This patch imports the unmodified current version of NetBSD libc. The NetBSD includes are in /nbsd_include, while the libc code itself is split between lib/nbsd_libc and common/lib/libc.
631 lines
18 KiB
Groff
631 lines
18 KiB
Groff
.\" $NetBSD: regex.3,v 1.21 2010/03/22 19:30:54 joerg Exp $
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.\"
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.\" Copyright (c) 1992, 1993, 1994
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Henry Spencer.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" Copyright (c) 1992, 1993, 1994 Henry Spencer.
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.\"
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.\" This code is derived from software contributed to Berkeley by
|
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.\" Henry Spencer.
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.\"
|
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.\" Redistribution and use in source and binary forms, with or without
|
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.\" modification, are permitted provided that the following conditions
|
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.\" are met:
|
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.\" 1. Redistributions of source code must retain the above copyright
|
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.\" notice, this list of conditions and the following disclaimer.
|
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.\" 2. Redistributions in binary form must reproduce the above copyright
|
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.\" notice, this list of conditions and the following disclaimer in the
|
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
|
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.\" may be used to endorse or promote products derived from this software
|
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)regex.3 8.4 (Berkeley) 3/20/94
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.\"
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.Dd December 29, 2003
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.Dt REGEX 3
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.Os
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.Sh NAME
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.Nm regex ,
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.Nm regcomp ,
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.Nm regexec ,
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.Nm regerror ,
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.Nm regfree
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.Nd regular-expression library
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|
.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In regex.h
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.Ft int
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.Fn regcomp "regex_t * restrict preg" "const char * restrict pattern" "int cflags"
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.Ft int
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.Fn regexec "const regex_t * restrict preg" "const char * restrict string" "size_t nmatch" "regmatch_t pmatch[]" "int eflags"
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.Ft size_t
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.Fn regerror "int errcode" "const regex_t * restrict preg" "char * restrict errbuf" "size_t errbuf_size"
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.Ft void
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.Fn regfree "regex_t *preg"
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|
.Sh DESCRIPTION
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|
These routines implement
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.St -p1003.2-92
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|
regular expressions (``RE''s);
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|
see
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.Xr re_format 7 .
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|
.Fn regcomp
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|
compiles an RE written as a string into an internal form,
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|
.Fn regexec
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|
matches that internal form against a string and reports results,
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|
.Fn regerror
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|
transforms error codes from either into human-readable messages,
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|
and
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|
.Fn regfree
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|
frees any dynamically-allocated storage used by the internal form
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|
of an RE.
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|
.Pp
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|
The header
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|
.In regex.h
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|
declares two structure types,
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.Fa regex_t
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|
and
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|
.Fa regmatch_t ,
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|
the former for compiled internal forms and the latter for match reporting.
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|
It also declares the four functions,
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a type
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.Fa regoff_t ,
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|
and a number of constants with names starting with ``REG_''.
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|
.Pp
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|
.Fn regcomp
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|
compiles the regular expression contained in the
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.Fa pattern
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string,
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subject to the flags in
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.Fa cflags ,
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and places the results in the
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.Fa regex_t
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|
structure pointed to by
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.Fa preg .
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.Fa cflags
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is the bitwise OR of zero or more of the following flags:
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.Bl -tag -width XXXREG_EXTENDED
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.It Dv REG_EXTENDED
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Compile modern (``extended'') REs, rather than the obsolete
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(``basic'') REs that are the default.
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.It Dv REG_BASIC
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This is a synonym for 0,
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provided as a counterpart to REG_EXTENDED to improve readability.
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.It Dv REG_NOSPEC
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Compile with recognition of all special characters turned off.
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All characters are thus considered ordinary, so the ``RE'' is a literal
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string.
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This is an extension, compatible with but not specified by
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.St -p1003.2-92 ,
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and should be used with caution in software intended to be portable to
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other systems.
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.Dv REG_EXTENDED
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and
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.Dv REG_NOSPEC
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may not be used in the same call to
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.Fn regcomp .
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.It Dv REG_ICASE
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Compile for matching that ignores upper/lower case distinctions.
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See
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.Xr re_format 7 .
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.It Dv REG_NOSUB
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Compile for matching that need only report success or failure, not
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what was matched.
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.It Dv REG_NEWLINE
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Compile for newline-sensitive matching.
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By default, newline is a completely ordinary character with no special
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meaning in either REs or strings.
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With this flag,
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`[^' bracket expressions and `.' never match newline,
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a `^' anchor matches the null string after any newline in the string
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in addition to its normal function,
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and the `$' anchor matches the null string before any newline in the
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string in addition to its normal function.
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.It Dv REG_PEND
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The regular expression ends, not at the first NUL, but just before the
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character pointed to by the
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.Fa re_endp
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member of the structure pointed to by
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.Fa preg .
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|
The
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.Fa re_endp
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member is of type
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.Fa "const\ char\ *" .
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This flag permits inclusion of NULs in the RE; they are considered
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ordinary characters.
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This is an extension, compatible with but not specified by
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.St -p1003.2-92 ,
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and should be used with caution in software intended to be portable to
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other systems.
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.El
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.Pp
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When successful,
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.Fn regcomp
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returns 0 and fills in the structure pointed to by
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.Fa preg .
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One member of that structure (other than
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.Fa re_endp )
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|
is publicized:
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.Fa re_nsub ,
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of type
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.Fa size_t ,
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|
contains the number of parenthesized subexpressions within the RE
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|
(except that the value of this member is undefined if the
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|
.Dv REG_NOSUB
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|
flag was used).
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|
If
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.Fn regcomp
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|
fails, it returns a non-zero error code;
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|
see
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.Sx DIAGNOSTICS .
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|
.Pp
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|
.Fn regexec
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|
matches the compiled RE pointed to by
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.Fa preg
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|
against the
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.Fa string ,
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subject to the flags in
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.Fa eflags ,
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and reports results using
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|
.Fa nmatch ,
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|
.Fa pmatch ,
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|
and the returned value.
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|
The RE must have been compiled by a previous invocation of
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|
.Fn regcomp .
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|
The compiled form is not altered during execution of
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|
.Fn regexec ,
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|
so a single compiled RE can be used simultaneously by multiple threads.
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|
.Pp
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|
By default,
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|
the NUL-terminated string pointed to by
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.Fa string
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is considered to be the text of an entire line, minus any terminating
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newline.
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|
The
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.Fa eflags
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argument is the bitwise OR of zero or more of the following flags:
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.Bl -tag -width XXXREG_NOTBOL
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.It Dv REG_NOTBOL
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|
The first character of the string
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is not the beginning of a line, so the `^' anchor should not match before it.
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This does not affect the behavior of newlines under
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.Dv REG_NEWLINE .
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.It Dv REG_NOTEOL
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The NUL terminating the string does not end a line, so the `$' anchor
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should not match before it.
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This does not affect the behavior of newlines under
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.Dv REG_NEWLINE .
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|
.It Dv REG_STARTEND
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|
The string is considered to start at
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.Fa string
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+
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.Fa pmatch[0].rm_so
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|
and to have a terminating NUL located at
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.Fa string
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+
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.Fa pmatch[0].rm_eo
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|
(there need not actually be a NUL at that location),
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|
regardless of the value of
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.Fa nmatch .
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|
See below for the definition of
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|
.Fa pmatch
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|
and
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.Fa nmatch .
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|
This is an extension, compatible with but not specified by
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.St -p1003.2-92 ,
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|
and should be used with caution in software intended to be portable to
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other systems.
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Note that a non-zero
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.Fa rm_so
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does not imply
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.Dv REG_NOTBOL ;
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.Dv REG_STARTEND
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|
affects only the location of the string, not how it is matched.
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|
.El
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|
.Pp
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|
See
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|
.Xr re_format 7
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|
for a discussion of what is matched in situations where an RE or a
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portion thereof could match any of several substrings of
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.Fa string .
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|
.Pp
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|
Normally,
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.Fn regexec
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returns 0 for success and the non-zero code
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.Dv REG_NOMATCH
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|
for failure.
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|
Other non-zero error codes may be returned in exceptional situations;
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|
see
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|
.Sx DIAGNOSTICS .
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|
.Pp
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|
If
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|
.Dv REG_NOSUB
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|
was specified in the compilation of the RE, or if
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|
.Fa nmatch
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|
is 0,
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|
.Fn regexec
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|
ignores the
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|
.Fa pmatch
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|
argument (but see below for the case where
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.Dv REG_STARTEND
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is specified).
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|
Otherwise,
|
|
.Fa pmatch
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|
points to an array of
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|
.Fa nmatch
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|
structures of type
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|
.Fa regmatch_t .
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|
Such a structure has at least the members
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|
.Fa rm_so
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|
and
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|
.Fa rm_eo ,
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|
both of type
|
|
.Fa regoff_t
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|
(a signed arithmetic type at least as large as an
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|
.Fa off_t
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|
and a
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|
.Fa ssize_t ) ,
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|
containing respectively the offset of the first character of a substring
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|
and the offset of the first character after the end of the substring.
|
|
Offsets are measured from the beginning of the
|
|
.Fa string
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|
argument given to
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|
.Fn regexec .
|
|
An empty substring is denoted by equal offsets,
|
|
both indicating the character following the empty substring.
|
|
.Pp
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|
The 0th member of the
|
|
.Fa pmatch
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|
array is filled in to indicate what substring of
|
|
.Fa string
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|
was matched by the entire RE.
|
|
Remaining members report what substring was matched by parenthesized
|
|
subexpressions within the RE;
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|
member
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|
.Fa i
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|
reports subexpression
|
|
.Fa i ,
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|
with subexpressions counted (starting at 1) by the order of their
|
|
opening parentheses in the RE, left to right.
|
|
Unused entries in the array\(emcorresponding either to subexpressions that
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|
did not participate in the match at all, or to subexpressions that do not
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exist in the RE (that is,
|
|
.Fa i
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|
\*[Gt]
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|
.Fa preg-\*[Gt]re_nsub )
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|
\(emhave both
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|
.Fa rm_so
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|
and
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|
.Fa rm_eo
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|
set to -1.
|
|
If a subexpression participated in the match several times,
|
|
the reported substring is the last one it matched.
|
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(Note, as an example in particular, that when the RE `(b*)+' matches `bbb',
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the parenthesized subexpression matches each of the three `b's and then
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an infinite number of empty strings following the last `b',
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so the reported substring is one of the empties.)
|
|
.Pp
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|
If
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|
.Dv REG_STARTEND
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|
is specified,
|
|
.Fa pmatch
|
|
must point to at least one
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|
.Fa regmatch_t
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|
(even if
|
|
.Fa nmatch
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|
is 0 or
|
|
.Dv REG_NOSUB
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|
was specified),
|
|
to hold the input offsets for
|
|
.Dv REG_STARTEND .
|
|
Use for output is still entirely controlled by
|
|
.Fa nmatch ;
|
|
if
|
|
.Fa nmatch
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|
is 0 or
|
|
.Dv REG_NOSUB
|
|
was specified,
|
|
the value of
|
|
.Fa pmatch [0]
|
|
will not be changed by a successful
|
|
.Fn regexec .
|
|
.Pp
|
|
.Fn regerror
|
|
maps a non-zero
|
|
.Fa errcode
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|
from either
|
|
.Fn regcomp
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|
or
|
|
.Fn regexec
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|
to a human-readable, printable message.
|
|
If
|
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.Fa preg
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is non-NULL,
|
|
the error code should have arisen from use of the
|
|
.Fa regex_t
|
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pointed to by
|
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.Fa preg ,
|
|
and if the error code came from
|
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.Fn regcomp ,
|
|
it should have been the result from the most recent
|
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.Fn regcomp
|
|
using that
|
|
.Fa regex_t . (
|
|
.Fn regerror
|
|
may be able to supply a more detailed message using information
|
|
from the
|
|
.Fa regex_t . )
|
|
.Fn regerror
|
|
places the NUL-terminated message into the buffer pointed to by
|
|
.Fa errbuf ,
|
|
limiting the length (including the NUL) to at most
|
|
.Fa errbuf_size
|
|
bytes.
|
|
If the whole message won't fit,
|
|
as much of it as will fit before the terminating NUL is supplied.
|
|
In any case,
|
|
the returned value is the size of buffer needed to hold the whole
|
|
message (including terminating NUL).
|
|
If
|
|
.Fa errbuf_size
|
|
is 0,
|
|
.Fa errbuf
|
|
is ignored but the return value is still correct.
|
|
.Pp
|
|
If the
|
|
.Fa errcode
|
|
given to
|
|
.Fn regerror
|
|
is first ORed with
|
|
.Dv REG_ITOA ,
|
|
the ``message'' that results is the printable name of the error code,
|
|
e.g. ``REG_NOMATCH'',
|
|
rather than an explanation thereof.
|
|
If
|
|
.Fa errcode
|
|
is
|
|
.Dv REG_ATOI ,
|
|
then
|
|
.Fa preg
|
|
shall be non-NULL and the
|
|
.Fa re_endp
|
|
member of the structure it points to
|
|
must point to the printable name of an error code;
|
|
in this case, the result in
|
|
.Fa errbuf
|
|
is the decimal digits of
|
|
the numeric value of the error code
|
|
(0 if the name is not recognized).
|
|
.Dv REG_ITOA
|
|
and
|
|
.Dv REG_ATOI
|
|
are intended primarily as debugging facilities;
|
|
they are extensions, compatible with but not specified by
|
|
.St -p1003.2-92 ,
|
|
and should be used with caution in software intended to be portable to
|
|
other systems.
|
|
Be warned also that they are considered experimental and changes are possible.
|
|
.Pp
|
|
.Fn regfree
|
|
frees any dynamically-allocated storage associated with the compiled RE
|
|
pointed to by
|
|
.Fa preg .
|
|
The remaining
|
|
.Fa regex_t
|
|
is no longer a valid compiled RE
|
|
and the effect of supplying it to
|
|
.Fn regexec
|
|
or
|
|
.Fn regerror
|
|
is undefined.
|
|
.Pp
|
|
None of these functions references global variables except for tables
|
|
of constants;
|
|
all are safe for use from multiple threads if the arguments are safe.
|
|
.Sh IMPLEMENTATION CHOICES
|
|
There are a number of decisions that
|
|
.St -p1003.2-92
|
|
leaves up to the implementor,
|
|
either by explicitly saying ``undefined'' or by virtue of them being
|
|
forbidden by the RE grammar.
|
|
This implementation treats them as follows.
|
|
.Pp
|
|
See
|
|
.Xr re_format 7
|
|
for a discussion of the definition of case-independent matching.
|
|
.Pp
|
|
There is no particular limit on the length of REs,
|
|
except insofar as memory is limited.
|
|
Memory usage is approximately linear in RE size, and largely insensitive
|
|
to RE complexity, except for bounded repetitions.
|
|
See BUGS for one short RE using them
|
|
that will run almost any system out of memory.
|
|
.Pp
|
|
A backslashed character other than one specifically given a magic meaning
|
|
by
|
|
.St -p1003.2-92
|
|
(such magic meanings occur only in obsolete [``basic''] REs)
|
|
is taken as an ordinary character.
|
|
.Pp
|
|
Any unmatched [ is a
|
|
.Dv REG_EBRACK
|
|
error.
|
|
.Pp
|
|
Equivalence classes cannot begin or end bracket-expression ranges.
|
|
The endpoint of one range cannot begin another.
|
|
.Pp
|
|
.Dv RE_DUP_MAX ,
|
|
the limit on repetition counts in bounded repetitions, is 255.
|
|
.Pp
|
|
A repetition operator (?, *, +, or bounds) cannot follow another
|
|
repetition operator.
|
|
A repetition operator cannot begin an expression or subexpression
|
|
or follow `^' or `|'.
|
|
.Pp
|
|
`|' cannot appear first or last in a (sub)expression or after another `|',
|
|
i.e. an operand of `|' cannot be an empty subexpression.
|
|
An empty parenthesized subexpression, `()', is legal and matches an
|
|
empty (sub)string.
|
|
An empty string is not a legal RE.
|
|
.Pp
|
|
A `{' followed by a digit is considered the beginning of bounds for a
|
|
bounded repetition, which must then follow the syntax for bounds.
|
|
A `{'
|
|
.Em not
|
|
followed by a digit is considered an ordinary character.
|
|
.Pp
|
|
`^' and `$' beginning and ending subexpressions in obsolete (``basic'')
|
|
REs are anchors, not ordinary characters.
|
|
.Sh DIAGNOSTICS
|
|
Non-zero error codes from
|
|
.Fn regcomp
|
|
and
|
|
.Fn regexec
|
|
include the following:
|
|
.Pp
|
|
.Bl -tag -width XXXREG_ECOLLATE -compact
|
|
.It Dv REG_NOMATCH
|
|
.Fn regexec
|
|
failed to match
|
|
.It Dv REG_BADPAT
|
|
invalid regular expression
|
|
.It Dv REG_ECOLLATE
|
|
invalid collating element
|
|
.It Dv REG_ECTYPE
|
|
invalid character class
|
|
.It Dv REG_EESCAPE
|
|
\e applied to unescapable character
|
|
.It Dv REG_ESUBREG
|
|
invalid backreference number
|
|
.It Dv REG_EBRACK
|
|
brackets [ ] not balanced
|
|
.It Dv REG_EPAREN
|
|
parentheses ( ) not balanced
|
|
.It Dv REG_EBRACE
|
|
braces { } not balanced
|
|
.It Dv REG_BADBR
|
|
invalid repetition count(s) in { }
|
|
.It Dv REG_ERANGE
|
|
invalid character range in [ ]
|
|
.It Dv REG_ESPACE
|
|
ran out of memory
|
|
.It Dv REG_BADRPT
|
|
?, *, or + operand invalid
|
|
.It Dv REG_EMPTY
|
|
empty (sub)expression
|
|
.It Dv REG_ASSERT
|
|
``can't happen''\(emyou found a bug
|
|
.It Dv REG_INVARG
|
|
invalid argument, e.g. negative-length string
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr grep 1 ,
|
|
.Xr sed 1 ,
|
|
.Xr re_format 7
|
|
.Pp
|
|
.St -p1003.2-92 ,
|
|
sections 2.8 (Regular Expression Notation)
|
|
and
|
|
B.5 (C Binding for Regular Expression Matching).
|
|
.Sh HISTORY
|
|
Originally written by Henry Spencer.
|
|
Altered for inclusion in the
|
|
.Bx 4.4
|
|
distribution.
|
|
.Sh BUGS
|
|
There is one known functionality bug.
|
|
The implementation of internationalization is incomplete:
|
|
the locale is always assumed to be the default one of
|
|
.St -p1003.2-92 ,
|
|
and only the collating elements etc. of that locale are available.
|
|
.Pp
|
|
The back-reference code is subtle and doubts linger about its correctness
|
|
in complex cases.
|
|
.Pp
|
|
.Fn regexec
|
|
performance is poor.
|
|
This will improve with later releases.
|
|
.Fa nmatch
|
|
exceeding 0 is expensive;
|
|
.Fa nmatch
|
|
exceeding 1 is worse.
|
|
.Fa regexec
|
|
is largely insensitive to RE complexity
|
|
.Em except
|
|
that back references are massively expensive.
|
|
RE length does matter; in particular, there is a strong speed bonus
|
|
for keeping RE length under about 30 characters,
|
|
with most special characters counting roughly double.
|
|
.Pp
|
|
.Fn regcomp
|
|
implements bounded repetitions by macro expansion,
|
|
which is costly in time and space if counts are large
|
|
or bounded repetitions are nested.
|
|
An RE like, say,
|
|
`((((a{1,100}){1,100}){1,100}){1,100}){1,100}'
|
|
will (eventually) run almost any existing machine out of swap space.
|
|
.Pp
|
|
There are suspected problems with response to obscure error conditions.
|
|
Notably,
|
|
certain kinds of internal overflow,
|
|
produced only by truly enormous REs or by multiply nested bounded repetitions,
|
|
are probably not handled well.
|
|
.Pp
|
|
Due to a mistake in
|
|
.St -p1003.2-92 ,
|
|
things like `a)b' are legal REs because `)' is a special character
|
|
only in the presence of a previous unmatched `('.
|
|
This can't be fixed until the spec is fixed.
|
|
.Pp
|
|
The standard's definition of back references is vague.
|
|
For example, does
|
|
`a\e(\e(b\e)*\e2\e)*d' match `abbbd'?
|
|
Until the standard is clarified, behavior in such cases should not be
|
|
relied on.
|
|
.Pp
|
|
The implementation of word-boundary matching is a bit of a kludge,
|
|
and bugs may lurk in combinations of word-boundary matching and anchoring.
|