xregex.texi

正则表达式库

\input texinfo
@c %**start of header
@setfilename regex.info
@settitle Regex
@c %**end of header

@c \\{fill-paragraph} works better (for me, anyway) if the text in the
@c source file isn't indented.
@paragraphindent 2

@c Define a new index for our magic constants.
@defcodeindex cn

@c Put everything in one index (arbitrarily chosen to be the concept index).
@syncodeindex cn cp
@syncodeindex ky cp
@syncodeindex pg cp
@syncodeindex tp cp
@syncodeindex vr cp

@c Here is what we use in the Info `dir' file:
@c * Regex: (regex).	Regular expression library.


@ifinfo
This file documents the GNU regular expression library.

Copyright (C) 1992, 1993 Free Software Foundation, Inc.

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.

@ignore
Permission is granted to process this file through TeX and print the
results, provided the printed document carries a copying permission
notice identical to this one except for the removal of this paragraph
(this paragraph not being relevant to the printed manual).
@end ignore

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided also that the
section entitled ``GNU General Public License'' is included exactly as
in the original, 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,
except that the section entitled ``GNU General Public License'' may be
included in a translation approved by the Free Software Foundation
instead of in the original English.
@end ifinfo


@titlepage

@title Regex
@subtitle edition 0.12a
@subtitle 19 September 1992
@author Kathryn A. Hargreaves
@author Karl Berry

@page

@vskip 0pt plus 1filll
Copyright @copyright{} 1992 Free Software Foundation.

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 copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided also that the
section entitled ``GNU General Public License'' is included exactly as
in the original, 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,
except that the section entitled ``GNU General Public License'' may be
included in a translation approved by the Free Software Foundation
instead of in the original English.

@end titlepage


@ifinfo
@node Top, Overview, (dir), (dir)
@top Regular Expression Library

This manual documents how to program with the GNU regular expression
library.  This is edition 0.12a of the manual, 19 September 1992.

The first part of this master menu lists the major nodes in this Info
document, including the index.  The rest of the menu lists all the
lower level nodes in the document.

@menu
* Overview::
* Regular Expression Syntax::
* Common Operators::
* GNU Operators::
* GNU Emacs Operators::
* What Gets Matched?::
* Programming with Regex::
* Copying::			Copying and sharing Regex.
* Index::			General index.
 --- The Detailed Node Listing ---

Regular Expression Syntax

* Syntax Bits::
* Predefined Syntaxes::
* Collating Elements vs. Characters::
* The Backslash Character::

Common Operators

* Match-self Operator::			Ordinary characters.
* Match-any-character Operator::	.
* Concatenation Operator::		Juxtaposition.
* Repetition Operators::		*  +  ? @{@}
* Alternation Operator::		|
* List Operators::			[...]  [^...]
* Grouping Operators::			(...)
* Back-reference Operator::		\digit
* Anchoring Operators::			^  $

Repetition Operators    

* Match-zero-or-more Operator::  *
* Match-one-or-more Operator::   +
* Match-zero-or-one Operator::   ?
* Interval Operators::           @{@}

List Operators (@code{[} @dots{} @code{]} and @code{[^} @dots{} @code{]})

* Character Class Operators::   [:class:]
* Range Operator::          start-end

Anchoring Operators    

* Match-beginning-of-line Operator::  ^
* Match-end-of-line Operator::        $

GNU Operators

* Word Operators::
* Buffer Operators::

Word Operators

* Non-Emacs Syntax Tables::
* Match-word-boundary Operator::	\b
* Match-within-word Operator::		\B
* Match-beginning-of-word Operator::	\<
* Match-end-of-word Operator::		\>
* Match-word-constituent Operator::	\w
* Match-non-word-constituent Operator::	\W

Buffer Operators    

* Match-beginning-of-buffer Operator::	\`
* Match-end-of-buffer Operator::	\'

GNU Emacs Operators

* Syntactic Class Operators::

Syntactic Class Operators

* Emacs Syntax Tables::
* Match-syntactic-class Operator::	\sCLASS
* Match-not-syntactic-class Operator::  \SCLASS

Programming with Regex

* GNU Regex Functions::
* POSIX Regex Functions::
* BSD Regex Functions::

GNU Regex Functions

* GNU Pattern Buffers::         The re_pattern_buffer type.
* GNU Regular Expression Compiling::  re_compile_pattern ()
* GNU Matching::                re_match ()
* GNU Searching::               re_search ()
* Matching/Searching with Split Data::  re_match_2 (), re_search_2 ()
* Searching with Fastmaps::     re_compile_fastmap ()
* GNU Translate Tables::        The `translate' field.
* Using Registers::             The re_registers type and related fns.
* Freeing GNU Pattern Buffers::  regfree ()

POSIX Regex Functions

* POSIX Pattern Buffers::		The regex_t type.
* POSIX Regular Expression Compiling::	regcomp ()
* POSIX Matching::			regexec ()
* Reporting Errors::			regerror ()
* Using Byte Offsets::			The regmatch_t type.
* Freeing POSIX Pattern Buffers::	regfree ()

BSD Regex Functions

* BSD Regular Expression Compiling::	re_comp ()
* BSD Searching::			re_exec ()
@end menu
@end ifinfo
@node Overview, Regular Expression Syntax, Top, Top
@chapter Overview

A @dfn{regular expression} (or @dfn{regexp}, or @dfn{pattern}) is a text
string that describes some (mathematical) set of strings.  A regexp
@var{r} @dfn{matches} a string @var{s} if @var{s} is in the set of
strings described by @var{r}.

Using the Regex library, you can:

@itemize @bullet

@item
see if a string matches a specified pattern as a whole, and 

@item
search within a string for a substring matching a specified pattern.

@end itemize

Some regular expressions match only one string, i.e., the set they
describe has only one member.  For example, the regular expression
@samp{foo} matches the string @samp{foo} and no others.  Other regular
expressions match more than one string, i.e., the set they describe has
more than one member.  For example, the regular expression @samp{f*}
matches the set of strings made up of any number (including zero) of
@samp{f}s.  As you can see, some characters in regular expressions match
themselves (such as @samp{f}) and some don't (such as @samp{*}); the
ones that don't match themselves instead let you specify patterns that
describe many different strings.

To either match or search for a regular expression with the Regex
library functions, you must first compile it with a Regex pattern
compiling function.  A @dfn{compiled pattern} is a regular expression
converted to the internal format used by the library functions.  Once
you've compiled a pattern, you can use it for matching or searching any
number of times.

The Regex library consists of two source files: @file{regex.h} and
@file{regex.c}.  
@pindex regex.h
@pindex regex.c
Regex provides three groups of functions with which you can operate on
regular expressions.  One group---the @sc{gnu} group---is more powerful
but not completely compatible with the other two, namely the @sc{posix}
and Berkeley @sc{unix} groups; its interface was designed specifically
for @sc{gnu}.  The other groups have the same interfaces as do the
regular expression functions in @sc{posix} and Berkeley
@sc{unix}.

We wrote this chapter with programmers in mind, not users of
programs---such as Emacs---that use Regex.  We describe the Regex
library in its entirety, not how to write regular expressions that a
particular program understands.


@node Regular Expression Syntax, Common Operators, Overview, Top
@chapter Regular Expression Syntax

@cindex regular expressions, syntax of
@cindex syntax of regular expressions

@dfn{Characters} are things you can type.  @dfn{Operators} are things in
a regular expression that match one or more characters.  You compose
regular expressions from operators, which in turn you specify using one
or more characters.

Most characters represent what we call the match-self operator, i.e.,
they match themselves; we call these characters @dfn{ordinary}.  Other
characters represent either all or parts of fancier operators; e.g.,
@samp{.} represents what we call the match-any-character operator
(which, no surprise, matches (almost) any character); we call these
characters @dfn{special}.  Two different things determine what
characters represent what operators:

@enumerate
@item
the regular expression syntax your program has told the Regex library to
recognize, and

@item
the context of the character in the regular expression.
@end enumerate

In the following sections, we describe these things in more detail.

@menu
* Syntax Bits::
* Predefined Syntaxes::
* Collating Elements vs. Characters::
* The Backslash Character::
@end menu


@node Syntax Bits, Predefined Syntaxes,  , Regular Expression Syntax
@section Syntax Bits 

@cindex syntax bits

In any particular syntax for regular expressions, some characters are
always special, others are sometimes special, and others are never
special.  The particular syntax that Regex recognizes for a given
regular expression depends on the value in the @code{syntax} field of
the pattern buffer of that regular expression.

You get a pattern buffer by compiling a regular expression.  @xref{GNU
Pattern Buffers}, and @ref{POSIX Pattern Buffers}, for more information
on pattern buffers.  @xref{GNU Regular Expression Compiling}, @ref{POSIX
Regular Expression Compiling}, and @ref{BSD Regular Expression
Compiling}, for more information on compiling.

Regex considers the value of the @code{syntax} field to be a collection
of bits; we refer to these bits as @dfn{syntax bits}.  In most cases,
they affect what characters represent what operators.  We describe the
meanings of the operators to which we refer in @ref{Common Operators},
@ref{GNU Operators}, and @ref{GNU Emacs Operators}.  

For reference, here is the complete list of syntax bits, in alphabetical
order:

@table @code

@cnindex RE_BACKSLASH_ESCAPE_IN_LIST
@item RE_BACKSLASH_ESCAPE_IN_LISTS
If this bit is set, then @samp{\} inside a list (@pxref{List Operators}
quotes (makes ordinary, if it's special) the following character; if
this bit isn't set, then @samp{\} is an ordinary character inside lists.
(@xref{The Backslash Character}, for what `\' does outside of lists.)

@cnindex RE_BK_PLUS_QM
@item RE_BK_PLUS_QM
If this bit is set, then @samp{\+} represents the match-one-or-more
operator and @samp{\?} represents the match-zero-or-more operator; if
this bit isn't set, then @samp{+} represents the match-one-or-more
operator and @samp{?} represents the match-zero-or-one operator.  This
bit is irrelevant if @code{RE_LIMITED_OPS} is set.

@cnindex RE_CHAR_CLASSES
@item RE_CHAR_CLASSES
If this bit is set, then you can use character classes in lists; if this
bit isn't set, then you can't.

@cnindex RE_CONTEXT_INDEP_ANCHORS
@item RE_CONTEXT_INDEP_ANCHORS
If this bit is set, then @samp{^} and @samp{$} are special anywhere outside
a list; if this bit isn't set, then these characters are special only in
certain contexts.  @xref{Match-beginning-of-line Operator}, and
@ref{Match-end-of-line Operator}.

@cnindex RE_CONTEXT_INDEP_OPS
@item RE_CONTEXT_INDEP_OPS
If this bit is set, then certain characters are special anywhere outside
a list; if this bit isn't set, then those characters are special only in
some contexts and are ordinary elsewhere.  Specifically, if this bit
isn't set then @samp{*}, and (if the syntax bit @code{RE_LIMITED_OPS}