shell `!` (event designator) cheat sheet

based on "a shell exclamation mark is not for yelling. be lazy." by filip roséen. applies to interactive bash, csh, tcsh, zsh — not scripts.

anatomy

![event][:word][:modifier]
    |      |        |
    |      |        '--> modifier    [ :h :t :r :e ... ]
    |      '-----------> which part  [ :0 :$ :* :2-3 ... ]
    '------------------> which line  [ !! !-2 !ssh !?needle? ... ]

! followed directly by : refers to the previous line.

event designators — which line

syntax	meaning
`!!`	previous command
`!-2`	two lines back
`!1337`	line 1337 from `history`
`!ssh`	most recent line starting with `ssh`
`!?needle?`	most recent line containing `needle`
`!#`	the current line, as typed so far
`^old^new^`	rerun previous command with first `old` → `new`

word designators — which part

example previous line: /path/to/script.sh "hello world" --enable 1337

syntax	selects	result
`!:0`	command word	`/path/to/script.sh`
`!:1`	2nd word (1st arg)	`hello world`
`!:$`	last word	`1337`
`!:1-2`	range	`hello world --enable`
`!:*`	all args	`hello world --enable 1337`
`!:1-`	all args but last	`hello world --enable`
`!:2*`	3rd word through last	`--enable 1337`

short forms: !$ = !:$, !* = !:*.

modifiers — transform the part

syntax	effect
`:h`	strip filename (like `dirname`)
`:t`	strip leading path (like `basename`)
`:r`	strip extension
`:e`	keep only extension
`:s/a/b/`	replace first `a` with `b`
`:gs/a/b/`	replace all `a` with `b`
`:p`	print, don't run (e.g. `!ssh:p`)

the four worth memorizing

syntax	use case
`!$`	last argument of previous command
`!:0`	rerun that annoyingly located script
`!$:h`	directory part of last argument
`!$:t`	filename part of last argument

everyday combos

$ apt install pkg          # permission denied
$ sudo !!                  # rerun with sudo

$ mkdir /var/mnt/cache
$ cd !$                    # cd into it

$ touch ~/projects/work/awesome.sh
$ cd !$:h                  # cd to its directory

$ ssh 10.240.33.109 -p2222 -i ~/.ssh/prod/ed25519
$ ssh 10.240.33.110 !:2*   # same flags, other host

$ ffmpeg -i /rec/day.mov !#:2:r.mkv   # reuse arg from current line, swap ext
$ scp !$:r.* example.com:/media

posix fallback: `fc`

works in any posix shell (except truly minimal ones like dash / busybox ash). edits history in $FCEDIT (fallback ed; many shells use $EDITOR).

syntax	effect
`fc`	edit previous command in editor, then run
`fc -2`	edit command 2 back
`fc grep`	edit last command starting with `grep`
`fc -3 -1`	last three commands in one buffer
`fc ssh -1`	from last `ssh` line through most recent
`fc -s ssh`	rerun last `ssh` command, no editor
`fc -s a=b ssh`	rerun last `ssh` command with `a` → `b`
`fc -e 'sed -i s/x/y/g' -3 -1`	rerun last 3 cmds through a non-interactive "editor"

turning it off / customizing

set +H                 # bash: disable history expansion
setopt nobanghist      # zsh: same
histchars='%^#'        # change trigger chars (event, substitution, comment)

common gotcha: echo "!dlrow olleh" → event not found (double quotes don't protect !; single quotes do).

Event Designators Cheat Sheet

shell ! (event designator) cheat sheet