Letters to the editor The most interesting additions

November  1995

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Emacs vs vi supplement

Editor's note:The following is a long letter from a reader describing the merits of VIM, a variation on vi.

One thing to consider when looking at editors is not only vi, but the vi clone VIM. VIM is an improved vi that gives you everything vi has and much more.

This is a summary of the differences between VIM and vi. It is not complete. See also reference.doc and look for comments in {}.

The most interesting additions

vi compatibility.

When the compatible option is set, all options are given a vi-compatible value. VIM will behave like the "real" vi as much as possible.

Multi level undo.

u goes backward in time, ctrl-R goes forward again. Set option undolines to the number of changes to be remembered (default 100). Set undolines to 0 for vi-compatible one-level undo.

When all changes in a buffer have been undone, the buffer is not considered changed anymore. You can exit it with :q, without <!>.

Multiple windows and buffers.

VIM can split the screen into several windows, each editing a different buffer or the same buffer at a different location. Buffers can still be loaded (and changed) but not displayed in a window. This is called a "hidden buffer." Many commands and options have been added for this facility, see windows.doc.

Repeat a series of commands.

q<c> starts recording typed characters into named register <c> (append to the register if register name is upper case). A subsequent q stops recording. The register can then be executed with the @<c> command. This is very useful to repeat a complex action.

Flexible insert mode.

The arrow keys can be used in insert mode to move around in the file. This breaks the insert in two parts as far as undo and redo is concerned.

CTRL-O can be used to execute a single command-mode command. This is almost the same as hitting ESC, typing the command and hitting a. For undo/redo only those inserts are remembered where something was actually inserted.

visual mode.

visual can be used to first choose a piece of text and then give a command to do something with it. This is an (easy to use) alternative to first giving the operator and then moving to the end of the text to be operated upon. v and V are used to start visual mode. v works on characters and V on lines. Move the cursor to extend the visual part. It is shown highlighted on the screen. By typing o the other end of the visual text can be moved. The visual text can be affected by an operator:

        d       delete
        c       change
        y       yank
        > or <  insert or delete indent
        !       filter through external program
        =       filter through indent
        :       start : command for the visual lines.
        Q       format text to textwidth columns
        J       join lines
        ~       swap case
        u       make lower-case
        U       make upper-case

Block operators.

With visual a rectangular block of text can be selected. Start visual with CTRL-V. The block can be deleted (d), yanked (y) or its case can be changed (~, u and U). A deleted or yanked block can be put into the text with the p and P commands.

Online help.

:help command and help key (F1 for DOS) display several pages of concise help. The name of the help file can be set with the helpfile option.

Command line editing.

You can insert or delete at any place in the command line using the cursor keys. The right/left cursor keys can be used to move forward/backward one character. The shifted right/left cursor keys can be used to move forward/backward one word. CTRL-B/CTRL-E can be used to go to the begin/end of the command line.

The command lines are remembered. The up/down cursor keys can be used to recall previous command lines. The history option can be set to the number of lines that will be remembered.

Command line completion.

While entering a command line (on the bottom line of the screen) <TAB> can be typed to complete

   what         example         where
- a command     :e<TAB>         at start of command line
- a tag         :ta no<TAB>     after :ta
- an option     :set sc<TAB>    after :set
- a filename    :e v<TAB>       after any command that accepts a filename

If there are multiple matches, CTRL-N (next) and CTRL-P (previous) will walk through the matches. <TAB> works line CTRL-N, but wraps around to the first match.

The wildchar option can be set to the character for command line completion, <TAB> is the default. CTRL-D can be typed after an (incomplete) wild-card; all matches will be listed. CTRL-A will insert all matches. CTRL-L will insert the longest common part of the matches.

Horizontal scrolling.

If the wrap option is off, long lines will not wrap and only part of them will be shown. When the cursor is moved to a part that is not shown, the screen will scroll horizontally. The minimal number of columns to scroll can be set with the sidescroll option.

Text formatting.

The textwidth (tw) option can be used to automatically limit the line length. This supplements the wrapmargin option of vi, which was not very useful. The Q operator can be used to format a piece of text (Q} formats a paragraph). Commands for text alignment: :center, :left and :right.

Edit-compile-edit speedup.

The :make command can be used to run the compilation and jump to the first error. Alternatively VIM can be started with the -e option from the compiler. A file with compiler error messages is interpreted. Each line in the error file is scanned for the name of a file, line number and error message. VIM starts editing at the first error. Optionally the name of the error file can be given with -e errorfile. The :cn command can be used to jump to the next error. :cl lists all the error messages. Other commands are available (almost the same as with Manx's Z editor). The errorfile option has the name of the file with error messages. The errorformat option can be set to a scanf-like string to handle output from many compilers. The makeprg option contains the name of the program to be executed with the :make command. The shellpipe option contains the string to be used to put the output of the compiler into the errorfile.

Command line options

When VIM is started with -v (view) then readonly mode is used (includes -n).

When VIM is started with -b (Binary) then some options are set to be able to edit binary or executable files.

When VIM is started with -s scriptfile, the characters read from scriptfile are treated as if you typed them. If end of file is reached before the editor exits, further characters are read from the console.

The -w option can be used to record all typed characters in a script file. This file can then be used to redo the editing, possibly on another file or after changing some commands in the script file.

The -n option disables the writing of a .swp file (see below).

The -c command option does the same as the the +command option.

The -T terminal option sets the terminal type.

The -e option starts VIM in quickfix mode.

The -o option opens a window for each argument. -o4 opens four windows.

In command mode

Missing command: Q (go to Ex mode). Missing Ex commands: append, change, insert, open, recover and z.

The command characters are shown in the last line of the screen. They are removed when the command is finished. If you do not want this (on a slow terminal) reset the showcmd option.

If the ruler option is set, the current cursor position is shown in the last line of the screen.

u and CTRL-R accept a count for the number of undos/redos.

U still works after having moved off of the last changed line and after u.

Nulls in the file are replaced by <LF> internally. This allows editing of binary files (more or less).

Characters with the 8th bit set are displayed. The characters between ~ and 0xa0 are displayed as ~?, ~@, ~A, etc., unless the graphic option is set.

= is an operator to filter lines through an external command (vi: lisp stuff). The name of the command can be set with the equalprg option. The default is indent.

][ goes to the next ending of a C function (} in column 1). [] goes to the previous ending of a C function (} in column 1).

]f, [f and gf start editing the file whose name is under the cursor. CTRL-W f splits the window and starts editint the file whose name is under the cursor.

* searches forward for the identifier under the cursor, # backward. K runs the program defined by the keywordprg option, with the identifier under the cursor as argument.

% can be preceded with a count. The cursor jumps to the line that percentage down in the file. The normal % function to jump to the matching brace skips braces inside quotes.

With the CTRL-] command, the cursor may be in the middle of the identifier.

The used tags are remembered. Commands that can be used with the tag stack are CTRL-T, :pop and :tag. :tags lists the tag stack.

The tags option can be set to a list of tag file names. Thus multiple tag files can be used.

Previously used file names are remembered in the alternate file name list. CTRL-^ accepts a count, which is an index in this list.

Search patterns have more features. The <NL> character is seen as part of the search pattern and the substitute string of :s. vi sees it as the end of the command.

Searches can put the cursor on the end of a match and may include a character offset.

Count added to ~, :next, :Next, n and N.

The command :next! with autowrite set does not write the file. In vi the file was written, but this is considered to be a bug, because one does not expect it and the file is not written with :rewind!.

5r<CR> replaces five characters by five line-breaks. vi replaces five characters with a single line break.

Added :wnext command. Same as :write followed by :next.

The :w! command always writes, also when the file is write protected.

If option tildeop has been set, ~ is an operator (must be followed by a movement command).

With the J (join) command you can reset the joinspaces (js) option to have only one space after a period (vi inserts two spaces).

cw can be used to change white space formed by several characters (vi is confusing: cw only changes one space, while dw deletes all white space).

o and O accept a count for repeating the insert (vi clears a part of display).

:dis command shows the contents of the yank register.

Previously used file names are remembered in the alternate file name list.
:files command shows the list of alternate filenames.
#<N> is replaced by the <N>th alternate filename in the list.
#< is replaced by the current filename without extension.

Flags after command not supported (no plans to include it).

On non-Unix systems :cd command shows current directory instead of going to the home directory. :pwd prints the current directory on all systems.

:source! command reads vi commands from a file.

:mkexrc command writes current modified options and mappings to a .exrc file. :mkVIMrc writes to a .VIMrc file.

No check for "tail recursion" with mappings. This allows things like :map! foo ^]foo.

The :put! command inserts the contents of a register above the current line.

The p and P commands of vi cannot be repeated with . when the putted text is less than a line. In VIM, they can always be repeated.

The named register . can be used with commands p, P and :put. The contents of the register is the last-inserted text.

:noremap command can be used to enter a mapping that will not be remapped. This is useful to exchange the meaning of two keys. :cmap, :cunmap and :cnoremap can be used for mapping in command line editing only. :imap, :iunmap and :inoremap can be used for mapping in insert mode only. Similar commands exist for abbreviations: :noreabbrev, :iabbrev :cabbrev, :iunabbrev, :cunabbrev, :inoreabbrev, :cnoreabbrev.

In vi the command :map foo bar would remove a previous mapping :map bug foo. This is considered a bug, so it is not included in VIM. :unmap! foo does remove :map! bug foo, because unmapping would be very difficult otherwise (this is vi compatible).

:@r command executes register r (is in some versions of vi).

The : register contains the last command line. The % register contains the current file name.

CTRL-O/CTRL-I can be used to jump to older/newer positions. These are the same positions as used with the TK command, but may be in another file. The :jumps command lists the older positions.

If the shiftround option is set, an indent is rounded to a multiple of shiftwidth with > and < commands.

The scrolljump option can be set to the minimal number of lines to scroll when the cursor gets off the screen. Use this when scrolling is slow.

Upper-case marks can be used to jump between files. The :marks command lists all currently set marks. The commands '] and `] jump to the end of the previous operator or end of the text inserted with the put command. '[ and `[ do jump to the start.

The shelltype option can be set to reflect the type of shell used.

The highlight option can be set for the highlight mode to be used for several commands.

The CTRL-A (add) and CTRL-X (subtract) commands are new. The count to the command (default 1) is added to/subtracted from the number at or after the cursor. That number may be decimal, octal (starts with a 0) or hexadecimal (starts with 0x). Very useful in macros.

With the :set command the prefix inv can be used to invert toggle options.

In both vi and VIM you can create a line break with the :substitute command by using a CTRL-M. For vi this means you cannot insert a real CTRL-M in the text. With VIM you can put a real CTRL-M in the text by preceding it with a CTRL-V.

In insert mode

If the revins option is set, insert happens backwards. This is for typing Hebrew. When inserting normal characters the cursor will not be shifted and the text moves rightwards. In replace mode the cursor will move leftwards. Backspace, CTRL-W and CTRL-U will also work in the opposite direction. CTRL-B toggles the revins option.

The backspace key can be used just like CTRL-D to remove auto-indents.

You can backspace, ctrl-U and CTRL-W over line breaks if the backspace (bs) option is set to non-zero. You can backspace over the start of insert if the backspace option is set to 2.

When the paste option is set, a few option are reset and mapping in insert mode and abbreviation are disabled. This allows for pasting text in windowing systems without unexpected results. When the paste option is reset, the old option values are restored.

CTRL-T/CTRL-D always insert/delete an indent in the current line, no matter what column the cursor is in.

CTRL-@ (insert previously inserted text) works always (vi: only when typed as first character).

CTRL-A works like CTRL-@ but does not leave insert mode.

CTRL-R <0-9a-z> can be used to insert the contents of a register.

When the smartindent (si) option is set, C programs will be better auto-indented.

CTRL-Y and CTRL-E can be used to copy a character from above/below the current cursor position.

After CTRL-V you can enter a three digit decimal number. This byte value is inserted in the text as a single character. Useful for international characters that are not on your keyboard.

When the expandtab (et) option is set, a <TAB> is expanded to the appropriate number of spaces.

The window always reflects the contents of the buffer (vi does not do this when changing text and in some other cases).

If VIM is compiled with DIGRAPHS defined, digraphs are supported. A set of normal Amiga digraphs is included. They are shown with the :digraph command. More can be added with :digraph {char1}{char2} {number}. A digraph is entered with CTRL-K {char1} {char2} or {char1} BS {char2} (only when digraph option is set).

When repeating an insert, e.g., 10atest <ESC> vi would only handle wrapmargin for the first insert. VIM does it for all.

In command line mode

ESC terminates the command line without executing it. In vi the command line would be executed, which is not what most people expect (hitting ESC should always get you back to command mode). To avoid problems with some obscure macros, an ESC in a macro will execute the command. If you want a typed ESC to execute the command like vi does you can fix this with
:cmap ^V<ESC> ^V<CR>

In general

Missing options: autoprint (ap), beautify (bf), edcompatible, hardtabs (ht), lisp, mesg, open, optimize (op), prompt, redraw, slowopen (slow), terse, window, w300, w1200 and w9600. These options can be set but are otherwise ignored.

When the compatible option is set, all options are set for maximum vi-compatibility

The ttimeout option is like timeout, but only works for cursor and function keys, not for ordinary mapped characters. The timoutlen option gives the number of milliseconds that is waited for. If the esckeys option is not set, cursor and function keys that start with <ESC> are not recognized in insert mode.

There is an option for each terminal string. Can be used when termcap is not supported or to change individual strings.

When the textmode option is set (default for DOS) <CR><LF> is used as line separator. When reset (default for Unix and Amiga) <LF> is used. When the textauto option is set, VIM tries to detect the type of line separator used by reading up to the first <LF>. The textmode option is set accordingly.

On systems that have no job control (most systems but BSD-Unix) the CTRL-Z, :stop or :suspend command starts a new shell.

If VIM is started on the Amiga without an interactive window for output, a window is opened (and :sh still works). You can give a device to use for editing with the -d argument, e.g., -d con:20/20/600/150.

On startup the VIMINIT or EXINIT environment variables, the file s:.VIMrc or s:.exrc and .VIMrc or .exrc are read for initialization commands. When reading .VIMrc and .exrc some commands are not allowed because of security reasons (shell commands and writing to a file, :map commands are echoed). This can be over-rided with the secure option.

Line-length can be at least up to the maximum value of an int (for the Amiga 32767 characters, for most 32-bit systems much larger). Editing such lines is not always possible. File length up to 2147483646 lines. If a line is larger than the screen, the last line is filled with <@>s and only the part of the line before that is shown (unless wrap option is reset).

The columns option is used to set or get the width of the display.

The name of the current file name is shown in the title bar of the window.

Wildcards in file names are expanded.

Option settings are read from the first and last few lines of the file. Option modelines determines how many lines are tried (default is 5). Note that this is different from the vi versions that can execute any Ex command in a modeline (a major security problem).

If the insertmode option is set (e.g., in .exrc), VIM starts in insert mode.

All text is kept in memory. Available memory limits the file size (and other things such as undo). This may be a problem with MS-DOS, is hardly a problem ont the Amiga and almost never with Unix.

If the backup or writebackup option is set: Before a file is overwritten, a backup file (.bak) is made. If the backup option is set it is left behind.

If the binary option is set and the file does not have an end-of-line for the last line, the end-of-line is not appended when writing.

VIM creates a file ending in .swp to store parts of the file that have been changed or that do not fit in memory. This file can be used to recover from an aborted editing session with VIM -r file. Using the swap file can be switched off by setting the updatecount option to 0 or starting VIM with the -n option. Use the directory option for placing the .swp file somewhere else.

The shortname (sn) option, when set, tells VIM that .bak and .swp filenames are to be DOS-like: 8 characters plus 3 for the extension. This should be used on messydos or crossdos filesystems on the Amiga. If this option is off, VIM tries to guess if DOS filename restrictions are effective.

Recovery after a crash has a smaller chance for success, because there is no temporary file.

Error messages are shown at least one second (vi overwrites error messages).

If VIM asks to "Hit RETURN to continue", you can hit any key. Characters other than <CR>, <LF> and <SPACE> are interpreted as the (start of) a command. (vi only accepts a command starting with :).

The contents of the numbered and unnamed registers is remembered when changing files.

--Name and firm indeterminate The editors respond: Unfortunately, this reader did not indicate where he or she found this document, or where to find VIM. Readers?

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Last updated: 1 November 1995

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