Autocmd

Nvim :help pages, generated from source using the tree-sitter-vimdoc parser.


Automatic commands autocommand
For a basic explanation, see section 40.3 in the user manual.

1. Introduction autocmd-intro

You can specify commands to be executed automatically 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 file.
E203 E204 E143 E855 E937 E952 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

:au :autocmd :au[tocmd] [group] {event} {aupat} [++once] [++nested] {cmd} Add {cmd} to the list of commands that Vim will execute automatically on {event} for a file matching {aupat} autocmd-pattern. Note: A quote character is seen as argument to the :autocmd and won't start a comment. Nvim always adds {cmd} after existing autocommands so they execute in the order in which they were defined. See autocmd-nested for [++nested]. autocmd-once If [++once] is supplied the command is executed once, then removed ("one shot").
The special pattern <buffer> or <buffer=N> defines a buffer-local autocommand. See autocmd-buflocal.
Note: The ":autocmd" command can only be followed by another command when the "|" appears where the pattern is expected. This works:
:augroup mine | au! BufRead | augroup END
But this sees "augroup" as part of the defined command:
:augroup mine | au! BufRead * | augroup END
:augroup mine | au BufRead * set tw=70 | augroup END
Instead you can put the group name into the command:
:au! mine BufRead *
:au mine BufRead * set tw=70
Or use :execute:
:augroup mine | exe "au! BufRead *" | augroup END
:augroup mine | exe "au BufRead * set tw=70" | augroup END
autocmd-expand 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.
:autocmd adds to the list of autocommands regardless of whether they are already present. When your .vimrc file is sourced twice, the autocommands will appear twice. To avoid this, define your autocommands in a group, so that you can easily clear them:
augroup vimrc
  " Remove all vimrc autocommands
  autocmd!
  au BufNewFile,BufRead *.html so <sfile>:h/html.vim
augroup END
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 message 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} {aupat} [++once] [++nested] {cmd} Remove all autocommands associated with {event} and {aupat}, and add the command {cmd}. See autocmd-once for [++once]. See autocmd-nested for [++nested].
:au[tocmd]! [group] {event} {aupat} Remove all autocommands associated with {event} and {aupat}.
:au[tocmd]! [group] * {aupat} Remove all autocommands associated with {aupat} for all events.
:au[tocmd]! [group] {event} Remove ALL autocommands for {event}. Warning: You should not do this without a group for BufRead and other common events, it can break plugins, syntax highlighting, etc.
:au[tocmd]! [group] Remove ALL autocommands. Note: a quote will be seen as argument to the :autocmd and won't start a comment. Warning: You should normally not do this without a group, it breaks plugins, syntax highlighting, etc.
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} {aupat} Show the autocommands associated with {event} and {aupat}.
:au[tocmd] [group] * {aupat} Show the autocommands associated with {aupat} 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.
In order to list buffer-local autocommands, use a pattern in the form <buffer> or <buffer=N>. See autocmd-buflocal.
:autocmd-verbose When 'verbose' is non-zero, listing an autocommand will also display where it was last defined. Example:
:verbose autocmd BufEnter
FileExplorer  BufEnter
    *          call s:LocalBrowse(expand("<amatch>"))
        Last set from /usr/share/vim/vim-7.0/plugin/NetrwPlugin.vim
See :verbose-cmd for more information.

5. Events autocmd-events E215 E216

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 theReadPre 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.
events {event} Nvim recognizes the following events. Names are case-insensitive.
BufAdd BufAdd Just after creating a new buffer which is added to the buffer list, or adding a buffer to the buffer list, a buffer in the buffer list was renamed. Not triggered for the initial buffers created during startup. Before BufEnter. NOTE: 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: Current buffer "%" may be different from the buffer being deleted "<afile>" and "<abuf>". Do not change to another buffer. BufEnter BufEnter After entering a buffer. Useful for setting options for a file type. Also executed when starting to edit a buffer. After BufAdd. After BufReadPost. BufFilePost BufFilePost After changing the name of the current buffer with the ":file" or ":saveas" command. BufFilePre BufFilePre Before changing the name of the current buffer with the ":file" or ":saveas" command. BufHidden BufHidden Before a buffer becomes hidden: 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: current buffer "%" may be different from the buffer being unloaded "<afile>". 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. BufModifiedSet BufModifiedSet After the 'modified' value of a buffer has been changed. 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: Current buffer "%" may be different from the buffer being created "<afile>". BufNewFile BufNewFile When starting to edit a file that doesn't exist. Can be used to read in a skeleton file. BufRead BufReadPost BufRead or BufReadPost When starting to edit a new buffer, after reading the file into the buffer, before processing modelines. See BufWinEnter to do something after processing modelines. Also triggered:
when writing an unnamed buffer in a way that the buffer gets a name
after successfully recovering a file
for the "filetypedetect" group when executing ":filetype detect" Not triggered:
for the :read file command
when the file doesn't exist BufReadCmd BufReadCmd Before starting to edit a new buffer. Should read the file into the buffer. Cmd-event 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. BufUnload BufUnload Before unloading a buffer, when the text in the buffer is going to be freed. After BufWritePost. Before BufDelete. Triggers for all loaded buffers when Vim is going to exit. NOTE: Current buffer "%" may be different from the buffer being unloaded "<afile>". Do not switch buffers or windows! Not triggered when exiting and v:dying is 2 or more. BufWinEnter BufWinEnter After a buffer is displayed in a window. This may be when the buffer is loaded (after processing modelines) or when a hidden buffer is displayed (and is no longer hidden).
Not triggered for :split without arguments, since the buffer does not change, or :split with a file already open in a window. Triggered for ":split" with the name of the current buffer, since it reloads that buffer. BufWinLeave BufWinLeave Before a buffer is removed from a window. Not when it's still visible in another window. Also triggered when exiting. Before BufUnload, BufHidden. NOTE: Current buffer "%" may be different from the buffer being unloaded "<afile>". Not triggered when exiting and v:dying is 2 or more. 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: Current buffer "%" may be different from the buffer being deleted "<afile>". Do not change to another buffer. BufWrite BufWritePre BufWrite or BufWritePre Before writing the whole buffer to a file. BufWriteCmd BufWriteCmd Before writing the whole buffer to a file. Should do the writing of the file and reset 'modified' if successful, unless '+' is in 'cpo' and writing to another file cpo-+. The buffer contents should not be changed. When the command resets 'modified' the undo information is adjusted to mark older undo states as 'modified', like :write does. Cmd-event BufWritePost BufWritePost After writing the whole buffer to a file (should undo the commands for BufWritePre). ChanInfo ChanInfo State of channel changed, for instance the client of a RPC channel described itself. Sets these v:event keys: info See nvim_get_chan_info() for the format of the info Dictionary. ChanOpen ChanOpen Just after a channel was opened. Sets these v:event keys: info See nvim_get_chan_info() for the format of the info Dictionary. CmdUndefined CmdUndefined When a user command is used but it isn't defined. Useful for defining a command only when it's used. The pattern is matched against the command name. Both <amatch> and <afile> expand to the command name. NOTE: Autocompletion won't work until the command is defined. An alternative is to always define the user command and have it invoke an autoloaded function. See autoload. CmdlineChanged CmdlineChanged After a change was made to the text inside command line. Be careful not to mess up the command line, it may cause Vim to lock up. <afile> expands to the cmdline-char. CmdlineEnter CmdlineEnter After entering the command-line (including non-interactive use of ":" in a mapping: use <Cmd> instead to avoid this). <afile> expands to the cmdline-char. Sets these v:event keys: cmdlevel cmdtype CmdlineLeave CmdlineLeave Before leaving the command-line (including non-interactive use of ":" in a mapping: use <Cmd> instead to avoid this). <afile> expands to the cmdline-char. Sets these v:event keys: abort (mutable) cmdlevel cmdtype Note: abort can only be changed from false to true: cannot execute an already aborted cmdline by changing it to false. CmdwinEnter CmdwinEnter After entering the command-line window. Useful for setting options specifically for this special type of window. <afile> expands 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. <afile> expands to a single character, indicating the type of command-line. cmdwin-char ColorScheme ColorScheme After loading a color scheme. :colorscheme Not triggered if the color scheme is not found. The pattern is matched against the colorscheme name. <afile> can be used for the name of the actual file where this option was set, and <amatch> for the new colorscheme name.
ColorSchemePre ColorSchemePre Before loading a color scheme. :colorscheme Useful to setup removing things added by a color scheme, before another one is loaded.
CompleteChanged CompleteChanged After each time the Insert mode completion menu changed. Not fired on popup menu hide, use CompleteDonePre or CompleteDone for that.
Sets these v:event keys: completed_item See complete-items. height nr of items visible width screen cells row top screen row col leftmost screen column size total nr of items scrollbar TRUE if visible
Non-recursive (event cannot trigger itself). Cannot change the text. textlock
The size and position of the popup are also available by calling pum_getpos().
CompleteDonePre CompleteDonePre After Insert mode completion is done. Either when something was completed or abandoning completion. ins-completion complete_info() can be used, the info is cleared after triggering CompleteDonePre. The v:completed_item variable contains information about the completed item.
CompleteDone CompleteDone After Insert mode completion is done. Either when something was completed or abandoning completion. ins-completion complete_info() cannot be used, the info is cleared before triggering CompleteDone. Use CompleteDonePre if you need it. v:completed_item gives the completed item.
CursorHold CursorHold When the user doesn't press a key for the time specified with 'updatetime'. Not 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. It is not triggered when waiting for a command argument to be typed, or a movement after an operator. While recording the CursorHold event is not triggered. q <CursorHold> Internally the autocommand is triggered by the <CursorHold> key. In an expression mapping getchar() may see this character.
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
CursorHoldI CursorHoldI Like CursorHold, but in Insert mode. Not triggered when waiting for another key, e.g. after CTRL-V, and not in CTRL-X mode insert_expand.
CursorMoved CursorMoved After the cursor was moved in Normal or Visual mode or to another window. Also when the text of the cursor line has been changed, e.g. with "x", "rx" or "p". Not always triggered when there is typeahead, while executing commands in a script file, or when an operator is pending. Always triggered when moving to another window. For an example see match-parens. Note: Cannot be skipped with :noautocmd. Careful: This is triggered very often, don't do anything that the user does not expect or that is slow. CursorMovedI CursorMovedI After the cursor was moved in Insert mode. Not triggered when the popup menu is visible. Otherwise the same as CursorMoved. DiffUpdated DiffUpdated After diffs have been updated. Depending on what kind of diff is being used (internal or external) this can be triggered on every change or when doing :diffupdate. DirChanged DirChanged After the current-directory was changed. The pattern can be: "window" to trigger on :lcd "tabpage" to trigger on :tcd "global" to trigger on :cd "auto" to trigger on 'autochdir'. Sets these v:event keys: cwd: current working directory scope: "global", "tabpage", "window" changed_window: v:true if we fired the event switching window (or tab) <afile> is set to the new directory name. Non-recursive (event cannot trigger itself). DirChangedPre DirChangedPre When the current-directory is going to be changed, as with DirChanged. The pattern is like with DirChanged. Sets these v:event keys: directory: new working directory scope: "global", "tabpage", "window" changed_window: v:true if we fired the event switching window (or tab) <afile> is set to the new directory name. Non-recursive (event cannot trigger itself). ExitPre ExitPre When using :quit, :wq in a way it makes Vim exit, or using :qall, just after QuitPre. Can be used to close any non-essential window. Exiting may still be cancelled if there is a modified buffer that isn't automatically saved, use VimLeavePre for really exiting. See also QuitPre, WinClosed. FileAppendCmd FileAppendCmd Before appending to a file. Should do the appending to the file. Use the '[ and '] marks for the range of lines. Cmd-event FileAppendPost FileAppendPost After appending to a file. FileAppendPre FileAppendPre Before appending to a file. Use the '[ and '] marks for the range of lines. FileChangedRO FileChangedRO Before making the first change to a read-only file. Can be used to checkout the file from a source control system. Not triggered when the change was caused by an autocommand. Triggered when making the first change in a buffer or the first change after 'readonly' was set, just before the change is applied to the text. WARNING: If the autocommand moves the cursor the effect of the change is undefined. E788 Cannot switch buffers. You can reload the buffer but not edit another one. E881 If the number of lines changes saving for undo may fail and the change will be aborted. 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 or when the size of the file changes. timestamp Triggered for each changed file, after:
executing a shell command
Not used when 'autoread' is set and the buffer was not changed. If a FileChangedShell autocommand exists the warning message and prompt is not given. v:fcs_reason indicates what happened. Set v:fcs_choice to control what happens next. NOTE: Current buffer "%" may be different from the buffer that was changed "<afile>". E246 E811 Cannot switch, jump to or delete buffers. Non-recursive (event cannot trigger itself). FileChangedShellPost FileChangedShellPost After handling a file that was changed outside of Vim. Can be used to update the statusline. FileReadCmd FileReadCmd Before reading a file with a ":read" command. Should do the reading of the file. Cmd-event 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. FileReadPre FileReadPre Before reading a file with a ":read" command. FileType FileType When the 'filetype' option has been set. The pattern is matched against the filetype. <afile> is the name of the file where this option was set. <amatch> is the new value of 'filetype'. Cannot switch windows or buffers. See filetypes. 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. Use the '[ and '] marks for the range of lines. Cmd-event FileWritePost FileWritePost After writing to a file, when not writing the whole buffer. FileWritePre FileWritePre Before writing to a file, when not writing the whole buffer. Use the '[ and '] marks for the range of lines. FilterReadPost FilterReadPost After reading a file from a filter command. Vim checks the pattern against the name of the current buffer as with FilterReadPre. Not triggered when 'shelltemp' is off. 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. Not triggered when 'shelltemp' is off. FilterWritePost FilterWritePost After writing a file for a filter command or making a diff with an external diff (see DiffUpdated for internal diff). Vim checks the pattern against the name of the current buffer as with FilterWritePre. Not triggered when 'shelltemp' is off. FilterWritePre FilterWritePre Before writing a file for a filter command or making a diff with an external 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. Not triggered when 'shelltemp' is off. FocusGained FocusGained Nvim got focus. FocusLost FocusLost Nvim lost focus. Also (potentially) when a GUI dialog pops up. FuncUndefined FuncUndefined When a user function is used but it isn't defined. Useful for defining a function only when it's used. The pattern is matched against the function name. Both <amatch> and <afile> are set to the name of the function. NOTE: When writing Vim scripts a better alternative is to use an autoloaded function. See autoload-functions. UIEnter UIEnter After a UI connects via nvim_ui_attach(), or after builtin TUI is started, after VimEnter. Sets these v:event keys: chan: channel-id of the UI UILeave UILeave After a UI disconnects from Nvim, or after builtin TUI is stopped, after VimLeave. Sets these v:event keys: chan: channel-id of the UI InsertChange InsertChange When typing <Insert> while in Insert or Replace mode. The v:insertmode variable indicates the new mode. Be careful not to move the cursor or do anything else that the user does not expect. InsertCharPre InsertCharPre When a character is typed in Insert mode, before inserting the char. The v:char variable indicates the char typed and can be changed during the event to insert a different character. When v:char is set to more than one character this text is inserted literally.
Cannot change the text. textlock Not triggered when 'paste' is set. InsertEnter InsertEnter Just before starting Insert mode. Also for Replace mode and Virtual Replace mode. The v:insertmode variable indicates the mode. Be careful not to do anything else that the user does not expect. The cursor is restored afterwards. If you do not want that set v:char to a non-empty string. InsertLeavePre InsertLeavePre Just before leaving Insert mode. Also when using CTRL-O i_CTRL-O. Be careful not to change mode or use :normal, it will likely cause trouble. InsertLeave InsertLeave Just after leaving Insert mode. Also when using CTRL-O i_CTRL-O. But not for i_CTRL-C. MenuPopup MenuPopup Just before showing the popup menu (under the right mouse button). Useful for adjusting the menu for what is under the cursor or mouse pointer. The pattern is matched against one or two characters representing the mode: n Normal v Visual o Operator-pending i Insert c Command line tl Terminal ModeChanged ModeChanged After changing the mode. The pattern is matched against 'old_mode:new_mode', for example match against *:c to simulate CmdlineEnter. The following values of v:event are set: old_mode The mode before it changed. new_mode The new mode as also returned by mode() called with a non-zero argument. When ModeChanged is triggered, old_mode will have the value of new_mode when the event was last triggered. This will be triggered on every minor mode change. Usage example to use relative line numbers when entering visual mode:
:au ModeChanged [vV\x16]*:* let &l:rnu = mode() =~# '^[vV\x16]'
:au ModeChanged *:[vV\x16]* let &l:rnu = mode() =~# '^[vV\x16]'
:au WinEnter,WinLeave * let &l:rnu = mode() =~# '^[vV\x16]'
OptionSet OptionSet After setting an option (except during startup). The autocmd-pattern is matched against the long option name. <amatch> indicates what option has been set.
v:option_type indicates whether it's global or local scoped. v:option_command indicates what type of set/let command was used (follow the tag to see the table). v:option_new indicates the newly set value. v:option_oldlocal has the old local value. v:option_oldglobal has the old global value. v:option_old indicates the old option value.
v:option_oldlocal is only set when :set or :setlocal or a modeline was used to set the option. Similarly v:option_oldglobal is only set when :set or :setglobal was used.
Note that when setting a global-local string option with :set, then v:option_old is the old global value. However, for all other kinds of options (local string options, global-local number options, ...) it is the old local value.
OptionSet is not triggered on startup and for the 'key' option for obvious reasons.
Usage example: Check for the existence of the directory in the 'backupdir' and 'undodir' options, create the directory if it doesn't exist yet.
Note: Do not reset the same option during this autocommand, that may break plugins. You can always use :noautocmd to prevent triggering OptionSet.
Non-recursive: :set in the autocommand does not trigger OptionSet again.
QuickFixCmdPre QuickFixCmdPre Before a quickfix command is run (:make, :lmake, :grep, :lgrep, :grepadd, :lgrepadd, :vimgrep, :lvimgrep, :vimgrepadd, :lvimgrepadd, :cfile, :cgetfile, :caddfile, :lfile, :lgetfile, :laddfile, :helpgrep, :lhelpgrep, :cexpr, :cgetexpr, :caddexpr, :cbuffer, :cgetbuffer, :caddbuffer). The pattern is matched against the command being run. When :grep is used but 'grepprg' is set to "internal" it still matches "grep". This command cannot be used to set the 'makeprg' and 'grepprg' variables. If this command causes an error, the quickfix command is not executed. QuickFixCmdPost QuickFixCmdPost Like QuickFixCmdPre, but after a quickfix command is run, before jumping to the first location. For :cfile and :lfile commands it is run after the error file is read and before moving to the first error. See QuickFixCmdPost-example. QuitPre QuitPre When using :quit, :wq or :qall, before deciding whether it closes the current window or quits Vim. For :wq the buffer is written before QuitPre is triggered. Can be used to close any non-essential window if the current window is the last ordinary window. See also ExitPre, WinClosed. RemoteReply RemoteReply When a reply from a Vim that functions as server was received server2client(). The pattern is matched against the {serverid}. <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. SearchWrapped SearchWrapped After making a search with n or N if the search wraps around the document back to the start/finish respectively. RecordingEnter RecordingEnter When a macro starts recording. The pattern is the current file name, and reg_recording() is the current register that is used. RecordingLeave RecordingLeave When a macro stops recording. The pattern is the current file name, and reg_recording() is the recorded register. reg_recorded() is only updated after this event. Sets these v:event keys: regcontents regname SessionLoadPost SessionLoadPost After loading the session file created using the :mksession command. ShellCmdPost ShellCmdPost After executing a shell command with :!cmd, :make and :grep. Can be used to check for any changed files. For non-blocking shell commands, see job-control. Signal Signal After Nvim receives a signal. The pattern is matched against the signal name. Only "SIGUSR1" and "SIGWINCH" are supported. Example:
autocmd Signal SIGUSR1 call some#func()
ShellFilterPost ShellFilterPost After executing a shell command with ":{range}!cmd", ":w !cmd" or ":r !cmd". Can be used to check for any changed files. SourcePre SourcePre Before sourcing a vim/lua file. :source <afile> is the name of the file being sourced. SourcePost SourcePost After sourcing a vim/lua file. :source <afile> is the name of the file being sourced. Not triggered when sourcing was interrupted. Also triggered after a SourceCmd autocommand was triggered. SourceCmd SourceCmd When sourcing a vim/lua file. :source <afile> is the name of the file being sourced. The autocommand must source this file. Cmd-event SpellFileMissing SpellFileMissing When trying to load a spell checking file and it can't be found. The pattern is matched against the language. <amatch> is the language, 'encoding' also matters. See spell-SpellFileMissing. StdinReadPost StdinReadPost During startup, after reading from stdin into the buffer, before executing modelines. -- StdinReadPre StdinReadPre During startup, before reading from stdin into the buffer. -- SwapExists SwapExists Detected an existing swap file when starting to edit a file. Only when it is possible to select a way to handle the situation, when Vim would ask the user what to do. The v:swapname variable holds the name of the swap file found, <afile> the file being edited. v:swapcommand may contain a command to be executed in the opened file. The commands should set the v:swapchoice variable to a string with one character to tell Vim what should be done next: 'o' open read-only 'e' edit the file anyway 'r' recover 'd' delete the swap file 'q' quit, don't edit the file 'a' abort, like hitting CTRL-C When set to an empty string the user will be asked, as if there was no SwapExists autocmd. E812 Cannot change to another buffer, change the buffer name or change directory. Syntax Syntax When the 'syntax' option has been set. The pattern is matched against the syntax name. <afile> expands to the name of the file where this option was set. <amatch> expands to the new value of 'syntax'. See :syn-on. TabEnter TabEnter Just after entering a tab page. tab-page After WinEnter. Before BufEnter. TabLeave TabLeave Just before leaving a tab page. tab-page After WinLeave. TabNew TabNew When creating a new tab page. tab-page After WinEnter. Before TabEnter. TabNewEntered TabNewEntered After entering a new tab page. tab-page After BufEnter. TabClosed TabClosed After closing a tab page. <afile> expands to the tab page number. TermOpen TermOpen When a terminal job is starting. Can be used to configure the terminal buffer. TermEnter TermEnter After entering Terminal-mode. After TermOpen. TermLeave TermLeave After leaving Terminal-mode. After TermClose. TermClose TermClose When a terminal job ends. Sets these v:event keys: status 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. May be triggered halfway through another event (file I/O, a shell command, or anything else that takes time). TextChanged TextChanged After a change was made to the text in the current buffer in Normal mode. That is after b:changedtick has changed (also when that happened before the TextChanged autocommand was defined). Not triggered when there is typeahead or when an operator is pending. Note: Cannot be skipped with :noautocmd. Careful: This is triggered very often, don't do anything that the user does not expect or that is slow. TextChangedI TextChangedI After a change was made to the text in the current buffer in Insert mode. Not triggered when the popup menu is visible. Otherwise the same as TextChanged. TextChangedP TextChangedP After a change was made to the text in the current buffer in Insert mode, only when the popup menu is visible. Otherwise the same as TextChanged. TextChangedT TextChangedT After a change was made to the text in the current buffer in Terminal-mode. Otherwise the same as TextChanged. TextYankPost TextYankPost Just after a yank or deleting command, but not if the black hole register quote_ is used nor for setreg(). Pattern must be *. Sets these v:event keys: inclusive operator regcontents regname regtype visual The inclusive flag combined with the '[ and '] marks can be used to calculate the precise region of the operation.
Non-recursive (event cannot trigger itself). Cannot change the text. textlock User User Not executed automatically. Use :doautocmd to trigger this, typically for "custom events" in a plugin. Example:
:autocmd User MyPlugin echom 'got MyPlugin event'
:doautocmd User MyPlugin
UserGettingBored UserGettingBored When the user presses the same key 42 times. Just kidding! :-) 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. Just before this event is triggered the v:vim_did_enter variable is set, so that you can do:
if v:vim_did_enter
  call s:init()
else
  au VimEnter * call s:init()
endif
VimLeave VimLeave Before exiting Vim, just after writing the .shada file. Executed only once, like VimLeavePre. Use v:dying to detect an abnormal exit. Use v:exiting to get the exit code. Not triggered if v:dying is 2 or more. VimLeavePre VimLeavePre Before exiting Vim, just before writing the .shada 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()
Use v:dying to detect an abnormal exit. Use v:exiting to get the exit code. Not triggered if v:dying is 2 or more. VimResized VimResized After the Vim window was resized, thus 'lines' and/or 'columns' changed. Not when starting up though. VimResume VimResume After Nvim resumes from suspend state. VimSuspend VimSuspend Before Nvim enters suspend state. WinClosed WinClosed When closing a window, just before it is removed from the window layout. The pattern is matched against the window-ID. Both <amatch> and <afile> are set to the window-ID. After WinLeave. Non-recursive (event cannot trigger itself). See also ExitPre, QuitPre. 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: For split and tabpage commands the WinEnter event is triggered after the split or tab command but before the file 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. Before WinClosed. WinNew WinNew When a new window was created. Not done for the first window, when Vim has just started. Before WinEnter.
WinScrolled WinScrolled After any window in the current tab page scrolled the text (horizontally or vertically) or changed width or height. See win-scrolled-resized.
The pattern is matched against the window-ID of the first window that scrolled or resized. Both <amatch> and <afile> are set to the window-ID.
v:event is set with information about size and scroll changes. WinScrolled-event
Only starts triggering after startup finished and the first screen redraw was done. Does not trigger when defining the first WinScrolled or WinResized event, but may trigger when adding more.
Non-recursive: the event will not trigger while executing commands for the WinScrolled event. However, if the command causes a window to scroll or change size, then another WinScrolled event will be triggered later.
WinResized WinResized After a window in the current tab page changed width or height. See win-scrolled-resized.
v:event is set with information about size changes. WinResized-event
Same behavior as WinScrolled for the pattern, triggering and recursiveness.

6. Patterns autocmd-pattern {aupat}

The {aupat} argument of :autocmd can be a comma-separated list. This works as if the command was given with each pattern separately. Thus this command:
:autocmd BufRead *.txt,*.info set et
Is equivalent to:
:autocmd BufRead *.txt set et
:autocmd BufRead *.info set et
The file pattern {aupat} 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 both the short file name (as you typed it) and the full file name (after expanding it to a full path and resolving symbolic links).
The special pattern <buffer> or <buffer=N> is used for buffer-local autocommands autocmd-buflocal. This pattern is not matched against the name of a buffer.
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 if 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 ~/.config/nvim/init.vim   so <afile>
: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; Unusual: includes path separators ? matches any single character \? matches a '?' . matches a '.' ~ matches a '~' , separates patterns \, matches a ',' { } like \( \) in a pattern , inside { }: like \| in a pattern \} literal } \{ literal { \\\{n,m\} like \{n,m} 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 Windows). This was done because the backslash is difficult to use in a pattern and to make the autocommands portable across different systems.
It is possible to use pattern items, but they may not work as expected, because of the translation done for the above.
autocmd-changes 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.
However, buffer-local autocommands will not be executed for a buffer that has been wiped out with :bwipe. After deleting the buffer with :bdel the buffer actually still exists (it becomes unlisted), thus the autocommands are still executed.

7. Buffer-local autocommands autocmd-buflocal autocmd-buffer-local

<buffer> <buffer=N> <buffer=abuf> E680
Buffer-local autocommands are attached to a specific buffer. They are useful if the buffer does not have a name and when the name does not match a specific pattern. But it also means they must be explicitly added to each buffer.
Instead of a pattern buffer-local autocommands use one of these forms: <buffer> current buffer <buffer=99> buffer number 99 <buffer=abuf> using <abuf> (only when executing autocommands) <abuf>
Examples:
:au CursorHold <buffer>  echo 'hold'
:au CursorHold <buffer=33>  echo 'hold'
:au BufNewFile * au CursorHold <buffer=abuf>  echo 'hold'
All the commands for autocommands also work with buffer-local autocommands, simply use the special string instead of the pattern. Examples:
:au! * <buffer>                     " remove buffer-local autocommands for
                                 " current buffer
:au! * <buffer=33>                     " remove buffer-local autocommands for
                                 " buffer #33
:bufdo :au! CursorHold <buffer>  " remove autocmd for given event for all
                                 " buffers
:au * <buffer>                     " list buffer-local autocommands for
                                 " current buffer
Note that when an autocommand is defined for the current buffer, it is stored with the buffer number. Thus it uses the form "<buffer=12>", where 12 is the number of the current buffer. You will see this when listing autocommands, for example.
To test for presence of buffer-local autocommands use the exists() function as follows:
:if exists("#CursorHold#<buffer=12>") | ... | endif
:if exists("#CursorHold#<buffer>") | ... | endif    " for current buffer
When a buffer is wiped out its buffer-local autocommands are also gone, of course. Note that when deleting a buffer, e.g., with ":bdel", it is only unlisted, the autocommands are still present. In order to see the removal of buffer-local autocommands:
:set verbose=6
It is not possible to define buffer-local autocommands for a non-existent buffer.

8. 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. To avoid confusion, the name should be different from existing {event} names, as this most likely will not do what you intended.
:augroup-delete E367 W19 E936 :aug[roup]! {name} Delete the autocmd group {name}. Don't use this if there is still an autocommand using this group! You will get a warning if doing it anyway. When the group is the current group you will get error E936.
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).
FileExplorer There is one group that is recognized by Vim: FileExplorer. If this group exists Vim assumes that editing a directory is possible and will trigger a plugin that lists the files in that directory. This is used by the netrw plugin. This allows you to do:
browse edit

9. 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 :doaut :doautocmd E217 :do[autocmd] [<nomodeline>] [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 ~/.config/nvim/init_cpp.vim
:au BufEnter *.cpp doau BufEnter x.c
Be careful to avoid endless loops. 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. Undefined group is an error. <nomodeline> After applying the autocommands the modelines are processed, so that their settings overrule the settings from autocommands when editing a file. This is skipped if <nomodeline> is specified. You probably want to use <nomodeline> for events not used when loading a buffer, such as User. Modelines are also skipped when no matching autocommands were executed.
:doautoa :doautoall :doautoa[ll] [<nomodeline>] [group] {event} [fname] Like ":doautocmd", but apply the autocommands to each loaded buffer. The current buffer is done last.
Note that [fname] is used to select the autocommands, not the buffers to which they are applied. Example:
augroup mine
  autocmd!
  autocmd FileType * echo expand('<amatch>')
augroup END
doautoall mine FileType Loaded-Buffer
Sourcing this script, you'll see as many "Loaded-Buffer" echoed as there are loaded buffers.
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.

10. 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 theWritePost commands should undo any changes to the buffer that were caused by theWritePre 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.
TheWritePre andAppendPre autocommands must not delete the buffer from which the lines are to be written.
The '[ and '] marks have a special position:
Before theReadPre event the '[ mark is set to the line just above where the new lines will be inserted.
Before theReadPost event the '[ mark is set to the first line that was just read, the '] mark to the last line.
Before executing the *WriteCmd, *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 don'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. For example, 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.
If you want to skip autocommands for one command, use the :noautocmd command modifier or 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 'shada' 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, writing or sourcing. 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.
For file read and write commands 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/netrwPlugin.vim for examples.

11. Disabling autocommands autocmd-disable

To disable autocommands for some time use the 'eventignore' option. Note that this may cause unexpected behavior, make sure you restore 'eventignore' afterwards, using a :try block with :finally.
:noautocmd :noa To disable autocommands for just one command use the ":noautocmd" command modifier. This will set 'eventignore' to "all" for the duration of the following command. Example:
:noautocmd w fname.gz
This will write the file without triggering the autocommands defined by the gzip plugin.
Note that some autocommands are not triggered right away, but only later. This specifically applies to CursorMoved and TextChanged.
Main
Commands index
Quick reference