3.4 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-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 his/her Viper customization file to a key sequence to be used for buffer search. There is no need to call viper-buffer-search-enable in that case.


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 customization file. For instance, if you don’t like the above feature, put this in the file:

(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.


Regular Expressions for [[ and ]]. Note that Emacs defines Regexps for paragraphs and sentences. See Paragraphs and Sentences in The GNU Emacs Manual, 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 period. 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 customization 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]

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 a period, as in Vi. However, repeated typing C-c M-p will cause Viper to show the previous destructive commands in the minibuffer. Subsequent hitting period 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]

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 their Viper customization 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 Tables in The GNU Emacs Manual, 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 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 customization 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 your Viper customization file 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 your Viper customization file:

(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 your Viper customization file, 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.


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.

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.