCII characters that your terminal cannot display. Most text-only terminals support just a single character set (use the variable default-terminal-coding-system (see Terminal Coding) to tell Emacs which one); characters which 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.

26.18 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 session, 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’.

For more information about unibyte operation, see Enabling Multibyte. Note particularly that you probably want to ensure that your initialization files are read as unibyte if they contain non-ASCII characters.

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 we don't have them yet.

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-only terminal, you should use the command M-x set-keyboard-coding-system or the variable keyboard-coding-system to specify which coding system your keyboard uses (see Terminal Coding). Enabling this feature will probably require you to use ESC to type Meta characters; however, on a console terminal or in xterm, you can arrange for Meta to be converted to ESC and still be able type 8-bit characters present directly on the keyboard or using Compose or AltGr keys. See User Input.

• For Latin-1 only, you can use the key C-x 8 as a “compose character” prefix for entry of non-ASCII Latin-1 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.

26.19 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.

To display a list of all supported charsets, type M-x list-character-sets. The list gives the names of charsets and additional information to identity each charset (see http://www.itscj.ipsj.or.jp/ISO-IR/ for details). 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 International Chars).

27 Major Modes

Emacs provides many alternative major modes, each of which customizes Emacs for editing text of a particular sort. The major modes are mutually exclusive, and each buffer has one major mode at any time. The mode line normally shows the name of the current major mode, in parentheses (see 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 should switch to the appropriate major mode, such as Lisp mode or Text mode.

Selecting a major mode changes the meanings of a few keys to become more specifically adapted to the language being edited. The ones that are changed frequently are <TAB>, <DEL>, and C-j. The prefix key C-c normally contains mode-specific commands. In addition, the commands which handle comments use the mode to determine how comments are to be delimited. Many major modes redefine the syntactical properties of characters appearing in the buffer. See Syntax.

The 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 remaining major modes are not intended for use on users' files; they are used in buffers created for specific purposes by Emacs, such as Dired mode for buffers made by Dired (see Dired), Message mode for buffers made by C-x m (see Sending Mail), and Shell mode for buffers used for communicating with an inferior shell process (see Interactive Shell).

Most programming-language major modes specify that only blank lines separate paragraphs. This is to make the paragraph commands useful. (See Paragraphs.) They also cause Auto Fill mode to use the definition of <TAB> to indent the new lines it creates. This is because most lines in a program are usually indented (see Indentation).

• Choosing Modes: How major modes are specified or chosen.

27.1 How Major Modes are Chosen

You can select a major mode explicitly for the current buffer, but most of the time Emacs determines which mode to use based on the file name or on special text in the file.

To explicitly select a new major, you use an M-x command. Take the name of a major mode and add -mode to get the name of the command to select that mode. Thus, you can enter Lisp mode by executing M-x lisp-mode.

When you visit a file, Emacs usually chooses the right 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 the contents of the file. Here is the exact procedure:

First, Emacs checks whether the file contains a file-local variable that specifies the major mode. If so, it uses that major mode, ignoring all other criteria. See File Variables. 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. Alternatively, you could write

     ; -*- mode: Lisp;-*-

The latter format allows you to specify local variables as well, like this:

     ; -*- mode: Lisp; tab-width: 4; -*-

Second, 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.

Third, 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 Init File). The value should be a list of elements of the form

     (regexp . mode-function)

where regexp is a regular expression (see Regexps), and mode-function is a Lisp function that toggles a major mode. 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 wit mode-function.

Fourth—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, Emacs discards the suffix that matched regexp and searches the list again for another match.

On systems with case-insensitive file names, such as Microsoft Windows, Emacs performs a single case-insensitive search through auto-mode-alist. On other systems, Emacs normally performs a single case-sensitive search through the alist. However, if you change the variable auto-mode-case-fold to t, Emacs performs a second case-insensitive search if the first search fails.

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 is consulted only after auto-mode-alist. By default, magic-fallback-mode-alist contains forms that check for image files, HTML/XML/SGML files, and Postscript files.

Once a major mode is chosen, Emacs sets the value of the variable major-mode to the symbol for that major mode (e.g., text-mode for Text mode). This is a per-buffer variable (see Locals); its buffer-local value is set automatically, and 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 it via the Customization interface (see Easy Customization), or by adding a line like this to your init file (see Init 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.

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. It also processes the file's ‘-*-’ line or local variables list (if any). See File Variables.

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). (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.

28 Indentation

This chapter describes the Emacs commands that add, remove, or adjust indentation.

<TAB>

Indent the current line appropriately, in a mode-dependent fashion.

C-j

Perform <RET> followed by <TAB> (newline-and-indent).

M-^

Merge the previous and the current line (delete-indentation). This would cancel the effect of a preceding C-j.

C-M-o

Split the current line at point; text on the line after point becomes a new line indented to the same column where point is located (split-line).

M-m

Move (forward or back) to the first nonblank character on the current line (back-to-indentation).

C-M-\

Indent lines in the region to the same column (indent-region).

C-x <TAB>

Shift lines in the region rigidly right or left (indent-rigidly).

M-i

Indent from point to the next prespecified tab stop column (tab-to-tab-stop).

M-x indent-relative

Indent from point to under an indentation point in the previous line.

The <TAB> key runs indent-for-tab-command in most major modes (in C and related modes, <TAB> runs a separate command, c-indent-line-or-region, which behaves similarly). The major mode determines just what this entails.

In text modes, <TAB> inserts some combination of space and tab characters to advance point to the next tab stop (see Tab Stops). If the region is active and spans multiple lines, it advances the first character of each of those lines to the next tab stop (see Using Region). For the purposes of this command, the position of the first non-whitespace character on the preceding line is treated as an additional tab stop. Thus, you can use <TAB> to “align” point with the preceding line.

In programming modes, <TAB> adds or removes some combination of space and tab characters at the start of the line, in a way that makes sense given the text in the preceding lines. If the region is active and spans multiple lines, all those lines are indented this way. If point was initially within the current line's indentation, it is positioned after that indentation; otherwise, it remains at same point in the newly-indented text. See Program Indent.

Normally, indentation commands insert (or remove) an optimal mix of tab characters and spaces to align to the desired column. Tab characters (ASCII code 9) are displayed as a stretch of empty space extending to the next display tab stop. By default, there is one display tab stop every eight columns; the number of columns is determined by the variable tab-width. You can insert a single tab character by typing C-q <TAB>. See Text Display.

The command M-i (tab-to-tab-stop) adjusts the whitespace characters around point, inserting just enough whitespace to advance point up to the next tab stop. By default, this involves deleting the existing whitespace and inserting a single tab character.

See Just Spaces, for how to disable use of tabs. However, C-q <TAB> always inserts a tab, even when tabs are disabled for the indentation commands.

The variable tab-always-indent tweaks the behavior of the <TAB> (indent-for-tab-command) command. The default value, t, gives the behavior described above. 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 Symbol Completion). 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 real tab character.

• Indentation Commands: Various commands and techniques for indentation.
• Tab Stops: You can set arbitrary "tab stops" and then indent to the next tab stop when you want to.
• Just Spaces: You can request indentation using just spaces.

28.1 Indentation Commands and Techniques

To move over the indentation on a line, do M-m (back-to-indentation). This command, given anywhere on a line, positions point at the first nonblank character on the line, if any, or else at the end of the line.

To insert an indented line before the current line, do C-a C-o <TAB>. To make an indented line after the current line, use C-e C-j.

If you just want to insert a tab character in the buffer, type C-q <TAB>.

C-M-o (split-line) moves the text from point to the end of the line vertically down, so that the current line becomes two lines. C-M-o first moves point forward over any spaces and tabs. Then it inserts after point a newline and enough indentation to reach the same column point is on. Point remains before the inserted newline; in this regard, C-M-o resembles C-o.

To join two lines cleanly, use the M-^ (delete-indentation) command. It deletes the indentation at the front of the current line, and the line boundary as well, replacing them 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 open parentheses or closing parentheses, or if the junction follows another newline. To delete just the indentation of a line, go to the beginning of the line and use M-\ (delete-horizontal-space), which deletes all spaces and tabs around the cursor.

If you have a fill prefix, M-^ deletes the fill prefix if it appears after the newline that is deleted. See Fill Prefix.

There are also commands for changing the indentation of several lines at once. They apply to all the lines that begin in the region. C-M-\ (indent-region) indents each line in the “usual” way, as if you had typed <TAB> at the beginning of the line. A numeric argument specifies the column to indent to, and each line is shifted left or right so that its first nonblank character appears in that column. C-x <TAB> (indent-rigidly) moves all of the lines in the region right by its argument (left, for negative arguments). The whole group of lines moves rigidly sideways, which is how the command gets its name.

To remove all indentation from all of the lines in the region, invoke C-x <TAB> with a large negative argument, such as -1000.

M-x indent-relative indents at point based on the previous line (actually, the last nonempty line). It inserts whitespace at point, moving point, until it is underneath the next indentation point in the previous line. An indentation point is the end of a sequence of whitespace or the end of the line. If point is farther right than any indentation point in the previous line, indent-relative runs tab-to-tab-stop (see Tab Stops), unless it is called with a numeric argument, in which case it does nothing.

See Format Indentation, for another way of specifying the indentation for part of your text.

28.2 Tab Stops

For typing in tables, you can use M-i (tab-to-tab-stop). This command inserts indentation before point, enough to reach the next tab stop column.

You can change the tab stops used by M-i and other indentation commands, so that they need not be spaced every eight characters, or even regularly spaced. The tab stops are stored in the variable tab-stop-list, as a list of column numbers in increasing order.

A convenient way to set the tab stops is with M-x edit-tab-stops, which creates and selects a buffer containing a description of the tab stop settings. You can edit this buffer to specify different tab stops, and then type C-c C-c to make those new tab stops take effect. The buffer uses Overwrite mode (see Minor Modes). edit-tab-stops records which buffer was current when you invoked it, and stores the tab stops back in that buffer; normally all buffers share the same tab stops and changing them in one buffer affects all, but if you happen to make tab-stop-list local in one buffer then edit-tab-stops in that buffer will edit the local settings.

Here is what the text representing the tab stops looks like for ordinary tab stops every eight columns.

             :       :       :       :       :       :
     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 remaining lines are present just to help you see where the colons are and know what to do.

Note that the tab stops that control tab-to-tab-stop 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, which occurs every tab-width columns regardless of the contents of tab-stop-list. See Text Display.

28.3 Tabs vs. Spaces

Emacs normally uses both tabs and spaces to indent lines. If you prefer, all indentation can be made from spaces only. To request this, set indent-tabs-mode to nil. This is a per-buffer variable, so altering the variable affects only the current buffer, but there is a default value which you can change as well. See Locals.

A tab is not always displayed in the same way. By default, tabs are eight columns wide, but some people like to customize their editors to use a different tab width (e.g., by changing the variable tab-width in Emacs). By using spaces only, you can make sure that your file looks the same regardless of the tab width setting.

There are also commands to convert tabs to spaces or vice versa, always preserving the columns of all nonblank 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.

29 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.

Emacs has other major modes for text which contains “embedded” commands, such as TeX and LaTeX (see TeX Mode); HTML and SGML (see HTML Mode); XML (see nXML Mode); and Groff and Nroff (see Nroff Mode). In addition, you can edit formatted text in WYSIWYG style (“what you see is what you get”), using Enriched mode (see Formatted Text).

If you need to edit pictures made out of text characters (commonly referred to as “ASCII art”), use Picture mode, a special major mode for editing such pictures. See Picture Mode.

The “automatic typing” features may be useful when writing text. see Top.

• Words: Moving over and killing words.
• Sentences: Moving over and killing sentences.
• Paragraphs: Moving over paragraphs.
• Pages: Moving over pages.
• Filling: Filling or justifying text.
• Case: Changing the case of text.
• Text Mode: The major modes for editing text files.
• Outline Mode: Editing outlines.
• TeX Mode: Editing input to the formatter TeX.
• HTML Mode: Editing HTML and SGML files.
• Nroff Mode: Editing input to the formatter nroff.
• Formatted Text: Editing formatted text directly in WYSIWYG fashion.
• Text Based Tables: Editing text-based tables in WYSIWYG fashion.

29.1 Words

Emacs has commands for moving over or operating on words. By convention, the keys for them are all Meta characters.

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-@

Mark 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 Transpose, for more on transposition.

To operate on the next n words with an operation which acts on the region, use the command M-@ (mark-word). This command does not move point, but sets the mark where M-f would move to. Once the mark is active, each additional M-@ advances the mark by one additional word. M-@ also accepts a numeric argument that says how many words to scan for the place to put the mark.

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.

29.2 Sentences

The Emacs commands for manipulating sentences and paragraphs are mostly on Meta keys, so as to be 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 and M-e (backward-sentence and forward-sentence) move to the beginning and end of the current sentence, respectively. They 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; they consider a sentence to end 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 makes a distinction between periods that end a sentence and periods that indicate abbreviations; that enables the Emacs sentence commands to distinguish, too. These commands do not stop for 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 Fill Commands) in related ways.

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 Regexps). 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 do not use periods to indicate the end of a sentence. For example, sentences in Thai end with a double space but without a period. Set the variable sentence-end-without-period to t in such cases.

29.3 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-{ moves to the beginning of the current or previous paragraph, while M-} moves to the end of the current or next paragraph. Blank lines and text-formatter command lines separate paragraphs and are not considered part of any paragraph. If there is a blank line before the paragraph, M-{ moves to the blank line, because that is convenient in practice.

In Text mode, an indented line is not a paragraph break. If you want indented lines to have this effect, use Paragraph-Indent Text mode instead. See Text Mode.

In major modes for programs, paragraphs begin and end only at blank lines. This makes the paragraph commands useful, even though there are no paragraphs as such in a program.

When you have set a fill prefix, then paragraphs are delimited by all lines which don't start with the fill prefix. See Filling.

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), the paragraph following point is surrounded by point and mark. 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; furthermore, each subsequent M-h further advances the mark by one paragraph.

The precise definition of a paragraph boundary is controlled by the variables paragraph-separate and paragraph-start. The value of paragraph-start is a regexp that should match any line that either starts or separates paragraphs. The value of paragraph-separate is another regexp that should match only 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. Each regular expression must match at the left margin. For example, in Fundamental mode, paragraph-start is "\f\\|[ \t]*$", and paragraph-separate is "[ \t\f]*$".

Normally it is desirable for page boundaries to separate paragraphs. The default values of these variables recognize the usual separator for pages.

29.4 Pages

Within some text files, text is divided into pages, which are delimited by the formfeed character (ASCII code 12, sometimes denoted as <control-L>). When you print hardcopy for a file, the formfeed character forces a page break: each page of the file goes on a separate page on paper. Most Emacs commands treat the formfeed character just like any other character: you can insert it with C-q C-l, and delete it with <DEL>. However, since pages are often meaningful divisions of the file, Emacs provides commands to move over them and operate on them.

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).

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 and the mark at the end. The page delimiter at the end is included (the mark follows it). The page delimiter at the front is excluded (point follows it).

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. The reason C-x C-p includes only the following page delimiter in the region is to ensure that.

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 Regexps). The normal value of this variable is "^\f", which matches a formfeed character at the beginning of a line.

29.5 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 leaves it unfilled. When you edit formatted text, you can specify a style of filling for each portion of the text (see Formatted Text).

• Auto Fill: Auto Fill mode breaks long lines automatically.
• Fill Commands: Commands to refill paragraphs and center lines.
• Fill Prefix: Filling paragraphs that are indented or in a comment, etc.
• Adaptive Fill: How Emacs can determine the fill prefix automatically.
• Refill: Keeping paragraphs filled.
• Longlines: Editing text with very long lines.

29.5.1 Auto Fill Mode

Auto Fill mode is a minor mode in which lines are broken automatically when they become too wide. Breaking happens only when you type a <SPC> or <RET>.

M-x auto-fill-mode

Enable or disable Auto Fill mode.

<SPC>

<RET>

In Auto Fill mode, break lines when appropriate.

M-x auto-fill-mode turns Auto Fill mode on if it was off, or off if it was on. With a positive numeric argument it always turns Auto Fill mode on, and with a negative argument always turns it off. You can see when Auto Fill mode is in effect by the presence of the word ‘Fill’ in the mode line, inside the parentheses. Auto Fill mode is a minor mode which is enabled or disabled for each buffer individually. See Minor Modes.

In Auto Fill mode, lines are broken automatically at spaces when they get longer than the desired width. Line breaking and rearrangement takes place 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 (recall that a newline is really a control-J). Also, C-o inserts a newline without line breaking.

Auto Fill mode works well with programming-language modes, because it indents new lines with <TAB>. If a line ending in a comment gets too long, the text of the comment is split into two comment lines. Optionally, new comment delimiters are inserted at the end of the first line and the beginning of the second so that each line is a separate comment; the variable comment-multi-line controls the choice (see Comments).

Adaptive filling (see Adaptive Fill) works for Auto Filling as well as for explicit fill commands. It takes a fill prefix automatically from the second or first line of a paragraph.

Auto Fill mode does not refill entire paragraphs; it can break lines but cannot merge lines. So editing in the middle of a paragraph can result in a paragraph that is not correctly filled. The easiest way to make the paragraph properly filled again is usually with the explicit fill commands. See Fill Commands.

Many users like Auto Fill mode and want to use it in all text files. The section on init files says how to arrange this permanently for yourself. See Init File.

29.5.2 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-o M-s

Center a line.

To refill a paragraph, use the command M-q (fill-paragraph). This operates on the paragraph that point is inside, or the one after point if point is between paragraphs. Refilling works by removing all the line-breaks, then inserting new ones where necessary. When there is an active region, this command operates on the text within the region like fill-region.

To refill many paragraphs, use M-x fill-region, which finds the paragraphs in the region and fills each of them.

M-q and fill-region use the same criteria as M-h 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.) Another way to control justification, and choose other styles of filling, is with the justification text property; see Format Justification.

The command M-o M-s (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).

The maximum line width for filling is in the variable fill-column. Altering the value of fill-column makes it local to the current buffer; until that time, the default value is in effect. The default is initially 70. See Locals. The easiest way to set fill-column 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.

Emacs commands normally consider 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 and not the end of a sentence. To preserve the distinction between these two ways of using a period, the fill commands do not break a line after a period followed by just one space.

If the variable sentence-end-double-space is nil, the fill commands expect and leave just one space at the end of a sentence. Ordinarily this variable is t, so the fill commands insist on two spaces for the end of a sentence, as explained above. See Sentences.

If the variable colon-double-space is non-nil, the fill commands put two spaces after a colon.

The variable fill-nobreak-predicate is a hook (an abnormal hook, see Hooks) specifying additional conditions where line-breaking is not allowed. Each function is called with no arguments, with point at a place where Emacs is considering breaking the line. If a function returns a non-nil value, then that's a bad place to break the line. Two standard functions you can use are fill-single-word-nobreak-p (don't break after the first word of a sentence or before the last) and fill-french-nobreak-p (don't break after ‘(’ or before ‘)’, ‘:’ or ‘?’).

29.5.3 The Fill Prefix

To fill a paragraph in which each line starts with a special marker (which might be a few spaces, giving an indented paragraph), you can use the fill prefix feature. The fill prefix is a string that Emacs expects every line to start with, and which is not included in filling. You can specify a fill prefix explicitly; Emacs can also deduce the fill prefix automatically (see Adaptive Fill).

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. 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 Locals.

The indentation text property provides another way to control the amount of indentation paragraphs receive. See Format Indentation.

29.5.4 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.

29.5.5 Refill Mode

Refill minor mode provides support for keeping paragraphs filled as you type or modify them in other ways. It provides an effect similar to typical word processor behavior. This works by running a paragraph-filling command at suitable times.

To toggle the use of Refill mode in the current buffer, type M-x refill-mode. When you are typing text, only characters which normally trigger auto filling, like the space character, will trigger refilling. This is to avoid making it too slow. Apart from self-inserting characters, other commands which modify the text cause refilling.

The current implementation is preliminary and not robust. You can get better “line wrapping” behavior using Longlines mode. See Longlines. However, Longlines mode has an important side-effect: the newlines that it inserts for you are not saved to disk, so the files that you make with Longlines mode will appear to be completely unfilled if you edit them without Longlines mode.

29.5.6 Long Lines Mode

Sometimes, you may come across “unfilled” text files, which Emacs normally displays as a bunch of extremely long lines. Comfortably reading and editing such files normally requires “word wrap”, a feature that breaks up each long text line into multiple screen lines in a readable manner—by putting the breaks at word boundaries. Many text editors, such as those built into many web browsers, perform word wrapping by default.

There are two different minor modes in Emacs that perform word wrapping. The first is Visual Line mode, which does it by altering the behavior of screen line continuation. See Visual Line Mode, for information about Visual Line mode.

Instead of using Visual Line mode, you can use a minor mode called Long Lines mode. Long Lines mode wraps lines by inserting or deleting soft newlines as you type (see Hard and Soft Newlines). These soft newlines won't show up when you save the buffer into a file, or when you copy the text into the kill ring, clipboard, or a register. Unlike Visual Line mode, Lone Lines mode breaks long lines at the fill column (see Fill Commands), rather than the right window edge. To enable Long Lines mode, type M-x longlines-mode. If the text is full of long lines, this also immediately “wraps” them all.

The word wrap performed by Long Lines mode is not the same as ordinary filling (see Fill Commands). It does not contract multiple spaces into a single space, recognize fill prefixes (see Fill Prefix), or perform adaptive filling (see Adaptive Fill). The reason for this is that a wrapped line is still, conceptually, a single line. Each soft newline is equivalent to exactly one space in that long line, and vice versa. However, you can still call filling functions such as M-q, and these will work as expected, inserting soft newlines that won't show up on disk or when the text is copied. You can even rely entirely on the normal fill commands by turning off automatic line wrapping, with C-u M-x longlines-auto-wrap. To turn automatic line wrapping back on, type M-x longlines-auto-wrap.

Type RET to insert a hard newline, one which automatic refilling will not remove. If you want to see where all the hard newlines are, type M-x longlines-show-hard-newlines. This will mark each hard newline with a special symbol. The same command with a prefix argument turns this display off.

Long Lines mode does not change normal text files that are already filled, since the existing newlines are considered hard newlines. Before Long Lines can do anything, you need to transform each paragraph into a long line. One way is to set fill-column to a large number (e.g., C-u 9999 C-x f), re-fill all the paragraphs, and then set fill-column back to its original value.

29.6 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).

The word conversion commands are the most useful. 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.

29.7 Text Mode

When you edit files of text in a human language, it's more convenient to use Text mode rather than Fundamental mode. To enter 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 Fill.

Text mode defines <TAB> to run indent-relative (see Indentation), so that you can conveniently indent a line like the previous line.

Text mode turns off the features concerned with comments except when you explicitly invoke them. It changes the syntax table so that single-quotes are considered part of words. However, if a word starts with single-quotes, these are treated as a prefix for purposes such as capitalization. That is, M-c will convert ‘'hello'’ into ‘'Hello'’, as expected.

If you indent the first lines of paragraphs, then you should use Paragraph-Indent Text mode rather than Text mode. In this 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-text-mode to enter this mode. Use M-x paragraph-indent-minor-mode to enable an equivalent minor mode in situations where you can't change the major mode—in mail composition, for instance.

Text mode, and all the modes based on it, define M-<TAB> as the command ispell-complete-word, which performs completion of the partial word in the buffer before point, using the spelling dictionary as the space of possible words. See Spelling. If your window manager defines M-<TAB> to switch windows, you can type <ESC> <TAB> or C-M-i.

Entering Text mode runs the hook text-mode-hook. Other major modes related to Text mode also run this hook, followed by hooks of their own; this includes Paragraph-Indent Text mode, Nroff mode, TeX mode, Outline mode, and Message mode. Hook functions on text-mode-hook can look at the value of major-mode to see which of these modes is actually being entered. See Hooks.

29.8 Outline Mode

Outline mode is a major mode much like Text mode but intended for editing outlines. It allows you to make parts of the text temporarily invisible so that you can see the outline structure. Type M-x outline-mode to switch to Outline mode as the major mode of the current buffer.

When Outline mode makes a line invisible, the line does not appear on the screen. The screen appears exactly as if the invisible line were deleted, except that an ellipsis (three periods in a row) appears at the end of the previous visible line. (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 lines.

Outline minor mode provides the same commands as the major mode, Outline mode, but you can use it in conjunction with other major modes. Type M-x outline-minor-mode to enable the Outline minor mode in the current buffer. You can also specify this in the text of a file, with a file local variable of the form ‘mode: outline-minor’ (see File Variables).

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.)

Entering Outline mode runs the hook text-mode-hook followed by the hook outline-mode-hook (see Hooks).

• Format: What the text of an outline looks like.
• Motion: Special commands for moving through outlines.
• Visibility: Commands to control what is visible.
• Views: Outlines and multiple views.
• Foldout: Folding means zooming in on outlines.

29.8.1 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 stars; the number of stars determines the depth of the heading in the outline structure. Thus, a heading line with one star is a major topic; all the heading lines with two stars between it and the next one-star 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.

29.8.2 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).

C-c C-n (outline-next-visible-heading) moves down to the next heading line. C-c C-p (outline-previous-visible-heading) moves similarly backward. Both accept numeric arguments as repeat counts. The names emphasize that invisible headings are skipped, but this is not really a special feature. All editing commands that look for lines ignore the invisible lines automatically.

More powerful motion commands understand the level structure of headings. C-c C-f (outline-forward-same-level) and C-c C-b (outline-backward-same-level) move from one heading line to another visible heading at the same depth in the outline. C-c C-u (outline-up-heading) moves backward to another heading that is less deeply nested.

29.8.3 Outline Visibility Commands

The other special commands of outline mode are used to make lines visible or invisible. Their names all start with hide or show. Most of them fall into pairs of opposites. They are not undoable; instead, you can undo right past them. Making lines visible or invisible is simply not recorded by the undo mechanism.

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 (hide-entry).

C-c C-e

Make the current heading line's body visible (show-entry).

C-c C-d

Make everything under the current heading invisible, not including the heading itself (hide-subtree).

C-c C-s

Make everything under the current heading visible, including body, subheadings, and their bodies (show-subtree).

C-c C-l

Make the body of the current heading line, and of all its subheadings, invisible (hide-leaves).

C-c C-k

Make all subheadings of the current heading line, at all levels, visible (show-branches).

C-c C-i

Make immediate subheadings (one level down) of the current heading line visible (show-children).

C-c C-t

Make all body lines in the buffer invisible (hide-body).

C-c C-a

Make all lines in the buffer visible (show-all).

C-c C-q

Hide everything except the top n levels of heading lines (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 (hide-other).

Two commands that are exact opposites are C-c C-c (hide-entry) and C-c C-e (show-entry). They apply to the body lines directly following the current heading line. Subheadings and their bodies are not affected.

Two more powerful opposites are C-c C-d (hide-subtree) and C-c C-s (show-subtree). Both apply to the current heading line's subtree: its body, all its subheadings, both direct and indirect, and all of their bodies. In other words, the subtree contains everything following the current heading line, up to and not including the next heading of the same or higher rank.

Intermediate between a visible subtree and an invisible one is having all the subheadings visible but none of the body. There are two commands for doing this, depending on whether you want to hide the bodies or make the subheadings visible. They are C-c C-l (hide-leaves) and C-c C-k (show-branches).

A little weaker than show-branches is C-c C-i (show-children). It makes just the direct subheadings visible—those one level down. Deeper subheadings remain invisible, if they were invisible.

Two commands have a blanket effect on the whole file. C-c C-t (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 (show-all) makes all lines visible. These commands can be thought of as a pair of opposites even though C-c C-a applies to more than just body lines.

The command C-c C-q (hide-sublevels) hides all but the top level headings. With a numeric argument n, it hides everything except the top n levels of heading lines.

The command C-c C-o (hide-other) hides everything except the heading and body text that point is in, plus its parents (the headers leading up from there to top level in the outline) and the top level headings.

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. You can also automatically make text visible as you navigate in it by using M-x reveal-mode.

29.8.4 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.

29.8.5 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 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 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 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 Control-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 this in your .emacs file:

     (eval-after-load "outline" '(require 'foldout))

29.9 TeX Mode

Emacs provides special major modes for editing files written in TeX and its related formats. TeX is a powerful text formatter written by Donald Knuth; like GNU Emacs, it is free software. LaTeX is a simplified input format for TeX, implemented using TeX macros. DocTeX is a special file format in which the LaTeX sources are written, combining sources with documentation. SliTeX is an obsolete special form of LaTeX.¹⁵

TeX mode has four variants: Plain TeX mode, LaTeX mode, DocTeX mode, and SliTeX mode. These distinct major modes differ only slightly, and are designed for editing the four different formats. Emacs selects the appropriate mode by looking at the contents of the buffer. (This is done by the tex-mode command, which is normally called automatically when you visit a TeX-like file. See Choosing 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 command M-x plain-tex-mode, M-x latex-mode, M-x slitex-mode, or doctex-mode.

Emacs also provides BibTeX mode, a major mode for editing BibTeX files. BibTeX is a tool for storing and formatting bibliographic references, which is commonly used together with LaTeX. In addition, the RefTeX package provides a minor mode which can be used in conjunction with LaTeX mode to manage bibliographic references. see Top.

• Editing: Special commands for editing in TeX mode.
• LaTeX: Additional commands for LaTeX input files.
• Printing: Commands for printing part of a file with TeX.
• Misc: Customization of TeX mode, and related features.

29.9.1 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 ‘''’. For convenience, TeX mode overrides the normal meaning of the key " with a command that inserts a pair of single-quotes or backquotes (tex-insert-quote). To be precise, it 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.)

To disable the " expansion feature, eliminate that binding in the local map (see Key Bindings).

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.

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 the ‘*Occur*’ buffer, and you can use C-c C-c or Mouse-2 in that buffer to go to a particular mismatch.

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.

29.9.2 LaTeX Editing Commands

LaTeX mode (and its obsolete variant, SliTeX mode) provide 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 (tex-latex-block).

C-c C-e

Close the innermost LaTeX block not yet closed (tex-close-latex-block).

In LaTeX input, ‘\begin’ and ‘\end’ commands are used to group blocks of text. To insert a ‘\begin’ and a matching ‘\end’ (on a new line following the ‘\begin’), use C-c C-o (tex-latex-block). A blank line is inserted between the two, and point is left there. You can use completion when you enter the block type; to specify additional block type names beyond the standard list, set the variable latex-block-names. For example, here's how to add ‘theorem’, ‘corollary’, and ‘proof’:

     (setq latex-block-names '("theorem" "corollary" "proof"))

In LaTeX input, ‘\begin’ and ‘\end’ commands must balance. You can use C-c C-e (tex-close-latex-block) to insert automatically a matching ‘\end’ to match the last unmatched ‘\begin’. It indents the ‘\end’ to match the corresponding ‘\begin’. It inserts a newline after ‘\end’ if point is at the beginning of a line.

29.9.3 TeX Printing Commands

You can invoke TeX as an inferior of Emacs on either the entire contents of the buffer or just a region at a time. Running TeX in this way on just one chapter is a good way to see what your changes look like without taking the time to format the entire file.

C-c C-r

Invoke TeX on the current region, together with the buffer's header (tex-region).

C-c C-b

Invoke TeX on the entire current buffer (tex-buffer).

C-c <TAB>

Invoke BibTeX on the current file (tex-bibtex-file).

C-c C-f

Invoke TeX on the current file (tex-file).

C-c C-l

Recenter the window showing output from the inferior 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-p

Print the output from the last C-c C-r, C-c C-b, or C-c C-f command (tex-print).

C-c C-v

Preview the output from the last C-c C-r, C-c C-b, or C-c C-f command (tex-view).

C-c C-q

Show the printer queue (tex-show-print-queue).

C-c C-c

Invoke some other compilation command on the entire current buffer (tex-compile).

You can pass the current buffer through an inferior TeX by means of C-c C-b (tex-buffer). The formatted output appears in a temporary file; to print it, type C-c C-p (tex-print). Afterward, you can use C-c C-q (tex-show-print-queue) to view the progress of your output towards being printed. If your terminal has the ability to display TeX output files, you can preview the output on the terminal with C-c C-v (tex-view).

You can specify the directory to use for running TeX by setting the variable tex-directory. "." is the default value. If your environment variable TEXINPUTS contains relative directory names, or if your files contains ‘\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".

If you want to specify which shell commands are used in the inferior TeX, you can do so by setting the values of the variables tex-run-command, latex-run-command, slitex-run-command, tex-dvi-print-command, tex-dvi-view-command, and tex-show-queue-command. The default values may (or may not) be appropriate for your system.

Normally, the file name given to these commands comes at the end of the command string; for example, ‘latex filename’. In some cases, however, the file name needs to be embedded in the command; an example is when 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 Shell). 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 an inferior 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 File Variables.

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).

29.9.4 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, 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.

For managing all kinds of references for LaTeX, you can use RefTeX. see Top.

29.10 SGML and HTML Modes

The major modes for SGML and HTML provide indentation support and commands for operating on tags. HTML mode is a slightly customized variant of SGML mode.

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 from within a tag or a comment, close this element 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).

C-c TAB

Toggle the visibility of existing tags in the buffer. This can be used as a cheap preview (sgml-tags-invisible).

The default mode for editing XML documents is called nXML mode (xml-mode or nxml-mode). This is a powerful major mode that can recognize many existing XML schema and use them to provide completion of XML elements via C-<RET> or M-<TAB>, as well as “on-the-fly” XML validation with error highlighting. It is described in its own manual. See nXML Mode.

However, you can also use SGML mode to edit XML, since XML is a strict subset of SGML. In XML, every opening tag must have an explicit closing tag. When the variable sgml-xml-mode is non-nil, the tag insertion commands described above always insert explicit closing tags as well. When you visit a file in SGML mode, Emacs determines whether it is XML by examining the file contents, and sets sgml-xml-mode accordingly.

29.11 Nroff Mode

Nroff mode is a mode like Text mode but modified to handle nroff commands present in the text. Invoke M-x nroff-mode to enter this mode. It differs from Text mode in only a few ways. All nroff command lines are considered paragraph separators, so that filling will never garble the nroff commands. Pages are separated by ‘.bp’ commands. Comments start with backslash-doublequote. Also, three special commands are provided that are not in Text mode:

M-n

Move to the beginning of the next line that isn't an nroff command (forward-text-line). An argument is a repeat count.

M-p

Like M-n but move up (backward-text-line).

M-?

Displays in the echo area the number of text lines (lines that are not nroff commands) in the region (count-text-lines).

The other feature of Nroff mode is that you can turn on Electric Nroff mode. This is a minor mode that you can turn on or off with M-x electric-nroff-mode (see Minor Modes). When the mode is on, each time you use <RET> to end a line that contains an nroff command that opens a kind of grouping, the matching nroff command to close that grouping is automatically inserted on the following line. For example, if you are at the beginning of a line and type . ( b <RET>, this inserts the matching command ‘.)b’ on a new line following point.

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).

Entering Nroff mode runs the hook text-mode-hook, followed by the hook nroff-mode-hook (see Hooks).

29.12 Editing Formatted Text

Enriched mode is a minor mode for editing files that contain formatted text in WYSIWYG fashion, as in a word processor. Currently, formatted text in Enriched mode can specify fonts, colors, underlining, margins, and types of filling and justification. In the future, we plan to implement other formatting features as well.

Enriched mode is a minor mode (see Minor Modes). It is typically used in conjunction with Text mode (see Text Mode), but you can also use it with other major modes such as Outline mode and Paragraph-Indent Text mode.

Potentially, Emacs can store formatted text files in various file formats. Currently, only one format is implemented: text/enriched format, which is defined by the MIME protocol. See Format Conversion, for details of how Emacs recognizes and converts file formats.

The Emacs distribution contains a formatted text file that can serve as an example. Its name is etc/enriched.doc. It contains samples illustrating all the features described in this section. It also contains a list of ideas for future enhancements.

• Requesting Formatted Text: Entering and exiting Enriched mode.
• Hard and Soft Newlines: There are two different kinds of newlines.
• Editing Format Info: How to edit text properties.
• Faces: Bold, italic, underline, etc.
• Color: Changing the color of text.
• Indent: Changing the left and right margins.
• Justification Centering, setting text flush with the left or right margin, etc.
• Special: The "special" text properties submenu.
• Forcing Enriched Mode: How to force use of Enriched mode.

29.12.1 Requesting to Edit Formatted Text

Whenever you visit a file that Emacs saved in the text/enriched format, Emacs automatically converts the formatting information in the file into Emacs's own internal format (known as text properties), and turns on Enriched mode.

To create a new file of formatted text, first visit the nonexistent file, then type M-x enriched-mode before you start inserting text. This command turns on Enriched mode. Do this before you begin inserting text, to ensure that the text you insert is handled properly.

More generally, the command enriched-mode turns Enriched mode on if it was off, and off if it was on. With a prefix argument, this command turns Enriched mode on if the argument is positive, and turns the mode off otherwise.

When you save a buffer while Enriched mode is enabled in it, Emacs automatically converts the text to text/enriched format while writing it into the file. When you visit the file again, Emacs will automatically recognize the format, reconvert the text, and turn on Enriched mode again.

You can add annotations for saving additional text properties, which Emacs normally does not save, by adding to enriched-translations. Note that the text/enriched standard requires any non-standard annotations to have names starting with ‘x-’, as in ‘x-read-only’. This ensures that they will not conflict with standard annotations that may be added later.

See Text Properties, for more information about text properties.

29.12.2 Hard and Soft Newlines

In formatted text, Emacs distinguishes between two different kinds of newlines, hard newlines and soft newlines. (You can enable or disable this feature separately in any buffer with the command use-hard-newlines.)

Hard newlines are used to separate paragraphs, or items in a list, or anywhere that there should always be a line break regardless of the margins. The <RET> command (newline) and C-o (open-line) insert hard newlines.

Soft newlines are used to make text fit between the margins. All the fill commands, including Auto Fill, insert soft newlines—and they delete only soft newlines.

Although hard and soft newlines look the same, it is important to bear the difference in mind. Do not use <RET> to break lines in the middle of filled paragraphs, or else you will get hard newlines that are barriers to further filling. Instead, let Auto Fill mode break lines, so that if the text or the margins change, Emacs can refill the lines properly. See Auto Fill.

On the other hand, in tables and lists, where the lines should always remain as you type them, you can use <RET> to end lines. For these lines, you may also want to set the justification style to unfilled. See Format Justification.

29.12.3 Editing Format Information

There are two ways to alter the formatting information for a formatted text file: with keyboard commands, and with the mouse.

The easiest way to add properties to your document is with the Text Properties menu. You can get to this menu in two ways: from the Edit menu in the menu bar (use <F10> e t if you have no mouse), or with C-Mouse-2 (hold the <CTRL> key and press the middle mouse button). There are also keyboard commands described in the following section.

These items in the Text Properties menu run commands directly:

Remove Face Properties

Delete from the region all face and color text properties (facemenu-remove-face-props).

Remove Text Properties

Delete all text properties from the region (facemenu-remove-all).

Describe Properties

List all the text properties, widgets, buttons, and overlays of the character following point (describe-text-properties).

Display Faces

Display a list of all the defined faces (list-faces-display).

Display Colors

Display a list of all the defined colors (list-colors-display).

The rest lead to submenus which are described in the following sections.

29.12.4 Faces in Formatted Text

The Faces submenu under Text Properties lists various Emacs faces including bold, italic, and underline (see Faces). These menu items operate on the region if it is active and nonempty. Otherwise, they specify to use that face for an immediately following self-inserting character. There is also an item ‘Other’ with which you can enter a face name through the minibuffer (see Standard Faces).

Instead of the Faces submenu, you can use these keyboard commands:

M-o d

Remove all face properties from the region (which includes specified colors), or force the following inserted character to have no face property (facemenu-set-default).

M-o b

Add the face bold to the region or to the following inserted character (facemenu-set-bold).

M-o i

Add the face italic to the region or to the following inserted character (facemenu-set-italic).

M-o l

Add the face bold-italic to the region or to the following inserted character (facemenu-set-bold-italic).

M-o u

Add the face underline to the region or to the following inserted character (facemenu-set-underline).

M-o o face <RET>

Add the face face to the region or to the following inserted character (facemenu-set-face).

With a prefix argument, all these commands apply to an immediately following self-inserting character, disregarding the region.

A self-inserting character normally inherits the face property (and most other text properties) from the preceding character in the buffer. If you use the above commands to specify face for the next self-inserting character, or the next section's commands to specify a foreground or background color for it, then it does not inherit the face property from the preceding character; instead it uses whatever you specified. It will still inherit other text properties, though.

Strictly speaking, these commands apply only to the first following self-inserting character that you type. But if you insert additional characters after it, they will inherit from the first one. So it appears that these commands apply to all of them.

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. This face is the same as italic unless you customize it (see Face Customization).

The fixed face means, “Use a fixed-width font for this part of the text.” Applying the fixed face to a part of the text will cause that part of the text to appear in a fixed-width font, even if the default font is variable-width. This applies to Emacs and to other systems that display text/enriched format. So if you specifically want a certain part of the text to use a fixed-width font, you should specify the fixed face for that part.

By default, the fixed face looks the same as bold. This is an attempt to distinguish it from default. You may wish to customize fixed to some other fixed-width medium font. See Face Customization.

If your terminal cannot display different faces, you will not be able to see them, but you can still edit documents containing faces, and even add faces and colors to documents. The faces you specify will be visible when the file is viewed on a terminal that can display them.

29.12.5 Colors in Formatted Text

You can specify foreground and background colors for portions of the text. Under Text Properties, there is a submenu for specifying the foreground color, and a submenu for specifying the background color. Each one lists all the colors that you have used in Enriched mode in the current Emacs session.

If the region is active, the command applies to the text in the region; otherwise, it applies to any immediately following self-inserting input. When Transient Mark mode is off (see Persistent Mark), it always applies to the region unless a prefix argument is given, in which case it applies to the following input.

Each of the two color submenus contains one additional item: ‘Other’. You can use this item to specify a color that is not listed in the menu; it reads the color name with the minibuffer. To display a list of available colors and their names, use the ‘Display Colors’ menu item in the Text Properties menu (see Editing Format Info).

Any color that you specify in this way, or that is mentioned in a formatted text file that you read in, is added to the corresponding color menu for the duration of the Emacs session.

There are no predefined key bindings for specifying colors, but you can do so with the extended commands M-x facemenu-set-foreground and M-x facemenu-set-background. Both of these commands read the name of the color with the minibuffer.

29.12.6 Indentation in Formatted Text

When editing formatted text, you can specify different amounts of indentation for the right or left margin of an entire paragraph or a part of a paragraph. The margins you specify automatically affect the Emacs fill commands (see Filling) and line-breaking commands.

The Indentation submenu of Text Properties provides a convenient interface for specifying these properties. The submenu contains four items:

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.

You can use these commands repeatedly to increase or decrease the indentation.

The most common way to use them is to change the indentation of an entire paragraph. For other uses, the effects of refilling can be hard to predict, except in some special cases like the one described next.

The most common other use is to format paragraphs with hanging indents, which means that the first line is indented less than subsequent lines. To set up a hanging indent, increase the indentation of the region starting after the first word of the paragraph and running until the end of the paragraph.

Indenting the first line of a paragraph is easier. Set the margin for the whole paragraph where you want it to be for the body of the paragraph, then indent the first line by inserting extra spaces or tabs.

The variable standard-indent specifies how many columns these commands should add to or subtract from the indentation. The default value is 4. The overall default right margin for Enriched mode is controlled by the variable fill-column, as usual.

There are also two commands for setting the left or right margin of the region absolutely: set-left-margin and set-right-margin. Enriched mode binds these commands to C-c [ and C-c ], respectively. You can specify the margin width either with a numeric argument or in the minibuffer.

Sometimes, as a result of editing, the filling of a paragraph becomes messed up—parts of the paragraph may extend past the left or right margins. When this happens, use M-q (fill-paragraph) to refill the paragraph.

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 Fill Prefix.

29.12.7 Justification in Formatted Text

When editing formatted text, you can specify various styles of justification for a paragraph. The style you specify automatically affects the Emacs fill commands.

The Justification submenu of Text Properties provides a convenient interface for specifying the style. The submenu contains five items:

Left

This is the most common style of justification (at least for English). Lines are aligned at the left margin but left uneven at the right.

Right

This aligns each line with the right margin. Spaces and tabs are added on the left, if necessary, to make lines line up on the right.

Full

This justifies the text, aligning both edges of each line. Justified text looks very nice in a printed book, where the spaces can all be adjusted equally, but it does not look as nice with a fixed-width font on the screen. Perhaps a future version of Emacs will be able to adjust the width of spaces in a line to achieve elegant justification.

Center

This centers every line between the current margins.

Unfilled

This turns off filling entirely. Each line will remain as you wrote it; the fill and auto-fill functions will have no effect on text which has this setting. You can, however, still indent the left margin. In unfilled regions, all newlines are treated as hard newlines (see Hard and Soft Newlines) .

In Enriched mode, you can also specify justification from the keyboard using the M-j prefix character:

M-j l

Make the region left-filled (set-justification-left).

M-j r

Make the region right-filled (set-justification-right).

M-j b

Make the region fully justified (set-justification-full).

M-j c

M-S

Make the region centered (set-justification-center).

M-j u

Make the region unfilled (set-justification-none).

Justification styles apply to entire paragraphs. All the justification-changing commands operate on the paragraph containing point, or, if the region is active, on all paragraphs which overlap the region.

The default justification style is specified by the variable default-justification. Its value should be one of the symbols left, right, full, center, or none. This is a per-buffer variable. Setting the variable directly affects only the current buffer. However, customizing it in a Custom buffer sets (as always) the default value for buffers that do not override it. See Locals, and Easy Customization.

29.12.8 Setting Other Text Properties

The Special Properties submenu of Text Properties can add or remove three other useful text properties: read-only, invisible and intangible. The intangible property disallows moving point within the text, the invisible text property hides text from display, and the read-only property disallows alteration of the text.

Each of these special properties has a menu item to add it to the region. The last menu item, ‘Remove Special’, removes all of these special properties from the text in the region.

Currently, the invisible and intangible properties are not saved in the text/enriched format. The read-only property is saved, but it is not a standard part of the text/enriched format, so other editors may not respect it.

29.12.9 Forcing Enriched Mode

Normally, Emacs knows when you are editing formatted text because it recognizes the special annotations used in the file that you visited. However, sometimes you must take special actions to convert file contents or turn on Enriched mode:

• When you visit a file that was created with some other editor, Emacs may not recognize the file as being in the text/enriched format. In this case, when you visit the file you will see the formatting commands rather than the formatted text. Type M-x format-decode-buffer to translate it. This also automatically turns on Enriched mode.
• When you insert a file into a buffer, rather than visiting it, Emacs does the necessary conversions on the text which you insert, but it does not enable Enriched mode. If you wish to do that, type M-x enriched-mode.

The command format-decode-buffer translates text in various formats into Emacs's internal format. It asks you to specify the format to translate from; however, normally you can type just <RET>, which tells Emacs to guess the format.

If you wish to look at a text/enriched file in its raw form, as a sequence of characters rather than as formatted text, use the M-x find-file-literally command. This visits a file, like find-file, but does not do format conversion. It also inhibits character code conversion (see Coding Systems) and automatic uncompression (see Compressed Files). To disable format conversion but allow character code conversion and/or automatic uncompression if appropriate, use format-find-file with suitable arguments.

29.13 Editing Text-based Tables

Table mode provides an easy and intuitive way to create and edit WYSIWYG text-based tables. Here is an example of such a table:

     +-----------------+--------------------------------+-----------------+
     |     Command     |          Description           |   Key Binding   |
     +-----------------+--------------------------------+-----------------+
     |  forward-char   |Move point right N characters   |       C-f       |
     |                 |(left if N is negative).        |                 |
     |                 |                                |                 |
     |                 |On reaching end of buffer, stop |                 |
     |                 |and signal error.               |                 |
     +-----------------+--------------------------------+-----------------+
     |  backward-char  |Move point left N characters    |       C-b       |
     |                 |(right if N is negative).       |                 |
     |                 |                                |                 |
     |                 |On attempt to pass beginning or |                 |
     |                 |end of buffer, stop and signal  |                 |
     |                 |error.                          |                 |
     +-----------------+--------------------------------+-----------------+

Table mode allows the contents of the table such as this one to be easily manipulated by inserting or deleting characters inside a cell. A cell is effectively a localized rectangular edit region and edits to a cell do not affect the contents of the surrounding cells. If the contents do not fit into a cell, then the cell is automatically expanded in the vertical and/or horizontal directions and the rest of the table is restructured and reformatted in accordance with the growth of the cell.

• Table Definition: What is a text based table.
• Table Creation: How to create a table.
• Table Recognition: How to activate and deactivate tables.
• Cell Commands: Cell-oriented commands in a table.
• Cell Justification: Justifying cell contents.
• Row Commands: Manipulating rows of table cell.
• Column Commands: Manipulating columns of table cell.
• Fixed Width Mode: Fixing cell width.
• Table Conversion: Converting between plain text and tables.
• Measuring Tables: Analyzing table dimension.
• Table Misc: Table miscellany.

29.13.1 What is a Text-based Table?

Keep the following examples of valid tables in mind as a reference while you read this section:

                   +--+----+---+     +-+     +--+-----+
                   |  |    |   |     | |     |  |     |
                   +--+----+---+     +-+     |  +--+--+
                   |  |    |   |             |  |  |  |
                   +--+----+---+             +--+--+  |
                                             |     |  |
                                             +-----+--+

A table consists of a rectangular frame whose inside 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 multiple rectangular cells, but cells cannot overlap.

The table frame and cell border lines are made of three special characters. These variables specify those characters:

table-cell-vertical-char

Holds the character used for vertical lines. The default value is ‘|’.

table-cell-horizontal-chars

Holds the characters used for horizontal lines. The default value is ‘"-="’.

table-cell-intersection-char

Holds the character used at where horizontal line and vertical line meet. The default value is ‘+’.

Based on this definition, the following five tables are examples of invalid tables:

        +-----+    +-----+       +--+    +-++--+    ++
        |     |    |     |       |  |    | ||  |    ++
        | +-+ |    |     |       |  |    | ||  |
        | | | |    +--+  |    +--+--+    +-++--+
        | +-+ |    |  |  |    |  |  |    +-++--+
        |     |    |  |  |    |  |  |    | ||  |
        +-----+    +--+--+    +--+--+    +-++--+
          a           b          c          d        e

From left to right:

1. Overlapped cells or non-rectangular cells are not allowed.
2. Same as a.
3. The border must be rectangular.
4. Cells must have a minimum width/height of one character.
5. Same as d.

29.13.2 How to Create a Table?

The command to create a table is table-insert. When called interactively, it asks for the number of columns, number of rows, cell width and cell height. The number of columns is the number of cells horizontally side by side. The number of rows is the number of cells vertically within the table's height. The cell width is a number of characters that each cell holds, left to right. The cell height is a number of lines each cell holds. The cell width and the cell height can be either an integer (when the value is constant across the table) or a series of integer, separated by spaces or commas, where each number corresponds to the next cell within a row from left to right, or the next cell within a column from top to bottom.

29.13.3 Table Recognition

Table mode maintains special text properties in the buffer to allow editing in a convenient fashion. When a buffer with tables is saved to its file, these text properties are lost, so when you visit this file again later, Emacs does not see a table, but just formatted text. To resurrect the table text properties, issue the M-x table-recognize command. It scans the current buffer, recognizes valid table cells, and attaches appropriate text properties to allow for table editing. The converse command, table-unrecognize, is used to remove the special text properties and convert the buffer back to plain text.

Special commands exist to enable or disable tables within a region, enable or disable individual tables, and enable/disable individual cells. These commands are:

M-x table-recognize-region

Recognize tables within the current region and activate them.

M-x table-unrecognize-region

Deactivate tables within the current region.

M-x table-recognize-table

Recognize the table under point and activate it.

M-x table-unrecognize-table

Deactivate the table under point.

M-x table-recognize-cell

Recognize the cell under point and activate it.

M-x table-unrecognize-cell

Deactivate the cell under point.

For another way of converting text into tables, see Table Conversion.

29.13.4 Commands for Table Cells

The commands table-forward-cell and table-backward-cell move point from the current cell to an adjacent cell forward and backward respectively. The order of the cells is cyclic: when point is in the last cell of a table, typing M-x table-forward-cell moves to the first cell in the table. Likewise M-x table-backward-cell from the first cell in a table moves to the last cell.

The command table-span-cell merges the current cell with the adjacent cell in a specified direction—right, left, above or below. You specify the direction with the minibuffer. It does not allow merges which don't result in a legitimate cell layout.

The command table-split-cell splits the current cell vertically or horizontally. This command is a wrapper to the direction specific commands table-split-cell-vertically and table-split-cell-horizontally. You specify the direction with a minibuffer argument.

The command table-split-cell-vertically splits the current cell vertically and creates a pair of cells above and below where point is located. The content in the original cell is split as well.

The command table-split-cell-horizontally splits the current cell horizontally and creates a pair of cells right and left of where point is located. If the cell being split is not empty, this asks you how to handle the cell contents. The three options are: split, left, or right. split splits the contents at point literally, while the left and right options move the entire contents into the left or right cell respectively.

The next four commands enlarge or shrink a cell. They use numeric arguments (see Arguments) to specify how many columns or rows to enlarge or shrink a particular table.

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.

29.13.5 Cell Justification

You can specify text justification for each cell. The justification is remembered independently for each cell and the subsequent editing of cell contents is subject to the specified justification.

The command table-justify ask you to specify what to justify: a cell, a column, or a row. If you select cell justification, this command sets the justification only for the current cell. Selecting column or row justification sets the justification for all the cells within a column or row respectively. The command then ask you which kind of justification to apply: left, center, right, top, middle, bottom, or none. Horizontal justification and vertical justification are specified independently. The options left, center, and right specify horizontal justification while the options top, middle, bottom, and none specify vertical justification. The vertical justification none effectively removes vertical justification. Horizontal justification must be one of left, center, or right.

Justification information is stored in the buffer as a part of text property. Therefore, this information is ephemeral and does not survive through the loss of the buffer (closing the buffer and revisiting the buffer erase any previous text properties). To countermand for this, the command table-recognize and other recognition commands (see Table Recognition) are equipped with a convenience feature (turned on by default). During table recognition, the contents of a cell are examined to determine which justification was originally applied to the cell and then applies this justification to the cell. This is a speculative algorithm and is therefore not perfect, however, the justification is deduced correctly most of the time. To disable this feature, customize the variable table-detect-cell-alignment and set it to nil.

29.13.6 Commands for Table Rows

The command table-insert-row inserts a row of cells before the current row in a table. The current row where point is located is pushed down after the newly inserted row. A numeric prefix argument specifies the number of rows to insert. Note that in order to insert rows after the last row at the bottom of a table, you must place point below the table—that is, outside the table—prior to invoking this command.

The command table-delete-row deletes a row of cells at point. A numeric prefix argument specifies the number of rows to delete.

29.13.7 Commands for Table Columns

The command table-insert-column inserts a column of cells to the left of the current row in a table. This pushes the current column to the right. To insert a column to the right side of the rightmost column, place point to the right of the rightmost column, which is outside of the table, prior to invoking this command. A numeric prefix argument specifies the number of columns to insert.

A command table-delete-column deletes a column of cells at point. A numeric prefix argument specifies the number of columns to delete.

29.13.8 Fix Width of Cells

The command table-fixed-width-mode toggles fixed width mode on and off. When fixed width mode is turned on, editing inside a cell never changes the cell width; when it is off, the cell width expands automatically in order to prevent a word from being folded into multiple lines. By default, fixed width mode is disabled.

29.13.9 Conversion Between Plain Text and Tables

The command table-capture captures plain text in a region and turns it into a table. Unlike table-recognize (see Table Recognition), the original text does not have a table appearance but may hold a logical table structure. For example, some elements separated by known patterns form a two dimensional structure which can be turned into a table.

Here's an example of data that table-capture can operate on. The numbers are horizontally separated by a comma and vertically separated by a newline character.

     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   |     |
     +-----+-----+-----+-----+

The conversion uses ‘,’ for the column delimiter and newline for a row delimiter, cells are left justified, and minimum cell width is 5.

The command table-release does the opposite of table-capture. It releases a table by removing the table frame and cell borders. This leaves the table contents as plain text. One of the useful applications of table-capture and table-release is to edit a text in layout. Look at the following three paragraphs (the latter two are indented with header lines):

     ‘table-capture’ is a powerful command, but mastering its
     power requires some practice.  Here are some things it can do:
     
     Parse Cell Items      By using column delimiter regular
                           expression and raw delimiter regular
                           expression, it parses the specified text
                           area and extracts cell items from
                           non-table text and then forms a table out
                           of them.
     
     Capture Text Area     When no delimiters are specified it
                           creates a single cell table.  The text in
                           the specified region is placed in that
                           cell.

Applying table-capture to a region containing the above three paragraphs, with empty strings for column delimiter regexp and row delimiter regexp, creates a table with a single cell like the following one.

     +-----------------------------------------------------------------+
     |‘table-capture’ is a powerful command, but mastering its         |
     |power requires some practice.  Here are some things it can do:   |
     |                                                                 |
     |Parse Cell Items      By using column delimiter regular          |
     |                      expression and raw delimiter regular       |
     |                      expression, it parses the specified text   |
     |                      area and extracts cell items from          |
     |                      non-table text and then forms a table out  |
     |                      of them.                                   |
     |                                                                 |
     |Capture Text Area     When no delimiters are specified it        |
     |                      creates a single cell table.  The text in  |
     |                      the specified region is placed in that     |
     |                      cell.                                      |
     +-----------------------------------------------------------------+

By splitting the cell appropriately we now have a table consisting of paragraphs occupying its own cell. Each cell can now be edited independently without affecting the layout of other cells.

     +-----------------------------------------------------------------+
     |‘table-capture’ is a powerful command, but mastering its         |
     |power requires some practice.  Here are some things it can do:   |
     +---------------------+-------------------------------------------+
     |Parse Cell Items     |By using column delimiter regular          |
     |                     |expression and raw delimiter regular       |
     |                     |expression, it parses the specified text   |
     |                     |area and extracts cell items from          |
     |                     |non-table text and then forms a table out  |
     |                     |of them.                                   |
     +---------------------+-------------------------------------------+
     |Capture Text Area    |When no delimiters are specified it        |
     |                     |creates a single cell table.  The text in  |
     |                     |the specified region is placed in that     |
     |                     |cell.                                      |
     +---------------------+-------------------------------------------+

By applying table-release, which does the opposite process, the contents become once again plain text. table-release works as a companion command to table-capture.

29.13.10 Analyzing Table Dimensions

The command table-query-dimension analyzes a table structure and reports information regarding its dimensions. In case of the above example table, the table-query-dimension command displays in echo area:

     Cell: (21w, 6h), Table: (67w, 16h), Dim: (2c, 3r), Total Cells: 5

This indicates that the current cell is 21 character wide and 6 lines high, the entire table is 67 characters wide and 16 lines high. The table has 2 columns and 3 rows. It has a total of 5 cells, since the first row has a spanned cell.

29.13.11 Table Miscellany

The command table-insert-sequence inserts a string into each cell. Each string is a part of a sequence i.e. a series of increasing integer numbers.

The command table-generate-source generates a table formatted for a specific markup language. It asks for a language (which must be one of html, latex, or cals), a destination buffer where to put the result, and the table caption (a string), and then inserts the generated table in the proper syntax into the destination buffer. The default destination buffer is table.lang, where lang is the language you specified.

30 Editing Programs

Emacs provides many features to facilitate editing programs. Some of these features can

• Find or move over top-level definitions (see Defuns).
• Apply the usual indentation conventions of the language (see Program Indent).
• Balance parentheses (see Parentheses).
• Insert, kill or align comments (see Comments).
• Highlight program syntax (see Font Lock).

This chapter describes these features and many more.

• Program Modes: Major modes for editing programs.
• Defuns: Commands to operate on major top-level parts of a program.
• Program Indent: Adjusting indentation to show the nesting.
• Parentheses: Commands that operate on parentheses.
• Comments: Inserting, killing, and aligning comments.
• Documentation: Getting documentation of functions you plan to call.
• Hideshow: Displaying blocks selectively.
• Symbol Completion: Completion on symbol names of your program or language.
• Glasses: Making identifiersLikeThis more readable.
• Semantic: Suite of editing tools based on source code parsing.
• Misc for Programs: Other Emacs features useful for editing programs.
• C Modes: Special commands of C, C++, Objective-C, Java, and Pike modes.
• Asm Mode: Asm mode and its special features.
• Fortran: Fortran mode and its special features.

30.1 Major Modes for Programming Languages

Emacs has specialized major modes for various programming languages. See Major Modes. A programming language major 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 customizes or provides facilities for compiling and debugging programs as well.

Ideally, Emacs should provide a major mode for each programming language that you might want to edit; if it doesn't have a mode for your favorite language, you can contribute one. But often the mode for one language can serve for other syntactically similar languages. The major mode for language l is called l-mode, and you can select it by typing M-x l-mode <RET>. See Choosing Modes.

The existing programming language major modes include Lisp, Scheme (a variant of Lisp) and the Scheme-based DSSSL expression language, Ada, ASM, AWK, C, C++, Delphi (Object Pascal), Fortran, Icon, IDL (CORBA), IDLWAVE, Java, Javascript, Metafont (TeX's companion for font creation), Modula2, Objective-C, Octave, Pascal, Perl, Pike, PostScript, Prolog, Python, Ruby, Simula, Tcl, and VHDL. An alternative mode for Perl is called CPerl mode. Modes are available for the scripting languages of the common GNU and Unix shells, VMS DCL, and MS-DOS/MS-Windows ‘BAT’ files. There are also major modes for editing makefiles, DNS master files, and various sorts of configuration files.

In most programming languages, indentation should vary from line to line to illustrate the structure of the program. So the major modes for programming languages arrange for <TAB> to update the indentation of the current line (see Program Indent). They also rebind <DEL> to treat a tab as if it were the equivalent number of spaces; this lets you delete one column of indentation without worrying whether the whitespace consists of spaces or tabs. Use C-b C-d to delete a tab character before point, in these modes.

Separate manuals are available for the modes for Ada (see Ada Mode), C/C++/Objective C/Java/Corba IDL/Pike/AWK (see CC Mode) and the IDLWAVE modes (see IDLWAVE). For Fortran mode, see Fortran.

Turning on a major mode runs a normal hook called the mode hook, which is the value of a Lisp variable. Each major mode has a mode hook, and the hook's name is always made from the mode command's name by adding ‘-hook’. For example, turning on C mode runs the hook c-mode-hook, while turning on Lisp mode runs the hook lisp-mode-hook. The purpose of the mode hook is to give you a place to set up customizations for that major mode. See Hooks.

30.2 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.

• Left Margin Paren: An open-paren or similar opening delimiter starts a defun if it is at the left margin.
• Moving by Defuns: Commands to move over or mark a major definition.
• Imenu: Making buffer indexes as menus.
• Which Function: Which Function mode shows which function you are in.

30.2.1 Left Margin Convention

Many programming-language modes assume by default that any opening delimiter found at the left margin is the start of a top-level definition, or defun. Therefore, don't put an opening delimiter at the left margin unless it should have that significance. For instance, never put an open-parenthesis at the left margin in a Lisp file unless it is the start of a top-level list.

The convention speeds up many Emacs operations, which would otherwise have to scan back to the beginning of the buffer to analyze the syntax of the code.

If you don't follow this convention, not only will you have trouble when you explicitly use the commands for motion by defuns; other features that use them will also give you trouble. This includes the indentation commands (see Program Indent) and Font Lock mode (see Font Lock).

The most likely problem case is when you want an opening delimiter at the start of a line inside a string. To avoid trouble, put an escape character (‘\’, in C and Emacs Lisp, ‘/’ in some other Lisp dialects) before the opening delimiter. This will not affect the contents of the string, but will prevent that opening delimiter from starting a defun. Here's an example:

       (insert "Foo:
     \(bar)
     ")

To help you catch violations of this convention, Font Lock mode highlights confusing opening delimiters (those that ought to be quoted) in bold red.

If you need to override this convention, you can do so by setting this user option:

Usually, you should leave this option at its default value of t. If your buffer contains parentheses or braces in column zero which don't start defuns, and it is somehow impractical to remove these parentheses or braces, it might be helpful to set the option to nil. Be aware that this might make scrolling and display in large buffers quite sluggish. Furthermore, the parentheses and braces must be correctly matched throughout the buffer for it to work properly.

30.2.2 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 Marking 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 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 sets the mark but does not move point; furthermore, each successive use of C-M-h extends the end of the region to include one more 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.

30.2.3 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 Tags, for a more powerful feature that handles multiple files together.)

If you type M-x 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.

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.

Imenu provides the information to guide Which Function mode (see Which Function). The Speedbar can also use it (see Speedbar).

30.2.4 Which Function Mode

Which Function mode is a minor mode that 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. This command applies to all buffers, both existing ones and those yet to be created. However, it takes effect only in certain major modes, those listed in the value of which-func-modes. If the value of which-func-modes is t rather than a list of modes, then Which Function mode applies to all major modes that know how to support it—in other words, all the major modes that support Imenu.

30.3 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.

• Basic Indent: Indenting a single line.
• Multi-line Indent: Commands to reindent many lines at once.
• Lisp Indent: Specifying how each Lisp function should be indented.
• C Indent: Extra features for indenting C and related modes.
• Custom C Indent: Controlling indentation style for C and related modes.

Emacs also provides a Lisp pretty-printer in the library pp. This program reformats a Lisp object with indentation chosen to look nice.

30.3.1 Basic Program Indentation Commands

The basic indentation commands indent a single line according to the usual conventions of the language you are editing.

<TAB>

Adjust indentation of current line.

C-j

Insert a newline, then adjust indentation of following line (newline-and-indent).

The basic indentation command is <TAB>. In any programming-language major mode, <TAB> gives the current line the correct indentation as determined from the previous lines. It does this by inserting or deleting whitespace at the beginning of the current line. If point was inside the whitespace at the beginning of the line, <TAB> puts it at the end of that whitespace; otherwise, <TAB> keeps point fixed with respect to the characters around it. If the region is active (see Mark), <TAB> indents every line within the region instead of just the current line. The function that <TAB> runs depends on the major mode; for instance, it is c-indent-line-or-region in C mode. Each function is aware of the syntax and conventions for its particular language.

Use C-q <TAB> to insert a tab character at point.

When entering lines of new code, use C-j (newline-and-indent), which inserts a newline and then adjusts indentation after it. (It also deletes any trailing whitespace which remains before the new newline.) For instance, C-j at the end of a line creates a blank line with appropriate indentation. In programming language modes, it is equivalent to <RET> <TAB>.

When Emacs indents a line that starts within a parenthetical grouping, it 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, the lines below will tend to follow it. This behavior is convenient in cases where you have overridden the standard result of <TAB> indentation (e.g., for aesthetic purposes).

Many programming-language modes assume that an open-parenthesis, open-brace or other opening delimiter at the left margin is the start of a function. This assumption speeds up indentation commands. If the text you are editing contains opening delimiters in column zero that aren't the beginning of a functions—even if these delimiters occur inside strings or comments—then you must set open-paren-in-column-0-is-defun-start. See Left Margin Paren.

Normally, Emacs indents lines using an “optimal” mix of tab and space characters. If you want Emacs to use spaces only, set indent-tabs-mode (see Just Spaces).

30.3.2 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 within the region. In addition, Emacs provides several other commands for indenting large chunks of code:

C-M-q

Reindent all the lines within one parenthetical grouping.

C-M-\

Reindent all lines in the region (indent-region).

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.

C-M-\ (indent-region) applies <TAB> to the region. This is useful when Transient Mark mode is disabled (see Persistent Mark), because in that case <TAB> does not act on the region.

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.

30.3.3 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. Normally you would use this for macro definitions and specify it using the declare construct (see Defining Macros).

30.3.4 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).

C-M-q

Reindent each line in the balanced expression that follows point (c-indent-exp). A prefix argument inhibits warning messages about invalid syntax.

<TAB>

Reindent the current line, and/or in some cases insert a tab character (c-indent-command).

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.

30.3.5 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 . <RET> style <RET>

Select a predefined style style (c-set-style).

A style is a named collection of customizations that can be used in C mode and the related modes. Styles, 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-\.

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.

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, and Customizing Indentation, 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.

30.4 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). 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.

• Expressions: Expressions with balanced parentheses.
• Moving by Parens: Commands for moving up, down and across in the structure of parentheses.
• Matching: Insertion of a close-delimiter flashes matching open.

30.4.1 Expressions with Balanced Parentheses

These commands deal with balanced expressions, also called sexps¹⁶.

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).

Each programming language major mode customizes the definition of balanced expressions to suit that language. Balanced expressions typically include symbols, numbers, and string constants, as well as any pair of matching delimiters and their contents. Some languages have obscure forms of expression syntax that nobody has bothered to implement in Emacs.

By convention, the keys for these commands are all Control-Meta characters. They usually act on expressions just as the corresponding Meta characters act on words. For instance, the command C-M-b moves backward over a balanced expression, just as M-b moves back over a word.

To move forward over a balanced expression, use C-M-f (forward-sexp). If the first significant character after point is an opening delimiter (‘(’ in Lisp; ‘(’, ‘[’ or ‘{’ in C), C-M-f moves past the matching closing delimiter. If the character begins a symbol, string, or number, C-M-f moves over that.

The command C-M-b (backward-sexp) moves backward over a balanced expression. The detailed rules are like those above for C-M-f, but with directions reversed. If there are prefix characters (single-quote, backquote and comma, in Lisp) preceding the expression, C-M-b moves back over them as well. The balanced expression commands move across comments as if they were whitespace, in most modes.

C-M-f or C-M-b with an argument repeats that operation the specified number of times; with a negative argument, it moves in the opposite direction.

Killing a whole balanced expression can be done with C-M-k (kill-sexp). C-M-k kills the characters that C-M-f would move over.

A somewhat random-sounding command which is nevertheless handy is C-M-t (transpose-sexps), which drags the previous balanced expression across the next one. An argument serves as a repeat count, moving the previous expression over that many following ones. A negative argument drags the previous balanced expression backwards across those before it (thus canceling out the effect of C-M-t with a positive argument). An argument of zero, rather than doing nothing, transposes the balanced expressions ending at or after point and the mark.

To set the region around the next balanced expression in the buffer, use C-M-<SPC> (mark-sexp), which sets mark at the same place that C-M-f would move to. C-M-<SPC> treats numeric arguments in the same way as C-M-f; in particular, a negative argument puts the mark at the beginning of the previous balanced expression. The alias C-M-@ is equivalent to C-M-<SPC>. While the mark is active, each successive use of C-M-<SPC> extends the region by shifting the mark by one sexp.

In languages that use infix operators, such as C, it is not possible to recognize all balanced expressions as such 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. Both ‘foo + bar’ and ‘foo’ are legitimate choices for “the expression following point” when point is at the ‘f’, so the expression commands must perforce choose one or the other to operate on. Note that ‘(foo + bar)’ is recognized as a single expression in C mode, because of the parentheses.

30.4.2 Moving in the Parenthesis Structure

The Emacs commands for handling parenthetical groupings see nothing except parentheses (or whatever characters must balance in the language you are working with). They ignore strings and comments (including any parentheses within them) and ignore parentheses quoted by an escape character. They are mainly intended for editing programs, but can be useful for editing any text that has parentheses. They are sometimes called “list” commands because in Lisp these groupings are lists.

These commands assume that the starting point is not inside a string or a comment. Sometimes you can invoke them usefully from one of these places (for example, when you have a parenthesised clause in a comment) but this is 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.

30.4.3 Automatic Display Of Matching Parentheses

The Emacs parenthesis-matching feature is designed to show automatically how parentheses (and other matching delimiters) match in the text. Whenever you type a self-inserting character that is a closing delimiter, the cursor moves momentarily to 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 parenthesis match display:

blink-matching-paren turns the feature on or off: nil disables it, but the default is t to enable match display.

blink-matching-delay says how many seconds to leave the cursor on the matching opening delimiter, before bringing it back to the real location of point; the default is 1, but on some systems it is useful to specify a fraction of a second.

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, scanning stops, and nothing is displayed. This is to prevent the scan for the matching delimiter from wasting lots of time when there is no match. The default is 102400.

Show Paren mode provides a more powerful kind of automatic matching. Whenever point is before an opening delimiter or after a closing delimiter, both that delimiter and its opposite delimiter are highlighted. Use the command M-x show-paren-mode to enable or disable this mode.

Show Paren mode uses the faces show-paren-match and show-paren-mismatch to highlight parentheses; you can customize them to control how highlighting looks. See Face Customization.

30.5 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 Spelling).

• Comment Commands: Inserting, killing, and aligning comments.
• Multi-Line Comments: Commands for adding and editing multi-line comments.
• Options for Comments: Customizing the comment features.

30.5.1 Comment Commands

The commands in this table insert, kill and align comments:

M-;

Insert or realign comment on current line; alternatively, comment or uncomment the region (comment-dwim).

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 (comment-indent-new-line). See Multi-Line Comments.

M-x comment-region

C-c C-c (in C-like modes)

Add or remove comment delimiters on 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, M-; either adds or removes comment delimiters on each line of the region. See Mark. If every line in the region is a comment, it removes comment delimiters from each; otherwise, it adds comment delimiters to each. You can also use the commands comment-region and uncomment-region to explicitly comment or uncomment the text in the region (see Multi-Line Comments). If you supply a prefix argument to M-; when a region is active, that specifies how many comment delimiters to add or how many to delete.

If the region is not active, M-; inserts a new comment if there is no comment already on the line. The new comment is normally aligned at a specific column called the comment column; if the text of the line extends past the comment column, M-; aligns the comment start string to a suitable boundary (usually, at least one space is inserted). The comment begins with the string Emacs thinks comments should start with (the value of comment-start; see below). Emacs places point after that string, so you can insert the text of the comment right away. If the major mode has specified a string to terminate comments, M-; inserts that string after point, to keep the syntax valid.

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 it. (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 text inside the comment.

C-u M-; kills any comment on the current line, along with the whitespace before it. To reinsert the comment on another line, move to the end of that line, do C-y, and then do M-; to realign it.

Note that C-u M-; is not a distinct key; it is M-; (comment-dwim) with a prefix argument. That command is programmed so that when it receives a prefix argument it calls comment-kill. However, comment-kill is a valid command in its own right, and you can bind it directly to a key if you wish.

Some major modes have special rules for aligning certain kinds of comments in certain contexts. For example, in Lisp code, comments which start with two semicolons are indented as if they were lines of code, instead of at the comment column. Comments which start with three semicolons are supposed to start at the left margin and are often used for sectioning purposes. Emacs understands these conventions by indenting a double-semicolon comment using <TAB>, and by not changing the indentation of a triple-semicolon comment at all.

     ;; 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.

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.

30.5.2 Multiple Lines of Comments

If you are typing a comment and wish to continue it on another line, you can use the command C-M-j or M-j (comment-indent-new-line). If comment-multi-line (see Options for Comments) is non-nil, it moves to a new line within the comment. Otherwise it closes the comment and starts a new comment on a new line. When Auto Fill mode is on, going past the fill column while typing a comment causes the comment to be continued in just this fashion.

To turn existing lines into comment lines, use the M-x comment-region command (or type C-c C-c in C-like modes). It adds comment delimiters to the lines that start in the region, thus commenting them out. With a negative argument, it does the opposite—it deletes comment delimiters from the lines in the region.

With a positive argument, comment-region duplicates the last character of the comment start sequence it adds; the argument specifies how many copies of the character to insert. Thus, in Lisp mode, C-u 2 M-x comment-region adds ‘;;’ to each line. Duplicating the comment delimiter is a way of calling attention to the comment. It can also affect how the comment is aligned or indented. In Lisp, for proper indentation, you should use an argument of two or three, if between defuns; if within a defun, it must be three.

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.

30.5.3 Options Controlling Comments

The comment column, the column at which Emacs tries to place comments, is stored in the variable comment-column. You can set it to a number explicitly. Alternatively, the command C-x ; (comment-set-column) sets the comment column to the column point is at. 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 variable comment-column is per-buffer: setting the variable in the normal fashion affects only the current buffer, but there is a default value which you can change with setq-default. See Locals. Many major modes initialize this variable for the current buffer.

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 is "/\\*+ *\\|//+ *", 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 Regexp Backslash.)

When a comment command makes a new comment, it inserts the value of comment-start to begin it. The value of comment-end is inserted after point, so that it will follow the text that you will insert into the comment. When comment-end is non-empty, it should start with a space. For example, in C mode, comment-start has the value "/* " and comment-end has the value " */".

The variable comment-padding specifies how many spaces comment-region should insert on each line between the comment delimiter and the line's original text. The default is 1, to insert one space. nil means 0. Alternatively, comment-padding can hold the actual string to insert.

The variable comment-multi-line controls how C-M-j (indent-new-comment-line) behaves when used inside a comment. Specifically, when comment-multi-line is nil, the command inserts a comment terminator, begins a new line, and finally inserts a comment starter. Otherwise it does not insert the terminator and starter, so it effectively continues the current comment across multiple lines. In languages that allow multi-line comments, the choice of value for this variable is a matter of taste. The default for this variable depends on the major mode.

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, in Lisp mode, the indent hook function bases its decision on how many semicolons begin an existing comment, and on the code in the preceding lines.

30.6 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.

• Info Lookup: Looking up library functions and commands in Info files.
• Man Page: Looking up man pages of library functions and commands.
• Lisp Doc: Looking up Emacs Lisp functions, etc.

30.6.1 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.

The major mode determines where to look for documentation for the symbol—which Info files to look in, and which indices to search. 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.

30.6.2 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 Misc Help). 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. It runs the man program to format the man page; if the system permits, it runs man asynchronously, so that you can keep on editing while the page is being formatted. (On MS-DOS and MS-Windows 3, you cannot edit while Emacs waits for man to finish.) 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 page 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 multiple 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 manual-entry prompts for the topic. For example, to read the man page for the C library function chmod (as opposed to a command of the same name), type M-x manual-entry <RET> chmod(2) <RET>. (chmod is a system call, so it is in section ‘2’.)

If you do not specify a section, the results depend on how the man program works on your system. Some of them display only the first man page they find. Others display all man pages that have the specified name, so you can move between them with the M-n and M-p keys¹⁷. The mode line shows how many manual pages are present in the Man buffer.

By default, Emacs highlights the text in man pages. For a long man page, highlighting can take substantial time. You can turn off highlighting of man pages by setting the variable Man-fontify-manpage-flag to nil.

If you insert the text of a man page into an Emacs buffer in some other fashion, you can use the command M-x Man-fontify-manpage to perform the same conversions that M-x manual-entry does.

An alternative way of reading manual pages is the M-x woman command¹⁸. Unlike M-x man, it does not run any external programs to format and display the man pages; instead it does the job in Emacs Lisp, so it works on systems such as MS-Windows, where the man program (and other programs it uses) are not generally available.

M-x woman prompts for a name of a manual page, and provides completion based on the list of manual pages that are installed on your machine; the list of available manual pages is computed automatically the first time you invoke woman. The word at point in the current buffer is used to suggest the default for the name of the manual page.

With a numeric argument, M-x woman recomputes the list of the manual pages used for completion. 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.

For more information about setting up and using M-x woman, see WoMan.

30.6.3 Emacs Lisp Documentation Lookup

As you edit Lisp code to be run in Emacs, you can use the commands C-h f (describe-function) and C-h v (describe-variable) to view documentation of functions and variables that you want to use. These commands use the minibuffer to read the name of a function or variable to document, and display the documentation in a window. Their default arguments are based on the code in the neighborhood of point. For C-h f, the default is the function called in the innermost list containing point. C-h v uses the symbol name around or adjacent to point as its default.

A more automatic but less powerful method is Eldoc mode. This minor mode constantly displays in the echo area the argument list for the function being called at point. (In other words, it finds the function call that point is contained in, and displays the argument list of that function.) If point is over a documented variable, it shows the first line of the variable's docstring. Eldoc mode applies in Emacs Lisp and Lisp Interaction modes, and perhaps a few others that provide special support for looking up doc strings. Use the command M-x eldoc-mode to enable or disable this feature.

30.7 Hideshow minor mode

Hideshow minor mode provides selective display of portions of a program, known as blocks. You can use M-x hs-minor-mode to enable or disable this mode, or add hs-minor-mode to the mode hook for certain major modes in order to enable it automatically for those modes.

Just what constitutes a block depends on the major mode. In C mode or C++ mode, they are delimited by braces, while in Lisp mode and similar modes they are delimited by parentheses. Multi-line comments also count as blocks.

C-c @ C-h

Hide the current block (hs-hide-block).

C-c @ C-s

Show the current block (hs-show-block).

C-c @ C-c

Either hide or show the current block (hs-toggle-hiding).

S-Mouse-2

Either hide or show the block you click on (hs-mouse-toggle-hiding).

C-c @ C-M-h

Hide all top-level blocks (hs-hide-all).

C-c @ C-M-s

Show everything in the buffer (hs-show-all).

C-c @ C-l

Hide all blocks n levels below this block (hs-hide-level).

These variables exist for customizing Hideshow mode.

hs-hide-comments-when-hiding-all

Non-nil says that hs-hide-all should hide comments too.

hs-isearch-open

Specifies what kind of hidden blocks incremental search should make visible. The value should be one of these four symbols:

code

Open only code blocks.

comment

Open only comments.

t

Open both code blocks and comments.

nil

Open neither code blocks nor comments.

hs-special-modes-alist

A list of elements, each specifying how to initialize Hideshow variables for one major mode. See the variable's documentation string for more information.

30.8 Completion for Symbol Names

In Emacs, completion is something you normally do in the minibuffer (see Completion). But one kind of completion is available in all buffers: completion for symbol names.

The character M-<TAB> runs a command to complete the partial symbol before point against the set of meaningful symbol names. This command inserts at point any additional characters that it can determine from the partial name.

If your window manager defines M-<TAB> to switch windows, you can type <ESC> <TAB> or C-M-i instead. However, most window managers let you customize these shortcuts, so you can change any that interfere with the way you use Emacs.

If the partial name in the buffer has multiple possible completions that differ in the very next character, so that it is impossible to complete even one more character, M-<TAB> displays a list of all possible completions in another window.

In most programming language major modes, M-<TAB> runs the command complete-symbol, which provides two kinds of completion. Normally it does completion based on a tags table (see Tags); with a numeric argument (regardless of the value), it does completion based on the names listed in the Info file indexes for your language. Thus, to complete the name of a symbol defined in your own program, use M-<TAB> with no argument; to complete the name of a standard library function, use C-u M-<TAB>. Of course, Info-based completion works only if there is an Info file for the standard library functions of your language, and only if it is installed at your site.

In Emacs-Lisp mode, the name space for completion normally consists of nontrivial symbols present in Emacs—those that have function definitions, values or properties. However, if there is an open-parenthesis immediately before the beginning of the partial symbol, only symbols with function definitions are considered as completions. The command which implements this is lisp-complete-symbol.

In Text mode and related modes, M-<TAB> completes words based on the spell-checker's dictionary. See Spelling.

30.9 Glasses minor mode

Glasses minor mode makes ‘unreadableIdentifiersLikeThis’ readable by altering the way they display. It knows two different ways to do this: by displaying underscores between a lower-case letter and the following capital letter, and by emboldening the capital letters. It does not alter the buffer text, only the way they display, so you can use it even on read-only buffers. You can use the command M-x glasses-mode to enable or disable the mode in the current buffer; you can also add glasses-mode to the mode hook of the programming language major modes in which you normally want to use Glasses mode.

30.10 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.

Most of the “language aware” features in Emacs, such as font lock (see Font Lock), rely on “rules of thumb”¹⁹ 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 parses each file you visit. Currently, Semantic understands C, C++, Scheme, Javascript, Java, HTML, and Make. 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 keybindings 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, for details.

30.11 Other Features Useful for Editing Programs

A number of 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 symbols names contain words (see Words); sentences can be found in strings and comments (see Sentences). Paragraphs in the strict sense can be found in program code (in long comments), but the paragraph commands are useful in other places too, because programming language major modes define paragraphs to begin and end at blank lines (see Paragraphs). 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.

The selective display feature is useful for looking at the overall structure of a function (see Selective Display). This feature hides the lines that are indented more than a specified amount. Programming modes often support Outline minor mode (see Outline Mode). The Foldout package provides folding-editor features (see Foldout).

The “automatic typing” features may be useful for writing programs. See Autotyping.

30.12 C and Related Modes

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.”) See CC Mode, for a more extensive description of these modes and their special features.

• Motion in C: Commands to move by C statements, etc.
• Electric C: Colon and other chars can automatically reindent.
• Hungry Delete: A more powerful DEL command.
• Other C Commands: Filling comments, viewing expansion of macros, and other neat features.

30.12.1 C Mode Motion Commands

This section describes commands for moving point, in C mode and related modes.

M-x c-beginning-of-defun

M-x c-end-of-defun

Move point to the beginning or end of the current function or top-level definition. These are found by searching for the least enclosing braces. (By contrast, beginning-of-defun and end-of-defun search for braces in column zero.) If you are editing code where the opening brace of a function isn't placed in column zero, you may wish to bind C-M-a and C-M-e to these commands. 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).

30.12.2 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, ‘/l’ appears in the mode line after the mode name:

C-c C-l

Toggle electric action (c-toggle-electric-state). With a prefix argument, this command enables electric action if the argument is positive, disables it if it is negative.

Electric characters insert newlines only when, in addition to the electric state, the auto-newline feature is enabled (indicated by ‘/la’ 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.

30.12.3 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>

c-hungry-delete-backwards—Delete the entire block of whitespace preceding point.

C-c C-d

C-c C-<DELETE>

C-c <DELETE>

c-hungry-delete-forward—Delete the entire block of whitespace following point.

As an alternative to the above commands, you can enable hungry delete mode. When this feature is enabled (indicated by ‘/h’ in the mode line after the mode name), a single <DEL> deletes all preceding whitespace, not just one space, and a single C-c 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)²⁰. 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.

30.12.4 Other Commands for C Mode

C-c C-w

M-x subword-mode

Enable (or disable) subword mode. In subword mode, Emacs's word commands recognize upper case letters in ‘StudlyCapsIdentifiers’ as word boundaries. This is indicated by the flag ‘/w’ on the mode line after the mode name (e.g. ‘C/law’). You can even use M-x subword-mode in non-CC Mode buffers.

In the GNU project, we recommend using underscores to separate words within an identifier in C or C++, rather than using case distinctions.

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 C-j (newline-and-indent), 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 C-j. We use c-initialization-hook here to make sure the keymap is loaded before we try to change it.

          (defun my-bind-clb ()
            (define-key c-mode-base-map "\C-j" '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.

M-x ff-find-related-file

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.

30.13 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.

30.14 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), 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’ and ‘.f95’. 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 revelant.

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), 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.

• Motion: Moving point by statements or subprograms.
• Indent: Indentation commands for Fortran.
• Comments: Inserting and aligning comments.
• Autofill: Auto fill support for Fortran.
• Columns: Measuring columns for valid Fortran.
• Abbrev: Built-in abbrevs for Fortran keywords.

30.14.1 Motion Commands

In addition to the normal commands for moving by and operating on “defuns” (Fortran subprograms—functions and subroutines, using the commands fortran-beginning-of-subprogram and fortran-end-of-subprogram; as well as modules for F90 mode), 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 block, whichever is encountered first. (f90-next-block). A code block is a subroutine, if–endif statement, and so forth. This command exists for F90 mode only, not Fortran mode. With a numeric argument, this moves forward that many blocks.

C-c C-a

Move point backward to the previous code 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.

30.14.2 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.

• Commands: Commands for indenting and filling Fortran.
• Contline: How continuation lines indent.
• Numbers: How line numbers auto-indent.
• Conv: Conventions you must obey to avoid trouble.
• Vars: Variables controlling Fortran indent style.

30.14.2.1 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 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 runs 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.

30.14.2.2 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.) 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,” with another style of 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 always 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 always consist of one tab character.

30.14.2.3 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 GNU Emacs.)

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.

30.14.2.4 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.

30.14.2.5 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 ended 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 is nil.

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 less than this much. 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 less than this much. The default is 8.

The variables controlling the indentation of comments are described in the following section.

30.14.3 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 also need to adjust fortran-comment-line-start-skip.

M-;

Align comment or insert new comment (comment-dwim).

C-x ;

Applies to nonstandard ‘!’ comments only.

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 statement indentation is fortran-minimum-statement-indent-fixed for fixed form continuation line style and fortran-minimum-statement-indent-tab for tab format 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 ; 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.

30.14.4 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 ForIndent Cont). 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.

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 turn-on-auto-fill to fortran-mode-hook. See Hooks.

30.14.5 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 character 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. 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.

30.14.6 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.

31 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 larger process of compiling and testing programs.

• Compilation: Compiling programs in languages other than Lisp (C, Pascal, etc.).
• Compilation Mode: The mode for visiting compiler errors.
• Compilation Shell: Customizing your shell properly for use in the compilation buffer.
• Grep Searching: Searching with grep.
• Flymake: Finding syntax errors on the fly.
• Debuggers: Running symbolic debuggers for non-Lisp programs.
• Executing Lisp: Various modes for editing Lisp programs, with different facilities for running the Lisp programs.
• Libraries: Creating Lisp programs to run in Emacs.
• Eval: Executing a single Lisp expression in Emacs.
• Interaction: Executing Lisp in an Emacs buffer.
• External Lisp: Communicating through Emacs with a separate Lisp.

31.1 Running Compilations under Emacs

Emacs can run compilers for noninteractive languages such as C and Fortran as inferior processes, feeding the error log into an Emacs buffer. It can also parse the error messages and show you the source lines where compilation errors occurred.

M-x compile

Run a compiler asynchronously under Emacs, with error messages going to the ‘*compilation*’ buffer.

M-x recompile

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, do M-x compile. This command reads a shell command line using the minibuffer, and then executes the command in an inferior shell, putting output in the buffer named ‘*compilation*’. The current buffer's default directory is used as the working directory for the execution of the command; normally, therefore, the compilation happens in this directory.

The default for the compilation command is normally ‘make -k’, which is correct most of the time for nontrivial programs. See Make. If you have done M-x compile before, the default each time is the command you used the previous time. compile stores this command in the variable compile-command, so setting that variable specifies the default for the next use of M-x compile. If a file specifies a file local value for compile-command, that provides the default when you type M-x compile in that file's buffer. See File Variables.

Starting a compilation displays the buffer ‘*compilation*’ in another window but does not select it. The buffer's mode line tells you whether compilation is finished, with the word ‘run’, ‘signal’ or ‘exit’ inside the parentheses. You do not have to keep this buffer visible; compilation continues in any case. While a compilation is going on, the string ‘Compiling’ appears in the mode lines of all windows. When this string disappears, the compilation is finished.

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. If point is not at the end of the buffer, it remains fixed while more compilation output is added at the end of the buffer.

If you change the variable compilation-scroll-output to a non-nil value, the compilation buffer will scroll automatically to follow the output as it comes in. If the value is first-error, the scrolling stops at the first error that appears, leaving point at that error. For any other non-nil value, the buffer continues scrolling until there is no more output.

To rerun the last compilation with the same command, type M-x recompile. This automatically 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.

When the compiler process terminates, 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), instead of ‘run’.

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 asks for confirmation before actually killing a compilation that is running. You can also kill the compilation process with M-x kill-compilation.

To run two compilations at once, start the first one, then rename the ‘*compilation*’ buffer (perhaps using rename-uniquely; see Misc Buffer), then switch buffers and start the other compilation. This will create a new ‘*compilation*’ buffer.

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 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

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.

31.2 Compilation Mode

The ‘*compilation*’ buffer uses a special major mode, Compilation mode, whose main feature is to provide a convenient way to visit the source line corresponding to an error message. These commands are also available in other special buffers that list locations in files, including those made by M-x grep and M-x occur.

M-g M-n

M-g n

C-x `

Visit the locus of the next error message or match.

M-g M-p

M-g p

Visit the locus of the previous error message or match.

<RET>

Visit the locus of the error message that point is on. This command is used in the compilation buffer.

Mouse-2

Visit the locus of the error message that you click on.

M-n

Find and highlight the locus of the next error message, without selecting the source buffer.

M-p

Find and highlight the locus of the previous error message, without selecting the source buffer.

M-}

Move point to the next error for a different file than the current one.

M-{

Move point to the previous error for a different file than the current one.

C-c C-f

Toggle Next Error Follow minor mode, which makes cursor motion in the compilation buffer produce automatic source display.

You can visit the source for any particular error message by moving point in the ‘*compilation*’ buffer to that error message and typing <RET> (compile-goto-error). Alternatively, you can click Mouse-2 on the error message; you need not switch to the ‘*compilation*’ buffer first. If you set the variable compilation-auto-jump-to-first-error to a non-nil value, Emacs automatically jumps to the first error, if any, as soon as it appears in the ‘*compilation*’ buffer.

To parse the compiler error messages sequentially, type C-x ` (next-error). The character following the C-x is the backquote or “grave accent,” not the single-quote. This command is available in all buffers, not just in ‘*compilation*’; it displays the next error message at the top of one window and source location of the error in another window. It also temporarily highlights the relevant source line, for a period controlled by the variable next-error-highlight.

The first time C-x ` is used after the start of a compilation, it moves to the first error's location. Subsequent uses of C-x ` advance down to subsequent errors. If you visit a specific error message with <RET> or Mouse-2, subsequent C-x ` commands advance from there. When C-x ` gets to the end of the buffer and finds no more error messages to visit, it fails and signals an Emacs error. C-u C-x ` starts scanning from the beginning of the compilation buffer, and goes to the first error's location.

By default, C-x ` skips less important messages. The variable compilation-skip-threshold controls this. If its value is 2, C-x ` skips anything less than error, 1 skips anything less than warning, and 0 doesn't skip any messages. The default is 1.

When the window has a left fringe, an arrow in the fringe points to the current message in the compilation buffer. The variable compilation-context-lines controls the number of lines of leading context to display before the current message. Going to an error message location scrolls the ‘*compilation*’ buffer to put the message that far down from the top. The value nil is special: if there's a left fringe, the window doesn't scroll at all if the message is already visible. If there is no left fringe, nil means display the message at the top of the window.

If you're not in the compilation buffer when you run next-error, Emacs will look for a buffer that contains error messages. First, it looks for one displayed in the selected frame, then for one that previously had next-error called on it, and then at the current buffer. Finally, Emacs looks at all the remaining buffers. next-error signals an error if it can't find any such buffer.

To parse messages from the compiler, Compilation mode uses the variable compilation-error-regexp-alist which lists various formats of error messages and tells Emacs how to extract the source file and the line number from the text of a message. If your compiler isn't supported, you can tailor Compilation mode to it by adding elements to that list. A similar variable grep-regexp-alist tells Emacs how to parse output of a grep command.

Compilation mode also redefines the keys <SPC> and <DEL> to scroll by screenfuls, and M-n (compilation-next-error) and M-p (compilation-previous-error) to move to the next or previous error message. You can also use M-{ (compilation-next-file and M-} (compilation-previous-file) to move up or down to an 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. For instance, moving the cursor to the next error message causes the location of that error to be displayed immediately.

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. This defines the keys <RET> and Mouse-2, as in the Compilation major mode.

Compilation minor mode works in any buffer, as long as the contents are in a format that it understands. In an Rlogin buffer (see Remote Host), Compilation minor mode automatically accesses remote source files by FTP (see File Names).

31.3 Subshells for Compilation

Emacs 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's name may be .bashrc, .profile, .cshrc, .shrc, or various other things, depending on the 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 = ...

There may well be other things that your shell's init file ought to do only for an interactive shell. You can use the same method to conditionalize them.

The MS-DOS “operating system” does not support asynchronous subprocesses; to work around this lack, M-x compile runs the compilation command synchronously on MS-DOS. As a consequence, you must wait until the command finishes before you can do anything else in Emacs. See MS-DOS.

31.4 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 buffer of matches uses Grep mode, which is a variant of Compilation mode (see Compilation Mode).

M-x grep

M-x lgrep

Run grep asynchronously under Emacs, with matching lines listed 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 buffer named ‘*grep*’.

M-x zrgrep

Run zgrep and collect output in the buffer named ‘*grep*’.

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 tag (see Tags) 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 C-x `, <RET>, and so forth, just like compilation errors.

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.

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 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.

Subdirectories listed in the variable grep-find-ignored-directories such as those typically used by various version control systems, like CVS and arch, are automatically skipped by rgrep.

31.5 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 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 activate Flymake mode, type M-x flymake-mode. You can move to the errors spotted by Flymake mode with M-x flymake-goto-next-error and M-x flymake-goto-prev-error. To display any error messages associated with the current line, use M-x flymake-display-err-menu-for-current-line.

For more details about using Flymake, see Flymake.

31.6 Running Debuggers Under Emacs

The GUD (Grand Unified Debugger) library provides an Emacs interface to a wide variety of symbolic debuggers. Unlike the GDB graphical interface, which only runs GDB (see GDB Graphical Interface), GUD can also run DBX, SDB, XDB, Perl's debugging mode, the Python debugger PDB, or the Java Debugger JDB.

In addition, Emacs contains a built-in system for debugging Emacs Lisp programs. See The Lisp Debugger, for information on the Emacs Lisp debugger.

• Starting GUD: How to start a debugger subprocess.
• Debugger Operation: Connection between the debugger and source buffers.
• Commands of GUD: Key bindings for common commands.
• GUD Customization: Defining your own commands for GUD.
• GDB Graphical Interface: An enhanced mode that uses GDB features to implement a graphical debugging environment through Emacs.

31.6.1 Starting GUD

There are several commands for starting a debugger under GUD, each corresponding to a particular debugger program.

M-x gdb <RET> file <RET>

Run GDB as a subprocess of Emacs. This uses an IDE-like graphical interface; see GDB Graphical Interface. Only GDB works with the graphical interface.

M-x gud-gdb <RET> file <RET>

Run GDB as a subprocess of Emacs. This command creates a buffer for input and output to GDB, and switches to it. If a GDB buffer already exists, it just switches to that buffer.

M-x dbx <RET> file <RET>

Run DBX as a subprocess of Emacs. Since Emacs does not implement a graphical interface for DBX, communication with DBX works by typing commands in the GUD interaction buffer. The same is true for all the other supported debuggers.

M-x xdb <RET> file <RET>

Run XDB as a subprocess of Emacs. Use the variable gud-xdb-directories to specify directories to search for source files.

M-x sdb <RET> file <RET>

Run SDB as a subprocess of Emacs.

Some versions of SDB do not mention source file names in their messages. When you use them, you need to have a valid tags table (see Tags) in order for GUD to find functions in the source code. If you have not visited a tags table or the tags table doesn't list one of the functions, you get a message saying ‘The sdb support requires a valid tags table to work’. If this happens, generate a valid tags table in the working directory and try again.

M-x perldb <RET> file <RET>

Run the Perl interpreter in debug mode to debug file, a Perl program.

M-x jdb <RET> file <RET>

Run the Java debugger to debug file.

M-x pdb <RET> file <RET>

Run the Python debugger to debug file.

Each of these commands takes one argument: a command line to invoke the debugger. In the simplest case, specify just the name of the executable file you want to debug. You may also use options that the debugger supports. However, shell wildcards and variables are not allowed. GUD assumes that the first argument not starting with a ‘-’ is the executable file name.

Tramp provides a facility to debug programs on remote hosts (see Running a debugger on a remote host), whereby both the debugger and the program being debugged are on the same remote host. This should not be confused with debugging programs remotely, where the program and the debugger run on different machines, as can be done using the GDB remote debugging feature, for example (see Debugging Remote Programs).

31.6.2 Debugger Operation

Generally when you run a debugger with GUD, the debugger uses an Emacs buffer for its ordinary input and output. This is called the GUD buffer. Input and output from the program you are debugging also use this buffer. We call this text command mode. The GDB Graphical Interface can use further buffers (see GDB Graphical Interface).

The debugger displays the source files of the program by visiting them in Emacs buffers. An arrow in the left fringe indicates the current execution line.²¹ Moving point in this buffer does not move the arrow. The arrow is not part of the file's text; it appears only on the screen.

You can start editing these source files at any time in the buffers that display them. If you do modify a source file, keep in mind that inserting or deleting lines will throw off the arrow's positioning; GUD has no way of figuring out which line corresponded before your changes to the line number in a debugger message. Also, you'll typically have to recompile and restart the program for your changes to be reflected in the debugger's tables.

The Tooltip facility (see Tooltips) provides support for GUD. You activate this feature by turning on the minor mode gud-tooltip-mode. Then you can display a variable's value in a tooltip simply by pointing at it with the mouse. This operates in the GUD buffer and in source buffers with major modes in the list gud-tooltip-modes. If the variable gud-tooltip-echo-area is non-nil then the variable's value is displayed in the echo area. When debugging a C program using the GDB Graphical Interface, you can also display macro definitions associated with an identifier when the program is not executing.

GUD tooltips are disabled when you use GDB in text command mode (see GDB Graphical Interface), because displaying an expression's value in GDB can sometimes expand a macro and result in a side effect that interferes with the program's operation. The GDB graphical interface supports GUD tooltips and assures they will not cause side effects.

31.6.3 Commands of GUD

The GUD interaction buffer uses a variant of Shell mode, so the Emacs commands of Shell mode are available (see Shell Mode). All the usual commands for your debugger are available, and you can use the Shell mode history commands to repeat them. If you wish, you can control your debugger process entirely through this buffer.

GUD mode also provides commands for setting and clearing breakpoints, for selecting stack frames, and for stepping through the program. These commands are available both in the GUD buffer and globally, but with different key bindings. It also has its own tool bar from which you can invoke the more common commands by clicking on the appropriate icon. This is particularly useful for repetitive commands like gud-next and gud-step, and allows you to keep the GUD buffer hidden.

The breakpoint commands are normally used in source file buffers, because that is the easiest way to specify where to set or clear the breakpoint. Here's the global command to set a breakpoint:

C-x <SPC>

Set a breakpoint on the source line that point is on.

Here are the other special commands provided by GUD. The keys starting with C-c are available only in the GUD interaction buffer. The key bindings that start with C-x C-a are available in the GUD interaction buffer and also in source files. Some of these commands are not available to all the supported debuggers.

C-c C-l

C-x C-a C-l

Display in another window the last line referred to in the GUD buffer (that is, the line indicated in the last location message). This runs the command gud-refresh.

C-c C-s

C-x C-a C-s

Execute a 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 a single line of code, stepping across entire function calls at full speed (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.

31.6.4 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; perldb-mode-hook, for Perl debugging mode; pdb-mode-hook, for PDB; jdb-mode-hook, for JDB. You can use these hooks to define custom key bindings for the debugger interaction buffer. See Hooks.

Here is a convenient way to define a command that sends a particular command string to the debugger, and set up a key binding for it in the debugger 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).

31.6.5 GDB Graphical Interface

The command gdb starts GDB in a graphical interface, using Emacs windows for display program state information. With it, you do not need to use textual GDB commands; you can control the debugging session with the mouse. For example, you can click in the fringe of a source buffer to set a breakpoint there, or on a stack frame in the stack buffer to select that frame.

This mode requires telling GDB that its “screen size” is unlimited, so it sets the height and width accordingly. For correct operation you must not change these values during the GDB session.

To run GDB in text command mode, like the other debuggers in Emacs, use M-x gud-gdb. You need to use text command mode to debug multiple programs within one Emacs session.

• GDB-UI Layout: Control the number of displayed buffers.
• Source Buffers: Use the mouse in the fringe/margin to control your program.
• Breakpoints Buffer: A breakpoint control panel.
• Stack Buffer: Select a frame from the call stack.
• Other GDB-UI Buffers: Input/output, locals, registers, assembler, threads and memory buffers.
• Watch Expressions: Monitor variable values in the speedbar.
• Reverse Debugging: Execute and reverse debug your program.

31.6.5.1 GDB User Interface Layout

If the variable gdb-many-windows is nil (the default value) then M-x gdb normally displays only the GUD buffer. However, if the variable gdb-show-main is also non-nil, it starts with two windows: one displaying the GUD 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 buffer (I/O of GDB)      |   Locals/Registers buffer      |
     |--------------------------------+--------------------------------+
     |   Primary Source buffer        |   I/O buffer for debugged pgm  |
     |--------------------------------+--------------------------------+
     |   Stack buffer                 |   Breakpoints/Threads buffer   |
     +--------------------------------+--------------------------------+

However, if gdb-use-separate-io-buffer is nil, the I/O buffer does not appear and the primary source buffer occupies the full width of the frame.

If you change the window layout, for example, while editing and re-compiling your program, then you can restore this standard window layout with the command gdb-restore-windows.

To switch between this standard layout and a simple layout containing just the GUD buffer and a source file, type M-x gdb-many-windows.

You may also specify additional GDB-related buffers to display, either in the same frame or a different one. Select the buffers you want with the ‘GUD->GDB-Windows’ and ‘GUD->GDB-Frames’ sub-menus. If the menu-bar is unavailable, type M-x gdb-display-buffertype-buffer or M-x gdb-frame-buffertype-buffer respectively, where buffertype is the relevant buffer type, such as ‘breakpoints’. Most of these buffers are read-only, and typing q in them kills them.

When you finish debugging, kill the GUD 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 continue debugging. When you restart execution, GDB will automatically find your new executable. Keeping the GUD 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.

31.6.5.2 Source Buffers

Many GDB commands can be entered using key bindings or the tool bar but sometimes it is quicker to use the fringe. These commands either manipulate breakpoints or control program execution. When there is no fringe, you can use the margin but this is only present when the source file already has a breakpoint.

You can click Mouse-1 in the fringe or display margin of a source buffer to set a breakpoint there and, on a graphical display, a red bullet will appear on that line. If a breakpoint already exists on that line, the same click will remove it. You can also enable or disable a breakpoint by clicking C-Mouse-1 on the bullet.

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 higher level frames.

If you drag the arrow in the fringe with Mouse-1 (gdb-mouse-until), execution will continue to the line where you release the button, provided it is still in the same frame. Alternatively, you can click Mouse-3 at some point in the fringe of this buffer and execution will advance to there. A similar command (gdb-mouse-jump) allows you to jump to a source line without executing the intermediate lines by clicking C-Mouse-3. 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.

Mouse-1

Set or clear a breakpoint.

C-Mouse-1

Enable or disable a breakpoint.

Mouse-3

Continue execution to here.

C-Mouse-3

Jump to here.

If the variable gdb-find-source-frame is non-nil and execution stops in a frame for which there is no source code e.g after an interrupt, then Emacs finds and displays the first frame further up stack for which there is source. If it is nil then the source buffer continues to display the last frame which maybe more useful, for example, when re-setting a breakpoint.

31.6.5.3 Breakpoints Buffer

The breakpoints buffer shows the existing breakpoints, watchpoints and catchpoints (see Breakpoints). It has these special commands, which mostly apply to the current breakpoint, the breakpoint which point is on.

<SPC>

Enable/disable the current breakpoint (gdb-toggle-breakpoint). On a graphical display, this changes the color of a bullet in the margin of a source buffer at the relevant line. This is red when the breakpoint is enabled and grey when it is disabled. Text-only terminals correspondingly display a ‘B’ or ‘b’.

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.

When gdb-many-windows is non-nil, the breakpoints buffer shares its window with the threads buffer. To switch from one to the other click with Mouse-1 on the relevant button in the header line.

31.6.5.4 Stack Buffer

The stack buffer displays a call stack, with one line for each of the nested subroutine calls (stack frames) now active in the program. See Backtraces.

An arrow in the fringe points to the selected frame or, if the fringe is not present, the number of the selected frame is displayed in reverse contrast. To select a frame in GDB, move point in the stack buffer to that stack frame and type <RET> (gdb-frames-select), or click Mouse-2 on a stack frame. If the locals buffer is visible, selecting a stack frame updates it to display the local variables of the new frame.

31.6.5.5 Other Buffers

Input/Output Buffer

If the variable gdb-use-separate-io-buffer is non-nil, the program being debugged takes its input and displays its output here. Otherwise it uses the GUD buffer for that. To toggle whether GUD mode uses this buffer, do M-x gdb-use-separate-io-buffer. This takes effect when you next restart the program you are debugging.

The history and replay commands from Shell mode are available here, as are the commands to send signals to the debugged program. See Shell Mode.

Locals Buffer

The locals buffer displays the values of local variables of the current frame for simple data types (see Frame Info). 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, move point to their name and press <RET>, or alternatively click Mouse-2 there, to examine their values. With earlier versions of GDB, use Mouse-2 or <RET> on the type description (‘[struct/union]’ or ‘[array]’). See Watch Expressions.

Registers Buffer

The registers buffer displays the values held by the registers (see Registers). 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. With earlier versions of GDB, you can press <SPC> to toggle the display of floating point registers (toggle-gdb-all-registers).

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.

Threads Buffer

The threads buffer displays a summary of all threads currently in your program (see Threads). Move point to any thread in the list and press <RET> to select it (gdb-threads-select) and display the associated source in the primary source buffer. Alternatively, click Mouse-2 on a thread to select it. If the locals buffer is visible, its contents update to display the variables that are local in the new thread.

When there is more than one main thread and the threads buffer is present, Emacs displays the selected thread number in the mode line of many of the GDB-UI Buffers.

Memory Buffer

The memory buffer lets you examine sections of program memory (see Memory). 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.

When gdb-many-windows is non-nil, the threads buffer shares its window with the breakpoints buffer, and the locals buffer with the registers buffer. To switch from one to the other click with Mouse-1 on the relevant button in the header line.

31.6.5.6 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. 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 re-entering the same function, 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.

31.6.5.7 Reverse Debugging

The GDB tool bar shares many buttons with the other GUD debuggers for tasks like stepping and printing expressions. It also has a further set of buttons that allow reverse debugging (see Process Record and Replay). This is useful when it takes a long time to reproduce the conditions where your program fails or for transient problems, like race conditions in multi-threaded programs, where a failure might otherwise be hard to reproduce.

To use reverse debugging, set a breakpoint slightly before the location of interest and run your program to that point. Enable process recording by clicking on the record button. At this point, a new set of buttons appear. These buttons allow program execution in the reverse direction. Run your program over the code where the problem occurs, and then use the new set of buttons to retrace your steps, examine values, and analyze the problem. When analysis is complete, turn off process recording by clicking on the record button again.

31.7 Executing Lisp Expressions

Emacs has several different major modes for Lisp and Scheme. They are the same in terms of editing commands, but differ in the commands for executing Lisp expressions. Each mode has its own purpose.

Emacs-Lisp mode

The mode for editing source files of programs to run in Emacs Lisp. This mode defines C-M-x to evaluate the current defun. See Lisp Libraries.

Lisp Interaction mode

The mode for an interactive session with Emacs Lisp. It defines C-j to evaluate the sexp before point and insert its value in the buffer. See Lisp Interaction.

Lisp mode

The mode for editing source files of programs that run in Lisps other than Emacs Lisp. This mode defines C-M-x to send the current defun to an inferior Lisp process. See External Lisp.

Inferior Lisp mode

The mode for an interactive session with an inferior Lisp process. This mode combines the special features of Lisp mode and Shell mode (see Shell Mode).

Scheme mode

Like Lisp mode but for Scheme programs.

Inferior Scheme mode

The mode for an interactive session with an inferior Scheme process.

Most editing commands for working with Lisp programs are in fact available globally. See Programs.

31.8 Libraries of Lisp Code for Emacs

Lisp code for Emacs editing commands is stored in files whose names conventionally end in .el. This ending tells Emacs to edit them in Emacs-Lisp mode (see Executing Lisp).

Emacs Lisp code can be compiled into byte-code, which loads faster, takes up less space, and executes faster. See Byte Compilation. By convention, the compiled code for a library goes in a separate file whose name ends in ‘.elc’. Thus, the compiled code for foo.el goes in foo.elc.

To execute a file of Emacs Lisp code, use M-x load-file. This command reads a file name using the minibuffer and then executes the contents of that file as Lisp code. It is not necessary to visit the file first; in any case, this command reads the file as found on disk, not text in an Emacs buffer.

Once a file of Lisp code is installed in the Emacs Lisp library directories, users can load it using M-x load-library. Programs can load it by calling load, a more primitive function that is similar but accepts some additional arguments.

M-x load-library differs from M-x load-file in that it searches a sequence of directories and tries three file names in each directory. Suppose your argument is lib; the three names are lib.elc, lib.el, and lastly just lib. If lib.elc exists, it is by convention the result of compiling lib.el; it is better to load the compiled file, since it will load and run faster.

If load-library finds that lib.el is newer than lib.elc file, it issues a warning, because it's likely that somebody made changes to the .el file and forgot to recompile it. Nonetheless, it loads lib.elc. This is because people often leave unfinished edits the source file, and don't recompile it until they think it is ready to use.

The variable load-path specifies the sequence of directories searched by M-x load-library. Its value should be a list of strings that are directory names; in addition, nil in this list stands for the current default directory. (Generally, it is not a good idea to put nil in the list; if you find yourself wishing that nil were in the list, most likely what you really want is to do M-x load-file this once.)

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, put them in a single directory and add that directory to load-path, by adding a line like this to your init file (see Init File):

     (add-to-list 'load-path "/path/to/lisp/libraries")

Some commands are autoloaded: when you run them, Emacs will automatically load the associated library first. For instance, the compile and compilation-mode commands (see Compilation) are autoloaded; if you call either command, Emacs automatically loads the compile library. In contrast, the command recompile is not autoloaded, so it is unavailable until you load the compile library.

By default, Emacs refuses to load compiled Lisp files which were compiled with XEmacs, a modified versions of Emacs—they can cause Emacs to crash. Set the variable load-dangerous-libraries to t if you want to try loading them.

31.9 Evaluating Emacs Lisp Expressions

Lisp programs intended to be run in Emacs should be edited in Emacs-Lisp mode; this happens automatically for file names ending in .el. By contrast, Lisp mode itself is used for editing Lisp programs intended for other Lisp systems. To switch to Emacs-Lisp mode explicitly, use the command M-x emacs-lisp-mode.

For testing of Lisp programs to run in Emacs, it is often useful to evaluate part of the program as it is found in the Emacs buffer. For example, after changing the text of a Lisp function definition, evaluating the definition installs the change for future calls to the function. Evaluation of Lisp expressions is also useful in any kind of editing, for invoking noninteractive functions (functions that are not commands).

M-:

Read a single Lisp expression in the minibuffer, evaluate it, and print the value in the echo area (eval-expression).

C-x C-e

Evaluate the Lisp expression before point, and print the value in the echo area (eval-last-sexp).

C-M-x

Evaluate the defun containing or after point, and print the value in the echo area (eval-defun).

M-x eval-region

Evaluate all the Lisp expressions in the region.

M-x eval-buffer

Evaluate all the Lisp expressions in the buffer.

M-: (eval-expression) is the most basic command for evaluating a Lisp expression interactively. It reads the expression using the minibuffer, so you can execute any expression on a buffer regardless of what the buffer contains. When the expression is evaluated, the current buffer is once again the buffer that was current when M-: was typed.

In Emacs-Lisp mode, the key C-M-x is bound to the command eval-defun, which parses the defun containing or following point as a Lisp expression and evaluates it. The value is printed in the echo area. This command is convenient for installing in the Lisp environment changes that you have just made in the text of a function definition.

C-M-x treats defvar expressions specially. Normally, evaluating a defvar expression does nothing if the variable it defines already has a value. But C-M-x unconditionally resets the variable to the initial value specified in the defvar expression. defcustom expressions are treated similarly. This special feature is convenient for debugging Lisp programs. Typing C-M-x on a defface expression reinitializes the face according to the defface specification.

The command C-x C-e (eval-last-sexp) evaluates the Lisp expression preceding point in the buffer, and displays the value in the echo area. It is available in all major modes, not just Emacs-Lisp mode. It does not treat defvar specially.

When the result of an evaluation is an integer, you can type C-x C-e a second time to display the value of the integer result in additional formats (octal, hexadecimal, and character).

If C-x C-e, or M-: is given a numeric argument, it inserts the value into the current buffer at point, rather than displaying it in the echo area. The argument's value does not matter. C-M-x with a numeric argument instruments the function definition for Edebug (see Instrumenting for Edebug).

The most general command for evaluating Lisp expressions from a buffer is eval-region. 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. This is a reasonable way to install the contents of a file of Lisp code that you are ready to test. Later, as you find bugs and change individual functions, use C-M-x on each function that you change. This keeps the Lisp world in step with the source file.

The two customizable variables 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. eval-expression-debug-on-error controls whether evaluation errors invoke the debugger when these commands are used; its default is t.

31.10 Lisp Interaction Buffers

When Emacs starts up, it contains a buffer named ‘*scratch*’, which is provided for evaluating Lisp expressions interactively inside Emacs. Its major mode is Lisp Interaction mode.

The simplest way to use the ‘*scratch*’ buffer is to insert Lisp expressions and type C-j (eval-print-last-sexp) after each expression. This command reads the Lisp expression before point, evaluates it, and inserts the value in printed representation before point. The result is a complete typescript of the expressions you have evaluated and their values.

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 string or nil. If you set it to the empty string, or nil, the initial message is suppressed.

All other commands in Lisp Interaction mode are the same as in Emacs Lisp mode. You can enable Lisp Interaction mode by typing M-x lisp-interaction-mode.

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.

31.11 Running an External Lisp

Emacs has facilities for running programs in other Lisp systems. You can run a Lisp process as an inferior of Emacs, and pass expressions to it to be evaluated. You can also pass changed function definitions directly from the Emacs buffers in which you edit the Lisp programs to the inferior Lisp process.

To run an inferior Lisp process, type M-x run-lisp. This runs the program named lisp, the same program you would run by typing lisp as a shell command, with both input and output going through an Emacs buffer named ‘*lisp*’. That is to say, any “terminal output” from Lisp will go into the buffer, advancing point, and any “terminal input” for Lisp comes from text in the buffer. (You can change the name of the Lisp executable file by setting the variable inferior-lisp-program.)

To give input to Lisp, go to the end of the buffer and type the input, terminated by <RET>. The ‘*lisp*’ buffer is in Inferior Lisp mode, which combines the special characteristics of Lisp mode with most of the features of Shell mode (see Shell Mode). The definition of <RET> to send a line to a subprocess is one of the features of Shell mode.

For the source files of programs to run in external Lisps, use Lisp mode. You can switch to this mode with M-x lisp-mode, and it is used automatically for files whose names end in .l, .lsp, or .lisp.

When you edit a function in a Lisp program you are running, the easiest way to send the changed definition to the inferior Lisp process is the key C-M-x. In Lisp mode, this runs the function lisp-eval-defun, which finds the defun around or following point and sends it as input to the Lisp process. (Emacs can send input to any inferior process regardless of what buffer is current.)

Contrast the meanings of C-M-x in Lisp mode (for editing programs to be run in another Lisp system) and Emacs-Lisp mode (for editing Lisp programs to be run in Emacs; see see Lisp Eval): in both modes it has the effect of installing the function definition that point is in, but the way of doing so is different according to where the relevant Lisp environment is found.

32 Maintaining Large Programs

This chapter describes Emacs features for maintaining large programs.

• Version Control: Using version control systems.
• Change Log: Maintaining a change history for your program.
• Tags: Go directly to any function in your program in one command. Tags remembers which file it is in.
• EDE: An integrated development environment for Emacs.
• Emerge: A convenient way of merging two versions of a program.

32.1 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 GNU Arch, Bazaar, CVS, Git, Mercurial, Monotone, RCS, SCCS/CSSC, and Subversion. Of these, the GNU project distributes CVS, Arch, 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).

• Introduction to VC: How version control works in general.
• VC Mode Line: How the mode line shows version control status.
• Basic VC Editing: How to edit a file under version control.
• Log Buffer: Features available in log entry buffers.
• Old Revisions: Examining and comparing old versions.
• Secondary VC Commands: The commands used a little less frequently.
• VC Directory Mode: Listing files managed by version control.
• Branches: Multiple lines of development.
• Remote Repositories: Efficient access to remote CVS servers.
• Revision Tags: Symbolic names for revisions.
• Miscellaneous VC: Various other commands and features of VC.
• Customizing VC: Variables that change VC's behavior.

32.1.1 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 Emacs, 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.

• Why Version Control?: Understanding the problems it addresses.
• Version Control Systems: Supported version control back-end systems.
• VCS Concepts: Words and concepts related to version control.
• VCS Merging: How file conflicts are handled.
• VCS Changesets: How changes are grouped.
• VCS Repositories: Where version control repositories are stored.
• Types of Log File: The VCS log in contrast to the ChangeLog.

32.1.1.1 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 to it. 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.

32.1.1.2 Supported Version Control Systems

VC currently works with many different version control systems, which it refers to as back ends:

• 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.

• CVS is the free version control system that was, until recently (circa 2008), used by the majority of free software projects. Nowadays, it is slowly being 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).

• GNU Arch is one of the earliest distributed version control systems (the other being Monotone). See VCS Concepts, for a description of distributed version control systems. It is no longer under active development, and has been deprecated in favor of Bazaar.

• Git is a distributed 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.

• Mercurial (hg) is a distributed version control system broadly resembling git. VC supports most Mercurial commands, with the exception of repository sync operations.

• Bazaar (bzr) is a distributed version control system that supports both repository-based and distributed versioning. VC supports most basic editing operations under Bazaar.

Previous versions of VC supported a version control system known as Meta-CVS. This support was dropped due to limited interest from users and developers.

32.1.1.3 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 commit (or check in) the changes; this records the changes in the repository, along with a descriptive log entry.

A copy of a file stored in a repository is called a revision. The history of a file is a sequence of revisions. Each revision is named by a revision ID. The format of the revision ID 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.

32.1.1.4 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 check out and 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 Interlocking). 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. Distributed version control systems, such as GNU Arch, 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.

32.1.1.5 Changeset-based vs File-based Version Control

On SCCS, RCS, CVS, and other early version control systems, 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 checkin 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.

32.1.1.6 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, and Subversion 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 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.

32.1.1.7 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 Log Buffer). This is called the version control log.

The other kind of log is the file ChangeLog (see Change Log). 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 Log. 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.

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 checking in the change (see Log Buffer). Or you can write the entry in the log buffer while checking in the change, and later use the C-x v a command to copy it to ChangeLog (see Change Logs and VC).

32.1.2 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 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. 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’.

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) 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.

32.1.3 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 on. 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).

The principal VC command is an all-purpose command, C-x v v (vc-next-action), that performs either registration, locking, merging or a check-in (depending on the situation) on the current VC fileset. You can use C-x v v in a file-visiting buffer or in a VC Directory buffer.

C-x v v

Perform the appropriate next version control operation on the VC fileset.

The precise action of C-x v v depends on the state of the VC fileset, and whether the version control system uses locking or merging. This is described in detail in the subsequent sections.

VC filesets are the way that VC mode bridges the gap between file-based and changeset-based version control systems. They are, essentially, a way to pass multiple file arguments as a group to version control commands. For example, on Subversion, a checkin with a multi-file VC fileset becomes a joint commit, as though you had typed svn commit with those file arguments at the shell command line. All files in a VC fileset must be under the same version control system; if they are not, Emacs signals an error when you attempt to execute a command on the fileset.

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.

• VC With A Merging VCS: Without locking: default mode for CVS.
• VC With A Locking VCS: RCS in its default mode, SCCS, and optionally CVS.
• Advanced C-x v v: Advanced features available with a prefix argument.

32.1.3.1 Basic Version Control with Merging

When your version control system is merging-based (the default for CVS and all newer version control systems), work files are always writable; you need not do anything special to begin editing a file. The status indicator on the mode line is ‘-’ if the file is unmodified; it flips to ‘:’ as soon as you save any changes (see VC Mode Line).

Here is what C-x v v does when using a merging-based system:

• If the work file is in a directory that is not controlled by any version control system, prompt for a repository type. Then, create a version control repository of that type and register the file with it.
• If the work file is in a directory that is controlled by a version control system but not registered with it, register the file.
• If the work file is the same as in the repository, do nothing.
• If you have not changed the work file, but some other user has checked in changes to the repository, merge those changes into the work file.
• If you have made modifications to the work file, attempt to commit the changes. To do this, Emacs first reads the log entry for the new revision (see Log Buffer). If some other user has committed changes to the repository since you last checked it out, the checkin fails. In that case, type C-x v v again to merge those changes into your own work file; this puts the work file into a “conflicted” state. Type C-x v v to clear the “conflicted” state; VC then regards the file as up-to-date and modified, and you can try to check it in again.

  To pick up any recent changes from the repository without trying to commit your own changes, type C-x v m <RET>. See Merging.

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, his 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 checking in 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 VC With A Locking VCS).

32.1.3.2 Basic Version Control with Locking

Under a locking-based version control system (such as SCCS, and RCS in its default mode), C-x v v does the following:

• If the file is not locked, lock it and make it writable, so that you can change it.
• If the file is locked by you, and contains changes, commit the changes. In order to do this, Emacs first reads the log entry for the new revision. See Log Buffer.
• If the file is locked by you, but you have not changed it since you locked it, release the lock and makes the file read-only again.
• If the file is locked by some other user, ask whether you want to “steal the lock” from that user. If you say yes, the file becomes locked by you, but a message is sent to the person who had formerly locked the file, to inform him of what has happened.

These rules also apply when you use CVS in locking mode, except that CVS does not support stealing a lock.

32.1.3.3 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.

• If the file is modified (or locked), you can specify the revision ID to use for the new version that you commit. This is one way to create a new branch (see Branches).
• If the file is not modified (and unlocked), you can specify the revision to select; this lets you start working from an older revision, or on another branch. If you do not enter any revision, that takes you to the highest (“head”) revision on the current branch; therefore C-u C-x v v <RET> is a convenient way to get the latest version of a file from the repository.
• Instead of the revision ID, you can also specify the name of a version control system. This is useful when one file is being managed with two version control systems at the same time (see Local Version Control).

32.1.4 Features of the Log Entry Buffer

When you tell VC to commit a change, it pops up a buffer called ‘*VC-Log*’. In this buffer, you should write a log entry describing the changes you have made (see Why Version Control?). After you are done, type C-c C-c; this exits the buffer and commits the change, together with your log entry.

While 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 ‘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: Bazaar recognizes all three headers, while git, Mercurial, and Monotone recognizes only ‘Author’ and ‘Summary’. If you specify a header for a version control that does not support it, the header is treated as part of the log entry.

Type C-c C-f (log-edit-show-files) to display a list of files in the current VC fileset. If you called C-x v v directly from a work file, the fileset consists of that single file; if you called C-x v v from a VC directory buffer (see VC Directory Mode), the fileset may consist of multiple files.

Type C-c C-d (log-edit-show-diff) to show a diff of the changes you have made (i.e., the differences between the work file and the repository revision from which you started editing). See Old Revisions.

If the current VC fileset includes one or more ChangeLog files (see Change Log), 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 that match the file(s) to be committed; if found, these entries are inserted. See Change Logs and VC, for the opposite way of working—generating ChangeLog entries from the revision control log.

To abort a check-in, 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 commit another file, 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 check-in.

If you change several source files for the same reason, it is often convenient to specify the same log entry for many of the files. (This is the normal way to do things on a changeset-oriented system, where comments are attached to changesets rather than the history of individual files.) The most convenient way to do this is to mark all the files in VC Directory Mode and commit from there; the log buffer will carry the fileset information with it and do a group commit when you type C-c C-c.

You can also browse the history of previous log entries to duplicate a checkin comment. This can be useful when you want several files to have checkin comments that vary only slightly from each other. The commands M-n, M-p, M-s and M-r for doing this work just like the minibuffer history commands (except that these versions are used outside the minibuffer).

Each time you commit a change, the log entry buffer is put into VC Log Edit mode, which involves running two hooks: text-mode-hook and vc-log-mode-hook. See Hooks.

32.1.5 Examining And Comparing Old Revisions

One of the convenient features of version control is the ability to examine any revision of a file, or compare two revisions.

C-x v ~

Prompt for a revision of the current file, and visit it in a buffer of its own (vc-revision-other-window).

C-x v =

Compare the files in the current fileset with the working revision(s) you started from (vc-diff). With a prefix argument, prompt for two revisions of the current fileset and compare them. You can call this command from a Dired buffer (see Dired).

C-x v D

Compare the entire tree corresponding to the current fileset with the tree you started from (vc-root-diff). With a prefix argument, prompt for two revisions and compare their trees.

C-x v g

Display an annotated version of the file: for each line, show the latest revision in which it was modified (vc-annotate).

To examine an old revision, visit the work file and type C-x v ~ revision <RET> (vc-revision-other-window). Here, revision is either the desired revision ID (see VCS Concepts), or the name of a tag or branch (see Tags). This command puts the text of the old revision in a file named filename.~revision~, and visits it in its own buffer in a separate window.

C-x v = (vc-diff) compares each file in the current VC fileset (saving them if necessary) with the repository revision(s) from which you started editing. Note that the latter may or may not be the latest revision of the file(s).

The diff is displayed in another window, in a Diff mode buffer (see Diff Mode) named *vc-diff*. In this buffer, 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, using the minibuffer, and displays the diff in a special buffer in another window. Instead of providing a revision ID, you can give an empty input, which specifies the current contents of the work file; or a tag or branch name (see Tags). If your version control system is file-based (e.g. CVS) rather than changeset-based (Subversion, GNU Arch, git, Mercurial), supplying a revision ID for a multi-file fileset (as opposed to a symbolic tag name) is unlikely to return diffs that are connected in any meaningful way.

The command C-x v D (vc-root-diff) is similar to C-x v =, but it compares the entire tree associated with the current VC fileset with the tree you started with. This means all the files controlled by the current version control repository, even those that are not part of the current VC fileset.

If you invoke C-x v = or C-u C-x v = from a buffer that is neither visiting a version-controlled file nor a VC directory buffer, these commands generate a diff of all registered files in the current directory and its subdirectories.

C-x v = works by running a variant of the diff utility designed to work with the version control system in use. The options to pass to the diff command are taken from the first non-nil value of vc-backend-diff-switches, vc-diff-switches, and diff-switches (see Comparing Files), in that order. 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...diff-switches’ variables default to nil, but some default to t. These are for those version control systems (e.g. SVN) whose diff implementations do not accept common options (e.g. ‘-c’) likely to be in diff-switches.

The buffer produced by C-x v = supports the commands of Compilation mode (see Compilation Mode), such as C-x ` and C-c C-c, in both the “old” and “new” text, and they always find the corresponding locations in the current work file. (Older revisions are not, in general, present as files on your disk.)

For some back ends, you can display the file annotated with per-line revision information, by typing C-x v g (vc-annotate). This creates a new buffer (the “annotate buffer”) displaying the file's text, with each part colored to show how old it is. Text colored red is new, blue means 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.

When you give a prefix argument to this command, Emacs reads two arguments using the minibuffer: the ID of which 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, that is to say, 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—the one after the revision 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.

32.1.6 The Secondary Commands of VC

This section explains the secondary commands of VC.

• Registering: Putting a file under version control.
• VC Change Log: Viewing the VC Change Log.
• VC Undo: Canceling changes before or after check-in.

32.1.6.1 Registering a File for Version Control

You can put any file under version control by simply visiting it, and then typing C-x v i (vc-register).

C-x v i

Register the visited file for version control.

To register the file, Emacs must choose which version control system to use for it. If the file's directory already contains files registered in a version control system, Emacs uses that system. If there is more than one system in use for a directory, Emacs uses the one that appears first in vc-handled-backends (see Customizing VC). On the other hand, if there are no files already registered, Emacs uses the first system from vc-handled-backends that could register the file (for example, you cannot register a file under CVS if its directory is not already part of a CVS tree); with the default value of vc-handled-backends, this means that Emacs uses RCS in this situation.

If locking is in use, C-x v i leaves the file unlocked and read-only. Type C-x v v if you wish to start editing it. After registering a file with CVS, you must subsequently commit the initial revision by typing C-x v v. Until you do that, the revision ID appears as ‘@@’ in the mode line.

The default initial revision ID for a newly registered file varies by what VCS you are using; normally it will be 1.1 on VCSes that use dot-pair revision IDs and 1 on VCSes that use monotonic IDs. You can specify a different default by setting the variable vc-default-init-revision, or you can give C-x v i a numeric argument; then it reads the initial revision ID for this particular file using the minibuffer.

If vc-initial-comment is non-nil, C-x v i reads an initial comment to describe the purpose of this source file. Reading the initial comment works like reading a log entry (see Log Buffer).

32.1.6.2 VC Change Log

C-x v l

Display revision control state and change history (vc-print-log).

C-x v L

Display the change history for the current repository (vc-print-root-log).

C-x v I

Display the changes that will be received with a pull operation (vc-log-incoming).

C-x v O

Display the changes that will be sent by the next push operation (vc-log-outgoing).

The command C-x v l (vc-print-log) displays a buffer named ‘*vc-change-log*’ in a new window. This buffer lists the changes to the current file, including the associated log entries. (These are the log entries associated with the version control system, i.e. the ones you enter via the ‘*VC-Log*’ buffer. See Log Buffer.) Point is centered at the revision of the file currently being visited. With a prefix argument, the command prompts for the revision to center on, and the maximum number of revisions to display. You can call this command from a Dired buffer (see Dired).

Type C-x v L (vc-print-root-log) to display a ‘*vc-change-log*’ buffer showing the history of the version-controlled directory tree as a whole. With a prefix argument, the command prompts for the maximum number of revisions to display. RCS, SCCS, and CVS do not support this feature.

On a distributed 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 repository. This other repository 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 repository from which changes would be pulled, and lists the changes accordingly. Similarly, C-x v O (vc-log-outgoing) shows the changes that will be sent to another repository, the next time you run the “push” command; with a prefix argument, it prompts for a specific repository to which changes would be pushed.

In the ‘*vc-change-log*’ buffer, you can use the following keys to move between the logs of revisions and of files, to view past revisions, to modify change comments, to view annotations and to view diffs:

p

Move to the previous revision-item in the buffer. (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-item (which most often corresponds to the previous revision of the file). A numeric prefix argument is a repeat count.

P

Move to the log of the previous file, when the logs of multiple files are in the log buffer (see VC Directory Mode). Otherwise, just move to the beginning of the log. A numeric prefix argument is a repeat count, so C-u 10 P would move backward 10 files.

N

Move to the log of the next file, when the logs of multiple files are in the log buffer (see VC Directory Mode). It also takes a numeric prefix argument as a repeat count.

a

Annotate the revision indicated by the current line.

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, like typing C-x v ~ and specifying this revision's ID (see Old Revisions).

d

Display the diff (see Comparing Files) between the revision indicated at the current line and the next earlier revision. This is useful to see what actually changed in the file when the revision indicated on the current line was committed.

D

Display the changeset diff (see Comparing Files) between the revision indicated at the current line and the next earlier revision. This is useful to see all the changes to all files that the revision indicated on the current line did when it was committed.

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, and CVS do not support this feature.

32.1.6.3 Undoing Version Control Actions

C-x v u

Revert the buffer and the file to the working revision from which you started editing the file.

C-x v c

Remove the last-entered change from the master for the visited file. This undoes your last check-in.

If you want to discard your current set of changes and revert to the working revision from which you started editing the file, use C-x v u (vc-revert-buffer). If the version control system is locking-based, this leaves the file unlocked, and you must lock it again before making new changes. C-x v u requires confirmation, unless it sees that you haven't made any changes with respect to the master copy of the working revision.

C-x v u is also the command to unlock a file if you lock it and then decide not to change it.

To cancel a change that you already committed, use C-x v c (vc-rollback). This command discards all record of the most recent checked-in revision, but only if your work file corresponds to that revision—you cannot use C-x v c to cancel a revision that is not the latest on its branch. Note that many version control systems do not support rollback at all; this command is something of a historical relic.

32.1.7 VC Directory Mode

When you are working on a large program, it is often useful to find out which files have changed within an entire directory tree, or to view the status of all files under version control at once, and to perform version control operations on collections of files. You can use the command C-x v d (vc-dir) to make a directory listing that includes only files relevant for version control. This creates a VC Directory buffer and displays it in a separate window.

The VC Directory buffer works with all the version control systems that VC supports. For CVS, Emacs also offers a more powerful facility called PCL-CVS. See About PCL-CVS.

• Buffer: What the buffer looks like and means.
• Commands: Commands to use in a VC directory buffer.

32.1.7.1 The VC Directory Buffer

The VC Directory buffer contains a list of version-controlled files in the current directory and its subdirectories. Files which are up-to-date (have no local differences from the repository copy) are usually hidden; if all files in a subdirectory are up-to-date, the subdirectory is hidden as well. There is an exception to this rule: if VC mode detects that a file has changed to an up-to-date state since you last looked at it, that file and its state are shown.

If a directory uses more that one version control system, you can select which system to use for the vc-dir command by invoking vc-dir with a prefix argument: C-u C-x v d.

The line for an individual file shows the version control state of the file. Under RCS and SCCS, the name of the user locking the file is shown; under CVS, an abbreviated version of the ‘cvs status’ output is used. Here is an example using CVS:

                            ./
         modified           file1.c
         needs-update       file2.c
         needs-merge        file3.c

In this example, ‘file1.c’ is modified with respect to the repository, and ‘file2.c’ is not. ‘file3.c’ is modified, but other changes have also been committed—you need to merge them with the work file before you can check it in.

In the above, if the repository were on a remote machine, VC only contacts it when the variable vc-stay-local (or vc-cvs-stay-local) is nil (see CVS Options). This is because access to the repository may be slow, or you may be working offline and not have access to the repository at all. As a consequence, VC would not be able to tell you that ‘file3.c’ is in the “merge” state; you would learn that only when you try to check-in your modified copy of the file, or use a command such as C-x v m.

In practice, this is not a problem because CVS handles this case consistently whenever it arises. In VC, you'll simply get prompted to merge the remote changes into your work file first. The benefits of less network communication usually outweigh the disadvantage of not seeing remote changes immediately.

When a VC directory displays subdirectories it omits some that should never contain any files under version control. By default, this includes Version Control subdirectories such as ‘RCS’ and ‘CVS’; you can customize this by setting the variable vc-directory-exclusion-list.

32.1.7.2 VC Directory Commands

VC Directory mode has a full set of navigation and marking commands for picking out filesets. Some of these are also available in a context menu invoked by mouse-2.

Up- and down-arrow keys move in the buffer; n and p also move vertically as in other list-browsing modes. <SPC> and <TAB> behave like down-arrow, and <BackTab> behaves like up-arrow.

Both C-m and f visit the file on the current line. o visits that file in another window. q dismisses the directory buffer.

x hides up-to-date files.

m marks the file or directory on the current line. If the region is active, m marks all the files in the region. There are some restrictions when marking: a file cannot be marked if any of its parent directories are marked, and a directory cannot be marked if any files in it or in its child directories are marked.

M marks all the files with the same VC state as the current file if the cursor is on a file. If the cursor is on a directory, it marks all child files. With a prefix argument: marks all files and directories.

u unmarks the file or directory on the current line. If the region is active, it unmarks all the files in the region.

U marks all the files with the same VC state as the current file if the cursor is on a file. If the cursor is on a directory, it unmarks all child files. With a prefix argument: unmarks all marked files and directories.

It is possible to do search, search and replace, incremental search, and incremental regexp search on multiple files. These commands will work on all the marked files or the current file if nothing is marked. If a directory is marked, the files in that directory shown in the VC directory buffer will be used.

S searches the marked files.

Q does a query replace on the marked files.

M-s a C-s does an incremental search on the marked files.

M-s a C-M-s does an incremental regular expression search on the marked files.

Commands are also accessible from the VC-dir menu. Note that some VC backends use the VC-dir menu to make available extra, backend-specific, commands. For example, Git and Bazaar allow you to manipulate stashes and shelves. (These provide a mechanism to temporarily store uncommitted changes somewhere out of the way, and bring them back at a later time.)

Normal VC commands with the C-x v prefix work in VC directory buffers. Some single-key shortcuts are available as well; =, +, l, i, and v behave as through prefixed with C-x v.

The command C-x v v (vc-next-action) operates on all the marked files, so that you can commit several files at once. If the underlying VC supports atomic commits of multiple-file changesets, C-x v v with a selected set of modified but not committed files will commit all of them at once as a single changeset.

When C-x v v (vc-next-action) operates on multiple files, all of those files must be either in the same state or in compatible states (added, modified and removed states are considered compatible). Otherwise it signals an error. This differs from the behavior of older versions of VC, which did not have fileset operations and simply did vc-next-action on each file individually.

If any files are in a state that calls for commit, C-x v v reads a single log entry and uses it for the changeset as a whole. If the underling VCS is file- rather than changeset-oriented, the log entry will be replicated into the history of each file.

32.1.8 Multiple Branches of a File

One use of version control is to maintain multiple “current” revisions of a file. For example, you might have different revisions of a program in which you are gradually adding various unfinished new features. Each such independent line of development is called a branch. VC allows you to create branches, switch between different branches, and merge changes from one branch to another. Please note, however, that branches are not supported for SCCS.

A file's main line of development is usually called the trunk. You can create multiple branches from the trunk. How the difference between trunk and branch is made visible is dependent on whether the VCS uses dot-pair or monotonic version IDs.

In VCSes with dot-pair revision IDs, the revisions on the trunk are normally IDed 1.1, 1.2, 1.3, etc. At any such revision, you can start an independent branch. A branch starting at revision 1.2 would have revision ID 1.2.1.1, and consecutive revisions on this branch would have IDs 1.2.1.2, 1.2.1.3, 1.2.1.4, and so on. If there is a second branch also starting at revision 1.2, it would consist of revisions 1.2.2.1, 1.2.2.2, 1.2.2.3, etc.

In VCSes with monotonic revision IDs, trunk revisions are IDed as 1, 2, 3, etc. A branch from (say) revision 2 might start with 2.1 and continue through 2.2, 2.3, etc. But naming conventions for branches and subbranches vary widely on these systems, and some (like Mercurial) never depart from the monotonic integer sequence at all. Consult the documentation of the VCS you are using.

If you omit the final component of a dot-pair revision ID, that is called a branch ID. It refers to the highest existing revision on that branch—the head revision of that branch. The branches in the dot-pair example above have branch IDs 1.2.1 and 1.2.2.

• Switching Branches: How to get to another existing branch.
• Creating Branches: How to start a new branch.
• Merging: Transferring changes between branches.
• Multi-User Branching: Multiple users working at multiple branches in parallel.

32.1.8.1 Switching between Branches

To switch between branches, type C-u C-x v v and specify the revision ID you want to select. On a locking-based system, this version is then visited unlocked (write-protected), so you can examine it before locking it. Switching branches in this way is allowed only when the file is not locked.

On a VCS with dot-pair IDs, you can omit the minor part, thus giving only the branch ID; this takes you to the head version on the chosen branch. If you only type <RET>, Emacs goes to the highest version on the trunk.

After you have switched to any branch (including the main branch), you stay on it for subsequent VC commands, until you explicitly select some other branch.

32.1.8.2 Creating New Branches

To create a new branch from a head revision (one that is the latest in the branch that contains it), first select that revision if necessary, lock it with C-x v v, and make whatever changes you want. Then, when you commit the changes, use C-u C-x v v. This lets you specify the 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.

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 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 automatically creates a new branch starting from the selected revision. You need not specially request a new branch, because that's the only way to add a new revision at a point that is not the head of a branch.

After the branch is created, you “stay” on it. That means that subsequent check-ins create new revisions on that branch. To leave the branch, you must explicitly select a different revision with C-u C-x v v. To transfer changes from one branch to another, use the merge command, described in the next section.

32.1.8.3 Merging Branches

When you have finished the changes on a certain branch, you will often want to incorporate them into the file's main line of development (the trunk). This is not a trivial operation, because development might also have proceeded on the trunk, so that you must merge the changes into a file that has already been changed otherwise. VC allows you to do this (and other things) with the vc-merge command.

C-x v m (vc-merge)

Merge changes into the work file.

C-x v m (vc-merge) takes a set of changes and merges it into the current version of the work file. It firsts asks you in the minibuffer where the changes should come from. If you just type <RET>, Emacs merges any changes that were made on the same branch since you checked the file out (we call this merging the news). This is the common way to pick up recent changes from the repository, regardless of whether you have already changed the file yourself.

You can also enter a branch ID or a pair of revision IDs in the minibuffer. Then C-x v m finds the changes from that branch, or the differences between the two revisions you specified, and merges them into the current revision of the current file.

As an example, suppose that you have finished a certain feature on branch 1.3.1. In the meantime, development on the trunk has proceeded to revision 1.5. To merge the changes from the branch to the trunk, first go to the head revision of the trunk, by typing C-u C-x v v <RET>. Revision 1.5 is now current. If locking is used for the file, type C-x v v to lock revision 1.5 so that you can change it. Next, type C-x v m 1.3.1 <RET>. This takes the entire set of changes on branch 1.3.1 (relative to revision 1.3, where the branch started, up to the last revision on the branch) and merges it into the current revision of the work file. You can now commit the changed file, thus creating revision 1.6 containing the changes from the branch.

It is possible to do further editing after merging the branch, before the next check-in. But it is usually wiser to commit the merged revision, then lock it and make the further changes. This will keep a better record of the history of changes.

When you merge changes into a file that has itself been modified, the changes might overlap. We call this situation a conflict, and reconciling the conflicting changes is called resolving a conflict.

Whenever conflicts occur during merging, VC detects them, tells you about them in the echo area, and asks whether you want help in merging. If you say yes, it starts an Ediff session (see Ediff).

If you say no, the conflicting changes are both inserted into the file, surrounded by conflict markers. The example below shows how a conflict region looks; the file is called ‘name’ and the current master file revision with user B's changes in it is 1.11.

     <<<<<<< name
       User A's version
     =======
       User B's version
     >>>>>>> 1.11

Then you can resolve the conflicts by editing the file manually. Or you can type M-x vc-resolve-conflicts after visiting the file. This starts an Ediff session, as described above. Don't forget to commit the merged version afterwards.

If there is more than one conflicted file in a merge, type M-x vc-find-conflicted-file after resolving the conflicts in each file. This command visits the next conflicted file, and moves point to the first conflict marker in that file.

32.1.8.4 Multi-User Branching

It is often useful for multiple developers to work simultaneously on different branches of a file. CVS and later systems allow this by default; for RCS, it is possible if you create multiple source directories. Each source directory should have a link named RCS which points to a common directory of RCS master files. Then each source directory can have its own choice of selected revisions, but all share the same common RCS records.

This technique works reliably and automatically, provided that the source files contain RCS version headers (see Version Headers). The headers enable Emacs to be sure, at all times, which revision ID is present in the work file.

If the files do not have version headers, you must instead tell Emacs explicitly in each session which branch you are working on. To do this, first find the file, then type C-u C-x v v and specify the correct branch ID. This ensures that Emacs knows which branch it is using during this particular editing session.

32.1.9 Remote Repositories

A common way of using CVS and other more advanced VCSes is to set up a central repository on some Internet host, then have each developer check out a personal working copy of the files on his local machine. Committing changes to the repository, and picking up changes from other users into one's own working area, then works by direct interactions with the repository server.

One difficulty is that access to a repository server is often slow, and that developers might need to work off-line as well. While only third-generation decentralized VCses such as GNU Arch or Mercurial really solve this problem, VC is designed to reduce the amount of network interaction necessary.

If you are using a truly decentralized VCS you can skip the rest of this section. It describes backup and local-repository techniques that are only useful for Subversion and earlier VCSes.

• Version Backups: Keeping local copies of repository versions.
• Local Version Control: Using another version system for local editing.

32.1.9.1 Version Backups

When VC sees that the repository for a file is on a remote machine, it automatically makes local backups of unmodified versions of the file—automatic version backups. This means that you can compare the file to the repository version (C-x v =), or revert to that version (C-x v u), without any network interactions.

The local copy of the unmodified file is called a version backup to indicate that it corresponds exactly to a version that is stored in the repository. Note that version backups are not the same as ordinary Emacs backup files (see Backup). But they follow a similar naming convention.

For a file that comes from a remote repository, VC makes a version backup whenever you save the first changes to the file, and removes it after you have committed your modified version to the repository. You can disable the making of automatic version backups by setting vc-cvs-stay-local to nil (see CVS Options).

The name of the automatic version backup for version version of file file is file.~version.~. This is almost the same as the name used by C-x v ~ (see Old Revisions), the only difference being the additional dot (‘.’) after the version number. This similarity is intentional, because both kinds of files store the same kind of information. The file made by C-x v ~ acts as a manual version backup.

All the VC commands that operate on old versions of a file can use both kinds of version backups. For instance, C-x v ~ uses either an automatic or a manual version backup, if possible, to get the contents of the version you request. Likewise, C-x v = and C-x v u use either an automatic or a manual version backup, if one of them exists, to get the contents of a version to compare or revert to. If you changed a file outside of Emacs, so that no automatic version backup was created for the previous text, you can create a manual backup of that version using C-x v ~, and thus obtain the benefit of the local copy for Emacs commands.

The only difference in Emacs's handling of manual and automatic version backups, once they exist, is that Emacs deletes automatic version backups when you commit to the repository. By contrast, manual version backups remain until you delete them.

32.1.9.2 Local Version Control

When you make many changes to a file that comes from a remote repository, it can be convenient to have version control on your local machine as well. You can then record intermediate versions, revert to a previous state, etc., before you actually commit your changes to the remote server.

VC lets you do this by putting a file under a second, local version control system, so that the file is effectively registered in two systems at the same time. For the description here, we will assume that the remote system is CVS, and you use RCS locally, although the mechanism works with any combination of version control systems (back ends).

To make it work with other back ends, you must make sure that the “more local” back end comes before the “more remote” back end in the setting of vc-handled-backends (see Customizing VC). By default, this variable is set up so that you can use remote CVS and local RCS as described here.

To start using local RCS for a file that comes from a remote CVS server, you must register the file in RCS, by typing C-u C-x v v rcs <RET>. (In other words, use vc-next-action with a prefix argument, and specify RCS as the back end.)

You can do this at any time; it does not matter whether you have already modified the file with respect to the version in the CVS repository. If possible, VC tries to make the RCS master start with the unmodified repository version, then checks in any local changes as a new version. This works if you have not made any changes yet, or if the unmodified repository version exists locally as a version backup (see Version Backups). If the unmodified version is not available locally, the RCS master starts with the modified version; the only drawback to this is that you cannot compare your changes locally to what is stored in the repository.

The version number of the RCS master is derived from the current CVS version, starting a branch from it. For example, if the current CVS version is 1.23, the local RCS branch will be 1.23.1. Version 1.23 in the RCS master will be identical to version 1.23 under CVS; your first changes are checked in as 1.23.1.1. (If the unmodified file is not available locally, VC will check in the modified file twice, both as 1.23 and 1.23.1.1, to make the revision numbers consistent.)

If you do not use locking under CVS (the default), locking is also disabled for RCS, so that editing under RCS works exactly as under CVS.

When you are done with local editing, you can commit the final version back to the CVS repository by typing C-u C-x v v cvs <RET>. This initializes the log entry buffer (see Log Buffer) to contain all the log entries you have recorded in the RCS master; you can edit them as you wish, and then commit in CVS by typing C-c C-c. If the commit is successful, VC removes the RCS master, so that the file is once again registered under CVS only. (The RCS master is not actually deleted, just renamed by appending ‘~’ to the name, so that you can refer to it later if you wish.)

While using local RCS, you can pick up recent changes from the CVS repository into your local file, or commit some of your changes back to CVS, without terminating local RCS version control. To do this, switch to the CVS back end temporarily, with the C-x v b command:

C-x v b

Switch to another back end that the current file is registered under (vc-switch-backend).

C-u C-x v b backend <RET>

Switch to backend for the current file.

C-x v b does not change the buffer contents, or any files; it only changes VC's perspective on how to handle the file. Any subsequent VC commands for that file will operate on the back end that is currently selected.

If the current file is registered in more than one back end, typing C-x v b “cycles” through all of these back ends. With a prefix argument, it asks for the back end to use in the minibuffer.

Thus, if you are using local RCS, and you want to pick up some recent changes in the file from remote CVS, first visit the file, then type C-x v b to switch to CVS, and finally use C-x v m <RET> to merge the news (see Merging). You can then switch back to RCS by typing C-x v b again, and continue to edit locally.

But if you do this, the revision numbers in the RCS master no longer correspond to those of CVS. Technically, this is not a problem, but it can become difficult to keep track of what is in the CVS repository and what is not. So we suggest that you return from time to time to CVS-only operation, by committing your local changes back to the repository using C-u C-x v v cvs <RET>.

32.1.10 Revision Tags

In a VCS with per-file revision numbers (such as SCCS, RCS, or CVS) tag is a named set of file versions (one for each registered file) that you can treat as a unit. In a VCS with per-repository version numbers (Subversion and most later ones) a tag is simply a symbolic name for a revision.

One important kind of tag is a release, a (theoretically) stable version of the system that is ready for distribution to users.

• Making Revision Tags: The tag facilities.
• Revision Tag Caveats: Things to be careful of when using tags.

32.1.10.1 Making and Using Revision Tags

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.

Tags are inexpensive, so you need not hesitate to create them whenever they are useful. Branches vary in cost depending on your VCS; in older ones they may be expensive.

You can give a tag or branch name as an argument to C-x v = or C-x v ~ (see Old Revisions). Thus, you can use it to compare a tagged version against the current files, or two tagged versions against each other.

32.1.10.2 Revision Tag Caveats

For 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.

There is no support for VC tags using GNU Arch yet.

Under older VCSes (SCCS, RCS, CVS, early versions of Subversion), renaming and deletion could create some difficulties with tags. This is not a VC-specific problem, but a general design issue in version control systems that was not solved effectively until the earliest third-generation systems.

In a file-oriented VCS, when you rename a registered file you need to rename its master along with it; the command vc-rename-file will do this automatically. 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.

32.1.11 Miscellaneous Commands and Features of VC

This section explains the less-frequently-used features of VC.

• Change Logs and VC: Generating a change log file from log entries.
• Renaming and VC: A command to rename both the source and master file correctly.
• Version Headers: Inserting version control headers into working files.

32.1.11.1 Change Logs and VC

If you use RCS or CVS for a program and also maintain a change log file for it (see Change Log), you can generate change log entries automatically from the version control log entries:

C-x v a

Visit the current directory's change log file and, for registered files in that directory, create new entries for versions checked in since the most recent entry in the change log file. (vc-update-change-log).

This command works with RCS or CVS only, not with any of the other back ends.

C-u C-x v a

As above, but only find entries for the current buffer's file.

M-1 C-x v a

As above, but find entries for all the currently visited files that are maintained with version control. This works only with RCS, and it puts all entries in the log for the default directory, which may not be appropriate.

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 text ‘Ignore log messages that start with `#'.’. Then C-x v a visits ChangeLog and inserts text like this:

     1999-05-22  Nathaniel Bowditch  <nat@apn.org>
     
             * rcs2log: Ignore log messages that start with `#'.

You can then edit the new change log entry further as you wish.

Some of the new change log entries may duplicate what's already in ChangeLog. You will have to remove these duplicates by hand.

Normally, the log entry for file foo is displayed as ‘* foo: text of log entry’. The ‘:’ after foo is omitted if the text of the log entry starts with ‘(functionname): ’. For example, if the log entry for vc.el is ‘(vc-do-command): Check call-process status.’, then the text in ChangeLog looks like this:

     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. For example, suppose the most recent check-ins have the following log entries:

They appear like this in ChangeLog:

     1999-04-01  Nathaniel Bowditch  <nat@apn.org>
     
             * vc.texinfo: Fix expansion typos.
     
             * vc.el, vc-hooks.el: Don't call expand-file-name.

Normally, C-x v a separates log entries by a blank line, but you can mark several related log entries to be clumped together (without an intervening blank line) by starting the text of each related log entry with a label of the form ‘{clumpname} ’. The label itself is not copied to ChangeLog. For example, suppose the log entries are:

Then the text in ChangeLog looks like this:

     1999-04-01  Nathaniel Bowditch  <nat@apn.org>
     
             * vc.texinfo: Fix expansion typos.
             * vc.el, vc-hooks.el: Don't call expand-file-name.

A log entry whose text begins with ‘#’ is not copied to ChangeLog. For example, if you merely fix some misspellings in comments, you can log the change with an entry beginning with ‘#’ to avoid putting such trivia into ChangeLog.

32.1.11.2 Renaming VC Work Files and Master Files

When you rename a registered file, you must also rename its master file correspondingly to get proper results. Use vc-rename-file to rename the source file as you specify, and rename its master file accordingly. It also updates any tags (see Revision Tags) that mention the file, so that they use the new name; despite this, the tag thus modified may not completely work (see Revision Tag Caveats).

Some back ends do not provide an explicit rename operation to their repositories. After issuing vc-rename-file, use C-x v v on the original and renamed buffers and provide the necessary edit log.

You cannot use vc-rename-file on a file that is locked by someone else.

32.1.11.3 Inserting Version Control Headers

Sometimes it is convenient to put version identification strings directly into working files. Certain special strings called version headers are replaced in each successive version by the number of that version, the name of the user who created it, and other relevant information. All of the back ends that VC supports have such a mechanism, except GNU Arch.

VC does not normally use the information contained in these headers. The exception is RCS—with RCS, version headers are sometimes more reliable than the master file to determine which version of the file you are editing. Note that in a multi-branch environment, version headers are necessary to make VC behave correctly (see Multi-User Branching).

Searching for RCS version headers is controlled by the variable vc-consult-headers. If it is non-nil (the default), Emacs searches for headers to determine the version number you are editing. Setting it to nil disables this feature.

Note that although CVS uses the same kind of version headers as RCS does, VC never searches for these headers if you are using CVS, regardless of the above setting.

You can use the C-x v h command (vc-insert-headers) to insert a suitable header string.

C-x v h

Insert headers in a file for use with your version-control system.

The default header string is ‘$Id$’ for RCS and ‘%W%’ for SCCS. You can specify other headers to insert by setting the variables vc-backend-header where backend is rcs or sccs.

Instead of a single string, you can specify a list of strings; then each string in the list is inserted as a separate header on a line of its own.

It may be necessary to use apparently-superfluous backslashes when writing the strings that you put in this variable. For instance, you might write "$Id\$" rather than "$Id$". The extra backslash prevents the string constant from being interpreted as a header, if the Emacs Lisp file containing it is maintained with version control.

Each header is inserted surrounded by tabs, inside comment delimiters, on a new line at point. Normally the ordinary comment start and comment end strings of the current mode are used, but for certain modes, there are special comment delimiters for this purpose; the variable vc-comment-alist specifies them. Each element of this list has the form (mode starter ender).

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 inserted as part of the header. A header line is inserted for each element that matches the buffer name, and for each string specified by vc-backend-header. The header line is made by processing the string from vc-backend-header with the format taken from the element. The default value for vc-static-header-alist is as follows:

     (("\\.c$" .
       "\n#ifndef lint\nstatic char vcid[] = \"\%s\";\n\
     #endif /* lint */\n"))

It specifies insertion of text of this form:

     
     #ifndef lint
     static char vcid[] = "string";
     #endif /* lint */

Note that the text above starts with a blank line.

If you use more than one version header in a file, put them close together in the file. The mechanism in revert-buffer that preserves markers may not handle markers positioned between two version headers.

32.1.12 Customizing VC

The variable vc-handled-backends determines which version control systems VC should handle. The default value is (RCS CVS SVN SCCS Bzr Git Hg Mtn Arch), 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 (see Local Version Control), 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, for details.

• General VC Options: Options that apply to multiple back ends.
• RCS and SCCS: Options for RCS and SCCS.
• CVS Options: Options for CVS.

32.1.12.1 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.

Normally the work file exists all the time, whether it is locked or not. If you set vc-keep-workfiles to nil, then checking in a new version with C-x v v deletes the work file; but any attempt to visit the file with Emacs creates it again. (With CVS, work files are always kept.)

Editing a version-controlled file through a symbolic link can be dangerous. It bypasses the version control system—you can edit the file without locking it, and fail to check your changes in. Also, your changes might overwrite those of another user. To protect against this, VC checks each symbolic link that you visit, to see if it points to a file under version control.

The variable vc-follow-symlinks controls what to do when a symbolic link points to a version-controlled file. If it is nil, VC only displays a warning message. If it is t, VC automatically follows the link, and visits the real file instead, telling you about this in the echo area. If the value is ask (the default), VC asks you each time whether to follow the link.

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. (This variable does not affect C-x v c; that operation is so drastic that it should always ask for confirmation.)

VC mode does much of its work by running the shell commands for the appropriate backend. If vc-command-messages is non-nil, VC displays messages to indicate which shell commands it runs, and additional messages when the commands finish.

You can specify additional directories to search for version control programs by setting the variable vc-path. These directories are searched before the usual search path. It is rarely necessary to set this variable, because VC normally finds the proper files automatically.

32.1.12.2 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 Version 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.

You can specify the criterion for whether to trust the file permissions by setting the variable vc-mistrust-permissions. Its value can be t (always mistrust the file permissions and check the master file), nil (always trust the file permissions), or a function of one argument which makes the decision. The argument is the directory name of the RCS subdirectory. A non-nil value from the function says to mistrust the file permissions. If you find that the file permissions of work files are changed erroneously, set vc-mistrust-permissions to t. Then VC always checks the master file to determine the file's status.

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-mistrust-permissions affects SCCS use, but vc-consult-headers does not.

32.1.12.3 Options specific for CVS

By default, CVS does not use locking to coordinate the activities of several users; anyone can change a work file at any time. However, there are ways to restrict this, resulting in behavior that resembles locking.

For one thing, you can set the CVSREAD environment variable (the value you use makes no difference). If this variable is defined, CVS makes your work files read-only by default. In Emacs, you must type C-x v v to make the file writable, so that editing works in fact similar as if locking was used. Note however, that no actual locking is performed, so several users can make their files writable at the same time. When setting CVSREAD for the first time, make sure to check out all your modules anew, so that the file protections are set correctly.

Another way to achieve something similar to locking is to use the watch feature of CVS. If a file is being watched, CVS makes it read-only by default, and you must also use C-x v v in Emacs to make it writable. VC calls cvs edit to make the file writable, and CVS takes care to notify other developers of the fact that you intend to change the file. See the CVS documentation for details on using the watch feature.

When a file's repository is on a remote machine, VC tries to keep network interactions to a minimum. This is controlled by the variable vc-cvs-stay-local. There is another variable, vc-stay-local, which enables the feature also for other back ends that support it, including CVS. In the following, we will talk only about vc-cvs-stay-local, but everything applies to vc-stay-local as well.

If vc-cvs-stay-local is t (the default), then VC uses only the entry in the local CVS subdirectory to determine the file's state (and possibly information returned by previous CVS commands). One consequence of this is that when you have modified a file, and somebody else has already checked in other changes to the file, you are not notified of it until you actually try to commit. (But you can try to pick up any recent changes from the repository first, using C-x v m <RET>, see Merging).

When vc-cvs-stay-local is t, VC also makes local version backups, so that simple diff and revert operations are completely local (see Version Backups).

On the other hand, if you set vc-cvs-stay-local to nil, then 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. It also does not make any version backups.

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.

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.

32.2 Change Logs

A change log file contains a chronological record of when and why you have changed a program, consisting of a sequence of entries describing individual changes. Normally it is kept in a file called ChangeLog in the same directory as the file you are editing, or one of its parent directories. A single ChangeLog file can record changes for all the files in its directory and all its subdirectories.

• Change Log Commands: Commands for editing change log files.
• Format of ChangeLog: What the change log file looks like.

32.2.1 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.

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.

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 next-error command (by default bound to C-x `) to move between entries in the Change Log, when Change Log mode is on. 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 in the same list.

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. In the VC log buffer, typing C-c C-a (log-edit-insert-changelog) inserts the relevant Change Log entry, if one exists (see Log Buffer). You can also insert a VC log entry into a Change Log buffer by typing C-x v a (vc-update-change-log) in the Change Log buffer (see Change Logs and VC).

32.2.2 Format of ChangeLog

A change log entry starts with a header line that contains the current date, your 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.

32.3 Tags Tables

A tag is a reference to a subunit in a program or in a document. In program source code, tags reference syntactic elements of the program: functions, subroutines, data types, macros, etc. In a document, tags reference chapters, sections, appendices, etc. Each tag specifies the name of the file where the corresponding subunit is defined, and the position of the subunit's definition in that file.

A tags table records the tags 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 use the ‘etags’ command, submitting it a document or the source code of a program. ‘etags’ writes the tags to a tags table file, or tags file in short. The conventional name for a tags file is TAGS.

Emacs uses the information recorded in tags tables in commands that search or replace through multiple source files: these commands use the names of the source files recorded in the tags table to know which files to search. Other commands, such as M-., which finds the definition of a function, use the recorded information about the function names and positions to find the source file and the position within that file where the function is defined.

See also the Ebrowse facility, which is tailored for C++. See Ebrowse.

• Tag Syntax: Tag syntax for various types of code and text files.
• Create Tags Table: Creating a tags table with etags.
• Etags Regexps: Create arbitrary tags using regular expressions.
• Select Tags Table: How to visit a tags table.
• Find Tag: Commands to find the definition of a specific tag.
• Tags Search: Using a tags table for searching and replacing.
• List Tags: Listing and finding tags defined in a file.

32.3.1 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. Tags for variables and functions in classes are named ‘class::variable’ and ‘class::function’. operator definitions have tag names like ‘operator+’.
• 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 text, the argument of any of the commands \chapter, \section, \subsection, \subsubsection, \eqno, \label, \ref, \cite, \bibitem, \part, \appendix, \entry, \index, \def, \newcommand, \renewcommand, \newenvironment or \renewenvironment is a tag.

  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.
• 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 name 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 beginning 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 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, 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.

You can also generate tags based on regexp matching (see Etags Regexps) to handle other formats and languages.

32.3.2 Creating Tags Tables

The etags program is used to create a tags table file. It knows the syntax of several languages, as described in 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.

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.

etags recognizes the language used in an input file based on its file name and contents. You can specify the language with the ‘--language=name’ option, described below.

If the tags table data become outdated due to changes in the files described in the table, the way to update the tags table is the same way it was made in the first place. If the tags table fails to record a tag, or records it for the wrong file, then Emacs cannot possibly find its definition until you update the tags table. However, if the position recorded in the tags table becomes a little bit wrong (due to other editing), the worst consequence is a slight delay in finding the tag. Even if the stored position is very far wrong, Emacs will still find the tag, after searching most of the file for it. That delay is hardly noticeable with today's computers.

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.

One tags table can virtually include another. Specify the included tags file name with the ‘--include=file’ option when creating the file that is to include it. The latter file then acts as if it covered all the source files specified in the included file, as well as the files it directly contains.

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 /dev/stdout.

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. The simplest way to circumvent this limit is to tell 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 -

Use the option ‘--language=name’ to specify the language explicitly. 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).

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.

‘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.

32.3.3 Etags Regexps

The ‘--regex’ option provides a general way of recognizing tags based on regexp matching. You can freely intermix this option with file names, and 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 GCC character escape sequences are supported (‘\a’ for bell, ‘\b’ for back space, ‘\d’ for delete, ‘\e’ for escape, ‘\f’ for formfeed, ‘\n’ for newline, ‘\r’ for carriage return, ‘\t’ for tab, and ‘\v’ for vertical tab).

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. You can find some examples 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(]+"\([^"]+\)"/'

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/'
  

32.3.4 Selecting a Tags Table

Emacs has at any time one selected tags table, and all the commands for working with tags tables use the selected one. To select a tags table, type M-x visit-tags-table, which reads the tags table file name as an argument, with TAGS in the default directory as the default.

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 setting the variable yourself is just as good. 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.

Using visit-tags-table when a tags table is already loaded gives you a choice: you can add the new tags table to the current list of tags tables, or start a new list. The tags commands use all the tags tables in the current 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 strings, like this:

     (setq tags-table-list
           '("~/emacs" "/usr/local/lib/emacs/src"))

This tells the tags commands to look at the TAGS files in your ~/emacs 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, as explained above.

Do not set both tags-file-name and tags-table-list.

32.3.5 Finding a Tag

The most important thing that a tags table enables you to do is to find the definition of a specific tag.

M-. tag <RET>

Find first definition of tag (find-tag).

C-u M-.

Find next alternate definition of last tag specified.

C-u - M-.

Go back to previous tag found.

C-M-. pattern <RET>

Find a tag whose name matches pattern (find-tag-regexp).

C-u C-M-.

Find the next tag whose name matches the last pattern used.

C-x 4 . tag <RET>

Find first definition of tag, but display it in another window (find-tag-other-window).

C-x 5 . tag <RET>

Find first definition of tag, and create a new frame to select the buffer (find-tag-other-frame).

M-*

Pop back to where you previously invoked M-. and friends.

M-. (find-tag) is the command to find the definition of a specified tag. It searches through the tags table for that tag, as a string, and then uses the tags table info to determine the file that the definition is in and the approximate character position in the file of the definition. Then find-tag visits that file, moves point to the approximate character position, and searches ever-increasing distances away to find the tag definition.

If an empty argument is given (just type <RET>), the balanced expression in the buffer before or around point is used as the tag argument. See Expressions.

You don't need to give M-. the full name of the tag; a part will do. This is because M-. finds tags in the table which contain tag as a substring. However, it prefers an exact match to a substring match. To find other tags that match the same substring, give find-tag a numeric argument, as in C-u M-.; this does not read a tag name, but continues searching the tags table's text for another tag containing the same substring last used. If you have a real <META> key, M-0 M-. is an easier alternative to C-u M-..

Like most commands that can switch buffers, find-tag 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 ., which invokes the command find-tag-other-window. The latter is C-x 5 ., which invokes find-tag-other-frame.

To move back to places you've found tags recently, use C-u - M-.; more generally, M-. with a negative numeric argument. This command can take you to another buffer. C-x 4 . with a negative argument finds the previous tag location in another window.

As well as going back to places you've found tags recently, you can go back to places from where you found them. Use M-*, which invokes the command pop-tag-mark, for this. Typically you would find and study the definition of something with M-. and then return to where you were with M-*.

Both C-u - M-. and M-* allow you to retrace your steps to a depth determined by the variable find-tag-marker-ring-length.

The command C-M-. (find-tag-regexp) visits the tags that match a specified regular expression. It is just like M-. except that it does regexp matching instead of substring matching.

32.3.6 Searching and Replacing with Tags Tables

The commands in this section visit and search all the files listed in the selected tags table, one by one. For these commands, the tags table serves only to specify a sequence of files to search. These commands scan the list of tags tables starting with the first tags table (if any) that describes the current file, proceed from there to the end of the list, and then scan from the beginning of the list until they have covered all the tables in the list.

M-x tags-search <RET> regexp <RET>

Search for regexp through the files in the selected tags table.

M-x tags-query-replace <RET> regexp <RET> replacement <RET>

Perform a query-replace-regexp on each file in the selected tags table.

M-,

Restart one of the commands above, from the current location of point (tags-loop-continue).

M-x tags-search reads a regexp using the minibuffer, then searches for matches in all the files in the selected tags table, one file at a time. It displays the name of the file being searched so you can follow its progress. As soon as it finds an occurrence, tags-search returns.

Having found one match, you probably want to find all the rest. To find one more match, type M-, (tags-loop-continue) to resume the tags-search. This searches the rest of the current buffer, followed by the remaining files of the tags table.

M-x tags-query-replace performs a single query-replace-regexp through all the files in the tags table. It reads a regexp to search for and a string to replace with, just like ordinary M-x query-replace-regexp. It searches much like M-x tags-search, but repeatedly, processing matches according to your input. See Replace, for more information on query replace.

You can control the case-sensitivity of tags search commands by customizing the value of the variable tags-case-fold-search. The default is to use the same setting as the value of case-fold-search (see Search Case).

It is possible to get through all the files in the tags table with a single invocation of M-x tags-query-replace. But often it is useful to exit temporarily, which you can do with any input event that has no special query replace meaning. You can resume the query replace subsequently by typing M-,; this command resumes the last tags search or replace command that you did. For instance, to skip the rest of the current file, you can type M-> M-,.

The commands in this section carry out much broader searches than the find-tag family. The find-tag commands search only for definitions of tags that match your substring or regexp. The commands tags-search and tags-query-replace find every occurrence of the regexp, as ordinary search commands and replace commands do in the current buffer.

These commands create buffers only temporarily for the files that they have to search (those which are not already visited in Emacs buffers). Buffers in which no match is found are quickly killed; the others continue to exist.

It may have struck you that tags-search is a lot like grep. You can also run grep itself as an inferior of Emacs and have Emacs show you the matching lines one by one. See Grep Searching.

32.3.7 Tags Table Inquiries

M-x list-tags <RET> file <RET>

Display a list of the tags defined in the program file file.

M-x tags-apropos <RET> regexp <RET>

Display a list of all tags matching regexp.

M-x list-tags reads the name of one of the files described by the selected tags table, and displays a list of all the tags defined in that file. The “file name” argument is really just a string to compare against the file names recorded in the tags table; it is read as a string rather than as a file name. Therefore, completion and defaulting are not available, and you must enter the file name the same way it appears in the tags table. Do not include a directory as part of the file name unless the file name recorded in the tags table includes a directory.

M-x tags-apropos is like apropos for tags (see Apropos). It finds all the tags in the selected tags table whose entries match regexp, and displays them. If the variable tags-apropos-verbose is non-nil, it displays the names of the tags files together with the tag names.

You can customize the appearance of the output by setting the variable tags-tag-face to a face. You can display additional output with M-x tags-apropos by customizing the variable tags-apropos-additional-actions—see its documentation for details.

You can also use the collection of tag names to complete a symbol name in the buffer. See Symbol Completion.

32.4 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.

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). The most common project types are ‘Make’, which uses Makefiles, and ‘Automake’, which uses GNU Automake (see 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.

32.5 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.

• Overview of Emerge: How to start Emerge. Basic concepts.
• Submodes of Emerge: Fast mode vs. Edit mode. Skip Prefers mode and Auto Advance mode.
• State of Difference: You do the merge by specifying state A or B for each difference.
• Merge Commands: Commands for selecting a difference, changing states of differences, etc.
• Exiting Emerge: What to do when you've finished the merge.
• Combining in Emerge: How to keep both alternatives for a difference.
• Fine Points of Emerge: Miscellaneous issues.

32.5.1 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.

32.5.2 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 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-mode) to set or clear Auto Advance mode. Use s s (emerge-skip-prefers-mode) 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.

32.5.3 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’.

32.5.4 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 in Emerge).

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.

32.5.5 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.

32.5.6 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 A buffer
     #else /* not NEW */
     version from B 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%a#else /* not NEW */\n%b#endif /* not NEW */\n"

32.5.7 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.

33 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 Abbrevs.

“Hippie” expansion generalizes abbreviation expansion. See Hippie Expansion.

• Abbrev Concepts: Fundamentals of defined abbrevs.
• Defining Abbrevs: Defining an abbrev, so it will expand when typed.
• Expanding Abbrevs: Controlling expansion: prefixes, canceling expansion.
• Editing Abbrevs: Viewing or editing the entire list of defined abbrevs.
• Saving Abbrevs: Saving the entire list of abbrevs for another session.
• Dynamic Abbrevs: Abbreviations for words already in the buffer.
• Dabbrev Customization: What is a word, for dynamic abbrevs. Case handling.

33.1 Abbrev Concepts

An abbrev is a word which 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 you can insert ‘find outer otter.’ into the buffer by typing f o o ..

Abbrevs expand only when Abbrev mode (a 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. abbrev-mode is also a variable; Abbrev mode is on when the variable is non-nil. The variable abbrev-mode automatically becomes local to the current buffer when it is set.

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. You can also save lists of abbrev definitions in files for use in later sessions. Some users keep extensive lists of abbrevs that they load in every session.

33.2 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>.

An argument of zero to C-x a g means to use the contents of the region as the expansion of the abbrev being defined.

The command C-x a l (add-mode-abbrev) is similar, but defines a mode-specific abbrev. Mode-specific abbrevs are active only in a particular major mode. C-x a l defines an abbrev for the major mode in effect at the time C-x a l is typed. The arguments work the same as for C-x a g.

If the abbrev text itself is already in the buffer, you can use the commands C-x a i g (inverse-add-global-abbrev) and C-x a i l (inverse-add-mode-abbrev) to define it as an abbrev by specify the expansion in the minibuffer. These commands are called “inverse” because they invert the meaning of the two text strings they use (one from the buffer and one read with the minibuffer).

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 define a new definition. When the 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.

33.3 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; thus, ‘foo’ expands into ‘find outer otter’; ‘Foo’ into ‘Find outer otter’, and ‘FOO’ into ‘FIND OUTER OTTER’ or ‘Find Outer Otter’ according to the variable abbrev-all-caps (setting it non-nil specifies ‘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 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 and bring back the abbrev itself by typing C-_ to undo (see Undo). This also undoes the insertion of the non-word character that expanded the abbrev. 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.

Expanding any abbrev runs abbrev-expand-functions, a special hook. Functions in this special hook can make arbitrary changes to the abbrev expansion. See Abbrev Expansion.

33.4 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...
     (lisp-mode-abbrev-table)
     "dk"          0    "define-key"
     (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) 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.

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.

33.5 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 quietly-read-abbrev-file <RET> file <RET>

Similar but do not display a message about what is going on.

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 Init 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.

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.

33.6 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 in the buffer 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, unless you have set dabbrev-check-all-buffers to nil.

For finer control over which buffers to scan, customize the variable dabbrev-ignored-buffer-regexps. Its value 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.

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.

33.7 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 of dabbrev-case-fold-search is case-fold-search, which is true by default, then the variable case-fold-search controls whether to ignore case while searching for expansions.

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 of dabbrev-case-replace is case-replace, which is true by default, then the variable case-replace controls whether to copy the expansion verbatim.

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 value nil has a special meaning: dynamic abbrevs are made of word characters, but expansions are made of word and symbol characters.

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.

34 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.

• Basic Picture: Basic concepts and simple commands of Picture Mode.
• Insert in Picture: Controlling direction of cursor motion after "self-inserting" characters.
• Tabs in Picture: Various features for tab stops and indentation.
• Rectangles in Picture: Clearing and superimposing rectangles.

34.1 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. There is no need to change C-a, as the choice of screen model does not affect beginnings of lines.

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 Rectangles in Picture).

34.2 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 <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 <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.

34.3 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 an 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.

34.4 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 argument, delete the text.

C-c C-w r

Similar, but save rectangle contents in register r first (picture-clear-rectangle-to-register).

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.

35 Sending Mail

To send an e-mail message in Emacs, type C-x m. This selects and initializes a buffer named ‘*mail*’, where you can edit the text and headers of the message. Finally, type C-c C-s or C-c C-c to send the message.

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 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) creates a new frame for the mail buffer.

Because the mail buffer is an ordinary Emacs buffer, you can switch to other buffers while in the middle of composing mail, and switch back later (or never). If you type C-x m again when you have been composing another message but have not sent it, Emacs asks for confirmation before erasing the old message. If you answer n, Emacs selects the mail buffer with its old contents, so you can finish the old message and send it. C-u C-x m is another way to do this. Sending the message marks the mail buffer “unmodified,” which avoids the need for confirmation when C-x m is next used.

If you want to send another message before finishing the current message, use the command M-x rename-uniquely to rename the current mail buffer (see Misc Buffer). Then you can use C-x m to make a new mail buffer, and work with each mail buffer independently.

Before using Emacs to send mail, you may need to customize the variable send-mail-function if your system is not set up to deliver mail directly via SMTP (see Mail Sending). In addition, you may need to customize user-mail-address if the system cannot receive mail via SMTP (see Mail Headers).

• Format: Format of a mail message.
• Headers: Details of some standard mail header fields.
• Aliases: Abbreviating and grouping mail addresses.
• Commands: Special commands for editing mail being composed.
• Signature: Adding a signature to every message.
• Amuse: Distracting the NSA; adding fortune messages.
• Methods: Using alternative mail-composition methods.

35.1 The Format of the Mail Buffer

An email message must contain certain pieces of information, called headers, which specify the message's sender, recipient(s), and so on.

At the top of the mail buffer is a set of header fields, where you can enter this information. You can insert and edit header fields using ordinary editing commands. See Header Editing, for commands specific to editing header fields.

Some header fields are automatically pre-initialized in the buffer, when appropriate; other headers, such as ‘Date’ and ‘Message-Id’, are normally omitted from the mail buffer and created automatically when the message is sent.

The line in the buffer that says

     --text follows this line--

separates the header fields from the body (or text) of the message. Everything above this 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. The text used for the delimiter line is controlled by the variable mail-header-separator.

Here is an example of what the headers and text in the mail buffer might look like.

     To: gnu@example.org
     CC: lungfish@example.com, byob@example.net
     Subject: The Emacs Manual
     --text follows this line--
     Please ignore this message.

35.2 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 (and in mailing addresses also). 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. Here is a table of commonly-used fields. Emacs pre-initializes some of these, depending on various options you can set. You can delete or alter any header field before you send the message, if you wish.

‘From’

The address of the sender (you). This should be a valid mailing address, as replies will normally go there. Emacs initializes this field using the variables user-full-name and user-mail-address; see below.

‘To’

The mailing address(es) to which the message is addressed. To list more than one address, use commas (not spaces) to separate them.

‘Subject’

A piece of text saying what the message is about. Most mail-reading programs can display a summary of messages, listing the subject of each message but not its text.

‘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 one 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 Babyl. 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’. You can use this header if, for some reason, your ‘From’ address is unable to 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’

This field contains one or more addresses. It is typically used when you reply to a message from a mailing list that you are subscribed to. It usually indicates that you want replies to go to the list, and that you do not need an extra copy sent directly to you.

‘In-reply-to’

A piece of text describing the message you are replying to. Some mail systems can use this information to correlate related pieces of mail. Normally, you never need to think about this, because it is filled in automatically when you reply to a message in Rmail (or any other mail program built into Emacs).

‘References’

The Message-Ids of previous related messages (a Message-Id is a unique identifier generated when a message is sent). Like ‘In-reply-to’, this is normally set up 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

The default contents of the ‘From’ header field are computed from the variables user-full-name and user-mail-address. On some operating systems, Emacs initializes these two variables using environment variables (see General Variables). If this information is unavailable or wrong, you can customize the variables yourself (see Easy Customization).

The value of the variable mail-from-style specifies how to format the address in the ‘From’ field:

nil

Use just the address, as in ‘king@grassland.com’.

parens

Use both address and full name, as in:
‘king@grassland.com (Elvis Parsley)’.

angles

Use both address and full name, as in:
‘Elvis Parsley <king@grassland.com>’.

any other value

Use angles for most addresses. However, if the address must be “quoted” to remain syntactically-valid under the angles format but not under the parens format, use parens instead. This is the default.

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.

35.3 Mail Aliases

You can define mail aliases, which are short mnemonic names that stand for mail addresses or groups of mail 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 in the following format:

     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>’.

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.

35.4 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.

• Mail Sending: Commands to send the message.
• Header Editing: Commands to move to header fields and edit them.
• Citing Mail: Quoting a message you are replying to.
• Mail Misc: Attachments, spell checking, etc.

35.4.1 Mail Sending

There are two commands to send a message you have been editing:

C-c C-c

Send the message, and deselect the mail buffer (message-send-and-exit).

C-c C-s

Send the message, and leave the mail buffer selected (message-send).

If you want to send a message and be done with it, type C-c C-c (mail-send-and-exit). This sends the message and then either deletes the window or switches to another buffer. It also “buries” the mail buffer, putting it at the lowest priority for reselection. This is the usual command for sending a message.

The command C-c C-s (message-send) sends the message and marks the mail buffer unmodified, but 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.

In a file-visiting buffer, sending the message does not clear the modified flag, because only saving the file should do that. Also, you don't get a warning if you try to send the same message twice.

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 Recognize Coding). 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.

The variable send-mail-function controls how the default mail user agent sends mail. Its value should be a function, which can be one of the following:

sendmail-send-it

Send mail using the system's default sendmail (or sendmail-compatible) program. This is the default on Unix and GNU, and works provided the system is a valid mail host (that is, provided it can deliver mail via SMTP).

mailclient-send-it

Pass the mail buffer on to the system's designated mail client (see mailclient.el). This is the default on Mac OS X and MS-Windows.

smtpmail-send-it

Send mail through an external mail host (e.g., your Internet service provider's SMTP server). You will need to tell Emacs how to contact the SMTP server, by customizing the variables smtpmail-smtp-server and smtpmail-auth-credentials. See Emacs SMTP Library.

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 more information.

35.4.2 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). 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.

35.4.3 Citing Mail

C-c C-y

Yank the selected message from Rmail (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 is active only when the mail buffer is invoked from a mail program 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.

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).

35.4.4 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 MIME (Multipurpose Internet Mail Extensions) 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’ (the default), 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 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 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.

35.5 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 mail-signature determines how Emacs handles the mail signature.

The default value of mail-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 mail-signature-file.

If you change mail-signature to a string, that specifies the text of the signature directly.

If you change mail-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.

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.

35.6 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 NSA²² 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.

35.7 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).

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 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.

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 Rmail).

36 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.

• Basic: Basic concepts of Rmail, and simple use.
• Scroll: Scrolling through a message.
• Motion: Moving to another message.
• Deletion: Deleting and expunging messages.
• Inbox: How mail gets into the Rmail file.
• Files: Using multiple Rmail files.
• Output: Copying messages out to files.
• Labels: Classifying messages by labeling them.
• Attrs: Certain standard labels, called attributes.
• Reply: Sending replies to messages you are viewing.
• Summary: Summaries show brief info on many messages.
• Sort: Sorting messages in Rmail.
• Display: How Rmail displays a message; customization.
• Coding: How Rmail handles decoding character sets.
• Editing: Editing message text and headers in Rmail.
• Digest: Extracting the messages from a digest message.
• Rot13: Reading messages encoded in the rot13 code.
• Movemail: More details of fetching new mail.
• Remote Mailboxes: Retrieving mail from remote mailboxes.
• Other Mailbox Formats: Retrieving mail from local mailboxes in various formats.

36.1 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 and use Rmail to move messages between them.

Within the Rmail file, messages are normally arranged sequentially in order of receipt; you can specify other ways to sort them (see Rmail Sorting). 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 Rmail Motion).

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 Rmail Deletion). To save the file without expunging, use C-x C-s. Rmail also saves the Rmail file after merging new mail from an inbox file (see Rmail Inbox).

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 Rmail Summary). 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 Save Commands). The Rmail command b, rmail-bury, buries the Rmail buffer and its summary buffer without expunging and saving the Rmail file.

36.2 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 C-v, M-v and M-<, but in Rmail scrolling is so frequent that it deserves to be easier.

<SPC>

Scroll forward (scroll-up).

<DEL>

Scroll backward (scroll-down).

.

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> synonyms of C-v (scroll-up) and M-v (scroll-down)

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. Similarly, the command / (rmail-end-of-message) scrolls forward to the end of the selected message.

36.3 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.

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.

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 Regexps) 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 Rmail 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.

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.

36.4 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 message. 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. d with a prefix argument is equivalent to C-d. Note that the Rmail summary versions of these commands behave slightly differently (see Rmail Summary Edit).

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.

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.

36.5 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 local 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 which 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 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 was originally written to use the Babyl format as its internal format. Since then, we have recognized that the usual inbox format (‘mbox’) on Unix and GNU systems is adequate for the job, and so since Emacs 23 Rmail uses that as its internal format. The Rmail file is still separate from the inbox file, even though their format is the same.

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 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.

36.6 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 Rmail Output).

i file <RET>

Read file into Emacs and run Rmail on it (rmail-input).

M-x set-rmail-inbox-list <RET> files <RET>

Specify inbox file names for current Rmail file to get mail from.

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 Rmail Output).

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.

36.7 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. 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 Rmail Display. 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. 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.)

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 returns a file name as a string. rmail-output-file-alist applies to both o and C-o.

36.8 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 same 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.

The command 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 Rmail Summary, 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 Rmail Sorting, for information on sorting messages with labels.

36.9 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 Rmail Deletion).

‘filed’

Means the message has been copied to some other file. Assigned by the o and C-o file output commands (see Rmail Output).

‘answered’

Means you have mailed an answer to the message. Assigned by the r command (rmail-reply). See Rmail Reply.

‘forwarded’

Means you have forwarded the message. Assigned by the f command (rmail-forward). See Rmail Reply.

‘edited’

Means you have edited the text of the message within Rmail. See Rmail Editing.

‘resent’

Means you have resent the message. Assigned by the command M-x rmail-resend. See Rmail Reply.

‘retried’

Means you have retried a failed outgoing message. Assigned by the command M-x rmail-retry-failure. See Rmail Reply.

All other labels are assigned or removed only by users, and have no standard meaning.

36.10 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. 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 the ‘*mail*’ 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 rmail-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, and any name starting with ‘info-’. (Those names are excluded because there is a convention of using them for large mailing lists to broadcast announcements.)

To omit the ‘CC’ field completely for a particular reply, enter the reply command with a numeric argument: C-u r or 1 r. This means to reply only to the sender of the original message.

Once the ‘*mail*’ 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*’ 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 Rmail Display), 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*’ buffer with the current message as the text, and a subject designating a forwarded 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.

Forwarding a message encloses it 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, 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. Thus, m can be used to reply to or forward a message; it can do anything r or f can do.

The c (rmail-continue) command resumes editing the ‘*mail*’ 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, or when you use the ‘Cancel’ item in the ‘Mail’ menu.

All the Rmail commands to send a message use the mail-composition method that you have chosen (see Mail Methods).

36.11 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.

• Rmail Make Summary: Making various sorts of summaries.
• Rmail Summary Edit: Manipulating messages from the summary.

36.11.1 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. You can use commas to separate multiple regular expressions. These are matched against the ‘To’, ‘From’, and ‘CC’ headers (with a prefix argument, this header is not included).

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. You can use commas to separate multiple regular expressions. 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. You can use commas to separate multiple regular expressions.

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.

36.11.2 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, a numeric argument to d, C-d and u serves as a repeat count. A negative argument reverses the meaning of d and C-d. Also, 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>.

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.

36.12 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 names.

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. Note that 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.

36.13 Display of Messages

This section describes how Rmail displays mail headers, MIME sections and attachments, and URLs.

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).

<BackTab>

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, 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, apart from a tagline button for some other action. 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.

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.

You can highlight and activate URLs in the Rmail buffer using Goto Address mode:

     (add-hook 'rmail-show-message-hook (lambda () (goto-address-mode 1)))

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.

36.14 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 Recognize Coding).

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 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.

36.15 Editing Within a Message

Most of the usual Emacs keybindings 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 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-].

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.

36.16 Digest Messages

A digest message is a message which exists to contain and carry several other messages. Digests are used on some moderated 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 much less computer time than transmitting the individual messages even though the total size is the same, because the per-message overhead in network mail transmission is considerable.

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.

36.17 Reading Rot13 Messages

Mailing list messages that might offend 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 might be offended to avoid seeing the real text of the message.

To view a buffer which 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.

36.18 movemail program

Rmail uses the movemail program to move mail from your inbox to your Rmail file (see Rmail Inbox). 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 native one, shipped with GNU Emacs (the “emacs version”) and the one included in GNU mailutils (the “mailutils version,” see movemail). They support the same command line syntax and the same basic subset of options. However, the Mailutils version offers additional features.

The Emacs version of movemail is able to retrieve mail from the usual UNIX mailbox formats and from remote mailboxes using the POP3 protocol.

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 short, a URL is:

     proto://[user[:password]@]host-or-file-name

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.

Proto can be one of:

mbox

Usual UNIX mailbox format. In this case, neither user nor pass are 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 and pass 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 and pass are not used, and host-or-file-name denotes the name of maildir mailbox, e.g., maildir://mail/inbox.

file

Any local mailbox format. Its actual format is detected automatically by movemail.

pop

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; e.g., pop://smith:guessme@remote.server.net.

imap

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; e.g., imap://smith:guessme@remote.server.net.

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 and exec-path, then in exec-directory.

36.19 Retrieving Mail from Remote Mailboxes

Some sites use a method called POP for accessing users' inbox data instead of storing the data in inbox files. By default, the Emacs movemail can work with POP (unless the Emacs configure script was run with the option ‘--without-pop’).

Similarly, the Mailutils movemail by default supports POP, unless it was configured with the ‘--disable-pop’ option.

Both versions of movemail only work with POP3, not with older versions of POP.

No matter which flavor of movemail you use, you can specify a POP inbox by using a POP URL (see Movemail). A POP URL is a “file name” of the form ‘pop://username@hostname’, where hostname is the host name or IP address 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’. 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.

For backward compatibility, Rmail also supports an alternative way of specifying remote POP mailboxes. Specifying an inbox name in the form ‘po:username:hostname’ is equivalent to ‘pop://username@hostname’. If you omit the :hostname part, the MAILHOST environment variable specifies the machine on which to look for the POP 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’. The password part is optional, as described above.

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.

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 (the Emacs movemail does so if Emacs was configured with the option --with-kerberos or --with-kerberos5). If it is supported, it is used by default whenever you attempt to retrieve POP mail when rmail-remote-password and rmail-remote-password-required are unset.

Some POP 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.

36.20 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, for the detailed description of movemail versions. For example, to access mail from a 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

37 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.

The Dired buffer is “read-only,” and inserting text in it is not allowed. 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.

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 Directories.

• Enter: How to invoke Dired.
• Navigation: Special motion commands in the Dired buffer.
• Deletion: Deleting files with Dired.
• Flagging Many Files: Flagging files based on their names.
• Visit: Other file operations through Dired.
• Marks vs Flags: Flagging for deletion vs marking.
• Operating on Files: How to copy, rename, print, compress, etc. either one file or several files.
• Shell Commands in Dired: Running a shell command on the marked files.
• Transforming File Names: Using patterns to rename multiple files.
• Comparison in Dired: Running `diff' by way of Dired.
• Subdirectories in Dired: Adding subdirectories to the Dired buffer.
• Subdir Switches: Subdirectory switches in Dired.
• Subdirectory Motion: Moving across subdirectories, and up and down.
• Hiding Subdirectories: Making subdirectories visible or invisible.
• Updating: Discarding lines for files of no interest.
• Find: Using `find' to choose the files for Dired.
• Wdired: Operating on files by editing the Dired buffer.
• Image-Dired: Viewing image thumbnails in Dired.
• Misc: Various other features.

37.1 Entering Dired

To invoke Dired, type C-x d (dired). This reads a directory 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. 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 name.

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 ‘=’.

On MS-Windows and MS-DOS systems, Emacs emulates ls; see ls in Lisp, for options and peculiarities of that emulation.

To display the Dired buffer in another window rather than in the selected window, use C-x 4 d (dired-other-window) instead of C-x d. C-x 5 d (dired-other-frame) uses a separate frame to display the Dired buffer.

37.2 Navigation in the Dired Buffer

All the usual Emacs cursor motion commands are available in Dired buffers. The keys C-n and C-p are redefined to 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 Dired Deletion).

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 Search, for information about incremental search.

Some additional navigation commands are available when the Dired buffer includes several directories. See Subdirectory Motion.

37.3 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.

u

Remove deletion flag on this line.

<DEL>

Move point to previous line and remove the deletion flag on that line.

x

Delete the files that are flagged for deletion.

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 argument serves as a repeat count.

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.

To delete the flagged files, type x (dired-do-flagged-delete). This command first 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. If the variable dired-recursive-deletes is non-nil, then Dired can delete nonempty directories including all their contents. That can be somewhat risky.

On some systems, there is a facility called the “Trash” or “Recycle Bin”, but Emacs does not use it by default. Thus, when you delete a file in Dired, it is gone forever. However, you can tell Emacs to use the Trash for file deletion, by changing the variable delete-by-moving-to-trash to t. See Misc File Ops, for more information about the Trash.

37.4 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 Save).

~

Flag all backup files (files whose names end with ‘~’) for deletion (see Backup).

. (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 Save.

~ (dired-flag-backup-files) flags all files whose names say they are backup files—that is, files whose names end in ‘~’. See Backup.

. (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.

37.5 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.

<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 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 named by the line you click 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, using M-x view-file (dired-view-file). Viewing a file with view-file is like visiting it, but is slanted toward moving around in the file conveniently and does not allow changing the file. See View File.

^

Visit the parent directory of the current directory (dired-up-directory). This is equivalent to moving to the line for .. and typing f there.

37.6 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 Dired Deletion, for commands to flag and unflag files.)

m

* m

Mark the current file with ‘*’ (dired-mark). With a numeric argument n, mark the next n files starting with the current file. (If n is negative, mark the previous −n 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).

<DEL>

* <DEL>

Move point to previous line and remove any mark on that line (dired-unmark-backward).

* !

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). The argument 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.

C-x u

C-_

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.

37.7 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.

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 variable dired-dwim-target is non-nil, and if there is another Dired buffer displayed in the next window, that other buffer's directory is suggested instead.

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.

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 nil, which means that directories cannot be copied.

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).

Dired automatically changes the visited file name of buffers associated with renamed files so that they refer to the new names.

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.

M modespec <RET>

Change the mode (also called “permission bits”) of the specified files (dired-do-chmod). This uses the chmod program, so modespec can be any argument that chmod can handle.

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 (different systems put chown in different places).

T timestamp <RET>

Touch the specified files (dired-do-touch). This means updating their modification times 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).

Z

Compress the specified files (dired-do-compress). If the file appears to be a compressed file already, uncompress it instead.

L

Load the specified Emacs Lisp files (dired-do-load). See Lisp Libraries.

B

Byte compile the specified Emacs Lisp files (dired-do-byte-compile). See Byte Compilation.

A regexp <RET>

Search all the specified files for the regular expression regexp (dired-do-search).

This command is a variant of tags-search. The search stops at the first match it finds; use M-, to resume the search and find the next match. See Tags Search.

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-query-replace-regexp).

This command is a variant of tags-query-replace. If you exit the query replace loop, you can use M-, to resume the scan and replace more matches. See Tags Search.

37.8 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.

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.

• Otherwise, if the command string contains ‘?’ surrounded by whitespace, Emacs runs the shell command once for each file, substituting the current file name for ‘?’ each time. You can use ‘?’ more than once in the command; the same file name replaces each occurrence.
• If the command string contains neither ‘*’ nor ‘?’, Emacs runs the shell command once for each file, adding the file name is added at the end. For example, ! uudecode <RET> runs uudecode on each file.

To iterate over the file names in a more complicated fashion, 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 ! 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 Dired Updating).

See Single Shell, for information about running shell commands outside Dired.

37.9 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 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>

These four commands rename, copy, make hard links and make 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 Replace). 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.

37.10 File Comparison with Dired

Here are two Dired commands that compare specified files using diff. They show the output in a buffer using Diff mode (see Comparing Files).

=

Compare the current file (the file at point) with another file (the file at the mark) using the diff program (dired-diff). The file at the mark is the first argument of diff, and the file at point is the second argument. This refers to the ordinary Emacs mark, not Dired marks; use C-<SPC> (set-mark-command) to set the mark at the first file's line (see Setting Mark).

M-=

Compare the current file with its latest backup file (dired-backup-diff). If the current file is itself a backup, compare it with the file it is a backup of; this way, you can compare a file with any one of its backups.

The backup file is the first file given to diff.

37.11 Subdirectories in Dired

A Dired buffer displays just one directory in the normal case; 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 the i command:

i

Insert the contents of a subdirectory later in the buffer.

Use the i (dired-maybe-insert-subdir) 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> takes you back to the old position in the buffer (the line describing that subdirectory). You can also use ‘^’ to return to the parent directory in the same Dired buffer.

Use the l command (dired-do-redisplay) to update the subdirectory's contents. Use C-u k on the subdirectory header line to delete the subdirectory (see Dired Updating). You can also hide and show inserted subdirectories (see Hiding Subdirectories).

37.12 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 using C-u l.

Dired preserves the switches if you revert the buffer. Deleting a subdirectory forgets about its switches.

Using dired-undo (usually bound to C-_ and C-x u) 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.

37.13 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-prev-dirline).

37.14 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 Dired Updating, for how to insert or delete a subdirectory listing.

37.15 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 the specified file lines from the buffer—not delete 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; but it does not operate on the current file as a last resort.

If you use k with a numeric prefix argument to kill the line for a file that is a directory, which you have inserted in the Dired buffer as a subdirectory, it deletes that subdirectory from the buffer as well. Typing C-u k on the header line for a subdirectory also deletes the subdirectory 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.

37.16 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 Grep Searching. 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 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, whose default value specifies using options ‘-ld’ for ls. If your listings are corrupted, you may need to change the value of this variable.

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.

37.17 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.

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.

37.18 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.

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.” This takes a long time if the directory contains many image files, and it asks for confirmation if the number of image files exceeds image-dired-show-all-from-dir-max-files.

With point in the thumbnail buffer, you can type RET (image-dired-display-thumbnail-original-image) to display a sized version of it in another window. This sizes the image to fit the window. Use the arrow keys to move around in the buffer. For easy browsing, use SPC (image-dired-display-next-thumbnail-original) to advance and display the next image. Typing DEL (image-dired-display-previous-thumbnail-original) backs up to the previous thumbnail and displays that instead.

To view and the image in its original size, either provide a prefix argument (C-u) before pressing RET, or 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. You can also delete the thumbnail image from the thumbnail buffer with C-d (image-dired-delete-char).

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-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 different). 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).

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.

37.19 Other Dired Features

The command + (dired-create-directory) reads a directory name, and creates the directory if it does not already exist.

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 Repeat Isearch, 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 headerline, 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 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 are “different” 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—each file name that does not appear in the other directory is “different.” 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 if the expression's value is non-nil, those files are considered “different.”

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 currently not supported.

38 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.

• Calendar Motion: Moving through the calendar; selecting a date.
• Scroll Calendar: Bringing earlier or later months onto the screen.
• Counting Days: How many days are there between two dates?
• General Calendar: Exiting or recomputing the calendar.
• Writing Calendar Files: Writing calendars to files of various formats.
• Holidays: Displaying dates of holidays.
• Sunrise/Sunset: Displaying local times of sunrise and sunset.
• Lunar Phases: Displaying phases of the moon.
• Other Calendars: Converting dates to other calendar systems.
• Diary: Displaying events from your diary.
• Appointments: Reminders when it's time to do something.
• Importing Diary: Converting diary events to/from other formats.
• Daylight Saving: How to specify when daylight saving time is active.
• Time Intervals: Keeping track of time intervals.
• Advanced Calendar/Diary Usage: Advanced Calendar/Diary customization.

38.1 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.

• Calendar Unit Motion: Moving by days, weeks, months, and years.
• Move to Beginning or End: Moving to start/end of weeks, months, and years.
• Specified Dates: Moving to the current date or another specific date.

38.1.1 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 commands themselves are not quite analogous. 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.

38.1.2 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 beginning 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.

38.1.3 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 ‘1990’, not ‘90’.

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).

38.2 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

<next>

Scroll calendar three months forward (calendar-scroll-left-three-months).

M-v

<prior>

Scroll calendar three months backward (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 <next> and <prior> are equivalent to C-v and M-v, just as they are in other modes.

38.3 Counting Days

M-=

Display the number of days in the current region (calendar-count-days-region).

To determine the number of days in the region, type M-= (calendar-count-days-region). The numbers of days shown is inclusive; that is, it includes the days specified by mark and point.

38.4 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

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.)

38.5 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 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.

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 (cal-tex-cursor-week).

t w 2

Generate a two-page calendar for one week (cal-tex-cursor-week2).

t w 3

Generate an ISO-style calendar for one week (cal-tex-cursor-week-iso).

t w 4

Generate a calendar for one Monday-starting week (cal-tex-cursor-week-monday).

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.

38.6 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.

h

Display holidays for the selected date (calendar-cursor-holidays).

Mouse-3 Holidays

Display any holidays for the date you click on.

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 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 Baha'i, 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.

38.7 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.

S

Display times of sunrise and sunset for the selected date (calendar-sunrise-sunset).

Mouse-3 Sunrise/sunset

Display times of sunrise and sunset for the date you click on.

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, for how daylight saving time is determined.

As a user, you might find it convenient to set the calendar location variables for your usual physical location in your .emacs file. And when you install Emacs on a machine, you can create a default.el file which sets them properly for the typical location of most users of that machine. See Init File.

38.8 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 Sunrise/Sunset.

38.9 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 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.

• Calendar Systems: The calendars Emacs understands (aside from Gregorian).
• To Other Calendar: Converting the selected date to various calendars.
• From Other Calendar: Moving to a date specified in another calendar.
• Mayan Calendar: Moving to a date specified in a Mayan calendar.

38.9.1 Supported Calendar Systems

The ISO commercial calendar is used largely in Europe.

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 B.C. 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 that far into the future.

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 Baha'i 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.

38.9.2 Converting To Other Calendars

The following commands describe the selected date (the date at point) in various other calendar systems:

Mouse-3 Other calendars

Display the date that you click on, expressed in various 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 Baha'i 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).

If you are using a graphic display, the easiest way to translate a date into other calendars is to click on it with Mouse-3, 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.)

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.

38.9.3 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 Baha'i 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 Strict Completion) 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 question 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.

38.9.4 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 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 Strict Completion) whenever it asks you to type a Mayan name, so you don't have to worry about spelling.

38.10 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.

The name of the diary file is specified by the variable diary-file; ~/diary is the default. Here's an example showing what that file looks like:

     12/22/1988  Twentieth wedding anniversary!!
     &1/1.       Happy New Year!
     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, 1989 Income tax due.
     &* 15       time cards due.

This format is essentially the same as the one used by the system's calendar utility. This example uses extra spaces to align the event descriptions of most of the entries. Such formatting is purely a matter of taste.

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.

• Displaying the Diary: Viewing diary entries and associated calendar dates.
• Format of Diary File: Entering events in your diary.
• Date Formats: Various ways you can specify dates.
• Adding to Diary: Commands to create diary entries.
• Special Diary Entries: Anniversaries, blocks of dates, cyclic entries, etc.

38.10.1 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.

d

Display all diary entries for the selected date (diary-view-entries).

Mouse-3 Diary

Display all diary entries for the date you click on.

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 window the diary entries for the selected date in the calendar. The mode line of the new window 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.

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 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 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 enter Emacs.

Many users like to receive notice of events in their diary as email. 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.

38.10.2 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; ~/diary is the default. The calendar utility program supports a subset of the format allowed by the Emacs diary facilities, so you can use that utility to view the diary file, with reasonable results aside from the entries it cannot understand.

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.

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:

     02/11/1989
           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.

You can inhibit the marking of certain diary entries in the calendar window; to do this, insert an ampersand diary-nonmarking-symbol (default ‘&’) at the beginning of the entry, before the date. This has no effect on display of the entry in the diary window; it affects only marks on dates in the calendar window. Nonmarking entries are especially useful for generic entries that would otherwise mark many different dates.

38.10.3 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.

     4/20/93  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, 1993. 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 ‘11/12/1989’ or ‘11/12/89’.

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 a ‘*’; 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.

38.10.4 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 Non-Gregorian Diary.

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 numeric 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.

38.10.5 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 1948) Arthur's birthday

This entry applies to October 31 in any year after 1948; ‘10 31 1948’ 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, 1990 through July 10, 1990:

     %%(diary-block 6 24 1990 7 10 1990) Vacation

The ‘6 24 1990’ indicates the starting date and the ‘7 10 1990’ 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 1990) Renew medication

This entry applies to March 1, 1990 and every 50th day following; ‘3 1 1990’ 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 numeric argument to the command. For example, C-u i a makes a nonmarking anniversary diary entry.

Marking sexp diary entries in the calendar is extremely 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.

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 Diary Entries.

38.11 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 several minutes beforehand that that 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, use the command 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.

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.

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.

38.12 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.

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 (default) 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 the result is appended to the target file.

38.13 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.

38.14 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.

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-modeline-display variable and set its value to t, or invoke the M-x timeclock-modeline-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, set 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 .timelog in your home directory. 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.

38.15 Customizing the Calendar and Diary

There are many customizations that you can use to make the calendar and diary suit your personal tastes.

• Calendar Customizing: Calendar layout and hooks.
• Holiday Customizing: Defining your own holidays.
• Date Display Format: Changing the format.
• Time Display Format: Changing the format.
• Diary Customizing: Defaults you can set.
• Non-Gregorian Diary: Diary entries based on other calendars.
• Diary Display: A choice of ways to display the diary.
• Fancy Diary Display: Sorting diary entries, using included diary files.
• Sexp Diary Entries: More flexible diary entries.

38.15.1 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-holiday-marker specifies how to mark a date as being 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, and calenday-today-marker is used by the function calendar-mark-today to mark today's date. By default, the calendar uses faces named holiday, diary, and calendar-today for these purposes.

The variable calendar-load-hook is a normal hook run when the calendar package is first loaded (before actually starting to display the calendar).

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.

38.15.2 Customizing the Holidays

Emacs knows about holidays defined by entries on one of several lists. The lists of holidays that Emacs uses are for general holidays (holiday-general-holidays), local holidays (holiday-local-holidays), sun- and moon-related holidays (holiday-solar-holidays), Baha'i holidays (holiday-bahai-holidays), Christian holidays (holiday-christian-holidays), Hebrew (Jewish) holidays (holiday-hebrew-holidays), Islamic (Muslim) holidays (holiday-islamic-holidays), Oriental holidays (holiday-oriental-holidays), and other holidays (holiday-other-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 eliminate the associated holidays.

The general holidays are, by default, holidays common throughout the United States.

There are no default local holidays, but your site may supply some.

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.

You can set the variable holiday-other-holidays to any list of holidays. This list, normally empty, is intended for individual use.

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 element 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 August:

     (holiday-float 8 1 4 "Hurricane Supplication Day")

Here the 8 specifies August, 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 Baha'i, 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 27 1991) "Lunar Eclipse") ((7 11 1991) "Solar Eclipse") ... )

38.15.3 Date Display Format

You can customize the manner of displaying dates in the diary, in mode lines, and in 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)))

This specifies a typical American format:

     (month "/" day "/" (substring year -2))

38.15.4 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).

38.15.5 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) 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"))

Other default styles are provided by diary-european-date-forms and diary-iso-date-forms.

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.

38.15.6 Diary Entries Using non-Gregorian Calendars

As well as entries based on the standard Gregorian calendar, your diary can have entries based on Baha'i, 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 and Baha'i entries, add diary-islamic-list-entries and diary-islamic-mark-entries, or diary-bahai-list-entries and diary-bahai-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 Baha'i 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 Baha'i, 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

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.

38.15.7 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, a minor mode that provides commands for scrolling and searching the text. For example, <SPC> and <DEL> scroll forward and backward, and <s> starts an incremental search. See the documentation of the function view-mode for more information.

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). 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).

38.15.8 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.

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.

38.15.9 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 1990) Renew medication (%d%s time)

looks like this:

     Renew medication (5th time)

in the fancy diary display on September 8, 1990.

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 Baha'i 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.)

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.

39 Document Viewing

DocView mode (doc-view-mode) is a viewer for DVI, Postscript (PS), and PDF 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) command, and displaying those images.

When you visit a PDF or DVI file, Emacs automatically switches to DocView mode. 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. (PDF and DVI files, unlike Postscript files, are not usually human-editable.) In either case, repeating C-c C-c (doc-view-toggle-display) toggles between DocView and the file text.

You can explicitly toggle DocView mode with the command M-x doc-view-mode, and DocView minor mode with the command 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.

When in DocView mode, you can enlarge or shrink the document with + (doc-view-enlarge) and - (doc-view-shrink). To specify the default size for DocView, set or customize the variable doc-view-resolution.

To kill the DocView buffer, type k (doc-view-kill-proc-and-buffer). To bury it, type q (quit-window).

• Navigation: Navigation inside DocView buffers.
• Searching: Searching inside documents.
• Slicing: Specifying which part of pages should be displayed.
• Conversion: Influencing and triggering conversion.

39.1 Navigation

When 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, <next> or C-x ] (doc-view-next-page). To display the previous page, type p, <prior> or C-x [ (doc-view-previous-page).

The <SPC> (doc-view-scroll-up-or-next-page) key 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).

39.2 Searching

While in DocView mode, you can search the file's text for a regular expression (see Regexps). 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.

39.3 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 s 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 s m (doc-view-set-slice-using-mouse), where you use the mouse to select the slice.

To cancel the selected slice, type s r (doc-view-reset-slice). Then DocView shows the entire page including its entire margins.

39.4 Conversion

For efficiency, DocView caches the images produced by gs. The name of this directory 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 a 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.

The zoom commands + (doc-view-enlarge) and - (doc-view-shrink) need to reconvert the document at the new size. The current page is converted first.

40 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—mail, remote directories, digests, and so on. Here we introduce Gnus and describe several basic features. For full details, see Gnus.

To start Gnus, type M-x gnus <RET>.

• Buffers of Gnus: The group, summary, and article buffers.
• Gnus Startup: What you should know about starting Gnus.
• Summary of Gnus: A short description of the basic Gnus commands.

40.1 Gnus Buffers

Unlike most Emacs packages, Gnus uses several buffers to display information and to receive commands. The three Gnus buffers users use most are the group buffer, the summary buffer and the article buffer.

The group buffer contains a list of newsgroups. 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. Use this buffer to select a specific group.

The summary buffer lists one line for each article in a single group. By default, the author, the subject and the line number are displayed for each article, but this is customizable, like most aspects of Gnus display. The summary buffer is created when you select a group in the group buffer, and is killed when you exit the group. Use this buffer to select an article.

The article buffer displays the article. In normal Gnus usage, you see this buffer but you don't select it—all useful article-oriented commands work in the summary buffer. But you can select the article buffer, and execute all Gnus commands from that buffer, if you want to.

40.2 When Gnus Starts Up

At startup, Gnus reads your .newsrc news initialization file and attempts to communicate with the local news server, which is a repository of news articles. The news server need not be the same computer you are logged in on.

If you start Gnus and connect to the server, but do not see any newsgroups listed in the group buffer, type L or A k to get a listing of all the groups. Then type u to toggle subscription to groups.

The first time you start Gnus, Gnus subscribes you to a few selected groups. All other groups start out as killed groups for you; you can list them with A k. All new groups that subsequently come to exist at the news server become zombie groups for you; type A z to list them. You can subscribe to a group shown in these lists using the u command.

When you quit Gnus with q, it automatically records in your .newsrc and .newsrc.eld initialization files the subscribed or unsubscribed status of all groups. You should normally not edit these files manually, but you may if you know how.

40.3 Summary of Gnus Commands

Reading news is a two-step process:

1. Choose a group in the group buffer.
2. Select articles from the summary buffer. Each article selected is displayed in the article buffer in a large window, below the summary buffer in its small window.

Each Gnus buffer has its own special commands; the meanings of any given key in the various Gnus buffers are usually analogous, even if not identical. Here are commands for the group and summary buffers:

q

In the group buffer, update your .newsrc initialization file and quit Gnus.

In the summary buffer, exit the current group and return to the group buffer. Thus, typing q twice quits Gnus.

L

In the group buffer, list all the groups available on your news server (except those you have killed). This may be a long list!

l

In the group buffer, list only the groups to which you subscribe and which contain unread articles.

u

In the group buffer, unsubscribe from (or subscribe to) the group listed in the line that point is on. When you quit Gnus by typing q, Gnus lists in your .newsrc file which groups you have subscribed to. The next time you start Gnus, you won't see this group, because Gnus normally displays only subscribed-to groups.

C-k

In the group buffer, “kill” the current line's group—don't even list it in .newsrc from now on. This affects future Gnus sessions as well as the present session.

When you quit Gnus by typing q, Gnus writes information in the file .newsrc describing all newsgroups except those you have “killed.”

<SPC>

In the group buffer, select the group on the line under the cursor and display the first unread article in that group.

In the summary buffer,

• Select the article on the line under the cursor if none is selected.
• Scroll the text of the selected article (if there is one).
• Select the next unread article if at the end of the current article.

Thus, you can move through all the articles by repeatedly typing <SPC>.

<DEL>

In the group buffer, move point to the previous group containing unread articles.

In the summary buffer, scroll the text of the article backwards.

n

Move point to the next unread group, or select the next unread article.

p

Move point to the previous unread group, or select the previous unread article.

C-n

C-p

Move point to the next or previous item, even if it is marked as read. This does not select the article or group on that line.

s

In the summary buffer, do an incremental search of the current text in the article buffer, just as if you switched to the article buffer and typed C-s.

M-s regexp <RET>

In the summary buffer, search forward for articles containing a match for regexp.

41 Running Shell Commands from Emacs

Emacs has commands for passing single command lines to inferior shell processes; it can also run a shell interactively with input and output to an Emacs buffer named ‘*shell*’ or run a shell inside a terminal emulator window.

M-! cmd <RET>

Run the shell command line cmd and display the output (shell-command).

M-| cmd <RET>

Run the shell command line cmd with region contents as input; optionally replace the region with the output (shell-command-on-region).

M-& cmd <RET>

Run the shell command line 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.

M-x eshell invokes a shell implemented entirely in Emacs. It is documented in a separate manual. See Eshell.

• Single Shell: How to run one shell command and return.
• Interactive Shell: Permanent shell taking input via Emacs.
• Shell Mode: Special Emacs commands used with permanent shell.
• Shell Prompts: Two ways to recognize shell prompts.
• History: Repeating previous commands in a shell buffer.
• Directory Tracking: Keeping track when the subshell changes directory.
• Options: Options for customizing Shell mode.
• Terminal emulator: An Emacs window as a terminal emulator.
• Term Mode: Special Emacs commands used in Term mode.
• Paging in Term: Paging in the terminal emulator.
• Remote Host: Connecting to another computer.
• Serial Terminal: Connecting to a serial port.

41.1 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 an Emacs buffer named ‘*Shell Command Output*’, which is displayed in another window but not selected (if the output is long).

For instance, one way to decompress a file foo.gz from Emacs is to type M-! gunzip foo.gz <RET>. That shell command normally creates the file foo and produces no terminal output.

A numeric argument, as in M-1 M-!, says to insert terminal output into the current buffer instead of a separate buffer. It puts point before the output, and sets the mark after the output. For instance, M-1 M-! gunzip < foo.gz <RET> would insert the uncompressed equivalent of foo.gz into the current buffer.

If the shell command line ends in ‘&’, it runs asynchronously. For a synchronous shell command, shell-command returns the command's exit status (0 means success), when it is called from a Lisp program. You do not get any status information for an asynchronous command, since it hasn't finished yet when shell-command returns.

You can also type M-& (async-shell-command) to execute a shell command asynchronously. This behaves exactly like calling shell-command with ‘&’, except that you do not need to add the ‘&’ to the shell command line.

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, meaning insert the output in the current buffer, it deletes the old region and the output replaces it as the contents of the region. It returns the command's exit status, like M-!.

One use for M-| is to run gpg to see what keys are in the buffer. For instance, if the buffer contains a GPG key, type C-x h M-| gpg <RET> to feed the entire buffer contents to the gpg program. That program will ignore everything except the encoded keys, and will output a list of the keys the buffer contains.

Both M-! and M-| use shell-file-name to specify the shell to use. This variable is initialized based on your SHELL environment variable when Emacs is started. If the file name is relative, Emacs searches the directories in the list exec-path; this list is initialized based on the environment variable PATH when Emacs is started. Your init file can override either or both of these default initializations (see Init File).

Both M-! and M-| wait for the shell command to complete, unless you end the command with ‘&’ to make it asynchronous. To stop waiting, type C-g to quit; that terminates the shell command with the signal SIGINT—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.

Asynchronous commands ending in ‘&’ feed their output into the buffer ‘*Async Shell Command*’. Output arrives in that buffer regardless of whether it is visible in a window.

To specify a coding system for M-! or M-|, use the command C-x <RET> c immediately beforehand. See Communication Coding.

Error output from these commands is normally intermixed with the regular output. But if the variable shell-command-default-error-buffer has a string as value, and it's the name of a buffer, M-! and M-| insert error output before point in that buffer.

41.2 Interactive Inferior Shell

To run a subshell interactively, use M-x shell. This creates (or reuses) a buffer named ‘*shell*’ and runs a subshell 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>.

Emacs does not wait for the subshell to do anything. You can switch windows or buffers and edit them while the shell is waiting, or while it is running a command. Output from the subshell waits until Emacs has time to process it; this happens whenever Emacs is waiting for keyboard input or for time to elapse.

Input lines, once you submit them, are displayed using the face comint-highlight-input, and prompts are displayed using the face comint-highlight-prompt. This makes it easier to see previous input lines in the buffer. See Faces.

To make multiple subshells, you can invoke M-x shell with a prefix argument (e.g. C-u M-x shell), which 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.

The file name used to load the subshell is the value of the variable explicit-shell-file-name, if that is non-nil. Otherwise, the environment variable ESHELL is used, or the environment variable SHELL if there is no ESHELL. If the file name specified is relative, the directories in the list exec-path are searched; this list is initialized based on the environment variable PATH when Emacs is started. Your init file can override either or both of these default initializations. (see Init File).

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 to fallback on ~/.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 Communication Coding.

Emacs sets the environment variable INSIDE_EMACS in the subshell to a comma-separated list including the Emacs version. Programs can check this variable to determine whether they are running inside an Emacs subshell.

Emacs also sets the EMACS environment variable (to t) if it is not already defined. Warning: This environment variable is deprecated. Programs that check this variable should be changed to check INSIDE_EMACS instead.

41.3 Shell Mode

Shell buffers use Shell mode, which defines several special keys attached to the C-c prefix. They are chosen to resemble the usual editing and job control characters present in shells that are not under Emacs, except that you must type C-c first. Here is a complete list of the special key bindings of Shell mode:

<RET>

At end of buffer send line as input; otherwise, copy current line to end of buffer and send it (comint-send-input). Copying a line in this way omits any prompt at the beginning of the line (text output by programs preceding your input). See Shell Prompts, for how Shell mode recognizes prompts.

<TAB>

Complete the command name or file name before point in the shell buffer (comint-dynamic-complete). <TAB> also completes history references (see History References) and environment variable names.

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.

M-?

Display temporarily a list of the possible completions of the file name before point in the shell buffer (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, C-d sends EOF to the subshell. Typed at any other position in the buffer, C-d 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. 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. This command used to be called comint-kill-output.

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 end 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 what its current directory is, so that Emacs can agree with the shell.

M-x 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 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.²³

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)

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 Debuggers) and M-x run-lisp (see 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.

41.4 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) considers the prompt to be any text output by a program at the beginning of an input line. However, if the variable comint-use-prompt-regexp is non-nil, then Comint mode uses a regular expression to recognize prompts. In Shell mode, shell-prompt-pattern specifies the regular expression.

The value of comint-use-prompt-regexp also affects many motion and paragraph commands. If the value is non-nil, the general Emacs motion commands behave as they normally do in buffers without special text properties. However, if the value is nil, the default, then Comint mode divides the buffer into two types of “fields” (ranges of consecutive characters having the same field text property): input and output. Prompts are part of the output. Most Emacs motion commands do not cross field boundaries, unless they move over multiple lines. For instance, when point is in input on the same line as a prompt, C-a puts point at the beginning of the input if comint-use-prompt-regexp is nil and at the beginning of the line otherwise.

In Shell mode, only shell prompts start new paragraphs. Thus, a paragraph consists of a prompt and the input and output that follow it. However, if comint-use-prompt-regexp is nil, the default, most paragraph commands do not cross field boundaries. This means that prompts, ranges of input, and ranges of non-prompt output behave mostly like separate paragraphs; with this setting, numeric arguments to most paragraph commands yield essentially undefined behavior. For the purpose of finding paragraph boundaries, Shell mode uses shell-prompt-pattern, regardless of comint-use-prompt-regexp.

41.5 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.

• Ring: Fetching commands from the history list.
• Copy: Moving to a command and then copying it.
• History References: Expanding ‘!’-style history references.

41.5.1 Shell History Ring

M-p

C-<UP>

Fetch the next earlier old shell command.

M-n

C-<DOWN>

Fetch the next later old shell command.

M-r

Begin an incremental regexp search of old shell commands.

C-c C-x

Fetch the next subsequent command from the history.

C-c .

Fetch one argument from an old shell command.

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, M-r and M-s. These work just like the minibuffer history commands except that they operate on the text at the end of the shell buffer, where you would normally insert text to send to the shell.

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-input-previous-argument) copies an individual argument from a previous command, like ESC . in Bash. 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 command instead, always using the same value of n (don't give a prefix argument when you repeat the C-c . command).

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.

41.5.2 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.

41.5.3 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.

Shell mode recognizes history references when they follow a prompt. See Shell Prompts, for how Shell mode recognizes prompts.

41.6 Directory Tracking

Shell mode keeps track of ‘cd’, ‘pushd’ and ‘popd’ commands given to the inferior shell, so it can keep the ‘*shell*’ buffer's default directory the same as the shell's working directory. It recognizes these commands syntactically, by examining lines of input that are sent.

If you use aliases for these commands, you can tell Emacs to recognize them also. For example, if the value of the variable shell-pushd-regexp matches the beginning of a shell command line, that line is regarded as a pushd command. Change this variable when you add aliases for ‘pushd’. Likewise, shell-popd-regexp and shell-cd-regexp are used to recognize commands with the meaning of ‘popd’ and ‘cd’. These commands are recognized only at the beginning of a shell command line.

If Emacs gets confused about changes in the current directory of the subshell, use the command M-x dirs to ask the shell what its current directory is. This command works for shells that support the most common command syntax; it may not work for unusual shells.

You can also use M-x dirtrack-mode to enable (or disable) an alternative method of tracking changes in the current directory. This method relies on your shell prompt containing the full current working directory at all times.

41.7 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.

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.

41.8 Emacs Terminal Emulator

To run a subshell in a 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 inferior subshell, as “terminal input.” Any “echoing” of your input is the responsibility of the subshell. The sole exception is the terminal escape character, which by default is C-c (see Term Mode). Any “terminal output” from the subshell goes into the buffer, advancing point.

Some programs (such as Emacs itself) need to control the appearance on the terminal screen in detail. They do this by sending special control codes. The exact control codes needed vary from terminal to terminal, but nowadays most terminals and terminal emulators (including xterm) understand the ANSI-standard (VT100-style) escape sequences. Term mode recognizes these escape sequences, and handles each one appropriately, changing the buffer so that the appearance of the window matches what it would be on a real terminal. You can actually run Emacs inside an Emacs Term window.

You can use Term mode to communicate with a device connected to a serial port of your computer. 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.

41.9 Term Mode

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 inferior subshell, except for the Term escape character, normally C-c.

To switch between line and char mode, use these commands:

C-c C-j

Switch to line mode. Do nothing if already in line mode.

C-c C-k

Switch to 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.

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’.

41.10 Page-At-A-Time Output

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. This command works in both line and char modes. When page-at-a-time is enabled, the mode-line displays the word ‘page’.

With page-at-a-time enabled, whenever Term receives more than a screenful of output since your last input, it pauses, displaying ‘**MORE**’ in the mode-line. Type <SPC> to display the next screenful of output. Type ? to see your other options. The interface is similar to the more program.

41.11 Remote Host Shell

You can login to a remote computer, using whatever commands you would from a regular terminal (e.g. using the telnet or rlogin commands), 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 separating comma.) Terminal types ‘ansi’ or ‘vt100’ will work on most systems.

41.12 Serial Terminal

If you have a device connected to a serial port of your computer, you can use Emacs to communicate with it. M-x serial-term will ask you for a serial port name and speed and will then open a new window in 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.

When you have opened the serial port connection, you will see output from the device in the window. Also, what you type in the window is sent to the device.

If the speed or the configuration is wrong, you cannot communicate with your device and will probably only see garbage output in the window.

42 Using Emacs as a Server

Various programs such as mail can invoke your choice of editor to edit a particular piece of text, such as a message that you are sending. By convention, most of these programs use the environment variable EDITOR to specify which editor to run. If you set EDITOR to ‘emacs’, they invoke Emacs—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 two ways to start an Emacs server:

The first is to run the command server-start in an existing Emacs process: either type M-x server-start, or put the expression (server-start) in your initialization file (see Init File). The existing Emacs process is the server; when you exit Emacs, the server dies with the Emacs process.

The second way to start an Emacs server is to run Emacs as a daemon, using the ‘--daemon’ command-line option. See Initial Options. When Emacs is started this way, it calls server-start after initialization, and returns control to the calling terminal instead of opening an initial frame; it then waits in the background, listening for edit requests.

Once an Emacs server is set up, you can use a shell command called emacsclient to connect to the existing Emacs process and tell it to visit a file. If you set the EDITOR environment variable to ‘emacsclient’, programs such as mail will use the existing Emacs process for editing.²⁴

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’ option (see emacsclient Options).

• Invoking emacsclient: Connecting to the Emacs server.
• emacsclient Options: Emacs client startup options.

42.1 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-only terminal (see Frames). You can then select that frame to begin editing.

If there is no Emacs server, the emacsclient program halts with an error message. If the Emacs process has no existing frame—which can happen if it was started as a daemon (see Emacs 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, or on a text-only terminal, using the ‘-c’ and ‘-t’ options. See emacsclient Options.

If you are running on a single text-only 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 Shell) 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.

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 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.

42.2 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 command to run if emacsclient fails to contact Emacs. This is useful when running emacsclient in a script. For example, the following setting for the EDITOR environment variable will always give you an editor, even if no Emacs server is running:

          EDITOR="emacsclient --alternate-editor emacs +%d %s"

As a special exception, if command is the empty string, then emacsclient starts Emacs in daemon mode 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 a new graphical frame, instead of using an existing Emacs frame. Emacs 23 can create a graphical frame even if it was started in a text-only terminal, provided it is able to connect to a graphical display. If no graphical display is available, Emacs creates a new text-only terminal frame (see Frames). If you omit a filename argument while supplying the ‘-c’ option, the new frame displays the ‘*scratch*’ buffer (see Buffers).

‘-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 for connecting to an Emacs server via TCP.

An Emacs server usually uses an operating system feature called a “local socket” to listen for connections. Some operating systems, such as Microsoft Windows, do not support local sockets; in that case, Emacs uses TCP instead. When you start the Emacs server, Emacs creates a server file containing some TCP information that emacsclient needs for making the connection. By default, the server file is in ~/.emacs.d/server/. On Microsoft Windows, if emacsclient does not find the server file there, it looks in the .emacs.d/server/ subdirectory of the directory pointed to by the APPDATA environment variable. You can tell emacsclient to use a specific server file with the ‘-f’ or ‘--server-file’ option, or by setting the EMACS_SERVER_FILE environment variable.

Even if local sockets are available, you can tell Emacs to use TCP by setting the variable server-use-tcp to t. One advantage of TCP is that the server can accept connections from remote machines. For this to work, you must (i) set the variable server-host to the hostname or IP address of the machine on which the Emacs server runs, and (ii) provide emacsclient with the server file. (One convenient way to do the latter is to put the server file on a networked file system such as NFS.)

‘-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.

‘-s server-name’

‘--socket-name=server-name’

Connect to the Emacs server named server-name. The server name is given by the variable server-name on the Emacs server. If this option is omitted, emacsclient connects to the first server it finds. (This option is not supported on MS-Windows.)

‘-t’

‘--tty’

‘-nw’

Create a new Emacs frame on the current text-only terminal, instead of using an existing Emacs frame. Emacs 23 can open a text-only terminal even if it was started in another text-only terminal, or on a graphical display. If you omit a filename argument while supplying this option, the new frame displays the ‘*scratch*’ buffer. See Buffers.

If you type C-x C-c (save-buffers-kill-terminal) in an Emacs frame created with emacsclient, via the ‘-c’ or ‘-t’ options, Emacs deletes the frame instead of killing the Emacs process itself. On a text-only terminal frame created with the ‘-t’ option, this returns control to the terminal. Emacs also marks all the server buffers for the client as finished, as though you had typed C-x # in all of them.

When Emacs is started as a daemon, all frames are considered client frames, so C-x C-c will never kill Emacs. To kill the Emacs process, type M-x kill-emacs.

43 Printing Hard Copies

Emacs provides commands for printing hard copies of either an entire buffer or just part of one, with or without page headers. You can invoke the printing commands directly, as detailed in the following section, or using the ‘File’ menu on the menu bar.

Aside from the commands described in this section, you can also “print” an Emacs buffer to HTML with M-x htmlfontify-buffer. This command converts the current buffer to a HTML file, replacing Emacs faces with CSS-based markup. In addition, see the hardcopy commands of Dired (see Misc File Ops) and the diary (see Displaying the Diary).

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.

The hardcopy commands (aside from the PostScript commands) pass extra switches to the lpr program based on the value of the variable lpr-switches. Its value should be a list of strings, each string an option starting with ‘-’. For example, to specify a line width of 80 columns for all the printing you do in Emacs, set lpr-switches like this:

     (setq lpr-switches '("-w80"))

You can specify the printer to use by setting the variable printer-name.

The variable lpr-command specifies the name of the printer program to run; the default value depends on your operating system type. On most systems, the default is "lpr". 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. lpr-add-switches should be nil if your printer program is not compatible with lpr.

• PostScript: Printing buffers or regions as PostScript.
• PostScript Variables: Customizing the PostScript printing commands.
• Printing Package: An optional advanced printing interface.

44 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 PostScript commands, ps-print-buffer and ps-print-region, print buffer contents in PostScript form. One command prints the entire buffer; the other, just the region. The corresponding ‘-with-faces’ commands, ps-print-buffer-with-faces and ps-print-region-with-faces, use PostScript features to show the faces (fonts and colors) in the text properties of the text being printed. The ‘-with-faces’ commands only work if they are used in a window system, so it has a way to determine color values.

Interactively, when you use a prefix argument (C-u), the command prompts the user for a file name, and saves the PostScript image in that file instead of sending it to the printer.

Noninteractively, the argument filename is treated as follows: if it is nil, send the image to the printer. If filename is a string, save the PostScript image in a file with that name.

If you are using a color display, you can print a buffer of program code with color highlighting by turning on Font-Lock mode in that buffer, and using ps-print-buffer-with-faces.

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.

Interactively, when you use a prefix argument (C-u), the command prompts the user for a file name, and saves the spooled PostScript image in that file instead of sending it to the printer.

Noninteractively, the argument filename is treated as follows: if it is nil, send the image to the printer. If filename is a string, save the PostScript image in a file with that name.

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.

The following section describes variables for customizing these commands.

45 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 illegible output, even if your screen colors only use shades of gray.

Alternatively, you can set ps-print-color-p to black-white to print colors on black/white printers.

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. It defaults to 8.5 points.

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.

46 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 Init 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.

47 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 accord with the ASCII character sequence.

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. 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. See below for an explanation.

M-x reverse-region

Reverse the order of the lines in the region. This is useful for sorting into descending order by fields or columns, 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.

48 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 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 Position Info.

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.

49 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 C-x 6 <RET> or <F2> <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.

50 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.

Ordinary text characters overwrite in Hexl mode. This is to reduce the risk of accidentally spoiling the alignment of data in the file. There are special commands for insertion. Here is a list of the commands of 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-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-<RET> for details.

51 Saving Emacs Sessions

Use the desktop library to save the state of Emacs from one session to another. Once you save the Emacs desktop—the buffers, their file names, major modes, buffer positions, and so on—then subsequent Emacs sessions reload the saved desktop.

You can save the desktop manually with the command M-x desktop-save. You can also enable automatic saving of the desktop when you exit Emacs, and automatic restoration of the last saved desktop when Emacs starts: use the Customization buffer (see Easy Customization) to set desktop-save-mode to t for future sessions, or add this line in your init file (see Init 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 the current directory. (More precisely, it looks in the directories specified by desktop-path, and uses the first desktop it finds.) Thus, you can have separate saved desktops in different directories, and the starting directory determines which one Emacs reloads. You can save the current desktop and reload one saved in another directory by typing M-x desktop-change-dir. Typing M-x desktop-revert reverts to the desktop previously reloaded.

Specify the option ‘--no-desktop’ on the command line when you don't want it to reload any saved desktop. 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.

By default, all the buffers in the desktop are restored at 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 kills all buffers except for internal ones, and clears the global variables listed in desktop-globals-to-clear. If you want this 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.

52 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.

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.

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.

53 Emulation

GNU Emacs can be programmed to emulate (more or less) most other editors. Standard facilities can emulate these:

CRiSP/Brief (PC editor)

You can turn on key bindings to emulate the CRiSP/Brief editor with M-x crisp-mode. Note that this rebinds M-x to exit Emacs unless you set the variable crisp-override-meta-x. You can also use the command M-x scroll-all-mode or set the variable crisp-load-scroll-all to emulate CRiSP's scroll-all feature (scrolling all windows together).

EDT (DEC VMS editor)

Turn on EDT emulation with the command M-x edt-emulation-on, while M-x edt-emulation-off restores normal Emacs command bindings.

Most of the EDT emulation commands are keypad keys, and most standard Emacs key bindings are still available. The EDT emulation rebindings are done in the global keymap, so there is no problem switching buffers or major modes while in EDT emulation.

TPU (DEC VMS editor)

M-x tpu-edt-on turns on emulation of the TPU editor emulating EDT.

vi (Berkeley editor)

Viper is the newest emulator for vi. It implements several levels of emulation; level 1 is closest to vi itself, while level 5 departs somewhat from strict emulation to take advantage of the capabilities of Emacs. To invoke Viper, type M-x viper-mode; it will guide you the rest of the way and ask for the emulation level. see Viper.

vi (another emulator)

M-x vi-mode enters a major mode that replaces the previously established major mode. All of the vi commands that, in real vi, enter “input” mode are programmed instead to return to the previous major mode. Thus, ordinary Emacs serves as vi's “input” mode.

Because vi emulation works through major modes, it does not work to switch buffers during emulation. Return to normal Emacs first.

If you plan to use vi emulation much, you probably want to bind a key to the vi-mode command.

vi (alternate emulator)

M-x vip-mode invokes another vi emulator, said to resemble real vi more thoroughly than M-x vi-mode. “Input” mode in this emulator is changed from ordinary Emacs so you can use <ESC> to go back to emulated vi command mode. To get from emulated vi command mode back to ordinary Emacs, type C-z.

This emulation does not work through major modes, and it is possible to switch buffers in various ways within the emulator. It is not so necessary to assign a key to the command vip-mode as it is with vi-mode because terminating insert mode does not use it.

see VIP, for full information.

WordStar (old wordprocessor)

M-x wordstar-mode provides a major mode with WordStar-like key bindings.

54 Hyperlinking and Navigation Features

Various modes documented elsewhere have hypertext features so that you can follow links, usually by clicking Mouse-2 on the link or typing <RET> while point is on the link. Clicking Mouse-1 quickly on the link also follows it. (Hold Mouse-1 for longer if you want to set point instead.)

Info mode, Help mode and the Dired-like modes are examples of modes that have links in the buffer. The Tags facility links between uses and definitions in source files, see Tags. Imenu provides navigation amongst items indexed in the current buffer, see Imenu. Info-lookup provides mode-specific lookup of definitions in Info indexes, see Documentation. Speedbar maintains a frame in which links to files, and locations in files are displayed, see Speedbar.

Other non-mode-specific facilities described in this section enable following links from the current buffer in a context-sensitive fashion.

• Browse-URL: Following URLs.
• Goto Address mode: Activating URLs.
• FFAP: Finding files etc. at point.

54.1 Following URLs

M-x browse-url <RET> url <RET>

Load a URL into a Web browser.

The Browse-URL package provides facilities for following URLs specifying links on the World Wide Web. Usually this works by invoking a web browser, but you can, for instance, arrange to invoke compose-mail from ‘mailto:’ URLs.

The general way to use this feature is to type M-x browse-url, which displays a specified URL. If point is located near a plausible URL, that URL is used as the default. Other commands are available 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, particularly browse-url-browser-function. You can invoke actions dependent on the type of URL by defining browse-url-browser-function as an association list. The package's commentary available via C-h p under the ‘hypermedia’ keyword provides more information. Packages with facilities for following URLs should always go through Browse-URL, so that the customization options for Browse-URL will affect all browsing in Emacs.

54.2 Activating URLs

M-x goto-address-mode

Activate URLs and e-mail addresses in the current buffer.

You can make URLs in the current buffer active with M-x goto-address-mode. This minor mode finds all the URLs in the buffer, highlights them, and turns them into buttons: if you click on a URL with Mouse-1 or Mouse-2 (see Mouse References), or move to the URL and type C-c <RET>, that displays the web page that the URL specifies. For a ‘mailto’ URL, it sends mail instead, using your selected mail-composition method (see Mail Methods).

It can be useful to add goto-address-mode to mode hooks and the hooks used to display an incoming message (e.g., rmail-show-message-hook for Rmail, and mh-show-mode-hook for MH-E). This is not needed for Gnus, which has a similar feature of its own.

54.3 Finding Files and URLs at Point

FFAP mode replaces certain key bindings for finding files, including C-x C-f, with commands that provide more sensitive 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.

This feature is useful for following references in mail or news buffers, README files, MANIFEST files, and so on. The ‘ffap’ package's commentary available via C-h p under the ‘files’ keyword and the ffap Custom group provide details.

You can turn on FFAP minor mode by calling ffap-bindings to make the following key bindings and to install hooks for using ffap 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

ffap-read-only, analogous to find-file-read-only.

C-x C-v

ffap-alternate-file, analogous to find-alternate-file.

C-x d directory <RET>

Start Dired on directory, defaulting to the directory name at point (dired-at-point).

C-x C-d

ffap-list-directory, analogous to list-directory.

C-x 4 f

ffap-other-window, analogous to find-file-other-window.

C-x 4 r

ffap-read-only-other-window, analogous to find-file-read-only-other-window.

C-x 4 d

ffap-dired-other-window, analogous to dired-other-window.

C-x 5 f

ffap-other-frame, analogous to find-file-other-frame.

C-x 5 r

ffap-read-only-other-frame, analogous to find-file-read-only-other-frame.

C-x 5 d

ffap-dired-other-frame, analogous to dired-other-frame.

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).

55 Dissociated Press

M-x dissociated-press is a command for scrambling a file of text either word by word or character by character. Starting from a buffer of straight English, it produces extremely amusing output. The input comes from the current Emacs buffer. Dissociated Press writes its output in a buffer named ‘*Dissociation*’, and redisplays that buffer after every couple of lines (approximately) so you can read the output as it comes out.

Dissociated Press asks every so often whether to continue generating output. Answer n to stop it. You can also stop at any time by typing C-g. The dissociation output remains in the ‘*Dissociation*’ buffer for you to copy elsewhere if you wish.

Dissociated Press operates by jumping at random from one point in the buffer to another. In order to produce plausible output rather than gibberish, it insists on a certain amount of overlap between the end of one run of consecutive words or characters and the start of the next. That is, if it has just output `president' and then decides to jump to a different point in the buffer, it might spot the `ent' in `pentagon' and continue from there, producing `presidentagon'. Long sample texts produce the best results.

A positive argument to M-x dissociated-press 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. In this mode, whole words are treated as the elements to be permuted, rather than characters. No argument is equivalent to an argument of two. For your againformation, the output goes only into the buffer ‘*Dissociation*’. The buffer you start with is not changed.

Dissociated Press produces results fairly like those of a Markov chain based on a frequency table constructed from the sample text. It is, however, an independent, ignoriginal invention. Dissociated Press 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. This makes for more plausible sounding results, and runs faster.

It is a mustatement that too much use of Dissociated Press can be a developediment to your real work, sometimes to the point of outragedy. And keep dissociwords out of your documentation, if you want it to be well userenced and properbose. Have fun. Your buggestions are welcome.

56 Other Amusements

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.

If you want a little more personal involvement, try M-x gomoku, which plays the game Go Moku with you.

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 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 decipher helps you to cryptanalyze a buffer which is encrypted in a simple monoalphabetic substitution cipher.

M-x dunnet runs an adventure-style exploration game, which is a bigger sort of puzzle.

M-x lm runs a relatively non-participatory game in which a robot attempts to maneuver towards a tree at the center of the window based on unique olfactory cues from each of the four directions.

M-x life runs Conway's “Life” cellular automaton.

M-x morse-region converts text in a region to Morse code and M-x unmorse-region converts it back. No cause for remorse.

M-x pong plays a Pong-like game, bouncing the ball off opposing bats.

M-x solitaire plays a game of solitaire in which you jump pegs across other pegs.

The animate package makes text dance. For an example, try M-x animate-birthday-present.

M-x studlify-region studlify-cases the region, producing text like this:

     M-x stUdlIfY-RegioN stUdlIfY-CaSeS thE region.

M-x tetris runs an implementation of the well-known Tetris game. Likewise, M-x snake provides an implementation of Snake.

When you are frustrated, try the famous Eliza program. Just do M-x doctor. End each input by typing <RET> twice.

When you are feeling strange, type M-x yow.

The command M-x zone plays games with the display when Emacs is idle.

57 Customization

This chapter describes some simple methods to customize the behavior of Emacs.

Apart from the methods described here, see X 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.

• Minor Modes: Each minor mode is a feature you can turn on independently of any others.
• Easy Customization: Convenient way to browse and change settings.
• Variables: Many Emacs commands examine Emacs variables to decide what to do; by setting variables, you can control their functioning.
• Key Bindings: The keymaps say what command each key runs. By changing them, you can "redefine keys".
• Syntax: The syntax table controls how words and expressions are parsed.
• Init File: How to write common customizations in the .emacs file.

57.1 Minor Modes

Minor modes are optional features which you can turn on or off. For example, Auto Fill mode is a minor mode in which <SPC> breaks lines between words as you type. Minor modes are independent of one another and of the selected major mode. Most minor modes say in the mode line when they are enabled; for example, ‘Fill’ in the mode line means that Auto Fill mode is enabled.

Each minor mode is associated with a command, called the mode command, which turns it on or off. The name of this command consists of the name of the minor mode, followed by ‘-mode’; for instance, the mode command for Auto Fill mode is auto-fill-mode. Calling the minor mode command with no prefix argument toggles the mode, turning it on if it was off, and off if it was on. A positive argument always turns the mode on, and a zero or negative argument always turns it off. Mode commands are usually invoked with M-x, but you can bind keys to them if you wish (see Key Bindings).

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 some minor modes—but not all—the value of the variable alone determines whether the mode is active: the mode command works simply by setting the variable, and changing the value of the variable has the same effect as calling the mode command. Because not all minor modes work this way, we recommend that you avoid changing the mode variables directly; use the mode commands instead.

Some minor modes are buffer-local: they apply only to the current buffer, so you can enable the mode in certain buffers and not others. Other minor modes are global: while enabled, they affect everything you do in the Emacs session, in all buffers. Some global minor modes are enabled by default.

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.
• Auto Save mode saves the buffer contents periodically to reduce the amount of work you can lose in case of a crash. See Auto Save.
• Enriched mode enables editing and saving of formatted text. See Formatted Text.
• Flyspell mode automatically highlights misspelled words. See 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 Faces.

• Linum mode displays each line's line number in the window's left margin. Its mode command is linum-mode.
• 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.

Here are some useful global minor modes. Since Line Number mode and Transient Mark mode can be enabled or disabled just by setting the value of the minor mode variable, you can set them differently for particular buffers, by explicitly making the corresponding variable local in those buffers. See Locals.

• Column Number mode enables display of the current column number in the mode line. See Mode Line.
• Delete Selection mode causes text insertion to first delete the text in the region, if the region is active. See Using Region.
• Icomplete mode displays an indication of available completions when you are in the minibuffer and completion is active. See Completion Options.
• Line Number mode enables display of the current line number in the mode line. It is enabled by default. See 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.
• 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 Mark.

57.2 Easy Customization Interface

Emacs has many settings which have values that you can change. Many are documented in this manual. Most settings are user options—that is to say, Lisp variables (see Variables)—and their names appear in the Variable Index (see Variable Index). The other settings are faces and their attributes (see Faces).

You can browse settings and change them using 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 in your initialization file (see Init File).

• Customization Groups: How settings are classified in a structure.
• Browsing Custom: Browsing and searching for settings.
• Changing a Variable: How to edit an option's value and set the option.
• Saving Customizations: Specifying the file for saving customizations.
• Face Customization: How to edit the attributes of a face.
• Specific Customization: Making a customization buffer for specific variables, faces, or groups.
• Custom Themes: How to define collections of customized options that can be loaded and unloaded together.

57.2.1 Customization Groups

For customization purposes, settings are organized into groups to help you find them. 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 and the second-level groups immediately under it. It looks like this, in part:

     /- 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.
     
     [External] : Interfacing to external utilities.
     
     more second-level groups
     
     \- Emacs group end ------------------------------------------------/

This says that the buffer displays the contents of the Emacs group. The other groups are listed because they are its contents. But they are listed differently, without indentation and dashes, because their contents are not included. Each group has a single-line documentation string; the Emacs group also has a ‘[State]’ line.

Most of the text in the customization buffer is read-only, but it typically includes some editable fields that you can edit. There are also buttons and links, which do something when you invoke them. To invoke a button or a link, either click on it with Mouse-1, or move point to it and type <RET>.

For example, the phrase ‘[State]’ that appears in a second-level group is a button. It operates on the same customization buffer. Each group name, such as ‘[Editing]’, is a hypertext link to that group; invoking it creates a new customization buffer, showing the group and its contents.

The Emacs group only contains other groups. These groups, in turn, can contain settings or still more groups. By browsing the hierarchy of groups, you will eventually find the feature you are interested in customizing. Then you can use the customization buffer to set that feature's settings. You can also go straight to a particular group by name, using the command M-x customize-group.

57.2.2 Browsing and Searching for Options and Faces

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, and puts them in a structure.

In this buffer, you can show the contents of a group by invoking the ‘[+]’ button. When the group contents are visible, this 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 and its contents, just that user option, or just that face. This is the way to change settings that you find with M-x customize-browse.

If you can guess part of the name of the settings you are interested in, M-x customize-apropos is another way to search for settings. However, unlike customize and customize-browse, customize-apropos can only find groups and settings that are loaded in the current Emacs session. See Customizing Specific Items.

57.2.3 Changing a Variable

Here is an example of what a variable (a user option) looks like in the customization buffer:

     Kill Ring Max: [Hide Value] 60
        [State]: STANDARD.
     Maximum length of kill ring before oldest elements are thrown away.

The text following ‘[Hide Value]’, ‘60’ in this case, indicates the current value of the variable. If you see ‘[Show Value]’ instead of ‘[Hide Value]’, it means that the value is hidden; the customization buffer initially hides values that take up several lines. Invoke ‘[Show Value]’ to show the value.

The line after the variable name indicates the customization state of the variable: in the example above, it says you have not changed the option yet. The ‘[State]’ button at the beginning of this line gives you a menu of various operations for customizing the variable.

The line after the ‘[State]’ line displays the beginning of the variable's documentation string. If there are more lines of documentation, this line ends with a ‘[More]’ button; invoke that to show the full documentation string.

To enter a new value for ‘Kill Ring Max’, move point to the value and edit it textually. For example, you can type M-d, then insert another number. As you begin to alter the text, you will see the ‘[State]’ line change to say that you have edited the value:

     [State]: EDITED, shown value does not take effect until you set or ...
                                                                save it.

Editing the value does not actually set the variable. To do that, you must set the variable. To do this, invoke the ‘[State]’ button and choose ‘Set for Current Session’.

The state of the variable changes visibly when you set it:

     [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 a field that is a file name, directory name, command name, or anything else for which completion is defined, you can type M-<TAB> (widget-complete) to do completion. (<ESC> <TAB> and C-M-i do the same thing.)

Some variables have a small fixed set of possible legitimate values. These variables don't let you edit the value textually. Instead, a ‘[Value Menu]’ button appears before the value; invoke this button to change the value. For a boolean “on or off” value, the button says ‘[Toggle]’, and it changes to the other value. ‘[Value Menu]’ and ‘[Toggle]’ simply edit the buffer; the changes take real effect when you use the ‘Set for Current Session’ operation.

Some variables have values with complex structure. For example, the value of file-coding-system-alist is an association list. Here is how it appears in the customization buffer:

     File Coding System Alist: [Hide Value]
     [INS] [DEL] File regexp: \.elc\'
                 Choice: [Value Menu] Encoding/decoding pair:
                 Decoding: emacs-mule
                 Encoding: emacs-mule
     [INS] [DEL] File regexp: \(\`\|/\)loaddefs.el\'
                 Choice: [Value Menu] Encoding/decoding pair:
                 Decoding: raw-text
                 Encoding: raw-text-unix
     [INS] [DEL] File regexp: \.tar\'
                 Choice: [Value Menu] Encoding/decoding pair:
                 Decoding: no-conversion
                 Encoding: no-conversion
     [INS] [DEL] File regexp:
                 Choice: [Value Menu] Encoding/decoding pair:
                 Decoding: undecided
                 Encoding: nil
     [INS]
        [State]: STANDARD.
     Alist to decide a coding system to use for a file I/O ...
                                     operation. [Hide Rest]
     The format is ((PATTERN . VAL) ...),
     where PATTERN is a regular expression matching a file name,
     [...more lines of documentation...]

Each association in the list appears on four lines, with several editable fields and/or buttons. You can edit the regexps and coding systems using ordinary editing commands. You can also invoke ‘[Value Menu]’ to switch to a different kind of value—for instance, to specify a function instead of a pair of coding systems.

To delete an association from the list, invoke the ‘[DEL]’ button for that item. To add an association, invoke ‘[INS]’ at the position where you want to add it. There is an ‘[INS]’ button between each pair of associations, another at the beginning and another at the end, so you can add a new association at any position in the list.

Two special commands, <TAB> and S-<TAB>, are useful for moving through the customization buffer. <TAB> (widget-forward) moves forward to the next button or editable field; S-<TAB> (widget-backward) moves backward to the previous button or editable field.

Typing <RET> on an editable field also moves forward, just 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.

Setting the variable changes its value in the current Emacs session; saving the value changes it for future sessions as well. To save the variable, invoke ‘[State]’ and select the ‘Save for Future Sessions’ operation. This works by writing code so as to set the variable again, each time you start Emacs (see Saving Customizations).

You can also restore the variable to its standard value by invoking ‘[State]’ and selecting the ‘Erase Customization’ operation. There are actually four reset operations:

‘Undo Edits’

If you have made some modifications and not yet set the variable, this restores the text in the customization buffer to match the actual value.

‘Reset to Saved’

This restores the value of the variable to the last saved value, and updates the text accordingly.

‘Erase Customization’

This sets the variable to its standard value, and updates the text accordingly. This also eliminates any saved value for the variable, so that you will get the standard value in future Emacs sessions.

‘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. The comment you enter will be saved, and displayed again if you again view the same variable in a customization buffer, even in another session.

The state of a group indicates whether anything in that group has been edited, set or saved.

Near the top of the customization buffer there are two lines of buttons:

      [Set for Current Session] [Save for Future Sessions]
      [Undo Edits] [Reset to Saved] [Erase Customization]   [Finish]

Invoking ‘[Finish]’ either buries or kills this customization buffer according to the setting of the option custom-buffer-done-kill; the default is to bury the buffer. Each of the other buttons performs an operation—set, save or reset—on each of the settings in the buffer that could meaningfully be set, saved or reset. They do not operate on settings whose values are hidden, nor on subgroups which are hidden or not visible in the buffer.

57.2.4 Saving Customizations

Saving customizations from the customization buffer works by writing code to a file. By reading this code, future sessions can set up the customizations again. Normally, the code is saved in your initialization file (see Init File).

You can choose to save your customizations in a file 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 "~/.emacs-custom.el")
     (load custom-file)

You can use custom-file to specify different customization files for different Emacs versions, like this:

     (cond ((< emacs-major-version 22)
            ;; Emacs 21 customization.
            (setq custom-file "~/.custom-21.el"))
           ((and (= emacs-major-version 22) (< emacs-minor-version 3))
            ;; Emacs 22 customization, before version 22.3.
            (setq custom-file "~/.custom-22.el"))
           (t
            ;; Emacs version 22.3 or later.
            (setq custom-file "~/.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.

57.2.5 Customizing Faces

In addition to variables, some customization groups also include faces. When you show the contents of a group, both the variables and the faces in the group appear in the customization buffer. Here is an example of how a face looks:

     Custom Changed Face:(sample) [Hide Face]
        [State]: STANDARD.
     Face used when the customize item has been changed.
     Parent groups: [Custom Magic Faces]
     Attributes: [ ] Font Family: *
                 [ ] Width: *
                 [ ] Height: *
                 [ ] Weight: *
                 [ ] Slant: *
                 [ ] Underline: *
                 [ ] Overline: *
                 [ ] Strike-through: *
                 [ ] Box around text: *
                 [ ] Inverse-video: *
                 [X] Foreground: white       (sample)
                 [X] Background: blue        (sample)
                 [ ] Stipple: *
                 [ ] Inherit: *

Each face attribute has its own line. The ‘[x]’ button before the attribute name indicates whether the attribute is enabled; ‘[X]’ means that it's enabled, and ‘[ ]’ means that it's disabled. You can enable or disable the attribute by clicking that button. When the attribute is enabled, you can change the attribute value in the usual ways.

For the colors, you can specify a color name (use M-x list-colors-display for a list of them) or a hexadecimal color specification of the form ‘#rrggbb’. (‘#000000’ is black, ‘#ff0000’ is red, ‘#00ff00’ is green, ‘#0000ff’ is blue, and ‘#ffffff’ is white.) On a black-and-white display, the colors you can use for the background are ‘black’, ‘white’, ‘gray’, ‘gray1’, and ‘gray3’. Emacs supports these shades of gray by using background stipple patterns instead of a color.

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 display. 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]’.

Another more basic way to set the attributes of a specific face is with M-x modify-face. This command reads the name of a face, then reads the attributes one by one. For the color and stipple attributes, the attribute's current value is the default—type just <RET> if you don't want to change that attribute. Type ‘none’ if you want to clear out the attribute.

57.2.6 Customizing Specific Items

Instead of finding the setting you want to change by navigating the structure of groups, here are other ways to specify the settings that you want to customize.

M-x customize-option <RET> option <RET>

Set up a customization buffer with just one user option variable, option.

M-x customize-face <RET> face <RET>

Set up a customization buffer with just one face, face.

M-x customize-group <RET> group <RET>

Set up a customization buffer with just one group, group.

M-x customize-apropos <RET> regexp <RET>

Set up a customization buffer with all the settings and groups that match regexp.

M-x customize-changed <RET> version <RET>

Set up a customization buffer with all the settings and groups whose meaning has changed since 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 alter a particular user option with the customization buffer, and you know its name, you can use the command M-x customize-option and specify the user option (variable) name. This sets up the customization buffer with just one user option—the one that you asked for. Editing, setting and saving the value work as described above, but only for the specified user option. Minibuffer completion is handy if you only know part of the name. However, this command can only see options that have been loaded in the current Emacs session.

Likewise, you can modify a specific face, chosen by name, using M-x customize-face. By default it operates on the face used on the character after point.

You can also set up the customization buffer with a specific group, using M-x customize-group. The immediate contents of the chosen group, including settings (user options and faces), and other groups, all appear as well (even if not already loaded). However, the subgroups' own contents are not included.

For a more general way of controlling what to customize, you can use M-x customize-apropos. You specify a regular expression as argument; then all loaded settings and groups whose names match this regular expression are set up in the customization buffer. If you specify an empty regular expression, this includes all loaded groups and settings—which takes a long time to set up.

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 special commands to revisit your previous changes. Use M-x customize-saved to look at the settings that you have saved. Use M-x customize-unsaved to look at the settings that you have set but not saved.

57.2.7 Customization Themes

Custom themes are collections of settings that can be enabled or disabled as a unit. You can use Custom themes to switch quickly and easily between various collections of settings, and to transfer such collections from one computer to another.

To define a Custom theme, use M-x customize-create-theme, which brings up a buffer named ‘*New Custom Theme*’. At the top of the buffer is an editable field where you can specify the name of the theme. Click on the button labelled ‘Insert Variable’ to add a variable to the theme, and click on ‘Insert Face’ to add a face. You can edit these values in the ‘*New Custom Theme*’ buffer like in an ordinary Customize buffer. To remove an option from the theme, click on its ‘State’ button and select ‘Delete’.

After adding the desired options, click on ‘Save Theme’ to save the Custom theme. This writes the theme definition to a file foo-theme.el (where foo is the theme name you supplied), in the directory ~/.emacs.d/. You can specify the directory by setting custom-theme-directory.

You can view and edit the settings of a previously-defined theme by clicking on ‘Visit Theme’ and specifying the theme name. You can also import the variables and faces that you have set using Customize by visiting the “special” theme named ‘user’. This theme, which records all the options that you set in the ordinary customization buffer, is always enabled, and always takes precedence over all other enabled Custom themes. Additionally, the ‘user’ theme is recorded with code in your .emacs file, rather than a user-theme.el file.

Once you have defined a Custom theme, you can use it by customizing the variable custom-enabled-themes. This is a list of Custom themes that are enabled, or put into effect. If you set custom-enabled-themes using the Customize interface, the theme definitions are automatically loaded from the theme files, if they aren't already. If you save the value of custom-enabled-themes for future Emacs sessions, those Custom themes will be enabled whenever Emacs is started up.

If two enabled themes specify different values for an option, the theme occurring earlier in custom-enabled-themes takes effect.

You can temporarily enable a Custom theme with M-x enable-theme. This prompts for a theme name in the minibuffer, loads the theme from the theme file if necessary, and enables the theme. You can disable any enabled theme with the command M-x disable-theme; this returns the options specified in the theme to their original values. To re-enable the theme, type M-x enable-theme again. If a theme file is changed during your Emacs session, you can reload it by typing M-x load-theme. (This also enables the theme.)

57.3 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.

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 user options. See Easy Customization, for information about using the Customize facility to set user options. 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 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 kind of value it expects (see Examining).

• Examining: Examining or setting one variable's value.
• Hooks: Hook variables let you specify programs for parts of Emacs to run on particular occasions.
• Locals: Per-buffer values of variables.
• File Variables: How files can specify variable values.
• Directory Variables: How variable values can be specified by directory.

57.3.1 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 single variable, use C-h v (describe-variable), which reads a variable name using the minibuffer, with completion. It 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'.
     fill-column's value is 70
     Local in buffer custom.texi; global value is 70
     Automatically becomes buffer-local when set in any fashion.
     
       Automatically becomes buffer-local when set in any fashion.
       This variable is safe as a file local variable if its value
       satisfies the predicate `integerp'.
     
     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 any variable name.

The most convenient way to set a specific user option 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 user option variables, but you can set any variable with a Lisp expression, using the function setq. Here is a setq expression to set fill-column:

     (setq fill-column 75)

To execute an expression like this one, go to the ‘*scratch*’ buffer, type in the expression, and then type C-j. See Lisp Interaction.

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 to set it those sessions (see Init File).

57.3.2 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. With rare exceptions, hooks in Emacs are empty when Emacs starts up, so the only hook functions in any given hook are the ones you explicitly put there as customization.

Most major modes run one or more mode hooks as the last step of initialization. This makes it easy for you to customize the behavior of the mode, by setting up a hook function to override the local variable assignments already made by the mode. But hooks are also used in other contexts. For example, the hook kill-emacs-hook runs just before quitting the Emacs job (see Exiting).

Most Emacs hooks are normal hooks. This means that running the hook operates by calling all the hook functions, unconditionally, 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 in Emacs whose name ends in ‘-hook’ is a normal hook.

There are also a few abnormal hooks. These variables' names end in ‘-hooks’ or ‘-functions’, instead of ‘-hook’. What makes these hooks abnormal is that there is something peculiar about 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 (see Visiting) is abnormal because as soon as one hook function returns a non-nil value, the rest are not called at all. The documentation of each abnormal hook variable explains in detail what is peculiar about it.

You can set a hook variable with setq like any other Lisp variable, but the recommended way to add a hook function to a hook (either normal or abnormal) is by calling add-hook. See Hooks.

For example, here's how to set up a hook to turn on Auto Fill mode when entering Text mode and other modes based on Text mode:

     (add-hook 'text-mode-hook 'turn-on-auto-fill)

The next example shows how to use a hook to customize the indentation of C code. (People often have strong personal preferences for one format compared to another.) Here the hook function is an anonymous lambda expression.

     (setq my-c-style
       '((c-comment-only-line-offset . 4)
         (c-cleanup-list . (scope-operator
                            empty-defun-braces
                            defun-close-semi))
         (c-offsets-alist . ((arglist-close . c-lineup-arglist)
                             (substatement-open . 0)))))
     
     (add-hook 'c-mode-common-hook
       '(lambda ()
          (c-add-style "my-style" my-c-style t)))

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 most recently added hook functions are executed first.

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.

57.3.3 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)

57.3.4 Local Variables in Files

A file can specify local variable values for use when you edit the file with Emacs. Visiting the file checks for local variable specifications; it automatically makes these variables local to the buffer, and sets them to the values specified in the file.

• Specifying File Variables: Specifying file local variables.
• Safe File Variables: Making sure file local variables are safe.

57.3.4.1 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 as shown above. The special variable/value pair mode: modename;, if present, specifies a major or minor mode; if you use this to specify a major mode, it should come first in the line. The values are used literally, and not evaluated.

You can use the command add-file-local-variable-prop-line instead of adding entries by hand. It prompts for a variable and value, and adds them to the first line in the appropriate way. The command delete-file-local-variable-prop-line deletes a variable from the line. The command copy-dir-locals-to-file-locals-prop-line copies directory-local variables (see Directory Variables) to the first line.

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).

Instead of 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.

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 comment lines start with ‘/*’ and end with ‘*/’.

You can construct the local variables list yourself, or use the command add-file-local-variable. This prompts for a variable and value, and adds them to the list. If necessary, it also adds the start and end markers. The command delete-file-local-variable deletes a variable from the list. The command copy-dir-locals-to-file-locals copies directory-local variables (see Directory Variables) to the list.

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 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 “variable names” have special meanings in a local variables list:

• mode enables the specified major or minor 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 visit the file in a unibyte buffer, if the value is t. See Enabling Multibyte.

These four “variables” are not really variables; setting them in any other context has no special meaning.

If mode is used to set a major mode, it should be the first “variable” in the list. Otherwise, the entries that precede it will usually have no effect, since most major modes kill all local variables as part of their initialization.

You can use the mode “variable” to enable minor modes as well as the major modes; in fact, you can use it more than once, first to set the major mode and then to enable minor modes which are specific to particular buffers.

Often, however, it is a mistake to enable minor modes this way. Most minor modes, like Auto Fill mode, represent individual user preferences. If you want to use a minor mode, it is better to set up major mode hooks with your init file to turn that minor mode on for yourself alone (see Init File), instead of using a local variable list to impose your taste on everyone.

Use the command 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 Modes.

57.3.4.2 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.

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).

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. 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.

57.3.5 Per-Directory Local Variables

A project is a collection of files on which you work together. Usually, the project's files are kept in one or more directories. Occasionally, you may wish to define Emacs settings that are common to all the files that belong to the project.

Emacs provides two ways to specify settings that are applicable to files in a specific directory: you can put a special file in that directory, or you can define a project class for that directory.

If you put a file with a special name .dir-locals.el²⁵ in a directory, Emacs will read it when it visits any file in that directory or any of its subdirectories, and apply the settings it specifies to the file's buffer. 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.)

The .dir-locals.el file should hold a specially-constructed list. This list maps Emacs mode names (symbols) to alists; each alist specifies values for variables to use when the respective mode is turned on. The special mode name ‘nil’ means that its alist applies to any mode. Instead of a mode name, you can specify a string that is a name of a subdirectory of the project's directory; then the corresponding alist applies to all the files in that subdirectory.

Here's an example of a .dir-locals.el file:

     ((nil . ((indent-tabs-mode . t)
              (tab-width . 4)
              (fill-column . 80)))
      (c-mode . ((c-file-style . "BSD")))
      (java-mode . ((c-file-style . "BSD")))
      ("src/imported"
       . ((nil . ((change-log-default-name . "ChangeLog.local"))))))

This example shows some settings for a hypothetical project. It sets ‘indent-tabs-mode’, tab-width, and fill-column for any file in the project's directory tree, and it sets the indentation style for any C or Java source file. Finally, it specifies a different ChangeLog file name for any file in the src/imported subdirectory of the directory where you put the .dir-locals.el file.

You can edit the .dir-locals.el file by hand, or use the command add-dir-local-variable. This prompts for a mode (or subdirectory), variable and value, and adds an entry to the file. The command delete-dir-local-variable deletes an entry. The command copy-file-locals-to-dir-locals copies file local variables (see File Variables) to the .dir-locals.el file.

Another method of specifying directory-local variables is to explicitly define a project class using dir-locals-set-class-variables, and then tell Emacs which directories correspond to that class, using dir-locals-set-directory-class. You can put calls to these functions in your ~/.emacs init file; this can be useful when you can't put .dir-locals.el in the directory for some reason, or if you want to keep in a single place settings for several directories that don't have a common parent. 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)

Unsafe directory-local variables are handled in the same way as unsafe file-local variables (see Safe File Variables).

57.4 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 Init Rebinding).

• Keymaps: Generalities. The global keymap.
• Prefix Keymaps: Keymaps for prefix keys.
• Local Keymaps: Major and minor modes have their own keymaps.
• Minibuffer Maps: The minibuffer uses its own local keymaps.
• Rebinding: How to redefine one key's meaning conveniently.
• Init Rebinding: Rebinding keys with your init file, .emacs.
• Modifier Keys: Using modifier keys in key bindings.
• Function Keys: Rebinding terminal function keys.
• Named ASCII Chars: Distinguishing <TAB> from C-i, and so on.
• Mouse Buttons: Rebinding mouse buttons in Emacs.
• Disabling: Disabling a command means confirmation is required before it can be executed. This is done to protect beginners from surprises.

57.4.1 Keymaps

As described in 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 global-set-key, work by storing the new binding in the proper place in the global map (see Rebinding).

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 depends 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.

57.4.2 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, for special information about menu bar key bindings. Mouse button events that invoke pop-up menus are also prefix keys; see Menu Keymaps, 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.

57.4.3 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.

57.4.4 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.
• Finally, minibuffer-local-filename-completion-map and minibuffer-local-must-match-filename-map are like the two previous ones, but they are specifically for file name completion. They do not bind <SPC>.

57.4.5 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 Init Rebinding, for a description of how to make key rebindings affect future Emacs sessions.

M-x global-set-key <RET> key cmd <RET>

Define key globally to run cmd.

M-x local-set-key <RET> key cmd <RET>

Define key locally (in the major mode now in effect) to run cmd.

M-x global-unset-key <RET> key

Make key undefined in the global map.

M-x local-unset-key <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 Shell), replacing the normal global definition of C-z:

     M-x global-set-key <RET> C-z shell <RET>

The global-set-key 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 global-set-key <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 global-unset-key. This makes the key undefined; if you type it, Emacs will just beep. Similarly, local-unset-key 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.

57.4.6 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 Init File, for a description of the initialization file.

There are several ways to write a key binding using Lisp. The simplest is to use the kbd macro, which converts a textual representation of a key sequence—similar to how we have written key sequences in this manual—into a form that can be passed as an argument to global-set-key. For example, here's how to bind C-z to the shell command (see Interactive Shell):

     (global-set-key (kbd "C-z") 'shell)

The single-quote before the command name, shell, 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 probably causes an error; it certainly isn't what you want.

Here are some additional examples, including binding function keys and mouse events:

     (global-set-key (kbd "C-c y") 'clipboard-yank)
     (global-set-key (kbd "C-M-q") 'query-replace)
     (global-set-key (kbd "<f5>") 'flyspell-mode)
     (global-set-key (kbd "C-<f5>") 'linum-mode)
     (global-set-key (kbd "C-<right>") 'forward-sentence)
     (global-set-key (kbd "<mouse-2>") 'mouse-save-then-kill)
     (global-set-key (kbd "C-<down-mouse-3>") 'mouse-yank-at-click)

Instead of using the kbd macro, you can use a Lisp string or vector to specify the key sequence. Using a string is simpler, but only works for ASCII characters and Meta-modified ASCII characters. For example, here's how to bind C-x M-l to make-symbolic-link (see Misc File Ops):

     (global-set-key "\C-x\M-l" 'make-symbolic-link)

To put <TAB>, <RET>, <ESC>, or <DEL> in the string, use the Emacs Lisp escape sequences ‘\t’, ‘\r’, ‘\e’, and ‘\d’ respectively. Here is an example which binds C-x <TAB> to indent-rigidly (see Indentation):

     (global-set-key "\C-x\t" 'indent-rigidly)

When the key sequence includes function keys or mouse button events, or non-ASCII characters such as C-= or H-a, you can use a vector to specify the key sequence. Each element in the vector stands for an input event; the elements are separated by spaces and surrounded by a pair of square brackets. If a vector element is a character, write it as a Lisp character constant: ‘?’ followed by the character as it would appear in a string. Function keys are represented by symbols (see Function Keys); simply write the symbol's name, with no other delimiters or punctuation. Here are some examples:

     (global-set-key [?\C-=] 'make-symbolic-link)
     (global-set-key [?\M-\C-=] 'make-symbolic-link)
     (global-set-key [?\H-a] 'make-symbolic-link)
     (global-set-key [f7] 'make-symbolic-link)
     (global-set-key [C-mouse-1] 'make-symbolic-link)

You can use a vector for the simple cases too:

     (global-set-key [?\C-z ?\M-l] 'make-symbolic-link)

Language and coding systems may cause problems with key bindings for non-ASCII characters. See Init Non-ASCII.

As described in Local Keymaps, major modes and minor modes can define local keymaps. These keymaps are constructed when the mode is used for the first time in a session. If you wish to change one of these keymaps, you must use the 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 in Texinfo mode:

     (add-hook 'texinfo-mode-hook
               '(lambda ()
                  (define-key texinfo-mode-map "\C-cp" 'backward-paragraph)
                  (define-key texinfo-mode-map "\C-cn" 'forward-paragraph)))

57.4.7 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 always 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.

For all other modifiers, you can make the modified alphabetical characters case-sensitive 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 these modifiers. However, you can customize Emacs to assign meanings to them. The modifier bits are labelled as ‘s-’, ‘H-’ and ‘A-’ respectively.

Even if your keyboard lacks these additional modifier keys, you can enter it 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.)

57.4.8 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

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 Init Rebinding, 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 in 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). You can rebind the keys to perform other tasks, such as issuing numeric prefix arguments.

57.4.9 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 “same” 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.

57.4.10 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:

     (global-set-key [mouse-2] 'split-window-vertically)

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). 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:

     (global-set-key [mode-line mouse-1] 'scroll-up)

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.

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.

57.4.11 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 .emacs 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")

You can make a command disabled either by editing the .emacs file directly, or with the command M-x disable-command, which edits the .emacs file for you. Likewise, M-x enable-command edits .emacs to enable a command permanently. See Init File.

If Emacs was invoked with the -q or --no-init-file options (see Initial Options), it will not edit your ~/.emacs init file. Doing so could lose information because Emacs has not read your init 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.

57.5 The Syntax Table

All the Emacs commands which parse words or balance parentheses are controlled by the syntax table. The syntax table says which characters are opening delimiters, which are parts of words, which are string quotes, and so on. It does this by assigning each character to one of fifteen-odd syntax classes. In some cases it specifies some additional information also.

Each major mode has its own syntax table (though related major modes sometimes share one syntax table), which it installs in each buffer that uses the mode. The syntax table installed in the current buffer is the one that all commands use, so we call it “the” syntax table.

To display a description of the contents of the current syntax table, type C-h s (describe-syntax). The description of each character includes the string you would have to give to modify-syntax-entry to set up that character's current syntax, starting with the character which designates its syntax class, plus some English text to explain its meaning.

A syntax table is actually a Lisp object, a char-table, whose elements are cons cells. For full information on the syntax table, see Syntax Tables.

57.6 The Init File, ~/.emacs

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. Emacs looks for your init file using the filenames ~/.emacs, ~/.emacs.el, or ~/.emacs.d/init.el; you can choose to use any one of these three names (see Find Init). Here, ~/ stands for your home directory.

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 Lisp Libraries) specifies these directories. Many sites put these files in the site-lisp subdirectory of the Emacs installation directory, typically /usr/local/share/emacs/site-lisp.

Byte-compiling your init file is not recommended (see Byte Compilation). 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 Emacs 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.

• Init Syntax: Syntax of constants in Emacs Lisp.
• Init Examples: How to do some things with an init file.
• Terminal Init: Each terminal type can have an init file.
• Find Init: How Emacs finds the init file.
• Init Non-ASCII: Using non-ASCII characters in an init file.

57.6.1 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) to 60.

You can set any Lisp variable with setq, but with certain variables setq won't do what you probably want in the .emacs file. Some variables automatically become buffer-local when set with setq; what you want in .emacs is to set the default value, using setq-default. 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 .emacs file, call the minor mode command. The following section has examples of both of these methods.

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 .emacs, 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 Control-Meta-A.

See Init Non-ASCII, 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 Init Non-ASCII, 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.

57.6.2 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 Lisp Libraries.

            (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 Locals). 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 Headers.

• 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.

            (add-hook 'text-mode-hook
              '(lambda () (auto-fill-mode 1)))
  

  This shows how to add a hook function to a normal hook variable (see Hooks). The function we supply is a list starting with lambda, with a single-quote in front of it to make it a list constant rather than an expression.

  It's beyond the scope of this manual to explain Lisp functions, but for this example it is enough to know that the effect is to execute (auto-fill-mode 1) when Text mode is entered. You can replace that with any other expression that you like, or with several expressions in a row.

  Emacs comes with a function named turn-on-auto-fill whose definition is (lambda () (auto-fill-mode 1)). Thus, a simpler way to write the above example is as follows:

            (add-hook 'text-mode-hook 'turn-on-auto-fill)
  

• 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 Lisp Libraries).

• Load the compiled Lisp file foo.elc from your home directory.

            (load "~/foo.elc")
  

  Here an absolute 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 Init Rebinding).

            (global-set-key "\C-xl" 'make-symbolic-link)
  

  or

            (define-key global-map "\C-xl" '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.

            (define-key lisp-mode-map "\C-xl" 'make-symbolic-link)
  

• Redefine all keys which now run next-line in Fundamental mode so that they run forward-line instead.

            (substitute-key-definition 'next-line 'forward-line
                                       global-map)
  

• Make C-x C-v undefined.

            (global-unset-key "\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.

            (condition case ()
                (set-face-background 'region "grey75")
              (error nil))
  

  A setq on a variable which does not exist is generally harmless, so those do not need a conditional.

57.6.3 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 and it 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 (or function-key-map before it). 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 term-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.

57.6.4 How Emacs Finds Your Init File

Normally Emacs uses the environment variable HOME (see HOME) to find .emacs; that's what ‘~’ means in a file name. If .emacs is not found inside ~/ (nor .emacs.el), Emacs looks for ~/.emacs.d/init.el (which, like ~/.emacs.el, can be byte-compiled).

However, if you run Emacs from a shell started by su, Emacs tries to find your own .emacs, 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 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.

57.6.5 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 Recognize Coding. 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.

To bind non-ASCII keys, you must use a vector (see Init Rebinding). 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.

Warning: if you change the keyboard encoding, or change between multibyte and unibyte mode, or anything that would alter which code C-q would insert for that character, this key binding may stop working. It is therefore advisable to use one and only one coding system, for your init file as well as the files you edit. For example, don't mix the ‘latin-1’ and ‘latin-9’ coding systems.

58 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 Edit.)

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 Persistent Mark). If you are in the middle of an incremental search, C-g does special things; it may take two successive C-g characters to get out of a search. See Incremental Search, for details.

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 MS-DOS Keyboard.

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 Edit.

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.

59 Dealing with Emacs Trouble

This section describes various conditions in which Emacs fails to work normally, and how to recognize them and correct them. For a list of additional problems you might encounter, see Bugs and problems, and the file etc/PROBLEMS in the Emacs distribution. Type C-h C-f to read the FAQ; type C-h C-p to read the PROBLEMS file.

• DEL Does Not Delete: What to do if <DEL> doesn't delete.
• Stuck Recursive: `[...]' in mode line around the parentheses.
• Screen Garbled: Garbage on the screen.
• Text Garbled: Garbage in the text.
• Memory Full: How to cope when you run out of memory.
• After a Crash: Recovering editing in an Emacs session that crashed.
• Emergency Escape: Emergency escape--- What to do if Emacs stops responding.
• Total Frustration: When you are at your wits' end.

59.1 If <DEL> Fails to Delete

Every keyboard has a large key, usually labelled <Backspace>, which is ordinarily used to erase the last character that you typed. We call this key the usual erasure key. In Emacs, it 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. If the usual erasure key deletes forwards instead of backwards, that is probably what happened—Emacs ought to be treating the <Backspace> key as <DEL>, but it isn't.

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-only terminal, if you find the usual erasure key 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-only terminal, if you want to ask for help when <BS> is treated as <DEL>, use <F1>; C-? may also work, if it sends character code 127.

To fix the problem automatically for every Emacs session, you can put one of the following lines into your .emacs file (see Init File). For the first case above, where <Backspace> deletes forwards instead of backwards, use this line to make <Backspace> act as <DEL> (resulting in behavior compatible with Emacs 20 and previous versions):

     (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.

59.2 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. This is called getting back to top level. See Recursive Edit.

59.3 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 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. To investigate the possibility that you have this sort of problem, try Emacs on another terminal made by a different manufacturer. If problems happen frequently on one kind of terminal but not another kind, it is likely to be a bad terminfo entry, though it could also be due to a bug in Emacs that appears for terminals that have or that lack specific features.

59.4 Garbage in the Text

If C-l shows that the text is wrong, first type C-h l to see what commands you typed to produce the observed results. Then try undoing the changes step by step using C-x u, 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. See Narrowing.

59.5 Running out of Memory

If you get the error message ‘Virtual memory exceeded’, save your modified buffers with C-x s. 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.

59.6 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.

59.7 Emergency Escape

On text-only 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 asks two questions before going back to what it had been doing:

     Auto-save? (y or n)
     Abort (and dump core)? (y or n)

Answer each one 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.

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 system call hangs or when Emacs is stuck in a tight loop in C code.

59.8 Help for Total Frustration

If using Emacs (or something else) becomes terribly frustrating and none of the techniques described above solve the problem, Emacs can still help you.

First, if the Emacs you are using is not responding to commands, type C-g C-g to get out of it and then start a new one.

Second, type M-x doctor <RET>.

The Emacs psychotherapist will help you feel better. Each time you say something to the psychotherapist, you must end it by typing <RET> <RET>. This indicates you are finished typing.

60 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. The following sections will help you to construct an effective bug report.

• Known Problems: How to read about known problems and bugs.
• Criteria: Have you really found a bug?
• Understanding Bug Reporting: How to report a bug effectively.
• Checklist: Steps to follow for a good bug report.
• Sending Patches: How to send a patch for GNU Emacs.

60.1 Reading Existing Bug Reports and Known Problems

Before reporting a bug, if at all possible please check to see if it is already known about. 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 in the Emacs distribution; 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. Often, there are suggestions for workarounds and solutions.
• Some additional user-level problems can be found in Bugs and problems.
• The ‘bug-gnu-emacs’ mailing list (also available as the newsgroup ‘gnu.emacs.bug’). This is where you will find most Emacs bug reports. You can read the list archives at http://lists.gnu.org/mailman/listinfo/bug-gnu-emacs. If you like, you can also subscribe to the list. Be aware that the sole purpose of this list is to provide the Emacs maintainers with information about bugs and feature requests. Reports may contain fairly large amounts of data; spectators should not complain about this.
• The bug tracker at http://debbugs.gnu.org. From early 2008, reports from the ‘bug-gnu-emacs’ list have been sent here. The tracker contains the same information as the mailing list, just in a different format. You may prefer to browse and read reports using the tracker.
• 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 http://lists.gnu.org/archive/html/emacs-pretest-bug/. From late 2007 to mid 2008, the address was an alias for the ‘emacs-devel’ mailing list. From mid 2008 onwards, it has been an alias for ‘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.

60.2 When Is There a Bug

If Emacs accesses an invalid memory location (“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 Emacs updates the display in a way that does not correspond to what is in the buffer, then it is certainly a bug. If a command seems to do the wrong thing but the problem corrects itself if you type C-l, it is a case of incorrect display updating.

Taking forever to complete a command can be a bug, but you must make certain that it was 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, or don't know for certain how the command is supposed to work, then it might actually be working right. Rather than jumping to conclusions, show the problem to someone who knows for certain.

Finally, 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 on-line documentation string of a function or variable disagrees with the manual, one of them must be wrong; that is a bug.

60.3 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.

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 will be useless; meanwhile, lacking the facts, we will have no real information about the bug.

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 best way to report the bug is with a sentence like the preceding one, because it gives all the facts.

A bad way would be to 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 is just as likely to 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 in the world that we could guess that we should try visiting a file with a ‘z’ in its name.

Alternatively, the problem might be due to the fact that the file starts with exactly 25 spaces. For this reason, you should make sure that you inform us of the exact contents of any file that is needed to reproduce the bug. What if the problem only occurs when you have typed the C-x C-a command previously? This is why we ask you to give the exact sequence of characters you typed since starting the Emacs session.

You should not even say “visit a file” instead of C-x C-f unless you know that it makes no difference which visiting command is used. 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.

So please don't guess any explanations when you report a bug. If you want to actually debug the problem, and report explanations that are more than guesses, that is useful—but please include the facts as well.

60.4 Checklist for Bug Reports

Before reporting a bug, first try to see if the problem has already been reported (see 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@gnu.org. (If you want to suggest an improvement or new feature, use the same address.) If you cannot send mail from inside Emacs, you can copy the text of your report to your normal mail client and send it to that address. Or you can simply send an email to that address describing the problem.

Your report will be sent to the ‘bug-gnu-emacs’ mailing list, and stored in the tracker at http://debbugs.gnu.org. Please try to 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 appears.

You do not need to know how the http://debbugs.gnu.org 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 by ftp and say where.

To enable maintainers to investigate a bug, your report should include all these things:

• 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.
• The operands given to the configure command when Emacs was installed (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 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.
• 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 .emacs customizations.

  One way to record the input to Emacs precisely is to write a dribble file. To start the file, execute the Lisp expression

            (open-dribble-file "~/dribble")
  

  using M-: or from the ‘*scratch*’ buffer just after starting Emacs. From then on, Emacs copies all your input to the specified dribble file until the Emacs process is killed.

• For possible display bugs, 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 execute the Lisp expression

            (open-termscript "~/termscript")
  

  using M-: or from the ‘*scratch*’ buffer just after starting Emacs. From then on, Emacs copies all terminal output to the specified termscript file as well, until the Emacs process is killed. If the problem happens when Emacs starts up, put this expression into your .emacs 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.

• If non-ASCII text or internationalization is relevant, the locale that was current when you started Emacs. 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
  

  Alternatively, use the locale command, if your system has it, to display your locale settings.

  You can use the M-! command to execute these commands from Emacs, and then copy the output from the ‘*Messages*’ buffer into the bug report. Alternatively, M-x getenv <RET> LC_ALL <RET> will display the value of LC_ALL in the echo area, and you can copy its output from the ‘*Messages*’ buffer.

• 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.

• 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 online 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.

  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. See The Lisp Debugger, 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.

• Check whether any programs you have loaded into the Lisp world, including your .emacs 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 .emacs 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.

• 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 do ‘gdb emacs’. It is important for the directory src to be current so that GDB will read the .gdbinit file in this directory.

  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 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 short listing 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.

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 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.

60.5 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.

• Send an explanation with your changes of what problem they fix or what improvement they 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 item in the http://debbugs.gnu.org tracker. Explain why your change fixes the bug.
• Always include a proper bug report for the problem you think you have fixed. 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.
• Include 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. 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 ignore your changes entirely.

  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.

• Use ‘diff -c’ to make your diffs. Diffs without context are hard to install reliably. More than that, they are hard to study; we must always study a patch to decide whether we want to install it. Unidiff format is better than contextless diffs, but not as easy to read as ‘-c’ format.

  If you have GNU diff, use ‘diff -c -F'^[_a-zA-Z0-9$]+ *('’ when making diffs of C code. This shows the name of the function that each change occurs in.

• 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 change 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 change log is to show people where to find what was changed. So you need to be specific about what functions you changed; in large functions, it's often helpful to indicate where within the function the change was.

  On the other hand, once you have shown people where to find the change, you need not explain its purpose in the change log. Thus, if you add a new function, all you need to say about it is that it is new. If you feel that the purpose needs explaining, it probably does—but put the explanation in comments in the code. It will be more useful there.

  Please read the ChangeLog files in the src and lisp directories to see what sorts of information to put in, and to learn the style that we use. See Change Log.

• 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 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 configuration files for a particular machine. These are safe because they can't create new bugs on other machines.

  Please help us keep up with the workload by designing the patch in a form that is clearly safe to install.

61 Contributing to Emacs Development

If you would like to help pretest Emacs releases to assure they work well, or if you would like to work on improving Emacs, please contact the maintainers at emacs-devel@gnu.org. A pretester should be prepared to investigate bugs as well as report them. If you'd like to work on improving Emacs, please ask for suggested projects or suggest your own ideas.

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@gnu.org before you start; it might be possible to suggest ways to make your extension fit in better with the rest of Emacs.

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 http://savannah.gnu.org/projects/emacs/ for details.

For more information on how to contribute, see the etc/CONTRIBUTE file in the Emacs distribution.

62 How To Get Help with GNU Emacs

If you need help installing, using or changing GNU Emacs, there are two ways to find it:

• Send a message to the mailing list help-gnu-emacs@gnu.org, or post your request on newsgroup gnu.emacs.help. (This mailing list and newsgroup interconnect, so it does not matter which one you use.)
• Look in the service directory for someone who might help you for a fee. The service directory is found in the file named etc/SERVICE in the Emacs distribution.

Appendix A GNU GENERAL PUBLIC LICENSE

     Copyright © 2007 Free Software Foundation, Inc. http://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

0. 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.

1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

    You may not impose any further restrictions on the exercise of the rights granted or affirmed under this License. For example, you may not impose a license fee, royalty, or other charge for exercise of rights granted under this License, and you may not initiate litigation (including a cross-claim or counterclaim in a lawsuit) alleging that any patent claim is infringed by making, using, selling, offering for sale, or importing the Program or any portion of it.

11. 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.

12. 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.

13. 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.

14. 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.

15. 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.

16. 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.

17. 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 http://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 http://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 http://www.gnu.org/philosophy/why-not-lgpl.html.

Appendix B GNU Free Documentation License

     Copyright © 2000, 2001, 2002, 2007, 2008, 2009 Free Software Foundation, Inc.
     http://fsf.org/
     
     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.

0. 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.

1. 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.

2. 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.

3. 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.

4. 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.

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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 Emacs 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 takes an argument, you can use either a space or an equal sign to separate the option name and the argument. Thus, 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.)

• Action Arguments: Arguments to visit files, load libraries, and call functions.
• Initial Options: Arguments that take effect while starting Emacs.
• Command Example: Examples of using command line arguments.
• Resume Arguments: Specifying arguments when you resume a running Emacs.
• Environment: Environment variables that Emacs uses.
• Display X: Changing the default display and using remote login.
• Font X: Choosing a font for text, under X.
• Colors: Choosing display colors.
• Window Size X: Start-up window size, under X.
• Borders X: Internal and external borders, under X.
• Title X: Specifying the initial frame's title.
• Icons X: Choosing what sort of icon to use, under X.
• Misc X: Other display options.

C.1 Action Arguments

Here is a table of action arguments:

‘file’

‘--file=file’

‘--find-file=file’

‘--visit=file’

Visit file using find-file. See Visiting.

When Emacs starts up, it displays the startup buffer in one window, and the buffer visiting file in another window (see 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 file is visited in a single window if one file argument was supplied; with two file arguments, Emacs displays the files in two different windows; with more than two file argument, Emacs displays the last file specified in one window, plus a Buffer Menu in a different window (see Several Buffers). To inhibit using the Buffer Menu for this, change the variable inhibit-startup-buffer-menu to t.

‘+linenum file’

Visit file using find-file, then go to line number linenum in it.

‘+linenum:columnnum file’

Visit file using find-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. See Lisp Libraries. If file is not an absolute file name, the library can be found either in the current directory, or in the Emacs library search path as specified with EMACSLOADPATH (see General Variables).

Warning: If previous command-line arguments have visited files, the current directory is the directory of the last file visited.

‘-L dir’

‘--directory=dir’

Add directory dir to the variable load-path.

‘-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 ‘*scratch*’ buffer (see Lisp Interaction). This is like what M-x insert-file does (see Misc File Ops).

‘--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.

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. The normal actions of Emacs are to first load site-start.el if it exists, then your own initialization file ~/.emacs if it exists, and finally default.el if it exists. See Init File. Certain options prevent loading of some of these files or substitute other files for them.

‘-t device’

‘--terminal=device’

Use device as the device for terminal input and output. ‘--terminal’ 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 Display X, 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 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 it has been explicitly requested.

‘--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 ‘#!’ as a comment delimiter.

‘-q’

‘--no-init-file’

Do not load your Emacs initialization file, and do not load the file default.el either (see Init File). Regardless of this switch, site-start.el is still loaded. When Emacs is invoked like this, the Customize facility does not allow options to be saved (see Easy Customization).

‘--no-site-file’

Do not load site-start.el. The options ‘-q’, ‘-u’ and ‘--batch’ have no effect on the loading of this file—this option and ‘-Q’ are the only options that block it.

‘--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).

‘-Q’

‘--quick’

Start emacs with minimum customizations, similar to using ‘-q’, ‘--no-site-file’, and ‘--no-splash’ together. This also stops Emacs from processing X resources by setting inhibit-x-resources to t (see Resources).

‘-daemon’

‘--daemon’

Start Emacs as a daemon—after Emacs starts up, it starts the Emacs server and disconnects from the terminal without opening any frames. You can then use the emacsclient command to connect to Emacs for editing. See Emacs Server, for information about using Emacs as a daemon.

‘-daemon=SERVER-NAME’

Start emacs in background as a daemon, and use SERVER-NAME as the server name.

‘--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.

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 Resuming Emacs with Arguments

You can specify action arguments for Emacs when you resume it after a suspension. To prepare for this, put the following code in your .emacs file (see Hooks):

     (add-hook 'suspend-hook 'resume-suspend-hook)
     (add-hook 'suspend-resume-hook 'resume-process-args)

As further preparation, you must execute the shell script emacs.csh (if you use csh as your shell) or emacs.bash (if you use bash as your shell). These scripts define an alias named edit, which will resume Emacs giving it new command line arguments such as files to visit. The scripts are found in the etc subdirectory of the Emacs distribution.

Only action arguments work properly when you resume Emacs. Initial arguments are not recognized—it's too late to execute them anyway.

Note that resuming Emacs (with or without arguments) must be done from within the shell that is the parent of the Emacs job. This is why edit is an alias rather than a program or a shell script. It is not possible to implement a resumption command that could be run from other subjobs of the shell; there is no way to define a command that could be made the value of EDITOR, for example. Therefore, this feature does not take the place of the Emacs Server feature (see Emacs Server).

The aliases use the Emacs Server feature if you appear to have a server Emacs running. However, they cannot determine this with complete accuracy. They may think that a server is still running when in actuality you have killed that Emacs, because the file /tmp/esrv... still exists. If this happens, find that file and delete it.

C.5 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 software) inherit the environment from Emacs, too.

Inside Emacs, the command M-x getenv gets the value of an environment variable. M-x setenv sets a variable in the Emacs environment. (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.

• General Variables: Environment variables that all versions of Emacs use.
• Misc Variables: Certain system-specific variables.
• MS-Windows Registry: An alternative to the environment on MS-Windows.

C.5.1 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 name.

EMACSDATA

Directory for the architecture-independent files that come with Emacs. This is used to initialize the Lisp variable data-directory.

EMACSDOC

Directory for the documentation string file, DOC-emacsversion. This is used to initialize the Lisp variable doc-directory.

EMACSLOADPATH

A colon-separated list of directories²⁷ to search for Emacs Lisp files—used to initialize load-path.

EMACSPATH

A colon-separated list of directories to search for executable files—used to initialize exec-path.

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 Headers).

ESHELL

Used for shell-mode to override the SHELL environment variable.

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 (~). 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.

INCPATH

A colon-separated list of directories. Used by the complete package to search for files.

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, if LANG is not already set in the environment when Emacs starts, Emacs sets it based on the system-wide default language, which you can set in the ‘Regional Settings’ Control Panel on some versions of MS-Windows.

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. (The default is ~/.mh_profile.)

NAME

Your real-world name.

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 in which executables reside. This is used to initialize the Emacs Lisp variable exec-path.

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 Headers.

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.

SMTPSERVER

The name of the outgoing mail server. Used by the SMTP library (see Top).

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. If the value of TERM indicates that Emacs runs in non-windowed mode from xterm or a similar terminal emulator, the background mode defaults to ‘light’, and Emacs will choose colors that are appropriate for a light background.

TERMCAP

The name of the termcap library file describing how to program the terminal specified by the TERM variable. This defaults to /etc/termcap.

TMPDIR

Used by the Emerge package as a prefix for temporary files.

TZ

This specifies the current time zone and possibly also daylight saving time information. 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 Backup Names).

C.5.2 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.

TEMP

TMP

On MS-DOS and MS-Windows, these specify the name of the directory for storing temporary files in.

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.

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.5.3 The MS-Windows System Registry

Under MS-Windows, the installation program addpm.exe adds values for emacs_dir, EMACSLOADPATH, EMACSDATA, EMACSPATH, EMACSDOC, SHELL and TERM to the HKEY_LOCAL_MACHINE section of the system registry, under /Software/GNU/Emacs. It does this because there is no standard place to set environment variables across different versions of Windows. Running addpm.exe is no longer strictly necessary in recent versions of Emacs, but if you are upgrading from an older version, running addpm.exe ensures that you do not have older registry entries from a previous installation, which may not be compatible with the latest version of Emacs.

When Emacs starts, as well as checking the environment, it also checks the System Registry for those variables and for HOME, LANG and PRELOAD_WINSOCK.

To determine the value of those variables, Emacs goes through the following procedure. First, the environment is checked. If the variable is not found there, Emacs looks for registry keys by that name 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, compiled-in defaults are used.

In addition to the environment variables above, you can also add many of the settings which on X belong in the .Xdefaults file (see X Resources) to the /Software/GNU/Emacs registry key. Settings you add to the HKEY_LOCAL_MACHINE section will affect all users of the machine. Settings you add to the HKEY_CURRENT_USER section will only affect you, and will override machine wide settings.

C.6 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. Occasionally you may need to specify the display yourself; for example, if you do a remote login and want to run a client program remotely, displaying on your local screen.

With Emacs, the main reason people change the default display is to let them log into another system, run Emacs on that system, but have the window displayed at their local terminal. You might need to log in to another system because the files you want to edit are there, or because the Emacs executable file you want to run is there.

The syntax of the DISPLAY environment variable is ‘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 rarely-used 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 direct use of the window system and GUI with the ‘-nw’ option. It tells Emacs to display using ordinary ASCII on its controlling terminal. This is also an initial option.

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.7 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 specification 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 other ways to specify the default font and font name formats.

C.8 Window Color Options

On a color display, you can specify which color to use for various parts of the Emacs display. To find out what colors are available on your system, type M-x list-colors-display, or press C-Mouse-2 and select ‘Display Colors’ from the pop-up menu. (A particular window system might support many more colors, but the list displayed by list-colors-display shows their portable subset that can be safely used on any display supported by Emacs.) If you do not specify colors, on windowed displays the default for the background is white and the default for all other colors is black. On a monochrome display, the foreground is black, the background is white, and the border is gray if the display supports that. On terminals, the background is usually black and the foreground is white.

Here is a list of the command-line options for specifying colors:

‘-fg color’

‘--foreground-color=color’

Specify the foreground color. color should be a standard color name, or a numeric specification of the color's red, green, and blue components as in ‘#4682B4’ or ‘RGB:46/82/B4’.

‘-bg color’

‘--background-color=color’

Specify the background color.

‘-bd color’

‘--border-color=color’

Specify the color of the border of the X window.

‘-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’

For a character terminal only, specify the mode of color support. This option is intended for overriding 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-only terminals as well as on graphical displays.

C.9 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 shall be the size of the screen. Normally no window manager decorations are shown.

‘-mm’

‘--maximized’

Specify that the Emacs frame shall be maximized. This normally means that the frame has window manager decorations.

‘-fh’

‘--fullheight’

Specify that the height shall be the height of the screen.

‘-fw’

‘--fullwidth’

Specify that the width shall 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 40 lines. 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 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 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 Resources); 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’ there may be some space around the frame anyway. That is because Emacs rounds the sizes so they are an even number of character heights and widths.

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.10 Internal and External Borders

An Emacs frame has an internal border and an external 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 external border is added by the window manager outside the frame; depending on the window manager you use, it may contain various boxes you can click on to move or iconify the window.

‘-ib width’

‘--internal-border=width’

Specify width as the width of the internal border (between the text and the main border), in pixels.

‘-bw width’

‘--border-width=width’

Specify width as the width of the main 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 external border (though the window manager may not pay attention to what you specify). The default width of the external border is 2.

C.11 Frame Titles

An Emacs frame may or may not have a specified title. The frame title, if specified, appears in window decorations and icons as the name of the frame. If an Emacs frame has no specified title, the default title has the form ‘invocation-name@machine’ (if there is only one frame) or the selected window's buffer name (if there is more than one frame).

You can specify a 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 Resources) also specifies the title for the initial Emacs frame.

C.12 Icons

‘-iconic’

‘--iconic’

Start Emacs in an iconified (“minimized”) state.

‘-nbi’

‘--no-bitmap-icon’

Do not use a picture of a gnu as 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 on the “taskbar”. 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.13 Other Display Options

‘-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, and tool tips, and turn off the blinking cursor. This can be useful for making a test case that simplifies debugging of display problems.

The ‘--xrm’ option (see 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. On MS-Windows, you can customize some of the same aspects using the system registry. See MS-Windows Registry.

When Emacs is built using an “X toolkit”, such as Lucid or LessTif, you need to use X resources to customize the appearance of the widgets, including the menu-bar, scroll-bar, and dialog boxes. This is because the libraries that implement these don't provide for customization through Emacs. GTK+ widgets use a separate system of “GTK resources”, which we will also describe.

• Resources: Using X resources with Emacs (in general).
• Table of Resources: Table of specific X resources that affect Emacs.
• Face Resources: X resources for customizing faces.
• Lucid Resources: X resources for Lucid menus.
• LessTif Resources: X resources for LessTif and Motif menus.
• GTK resources: Resources for GTK widgets.

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’.

(MS-Windows systems do not support X resource files; on Windows, Emacs looks for X resources in the Windows Registry, first under the key ‘HKEY_CURRENT_USER\SOFTWARE\GNU\Emacs’ and then under the key ‘HKEY_LOCAL_MACHINE\SOFTWARE\GNU\Emacs’. 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. 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.borderWidth: 2

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 ‘borderWidth’ resource that controls the width of the external border for graphical frames.

Resources are grouped into named classes. For instance, the ‘BorderWidth’ class contains both the ‘borderWidth’ resource (which we just described), as well as the ‘internalBorder’ resource, which controls the width of the internal border for graphical frames. Instead of using a resource name, you can use a class name to specify the same value for all resources in that class. Here's an example:

     emacs.BorderWidth: 2

If you specify a value for a class, it becomes the default for all resources in that class. You can specify values for individual resources as well; these override the class value, for those particular resources. The following example specifies 2 as the default width for all borders, but overrides this value with 4 for the external border:

     emacs.BorderWidth: 2
     emacs.borderWidth: 4

The order in which the lines appear in the file does not matter. One way to experiment with the effect of different resource settings is to use the editres program. See the editres man page for more details.

Emacs does not process X resources at all if you set the variable inhibit-x-resources to a non-nil value, or if you specify the ‘-Q’ (or ‘--quick’) command-line argument (see Initial Options). (The ‘-Q’ argument automatically sets inhibit-x-resources to t.)

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-values’

‘--xrm=resource-values’

This option specifies X resource values for the present Emacs job.

resource-values should have the same format that you would use inside a file of X resources. To include multiple resource specifications in resource-values, put a newline between them, just as you would in a file. You can also use ‘#include "filename"’ 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

This table lists the resource names that designate options for Emacs, not counting those for the appearance of the menu bar, each with the class that it belongs to:

background (class Background)

Background color name.

bitmapIcon (class BitmapIcon)

Use a bitmap icon (a picture of a gnu) if ‘on’, let the window manager choose an icon if ‘off’.

borderColor (class BorderColor)

Color name for the external border.

borderWidth (class BorderWidth)

Width in pixels of the external border.

cursorColor (class Foreground)

Color name for text cursor (point).

cursorBlink (class CursorBlink)

Specifies whether to make the cursor blink. The default is ‘on’. Use ‘off’ or ‘false’ to turn cursor blinking off.

font (class Font)

Font name for the default font. See Fonts. You can also specify a fontset name (see Fontsets).

fontBackend (class FontBackend)

The backend(s) to use for drawing fonts; if multiple backends are specified, they must be comma-delimited and given in order of precedence. On X, 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 can leave this resource unset, in which case Emacs tries using all font backends available on your graphical device.

foreground (class Foreground)

Color name for text.

geometry (class Geometry)

Window size and position. Be careful not to specify this resource as ‘emacs*geometry’, because that may affect individual menus as well as the Emacs frame itself.

If this resource specifies a position, that position applies only to the initial Emacs frame (or, in the case of a resource for a specific frame name, only that frame). However, the size, if specified here, applies to all frames.

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 Window Size X).

Note that this applies to the initial frame only.

iconName (class Title)

Name to display in the icon.

internalBorder (class BorderWidth)

Width in pixels of the internal border.

lineSpacing (class LineSpacing)

Additional space (leading) between lines, in pixels.

menuBar (class MenuBar)

Give frames menu bars if ‘on’; don't have menu bars if ‘off’. See Lucid Resources, and LessTif Resources, for how to control the appearance of the menu bar if you have one.

minibuffer (class Minibuffer)

If ‘none’, don't 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.

pointerColor (class Foreground)

Color of the mouse cursor.

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.

scrollBarWidth (class ScrollBarWidth)

The scroll bar width in pixels, equivalent to the frame parameter scroll-bar-width.

selectionFont (class SelectionFont)

Font name for pop-up menu items, in non-toolkit versions of Emacs. (For toolkit versions, see Lucid Resources, also see LessTif 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)

Number of lines to reserve for the tool bar. A zero value suppresses the tool bar. For the Emacs tool bar (i.e. not Gtk+), if the value is non-zero and auto-resize-tool-bars is non-nil, the tool bar's size will be changed automatically so that all tool bar items are visible. If the value of auto-resize-tool-bars is grow-only, the tool bar expands automatically, but does not contract automatically. To contract the tool bar, you must redraw the frame by entering C-l. For the Gtk+ tool bar, any non-zero value means on and auto-resize-tool-bars has no effect.

useXIM (class UseXIM)

Turn off use of X input methods (XIM) if ‘false’ or ‘off’. This is only relevant if your Emacs is actually built with XIM support. It is potentially useful to turn off XIM for efficiency, especially slow X client/server links.

verticalScrollBars (class ScrollBars)

Give frames scroll bars if ‘on’; don't have scroll bars if ‘off’.

visualClass (class VisualClass)

Specify the “visual” that X should use. This tells X how to handle colors.

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. Most terminals only allow a few “visuals,” and the ‘dpyinfo’ program outputs information saying which ones.

D.3 X Resources for Faces

You can use resources to customize the appearance of particular faces (see Faces):

face.attributeForeground

Foreground color for face face.

face.attributeBackground

Background color for face face.

face.attributeUnderline

Underline flag for face face. Use ‘on’ or ‘true’ for yes.

face.attributeStrikeThrough

face.attributeOverline

face.attributeBox

face.attributeInverse

Likewise, for other boolean font attributes.

face.attributeStipple

The name of a pixmap data file to use for the stipple pattern, or false to not use stipple for the face face.

face.attributeBackgroundPixmap

The background pixmap for the face face. Should be a name of a pixmap file or false.

face.attributeFont

Font name (full XFD name or valid X abbreviation) for face face. Instead of this, you can specify the font through separate attributes.

Instead of using attributeFont to specify a font name, you can select a font through these separate attributes:

face.attributeFamily

Font family for face face.

face.attributeHeight

Height of the font to use for face face: either an integer specifying the height in units of 1/10pt, or a floating point number that specifies a scale factor to scale the underlying face's default font, or a function to be called with the default height which will return a new height.

face.attributeWidth

face.attributeWeight

face.attributeSlant

Each of these resources corresponds to a like-named font attribute, and you write the resource value the same as the symbol you would use for the font attribute value.

face.attributeBold

Bold flag for face face—instead of attributeWeight. Use ‘on’ or ‘true’ for yes.

face.attributeItalic

Italic flag for face face—instead of attributeSlant.

D.4 Lucid Menu X Resources

If the Emacs installed at your site was built to use the X toolkit with the Lucid menu widgets, then the menu bar is a separate widget and has its own resources. The resource names contain ‘pane.menubar’ (following, as always, the name of the Emacs invocation, or ‘Emacs’, which stands for all Emacs invocations). Specify them like this:

     Emacs.pane.menubar.resource:  value

For example, to specify the font ‘8x16’ for the menu-bar items, write this:

     Emacs.pane.menubar.font:  8x16

Resources for non-menubar toolkit pop-up menus have ‘menu*’ instead of ‘pane.menubar’. For example, to specify the font ‘8x16’ for the pop-up menu items, write this:

     Emacs.menu*.font:  8x16

For dialog boxes, use ‘dialog*’:

     Emacs.dialog*.font:  8x16

The Lucid menus can display multilingual text in your locale. For more information about fontsets see the man page for XCreateFontSet. To enable multilingual menu text you specify a fontSet resource instead of the font resource. If both font and fontSet resources are specified, the fontSet resource is used.

Thus, to specify ‘-*-helvetica-medium-r-*--*-120-*-*-*-*-*-*,*’ for both the popup and menu bar menus, write this:

     Emacs*menu*fontSet:  -*-helvetica-medium-r-*--*-120-*-*-*-*-*-*,*

The ‘*menu*’ as a wildcard matches ‘pane.menubar’ and ‘menu...’.

Experience shows that on some systems you may need to add ‘shell.’ before the ‘pane.menubar’ or ‘menu*’. On some other systems, you must not add ‘shell.’. The generic wildcard approach should work on both kinds of systems.

Here is a list of the specific resources for menu bars and pop-up menus:

font

Font for menu item text.

fontSet

Fontset for menu item text.

foreground

Color of the foreground.

background

Color of the background.

buttonForeground

In the menu bar, the color of the foreground for a selected item.

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 line around the widget. Default is 1.

Also determines the thickness of shadow lines around other objects, for instance 3D buttons and arrows. If you have the impression that the arrows in the menus do not stand out clearly enough or that the difference between “in” and “out” buttons is difficult to see, set this to 2. If you have no problems with visibility, the default probably looks better. The background color may also have some effect on the contrast.

margin

The margin of the menu bar, in characters. Default is 1.

D.5 LessTif Menu X Resources

If the Emacs installed at your site was built to use the X toolkit with the LessTif or Motif widgets, then the menu bar, the dialog boxes, the pop-up menus, and the file-selection box are separate widgets and have their own resources.

The resource names for the menu bar contain ‘pane.menubar’ (following, as always, the name of the Emacs invocation, or ‘Emacs’, which stands for all Emacs invocations). Specify them like this:

     Emacs.pane.menubar.subwidget.resource:  value

Each individual string in the menu bar is a subwidget; the subwidget's name is the same as the menu item string. For example, the word ‘File’ in the menu bar is part of a subwidget named ‘emacs.pane.menubar.File’. Most likely, 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 the menu-bar items, write this:

     Emacs.pane.menubar.*.fontList:  8x16

This also specifies the resource value for submenus.

Each item in a submenu in the menu bar 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.)

It's impossible to specify a resource for all the menu-bar items without also specifying it for the submenus as well. So if you want the submenu items to look different from the menu bar itself, you must ask for that in two steps. First, specify the resource for all of them; then, override the value for submenus alone. Here is an example:

     Emacs.pane.menubar.*.fontList:  8x16
     Emacs.pane.menubar.popup_*.fontList: 8x16

For LessTif pop-up menus, use ‘menu*’ instead of ‘pane.menubar’. For example, to specify the font ‘8x16’ for the pop-up menu items, write this:

     Emacs.menu*.fontList:  8x16

For LessTif dialog boxes, use ‘dialog’ instead of ‘menu’:

     Emacs.dialog*.fontList: 8x16
     Emacs.dialog*.foreground: hotpink

To specify resources for the LessTif file-selection box, use ‘fsb*’, like this:

     Emacs.fsb*.fontList: 8x16

Here is a list of the specific 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.6 GTK resources

If Emacs was built to use the GTK widget set, then the menu bar, tool bar, scroll bar and the dialogs are customized with the standard GTK customization file, ~/.gtkrc-2.0, or with the Emacs specific file ~/.emacs.d/gtkrc. We recommend that you use ~/.emacs.d/gtkrc for customizations, since ~/.gtkrc-2.0 seems to be ignored when running GConf with GNOME. These files apply only to GTK widget features. To customize Emacs font, background, faces, etc., use the normal X resources (see Resources).

Some GTK themes override these mechanisms, which means that using these mechanisms will not work to customize them.

In these files you first define a style and say what it means; then you specify to apply the style to various widget types (see GTK widget names). Here is an example of how to change the font for Emacs menus:

     # Define the style ‘menufont’.
     style "menufont"
     {
       font_name = "helvetica bold 14"  # This is a Pango font name
     }
     
     # Specify that widget type ‘*emacs-menuitem*’ uses ‘menufont’.
     widget "*emacs-menuitem*" style "menufont"

Here is a more elaborate example, showing how to change the parts of the scroll bar:

     style "scroll"
     {
       fg[NORMAL] = "red"     # The arrow color.
       bg[NORMAL] = "yellow"  # The thumb and background around the arrow.
       bg[ACTIVE] = "blue"    # The trough color.
       bg[PRELIGHT] = "white" # The thumb color when the mouse is over it.
     }
     
     widget "*verticalScrollBar*" style "scroll"

There are also parameters that affect GTK as a whole. For example, the property gtk-font-name sets the default font for GTK. You must use Pango font names (see GTK styles). A GTK resources file that just sets a default font looks like this:

     gtk-font-name = "courier 12"

The GTK resources file is fully described in the GTK API document. This can be found in prefix/share/gtk-doc/html/gtk/gtk-resource-files.html, where prefix is the directory in which the GTK libraries were installed (usually /usr or /usr/local). You can also find the document online, at http://developer.gnome.org/doc/API/2.0/gtk/gtk-Resource-Files.html.

• GTK widget names: How widgets in GTK are named in general.
• GTK Names in Emacs: GTK widget names in Emacs.
• GTK styles: What can be customized in a GTK widget.

D.6.1 GTK widget names

A GTK widget is specified by its widget class and widget name. The widget class is the type of the widget: for example, GtkMenuBar. The widget name is the name given to a specific widget. 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.

When assigning a style to a widget, you can use the absolute class name or the absolute widget name.

There are two commands to specify changes for widgets:

widget_class

specifies a style for widgets based on the absolute class name.

widget

specifies a style for widgets based on the absolute class name, or just the class.

You must specify the class and the style in double-quotes, and put these commands at the top level in the GTK customization file, like this:

     style "menufont"
     {
       font_name = "helvetica bold 14"
     }
     
     widget "top.box.menubar" style "menufont"
     widget_class "GtkWindow.GtkVBox.GtkMenuBar" style "menufont"

Matching of absolute names uses shell wildcard syntax: ‘*’ matches zero or more characters and ‘?’ matches one character. This example assigns base_style to all widgets:

     widget "*" style "base_style"

Given the absolute class name GtkWindow.GtkVBox.GtkMenuBar and the corresponding absolute widget name top.box.menubar, all these examples specify my_style for the menu bar:

     widget_class "GtkWindow.GtkVBox.GtkMenuBar" style "my_style"
     widget_class "GtkWindow.*.GtkMenuBar" style "my_style"
     widget_class "*GtkMenuBar" style "my_style"
     widget "top.box.menubar" style "my_style"
     widget "*box*menubar" style "my_style"
     widget "*menubar" style "my_style"
     widget "*menu*" style "my_style"

D.6.2 GTK Widget Names in Emacs

In Emacs, the top level widget for a frame is a GtkWindow that contains a GtkVBox. The GtkVBox contains the GtkMenuBar and a GtkFixed widget. The vertical scroll bars, GtkVScrollbar, are contained in the GtkFixed widget. The text you write in Emacs is drawn in the GtkFixed widget.

Dialogs in Emacs are GtkDialog widgets. The file dialog is a GtkFileSelection widget.

To set a style for the menu bar using the absolute class name, use:

     widget_class "GtkWindow.GtkVBox.GtkMenuBar" style "my_style"

For the scroll bar, the absolute class name is:

     widget_class
       "GtkWindow.GtkVBox.GtkFixed.GtkVScrollbar"
          style "my_style"

The names for the emacs widgets, and their classes, are:

emacs-filedialog	GtkFileSelection
emacs-dialog	GtkDialog
Emacs	GtkWindow
pane	GtkVHbox
emacs	GtkFixed
verticalScrollBar	GtkVScrollbar
emacs-toolbar	GtkToolbar
menubar	GtkMenuBar
emacs-menuitem	anything in menus

Thus, for Emacs you can write the two examples above as:

     widget "Emacs.pane.menubar" style "my_style"
     widget "Emacs.pane.emacs.verticalScrollBar" style "my_style"

GTK absolute names are quite strange when it comes to menus and dialogs. The names do not start with ‘Emacs’, as they are free-standing windows and not contained (in the GTK sense) by the Emacs GtkWindow. To customize the dialogs and menus, 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 specify a customization in ~/.emacs.d/gtkrc, then it automatically applies only to Emacs, since other programs don't read that file. For example, the drop down menu in the file dialog can not be customized by any absolute widget name, only by an absolute class name. This is because the widgets in the drop down menu do not have names and the menu is not contained in the Emacs GtkWindow. To have all menus in Emacs look the same, use this in ~/.emacs.d/gtkrc:

     widget_class "*Menu*" style "my_menu_style"

D.6.3 GTK styles

In a GTK style you specify the appearance widgets shall have. You can specify foreground and background color, background pixmap and font. The edit widget (where you edit the text) in Emacs is a GTK widget, but trying to specify a style for the edit widget will have no effect. This is so that Emacs compiled for GTK is compatible with Emacs compiled for other X toolkits. The settings for foreground, background and font for the edit widget is taken from the X resources; see Resources. Here is an example of two style declarations, ‘default’ and ‘ruler’:

     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 pressed but not released yet (“armed”) 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 can not 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 Pango font name, for example ‘Sans Italic 10’, ‘Helvetica Bold 12’, ‘Courier 14’, ‘Times 18’. See below for exact syntax. The names are case insensitive.

There are three ways to specify a color: by name, in hexadecimal form, and with an RGB triplet.

A color name is written within double quotes, for example "red".

Hexadecimal form is the same as in X: #rrrrggggbbbb, where all three color specs must have the same number of hex digits (1, 2, 3 or 4).

An RGB triplet looks like { r, g, b }, where r, g and b are either integers in the range 0-65535 or floats in the range 0.0-1.0.

Pango font names have the form “family-list style-options size.” family-list is a comma separated list of font families optionally terminated by a comma. This way you can specify several families and the first one found will be used. family corresponds to the second part in an X font name, for example in

     -adobe-times-medium-r-normal--12-120-75-75-p-64-iso10646-1

the family name is ‘times’.

style-options is a whitespace separated list of words where each word is a style, variant, weight, or stretch. The default value for all of these is normal.

A `style' corresponds to the fourth part of an X font name. In X font names it is the character ‘r’, ‘i’ or ‘o’; in Pango font names the corresponding values are normal, italic, or oblique.

A `variant' is either normal or small-caps. Small caps is a font with the lower case characters replaced by smaller variants of the capital characters.

Weight describes the “boldness” of a font. It corresponds to the third part of an X font name. It is one of ultra-light, light, normal, bold, ultra-bold, or heavy.

Stretch gives the width of the font relative to other designs within a family. It corresponds to the fifth part of an X font name. It is one of ultra-condensed, extra-condensed, condensed, semi-condensed, normal, semi-expanded, expanded, extra-expanded, or ultra-expanded.

size is a decimal number that describes the font size in points.

Appendix E Emacs 22 Antinews

For those users who live backwards in time, here is information about downgrading to Emacs version 22.3. We hope you will enjoy the greater simplicity that results from the absence of many Emacs 23.3 features.

• We have switched to a character representation specially designed for Emacs. Rather than forcing all the widely used scripts into artificial alignment, as Unicode does, Emacs treats them all equally, giving each one a place in the space of character codes. We have eliminated the confusing practice, in Emacs 23, whereby one character can belong to multiple character sets. Now each script has its own variant, and they all are different as far as Emacs is concerned. For example, there's a Latin-1 c-cedilla character, and there's a Latin-2 c-cedilla; searching a buffer for the Latin-1 variant only finds that variant, but not the others.
• Emacs now uses its own special internal encoding for non-ASCII characters, known as ‘emacs-mule’. This was imperative to support several different variants of the same character, each one belonging to its own script: ‘emacs-mule’ marks each character with its script, to better discern them from one another.
• For simplicity, the functions encode-coding-region and decode-coding-region no longer accept an argument saying where to store the result of their conversions. The result always replaces the original, so there's no need to look for it elsewhere.
• Emacs no longer performs font anti-aliasing. If your fonts look ugly, try choosing a larger font and increasing the screen resolution. Admittedly, this becomes difficult as you go further back in time, since available screen resolutions will decrease.
• The Fontconfig font library is no longer supported. To specify a font, you must use an XLFD (X Logical Font Descriptor). The other ways of specifying fonts—so-called “Fontconfig” and “GTK” font names—are redundant, so they have been removed.
• Transient Mark mode is now disabled by default. Furthermore, some commands that operate specifically on the region when it is active and Transient Mark mode is enabled (such as fill-paragraph ispell-word, and indent-for-tab-command), no longer do so.
• Holding <shift> while typing a motion command no longer creates a temporarily active region, since that's inconsistent with how Emacs normally handles keybindings. The variable shift-select-mode has been deleted. You can, however, still create temporarily active regions by dragging the mouse.
• The line motion commands, C-n and C-p, now move by logical text lines, not screen lines. Even if a long text line is continued over multiple screen lines, C-n and C-p treat it as a single line, because that's ultimately what it is.
• Visual Line mode, which provides “word wrap” functionality, has been removed. You can still use Long Lines mode to gain an approximation of word wrapping, though this has some drawbacks—for instance, syntax highlighting often doesn't work well on wrapped lines.
• C-l now runs recenter instead of recenter-top-bottom. This always sets the current line at the center of the window, instead of cycling through the center, top, and bottom of the window on successive invocations. This lets you type C-l C-l C-l C-l to be absolutely sure that you have recentered the line.
• The way Emacs generates possible minibuffer completions is now much simpler to understand. It matches alternatives to the text before point, ignoring the text after point; it also does not attempt to perform partial completion if the first completion attempt fails.
• Typing M-n at the start of the minibuffer history list no longer attempts to generate guesses of possible minibuffer input. It instead does the straightforward thing, by issuing the message ‘End of history; no default available’.
• Individual buffers can no longer display faces specially. The text scaling commands C-x C-+, C-x C--, and C-x C-0 have been removed, and so has the buffer face menu bound to S-down-mouse-1.
• VC no longer supports fileset-based operations on distributed version control systems (DVCSs) such as Arch, Bazaar, Subversion, Mercurial, and Git. For instance, multi-file commits will be performed by committing one file at a time. As you go further back in time, we will remove DVCS support entirely, so you should migrate your projects to CVS.
• Rmail now uses a special file format, Babyl format, specifically designed for storing and editing mail. When you visit a file in Rmail, or get new mail, Rmail converts it automatically to Babyl format.
• Emacs can no longer display frames on X windows and text terminals (ttys) simultaneously. If you start Emacs as an X application, it can only create X frames; if you start Emacs on a tty, it can only use that tty. No more confusion about which type of frame emacsclient will use in any given Emacs session!
• Emacs can no longer be started as a daemon. You can be sure that if you don't see Emacs, then it's not running.
• Emacs has added support for many soon-to-be-non-obsolete platforms, including VMS, DECstation, SCO Unix, and systems lacking alloca. Support for Sun windows has been added.
• To keep up with decreasing computer memory capacity and disk space, many other functions and files have been eliminated in Emacs 22.3.

Appendix F Emacs and Mac OS / GNUstep

This section describes the peculiarities of using Emacs built with the GNUstep libraries on GNU/Linux or other operating systems, or on Mac OS X with native window system support. On Mac OS X, Emacs can be built either without window system support, with X11, or with the Cocoa interface; this section only applies to the Cocoa build. Emacs does not support earlier versions of Mac OS.

For various historical and technical reasons, Emacs uses the term ‘Nextstep’ internally, instead of “Cocoa” or “Mac OS X”; 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, the GNUstep support is alpha status (see GNUstep Support), but we hope to improve it in the future.

• Mac / GNUstep Basics: Basic Emacs usage under GNUstep or Mac OS.
• Mac / GNUstep Customization: Customizations under GNUstep or Mac OS.
• Mac / GNUstep Events: How window system events are handled.
• GNUstep Support: Details on status of GNUstep support.

F.1 Basic Emacs usage under Mac OS 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 keybindings using this modifier key that mimic other Mac / GNUstep applications (see Mac / GNUstep Events). You can change these bindings in the usual way (see Key Bindings).

The variable ns-right-alternate-modifier controls the behavior of the right <alt> and <option> keys. These keys behave like the left-hand keys if the value is left (the default). A value of control, meta, alt, super, or hyper makes them behave like the corresponding modifier keys; a value of none tells Emacs to ignore them.

The standard Mac / GNUstep font and color panels are accessible via Lisp commands. To use the color panel, drag from it to an Emacs frame to change the foreground color of the face at that position (if the <shift> key is held down, it changes the background color instead). To discard the settings, create a new frame and close the altered one.

<S-Mouse-1> (i.e., clicking the left mouse button while holding down the <Shift> key) 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 Temporary Face Changes). 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 Mac OS X 10.5 and later, using the /etc/paths files and the /etc/paths.d directory.

F.2 Mac / GNUstep Customization

Emacs can be customized in several ways in addition to the standard customization buffers and the Options menu.

F.2.1 Font and Color Panels

The Font Panel may be accessed with M-x ns-popup-font-panel. It will set the default font in the frame most recently used or clicked on.

You can bring up a color panel with M-x ns-popup-color-panel. and drag the color you want over the emacs face you want to change. Normal dragging will alter the foreground color. Shift dragging will alter the background color.

Useful in this context is the listing of all faces obtained by <M-x> list-faces-display.

F.2.2 Open files by dragging to an Emacs window

The default behaviour when a user drags files from another application into an Emacs frame is to insert the contents of all the dragged files into the current buffer. To remap the ns-drag-file event to open the dragged files in the current frame use the following line:

     (define-key global-map [ns-drag-file] 'ns-find-file)

F.3 Windowing System Events under Mac OS / GNUstep

Nextstep applications receive a number of special events which have no X equivalent. These are sent as specially defined “keys”, 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 <ns-open-file> 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 an existing 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.

You can bind <ns-pop-up-frames> and <ns-open-temp-file> to other Lisp functions. When the event is registered, the name of the file to open is stored in the variable ns-input-file.

<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-drag-file>

This event occurs when a user drags files from another application into an Emacs frame. The default behavior is to insert the contents of all the dragged files into the current buffer (ns-insert-files). The list of dragged files is stored in the variable ns-input-file.

<ns-drag-color>

This event occurs when a user drags a color from the color well (or some other source) into an Emacs frame. The default behavior is to alter the foreground color of the area the color was dragged onto (ns-set-foreground-at-mouse). If this event is issued with a <Shift> modifier, Emacs changes the background color instead (ns-set-background-at-mouse). The name of the dragged color is stored in the variable ns-input-color.

<ns-change-font>

This event occurs when the user selects a font in a Nextstep font panel (which can be opened with Cmd-t). The default behavior is to adjust the font of the selected frame (ns-respond-to-changefont). The name and size of the selected font are stored in the variables ns-input-font and ns-input-fontsize, respectively.

<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.

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><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 some issues to be addressed. Interested developers should contact emacs-devel@gnu.org.

Appendix G 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” (also known as “MS-DOG”). However, Emacs features that are relevant only to MS-DOS are described in a separate section (see MS-DOS).

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.

• Windows Startup: How to start Emacs on Windows.
• Text and Binary: Text files use CRLF to terminate lines.
• Windows Files: File-name conventions on Windows.
• ls in Lisp: Emulation of ls for Dired.
• Windows HOME: Where Emacs looks for your .emacs and where it starts up.
• Windows Keyboard: Windows-specific keyboard features.
• Windows Mouse: Windows-specific mouse features.
• Windows Processes: Running subprocesses on Windows.
• Windows Printing: How to specify the printer on MS-Windows.
• Windows Fonts: Specifying fonts on MS-Windows.
• Windows Misc: Miscellaneous Windows features.
• MS-DOS: Using Emacs on MS-DOS (otherwise known as MS-DOG).

G.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 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.
3. 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.
4. Via the Emacs client program, emacsclient.exe or emacsclientw.exe. This allows to invoke Emacs from other programs, and to reuse a running Emacs process for serving editing jobs required by other programs. See Emacs 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.

G.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 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 linefeed into newline when reading files, and converts newline into carriage-return 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 Position Info) 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 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 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 linefeed.

To visit a file and specify whether it uses DOS-style or Unix-style end-of-line, specify a coding system (see Text Coding). 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 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 dos2unix.

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 add-untranslated-filesystem. It takes one argument: the file system name, including a drive letter and optionally a directory. For example,

     (add-untranslated-filesystem "Z:")

designates drive Z as an untranslated file system, and

     (add-untranslated-filesystem "Z:\\foo")

designates directory \foo on drive Z as an untranslated file system.

Most often you would use add-untranslated-filesystem in your .emacs file, or in site-start.el so that all the users at your site get the benefit of it.

To countermand the effect of add-untranslated-filesystem, use the function remove-untranslated-filesystem. This function takes one argument, which should be a string just like the one that was used previously with 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 create new files with the Unix-style convention of using newline at the end of a line. See Coding Systems.

Some kinds of files should not be converted at all, because their contents are not really text. Therefore, Emacs on MS-Windows distinguishes certain files as binary files. (This distinction is not part of MS-Windows; it is made by Emacs only.) Binary files include executable programs, compressed archives, etc. Emacs uses the file name to decide whether to treat a file as binary: the variable file-name-buffer-file-type-alist defines the file-name patterns that indicate binary files. If a file name matches one of the patterns for binary files (those whose associations are of the type (pattern . t), Emacs reads and writes that file using the no-conversion coding system (see Coding Systems) which turns off all coding-system conversions, not only the EOL conversion. file-name-buffer-file-type-alist also includes file-name patterns for files which are known to be Windows-style text files with carriage-return linefeed EOL format, such as CONFIG.SYS; Emacs always writes those files with Windows-style EOLs.

If a file which belongs to an untranslated file system matches one of the file-name patterns in file-name-buffer-file-type-alist, the EOL conversion is determined by file-name-buffer-file-type-alist.

G.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.

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 XFAT volumes.

G.4 Emulation of ls on MS-Windows

Dired normally uses the external program ls (or its close work-alike) to produce the directory listing displayed in Dired buffers (see Dired). 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, -i, -G, -g, -R, -r, -S, -s, -t, -U, -u, 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.

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 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 variable ls-lisp-emulation controls the flavour 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 (links) on Windows NT/2K/XP/2K3 and to nil on Windows 9X. 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. Note that this option needs to be set before ls-lisp.el is loaded, which means that on MS-Windows and MS-DOS you will have to set the value from your .emacs file and then restart Emacs, since ls-lisp.el is preloaded.

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, 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.

G.5 HOME and Startup Directories on MS-Windows

The Windows equivalent of the HOME directory is the user-specific application data directory. The actual location depends on your Windows version and system configuration; typical values are C:\Documents and Settings\username\Application Data on Windows 2K/XP and later, and either C:\WINDOWS\Application Data or C:\WINDOWS\Profiles\username\Application Data on the older Windows 9X/ME systems.

HOME can also be set in the system registry, for details see MS-Windows Registry.

The home directory is where your init file .emacs is stored. When Emacs starts, it first checks whether the environment variable HOME is set. If it is, it looks for the init file in the directory pointed by HOME. If HOME is not defined, Emacs checks for an existing .emacs file in C:\, the root directory of drive C:²⁸. If there's no such file in C:\, Emacs next uses the Windows system calls to find out the exact location of your application data directory. If that system call fails, Emacs falls back to C:\.

Whatever the final place is, Emacs sets the value of the HOME environment variable to point to it, and it will use that location for other files and directories it normally creates in the user's home directory.

You can always find out where 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>.

Because MS-DOS does not allow file names with leading dots, and because older Windows systems made it hard to create files with such names, the Windows port of Emacs supports an alternative name _emacs as a fallback, if such a file exists in the home directory, whereas .emacs does not.

G.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, C-a, and W-<SPC>. You can redefine some of them with meanings more like the MS-Windows meanings by enabling CUA Mode (see CUA Bindings).

The <F10> key on Windows activates the menu bar in a way that makes it possible to use the menus without a mouse. In this mode, the arrow keys traverse the menus, <RET> selects a highlighted menu item, and <ESC> closes the menu.

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>, for its own use. These key combinations are intercepted by the system before Emacs can see them. 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. This functions registers a key sequence as a hot key, overriding the special meaning of that key sequence for Windows. (MS-Windows is told that the key sequence is a hot key only when one of the Emacs windows has focus, so that the special keys still have their usual meaning for other Windows applications.)

The argument to w32-register-hot-key must be a single key, with or without modifiers, in vector form that would be acceptable to define-key. The meta modifier is interpreted as the <ALT> key if w32-alt-is-meta is t (the default), and the hyper modifier is always interpreted as the Windows key (usually labeled with <start> and the Windows logo). If the function succeeds in registering the key sequence, it returns the hotkey ID, a number; otherwise it returns nil.

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.

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 they 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.

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' 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.²⁹

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.

G.7 Mouse Usage on MS-Windows

This section describes the Windows-specific variables related to 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.

G.8 Subprocesses on Windows 9X/ME and Windows NT/2K/XP

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 both Windows 9X/ME and Windows NT/2K/XP as long as you run only 32-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/2K/XP, 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 CTL-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, use that character to escape any quote characters that appear; otherwise chose a suitable escape character based on the type of the program.

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.

G.9 Printing and MS-Windows

Printing commands, such as lpr-buffer (see Printing) and ps-print-buffer (see PostScript) 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 Windows automatically determines your default printer and sets the variable printer-name to that printer's 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 which 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 specify where to find it.) 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 PostScript Variables), 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.)

G.10 Specifying Fonts on MS-Windows

Starting with Emacs 23, 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 23 supports a number of backends. Currently, the gdi and uniscribe font backends are supported on Windows. 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. Some languages requiring complex layout can only be properly supported by the uniscribe backend. By default, both backends are enabled if supported, with uniscribe taking priority over gdi.

Optional properties common to all font backends 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.

Options specific to GDI fonts:

script

Specifies a unicode subrange the font should support.

The following scripts are recognized on Windows: latin, greek, coptic, cyrillic, armenian, hebrew, arabic, syriac, nko, thaana, devanagari, bengali, gurmukhi, gujarati, oriya, tamil, telugu, kannada, malayam, sinhala, thai, lao, tibetan, myanmar, georgian, hangul, ethiopic, cherokee, canadian-aboriginal, ogham, runic, khmer, mongolian, symbol, braille, han, ideographic-description, cjk-misc, kana, bopomofo, kanbun, yi, byzantine-musical-symbol, musical-symbol, and mathematical.

antialias

Specifies the antialiasing to use for the font. 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.

G.11 Miscellaneous Windows-specific features

This section describes miscellaneous Windows-specific features.

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 by 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.

G.12 Emacs and MS-DOS

This section briefly describes the peculiarities of using Emacs on the MS-DOS “operating system” (also known as “MS-DOG”). Information about peculiarities common to MS-DOS and Microsoft's current operating systems Windows (also known as “Losedows”) is in Microsoft Windows.

If you build Emacs for MS-DOS, the binary will also run on Windows 3.X, Windows NT, Windows 9X/ME, Windows 2000/XP, or OS/2 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 and Binary, for information about Emacs' special handling of text files under MS-DOS (and Windows).

• Keyboard: Keyboard conventions on MS-DOS.
• Mouse: Mouse conventions on MS-DOS.
• Display: Fonts, frames and display size on MS-DOS.
• Files: File name conventions on MS-DOS.
• Printing: Printing specifics on MS-DOS.
• I18N: Support for internationalization on MS-DOS.
• Processes: Running subprocesses on MS-DOS.

G.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). 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.
     (define-key function-key-map [kp-enter] [?\C-j])

G.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 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 Mouse References) 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). 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.

G.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 Frame Parameters) and the list-faces-display command (see Faces) to see what colors and faces are available and what they look like.

See MS-DOS and MULE, 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-only terminals (see Frames). 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 mode4350 command switches the display to 43 or 50 lines, depending on your hardware; the 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.

G.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 Init 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 Backup Names) 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 directory 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.

G.12.5 Printing and MS-DOS

Printing commands, such as lpr-buffer (see Printing) and ps-print-buffer (see PostScript) 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 Windows Printing, 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 which 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 MS-DOS and MULE. 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.

G.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), 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 which 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 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.

G.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 Windows Processes.

Printing commands, such as lpr-buffer (see Printing) and ps-print-buffer (see PostScript), work in MS-DOS by sending the output to one of the printer ports. See MS-DOS Printing.

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 where other platforms use the system ls command. 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, http://www.gnu.org. For software tasks and other ways to contribute, see http://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 which 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.

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 `numeric argument.'

ASCII character

An ASCII character is either an ASCII control character or an ASCII printing character. See 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 printing characters include letters, digits, space, and these 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.

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 Save.

Autoloading

Emacs can automatically load Lisp libraries when a Lisp program requests a function from those libraries. This is called `autoloading.' See Lisp Libraries.

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 `quitting'). See Checklist.

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.

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 by Parens). Automatic balancing works by blinking or highlighting the delimiter that matches the one you just inserted (see Matching Parens).

Balanced Expressions

A balanced expression is a syntactically recognizable expression, such as a symbol, number, string constant, block, or parenthesized expression in C. See Balanced Expressions.

Balloon Help

See `tooltips.'

Base Buffer

A base buffer is a buffer whose text is shared by an indirect buffer (q.v.).

Bind

To bind a key sequence means to give it a binding (q.v.). See Rebinding.

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.

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.

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 Borders X). 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 can 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 Buffers.

Buffer Selection History

Emacs keeps a buffer selection history which records how recently each Emacs buffer has been selected. This is used for choosing a buffer to select. See 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 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 Mouse Buttons.

By Default

See `default.'

Byte Compilation

See `compilation.'

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, for the commands for case conversion.

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 User Input.

Character Set

Emacs supports a number of character sets, each of which represents a particular alphabet or script. See International.

Character Terminal

See `text-only 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 Mouse Buttons.

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 Clipboard.

Coding System

A coding system is an encoding for representing 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. 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 Commands.

Command History

See `minibuffer history.'

Command Name

A command name is the name of a Lisp symbol which is a command (see Commands). You can invoke any command by its name using M-x (see M-x).

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 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 Common Lisp.

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) and programs in C and other languages (see Compilation).

Complete Key

A complete key is a key sequence which 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 (q.v.) 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 (but see `Truncation') takes up more than one screen line when displayed. 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 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 Copying.

<CTRL>

The <CTRL> or “control” key is what you hold down in order to enter a control character (q.v.). See also `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 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 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 Face Customization), or by rebinding key sequences (see Keymaps).

Cut and Paste

See `killing' and `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 runs in the background and does not open a display. You can then connect to it with the emacsclient program. See Emacs 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 Minibuffer.

Default

A default is the value that is used for a certain purpose if and when you do not 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-Windows and MS-DOS, file names which 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 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 Misc File Ops.

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 Rmail Deletion.

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 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 Directories.

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.

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.

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 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 Bugs.

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 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.

EOL

See `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.

Expression

See `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 Faces.

File Locking

Emacs uses file locking to notice when two different users start to edit one file at the same time. See Interlocking.

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.

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. 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. For example, all comments (q.v.) might be colored red. See Font Lock.

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.

Formatted Text

Formatted text is text that displays with formatting information while you edit. Formatting information includes fonts, colors, and specified margins. See Formatted Text.

Formfeed Character

See `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. 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 Copying.

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 Fringes). Emacs displays the fringe using a special face (q.v.) called fringe. See fringe.

FSF

See `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 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 `tags table'). See Global Mark Ring.

Global Substitution

Global substitution means replacing each occurrence of one string by another string throughout a large amount of text. See Replace.

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 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 Mark). Incremental search also highlights matches (see Incremental Search). See also `font lock.'

Hardcopy

Hardcopy means printed output. Emacs has various commands for printing the contents of Emacs buffers. See Printing.

<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 any 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 graphics 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 User Input.

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 (q.v.) in which the mail is then stored permanently or until explicitly deleted. See Rmail Inbox.

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 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.

Interlocking

Interlocking is a feature for warning when you start to alter a file that someone else is already editing. See Interlocking.

Isearch

See `incremental search.'

Justification

Justification means adding extra spaces within lines of text in order to adjust the position of the text edges. See Format Justification.

Key Binding

See `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.) which invokes a command. What some programs call “assigning a keyboard shortcut,” Emacs calls “binding a key sequence.” See `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 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.

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.

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).

Line Wrapping

See `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 by Parens.

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 Locals.

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 M-x.

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 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 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 Mark.

Mark Ring

The mark ring is used to hold several recent previous locations of the mark, just 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 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 `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 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 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.

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.

MULE

MULE refers to the Emacs features for editing multilingual non-ASCII text using multibyte characters (q.v.). See International.

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 `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 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 the right. See Minor Modes.

Page

A page is a unit of text, delimited by formfeed characters (ASCII control-L, code 014) coming 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. See Syntax.

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 `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 Rmail File

Your primary Rmail file is the file named ‘RMAIL’ in your home directory. That's where Rmail stores your incoming mail, unless you specify a different file name. See Rmail.

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 kill commands set the primary selection and the yank command uses the primary selection when appropriate. See Killing.

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 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 Echo Area).

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.

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 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 indicates recursive editing levels with square brackets (‘[’ and ‘]’). See Recursive Edit.

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 `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 Regexps.

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 connected to the same network as your machine, and (obviously) that you have a supported method to gain access to those files. See Remote Files.

Repeat Count

See `numeric argument.'

Replacement

See `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. Emacs lets you revert a buffer by re-reading its file from disk. See Reverting.

Rmail File

An Rmail file is a file containing text in the format used by Rmail for storing mail. See Rmail.

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.

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 Search.

Search Path

A search path is a list of directory names, 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 Lisp Libraries.

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.

Selected Window

The selected window is the one your input currently operates on. See Basic Window.

Selecting a Buffer

Selecting a buffer means making it the current (q.v.) buffer. See Select Buffer.

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.

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 Interlocking.

<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.

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 Spelling.

String

A string is a kind of Lisp data object which 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 `global substitution.'

Syntax Highlighting

See `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.

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 User Input.

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.

<TAB>

<TAB> is the tab character. In Emacs it is typically used for indentation or completion.

Tags Table

A tags table is a file that serves as an index to the function definitions in one or more other files. See Tags.

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 Bugs.

Text

`Text' has two meanings (see Text):

• 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-only Terminal

A text-only 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-only 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 Info.

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.

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 Transpose).

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 also `continuation line.' See Truncation.

TTY

See `text-only 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.

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.

Whitespace

Whitespace is any run of consecutive formatting characters (space, tab, newline, and backspace).

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 Screen, for basic information on how Emacs uses the screen. See Windows, for commands to control the use of windows. Some other editors use the term “window” for what we call a `frame' (q.v.) 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 `abbrev.'

Word Search

Word search is searching for a sequence of words, considering the punctuation between them as insignificant. See Word Search.

WYSIWYG

WYSIWYG stands for “What you see is what you get.” Emacs generally provides WYSIWYG editing for files of characters; in Enriched mode (see Formatted Text), it provides WYSIWYG editing for files that include text formatting information.

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 we currently distribute; if you know of someone we have omitted, please report that as a manual bug. More comprehensive information is available in the ChangeLog files, summarized in the file etc/AUTHORS in the distribution.

• Per Abrahamsen wrote the customization facilities, as well as double.el, for typing accented characters not normally available from the keyboard; xt-mouse.el, which allows mouse commands through Xterm; gnus-cus.el, which implements customization commands for Gnus; gnus-cite.el, a citation-parsing facility for news articles); gnus-score.el, scoring for Gnus; cpp.el, which hides or highlights parts of C programs according to preprocessor conditionals; and the widget library files wid-browse.el, wid-edit.el, widget.el. He also co-wrote gnus-soup.el.
• Tomas Abrahamsson wrote artist.el, a package for producing ASCII art with a mouse or with keyboard keys.
• Jay K. Adams wrote jka-compr.el and jka-cmpr-hook.el, providing automatic decompression and recompression for compressed files.
• Michael Albinus wrote dbus.el, a package that implements the D-Bus message bus protocol; zeroconf.el, a mode for browsing Avahi services; and xesam.el, a Xesam-based search engine interface. He and Kai Großjohann wrote the Tramp package, which provides transparent remote file editing using rcp, ssh, ftp, and other network protocols. He and Daniel Pittman wrote tramp-cache.el.
• Ralf Angeli wrote scroll-lock.el, a minor mode which keeps the point vertically fixed by scrolling the window when moving up and down in the buffer.
• Joe Arceneaux wrote the original text property implementation, and implemented support for X11.
• Miles Bader wrote image-file.el, support code for visiting image files; minibuf-eldef.el, a minor mode that hides the minibuffer default value when appropriate; rfn-eshadow.el, shadowing of read-file-name input; mb-depth.el, display of minibuffer depth; button.el, the library that implements clickable buttons; face-remap.el, a package for changing the default face in individual buffers; and macroexp.el for macro-expansion.
• David Bakhash wrote strokes.el, a mode for controlling Emacs by moving the mouse in particular patterns.
• Eli Barzilay wrote calculator.el, a desktop calculator for Emacs.
• Steven L. Baur wrote footnote.el which lets you include footnotes in email messages; and gnus-audio.el and earcon.el, which provide sound effects for Gnus. He also wrote gnus-setup.el.
• Alexander L. Belikoff, Sergey Berezin, Sacha Chua, David Edmondson, Noah Friedman, Andreas Fuchs, Mario Lang, Ben Mesander, Lawrence Mitchell, Gergely Nagy, Michael Olson, Per Persson, Jorgen Schaefer, Alex Schroeder, and Tom Tromey wrote ERC, an advanced Internet Relay Chat client (for more information, see the file CREDITS in the ERC distribution).
• Scott Bender, Michael Brouwer, Christophe de Dinechin, Carl Edman, Christian Limpach and Adrian Robert developed and maintained the NeXTstep port of Emacs.
• Anna M. Bigatti wrote cal-html.el, which produces HTML calendars.
• Ray Blaak and Simon South wrote delphi.el, a mode for editing Delphi (Object Pascal) source code.
• Martin Blais, Stefan Merten, and David Goodger wrote rst.el, a mode for editing reStructuredText documents.
• Jim Blandy wrote Emacs 19's input system, brought its configuration and build process up to the GNU coding standards, and contributed to the frame support and multi-face support. Jim also wrote tvi970.el, terminal support for the TeleVideo 970 terminals; and co-wrote wyse50.el (q.v.).
• Per Bothner wrote term.el, a terminal emulator in an Emacs buffer.
• Terrence M. Brannon wrote landmark.el, a neural-network robot that learns landmarks.
• Frank Bresz wrote diff.el, a program to display diff output.
• Peter Breton implemented dirtrack.el, a library for tracking directory changes in shell buffers; filecache.el, which records which directories your files are in; locate.el, which interfaces to the locate command; find-lisp.el, an Emacs Lisp emulation of the find program; net-utils.el; and the “generic mode” feature.
• Emmanuel Briot wrote xml.el, an XML parser for Emacs; and ada-prj.el, editing of Ada mode project files, as well as co-authoring ada-mode.el and ada-xref.el.
• Kevin Broadey wrote foldout.el, providing folding extensions to Emacs's outline modes.
• David M. Brown wrote array.el, for editing arrays and other tabular data.
• W/lodek Bzyl and Ryszard Kubiak wrote ogonek.el, a package for changing the encoding of Polish characters.
• Bill Carpenter provided feedmail.el, a package for massaging outgoing mail messages and sending them through various popular mailers.
• Per Cederqvist and Inge Wallin wrote ewoc.el, an Emacs widget for manipulating object collections. Per Cederqvist, Inge Wallin, and Thomas Bellman wrote avl-tree.el, for balanced binary trees.
• Hans Chalupsky wrote advice.el, an overloading mechanism for Emacs Lisp functions; and trace.el, a tracing facility for Emacs Lisp.
• Chris Chase, Carsten Dominik, and J. D. Smith wrote IDLWAVE mode, for editing IDL and WAVE CL.
• Bob Chassell wrote texnfo-upd.el, texinfo.el, and makeinfo.el, modes and utilities for working with Texinfo files; and page-ext.el, commands for extended page handling.
• Jihyun Cho wrote hanja-util.el and hangul.el, utilities for Korean Hanja.
• Andrew Choi and Yamamoto Mitsuharu wrote the Carbon support, used prior to Emacs 23 for Mac OS.
• Chong Yidong was the Emacs co-maintainer for Emacs 23. He made many improvements to the Emacs display engine; and, together with Kai Großjohann and Alex Schroeder, wrote longlines.el, a minor mode for wrapping long lines.
• James Clark wrote SGML mode, a mode for editing SGML documents; and nXML mode, a mode for editing XML documents. He also contributed to Emacs's dumping procedures.
• Mike Clarkson wrote edt.el, an emulation of DEC's EDT editor.
• Glynn Clements provided gamegrid.el and a couple of games that use it, Snake and Tetris.
• Andrew Cohen wrote spam-wash.el, to decode and clean email before it is analysed for spam.
• Georges Brun-Cottan and Stefan Monnier wrote easy-mmode.el, a package for easy definition of major and minor modes.
• Andrew Csillag wrote M4 mode (m4-mode.el).
• Doug Cutting and Jamie Zawinski wrote disass.el, a disassembler for compiled Emacs Lisp code.
• Mathias Dahl wrote image-dired.el, a package for viewing image files as “thumbnails.”
• Vivek Dasmohapatra wrote htmlfontify.el, to convert a buffer or source tree to HTML.
• Michael DeCorte wrote emacs.csh, a C-shell script that starts a new Emacs job, or restarts a paused Emacs if one exists.
• Gary Delp wrote mailpost.el, an interface between RMAIL and the /usr/uci/post mailer.
• Matthieu Devin wrote delsel.el, a package to make newly-typed text replace the current selection.
• Eric Ding wrote goto-addr.el,
• Jan Djärv added support for the GTK+ toolkit and X drag-and-drop.
• Carsten Dominik wrote RefTeX, a package for setting up labels and cross-references in LaTeX documents; and co-wrote IDLWAVE mode (q.v.). He was the main author of Org mode, for maintaining notes, todo lists, and project planning. Thomas Baumann, Lennart Borgman, Baoqiu Cui, Daniel German, Bastien Guerry, Tassilo Horn, Philip Jackson, Tokuya Kameshima, Ross Patterson, Sebastian Rose, Eric Schulte, Andy Stewart, David O'Toole, John Wiegley, and Piotr Zielinski also wrote various Org mode components.
• Scott Draves wrote tq.el, help functions for maintaining transaction queues between Emacs and its subprocesses.
• Benjamin Drieu wrote pong.el, an implementation of the classical pong game.
• Viktor Dukhovni wrote support for dumping under SunOS version 4.
• John Eaton and Kurt Hornik wrote Octave mode.
• Rolf Ebert co-wrote Ada mode.
• Stephen Eglen wrote mspools.el, which tells you which Procmail folders have mail waiting in them; and iswitchb.el, a feature for incremental reading and completion of buffer names.
• Torbjörn Einarsson wrote f90.el, a mode for Fortran 90 files.
• Tsugutomo Enami co-wrote the support for international character sets.
• David Engster wrote mairix.el and nnmairix.el, an interface to the Mairix indexing tool.
• Hans Henrik Eriksen wrote simula.el, a mode for editing SIMULA 87 code.
• Michael Ernst wrote reposition.el, a command for recentering a function's source code and preceding comment on the screen.
• Ata Etemadi wrote cdl.el, functions for working with Common Data Language source code.
• Frederick Farnbach implemented morse.el, which converts text to Morse code.
• Oscar Figueiredo wrote EUDC, the Emacs Unified Directory Client, which is an interface to directory servers via LDAP, CCSO PH/QI, or BBDB; and ldap.el, the LDAP client interface.
• Fred Fish wrote the support for dumping COFF executable files.
• Karl Fogel wrote bookmark.el, which implements named placeholders; mail-hist.el, a history mechanism for outgoing mail messages; and saveplace.el, for preserving point's location in files between editing sessions.
• Gary Foster wrote crisp.el, the emulation for CRiSP and Brief editors; and scroll-all.el, a mode for scrolling several buffers together.
• Noah Friedman wrote rlogin.el, an interface to Rlogin, type-break.el, which reminds you to take periodic breaks from typing, and eldoc-mode, a mode to show the defined parameters or the doc string for the Lisp function near point.
• Shigeru Fukaya wrote a testsuite for the byte-compiler.
• Keith Gabryelski wrote hexl.el, a mode for editing binary files.
• Kevin Gallagher rewrote and enhanced the EDT emulation, and wrote flow-ctrl.el, a package for coping with unsuppressible XON/XOFF flow control.
• Kevin Gallo added multiple-frame support for Windows NT and wrote w32-win.el, support functions for the MS-Windows window system.
• Juan León Lahoz García wrote wdired.el, a package for performing file operations by directly editing Dired buffers.
• Howard Gayle wrote much of the C and Lisp code for display tables and case tables. He also wrote rot13.el, a command to display the plain-text form of a buffer encoded with the Caesar cipher; vt100-led.el, a package for controlling the LEDs on VT100-compatible terminals; and much of the support for ISO-8859 European character sets (which includes iso-ascii.el, iso-insert.el, iso-swed.el, iso-syntax.el, iso-transl.el, and swedish.el).
• Stephen Gildea made the Emacs quick reference card, and made many contributions for time-stamp.el, a package for maintaining last-change time stamps in files.
• Julien Gilles wrote gnus-ml.el, a mailing list minor mode for Gnus.
• David Gillespie wrote the Common Lisp compatibility packages; Calc, an advanced calculator and mathematical tool, since maintained and developed by Jay Belanger; complete.el, a partial completion mechanism; and edmacro.el, a package for editing keyboard macros.
• Bob Glickstein wrote sregex.el, a facility for writing regexps using a Lisp-like syntax.
• Boris Goldowsky wrote avoid.el, a package to keep the mouse cursor out of the way of the text cursor; shadowfile.el, a package for keeping identical copies of files in more than one place; format.el, a package for reading and writing files in various formats; enriched.el, a package for saving text properties in files; facemenu.el, a package for specifying faces; and descr-text.el, describing text and character properties.
• Michelangelo Grigni wrote ffap.el which visits a file, taking the file name from the buffer.
• Odd Gripenstam wrote dcl-mode.el for editing DCL command files.
• Michael Gschwind wrote iso-cvt.el, a package to convert between the ISO 8859-1 character set and the notations for non-ASCII characters used by TeX and net tradition.
• Bastien Guerry wrote gnus-bookmark.el, bookmark support for Gnus; as well as contributing to Org mode (q.v.).
• Henry Guillaume wrote find-file.el, a package to visit files related to the currently visited file.
• Doug Gwyn wrote the portable alloca implementation.
• Ken'ichi Handa implemented most of the support for international character sets, and wrote most of the Emacs 23 font handling code. He also wrote composite.el, which provides a minor mode that composes characters automatically when they are displayed; isearch-x.el, a facility for searching non-ASCII text; and ps-bdf.el, a BDF font support for printing non-ASCII text on a PostScript printer. Together with Naoto Takahashi, he wrote quail.el, an input facility for typing non-ASCII text from an ASCII keyboard.
• Jesper Harder wrote yenc.el, for decoding yenc encoded messages.
• K. Shane Hartman wrote chistory.el and echistory.el, packages for browsing command history lists; electric.el and helper.el, which provide an alternative command loop and appropriate help facilities; emacsbug.el, a package for reporting Emacs bugs; picture.el, a mode for editing ASCII pictures; and view.el, a package for perusing files and buffers without editing them.
• John Heidemann wrote mouse-copy.el and mouse-drag.el, which provide alternative mouse-based editing and scrolling features.
• Jon K Hellan wrote utf7.el, support for mail-safe transformation format of Unicode.
• Markus Heritsch co-wrote Ada mode.
• Karl Heuer wrote the original blessmail script, implemented the intangible text property, and rearranged the structure of the Lisp_Object type to allow for more data bits.
• Manabu Higashida ported Emacs to MS-DOS.
• Anders Holst wrote hippie-exp.el, a versatile completion and expansion package.
• Tassilo Horn wrote DocView mode, allowing viewing of PDF, PostScript and DVI documents.
• Tom Houlder wrote mantemp.el, which generates manual C++ template instantiations.
• Joakim Hove wrote html2text.el, a html to plain text converter.
• Denis Howe wrote browse-url.el, a package for invoking a WWW browser to display a URL.
• Lars Magne Ingebrigtsen did a major redesign of the Gnus news-reader and wrote many of its parts. Several of these are now general components of Emacs: dns.el for Domain Name Service lookups; format-spec.el for formatting arbitrary format strings; netrc.el for parsing of .netrc files; and time-date.el for general date and time handling. Components of Gnus have also been written by: Nagy Andras, David Blacka, Scott Byer, Kevin Greiner, Kai Großjohann, Joe Hildebrand, Paul Jarc, Sascha Lüdecke, David Moore, Jim Radford, Benjamin Rutt, Raymond Scholz, Thomas Steffen, Reiner Steib, Didier Verna, Ilja Weis, Katsumi Yamaoka, Teodor Zlatanov, and others (see Contributors).
• Andrew Innes contributed extensively to the MS-Windows support.
• Seiichiro Inoue improved Emacs's XIM support.
• Philip Jackson wrote find-cmd.el, to build a find command-line.
• Ulf Jasper wrote icalendar.el, a package for converting Emacs diary entries to and from the iCalendar format; newsticker.el, an RSS and Atom based Newsticker; and bubbles.el, a puzzle game.
• Kyle Jones wrote life.el, a package to play Conway's “life” game.
• Terry Jones wrote shadow.el, a package for finding potential load-path problems when some Lisp file “shadows” another.
• Simon Josefsson wrote dns-mode.el, an editing mode for Domain Name System master files; dig.el, a Domain Name System interface; flow-fill.el, a package for interpreting RFC2646 formatted text in messages; fringe.el, a package for customizing the fringe; imap.el, an Emacs Lisp library for talking to IMAP servers; password-cache.el, a password reader; nnimap.el, the IMAP back-end for Gnus; url-imap.el for the URL library; rfc2104.el, a hashed message authentication facility; the Gnus S/MIME and Sieve components; and tls.el and starttls.el for the Transport Layer Security protocol.
• Arne Jørgensen wrote latexenc.el, a package to automatically guess the correct coding system in LaTeX files.
• Alexandre Julliard wrote vc-git.el, support for the Git version control system.
• Tomoji Kagatani implemented smtpmail.el, used for sending out mail with SMTP.
• Ivan Kanis wrote vc-hg.el, support for the Mercurial version control system.
• Henry Kautz wrote bib-mode.el, a mode for maintaining bibliography databases compatible with refer (the troff version) and lookbib, and refbib.el, a package to convert those databases to the format used by the LaTeX text formatting package.
• Taichi Kawabata added support for Devanagari script and the Indian languages, and wrote ucs-normalize.el for Unicode normalization.
• Taro Kawagishi implented the MD4 Message Digest Algorithm in Lisp; and wrote ntlm.el and sasl-ntlm.el for NT LanManager authentication support.
• Howard Kaye wrote sort.el, commands to sort text in Emacs buffers.
• Michael Kifer wrote ediff, an interactive interface to the diff, patch, and merge programs; and Viper, the newest emulation for VI.
• Richard King wrote the first version of userlock.el and filelock.c, which provide simple support for multiple users editing the same file. He also wrote the initial version of uniquify.el, a facility to make buffer names unique by adding parts of the file's name to the buffer name.
• Peter Kleiweg wrote ps-mode.el, a mode for editing PostScript files and running a PostScript interpreter interactively from within Emacs.
• Shuhei Kobayashi wrote hex-util.el, for operating on hexadecimal strings; support for HMAC (Keyed-Hashing for Message Authentication); and a Lisp implementation of the SHA1 Secure Hash Algorithm.
• Pavel Kobyakov wrote flymake.el, a minor mode for performing on-the-fly syntax checking.
• David M. Koppelman wrote hi-lock.el, a minor mode for interactive automatic highlighting of parts of the buffer text.
• Koseki Yoshinori wrote iimage.el, a minor mode for displaying inline images.
• Robert Krawitz wrote the original xmenu.c, part of Emacs's pop-up menu support.
• Sebastian Kremer wrote dired-mode, with contributions by Lawrence R. Dodd. He also wrote ls-lisp.el, a Lisp emulation of the ls command for platforms which don't have ls as a standard program.
• Ken Stevens wrote ispell.el, a spell-checker interface.
• David Ka*gedal wrote tempo.el, providing support for easy insertion of boilerplate text and other common constructions.
• Daniel LaLiberte wrote edebug.el, a source-level debugger for Emacs Lisp; cl-specs.el, specifications to help edebug debug code written using David Gillespie's Common Lisp support; cust-print.el, a customizable package for printing lisp objects; and isearch.el, Emacs's incremental search minor mode. He also co-wrote hideif.el (q.v.).
• Karl Landstrom and Daniel Colascione wrote js.el, a mode for editing JavaScript.
• Vinicius Jose Latorre wrote the Emacs printing facilities, as well as ps-print (with Jim Thompson, Jacques Duthen, and Kenichi Handa), a package for pretty-printing Emacs buffers to PostScript printers; delim-col.el, a package to arrange text into columns; ebnf2ps.el, a package that translates EBNF grammar to a syntactic chart that can be printed to a PostScript printer; and whitespace.el, a package that detects and cleans up excess whitespace in a file. The previous version of whitespace.el, used prior to Emacs 23, was written by Rajesh Vaidheeswarran.
• Frederic Lepied wrote expand.el, which uses the abbrev mechanism for inserting programming constructs.
• Peter Liljenberg wrote elint.el, a Lint-style code checker for Emacs Lisp programs.
• Lars Lindberg wrote msb.el, which provides more flexible menus for buffer selection; co-wrote imenu.el (q.v.); and rewrote dabbrev.el, originally written by Don Morrison.
• Anders Lindgren wrote autorevert.el, a package for automatically reverting files visited by Emacs that were changed on disk; cwarn.el, a package to highlight suspicious C and C++ constructs; and follow.el, a minor mode to synchronize windows that show the same buffer.
• Thomas Link wrote filesets.el, a package for handling sets of files.
• Juri Linkov wrote misearch.el, extending isearch to multi-buffer searches; the code in files-x.el for handling file- and directory-local variables; and the info-finder feature that creates a virtual Info manual of package keywords.
• Károly Lo''rentey wrote the “multi-terminal” code, which allows Emacs to run on graphical and text-only terminals simultaneously.
• Martin Lorentzon wrote vc-annotate.el, support for version control annotation.
• Dave Love wrote much of the code dealing with Unicode support and Latin-N unification. He added support for many coding systems, including the various UTF-7 and UTF-16 coding systems. He also wrote autoarg-mode, a global minor mode whereby digit keys supply prefix arguments; autoarg-kp-mode, which redefines the keypad numeric keys to digit arguments; autoconf.el, a mode for editing Autoconf files; cfengine.el, a mode for editing Cfengine files; elide-head.el, a package for eliding boilerplate text from file headers; hl-line.el, a minor mode for highlighting the line in the current window on which point is; cap-words.el, a minor mode for motion in “CapitalizedWordIdentifiers”; latin1-disp.el, a package that lets you display ISO 8859 characters on Latin-1 terminals by setting up appropriate display tables; python.el, a major mode for the Python programming language; refill.el, a mode for automatic paragraph refilling, akin to typical word processors; smiley.el, a facility for displaying smiley faces; sym-comp.el, a library for performing mode-dependent symbol completion; benchmark.el for timing code execution; and tool-bar.el, a mode to control the display of the Emacs tool bar. With Riccardo Murri he wrote vc-bzr.el, support for the Bazaar version control system.
• Eric Ludlam wrote the Speedbar package; checkdoc.el, for checking doc strings in Emacs Lisp programs; dframe.el, providing dedicated frame support modes; ezimage.el, a generalized way to place images over text; chart.el for drawing bar charts etc; and the EIEIO (Enhanced Implementation of Emacs Interpreted Objects) package. He was also the main author of the CEDET (Collection of Emacs Development Environment Tools) package. Portions were also written by Jan Moringen, David Ponce, and Joakim Verona.
• Alan Mackenzie wrote the integrated AWK support in CC Mode, and maintained CC Mode from Emacs 22 onwards.
• Christopher J. Madsen wrote decipher.el, a package for cracking simple substitution ciphers.
• Neil M. Mager wrote appt.el, functions to notify users of their appointments. It finds appointments recorded in the diary files used by the calendar package.
• Ken Manheimer wrote allout.el, a mode for manipulating and formatting outlines, and icomplete.el, which provides incremental completion feedback in the minibuffer.
• Bill Mann wrote perl-mode.el, a mode for editing Perl code.
• Brian Marick and Daniel LaLiberte wrote hideif.el, support for hiding selected code within C #ifdef clauses.
• Simon Marshall wrote regexp-opt.el, which generates a regular expression from a list of strings; and the fast-lock and lazy-lock font-lock support modes. He also extended comint.el and shell.el, originally written by Olin Shivers.
• Bengt Martensson, Dirk Herrmann, Marc Shapiro, Mike Newton, Aaron Larson, and Stefan Schoef, wrote bibtex.el, a mode for editing BibTeX bibliography files.
• Charlie Martin wrote autoinsert.el, which provides automatic mode-sensitive insertion of text into new files.
• Yukihiro Matsumoto and Nobuyoshi Nakada wrote Ruby-mode.
• Thomas May wrote blackbox.el, a version of the traditional blackbox game.
• Roland McGrath wrote compile.el (since updated by Daniel Pfeiffer), a package for running compilations in a buffer, and then visiting the locations reported in error messages; etags.el, a package for jumping to function definitions and searching or replacing in all the files mentioned in a TAGS file; find-dired.el, for using dired commands on output from the find program, with Sebastian Kremer; grep.el for running the grep command; map-ynp.el, a general purpose boolean question-asker; autoload.el, providing semi-automatic maintenance of autoload files.
• Michael McNamara and Wilson Snyder wrote Verilog mode.
• David Megginson wrote derived.el, which allows one to define new major modes by inheriting key bindings and commands from existing major modes.
• Will Mengarini wrote repeat.el, a command to repeat the preceding command with its arguments.
• Richard Mlynarik wrote cl-indent.el, a package for indenting Common Lisp code; ebuff-menu.el, an “electric” browser for buffer listings; ehelp.el, bindings for browsing help screens; rfc822.el, a parser for E-mail addresses in the RFC-822 format, used in mail messages and news articles; terminal.el, a terminal emulator for Emacs subprocesses; and yow.el, an essential utility.
• Gerd Moellmann was the Emacs maintainer from the beginning of Emacs 21 development until the release of 21.1. He wrote the new display engine used from Emacs 21 onwards, and the asynchronous timers facility. He also wrote ebrowse, the C++ browser; jit-lock.el, the Just-In-Time font-lock support mode; tooltip.el, a package for displaying tooltips; authors.el, a package for maintaining the AUTHORS file; and rx.el, a regular expression constructor.
• Stefan Monnier was the Emacs co-maintainer for Emacs 23. He added support for Arch and Subversion to VC, re-wrote much of the Emacs server to use the built-in networking primitives, and re-wrote the abbrev and minibuffer completion code for Emacs 23. He also wrote PCL-CVS, a directory-level front end to the CVS version control system; reveal.el, a minor mode for automatically revealing invisible text; smerge-mode.el, a minor mode for resolving diff3 conflicts; diff-mode.el, a mode for viewing and editing context diffs; css-mode.el for Cascading Style Sheets; bibtex-style.el for BibTeX Style files; and mpc.el, a client for the “Music Player Daemon”.
• Morioka Tomohiko wrote several packages for MIME support in Gnus and elsewhere.
• Takahashi Naoto co-wrote quail.el (q.v.), and wrote robin.el, another input method.
• Sen Nagata wrote crm.el, a package for reading multiple strings with completion, and rfc2368.el, support for mailto: URLs.
• Erik Naggum wrote the time-conversion functions. He also wrote disp-table.el, a package for dealing with display tables; mailheader.el, a package for parsing email headers; and parse-time.el, a package for parsing time strings.
• Thomas Neumann and Eric Raymond wrote make-mode.el, a mode for editing makefiles.
• Thien-Thi Nguyen and Dan Nicolaescu wrote hideshow.el, a minor mode for selectively displaying blocks of text.
• Dan Nicolaescu added support for running Emacs as a daemon. He also wrote romanian.el, support for editing Romanian text; iris-ansi.el, support for running Emacs on SGI's xwsh and winterm terminal emulators; and vc-dir.el, displaying the status of version-controlled directories.
• Jurgen Nickelsen wrote ws-mode.el, providing WordStar emulation.
• Hrvoje Niksic wrote savehist.el, for saving the minibuffer history between Emacs sessions.
• Jeff Norden wrote kermit.el, a package to help the Kermit dialup communications program run comfortably in an Emacs shell buffer.
• Andrew Norman wrote ange-ftp.el, providing transparent FTP support.
• Edward O'Connor wrote json.el, a file for parsing and generating JSON files.
• Kentaro Ohkouchi created the Emacs icons used beginning with Emacs 23.
• Alexandre Oliva wrote gnus-mlspl.el, a group params-based mail splitting mechanism.
• Takaaki Ota wrote table.el, a package for creating and editing embedded text-based tables.
• Pieter E. J. Pareit wrote mixal-mode.el, an editing mode for the MIX assembly language.
• David Pearson wrote quickurl.el, a simple method of inserting a URL into the current buffer based on text at point; 5x5.el, a game to fill all squares on the field.
• Jeff Peck wrote sun.el, key bindings for sunterm keys.
• Damon Anton Permezel wrote hanoi.el, an animated demonstration of the “Towers of Hanoi” puzzle.
• William M. Perry wrote mailcap.el (with Lars Magne Ingebrigtsen), a MIME media types configuration facility; mwheel.el, a package for supporting mouse wheels; co-wrote (with Dave Love) socks.el, a Socks v5 client; and developed the URL package.
• Per Persson wrote gnus-vm.el, the VM interface for Gnus.
• Jens Petersen wrote find-func.el, which makes it easy to find the source code for an Emacs Lisp function or variable.
• Daniel Pfeiffer wrote conf-mode.el, a mode for editing configuration files; copyright.el, a package for updating copyright notices in files; executable.el, a package for executing interpreter scripts; sh-script.el, a mode for editing shell scripts; skeleton.el, implementing a concise language for writing statement skeletons; and two-column.el, a minor mode for simultaneous two-column editing.

  Daniel also rewrote apropos.el (originally written by Joe Wells), for finding commands, functions, and variables matching a regular expression; and, together with Jim Blandy, co-authored wyse50.el, support for Wyse 50 terminals. He also co-wrote compile.el (q.v.) and ada-stmt.el.

• Richard L. Pieri wrote pop3.el, a Post Office Protocol (RFC 1460) interface for Emacs.
• Fred Pierresteguy and Paul Reilly made Emacs work with X Toolkit widgets.
• François Pinard, Greg McGary, and Bruno Haible wrote po.el, support for PO translation files.
• Christian Plaunt wrote soundex.el, an implementation of the Soundex algorithm for comparing English words by their pronunciation.
• David Ponce wrote recentf.el, a package that puts a menu of recently visited files in the Emacs menu bar; ruler-mode.el, a minor mode for displaying a ruler in the header line; and tree-widget.el, a package to display hierarchical data structures.
• Francesco A. Potorti wrote cmacexp.el, providing a command which runs the C preprocessor on a region of a file and displays the results. He also expanded and redesigned the etags program.
• Michael D. Prange and Steven A. Wood wrote fortran.el, a mode for editing Fortran code.
• Ashwin Ram wrote refer.el, commands to look up references in bibliography files by keyword.
• Eric S. Raymond wrote vc.el, an interface to the RCS and SCCS source code version control systems, with Paul Eggert; gud.el, a package for running source-level debuggers like GDB and SDB in Emacs; asm-mode.el, a mode for editing assembly language code; AT386.el, terminal support package for IBM's AT keyboards; cookie1.el, support for “fortune-cookie” programs like yow.el and spook.el; finder.el, a package for finding Emacs Lisp packages by keyword and topic; keyswap.el, code to swap the <BS> and <DEL> keys; loadhist.el, functions for loading and unloading Emacs features; lisp-mnt.el, functions for working with the special headers used in Emacs Lisp library files; and code to set and make use of the load-history lisp variable, which records the source file from which each lisp function loaded into Emacs came.
• Edward M. Reingold wrote the extensive calendar and diary support, with contributions from Stewart Clamen (cal-mayan.el), Nachum Dershowitz (cal-hebrew.el), Paul Eggert (cal-dst.el), Steve Fisk (cal-tex.el), Michael Kifer (cal-x.el), Lara Rios (cal-menu.el), and Denis B. Roegel (solar.el). Andy Oram contributed to its documentation. Reingold also contributed to tex-mode.el, a mode for editing TeX files, as did William F. Schelter, Dick King, Stephen Gildea, Michael Prange, and Jacob Gore.
• David Reitter wrote mailclient.el which can send mail via the system's designated mail client.
• Alex Rezinsky wrote which-func.el, a mode that shows the name of the current function in the mode line.
• Rob Riepel wrote tpu-edt.el and its associated files, providing an emulation of the VMS TPU text editor emulating the VMS EDT editor, and vt-control.el, providing some control functions for the DEC VT line of terminals.
• Nick Roberts wrote t-mouse.el, for mouse support in text terminals; and gdb-ui.el, a graphical user interface to GDB. Together with Dmitry Dzhus, he wrote gdb-mi.el, the successor to gdb-ui.el.
• Danny Roozendaal implemented handwrite.el, which converts text into “handwriting.”
• Markus Rost wrote cus-test.el, a testing framework for customize.
• Guillermo J. Rozas wrote scheme.el, a mode for editing Scheme and DSSSL code, and fakemail.c, an interface to the System V mailer.
• Ivar Rummelhoff wrote winner.el, which records recent window configurations so you can move back to them.
• Jason Rumney ported the Emacs 21 display engine to MS-Windows, and has contributed extensively to the MS-Windows port of Emacs.
• Wolfgang Rupprecht wrote Emacs 19's floating-point support (including float-sup.el and floatfns.c), and sup-mouse.el, support for the Supdup mouse on lisp machines.
• Kevin Ryde wrote info-xref.el, a library for checking references in Info files.
• James B. Salem and Brewster Kahle wrote completion.el, providing dynamic word completion.
• Masahiko Sato wrote vip.el, an emulation of the VI editor.
• Holger Schauer wrote fortune.el, a package for using fortune in message signatures.
• William Schelter wrote telnet.el, support for telnet sessions within Emacs.
• Ralph Schleicher wrote battery.el, a package for displaying laptop computer battery status, and info-look.el, a package for looking up Info documentation for symbols in the buffer.
• Michael Schmidt and Tom Perrine wrote modula2.el, a mode for editing Modula-2 code, based on work by Mick Jordan and Peter Robinson.
• Ronald S. Schnell wrote dunnet.el, a text adventure game.
• Philippe Schnoebelen wrote gomoku.el, a Go Moku game played against Emacs; and mpuz.el, a multiplication puzzle.
• Rainer Schoepf contributed to Alpha and OSF1 support.
• Jan Schormann wrote solitaire.el, an implementation of the Solitaire game.
• Alex Schroeder wrote ansi-color.el, a package for translating ANSI color escape sequences to Emacs faces; sql.el, a package for interactively running an SQL interpreter in an Emacs buffer; cus-theme.el, an interface for custom themes; master.el, a package for making a buffer ‘master’ over another; and spam-stat.el, for statistical detection of junk email. He also wrote parts of the IRC client ERC (q.v.).
• Randal Schwartz wrote pp.el, a pretty-printer for lisp objects.
• Oliver Seidel wrote todo-mode.el, a package for maintaining TODO list files.
• Manuel Serrano wrote the Flyspell package, which does spell checking as you type.
• Hovav Shacham wrote windmove.el, a set of commands for selecting windows based on their geometrical position on the frame.
• Stanislav Shalunov wrote uce.el, for responding to unsolicited commercial email.
• Richard Sharman wrote hilit-chg.el, which uses colors to show recent editing changes.
• Olin Shivers wrote comint.el, a library for modes running interactive command-line-oriented subprocesses, and shell.el, for running inferior shells (both since extended by Simon Marshall); cmuscheme.el, for running inferior Scheme processes; inf-lisp.el, for running inferior Lisp process.
• Espen Skoglund wrote pascal.el, a mode for editing Pascal code.
• Rick Sladkey wrote backquote.el, a lisp macro for creating mostly-constant data.
• Lynn Slater wrote help-macro.el, a macro for writing interactive help for key bindings.
• Chris Smith wrote icon.el, a mode for editing Icon code.
• David Smith wrote ielm.el, a mode for interacting with the Emacs Lisp interpreter as a subprocess.
• Paul D. Smith wrote snmp-mode.el.
• William Sommerfeld wrote scribe.el, a mode for editing Scribe files, and server.el, a package allowing programs to send files to an extant Emacs job to be edited.
• Andre Spiegel made many contributions to the Emacs Version Control package, and in particular made it support multiple back ends.
• Michael Staats wrote pc-select.el, which rebinds keys for selecting regions to follow many other systems.
• Richard Stallman invented Emacs. He is the original author of GNU Emacs, and has been Emacs maintainer over several non-contiguous periods. In addition to much of the “core” Emacs code, he has written easymenu.el, a facility for defining Emacs menus; image-mode.el, support for visiting image files; menu-bar.el, the Emacs menu bar support code; paren.el, a package to make matching parentheses stand out in color; and also co-authored portions of CC mode.
• Sam Steingold wrote gulp.el, a facility for asking package maintainers for updated versions of their packages via e-mail, and midnight.el, a package for running a command every midnight.
• Ake Stenhoff and Lars Lindberg wrote imenu.el, a framework for browsing indices made from buffer contents.
• Peter Stephenson wrote vcursor.el, which implements a “virtual cursor” that you can move with the keyboard and use for copying text.
• Ken Stevens wrote the initial version of ispell.el and maintains that package since Ispell 3.1 release.
• Kim F. Storm made many improvements to the Emacs display engine, process support, and networking support. He also wrote bindat.el, a package for encoding and decoding binary data; CUA mode, which allows Emacs to emulate the standard CUA key bindings; ido.el, a package for selecting buffers and files quickly; keypad.el for simplified keypad bindings; and kmacro.el, the keyboard macro facility.
• Martin Stjernholm co-authored CC Mode, a major editing mode for C, C++, Objective-C, Java, Pike, CORBA IDL, and AWK code.
• Steve Strassman did not write spook.el, and even if he did, he really didn't mean for you to use it in an anarchistic way.
• Olaf Sylvester wrote bs.el, a package for manipulating Emacs buffers.
• Tibor S<imko and Milan Zamazal wrote slovak.el, support for editing text in Slovak language.
• Luc Teirlinck wrote help-at-pt.el, providing local help through the keyboard.
• Jean-Philippe Theberge wrote thumbs.el, a package for viewing image files as “thumbnails.”
• Spencer Thomas wrote the original dabbrev.el, providing a command which completes the partial word before point, based on other nearby words for which it is a prefix. He also wrote the original dumping support.
• Toru Tomabechi contributed to Tibetan support.
• Markus Triska wrote linum.el, a minor mode that displays line numbers in the left margin.
• Tom Tromey and Chris Lindblad wrote tcl.el, a mode for editing Tcl/Tk source files and running a Tcl interpreter as an Emacs subprocess.
• Tom Tromey wrote bug-reference.el, providing clickable links to bug reports.
• Eli Tziperman wrote rmail-spam-filter.el, a spam filter for RMAIL.
• Daiki Ueno wrote starttls.el, support for Transport Layer Security protocol; sasl-cram.el and sasl-digest.el (with Kenichi Okada), and sasl.el, support for Simple Authentication and Security Layer (SASL); and the EasyPG (and its predecessor PGG) package, for GnuPG and PGP support.
• Masanobu Umeda wrote GNUS, a feature-rich reader for Usenet news that was the ancestor of the current Gnus package. He also wrote prolog.el, a mode for editing Prolog code; rmailsort.el, a package for sorting messages in RMAIL folders; metamail.el, an interface to the Metamail program; gnus-kill.el, the Kill File mode for Gnus; gnus-mh.el, an mh-e interface for Gnus; gnus-msg.el, a mail and post interface for Gnus; and timezone.el, providing functions for dealing with time zones.
• Neil W. Van Dyke wrote webjump.el, a “hot links” package.
• Didier Verna wrote rect.el, a package of functions for operations on rectangle regions of text. He also contributed to Gnus (q.v.).
• Ulrik Vieth implemented meta-mode.el, for editing MetaFont code.
• Geoffrey Voelker wrote the Windows NT support. He also wrote dos-w32.el, functions shared by the MS-DOS and MS-Windows ports of Emacs, and w32-fns.el, MS-Windows specific support functions.
• Johan Vromans wrote forms.el and its associated files, a mode for filling in forms. He also wrote iso-acc.el, a minor mode providing electric accent keys.
• Colin Walters wrote Ibuffer, an enhanced buffer menu.
• Barry Warsaw wrote assoc.el, a set of utility functions for working with association lists; cc-mode.el, a mode for editing C, C++, and Java code, based on earlier work by Dave Detlefs, Stewart Clamen, and Richard Stallman; elp.el, a profiler for Emacs Lisp programs; man.el, a mode for reading UNIX manual pages; regi.el, providing an AWK-like functionality for use in lisp programs; reporter.el, providing customizable bug reporting for lisp packages; and supercite.el, a minor mode for quoting sections of mail messages and news articles.
• Christoph Wedler wrote antlr-mode.el, a major mode for ANTLR grammar files.
• Morten Welinder helped port Emacs to MS-DOS, and introduced face support into the MS-DOS port of Emacs. He also wrote desktop.el, facilities for saving some of Emacs's state between sessions; timer.el, the Emacs facility to run commands at a given time or frequency, or when Emacs is idle, and its C-level support code; pc-win.el, the MS-DOS “window-system” support; internal.el, an “internal terminal” emulator for the MS-DOS port of Emacs; arc-mode.el, the mode for editing compressed archives; s-region.el, commands for setting the region using the shift key and motion commands; and dos-fns.el, functions for use under MS-DOS.
• Joe Wells wrote the original version of apropos.el (q.v.); resume.el, support for processing command-line arguments after resuming a suspended Emacs job; and mail-extr.el, a package for extracting names and addresses from mail headers, with contributions from Jamie Zawinski.
• Rodney Whitby and Reto Zimmermann wrote vhdl-mode.el, a major mode for editing VHDL source code.
• John Wiegley wrote align.el, a set of commands for aligning text according to regular-expression based rules; isearchb.el for fast buffer switching; timeclock.el, a package for keeping track of time spent on projects; the Baha'i calendar support; pcomplete.el, a programmable completion facility; remember.el, a mode for jotting down things to remember; eudcb-mab.el, an address book backend for the Emacs Unified Directory Client; and eshell, a command shell implemented entirely in Emacs Lisp. He also contributed to Org mode (q.v.).
• Ed Wilkinson wrote b2m.c, a program to convert mail files from RMAIL format to Unix mbox format.
• Mike Williams wrote mouse-sel.el, providing enhanced mouse selection; and thingatpt.el, a library of functions for finding the “thing” (word, line, s-expression) containing point.
• Roland Winkler wrote proced.el, a system process editor.
• Bill Wohler wrote MH-E, the Emacs interface to the MH mail system; making use of earlier work by James R. Larus. Satyaki Das, Peter S. Galbraith, Stephen Gildea, and Jeffrey C. Honig also wrote various MH-E components.
• Dale R. Worley wrote emerge.el, a package for interactively merging two versions of a file.
• Francis J. Wright wrote woman.el, a package for browsing manual pages without the man command.
• Tom Wurgler wrote emacs-lock.el, which makes it harder to exit with valuable buffers unsaved.
• Masatake Yamato wrote ld-script.el, an editing mode for GNU linker scripts, and contributed subword handling in CC mode.
• Jonathan Yavner wrote testcover.el, a package for keeping track of the testing status of Emacs Lisp code; unsafep.el to determine if a Lisp form is safe; and the SES spreadsheet package.
• Ryan Yeske wrote rcirc.el a simple Internet Relay Chat client.
• Ilya Zakharevich and Bob Olson wrote cperl-mode.el, a major mode for editing Perl code. Ilya Zakharevich also wrote tmm.el, a mode for accessing the Emacs menu bar on a text-mode terminal.
• Milan Zamazal wrote czech.el, support for editing Czech text; glasses.el, a package for easier reading of source code that uses illegible identifier names; and tildify.el, commands for adding hard spaces to text, TeX, and SGML/HTML files.
• Victor Zandy wrote zone.el, a package for people who like to zone out in front of Emacs.
• Eli Zaretskii made many standard Emacs features work on MS-DOS and Microsoft Windows. He also wrote tty-colors.el, which implements transparent mapping of X colors to tty colors; and rxvt.el.
• Jamie Zawinski wrote much of the support for faces and X selections. With Hallvard Furuseth, he wrote the optimizing byte compiler used from Emacs 19 onwards. He also wrote mailabbrev.el, a package that provides automatic expansion of mail aliases, and tar-mode.el, which provides simple viewing and editing commands for tar files.
• Andrew Zhilin created the Emacs 22 icons.
• Shenghuo Zhu wrote binhex.el, a package for reading and writing binhex files; mm-partial.el, message/partial support for MIME messages; rfc1843.el, an HZ decoding package; uudecode.el, an Emacs Lisp decoder for uuencoded data; and webmail.el, an interface to Web mail. He also wrote several other Gnus components.
• Ian T. Zimmerman wrote gametree.el.
• Reto Zimmermann wrote vera-mode.el.
• Neal Ziring and Felix S. T. Wu wrote vi.el, an emulation of the VI text editor.
• Detlev Zundel wrote re-builder.el, a package for building regexps with visual feedback.

Key (Character) Index

• ! (Dired): Shell Commands in Dired
• " (TeX mode): TeX Editing
• # (Dired): Flagging Many Files
• $ (Dired): Hiding Subdirectories
• % & (Dired): Flagging Many Files
• % 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
• * ! (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
• * s (Dired): Marks vs Flags
• * t (Dired): Marks vs Flags
• * u (Dired): Marks vs Flags
• + (Dired): Misc Dired Features
• . (Calendar mode): Specified Dates
• . (Dired): Flagging Many Files
• . (Rmail): Rmail Scrolling
• / (Rmail): Rmail Scrolling
• < (Calendar mode): Scroll Calendar
• < (Dired): Subdirectory Motion
• < (Rmail): Rmail Motion
• <TAB> (Help mode): Help Mode
• = (Dired): Comparison in Dired
• > (Calendar mode): Scroll Calendar
• > (Dired): Subdirectory Motion
• > (Rmail): Rmail Motion
• ^ (Dired): Dired Visiting
• a (Calendar mode): Holidays
• A (Dired): Operating on Files
• a (Rmail): Rmail Labels
• AltGr (MS-Windows): Windows Keyboard
• B (Dired): Operating on Files
• b (Rmail summary): Rmail Summary Edit
• b (Rmail): Rmail Basics
• BS (MS-DOS): MS-DOS Keyboard
• C (Dired): Operating on Files
• c (Rmail): Rmail Reply
• C-/: Undo
• C-<SPC> C-<SPC>: Persistent Mark
• C-<TAB>: File Name Cache
• C-@: Setting Mark
• C-\: Select Input Method
• C-]: Quitting
• C-_: Undo
• C-_ (Dired): Marks vs Flags
• 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-BREAK (MS-DOS): MS-DOS Keyboard
• C-c ' (Picture mode): Insert in Picture
• C-c , <SPC>: Semantic
• C-c , J: Semantic
• C-c , j: Semantic
• C-c , l: 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 <DEL> (C Mode): Hungry Delete
• C-c <DELETE> (C Mode): Hungry Delete
• 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 Mode
• 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 [ (Enriched mode): Format Indentation
• C-c \ (Picture mode): Insert in Picture
• C-c ] (Enriched mode): Format Indentation
• C-c ^ (Picture mode): Insert in Picture
• C-c ` (Picture mode): Insert in Picture
• C-c C-<DEL> (C Mode): Hungry Delete
• C-c C-<DELETE> (C Mode): Hungry Delete
• C-c C-\ (C mode): Other C Commands
• C-c C-\ (Shell mode): Shell Mode
• C-c C-a (C mode): Electric C
• C-c C-a (F90 mode): Fortran Motion
• 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 (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): Multi-Line Comments
• C-c C-c (Edit Abbrevs): Editing Abbrevs
• C-c C-c (Edit Tab Stops): Tab Stops
• 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 (Outline mode): Outline Visibility
• C-c C-d (Picture mode): Basic Picture
• C-c C-d (SGML mode): HTML Mode
• 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 (Outline mode): Outline Visibility
• C-c C-e (Shell mode): Shell Mode
• C-c C-f (GUD): Commands of GUD
• 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): Paging in Term
• C-c C-q (TeX mode): TeX Print
• 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 (Outline mode): Outline Visibility
• C-c C-s (Shell mode): Shell Mode
• C-c C-t (GUD): Commands of GUD
• 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 (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 RET (Shell mode): Shell History Copying
• C-c TAB (Picture mode): Tabs in Picture
• C-c TAB (SGML mode): HTML Mode
• C-c TAB (TeX mode): TeX Print
• C-c { (TeX mode): TeX Editing
• C-c } (TeX mode): TeX Editing
• 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-f: Moving Point
• C-f (Calendar mode): Calendar Unit Motion
• C-g: Quitting
• C-g (MS-DOS): MS-DOS Keyboard
• C-h: Help
• C-h .: Help Echo
• C-h a: Apropos
• C-h b: Misc Help
• C-h C: Coding Systems
• C-h c: Key Help
• C-h C-\: Select Input Method
• 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-m: Help Files
• C-h C-n: Help Files
• C-h C-o: Help Files
• C-h C-p: Help Files
• C-h C-t: Help Files
• C-h C-w: Help Files
• 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: Select Input Method
• C-h i: Misc Help
• C-h K: Key Help
• C-h k: Key Help
• C-h L: Language Environments
• C-h l: Misc Help
• C-h m: Misc Help
• C-h p: Library Keywords
• C-h s: Syntax
• C-h S: Info Lookup
• C-h S: Misc Help
• C-h t: Basic
• C-h v: Name Help
• C-h w: Key Help
• C-j: Basic Indent
• 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): Summary of Gnus
• C-l: Scrolling
• C-M-%: Query Replace
• C-M-.: Find Tag
• C-M-/: Dynamic Abbrevs
• C-M-<SPC>: Expressions
• C-M-@: Expressions
• C-M-\: Indentation Commands
• 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-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-j: Multi-Line Comments
• C-M-j (Fortran mode): ForIndent Commands
• C-M-k: Expressions
• C-M-l: Scrolling
• 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-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-x (Emacs-Lisp mode): Lisp Eval
• C-M-x (Lisp mode): External Lisp
• C-Mouse-1: Menu Mouse Clicks
• C-Mouse-2: Menu Mouse Clicks
• C-mouse-2 (mode line): Mode Line Mouse
• C-Mouse-2 (scroll bar): Mode Line Mouse
• 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 (Gnus Group mode): Summary of Gnus
• C-n (Gnus Summary mode): Summary of Gnus
• C-o: Blank Lines
• 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 (Gnus Group mode): Summary of Gnus
• C-p (Gnus Summary mode): Summary of Gnus
• C-q: Inserting Text
• C-r: Basic Isearch
• C-s: Basic Isearch
• C-S-backspace: Killing by Lines
• C-S-Mouse-3 (FFAP): FFAP
• C-SPC: Setting Mark
• C-SPC C-SPC: Mark Ring
• C-t: Transpose
• C-t d (Image-Dired): Image-Dired
• 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: Persistent Mark
• C-u C-x v =: Old Revisions
• C-u M-;: Comment Commands
• C-u TAB: Multi-line Indent
• C-v: Scrolling
• C-v (Calendar mode): Scroll Calendar
• C-w: Other Kill Commands
• 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 .: Find Tag
• C-x 4 0: Change Window
• C-x 4 a: Change Log Commands
• C-x 4 b: Select Buffer
• C-x 4 b (Iswitchb mode): Iswitchb
• C-x 4 c: Indirect Buffers
• C-x 4 C-o (Iswitchb mode): Iswitchb
• 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 .: Find Tag
• 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 b (Iswitchb mode): Iswitchb
• 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 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: Unibyte Mode
• C-x 8 RET: Inserting Text
• C-x ;: Options for Comments
• C-x <: Horizontal Scrolling
• C-x <LEFT>: Select Buffer
• C-x <RET> F: File Name Coding
• C-x <RIGHT>: Select Buffer
• C-x =: International Chars
• C-x =: Position Info
• C-x >: Horizontal Scrolling
• C-x [: Pages
• C-x [ (Calendar mode): Calendar Unit Motion
• C-x ]: Pages
• C-x ] (Calendar mode): Calendar Unit Motion
• C-x ^: Change Window
• C-x `: Compilation Mode
• 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 b (Iswitchb mode): Iswitchb
• C-x C-+: Temporary Face Changes
• C-x C--: Temporary Face Changes
• C-x C-0: Temporary Face Changes
• C-x C-<SPC>: Global Mark Ring
• C-x C-=: Temporary Face Changes
• C-x C-a (GUD): 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-d: Directories
• C-x C-e: Lisp Eval
• C-x C-f: Visiting
• C-x C-f (FFAP): FFAP
• 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 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-l: Case
• 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-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-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 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 +: RegNumbers
• C-x r b: Bookmarks
• C-x r c: Rectangles
• C-x r d: Rectangles
• C-x r f: RegConfig
• C-x r i: RegText
• C-x r j: RegPos
• C-x r k: Rectangles
• C-x r l: Bookmarks
• C-x r m: Bookmarks
• C-x r n: RegNumbers
• C-x r o: Rectangles
• C-x r r: RegRect
• C-x r s: RegText
• C-x r SPC: RegPos
• C-x r t: Rectangles
• C-x r w: RegConfig
• 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 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 s: Save Commands
• C-x SPC: Commands of GUD
• C-x TAB: Indentation Commands
• C-x TAB (Enriched mode): Format Indentation
• C-x u: Undo
• C-x v =: Old Revisions
• C-x v a: Change Logs and VC
• C-x v b: Local Version Control
• C-x v c: VC Undo
• C-x v d: VC Directory Mode
• C-x v g: Old Revisions
• C-x v h: Version Headers
• C-x v i: Registering
• C-x v l: VC Change Log
• C-x v m: Merging
• C-x v r: Making Revision Tags
• C-x v s: Making Revision Tags
• C-x v u: VC Undo
• C-x v v: Basic VC Editing
• C-x v ~: Old Revisions
• 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 r: Highlight Interactively
• C-x z: Repeating
• C-x }: Change Window
• C-y: Kill Ring
• C-z: Exiting
• C-z (X windows): Frame Commands
• d (Calendar mode): Displaying the Diary
• D (Dired): Operating on Files
• d (Dired): Dired Deletion
• D (GDB breakpoints buffer): Breakpoints Buffer
• D (GDB speedbar): Watch Expressions
• d (Rmail): Rmail Deletion
• DEL (and major modes): Major Modes
• DEL (Dired): Dired Deletion
• DEL (Gnus): Summary of Gnus
• DEL (MS-DOS): MS-DOS Keyboard
• DEL (programming modes): Program Modes
• DEL (Rmail): Rmail Scrolling
• DOWN: Moving Point
• e (Dired): Dired Visiting
• e (Rmail): Rmail Editing
• ESC ESC ESC: Quitting
• f (Dired): Dired Visiting
• f (Rmail): Rmail Reply
• F1: Help
• F10: Menu Bar
• F10 (MS-Windows): Windows Keyboard
• 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 (Dired): Dired Updating
• G (Dired): Operating on Files
• 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 (Calendar mode): Holidays
• H (Dired): Operating on Files
• h (Rmail): Rmail Make Summary
• Help: Help
• i (Dired): Subdirectories in Dired
• i (Rmail): Rmail Files
• i a (Calendar mode): Special Diary Entries
• i b (Calendar mode): Special Diary Entries
• i c (Calendar mode): Special Diary Entries
• i d (Calendar mode): Adding to Diary
• i m (Calendar mode): Adding to Diary
• i w (Calendar mode): Adding to Diary
• i y (Calendar mode): Adding to Diary
• INSERT: Minor Modes
• j (Dired): Dired Navigation
• j (Rmail): Rmail Motion
• k (Dired): Dired Updating
• k (Rmail): Rmail Labels
• l (Dired): Dired Updating
• L (Dired): Operating on Files
• l (Gnus Group mode): Summary of Gnus
• L (Gnus Group mode): Summary of Gnus
• l (Rmail): Rmail Make Summary
• LEFT: Moving Point
• m (Calendar mode): Displaying the Diary
• M (Calendar mode): Lunar Phases
• M (Dired): Operating on Files
• m (Dired): Marks vs Flags
• m (Rmail): Rmail Reply
• M-!: Single Shell
• M-$: Spelling
• M-$ (Dired): Hiding Subdirectories
• M-%: Query Replace
• M-% (Incremental search): Special Isearch
• M-': Expanding Abbrevs
• M-*: Find Tag
• M-,: Tags Search
• M--: Arguments
• M-- M-c: Fixing Case
• M-- M-l: Fixing Case
• M-- M-u: Fixing Case
• M-.: Find Tag
• M-/: Dynamic Abbrevs
• M-1: Arguments
• M-:: Lisp Eval
• M-;: Comment Commands
• M-<: Moving Point
• M-< (Calendar mode): Move to Beginning or End
• M-=: Position Info
• M-= (Calendar mode): Counting Days
• M-= (Dired): Comparison in Dired
• M->: Moving Point
• M-> (Calendar mode): Move to Beginning or End
• M-? (Nroff mode): Nroff Mode
• M-? (Shell mode): Shell Mode
• M-@: Words
• M-\: Deletion
• M-^: Indentation Commands
• M-^ (Fortran mode): ForIndent Commands
• M-`: Menu Bar
• 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-d: Words
• M-DEL: Words
• M-DEL (Dired): Marks vs Flags
• 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-f: Words
• M-g M-n: Compilation Mode
• M-g n: Compilation Mode
• M-h: Paragraphs
• M-i: Tab Stops
• M-i: Indentation
• M-j: Multi-Line Comments
• M-j b (Enriched mode): Format Justification
• M-j c (Enriched mode): Format Justification
• M-j l (Enriched mode): Format Justification
• M-j r (Enriched mode): Format Justification
• M-j u (Enriched mode): Format Justification
• M-k: Sentences
• M-l: Case
• 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 (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): Format Faces
• M-o d (Enriched mode): Format Faces
• M-o i (Enriched mode): Format Faces
• M-o l (Enriched mode): Format Faces
• M-o M-s (Text mode): Fill Commands
• M-o o (Enriched mode): Format Faces
• M-o u (Enriched mode): Format Faces
• 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 (minibuffer history): Minibuffer History
• M-r (Shell mode): Shell Ring
• M-S (Enriched mode): Format Justification
• M-s (Gnus Summary mode): Summary of Gnus
• M-s (minibuffer history): Minibuffer History
• M-s (Rmail): Rmail Motion
• M-s o: Other Repeating Search
• M-s w: Word Search
• 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-v: Scrolling
• M-v (Calendar mode): Scroll Calendar
• M-w: Other Kill Commands
• M-x: M-x
• M-y: Earlier Kills
• M-z: Other Kill Commands
• 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 (scroll bar): Mode Line Mouse
• Mouse-1 (selection): Mouse References
• Mouse-2: Mouse Commands
• Mouse-2 (GDB breakpoints buffer): Breakpoints Buffer
• Mouse-2 (mode line): Mode Line Mouse
• Mouse-2 (selection): Mouse References
• Mouse-3: Mouse Commands
• Mouse-3 (mode line): Mode Line Mouse
• n (Gnus): Summary of Gnus
• n (Rmail): Rmail Motion
• next: Scrolling
• o (Calendar mode): Specified Dates
• O (Dired): Operating on Files
• o (Dired): Dired Visiting
• o (Occur mode): Other Repeating Search
• o (Rmail): Rmail Output
• p (Calendar mode): To Other Calendar
• P (Dired): Operating on Files
• p (Gnus): Summary of Gnus
• p (Rmail): Rmail Motion
• p d (Calendar mode): General Calendar
• PageDown: Scrolling
• PageUp: Scrolling
• prior: Scrolling
• q (Calendar mode): General Calendar
• Q (Dired): Operating on Files
• q (Gnus Group mode): Summary of Gnus
• q (Rmail summary): Rmail Summary Edit
• Q (Rmail summary): Rmail Summary Edit
• q (Rmail): Rmail Basics
• R (Dired): Operating on Files
• r (Rmail): Rmail Reply
• RET: Inserting Text
• RET (Dired): Dired Visiting
• RET (GDB breakpoints buffer): Breakpoints Buffer
• RET (GDB speedbar): Watch Expressions
• RET (Occur mode): Other Repeating Search
• RET (Shell mode): Shell Mode
• RIGHT: Moving Point
• s (Calendar mode): Displaying the Diary
• S (Calendar mode): Sunrise/Sunset
• s (Dired): Dired Updating
• S (Dired): Operating on Files
• s (Gnus Summary mode): Summary of Gnus
• s (Rmail): Rmail Basics
• S-<TAB> (Help mode): Help Mode
• S-Mouse-2: Hideshow
• S-Mouse-3 (FFAP): FFAP
• S-TAB (customization buffer): Changing a Variable
• SPC: Completion Commands
• SPC (Calendar mode): General Calendar
• SPC (Dired): Dired Navigation
• SPC (GDB breakpoints buffer): Breakpoints Buffer
• SPC (Gnus): Summary of Gnus
• SPC (Rmail): Rmail Scrolling
• t (Calendar mode): Writing Calendar Files
• T (Dired): Operating on Files
• t (Dired): Marks vs Flags
• t (Rmail): Rmail Display
• TAB: Completion Commands
• TAB (and major modes): Major Modes
• TAB (completion): Completion Example
• TAB (customization buffer): Changing a Variable
• TAB (GUD): Commands of GUD
• TAB (Message mode): Header Editing
• TAB (programming modes): Basic Indent
• TAB (Shell mode): Shell Mode
• TAB (Text mode): Text Mode
• u (Calendar mode): Holidays
• u (Dired deletion): Dired Deletion
• U (Dired): Marks vs Flags
• u (Dired): Marks vs Flags
• u (Gnus Group mode): Summary of Gnus
• u (Rmail): Rmail Deletion
• UP: Moving Point
• v (Dired): Dired Visiting
• v (Rmail): Rmail Display
• w (Dired): Misc Dired Features
• w (Rmail): Rmail Output
• x (Calendar mode): Holidays
• X (Dired): Shell Commands in Dired
• x (Dired): Dired Deletion
• x (Rmail): Rmail Deletion
• Z (Dired): Operating on Files
• ~ (Dired): Flagging Many Files

Command-Line Options Index

• +linenum: Action Arguments
• --background-color: Colors
• --basic-display: Misc X
• --batch: Initial Options
• --border-color: Colors
• --border-width: Borders X
• --color: Colors
• --cursor-color: Colors
• --daemon: Initial Options
• --debug-init: Initial Options
• --directory: Action Arguments
• --display: Initial Options
• --eval: Action Arguments
• --execute: Action Arguments
• --file: Action Arguments
• --find-file: Action Arguments
• --font: Font X
• --foreground-color: Colors
• --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
• --insert: Action Arguments
• --internal-border: Borders X
• --kill: Action Arguments
• --line-spacing: Misc X
• --load: Action Arguments
• --maximized: Window Size X
• --mouse-color: Colors
• --name: Resources
• --no-bitmap-icon: Icons X
• --no-blinking-cursor: Misc X
• --no-desktop: Initial Options
• --no-init-file: Initial Options
• --no-site-file: Initial Options
• --no-splash: Initial Options
• --no-window-system: Initial Options
• --quick: Initial Options
• --reverse-video: Colors
• --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
• -bg: Colors
• -bw: Borders X
• -cr: Colors
• -D: Misc X
• -d: Initial Options
• -daemon: Initial Options
• -f: Action Arguments
• -fg: Colors
• -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
• -nbc: Misc X
• -nbi: Icons X
• -nw: Initial Options
• -Q: Initial Options
• -q: Initial Options
• -r: Colors
• -rv: Colors
• -T: Title X
• -t: Initial Options
• -u: Initial Options
• -vb: Misc X

Command and Function Index

• 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
• 5x5: Amusements
• abbrev-mode: Abbrev Concepts
• abbrev-prefix-mark: Expanding Abbrevs
• abort-recursive-edit: Quitting
• 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: Misc File Ops
• add-untranslated-filesystem: Text and Binary
• animate-birthday-present: Amusements
• append-next-kill: Appending Kills
• append-to-buffer: Accumulating Text
• append-to-file: Accumulating Text
• append-to-register: RegText
• 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-value: Apropos
• apropos-variable: Apropos
• ask-user-about-lock: Interlocking
• auto-compression-mode: Compressed Files
• auto-fill-mode: Auto Fill
• auto-lower-mode: Frame Parameters
• auto-raise-mode: Frame Parameters
• auto-revert-mode: Reverting
• auto-revert-tail-mode: Reverting
• auto-save-mode: Auto Save Control
• back-to-indentation: Indentation Commands
• backward-char: Moving Point
• 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-text-line: Nroff Mode
• 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-write: Bookmarks
• browse-url: Browse-URL
• browse-url: Help Mode
• browse-url-at-mouse: Browse-URL
• browse-url-at-point: Browse-URL
• bs-show: Buffer Menus
• bubbles: Amusements
• buffer-menu: Several Buffers
• buffer-menu-other-window: Several Buffers
• 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-electric-backspace: Program Modes
• 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-hungry-delete-backwards: Hungry Delete
• c-hungry-delete-forward: Hungry Delete
• c-indent-command: C Indent
• c-indent-command: Basic Indent
• c-indent-defun: C Indent
• c-indent-exp: 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-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-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: 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
• cd: File Names
• center-line: Fill Commands
• change-log-merge: Change Log Commands
• change-log-mode: Change Log Commands
• 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-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-complete: 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-input-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-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
• comment-dwim: Comment Commands
• comment-indent-new-line: Multi-Line Comments
• comment-kill: Comment Commands
• comment-region: Multi-Line Comments
• 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
• complete-symbol: Symbol Completion
• compose-mail: Sending Mail
• compose-mail-other-frame: Sending Mail
• compose-mail-other-window: Sending Mail
• copy-dir-locals-to-file-locals: Specifying File Variables
• copy-dir-locals-to-file-locals-prop-line: Specifying File Variables
• copy-directory: Misc File Ops
• copy-file: Misc File Ops
• copy-file-locals-to-dir-locals: Directory Variables
• copy-rectangle-to-register: RegRect
• copy-to-buffer: Accumulating Text
• copy-to-register: RegText
• count-lines-page: Pages
• count-lines-region: Position Info
• count-text-lines: Nroff Mode
• cpp-highlight-buffer: Other C Commands
• create-fontset-from-fontset-spec: Defining Fontsets
• crisp-mode: Emulation
• cua-mode: CUA Bindings
• customize: Easy Customization
• customize-apropos: Specific Customization
• customize-browse: Browsing Custom
• customize-changed: Specific Customization
• customize-create-theme: Custom Themes
• customize-face: Specific Customization
• customize-group: Specific Customization
• customize-option: Specific Customization
• customize-saved: Specific Customization
• customize-unsaved: Specific Customization
• cwarn-mode: Other C Commands
• dabbrev-completion: Dynamic Abbrevs
• dabbrev-expand: Dynamic Abbrevs
• dbx: Starting GUD
• debug_print: Checklist
• decipher: Amusements
• default-value: Locals
• define-abbrevs: Saving Abbrevs
• define-global-abbrev: Defining Abbrevs
• define-key: Init Rebinding
• define-mode-abbrev: Defining Abbrevs
• delete-backward-char: Deletion
• delete-blank-lines: Blank Lines
• delete-char: Deletion
• delete-dir-local-variable: Directory Variables
• 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: Mouse Commands
• 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-character-set: Charsets
• describe-coding-system: Coding Systems
• describe-copying: Help Files
• describe-distribution: Help Files
• 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-language-environment: Language Environments
• describe-mode: Misc Help
• describe-no-warranty: Help Files
• describe-syntax: Syntax
• describe-text-properties: Editing Format Info
• describe-variable: Name Help
• desktop-change-dir: Saving Emacs Sessions
• desktop-clear: Saving Emacs Sessions
• desktop-revert: Saving Emacs Sessions
• desktop-save: Saving Emacs Sessions
• diary: Displaying the Diary
• diary-anniversary: Sexp Diary Entries
• diary-anniversary: Special 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-coptic-date: Sexp Diary Entries
• diary-cyclic: Sexp Diary Entries
• diary-cyclic: Special 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: Sexp Diary Entries
• diary-float: Special Diary Entries
• diary-french-date: 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-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-context->unified: 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-mode: Diff Mode
• diff-refine-hunk: Diff Mode
• diff-restrict-view: Diff Mode
• diff-reverse-direction: Diff Mode
• diff-show-trailing-whitespaces: 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-backup-diff: Comparison in Dired
• 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-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-copy: Operating on Files
• dired-do-copy-regexp: Transforming File Names
• dired-do-delete: Operating on Files
• dired-do-flagged-delete: Dired Deletion
• dired-do-hardlink: Operating on Files
• dired-do-hardlink-regexp: Transforming File Names
• dired-do-kill-lines: Dired Updating
• dired-do-load: Operating on Files
• dired-do-print: Operating on Files
• dired-do-query-replace-regexp: Operating on Files
• dired-do-redisplay: Dired Updating
• dired-do-rename: Operating on Files
• dired-do-rename-regexp: Transforming File Names
• dired-do-search: Operating on Files
• 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-hide-all: Hiding Subdirectories
• dired-hide-subdir: Hiding Subdirectories
• 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-marked-file: Marks vs Flags
• dired-next-subdir: Subdirectory Motion
• dired-other-frame: Dired Enter
• dired-other-window: Dired Enter
• dired-prev-dirline: Subdirectory Motion
• dired-prev-marked-file: Marks vs Flags
• dired-prev-subdir: Subdirectory Motion
• 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-local-help: Help Echo
• display-time: Optional Mode Line
• dissociated-press: Dissociated Press
• do-auto-save: Auto Save Control
• doc-view-clear-cache: Conversion
• doc-view-enlarge: Document View
• doc-view-first-page: Navigation
• doc-view-goto-page: Navigation
• doc-view-kill-proc: Conversion
• doc-view-kill-proc-and-buffer: Conversion
• doc-view-last-page: Navigation
• doc-view-mode: Document View
• doc-view-next-page: Navigation
• doc-view-previous-page: Navigation
• doc-view-reset-slice: Slicing
• doc-view-scroll-down-or-previous-page: Navigation
• doc-view-scroll-up-or-next-page: Navigation
• doc-view-search: Searching
• doc-view-search-backward: Searching
• doc-view-set-slice: Slicing
• doc-view-set-slice-using-mouse: Slicing
• doc-view-show-tooltip: Searching
• doc-view-shrink: Document View
• doc-view-toggle-display: Document View
• doctex-mode: TeX Mode
• doctor: Total Frustration
• down-list: Moving by Parens
• downcase-region: Case
• downcase-word: Case
• dunnet: Amusements
• edit-abbrevs: Editing Abbrevs
• edit-kbd-macro: Edit Keyboard Macro
• edit-tab-stops: Tab Stops
• edit-tab-stops: Indentation
• edit-tab-stops-note-changes: Tab Stops
• edt-emulation-off: Emulation
• edt-emulation-on: Emulation
• eldoc-mode: Lisp Doc
• electric-nroff-mode: Nroff Mode
• emacs-lisp-mode: Lisp Eval
• emacs-version: Understanding Bug Reporting
• emerge-auto-advance-mode: 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-mode: Submodes of Emerge
• 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: Requesting Formatted Text
• 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
• exchange-point-and-mark: Setting Mark
• execute-extended-command: M-x
• exit-calendar: General Calendar
• exit-recursive-edit: Recursive Edit
• expand-abbrev: Expanding Abbrevs
• expand-region-abbrevs: Expanding Abbrevs
• 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: Format Colors
• facemenu-set-bold: Format Faces
• facemenu-set-bold-italic: Format Faces
• facemenu-set-default: Format Faces
• facemenu-set-face: Format Faces
• facemenu-set-foreground: Format Colors
• facemenu-set-italic: Format Faces
• facemenu-set-underline: Format Faces
• ff-find-related-file: Other C Commands
• ffap: FFAP
• ffap-menu: FFAP
• ffap-mode: FFAP
• ffap-next: FFAP
• file-cache-add-directory: File Name Cache
• file-cache-minibuffer-complete: File Name Cache
• file-name-shadow-mode: Minibuffer File
• 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-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-tag: Find Tag
• find-tag-other-frame: Find Tag
• find-tag-other-window: Find Tag
• find-tag-regexp: Find Tag
• finder-by-keyword: Library Keywords
• flush-lines: Other Repeating Search
• flyspell-mode: Spelling
• flyspell-prog-mode: Spelling
• foldout-exit-fold: Foldout
• foldout-zoom-subtree: Foldout
• follow-mode: Follow Mode
• font-lock-add-keywords: Font Lock
• font-lock-mode: Font Lock
• font-lock-remove-keywords: Font Lock
• format-find-file: Forcing 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-char: Moving Point
• forward-list: Moving by Parens
• forward-page: Pages
• forward-paragraph: Paragraphs
• forward-sentence: Sentences
• forward-sexp: Expressions
• forward-text-line: Nroff Mode
• forward-word: Words
• frame-configuration-to-register: RegConfig
• fringe-mode: Fringes
• gdb: Starting GUD
• gdb-delete-breakpoint: Breakpoints Buffer
• gdb-edit-value: Watch Expressions
• gdb-frames-select: Stack Buffer
• gdb-goto-breakpoint: Breakpoints Buffer
• gdb-many-windows: GDB-UI Layout
• gdb-restore-windows: GDB-UI Layout
• gdb-threads-select: Other GDB-UI Buffers
• gdb-toggle-breakpoint: Breakpoints Buffer
• gdb-var-delete: Watch Expressions
• getenv: Environment
• glasses-mode: Glasses
• global-auto-revert-mode: Reverting
• global-cwarn-mode: Other C Commands
• global-font-lock-mode: Font Lock
• global-hl-line-mode: Cursor Display
• global-set-key: Rebinding
• global-unset-key: Rebinding
• global-visual-line-mode: Visual Line Mode
• gnus: Gnus
• gnus-group-exit: Summary of Gnus
• gnus-group-kill-group: Summary of Gnus
• gnus-group-list-all-groups: Summary of Gnus
• gnus-group-list-groups: Summary of Gnus
• gnus-group-next-group: Summary of Gnus
• gnus-group-next-unread-group: Summary of Gnus
• gnus-group-prev-group: Summary of Gnus
• gnus-group-prev-unread-group: Summary of Gnus
• gnus-group-read-group: Summary of Gnus
• gnus-group-unsubscribe-current-group: Summary of Gnus
• gnus-summary-isearch-article: Summary of Gnus
• gnus-summary-next-subject: Summary of Gnus
• gnus-summary-next-unread-article: Summary of Gnus
• gnus-summary-prev-page: Summary of Gnus
• gnus-summary-prev-subject: Summary of Gnus
• gnus-summary-prev-unread-article: Summary of Gnus
• gnus-summary-search-article-forward: Summary of Gnus
• gomoku: Amusements
• goto-address-mode: Goto Address mode
• goto-char: Moving Point
• goto-followup-to: Header Editing
• goto-line: Select Buffer
• goto-line: 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
• 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-until: Commands of GUD
• gud-up: Commands of GUD
• gud-watch: Watch Expressions
• handwrite: PostScript
• hanoi: Amusements
• help-command: Help
• help-for-help: Help
• help-next-ref: Help Mode
• help-previous-ref: Help Mode
• help-with-tutorial: Basic
• hi-lock-find-patterns: Highlight Interactively
• hi-lock-mode: Highlight Interactively
• hi-lock-write-interactive-patterns: Highlight Interactively
• hide-body: Outline Visibility
• hide-entry: Outline Visibility
• hide-ifdef-mode: Other C Commands
• hide-leaves: Outline Visibility
• hide-other: Outline Visibility
• hide-sublevels: Outline Visibility
• hide-subtree: Outline Visibility
• highlight-changes-mode: Highlight Interactively
• highlight-lines-matching-regexp: Highlight Interactively
• highlight-regexp: Highlight Interactively
• hl-line-mode: Cursor Display
• holidays: Holidays
• 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
• html-mode: HTML Mode
• htmlfontify-buffer: Printing
• icalendar-export-file, icalendar-export-region: Importing Diary
• icalendar-import-buffer: Importing Diary
• icalendar-import-file: Importing Diary
• icomplete-mode: Completion Options
• ielm: Lisp Interaction
• image-dired-display-thumbs: Image-Dired
• image-mode: File Conveniences
• image-toggle-display: File Conveniences
• imenu: Imenu
• imenu-add-menubar-index: Imenu
• increase-left-margin: Format Indentation
• increment-register: RegNumbers
• indent-code-rigidly: Multi-line Indent
• indent-for-tab-command: Basic Indent
• 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: Info Lookup
• info-lookup-symbol: Misc Help
• insert-abbrevs: Saving Abbrevs
• insert-file: Misc File Ops
• insert-file-literally: Misc File Ops
• insert-kbd-macro: Save Keyboard Macro
• insert-register: RegText
• inverse-add-global-abbrev: Defining Abbrevs
• inverse-add-mode-abbrev: Defining Abbrevs
• isearch-backward: Basic Isearch
• isearch-backward-regexp: Regexp Search
• isearch-forward: Basic Isearch
• isearch-forward-regexp: Regexp Search
• isearch-forward-word: Word Search
• isearch-toggle-input-method: Special Isearch
• isearch-toggle-specified-input-method: Special Isearch
• iso-gtex2iso: TeX Misc
• iso-iso2gtex: TeX Misc
• iso-iso2tex: TeX Misc
• iso-tex2iso: TeX Misc
• ispell: Spelling
• ispell-buffer: Spelling
• ispell-complete-word: Spelling
• ispell-kill-ispell: Spelling
• ispell-message: Mail Misc
• ispell-region: Spelling
• ispell-word: Spelling
• iswitchb-mode: Iswitchb
• jdb: Starting GUD
• jump-to-register: RegPos
• just-one-space: Deletion
• kbd: Init Rebinding
• kbd-macro-query: Keyboard Macro Query
• keep-lines: Other Repeating Search
• keyboard-escape-quit: Quitting
• keyboard-quit: Quitting
• kill-all-abbrevs: Defining Abbrevs
• kill-buffer: Kill Buffer
• kill-buffer-and-window: Change Window
• kill-compilation: Compilation
• kill-emacs: Exiting
• kill-line: Killing by Lines
• kill-local-variable: Locals
• kill-matching-buffers: Kill Buffer
• 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-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
• latex-mode: TeX Mode
• lgrep: Grep Searching
• life: Amusements
• line-number-mode: Optional Mode Line
• linum-mode: Minor Modes
• lisp-complete-symbol: Symbol Completion
• lisp-eval-defun: External Lisp
• lisp-interaction-mode: Lisp Interaction
• lisp-mode: External Lisp
• 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: Standard Faces
• list-holidays: Holidays
• list-input-methods: Select Input Method
• list-matching-lines: Other Repeating Search
• list-tags: List Tags
• lm: Amusements
• load: Lisp Libraries
• load-file: Lisp Libraries
• load-library: Lisp Libraries
• load-theme: Custom Themes
• local-set-key: Rebinding
• local-unset-key: Rebinding
• locate: Dired and Find
• locate-with-filter: Dired and Find
• log-edit-insert-changelog: Log Buffer
• log-edit-show-diff: Log Buffer
• log-edit-show-files: Log Buffer
• longlines-auto-wrap: Longlines
• longlines-mode: Longlines
• longlines-show-hard-newlines: Longlines
• lpr-buffer: Printing
• lpr-region: Printing
• lunar-phases: Lunar Phases
• mail-abbrev-insert-alias: Mail Aliases
• mail-attach-file: Mail Misc
• mail-fill-yanked-message: Citing Mail
• mail-text: Header Editing
• make-frame-command: Creating Frames
• make-frame-on-display: Multiple Displays
• make-indirect-buffer: Indirect Buffers
• make-local-variable: Locals
• make-symbolic-link: Misc File Ops
• make-variable-buffer-local: Locals
• Man-fontify-manpage: Man Page
• manual-entry: Man Page
• mark-defun: Moving by Defuns
• mark-page: Pages
• mark-paragraph: Paragraphs
• mark-sexp: Expressions
• mark-sexp: Marking Objects
• mark-whole-buffer: Marking Objects
• mark-word: Words
• mark-word: Marking Objects
• menu-bar-mode: Menu Bars
• menu-bar-open: Menu Bar
• 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-complete: Completion Commands
• minibuffer-complete-word: Completion Commands
• mode, thumbs: File Conveniences
• mode25: MS-DOS Display
• mode4350: MS-DOS Display
• modify-face: Face Customization
• morse-region: Amusements
• mouse-avoidance-mode: Mouse Avoidance
• mouse-buffer-menu: Buffer Menus
• mouse-choose-completion: Completion Commands
• 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: Wheeled Mice
• mouse-yank-at-click: Mouse Commands
• mouse-yank-secondary: Secondary Selection
• move-beginning-of-line: Moving Point
• move-end-of-line: Moving Point
• move-to-window-line: Moving Point
• mpuz: Amusements
• msb-mode: Buffer Menus
• msdos-set-mouse-buttons: MS-DOS Mouse
• multi-occur: Other Repeating Search
• multi-occur-in-matching-buffers: Other Repeating Search
• narrow-to-defun: Narrowing
• narrow-to-page: Narrowing
• narrow-to-region: Narrowing
• negative-argument: Arguments
• newline-and-indent: Basic Indent
• next-buffer: Select Buffer
• next-completion: Completion Commands
• next-error: Compilation Mode
• next-error-follow-minor-mode: Compilation Mode
• next-history-element: Minibuffer History
• next-line: Moving Point
• next-logical-line: Visual Line Mode
• next-matching-history-element: Minibuffer History
• normal-erase-is-backspace-mode: DEL Does Not Delete
• normal-mode: Choosing Modes
• not-modified: Save Commands
• nroff-mode: Nroff Mode
• number-to-register: RegNumbers
• nxml-mode: HTML Mode
• nxml-mode: Text
• occur: Other Repeating Search
• open-dribble-file: Checklist
• open-line: Blank Lines
• open-rectangle: Rectangles
• open-termscript: Checklist
• other-frame: Frame Commands
• other-window: Other Window
• outline-backward-same-level: Outline Motion
• outline-forward-same-level: Outline Motion
• outline-minor-mode: Outline Mode
• outline-mode: Outline Mode
• outline-next-visible-heading: Outline Motion
• outline-previous-visible-heading: Outline Motion
• outline-up-heading: Outline Motion
• overwrite-mode: Minor Modes
• 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: RegPos
• pong: Amusements
• pop-global-mark: Global Mark Ring
• pop-tag-mark: Find Tag
• pr-interface: Printing Package
• prefer-coding-system: Recognize Coding
• prepend-to-buffer: Accumulating Text
• prepend-to-register: RegText
• previous-buffer: Select Buffer
• previous-completion: Completion Commands
• previous-history-element: Minibuffer History
• previous-line: Moving Point
• 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
• 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
• quail-set-keyboard-layout: Select Input Method
• quail-show-key: Select Input Method
• query-replace: Query Replace
• query-replace-regexp: Query Replace
• quietly-read-abbrev-file: Saving Abbrevs
• quoted-insert: Inserting Text
• re-search-backward: Regexp Search
• re-search-forward: Regexp Search
• read-abbrev-file: Saving Abbrevs
• recenter-top-bottom: Scrolling
• recentf-edit-list: File Conveniences
• recentf-mode: 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
• remove-hook: Hooks
• remove-untranslated-filesystem: Text and Binary
• rename-buffer: Misc Buffer
• rename-file: Misc File Ops
• rename-uniquely: Misc Buffer
• repeat: Repeating
• repeat-complex-command: Repetition
• replace-regexp: Regexp Replace
• replace-string: Unconditional Replace
• report-emacs-bug: Checklist
• reposition-window: Scrolling
• reveal-mode: Outline Visibility
• revert-buffer: Reverting
• revert-buffer (Dired): Dired Updating
• revert-buffer-with-coding-system: Text Coding
• rgrep: Grep Searching
• rmail: Rmail
• rmail-add-label: Rmail Labels
• rmail-beginning-of-message: Rmail Scrolling
• rmail-bury: Rmail Basics
• 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-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
• run-lisp: External Lisp
• save-buffer: Save Commands
• save-buffers-kill-terminal: Exiting
• save-some-buffers: Save Commands
• scroll-all-mode: Emulation
• scroll-bar-mode: Scroll Bars
• scroll-down: Scrolling
• scroll-left: Horizontal Scrolling
• scroll-other-window: Other Window
• scroll-right: Horizontal Scrolling
• scroll-up: Scrolling
• sdb: Starting GUD
• search-backward: Nonincremental Search
• search-forward: Nonincremental Search
• select-frame-by-name: Non-Window Terminals
• send-invisible: Shell Mode
• serial-term: Serial Terminal
• server-edit: Invoking emacsclient
• server-start: Emacs Server
• set-buffer-file-coding-system: Text Coding
• set-buffer-process-coding-system: Communication Coding
• set-face-background: Faces
• set-face-foreground: Faces
• 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: Non-Window Terminals
• set-fringe-style: Fringes
• set-goal-column: Moving Point
• set-input-method: Select Input Method
• set-justification-center: Format Justification
• set-justification-full: Format Justification
• set-justification-left: Format Justification
• set-justification-none: Format Justification
• set-justification-right: Format Justification
• set-keyboard-coding-system: Terminal Coding
• set-language-environment: Language Environments
• set-left-margin: Format Indentation
• set-locale-environment: Language Environments
• set-mark-command: Setting Mark
• set-next-selection-coding-system: Communication Coding
• set-right-margin: Format 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
• 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-forward-command: Shell Mode
• shell-pushd-dextract: Shell Options
• shell-pushd-dunique: Shell Options
• shell-pushd-tohome: Shell Options
• show-all: Outline Visibility
• show-branches: Outline Visibility
• show-children: Outline Visibility
• show-entry: Outline Visibility
• show-paren-mode: Matching
• show-subtree: Outline Visibility
• 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-horizontally: Split Window
• split-window-vertically: Split Window
• spook: Mail Amusements
• standard-display-8bit: Unibyte Mode
• string-insert-rectangle: Rectangles
• string-rectangle: Rectangles
• studlify-region: Amusements
• substitute-key-definition: Init Examples
• subword-mode: Other C Commands
• sunrise-sunset: Sunrise/Sunset
• suspend-frame: Frame Commands
• suspend-frame: Exiting
• switch-to-buffer: Select Buffer
• switch-to-buffer-other-frame: Select Buffer
• switch-to-buffer-other-window: Select Buffer
• switch-to-completions: Completion Commands
• tab-to-tab-stop: Tab Stops
• tab-to-tab-stop: Indentation
• tabify: Just Spaces
• table-backward-cell: Cell Commands
• table-capture: Table Conversion
• table-delete-row: Row Commands
• table-fixed-width-mode: Fixed Width Mode
• table-forward-cell: Cell Commands
• table-generate-source: Table Misc
• table-heighten-cell: Cell Commands
• table-insert: Table Creation
• table-insert-column: Column Commands
• table-insert-row: Row Commands
• table-insert-sequence: Table Misc
• table-justify: Cell Justification
• table-narrow-cell: Cell Commands
• table-query-dimension: Measuring Tables
• 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
• tags-apropos: List Tags
• tags-loop-continue: Tags Search
• tags-query-replace: Tags Search
• tags-search: Tags Search
• term: Terminal emulator
• term-char-mode: Term Mode
• term-line-mode: Term Mode
• term-pager-toggle: Paging in Term
• tetris: Amusements
• tex-bibtex-file: TeX Print
• tex-buffer: TeX Print
• tex-close-latex-block: LaTeX Editing
• tex-compile: TeX Print
• tex-file: TeX Print
• tex-insert-braces: TeX Editing
• tex-insert-quote: TeX Editing
• tex-kill-job: TeX Print
• tex-latex-block: LaTeX Editing
• tex-mode: TeX Mode
• tex-print: TeX Print
• tex-recenter-output-buffer: TeX Print
• tex-region: TeX Print
• tex-show-print-queue: TeX Print
• tex-terminate-paragraph: TeX Editing
• tex-validate-region: TeX Editing
• tex-view: TeX Print
• text-mode: Text Mode
• text-scale-adjust: Temporary Face Changes
• text-scale-decrease: Temporary Face Changes
• text-scale-increase: Temporary Face Changes
• text-scale-mode: Temporary Face Changes
• text-scale-set: Temporary Face Changes
• thumbs-mode: File Conveniences
• time-stamp: Time Stamps
• timeclock-change: Time Intervals
• timeclock-in: Time Intervals
• timeclock-modeline-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-enable-multibyte-characters: Enabling Multibyte
• toggle-gdb-all-registers: Other GDB-UI Buffers
• toggle-input-method: Select Input Method
• toggle-read-only: Misc Buffer
• toggle-scroll-bar: Scroll Bars
• toggle-truncate-lines: Line Truncation
• tool-bar-mode: Tool Bars
• tooltip-mode: Tooltips
• top-level: Quitting
• tpu-edt-on: Emulation
• transient-mark-mode: Persistent Mark
• transpose-chars: Transpose
• transpose-lines: Transpose
• transpose-sexps: Expressions
• transpose-words: Transpose
• tty-suppress-bold-inverse-default-colors: Display Custom
• turn-on-flyspell: Spelling
• turn-on-font-lock: Font Lock
• ucs-insert: Inserting Text
• undigestify-rmail-message: Rmail Digest
• undo: Undo
• undo-only: 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
• variable-pitch-mode: Temporary Face Changes
• vc-annotate: Old Revisions
• vc-create-tag: Making Revision Tags
• vc-diff: Old Revisions
• vc-dir: VC Directory Mode
• vc-find-conflicted-file: Merging
• vc-insert-headers: Version Headers
• vc-merge: Merging
• vc-next-action: Basic VC Editing
• vc-print-log: VC Change Log
• vc-print-root-log: VC Change Log
• vc-register: Registering
• vc-rename-file: Renaming and VC
• vc-resolve-conflicts: Merging
• vc-retrieve-tag: Making Revision Tags
• vc-revert-buffer: VC Undo
• vc-revision-other-window: Old Revisions
• vc-rollback: VC Undo
• vc-switch-backend: Local Version Control
• vc-update-change-log: Change Logs and VC
• vi-mode: Emulation
• view-buffer: Misc Buffer
• 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-external-packages: Help Files
• view-file: Misc File Ops
• view-hello-file: International Chars
• view-lossage: Misc Help
• view-order-manuals: Help Files
• view-register: Registers
• vip-mode: Emulation
• viper-mode: Emulation
• visit-tags-table: Select Tags Table
• visual-line-mode: Visual Line Mode
• w32-register-hot-key: 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: International Chars
• what-cursor-position: Position Info
• what-line: Position Info
• what-page: Position Info
• where-is: Key Help
• which-function-mode: Which Function
• widen: Narrowing
• widget-backward: Changing a Variable
• widget-complete: Changing a Variable
• widget-forward: Changing a Variable
• windmove-default-keybindings: Window Convenience
• windmove-right: Window Convenience
• window-configuration-to-register: RegConfig
• winner-mode: Window Convenience
• woman: Man Page
• word-search-backward: Word Search
• word-search-forward: Word Search
• wordstar-mode: Emulation
• write-abbrev-file: Saving Abbrevs
• write-file: Save Commands
• write-region: Misc File Ops
• xdb: Starting GUD
• yank: Kill Ring
• yank-pop: Earlier Kills
• yank-rectangle: Rectangles
• yow: Amusements
• zap-to-char: Other Kill Commands
• zone: Amusements
• zrgrep: Grep Searching

Variable Index

• abbrev-all-caps: Expanding Abbrevs
• abbrev-file-name: Saving Abbrevs
• abbrev-mode: Abbrev Concepts
• 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-keep-changes-together: Change Log Commands
• 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
• apropos-do-all: Apropos
• apropos-documentation-sort-by-scores: Apropos
• apropos-sort-by-scores: Apropos
• 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-check-vc-info: VC Mode Line
• auto-revert-interval: Reverting
• 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-timeout: Auto Save Control
• auto-save-visited-file-name: Auto Save Files
• 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 Names
• backup-enable-predicate: Backup
• battery-mode-line-format: Optional Mode Line
• baud-rate: Display Custom
• bdf-directory-list: PostScript Variables
• blink-cursor-alist: Cursor Display
• blink-matching-delay: Matching
• blink-matching-paren: Matching
• blink-matching-paren-distance: Matching
• bookmark-save-flag: Bookmarks
• bookmark-search-size: Bookmarks
• browse-url-browser-function: Browse-URL
• buffer-file-coding-system: Output Coding
• buffer-read-only: Misc Buffer
• buffer-stale-function: Supporting additional buffers
• c-default-style: Custom C Indent
• c-hungry-delete-key: Hungry Delete
• c-mode-hook: Program Modes
• c-tab-always-indent: 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-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-load-hook: Calendar Customizing
• calendar-location-name: Sunrise/Sunset
• calendar-longitude: Sunrise/Sunset
• calendar-mark-diary-entries-flag: Displaying the Diary
• calendar-mark-holidays-flag: Holidays
• 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-today-invisible-hook: 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
• calenday-today-marker: Calendar Customizing
• cannot-suspend: Exiting
• case-fold-search: Search Case
• case-replace: Replacement and Case
• 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
• clone-indirect-buffer-hook: Indirect Buffers
• coding: Specify Coding
• colon-double-space: Fill Commands
• comint-completion-addsuffix: Shell Options
• comint-completion-autolist: Shell Options
• comint-completion-fignore: Shell Mode
• comint-completion-recexact: Shell Options
• comint-input-autoexpand: History References
• comint-input-ignoredups: Shell Options
• comint-move-point-for-output: Shell Options
• comint-prompt-read-only: Shell Options
• comint-prompt-regexp: Shell Prompts
• comint-scroll-show-maximum-output: Shell Options
• comint-scroll-to-bottom-on-input: 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-indent-function: Options for Comments
• comment-multi-line: Options for 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-auto-jump-to-first-error: Compilation Mode
• compilation-environment: Compilation
• compilation-error-regexp-alist: Compilation Mode
• compilation-scroll-output: Compilation
• compilation-skip-threshold: Compilation Mode
• compile-command: Compilation
• completion-auto-help: Completion Options
• completion-ignored-extensions: Completion Options
• completion-styles: Completion Options
• confirm-kill-emacs: Exiting
• confirm-nonexistent-file-or-buffer: Select Buffer
• confirm-nonexistent-file-or-buffer: Visiting
• crisp-override-meta-x: Emulation
• 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
• custom-buffer-done-function: Changing a Variable
• custom-enabled-themes: Custom Themes
• custom-file: Saving Customizations
• custom-theme-directory: Custom Themes
• 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-ignored-buffer-regexps: Dynamic Abbrevs
• dabbrev-limit: Dynamic Abbrevs
• dbx-mode-hook: GUD Customization
• debug-on-quit: Checklist
• default-directory: File Names
• default-input-method: Select Input Method
• default-justification: Format Justification
• delete-auto-save-files: Auto Save Files
• delete-by-moving-to-trash: Dired Deletion
• delete-by-moving-to-trash: Misc File Ops
• delete-old-versions: Backup Deletion
• desktop-clear-preserve-buffers-regexp: Saving Emacs Sessions
• desktop-globals-to-clear: Saving Emacs Sessions
• desktop-path: Saving Emacs Sessions
• desktop-restore-eager: Saving Emacs Sessions
• desktop-save-mode: Saving Emacs Sessions
• diary-bahai-entry-symbol: Non-Gregorian Diary
• 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: Format of Diary File
• 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-switches: Comparing Files
• diff-update-on-the-fly: Diff Mode
• directory-abbrev-alist: File Aliases
• directory-free-space-args: Directories
• directory-free-space-program: Directories
• dired-auto-revert-buffer: Dired Updating
• dired-chown-program: Operating on Files
• dired-copy-preserve-time: Operating on Files
• dired-dwim-target: Operating on Files
• dired-garbage-files-regexp: Flagging Many Files
• dired-isearch-filenames: Dired Navigation
• dired-kept-versions: Flagging Many Files
• dired-listing-switches: Dired Enter
• dired-listing-switches (MS-DOS): MS-DOS Processes
• dired-recursive-copies: Operating on Files
• dired-recursive-deletes: Dired Deletion
• display-battery-mode: Optional Mode Line
• display-buffer-reuse-frames: Select Buffer
• display-hourglass: 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-open-file-other-window: Drag and Drop
• doc-view-cache-directory: Conversion
• doc-view-continuous: Navigation
• doc-view-resolution: Document View
• 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
• echo-keystrokes: Display Custom
• emacs-lisp-mode-hook: Program Modes
• 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-translations: Requesting Formatted Text
• 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
• eval-expression-debug-on-error: Lisp Eval
• eval-expression-print-length: Lisp Eval
• eval-expression-print-level: Lisp Eval
• even-window-heights: Select Buffer
• exit-language-environment-hook: Language Environments
• explicit-shell-file-name: Interactive Shell
• ff-related-file-alist: Other C Commands
• file-coding-system-alist: Recognize Coding
• file-name-buffer-file-type-alist: Text and Binary
• file-name-coding-system: File Name Coding
• fill-column: Fill Commands
• 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-tag-marker-ring-length: Find Tag
• focus-follows-mouse: Frame Commands
• foldout-mouse-modifiers: Foldout
• font-lock-beginning-of-syntax-function: Font Lock
• font-lock-maximum-decoration: Font Lock
• font-lock-maximum-size: 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
• gdb-delete-out-of-scope: Watch Expressions
• gdb-many-windows: GDB-UI Layout
• gdb-mode-hook: GUD Customization
• gdb-show-changed-values: Watch Expressions
• gdb-speedbar-auto-raise: Watch Expressions
• gdb-use-colon-colon-notation: Watch Expressions
• gdb-use-separate-io-buffer: Other GDB-UI Buffers
• global-cwarn-mode: Other C Commands
• global-font-lock-mode: Font Lock
• grep-regexp-alist: Compilation Mode
• gud-gdb-command-name: GDB Graphical Interface
• gud-tooltip-echo-area: Debugger Operation
• gud-tooltip-mode: Debugger Operation
• gud-xdb-directories: Starting GUD
• help-at-pt-display-when-idle: Help Echo
• help-map: Prefix Keymaps
• hi-lock-exclude-modes: Highlight Interactively
• hi-lock-file-patterns-policy: Highlight Interactively
• hide-ifdef-shadow: Other C Commands
• highlight-nonselected-windows: Mark
• 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
• 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
• image-dired-external-viewer: Image-Dired
• imenu-auto-rescan: 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
• inhibit-eol-conversion: Recognize Coding
• inhibit-iso-escape-detection: Recognize Coding
• inhibit-startup-buffer-menu: Action Arguments
• inhibit-startup-screen: Initial Options
• inhibit-startup-screen: Entering Emacs
• initial-environment: Environment
• initial-scratch-message: Lisp Interaction
• input-method-highlight-flag: Input Methods
• input-method-verbose-flag: Input Methods
• insert-default-directory: File Names
• insert-default-directory: Minibuffer File
• interpreter-mode-alist: Choosing Modes
• isearch-allow-scroll: Isearch Scroll
• isearch-lazy-highlight: Repeat Isearch
• isearch-mode-map: Special Isearch
• isearch-resume-in-command-history: Repetition
• ispell-complete-word-dict: Spelling
• ispell-dictionary: Spelling
• ispell-local-dictionary: Spelling
• ispell-personal-dictionary: Spelling
• jdb-mode-hook: GUD Customization
• kept-new-versions: Backup Deletion
• kept-old-versions: Backup Deletion
• keyboard-coding-system: Terminal Coding
• kill-buffer-hook: Kill Buffer
• kill-do-not-save-duplicates: Kill Options
• kill-read-only-ok: Kill Options
• kill-ring: Earlier Kills
• kill-ring-max: Earlier Kills
• kill-whole-line: Killing by Lines
• kmacro-ring-max: Keyboard Macro Ring
• large-file-warning-threshold: Visiting
• latex-block-names: LaTeX Editing
• latex-mode-hook: TeX Misc
• latex-run-command: TeX Print
• latin1-display: Undisplayable Characters
• 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-directory-brief-switches: Directories
• list-directory-verbose-switches: Directories
• load-dangerous-libraries: Lisp Libraries
• load-path: 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
• 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-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-use-insert-directory-program: ls in Lisp
• ls-lisp-use-localized-time-format: ls in Lisp
• ls-lisp-verbosity: ls in Lisp
• magic-fallback-mode-alist: Choosing Modes
• magic-mode-alist: Choosing Modes
• mail-citation-hook: Citing Mail
• mail-default-headers: Mail Headers
• mail-from-style: Mail Headers
• mail-header-separator: Mail Format
• mail-mode-hook: Mail Misc
• mail-personal-alias-file: Mail Aliases
• mail-setup-hook: Mail Misc
• mail-signature: Mail Signature
• mail-signature-file: Mail Signature
• mail-user-agent: Mail Methods
• major-mode: Choosing Modes
• make-backup-file-name-function: Backup Names
• make-backup-files: Backup
• make-pointer-invisible: Mouse Avoidance
• make-pointer-invisible: Display Custom
• Man-fontify-manpage-flag: Man Page
• Man-switches: Man Page
• mark-even-if-inactive: Mark Ring
• mark-ring-max: Mark Ring
• max-mini-window-height: Minibuffer Edit
• menu-bar-mode: Menu Bars
• message-log-max: Echo Area
• message-send-hook: Mail Sending
• midnight-hook: Kill Buffer
• midnight-mode: Kill Buffer
• minibuffer-local-completion-map: Minibuffer Maps
• minibuffer-local-filename-completion-map: Minibuffer Maps
• minibuffer-local-map: Minibuffer Maps
• minibuffer-local-must-match-filename-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-copy-region: Mouse Commands
• mouse-highlight: Mouse References
• mouse-scroll-min-lines: Mouse Commands
• mouse-wheel-follow-mouse: Wheeled Mice
• mouse-wheel-progressive-speed: Wheeled Mice
• mouse-wheel-scroll-amount: Wheeled Mice
• mouse-yank-at-point: Mouse Commands
• next-error-highlight: Compilation Mode
• next-line-add-newlines: Moving Point
• next-screen-context-lines: Scrolling
• no-redraw-on-reenter: Display Custom
• nobreak-char-display: Text Display
• normal-erase-is-backspace: DEL Does Not Delete
• nroff-mode-hook: Nroff Mode
• ns-pop-up-frames: Mac / GNUstep Events
• ns-standard-fontset-spec: Defining Fontsets
• open-paren-in-column-0-is-defun-start: Left Margin Paren
• outline-level: Outline Format
• outline-minor-mode-prefix: Outline Mode
• outline-mode-hook: Outline Mode
• outline-regexp: Outline Format
• overflow-newline-into-fringe: Line Truncation
• overline-margin: Display Custom
• page-delimiter: Pages
• paragraph-separate: Paragraphs
• paragraph-start: Paragraphs
• 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
• print-region-function (MS-DOS): Windows Printing
• printer-name: Printing
• printer-name, (MS-DOS/MS-Windows): Windows Printing
• 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
• read-buffer-completion-ignore-case: Completion Options
• read-file-name-completion-ignore-case: Completion Options
• read-mail-command: Mail Methods
• read-quoted-char-radix: Inserting Text
• recenter-positions: Scrolling
• recenter-redisplay: Scrolling
• recentf-mode: File Conveniences
• require-final-newline: Customize Save
• resize-mini-windows: Minibuffer Edit
• revert-without-query: Reverting
• rmail-decode-mime-charset: Recognize Coding
• rmail-delete-after-output: Rmail Output
• rmail-delete-message-hook: Rmail Deletion
• rmail-displayed-headers: Rmail Display
• rmail-dont-reply-to-names: Rmail Reply
• rmail-edit-mode-hook: Rmail Editing
• rmail-enable-mime: Rmail Display
• rmail-file-coding-system: Recognize 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-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-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-window-size: Rmail Make Summary
• safe-local-eval-forms: Safe File Variables
• safe-local-variable-values: Safe File Variables
• same-window-buffer-names: Force Same Window
• same-window-regexps: Force Same Window
• save-abbrevs: Saving Abbrevs
• save-interprogram-paste-before-kill: Cut/Paste Other App
• scheme-mode-hook: Program Modes
• scroll-all-mode: Window Convenience
• scroll-bar-mode: Scroll Bars
• scroll-bar-width: Scroll Bars
• scroll-conservatively: Auto Scrolling
• scroll-down-aggressively: Auto Scrolling
• scroll-margin: Auto Scrolling
• scroll-preserve-screen-position: Scrolling
• scroll-up-aggressively: Auto Scrolling
• sdb-mode-hook: GUD Customization
• search-slow-speed: Slow Isearch
• search-slow-window-lines: Slow Isearch
• search-whitespace-regexp: Regexp Search
• select-active-regions: Cut/Paste Other App
• selective-display-ellipses: Selective Display
• send-mail-function: Mail Sending
• sendmail-coding-system: Mail Sending
• sendmail-coding-system: Output Coding
• sentence-end: Sentences
• sentence-end-double-space: Sentences
• sentence-end-without-period: Sentences
• server-host: emacsclient Options
• server-kill-new-buffers: Invoking emacsclient
• server-name: Emacs Server
• server-temp-file-regexp: Invoking emacsclient
• server-use-tcp: emacsclient Options
• server-window: Invoking emacsclient
• set-language-environment-hook: Language Environments
• set-mark-command-repeat-pop: Mark Ring
• sgml-xml-mode: HTML Mode
• shell-cd-regexp: Directory Tracking
• shell-command-default-error-buffer: Single Shell
• shell-command-regexp: Shell Mode
• shell-completion-execonly: Shell Options
• shell-completion-fignore: Shell Mode
• shell-file-name: Single Shell
• shell-input-ring-file-name: Shell Ring
• shell-popd-regexp: Directory Tracking
• shell-prompt-pattern: Shell Prompts
• shell-pushd-regexp: Directory Tracking
• show-trailing-whitespace: Useless Whitespace
• slitex-mode-hook: TeX Misc
• slitex-run-command: TeX Print
• small-temporary-file-directory: Backup
• sort-fold-case: Sorting
• sort-numeric-base: Sorting
• special-display-buffer-names: Special Buffer Frames
• special-display-frame-alist: Special Buffer Frames
• special-display-regexps: Special Buffer Frames
• split-height-threshold: Pop Up Window
• split-width-threshold: Pop Up Window
• split-window-keep-point: Split Window
• standard-fontset-spec: Defining Fontsets
• standard-indent: Format Indentation
• suggest-key-bindings: M-x
• tab-always-indent: Indentation
• tab-stop-list: Tab Stops
• tab-width: Indentation
• 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: List Tags
• tags-apropos-verbose: List Tags
• tags-case-fold-search: Tags Search
• tags-file-name: Select Tags Table
• tags-table-list: Select Tags Table
• tags-tag-face: List Tags
• temporary-file-directory: Backup
• term-file-prefix: Terminal Init
• term-setup-hook: Terminal Init
• 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-run-command: TeX Print
• tex-shell-hook: TeX Misc
• tex-show-queue-command: TeX Print
• 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-modeline-display: Time Intervals
• tool-bar-mode: Tool Bars
• tooltip-delay: Tooltips
• tooltip-gud-modes: Debugger Operation
• track-eol: Moving Point
• truncate-lines: Line Truncation
• truncate-partial-width-windows: Split Window
• 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
• user-full-name: Mail Headers
• user-mail-address: Init Examples
• user-mail-address: Mail Headers
• user-mail-address, initialization: General Variables
• vc-backend-header: Version Headers
• vc-command-messages: General VC Options
• vc-comment-alist: Version Headers
• vc-consult-headers: RCS and SCCS
• vc-cvs-global-switches: CVS Options
• vc-cvs-stay-local: CVS Options
• vc-cvs-stay-local: VC Directory Buffer
• vc-default-init-revision: Registering
• vc-diff-switches: Old Revisions
• vc-directory-exclusion-list: VC Directory Buffer
• vc-follow-symlinks: General VC Options
• vc-handled-backends: Customizing VC
• vc-initial-comment: Registering
• vc-keep-workfiles: General VC Options
• vc-log-mode-hook: Log Buffer
• vc-log-show-limit: VC Change Log
• vc-make-backup-files: General VC Options
• vc-make-backup-files: Backup
• vc-mistrust-permissions: RCS and SCCS
• vc-path: General VC Options
• vc-rcs-diff-switches: Old Revisions
• vc-static-header-alist: Version Headers
• vc-stay-local: CVS Options
• vc-stay-local: VC Directory Buffer
• vc-suppress-confirm: General VC Options
• version-control: Backup Names
• visible-bell: Display Custom
• visible-cursor: Cursor Display
• 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-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-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-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-use-visible-system-caret: Windows Misc
• which-func-modes: Which Function
• window-min-height: Change Window
• window-min-width: Change Window
• write-region-inhibit-fsync: Customize Save
• x-cut-buffer-max: Cut/Paste Other App
• x-gtk-file-dialog-help-text: Dialog Boxes
• x-gtk-show-hidden-files: Dialog Boxes
• x-gtk-use-old-file-dialog: Dialog Boxes
• x-mouse-click-focus-ignore-position: Mouse Commands
• x-select-enable-clipboard: Clipboard
• x-select-request-type: Communication Coding
• x-stretch-cursor: Cursor Display
• x-underline-at-descent-line: Display Custom
• xdb-mode-hook: GUD Customization
• yank-excluded-properties: Kill Ring
• yank-pop-change-selection: Cut/Paste Other App

Concept Index

• $ in file names: File Names
• ( in leftmost column: Left Margin Paren
• ‘*Messages*’ buffer: Echo Area
• –/—/.-./.../.: Amusements
• .dir-locals.el file: Directory Variables
• .mailrc file: Mail Aliases
• .timelog file: Time Intervals
• // in file name: Minibuffer File
• 8-bit display: Unibyte Mode
• 8-bit input: Unibyte Mode
• <BACKSPACE> vs <DEL>: DEL Does Not Delete
• <DEL> vs <BACKSPACE>: DEL Does Not Delete
• <ESC> replacing <Meta> key: User Input
• ‘?’ in display: International Chars
• _emacs init file, MS-Windows: Windows HOME
• A and B buffers (Emerge): Overview of Emerge
• 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
• adaptive filling: Adaptive Fill
• Adding to the kill ring in Dired.: Misc Dired Features
• addpm, MS-Windows installation program: MS-Windows Registry
• adjust buffer face height: Temporary Face Changes
• againformation: Dissociated Press
• aggressive scrolling: Auto Scrolling
• alarm clock: Appointments
• alignment for comments: Comment Commands
• Alt key (MS-Windows): Windows Keyboard
• Alt key invokes menu (Windows): Windows Keyboard
• 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
• anonymous FTP: Remote Files
• appending kills in the ring: Appending Kills
• appointment notification: Appointments
• apropos: Apropos
• apropos search results, order by score: Apropos
• arc: File Archives
• Arch: Version Control Systems
• Archive mode: File Archives
• arguments (command line): Emacs Invocation
• arguments to commands: Arguments
• arrow keys: Moving Point
• ASCII: User Input
• ASCII art: Text
• Asm mode: Asm Mode
• assembler mode: Asm Mode
• astronomical day numbers: Calendar Systems
• 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 Save mode: Auto Save
• Auto-Lower mode: Frame Parameters
• Auto-Raise mode: Frame Parameters
• Auto-Revert mode: Reverting
• auto-save for remote files: Auto Save Files
• autoload: Lisp Libraries
• autoload Lisp libraries: Init Examples
• automatic typing: Text
• automatic version backups: Version Backups
• autotyping: Text
• available colors: Colors
• avoiding mouse in the way of your typing: Mouse Avoidance
• AWK mode: C Modes
• back end (version control): Version Control Systems
• back reference, in regexp: Regexp Backslash
• back reference, in regexp replacement: Regexp Replace
• background color, command-line argument: Colors
• background mode, on xterm: General Variables
• background syntax highlighting: Font Lock
• backtrace for bug reports: Checklist
• backup file: Backup
• backup file names on MS-DOS: MS-DOS File Names
• backup, and user-id: Backup Copying
• backups for remote files: Remote Files
• Baha'i calendar: Calendar Systems
• balanced expression: Expressions
• balloon help: Help Echo
• base buffer: Indirect Buffers
• batch mode: Initial Options
• Bazaar: Version Control Systems
• binary files, on MS-DOS/MS-Windows: Text and Binary
• binding: Commands
• binding keyboard macros: Save Keyboard Macro
• binding keys: Rebinding
• blank lines: Blank Lines
• blank lines in programs: Multi-Line Comments
• blinking cursor disable, command-line argument: Misc X
• body lines (Outline mode): Outline Format
• bold font: Face Customization
• bookmarks: Bookmarks
• border color, command-line argument: Colors
• borders (X Window System): Borders X
• boredom: Amusements
• brace in column zero and fontification: Font Lock
• braces, moving across: Moving by Parens
• branch (version control): Branches
• Brief emulation: Emulation
• Browse-URL: Browse-URL
• buffer definitions index: Imenu
• buffer list, customizable: Buffer Menus
• buffer menu: Buffer Menus
• buffer menu: Several Buffers
• buffer size display: Optional Mode Line
• buffer size, maximum: Buffers
• buffers: Buffers
• buggestion: Dissociated Press
• bugs: Bugs
• building programs: Building
• button down events: Mouse Buttons
• 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 editing: Programs
• C mode: C Modes
• C++ class browser, tags: Tags
• 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
• candle lighting times: Sexp Diary Entries
• capitalizing words: Case
• case conversion: Case
• case-sensitivity and completion: Completion Options
• case-sensitivity and tags search: Tags Search
• categories of characters: Regexp Backslash
• cell text justification: Cell Justification
• Celtic: International
• centering: Fill Commands
• centralized version control: VCS Repositories
• change buffers: Select Buffer
• change log: Change Log
• Change Log mode: Change Log Commands
• changes, undoing: Undo
• changesets: 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
• character set (keyboard): User Input
• character set of character at point: International Chars
• character syntax: Init Syntax
• characters (in text): Text Display
• characters in a certain charset: Charsets
• characters which belong to a specific language: Regexp Backslash
• charsets: Charsets
• checking out files: VCS Concepts
• checking spelling: Spelling
• checking syntax: Flymake
• Chinese: International
• Chinese calendar: Calendar Systems
• choosing a major mode: Choosing Modes
• ciphers: Amusements
• citing mail: Citing Mail
• class browser, C++: Tags
• click events: Mouse Buttons
• client-side fonts: Fonts
• clipboard: Clipboard
• codepage, MS-DOS: MS-DOS and MULE
• coding systems: Coding Systems
• collision: Interlocking
• color customization, in init file: Creating Frames
• color emulation on black-and-white printers: PostScript Variables
• color of window, from command line: Colors
• 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
• comments: Comments
• comments on customized settings: Changing a Variable
• 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 under MS-DOS: MS-DOS Processes
• complete key: Keys
• completion: Completion
• completion (Lisp symbols): Symbol Completion
• completion (symbol names): Symbol Completion
• compose character: Unibyte Mode
• compressing files (in Dired): Operating on Files
• compression: Compressed Files
• Conf mode: Program Modes
• confirming in the minibuffer: Select Buffer
• confirming in the minibuffer: Visiting
• conflicts: Merging
• connecting to remote host: Remote Host
• continuation line: Continuation Lines
• contributing to Emacs: Contributing
• Control: User Input
• control characters: User Input
• Control-Meta: Expressions
• converting text to upper or lower case: Case
• Coptic calendar: Calendar Systems
• copy: Clipboard
• copying files: Misc File Ops
• copying files (in Dired): Operating on Files
• copying text: Yanking
• CORBA IDL mode: C Modes
• correcting spelling: Spelling
• CPerl mode: Program Modes
• crashes: Auto Save
• create a text-based table: Table Creation
• creating files: Visiting
• creating frames: Creating Frames
• CRiSP mode: Emulation
• cryptanalysis: Amusements
• CSSC: Version Control Systems
• CUA key bindings: CUA Bindings
• current buffer: Buffers
• current function name in mode line: Which Function
• cursor: Point
• cursor color, command-line argument: Colors
• 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, locating visually: Cursor Display
• custom themes: Custom Themes
• 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
• cut: Clipboard
• cut and paste: Glossary
• cut buffer: Cut/Paste Other App
• cutting text: Killing
• cvs: VC Directory Mode
• CVS: Version Control Systems
• CVS directory mode: VC Directory Mode
• cvs watch feature: CVS Options
• CVSREAD environment variable (CVS): CVS Options
• CWarn mode: Other C Commands
• Cyrillic: International
• Czech: International
• daemon, Emacs: Emacs Server
• day of year: General Calendar
• daylight saving time: Daylight Saving
• DBX: Debuggers
• dead character: Unibyte Mode
• 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 face height: Temporary Face Changes
• default argument: Minibuffer
• default-frame-alist: Creating Frames
• default.el file, not loading: Initial Options
• default.el, the default init file: Init File
• defining keyboard macros: Keyboard Macros
• defuns: Moving by Defuns
• delete column in table: Column Commands
• delete row in table: Row Commands
• Delete Selection mode: Mouse Commands
• Delete Selection mode: Using Region
• deleting auto-save files: Flagging Many Files
• deleting blank lines: Blank Lines
• deleting characters and lines: Erasing
• deleting files (in Dired): Dired Deletion
• deleting some backup files: Flagging Many Files
• deletion: Killing
• deletion (of files): Misc File Ops
• deletion (Rmail): Rmail Deletion
• Delphi mode: Program Modes
• desktop: Saving Emacs Sessions
• desktop shortcut, MS-Windows: Windows Startup
• Devanagari: International
• developediment: Dissociated Press
• device for Emacs terminal I/O: Initial Options
• dialog boxes: Dialog Boxes
• 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 local variables: Directory Variables
• directory name abbreviation: File Aliases
• directory tracking: Directory Tracking
• directory where Emacs starts on MS-Windows: Windows Startup
• Dired: Dired
• Dired and version control: Misc Dired Features
• Dired sorting: Dired Updating
• Dired, and MS-Windows/MS-DOS: ls in Lisp
• 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 name (X Window System): Display X
• display of buffer size: Optional Mode Line
• display of line number: Optional Mode Line
• DNS mode: Program Modes
• doc-view-minor-mode: Document View
• DocTeX mode: TeX Mode
• doctor: Total Frustration
• document viewer (DocView): Document View
• 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
• Dutch: International
• DVI file: Document View
• Ebrowse: Tags
• echo area: 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
• EDT: Emulation
• Eldoc mode: Lisp Doc
• Eliza: Total Frustration
• Emacs as a server: Emacs Server
• Emacs Development Environment: EDE
• EMACS environment variable: Interactive Shell
• Emacs icon, a gnu: Icons X
• Emacs initialization file: Init File
• Emacs-Lisp mode: Lisp Eval
• EMACS_SERVER_FILE environment variable: emacsclient Options
• emacsclient: Emacs Server
• emacsclient invocation: Invoking emacsclient
• emacsclient options: emacsclient Options
• emacsclient.exe: Windows Startup
• emacsclientw.exe: Windows Startup
• email: Sending Mail
• Emerge: Emerge
• emulating other editors: Emulation
• emulation of Brief: Emulation
• encoding of characters: International
• end-of-line conversion: Coding Systems
• end-of-line conversion on MS-DOS/MS-Windows: Text and Binary
• end-of-line conversion, mode-line indication: Mode Line
• enlarge a table cell: Cell Commands
• Enriched mode: Formatted Text
• entering Emacs: Entering Emacs
• environment variables: Environment
• environment variables for subshells: Interactive Shell
• environment variables in file names: File Names
• erasing characters and lines: Erasing
• error log: Compilation
• error message in the echo area: Echo Area
• errors in init file: Initial Options
• escape sequences in files: Recognize Coding
• ESHELL environment variable: Interactive Shell
• etags program: Create Tags Table
• Ethiopic: International
• Ethiopic calendar: Calendar Systems
• Euro sign: Language Environments
• European character sets: Unibyte Mode
• evaluate expression, command-line argument: Action Arguments
• 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
• face at point: International Chars
• face colors, setting: Faces
• face customization, in init file: Creating Frames
• faces: Faces
• faces for highlighting query replace: Query Replace
• faces for highlighting search matches: Basic Isearch
• faces under MS-DOS: MS-DOS Display
• failed merges: Comparing Files
• Feedmail: Mail Sending
• FFAP minor mode: FFAP
• 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 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, quote special characters: Quoted File Names
• 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-name completion, on MS-Windows: Windows Files
• files: Files
• files, visiting and saving: Visiting
• filesets: Filesets
• filesets, VC: Basic VC Editing
• fill prefix: Fill Prefix
• filling text: Filling
• find: File Name Cache
• find and Dired: Dired and Find
• find Info manual by its file name: Misc Help
• 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
• fix width of table cells: Fixed Width Mode
• fixing incorrectly decoded mail messages: Rmail Coding
• flagging files (in Dired): Dired Deletion
• flagging many files for deletion (in Dired): Flagging Many Files
• Flyspell mode: Spelling
• folding editing: Foldout
• Follow mode: Follow Mode
• font (default): Creating Frames
• font antialiasing (MS Windows): Windows Fonts
• font for menus: Table of Resources
• Font Lock mode: Font Lock
• font name (X Window System): Font X
• font of character at point: International Chars
• font properties (MS Windows gdi backend): Windows Fonts
• font properties (MS Windows): Windows Fonts
• font scripts (MS Windows): Windows Fonts
• font specification (MS Windows): Windows Fonts
• font unicode subranges (MS Windows): Windows Fonts
• fontconfig: Fonts
• fonts: Fonts
• fonts and faces: Face Customization
• fonts for PostScript printing: PostScript Variables
• fonts for various scripts: Language Environments
• fonts, emulating under MS-DOS: MS-DOS Display
• fontsets: Fontsets
• fontsets, modifying: Modifying Fontsets
• foreground color, command-line argument: Colors
• formatted text: Formatted Text
• formfeed character: Pages
• Fortran 77 and Fortran 90, 95, 2003: 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 focus policy, MS-Windows: Windows Misc
• frame size under MS-DOS: MS-DOS Display
• frame title, command-line argument: Title X
• frames: Frames
• frames on MS-DOS: MS-DOS Display
• French Revolutionary calendar: Calendar Systems
• fringe face: Standard Faces
• fringes: Fringes
• fringes, and continuation lines: Continuation Lines
• fringes, and current execution line in GUD: Debugger Operation
• fringes, and unused line indication: Useless Whitespace
• 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 definition: Commands
• function key: Keymaps
• function, move to beginning or end: Moving by Defuns
• gamma correction: Table of Resources
• gateway, and remote file access with ange-ftp: Remote Files
• GDB: Debuggers
• GDB commands in Fringe: Source Buffers
• GDB User Interface layout: GDB-UI Layout
• geometry of Emacs window: Window Size X
• geometry, command-line argument: Window Size X
• German: International
• getting help with keys: Basic Help
• Ghostscript, use for PostScript printing: Windows Printing
• git: Version Control Systems
• Glasses mode: Glasses
• Global Auto-Revert mode: Reverting
• global keymap: Keymaps
• global mark: CUA Bindings
• global mark ring: Global Mark Ring
• global substitution: Replace
• GNU Arch: Version Control Systems
• Gnus: Gnus
• GNUstep: Mac OS / GNUstep
• Go Moku: Amusements
• Goto Address mode: Goto Address mode
• graphic characters: Inserting Text
• Greek: International
• Gregorian calendar: Other Calendars
• growing minibuffer: Minibuffer Edit
• GTK resources and customization: GTK resources
• GTK styles: GTK styles
• GTK widget classes: GTK Names in Emacs
• GTK widget names: GTK Names in Emacs
• GTK widget names: GTK widget names
• GUD library: Debuggers
• gzip: Compressed Files
• handwriting: PostScript
• hard links (creation): Misc File Ops
• hard links (in Dired): Operating on Files
• hard links (visiting): File Aliases
• hard newline: Hard and Soft Newlines
• hardcopy: Printing
• head revision: Branches
• header (TeX mode): TeX Print
• header line (Dired): Subdirectory Motion
• headers (of mail message): Mail Headers
• heading lines (Outline mode): Outline Format
• Hebrew: International
• Hebrew calendar: Calendar Systems
• height of minibuffer: Minibuffer Edit
• help: Help
• help text, in GTK+ file chooser: Dialog Boxes
• help, viewing web pages: Help Mode
• 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
• 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 region: Persistent Mark
• Hindi: International
• history of commands: Repetition
• history of minibuffer input: Minibuffer History
• 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
• hook: Hooks
• 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
• hyperlinking: Hyperlinking
• iCalendar support: Importing Diary
• Icomplete mode: Completion Options
• Icon mode: Program Modes
• iconifying: Exiting
• icons (X Window System): Icons X
• icons, toolbar: Tool Bars
• identifiers, making long ones readable: Glasses
• IDL mode: C Modes
• ignored file names, in completion: Completion Options
• ignoriginal: Dissociated Press
• image-dired: Image-Dired
• image-dired mode: Image-Dired
• images, viewing: File Conveniences
• IMAP mailboxes: Remote Mailboxes
• in-situ subdirectory (Dired): Subdirectories in Dired
• inbox file: Rmail Inbox
• incorrect fontification: Font Lock
• increase buffer face height: Temporary Face Changes
• incremental search: Incremental Search
• 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
• Info index completion: Symbol Completion
• init file: Init File
• init file .emacs on MS-Windows: Windows HOME
• init file, and non-ASCII characters: Enabling Multibyte
• init file, default name under MS-DOS: MS-DOS File Names
• init file, not loading: Initial Options
• initial options (command line): Emacs Invocation
• initial revision ID to register: Registering
• initial-frame-alist: Creating Frames
• input event: User Input
• input methods: Input Methods
• input methods, X: Table of Resources
• input with the keyboard: User Input
• insert column in table: Column Commands
• insert file contents, command-line argument: Action Arguments
• insert row in table: Row Commands
• insert string into table cells: Table Misc
• inserted subdirectory (Dired): Subdirectories in Dired
• inserting blank lines: Blank Lines
• insertion: Inserting Text
• INSIDE_EMACS environment variable: Interactive Shell
• Integrated development environment: EDE
• interactive highlighting: Highlight Interactively
• 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
• Intlfonts for PostScript printing: PostScript Variables
• Intlfonts package, installation: Language Environments
• invisible lines: Outline Mode
• invocation (command line arguments): Emacs Invocation
• invoking Emacs from Windows Explorer: Windows Startup
• IPA: International
• isearch: Incremental Search
• 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
• Iswitchb mode: Iswitchb
• italic font: Face Customization
• Japanese: International
• jar: File Archives
• Java class archives: File Archives
• Java mode: C Modes
• Javascript mode: Program Modes
• JDB: Debuggers
• Julian calendar: Calendar Systems
• Julian day numbers: Calendar Systems
• just-in-time (JIT) font-lock: Font Lock
• justification: Fill Commands
• Kerberos POP authentication: Remote Mailboxes
• key: Keys
• key bindings: Key Bindings
• key rebinding, permanent: Init File
• key rebinding, this session: Rebinding
• key sequence: Keys
• keyboard input: User Input
• keyboard macro: Keyboard Macros
• 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
• 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: Killing
• Korean: International
• label (Rmail): Rmail Labels
• landmark game: Amusements
• language environment, automatic selection on MS-DOS: MS-DOS and MULE
• language environments: Language Environments
• Lao: International
• LaTeX mode: TeX Mode
• LaTeX references: TeX Misc
• Latin: International
• Latin-1 TeX encoding: TeX Misc
• lazy search highlighting: Repeat Isearch
• leading: Table of Resources
• leaving Emacs: Exiting
• LessTif Widget X Resources: LessTif Resources
• libraries: Lisp Libraries
• Life: Amusements
• line endings: Coding Systems
• line number commands: Position Info
• line number display: Optional Mode Line
• line spacing: Table of Resources
• line spacing, command-line argument: Misc X
• line truncation, and fringes: Line Truncation
• line truncation, and fringes: Continuation Lines
• line wrapping: Continuation Lines
• lines, highlighting: Highlight Interactively
• links (customization buffer): Customization Groups
• Linum mode: Minor Modes
• Lisp character syntax: Init Syntax
• Lisp editing: Programs
• Lisp files byte-compiled by XEmacs: Lisp Libraries
• Lisp files, and multibyte operation: Enabling Multibyte
• 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
• load init file of another user: Initial Options
• 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 back end (version control): Local Version Control
• local keymap: Local Keymaps
• local variables: Locals
• local variables in files: File Variables
• local variables, for all files in a directory: Directory Variables
• local version control: Local Version Control
• locale, date format: Time Stamps
• locales: Language Environments
• location of point: Position Info
• locking (CVS): CVS Options
• locking files: Interlocking
• locking versus merging: VCS Merging
• locking, non-strict (RCS): RCS and SCCS
• log File, types of: Types of Log File
• logging keystrokes: Checklist
• long file names in DOS box under Windows 95/NT: MS-DOS File Names
• Long Lines minor mode: Longlines
• looking for a subject in documentation: Help
• lpr usage under MS-DOS: Windows Printing
• ls emulation: ls in Lisp
• Lucid Widget X Resources: Lucid Resources
• lzh: File Archives
• M-: User Input
• M-<TAB> vs Alt-<TAB> (MS-Windows): Windows Keyboard
• M4 mode: Program Modes
• Mac OS X: Mac OS / GNUstep
• Macintosh: Mac OS / GNUstep
• Macintosh end-of-line conversion: Coding Systems
• Macintosh key bindings: Emulation
• 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
• major modes: Major Modes
• make: Compilation
• Makefile mode: Program Modes
• making pictures out of text characters: Picture Mode
• man pages, and local file variables: Specifying File Variables
• manipulating paragraphs: Paragraphs
• manipulating sentences: Sentences
• manipulating text: Text
• manual page: Man Page
• manual pages, on MS-DOS/MS-Windows: Man Page
• manual version backups: Version Backups
• manuals, on-line: Misc Help
• Marathi: International
• 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
• Markov chain: Dissociated Press
• 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: Calendar Systems
• Mayan calendar round: Mayan Calendar
• Mayan haab calendar: Mayan Calendar
• Mayan long count: Mayan Calendar
• Mayan tzolkin calendar: Mayan Calendar
• memory full: Memory Full
• menu bar: Table of Resources
• menu bar: Menu Bar
• menu bar access using keyboard (MS-Windows): Windows Keyboard
• menu bar appearance: Standard Faces
• Menu Bar mode: Menu Bars
• menu face, no effect if customized: Standard Faces
• Menu X Resources (LessTif widgets): LessTif Resources
• Menu X Resources (Lucid widgets): Lucid Resources
• Mercurial: Version Control Systems
• merge buffer (Emerge): Overview of Emerge
• merges, failed: Comparing Files
• merging changes: Merging
• merging files: Emerge
• message: Sending Mail
• Message mode: Mail Commands
• Message mode for sending mail: Mail Methods
• message number: 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 Windows: Microsoft Windows
• Midnight mode: Kill Buffer
• MIME: Mail Misc
• MIME messages (Rmail): Rmail Display
• minibuffer: Minibuffer
• minibuffer: Echo Area
• minibuffer confirmation: Select Buffer
• minibuffer confirmation: Visiting
• minibuffer history: Minibuffer History
• minibuffer history, searching: Isearch Minibuffer
• minibuffer keymaps: Minibuffer Maps
• minibuffer-prompt face: Standard Faces
• minimizing a frame: Exiting
• minimizing a frame at startup: Icons X
• minor mode keymap: Local Keymaps
• minor modes: Minor Modes
• mistakes, correcting: Fixit
• mode hook: 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 Save: Auto Save
• mode, Auto-Revert: Reverting
• 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, CRiSP: Emulation
• mode, Delete Selection: Mouse Commands
• mode, Delete Selection: Using Region
• mode, DocTeX: TeX Mode
• mode, DocView: Document View
• mode, Emacs-Lisp: Lisp Eval
• mode, Enriched: Formatted Text
• mode, Follow: Follow Mode
• mode, Font Lock: Font Lock
• mode, Fortran: Fortran
• mode, Global Auto-Revert: Reverting
• mode, Hexl: Editing Binary Files
• mode, HTML: HTML Mode
• mode, Iswitchb: Iswitchb
• mode, Java: C Modes
• mode, LaTeX: TeX Mode
• mode, Mail: Mail Methods
• mode, major: Major Modes
• mode, Menu Bar: Menu Bars
• mode, Message: Mail Commands
• mode, minor: Minor Modes
• mode, Mouse Wheel: Wheeled Mice
• mode, MSB: Buffer Menus
• mode, nXML: HTML Mode
• mode, nXML: Text
• mode, Objective C: C Modes
• mode, Outline: Outline Mode
• mode, Overwrite: Minor Modes
• mode, Paragraph-Indent Text: Text Mode
• mode, Pike: C Modes
• mode, Scroll Bar: Scroll Bars
• mode, Scroll-all: Window Convenience
• mode, SGML: HTML Mode
• mode, Shell: Shell Mode
• mode, SliTeX: TeX Mode
• mode, tar: File Archives
• mode, Term: Term Mode
• mode, TeX: TeX Mode
• mode, Text: Text Mode
• mode, Tool Bar: Tool Bars
• mode, Transient Mark: Persistent Mark
• mode, View: Misc File Ops
• mode, Winner: Window Convenience
• mode, XML: Text
• modes for programming languages: Program Modes
• modes, Long Lines: Longlines
• modes, Refill: Refill
• modification dates: Time Stamps
• modified (buffer): Visiting
• modifier keys: Modifier Keys
• modifier keys: User Input
• Modula2 mode: Program Modes
• moon, phases of: Lunar Phases
• Morse code: Amusements
• Motif key bindings: Emulation
• mouse avoidance: Mouse Avoidance
• mouse button events: Mouse Buttons
• mouse buttons (what they do): Mouse Commands
• mouse on mode line: Mode Line Mouse
• mouse pointer: Display Custom
• mouse pointer color, command-line argument: Colors
• mouse support: Text-Only Mouse
• mouse support under MS-DOS: MS-DOS Mouse
• mouse wheel: Wheeled Mice
• Mouse Wheel minor mode: Wheeled Mice
• mouse, and MS-Windows: Windows Mouse
• 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-DOG: MS-DOS
• 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: Cut/Paste Other App
• MS-Windows, Emacs peculiarities: Microsoft Windows
• MSB mode: Buffer Menus
• MULE: International
• multibyte characters: International
• multibyte operation, and Lisp files: Enabling Multibyte
• multiple displays: Multiple Displays
• multiple views of outline: Outline Views
• multiple windows in Emacs: Windows
• multiple-file search and replace: Tags Search
• Multipurpose Internet Mail Extensions: Mail Misc
• mustatement: Dissociated Press
• narrowing: Narrowing
• narrowing, and line number display: Optional Mode Line
• navigation: Hyperlinking
• ‘net use’, and printing on MS-Windows: Windows Printing
• networked printers (MS-Windows): Windows Printing
• newline: Inserting Text
• newlines, hard and soft: Hard and Soft Newlines
• Next Error Follow mode: Compilation Mode
• NFS and quitting: Quitting
• nil: Glossary
• no-break hyphen, display: Text Display
• no-break space, display: Text Display
• non-ASCII characters in .emacs: Init Non-ASCII
• non-ASCII keys, binding: Init Non-ASCII
• 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-strict locking (RCS): RCS and SCCS
• non-window terminals: Non-Window Terminals
• nonincremental search: Nonincremental Search
• normal hook: Hooks
• nroff: Nroff Mode
• NSA: Mail Amusements
• numeric arguments: Arguments
• nXML mode: HTML Mode
• nXML mode: Text
• Objective C mode: C Modes
• Octave mode: Program Modes
• omer count: Sexp Diary Entries
• on-line manuals: Misc Help
• open file: Visiting
• open-parenthesis in leftmost column: Left Margin Paren
• operating on files in Dired: Operating on Files
• operations on a marked region: Using Region
• option, user: Variables
• options (command line): Emacs Invocation
• other editors: Emulation
• out of memory: Memory Full
• Outline mode: Outline Mode
• outline with multiple views: Outline Views
• outragedy: Dissociated Press
• overlays at character position: Editing Format Info
• override character terminal color support: Colors
• Overwrite mode: Minor Modes
• page-at-a-time: Paging in Term
• pages: Pages
• Pango font name: GTK styles
• 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: Font Lock
• parenthetical groupings: Moving by Parens
• parts of the screen: Screen
• paste: Clipboard
• pasting: Yanking
• patches, editing: Diff Mode
• patches, sending: Sending Patches
• PC key bindings: Emulation
• PC selection: Emulation
• PCL-CVS: VC Directory Mode
• PDB: Debuggers
• PDF file: Document View
• per-buffer variables: Locals
• per-directory local variables: Directory Variables
• Perl mode: Program Modes
• Perldb: Debuggers
• Persian calendar: Calendar Systems
• phases of the moon: Lunar Phases
• Picture mode and rectangles: Rectangles in Picture
• pictures: Picture Mode
• Pike mode: C Modes
• point: Point
• point location: Position Info
• point location, on MS-DOS: Text and Binary
• Polish: International
• Pong game: Amusements
• POP mailboxes: Remote Mailboxes
• position and size of Emacs frame: Window Size X
• Postscript file: Document View
• PostScript mode: Program Modes
• prefix arguments: Arguments
• prefix key: Keys
• preprocessor highlighting: Other C Commands
• presidentagon: Dissociated Press
• pretty-printer: Program Indent
• primary Rmail file: Rmail Basics
• primary selection: Cut/Paste Other App
• printing: Printing
• printing files (in Dired): Operating on Files
• Printing package: Printing Package
• printing under MS-DOS: MS-DOS Processes
• program building: Building
• program editing: Programs
• Prolog mode: Program Modes
• prompt: Minibuffer
• prompt, shell: Shell Prompts
• properbose: Dissociated Press
• PS file: Document View
• puzzles: Amusements
• Python mode: Program Modes
• query replace: Query Replace
• quitting: Quitting
• quitting (in search): Error in Isearch
• quitting Emacs: Exiting
• quitting on MS-DOS: MS-DOS Keyboard
• quoting: Inserting Text
• quoting file names: Quoted File Names
• rar: File Archives
• RCS: Version Control Systems
• read-only buffer: Misc Buffer
• read-only text, killing: Kill Options
• reading mail: Rmail
• reading netnews: Gnus
• rebinding keys, permanently: Init File
• rebinding major mode keys: Init Rebinding
• rebinding mouse buttons: Mouse Buttons
• rebinding non-ASCII keys: Init Non-ASCII
• rectangle: Rectangles
• rectangle highlighting: CUA Bindings
• rectangles and Picture mode: Rectangles in Picture
• recursive copying: Operating on Files
• recursive deletion: Dired Deletion
• recursive editing level: Recursive Edit
• recycle bin: Misc File Ops
• redefining keys, this session: Rebinding
• redo: Undo
• references, LaTeX: TeX Misc
• Refill minor mode: Refill
• refilling text, word processor style: Longlines
• refilling text, word processor style: Refill
• refreshing displayed files: Dired Updating
• RefTeX package: TeX Misc
• regexp: Regexps
• regexp search: Regexp Search
• region: Mark
• region highlighting: Persistent Mark
• registered file: VCS Concepts
• registers: Registers
• Registry (MS-Windows): Resources
• registry, setting environment variables and resources on MS-Windows: MS-Windows Registry
• 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: Remote Repositories
• remote repositories (CVS): CVS Options
• remove indentation: Indentation Commands
• renaming files (in Dired): Operating on Files
• repeating a command: Repeating
• replacement: Replace
• reply to a message: Rmail Reply
• reporting bugs: Checklist
• repository: VCS Concepts
• reread a file: Reverting
• resizing minibuffer: Minibuffer Edit
• 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 POP inboxes: Remote Mailboxes
• reverse video, command-line argument: Colors
• revision: VCS Concepts
• revision ID: VCS Concepts
• revision ID in version control: Advanced C-x v v
• risky variable: Safe File Variables
• Rlogin: Remote Host
• Rmail: Rmail
• Rmail file sorting: Rmail Sorting
• Romanian: International
• rosh hodesh: Sexp Diary Entries
• rot13 code: Rmail Rot13
• Ruby mode: Program Modes
• runemacs.exe: Windows Startup
• running a hook: Hooks
• running Lisp functions: Building
• saved echo area messages: Echo Area
• saving a setting: Changing a Variable
• saving file name in a register: RegFiles
• saving files: Visiting
• saving keyboard macros: Save Keyboard Macro
• saving number in a register: RegNumbers
• saving position in a register: RegPos
• saving rectangle in a register: RegRect
• saving sessions: Saving Emacs Sessions
• saving text in a register: RegText
• saving window configuration in a register: RegConfig
• SCCS: Version Control Systems
• screen: Screen
• screen reader software, MS-Windows: Windows Misc
• script mode: Initial Options
• Scroll Bar mode: Scroll Bars
• Scroll-all mode: Window Convenience
• scrollbar width: Table of Resources
• scrolling: Scrolling
• scrolling all windows: Emulation
• scrolling in the calendar: Scroll Calendar
• scrolling windows together: Window Convenience
• SDB: Debuggers
• search and replace in multiple files: Tags Search
• search and replace in multiple files (in Dired): Operating on Files
• search for a regular expression: Regexp Search
• search multiple files (in Dired): Operating on Files
• search ring: Repeat Isearch
• search-and-replace commands: Replace
• searching: Search
• searching Dired buffers: Dired Navigation
• searching documentation efficiently: Help
• searching in Rmail: Rmail Motion
• searching multiple files via Dired: Misc Dired Features
• secondary selection: Secondary Selection
• sections of manual pages: Man Page
• selected buffer: Buffers
• selected window: Basic Window
• selecting buffers in other windows: Pop Up Window
• selection, primary: Cut/Paste Other App
• selective display: Selective Display
• selective undo: Undo
• self-documentation: Help
• Semantic package: Semantic
• sending mail: Sending Mail
• sending patches for GNU Emacs: Sending Patches
• Sendmail: Mail Sending
• sentences: Sentences
• server file: emacsclient Options
• server, using Emacs as: Emacs Server
• server-side fonts: Fonts
• set buffer face height: Temporary Face Changes
• setting a mark: Mark
• setting variables: Examining
• settings: Easy Customization
• settings, how to save: Changing a Variable
• settings, how to set: Changing a Variable
• sexp: Expressions
• sexp diary entries: Sexp Diary Entries
• SGML mode: HTML Mode
• shadow files: File Shadowing
• shell commands: Shell
• shell commands, Dired: Shell Commands in Dired
• SHELL environment variable: Interactive 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
• shift-selection: Setting Mark
• Show Paren mode: Matching
• showing hidden subdirectories (Dired): Hiding Subdirectories
• shrink a table cell: Cell Commands
• shy group, in regexp: Regexp Backslash
• Simula mode: Program Modes
• simulation of middle mouse button: Windows Mouse
• simultaneous editing: Interlocking
• single-frame terminals: Non-Window Terminals
• site init file: Init File
• site-start.el file, not loading: Initial Options
• site-start.el, the site startup file: Init File
• size of minibuffer: Minibuffer Edit
• skeletons: Text
• slashes repeated in file name: Minibuffer File
• SliTeX mode: TeX Mode
• Slovak: International
• Slovenian: International
• slow display during scrolling: Font Lock
• Smerge mode: Comparing Files
• SMTP: Mail Sending
• Snake: Amusements
• soft hyphen, display: 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: International
• specific version control system: Advanced C-x v v
• specify default font from the command line: Font X
• 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
• split table cell: Cell Commands
• splitting columns: Two-Column
• standard colors on a character terminal: Colors
• 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
• 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
• StudlyCaps: Amusements
• StudlyCaps, making them readable: Glasses
• style (for indentation): Custom C Indent
• subdirectories in Dired: Subdirectories in Dired
• subprocesses on MS-Windows: Windows Processes
• subscribe groups: Summary of Gnus
• subshell: Shell
• subtree (Outline mode): Outline Visibility
• Subversion: Version Control Systems
• summary (Rmail): Rmail Summary
• summing time intervals: Time Intervals
• sunrise and sunset: Sunrise/Sunset
• Super (under MS-DOS): MS-DOS Keyboard
• suspending: Exiting
• suspicious constructions in C, C++: Other C Commands
• SVN: Version Control Systems
• switch buffers: Select Buffer
• switches (command line): Emacs Invocation
• symbolic links (creation in Dired): Operating on Files
• symbolic links (creation): Misc File Ops
• 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
• syntax table: Syntax
• t: Glossary
• tab stops: Tab Stops
• table column commands: Column Commands
• table creation: Table Creation
• table dimensions: Measuring Tables
• table for HTML and LaTeX: Table Misc
• table in language format: Table Misc
• table mode: Text Based Tables
• table recognition: Table Recognition
• table row commands: Row Commands
• table to text: Table Conversion
• tables, indentation for: Tab Stops
• tabs: Indentation
• tags and tag tables: Tags
• tags and version control: Revision Tags
• tags, C++: Tags
• tags-based completion: Symbol Completion
• Tar mode: File Archives
• Tcl mode: Program Modes
• techniquitous: Dissociated Press
• Telnet: Remote Host
• templates: Text
• TERM environment variable: Checklist
• 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 colors, from command line: Colors
• Text mode: Text Mode
• text properties at point: International Chars
• text properties of characters: Editing Format Info
• text to table: Table Conversion
• text-based tables: Text Based Tables
• text-based tables, split a cell: Cell Commands
• text/enriched MIME format: Formatted Text
• Thai: International
• Tibetan: International
• time (on mode line): Optional Mode Line
• time intervals, summing: Time Intervals
• time stamps: Time Stamps
• timeclock: Time Intervals
• TLS encryption (Rmail): Remote Mailboxes
• toggling marks (in Dired): Marks vs Flags
• tool bar: Table of Resources
• Tool Bar mode: Tool Bars
• tooltips: Tooltips
• tooltips: Help Echo
• tooltips with GUD: Debugger Operation
• top level: Mode Line
• tower of Hanoi: Amusements
• TPU: Emulation
• trailing whitespace: Useless Whitespace
• Tramp: Remote Files
• Transient Mark mode: Persistent Mark
• transposition of expressions: Expressions
• trash: Misc File Ops
• triple clicks: Mouse Buttons
• truenames of files: File Aliases
• truncation: Line Truncation
• truncation: Continuation Lines
• trunk (version control): Branches
• Turkish: International
• turn multibyte support on or off: Enabling Multibyte
• two directories (in Dired): Operating on Files
• two-column editing: Two-Column
• types of log file: Types of Log File
• typos, fixing: Fixit
• 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
• unibyte operation, and Lisp files: Enabling Multibyte
• Unicode: International Chars
• Unicode: Inserting Text
• unique buffer names: Uniquify
• unmarking files (in Dired): Marks vs Flags
• unsubscribe groups: Summary of Gnus
• 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
• URL, viewing in help: Help Mode
• URLs: Browse-URL
• URLs, activating: Goto Address mode
• use-hard-newlines: Hard and Soft Newlines
• user name for remote file access: Remote Files
• user option: Variables
• user options, how to set: Changing a Variable
• userenced: Dissociated Press
• using tab stops in making tables: Tab Stops
• usual erasure key: DEL Does Not Delete
• UTF-8: Language Environments
• variable: Variables
• variable pitch mode: Temporary Face Changes
• variables, how to set: Changing a Variable
• version backups: Version Backups
• version control: Version Control
• version control log: Types of Log File
• VERSION_CONTROL environment variable: Backup Names
• vertical scroll bars, command-line argument: Misc X
• VHDL mode: Program Modes
• vi: Emulation
• Vietnamese: International
• View mode: Misc File Ops
• viewing: Misc File Ops
• 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 mode: Visual Line Mode
• Watching expressions in GDB: Watch Expressions
• watching files (CVS): CVS Options
• wdired mode: Wdired
• Web: Browse-URL
• web pages, viewing in help: Help Mode
• weeks, which day they start on: Move to Beginning or End
• wheel, mouse: Wheeled Mice
• 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 scroll bar: Scroll Bars
• wildcard characters in file names: Visiting
• Windmove package: Window Convenience
• window configuration changes, undoing: Window Convenience
• 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
• Winner mode: Window Convenience
• word processing: Formatted Text
• word search: Word Search
• word wrap: Longlines
• word wrap: Visual Line Mode
• word wrap: Continuation Lines
• words: Words
• words, case conversion: Case
• WordStar: Emulation
• work file: VCS Concepts
• World Wide Web: Browse-URL
• wrapping: Continuation Lines
• WYSIWYG: Formatted Text
• X cutting and pasting: Cut/Paste Other App
• X defaults file: Fonts
• X input methods: Table of Resources
• X Logical Font Description: Fonts
• X resources: Resources
• X resources file: Fonts
• X selection: Cut/Paste Other App
• XDB: Debuggers
• XIM: Table of Resources
• XLFD: Fonts
• XML schema: HTML Mode
• xterm: Text-Only Mouse
• yahrzeits: Sexp Diary Entries
• yahrzeits: From Other Calendar
• yanking: Yanking
• yanking and text properties: Kill Ring
• yanking previous kills: Earlier Kills
• zip: File Archives
• Zippy: Amusements
• Zmacs mode: Persistent Mark
• zoo: File Archives
• ~/.emacs.d/gtkrc file: GTK resources
• ~/.gtkrc-2.0 file: GTK resources
• ~/.Xdefaults file: Resources
• ~/.Xresources file: Resources