history.3

这个是LINUX下的GDB调度工具的源码

.\"
.\" MAN PAGE COMMENTS to
.\"
.\"	Chet Ramey
.\"	Information Network Services
.\"	Case Western Reserve University
.\"	[e-mail]
.\"
.\"	Last Change: Thu Jan 31 16:08:07 EST 2002
.\"
.TH HISTORY 3 "2002 January 31" "GNU History 4.3"
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.SH NAME
history \- GNU History Library
.SH COPYRIGHT
.if t The GNU History Library is Copyright \(co 1989-2002 by the Free Software Foundation, Inc.
.if n The GNU History Library is Copyright (C) 1989-2002 by the Free Software Foundation, Inc.
.SH DESCRIPTION
Many programs read input from the user a line at a time.  The GNU
History library is able to keep track of those lines, associate arbitrary
data with each line, and utilize information from previous lines in
composing new ones. 
.PP
.SH "HISTORY EXPANSION"
.PP
The history library supports a history expansion feature that
is identical to the history expansion in
.BR bash.
This section describes what syntax features are available.
.PP
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.
.PP
History expansion is usually performed immediately after a complete line
is read.
It takes place in two parts.
The first is to determine which line from the history list
to use during substitution.
The second is to select portions of that line for inclusion into
the current one.
The line selected from the history is the \fIevent\fP,
and the portions of that line that are acted upon are \fIwords\fP.
Various \fImodifiers\fP are available to manipulate the selected words.
The line is broken into words in the same fashion as \fBbash\fP
does when reading input,
so that several words that would otherwise be separated 
are considered one word when surrounded by quotes (see the
description of \fBhistory_tokenize()\fP below).
History expansions are introduced by the appearance of the
history expansion character, which is \^\fB!\fP\^ by default.
Only backslash (\^\fB\e\fP\^) and single quotes can quote
the history expansion character.
.SS Event Designators
.PP
An event designator is a reference to a command line entry in the
history list.
.PP
.PD 0
.TP
.B !
Start a history substitution, except when followed by a
.BR blank ,
newline, = or (.
.TP
.B !\fIn\fR
Refer to command line
.IR n .
.TP
.B !\-\fIn\fR
Refer to the current command line minus
.IR n .
.TP
.B !!
Refer to the previous command.  This is a synonym for `!\-1'.
.TP
.B !\fIstring\fR
Refer to the most recent command starting with 
.IR string .
.TP
.B !?\fIstring\fR\fB[?]\fR
Refer to the most recent command containing
.IR string .
The trailing \fB?\fP may be omitted if
.I string
is followed immediately by a newline.
.TP
.B \d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u
Quick substitution.  Repeat the last command, replacing
.I string1
with
.IR string2 .
Equivalent to
``!!:s/\fIstring1\fP/\fIstring2\fP/''
(see \fBModifiers\fP below).
.TP
.B !#
The entire command line typed so far.
.PD
.SS Word Designators
.PP
Word designators are used to select desired words from the event.
A 
.B :
separates the event specification from the word designator.
It may be omitted if the word designator begins with a
.BR ^ ,
.BR $ ,
.BR * ,
.BR \- ,
or
.BR % .
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.
.PP
.PD 0
.TP
.B 0 (zero)
The zeroth word.  For the shell, this is the command
word.
.TP
.I n
The \fIn\fRth word.
.TP
.B ^
The first argument.  That is, word 1.
.TP
.B $
The last argument.
.TP
.B %
The word matched by the most recent `?\fIstring\fR?' search.
.TP
.I x\fB\-\fPy
A range of words; `\-\fIy\fR' abbreviates `0\-\fIy\fR'.
.TP
.B *
All of the words but the zeroth.  This is a synonym
for `\fI1\-$\fP'.  It is not an error to use
.B *
if there is just one
word in the event; the empty string is returned in that case.
.TP
.B x*
Abbreviates \fIx\-$\fP.
.TP
.B x\-
Abbreviates \fIx\-$\fP like \fBx*\fP, but omits the last word.
.PD
.PP
If a word designator is supplied without an event specification, the
previous command is used as the event.
.SS Modifiers
.PP
After the optional word designator, there may appear a sequence of
one or more of the following modifiers, each preceded by a `:'.
.PP
.PD 0
.PP
.TP
.B h
Remove a trailing file name component, leaving only the head.
.TP
.B t
Remove all leading file name components, leaving the tail.
.TP
.B r
Remove a trailing suffix of the form \fI.xxx\fP, leaving the
basename.
.TP
.B e
Remove all but the trailing suffix.
.TP
.B p
Print the new command but do not execute it.
.TP
.B q
Quote the substituted words, escaping further substitutions.
.TP
.B x
Quote the substituted words as with
.BR q ,
but break into words at
.B blanks
and newlines.
.TP
.B s/\fIold\fP/\fInew\fP/
Substitute
.I new
for the first occurrence of
.I old
in the event line.  Any delimiter can be used in place of /.  The
final delimiter is optional if it is the last character of the
event line.  The delimiter may be quoted in
.I old
and
.I new
with a single backslash.  If & appears in
.IR new ,
it is replaced by
.IR old .
A single backslash will quote the &.  If
.I old
is null, it is set to the last
.I old
substituted, or, if no previous history substitutions took place,
the last
.I string
in a
.B !?\fIstring\fR\fB[?]\fR
search.
.TP
.B &
Repeat the previous substitution.
.TP
.B g
Cause changes to be applied over the entire event line.  This is
used in conjunction with `\fB:s\fP' (e.g., `\fB:gs/\fIold\fP/\fInew\fP/\fR')
or `\fB:&\fP'.  If used with
`\fB:s\fP', any delimiter can be used
in place of /, and the final delimiter is optional
if it is the last character of the event line.
.PD
.SH "PROGRAMMING WITH HISTORY FUNCTIONS"
This section describes how to use the History library in other programs.
.SS Introduction to History
.PP
The programmer using the History library has available functions
for remembering lines on a history list, associating arbitrary data
with a line, removing lines from the list, searching through the list
for a line containing an arbitrary text string, and referencing any line
in the list directly.  In addition, a history \fIexpansion\fP function
is available which provides for a consistent user interface across
different programs.
.PP
The user using programs written with the History library has the
benefit of a consistent user interface with a set of well-known
commands for manipulating the text of previous lines and using that text
in new commands.  The basic history manipulation commands are
identical to
the history substitution provided by \fBbash\fP.
.PP
If the programmer desires, he can use the Readline library, which
includes some history manipulation by default, and has the added
advantage of command line editing.
.PP
Before declaring any functions using any functionality the History
library provides in other code, an application writer should include
the file
.FN <readline/history.h>
in any file that uses the
History library's features.  It supplies extern declarations for all
of the library's public functions and variables, and declares all of
the public data structures.

.SS History Storage
.PP
The history list is an array of history entries.  A history entry is
declared as follows:
.PP
.Vb "typedef void *" histdata_t;
.PP
.nf
typedef struct _hist_entry {
  char *line;
  histdata_t data;
} HIST_ENTRY;
.fi
.PP
The history list itself might therefore be declared as
.PP
.Vb "HIST_ENTRY **" the_history_list;
.PP
The state of the History library is encapsulated into a single structure:
.PP
.nf
/*
 * A structure used to pass around the current state of the history.
 */
typedef struct _hist_state {
  HIST_ENTRY **entries; /* Pointer to the entries themselves. */
  int offset;           /* The location pointer within this array. */
  int length;           /* Number of elements within this array. */
  int size;             /* Number of slots allocated to this array. */
  int flags;
} HISTORY_STATE;
.fi
.PP
If the flags member includes \fBHS_STIFLED\fP, the history has been
stifled.
.SH "History Functions"
.PP