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5.5 Command History

Previously executed commands are stored in a history list. The C shell 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 , history , and savehist also affect the history mechanism. Accessing the history list involves three things:

  • Making command substitutions (using ! and ^ )

  • Making argument substitutions (specific words within a command)

  • Using modifiers to extract or replace parts of a command or word

5.5.1 Command Substitution

! Begin a history substitution
!! Previous command
! N Command number N in history list
!- N N th 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, then append string

! N string Command N , then append string
!{ s1 } s2

Most recent command starting with string s1 , then append string s2

^ old ^ new ^

Quick substitution; change string old to new in previous command; execute modified command

5.5.2 Command Substitution Examples

The following command is assumed:

3% vi cprogs/01.c ch002 ch03

Event Number Command Typed Command Executed
4 ^00^0 vi cprogs/01.c ch02 ch03
5 nroff !* nroff cprogs/01.c ch02 ch03
6 nroff !$ nroff ch03
7 !vi vi cprogs/01.c ch02 ch03
8 !6 nroff ch03
9 !?01 vi cprogs/01.c ch02 ch03
10 !{nr}.new nroff ch03.new
11 !!|lp nroff ch03.new | lp
12 more !?pr?% more cprogs/01.c

5.5.3 Word Substitution

Word specifiers allow you to retrieve individual words from previous command lines. Colons may precede any word specifier. After an event number, colons are optional unless shown here.

:0 Command name
: n Argument number n
^ First argument
$ Last argument
: n - m Arguments n through m
- m

Words 0 through m ; same as :0- m

: n - Arguments n through next-to-last
: n *

Arguments n through last; same as n -$

* All arguments; same as ^-$ or 1-$
# Current command line up to this point; fairly useless

5.5.4 Word Substitution Examples

The following command is assumed:

13% cat ch01 ch02 ch03 biblio back

Event Number Command Typed Command Executed
14 ls !13^ ls ch01
15 sort !13:* sort ch01 ch02 ch03 biblio back
16 lp !cat:3* lp ch03 biblio back
17 !cat:0-3 cat ch01 ch02 ch03
18 vi !-5:4 vi biblio

5.5.5 History Modifiers

Command and word substitutions can be modified by one or more of these:

5.5.5.1 Printing, Substitution, and Quoting

:p Display command but don't execute.
:s/ old / new

Substitute string new for old , first instance only.

:gs/ old / new Substitute string new for old , all instances.
:&

Repeat previous substitution (:s or ^ command), first instance only.

:g& Repeat previous substitution, all instances.
:q Quote a word list.
:x Quote separate words.

5.5.5.2 Truncation

:r Extract the first available pathname root.
:gr Extract all pathname roots.
:e Extract the first available pathname extension.
:ge Extract all pathname extensions.
:h Extract the first available pathname header.
:gh Extract all pathname headers.
:t Extract the first available pathname tail.
:gt Extract all pathname tails.

5.5.6 History Modifier Examples

From the table in the section "Word Substitution Examples," command number 17 is:

17% cat ch01 ch02 ch03

Event # Command Typed Command Executed
19 !17:s/ch/CH/ cat CH01 ch02 ch03
20 !:g& cat CH01 CH02 CH03
21 !more:p more cprogs/01.c (displayed only)
22 cd !$:h cd cprogs
23 vi !mo:$:t vi 01.c
24 grep stdio !$ grep stdio 01.c
25 ^stdio^include stdio^:q grep "include stdio" 01.c
26 nroff !21:t:p nroff 01.c (is that want I wanted?)
27 !! nroff 01.c (execute it)


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