! Bash

Event designators
Event designator is a reference to a command line entry in the History list.

! Start a command replacement, when the following letter is not "space, line feed, carriage return, = and.
! N Reference command line N.
! -N references the current command line minus n.
!! Reference the previous command. This is '! -1.
! String
Reference the latest string-based command.
!? String [?]
Reference the latest command that contains a string. Tail? Can be ignored. If the string is followed by a new line character.
^ String1 ^ string2 ^
Quick replacement. Repeat the previous command to replace string1 with string2. and ''!! : S/string1/string2/''is equivalent (see the modifier (modifiers) below )).
! # The entire command line entered so far.