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This chapter describes how to use the GNU History Library interactively, from a user’s standpoint. It should be considered a user’s guide. For information on using the GNU History Library in your own programs, @pxref{Programming with GNU History}.
1.1 Interactive History Expansion | What it feels like using History as a user. |
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The History library provides a history expansion feature that is similar
to the history expansion provided by csh
. This section
describes the syntax used to manipulate the history information.
History expansions introduce words from the history list into the input stream, making it easy to repeat commands, insert the arguments to a previous command into the current input line, or fix errors in previous commands quickly.
History expansion takes place in two parts. The first is to determine which line from the previous history should be used during substitution. The second is to select portions of that line for inclusion into the current one. The line selected from the previous history is called the event, and the portions of that line that are acted upon are called words. Various modifiers are available to manipulate the selected words. The line is broken into words in the same fashion that Bash does, so that several English (or Unix) words surrounded by quotes are considered as one word. History expansions are introduced by the appearance of the history expansion character, which is ‘!’ by default.
1.1.1 Event Designators | How to specify which history line to use. | |
1.1.2 Word Designators | Specifying which words are of interest. | |
1.1.3 Modifiers | Modifying the results of substitution. |
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An event designator is a reference to a command line entry in the history list.
!
Start a history substitution, except when followed by a space, tab, the end of the line, <=> or <(>.
!n
Refer to command line n.
!-n
Refer to the command n lines back.
!!
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 trailing ‘?’ may be omitted if the string is followed immediately by a newline.
^string1^string2^
Quick Substitution. Repeat the last command, replacing string1
with string2. Equivalent to
!!:s/string1/string2/
.
!#
The entire command line typed so far.
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Word designators are used to select desired words from the event. A ‘:’ separates the event specification from the word designator. It can be omitted if the word designator begins with a ‘^’, ‘$’, ‘*’, ‘-’, or ‘%’. Words are numbered from the beginning of the line, with the first word being denoted by 0 (zero). Words are inserted into the current line separated by single spaces.
0 (zero)
The 0
th word. For many applications, this is the command word.
n
The nth word.
^
The first argument; that is, word 1.
$
The last argument.
%
The word matched by the most recent ‘?string?’ search.
x-y
A range of words; ‘-y’ abbreviates ‘0-y’.
*
All of the words, except the 0
th. This is a synonym for ‘1-$’.
It is not an error to use ‘*’ if there is just one word in the event;
the empty string is returned in that case.
x*
Abbreviates ‘x-$’
x-
Abbreviates ‘x-$’ like ‘x*’, but omits the last word.
If a word designator is supplied without an event specification, the previous command is used as the event.
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After the optional word designator, you can add a sequence of one or more of the following modifiers, each preceded by a ‘:’.
h
Remove a trailing pathname component, leaving only the head.
t
Remove all leading pathname components, leaving the tail.
r
Remove a trailing suffix of the form ‘.suffix’, leaving the basename.
e
Remove all but the trailing suffix.
p
Print the new command but do not execute it.
s/old/new/
Substitute new for the first occurrence of old in the event line. Any delimiter may be used in place of ‘/’. The delimiter may be quoted in old and new with a single backslash. If ‘&’ appears in new, it is replaced by old. A single backslash will quote the ‘&’. The final delimiter is optional if it is the last character on the input line.
&
Repeat the previous substitution.
g
Cause changes to be applied over the entire event line. Used in
conjunction with ‘s’, as in gs/old/new/
,
or with ‘&’.
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