Mac OS X in a Nutshell

Command History

Previously executed commands are stored in a history list. tcsh lets you access this list so you can verify commands, repeat them, or execute modified versions of them. The history built-in command displays the history list; the predefined variables histchars and history also affect the history mechanism. There are four ways to use the history list:

• Rerun a previous command.

• Make command substitutions.

• Make argument substitutions (replace specific words in a command).

• Extract or replace parts of a command or word.

The following subsections describe the csh tools for editing and rerunning commands. If you are running tcsh, you can use any of these features. In addition, you can use the arrow keys to move around in the command line and then use the editing features described later in Section 21.7.4 to modify the command. The tcsh arrow keys are described in the following table:

Key	Description
Up Arrow	Previous command.
Down Arrow	Next command.
Left Arrow	Move left in command line.
Right Arrow	Move right in command line.

Command Substitution

Command	Description
!	Begin a history substitution.
!!	Previous command.
! N	Command number N in history list.
!- N	Nth command back from current command.
! string	Most recent command that starts with string.
!? string?	Most recent command that contains string.
!? string?%	Most recent command argument that contains string.
!$	Last argument of previous command.
!! string	Previous command, ...