path: root/runtime/doc/autocmd.txt

*autocmd.txt*   For Vim version 7.0aa.  Last change: 2004 Apr 20


		  VIM REFERENCE MANUAL    by Bram Moolenaar


Automatic commands					*autocommand*

For a basic explanation, see section |40.3| in the user manual.

1.  Introduction		|autocmd-intro|
2.  Defining autocommands	|autocmd-define|
3.  Removing autocommands	|autocmd-remove|
4.  Listing autocommands	|autocmd-list|
5.  Events			|autocmd-events|
6.  Patterns			|autocmd-patterns|
7.  Groups			|autocmd-groups|
8.  Executing autocommands	|autocmd-execute|
9.  Using autocommands		|autocmd-use|

{Vi does not have any of these commands}
{only when the |+autocmd| feature has not been disabled at compile time}

==============================================================================
1. Introduction						*autocmd-intro*

You can specify commands to be executed automatically for when reading or
writing a file, when entering or leaving a buffer or window, and when exiting
Vim.  For example, you can create an autocommand to set the 'cindent' option
for files matching *.c.  You can also use autocommands to implement advanced
features, such as editing compressed files (see |gzip-example|).  The usual
place to put autocommands is in your .vimrc or .exrc file.

							*E203* *E204* *E143*
WARNING: Using autocommands is very powerful, and may lead to unexpected side
effects.  Be careful not to destroy your text.
- It's a good idea to do some testing on an expendable copy of a file first.
  For example: If you use autocommands to decompress a file when starting to
  edit it, make sure that the autocommands for compressing when writing work
  correctly.
- Be prepared for an error halfway through (e.g., disk full).  Vim will mostly
  be able to undo the changes to the buffer, but you may have to clean up the
  changes to other files by hand (e.g., compress a file that has been
  decompressed).
- If the BufRead* events allow you to edit a compressed file, the FileRead*
  events should do the same (this makes recovery possible in some rare cases).
  It's a good idea to use the same autocommands for the File* and Buf* events
  when possible.

==============================================================================
2. Defining autocommands				*autocmd-define*

Note: The ":autocmd" command cannot be followed by another command, since any
'|' is considered part of the command.

							*:au* *:autocmd*
:au[tocmd] [group] {event} {pat} [nested] {cmd}
			Add {cmd} to the list of commands that Vim will
			execute automatically on {event} for a file matching
			{pat}.  Vim always adds the {cmd} after existing
			autocommands, so that the autocommands execute in the
			order in which they were given.  See |autocmd-nested|
			for [nested].

Note that special characters (e.g., "%", "<cword>") in the ":autocmd"
arguments are not expanded when the autocommand is defined.  These will be
expanded when the Event is recognized, and the {cmd} is executed.  The only
exception is that "<sfile>" is expanded when the autocmd is defined.  Example:
>
	:au BufNewFile,BufRead *.html so <sfile>:h/html.vim

Here Vim expands <sfile> to the name of the file containing this line.

When your .vimrc file is sourced twice, the autocommands will appear twice.
To avoid this, put this command in your .vimrc file, before defining
autocommands: >

	:autocmd!	" Remove ALL autocommands for the current group.

If you don't want to remove all autocommands, you can instead use a variable
to ensure that Vim includes the autocommands only once: >

	:if !exists("autocommands_loaded")
	:  let autocommands_loaded = 1
	:  au ...
	:endif

When the [group] argument is not given, Vim uses the current group (as defined
with ":augroup"); otherwise, Vim uses the group defined with [group].  Note
that [group] must have been defined before.  You cannot define a new group
with ":au group ..."; use ":augroup" for that.

While testing autocommands, you might find the 'verbose' option to be useful: >
	:set verbose=9
This setting makes Vim echo the autocommands as it executes them.

When defining an autocommand in a script, it will be able to call functions
local to the script and use mappings local to the script.  When the event is
triggered and the command executed, it will run in the context of the script
it was defined in.  This matters if |<SID>| is used in a command.

When executing the commands, the messages from one command overwrites a
previous message.  This is different from when executing the commands
manually.  Mostly the screen will not scroll up, thus there is no hit-enter
prompt.  When one command outputs two messages this can happen anyway.

==============================================================================
3. Removing autocommands				*autocmd-remove*

:au[tocmd]! [group] {event} {pat} [nested] {cmd}
			Remove all autocommands associated with {event} and
			{pat}, and add the command {cmd}.  See
			|autocmd-nested| for [nested].

:au[tocmd]! [group] {event} {pat}
			Remove all autocommands associated with {event} and
			{pat}.

:au[tocmd]! [group] * {pat}
			Remove all autocommands associated with {pat} for all
			events.

:au[tocmd]! [group] {event}
			Remove ALL autocommands for {event}.

:au[tocmd]! [group]	Remove ALL autocommands.

When the [group] argument is not given, Vim uses the current group (as defined
with ":augroup"); otherwise, Vim uses the group defined with [group].

==============================================================================
4. Listing autocommands					*autocmd-list*

:au[tocmd] [group] {event} {pat}
			Show the autocommands associated with {event} and
			{pat}.

:au[tocmd] [group] * {pat}
			Show the autocommands associated with {pat} for all
			events.

:au[tocmd] [group] {event}
			Show all autocommands for {event}.

:au[tocmd] [group]	Show all autocommands.

If you provide the [group] argument, Vim lists only the autocommands for
[group]; otherwise, Vim lists the autocommands for ALL groups.  Note that this
argument behavior differs from that for defining and removing autocommands.

==============================================================================
5. Events					*autocmd-events* *E215* *E216*

					*autocommand-events* *{event}*
Vim recognizes the following events.  Vim ignores the case of event names
(e.g., you can use "BUFread" or "bufread" instead of "BufRead").

							*BufNewFile*
BufNewFile			When starting to edit a file that doesn't
				exist.  Can be used to read in a skeleton
				file.
						*BufReadPre* *E200* *E201*
BufReadPre			When starting to edit a new buffer, before
				reading the file into the buffer.  Not used
				if the file doesn't exist.
						*BufRead* *BufReadPost*
BufRead or BufReadPost		When starting to edit a new buffer, after
				reading the file into the buffer, before
				executing the modelines.  See |BufWinEnter|
				for when you need to do something after
				processing the modelines.
				This does NOT work for ":r file".  Not used
				when the file doesn't exist.  Also used after
				successfully recovering a file.
							*BufReadCmd*
BufReadCmd			Before starting to edit a new buffer.  Should
				read the file into the buffer. |Cmd-event|
							*BufFilePre*
BufFilePre			Before changing the name of the current buffer
				with the ":file" or ":saveas" command.
							*BufFilePost*
BufFilePost			After changing the name of the current buffer
				with the ":file" or ":saveas" command.
							*FileReadPre*
FileReadPre			Before reading a file with a ":read" command.
							*FileReadPost*
FileReadPost			After reading a file with a ":read" command.
				Note that Vim sets the '[ and '] marks to the
				first and last line of the read.  This can be
				used to operate on the lines just read.
							*FileReadCmd*
FileReadCmd			Before reading a file with a ":read" command.
				Should do the reading of the file. |Cmd-event|
							*FilterReadPre* *E135*
FilterReadPre			Before reading a file from a filter command.
				Vim checks the pattern against the name of
				the current buffer, not the name of the
				temporary file that is the output of the
				filter command.
							*FilterReadPost*
FilterReadPost			After reading a file from a filter command.
				Vim checks the pattern against the name of
				the current buffer as with FilterReadPre.
							*FileType*
FileType			When the 'filetype' option has been set.
				<afile> can be used for the name of the file
				where this option was set, and <amatch> for
				the new value of 'filetype'.
				See |filetypes|.
							*Syntax*
Syntax				When the 'syntax' option has been set.
				<afile> can be used for the name of the file
				where this option was set, and <amatch> for
				the new value of 'syntax'.
				See |:syn-on|.
							*StdinReadPre*
StdinReadPre			Before reading from stdin into the buffer.
				Only used when the "-" argument was used when
				Vim was started |--|.
							*StdinReadPost*
StdinReadPost			After reading from the stdin into the buffer,
				before executing the modelines.  Only used
				when the "-" argument was used when Vim was
				started |--|.
						*BufWrite* *BufWritePre*
BufWrite or BufWritePre		Before writing the whole buffer to a file.
							*BufWritePost*
BufWritePost			After writing the whole buffer to a file
				(should undo the commands for BufWritePre).
							*BufWriteCmd*
BufWriteCmd			Before writing the whole buffer to a file.
				Should do the writing of the file and reset
				'modified' if successful.  The buffer contents
				should not be changed.  |Cmd-event|
							*FileWritePre*
FileWritePre			Before writing to a file, when not writing the
				whole buffer.
							*FileWritePost*
FileWritePost			After writing to a file, when not writing the
				whole buffer.
							*FileWriteCmd*
FileWriteCmd			Before writing to a file, when not writing the
				whole buffer.  Should do the writing to the
				file.  Should not change the buffer.
				|Cmd-event|
							*FileAppendPre*
FileAppendPre			Before appending to a file.
							*FileAppendPost*
FileAppendPost			After appending to a file.
							*FileAppendCmd*
FileAppendCmd			Before appending to a file.  Should do the
				appending to the file. |Cmd-event|
							*FilterWritePre*
FilterWritePre			Before writing a file for a filter command or
				making a diff.
				Vim checks the pattern against the name of
				the current buffer, not the name of the
				temporary file that is the output of the
				filter command.
							*FilterWritePost*
FilterWritePost			After writing a file for a filter command or
				making a diff.
				Vim checks the pattern against the name of
				the current buffer as with FilterWritePre.
							*FileChangedShell*
FileChangedShell		When Vim notices that the modification time of
				a file has changed since editing started.
				Also when the file attributes of the file
				change. |timestamp|
				Mostly triggered after executing a shell
				command, but also with a |:checktime| command
				or when Vim regains input focus.
				This autocommand is triggered for each changed
				file.  It is not used when 'autoread' is set
				and the buffer was not changed.  If a
				FileChangedShell autocommand is present the
				warning message and prompt is not given.
				This is useful for reloading related buffers
				which are affected by a single command.
				NOTE: When this autocommand is executed, the
				current buffer "%" may be different from the
				buffer that was changed "<afile>".
				NOTE: The commands must not change the current
				buffer, jump to another buffer or delete a
				buffer.  *E246*
				NOTE: This event never nests, to avoid an
				endless loop.  This means that while executing
				commands for the FileChangedShell event no
				other FileChangedShell event will be
				triggered.
							*FileChangedRO*
FileChangedRO			Before making the first change to a read-only
				file.  Can be used to check-out the file from
				a source control system.  Not triggered when
				the change was caused by an autocommand.
				WARNING: This event is triggered when making a
				change, just before the change is applied to
				the text.  If the autocommand moves the cursor
				the effect of the change is undefined.
							*FocusGained*
FocusGained			When Vim got input focus.  Only for the GUI
				version and a few console versions where this
				can be detected.
							*FocusLost*
FocusLost			When Vim lost input focus.  Only for the GUI
				version and a few console versions where this
				can be detected.
							*FuncUndefined*
FuncUndefined			When a user function is used but it isn't
				defined.  Useful for defining a function only
				when it's used.  Both <amatch> and <afile> are
				set to the name of the function.
							*CursorHold*
CursorHold			When the user doesn't press a key for the time
				specified with 'updatetime'.  Not re-triggered
				until the user has pressed a key (i.e. doesn't
				fire every 'updatetime' ms if you leave Vim to
				make some coffee. :)  See |CursorHold-example|
				for previewing tags.
				This event is only triggered in Normal mode.
				Note: Interactive commands cannot be used for
				this event.  There is no hit-enter prompt,
				the screen is updated directly (when needed).
				Note: In the future there will probably be
				another option to set the time.
				Hint: to force an update of the status lines
				use: >
					:let &ro = &ro
<				{only on Amiga, Unix, Win32, MSDOS and all GUI
				versions}
							*BufEnter*
BufEnter			After entering a buffer.  Useful for setting
				options for a file type.  Also executed when
				starting to edit a buffer, after the
				BufReadPost autocommands.
							*BufLeave*
BufLeave			Before leaving to another buffer.  Also when
				leaving or closing the current window and the
				new current window is not for the same buffer.
				Not used for ":qa" or ":q" when exiting Vim.
							*BufWinEnter*
BufWinEnter			After a buffer is displayed in a window.  This
				can be when the buffer is loaded (after
				processing the modelines), when a hidden
				buffer is displayed in a window (and is no
				longer hidden) or a buffer already visible in
				a window is also displayed in another window.
							*BufWinLeave*
BufWinLeave			Before a buffer is removed from a window.
				Not when it's still visible in another window.
				Also triggered when exiting.  It's triggered
				before BufUnload or BufHidden.
				NOTE: When this autocommand is executed, the
				current buffer "%" may be different from the
				buffer being unloaded "<afile>".
							*BufUnload*
BufUnload			Before unloading a buffer.  This is when the
				text in the buffer is going to be freed.  This
				may be after a BufWritePost and before a
				BufDelete.  Also used for all buffers that are
				loaded when Vim is going to exit.
				NOTE: When this autocommand is executed, the
				current buffer "%" may be different from the
				buffer being unloaded "<afile>".
							*BufHidden*
BufHidden			Just after a buffer has become hidden.  That
				is, when there are no longer windows that show
				the buffer, but the buffer is not unloaded or
				deleted.  Not used for ":qa" or ":q" when
				exiting Vim.
				NOTE: When this autocommand is executed, the
				current buffer "%" may be different from the
				buffer being unloaded "<afile>".
							*BufNew*
BufNew				Just after creating a new buffer.  Also used
				just after a buffer has been renamed.  When
				the buffer is added to the buffer list BufAdd
				will be triggered too.
				NOTE: When this autocommand is executed, the
				current buffer "%" may be different from the
				buffer being created "<afile>".
							*BufCreate* *BufAdd*
BufAdd or BufCreate		Just after creating a new buffer which is
				added to the buffer list, or adding a buffer
				to the buffer list.
				Also used just after a buffer in the buffer
				list has been renamed.
				The BufCreate event is for historic reasons.
				NOTE: When this autocommand is executed, the
				current buffer "%" may be different from the
				buffer being created "<afile>".
							*BufDelete*
BufDelete			Before deleting a buffer from the buffer list.
				The BufUnload may be called first (if the
				buffer was loaded).
				Also used just before a buffer in the buffer
				list is renamed.
				NOTE: When this autocommand is executed, the
				current buffer "%" may be different from the
				buffer being deleted "<afile>".
							*BufWipeout*
BufWipeout			Before completely deleting a buffer.  The
				BufUnload and BufDelete events may be called
				first (if the buffer was loaded and was in the
				buffer list).  Also used just before a buffer
				is renamed (also when it's not in the buffer
				list).
				NOTE: When this autocommand is executed, the
				current buffer "%" may be different from the
				buffer being deleted "<afile>".
							*WinEnter*
WinEnter			After entering another window.  Not done for
				the first window, when Vim has just started.
				Useful for setting the window height.
				If the window is for another buffer, Vim
				executes the BufEnter autocommands after the
				WinEnter autocommands.
				Note: When using ":split fname" the WinEnter
				event is triggered after the split but before
				the file "fname" is loaded.
							*WinLeave*
WinLeave			Before leaving a window.  If the window to be
				entered next is for a different buffer, Vim
				executes the BufLeave autocommands before the
				WinLeave autocommands (but not for ":new").
				Not used for ":qa" or ":q" when exiting Vim.
							*CmdwinEnter*
CmdwinEnter			After entering the command-line window.
				Useful for setting options specifically for
				this special type of window.  This is
				triggered _instead_ of BufEnter and WinEnter.
				<afile> is set to a single character,
				indicating the type of command-line.
				|cmdwin-char|
							*CmdwinLeave*
CmdwinLeave			Before leaving the command-line window.
				Useful to clean up any global setting done
				with CmdwinEnter.  This is triggered _instead_
				of BufLeave and WinLeave.
				<afile> is set to a single character,
				indicating the type of command-line.
				|cmdwin-char|
							*GUIEnter*
GUIEnter			After starting the GUI successfully, and after
				opening the window.  It is triggered before
				VimEnter when using gvim.  Can be used to
				position the window from a .gvimrc file: >
	:autocmd GUIEnter * winpos 100 50
<							*VimEnter*
VimEnter			After doing all the startup stuff, including
				loading .vimrc files, executing the "-c cmd"
				arguments, creating all windows and loading
				the buffers in them.
							*VimLeavePre*
VimLeavePre			Before exiting Vim, just before writing the
				.viminfo file.  This is executed only once,
				if there is a match with the name of what
				happens to be the current buffer when exiting.
				Mostly useful with a "*" pattern. >
	:autocmd VimLeavePre * call CleanupStuff()
<				To detect an abnormal exit use |v:dying|.
							*VimLeave*
VimLeave			Before exiting Vim, just after writing the
				.viminfo file.  Executed only once, like
				VimLeavePre.
				To detect an abnormal exit use |v:dying|.
							*EncodingChanged*
EncodingChanged			Fires off when the 'encoding' option is
				changed.  Useful to set up fonts, for example.
							*FileEncoding*
FileEncoding			Obsolete.  It still works and is equivalent
				to |EncodingChanged|.
							*RemoteReply*
RemoteReply			When a reply from a Vim that functions as
				server was received |server2client()|.
				<amatch> is equal to the {serverid} from which
				the reply was sent, and <afile> is the actual
				reply string.
				Note that even if an autocommand is defined,
				the reply should be read with |remote_read()|
				to consume it.
							*TermChanged*
TermChanged			After the value of 'term' has changed.  Useful
				for re-loading the syntax file to update the
				colors, fonts and other terminal-dependent
				settings.  Executed for all loaded buffers.
							*TermResponse*
TermResponse			After the response to |t_RV| is received from
				the terminal.  The value of |v:termresponse|
				can be used to do things depending on the
				terminal version.
							*UserGettingBored*
UserGettingBored		When the user hits CTRL-C.  Just kidding! :-)
							*User*
User				Never executed automatically.  To be used for
				autocommands that are only executed with
				":doautocmd".

You can specify a comma-separated list of event names.  No white space can be
used in this list.  The command applies to all the events in the list.

For READING FILES there are four kinds of events possible:
	BufNewFile			starting to edit a non-existent file
	BufReadPre	BufReadPost	starting to edit an existing file
	FilterReadPre	FilterReadPost	read the temp file with filter output
	FileReadPre	FileReadPost	any other file read
Vim uses only one of these four kinds when reading a file.  The "Pre" and
"Post" events are both triggered, before and after reading the file.

Note that the autocommands for the *ReadPre events and all the Filter events
are not allowed to change the current buffer (you will get an error message if
this happens).  This is to prevent the file to be read into the wrong buffer.

Note that the 'modified' flag is reset AFTER executing the BufReadPost
and BufNewFile autocommands.  But when the 'modified' option was set by the
autocommands, this doesn't happen.

You can use the 'eventignore' option to ignore a number of events or all
events.

==============================================================================
6. Patterns					*autocmd-patterns* *{pat}*

The file pattern {pat} is tested for a match against the file name in one of
two ways:
1. When there is no '/' in the pattern, Vim checks for a match against only
   the tail part of the file name (without its leading directory path).
2. When there is a '/' in the pattern,  Vim checks for a match against the
   both short file name (as you typed it) and the full file name (after
   expanding it to a full path and resolving symbolic links).

Examples: >
	:autocmd BufRead *.txt		set et
Set the 'et' option for all text files. >

	:autocmd BufRead /vim/src/*.c	set cindent
Set the 'cindent' option for C files in the /vim/src directory. >

	:autocmd BufRead /tmp/*.c	set ts=5
If you have a link from "/tmp/test.c" to "/home/nobody/vim/src/test.c", and
you start editing "/tmp/test.c", this autocommand will match.

Note:  To match part of a path, but not from the root directory, use a '*' as
the first character.  Example: >
	:autocmd BufRead */doc/*.txt	set tw=78
This autocommand will for example be executed for "/tmp/doc/xx.txt" and
"/usr/home/piet/doc/yy.txt".  The number of directories does not matter here.


The file name that the pattern is matched against is after expanding
wildcards.  Thus is you issue this command: >
	:e $ROOTDIR/main.$EXT
The argument is first expanded to: >
	/usr/root/main.py
Before it's matched with the pattern of the autocommand.  Careful with this
when using events like FileReadCmd, the value of <amatch> may not be what you
expect.


Environment variables can be used in a pattern: >
	:autocmd BufRead $VIMRUNTIME/doc/*.txt  set expandtab
And ~ can be used for the home directory (if $HOME is defined): >
	:autocmd BufWritePost ~/.vimrc   so ~/.vimrc
	:autocmd BufRead ~archive/*      set readonly
The environment variable is expanded when the autocommand is defined, not when
the autocommand is executed.  This is different from the command!

							*file-pattern*
The pattern is interpreted like mostly used in file names:
	*	matches any sequence of characters
	?	matches any single character
	\?	matches a '?'
	.	matches a '.'
	~	matches a '~'
	,	separates patterns
	\,	matches a ','
	{ }	like \( \) in a |pattern|
	,	inside { }: like \| in a |pattern|
	\	special meaning like in a |pattern|
	[ch]	matches 'c' or 'h'
	[^ch]   match any character but 'c' and 'h'

Note that for all systems the '/' character is used for path separator (even
MS-DOS and OS/2).  This was done because the backslash is difficult to use
in a pattern and to make the autocommands portable across different systems.


Matching with the pattern is done when an event is triggered.  Changing the
buffer name in one of the autocommands, or even deleting the buffer, does not
change which autocommands will be executed.  Example: >

	au BufEnter *.foo  bdel
	au BufEnter *.foo  set modified

This will delete the current buffer and then set 'modified' in what has become
the current buffer instead.  Vim doesn't take into account that "*.foo"
doesn't match with that buffer name.  It matches "*.foo" with the name of the
buffer at the moment the event was triggered.

==============================================================================
7. Groups						*autocmd-groups*

Autocommands can be put together in a group.  This is useful for removing or
executing a group of autocommands.  For example, all the autocommands for
syntax highlighting are put in the "highlight" group, to be able to execute
":doautoall highlight BufRead" when the GUI starts.

When no specific group is selected, Vim uses the default group.  The default
group does not have a name.  You cannot execute the autocommands from the
default group separately; you can execute them only by executing autocommands
for all groups.

Normally, when executing autocommands automatically, Vim uses the autocommands
for all groups.  The group only matters when executing autocommands with
":doautocmd" or ":doautoall", or when defining or deleting autocommands.

The group name can contain any characters except white space.  The group name
"end" is reserved (also in uppercase).

The group name is case sensitive.  Note that this is different from the event
name!

							*:aug* *:augroup*
:aug[roup] {name}		Define the autocmd group name for the
				following ":autocmd" commands.  The name "end"
				or "END" selects the default group.

						*:augroup-delete* *E367*
:aug[roup]! {name}		Delete the autocmd group {name}.  Don't use
				this if there is still an autocommand using
				this group!  This is not checked.

To enter autocommands for a specific group, use this method:
1. Select the group with ":augroup {name}".
2. Delete any old autocommands with ":au!".
3. Define the autocommands.
4. Go back to the default group with "augroup END".

Example: >
	:augroup uncompress
	:  au!
	:  au BufEnter *.gz	%!gunzip
	:augroup END

This prevents having the autocommands defined twice (e.g., after sourcing the
.vimrc file again).

==============================================================================
8. Executing autocommands				*autocmd-execute*

Vim can also execute Autocommands non-automatically.  This is useful if you
have changed autocommands, or when Vim has executed the wrong autocommands
(e.g., the file pattern match was wrong).

Note that the 'eventignore' option applies here too.  Events listed in this
option will not cause any commands to be executed.

					*:do* *:doau* *:doautocmd* *E217*
:do[autocmd] [group] {event} [fname]
			Apply the autocommands matching [fname] (default:
			current file name) for {event} to the current buffer.
			You can use this when the current file name does not
			match the right pattern, after changing settings, or
			to execute autocommands for a certain event.
			It's possible to use this inside an autocommand too,
			so you can base the autocommands for one extension on
			another extension.  Example: >
				:au Bufenter *.cpp so ~/.vimrc_cpp
				:au Bufenter *.cpp doau BufEnter x.c
<			Be careful to avoid endless loops.  See
			|autocmd-nested|.

			When the [group] argument is not given, Vim executes
			the autocommands for all groups.  When the [group]
			argument is included, Vim executes only the matching
			autocommands for that group.  Note: if you use an
			undefined group name, Vim gives you an error message.

						*:doautoa* *:doautoall*
:doautoa[ll] [group] {event} [fname]
			Like ":doautocmd", but apply the autocommands to each
			loaded buffer.  Note that {fname} is used to select
			the autocommands, not the buffers to which they are
			applied.
			Careful: Don't use this for autocommands that delete a
			buffer, change to another buffer or change the
			contents of a buffer; the result is unpredictable.
			This command is intended for autocommands that set
			options, change highlighting, and things like that.

==============================================================================
9. Using autocommands					*autocmd-use*

For WRITING FILES there are four possible sets of events.  Vim uses only one
of these sets for a write command:

BufWriteCmd	BufWritePre	BufWritePost	writing the whole buffer
		FilterWritePre	FilterWritePost	writing to filter temp file
FileAppendCmd	FileAppendPre	FileAppendPost	appending to a file
FileWriteCmd	FileWritePre	FileWritePost	any other file write

When there is a matching "*Cmd" autocommand, it is assumed it will do the
writing.  No further writing is done and the other events are not triggered.
|Cmd-event|

Note that the *WritePost commands should undo any changes to the buffer that
were caused by the *WritePre commands; otherwise, writing the file will have
the side effect of changing the buffer.

Before executing the autocommands, the buffer from which the lines are to be
written temporarily becomes the current buffer.  Unless the autocommands
change the current buffer or delete the previously current buffer, the
previously current buffer is made the current buffer again.

The *WritePre and *AppendPre autocommands must not delete the buffer from
which the lines are to be written.

The '[ and '] marks have a special position:
- Before the *ReadPre event the '[ mark is set to the line just above where
  the new lines will be inserted.
- Before the *ReadPost event the '[ mark is set to the first line that was
  just read, the '] mark to the last line.
- Before executing the *WritePre and *AppendPre autocommands the '[ mark is
  set to the first line that will be written, the '] mark to the last line.
Careful: '[ and '] change when using commands that change the buffer.

In commands which expect a file name, you can use "<afile>" for the file name
that is being read |:<afile>| (you can also use "%" for the current file
name).  "<abuf>" can be used for the buffer number of the currently effective
buffer.  This also works for buffers that doesn't have a name.  But it doesn't
work for files without a buffer (e.g., with ":r file").

							*gzip-example*
Examples for reading and writing compressed files: >
  :augroup gzip
  :  autocmd!
  :  autocmd BufReadPre,FileReadPre	*.gz set bin
  :  autocmd BufReadPost,FileReadPost	*.gz '[,']!gunzip
  :  autocmd BufReadPost,FileReadPost	*.gz set nobin
  :  autocmd BufReadPost,FileReadPost	*.gz execute ":doautocmd BufReadPost " . expand("%:r")
  :  autocmd BufWritePost,FileWritePost	*.gz !mv <afile> <afile>:r
  :  autocmd BufWritePost,FileWritePost	*.gz !gzip <afile>:r

  :  autocmd FileAppendPre		*.gz !gunzip <afile>
  :  autocmd FileAppendPre		*.gz !mv <afile>:r <afile>
  :  autocmd FileAppendPost		*.gz !mv <afile> <afile>:r
  :  autocmd FileAppendPost		*.gz !gzip <afile>:r
  :augroup END

The "gzip" group is used to be able to delete any existing autocommands with
":autocmd!", for when the file is sourced twice.

("<afile>:r" is the file name without the extension, see |:_%:|)

The commands executed for the BufNewFile, BufRead/BufReadPost, BufWritePost,
FileAppendPost and VimLeave events do not set or reset the changed flag of the
buffer.  When you decompress the buffer with the BufReadPost autocommands, you
can still exit with ":q".  When you use ":undo" in BufWritePost to undo the
changes made by BufWritePre commands, you can still do ":q" (this also makes
"ZZ" work).  If you do want the buffer to be marked as modified, set the
'modified' option.

To execute Normal mode commands from an autocommand, use the ":normal"
command.  Use with care!  If the Normal mode command is not finished, the user
needs to type characters (e.g., after ":normal m" you need to type a mark
name).

If you want the buffer to be unmodified after changing it, reset the
'modified' option.  This makes it possible to exit the buffer with ":q"
instead of ":q!".

							*autocmd-nested* *E218*
By default, autocommands do not nest.  If you use ":e" or ":w" in an
autocommand, Vim does not execute the BufRead and BufWrite autocommands for
those commands.  If you do want this, use the "nested" flag for those commands
in which you want nesting.  For example: >
  :autocmd FileChangedShell *.c nested e!
The nesting is limited to 10 levels to get out of recursive loops.

It's possible to use the ":au" command in an autocommand.  This can be a
self-modifying command!  This can be useful for an autocommand that should
execute only once.

There is currently no way to disable the autocommands.  If you want to write a
file without executing the autocommands for that type of file, write it under
another name and rename it with a shell command.  In some situations you can
use the 'eventignore' option.

Note: When reading a file (with ":read file" or with a filter command) and the
last line in the file does not have an <EOL>, Vim remembers this.  At the next
write (with ":write file" or with a filter command), if the same line is
written again as the last line in a file AND 'binary' is set, Vim does not
supply an <EOL>.  This makes a filter command on the just read lines write the
same file as was read, and makes a write command on just filtered lines write
the same file as was read from the filter.  For example, another way to write
a compressed file: >

  :autocmd FileWritePre *.gz   set bin|'[,']!gzip
  :autocmd FileWritePost *.gz  undo|set nobin
<
							*autocommand-pattern*
You can specify multiple patterns, separated by commas.  Here are some
examples: >

  :autocmd BufRead   *		set tw=79 nocin ic infercase fo=2croq
  :autocmd BufRead   .letter	set tw=72 fo=2tcrq
  :autocmd BufEnter  .letter	set dict=/usr/lib/dict/words
  :autocmd BufLeave  .letter	set dict=
  :autocmd BufRead,BufNewFile   *.c,*.h	set tw=0 cin noic
  :autocmd BufEnter  *.c,*.h	abbr FOR for (i = 0; i < 3; ++i)<CR>{<CR>}<Esc>O
  :autocmd BufLeave  *.c,*.h	unabbr FOR

For makefiles (makefile, Makefile, imakefile, makefile.unix, etc.): >

  :autocmd BufEnter  ?akefile*	set include=^s\=include
  :autocmd BufLeave  ?akefile*	set include&

To always start editing C files at the first function: >

  :autocmd BufRead   *.c,*.h	1;/^{

Without the "1;" above, the search would start from wherever the file was
entered, rather than from the start of the file.

						*skeleton* *template*
To read a skeleton (template) file when opening a new file: >

  :autocmd BufNewFile  *.c	0r ~/vim/skeleton.c
  :autocmd BufNewFile  *.h	0r ~/vim/skeleton.h
  :autocmd BufNewFile  *.java	0r ~/vim/skeleton.java

To insert the current date and time in a *.html file when writing it: >

  :autocmd BufWritePre,FileWritePre *.html   ks|call LastMod()|'s
  :fun LastMod()
  :  if line("$") > 20
  :    let l = 20
  :  else
  :    let l = line("$")
  :  endif
  :  exe "1," . l . "g/Last modified: /s/Last modified: .*/Last modified: " .
  :  \ strftime("%Y %b %d")
  :endfun

You need to have a line "Last modified: <date time>" in the first 20 lines
of the file for this to work.  Vim replaces <date time> (and anything in the
same line after it) with the current date and time.  Explanation:
	ks		mark current position with mark 's'
	call LastMod()  call the LastMod() function to do the work
	's		return the cursor to the old position
The LastMod() function checks if the file is shorter than 20 lines, and then
uses the ":g" command to find lines that contain "Last modified: ".  For those
lines the ":s" command is executed to replace the existing date with the
current one.  The ":execute" command is used to be able to use an expression
for the ":g" and ":s" commands.  The date is obtained with the strftime()
function.  You can change its argument to get another date string.

When entering :autocmd on the command-line, completion of events and command
names may be done (with <Tab>, CTRL-D, etc.) where appropriate.

Vim executes all matching autocommands in the order that you specify them.
It is recommended that your first autocommand be used for all files by using
"*" as the file pattern.  This means that you can define defaults you like
here for any settings, and if there is another matching autocommand it will
override these.  But if there is no other matching autocommand, then at least
your default settings are recovered (if entering this file from another for
which autocommands did match).  Note that "*" will also match files starting
with ".", unlike Unix shells.

						    *autocmd-searchpat*
Autocommands do not change the current search patterns.  Vim saves the current
search patterns before executing autocommands then restores them after the
autocommands finish.  This means that autocommands do not affect the strings
highlighted with the 'hlsearch' option.  Within autocommands, you can still
use search patterns normally, e.g., with the "n" command.
If you want an autocommand to set the search pattern, such that it is used
after the autocommand finishes, use the ":let @/ =" command.
The search-highlighting cannot be switched off with ":nohlsearch" in an
autocommand.  Use the 'h' flag in the 'viminfo' option to disable search-
highlighting when starting Vim.

							*Cmd-event*
When using one of the "*Cmd" events, the matching autocommands are expected to
do the file reading or writing.  This can be used when working with a special
kind of file, for example on a remote system.
CAREFUL: If you use these events in a wrong way, it may have the effect of
making it impossible to read or write the matching files!  Make sure you test
your autocommands properly.  Best is to use a pattern that will never match a
normal file name, for example "ftp://*".

When defining a BufReadCmd it will be difficult for Vim to recover a crashed
editing session.  When recovering from the original file, Vim reads only those
parts of a file that are not found in the swap file.  Since that is not
possible with a BufReadCmd, use the |:preserve| command to make sure the
original file isn't needed for recovery.  You might want to do this only when
you expect the file to be modified.

The |v:cmdarg| variable holds the "++enc=" and "++ff=" argument that are
effective.  These should be used for the command that reads/writes the file.
The |v:cmdbang| variable is one when "!" was used, zero otherwise.

See the $VIMRUNTIME/plugin/netrw.vim for examples.

 vim:tw=78:ts=8:ft=help:norl: