This chapter describes how to use the GNU History Library interactively, from a user's standpoint. It should be considered a user's guide.
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 history list 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 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 words surrounded by quotes are considered one word. History expansions are introduced by the appearance of the history expansion character, which is `!' by default.
An event designator is a reference to a command line entry in the history list.
Word designators are used to select desired words from the event. A `:' separates the event specification from the word designator. It may be omitted if the word designator begins with a `^', `$', `*', `-', or `%'. Words are numbered from the beginning of the line, with the first word being denoted by 0 (zero). Words are inserted into the current line separated by single spaces.
Here are the word designators:
0th word. For many applications, this is the command word.
0th. This is a synonym for `1-$'. It is not an error to use `*' if there is just one word in the event; the empty string is returned in that case.
If a word designator is supplied without an event specification, the previous command is used as the event.
After the optional word designator, you can add a sequence of one or more of the following modifiers, each preceded by a `:'.
gs/old/new/, or with `&'.
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