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This file documents the user interface to the GNU History library.

Copyright (C) 1988-1999 Free Software Foundation, Inc.

Authored by Brian Fox and Chet Ramey.

Permission is granted to make and distribute verbatim copies of this manual

provided the copyright notice and this permission notice are preserved on

all copies.

Permission is granted to process this file through Tex and print the

results, provided the printed document carries copying permission notice

identical to this one except for the removal of this paragraph (this

paragraph not being relevant to the printed manual).

Permission is granted to copy and distribute modified versions of this

manual under the conditions for verbatim copying, provided also that the

GNU Copyright statement is available to the distributee, and provided that

the entire resulting derived work is distributed under the terms of a

permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual

into another language, under the above conditions for modified versions.

@end ignore

@node Using History Interactively

@chapter Using History Interactively

@ifclear BashFeatures

@defcodeindex bt

@end ifclear

@ifset BashFeatures

This chapter describes how to use the @sc{gnu} History Library

interactively, from a user's standpoint.

It should be considered a user's guide.

For information on using the @sc{gnu} History Library in other programs,

see the @sc{gnu} Readline Library Manual.

@end ifset

@ifclear BashFeatures

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}.

@end ifclear

@ifset BashFeatures

@menu

* Bash History Facilities::     How Bash lets you manipulate your command

                                history.

* Bash History Builtins::       The Bash builtin commands that manipulate

                                the command history.

* History Interaction::         What it feels like using History as a user.

@end menu

@end ifset

@ifclear BashFeatures

@menu

* History Interaction::         What it feels like using History as a user.

@end menu

@end ifclear

@ifset BashFeatures

@node Bash History Facilities

@section Bash History Facilities

@cindex command history

@cindex history list

When the @samp{-o history} option to the @code{set} builtin

is enabled (@pxref{The Set Builtin}),

the shell provides access to the @var{command history},

the list of commands previously typed.

The value of the @code{HISTSIZE} shell variable is used as the

number of commands to save in a history list.

The text of the last @code{$HISTSIZE}

commands (default 500) is saved.

The shell stores each command in the history list prior to

parameter and variable expansion

but after history expansion is performed, subject to the

values of the shell variables

@code{HISTIGNORE} and @code{HISTCONTROL}.

When the shell starts up, the history is initialized from the

file named by the @code{HISTFILE} variable (default @file{~/.bash_history}).

The file named by the value of @code{HISTFILE} is truncated, if

necessary, to contain no more than the number of lines specified by

the value of the @code{HISTFILESIZE} variable.

When an interactive shell exits, the last

@code{$HISTSIZE} lines are copied from the history list to the file

named by @code{$HISTFILE}.

If the @code{histappend} shell option is set (@pxref{Bash Builtins}),

the lines are appended to the history file,

otherwise the history file is overwritten.

If @code{HISTFILE}

is unset, or if the history file is unwritable, the history is

not saved.  After saving the history, the history file is truncated

to contain no more than @code{$HISTFILESIZE}

lines.  If @code{HISTFILESIZE} is not set, no truncation is performed.

The builtin command @code{fc} may be used to list or edit and re-execute

a portion of the history list.

The @code{history} builtin may be used to display or modify the history

list and manipulate the history file.

When using command-line editing, search commands

are available in each editing mode that provide access to the

history list (@pxref{Commands For History}).

The shell allows control over which commands are saved on the history

list.  The @code{HISTCONTROL} and @code{HISTIGNORE}

variables may be set to cause the shell to save only a subset of the

commands entered.

The @code{cmdhist}

shell option, if enabled, causes the shell to attempt to save each

line of a multi-line command in the same history entry, adding

semicolons where necessary to preserve syntactic correctness.

The @code{lithist}

shell option causes the shell to save the command with embedded newlines

instead of semicolons.

The @code{shopt} builtin is used to set these options.

@xref{Bash Builtins}, for a description of @code{shopt}.

@node Bash History Builtins

@section Bash History Builtins

@cindex history builtins

Bash provides two builtin commands which manipulate the

history list and history file.

@table @code

@item fc

@btindex fc

@example

@code{fc [-e @var{ename}] [-nlr] [@var{first}] [@var{last}]}

@code{fc -s [@var{pat}=@var{rep}] [@var{command}]}

@end example

Fix Command.  In the first form, a range of commands from @var{first} to

@var{last} is selected from the history list.  Both @var{first} and

@var{last} may be specified as a string (to locate the most recent

command beginning with that string) or as a number (an index into the

history list, where a negative number is used as an offset from the

current command number).  If @var{last} is not specified it is set to

@var{first}.  If @var{first} is not specified it is set to the previous

command for editing and @minus{}16 for listing.  If the @samp{-l} flag is

given, the commands are listed on standard output.  The @samp{-n} flag

suppresses the command numbers when listing.  The @samp{-r} flag

reverses the order of the listing.  Otherwise, the editor given by

@var{ename} is invoked on a file containing those commands.  If

@var{ename} is not given, the value of the following variable expansion

is used: @code{$@{FCEDIT:-$@{EDITOR:-vi@}@}}.  This says to use the

value of the @code{FCEDIT} variable if set, or the value of the

@code{EDITOR} variable if that is set, or @code{vi} if neither is set.

When editing is complete, the edited commands are echoed and executed.

In the second form, @var{command} is re-executed after each instance

of @var{pat} in the selected command is replaced by @var{rep}.

A useful alias to use with the @code{fc} command is @code{r='fc -s'}, so

that typing @samp{r cc} runs the last command beginning with @code{cc}

and typing @samp{r} re-executes the last command (@pxref{Aliases}).

@item history

@btindex history

@example

history [@var{n}]

history -c

history -d @var{offset}

history [-anrw] [@var{filename}]

history -ps @var{arg}

@end example

With no options, display the history list with line numbers.

Lines prefixed with with a @samp{*} have been modified.

An argument of @var{n} lists only the last @var{n} lines.

Options, if supplied, have the following meanings:

@table @code

@item -c

Clear the history list.  This may be combined

with the other options to replace the history list completely.

@item -d @var{offset}

Delete the history entry at position @var{offset}.

@var{offset} should be specified as it appears when the history is

displayed.

@item -a

Append the new

history lines (history lines entered since the beginning of the

current Bash session) to the history file.

@item -n

Append the history lines not already read from the history file

to the current history list.  These are lines appended to the history

file since the beginning of the current Bash session.

@item -r

Read the current history file and append its contents to

the history list.

@item -w

Write out the current history to the history file.

@item -p

Perform history substitution on the @var{arg}s and display the result

on the standard output, without storing the results in the history list.

@item -s

The @var{arg}s are added to the end of

the history list as a single entry.

@end table

When any of the @samp{-w}, @samp{-r}, @samp{-a}, or @samp{-n} options is

used, if @var{filename}

is given, then it is used as the history file.  If not, then

the value of the @code{HISTFILE} variable is used.

@end table

@end ifset

@node History Interaction

@section History Expansion

@cindex history expansion

The History library provides a history expansion feature that is similar

to the history expansion provided by @code{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

@dfn{event}, and the portions of that line that are acted upon are

called @dfn{words}.  Various @dfn{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 @samp{!} by default.

@ifset BashFeatures

Only @samp{\} and @samp{'} may be used to escape the history expansion

character.

@end ifset

@ifset BashFeatures

Several shell options settable with the @code{shopt}

builtin (@pxref{Bash Builtins}) may be used to tailor

the behavior of history expansion.  If the

@code{histverify} shell option is enabled, and Readline

is being used, history substitutions are not immediately passed to

the shell parser.

Instead, the expanded line is reloaded into the Readline

editing buffer for further modification.

If Readline is being used, and the @code{histreedit}

shell option is enabled, a failed history expansion will be

reloaded into the Readline editing buffer for correction.

The @samp{-p} option to the @code{history} builtin command

may be used to see what a history expansion will do before using it.

The @samp{-s} option to the @code{history} builtin may be used to

add commands to the end of the history list without actually executing

them, so that they are available for subsequent recall.

This is most useful in conjunction with Readline.

The shell allows control of the various characters used by the

history expansion mechanism with the @code{histchars} variable.

@end ifset

@menu

* Event Designators::   How to specify which history line to use.

* Word Designators::    Specifying which words are of interest.

* Modifiers::           Modifying the results of substitution.

@end menu

@node Event Designators

@subsection Event Designators

@cindex event designators

An event designator is a reference to a command line entry in the

history list.

@cindex history events

@table @asis

@item @code{!}

Start a history substitution, except when followed by a space, tab,

the end of the line, @samp{=} or @samp{(}.

@item @code{!@var{n}}

Refer to command line @var{n}.

@item @code{!-@var{n}}

Refer to the command @var{n} lines back.

@item @code{!!}

Refer to the previous command.  This is a synonym for @samp{!-1}.

@item @code{!@var{string}}

Refer to the most recent command starting with @var{string}.

@item @code{!?@var{string}[?]}

Refer to the most recent command containing @var{string}.  The trailing

@samp{?} may be omitted if the @var{string} is followed immediately by

a newline.

@item @code{^@var{string1}^@var{string2}^}

Quick Substitution.  Repeat the last command, replacing @var{string1}

with @var{string2}.  Equivalent to

@code{!!:s/@var{string1}/@var{string2}/}.

@item @code{!#}

The entire command line typed so far.

@end table

@node Word Designators

@subsection Word Designators

Word designators are used to select desired words from the event.

A @samp{:} separates the event specification from the word designator.  It

may be omitted if the word designator begins with a @samp{^}, @samp{$},

@samp{*}, @samp{-}, or @samp{%}.  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.

@need 0.75

For example,

@table @code

@item !!

designates the preceding command.  When you type this, the preceding

command is repeated in toto.

@item !!:$

designates the last argument of the preceding command.  This may be

shortened to @code{!$}.

@item !fi:2

designates the second argument of the most recent command starting with

the letters @code{fi}.

@end table

@need 0.75

Here are the word designators:

@table @code

@item 0 (zero)

The @code{0}th word.  For many applications, this is the command word.

@item @var{n}

The @var{n}th word.

@item ^

The first argument; that is, word 1.

@item $

The last argument.

@item %

The word matched by the most recent @samp{?@var{string}?} search.

@item @var{x}-@var{y}

A range of words; @samp{-@var{y}} abbreviates @samp{0-@var{y}}.

@item *

All of the words, except the @code{0}th.  This is a synonym for @samp{1-$}.

It is not an error to use @samp{*} if there is just one word in the event;

the empty string is returned in that case.

@item @var{x}*

Abbreviates @samp{@var{x}-$}

@item @var{x}-

Abbreviates @samp{@var{x}-$} like @samp{@var{x}*}, but omits the last word.

@end table

If a word designator is supplied without an event specification, the

previous command is used as the event.

@node Modifiers

@subsection Modifiers

After the optional word designator, you can add a sequence of one or more

of the following modifiers, each preceded by a @samp{:}.

@table @code

@item h

Remove a trailing pathname component, leaving only the head.

@item t

Remove all leading  pathname  components, leaving the tail.

@item r

Remove a trailing suffix of the form @samp{.@var{suffix}}, leaving

the basename.

@item e

Remove all but the trailing suffix.

@item p

Print the new command but do not execute it.

@ifset BashFeatures

@item q

Quote the substituted words, escaping further substitutions.

@item x

Quote the substituted words as with @samp{q},

but break into words at spaces, tabs, and newlines.

@end ifset

@item s/@var{old}/@var{new}/

Substitute @var{new} for the first occurrence of @var{old} in the

event line.  Any delimiter may be used in place of @samp{/}.

The delimiter may be quoted in @var{old} and @var{new}

with a single backslash.  If @samp{&} appears in @var{new},

it is replaced by @var{old}.  A single backslash will quote

the @samp{&}.  The final delimiter is optional if it is the last

character on the input line.

@item &

Repeat the previous substitution.

@item g

Cause changes to be applied over the entire event line.  Used in

conjunction with @samp{s}, as in @code{gs/@var{old}/@var{new}/},

or with @samp{&}.

@end table