Event Designators
       An  event designator is a reference to a command line entry in the his-
       tory list.

       !      Start a history substitution, except when followed by  a  blank,
              newline,  carriage return, = or ( (when the extglob shell option
              is enabled using the shopt builtin).
       !n     Refer to command line n.
       !-n    Refer to the current command line minus n.
       !!     Refer to the previous command.  This is a synonym for '!-1'.
       !string
              Refer to the most recent command starting with string.
       !?string[?]
              Refer to the most recent command containing string.  The  trail-
              ing ? may be omitted if string is followed immediately by a new-
              line.
       ^string1^string2^
              Quick substitution.  Repeat the last command, replacing  string1
              with string2.  Equivalent to ''!!:s/string1/string2/'' (see Mod-
              ifiers below).
       !#     The entire command line typed so far.