.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" documentation and/or other materials provided with the distribution.
-.\" 3. All advertising materials mentioning features or use of this software
-.\" must display the following acknowledgement:
-.\" This product includes software developed by the University of
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.\" may be used to endorse or promote products derived from this software
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.\" @(#)regex.3 8.4 (Berkeley) 3/20/94
-.\" $FreeBSD: src/lib/libc/regex/regex.3,v 1.12 2002/12/19 09:40:23 ru Exp $
+.\" $FreeBSD: src/lib/libc/regex/regex.3,v 1.21 2007/01/09 00:28:04 imp Exp $
.\"
-.Dd October 2, 2002
+.Dd Sept 29, 2011
.Dt REGEX 3
.Os
.Sh NAME
.Nm regcomp ,
-.Nm regexec ,
+.Nm regcomp_l ,
.Nm regerror ,
-.Nm regfree
+.Nm regexec ,
+.Nm regfree ,
+.Nm regncomp ,
+.Nm regncomp_l ,
+.Nm regnexec ,
+.Nm regnwcomp ,
+.Nm regnwcomp_l ,
+.Nm regnwexec ,
+.Nm regwcomp ,
+.Nm regwcomp_l ,
+.Nm regwexec
.Nd regular-expression library
-.Sh LIBRARY
-.Lb libc
.Sh SYNOPSIS
+.Sy (Standards-compliant APIs)
+.Pp
.In regex.h
.Ft int
.Fo regcomp
-.Fa "regex_t * restrict preg" "const char * restrict pattern" "int cflags"
-.Fc
-.Ft int
-.Fo regexec
-.Fa "const regex_t * restrict preg" "const char * restrict string"
-.Fa "size_t nmatch" "regmatch_t pmatch[restrict]" "int eflags"
+.Fa "regex_t *restrict preg"
+.Fa "const char *restrict pattern"
+.Fa "int cflags"
.Fc
.Ft size_t
.Fo regerror
-.Fa "int errcode" "const regex_t * restrict preg"
-.Fa "char * restrict errbuf" "size_t errbuf_size"
+.Fa "int errcode"
+.Fa "const regex_t *restrict preg"
+.Fa "char *restrict errbuf"
+.Fa "size_t errbuf_size"
+.Fc
+.Ft int
+.Fo regexec
+.Fa "const regex_t *restrict preg"
+.Fa "const char *restrict string"
+.Fa "size_t nmatch"
+.Fa "regmatch_t pmatch[restrict]"
+.Fa "int eflags"
.Fc
.Ft void
-.Fn regfree "regex_t *preg"
+.Fo regfree
+.Fa "regex_t *preg"
+.Fc
+.Pp
+.Sy (Non-portable extensions)
+.Ft int
+.Fo regncomp
+.Fa "regex_t *restrict preg"
+.Fa "const char *restrict pattern"
+.Fa "size_t len"
+.Fa "int cflags"
+.Fc
+.Ft int
+.Fo regnexec
+.Fa "const regex_t *restrict preg"
+.Fa "const char *restrict string"
+.Fa "size_t len"
+.Fa "size_t nmatch"
+.Fa "regmatch_t pmatch[restrict]"
+.Fa "int eflags"
+.Fc
+.Ft int
+.Fo regwcomp
+.Fa "regex_t *restrict preg"
+.Fa "const wchar_t *restrict widepat"
+.Fa "int cflags"
+.Fc
+.Ft int
+.Fo regwexec
+.Fa "const regex_t *restrict preg"
+.Fa "const wchar_t *restrict widestr"
+.Fa "size_t nmatch"
+.Fa "regmatch_t pmatch[restrict]"
+.Fa "int eflags"
+.Fc
+.Ft int
+.Fo regwncomp
+.Fa "regex_t *restrict preg"
+.Fa "const wchar_t *restrict widepat"
+.Fa "size_t len"
+.Fa "int cflags"
+.Fc
+.Ft int
+.Fo regwnexec
+.Fa "const regex_t *restrict preg"
+.Fa "const wchar_t *restrict widestr"
+.Fa "size_t len"
+.Fa "size_t nmatch"
+.Fa "regmatch_t pmatch[restrict]"
+.Fa "int eflags"
+.Fc
+.In regex.h
+.In xlocale.h
+.Ft int
+.Fo regcomp_l
+.Fa "regex_t *restrict preg"
+.Fa "const char *restrict pattern"
+.Fa "int cflags"
+.Fa "locale_t restrict"
+.Fc
+.Ft int
+.Fo regncomp_l
+.Fa "regex_t *restrict preg"
+.Fa "const char *restrict pattern"
+.Fa "size_t len"
+.Fa "int cflags"
+.Fa "locale_t restrict"
+.Fc
+.Ft int
+.Fo regwcomp_l
+.Fa "regex_t *restrict preg"
+.Fa "const wchar_t *restrict widepat"
+.Fa "int cflags"
+.Fa "locale_t restrict"
+.Fc
+.Ft int
+.Fo regwncomp_l
+.Fa "regex_t *restrict preg"
+.Fa "const wchar_t *restrict widepat"
+.Fa "size_t len"
+.Fa "int cflags"
+.Fa "locale_t restrict"
+.Fc
.Sh DESCRIPTION
These routines implement
.St -p1003.2
The
.Fn regcomp
function
-compiles an RE written as a string into an internal form,
+compiles an RE, written as a string, into an internal form.
.Fn regexec
-matches that internal form against a string and reports results,
+matches that internal form against a string and reports results.
.Fn regerror
-transforms error codes from either into human-readable messages,
-and
+transforms error codes from either into human-readable messages.
.Fn regfree
frees any dynamically-allocated storage used by the internal form
of an RE.
.Pp
The header
-.Aq Pa regex.h
+.In regex.h
declares two structure types,
.Ft regex_t
and
may not be used
in the same call to
.Fn regcomp .
+.It Dv REG_LITERAL
+An alias of
+.Dv REG_NOSPEC .
.It Dv REG_ICASE
Compile for matching that ignores upper/lower case distinctions.
See
anchor matches the null string before any newline in the
string in addition to its normal function.
.It Dv REG_PEND
+(Note that
+.Dv REG_PEND
+is not recognized by any of the wide character or
+.Dq Nm n
+variants.
+Besides, the
+.Dq Nm n
+variants can be used instead of
+.Dv REG_PEND ;
+see EXTENDED APIS below.)
The regular expression ends,
not at the first NUL,
but just before the character pointed to by the
.St -p1003.2 ,
and should be used with
caution in software intended to be portable to other systems.
+.It Dv REG_ENHANCED
+Recognized enhanced regular expression features; see
+.Xr re_format 7
+for details.
+This is an extension not specified by
+.St -p1003.2 ,
+and should be used with
+caution in software intended to be portable to other systems.
+.It Dv REG_MINIMAL
+Use minimal (non-greedy) repetitions instead of the normal greedy ones; see
+.Xr re_format 7
+for details.
+(This only applies when both
+.Dv REG_ENHANCED
+and
+.Dv REG_EXTENDED
+are also set.)
+This is an extension not specified by
+.St -p1003.2 ,
+and should be used with
+caution in software intended to be portable to other systems.
+.It Dv REG_UNGREEDY
+Alias of
+.Dv REG_MINIMAL .
.El
.Pp
When successful,
limiting the length (including the NUL) to at most
.Fa errbuf_size
bytes.
-If the whole message won't fit,
+If the whole message will not 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
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 EXTENDED APIS
+These extended APIs are available in Mac OS X 10.8 and beyond, when the
+deployment target is 10.8 or later.
+It should also be noted that any of the
+.Fn regcomp
+variants may be used to initialize a
+.Ft regex_t
+structure, that can then be passed to any of the
+.Fn regexec
+variants.
+So it is quite legal to compile a wide character RE and use it to match a
+multibyte character string, or vice versa.
+.Pp
+The
+.Fn regncomp
+routine compiles regular expressions like
+.Fn regcomp ,
+but the length of the regular expression string is specified, allowing a string
+that is not NUL terminated and/or contains NUL characters.
+This is a modern replacement for using
+.Fn regcomp
+with the
+.Dv REG_PEND
+option.
+.Pp
+Similarly, the
+.Fn regnexec
+routine is like
+.Fn regexec ,
+but the length of the string to match is specified, allowing a string
+that is not NUL terminated and/or contains NUL characters.
+.Pp
+The
+.Fn regwcomp
+and
+.Fn regwexec
+variants take a wide-character
+.Vt ( wchar_t )
+string for the regular expression and string to match.
+And
+.Fn regwncomp
+and
+.Fn regwnexec
+are variants that allow specifying the wide character string length, and
+so allows wide character strings that are not NUL terminated and/or
+contains NUL characters.
+.Sh INTERACTION WITH THE LOCALE
+When
+.Fn regcomp
+or one of its variants is run, the regular expression is compiled into an
+internal form, which may include specific information about the locale currently
+in effect, such as equivalence classes or multi-character collation symbols.
+So a reference to the current locale is also stored with the internal form,
+so that when
+.Fn regexec
+is run, it can use the same locale (even if the locale is changed in-between
+the calls to
+.Fn regcomp
+and
+.Fn regexec ) .
+.Pp
+To provide more direct control over which locale is used,
+routines with
+.Dq Nm _l
+appended to their names are provided that work just like the variants
+without the
+.Dq Nm _l ,
+except that a locale (via a
+.Vt locale_t
+variable type) is specified directly.
+Note that only variants of
+.Fn regcomp
+have
+.Dq Nm _l
+variants, since the
+.Fn regexec
+variants just use the reference to the locale stored in the internal form.
.Sh IMPLEMENTATION CHOICES
+The
+.Nm regex
+implementation in Mac OS X 10.8 and later is based on a heavily modified subset
+of TRE (http://laurikari.net/tre/).
+This provides improved performance, better conformance and additional features.
+However, both API and binary compatibility have been maintained with previous
+releases, so binaries
+built on previous releases should work on 10.8 and later, and binaries built on
+10.8 and later should be able to run on previous releases (as long as none of
+the new variants or new features are used.
+.Pp
There are a number of decisions that
.St -p1003.2
leaves up to the implementor,
.Ql +\& ,
or bounds)
cannot follow another
-repetition operator.
+repetition operator, except for the use of
+.Ql ?\&
+for minimal repetition (for enhanced extended REs; see
+.Xr re_format 7
+for details).
A repetition operator cannot begin an expression or subexpression
or follow
.Ql ^\&
.Ql |\&
cannot appear first or last in a (sub)expression or after another
.Ql |\& ,
-i.e. an operand of
+i.e., an operand of
.Ql |\&
cannot be an empty subexpression.
An empty parenthesized subexpression,
beginning and ending subexpressions in obsolete
.Pq Dq basic
REs are anchors, not ordinary characters.
-.Sh SEE ALSO
-.Xr grep 1 ,
-.Xr re_format 7
-.Pp
-.St -p1003.2 ,
-sections 2.8 (Regular Expression Notation)
-and
-B.5 (C Binding for Regular Expression Matching).
.Sh DIAGNOSTICS
Non-zero error codes from
.Fn regcomp
.It Dv REG_EMPTY
empty (sub)expression
.It Dv REG_ASSERT
-can't happen - you found a bug
+cannot happen - you found a bug
.It Dv REG_INVARG
-invalid argument, e.g. negative-length string
+invalid argument, e.g.\& negative-length string
+.It Dv REG_ILLSEQ
+illegal byte sequence (bad multibyte character)
.El
+.Sh SEE ALSO
+.Xr grep 1 ,
+.Xr re_format 7
+.Pp
+.St -p1003.2 ,
+sections 2.8 (Regular Expression Notation)
+and
+B.5 (C Binding for Regular Expression Matching).
.Sh HISTORY
-Originally written by
-.An Henry Spencer .
-Altered for inclusion in the
+The
+.Nm regex
+implementation is based on a heavily modified subset of TRE
+(http://laurikari.net/tre/), originally written by Ville Laurikari.
+Previous releases used an implementation originally written by
+.An Henry Spencer ,
+and altered for inclusion in the
.Bx 4.4
distribution.
.Sh BUGS
-This is an alpha release with known defects.
-Please report problems.
+The beginning-of-line and end-of-line anchors (
+.Dq ^\&
+and
+.Dq $\& )
+are currently implemented so that repetitions can not be applied to them.
+The standards are unclear about whether this is legal, but other
+.Nm regex
+packages do support this case.
+It is best to avoid this non-portable (and not really very useful) case.
.Pp
The back-reference code is subtle and doubts linger about its correctness
in complex cases.
.Pp
The
.Fn regexec
-function
-performance is poor.
-This will improve with later releases.
-The
-.Fa nmatch
-argument
-exceeding 0 is expensive;
-.Fa nmatch
-exceeding 1 is worse.
-The
-.Fn regexec
-function
-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.
+variants use one of two internal matching engines.
+The normal one is linear worst-case time in the length of the text being
+searched, and quadratic worst-case time in the length of the used regular
+expression.
+When back-references are used, a slower, backtracking engine is used.
+While all backtracking matching engines suffer from extreme slowness for certain
+pathological cases, the normal engines doesn't suffer from these cases.
+It is advised to avoid back-references whenever possible.
.Pp
The
.Fn regcomp
-function
+variants
implements bounded repetitions by macro expansion,
which is costly in time and space if counts are large
or bounded repetitions are nested.
.Ql "((((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 ,
things like
is
a special character only in the presence of a previous unmatched
.Ql (\& .
-This can't be fixed until the spec is fixed.
+This cannot be fixed until the spec is fixed.
.Pp
The standard's definition of back references is vague.
For example, does
.Ql "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.
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