Viper

We believe that one or more of the following statements are adequate descriptions of Viper: 

     Viper Is a Package for Emacs Rebels;
     it is a VI Plan for Emacs Rescue
     and/or a venomous VI PERil.

Technically speaking, Viper is a Vi emulation package for Emacs. It implements all Vi and Ex commands, occasionally improving on them and adding many new features. It gives the user the best of both worlds: Vi keystrokes for editing combined with the power of the Emacs environment.

Viper emulates Vi at several levels, from the one that closely follows Vi conventions to the one that departs from many of them. It has many customizable options, which can be used to tailor Viper to the work habits of various users. This manual describes Viper, concentrating on the differences from Vi and new features of Viper.

Viper, formerly known as VIP-19, was written by Michael Kifer. It is based on VIP version 3.5 by Masahiko Sato and VIP version 4.4 by Aamod Sane. About 15% of the code still comes from those older packages.

Viper is intended to be usable without reading this manual; the defaults are set to make Viper as close to Vi as possible. At startup, Viper will try to set the most appropriate default environment for you, based on your familiarity with Emacs. It will also tell you the basic GNU Emacs window management commands to help you start immediately.

Although this manual explains how to customize Viper, some basic familiarity with Emacs Lisp is a plus.

It is recommended that you read the Overview node. The other nodes may be visited as needed.

Comments and bug reports are welcome. kifer@cs.stonybrook.edu is the current address for Viper bug reports. Please use the Ex command :submitReport for this purpose.

Copyright © 1995–1997, 2001–2013 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 no Invariant Sections, 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.”

Overview Read for a smoother start
Improvements over Vi New features, Improvements
Customization How to customize Viper
Commands Vi and Ex Commands
Key Index Index of Vi and Ex Commands
Function Index Index of Viper Functions
Variable Index Index of Viper Variables
Package Index Index of Packages Mentioned in this Document
Concept Index Vi, Ex and Emacs concepts
Acknowledgments
GNU Free Documentation License The license for this documentation.

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1 Overview of Viper

Viper is a Vi emulation on top of Emacs. At the same time, Viper provides a virtually unrestricted access to Emacs facilities. Perfect compatibility with Vi is possible but not desirable. This chapter tells you about the Emacs ideas that you should know about, how to use Viper within Emacs and some incompatibilities.

This manual is written with the assumption that you are an experienced Vi user who wants to switch to Emacs while retaining the ability to edit files Vi style. Incredible as it might seem, there are experienced Emacs users who use Viper as a backdoor into the superior (as every Vi user already knows) world of Vi! These users are well familiar with Emacs bindings and prefer them in some cases, especially in the Vi Insert state. John Hawkins <jshawkin@eecs.umich.edu> has provided a set of customizations, which enables additional Emacs bindings under Viper. These customizations can be included in your ~/.viper file and are found at the following URL: http://traeki.freeshell.org/files/viper-sample.

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1.1 Emacs Preliminaries

Emacs can edit several files at once. A file in Emacs is placed in a buffer that usually has the same name as the file. Buffers are also used for other purposes, such as shell interfaces, directory editing, etc. See Directory Editor, for an example.

A buffer has a distinguished position called the point. A point is always between 2 characters, and is looking at the right hand character. The cursor is positioned on the right hand character. Thus, when the point is looking at the end-of-line, the cursor is on the end-of-line character, i.e., beyond the last character on the line. This is the default Emacs behavior.

The default settings of Viper try to mimic the behavior of Vi, preventing the cursor from going beyond the last character on the line. By using Emacs commands directly (such as those bound to arrow keys), it is possible to get the cursor beyond the end-of-line. However, this won't (or shouldn't) happen if you restrict yourself to standard Vi keys, unless you modify the default editing style. See Customization.

In addition to the point, there is another distinguished buffer position called the mark. See Mark, for more info on the mark. The text between the point and the mark is called the region of the buffer. For the Viper user, this simply means that in addition to the Vi textmarkers a–z, there is another marker called mark. This is similar to the unnamed Vi marker used by the jump commands `` and '', which move the cursor to the position of the last absolute jump. Viper provides access to the region in most text manipulation commands as r and R suffix to commands that operate on text regions, e.g., dr to delete region, etc.

Furthermore, Viper lets Ex-style commands to work on the current region. This is done by typing a digit argument before :. For instance, typing 1: will prompt you with something like :123,135, assuming that the current region starts at line 123 and ends at line 135. There is no need to type the line numbers, since Viper inserts them automatically in front of the Ex command.

See Basics, for more info.

Emacs divides the screen into tiled windows. You can see the contents of a buffer through the window associated with the buffer. The cursor of the screen is positioned on the character after point. Every window has a mode line that displays information about the buffer. You can change the format of the mode line, but normally if you see ‘**’ at the beginning of a mode line it means that the buffer is modified. If you write out the contents of a buffer to a file, then the buffer will become not modified. Also if you see ‘%%’ at the beginning of the mode line, it means that the file associated with the buffer is write protected. The mode line will also show the buffer name and current major and minor modes (see below). A special buffer called Minibuffer is displayed as the last line in a minibuffer window. The minibuffer window is used for command input output. Viper uses minibuffer window for / and : commands.

An Emacs buffer can have a major mode that customizes Emacs for editing text of a particular sort by changing the functionality of the keys. Keys are defined using a keymap that records the bindings between keystrokes and functions. The global keymap is common to all the buffers. Additionally, each buffer has its local keymap that determines the mode of the buffer. If a function is bound to some key in the local keymap then that function will be executed when you type the key. If no function is bound to a key in the local map, however, the function bound to the key in the global map will be executed. See Major Modes, for more information.

A buffer can also have a minor mode. Minor modes are options that you can use or not. A buffer in text-mode can have auto-fill-mode as minor mode, which can be turned off or on at any time. In Emacs, a minor mode may have it own keymap, which overrides the local keymap when the minor mode is turned on. For more information, see Minor Modes

Viper is implemented as a collection of minor modes. Different minor modes are involved when Viper emulates Vi command mode, Vi insert mode, etc. You can also turn Viper on and off at any time while in Vi command mode. See States in Viper, for more information.

Emacs uses Control and Meta modifiers. These are denoted as C and M, e.g., ^Z as C-z and Meta-x as M-x. The Meta key is usually located on each side of the Space bar; it is used in a manner similar to the Control key, e.g., M-x means typing x while holding the Meta key down. For keyboards that do not have a Meta key, <ESC> is used as Meta. Thus M-x is typed as <ESC> x. Viper uses <ESC> to switch from Insert state to Vi state. Therefore Viper defines C-\ as its Meta key in Vi state. See Vi State, for more info.

Emacs is structured as a Lisp interpreter around a C core. Emacs keys cause Lisp functions to be called. It is possible to call these functions directly, by typing M-x function-name.

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1.2 Loading Viper

The most common way to load it automatically is to include the following lines (in the given order!): 

     (setq viper-mode t)
     (require 'viper)

in your ~/.emacs file. The .emacs file is placed in your home directory and it is be executed every time you invoke Emacs. This is the place where all general Emacs customization takes place. Beginning with version 20.0, Emacsen have an interactive interface, which simplifies the job of customization significantly.

Viper also uses the file ~/.viper for Viper-specific customization. The location of Viper customization file can be changed by setting the variable viper-custom-file-name in .emacs prior to loading Viper.

The latest versions of Emacs have an interactive customization facility, which allows you to (mostly) bypass the use of the .emacs and .viper files. You can reach this customization facility from within Viper's VI state by executing the Ex command :customize.

Once invoked, Viper will arrange to bring up Emacs buffers in Vi state whenever this makes sense. See Packages that Change Keymaps, to find out when forcing Vi command state on a buffer may be counter-productive.

Even if your .emacs file does not invoke Viper automatically, you can still load Viper and enter the Vi command state by typing the following from within Emacs: 

     M-x viper-mode

When Emacs first comes up, if you have not specified a file on the command line, it will show the ‘*scratch*’ buffer, in the ‘Lisp Interaction’ mode. After you invoke Viper, you can start editing files by using :e, :vi, or v commands. (See File and Buffer Handling, for more information on v and other new commands that, in many cases, are more convenient than :e, :vi, and similar old-style Vi commands.)

Finally, if at some point you would want to de-Viperize your running copy of Emacs after Viper has been loaded, the command M-x viper-go-away will do it for you. The function toggle-viper-mode toggles Viperization of Emacs on and off.

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1.3 States in Viper

Viper has four states, Emacs, Vi, Insert, and Replace.

‘Emacs state’
This is the state plain vanilla Emacs is normally in. After you have loaded Viper, C-z will normally take you to Vi command state. Another C-z will take you back to Emacs state. This toggle key can be changed, see Customization You can also type M-x viper-mode to change to Vi state.

For users who chose to set their user level to 1 at Viper setup time, switching to Emacs state is deliberately made harder in order to not confuse the novice user. In this case, C-z will either iconify Emacs (if Emacs runs as an application under X) or it will stop Emacs (if Emacs runs on a dumb terminal or in an Xterm window).

‘Vi state’
This is the Vi command mode. Any of the Vi commands, such as i, o, a, ..., will take you to Insert state. All Vi commands may be used in this mode. Most Ex commands can also be used. For a full list of Ex commands supported by Viper, type : and then <TAB>. To get help on any issue, including the Ex commands, type :help. This will invoke Viper Info (if it is installed). Then typing i will prompt you for a topic to search in the index. Note: to search for Ex commands in the index, you should start them with a :, e.g., :WW.

In Viper, Ex commands can be made to work on the current Emacs region. This is done by typing a digit argument before :. For instance, typing 1: will prompt you with something like :123,135, assuming that the current region starts at line 123 and ends at line 135. There is no need to type the line numbers, since Viper inserts them automatically in front of the Ex command.

‘Insert state’
Insert state is the Vi insertion mode. <ESC> will take you back to Vi state. Insert state editing can be done, including auto-indentation. By default, Viper disables Emacs key bindings in Insert state.
‘Replace state’
Commands like cw invoke the Replace state. When you cross the boundary of a replacement region (usually designated via a ‘$’ sign), it will automatically change to Insert state. You do not have to worry about it. The key bindings remain practically the same as in Insert state. If you type <ESC>, Viper will switch to Vi command mode, terminating the replacement state.

The modes are indicated on the mode line as <E>, <I>, <V>, and <R>, so that the multiple modes do not confuse you. Most of your editing can be done in Vi and Insert states. Viper will try to make all new buffers be in Vi state, but sometimes they may come up in Emacs state. C-z will take you to Vi state in such a case. In some major modes, like Dired, Info, Gnus, etc., you should not switch to Vi state (and Viper will not attempt to do so) because these modes are not intended for text editing and many of the Vi keys have special meaning there. If you plan to read news, browse directories, read mail, etc., from Emacs (which you should start doing soon!), you should learn about the meaning of the various keys in those special modes (typing C-h m in a buffer provides help with key bindings for the major mode of that buffer).

If you switch to Vi in Dired or similar modes, no harm is done. It is just that the special key bindings provided by those modes will be temporarily overshadowed by Viper's bindings. Switching back to Viper's Emacs state will revive the environment provided by the current major mode.

States in Viper are orthogonal to Emacs major modes, such as C mode or Dired mode. You can turn Viper on and off for any Emacs state. When Viper is turned on, Vi state can be used to move around. In Insert state, the bindings for these modes can be accessed. For beginners (users at Viper levels 1 and 2), these bindings are suppressed in Insert state, so that new users are not confused by the Emacs states. Note that unless you allow Emacs bindings in Insert state, you cannot do many interesting things, like language sensitive editing. For the novice user (at Viper level 1), all major mode bindings are turned off in Vi state as well. This includes the bindings for key sequences that start with C-c, which practically means that all major mode bindings are unsupported. See Customization, to find out how to allow Emacs keys in Insert state.

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1.3.1 Emacs State

You will be in this mode only by accident (hopefully). This is the state Emacs is normally in (imagine!!). Now leave it as soon as possible by typing C-z. Then you will be in Vi state (sigh of relief) :-).

Emacs state is actually a Viperism to denote all the major and minor modes (see Emacs Preliminaries) other than Viper that Emacs can be in. Emacs can have several modes, such as C mode for editing C programs, LaTeX mode for editing LaTeX documents, Dired for directory editing, etc. These are major modes, each with a different set of key-bindings. Viper states are orthogonal to these Emacs major modes. The presence of these language sensitive and other modes is a major win over Vi. See Improvements over Vi, for more.

The bindings for these modes can be made available in the Viper Insert state as well as in Emacs state. Unless you specify your user level as 1 (a novice), all major mode key sequences that start with C-x and C-c are also available in Vi state. This is important because major modes designed for editing files, such as cc-mode or latex-mode, use key sequences that begin with C-x and C-c.

There is also a key that lets you temporarily escape to Vi command state from the Insert state: typing C-z will let you execute a single Vi command while staying in Viper's Insert state.

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1.3.2 Vi State

This is the Vi command mode. When Viper is in Vi state, you will see the sign <V> in the mode line. Most keys will work as in Vi. The notable exceptions are:

C-x
C-x is used to invoke Emacs commands, mainly those that do window management. C-x 2 will split a window, C-x 0 will close a window. C-x 1 will close all other windows. C-xb is used to switch buffers in a window, and C-xo to move through windows. These are about the only necessary keystrokes. For the rest, see the GNU Emacs Manual.
C-c
For user levels 2 and higher, this key serves as a prefix key for the key sequences used by various major modes. For users at Viper level 1, C-c simply beeps.
C-g and C-]
These are the Emacs ‘quit’ keys. There will be cases where you will have to use C-g to quit. Similarly, C-] is used to exit ‘Recursive Edits’ in Emacs for which there is no comparable Vi functionality and no key-binding. Recursive edits are indicated by ‘[]’ brackets framing the modes on the mode line. See Recursive Edit. At user level 1, C-g is bound to viper-info-on-file function instead.
C-\
Viper uses <ESC> as a switch between Insert and Vi states. Emacs uses <ESC> for Meta. The Meta key is very important in Emacs since many functions are accessible only via that key as M-x function-name. Therefore, we need to simulate it somehow. In Viper's Vi, Insert, and Replace states, the meta key is set to be C-\. Thus, to get M-x, you should type C-\ x (if the keyboard has no Meta key, which is rare these days). This works both in the Vi command state and in the Insert and Replace states. In Vi command state, you can also use \ <ESC> as the meta key.

Note: Emacs binds C-\ to a function that offers to change the keyboard input method in the multilingual environment. Viper overrides this binding. However, it is still possible to switch the input method by typing \ C-\ in the Vi command state and C-z \ C-\ in the Insert state. Or you can use the MULE menu in the menubar.

Other differences are mostly improvements. The ones you should know about are:
‘Undo’
u will undo. Undo can be repeated by the . key. Undo itself can be undone. Another u will change the direction. The presence of repeatable undo means that U, undoing lines, is not very important. Therefore, U also calls viper-undo.
‘Counts’
Most commands, ~, [[, p, /, ..., etc., take counts.
‘Regexps’
Viper uses Emacs Regular Expressions for searches. These are a superset of Vi regular expressions, excepting the change-of-case escapes ‘\u’, ‘\L’, ..., etc. See Syntax of Regular Expressions, for details. Files specified to :e use csh regular expressions (globbing, wildcards, what have you). However, the function viper-toggle-search-style, bound to C-c /, lets the user switch from search with regular expressions to plain vanilla search and vice versa. It also lets one switch from case-sensitive search to case-insensitive and back. See Viper Specials, for more details.
‘Ex commands’
The current working directory of a buffer is automatically inserted in the minibuffer if you type :e then space. Absolute filenames are required less often in Viper. For file names, Emacs uses a convention that is slightly different from other programs. It is designed to minimize the need for deleting file names that Emacs provides in its prompts. (This is usually convenient, but occasionally the prompt may suggest a wrong file name for you.) If you see a prompt /usr/foo/ and you wish to edit the file ~/.viper, you don't have to erase the prompt. Instead, simply continue typing what you need. Emacs will interpret /usr/foo/~/.viper correctly. Similarly, if the prompt is ~/foo/ and you need to get to /bar/file, keep typing. Emacs interprets ~/foo//bar/ as /bar/file, since when it sees ‘//’, it understands that ~/foo/ is to be discarded.

The command :cd will change the default directory for the current buffer. The command :e will interpret the filename argument in csh. See Customization, if you want to change the default shell. The command :next takes counts from :args, so that :rew is obsolete. Also, :args will show only the invisible files (i.e., those that are not currently seen in Emacs windows).

When applicable, Ex commands support file completion and history. This means that by typing a partial file name and then <TAB>, Emacs will try to complete the name or it will offer a menu of possible completions. This works similarly to Tcsh and extends the behavior of Csh. While Emacs is waiting for a file name, you can type M-p to get the previous file name you typed. Repeatedly typing M-p and M-n will let you browse through the file history.

Like file names, partially typed Ex commands can be completed by typing <TAB>, and Viper keeps the history of Ex commands. After typing :, you can browse through the previously entered Ex commands by typing M-p and M-n. Viper tries to rationalize when it puts Ex commands on the history list. For instance, if you typed :w! foo, only :w! will be placed on the history list. This is because the last history element is the default that can be invoked simply by typing : <RET>. If :w! foo were placed on the list, it would be all to easy to override valuable data in another file. Reconstructing the full command, :w! foo, from the history is still not that hard, since Viper has a separate history for file names. By typing : M-p, you will get :w! in the minibuffer. Then, repeated M-p will get you through the file history, inserting one file name after another.

In contrast to :w! foo, if the command were :r foo, the entire command will appear in the history list. This is because having :r alone as a default is meaningless, since this command requires a file argument.

As in Vi, Viper's destructive commands can be re-executed by typing `.'. However, in addition, Viper keeps track of the history of such commands. This history can be perused by typing C-c M-p and C-c M-n. Having found the appropriate command, it can be then executed by typing `.'. See Improvements over Vi, for more information.

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1.3.3 Insert State

To avoid confusing the beginner (at Viper level 1 and 2), Viper makes only the standard Vi keys available in Insert state. The implication is that Emacs major modes cannot be used in Insert state. It is strongly recommended that as soon as you are comfortable, make the Emacs state bindings visible (by changing your user level to 3 or higher). See Customization, to see how to do this.

Once this is done, it is possible to do quite a bit of editing in Insert state. For instance, Emacs has a yank command, C-y, which is similar to Vi's p. However, unlike p, C-y can be used in Insert state of Viper. Emacs also has a kill ring where it keeps pieces of text you deleted while editing buffers. The command M-y is used to delete the text previously put back by Emacs's C-y or by Vi's p command and reinsert text that was placed on the kill-ring earlier.

This works both in Vi and Insert states. In Vi state, M-y is a much better alternative to the usual Vi's way of recovering the 10 previously deleted chunks of text. In Insert state, you can use this as follows. Suppose you deleted a piece of text and now you need to re-insert it while editing in Insert mode. The key C-y will put back the most recently deleted chunk. If this is not what you want, type M-y repeatedly and, hopefully, you will find the chunk you want.

Finally, in Insert and Replace states, Viper provides the history of pieces of text inserted in previous insert or replace commands. These strings of text can be recovered by repeatedly typing C-c M-p or C-c M-n while in Insert or Replace state. (This feature is disabled in the minibuffer: the above keys are usually bound to other histories, which are more appropriate in the minibuffer.)

You can call Meta functions from Insert state. As in Vi state, the Meta key is C-\. Thus M-x is typed as C-\ x.

Other Emacs commands that are useful in Insert state are C-e and C-a, which move the cursor to the end and the beginning of the current line, respectively. You can also use M-f and M-b, which move the cursor forward (or backward) one word. If your display has a Meta key, these functions are invoked by holding the Meta key and then typing f and b, respectively. On displays without the Meta key, these functions are invoked by typing C-\ f and C-\ b (C-\ simulates the Meta key in Insert state, as explained above).

The key C-z is sometimes also useful in Insert state: it allows you to execute a single command in Vi state without leaving the Insert state! For instance, C-z d2w will delete the next two words without leaving the Insert state.

When Viper is in Insert state, you will see <I> in the mode line.

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1.3.4 Replace State

This state is entered through Vi replacement commands, such as C, cw, etc., or by typing R. In Replace state, Viper puts <R> in the mode line to let you know which state is in effect. If Replace state is entered through R, Viper stays in that state until the user hits <ESC>. If this state is entered via the other replacement commands, then Replace state is in effect until you hit <ESC> or until you cross the rightmost boundary of the replacement region. In the latter case, Viper changes its state from Replace to Insert (which you will notice by the change in the mode line).

Since Viper runs under Emacs, it is possible to switch between buffers while in Replace state. You can also move the cursor using the arrow keys (even on dumb terminals!) and the mouse. Because of this freedom (which is unattainable in regular Vi), it is possible to take the cursor outside the replacement region. (This may be necessary for several reasons, including the need to enable text selection and region-setting with the mouse.)

The issue then arises as to what to do when the user hits the <ESC> key. In Vi, this would cause the text between cursor and the end of the replacement region to be deleted. But what if, as is possible in Viper, the cursor is not inside the replacement region?

To solve the problem, Viper keeps track of the last cursor position while it was still inside the replacement region. So, in the above situation, Viper would delete text between this position and the end of the replacement region.

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1.4 The Minibuffer

The minibuffer is where commands are entered in. Editing can be done by commands from Insert state, namely:

C-h
Backspace
C-w
Delete Word
C-u
Erase line
C-v
Quote the following character
<RET>
Execute command
C-g and C-]
Emacs quit and abort keys. These may be necessary. See Vi State, for an explanation.
M-p and M-n
These keys are bound to functions that peruse minibuffer history. The precise history to be perused depends on the context. It may be the history of search strings, Ex commands, file names, etc.
C-s
If the minibuffer is entered via the Viper search commands / or ?, then this key inserts the last search string used by the Emacs incremental search command (which is bound to C-s everywhere except in this case).

Most of the Emacs keys are functional in the minibuffer. While in the minibuffer, Viper tries to make editing resemble Vi's behavior when the latter is waiting for the user to type an Ex command. In particular, you can use the regular Vi commands to edit the minibuffer. You can switch between the Vi state and Insert state at will, and even use the replace mode. Initially, the minibuffer comes up in Insert state.

Some users prefer plain Emacs bindings in the minibuffer. To this end, set viper-vi-style-in-minibuffer to nil in .viper. See Customization, to learn how to do this.

When the minibuffer changes Viper states, you will notice that the appearance of the text there changes as well. This is useful because the minibuffer has no mode line to tell which Vi state it is in. The appearance of the text in the minibuffer can be changed. See Viper Specials, for more details.

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1.5 Multiple Files in Viper

Viper can edit multiple files. This means, for example that you never need to suffer through No write since last change errors. Some Viper elements are common over all the files.

‘Textmarkers’
Textmarkers remember files and positions. If you set marker ‘a’ in file foo, start editing file bar and type 'a, then YOU WILL SWITCH TO FILE foo. You can see the contents of a textmarker using the Viper command [<a-z> where <a-z> are the textmarkers, e.g., [a to view marker ‘a’ .
‘Repeated Commands’
Command repetitions are common over files. Typing !! will repeat the last ! command whichever file it was issued from. Typing . will repeat the last command from any file, and searches will repeat the last search. Ex commands can be repeated by typing : <RET>. Note: in some rare cases, that : <RET> may do something dangerous. However, usually its effect can be undone by typing u.
‘Registers’
Registers are common to files. Also, text yanked with y can be put back (p) into any file. The Viper command ]<a-z>, where <a-z> are the registers, can be used to look at the contents of a register, e.g., type ]a to view register ‘a’.

There is one difference in text deletion that you should be aware of. This difference comes from Emacs and was adopted in Viper because we find it very useful. In Vi, if you delete a line, say, and then another line, these two deletions are separated and are put back separately if you use the ‘p’ command. In Emacs (and Viper), successive series of deletions that are not interrupted by other commands are lumped together, so the deleted text gets accumulated and can be put back as one chunk. If you want to break a sequence of deletions so that the newly deleted text could be put back separately from the previously deleted text, you should perform a non-deleting action, e.g., move the cursor one character in any direction.

‘Absolute Filenames’
The current directory name for a file is automatically prepended to the file name in any :e, :r, :w, etc., command (in Emacs, each buffer has a current directory). This directory is inserted in the minibuffer once you type space after :e, r, etc. Viper also supports completion of file names and Ex commands (<TAB>), and it keeps track of command and file history (M-p, M-n). Absolute filenames are required less often in Viper.

You should be aware that Emacs interprets /foo/bar//bla as /bla and /foo/~/bar as ~/bar. This is designed to minimize the need for erasing file names that Emacs suggests in its prompts, if a suggested file name is not what you wanted.

The command :cd will change the default directory for the current Emacs buffer. The Ex command :e will interpret the filename argument in ‘csh’, by default. See Customization, if you want to change this.

Currently undisplayed files can be listed using the :ar command. The command :n can be given counts from the :ar list to switch to other files. For example, use `:n3' to move to the third file in that list.

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1.6 Unimplemented Features

Unimplemented features include:

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2 Improvements over Vi

Some common problems with Vi and Ex have been solved in Viper. This includes better implementation of existing commands, new commands, and the facilities provided by Emacs.

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2.1 Basics

The Vi command set is based on the idea of combining motion commands with other commands. The motion command is used as a text region specifier for other commands. We classify motion commands into point commands and line commands.

The point commands are:

h, l, 0, $, w, W, b, B, e, E, (, ), /, ?, `, f, F, t, T, %, ;, ,, ^

The line commands are:

j, k, +, -, H, M, L, {, }, G, ', [[, ]], []

If a point command is given as an argument to a modifying command, the region determined by the point command will be affected by the modifying command. On the other hand, if a line command is given as an argument to a modifying command, the region determined by the line command will be enlarged so that it will become the smallest region properly containing the region and consisting of whole lines (we call this process expanding the region), and then the enlarged region will be affected by the modifying command. Text Deletion Commands (see Deleting Text), Change commands (see Changing Text), even Shell Commands (see Shell Commands) use these commands to describe a region of text to operate on. Thus, type dw to delete a word, >} to shift a paragraph, or !'afmt to format a region from ‘point’ to textmarker ‘a’.

Viper adds the region specifiers ‘r’ and ‘R’. Emacs has a special marker called mark. The text-area between the current cursor position point and the mark is called the region. ‘r’ specifies the raw region and ‘R’ is the expanded region (i.e., the minimal contiguous chunk of full lines that contains the raw region). dr will now delete the region, >r will shift it, etc. r,R are not motion commands, however. The special mark is set by m. and other commands. See Marking, for more info.

Viper also adds counts to most commands for which it would make sense.

In the Overview chapter, some Multiple File issues were discussed (see Multiple Files in Viper). In addition to the files, Emacs has buffers. These can be seen in the :args list and switched using :next if you type :set ex-cycle-through-non-files t, or specify (setq ex-cycle-through-non-files t) in your .viper file. See Customization, for details.

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2.2 Undo and Backups

Viper provides multiple undo. The number of undo's and the size is limited by the machine. The Viper command u does an undo. Undo can be repeated by typing . (a period). Another u will undo the undo, and further . will repeat it. Typing u does the first undo, and changes the direction.

Since the undo size is limited, Viper can create backup files and auto-save files. It will normally do this automatically. It is possible to have numbered backups, etc. For details, see Backup and Auto-Save

The results of the 9 previous changes are available in the 9 numeric registers, as in Vi. The extra goody is the ability to view these registers, in addition to being able to access them through p and M-y (See Insert State, for details.) The Viper command ] register will display the contents of any register, numeric or alphabetical. The related command [ textmarker will show the text around the textmarker. ‘register’ and ‘textmarker’ can be any letters from a through z.

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2.3 History

History is provided for Ex commands, Vi searches, file names, pieces of text inserted in earlier commands that use Insert or Replace state, and for destructive commands in Vi state. These are useful for fixing those small typos that screw up searches and :s, and for eliminating routine associated with repeated typing of file names or pieces of text that need to be inserted frequently. At the : or / prompts in the minibuffer, you can do the following:

M-p and M-n
To move to previous and next history items. This causes the history items to appear on the command line, where you can edit them, or simply type Return to execute.
M-r and M-s
To search backward and forward through the history.
<RET>
Type <RET> to accept a default (which is displayed in the prompt).

The history of insertions can be perused by typing C-c M-p and C-c M-n while in Insert or Replace state. The history of destructive Vi commands can be perused via the same keys when Viper is in Vi state. See Viper Specials, for details.

All Ex commands have a file history. For instance, typing :e, space and then M-p will bring up the name of the previously typed file name. Repeatedly typing M-p, M-n, etc., will let you browse through the file history.

Similarly, commands that have to do with switching buffers have a buffer history, and commands that expect strings or regular expressions keep a history on those items.

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2.4 Macros and Registers

Viper facilitates the use of Emacs-style keyboard macros. @# will start a macro definition. As you type, the commands will be executed, and remembered (This is called “learn mode” in some editors.) @register will complete the macro, putting it into ‘register’, where ‘register’ is any character from ‘a’ through ‘z’. Then you can execute this macro using @register. It is, of course, possible to yank some text into a register and execute it using @register. Typing @@, @RET, or @C-j will execute the last macro that was executed using @register.

Viper will automatically lowercase the register, so that pressing the SHIFT key for @ will not create problems. This is for @ macros and "p only. In the case of y, "Ayy will append to register a. For [,],',`, it is an error to use a Uppercase register name.

The contents of a register can be seen by ]register. ([textmarker will show the contents of a textmarker).

The last keyboard macro can also be executed using *, and it can be yanked into a register using @!register. This is useful for Emacs style keyboard macros defined using C-x( and C-x). Emacs keyboard macros have more capabilities. See Keyboard Macros, for details.

Keyboard Macros allow an interesting form of Query-Replace: /pattern or n to go to the next pattern (the query), followed by a Keyboard Macro execution @@ (the replace).

Viper also provides Vi-style macros. See Vi Macros, for details.

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2.5 Completion

Completion is done when you type <TAB>. The Emacs completer does not grok wildcards in file names. Once you type a wildcard, the completer will no longer work for that file name. Remember that Emacs interprets a file name of the form /foo//bar as /bar and /foo/~/bar as ~/bar.

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2.6 Improved Search

Viper provides buffer search, the ability to search the buffer for a region under the cursor. You have to turn this on in .viper either by calling 

     (viper-buffer-search-enable)

or by setting viper-buffer-search-char to, say, f3: 

     (setq viper-buffer-search-char ?g)

If the user calls viper-buffer-search-enable explicitly (the first method), then viper-buffer-search-char will be set to g. Regardless of how this feature is enabled, the key viper-buffer-search-char will take movement commands, like w,/,e, to find a region and then search for the contents of that region. This command is very useful for searching for variable names, etc., in a program. The search can be repeated by n or reversed by N.

Emacs provides incremental search. As you type the string in, the cursor will move to the next match. You can snarf words from the buffer as you go along. Incremental Search is normally bound to C-s and C-r. See Customization, to find out how to change the bindings of C-r or C-s. For details, see Incremental Search

Viper also provides a query replace function that prompts through the minibuffer. It is invoked by the Q key in Vi state.

On a window display, Viper supports mouse search, i.e., you can search for a word by clicking on it. See Viper Specials, for details.

Finally, on a window display, Viper highlights search patterns as it finds them. This is done through what is known as faces in Emacs. The variable that controls how search patterns are highlighted is viper-search-face. If you don't want any highlighting at all, put 

     (copy-face 'default 'viper-search-face)

in ~/.viper. If you want to change how patterns are highlighted, you will have to change viper-search-face to your liking. The easiest way to do this is to use Emacs customization widget, which is accessible from the menubar. Viper customization group is located under the Emulations customization group, which in turn is under the Editing group (or simply by typing :customize). All Viper faces are grouped together under Viper's Highlighting group.

Try it: it is really simple!

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2.7 Abbreviation Facilities

It is possible in Emacs to define abbrevs based on the contents of the buffer. Sophisticated templates can be defined using the Emacs abbreviation facilities. See Abbreviations, for details.

Emacs also provides Dynamic Abbreviations. Given a partial word, Emacs will search the buffer to find an extension for this word. For instance, one can type ‘Abbreviations’ by typing ‘A’, followed by a keystroke that completed the ‘A’ to ‘Abbreviations’. Repeated typing will search further back in the buffer, so that one could get ‘Abbrevs’ by repeating the keystroke, which appears earlier in the text. Emacs binds this to <ESC> /, so you will have to find a key and bind the function dabbrev-expand to that key. Facilities like this make Vi's :ab command obsolete.

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2.8 Movement and Markers

Viper can be set free from the line–limited movements in Vi, such as l refusing to move beyond the line, <ESC> moving one character back, etc. These derive from Ex, which is a line editor. If your .viper contains 

     (setq viper-ex-style-motion nil)

the motion will be a true screen editor motion. One thing you must then watch out for is that it is possible to be on the end-of-line character. The keys x and % will still work correctly, i.e., as if they were on the last character.

The word-movement commands w, e, etc., and the associated deletion/yanking commands, dw, yw, etc., can be made to understand Emacs syntax tables. If the variable viper-syntax-preference is set to strict-vi then the meaning of word is the same as in Vi. However, if the value is reformed-vi (the default) then the alphanumeric symbols will be those specified by the current Emacs syntax table (which may be different for different major modes) plus the underscore symbol _, minus some non-word symbols, like '.;,|, etc. Both strict-vi and reformed-vi work close to Vi in traditional cases, but reformed-vi does a better job when editing text in non-Latin alphabets.

The user can also specify the value emacs, which would make Viper use exactly the Emacs notion of word. In particular, the underscore may not be part of a word. Finally, if viper-syntax-preference is set to extended, Viper words would consist of characters that are classified as alphanumeric or as parts of symbols. This is convenient for writing programs and in many other situations.

viper-syntax-preference is a local variable, so it can have different values for different major modes. For instance, in programming modes it can have the value extended. In text modes where words contain special characters, such as European (non-English) letters, Cyrillic letters, etc., the value can be reformed-vi or emacs.

Changes to viper-syntax-preference should be done in the hooks to various major modes by executing viper-set-syntax-preference as in the following example: 

     (viper-set-syntax-preference nil "emacs")

The above discussion of the meaning of Viper's words concerns only Viper's movement commands. In regular expressions, words remain the same as in Emacs. That is, the expressions \w, \>, \<, etc., use Emacs's idea of what is a word, and they don't look into the value of variable viper-syntax-preference. This is because Viper doesn't change syntax tables in fear of upsetting the various major modes that set these tables.

Textmarkers in Viper remember the file and the position, so that you can switch files by simply doing 'a. If you set up a regimen for using Textmarkers, this is very useful. Contents of textmarkers can be viewed by [marker. (Contents of registers can be viewed by ]register).

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2.9 New Commands

These commands have no Vi analogs.

C-x, C-c
These two keys invoke many important Emacs functions. For example, if you hit C-x followed by 2, then the current window will be split into 2. Except for novice users, C-c is also set to execute an Emacs command from the current major mode. <ESC> will do the same, if you configure <ESC> as Meta by setting viper-no-multiple-ESC to nil in .viper. See Customization. C-\ in Insert, Replace, or Vi states will make Emacs think Meta has been hit.
\
Escape to Emacs to execute a single Emacs command. For instance, \ <ESC> will act like a Meta key.
Q
Q is for query replace. By default, each string to be replaced is treated as a regular expression. You can use (setq viper-re-query-replace nil) in your .emacs file to turn this off. (For normal searches, :se nomagic will work. Note that :se nomagic turns Regexps off completely, unlike Vi).
v
V
C-v
These keys are used to visit files. v will switch to a buffer visiting file whose name can be entered in the minibuffer. V is similar, but will use a window different from the current window. C-v is like V, except that a new frame (X window) will be used instead of a new Emacs window.
#
If followed by a certain character ch, it becomes an operator whose argument is the region determined by the motion command that follows (indicated as <move>). Currently, ch can be one of c, C, g, q, and s. For instance, #qr will prompt you for a string and then prepend this string to each line in the buffer.
# c
Change upper-case characters in the region to lower-case (downcase-region). Emacs command M-l does the same for words.
# C
Change lower-case characters in the region to upper-case. For instance, # C 3 w will capitalize 3 words from the current point (upcase-region). Emacs command M-u does the same for words.
# g
Execute last keyboard macro for each line in the region (viper-global-execute).
# q
Insert specified string at the beginning of each line in the region (viper-quote-region). The default string is composed of the comment character(s) appropriate for the current major mode.
# s
Check spelling of words in the region (spell-region). The function used for spelling is determined from the variable viper-spell-function.
*
Call last keyboard macro.
m .
Set mark at point and push old mark off the ring
m<
m>
Set mark at beginning and end of buffer, respectively.
m,
Jump to mark and pop mark off the ring. See Mark, for more info.
] register
View contents of register
[ textmarker
View filename and position of textmarker
@#
@register
@!
Begin/end keyboard macro. @register has a different meaning when used after a @#. See Macros and Registers, for details
[]
Go to end of heading.
g <movement command>
Search buffer for text delimited by movement command. The canonical example is gw to search for the word under the cursor. See Improved Search, for details.
C-g and C-]
Quit and Abort Recursive edit. These may be necessary on occasion. See Vi State, for a reason.
C-c C-g
Hitting C-c followed by C-g will display the information on the current buffer. This is the same as hitting C-g in Vi, but, as explained above, C-g is needed for other purposes in Emacs.
C-c /
Without a prefix argument, this command toggles case-sensitive/case-insensitive search modes and plain vanilla/regular expression search. With the prefix argument 1, i.e., 1 C-c /, this toggles case-sensitivity; with the prefix argument 2, toggles plain vanilla search and search using regular expressions. See Viper Specials, for alternative ways to invoke this function.
M-p and M-n
In the minibuffer, these commands navigate through the minibuffer histories, such as the history of search strings, Ex commands, etc.
C-s
If the minibuffer is entered via a Viper search commands / or ?, then typing this key inserts the last search string used by the Emacs incremental search command (that is bound to C-s everywhere except in this case).
C-c M-p and C-c M-n
In Insert or Replace state, these commands let the user peruse the history of insertion strings used in previous insert or replace commands. Try to hit C-c M-p or C-c M-n repeatedly and see what happens. See Viper Specials, for more.

In Vi state, these commands let the user peruse the history of Vi-style destructive commands, such as dw, J, a, etc. By repeatedly typing C-c M-p or C-c M-n you will cycle Viper through the recent history of Vi commands, displaying the commands one by one. Once an appropriate command is found, it can be executed by typing `.'.

Since typing C-c M-p is tedious, it is more convenient to bind an appropriate function to a function key on the keyboard and use that key. See Viper Specials, for details.

Ex commands
The commands :args, :next, :pre behave differently. :pwd exists to get current directory. The commands :b and :B switch buffers around. See File and Buffer Handling, for details. There are also the new commands :RelatedFile and PreviousRelatedFile (which abbreviate to R and P, respectively. See Viper Specials, for details.

Apart from the new commands, many old commands have been enhanced. Most notably, Vi style macros are much more powerful in Viper than in Vi. See Vi Macros, for details.

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2.10 Useful Packages

Some Emacs packages are mentioned here as an aid to the new Viper user, to indicate what Viper is capable of. A vast number comes with the standard Emacs distribution, and many more exist on the net and on the archives.

This manual also mentions some Emacs features a new user should know about. The details of these are found in the GNU Emacs Manual.

The features first. For details, look up the Emacs Manual.

‘Make’
Makes and Compiles can be done from the editor. Error messages will be parsed and you can move to the error lines.
‘Shell’
You can talk to Shells from inside the editor. Your entire shell session can be treated as a file.
‘Mail’
Mail can be read from and sent within the editor. Several sophisticated packages exist.
‘Language Sensitive Editing’
Editing modes are written for most computer languages in existence. By controlling indentation, they catch punctuation errors.

The packages, below, represents a drop in the sea of special-purpose packages that come with standard distribution of Emacs.

‘Transparent FTP’
ange-ftp.el can ftp from the editor to files on other machines transparent to the user.
‘RCS Interfaces’
vc.el for doing RCS commands from inside the editor
‘Directory Editor’
dired.el for editing contents of directories and for navigating in the file system.
‘Syntactic Highlighting’
font-lock.el for automatic highlighting various parts of a buffer using different fonts and colors.
‘Saving Emacs Configuration’
desktop.el for saving/restoring configuration on Emacs exit/startup.
‘Spell Checker’
ispell.el for spell checking the buffer, words, regions, etc.
‘File and Buffer Comparison’
ediff.el for finding differences between files and for applying patches.

Emacs Lisp archives exist on ‘archive.cis.ohio-state.edu’ and ‘wuarchive.wustl.edu’

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3 Customization

Customization can be done in 2 ways.

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3.1 Rudimentary Changes

An easy way to customize Viper is to change the values of constants used in Viper. Here is the list of the constants used in Viper and their default values. The corresponding :se command is also indicated. (The symbols t and nil represent “true” and “false” in Lisp).

Viper supports both the abbreviated Vi variable names and their full names. Variable completion is done on full names only. <TAB> and <SPC> complete variable names. Typing `=' will complete the name and then will prompt for a value, if applicable. For instance, :se au <SPC> will complete the command to :set autoindent; :se ta <SPC> will complete the command and prompt further like this: :set tabstop = . However, typing :se ts <SPC> will produce a “No match” message because ts is an abbreviation for tabstop and Viper supports completion on full names only. However, you can still hit <RET> or =, which will complete the command like this: :set ts = and Viper will be waiting for you to type a value for the tabstop variable. To get the full list of Vi variables, type :se <SPC> <TAB>.

viper-auto-indent nil
:se ai (:se autoindent)
:se ai-g (:se autoindent-global)
If t, enable auto indentation. by <RET>, o or O command.

viper-auto-indent is a local variable. To change the value globally, use setq-default. It may be useful for certain major modes to have their own values of viper-auto-indent. This can be achieved by using setq to change the local value of this variable in the hooks to the appropriate major modes.

:se ai changes the value of viper-auto-indent in the current buffer only; :se ai-g does the same globally.

viper-electric-mode t
If not nil, auto-indentation becomes electric, which means that <RET>, O, and o indent cursor according to the current major mode. In the future, this variable may control additional electric features.

This is a local variable: setq changes the value of this variable in the current buffer only. Use setq-default to change the value in all buffers.

viper-case-fold-search nil
:se ic (:se ignorecase)
If not nil, search ignores cases. This can also be toggled by quickly hitting / twice.
viper-re-search nil
:se magic
If not nil, search will use regular expressions; if nil then use vanilla search. This behavior can also be toggled by quickly hitting / trice.
buffer-read-only
:se ro (:se readonly)
Set current buffer to read only. To change globally put (setq-default buffer-read-only t) in your .emacs file.
blink-matching-paren t
:se sm (:se showmatch)
Show matching parens by blinking cursor.
tab-width t (default setting via setq-default)
:se ts=value (:se tabstop=value)
:se ts-g=value (:se tabstop-global=value)
tab-width is a local variable that controls the width of the tab stops. To change the value globally, use setq-default; for local settings, use setq.

The command :se ts sets the tab width in the current buffer only; it has no effect on other buffers.

The command :se ts-g sets tab width globally, for all buffers where the tab is not yet set locally, including the new buffers.

Note that typing <TAB> normally doesn't insert the tab, since this key is usually bound to a text-formatting function, indent-for-tab-command (which facilitates programming and document writing). Instead, the tab is inserted via the command viper-insert-tab, which is bound to S-tab (shift + tab).

On some non-windowing terminals, Shift doesn't modify the <TAB> key, so S-tab behaves as if it were <TAB>. In such a case, you will have to bind viper-insert-tab to some other convenient key.

viper-shift-width 8
:se sw=value (:se shiftwidth=value)
The number of columns shifted by > and < commands.
viper-search-wrap-around t
:se ws (:se wrapscan)
If not nil, search wraps around the end/beginning of buffer.
viper-search-scroll-threshold 2
If search lands within this many lines of the window top or bottom, the window will be scrolled up or down by about 1/7-th of its size, to reveal the context. If the value is negative, don't scroll.
viper-tags-file-name "TAGS"
The name of the file used as the tag table.
viper-re-query-replace nil
If not nil, use reg-exp replace in query replace.
viper-want-ctl-h-help nil
If not nil, C-h is bound to help-command; otherwise, C-h is bound as usual in Vi.
viper-vi-style-in-minibuffer t
If not nil, Viper provides a high degree of compatibility with Vi insert mode when you type text in the minibuffer; if nil, typing in the minibuffer feels like plain Emacs.
viper-no-multiple-ESC t
If you set this to nil, you can use <ESC> as Meta in Vi state. Normally, this is not necessary, since graphical displays have separate Meta keys (usually on each side of the space bar). On a dumb terminal, Viper sets this variable to twice, which is almost like nil, except that double <ESC> beeps. This, too, lets <ESC> to be used as a Meta.
viper-fast-keyseq-timeout 200
Key sequences separated by this many milliseconds are treated as Vi-style keyboard macros. If the key sequence is defined as such a macro, it will be executed. Otherwise, it is processed as an ordinary sequence of typed keys.

Setting this variable too high may slow down your typing. Setting it too low may make it hard to type macros quickly enough.

viper-ex-style-motion t
Set this to nil, if you want l,h to cross lines, etc. See Movement and Markers, for more info.
viper-ex-style-editing t
Set this to nil, if you want C-h and <DEL> to not stop at the beginning of a line in Insert state, <X> and <x> to delete characters across lines in Vi command state, etc.
viper-ESC-moves-cursor-back t
It t, cursor moves back 1 character when switching from insert state to vi state. If nil, the cursor stays where it was before the switch.
viper-always t
t means: leave it to Viper to decide when a buffer must be brought up in Vi state, Insert state, or Emacs state. This heuristics works well in virtually all cases. nil means you either has to invoke viper-mode manually for each buffer (or you can add viper-mode to the appropriate major mode hooks using viper-load-hook).

This option must be set in the file ~/.viper.

viper-custom-file-name "~/.viper"
File used for Viper-specific customization. Change this setting, if you want. Must be set in .emacs (not .viper!) before Viper is loaded. Note that you have to set it as a string inside double quotes.
viper-spell-function 'ispell-region
Function used by the command #c<move> to spell.
viper-glob-function
The value of this variable is the function symbol used to expand wildcard symbols. This is platform-dependent. The default tries to set this variable to work with most shells, MS Windows, OS/2, etc. However, if it doesn't work the way you expect, you should write your own. Use viper-glob-unix-files and viper-glob-mswindows-files in viper-util.el as examples.

This feature is used to expand wildcards in the Ex command :e. Note that Viper doesn't support wildcards in the :r and :w commands, because file completion is a better mechanism.

ex-cycle-other-window t
If not nil, :n and :b will cycle through files in another window, if one exists.
ex-cycle-through-non-files nil
:n does not normally cycle through buffers. Set this to get buffers also.
viper-want-emacs-keys-in-insert
This is set to nil for user levels 1 and 2 and to t for user levels 3 and 4. Users who specify level 5 are allowed to set this variable as they please (the default for this level is t). If set to nil, complete Vi compatibility is provided in Insert state. This is really not recommended, as this precludes you from using language-specific features provided by the major modes.
viper-want-emacs-keys-in-vi
This is set to nil for user level 1 and to t for user levels 2–4. At level 5, users are allowed to set this variable as they please (the default for this level is t). If set to nil, complete Vi compatibility is provided in Vi command state. Setting this to nil is really a bad idea, unless you are a novice, as this precludes the use of language-specific features provided by the major modes.
viper-keep-point-on-repeat t
If not nil, point is not moved when the user repeats the previous command by typing `.' This is very useful for doing repeated changes with the . key.
viper-repeat-from-history-key 'f12
Prefix key used to invoke the macros f12 1 and f12 2 that repeat the second-last and the third-last destructive command. Both these macros are bound (as Viper macros) to viper-repeat-from-history, which checks the second key by which it is invoked to see which of the previous commands to invoke. Viper binds f12 1 and f12 2 only, but the user can bind more in ~/.viper. See Vi Macros, for how to do this.
viper-keep-point-on-undo nil
If not nil, Viper tries to not move point when undoing commands. Instead, it will briefly move the cursor to the place where change has taken place. However, if the undone piece of text is not seen in window, then point will be moved to the place where the change took place. Set it to t and see if you like it better.
viper-delete-backwards-in-replace nil
If not nil, <DEL> key will delete characters while moving the cursor backwards. If nil, the cursor will move backwards without deleting anything.
viper-replace-overlay-face 'viper-replace-overlay-face
On a graphical display, Viper highlights replacement regions instead of putting a ‘$’ at the end. This variable controls the so called face used to highlight the region.

By default, viper-replace-overlay-face underlines the replacement on monochrome displays and also lays a stipple over them. On color displays, replacement regions are highlighted with color.

If you know something about Emacs faces and don't like how Viper highlights replacement regions, you can change viper-replace-overlay-face by specifying a new face. (Emacs faces are described in the Emacs Lisp reference.) On a color display, the following customization method is usually most effective: 

          (set-face-foreground viper-replace-overlay-face "DarkSlateBlue")
          (set-face-background viper-replace-overlay-face "yellow")

For a complete list of colors available to you, evaluate the expression (x-defined-colors). (Type it in the buffer *scratch* and then hit the C-j key.

viper-replace-overlay-cursor-color "Red"
Cursor color when it is inside the replacement region. This has effect only on color displays and only when Emacs runs as an X application.
viper-insert-state-cursor-color nil
If set to a valid color, this will be the cursor color when Viper is in insert state.
viper-emacs-state-cursor-color nil
If set to a valid color, this will be the cursor color when Viper is in emacs state.
viper-replace-region-end-delimiter "$"
A string used to mark the end of replacement regions. It is used only on TTYs or if viper-use-replace-region-delimiters is non-nil.
viper-replace-region-start-delimiter ""
A string used to mark the beginning of replacement regions. It is used only on TTYs or if viper-use-replace-region-delimiters is non-nil.
viper-use-replace-region-delimiters
If non-nil, Viper will always use viper-replace-region-end-delimiter and viper-replace-region-start-delimiter to delimit replacement regions, even on color displays (where this is unnecessary). By default, this variable is non-nil only on TTYs or monochrome displays.
viper-allow-multiline-replace-regions t
If non-nil, multi-line text replacement regions, such as those produced by commands c55w, 3C, etc., will stay around until the user exits the replacement mode. In this variable is set to nil, Viper will emulate the standard Vi behavior, which supports only intra-line replacement regions (and multi-line replacement regions are deleted).
viper-toggle-key "\C-z"
Specifies the key used to switch from Emacs to Vi and back. Must be set in .viper. This variable can't be changed interactively after Viper is loaded.

In Insert state, this key acts as a temporary escape to Vi state, i.e., it will set Viper up so that the very next command will be executed as if it were typed in Vi state.

viper-buffer-search-char nil
Key used for buffer search. See Viper Specials, for details.
viper-surrounding-word-function 'viper-surrounding-word
The value of this variable is a function name that is used to determine what constitutes a word clicked upon by the mouse. This is used by mouse search and insert.
viper-search-face 'viper-search-face
Variable that controls how search patterns are highlighted when they are found.
viper-vi-state-hook nil
List of parameterless functions to be run just after entering the Vi command state.
viper-insert-state-hook nil
Same for Insert state. This hook is also run after entering Replace state.
viper-replace-state-hook nil
List of (parameterless) functions called just after entering Replace state (and after all viper-insert-state-hook).
viper-emacs-state-hook nil
List of (parameterless) functions called just after switching from Vi state to Emacs state.
viper-load-hook nil
List of (parameterless) functions called just after loading Viper. This is the last chance to do customization before Viper is up and running.
You can reset some of these constants in Viper with the Ex command :set (when so indicated in the table). Or you can include a line like this in your .viper file: 
     (setq viper-case-fold-search t)

Next: , Previous: Rudimentary Changes, Up: Customization

3.2 Key Bindings

Viper lets you define hot keys, i.e., you can associate keyboard keys such as F1, Help, PgDn, etc., with Emacs Lisp functions (that may already exist or that you will write). Each key has a "preferred form" in Emacs. For instance, the Up key's preferred form is [up], the Help key's preferred form is [help], and the Undo key has the preferred form [f14]. You can find out the preferred form of a key by typing M-x describe-key-briefly and then typing the key you want to know about.

Under the X Window System, every keyboard key emits its preferred form, so you can just type 

     (global-set-key [f11] 'calendar)                        ; L1, Stop
     (global-set-key [f14] 'undo)                            ; L4, Undo

to bind L1 (a key that exists on some SUN workstations) so it will invoke the Emacs Calendar and to bind L4 so it will undo changes. However, on a dumb terminal or in an Xterm window, even the standard arrow keys may not emit the right signals for Emacs to understand. To let Emacs know about those keys, you will have to find out which key sequences they emit by typing C-q and then the key (you should switch to Emacs state first). Then you can bind those sequences to their preferred forms using input-decode-map as follows: 

     (cond ((string= (getenv "TERM") "xterm")
     (define-key input-decode-map "\e[192z" [f11])    ; L1
     (define-key input-decode-map "\e[195z" [f14])    ; L4, Undo

The above illustrates how to do this for Xterm. On VT100, you would have to replace "xterm" with "vt100" and also change the key sequences (the same key may emit different sequences on different types of terminals).

The above keys are global, so they are overwritten by the local maps defined by the major modes and by Viper itself. Therefore, if you wish to change a binding set by a major mode or by Viper, read this.

Viper users who wish to specify their own key bindings should be concerned only with the following three keymaps: viper-vi-global-user-map for Vi state commands, viper-insert-global-user-map for Insert state commands, and viper-emacs-global-user-map for Emacs state commands (note: customized bindings for Emacs state made to viper-emacs-global-user-map are not inherited by Insert state).

For more information on Viper keymaps, see the header of the file viper.el. If you wish to change a Viper binding, you can use the define-key command, to modify viper-vi-global-user-map, viper-insert-global-user-map, and viper-emacs-global-user-map, as explained below. Each of these key maps affects the corresponding Viper state. The keymap viper-insert-global-user-map also affects Viper's Replace state.

If you want to bind a key, say C-v, to the function that scrolls page down and to make 0 display information on the current buffer, putting this in .viper will do the trick in Vi state: 

     (define-key viper-vi-global-user-map "\C-v" 'scroll-down)

To set a key globally, 

     (define-key viper-emacs-global-user-map "\C-c m" 'smail)
     (define-key viper-vi-global-user-map "0" 'viper-info-on-file)

Note, however, that this binding may be overwritten by other keymaps, since the global keymap has the lowest priority. To make sure that nothing will override a binding in Emacs state, you can write this: 

     (define-key viper-emacs-global-user-map "\C-c m" 'smail)

To customize the binding for C-h in Insert state: 

     (define-key viper-insert-global-user-map "\C-h"
       'my-del-backwards-function)

Each Emacs command key calls some Lisp function. If you have enabled the Help, (see Rudimentary Changes) C-h k will show you the function for each specific key; C-h b will show all bindings, and C-h m will provide information on the major mode in effect. If Help is not enabled, you can still get help in Vi state by prefixing the above commands with \, e.g., \ C-h k (or you can use the Help menu in the menu bar, if Emacs runs under X).

Viper users can also change bindings on a per major mode basis. As with global bindings, this can be done separately for each of the three main Viper states. To this end, Viper provides the function viper-modify-major-mode. To modify keys in Emacs state for my-favorite-major-mode, the user needs to create a sparse keymap, say, my-fancy-map, bind whatever keys necessary in that keymap, and put 

     (viper-modify-major-mode 'dired-mode 'emacs-state my-fancy-map)

in ~/.viper. To do the same in Vi and Insert states, you should use vi-state and insert-state. Changes in Insert state are also in effect in Replace state. For instance, suppose that the user wants to use dd in Vi state under Dired mode to delete files, u to unmark files, etc. The following code in ~/.viper will then do the job: 

     (setq my-dired-modifier-map (make-sparse-keymap))
     (define-key my-dired-modifier-map "dd" 'dired-flag-file-deletion)
     (define-key my-dired-modifier-map "u" 'dired-unmark)
     (viper-modify-major-mode 'dired-mode 'vi-state my-dired-modifier-map)

A Vi purist may want to modify Emacs state under Dired mode so that k, l, etc., will move around in directory buffers, as in Vi. Although this is not recommended, as these keys are bound to useful Dired functions, the trick can be accomplished via the following code: 

     (setq my-dired-vi-purist-map (make-sparse-keymap))
     (define-key my-dired-vi-purist-map "k" 'viper-previous-line)
     (define-key my-dired-vi-purist-map "l" 'viper-forward-char)
     (viper-modify-major-mode 'dired-mode
                              'emacs-state my-dired-vi-purist-map)

Yet another way to customize key bindings in a major mode is to edit the list viper-major-mode-modifier-list using the customization widget. (This variable is in the Viper-misc customization group.) The elements of this list are triples of the form: (major-mode viper-state keymap), where the keymap contains bindings that are supposed to be active in the given major mode and the given viper-state.

Effects similar to key binding changes can be achieved by defining Vi keyboard macros using the Ex commands :map and :map!. The difference is that multi-key Vi macros do not override the keys they are bound to, unless these keys are typed in quick succession. So, with macros, one can use the normal keys alongside with the macros. If per-mode modifications are needed, the user can try both ways and see which one is more convenient. See Vi Macros, for details.

Note: in major modes that come up in Emacs state by default, the aforesaid modifications may not take place immediately (but only after the buffer switches to some other Viper state and then back to Emacs state). To avoid this, one should add viper-change-state-to-emacs to an appropriate hook of that major mode. (Check the function viper-set-hooks in viper.el for examples.) However, if you did not set viper-always to nil, chances are that you won't need to perform the above procedure, because Viper will take care of most useful defaults.

Finally, Viper has a facility that lets the user define per-buffer bindings, i.e., bindings that are in effect in some specific buffers only. Unlike per-mode bindings described above, per-buffer bindings can be defined based on considerations other than the major mode. This is done via the function viper-add-local-keys, which lets one specify bindings that should be in effect in the current buffer only and for a specific Viper state. For instance, 

     (viper-add-local-keys 'vi-state '(("ZZ" . TeX-command-master)
                                      ("ZQ" . viper-save-kill-buffer)))

redefines ZZ to invoke TeX-command-master in vi-state and ZQ to save-then-kill the current buffer. These bindings take effect only in the buffer where this command is executed. The typical use of this function is to execute the above expression from within a function that is included in a hook to some major mode. For instance, the above expression could be called from a function, my-tex-init, which may be added to tex-mode-hook as follows: 

     (add-hook 'tex-mode-hook 'my-tex-init)

When TeX mode starts, the hook is executed and the above Lisp expression is evaluated. Then, the bindings for ZZ and ZQ are changed in Vi command mode for all buffers in TeX mode.

Another useful application is to bind ZZ to send-mail in the Mail mode buffers (the specifics of this depend on which mail package you are using, rmail, mh-e, vm, etc. For instance, here is how to do this for mh-e, the Emacs interface to MH: 

     (defun mh-add-vi-keys ()
       "Set up ZZ for MH-e and XMH."
       (viper-add-local-keys 'vi-state '(("ZZ" . mh-send-letter))))
     (add-hook 'mh-letter-mode-hook 'mh-add-vi-keys)

You can also use viper-add-local-keys to set per buffer bindings in Insert state and Emacs state by passing as a parameter the symbols insert-state and emacs-state, respectively. As with global bindings, customized local bindings done to Emacs state are not inherited by Insert state.

On rare occasions, local keys may be added by mistake. Usually this is done indirectly, by invoking a major mode that adds local keys (e.g., shell-mode redefines <RET>). In such a case, exiting the wrong major mode won't rid you from unwanted local keys, since these keys are local to Viper state and the current buffer, not to the major mode. In such situations, the remedy is to type M-x viper-zap-local-keys.

So much about Viper-specific bindings. See Customization, and the Emacs quick reference card for the general info on key bindings in Emacs.

Next: , Previous: Key Bindings, Up: Customization

3.2.1 Packages that Change Keymaps

Viper is designed to coexist with all major and minor modes of Emacs. This means that bindings set by those modes are generally available with Viper (unless you explicitly prohibit them by setting viper-want-emacs-keys-in-vi and viper-want-emacs-keys-in-insert to nil). If viper-always is set to t (which is the default), Viper will try to bring each buffer in the Viper state that is most appropriate for that buffer. Usually, this would be the Vi state, but sometimes it could be the Insert state or the Emacs state.

Some major mode bindings will necessarily be overwritten by Viper. Indeed, in Vi state, most of the 1-character keys are used for Vi-style editing. This usually causes no problems because most packages designed for editing files typically do not bind such keys. Instead, they use key sequences that start with C-x and C-c. This is why it was so important for us to free up C-x and C-c. It is common for language-specific major modes to bind <TAB> and C-j (the line feed) keys to various formatting functions. This is extremely useful, but may require some getting used to for a Vi user. If you decide that this feature is not for you, you can re-bind these keys as explained earlier (see Customization).

Binding for <TAB> is one of the most unusual aspects of Viper for many novice users. In Emacs, <TAB> is used to format text and programs, and is extremely useful. For instance, hitting <TAB> causes the current line to be re-indented in accordance with the context. In programming, this is very important, since improper automatic indentation would immediately alert the programmer to a possible error. For instance, if a ) or a " is missing somewhere above the current line, <TAB> is likely to mis-indent the line.

For this reason, Viper doesn't change the standard Emacs binding of <TAB>, thereby sacrificing Vi compatibility (except for users at level 1). Instead, in Viper, the key S-tab (shift+ tab) is chosen to emulate Vi's <TAB>.

We should note that on some non-windowing terminals, Shift doesn't modify the <TAB> key, so S-tab behaves as if it were <TAB>. In such a case, you will have to bind viper-insert-tab to some other convenient key.

Some packages, notably Dired, Gnus, Info, etc., attach special meaning to common keys like <SPC>, x, d, v, and others. This means that Vi command state is inappropriate for working with these packages. Fortunately, these modes operate on read-only buffers and are designed not for editing files, but for special-purpose browsing, reading news, mail, etc., and Vi commands are meaningless in these situations. For this reason, Viper doesn't force Vi state on such major modes—it brings them in Emacs state. You can switch to Vi state by typing C-z if, for instance, you want to do Vi-style search in a buffer (although, usually, incremental search, which is bound to C-s, is sufficient in these situations). But you should then switch back to Emacs state if you plan to continue using these major modes productively. You can also switch to Vi temporarily, to execute just one command. This is done by typing C-c \. (In some of these modes, / and : are bound Vi-style, unless these keys perform essential duties.)

If you would like certain major modes to come up in Emacs state rather than Vi state (but Viper thinks otherwise), you should put these major modes on the viper-emacs-state-mode-list list and delete them from viper-vi-state-mode-list. Likewise, you can force Viper's Insert state on a major mode by putting it in viper-insert-state-mode-list. It is also possible to impose Vi on some major modes, even though they may bind common keys to specialized commands. This might make sense for modes that bind only a small number of common keys. For instance, Viper subverts the Shell mode by changing the bindings for C-m and C-d using viper-add-local-keys described in the section on customization (see Customization).

In some cases, some minor modes might override certain essential bindings in Vi command state. This is not a big problem because this can happen only in the beginning, when the minor mode kicks in. Typing M-x viper-mode will correct the situation. Viper knows about several such minor modes and takes care of them, so the above trick is usually not necessary. If you find that some minor mode, e.g., nasty-mode interferes with Viper, putting the following in .viper should fix the problem: 

     (viper-harness-minor-mode "nasty-mode")

The argument to viper-harness-minor-mode is the name of the file for the offending minor mode with the suffixes .el and .elc removed.

It may not be always obvious which minor mode is at fault. The only guidance here is to look into the file that defines the minor mode you are suspecting, say nasty-mode.el, and see if it has a variable called nasty-mode-map. Then check if there is a statement of the form 

     (define-key nasty-mode-map key function)

that binds the misbehaving keys. If so, use the above line to harness nasty-mode. If your suspicion is wrong, no harm is done if you harness a minor mode that doesn't need to be harnessed.

It is recommended to harness even those minor modes that don't override Viper keys, but still have their own keymaps. A general way to make a minor mode, my-mode, compatible with Viper is to have the file my-mode.el include the following code: 

     (when (fboundp 'viper-harness-minor-mode)
       (let ((lib (file-name-sans-extension
                    (file-name-nondirectory load-file-name))))
         (viper-harness-minor-mode lib)))

Next: , Previous: Packages that Change Keymaps, Up: Customization

3.3 Viper Specials

Viper extends Vi with a number of useful features. This includes various search functions, histories of search strings, Ex commands, insertions, and Vi's destructive commands. In addition, Viper supports file name completion and history, completion of Ex commands and variables, and many other features. Some of these features are explained in detail elsewhere in this document. Other features are explained here.

(viper-buffer-search-enable)
viper-buffer-search-char nil
Enable buffer search. Explicit call to viper-buffer-search-enable sets viper-buffer-search-char to g. Alternatively, the user can set viper-buffer-search-char in .viper to a key sequence to be used for buffer search. There is no need to call viper-buffer-search-enable in that case.
viper-toggle-search-style
This function, bound to C-c /, lets one toggle case-sensitive and case-insensitive search, and also switch between plain vanilla search and search via regular expressions. Without the prefix argument, the user is asked which mode to toggle. With prefix argument 1, this toggles case-sensitivity. With prefix argument 2, regular expression/vanilla search will be toggled.

However, we found that the most convenient way to toggle these options is to bind a Vi macro to bind // to toggles case sensitivity and to /// to toggles vanilla search. Thus, quickly hitting / twice will switch Viper from case sensitive search to case-insensitive. Repeating this once again will restore the original state. Likewise, quickly hitting / three times will switch you from vanilla-style search to search via regular expressions. If you hit something other than / after the first / or if the second / doesn't follow quickly enough, then Viper will issue the usual prompt / and will wait for input, as usual in Vi. If you don't like this behavior, you can “unrecord” these macros in your ~/.viper file. For instance, if you don't like the above feature, put this in ~/.viper: 

          (viper-set-searchstyle-toggling-macros 'undefine)

If you don't like this feature as a default, but would still like to have it in some major modes, you can do so by first unsetting it globally, as shown above, and then setting it in the desired major modes as follows: 

          (viper-set-searchstyle-toggling-macros nil 'c-mode)
          (viper-set-searchstyle-toggling-macros nil 'lisp-mode)

Vi-isms in Emacs state
Some people find it useful to use the Vi-style search key, `/', to invoke search in modes which Viper leaves in emacs-state. These modes are: dired-mode, mh-folder-mode, Info-mode, and Buffer-menu-mode (more may be added in the future). So, in the above modes, Viper binds `/' so that it will behave Vi-style. Furthermore, in those major modes, Viper binds `:' to invoke ex-style commands, like in vi-state. And, as described above, `//' and `///' get bound to Vi-style macros that toggle case-insensitivity and regexp-search.

If you don't like these features—which I don't really understand—you can unbind `/' and `:' in viper-dired-modifier-map (for Dired) or in viper-slash-and-colon-map, for other modes. To unbind the macros `//' and `///' for a major mode where you feel they are undesirable, execute viper-set-emacs-state-searchstyle-macros with a non-nil argument. This can be done either interactively, by supplying a prefix argument, or by placing 

          (viper-set-emacs-state-searchstyle-macros 'undefine)

in the hook to the major mode (e.g., dired-mode-hook). See Vi Macros, for more information on Vi macros.

viper-heading-start
viper-heading-end
Regular Expressions for [[ and ]]. Note that Emacs defines Regexps for paragraphs and sentences. See Paragraphs and Sentences, for details.
M-x viper-set-expert-level
Change your user level interactively.
viper-smart-suffix-list '("" "tex" "c" "cc" "el" "p")
Viper supports Emacs-style file completion when it prompts the user for a file name. However, in many cases, the same directory may contain files with identical prefix but different suffixes, e.g., prog.c, prog.o, paper.tex, paper.dvi. In such cases, completion will stop at the `.'. If the above variable is a list of strings representing suffixes, Viper will try these suffixes in the order listed and will check if the corresponding file exists.

For instance, if completion stopped at `paper.' and the user typed <RET>, then Viper will check if the files `paper.', `paper.tex', `paper.c', etc., exist. It will take the first such file. If no file exists, Viper will give a chance to complete the file name by typing the appropriate suffix. If `paper.' was the intended file name, hitting return will accept it.

To turn this feature off, set the above variable to nil.

viper-insertion-ring-size 14
Viper remembers what was previously inserted in Insert and Replace states. Several such recent insertions are kept in a special ring of strings of size viper-insertion-ring-size. If you enter Insert or Replace state you can reinsert strings from this ring by typing C-c M-p or C-c M-n. The former will search the ring in the direction of older insertions, and the latter will search in the direction of newer insertions. Hitting C-c M-p or C-c M-n in succession will undo the previous insertion from the ring and insert the next item on the ring. If a larger ring size is needed, change the value of the above variable in the ~/.viper file.

Since typing these sequences of keys may be tedious, it is suggested that the user should bind a function key, such as f31, as follows: 

          (define-key viper-insert-global-user-map [f31]
                      'viper-insert-prev-from-insertion-ring)

This binds f31 (which is usually R11 on a Sun workstation) to the function that inserts the previous string in the insertion history. To rotate the history in the opposite direction, you can either bind an unused key to viper-insert-next-from-insertion-ring or hit any digit (1 to 9) then f31.

One should not bind the above functions to M-p or M-n, since this will interfere with the minibuffer histories and, possibly, other major modes.

viper-command-ring-size 14
Viper keeps track of the recent history of destructive commands, such as dw, i, etc. In Vi state, the most recent command can be re-executed by hitting `.', as in Vi. However, repeated typing C-c M-p will cause Viper to show the previous destructive commands in the minibuffer. Subsequent hitting `.' will execute the command that was displayed last. The key C-c M-n will cycle through the command history in the opposite direction. Since typing C-c M-p may be tedious, it is more convenient to bind an appropriate function to an unused function key on the keyboard and use that key. For instance, the following 
          (define-key viper-vi-global-user-map [f31]
                      'viper-prev-destructive-command)

binds the key f31 (which is usually R11 on a Sun workstation) to the function that searches the command history in the direction of older commands. To search in the opposite direction, you can either bind an unused key to viper-next-destructive-command or hit any digit (1 to 9) then f31.

One should not bind the above functions to M-p or M-n, since this will interfere with the minibuffer histories and, possibly, other major modes.

viper-minibuffer-vi-face 'viper-minibuffer-vi-face
viper-minibuffer-insert-face 'viper-minibuffer-insert-face
viper-minibuffer-emacs-face 'viper-minibuffer-emacs-face
These faces control the appearance of the minibuffer text in the corresponding Viper states. You can change the appearance of these faces through Emacs's customization widget, which is accessible through the menubar.

Viper is located in this widget under the Emulations customization subgroup of the Editing group. All Viper faces are grouped together in Viper's Highlighting customization subgroup.

Note that only the text you type in is affected by the above faces. Prompts and minibuffer messages are not affected.

Purists who do not like adornments in the minibuffer can always zap them by putting 

          (copy-face 'default 'viper-minibuffer-vi-face)
          (copy-face 'default 'viper-minibuffer-insert-face)
          (copy-face 'default 'viper-minibuffer-emacs-face)

in the ~/.viper file or through the customization widget, as described above. However, in that case, the user will not have any indication of the current Viper state in the minibuffer. (This is important if the user accidentally switches to another Viper state by typing <ESC> or C-z).

M-x viper-go-away
Make Viper disappear from the face of your running Emacs instance. If your fingers start aching again, M-x viper-mode might save your day.
M-x toggle-viper-mode
Toggle Viperization of Emacs on and off.

Viper provides some support for multi-file documents and programs. If a document consists of several files we can designate one of them as a master and put the following at the end of that file: 

     ;; Local Variables:
     ;; eval: (viper-setup-master-buffer "file1" "file2" "file3" "file4")
     ;; End:

where file1 to file4 are names of files related to the master file. Next time, when the master file is visited, the command viper-setup-master-buffer will be evaluated and the above files will be associated with the master file. Then, the new Ex command :RelatedFile (abbr. :R) will display files 1 to 4 one after another, so you can edit them. If a file is not in any Emacs buffer, it will be visited. The command PreviousRelatedFile (abbr., :P) goes through the file list in the opposite direction. These commands are akin to :n and :N, but they allow the user to focus on relevant files only.

Note that only the master file needs to have the aforementioned block of commands. Also, ";;" above can be replaced by some other markers. Semicolon is good for Lisp programs, since it is considered a comment designator there. For LaTeX, this could be "%%%", and for C the above block should be commented out.

Even though these commands are sometimes useful, they are no substitute for the powerful tag table facility of Emacs. Viper's :tag command in a primitive interface to Emacs tags. See Tags, for more information on tags.

The following two commands are normally bound to a mouse click and are part of Viper. They work only if Emacs runs as an application under X Windows (or under some other window system for which a port of GNU Emacs 20 is available). Clicking the mouse when Emacs is invoked in an Xterm window (using emacs -nw) will do no good.

viper-mouse-search-key (meta shift 1)
This variable controls the mouse-search feature of Viper. The default value states that holding Meta and Shift keys while clicking mouse button 1 should initiate search for a region under the mouse pointer (defined below). This command can take a prefix argument, which indicates the occurrence of the pattern to search for.

Note: while loading initially, Viper binds this mouse action only if it is not already bound to something else. If you want to use the mouse-search feature, and the Meta-Shift-Mouse-1 mouse action is already bound to something else, you can rebind the mouse-search feature by setting viper-mouse-search-key to something else in your ~/.viper file: 

          (setq viper-mouse-search-key '(meta 1))

This would bind mouse search to the action invoked by pressing the Meta key and clicking mouse button 1. The allowed values of viper-mouse-search-key are lists that contain a mouse-button number (1,2, or 3) and any combination of the words `control', `meta', and `shift'.

If the requested mouse action (e.g., (meta 1)) is already taken for other purposes then you have to confirm your intention by placing the following command in ~/.viper after setting viper-mouse-search-key: 

          (viper-bind-mouse-search-key 'force)

You can also change this setting interactively, through the customization widget of Emacs (type :customize).

The region that is chosen as a pattern to search for is determined as follows. If search is invoked via a single click, Viper chooses the region that lies between the beginning of the “word” under the pointer (“word” is understood in Vi sense) and the end of that word. The only difference with Vi's words is that in Lisp major modes `-' is considered an alphanumeric symbol. This is done for the convenience of working with Lisp symbols, which often have an `-' in them. Also, if you click on a non-alphanumeric character that is not a word separator (in Vi sense) then this character will also be considered alphanumeric, provided that it is adjacent (from either side) to an alphanumeric character. This useful feature gives added control over the patterns selected by the mouse click.

On a double-click, the region is determined by the beginning of the current Vi's “Word” (i.e., the largest non-separator chunk of text) and the End of that “Word” (as determined by the E command).

On a triple-click, the region consists of the entire line where the click occurred with all leading and trailing spaces and tabs removed.


viper-mouse-insert-key (meta shift 2)
This variable controls the mouse-insert feature of Viper. The above default value states that holding Meta and Shift keys while clicking mouse button 2 should insert the region surrounding the mouse pointer. The rules defining this region are the same as for mouse-search. This command takes an optional prefix argument, which indicates how many such regions to snarf from the buffer and insert. (In case of a triple-click, the prefix argument is ignored.)

Note: while loading initially, Viper binds this mouse action only if it not already bound to something else. If you want to use this feature and the default mouse action is already bound, you can rebind mouse-insert by placing this command in ~/.viper: 

          (setq viper-mouse-insert-key '(meta 2))

If you want to bind mouse-insert to an action even if this action is already taken for other purposes in Emacs, then you should add this command to ~/.viper, after setting viper-mouse-insert-key: 

          (viper-bind-mouse-insert-key 'force)

This value can also be changed via the Emacs customization widget at the menubar.

viper-multiclick-timeout
This variable controls the rate at which double-clicking must occur for the purpose of mouse search and mouse insert. By default, this is set to double-click-time in Emacs and to mouse-track-multi-click-time milliseconds in XEmacs.
Note: The above functions search and insert in the selected window of the latest active frame. This means that you can click in another window or another frame and have search or insertion done in the frame and window you just left. This lets one use these functions in a multi-frame configuration. However, this may require some getting used to. For instance, if you are typing in a frame, A, and then move the mouse to frame B and click to invoke mouse search, search (or insertion) will be performed in frame A. To perform search/insertion in frame B, you will first have to shift focus there, which doesn't happen until you type a character or perform some other action in frame B—mouse search doesn't shift focus.

If you decide that you don't like the above feature and always want search/insertion be performed in the frame where the click occurs, don't bind (and unbind, if necessary) viper-mouse-catch-frame-switch from the mouse event it is bound to.

Mouse search is integrated with Vi-style search, so you can repeat it with n and N. It should be also noted that, while case-sensitivity of search in Viper is controlled by the variable viper-case-fold-search, the case of mouse search is controlled by the Emacs variable case-fold-search, which may be set differently from viper-case-fold-search. Therefore, case-sensitivity of mouse search may be different from that of the usual Vi-style search.

Finally, if the way Viper determines the word to be searched for or to be inserted is not what you want, there is a variable, viper-surrounding-word-function, which can be changed to indicate another function for snarfing words out of the buffer. The catch is that you will then have to write such a function and make it known to your Emacs. The function viper-surrounding-word in viper.el can be used as a guiding example.

Previous: Viper Specials, Up: Customization

3.4 Vi Macros

Viper supports much enhanced Vi-style macros and also facilitates the use of Emacs-style macros. To define a temporary macro, it is generally more convenient to use Emacs keyboard macro facility. Emacs keyboard macros are usually defined anonymously, and the latest macro can be executed by typing C-x e (or *, if Viper is in Vi state). If you need to use several temporary macros, Viper lets you save them to a register (a lowercase letter); such macros can then be executed by typing @a in Vi state (if a macro was previously saved in register a). See Macros and Registers, for details.

If, however, you need to use a macro regularly, it must be given a permanent name and saved. Emacs manual explains how to do this, but invocation of named Emacs macros is quite different from Vi's. First, invocation of permanent Emacs macros takes time because it requires typing too many keys (to a Vi user's taste, anyway). Second, binding such macros to function keys, for fast access, hogs valuable real estate on the keyboard.

Vi-style macros are better in that respect, since Vi lets the user overload the meaning of key sequences: keys typed in fast succession are treated specially, if this key sequence is bound to a macro.

Viper provides Vi-style keyboard macros through the usual Ex commands, :map and :map!. These macros are much more powerful in Viper than they are in the original Vi and in other emulators. This is because Viper implements an enhanced vi-style interface to the powerful Emacs keyboard macro facility.

First, any Emacs command can be executed while defining a macro, not just the Vi commands. In particular, the user can invoke Emacs commands via M-x command-name or by pressing various function keys on the keyboard. One can even use the mouse, although this is usually not useful and is not recommended (and macros defined with the use of the mouse cannot be saved in command history and in the startup file, for future use).

Macros defined by mixing Vi and Emacs commands are represented as vectors. So, don't be confused when you see one (usually through the history of Ex commands). For instance, if gg is defined by typing l, the up-arrow key and M-x next-line, its definition will look as follows in Emacs: 

     [l up (meta x) n e x t - l i n e return]

Second, Viper macros are defined in a WYSIWYG style. This means that commands are executed as you type them, so you can see precisely what is being defined. Third, macros can be bound to arbitrary sequences of keys, not just to printable keys. For instance, one can define a macro that will be invoked by hitting f3 then f2 function keys. (The keys delete and backspace are excluded; also, a macro invocation sequence can't start with <ESC>. Some other keys, such as f1 and help, can't be bound to macros under Emacs, since they are bound in key-translation-map, which overrides any other binding the user gives to keys. In general, keys that have a binding in key-translation-map can't be bound to a macro.)

Fourth, in Viper, one can define macros that are specific to a given buffer, a given major mode, or macros that are defined for all buffers. In fact, the same macro name can have several different definitions: one global, several definitions for various major modes, and definitions for various specific buffers. Buffer-specific definitions override mode-specific definitions, which, in turn, override global definitions.

As if all that is not enough, Viper (through its interface to Emacs macros) lets the user define keyboard macros that ask for confirmation or even prompt the user for input and then continue. To do this, one should type C-x q (for confirmation) or C-u C-x q (for prompt). For details, see Customization

When the user finishes defining a macro (which is done by typing C-x), a departure from Vi), you will be asked whether you want this macro to be global, mode-specific, or buffer-specific. You will also be given a chance to save the macro in your ~/.viper file. This is the easiest way to save a macro and make it permanently available. If you work your startup files with bare hands, here is how Viper saves the above macro so that it will be available in Viper's Insert state (and Replace state) in buffer my-buf only: 

     (viper-record-kbd-macro "gg" 'insert-state
            [l up (meta x) n e x t - l i n e return]
            "my-buf")

To do the same for Vi state and all buffers with the major mode cc-mode, use: 

     (viper-record-kbd-macro "gg" 'vi-state
            [l up (meta x) n e x t - l i n e return]
            'cc-mode)

Both macro names and macro definitions are vectors of symbols that denote keys on the keyboard. Some keys, like \, , or digit-keys must be escaped with a backslash. Modified keys are represented as lists. For instance, holding Meta and Control and pressing f4 is represented as (control meta f4). If all members of a vectors are printable characters (or sequences, such as \e, \t, for <ESC> and <TAB>), then they can also be represented as strings: 

     (viper-record-kbd-macro "aa" 'vi-state  "aaa\e"  "my-buffer")

Thus, typing aa fast in Vi state will switch Viper to Insert state (due to the first a), insert aa, and then it will switch back to Vi state. All this will take effect only in the buffer named my-buffer.

Note that the last argument to viper-record-kbd-macro must be either a string (a buffer name), a symbol representing a major mode, or t; the latter says that the macro is to be defined for all buffers (which is how macros are defined in original Vi).

For convenience, Viper also lets you define Vi-style macros in its Emacs state. There is no Ex command, like :map and :map! for doing this, but the user can include such a macro in the ~/.viper file. The only thing is that the viper-record-kbd-macro command should specify emacs-state instead of vi-state or insert-state.

The user can get rid of a macro either by using the Ex commands :unmap and :unmap! or by issuing a call to viper-unrecord-kbd-macro. The latter is more powerful, since it can delete macros even in emacs-state. However, viper-unrecord-kbd-macro is usually needed only when the user needs to get rid of the macros that are already predefined in Viper. The syntax is: 

     (viper-unrecord-kbd-macro macro state)

The second argument must be vi-state, insert-state, or emacs-state. The first argument is a name of a macro. To avoid mistakes in specifying names of existing macros, type M-x viper-describe-kbd-macros and use a name from the list displayed by this command.

If an error occurs during macro definition, Emacs aborts the process, and it must be repeated. This is analogous to Vi, except that in Vi the user doesn't know there is an error until the macro is actually run. All that means that in order for a definition to be successful, the user must do some simple planning of the process in advance, to avoid errors. For instance, if you want to map gg to llll in Vi state, you must make sure that there is enough room on the current line. Since l moves the cursor forward, it may signal an error on reaching the end of line, which will abort the definition.

These precautions are necessary only when defining macros; they will help avoid the need to redo the job. When macros are actually run, an error during the execution will simply terminate the current execution (but the macro will remain mapped).

A macro name can be a string of characters or a vector of keys. The latter makes it possible to define macros bound to, say, double-hits on a function key, such as up or f13. This is very useful if you run out of function keys on your keyboard; it makes Viper macro facility a keyboard doubler, so to speak.

Elsewhere (See Key Bindings, for details), we review the standard Emacs mechanism for binding function keys to commands. For instance, 

     (global-set-key [f13] 'repeat-complex-command)

binds the key f13 to the Emacs function that repeats the last minibuffer command. Under Viper, however, you may still use this key for additional purposes, if you bind, say, a double-hitting action for that key to some other function. Emacs doesn't allow the user to do that, but Viper does this through its keyboard macro facility. To do this, type :map first. When you are asked to enter a macro name, hit f13 twice, followed by <RET> or <SPC>.

Emacs will now start the mapping process by actually executing Vi and Emacs commands, so that you could see what will happen each time the macro is executed. Suppose now we wanted to bind the key sequence f13 f13 to the command eval-last-sexp. To accomplish this, we can type M-x eval-last-sexp followed by C-x ). If you answer positively to Viper's offer to save this macro in ~/.viper for future uses, the following will be inserted in that file: 

     (viper-record-kbd-macro [f16 f16] 'vi-state
              [(meta x) e v a l - l a s t - s e x p]
              'lisp-interaction-mode)

To illustrate the above point, Viper provides two canned macros, which, by default, are bound to [f12 \1] and [f12 \2] (invoked by typing f12 then 1 and 2, respectively). These macros are useful shortcuts to Viper's command ring history. The first macro will execute the second-last destructive command (the last one is executed by ., as usual). The second macro executes the third-last command.

If you need to go deeper into the command history, you will have to use other commands, as described earlier in this section; or you can bind, say, f12 \3 like this: 

     (viper-record-kbd-macro [f12 \3] 'vi-state
                           [(meta x) r e p e a t - f r o m - h i s t o r y]
                           t)

Note that even though the macro uses the function key f12, the key is actually free and can still be bound to some Emacs function via define-key or global-set-key.

Viper allows the user to define macro names that are prefixes of other macros. For instance, one can define [[ and [[[[ to be macros. If you type the exact sequence of such keys and then pause, Viper will execute the right macro. However, if you don't pause and, say, type [[[[text then the conflict is resolved as follows. If only one of the key sequences, [[ or [[[[ has a definition applicable to the current buffer, then, in fact, there is no conflict and the right macro will be chosen. If both have applicable definitions, then the first one found will be executed. Usually this is the macro with a shorter name. So, in our case, [[[[text will cause the macro [[ to be executed twice and then the remaining keys, t e x t, will be processed.

When defining macros using :map or :map!, the user enters the actually keys to be used to invoke the macro. For instance, you should hit the actual key f6 if it is to be part of a macro name; you do not write f 6. When entering keys, Viper displays them as strings or vectors (e.g., "abc" or [f6 f7 a]). The same holds for unmapping. Hitting <TAB> while typing a macro name in the :unmap or :unmap! command will cause name completion. Completions are displayed as strings or vectors. However, as before, you don't actually type ‘"’, ‘[’, or ‘]’ that appear in the completions. These are meta-symbols that indicate whether the corresponding macro name is a vector or a string.

One last difference from Vi: Vi-style keyboard macros cannot be defined in terms of other Vi-style keyboard macros (but named Emacs macros are OK). More precisely, while defining or executing a macro, the special meaning of key sequences (as Vi macros) is ignored. This is because it is all too easy to create an infinite loop in this way. Since Viper macros are much more powerful than Vi's it is impossible to detect such loops. In practice, this is not really a limitation but, rather, a feature.

We should also note that Vi macros are disabled in the minibuffer, which helps keep some potential troubles away.

The rate at which the user must type keys in order for them to be recognized as a timeout macro is controlled by the variable viper-fast-keyseq-timeout, which defaults to 200 milliseconds.

For the most part, Viper macros defined in ~/.viper can be shared between X and TTY modes. The problem with TTY may be that the function keys there generate sequences of events instead of a single event (as under a window system). Emacs maps some of these sequences back to the logical keys (e.g., the sequences generated by the arrow keys are mapped to up, left, etc.). However, not all function keys are mapped in this way. Macros that are bound to key sequences that contain such unmapped function keys have to be redefined for TTY's (and possibly for every type of TTY you may be using). To do this, start Emacs on an appropriate TTY device and define the macro using :map, as usual.

Finally, Viper provides a function that conveniently displays all macros currently defined. To see all macros along with their definitions, type M-x viper-describe-kbd-macros.

Previous: Customization, Up: Top

4 Commands

This section is a semi-automatically bowdlerized version of the Vi reference created by
‘maart@cs.vu.nl’ and others. It can be found on the Vi archives. This reference has been adapted for Viper.

Next: , Previous: Commands, Up: Commands

4.1 Groundwork

The VI command set is based on the idea of combining motion commands with other commands. The motion command is used as a text region specifier for other commands. We classify motion commands into point commands and line commands.

The point commands are:

h, l, 0, $, w, W, b, B, e, E, (, ), /, ?, `, f, F, t, T, %, ;, ,, ^

The line commands are:

j, k, +, -, H, M, L, {, }, G, ', [[, ]], []
Text Deletion Commands (see Deleting Text), Change commands (see Changing Text), even Shell Commands (see Shell Commands) use these commands to describe a region of text to operate on.

Viper adds two region descriptors, r and R. These describe the Emacs regions (see Basics), but they are not movement commands.

The command description uses angle brackets ‘<>’ to indicate metasyntactic variables, since the normal conventions of using simple text can be confusing with Viper where the commands themselves are characters. Watch out where < shift commands and <count> are mentioned together!!!

‘<move>’ refers to the above movement commands, and ‘<a-z>’ refers to registers or textmarkers from ‘a’ to ‘z’. Note that the ‘<move>’ is described by full move commands, that is to say they will take counts, and otherwise behave like normal move commands. ‘<address>’ refers to Ex line addresses, which include

. <No address>
Current line
.+n .-n
Add or subtract for current line
number
Actual line number, use .= to get the line number
'<a-z>
Textmarker
$
Last line
x,y
Where x and y are one of the above
%
For the whole file, same as (1,$).
/<pat>/
?<pat>?
Next or previous line with pattern <pat>.

Note that the pattern is allowed to contain newline character (inserted as C-qC-j). Therefore, one can search for patterns that span several lines.

Note that ‘%’ is used in Ex commands :e and :r <shell-cmd> to mean current file. If you want a ‘%’ in your command, it must be escaped as ‘\%’. Note that :w and the regular :r <file> command doesn't support the meta symbols ‘%’ and ‘#’, because file history is a better mechanism. Similarly, ‘#’ expands to the previous file. The previous file is the first file in :args listing. This defaults to previous window in the VI sense if you have one window only.

Others like ‘<args> -- arguments’, ‘<cmd> -- command’ etc. should be fairly obvious.

Common characters referred to include:

<sp>
Space
<ht>
Tab
<lf>
Linefeed
<esc>
Escape
<cr>
Return, Enter
We also use ‘word’ for alphanumeric/non-alphanumeric words, and ‘WORD’ for whitespace delimited words. ‘char’ refers to any ASCII character, ‘CHAR’ to non-whitespace character. Brackets ‘[]’ indicate optional parameters; ‘<count>’ also optional, usually defaulting to 1. Brackets are elided for ‘<count>’ to eschew obfuscation.

Viper's idea of Vi's words is slightly different from Vi. First, Viper words understand Emacs symbol tables. Therefore, all symbols declared to be alphanumeric in a symbol table can automatically be made part of the Viper word. This is useful when, for instance, editing text containing European, Cyrillic, Japanese, etc., texts.

Second, Viper lets you depart from Vi's idea of a word by changing the a syntax preference via the customization widget (the variable viper-syntax-preference) or by executing viper-set-syntax-preference interactively.

By default, Viper syntax preference is reformed-vi, which means that Viper considers only those symbols to be part of a word that are specified as word-symbols by the current Emacs syntax table (which may be different for different major modes) plus the underscore symbol _, minus the symbols that are not considered words in Vi (e.g., `,',;, etc.), but may be considered as word-symbols by various Emacs major modes. Reformed-Vi works very close to Vi, and it also recognizes words in other alphabets. Therefore, this is the most appropriate mode for editing text and is likely to fit all your needs.

You can also set Viper syntax preference to strict-vi, which would cause Viper to view all non-English letters as non-word-symbols.

You can also specify emacs as your preference, which would make Viper use exactly the same notion of a word as Emacs does. In particular, the underscore may not be part of a word in some major modes.

Finally, if viper-syntax-preference is set to extended, Viper words would consist of characters that are classified as alphanumeric or as parts of symbols. This is convenient for editing programs.

viper-syntax-preference is a local variable, so it can have different values for different major modes. For instance, in programming modes it can have the value extended. In text modes where words contain special characters, such as European (non-English) letters, Cyrillic letters, etc., the value can be reformed-vi or emacs. If you consider using different syntactic preferences for different major modes, you should execute, for example, 

     (viper-set-syntax-preference nil "extended")

in the appropriate major mode hooks.

The above discussion concerns only the movement commands. In regular expressions, words remain the same as in Emacs. That is, the expressions \w, \>, \<, etc., use Emacs's idea of what is a word, and they don't look into the value of variable viper-syntax-preference. This is because Viper avoids changing syntax tables in order to not thwart the various major modes that set these tables.

The usual Emacs convention is used to indicate Control Characters, i.e., C-h for Control-h. Do not confuse this with a sequence of separate characters C, -, h!!! The ^ is itself, never used to indicate a Control character.

Finally, we note that Viper's Ex-style commands can be made to work on the current Emacs region. This is done by typing a digit argument before :. For instance, typing 1: will prompt you with something like :123,135, assuming that the current region starts at line 123 and ends at line 135. There is no need to type the line numbers, since Viper inserts them automatically in front of the Ex command.

Next: , Previous: Groundwork, Up: Commands

4.2 Text Handling

Next: , Up: Text Handling

4.2.1 Move Commands

<count> h C-h
<count> chars to the left.
<count> j <lf> C-n
<count> lines downward.
<count> l <sp>
<count> chars to the right.
<count> k C-p
<count> lines upward.
<count> $
To the end of line <count> from the cursor.
<count> ^
To the first CHAR <count> − 1 lines lower.
<count> -
To the first CHAR <count> lines higher.
<count> + <cr>
To the first CHAR <count> lines lower.
0
To the first char of the line.
<count> |
To column <count>
<count> f<char>
<count> <char>s to the right (find).
<count> t<char>
Till before <count> <char>s to the right.
<count> F<char>
<count> <char>s to the left.
<count> T<char>
Till after <count> <char>s to the left.
<count> ;
Repeat latest f t F T <count> times.
<count> ,
Repeat latest f t F T <count> times in opposite direction.
<count> w
<count> words forward.
<count> W
<count> WORDS forward.
<count> b
<count> words backward.
<count> B
<count> WORDS backward.
<count> e
To the end of word <count> forward.
<count> E
To the end of WORD <count> forward.
<count> G
Go to line <count> (default end-of-file).
<count> H
To line <count> from top of the screen (home).
<count> L
To line <count> from bottom of the screen (last).
M
To the middle line of the screen.
<count> )
<count> sentences forward.
<count> (
<count> sentences backward.
<count> }
<count> paragraphs forward.
<count> {
<count> paragraphs backward.
<count> ]]
To the <count>th heading.
<count> [[
To the <count>th previous heading.
<count> []
To the end of <count>th heading.
m<a-z>
Mark the cursor position with a letter.
`<a-z>
To the mark.
'<a-z>
To the first CHAR of the line with the mark.
[<a-z>
Show contents of textmarker.
]<a-z>
Show contents of register.
``
To the cursor position before the latest absolute jump (of which are examples / and G).
''
To the first CHAR of the line on which the cursor was placed before the latest absolute jump.
<count> /<string>
To the <count>th occurrence of <string>.
<count> /<cr>
To the <count>th occurrence of <string> from previous / or ?.
<count> ?<string>
To the <count>th previous occurrence of <string>.
<count> ?<cr>
To the <count>th previous occurrence of <string> from previous ? or /.
n
Repeat latest / ? (next).
N
Repeat latest search in opposite direction.
C-c /
Without a prefix argument, this command toggles case-sensitive/case-insensitive search modes and plain vanilla/regular expression search. With the prefix argument 1, i.e., 1 C-c /, this toggles case-sensitivity; with the prefix argument 2, toggles plain vanilla search and search using regular expressions. See Viper Specials, for alternative ways to invoke this function.
%
Find the next bracket/parenthesis/brace and go to its match. By default, Viper ignores brackets/parentheses/braces that occur inside parentheses. You can change this by setting viper-parse-sexp-ignore-comments to nil in your .viper file. This option can also be toggled interactively if you quickly hit %%%.

This latter feature is implemented as a vi-style keyboard macro. If you don't want this macro, put 

          (viper-set-parsing-style-toggling-macro 'undefine)

in your ~/.viper file.

Next: , Previous: Move Commands, Up: Text Handling

4.2.2 Marking

Emacs mark is referred to in the region specifiers r and R. See Emacs Preliminaries, and See Basics, for explanation. Also see Mark, for an explanation of the Emacs mark ring.

m<a-z>
Mark the current file and position with the specified letter.
m .
Set the Emacs mark (see Emacs Preliminaries) at point.
m ^
Set the Emacs mark (see Emacs Preliminaries) back to where it was last set with the m. command. This is useful when you set the mark with m., but then some other command (such as L or G) changes it in a way that you didn't like.
m <
Set the Emacs mark at beginning of buffer.
m >
Set the Emacs mark at end of buffer.
m ,
Jump to the Emacs mark.
:mark <char>
Mark position with text marker named <char>. This is an Ex command.
:k <char>
Same as :mark.
``
Exchange point and mark.
''
Exchange point and mark and go to the first CHAR on line.
'<a-z>
Go to specified Viper mark.
`<a-z>
Go to specified Viper mark and go to the first CHAR on line.

Next: , Previous: Marking, Up: Text Handling

4.2.3 Appending Text

See Options, to see how to change tab and shiftwidth size. See the GNU Emacs manual, or try C-ha tabs (If you have turned Emacs help on). Check out the variable indent-tabs-mode to put in just spaces. Also see options for word-wrap.

<count> a
<count> times after the cursor.
<count> A
<count> times at the end of line.
<count> i
<count> times before the cursor (insert).
<count> I
<count> times before the first CHAR of the line
<count> o
On a new line below the current (open). The count is only useful on a slow terminal.
<count> O
On a new line above the current. The count is only useful on a slow terminal.
<count> ><move>
Shift the lines described by <count><move> one shiftwidth to the right (layout!).
<count> >>
Shift <count> lines one shiftwidth to the right.
<count> ["<a-z1-9>]p
Put the contents of the (default undo) buffer <count> times after the cursor. The register will be automatically down-cased.
<count> ["<a-z1-9>]P
Put the contents of the (default undo) buffer <count> times before the cursor. The register will
[<a-z>
Show contents of textmarker.
]<a-z>
Show contents of register.
<count> .
Repeat previous command <count> times. For destructive commands as well as undo.
f1 1 and f1 2
While . repeats the last destructive command, these two macros repeat the second-last and the third-last destructive commands. See Vi Macros, for more information on Vi macros.
C-c M-p and C-c M-n
In Vi state, these commands help peruse the history of Vi's destructive commands. Successive typing of C-c M-p causes Viper to search the history in the direction of older commands, while hitting C-c M-n does so in reverse order. Each command in the history is displayed in the minibuffer. The displayed command can then be executed by typing `.'.

Since typing the above sequences of keys may be tedious, the functions doing the perusing can be bound to unused keyboard keys in the ~/.viper file. See Viper Specials, for details.

Next: , Previous: Appending Text, Up: Text Handling

4.2.4 Editing in Insert State

Minibuffer can be edited similarly to Insert state, and you can switch between Insert/Replace/Vi states at will. Some users prefer plain Emacs feel in the minibuffer. To this end, set viper-vi-style-in-minibuffer to nil.

C-v
Deprive the next char of its special meaning (quoting).
C-h
One char back.
C-w
One word back.
C-u
Back to the begin of the change on the current line.

Next: , Previous: Editing in Insert State, Up: Text Handling

4.2.5 Deleting Text

There is one difference in text deletion that you should be aware of. This difference comes from Emacs and was adopted in Viper because we find it very useful. In Vi, if you delete a line, say, and then another line, these two deletions are separated and are put back separately if you use the ‘p’ command. In Emacs (and Viper), successive series of deletions that are not interrupted by other commands are lumped together, so the deleted text gets accumulated and can be put back as one chunk. If you want to break a sequence of deletions so that the newly deleted text could be put back separately from the previously deleted text, you should perform a non-deleting action, e.g., move the cursor one character in any direction.

<count> x
Delete <count> chars under and after the cursor.
<count> X
Delete <count> chars before the cursor.
<count> d<move>
Delete from point to endpoint of <count><move>.
<count> dd
Delete <count> lines.
D
The rest of the line.
<count> <<move>
Shift the lines described by <count><move> one shiftwidth to the left (layout!).
<count> <<
Shift <count> lines one shiftwidth to the left.

Next: , Previous: Deleting Text, Up: Text Handling

4.2.6 Changing Text

<count> r<char>
Replace <count> chars by <char>; no <esc>.
<count> R
Overwrite the rest of the line, appending change count − 1 times.
<count> s
Substitute <count> chars.
<count> S
Change <count> lines.
<count> c<move>
Change from begin to endpoint of <count><move>.
<count> cc
Change <count> lines.
<count> C
The rest of the line and <count> − 1 next lines.
<count> =<move>
Reindent the region described by move.
<count> ~
Switch lower and upper cases.
<count> J
Join <count> lines (default 2).
:[x,y]s/<pat>/<repl>/<f>
Substitute (on lines x through y) the pattern <pat> (default the last pattern) with <repl>. Useful flags <f> are ‘g’ for ‘global’ (i.e., change every non-overlapping occurrence of <pat>) and ‘c’ for ‘confirm’ (type ‘y’ to confirm a particular substitution, else ‘n’ ). Instead of / any punctuation CHAR unequal to <space> <tab> and <lf> can be used as delimiter.

In Emacs, ‘\&’ stands for the last matched expression, so s/[ab]+/\&\&/ will double the string matched by [ab]. Viper doesn't treat ‘&’ specially, unlike Vi: use ‘\&’ instead.

Viper does not parse search patterns and does not expand special symbols found there (e.g., ‘~’ is not expanded to the result of the previous substitution).

Note: The newline character (inserted as C-qC-j) can be used in <repl>.

:[x,y]copy [z]
Copy text between x and y to the position after z.
:[x,y]t [z]
Same as :copy.
:[x,y]move [z]
Move text between x and y to the position after z.
&
Repeat latest Ex substitute command, e.g., :s/wrong/right.
:x,yp
:g/Pat/p
:v/Pat/p
The above commands display certain buffer lines in a temporary buffer. The first form above displays the buffer lines between x and y. The second displays the lines of the buffer, which match a given pattern. The third form displays the lines that do not match the given pattern.
#c<move>
Change upper-case characters in the region to lower-case.
#C<move>
Change lower-case characters in the region to upper-case.
#q<move>
Insert specified string at the beginning of each line in the region
C-c M-p and C-c M-n
In Insert and Replace states, these keys are bound to commands that peruse the history of the text previously inserted in other insert or replace commands. By repeatedly typing C-c M-p or C-c M-n, you will cause Viper to insert these previously used strings one by one. When a new string is inserted, the previous one is deleted.

In Vi state, these keys are bound to functions that peruse the history of destructive Vi commands. See Viper Specials, for details.

Next: , Previous: Changing Text, Up: Text Handling

4.2.7 Search and Replace

See Groundwork, for Ex address syntax. See Options, to see how to get literal (non-regular-expression) search and how to stop search from wrapping around.

C-c /
Toggle case-sensitive search. With prefix argument, toggle vanilla/regular expression search.
<count> /<string>
To the <count>th occurrence of <string>.

Viper does not parse search patterns and does not expand special symbols found there (e.g., ‘~’ is not expanded to the result of the previous substitution).

After typing / or ? all the usual Emacs minibuffer commands, such as M-p and M-n are available. In addition, typing C-s will insert the last search string used by the Emacs incremental search command (which is bound to C-s everywhere except in this case).

<count> ?<string>
To the <count>th previous occurrence of <string>.
<count> g<move>
Search for the text described by move. (off by default)
n
Repeat latest / ? (next).
N
Idem in opposite direction.
%
Find the next bracket and go to its match
:[x,y]g/<string>/<cmd>
Search globally [from line x to y] for <string> and execute the Ex <cmd> on each occurrence.
:[x,y]v/<string>/<cmd>
Execute <cmd> on the lines that don't match.
#g<move>
Execute the last keyboard macro for each line in the region. See Macros and Registers, for more info.
Q
Query Replace.
:ta <name>
Search in the tags file where <name> is defined (file, line), and go to it.
:[x,y]s/<pat>/<repl>/<f>
Substitute (on lines x through y) the pattern <pat> (default the last pattern) with <repl>. Useful flags <f> are ‘g’ for ‘global’ (i.e., change every non-overlapping occurrence of <pat>) and ‘c’ for ‘confirm’ (type ‘y’ to confirm a particular substitution, else ‘n’). Instead of / any punctuation character other than <space> <tab> and <lf> can be used as delimiter.

Note: The newline character (inserted as C-qC-j) can be used in <repl>.

&
Repeat latest Ex substitute command, e.g., :s/wrong/right.
:global /<pattern>/<ex-command>
:g /<pattern>/<ex-command>
Execute <ex-command> on all lines that match <pattern>.
:vglobal /<pattern>/<ex-command>
:v /<pattern>/<ex-command>
Execute <ex-command> on all lines that do not match <pattern>.

Next: , Previous: Search and Replace, Up: Text Handling

4.2.8 Yanking

<count> y<move>
Yank from begin to endpoint of <count><move>.
<count> "<a-z>y<move>
Yank from begin to endpoint of <count><move> to register.
<count> "<A-Z>y<move>
Yank from begin to endpoint of <count><move> and append to register.
<count> yy
<count> lines.
<count> Y
Idem (should be equivalent to y$ though).
m<a-z>
Mark the cursor position with a letter.
[<a-z>
Show contents of textmarker.
]<a-z>
Show contents of register.
<count> ["<a-z1-9>]p
Put the contents of the (default undo) buffer <count> times after the cursor. The register will be automatically down-cased.
<count> ["<a-z1-9>]P
Put the contents of the (default undo) buffer <count> times before the cursor. The register will

Previous: Yanking, Up: Text Handling

4.2.9 Undoing

u U
Undo the latest change.
.
Repeat undo.
:q!
Quit Vi without writing.
:e!
Re-edit a messed-up file.
:rec
Recover file from autosave. Viper also creates backup files that have a ‘~’ appended to them.

Next: , Previous: Text Handling, Up: Commands

4.3 Display

C-g
At user level 1, give file name, status, current line number and relative position.
At user levels 2 and higher, abort the current command.
C-c g
Give file name, status, current line number and relative position—all user levels.
C-l
Refresh the screen.
<count> C-e
Expose <count> more lines at bottom, cursor stays put (if possible).
<count> C-y
Expose <count> more lines at top, cursor stays put (if possible).
<count> C-d
Scroll <count> lines downward (default the number of the previous scroll; initialization: half a page).
<count> C-u
Scroll <count> lines upward (default the number of the previous scroll; initialization: half a page).
<count> C-f
<count> pages forward.
<count> C-b
<count> pages backward (in older versions C-b only works without count).
<count> z<cr>
zH
Put line <count> at the top of the window (default the current line).
<count> z-
zL
Put line <count> at the bottom of the window (default the current line).
<count> z.
zM
Put line <count> in the center of the window (default the current line).

Next: , Previous: Display, Up: Commands

4.4 File and Buffer Handling

In all file handling commands, space should be typed before entering the file name. If you need to type a modifier, such as >> or !, don't put any space between the command and the modifier.

Note that many Ex commands, e.g., :w, accept command arguments. The effect is that the command would start acting on the current region. For instance, if the current region spans the lines 11 through 22, then if you type 1:w you would see ‘:11,22w’ in the minibuffer.

:q
Quit buffer except if modified.
:q!
Quit buffer without checking. In Viper, these two commands are identical. Confirmation is required if exiting modified buffers that visit files.
:suspend
:stop
Suspend Viper
:[x,y] w
Write the file. Viper makes sure that a final newline is always added to any file where this newline is missing. This is done by setting Emacs variable require-final-newline to t. If you don't like this feature, use setq-default to set require-final-newline to nil. This must be done in .viper file.
:[x,y] w <name>
Write to the file <name>.
:[x,y] w>> <name>
Append the buffer to the file <name>. There should be no space between w and >>. Type space after the >> and see what happens.
:w! <name>
Overwrite the file <name>. In Viper, :w and :w! are identical. Confirmation is required for writing to an existing file (if this is not the file the buffer is visiting) or to a read-only file.
:x,y w <name>
Write lines x through y to the file <name>.
:wq
Write the file and kill buffer.
:r <file> [<file> ...]
Read file into a buffer, inserting its contents after the current line.
:xit
Same as :wq.
:Write
:W
Save all unsaved buffers, asking for confirmation.
:WWrite
:WW
Like W, but without asking for confirmation.
ZZ
Save current buffer and kill it. If user level is 1, then save all files and kill Emacs. Killing Emacs is the wrong way to use it, so you should switch to higher user levels as soon as possible.
:x [<file>]
Save and kill buffer.
:x! [<file>]
:w![<file>] and :q.
:pre
Preserve the file—autosave buffers.
:rec
Recover file from autosave.
:f [<file>]
without the argument, prints file name and character/line information afout the currently visited file. With an argument, sets the currently visited filename to file.
:cd [<dir>]
Set the working directory to <dir> (default home directory).
:pwd
Print present working directory.
:e [+<cmd>] <files>
Edit files. If no filename is given, edit the file visited by the current buffer. If buffer was modified or the file changed on disk, ask for confirmation. Unlike Vi, Viper allows :e to take multiple arguments. The first file is edited the same way as in Vi. The rest are visited in the usual Emacs way.
:e! [+<cmd>] <files>
Re-edit file. If no filename, re-edit current file. In Viper, unlike Vi, e! is identical to :e. In both cases, the user is asked to confirm if there is a danger of discarding changes to a buffer.
:q!
Quit Vi without writing.
C-^
Edit the alternate (normally the previous) file.
:rew
Obsolete
:args
List files not shown anywhere with counts for next
:n [count] [+<cmd>] [<files>]
Edit <count> file, or edit files. The count comes from :args.
:N [count] [+<cmd>] [<files>]
Like :n, but the meaning of the variable ex-cycle-other-window is reversed.
:b
Switch to another buffer. If ex-cycle-other-window is t, switch in another window. Buffer completion is supported. The variable viper-read-buffer-function controls which function is actually used to read the buffer name. The default is read-buffer, but better alternatives are also available in Emacs (e.g., iswitchb-read-buffer).
:B
Like :b, but the meaning of ex-cycle-other-window is reversed.
:<address>r <name>
Read the file <name> into the buffer after the line <address>.
v, V, C-v
Edit a file in current or another window, or in another frame. File name is typed in minibuffer. File completion and history are supported.

Next: , Previous: File and Buffer Handling, Up: Commands

4.5 Mapping

:map <string>
Start defining a Vi-style keyboard macro. For instance, typing :map www followed by :!wc % and then typing C-x ) will cause www to run wc on current file (Vi replaces ‘%’ with the current file name).
C-x )
Finish defining a keyboard macro. In Viper, this command completes the process of defining all keyboard macros, whether they are Emacs-style or Vi-style. This is a departure from Vi, needed to allow WYSIWYG mapping of keyboard macros and to permit the use of function keys and arbitrary Emacs functions in the macros.
:unmap <string>
Deprive <string> of its mappings in Vi state.
:map! <string>
Map a macro for Insert state.
:unmap! <string>
Deprive <string> of its mapping in Insert state (see :unmap).
@<a-z>
In Vi state, execute the contents of register as a command.
@@
In Vi state, repeat last register command.
@#
In Vi state, begin keyboard macro. End with @<a-z>. This will put the macro in the proper register. Register will be automatically down-cased. See Macros and Registers, for more info.
@!<a-z>
In Vi state, yank anonymous macro to register
*
In Vi state, execute anonymous macro (defined by C-x( and C-x )).
C-x e
Like *, but works in all Viper states.
#g<move>
Execute the last keyboard macro for each line in the region. See Macros and Registers, for more info.
[<a-z>
Show contents of textmarker.
]<a-z>
Show contents of register.

Next: , Previous: Mapping, Up: Commands

4.6 Shell Commands

The symbol ‘%’ is used in Ex shell commands to mean current file. If you want a ‘%’ in your command, it must be escaped as ‘\%’. However if ‘%’ is the first character, it stands as the address for the whole file. Similarly, ‘#’ expands to the previous file. The previous file is the first file in :args listing. This defaults to the previous file in the VI sense if you have one window.

Symbols ‘%’ and ‘#’ are also used in the Ex commands :e and :r <shell-cmd>. The commands :w and the regular :r <file> command don't support these meta symbols, because file history is a better mechanism.

:sh
Execute a subshell in another window
:[x,y]!<cmd>
Execute a shell <cmd> [on lines x through y; % is replace by current file, \% is changed to %
:[x,y]!! [<args>]
Repeat last shell command [and append <args>].
:!<cmd>
Just execute command and display result in a buffer.
:!! <args>
Repeat last shell command and append <args>
<count> !<move><cmd>
The shell executes <cmd>, with standard input the lines described by <count><move>, next the standard output replaces those lines (think of ‘cb’, ‘sort’, ‘nroff’, etc.).
<count> !!<cmd>
Give <count> lines as standard input to the shell <cmd>, next let the standard output replace those lines.
:[x,y] w !<cmd>
Let lines x to y be standard input for <cmd> (notice the <sp> between w and !).
:<address>r !<cmd>
Put the output of <cmd> after the line <address> (default current).
:<address>r <name>
Read the file <name> into the buffer after the line <address> (default current).
:make
Run the make command in the current directory.

Next: , Previous: Shell Commands, Up: Commands

4.7 Options

autoindent
ai
autoindent: In append mode after a <cr> the cursor will move directly below the first character on the previous line. This setting affects the current buffer only.
autoindent-global
ai-global
Same as `autoindent', but affects all buffers.
noautoindent
noai
Cancel autoindent.
noautoindent-global
noai-g
Cancel autoindent-global.
ignorecase
ic
ignorecase: No distinction between upper and lower cases when searching.
noignorecase
noic
Cancel ignorecase.
magic
ma
Regular expressions used in searches; nomagic means no regexps.
nomagic
noma
Cancel magic.
readonly
ro
readonly: The file is not to be changed. If the user attempts to write to this file, confirmation will be requested.
noreadonly
noro
Cancel readonly.
shell=<string>
sh=<string>
shell: The program to be used for shell escapes (default ‘$SHELL’ (default /bin/sh)).
shiftwidth=<count>
sw=<count>
shiftwidth: Gives the shiftwidth (default 8 positions).
showmatch
sm
showmatch: Whenever you append a ), Vi shows its match if it's on the same page; also with { and }. If there's no match, Vi will beep.
noshowmatch
nosm
Cancel showmatch.
tabstop=<count>
ts=<count>
tabstop: The length of a <ht>; warning: this is only IN the editor, outside of it <ht>s have their normal length (default 8 positions). This setting affects the current buffer only.
tabstop-global
ts-g
Same as `tabstop', but affects all buffers.
wrapmargin=<count>
wm=<count>
wrapmargin: In append mode Vi automatically puts a <lf> whenever there is a <sp> or <ht> within <wm> columns from the right margin.
wrapscan
ws
wrapscan: When searching, the end is considered ‘stuck’ to the begin of the file.
nowrapscan
nows
Cancel wrapscan.
:set <option>
Turn <option> on.
:set no<option>
Turn <option> off.
:set <option>=<value>
Set <option> to <value>.

Previous: Options, Up: Commands

4.8 Emacs Related Commands

C-\
Begin Meta command in Vi or Insert states. Most often used as C-\ x (M-x).

Note: Emacs binds C-\ to a function that offers to change the keyboard input method in the multilingual environment. Viper overrides this binding. However, it is still possible to switch the input method by typing \ C-\ in the Vi command state and C-z \ C-\ in the Insert state. Or you can use the MULE menu on the menubar.

C-z
In Insert and Replace states, prepare Viper to accept the next command and execute it as if Viper was in Vi state. Then return to Insert state.

In Vi state, switch to Emacs state; in Emacs state, switch to Vi state.

C-c \
Switches to Vi state for the duration of a single command. Then goes back to the original Viper state. Works from Vi, Insert, Replace, and Emacs states.
C-x0
Close Window
C-x1
Close Other Windows
C-x2
Split Window
C-xo
Move among windows
C-xC-f
Emacs find-file, useful in Insert state
C-y
Put back the last killed text. Similar to Vi's p, but also works in Insert and Replace state. This command doesn't work in Vi command state, since this binding is taken for something else.
M-y
Undoes the last C-y and puts another kill from the kill ring. Using this command, you can try may different kills until you find the one you need.

Up: Commands

4.9 Mouse-bound Commands

The following two mouse actions are normally bound to special search and insert commands in of Viper:

S-Mouse-1
Holding Shift and clicking mouse button 1 will initiate search for a region under the mouse pointer. This command can take a prefix argument. Note: Viper sets this binding only if this mouse action is not already bound to something else. See Viper Specials, for more information.
S-Mouse-2
Holding Shift and clicking button 2 of the mouse will insert a region surrounding the mouse pointer. This command can also take a prefix argument. Note: Viper sets this binding only if this mouse action is not already bound to something else. See Viper Specials, for more details.

Up: Top

Acknowledgments

Viper, formerly known as VIP-19, was written by Michael Kifer. Viper is based on the original VIP package by Masahiko Sato and on its enhancement, VIP 4.4, by Aamod Sane. This manual is an adaptation of the manual for VIP 4.4, which, in turn, was based on Sato's manual for VIP 3.5.

Many contributors on the Net pointed out bugs and suggested a number of useful features. Scott Bronson and Samuel Padgett contributed patches that were incorporated in this code. Here is a hopefully complete list of contributors: 

     aaronl@vitelus.com (Aaron Lehmann),
     ahg@panix.com (Al Gelders),
     amade@diagram.fr (Paul-Bernard Amade),
     ascott@fws214.intel.com (Andy Scott),
     bronson@trestle.com (Scott Bronson),
     cook@biostat.wisc.edu (Tom Cook),
     csdayton@midway.uchicago.edu (Soren Dayton),
     dave@hellgate.utah.edu,
     dm@scs.cs.nyu.edu (David Mazieres),
     dominik@strw.LeidenUniv.nl (Carsten Dominik),
     dwallach@cs.princeton.edu (Dan Wallach),
     dwight@toolucky.llnl.gov (Dwight Shih),
     dxc@xprt.net (David X Callaway),
     edmonds@edmonds.home.cs.ubc.ca (Brian Edmonds),
     gin@mo.msk.ru (Golubev I.N.),
     gviswana@cs.wisc.edu (Guhan Viswanathan),
     gvr@halcyon.com (George V. Reilly),
     hatazaki@bach.convex.com (Takao Hatazaki),
     hpz@ibmhpz.aug.ipp-garching.mpg.de (Hans-Peter Zehrfeld),
     irie@t.email.ne.jp (Irie Tetsuya),
     jackr@dblues.engr.sgi.com (Jack Repenning),
     jamesm@bga.com (D.J. Miller II),
     jjm@hplb.hpl.hp.com (Jean-Jacques Moreau),
     jl@cse.ogi.edu (John Launchbury),
     jobrien@hchp.org (John O'Brien),
     johnw@borland.com (John Wiegley),
     kanze@gabi-soft.fr (James Kanze),
     kin@isi.com (Kin Cho),
     kwzh@gnu.org (Karl Heuer),
     lindstro@biostat.wisc.edu (Mary Lindstrom),
     lektu@terra.es (Juanma Barranquero),
     lennart.borgman.073@student.lu.se (Lennart Borgman),
     minakaji@osaka.email.ne.jp (Mikio Nakajima),
     Mark.Bordas@East.Sun.COM (Mark Bordas),
     meyering@comco.com (Jim Meyering),
     martin@xemacs.org (Martin Buchholz),
     mbutler@redfernnetworks.com (Malcolm Butler),
     mveiga@dit.upm.es (Marcelino Veiga Tuimil),
     paulk@summit.esg.apertus.com (Paul Keusemann),
     pfister@cs.stonybrook.edu (Hanspeter Pfister),
     phil_brooks@MENTORG.COM (Phil Brooks),
     pogrell@informatik.hu-berlin.de (Lutz Pogrell),
     pradyut@cs.uchicago.edu (Pradyut Shah),
     roderick@argon.org (Roderick Schertler),
     rxga@ulysses.att.com,
     sawdey@lcse.umn.edu (Aaron Sawdey),
     simonb@prl.philips.co.uk (Simon Blanchard),
     spadgett1@nc.rr.com (Samuel Padgett),
     stephen@farrell.org (Stephen Farrell),
     storm@cua.dk (Kim F. Storm),
     sudish@MindSpring.COM (Sudish Joseph),
     schwab@issan.informatik.uni-dortmund.de (Andreas Schwab)
     terra@diku.dk (Morten Welinder),
     thanh@informatics.muni.cz (Han The Thanh),
     toma@convex.convex.com,
     vrenjak@sun1.racal.com (Milan Vrenjak),
     whicken@dragon.parasoft.com (Wendell Hicken),
     zapman@cc.gatech.edu (Jason Zapman II),

Up: Top

Appendix A GNU Free Documentation License

Version 1.3, 3 November 2008
     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.
  1. PREAMBLE

    The purpose of this License is to make a manual, textbook, or other functional and useful document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

    This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

    We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

  2. APPLICABILITY AND DEFINITIONS

    This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

    A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

    A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

    The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

    The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

    A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.

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    The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.

  3. VERBATIM COPYING

    You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

    You may also lend copies, under the same conditions stated above, and you may publicly display copies.

  4. COPYING IN QUANTITY

    If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

    If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

    If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

    It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

  5. MODIFICATIONS

    You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

    1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
    2. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.
    3. State on the Title page the name of the publisher of the Modified Version, as the publisher.
    4. Preserve all the copyright notices of the Document.
    5. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
    6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
    7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.
    8. Include an unaltered copy of this License.
    9. Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
    10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the “History” section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
    11. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
    12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
    13. Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version.
    14. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title with any Invariant Section.
    15. Preserve any Warranty Disclaimers.

    If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.

    You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties—for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

    You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

    The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

  6. COMBINING DOCUMENTS

    You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

    The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

    In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements.”

  7. COLLECTIONS OF DOCUMENTS

    You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

    You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

  8. AGGREGATION WITH INDEPENDENT WORKS

    A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

    If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document's Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

  9. TRANSLATION

    Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

    If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

  10. TERMINATION

    You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.

    However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

    Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

    Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it.

  11. FUTURE REVISIONS OF THIS LICENSE

    The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

    Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Document.

  12. RELICENSING

    “Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A “Massive Multiauthor Collaboration” (or “MMC”) contained in the site means any set of copyrightable works thus published on the MMC site.

    “CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization.

    “Incorporate” means to publish or republish a Document, in whole or in part, as part of another Document.

    An MMC is “eligible for relicensing” if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.

    The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page: 

       Copyright (C)  year  your name.
       Permission is granted to copy, distribute and/or modify this document
       under the terms of the GNU Free Documentation License, Version 1.3
       or any later version published by the Free Software Foundation;
       with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
       Texts.  A copy of the license is included in the section entitled ``GNU
       Free Documentation License''.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with...Texts.” line with this: 

         with the Invariant Sections being list their titles, with
         the Front-Cover Texts being list, and with the Back-Cover Texts
         being list.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.

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