@ignore
This file documents the user interface to the GNU History library.
-Copyright (C) 1988, 1991 Free Software Foundation, Inc.
+Copyright (C) 1988, 1991, 1996 Free Software Foundation, Inc.
Authored by Brian Fox and Chet Ramey.
Permission is granted to make and distribute verbatim copies of this manual
@pxref{Programming with GNU History}.
@end ifclear
+@ifset BashFeatures
@menu
+* Bash History Facilities:: How Bash lets you manipulate your 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 text of the last
+@code{HISTSIZE}
+commands (default 500) is saved in a history list. 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}).
+@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 @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} (@pxref{Korn Shell Builtins})
+may be used to list or edit and re-execute a portion of
+the history list. The @code{history} builtin (@pxref{C Shell Builtins})
+can be used to display or modify the history list and
+manipulate the history file.
+When using the command-line editing, search commands
+are available in each editing mode that provide access to the
+history list.
+
+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.
+@xref{Bash Builtins} for a description of @code{shopt}.
+@end ifset
@node History Interaction
-@section History Interaction
-@cindex expansion
+@section Interactive History Expansion
+@cindex history expansion
The History library provides a history expansion feature that is similar
-to the history expansion provided by @code{csh}. The following text
+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 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
@dfn{event}, and the portions of that line that are acted upon are
-called @dfn{words}. The line is broken into words in the same fashion
+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 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 @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.
+
+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.
Start a history substitution, except when followed by a space, tab,
the end of the line, @key{=} or @key{(}.
-@item @code{!!}
-Refer to the previous command. This is a synonym for @code{!-1}.
-
-@item @code{!n}
+@item @code{!@var{n}}
Refer to command line @var{n}.
-@item @code{!-n}
+@item @code{!-@var{n}}
Refer to the command @var{n} lines back.
-@item @code{!string}
+@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{!?string}[@code{?}]
-Refer to the most recent command containing @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{!#}
-The entire command line typed so far.
-
-@item @code{^string1^string2^}
+@item @code{^@var{string1}^@var{string2}^}
Quick Substitution. Repeat the last command, replacing @var{string1}
with @var{string2}. Equivalent to
-@code{!!:s/string1/string2/}.
+@code{!!:s/@var{string1}/@var{string2}/}.
+
+@item @code{!#}
+The entire command line typed so far.
@end table
@node Word Designators
@subsection Word Designators
-A @key{:} separates the event specification from the word designator. It
-can be omitted if the word designator begins with a @key{^}, @key{$},
-@key{*} or @key{%}. Words are numbered from the beginning of the line,
-with the first word being denoted by a 0 (zero).
+Word designators are used to select desired words from the event.
+A @samp{:} separates the event specification from the word designator. It
+can 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.
@table @code
@item 0 (zero)
The @code{0}th word. For many applications, this is the command word.
-@item n
+@item @var{n}
The @var{n}th word.
@item ^
-The first argument; that is, word 1.
+The first argument; that is, word 1.
@item $
The last argument.
@item %
-The word matched by the most recent @code{?string?} search.
+The word matched by the most recent @samp{?@var{string}?} search.
-@item x-y
-A range of words; @code{-@var{y}} abbreviates @code{0-@var{y}}.
+@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 @code{1-$}.
-It is not an error to use @key{*} if there is just one word in the event;
+All of the words, except the @code{0}th. This is a synonym for @samp{1-$}.
+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 x*
-Abbreviates @code{x-$}
+@item @var{x}*
+Abbreviates @samp{@var{x}-$}
-@item x-
-Abbreviates @code{x-$} like @code{x*}, but omits the last word.
+@item @var{x}-
+Abbreviates @samp{@var{x}-$} 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 @key{:}.
+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.
+Remove a trailing suffix of the form @samp{.@var{suffix}}, leaving
+the basename.
@item e
Remove all but the trailing suffix.
-@item t
-Remove all leading pathname components, leaving the tail.
-
@item p
Print the new command but do not execute it.
Quote the substituted words, escaping further substitutions.
@item x
-Quote the substituted words as with @code{q},
+Quote the substituted words as with @samp{q},
but break into words at spaces, tabs, and newlines.
@end ifset
-@item s/old/new/
+@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 @key{/}.
+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 @key{&} appears in @var{new},
+with a single backslash. If @samp{&} appears in @var{new},
it is replaced by @var{old}. A single backslash will quote
-the @key{&}. The final delimiter is optional if it is the last
+the @samp{&}. The final delimiter is optional if it is the last
character on the input line.
@item &
@item g
Cause changes to be applied over the entire event line. Used in
-conjunction with @code{s}, as in @code{gs/old/new/}, or with
-@code{&}.
+conjunction with @samp{s}, as in @code{gs/@var{old}/@var{new}/},
+or with @samp{&}.
@end table
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