188 lines
6.3 KiB
Text
Executable file
188 lines
6.3 KiB
Text
Executable file
@ifinfo
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This file documents the GNU History library.
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Copyright (C) 1988 Free Software Foundation, Inc.
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Authored by Brian Fox.
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Permission is granted to make and distribute verbatim copies of this manual
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provided the copyright notice and this permission notice are preserved on
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all copies.
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@end ifinfo
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@ignore
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Permission is granted to process this file through Tex and print the
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results, provided the printed document carries copying permission notice
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identical to this one except for the removal of this paragraph (this
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paragraph not being relevant to the printed manual).
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Permission is granted to copy and distribute modified versions of this
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manual under the conditions for verbatim copying, provided also that the
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GNU Copyright statement is available to the distributee, and provided that
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the entire resulting derived work is distributed under the terms of a
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permission notice identical to this one.
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Permission is granted to copy and distribute translations of this manual
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into another language, under the above conditions for modified versions.
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@end ignore
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@node History Top,,,
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@appendix Command Line History
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@ifinfo
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This file is meant to be an inclusion in the documentation of programs
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that use the history library features. There is also a standalone
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document, entitled @file{history.texinfo}.
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@end ifinfo
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This Appendix describes the GNU History library, a programming tool that
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provides a consistent user interface for recalling lines of previously
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typed input.
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@menu
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* Introduction to History:: What is the GNU History library for?
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* History Interaction:: What it feels like using History as a user.
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@end menu
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@node Introduction to History, History Interaction, History Top, Top
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@appendixsec Introduction to History
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Many programs read input from the user a line at a time. The GNU history
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library is able to keep track of those lines, associate arbitrary data with
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each line, and utilize information from previous lines in making up new
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ones.
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The programmer using the History library has available to him functions
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for remembering lines on a history stack, associating arbitrary data
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with a line, removing lines from the stack, searching through the stack
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for a line containing an arbitrary text string, and referencing any line
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on the stack directly. In addition, a history @dfn{expansion} function
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is available which provides for a consistent user interface across many
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different programs.
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When you use programs written with the History library, you have the
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benefit of a consistent user interface, with a set of well-known
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commands for manipulating the text of previous lines and using that text
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in new commands. The basic history manipulation commands are similar to
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the history substitution used by Csh.
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GNU programs often also use the Readline library, which includes history
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manipulation by default, and has the added advantage of Emacs style
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command line editing.
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@node History Interaction, , Introduction to History, Top
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@appendixsec History Interaction
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@cindex expansion
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The History library provides a history expansion feature that is similar
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to the history expansion in Csh. The following text describes what
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syntax features are available.
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History expansion takes place in two parts. The first is to determine
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which line from the previous history should be used during substitution.
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The second is to select portions of that line for inclusion into the
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current one. The line selected from the previous history is called the
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@dfn{event}, and the portions of that line that are acted upon are
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called @dfn{words}. The line is broken into words in the same fashion
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used by the Bash shell, so that several words surrounded by quotes are
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treated as if they were a single word.
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@menu
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* Event Designators:: How to specify which history line to use. *
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Word Designators:: Specifying which words are of interest. *
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Modifiers:: Modifying the results of susbstitution.
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@end menu
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@node Event Designators, Word Designators, , History Interaction
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@appendixsubsec Event Designators
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@cindex event designators
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An event designator is a reference to a command line entry in the
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history list.
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@table @asis
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@item @code{!}
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Start a history subsititution, except when followed by a space, tab, or
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the end of the line; or by @samp{=} or @samp{(}.
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@item @code{!!}
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Refer to the previous command. This is a synonym for @code{!-1}.
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@item @code{!@var{n}}
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Refer to command line @var{n}.
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@item @code{!-@var{n}}
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Refer to the command line @var{n} lines back.
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@item @code{!@var{string}}
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Refer to the most recent command starting with @var{string}.
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@item @code{!?@var{string}}[@code{?}]
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Refer to the most recent command containing @var{string}.
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@end table
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@node Word Designators, Modifiers, Event Designators, History Interaction
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@appendixsubsec Word Designators
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A @samp{:} separates the event specification from the word designator. It
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can be omitted if the word designator begins with a @samp{^}, @samp{$},
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@samp{*} or @samp{%}. Words are numbered from the beginning of the line,
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with the first word being denoted by a 0 (zero).
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@table @code
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@item 0 (zero)
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The zero'th word. For many applications, this is the command word.
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@item n
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The @var{n}'th word.
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@item ^
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The first argument. that is, word 1.
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@item $
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The last argument.
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@item %
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The word matched by the most recent @code{?@var{string}?} search.
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@item @var{x}-@var{y}
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A range of words; @code{-@var{y}} abbreviates @code{0-@var{y}}.
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@item *
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All of the words, excepting the zero'th. This is a synonym for @samp{1-$}.
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It is not an error to use @samp{*} if there is just one word in the event.
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The empty string is returned in that case.
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@end table
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@node Modifiers, , Word Designators, History Interaction
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@appendixsubsec Modifiers
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After the optional word designator, you can add a sequence of one or more
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of the following modifiers, each preceded by a @samp{:}.
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@table @code
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@item #
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The entire command line typed so far. This means the current command,
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not the previous command, so it really isn't a word designator, and doesn't
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belong in this section.
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@item h
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Remove a trailing pathname component, leaving only the head.
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@item r
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Remove a trailing suffix of the form @samp{.@var{suffix}}, leaving the basename.
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@item e
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Remove all but the suffix.
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@item t
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Remove all leading pathname components, leaving the tail.
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@item p
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Print the new command but do not execute it. This takes effect
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immediately, so it should be the last specifier on the line.
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@end table
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