viper: Vi State
1.3.2 Vi State
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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. 
Recursive
Edit (emacs)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. Syntax of Regular Expressions
(emacs)Regexps, 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. 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
‘~/.file’, you don’t have to erase the prompt. Instead, simply
continue typing what you need. Emacs will interpret
‘/usr/foo/~/.file’ 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’. 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 a
period (‘.’). 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 a period. Improvements over Vi, for more information.
Info Catalog
viper: Emacs State
viper: States in Viper
viper: Insert State