11 Sep 2007
There are three fields (separated by colons) that can be manipulated using the bang history command:
EventDesignator:WordDesignator:Modifier
Event Designator
An event designator is a reference to a command line entry in the history list – man bash for more.
!n – Refer to command line n.
!-n – Refer to the current command line minus n.
!! – Refers to the previous command (synonym for ‘!-1) – useful if you after typing a command you release you need to add sudo: vi /etc/apt/source.list, error, sudo !!
For example:
<br />
$ history | tail -3<br />
195 echo foo<br />
196 echo bar<br />
197 history | tail -3<br />
$ !195<br />
echo foo<br />
foo<br />
$ !-3<br />
echo bar<br />
bar
Word Designator
Word designators are used to select desired words from the event- man bash for more. An event designator such as !! is followed by a colon then a word designator.
Numbers, where 0 is the command name and 1 the first argument, 2 the second arg, etc
* for everything except the command name
^ for the first argument, $ for the last argument
x-y for a range, where x and y can be numbers or ^,$
-y, x*, x- and other combinations
For example:
<br />
$ echo foo bar qux<br />
foo bar qux<br />
$ echo !!:0<br />
echo echo<br />
echo<br />
$ echo foo bar qux<br />
foo bar qux<br />
$ echo !!:1-2<br />
echo foo bar<br />
foo bar<br />
$ echo foo bar qux<br />
foo bar qux<br />
$ echo !!:2-$<br />
echo bar qux<br />
bar qux
Modifier
Modifies the word picked out so far – man bash for more.
h – remove a trailing file name component, leaving only the head.
t – remove all leading file name components, leaving the tail.
r – remove a trailing suffix of the form .xxx, leaving the basename.
etc.
For example:
<br />
$ ls /etc/apt/sources.list<br />
/etc/apt/sources.list<br />
$ cd !:1:h<br />
cd /etc/apt<br />
$ cat !-2:1:t<br />
cat sources.list<br />
$ cd; ls /etc/apt/sources.list<br />
/etc/apt/sources.list<br />
$ ls !:1:r<br />
ls /etc/apt/sources<br />
$ ls !:1:t:r<br />
ls sources<br />
!:s/apt/foo/<br />
ls /etc/foo/sources.list<br />
Notice how multiple operators can be combined, and how !! can be replaced with ! if immediately followed by a colon.