7bdf80e571
in a bunch of man pages. Use the correct .Bx (BSD UNIX) or .At (AT&T UNIX) macros instead of explicitly specifying the version in the text in a bunch of man pages.
541 lines
16 KiB
Groff
541 lines
16 KiB
Groff
.\" Copyright (c) 1992, 1993, 1994 Henry Spencer.
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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.
|
|
.\" 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
|
|
.\" 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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.TH REGEX 3 "March 20, 1994"
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.de ZR
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.\" one other place knows this name: the SEE ALSO section
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.IR re_format (7) \\$1
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..
|
|
.SH NAME
|
|
regcomp, regexec, regerror, regfree \- regular-expression library
|
|
.SH SYNOPSIS
|
|
.ft B
|
|
.\".na
|
|
#include <sys/types.h>
|
|
.br
|
|
#include <regex.h>
|
|
.HP 10
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|
int regcomp(regex_t\ *preg, const\ char\ *pattern, int\ cflags);
|
|
.HP
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|
int\ regexec(const\ regex_t\ *preg, const\ char\ *string,
|
|
size_t\ nmatch, regmatch_t\ pmatch[], int\ eflags);
|
|
.HP
|
|
size_t\ regerror(int\ errcode, const\ regex_t\ *preg,
|
|
char\ *errbuf, size_t\ errbuf_size);
|
|
.HP
|
|
void\ regfree(regex_t\ *preg);
|
|
.\".ad
|
|
.ft
|
|
.SH DESCRIPTION
|
|
These routines implement POSIX 1003.2 regular expressions (``RE''s);
|
|
see
|
|
.ZR .
|
|
.I Regcomp
|
|
compiles an RE written as a string into an internal form,
|
|
.I regexec
|
|
matches that internal form against a string and reports results,
|
|
.I regerror
|
|
transforms error codes from either into human-readable messages,
|
|
and
|
|
.I regfree
|
|
frees any dynamically-allocated storage used by the internal form
|
|
of an RE.
|
|
.PP
|
|
The header
|
|
.I <regex.h>
|
|
declares two structure types,
|
|
.I regex_t
|
|
and
|
|
.IR regmatch_t ,
|
|
the former for compiled internal forms and the latter for match reporting.
|
|
It also declares the four functions,
|
|
a type
|
|
.IR regoff_t ,
|
|
and a number of constants with names starting with ``REG_''.
|
|
.PP
|
|
.I Regcomp
|
|
compiles the regular expression contained in the
|
|
.I pattern
|
|
string,
|
|
subject to the flags in
|
|
.IR cflags ,
|
|
and places the results in the
|
|
.I regex_t
|
|
structure pointed to by
|
|
.IR preg .
|
|
.I Cflags
|
|
is the bitwise OR of zero or more of the following flags:
|
|
.IP REG_EXTENDED \w'REG_EXTENDED'u+2n
|
|
Compile modern (``extended'') REs,
|
|
rather than the obsolete (``basic'') REs that
|
|
are the default.
|
|
.IP REG_BASIC
|
|
This is a synonym for 0,
|
|
provided as a counterpart to REG_EXTENDED to improve readability.
|
|
.IP REG_NOSPEC
|
|
Compile with recognition of all special characters turned off.
|
|
All characters are thus considered ordinary,
|
|
so the ``RE'' is a literal string.
|
|
This is an extension,
|
|
compatible with but not specified by POSIX 1003.2,
|
|
and should be used with
|
|
caution in software intended to be portable to other systems.
|
|
REG_EXTENDED and REG_NOSPEC may not be used
|
|
in the same call to
|
|
.IR regcomp .
|
|
.IP REG_ICASE
|
|
Compile for matching that ignores upper/lower case distinctions.
|
|
See
|
|
.ZR .
|
|
.IP REG_NOSUB
|
|
Compile for matching that need only report success or failure,
|
|
not what was matched.
|
|
.IP REG_NEWLINE
|
|
Compile for newline-sensitive matching.
|
|
By default, newline is a completely ordinary character with no special
|
|
meaning in either REs or strings.
|
|
With this flag,
|
|
`[^' bracket expressions and `.' never match newline,
|
|
a `^' anchor matches the null string after any newline in the string
|
|
in addition to its normal function,
|
|
and the `$' anchor matches the null string before any newline in the
|
|
string in addition to its normal function.
|
|
.IP REG_PEND
|
|
The regular expression ends,
|
|
not at the first NUL,
|
|
but just before the character pointed to by the
|
|
.I re_endp
|
|
member of the structure pointed to by
|
|
.IR preg .
|
|
The
|
|
.I re_endp
|
|
member is of type
|
|
.IR const\ char\ * .
|
|
This flag permits inclusion of NULs in the RE;
|
|
they are considered ordinary characters.
|
|
This is an extension,
|
|
compatible with but not specified by POSIX 1003.2,
|
|
and should be used with
|
|
caution in software intended to be portable to other systems.
|
|
.PP
|
|
When successful,
|
|
.I regcomp
|
|
returns 0 and fills in the structure pointed to by
|
|
.IR preg .
|
|
One member of that structure
|
|
(other than
|
|
.IR re_endp )
|
|
is publicized:
|
|
.IR re_nsub ,
|
|
of type
|
|
.IR size_t ,
|
|
contains the number of parenthesized subexpressions within the RE
|
|
(except that the value of this member is undefined if the
|
|
REG_NOSUB flag was used).
|
|
If
|
|
.I regcomp
|
|
fails, it returns a non-zero error code;
|
|
see DIAGNOSTICS.
|
|
.PP
|
|
.I Regexec
|
|
matches the compiled RE pointed to by
|
|
.I preg
|
|
against the
|
|
.IR string ,
|
|
subject to the flags in
|
|
.IR eflags ,
|
|
and reports results using
|
|
.IR nmatch ,
|
|
.IR pmatch ,
|
|
and the returned value.
|
|
The RE must have been compiled by a previous invocation of
|
|
.IR regcomp .
|
|
The compiled form is not altered during execution of
|
|
.IR regexec ,
|
|
so a single compiled RE can be used simultaneously by multiple threads.
|
|
.PP
|
|
By default,
|
|
the NUL-terminated string pointed to by
|
|
.I string
|
|
is considered to be the text of an entire line, minus any terminating
|
|
newline.
|
|
The
|
|
.I eflags
|
|
argument is the bitwise OR of zero or more of the following flags:
|
|
.IP REG_NOTBOL \w'REG_STARTEND'u+2n
|
|
The first character of
|
|
the string
|
|
is not the beginning of a line, so the `^' anchor should not match before it.
|
|
This does not affect the behavior of newlines under REG_NEWLINE.
|
|
.IP REG_NOTEOL
|
|
The NUL terminating
|
|
the string
|
|
does not end a line, so the `$' anchor should not match before it.
|
|
This does not affect the behavior of newlines under REG_NEWLINE.
|
|
.IP REG_STARTEND
|
|
The string is considered to start at
|
|
\fIstring\fR\ + \fIpmatch\fR[0].\fIrm_so\fR
|
|
and to have a terminating NUL located at
|
|
\fIstring\fR\ + \fIpmatch\fR[0].\fIrm_eo\fR
|
|
(there need not actually be a NUL at that location),
|
|
regardless of the value of
|
|
.IR nmatch .
|
|
See below for the definition of
|
|
.IR pmatch
|
|
and
|
|
.IR nmatch .
|
|
This is an extension,
|
|
compatible with but not specified by POSIX 1003.2,
|
|
and should be used with
|
|
caution in software intended to be portable to other systems.
|
|
Note that a non-zero \fIrm_so\fR does not imply REG_NOTBOL;
|
|
REG_STARTEND affects only the location of the string,
|
|
not how it is matched.
|
|
.PP
|
|
See
|
|
.ZR
|
|
for a discussion of what is matched in situations where an RE or a
|
|
portion thereof could match any of several substrings of
|
|
.IR string .
|
|
.PP
|
|
Normally,
|
|
.I regexec
|
|
returns 0 for success and the non-zero code REG_NOMATCH for failure.
|
|
Other non-zero error codes may be returned in exceptional situations;
|
|
see DIAGNOSTICS.
|
|
.PP
|
|
If REG_NOSUB was specified in the compilation of the RE,
|
|
or if
|
|
.I nmatch
|
|
is 0,
|
|
.I regexec
|
|
ignores the
|
|
.I pmatch
|
|
argument (but see below for the case where REG_STARTEND is specified).
|
|
Otherwise,
|
|
.I pmatch
|
|
points to an array of
|
|
.I nmatch
|
|
structures of type
|
|
.IR regmatch_t .
|
|
Such a structure has at least the members
|
|
.I rm_so
|
|
and
|
|
.IR rm_eo ,
|
|
both of type
|
|
.I regoff_t
|
|
(a signed arithmetic type at least as large as an
|
|
.I off_t
|
|
and a
|
|
.IR ssize_t ),
|
|
containing respectively the offset of the first character of a substring
|
|
and the offset of the first character after the end of the substring.
|
|
Offsets are measured from the beginning of the
|
|
.I string
|
|
argument given to
|
|
.IR regexec .
|
|
An empty substring is denoted by equal offsets,
|
|
both indicating the character following the empty substring.
|
|
.PP
|
|
The 0th member of the
|
|
.I pmatch
|
|
array is filled in to indicate what substring of
|
|
.I string
|
|
was matched by the entire RE.
|
|
Remaining members report what substring was matched by parenthesized
|
|
subexpressions within the RE;
|
|
member
|
|
.I i
|
|
reports subexpression
|
|
.IR i ,
|
|
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
|
|
did not participate in the match at all, or to subexpressions that do not
|
|
exist in the RE (that is, \fIi\fR\ > \fIpreg\fR\->\fIre_nsub\fR)\(emhave both
|
|
.I rm_so
|
|
and
|
|
.I rm_eo
|
|
set to \-1.
|
|
If a subexpression participated in the match several times,
|
|
the reported substring is the last one it matched.
|
|
(Note, as an example in particular, that when the RE `(b*)+' matches `bbb',
|
|
the parenthesized subexpression matches each of the three `b's and then
|
|
an infinite number of empty strings following the last `b',
|
|
so the reported substring is one of the empties.)
|
|
.PP
|
|
If REG_STARTEND is specified,
|
|
.I pmatch
|
|
must point to at least one
|
|
.I regmatch_t
|
|
(even if
|
|
.I nmatch
|
|
is 0 or REG_NOSUB was specified),
|
|
to hold the input offsets for REG_STARTEND.
|
|
Use for output is still entirely controlled by
|
|
.IR nmatch ;
|
|
if
|
|
.I nmatch
|
|
is 0 or REG_NOSUB was specified,
|
|
the value of
|
|
.IR pmatch [0]
|
|
will not be changed by a successful
|
|
.IR regexec .
|
|
.PP
|
|
.I Regerror
|
|
maps a non-zero
|
|
.I errcode
|
|
from either
|
|
.I regcomp
|
|
or
|
|
.I regexec
|
|
to a human-readable, printable message.
|
|
If
|
|
.I preg
|
|
is non-NULL,
|
|
the error code should have arisen from use of
|
|
the
|
|
.I regex_t
|
|
pointed to by
|
|
.IR preg ,
|
|
and if the error code came from
|
|
.IR regcomp ,
|
|
it should have been the result from the most recent
|
|
.I regcomp
|
|
using that
|
|
.IR regex_t .
|
|
.RI ( Regerror
|
|
may be able to supply a more detailed message using information
|
|
from the
|
|
.IR regex_t .)
|
|
.I Regerror
|
|
places the NUL-terminated message into the buffer pointed to by
|
|
.IR errbuf ,
|
|
limiting the length (including the NUL) to at most
|
|
.I 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
|
|
.I errbuf_size
|
|
is 0,
|
|
.I errbuf
|
|
is ignored but the return value is still correct.
|
|
.PP
|
|
If the
|
|
.I errcode
|
|
given to
|
|
.I regerror
|
|
is first ORed with REG_ITOA,
|
|
the ``message'' that results is the printable name of the error code,
|
|
e.g. ``REG_NOMATCH'',
|
|
rather than an explanation thereof.
|
|
If
|
|
.I errcode
|
|
is REG_ATOI,
|
|
then
|
|
.I preg
|
|
shall be non-NULL and the
|
|
.I 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
|
|
.I errbuf
|
|
is the decimal digits of
|
|
the numeric value of the error code
|
|
(0 if the name is not recognized).
|
|
REG_ITOA and REG_ATOI are intended primarily as debugging facilities;
|
|
they are extensions,
|
|
compatible with but not specified by POSIX 1003.2,
|
|
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
|
|
.I Regfree
|
|
frees any dynamically-allocated storage associated with the compiled RE
|
|
pointed to by
|
|
.IR preg .
|
|
The remaining
|
|
.I regex_t
|
|
is no longer a valid compiled RE
|
|
and the effect of supplying it to
|
|
.I regexec
|
|
or
|
|
.I 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 1003.2 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
|
|
.ZR
|
|
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 1003.2 (such magic meanings occur only in obsolete [``basic''] REs)
|
|
is taken as an ordinary character.
|
|
.PP
|
|
Any unmatched [ is a REG_EBRACK error.
|
|
.PP
|
|
Equivalence classes cannot begin or end bracket-expression ranges.
|
|
The endpoint of one range cannot begin another.
|
|
.PP
|
|
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 `{' \fInot\fR 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 SEE ALSO
|
|
grep(1), re_format(7)
|
|
.PP
|
|
POSIX 1003.2, sections 2.8 (Regular Expression Notation)
|
|
and
|
|
B.5 (C Binding for Regular Expression Matching).
|
|
.SH DIAGNOSTICS
|
|
Non-zero error codes from
|
|
.I regcomp
|
|
and
|
|
.I regexec
|
|
include the following:
|
|
.PP
|
|
.nf
|
|
.ta \w'REG_ECOLLATE'u+3n
|
|
REG_NOMATCH regexec() failed to match
|
|
REG_BADPAT invalid regular expression
|
|
REG_ECOLLATE invalid collating element
|
|
REG_ECTYPE invalid character class
|
|
REG_EESCAPE \e applied to unescapable character
|
|
REG_ESUBREG invalid backreference number
|
|
REG_EBRACK brackets [ ] not balanced
|
|
REG_EPAREN parentheses ( ) not balanced
|
|
REG_EBRACE braces { } not balanced
|
|
REG_BADBR invalid repetition count(s) in { }
|
|
REG_ERANGE invalid character range in [ ]
|
|
REG_ESPACE ran out of memory
|
|
REG_BADRPT ?, *, or + operand invalid
|
|
REG_EMPTY empty (sub)expression
|
|
REG_ASSERT ``can't happen''\(emyou found a bug
|
|
REG_INVARG invalid argument, e.g. negative-length string
|
|
.fi
|
|
.SH HISTORY
|
|
Originally written by Henry Spencer.
|
|
Altered for inclusion in the
|
|
.Bx 4.4
|
|
distribution.
|
|
.SH BUGS
|
|
This is an alpha release with known defects.
|
|
Please report problems.
|
|
.PP
|
|
There is one known functionality bug.
|
|
The implementation of internationalization is incomplete:
|
|
the locale is always assumed to be the default one of 1003.2,
|
|
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
|
|
.I Regexec
|
|
performance is poor.
|
|
This will improve with later releases.
|
|
.I Nmatch
|
|
exceeding 0 is expensive;
|
|
.I nmatch
|
|
exceeding 1 is worse.
|
|
.I Regexec
|
|
is largely insensitive to RE complexity \fIexcept\fR 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
|
|
.I 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}'
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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 1003.2, 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.
|