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Line 25 INTRODUCTION	Line 25 INTRODUCTION
items, and there is an option for requesting some minor changes that	items, and there is an option for requesting some minor changes that
give better JavaScript compatibility.	give better JavaScript compatibility.

	Starting with release 8.30, it is possible to compile two separate PCRE
	libraries: the original, which supports 8-bit character strings
	(including UTF-8 strings), and a second library that supports 16-bit
	character strings (including UTF-16 strings). The build process allows
	either one or both to be built. The majority of the work to make this
	possible was done by Zoltan Herczeg.

	The two libraries contain identical sets of functions, except that the
	names in the 16-bit library start with pcre16_ instead of pcre_. To
	avoid over-complication and reduce the documentation maintenance load,
	most of the documentation describes the 8-bit library, with the differ-
	ences for the 16-bit library described separately in the pcre16 page.
	References to functions or structures of the form pcre[16]_xxx should
	be read as meaning "pcre_xxx when using the 8-bit library and
	pcre16_xxx when using the 16-bit library".

The current implementation of PCRE corresponds approximately with Perl	The current implementation of PCRE corresponds approximately with Perl
5.12, including support for UTF-8 encoded strings and Unicode general	5.12, including support for UTF-8/16 encoded strings and Unicode gen-
category properties. However, UTF-8 and Unicode support has to be	eral category properties. However, UTF-8/16 and Unicode support has to
explicitly enabled; it is not the default. The Unicode tables corre-	be explicitly enabled; it is not the default. The Unicode tables corre-
spond to Unicode release 6.0.0.	spond to Unicode release 6.0.0.

In addition to the Perl-compatible matching function, PCRE contains an	In addition to the Perl-compatible matching function, PCRE contains an
Line 39 INTRODUCTION	Line 55 INTRODUCTION

PCRE is written in C and released as a C library. A number of people	PCRE is written in C and released as a C library. A number of people
have written wrappers and interfaces of various kinds. In particular,	have written wrappers and interfaces of various kinds. In particular,
Google Inc. have provided a comprehensive C++ wrapper. This is now	Google Inc. have provided a comprehensive C++ wrapper for the 8-bit
included as part of the PCRE distribution. The pcrecpp page has details	library. This is now included as part of the PCRE distribution. The
of this interface. Other people's contributions can be found in the	pcrecpp page has details of this interface. Other people's contribu-
Contrib directory at the primary FTP site, which is:	tions can be found in the Contrib directory at the primary FTP site,
	which is:

ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre	ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre

Details of exactly which Perl regular expression features are and are	Details of exactly which Perl regular expression features are and are
not supported by PCRE are given in separate documents. See the pcrepat-	not supported by PCRE are given in separate documents. See the pcrepat-
tern and pcrecompat pages. There is a syntax summary in the pcresyntax	tern and pcrecompat pages. There is a syntax summary in the pcresyntax
page.	page.

Some features of PCRE can be included, excluded, or changed when the	Some features of PCRE can be included, excluded, or changed when the
library is built. The pcre_config() function makes it possible for a	library is built. The pcre_config() function makes it possible for a
client to discover which features are available. The features them-	client to discover which features are available. The features them-
selves are described in the pcrebuild page. Documentation about build-	selves are described in the pcrebuild page. Documentation about build-
ing PCRE for various operating systems can be found in the README and	ing PCRE for various operating systems can be found in the README and
NON-UNIX-USE files in the source distribution.	NON-UNIX-USE files in the source distribution.

The library contains a number of undocumented internal functions and	The libraries contains a number of undocumented internal functions and
data tables that are used by more than one of the exported external	data tables that are used by more than one of the exported external
functions, but which are not intended for use by external callers.	functions, but which are not intended for use by external callers.
Their names all begin with "_pcre_", which hopefully will not provoke	Their names all begin with "_pcre_" or "_pcre16_", which hopefully will
any name clashes. In some environments, it is possible to control which	not provoke any name clashes. In some environments, it is possible to
external symbols are exported when a shared library is built, and in	control which external symbols are exported when a shared library is
these cases the undocumented symbols are not exported.	built, and in these cases the undocumented symbols are not exported.


USER DOCUMENTATION	USER DOCUMENTATION

The user documentation for PCRE comprises a number of different sec-	The user documentation for PCRE comprises a number of different sec-
tions. In the "man" format, each of these is a separate "man page". In	tions. In the "man" format, each of these is a separate "man page". In
the HTML format, each is a separate page, linked from the index page.	the HTML format, each is a separate page, linked from the index page.
In the plain text format, all the sections, except the pcredemo sec-	In the plain text format, all the sections, except the pcredemo sec-
tion, are concatenated, for ease of searching. The sections are as fol-	tion, are concatenated, for ease of searching. The sections are as fol-
lows:	lows:

pcre this document	pcre this document
	pcre16 details of the 16-bit library
pcre-config show PCRE installation configuration information	pcre-config show PCRE installation configuration information
pcreapi details of PCRE's native C API	pcreapi details of PCRE's native C API
pcrebuild options for building PCRE	pcrebuild options for building PCRE
pcrecallout details of the callout feature	pcrecallout details of the callout feature
pcrecompat discussion of Perl compatibility	pcrecompat discussion of Perl compatibility
pcrecpp details of the C++ wrapper	pcrecpp details of the C++ wrapper for the 8-bit library
pcredemo a demonstration C program that uses PCRE	pcredemo a demonstration C program that uses PCRE
pcregrep description of the pcregrep command	pcregrep description of the pcregrep command (8-bit only)
pcrejit discussion of the just-in-time optimization support	pcrejit discussion of the just-in-time optimization support
pcrelimits details of size and other limits	pcrelimits details of size and other limits
pcrematching discussion of the two matching algorithms	pcrematching discussion of the two matching algorithms
Line 92 USER DOCUMENTATION	Line 110 USER DOCUMENTATION
pcrepattern syntax and semantics of supported	pcrepattern syntax and semantics of supported
regular expressions	regular expressions
pcreperform discussion of performance issues	pcreperform discussion of performance issues
pcreposix the POSIX-compatible C API	pcreposix the POSIX-compatible C API for the 8-bit library
pcreprecompile details of saving and re-using precompiled patterns	pcreprecompile details of saving and re-using precompiled patterns
pcresample discussion of the pcredemo program	pcresample discussion of the pcredemo program
pcrestack discussion of stack usage	pcrestack discussion of stack usage
pcresyntax quick syntax reference	pcresyntax quick syntax reference
pcretest description of the pcretest testing command	pcretest description of the pcretest testing command
pcreunicode discussion of Unicode and UTF-8 support	pcreunicode discussion of Unicode and UTF-8/16 support

In addition, in the "man" and HTML formats, there is a short page for	In addition, in the "man" and HTML formats, there is a short page for
each C library function, listing its arguments and results.	each 8-bit C library function, listing its arguments and results.


AUTHOR	AUTHOR
Line 110 AUTHOR	Line 128 AUTHOR
University Computing Service	University Computing Service
Cambridge CB2 3QH, England.	Cambridge CB2 3QH, England.

Putting an actual email address here seems to have been a spam magnet,	Putting an actual email address here seems to have been a spam magnet,
so I've taken it away. If you want to email me, use my two initials,	so I've taken it away. If you want to email me, use my two initials,
followed by the two digits 10, at the domain cam.ac.uk.	followed by the two digits 10, at the domain cam.ac.uk.


REVISION	REVISION

Last updated: 24 August 2011	Last updated: 10 January 2012
Copyright (c) 1997-2011 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------


	PCRE(3) PCRE(3)


	NAME
	PCRE - Perl-compatible regular expressions

	#include <pcre.h>


	PCRE 16-BIT API BASIC FUNCTIONS

	pcre16 *pcre16_compile(PCRE_SPTR16 pattern, int options,
	const char *errptr, int erroffset,
	const unsigned char *tableptr);

	pcre16 *pcre16_compile2(PCRE_SPTR16 pattern, int options,
	int *errorcodeptr,
	const char *errptr, int erroffset,
	const unsigned char *tableptr);

	pcre16_extra pcre16_study(const pcre16 code, int options,
	const char **errptr);

	void pcre16_free_study(pcre16_extra *extra);

	int pcre16_exec(const pcre16 code, const pcre16_extra extra,
	PCRE_SPTR16 subject, int length, int startoffset,
	int options, int *ovector, int ovecsize);

	int pcre16_dfa_exec(const pcre16 code, const pcre16_extra extra,
	PCRE_SPTR16 subject, int length, int startoffset,
	int options, int *ovector, int ovecsize,
	int *workspace, int wscount);


	PCRE 16-BIT API STRING EXTRACTION FUNCTIONS

	int pcre16_copy_named_substring(const pcre16 *code,
	PCRE_SPTR16 subject, int *ovector,
	int stringcount, PCRE_SPTR16 stringname,
	PCRE_UCHAR16 *buffer, int buffersize);

	int pcre16_copy_substring(PCRE_SPTR16 subject, int *ovector,
	int stringcount, int stringnumber, PCRE_UCHAR16 *buffer,
	int buffersize);

	int pcre16_get_named_substring(const pcre16 *code,
	PCRE_SPTR16 subject, int *ovector,
	int stringcount, PCRE_SPTR16 stringname,
	PCRE_SPTR16 *stringptr);

	int pcre16_get_stringnumber(const pcre16 *code,
	PCRE_SPTR16 name);

	int pcre16_get_stringtable_entries(const pcre16 *code,
	PCRE_SPTR16 name, PCRE_UCHAR16 first, PCRE_UCHAR16 last);

	int pcre16_get_substring(PCRE_SPTR16 subject, int *ovector,
	int stringcount, int stringnumber,
	PCRE_SPTR16 *stringptr);

	int pcre16_get_substring_list(PCRE_SPTR16 subject,
	int ovector, int stringcount, PCRE_SPTR16 *listptr);

	void pcre16_free_substring(PCRE_SPTR16 stringptr);

	void pcre16_free_substring_list(PCRE_SPTR16 *stringptr);


	PCRE 16-BIT API AUXILIARY FUNCTIONS

	pcre16_jit_stack *pcre16_jit_stack_alloc(int startsize, int maxsize);

	void pcre16_jit_stack_free(pcre16_jit_stack *stack);

	void pcre16_assign_jit_stack(pcre16_extra *extra,
	pcre16_jit_callback callback, void *data);

	const unsigned char *pcre16_maketables(void);

	int pcre16_fullinfo(const pcre16 code, const pcre16_extra extra,
	int what, void *where);

	int pcre16_refcount(pcre16 *code, int adjust);

	int pcre16_config(int what, void *where);

	const char *pcre16_version(void);

	int pcre16_pattern_to_host_byte_order(pcre16 *code,
	pcre16_extra extra, const unsigned char tables);


	PCRE 16-BIT API INDIRECTED FUNCTIONS

	void (pcre16_malloc)(size_t);

	void (pcre16_free)(void );

	void (pcre16_stack_malloc)(size_t);

	void (pcre16_stack_free)(void );

	int (pcre16_callout)(pcre16_callout_block );


	PCRE 16-BIT API 16-BIT-ONLY FUNCTION

	int pcre16_utf16_to_host_byte_order(PCRE_UCHAR16 *output,
	PCRE_SPTR16 input, int length, int *byte_order,
	int keep_boms);


	THE PCRE 16-BIT LIBRARY

	Starting with release 8.30, it is possible to compile a PCRE library
	that supports 16-bit character strings, including UTF-16 strings, as
	well as or instead of the original 8-bit library. The majority of the
	work to make this possible was done by Zoltan Herczeg. The two
	libraries contain identical sets of functions, used in exactly the same
	way. Only the names of the functions and the data types of their argu-
	ments and results are different. To avoid over-complication and reduce
	the documentation maintenance load, most of the PCRE documentation
	describes the 8-bit library, with only occasional references to the
	16-bit library. This page describes what is different when you use the
	16-bit library.

	WARNING: A single application can be linked with both libraries, but
	you must take care when processing any particular pattern to use func-
	tions from just one library. For example, if you want to study a pat-
	tern that was compiled with pcre16_compile(), you must do so with
	pcre16_study(), not pcre_study(), and you must free the study data with
	pcre16_free_study().


	THE HEADER FILE

	There is only one header file, pcre.h. It contains prototypes for all
	the functions in both libraries, as well as definitions of flags,
	structures, error codes, etc.


	THE LIBRARY NAME

	In Unix-like systems, the 16-bit library is called libpcre16, and can
	normally be accesss by adding -lpcre16 to the command for linking an
	application that uses PCRE.


	STRING TYPES

	In the 8-bit library, strings are passed to PCRE library functions as
	vectors of bytes with the C type "char *". In the 16-bit library,
	strings are passed as vectors of unsigned 16-bit quantities. The macro
	PCRE_UCHAR16 specifies an appropriate data type, and PCRE_SPTR16 is
	defined as "const PCRE_UCHAR16 *". In very many environments, "short
	int" is a 16-bit data type. When PCRE is built, it defines PCRE_UCHAR16
	as "short int", but checks that it really is a 16-bit data type. If it
	is not, the build fails with an error message telling the maintainer to
	modify the definition appropriately.


	STRUCTURE TYPES

	The types of the opaque structures that are used for compiled 16-bit
	patterns and JIT stacks are pcre16 and pcre16_jit_stack respectively.
	The type of the user-accessible structure that is returned by
	pcre16_study() is pcre16_extra, and the type of the structure that is
	used for passing data to a callout function is pcre16_callout_block.
	These structures contain the same fields, with the same names, as their
	8-bit counterparts. The only difference is that pointers to character
	strings are 16-bit instead of 8-bit types.


	16-BIT FUNCTIONS

	For every function in the 8-bit library there is a corresponding func-
	tion in the 16-bit library with a name that starts with pcre16_ instead
	of pcre_. The prototypes are listed above. In addition, there is one
	extra function, pcre16_utf16_to_host_byte_order(). This is a utility
	function that converts a UTF-16 character string to host byte order if
	necessary. The other 16-bit functions expect the strings they are
	passed to be in host byte order.

	The input and output arguments of pcre16_utf16_to_host_byte_order() may
	point to the same address, that is, conversion in place is supported.
	The output buffer must be at least as long as the input.

	The length argument specifies the number of 16-bit data units in the
	input string; a negative value specifies a zero-terminated string.

	If byte_order is NULL, it is assumed that the string starts off in host
	byte order. This may be changed by byte-order marks (BOMs) anywhere in
	the string (commonly as the first character).

	If byte_order is not NULL, a non-zero value of the integer to which it
	points means that the input starts off in host byte order, otherwise
	the opposite order is assumed. Again, BOMs in the string can change
	this. The final byte order is passed back at the end of processing.

	If keep_boms is not zero, byte-order mark characters (0xfeff) are
	copied into the output string. Otherwise they are discarded.

	The result of the function is the number of 16-bit units placed into
	the output buffer, including the zero terminator if the string was
	zero-terminated.


	SUBJECT STRING OFFSETS

	The offsets within subject strings that are returned by the matching
	functions are in 16-bit units rather than bytes.


	NAMED SUBPATTERNS

	The name-to-number translation table that is maintained for named sub-
	patterns uses 16-bit characters. The pcre16_get_stringtable_entries()
	function returns the length of each entry in the table as the number of
	16-bit data units.


	OPTION NAMES

	There are two new general option names, PCRE_UTF16 and
	PCRE_NO_UTF16_CHECK, which correspond to PCRE_UTF8 and
	PCRE_NO_UTF8_CHECK in the 8-bit library. In fact, these new options
	define the same bits in the options word.

	For the pcre16_config() function there is an option PCRE_CONFIG_UTF16
	that returns 1 if UTF-16 support is configured, otherwise 0. If this
	option is given to pcre_config(), or if the PCRE_CONFIG_UTF8 option is
	given to pcre16_config(), the result is the PCRE_ERROR_BADOPTION error.


	CHARACTER CODES

	In 16-bit mode, when PCRE_UTF16 is not set, character values are
	treated in the same way as in 8-bit, non UTF-8 mode, except, of course,
	that they can range from 0 to 0xffff instead of 0 to 0xff. Character
	types for characters less than 0xff can therefore be influenced by the
	locale in the same way as before. Characters greater than 0xff have
	only one case, and no "type" (such as letter or digit).

	In UTF-16 mode, the character code is Unicode, in the range 0 to
	0x10ffff, with the exception of values in the range 0xd800 to 0xdfff
	because those are "surrogate" values that are used in pairs to encode
	values greater than 0xffff.

	A UTF-16 string can indicate its endianness by special code knows as a
	byte-order mark (BOM). The PCRE functions do not handle this, expecting
	strings to be in host byte order. A utility function called
	pcre16_utf16_to_host_byte_order() is provided to help with this (see
	above).


	ERROR NAMES

	The errors PCRE_ERROR_BADUTF16_OFFSET and PCRE_ERROR_SHORTUTF16 corre-
	spond to their 8-bit counterparts. The error PCRE_ERROR_BADMODE is
	given when a compiled pattern is passed to a function that processes
	patterns in the other mode, for example, if a pattern compiled with
	pcre_compile() is passed to pcre16_exec().

	There are new error codes whose names begin with PCRE_UTF16_ERR for
	invalid UTF-16 strings, corresponding to the PCRE_UTF8_ERR codes for
	UTF-8 strings that are described in the section entitled "Reason codes
	for invalid UTF-8 strings" in the main pcreapi page. The UTF-16 errors
	are:

	PCRE_UTF16_ERR1 Missing low surrogate at end of string
	PCRE_UTF16_ERR2 Invalid low surrogate follows high surrogate
	PCRE_UTF16_ERR3 Isolated low surrogate
	PCRE_UTF16_ERR4 Invalid character 0xfffe


	ERROR TEXTS

	If there is an error while compiling a pattern, the error text that is
	passed back by pcre16_compile() or pcre16_compile2() is still an 8-bit
	character string, zero-terminated.


	CALLOUTS

	The subject and mark fields in the callout block that is passed to a
	callout function point to 16-bit vectors.


	TESTING

	The pcretest program continues to operate with 8-bit input and output
	files, but it can be used for testing the 16-bit library. If it is run
	with the command line option -16, patterns and subject strings are con-
	verted from 8-bit to 16-bit before being passed to PCRE, and the 16-bit
	library functions are used instead of the 8-bit ones. Returned 16-bit
	strings are converted to 8-bit for output. If the 8-bit library was not
	compiled, pcretest defaults to 16-bit and the -16 option is ignored.

	When PCRE is being built, the RunTest script that is called by "make
	check" uses the pcretest -C option to discover which of the 8-bit and
	16-bit libraries has been built, and runs the tests appropriately.


	NOT SUPPORTED IN 16-BIT MODE

	Not all the features of the 8-bit library are available with the 16-bit
	library. The C++ and POSIX wrapper functions support only the 8-bit
	library, and the pcregrep program is at present 8-bit only.


	AUTHOR

	Philip Hazel
	University Computing Service
	Cambridge CB2 3QH, England.


	REVISION

	Last updated: 08 January 2012
	Copyright (c) 1997-2012 University of Cambridge.
	------------------------------------------------------------------------------


PCREBUILD(3) PCREBUILD(3)	PCREBUILD(3) PCREBUILD(3)


Line 158 PCRE BUILD-TIME OPTIONS	Line 501 PCRE BUILD-TIME OPTIONS
is not described.	is not described.


	BUILDING 8-BIT and 16-BIT LIBRARIES

	By default, a library called libpcre is built, containing functions
	that take string arguments contained in vectors of bytes, either as
	single-byte characters, or interpreted as UTF-8 strings. You can also
	build a separate library, called libpcre16, in which strings are con-
	tained in vectors of 16-bit data units and interpreted either as sin-
	gle-unit characters or UTF-16 strings, by adding

	--enable-pcre16

	to the configure command. If you do not want the 8-bit library, add

	--disable-pcre8

	as well. At least one of the two libraries must be built. Note that the
	C++ and POSIX wrappers are for the 8-bit library only, and that pcre-
	grep is an 8-bit program. None of these are built if you select only
	the 16-bit library.


BUILDING SHARED AND STATIC LIBRARIES	BUILDING SHARED AND STATIC LIBRARIES

The PCRE building process uses libtool to build both shared and static	The PCRE building process uses libtool to build both shared and static
Line 172 BUILDING SHARED AND STATIC LIBRARIES	Line 536 BUILDING SHARED AND STATIC LIBRARIES

C++ SUPPORT	C++ SUPPORT

By default, the configure script will search for a C++ compiler and C++	By default, if the 8-bit library is being built, the configure script
header files. If it finds them, it automatically builds the C++ wrapper	will search for a C++ compiler and C++ header files. If it finds them,
library for PCRE. You can disable this by adding	it automatically builds the C++ wrapper library (which supports only
	8-bit strings). You can disable this by adding

--disable-cpp	--disable-cpp

to the configure command.	to the configure command.


UTF-8 SUPPORT	UTF-8 and UTF-16 SUPPORT

To build PCRE with support for UTF-8 Unicode character strings, add	To build PCRE with support for UTF Unicode character strings, add

--enable-utf8	--enable-utf

to the configure command. Of itself, this does not make PCRE treat	to the configure command. This setting applies to both libraries,
strings as UTF-8. As well as compiling PCRE with this option, you also	adding support for UTF-8 to the 8-bit library and support for UTF-16 to
have have to set the PCRE_UTF8 option when you call the pcre_compile()	the 16-bit library. There are no separate options for enabling UTF-8
or pcre_compile2() functions.	and UTF-16 independently because that would allow ridiculous settings
	such as requesting UTF-16 support while building only the 8-bit
	library. It is not possible to build one library with UTF support and
	the other without in the same configuration. (For backwards compatibil-
	ity, --enable-utf8 is a synonym of --enable-utf.)

If you set --enable-utf8 when compiling in an EBCDIC environment, PCRE	Of itself, this setting does not make PCRE treat strings as UTF-8 or
	UTF-16. As well as compiling PCRE with this option, you also have have
	to set the PCRE_UTF8 or PCRE_UTF16 option when you call one of the pat-
	tern compiling functions.

	If you set --enable-utf when compiling in an EBCDIC environment, PCRE
expects its input to be either ASCII or UTF-8 (depending on the runtime	expects its input to be either ASCII or UTF-8 (depending on the runtime
option). It is not possible to support both EBCDIC and UTF-8 codes in	option). It is not possible to support both EBCDIC and UTF-8 codes in
the same version of the library. Consequently, --enable-utf8 and	the same version of the library. Consequently, --enable-utf and
--enable-ebcdic are mutually exclusive.	--enable-ebcdic are mutually exclusive.


UNICODE CHARACTER PROPERTY SUPPORT	UNICODE CHARACTER PROPERTY SUPPORT

UTF-8 support allows PCRE to process character values greater than 255	UTF support allows the libraries to process character codepoints up to
in the strings that it handles. On its own, however, it does not pro-	0x10ffff in the strings that they handle. On its own, however, it does
vide any facilities for accessing the properties of such characters. If	not provide any facilities for accessing the properties of such charac-
you want to be able to use the pattern escapes \P, \p, and \X, which	ters. If you want to be able to use the pattern escapes \P, \p, and \X,
refer to Unicode character properties, you must add	which refer to Unicode character properties, you must add

--enable-unicode-properties	--enable-unicode-properties

to the configure command. This implies UTF-8 support, even if you have	to the configure command. This implies UTF support, even if you have
not explicitly requested it.	not explicitly requested it.

Including Unicode property support adds around 30K of tables to the	Including Unicode property support adds around 30K of tables to the
Line 282 WHAT \R MATCHES	Line 656 WHAT \R MATCHES

POSIX MALLOC USAGE	POSIX MALLOC USAGE

When PCRE is called through the POSIX interface (see the pcreposix doc-	When the 8-bit library is called through the POSIX interface (see the
umentation), additional working storage is required for holding the	pcreposix documentation), additional working storage is required for
pointers to capturing substrings, because PCRE requires three integers	holding the pointers to capturing substrings, because PCRE requires
per substring, whereas the POSIX interface provides only two. If the	three integers per substring, whereas the POSIX interface provides only
number of expected substrings is small, the wrapper function uses space	two. If the number of expected substrings is small, the wrapper func-
on the stack, because this is faster than using malloc() for each call.	tion uses space on the stack, because this is faster than using mal-
The default threshold above which the stack is no longer used is 10; it	loc() for each call. The default threshold above which the stack is no
can be changed by adding a setting such as	longer used is 10; it can be changed by adding a setting such as

--with-posix-malloc-threshold=20	--with-posix-malloc-threshold=20

Line 303 HANDLING VERY LARGE PATTERNS	Line 677 HANDLING VERY LARGE PATTERNS
nation metacharacter). By default, two-byte values are used for these	nation metacharacter). By default, two-byte values are used for these
offsets, leading to a maximum size for a compiled pattern of around	offsets, leading to a maximum size for a compiled pattern of around
64K. This is sufficient to handle all but the most gigantic patterns.	64K. This is sufficient to handle all but the most gigantic patterns.
Nevertheless, some people do want to process truyl enormous patterns,	Nevertheless, some people do want to process truly enormous patterns,
so it is possible to compile PCRE to use three-byte or four-byte off-	so it is possible to compile PCRE to use three-byte or four-byte off-
sets by adding a setting such as	sets by adding a setting such as

--with-link-size=3	--with-link-size=3

to the configure command. The value given must be 2, 3, or 4. Using	to the configure command. The value given must be 2, 3, or 4. For the
longer offsets slows down the operation of PCRE because it has to load	16-bit library, a value of 3 is rounded up to 4. Using longer offsets
additional bytes when handling them.	slows down the operation of PCRE because it has to load additional data
	when handling them.


AVOIDING EXCESSIVE STACK USAGE	AVOIDING EXCESSIVE STACK USAGE

When matching with the pcre_exec() function, PCRE implements backtrack-	When matching with the pcre_exec() function, PCRE implements backtrack-
ing by making recursive calls to an internal function called match().	ing by making recursive calls to an internal function called match().
In environments where the size of the stack is limited, this can se-	In environments where the size of the stack is limited, this can se-
verely limit PCRE's operation. (The Unix environment does not usually	verely limit PCRE's operation. (The Unix environment does not usually
suffer from this problem, but it may sometimes be necessary to increase	suffer from this problem, but it may sometimes be necessary to increase
the maximum stack size. There is a discussion in the pcrestack docu-	the maximum stack size. There is a discussion in the pcrestack docu-
mentation.) An alternative approach to recursion that uses memory from	mentation.) An alternative approach to recursion that uses memory from
the heap to remember data, instead of using recursive function calls,	the heap to remember data, instead of using recursive function calls,
has been implemented to work round the problem of limited stack size.	has been implemented to work round the problem of limited stack size.
If you want to build a version of PCRE that works this way, add	If you want to build a version of PCRE that works this way, add

--disable-stack-for-recursion	--disable-stack-for-recursion

to the configure command. With this configuration, PCRE will use the	to the configure command. With this configuration, PCRE will use the
pcre_stack_malloc and pcre_stack_free variables to call memory manage-	pcre_stack_malloc and pcre_stack_free variables to call memory manage-
ment functions. By default these point to malloc() and free(), but you	ment functions. By default these point to malloc() and free(), but you
can replace the pointers so that your own functions are used instead.	can replace the pointers so that your own functions are used instead.

Separate functions are provided rather than using pcre_malloc and	Separate functions are provided rather than using pcre_malloc and
pcre_free because the usage is very predictable: the block sizes	pcre_free because the usage is very predictable: the block sizes
requested are always the same, and the blocks are always freed in	requested are always the same, and the blocks are always freed in
reverse order. A calling program might be able to implement optimized	reverse order. A calling program might be able to implement optimized
functions that perform better than malloc() and free(). PCRE runs	functions that perform better than malloc() and free(). PCRE runs
noticeably more slowly when built in this way. This option affects only	noticeably more slowly when built in this way. This option affects only
the pcre_exec() function; it is not relevant for pcre_dfa_exec().	the pcre_exec() function; it is not relevant for pcre_dfa_exec().


LIMITING PCRE RESOURCE USAGE	LIMITING PCRE RESOURCE USAGE

Internally, PCRE has a function called match(), which it calls repeat-	Internally, PCRE has a function called match(), which it calls repeat-
edly (sometimes recursively) when matching a pattern with the	edly (sometimes recursively) when matching a pattern with the
pcre_exec() function. By controlling the maximum number of times this	pcre_exec() function. By controlling the maximum number of times this
function may be called during a single matching operation, a limit can	function may be called during a single matching operation, a limit can
be placed on the resources used by a single call to pcre_exec(). The	be placed on the resources used by a single call to pcre_exec(). The
limit can be changed at run time, as described in the pcreapi documen-	limit can be changed at run time, as described in the pcreapi documen-
tation. The default is 10 million, but this can be changed by adding a	tation. The default is 10 million, but this can be changed by adding a
setting such as	setting such as

--with-match-limit=500000	--with-match-limit=500000

to the configure command. This setting has no effect on the	to the configure command. This setting has no effect on the
pcre_dfa_exec() matching function.	pcre_dfa_exec() matching function.

In some environments it is desirable to limit the depth of recursive	In some environments it is desirable to limit the depth of recursive
calls of match() more strictly than the total number of calls, in order	calls of match() more strictly than the total number of calls, in order
to restrict the maximum amount of stack (or heap, if --disable-stack-	to restrict the maximum amount of stack (or heap, if --disable-stack-
for-recursion is specified) that is used. A second limit controls this;	for-recursion is specified) that is used. A second limit controls this;
it defaults to the value that is set for --with-match-limit, which	it defaults to the value that is set for --with-match-limit, which
imposes no additional constraints. However, you can set a lower limit	imposes no additional constraints. However, you can set a lower limit
by adding, for example,	by adding, for example,

--with-match-limit-recursion=10000	--with-match-limit-recursion=10000

to the configure command. This value can also be overridden at run	to the configure command. This value can also be overridden at run
time.	time.


CREATING CHARACTER TABLES AT BUILD TIME	CREATING CHARACTER TABLES AT BUILD TIME

PCRE uses fixed tables for processing characters whose code values are	PCRE uses fixed tables for processing characters whose code values are
less than 256. By default, PCRE is built with a set of tables that are	less than 256. By default, PCRE is built with a set of tables that are
distributed in the file pcre_chartables.c.dist. These tables are for	distributed in the file pcre_chartables.c.dist. These tables are for
ASCII codes only. If you add	ASCII codes only. If you add

--enable-rebuild-chartables	--enable-rebuild-chartables

to the configure command, the distributed tables are no longer used.	to the configure command, the distributed tables are no longer used.
Instead, a program called dftables is compiled and run. This outputs	Instead, a program called dftables is compiled and run. This outputs
the source for new set of tables, created in the default locale of your	the source for new set of tables, created in the default locale of your
C runtime system. (This method of replacing the tables does not work if	C runtime system. (This method of replacing the tables does not work if
you are cross compiling, because dftables is run on the local host. If	you are cross compiling, because dftables is run on the local host. If
you need to create alternative tables when cross compiling, you will	you need to create alternative tables when cross compiling, you will
have to do so "by hand".)	have to do so "by hand".)


USING EBCDIC CODE	USING EBCDIC CODE

PCRE assumes by default that it will run in an environment where the	PCRE assumes by default that it will run in an environment where the
character code is ASCII (or Unicode, which is a superset of ASCII).	character code is ASCII (or Unicode, which is a superset of ASCII).
This is the case for most computer operating systems. PCRE can, how-	This is the case for most computer operating systems. PCRE can, how-
ever, be compiled to run in an EBCDIC environment by adding	ever, be compiled to run in an EBCDIC environment by adding

--enable-ebcdic	--enable-ebcdic

to the configure command. This setting implies --enable-rebuild-charta-	to the configure command. This setting implies --enable-rebuild-charta-
bles. You should only use it if you know that you are in an EBCDIC	bles. You should only use it if you know that you are in an EBCDIC
environment (for example, an IBM mainframe operating system). The	environment (for example, an IBM mainframe operating system). The
--enable-ebcdic option is incompatible with --enable-utf8.	--enable-ebcdic option is incompatible with --enable-utf.


PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT	PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
Line 416 PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT	Line 791 PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
--enable-pcregrep-libbz2	--enable-pcregrep-libbz2

to the configure command. These options naturally require that the rel-	to the configure command. These options naturally require that the rel-
evant libraries are installed on your system. Configuration will fail	evant libraries are installed on your system. Configuration will fail
if they are not.	if they are not.


PCREGREP BUFFER SIZE	PCREGREP BUFFER SIZE

pcregrep uses an internal buffer to hold a "window" on the file it is	pcregrep uses an internal buffer to hold a "window" on the file it is
scanning, in order to be able to output "before" and "after" lines when	scanning, in order to be able to output "before" and "after" lines when
it finds a match. The size of the buffer is controlled by a parameter	it finds a match. The size of the buffer is controlled by a parameter
whose default value is 20K. The buffer itself is three times this size,	whose default value is 20K. The buffer itself is three times this size,
but because of the way it is used for holding "before" lines, the long-	but because of the way it is used for holding "before" lines, the long-
est line that is guaranteed to be processable is the parameter size.	est line that is guaranteed to be processable is the paramete est line that is guaranteed to be processable is the paramete
You can change the default parameter value by adding, for example,	You can change the default parameter value by adding, for example,

--with-pcregrep-bufsize=50K	--with-pcregrep-bufsize=50K
Line 442 PCRETEST OPTION FOR LIBREADLINE SUPPORT	Line 817 PCRETEST OPTION FOR LIBREADLINE SUPPORT

--enable-pcretest-libreadline	--enable-pcretest-libreadline

to the configure command, pcretest is linked with the libreadline	to the configure command, pcretest is linked with the libreadline
library, and when its input is from a terminal, it reads it using the	library, and when its input is from a terminal, it reads it using the
readline() function. This provides line-editing and history facilities.	readline() function. This provides line-editing and history facilities.
Note that libreadline is GPL-licensed, so if you distribute a binary of	Note that libreadline is GPL-licensed, so if you distribute a binary of
pcretest linked in this way, there may be licensing issues.	pcretest linked in this way, there may be licensing issues.

Setting this option causes the -lreadline option to be added to the	Setting this option causes the -lreadline option to be added to the
pcretest build. In many operating environments with a sytem-installed	pcretest build. In many operating environments with a sytem-installed
libreadline this is sufficient. However, in some environments (e.g. if	libreadline this is sufficient. However, in some environments (e.g. if
an unmodified distribution version of readline is in use), some extra	an unmodified distribution version of readline is in use), some extra
configuration may be necessary. The INSTALL file for libreadline says	configuration may be necessary. The INSTALL file for libreadline says
this:	this:

"Readline uses the termcap functions, but does not link with the	"Readline uses the termcap functions, but does not link with the
termcap or curses library itself, allowing applications which link	termcap or curses library itself, allowing applications which link
with readline the to choose an appropriate library."	with readline the to choose an appropriate library."

If your environment has not been set up so that an appropriate library	If your environment has not been set up so that an appropriate library
is automatically included, you may need to add something like	is automatically included, you may need to add something like

LIBS="-ncurses"	LIBS="-ncurses"
Line 469 PCRETEST OPTION FOR LIBREADLINE SUPPORT	Line 844 PCRETEST OPTION FOR LIBREADLINE SUPPORT

SEE ALSO	SEE ALSO

pcreapi(3), pcre_config(3).	pcreapi(3), pcre16, pcre_config(3).


AUTHOR	AUTHOR
Line 481 AUTHOR	Line 856 AUTHOR

REVISION	REVISION

Last updated: 06 September 2011	Last updated: 07 January 2012
Copyright (c) 1997-2011 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------


Line 498 PCRE MATCHING ALGORITHMS	Line 873 PCRE MATCHING ALGORITHMS
This document describes the two different algorithms that are available	This document describes the two different algorithms that are available
in PCRE for matching a compiled regular expression against a given sub-	in PCRE for matching a compiled regular expression against a given sub-
ject string. The "standard" algorithm is the one provided by the	ject string. The "standard" algorithm is the one provided by the
pcre_exec() function. This works in the same was as Perl's matching	pcre_exec() and pcre16_exec() functions. These work in the same was as
function, and provides a Perl-compatible matching operation.	Perl's matching function, and provide a Perl-compatible matching opera-
	tion. The just-in-time (JIT) optimization that is described in the
	pcrejit documentation is compatible with these functions.

An alternative algorithm is provided by the pcre_dfa_exec() function;	An alternative algorithm is provided by the pcre_dfa_exec() and
this operates in a different way, and is not Perl-compatible. It has	pcre16_dfa_exec() functions; they operate in a different way, and are
advantages and disadvantages compared with the standard algorithm, and	not Perl-compatible. This alternative has advantages and disadvantages
these are described below.	compared with the standard algorithm, and these are described below.

When there is only one possible way in which a given subject string can	When there is only one possible way in which a given subject string can
match a pattern, the two algorithms give the same answer. A difference	match a pattern, the two algorithms give the same answer. A difference
Line 632 THE ALTERNATIVE MATCHING ALGORITHM	Line 1009 THE ALTERNATIVE MATCHING ALGORITHM
6. Callouts are supported, but the value of the capture_top field is	6. Callouts are supported, but the value of the capture_top field is
always 1, and the value of the capture_last field is always -1.	always 1, and the value of the capture_last field is always -1.

7. The \C escape sequence, which (in the standard algorithm) matches a	7. The \C escape sequence, which (in the standard algorithm) always
single byte, even in UTF-8 mode, is not supported in UTF-8 mode,	matches a single data unit, even in UTF-8 or UTF-16 modes, is not sup-
because the alternative algorithm moves through the subject string one	ported in these modes, because the alternative algorithm moves through
character at a time, for all active paths through the tree.	the subject string one character (not data unit) at a time, for all
	active paths through the tree.

8. Except for (FAIL), the backtracking control verbs such as (PRUNE)	8. Except for (FAIL), the backtracking control verbs such as (PRUNE)
are not supported. (*FAIL) is supported, and behaves like a failing	are not supported. (*FAIL) is supported, and behaves like a failing
negative assertion.	negative assertion.


ADVANTAGES OF THE ALTERNATIVE ALGORITHM	ADVANTAGES OF THE ALTERNATIVE ALGORITHM

Using the alternative matching algorithm provides the following advan-	Using the alternative matching algorithm provides the following advan-
tages:	tages:

1. All possible matches (at a single point in the subject) are automat-	1. All possible matches (at a single point in the subject) are automat-
ically found, and in particular, the longest match is found. To find	ically found, and in particular, the longest match is found. To find
more than one match using the standard algorithm, you have to do kludgy	more than one match using the standard algorithm, you have to do kludgy
things with callouts.	things with callouts.

2. Because the alternative algorithm scans the subject string just	2. Because the alternative algorithm scans the subject string just
once, and never needs to backtrack, it is possible to pass very long	once, and never needs to backtrack (except for lookbehinds), it is pos-
subject strings to the matching function in several pieces, checking	sible to pass very long subject strings to the matching function in
for partial matching each time. Although it is possible to do multi-	several pieces, checking for partial matching each time. Although it is
segment matching using the standard algorithm (pcre_exec()), by retain-	possible to do multi-segment matching using the standard algorithm by
ing partially matched substrings, it is more complicated. The pcrepar-	retaining partially matched substrings, it is more complicated. The
tial documentation gives details of partial matching and discusses	pcrepartial documentation gives details of partial matching and dis-
multi-segment matching.	cusses multi-segment matching.


DISADVANTAGES OF THE ALTERNATIVE ALGORITHM	DISADVANTAGES OF THE ALTERNATIVE ALGORITHM

The alternative algorithm suffers from a number of disadvantages:	The alternative algorithm suffers from a number of disadvantages:

1. It is substantially slower than the standard algorithm. This is	1. It is substantially slower than the standard algorithm. This is
partly because it has to search for all possible matches, but is also	partly because it has to search for all possible matches, but is also
because it is less susceptible to optimization.	because it is less susceptible to optimization.

2. Capturing parentheses and back references are not supported.	2. Capturing parentheses and back references are not supported.
Line 685 AUTHOR	Line 1063 AUTHOR

REVISION	REVISION

Last updated: 19 November 2011	Last updated: 08 January 2012
Copyright (c) 1997-2010 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------


Line 696 PCREAPI(3)	Line 1074 PCREAPI(3)
NAME	NAME
PCRE - Perl-compatible regular expressions	PCRE - Perl-compatible regular expressions

	#include <pcre.h>


PCRE NATIVE API BASIC FUNCTIONS	PCRE NATIVE API BASIC FUNCTIONS

#include <pcre.h>

pcre pcre_compile(const char pattern, int options,	pcre pcre_compile(const char pattern, int options,
const char *errptr, int erroffset,	const char *errptr, int erroffset,
const unsigned char *tableptr);	const unsigned char *tableptr);
Line 719 PCRE NATIVE API BASIC FUNCTIONS	Line 1097 PCRE NATIVE API BASIC FUNCTIONS
const char *subject, int length, int startoffset,	const char *subject, int length, int startoffset,
int options, int *ovector, int ovecsize);	int options, int *ovector, int ovecsize);


PCRE NATIVE API AUXILIARY FUNCTIONS

pcre_jit_stack *pcre_jit_stack_alloc(int startsize, int maxsize);

void pcre_jit_stack_free(pcre_jit_stack *stack);

void pcre_assign_jit_stack(pcre_extra *extra,
pcre_jit_callback callback, void *data);

int pcre_dfa_exec(const pcre code, const pcre_extra extra,	int pcre_dfa_exec(const pcre code, const pcre_extra extra,
const char *subject, int length, int startoffset,	const char *subject, int length, int startoffset,
int options, int *ovector, int ovecsize,	int options, int *ovector, int ovecsize,
int *workspace, int wscount);	int *workspace, int wscount);


	PCRE NATIVE API STRING EXTRACTION FUNCTIONS

int pcre_copy_named_substring(const pcre *code,	int pcre_copy_named_substring(const pcre *code,
const char subject, int ovector,	const char subject, int ovector,
int stringcount, const char *stringname,	int stringcount, const char *stringname,
Line 765 PCRE NATIVE API AUXILIARY FUNCTIONS	Line 1136 PCRE NATIVE API AUXILIARY FUNCTIONS

void pcre_free_substring_list(const char **stringptr);	void pcre_free_substring_list(const char **stringptr);


	PCRE NATIVE API AUXILIARY FUNCTIONS

	pcre_jit_stack *pcre_jit_stack_alloc(int startsize, int maxsize);

	void pcre_jit_stack_free(pcre_jit_stack *stack);

	void pcre_assign_jit_stack(pcre_extra *extra,
	pcre_jit_callback callback, void *data);

const unsigned char *pcre_maketables(void);	const unsigned char *pcre_maketables(void);

int pcre_fullinfo(const pcre code, const pcre_extra extra,	int pcre_fullinfo(const pcre code, const pcre_extra extra,
int what, void *where);	int what, void *where);

int pcre_info(const pcre code, int optptr, int *firstcharptr);

int pcre_refcount(pcre *code, int adjust);	int pcre_refcount(pcre *code, int adjust);

int pcre_config(int what, void *where);	int pcre_config(int what, void *where);

char *pcre_version(void);	const char *pcre_version(void);

	int pcre_pattern_to_host_byte_order(pcre *code,
	pcre_extra extra, const unsigned char tables);


PCRE NATIVE API INDIRECTED FUNCTIONS	PCRE NATIVE API INDIRECTED FUNCTIONS

void (pcre_malloc)(size_t);	void (pcre_malloc)(size_t);
Line 792 PCRE NATIVE API INDIRECTED FUNCTIONS	Line 1174 PCRE NATIVE API INDIRECTED FUNCTIONS
int (pcre_callout)(pcre_callout_block );	int (pcre_callout)(pcre_callout_block );


	PCRE 8-BIT AND 16-BIT LIBRARIES

	From release 8.30, PCRE can be compiled as a library for handling
	16-bit character strings as well as, or instead of, the original
	library that handles 8-bit character strings. To avoid too much compli-
	cation, this document describes the 8-bit versions of the functions,
	with only occasional references to the 16-bit library.

	The 16-bit functions operate in the same way as their 8-bit counter-
	parts; they just use different data types for their arguments and
	results, and their names start with pcre16_ instead of pcre_. For every
	option that has UTF8 in its name (for example, PCRE_UTF8), there is a
	corresponding 16-bit name with UTF8 replaced by UTF16. This facility is
	in fact just cosmetic; the 16-bit option names define the same bit val-
	ues.

	References to bytes and UTF-8 in this document should be read as refer-
	ences to 16-bit data quantities and UTF-16 when using the 16-bit
	library, unless specified otherwise. More details of the specific dif-
	ferences for the 16-bit library are given in the pcre16 page.


PCRE API OVERVIEW	PCRE API OVERVIEW

PCRE has its own native API, which is described in this document. There	PCRE has its own native API, which is described in this document. There
are also some wrapper functions that correspond to the POSIX regular	are also some wrapper functions (for the 8-bit library only) that cor-
expression API, but they do not give access to all the functionality.	respond to the POSIX regular expression API, but they do not give
They are described in the pcreposix documentation. Both of these APIs	access to all the functionality. They are described in the pcreposix
define a set of C function calls. A C++ wrapper is also distributed	documentation. Both of these APIs define a set of C function calls. A
with PCRE. It is documented in the pcrecpp page.	C++ wrapper (again for the 8-bit library only) is also distributed with
	PCRE. It is documented in the pcrecpp page.

The native API C function prototypes are defined in the header file	The native API C function prototypes are defined in the header file
pcre.h, and on Unix systems the library itself is called libpcre. It	pcre.h, and on Unix-like systems the (8-bit) library itself is called
can normally be accessed by adding -lpcre to the command for linking an	libpcre. It can normally be accessed by adding -lpcre to the command
application that uses PCRE. The header file defines the macros	for linking an application that uses PCRE. The header file defines the
PCRE_MAJOR and PCRE_MINOR to contain the major and minor release num-	macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release
bers for the library. Applications can use these to include support	numbers for the library. Applications can use these to include support
for different releases of PCRE.	for different releases of PCRE.

In a Windows environment, if you want to statically link an application	In a Windows environment, if you want to statically link an application
Line 865 PCRE API OVERVIEW	Line 1270 PCRE API OVERVIEW
built are used.	built are used.

The function pcre_fullinfo() is used to find out information about a	The function pcre_fullinfo() is used to find out information about a
compiled pattern; pcre_info() is an obsolete version that returns only	compiled pattern. The function pcre_version() returns a pointer to a
some of the available information, but is retained for backwards com-	string containing the version of PCRE and its date of release.
patibility. The function pcre_version() returns a pointer to a string
containing the version of PCRE and its date of release.

The function pcre_refcount() maintains a reference count in a data	The function pcre_refcount() maintains a reference count in a data
block containing a compiled pattern. This is provided for the benefit	block containing a compiled pattern. This is provided for the benefit
Line 955 SAVING PRECOMPILED PATTERNS FOR LATER USE	Line 1358 SAVING PRECOMPILED PATTERNS FOR LATER USE
The compiled form of a regular expression can be saved and re-used at a	The compiled form of a regular expression can be saved and re-used at a
later time, possibly by a different program, and even on a host other	later time, possibly by a different program, and even on a host other
than the one on which it was compiled. Details are given in the	than the one on which it was compiled. Details are given in the
pcreprecompile documentation. However, compiling a regular expression	pcreprecompile documentation, which includes a description of the
with one version of PCRE for use with a different version is not guar-	pcre_pattern_to_host_byte_order() function. However, compiling a regu-
anteed to work and may cause crashes.	lar expression with one version of PCRE for use with a different ver-
	sion is not guaranteed to work and may cause crashes.


CHECKING BUILD-TIME OPTIONS	CHECKING BUILD-TIME OPTIONS

int pcre_config(int what, void *where);	int pcre_config(int what, void *where);

The function pcre_config() makes it possible for a PCRE client to dis-	The function pcre_config() makes it possible for a PCRE client to dis-
cover which optional features have been compiled into the PCRE library.	cover which optional features have been compiled into the PCRE library.
The pcrebuild documentation has more details about these optional fea-	The pcrebuild documentation has more details about these optional fea-
tures.	tures.

The first argument for pcre_config() is an integer, specifying which	The first argument for pcre_config() is an integer, specifyin The first argument for pcre_config() is an integer, specifyin
information is required; the second argument is a pointer to a variable	information is required; the second argument is a pointer to a variable
into which the information is placed. The following information is	into which the information is placed. The returned value is zero on
	success, or the negative error code PCRE_ERROR_BADOPTION if the value
	in the first argument is not recognized. The following information is
available:	available:

PCRE_CONFIG_UTF8	PCRE_CONFIG_UTF8

The output is an integer that is set to one if UTF-8 support is avail-	The output is an integer that is set to one if UTF-8 support is avail-
able; otherwise it is set to zero.	able; otherwise it is set to zero. If this option is given to the
	16-bit version of this function, pcre16_config(), the result is
	PCRE_ERROR_BADOPTION.

	PCRE_CONFIG_UTF16

	The output is an integer that is set to one if UTF-16 support is avail-
	able; otherwise it is set to zero. This value should normally be given
	to the 16-bit version of this function, pcre16_config(). If it is given
	to the 8-bit version of this function, the result is PCRE_ERROR_BADOP-
	TION.

PCRE_CONFIG_UNICODE_PROPERTIES	PCRE_CONFIG_UNICODE_PROPERTIES

The output is an integer that is set to one if support for Unicode	The output is an integer that is s The output is an integer that is set to one if support for Unicode
character properties is available; otherwise it is set to zero.	character properties is available; otherwise it is set to zero.

PCRE_CONFIG_JIT	PCRE_CONFIG_JIT
Line 989 CHECKING BUILD-TIME OPTIONS	Line 1405 CHECKING BUILD-TIME OPTIONS
The output is an integer that is set to one if support for just-in-time	The output is an integer that is set to one if support for just-in-time
compiling is available; otherwise it is set to zero.	compiling is available; otherwise it is set to zero.

	PCRE_CONFIG_JITTARGET

	The output is a pointer to a zero-terminated "const char *" string. If
	JIT support is available, the string contains the name of the architec-
	ture for which the JIT compiler is configured, for example "x86 32bit
	(little endian + unaligned)". If JIT support is not available, the
	result is NULL.

PCRE_CONFIG_NEWLINE	PCRE_CONFIG_NEWLINE

The output is an integer whose value specifies the default character	The output is an integer whose value specifies the default character
sequence that is recognized as meaning "newline". The four values that	sequence that is recognized as meaning "newline". The four values that
are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,	are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
and -1 for ANY. Though they are derived from ASCII, the same values	and -1 for ANY. Though they are derived from ASCII, the same values
are returned in EBCDIC environments. The default should normally corre-	are returned in EBCDIC environments. The default should normally corre-
spond to the standard sequence for your operating system.	spond to the standard sequence for your operating system.

PCRE_CONFIG_BSR	PCRE_CONFIG_BSR

The output is an integer whose value indicates what character sequences	The output is an integer whose value indicates what character sequences
the \R escape sequence matches by default. A value of 0 means that \R	the \R escape sequence matches by default. A value of 0 means that \R
matches any Unicode line ending sequence; a value of 1 means that \R	matches any Unicode line ending sequence; a value of 1 means that \R
matches only CR, LF, or CRLF. The default can be overridden when a pat-	matches only CR, LF, or CRLF. The default can be overridden when a pat-
tern is compiled or matched.	tern is compiled or matched.

PCRE_CONFIG_LINK_SIZE	PCRE_CONFIG_LINK_SIZE

The output is an integer that contains the number of bytes used for	The output is an integer that contains the number of bytes used for
internal linkage in compiled regular expressions. The value is 2, 3, or	internal linkage in compiled regular expressions. For the 8-bit
4. Larger values allow larger regular expressions to be compiled, at	library, the value can be 2, 3, or 4. For the 16-bit library, the value
the expense of slower matching. The default value of 2 is sufficient	is either 2 or 4 and is still a number of bytes. The default value of 2
for all but the most massive patterns, since it allows the compiled	is sufficient for all but the most massive patterns, since it allows
pattern to be up to 64K in size.	the compiled pattern to be up to 64K in size. Larger values allow
	larger regular expressions to be compiled, at the expense of slower
	matching.

PCRE_CONFIG_POSIX_MALLOC_THRESHOLD	PCRE_CONFIG_POSIX_MALLOC_THRESHOLD

The output is an integer that contains the threshold above which the	The output is an integer that contains the threshold above which the
POSIX interface uses malloc() for output vectors. Further details are	POSIX interface uses malloc() for output vectors. Further details are
given in the pcreposix documentation.	given in the pcreposix documentation.

PCRE_CONFIG_MATCH_LIMIT	PCRE_CONFIG_MATCH_LIMIT

The output is a long integer that gives the default limit for the num-	The output is a long integer that gives the default limit for the num-
ber of internal matching function calls in a pcre_exec() execution.	ber of internal matching function calls in a pcre_exec() execution.
Further details are given with pcre_exec() below.	Further details are given with pcre_exec() below.

PCRE_CONFIG_MATCH_LIMIT_RECURSION	PCRE_CONFIG_MATCH_LIMIT_RECURSION

The output is a long integer that gives the default limit for the depth	The output is a long integer that gives the default limit for the depth
of recursion when calling the internal matching function in a	of recursion when calling the internal matching function in a
pcre_exec() execution. Further details are given with pcre_exec()	pcre_exec() execution. Further details are given with pcre_exec()
below.	below.

PCRE_CONFIG_STACKRECURSE	PCRE_CONFIG_STACKRECURSE

The output is an integer that is set to one if internal recursion when	The output is an integer that is set to one if internal recursion when
running pcre_exec() is implemented by recursive function calls that use	running pcre_exec() is implemented by recursive function calls that use
the stack to remember their state. This is the usual way that PCRE is	the stack to remember their state. This is the usual way that PCRE is
compiled. The output is zero if PCRE was compiled to use blocks of data	compiled. The output is zero if PCRE was compiled to use blocks of data
on the heap instead of recursive function calls. In this case,	on the heap instead of recursive function calls. In this case,
pcre_stack_malloc and pcre_stack_free are called to manage memory	pcre_stack_malloc and pcre_stack_free are called to manage memory
blocks on the heap, thus avoiding the use of the stack.	blocks on the heap, thus avoiding the use of the stack.


Line 1058 COMPILING A PATTERN	Line 1484 COMPILING A PATTERN

Either of the functions pcre_compile() or pcre_compile2() can be called	Either of the functions pcre_compile() or pcre_compile2() can be called
to compile a pattern into an internal form. The only difference between	to compile a pattern into an internal form. The only difference between
the two interfaces is that pcre_compile2() has an additional argument,	the two interfaces is that pcre_compile2() has an additional argument,
errorcodeptr, via which a numerical error code can be returned. To	errorcodeptr, via which a numerical error code can be returned. To
avoid too much repetition, we refer just to pcre_compile() below, but	avoid too much repetition, we refer just to pcre_compile() below, but
the information applies equally to pcre_compile2().	the information applies equally to pcre_compile2().

The pattern is a C string terminated by a binary zero, and is passed in	The pattern is a C string terminated by a binary zero, and is passed in
the pattern argument. A pointer to a single block of memory that is	the pattern argument. A pointer to a single block of memory that is
obtained via pcre_malloc is returned. This contains the compiled code	obtained via pcre_malloc is returned. This contains the compiled code
and related data. The pcre type is defined for the returned block; this	and related data. The pcre type is defined for the returned block; this
is a typedef for a structure whose contents are not externally defined.	is a typedef for a structure whose contents are not externally defined.
It is up to the caller to free the memory (via pcre_free) when it is no	It is up to the caller to free the memory (via pcre_free) when it is no
longer required.	longer required.

Although the compiled code of a PCRE regex is relocatable, that is, it	Although the compiled code of a PCRE regex is relocatable, that is, it
does not depend on memory location, the complete pcre data block is not	does not depend on memory location, the complete pcre data block is not
fully relocatable, because it may contain a copy of the tableptr argu-	fully relocatable, because it may contain a copy of the tableptr argu-
ment, which is an address (see below).	ment, which is an address (see below).

The options argument contains various bit settings that affect the com-	The options argument contains various bit settings that affect the com-
pilation. It should be zero if no options are required. The available	pilation. It should be zero if no options are required. The available
options are described below. Some of them (in particular, those that	options are described below. Some of them (in particular, those that
are compatible with Perl, but some others as well) can also be set and	are compatible with Perl, but some others as well) can also be set and
unset from within the pattern (see the detailed description in the	unset from within the pattern (see the detailed description in the
pcrepattern documentation). For those options that can be different in	pcrepattern documentation). For those options that can be different in
different parts of the pattern, the contents of the options argument	different parts of the pattern, the contents of the options argument
specifies their settings at the start of compilation and execution. The	specifies their settings at the start of compilation and execution. The
PCRE_ANCHORED, PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK, and	PCRE_ANCHORED, PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK, and
PCRE_NO_START_OPT options can be set at the time of matching as well as	PCRE_NO_START_OPT options can be set at the time of matching as well as
at compile time.	at compile time.

If errptr is NULL, pcre_compile() returns NULL immediately. Otherwise,	If errptr is NULL, pcre_compile() returns NULL immediately. Otherwise,
if compilation of a pattern fails, pcre_compile() returns NULL, and	if compilation of a pattern fails, pcre_compile() retur if compilation of a pattern fails, pcre_compile() retur
sets the variable pointed to by errptr to point to a textual error mes-	sets the variable pointed to by errptr to point to a textual error mes-
sage. This is a static string that is part of the library. You must not	sage. This is a static string that is part of the library. You must not
try to free it. Normally, the offset from the start of the pattern to	try to free it. Normally, the offset from the start of the pattern to
the byte that was being processed when the error was discovered is	the byte that was being processed when the error was discovered is
placed in the variable pointed to by erroffset, which must not be NULL	placed in the variable pointed to by erroffset, which must not be NULL
(if it is, an immediate error is given). However, for an invalid UTF-8	(if it is, an immediate error is given). However, for an invalid UTF-8
string, the offset is that of the first byte of the failing character.	string, the offset is that of the first byte of the failing character.
Also, some errors are not detected until checks are carried out when
the whole pattern has been scanned; in these cases the offset passed
back is the length of the pattern.

	Some errors are not detected until the whole pattern has been scanned;
	in these cases, the offset passed back is the length of the pattern.
Note that the offset is in bytes, not characters, even in UTF-8 mode.	Note that the offset is in bytes, not characters, even in UTF-8 mode.
It may sometimes point into the middle of a UTF-8 character.	It may sometimes point into the middle of a UTF-8 character.

Line 1303 COMPILING A PATTERN	Line 1728 COMPILING A PATTERN
recognized. The Unicode newline sequences are the three just mentioned,	recognized. The Unicode newline sequences are the three just mentioned,
plus the single characters VT (vertical tab, U+000B), FF (formfeed,	plus the single characters VT (vertical tab, U+000B), FF (formfeed,
U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS	U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS
(paragraph separator, U+2029). The last two are recognized only in	(paragraph separator, U+2029). For the 8-bit library, the last two are
UTF-8 mode.	recognized only in UTF-8 mode.

The newline setting in the options word uses three bits that are	The newline setting in the options word uses three bits that are
treated as a number, giving eight possibilities. Currently only six are	treated as a number, giving eight possibilities. Currently only six are
Line 1361 COMPILING A PATTERN	Line 1786 COMPILING A PATTERN
PCRE_UTF8	PCRE_UTF8

This option causes PCRE to regard both the pattern and the subject as	This option causes PCRE to regard both the pattern and the subject as
strings of UTF-8 characters instead of single-byte character strings.	strings of UTF-8 characters instead of single-byte strings. However, it
However, it is available only when PCRE is built to include UTF-8 sup-	is available only when PCRE is built to include UTF support. If not,
port. If not, the use of this option provokes an error. Details of how	the use of this option provokes an error. Details of how this option
this option changes the behaviour of PCRE are given in the pcreunicode	changes the behaviour of PCRE are given in the pcreunicode page.
page.

PCRE_NO_UTF8_CHECK	PCRE_NO_UTF8_CHECK

When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is	When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
automatically checked. There is a discussion about the validity of	automatically checked. There is a discussion about the validity of
UTF-8 strings in the main pcre page. If an invalid UTF-8 sequence of	UTF-8 strings in the pcreunicode page. If an invalid UTF-8 sequence is
bytes is found, pcre_compile() returns an error. If you already know	found, pcre_compile() returns an error. If you already know that your
that your pattern is valid, and you want to skip this check for perfor-	pattern is valid, and you want to skip this check for performance rea-
mance reasons, you can set the PCRE_NO_UTF8_CHECK option. When it is	sons, you can set the PCRE_NO_UTF8_CHECK option. When it is set, the
set, the effect of passing an invalid UTF-8 string as a pattern is	effect of passing an invalid UTF-8 string as a pattern is undefined. It
undefined. It may cause your program to crash. Note that this option	may cause your program to crash. Note that this option can also be
can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the	passed to pcre_exec() and pcre_dfa_exec(), to suppress the validity
UTF-8 validity checking of subject strings.	checking of subject strings.


COMPILATION ERROR CODES	COMPILATION ERROR CODES

The following table lists the error codes than may be returned by	The following table lists the error codes than may be returned by
pcre_compile2(), along with the error messages that may be returned by	pcre_compile2(), along with the error messages that may be returned by
both compiling functions. As PCRE has developed, some error codes have	both compiling functions. Note that error messages are always 8-bit
fallen out of use. To avoid confusion, they have not been re-used.	ASCII strings, even in 16-bit mode. As PCRE has developed, some error
	codes have fallen out of use. To avoid confusion, they have not been
	re-used.

0 no error	0 no error
1 \ at end of pattern	1 \ at end of pattern
Line 1420 COMPILATION ERROR CODES	Line 1846 COMPILATION ERROR CODES
29 (?R or (?[+-]digits must be followed by )	29 (?R or (?[+-]digits must be followed by )
30 unknown POSIX class name	30 unknown POSIX class name
31 POSIX collating elements are not supported	31 POSIX collating elements are not supported
32 this version of PCRE is not compiled with PCRE_UTF8 support	32 this version of PCRE is compiled without UTF support
33 [this code is not in use]	33 [this code is not in use]
34 character value in \x{...} sequence is too large	34 character value in \x{...} sequence is too large
35 invalid condition (?(0)	35 invalid condition (?(0)
Line 1432 COMPILATION ERROR CODES	Line 1858 COMPILATION ERROR CODES
41 unrecognized character after (?P	41 unrecognized character after (?P
42 syntax error in subpattern name (missing terminator)	42 syntax error in subpattern name (missing terminator)
43 two named subpatterns have the same name	43 two named subpatterns have the same name
44 invalid UTF-8 string	44 invalid UTF-8 string (specifically UTF-8)
45 support for \P, \p, and \X has not been compiled	45 support for \P, \p, and \X has not been compiled
46 malformed \P or \p sequence	46 malformed \P or \p sequence
47 unknown property name after \P or \p	47 unknown property name after \P or \p
48 subpattern name is too long (maximum 32 characters)	48 subpattern name is too long (maximum 32 characters)
49 too many named subpatterns (maximum 10000)	49 too many named subpatterns (maximum 10000)
50 [this code is not in use]	50 [this code is not in use]
51 octal value is greater than \377 (not in UTF-8 mode)	51 octal value is greater than \377 in 8-bit non-UTF-8 mode
52 internal error: overran compiling workspace	52 internal error: overran compiling workspace
53 internal error: previously-checked referenced subpattern	53 internal error: previously-checked referenced subpattern
not found	not found
Line 1458 COMPILATION ERROR CODES	Line 1884 COMPILATION ERROR CODES
65 different names for subpatterns of the same number are	65 different names for subpatterns of the same number are
not allowed	not allowed
66 (*MARK) must have an argument	66 (*MARK) must have an argument
67 this version of PCRE is not compiled with PCRE_UCP support	67 this version of PCRE is not compiled with Unicode property
	support
68 \c must be followed by an ASCII character	68 \c must be followed by an ASCII character
69 \k is not followed by a braced, angle-bracketed, or quoted name	69 \k is not followed by a braced, angle-bracketed, or quoted name
	70 internal error: unknown opcode in find_fixedlength()
	71 \N is not supported in a class
	72 too many forward references
	73 disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
	74 invalid UTF-16 string (specifically UTF-16)

The numbers 32 and 10000 in errors 48 and 49 are defaults; different	The numbers 32 and 10000 in errors 48 and 49 are defaults; different
values may be used if the limits were changed when PCRE was built.	values may be used if the limits were changed when PCRE was built.


Line 1471 STUDYING A PATTERN	Line 1903 STUDYING A PATTERN
pcre_extra pcre_study(const pcre code, int options	pcre_extra pcre_study(const pcre code, int options
const char **errptr);	const char **errptr);

If a compiled pattern is going to be used several times, it is worth	If a compiled pattern is going to be used several times, it is worth
spending more time analyzing it in order to speed up the time taken for	spending more time analyzing it in order to speed up the time taken for
matching. The function pcre_study() takes a pointer to a compiled pat-	matching. The function pcre_study() takes a pointer to a compiled pat-
tern as its first argument. If studying the pattern produces additional	tern as its first argument. If studying the pattern produces additional
information that will help speed up matching, pcre_study() returns a	information that will help speed up matching, pcre_study() returns a
pointer to a pcre_extra block, in which the study_data field points to	pointer to a pcre_extra block, in which the study_data field points to
the results of the study.	the results of the study.

The returned value from pcre_study() can be passed directly to	The returned value from pcre_study() can be passed directly to
pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block also con-	pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block also con-
tains other fields that can be set by the caller before the block is	tains other fields that can be set by the caller before the block is
passed; these are described below in the section on matching a pattern.	passed; these are described below in the section on matching a pattern.

If studying the pattern does not produce any useful information,	If studying the pattern does not produce any useful information,
pcre_study() returns NULL. In that circumstance, if the calling program	pcre_study() returns NULL. In that circumstance, if the calling program
wants to pass any of the other fields to pcre_exec() or	wants to pass any of the other fields to pcre_exec() or
pcre_dfa_exec(), it must set up its own pcre_extra block.	pcre_dfa_exec(), it must set up its own pcre_extra block.

The second argument of pcre_study() contains option bits. There is only	The second argument of pcre_study() contains option bits. There is only
one option: PCRE_STUDY_JIT_COMPILE. If this is set, and the just-in-	one option: PCRE_STUDY_JIT_COMPILE. If this is set, and the just-in-
time compiler is available, the pattern is further compiled into	time compiler is available, the pattern is further compiled into
machine code that executes much faster than the pcre_exec() matching	machine code that executes much faster than the pcre_exec() matching
function. If the just-in-time compiler is not available, this option is	function. If the just-in-time compiler is not available, this option is
ignored. All other bits in the options argument must be zero.	ignored. All other bits in the options argument must be zero.

JIT compilation is a heavyweight optimization. It can take some time	JIT compilation is a heavyweight optimization. It can take some time
for patterns to be analyzed, and for one-off matches and simple pat-	for patterns to be analyzed, and for one-off matches and simple pat-
terns the benefit of faster execution might be offset by a much slower	terns the benefit of faster execution might be offset by a much slower
study time. Not all patterns can be optimized by the JIT compiler. For	study time. Not all patterns can be optimized by the JIT compiler. For
those that cannot be handled, matching automatically falls back to the	those that cannot be handled, matching automatically falls back to the
pcre_exec() interpreter. For more details, see the pcrejit documenta-	pcre_exec() interpreter. For more details, see the pcrejit documenta-
tion.	tion.

The third argument for pcre_study() is a pointer for an error message.	The third argument for pcre_study() is a pointer for an error message.
If studying succeeds (even if no data is returned), the variable it	If studying succeeds (even if no data is returned), the variable it
points to is set to NULL. Otherwise it is set to point to a textual	points to is set to NULL. Otherwise it is set to point to a textual
error message. This is a static string that is part of the library. You	error message. This is a static string that is part of the library. You
must not try to free it. You should test the error pointer for NULL	must not try to free it. You should test the error pointer for NULL
after calling pcre_study(), to be sure that it has run successfully.	after calling pcre_study(), to be sure that it has run successfully.

When you are finished with a pattern, you can free the memory used for	When you are finished with a pattern, you can free the memory used for
the study data by calling pcre_free_study(). This function was added to	the study data by calling pcre_free_study(). This function was added to
the API for release 8.20. For earlier versions, the memory could be	the API for release 8.20. For earlier versions, the memory could be
freed with pcre_free(), just like the pattern itself. This will still	freed with pcre_free(), just like the pattern itself. This will still
work in cases where PCRE_STUDY_JIT_COMPILE is not used, but it is	work in cases where PCRE_STUDY_JIT_COMPILE is not used, but it is
advisable to change to the new function when convenient.	advisable to change to the new function when convenient.

This is a typical way in which pcre_study() is used (except that in a	This is a typical way in which pcre_study() is used (except that in a
real application there should be tests for errors):	real application there should be tests for errors):

int rc;	int rc;
Line 1538 STUDYING A PATTERN	Line 1970 STUDYING A PATTERN
Studying a pattern does two things: first, a lower bound for the length	Studying a pattern does two things: first, a lower bound for the length
of subject string that is needed to match the pattern is computed. This	of subject string that is needed to match the pattern is computed. This
does not mean that there are any strings of that length that match, but	does not mean that there are any strings of that length that match, but
it does guarantee that no shorter strings match. The value is used by	it does guarantee that no shorter strings match. The value is used by
pcre_exec() and pcre_dfa_exec() to avoid wasting time by trying to	pcre_exec() and pcre_dfa_exec() to avoid wasting time by trying to
match strings that are shorter than the lower bound. You can find out	match strings that are shorter than the lower bound. You can find out
the value in a calling program via the pcre_fullinfo() function.	the value in a calling program via the pcre_fullinfo() function.

Studying a pattern is also useful for non-anchored patterns that do not	Studying a pattern is also useful for non-anchored patterns that do not
have a single fixed starting character. A bitmap of possible starting	have a single fixed starting character. A bitmap of possible starting
bytes is created. This speeds up finding a position in the subject at	bytes is created. This speeds up finding a position in the subject at
which to start matching.	which to start matching. (In 16-bit mode, the bitmap is used for 16-bit
	values less than 256.)

These two optimizations apply to both pcre_exec() and pcre_dfa_exec().	These two optimizations apply to both pcre_exec() and pcre_dfa_exec().
However, they are not used by pcre_exec() if pcre_study() is called	However, they are not used by pcre_exec() if pcre_study() is called
Line 1623 INFORMATION ABOUT A PATTERN	Line 2056 INFORMATION ABOUT A PATTERN
int what, void *where);	int what, void *where);

The pcre_fullinfo() function returns information about a compiled pat-	The pcre_fullinfo() function returns information about a compiled pat-
tern. It replaces the obsolete pcre_info() function, which is neverthe-	tern. It replaces the pcre_info() function, which was removed from the
less retained for backwards compability (and is documented below).	library at version 8.30, after more than 10 years of obsolescence.

The first argument for pcre_fullinfo() is a pointer to the compiled	The first argument for pcre_fullinfo() is a pointer to the compiled
pattern. The second argument is the result of pcre_study(), or NULL if	pattern. The second argument is the result of pcre_study(), or NULL if
Line 1633 INFORMATION ABOUT A PATTERN	Line 2066 INFORMATION ABOUT A PATTERN
variable to receive the data. The yield of the function is zero for	variable to receive the data. The yield of the function is zero for
success, or one of the following negative numbers:	success, or one of the following negative numbers:

PCRE_ERROR_NULL the argument code was NULL	PCRE_ERROR_NULL the argument code was NULL
the argument where was NULL	the argument where was NULL
PCRE_ERROR_BADMAGIC the "magic number" was not found	PCRE_ERROR_BADMAGIC the "magic number" was not found
PCRE_ERROR_BADOPTION the value of what was invalid	PCRE_ERROR_BADENDIANNESS the pattern was compiled with different
	endianness
	PCRE_ERROR_BADOPTION the value of what was invalid

The "magic number" is placed at the start of each compiled pattern as	The "magic number" is placed at the start of each compiled pattern as
an simple check against passing an arbitrary memory pointer. Here is a	an simple check against passing an arbitrary memory pointer. The endi-
typical call of pcre_fullinfo(), to obtain the length of the compiled	anness error can occur if a compiled pattern is saved and reloaded on a
pattern:	different host. Here is a typical call of pcre_fullinfo(), to obtain
	the length of the compiled pattern:

int rc;	int rc;
size_t length;	size_t length;
Line 1651 INFORMATION ABOUT A PATTERN	Line 2087 INFORMATION ABOUT A PATTERN
PCRE_INFO_SIZE, /* what is required */	PCRE_INFO_SIZE, /* what is required */
&length); /* where to put the data */	&length); /* where to put the data */

The possible values for the third argument are defined in pcre.h, and	The possible values for the third argument are defined The possible values for the third argument are defined in pcre.h, and
are as follows:	are as follows:

PCRE_INFO_BACKREFMAX	PCRE_INFO_BACKREFMAX

Return the number of the highest back reference in the pattern. The	Return the number of the highest back reference in the pattern. The
fourth argument should point to an int variable. Zero is returned if	fourth argument should point to an int variable. Zero is returned if
there are no back references.	there are no back references.

PCRE_INFO_CAPTURECOUNT	PCRE_INFO_CAPTURECOUNT

Return the number of capturing subpatterns in the pattern. The fourth	Return the number of capturing subpatterns in the pattern. The fourth
argument should point to an int variable.	argument should point to an int variable.

PCRE_INFO_DEFAULT_TABLES	PCRE_INFO_DEFAULT_TABLES

Return a pointer to the internal default character tables within PCRE.	Return a pointer to the internal default character tables within PCRE.
The fourth argument should point to an unsigned char * variable. This	The fourth argument should point to an unsigned char * variable. This
information call is provided for internal use by the pcre_study() func-	information call is provided for internal use by the pcre_study() func-
tion. External callers can cause PCRE to use its internal tables by	tion. External callers can cause PCRE to use its internal tables by
passing a NULL table pointer.	passing a NULL table pointer.

PCRE_INFO_FIRSTBYTE	PCRE_INFO_FIRSTBYTE

Return information about the first byte of any matched string, for a	Return information about the first data unit of any matched string, for
non-anchored pattern. The fourth argument should point to an int vari-	a non-anchored pattern. (The name of this option refers to the 8-bit
able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old name	library, where data units are bytes.) The fourth argument should point
is still recognized for backwards compatibility.)	to an int variable.

If there is a fixed first byte, for example, from a pattern such as	If there is a fixed first value, for example, the letter "c" from a
(cat\|cow\|coyote), its value is returned. Otherwise, if either	pattern such as (cat\|cow\|coyote), its value is returned. In the 8-bit
	library, the value is always less than 256; in the 16-bit library the
	value can be up to 0xffff.

(a) the pattern was compiled with the PCRE_MULTILINE option, and every	branch starts with "^", or

	(a) the pattern was compiled with the PCRE_MULTILINE option, and every
branch starts with "^", or	branch starts with "^", or

(b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not	(b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
set (if it were set, the pattern would be anchored),	set (if it were set, the pattern would be anchored),

-1 is returned, indicating that the pattern matches only at the start	-1 is returned, indicating that the pattern matches only at the start
of a subject string or after any newline within the string. Otherwise	of a subject string or after any newline within the string. Otherwise
-2 is returned. For anchored patterns, -2 is returned.	-2 is returned. For anchored patterns, -2 is returned.

PCRE_INFO_FIRSTTABLE	PCRE_INFO_FIRSTTABLE

If the pattern was studied, and this resulted in the construction of a	If the pattern was studied, and this resulted in the construction of a
256-bit table indicating a fixed set of bytes for the first byte in any	256-bit table indicating a fixed set of values for the first data unit
matching string, a pointer to the table is returned. Otherwise NULL is	in any matching string, a pointer to the table is returned. Otherwise
returned. The fourth argument should point to an unsigned char * vari-	NULL is returned. The fourth argument should point to an unsigned char
able.	* variable.

PCRE_INFO_HASCRORLF	PCRE_INFO_HASCRORLF

Return 1 if the pattern contains any explicit matches for CR or LF	Return 1 if the pattern contains any explicit matches for CR or LF
characters, otherwise 0. The fourth argument should point to an int	characters, otherwise 0. The fourth argument should point to an int
variable. An explicit match is either a literal CR or LF character, or	variable. An explicit match is either a literal CR or LF character, or
\r or \n.	\r or \n.

PCRE_INFO_JCHANGED	PCRE_INFO_JCHANGED

Return 1 if the (?J) or (?-J) option setting is used in the pattern,	Return 1 if the (?J) or (?-J) option setting is used in the pattern,
otherwise 0. The fourth argument should point to an int variable. (?J)	otherwise 0. The fourth argument should point to an int variable. (?J)
and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.	and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.

PCRE_INFO_JIT	PCRE_INFO_JIT

Return 1 if the pattern was studied with the PCRE_STUDY_JIT_COMPILE	Return 1 if the pattern was studied with the PCRE_STUDY_JIT_COMPILE
option, and just-in-time compiling was successful. The fourth argument	option, and just-in-time compiling was successful. The fourth argument
should point to an int variable. A return value of 0 means that JIT	should point to an int variable. A return value of 0 means that JIT
support is not available in this version of PCRE, or that the pattern	support is not available in this version of PCRE, or that the pattern
was not studied with the PCRE_STUDY_JIT_COMPILE option, or that the JIT	was not studied with the PCRE_STUDY_JIT_COMPILE option, or that the JIT
compiler could not handle this particular pattern. See the pcrejit doc-	compiler could not handle this particular pattern. See the pcrejit doc-
umentation for details of what can and cannot be handled.	umentation for details of what can and cannot be handled.
Line 1727 INFORMATION ABOUT A PATTERN	Line 2167 INFORMATION ABOUT A PATTERN
PCRE_INFO_JITSIZE	PCRE_INFO_JITSIZE

If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE	If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE
option, return the size of the JIT compiled code, otherwise return	option, return the size of the JIT compiled code, otherwise return
zero. The fourth argument should point to a size_t variable.	zero. The fourth argument should point to a size_t variable.

PCRE_INFO_LASTLITERAL	PCRE_INFO_LASTLITERAL

Return the value of the rightmost literal byte that must exist in any	Return the value of the rightmost literal data unit that must exist in
matched string, other than at its start, if such a byte has been	any matched string, other than at its start, if such a value has been
recorded. The fourth argument should point to an int variable. If there	recorded. The fourth argument should point to an int variable. If there
is no such byte, -1 is returned. For anchored patterns, a last literal	is no such value, -1 is returned. For anchored patterns, a last literal
byte is recorded only if it follows something of variable length. For	value is recorded only if it follows something of variable length. For
example, for the pattern /^a\d+z\d+/ the returned value is "z", but for	example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
/^a\dz\d/ the returned value is -1.	/^a\dz\d/ the returned value is -1.

PCRE_INFO_MINLENGTH	PCRE_INFO_MINLENGTH

If the pattern was studied and a minimum length for matching subject	If the pattern was studied and a minimum length for matching subject
strings was computed, its value is returned. Otherwise the returned	strings was computed, its value is returned. Otherwise the returned
value is -1. The value is a number of characters, not bytes (this may	value is -1. The value is a number of characters, which in UTF-8 mode
be relevant in UTF-8 mode). The fourth argument should point to an int	may be different from the number of bytes. The fourth argument should
variable. A non-negative value is a lower bound to the length of any	point to an int variable. A non-negative value is a lower bound to the
matching string. There may not be any strings of that length that do	length of any matching string. There may not be any strings of that
actually match, but every string that does match is at least that long.	length that do actually match, but every string that does match is at
	least that long.

PCRE_INFO_NAMECOUNT	PCRE_INFO_NAMECOUNT
PCRE_INFO_NAMEENTRYSIZE	PCRE_INFO_NAMEENTRYSIZE
Line 1768 INFORMATION ABOUT A PATTERN	Line 2209 INFORMATION ABOUT A PATTERN
gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size	gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
of each entry; both of these return an int value. The entry size	of each entry; both of these return an int value. The entry size
depends on the length of the longest name. PCRE_INFO_NAMETABLE returns	depends on the length of the longest name. PCRE_INFO_NAMETABLE returns
a pointer to the first entry of the table (a pointer to char). The	a pointer to the first entry of the table. This is a pointer to char in
first two bytes of each entry are the number of the capturing parenthe-	the 8-bit library, where the first two bytes of each entry are the num-
sis, most significant byte first. The rest of the entry is the corre-	ber of the capturing parenthesis, most significant byte first. In the
sponding name, zero terminated.	16-bit library, the pointer points to 16-bit data units, the first of
	which contains the parenthesis number. The rest of the entry is the
	corresponding name, zero terminated.

The names are in alphabetical order. Duplicate names may appear if (?\|	The names are in alphabetical order. Duplicate names may appear if (?\|
is used to create multiple groups with the same number, as described in	is used to create multiple groups with the same number, as described in
Line 1784 INFORMATION ABOUT A PATTERN	Line 2227 INFORMATION ABOUT A PATTERN
terns may have lower numbers.	terns may have lower numbers.

As a simple example of the name/number table, consider the following	As a simple example of the name/number table, consider the following
pattern (assume PCRE_EXTENDED is set, so white space - including new-	pattern after compilation by the 8-bit library (assume PCRE_EXTENDED is
lines - is ignored):	set, so white space - including newlines - is ignored):

(?<date> (?<year>(\d\d)?\d\d) -	(?<date> (?<year>(\d\d)?\d\d) -
(?<month>\d\d) - (?<day>\d\d) )	(?<month>\d\d) - (?<day>\d\d) )
Line 1838 INFORMATION ABOUT A PATTERN	Line 2281 INFORMATION ABOUT A PATTERN

PCRE_INFO_SIZE	PCRE_INFO_SIZE

Return the size of the compiled pattern. The fourth argument should	Return the size of the compiled pattern in bytes (for both libraries).
point to a size_t variable. This value does not include the size of the	The fourth argument should point to a size_t variable. This value does
pcre structure that is returned by pcre_compile(). The value that is	not include the size of the pcre structure that is returned by
passed as the argument to pcre_malloc() when pcre_compile() is getting	pcre_compile(). The value that is passed as the argument to pcre_mal-
memory in which to place the compiled data is the value returned by	loc() when pcre_compile() is getting memory in which to place the com-
this option plus the size of the pcre structure. Studying a compiled	piled data is the value returned by this option plus the size of the
pattern, with or without JIT, does not alter the value returned by this	pcre structure. Studying a compiled pattern, with or without JIT, does
option.	not alter the value returned by this option.

PCRE_INFO_STUDYSIZE	PCRE_INFO_STUDYSIZE

Return the size of the data block pointed to by the study_data field in	Return the size in bytes of the data block pointed to by the study_data
a pcre_extra block. If pcre_extra is NULL, or there is no study data,	field in a pcre_extra block. If pcre_extra is NULL, or there is no
zero is returned. The fourth argument should point to a size_t vari-	study data, zero is returned. The fourth argument should point to a
able. The study_data field is set by pcre_study() to record informa-	size_t variable. The study_data field is set by pcre_study() to record
tion that will speed up matching (see the section entitled "Studying a	information that will speed up matching (see the section entitled
pattern" above). The format of the study_data block is private, but its	"Studying a pattern" above). The format of the study_data block is pri-
length is made available via this option so that it can be saved and	vate, but its length is made available via this option so that it can
restored (see the pcreprecompile documentation for details).	be saved and restored (see the pcreprecompile documentation for
	details).


OBSOLETE INFO FUNCTION

int pcre_info(const pcre code, int optptr, int *firstcharptr);

The pcre_info() function is now obsolete because its interface is too
restrictive to return all the available data about a compiled pattern.
New programs should use pcre_fullinfo() instead. The yield of
pcre_info() is the number of capturing subpatterns, or one of the fol-
lowing negative numbers:

PCRE_ERROR_NULL the argument code was NULL
PCRE_ERROR_BADMAGIC the "magic number" was not found

If the optptr argument is not NULL, a copy of the options with which
the pattern was compiled is placed in the integer it points to (see
PCRE_INFO_OPTIONS above).

If the pattern is not anchored and the firstcharptr argument is not
NULL, it is used to pass back information about the first character of
any matched string (see PCRE_INFO_FIRSTBYTE above).


REFERENCE COUNTS	REFERENCE COUNTS

int pcre_refcount(pcre *code, int adjust);	int pcre_refcount(pcre *code, int adjust);

The pcre_refcount() function is used to maintain a reference count in	The pcre_refcount() function is used to maintain a reference count in
the data block that contains a compiled pattern. It is provided for the	the data block that contains a compiled pattern. It is provided for the
benefit of applications that operate in an object-oriented manner,	benefit of applications that operate in an object-oriented manner,
where different parts of the application may be using the same compiled	where different parts of the application may be using the same compiled
pattern, but you want to free the block when they are all done.	pattern, but you want to free the block when they are all done.

When a pattern is compiled, the reference count field is initialized to	When a pattern is compiled, the reference count field is initialized to
zero. It is changed only by calling this function, whose action is to	zero. It is changed only by calling this function, whose action is to
add the adjust value (which may be positive or negative) to it. The	add the adjust value (which may be positive or negative) to it. The
yield of the function is the new value. However, the value of the count	yield of the function is the new value. However, the value of the count
is constrained to lie between 0 and 65535, inclusive. If the new value	is constrained to lie between 0 and 65535, inclusive. If the new value
is outside these limits, it is forced to the appropriate limit value.	is outside these limits, it is forced to the appropriate limit value.

Except when it is zero, the reference count is not correctly preserved	Except when it is zero, the reference count is not correctly preserved
if a pattern is compiled on one host and then transferred to a host	if a pattern is compiled on one host and then transferred to a host
whose byte-order is different. (This seems a highly unlikely scenario.)	whose byte-order is different. (This seems a highly unlikely scenario.)


Line 1909 MATCHING A PATTERN: THE TRADITIONAL FUNCTION	Line 2331 MATCHING A PATTERN: THE TRADITIONAL FUNCTION
const char *subject, int length, int startoffset,	const char *subject, int length, int startoffset,
int options, int *ovector, int ovecsize);	int options, int *ovector, int ovecsize);

The function pcre_exec() is called to match a subject string against a	The function pcre_exec() is called to match a subject string against a
compiled pattern, which is passed in the code argument. If the pattern	compiled pattern, which is passed in the code argument. If the pattern
was studied, the result of the study should be passed in the extra	was studied, the result of the study should be passed in the extra
argument. You can call pcre_exec() with the same code and extra argu-	argument. You can call pcre_exec() with the same code and extra argu-
ments as many times as you like, in order to match different subject	ments as many times as you like, in order to match different subject
strings with the same pattern.	strings with the same pattern.

This function is the main matching facility of the library, and it	This function is the main matching facility of the library, and it
operates in a Perl-like manner. For specialist use there is also an	operates in a Perl-like manner. For specialist use there is also an
alternative matching function, which is described below in the section	alternative matching function, which is described below in the section
about the pcre_dfa_exec() function.	about the pcre_dfa_exec() function.

In most applications, the pattern will have been compiled (and option-	In most applications, the pattern will have been compiled (and option-
ally studied) in the same process that calls pcre_exec(). However, it	ally studied) in the same process that calls pcre_exec(). However, it
is possible to save compiled patterns and study data, and then use them	is possible to save compiled patterns and study data, and then use them
later in different processes, possibly even on different hosts. For a	later in different processes, possibly even on different hosts. For a
discussion about this, see the pcreprecompile documentation.	discussion about this, see the pcreprecompile documentation.

Here is an example of a simple call to pcre_exec():	Here is an example of a simple call to pcre_exec():
Line 1943 MATCHING A PATTERN: THE TRADITIONAL FUNCTION	Line 2365 MATCHING A PATTERN: THE TRADITIONAL FUNCTION

Extra data for pcre_exec()	Extra data for pcre_exec()

If the extra argument is not NULL, it must point to a pcre_extra data	If the extra argument is not NULL, it must point to a pcre_extra data
block. The pcre_study() function returns such a block (when it doesn't	block. The pcre_study() function returns such a block (when it doesn't
return NULL), but you can also create one for yourself, and pass addi-	return NULL), but you can also create one for yourself, and pass addi-
tional information in it. The pcre_extra block contains the following	tional information in it. The pcre_extra block contains the following
fields (not necessarily in this order):	fields (not necessarily in this order):

unsigned long int flags;	unsigned long int flags;
Line 1958 MATCHING A PATTERN: THE TRADITIONAL FUNCTION	Line 2380 MATCHING A PATTERN: THE TRADITIONAL FUNCTION
const unsigned char *tables;	const unsigned char *tables;
unsigned char **mark;	unsigned char **mark;

	In the 16-bit version of this structure, the mark field has type
	"PCRE_UCHAR16 **".

The flags field is a bitmap that specifies which of the other fields	The flags field is a bitmap that specifies which of the other fields
are set. The flag bits are:	are set. The flag bits are:

Line 2036 MATCHING A PATTERN: THE TRADITIONAL FUNCTION	Line 2461 MATCHING A PATTERN: THE TRADITIONAL FUNCTION
tion for a discussion of saving compiled patterns for later use.	tion for a discussion of saving compiled patterns for later use.

If PCRE_EXTRA_MARK is set in the flags field, the mark field must be	If PCRE_EXTRA_MARK is set in the flags field, the mark field must be
set to point to a char * variable. If the pattern contains any back-	set to point to a suitable variable. If the pattern contains any back-
tracking control verbs such as (*MARK:NAME), and the execution ends up	tracking control verbs such as (*MARK:NAME), and the execution ends up
with a name to pass back, a pointer to the name string (zero termi-	with a name to pass back, a pointer to the name string (zero termi-
nated) is placed in the variable pointed to by the mark field. The	nated) is placed in the variable pointed to by the mark field. The
names are within the compiled pattern; if you wish to retain such a	names are within the compiled pattern; if you wish to retain such a
name you must copy it before freeing the memory of a compiled pattern.	name you must copy it before freeing the memory of a compiled pattern.
If there is no name to pass back, the variable pointed to by the mark	If there is no name to pass back, the variable pointed to by the mark
field set to NULL. For details of the backtracking control verbs, see	field is set to NULL. For details of the backtracking control verbs,
the section entitled "Backtracking control" in the pcrepattern documen-	see the section entitled "Backtracking control" in the pcrepattern doc-
tation.	umentation.

Option bits for pcre_exec()	Option bits for pcre_exec()

Line 2219 MATCHING A PATTERN: THE TRADITIONAL FUNCTION	Line 2644 MATCHING A PATTERN: THE TRADITIONAL FUNCTION
UTF-8 string is automatically checked when pcre_exec() is subsequently	UTF-8 string is automatically checked when pcre_exec() is subsequently
called. The value of startoffset is also checked to ensure that it	called. The value of startoffset is also checked to ensure that it
points to the start of a UTF-8 character. There is a discussion about	points to the start of a UTF-8 character. There is a discussion about
the validity of UTF-8 strings in the section on UTF-8 support in the	the validity of UTF-8 strings in the pcreunicode page. If an invalid
main pcre page. If an invalid UTF-8 sequence of bytes is found,	sequence of bytes is found, pcre_exec() returns the error
pcre_exec() returns the error PCRE_ERROR_BADUTF8 or, if PCRE_PAR-	PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a
TIAL_HARD is set and the problem is a truncated UTF-8 character at the	truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In
end of the subject, PCRE_ERROR_SHORTUTF8. In both cases, information	both cases, information about the precise nature of the error may also
about the precise nature of the error may also be returned (see the	be returned (see the descriptions of these errors in the section enti-
descriptions of these errors in the section entitled Error return val-	tled Error return values from pcre_exec() below). If startoffset con-
ues from pcre_exec() below). If startoffset contains a value that does	tains a value that does not point to the start of a UTF-8 character (or
not point to the start of a UTF-8 character (or to the end of the sub-	to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned.
ject), PCRE_ERROR_BADUTF8_OFFSET is returned.

If you already know that your subject is valid, and you want to skip	If you already know that your subject is valid, and you want to skip
these checks for performance reasons, you can set the	these checks for performance reasons, you can set the
PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might want to	PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might want to
do this for the second and subsequent calls to pcre_exec() if you are	do this for the second and subsequent calls to pcre_exec() if you are
making repeated calls to find all the matches in a single subject	making repeated calls to find all the matches in a single subject
string. However, you should be sure that the value of startoffset	string. However, you should be sure that the value of startoffset
points to the start of a UTF-8 character (or the end of the subject).	points to the start of a character (or the end of the subject). When
When PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8	PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid string as a
string as a subject or an invalid value of startoffset is undefined.	subject or an invalid value of startoffset is undefined. Your program
Your program may crash.	may crash.

PCRE_PARTIAL_HARD	PCRE_PARTIAL_HARD
PCRE_PARTIAL_SOFT	PCRE_PARTIAL_SOFT

These options turn on the partial matching feature. For backwards com-	These options turn on the partial matching feature. For backwards com-
patibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial	patibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
match occurs if the end of the subject string is reached successfully,	match occurs if the end of the subject string is reached successfully,
but there are not enough subject characters to complete the match. If	but there are not enough subject characters to complete the match. If
this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,	this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
matching continues by testing any remaining alternatives. Only if no	matching continues by testing any remaining alternatives. Only if no
complete match can be found is PCRE_ERROR_PARTIAL returned instead of	complete match can be found is PCRE_ERROR_PARTIAL returned instead of
PCRE_ERROR_NOMATCH. In other words, PCRE_PARTIAL_SOFT says that the	PCRE_ERROR_NOMATCH. In other words, PCRE_PARTIAL_SOFT says that the
caller is prepared to handle a partial match, but only if no complete	caller is prepared to handle a partial match, but only if no complete
match can be found.	match can be found.

If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this	If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this
case, if a partial match is found, pcre_exec() immediately returns	case, if a partial match is found, pcre_exec() immediately returns
PCRE_ERROR_PARTIAL, without considering any other alternatives. In	PCRE_ERROR_PARTIAL, without considering any other alternatives. In
other words, when PCRE_PARTIAL_HARD is set, a partial match is consid-	other words, when PCRE_PARTIAL_HARD is set, a partial match is consid-
ered to be more important that an alternative complete match.	ered to be more important that an alternative complete match.

In both cases, the portion of the string that was inspected when the	In both cases, the portion of the string that was inspected when the
partial match was found is set as the first matching string. There is a	partial match was found is set as the first matching string. There is a
more detailed discussion of partial and multi-segment matching, with	more detailed discussion of partial and multi-segment matching, with
examples, in the pcrepartial documentation.	examples, in the pcrepartial documentation.

The string to be matched by pcre_exec()	The string to be matched by pcre_exec()

The subject string is passed to pcre_exec() as a pointer in subject, a	The subject string is passed to pcre_exec() as a pointer in subject, a
length (in bytes) in length, and a starting byte offset in startoffset.	length in bytes in length, and a starting byte offset in startoffset.
If this is negative or greater than the length of the subject,	If this is negative or greater than the length of the subject,
pcre_exec() returns PCRE_ERROR_BADOFFSET. When the starting offset is	pcre_exec() returns PCRE_ERROR_BADOFFSET. When the starting offset is
zero, the search for a match starts at the beginning of the subject,	zero, the search for a match starts at the beginning of the subject,
and this is by far the most common case. In UTF-8 mode, the byte offset	and this is by far the most common case. In UTF-8 mode, the byte offset
must point to the start of a UTF-8 character (or the end of the sub-	must point to the start of a UTF-8 character (or the end of the sub-
ject). Unlike the pattern string, the subject may contain binary zero	ject). Unlike the pattern string, the subject may contain binary zero
bytes.	bytes.

A non-zero starting offset is useful when searching for another match	A non-zero starting offset is useful when searching for another match
in the same subject by calling pcre_exec() again after a previous suc-	in the same subject by calling pcre_exec() again after a previous suc-
cess. Setting startoffset differs from just passing over a shortened	cess. Setting startoffset differs from just passing over a shortened
string and setting PCRE_NOTBOL in the case of a pattern that begins	string and setting PCRE_NOTBOL in the case of a pattern that begins
with any kind of lookbehind. For example, consider the pattern	with any kind of lookbehind. For example, consider the pattern

\Biss\B	\Biss\B

which finds occurrences of "iss" in the middle of words. (\B matches	which finds occurrences of "iss" in the middle of words. (\B matches
only if the current position in the subject is not a word boundary.)	only if the current position in the subject is not a word boundary.)
When applied to the string "Mississipi" the first call to pcre_exec()	When applied to the string "Mississipi" the first call to pcre_exec()
finds the first occurrence. If pcre_exec() is called again with just	finds the first occurrence. If pcre_exec() is called again with just
the remainder of the subject, namely "issipi", it does not match,	the remainder of the subject, namely "issipi", it does not match,
because \B is always false at the start of the subject, which is deemed	because \B is always false at the start of the subject, which is deemed
to be a word boundary. However, if pcre_exec() is passed the entire	to be a w to be a word boundary. However, if pcre_exec() is passed the entire
string again, but with startoffset set to 4, it finds the second occur-	string again, but with startoffset set to 4, it finds the second occur-
rence of "iss" because it is able to look behind the starting point to	rence of "iss" because it is able to look behind the starting point to
discover that it is preceded by a letter.	discover that it is preceded by a letter.

Finding all the matches in a subject is tricky when the pattern can	Finding all the matches in a subject is tricky when the pattern can
match an empty string. It is possible to emulate Perl's /g behaviour by	match an empty string. It is possible to emulate Perl's /g behaviour by
first trying the match again at the same offset, with the	first trying the match again at the same offset, with the
PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED options, and then if that	PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED options, and then if that
fails, advancing the starting offset and trying an ordinary match	fails, advancing the starting offset and trying an ordinary match
again. There is some code that demonstrates how to do this in the pcre-	again. There is some code that demonstrates how to do this in the pcre-
demo sample program. In the most general case, you have to check to see	demo sample program. In the most general case, you have to check to see
if the newline convention recognizes CRLF as a newline, and if so, and	if the newline convention recognizes CRLF as a newline, and if so, and
the current character is CR followed by LF, advance the starting offset	the current character is CR followed by LF, advance the starting offset
by two characters instead of one.	by two characters instead of one.

If a non-zero starting offset is passed when the pattern is anchored,	If a non-zero starting offset is passed when the pattern is anchored,
one attempt to match at the given offset is made. This can only succeed	one attempt to match at the given offset is made. This can only succeed
if the pattern does not require the match to be at the start of the	if the pattern d if the pattern d
subject.	subject.

How pcre_exec() returns captured substrings	How pcre_exec() returns captured substrings

In general, a pattern matches a certain portion of the subject, and in	In general, a pattern matches a certain portion of the subject, and in
addition, further substrings from the subject may be picked out by	addition, further substrings from the subject may be picked out by
parts of the pattern. Following the usage in Jeffrey Friedl's book,	parts of the pattern. Following the usage in Jeffrey Friedl's book,
this is called "capturing" in what follows, and the phrase "capturing	this is called "capturing" in what follows, and the phrase "capturing
subpattern" is used for a fragment of a pattern that picks out a sub-	subpattern" is used for a fragment of a pattern that picks out a sub-
string. PCRE supports several other kinds of parenthesized subpattern	string. PCRE supports several other kinds of parenthesized subpattern
that do not cause substrings to be captured.	that do not cause substrings to be captured.

Captured substrings are returned to the caller via a vector of integers	Captured substrings are returned to the caller via a vector of integers
whose address is passed in ovector. The number of elements in the vec-	whose address is passed in ovector. The number of elements in the vec-
tor is passed in ovecsize, which must be a non-negative number. Note:	tor is passed in ovecsize, which must be a non-negative number. Note:
this argument is NOT the size of ovector in bytes.	this argument is NOT the size of ovector in bytes.

The first two-thirds of the vector is used to pass back captured sub-	The first two-thirds of the vector is used to pass back captured sub-
strings, each substring using a pair of integers. The remaining third	strings, each substring using a pair of integers. The remaining third
of the vector is used as workspace by pcre_exec() while matching cap-	of the vector is used as workspace by pcre_exec() while matching cap-
turing subpatterns, and is not available for passing back information.	turing subpatterns, and is not available for passing back information.
The number passed in ovecsize should always be a multiple of three. If	The number passed in ovecsize should always be a multiple of three. If
it is not, it is rounded down.	it is not, it is rounded down.

When a match is successful, information about captured substrings is	When a match is successful, information about captured substrings is
returned in pairs of integers, starting at the beginning of ovector,	returned in pairs of integers, starting at the beginning of ovector,
and continuing up to two-thirds of its length at the most. The first	and continuing up to two-thirds of its length at the most. The first
element of each pair is set to the byte offset of the first character	element of each pair is set to the byte offset of the first character
in a substring, and the second is set to the byte offset of the first	in a substring, and the second is set to the byte offset of the first
character after the end of a substring. Note: these values are always	character after the end of a substring. Note: these values are always
byte offsets, even in UTF-8 mode. They are not character counts.	byte offsets, even in UTF-8 mode. They are not character counts.

The first pair of integers, ovector[0] and ovector[1], identify the	The first pair of integers, ovector[0] and ovector[1], identify the
portion of the subject string matched by the entire pattern. The next	portion of the subject string matched by the entire pattern. The next
pair is used for the first capturing subpattern, and so on. The value	pair is used for the first capturing subpattern, and so on. The value
returned by pcre_exec() is one more than the highest numbered pair that	returned by pcre_exec() is one more than the highest numbered pair that
has been set. For example, if two substrings have been captured, the	has been set. For example, if two substrings have been captured, the
returned value is 3. If there are no capturing subpatterns, the return	returned value is 3. If there are no capturing subpatterns, the return
value from a successful match is 1, indicating that just the first pair	value from a successful match is 1, indicating that just the first pair
of offsets has been set.	of offsets has been set.

If a capturing subpattern is matched repeatedly, it is the last portion	If a capturing subpattern is matched repeatedly, it is the last portion
of the string that it matched that is returned.	of the string that it matched that is returned.

If the vector is too small to hold all the captured substring offsets,	If the vector is too small to hold all the captured substring offsets,
it is used as far as possible (up to two-thirds of its length), and the	it is used as far as possible (up to two-thirds of its length), and the
function returns a value of zero. If neither the actual string matched	function returns a value of zero. If neither the actual string matched
not any captured substrings are of interest, pcre_exec() may be called	not any captured substrings are of interest, pcre_exec() may be called
with ovector passed as NULL and ovecsize as zero. However, if the pat-	with ovector passed as NULL and ovecsize as zero. However, if the pat-
tern contains back references and the ovector is not big enough to	tern contains back references and the ovector is not big enough to
remember the related substrings, PCRE has to get additional memory for	remember the related substrings, PCRE has to get additional memory for
use during matching. Thus it is usually advisable to supply an ovector	use during matching. Thus it is usually advisable to supply an ovector
of reasonable size.	of reasonable size.

There are some cases where zero is returned (indicating vector over-	There are some cases where zero is returned (indicating vector over-
flow) when in fact the vector is exactly the right size for the final	flow) when in fact the vector is exactly the right size for the final
match. For example, consider the pattern	match. For example, consider the pattern

(a)(?:(b)c\|bd)	(a)(?:(b)c\|bd)

If a vector of 6 elements (allowing for only 1 captured substring) is	If a vector of 6 elements (allowing for only 1 captured substring) is
given with subject string "abd", pcre_exec() will try to set the second	given with subject string "abd", pcre_exec() will try to set the second
captured string, thereby recording a vector overflow, before failing to	captured string, thereby recording a vector overflow, before failing to
match "c" and backing up to try the second alternative. The zero	match "c" and backing up to try the second alternative. The zero
return, however, does correctly indicate that the maximum number of	return, however, does correctly indicate that the maximum number of
slots (namely 2) have been filled. In similar cases where there is tem-	slots (namely 2) have been filled. In similar cases where there is tem-
porary overflow, but the final number of used slots is actually less	porary overflow, but the final number of used slots is actually less
than the maximum, a non-zero value is returned.	than the maximum, a non-zero value is returned.

The pcre_fullinfo() function can be used to find out how many capturing	The pcre_fullinfo() function can be used to find out how many capturing
subpatterns there are in a compiled pattern. The smallest size for	subpatterns there are in a compiled pattern. The smallest size for
ovector that will allow for n captured substrings, in addition to the	ovector that will allow for n captured substrings, in addition to the
offsets of the substring matched by the whole pattern, is (n+1)*3.	offsets of the substring matched by the whole pattern, is (n+1)*3.

It is possible for capturing subpattern number n+1 to match some part	It is possible for capturing subpattern number n+1 to match some part
of the subject when subpattern n has not been used at all. For example,	of the subject when subpattern n has not been used at all. For example,
if the string "abc" is matched against the pattern (a\|(z))(bc) the	if the string "abc" is matched against the pattern (a\|(z))(bc) the
return from the function is 4, and subpatterns 1 and 3 are matched, but	return from the function is 4, and subpatterns 1 and 3 are matched, but
2 is not. When this happens, both values in the offset pairs corre-	2 is not. When this happens, both values in the offset pairs corre-
sponding to unused subpatterns are set to -1.	sponding to unused subpatterns are set to -1.

Offset values that correspond to unused subpatterns at the end of the	Offset values that correspond to unused subpatterns at the end of the
expression are also set to -1. For example, if the string "abc" is	expression are also set to -1. For example, if the string "abc" is
matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not	matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
matched. The return from the function is 2, because the highest used	matched. The return from the function is 2, because the highest used
capturing subpattern number is 1, and the offsets for for the second	capturing subpattern number is 1, and the offsets for for the second
and third capturing subpatterns (assuming the vector is large enough,	and third capturing subpatterns (assuming the vector is large enough,
of course) are set to -1.	of course) are set to -1.

Note: Elements in the first two-thirds of ovector that do not corre-	Note: Elements in the first two-thirds of ovector that do not corre-
spond to capturing parentheses in the pattern are never changed. That	spond to capturing parentheses in the pattern are never changed. That
is, if a pattern contains n capturing parentheses, no more than ovec-	is, if a pattern contains n capturing parentheses, no more than ovec-
tor[0] to ovector[2n+1] are set by pcre_exec(). The other elements (in	tor[0] to ovector[2n+1] are set by pcre_exec(). The other elements (in
the first two-thirds) retain whatever values they previously had.	the first two-thirds) retain whatever values they previously had.

Some convenience functions are provided for extracting the captured	Some convenience functions are provided for extracting the captured
substrings as separate strings. These are described below.	substrings as separate strings. These are described below.

Error return values from pcre_exec()	Error return values from pcre_exec()

If pcre_exec() fails, it returns a negative number. The following are	If pcre_exec() fails, it returns a negative number. The following are
defined in the header file:	defined in the header file:

PCRE_ERROR_NOMATCH (-1)	PCRE_ERROR_NOMATCH (-1)
Line 2420 MATCHING A PATTERN: THE TRADITIONAL FUNCTION	Line 2844 MATCHING A PATTERN: THE TRADITIONAL FUNCTION

PCRE_ERROR_NULL (-2)	PCRE_ERROR_NULL (-2)

Either code or subject was passed as NULL, or ovector was NULL and	Either code or subject was passed as NULL, or ovector was NULL and
ovecsize was not zero.	ovecsize was not zero.

PCRE_ERROR_BADOPTION (-3)	PCRE_ERROR_BADOPTION (-3)
Line 2429 MATCHING A PATTERN: THE TRADITIONAL FUNCTION	Line 2853 MATCHING A PATTERN: THE TRADITIONAL FUNCTION

PCRE_ERROR_BADMAGIC (-4)	PCRE_ERROR_BADMAGIC (-4)

PCRE stores a 4-byte "magic number" at the start of the compiled code,	PCRE stores a 4-byte "magic number" at the start of the compiled code,
to catch the case when it is passed a junk pointer and to detect when a	to catch the case when it is passed a junk pointer and to detect when a
pattern that was compiled in an environment of one endianness is run in	pattern that was compiled in an environment of one endianness is run in
an environment with the other endianness. This is the error that PCRE	an environment with the other endianness. This is the err an environment with the other endianness. This is the error that PCRE
gives when the magic number is not present.	gives when the magic number is not present.

PCRE_ERROR_UNKNOWN_OPCODE (-5)	PCRE_ERROR_UNKNOWN_OPCODE (-5)

While running the pattern match, an unknown item was encountered in the	While running the pattern match, an unknown item was encountered in the
compiled pattern. This error could be caused by a bug in PCRE or by	compiled pattern. This error could be caused by a bug in PCRE or by
overwriting of the compiled pattern.	overwriting of the compiled pattern.

PCRE_ERROR_NOMEMORY (-6)	PCRE_ERROR_NOMEMORY (-6)

If a pattern contains back references, but the ovector that is passed	If a pattern contains back references, but the ovector that is passed
to pcre_exec() is not big enough to remember the referenced substrings,	to pcre_exec() is not big enough to remember the referenced substrings,
PCRE gets a block of memory at the start of matching to use for this	PCRE gets a block of memory at the start of matching to use for this
purpose. If the call via pcre_malloc() fails, this error is given. The	purpose. If the call via pcre_malloc() fails, this error is given. The
memory is automatically freed at the end of matching.	memory is automatically freed at the end of matching.

This error is also given if pcre_stack_malloc() fails in pcre_exec().	This error is also given if pcre_stack_malloc() fails in pcre_exec().
This can happen only when PCRE has been compiled with --disable-stack-	This can happen only when PCRE has been compiled with --disable-stack-
for-recursion.	for-recursion.

PCRE_ERROR_NOSUBSTRING (-7)	PCRE_ERROR_NOSUBSTRING (-7)

This error is used by the pcre_copy_substring(), pcre_get_substring(),	This error is used by the pcre_copy_substring(), pcre_get_substring(),
and pcre_get_substring_list() functions (see below). It is never	and pcre_get_substring_list() functions (see below). It is never
returned by pcre_exec().	returned by pcre_exec().

PCRE_ERROR_MATCHLIMIT (-8)	PCRE_ERROR_MATCHLIMIT (-8)

The backtracking limit, as specified by the match_limit field in a	The backtracking limit, as specified by the match_limit field in a
pcre_extra structure (or defaulted) was reached. See the description	pcre_extra structure (or defaulted) was reached. See the description
above.	above.

PCRE_ERROR_CALLOUT (-9)	PCRE_ERROR_CALLOUT (-9)

This error is never generated by pcre_exec() itself. It is provided for	This error is never generated by pcre_exec() itself. It is provided for
use by callout functions that want to yield a distinctive error code.	use by callout functions that want to yield a distinctive error code.
See the pcrecallout documentation for details.	See the pcrecallout documentation for details.

PCRE_ERROR_BADUTF8 (-10)	PCRE_ERROR_BADUTF8 (-10)

A string that contains an invalid UTF-8 byte sequence was passed as a	A string that contains an invalid UTF-8 byte sequence was passed as a
subject, and the PCRE_NO_UTF8_CHECK option was not set. If the size of	subject, and the PCRE_NO_UTF8_CHECK option was not set. If the size of
the output vector (ovecsize) is at least 2, the byte offset to the	the output vector (ovecsize) is at least 2, the byte offset to the
start of the the invalid UTF-8 character is placed in the first ele-	start of the the invalid UTF-8 character is placed in the first ele-
ment, and a reason code is placed in the second element. The reason	ment, and a reason code is placed in the second element. The reason
codes are listed in the following section. For backward compatibility,	codes are listed in the following section. For backward compatibility,
if PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8 char-	if PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8 char-
acter at the end of the subject (reason codes 1 to 5),	acter at the end of the subject (reason codes 1 to 5),
PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.	PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.

PCRE_ERROR_BADUTF8_OFFSET (-11)	PCRE_ERROR_BADUTF8_OFFSET (-11)

The UTF-8 byte sequence that was passed as a subject was checked and	The UTF-8 byte sequence that was passed as a subject was checked and
found to be valid (the PCRE_NO_UTF8_CHECK option was not set), but the	found to be valid (the PCRE_NO_UTF8_CHECK option was not set), but the
value of startoffset did not point to the beginning of a UTF-8 charac-	value of startoffset did not point to the beginning of a UTF-8 charac-
ter or the end of the subject.	ter or the end of the subject.

PCRE_ERROR_PARTIAL (-12)	PCRE_ERROR_PARTIAL (-12)

The subject string did not match, but it did match partially. See the	The subject string did not match, but it did match partiall The subject string did not match, but it did match partially. See the
pcrepartial documentation for details of partial matching.	pcrepartial documentation for details of partial matching.

PCRE_ERROR_BADPARTIAL (-13)	PCRE_ERROR_BADPARTIAL (-13)

This code is no longer in use. It was formerly returned when the	This code is no longer in use. It was formerly returned when the
PCRE_PARTIAL option was used with a compiled pattern containing items	PCRE_PARTIAL option was used with a compiled pattern containing items
that were not supported for partial matching. From release 8.00	that were not supported for partial matching. From release 8.00
onwards, there are no restrictions on partial matching.	onwards, there are no restrictions on partial matching.

PCRE_ERROR_INTERNAL (-14)	PCRE_ERROR_INTERNAL (-14)

An unexpected internal error has occurred. This error could be caused	An unexpected internal error has occurred. This error could be caused
by a bug in PCRE or by overwriting of the compiled pattern.	by a bug in PCRE or by overwriting of the compiled pattern.

PCRE_ERROR_BADCOUNT (-15)	PCRE_ERROR_BADCOUNT (-15)
Line 2514 MATCHING A PATTERN: THE TRADITIONAL FUNCTION	Line 2938 MATCHING A PATTERN: THE TRADITIONAL FUNCTION
PCRE_ERROR_RECURSIONLIMIT (-21)	PCRE_ERROR_RECURSIONLIMIT (-21)

The internal recursion limit, as specified by the match_limit_recursion	The internal recursion limit, as specified by the match_limit_recursion
field in a pcre_extra structure (or defaulted) was reached. See the	field in a pcre_extra structure (or defaulted) was reached. See the
description above.	description above.

PCRE_ERROR_BADNEWLINE (-23)	PCRE_ERROR_BADNEWLINE (-23)
Line 2528 MATCHING A PATTERN: THE TRADITIONAL FUNCTION	Line 2952 MATCHING A PATTERN: THE TRADITIONAL FUNCTION

PCRE_ERROR_SHORTUTF8 (-25)	PCRE_ERROR_SHORTUTF8 (-25)

This error is returned instead of PCRE_ERROR_BADUTF8 when the subject	This error is returned instead of PCRE_ERROR_BADUTF8 when the subject
string ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD	string ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD
option is set. Information about the failure is returned as for	option is set. Information about the failure is returned as for
PCRE_ERROR_BADUTF8. It is in fact sufficient to detect this case, but	PCRE_ERROR_BADUTF8. It is in fact sufficient to detect this case, but
this special error code for PCRE_PARTIAL_HARD precedes the implementa-	this special error code for PCRE_PARTIAL_HARD precedes the implementa-
tion of returned information; it is retained for backwards compatibil-	tion of returned information; it is retained for backwards compatibil-
ity.	ity.

PCRE_ERROR_RECURSELOOP (-26)	PCRE_ERROR_RECURSELOOP (-26)

This error is returned when pcre_exec() detects a recursion loop within	This error is returned when pcre_exec() detects a recursion loop within
the pattern. Specifically, it means that either the whole pattern or a	the pattern. Specifically, it means that either the whole pattern or a
subpattern has been called recursively for the second time at the same	subpattern has been called recursively for the second time at the same
position in the subject string. Some simple patterns that might do this	position in the subject string. Some simple patterns that might do this
are detected and faulted at compile time, but more complicated cases,	are detected and faulted at compile time, but more complicate are detected and faulted at compile time, but more complicate
in particular mutual recursions between two different subpatterns, can-	in particular mutual recursions between two different subpatterns, can-
not be detected until run time.	not be detected until run time.

PCRE_ERROR_JIT_STACKLIMIT (-27)	PCRE_ERROR_JIT_STACKLIMIT (-27)

This error is returned when a pattern that was successfully studied	This error is returned when a pattern that was successfully studied
using the PCRE_STUDY_JIT_COMPILE option is being matched, but the mem-	using the PCRE_STUDY_JIT_COMPILE option is being matched, but the mem-
ory available for the just-in-time processing stack is not large	ory available for the just-in-time processing stack is not large
enough. See the pcrejit documentation for more details.	enough. See the pcrejit documentation for more details.

	PCRE_ERROR_BADMODE (-28)

	This error is given if a pattern that was compiled by the 8-bit library
	is passed to a 16-bit library function, or vice versa.

	PCRE_ERROR_BADENDIANNESS (-29)

	This error is given if a pattern that was compiled and saved is
	reloaded on a host with different endianness. The utility function
	pcre_pattern_to_host_byte_order() can be used to convert such a pattern
	so that it runs on the new host.

Error numbers -16 to -20 and -22 are not used by pcre_exec().	Error numbers -16 to -20 and -22 are not used by pcre_exec().

Reason codes for invalid UTF-8 strings	Reason codes for invalid UTF-8 strings

	This section applies only to the 8-bit library. The corresponding
	information for the 16-bit library is given in the pcre16 page.

When pcre_exec() returns either PCRE_ERROR_BADUTF8 or PCRE_ERROR_SHORT-	When pcre_exec() returns either PCRE_ERROR_BADUTF8 or PCRE_ERROR_SHORT-
UTF8, and the size of the output vector (ovecsize) is at least 2, the	UTF8, and the size of the output vector (ovecsize) is at least 2, the
offset of the start of the invalid UTF-8 character is placed in the	offset of the start of the invalid UTF-8 character is placed in the
Line 2824 FINDING ALL POSSIBLE MATCHES	Line 3263 FINDING ALL POSSIBLE MATCHES
matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.	matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.


	OBTAINING AN ESTIMATE OF STACK USAGE

	Matching certain patterns using pcre_exec() can use a lot of process
	stack, which in certain environments can be rather limited in size.
	Some users find it helpful to have an estimate of the amount of stack
	that is used by pcre_exec(), to help them set recursion limits, as
	described in the pcrestack documentation. The estimate that is output
	by pcretest when called with the -m and -C options is obtained by call-
	ing pcre_exec with the values NULL, NULL, NULL, -999, and -999 for its
	first five arguments.

	Normally, if its first argument is NULL, pcre_exec() immediately
	returns the negative error code PCRE_ERROR_NULL, but with this special
	combination of arguments, it returns instead a negative number whose
	absolute value is the approximate stack frame size in bytes. (A nega-
	tive number is used so that it is clear that no match has happened.)
	The value is approximate because in some cases, recursive calls to
	pcre_exec() occur when there are one or two additional variables on the
	stack.

	If PCRE has been compiled to use the heap instead of the stack for
	recursion, the value returned is the size of each block that is
	obtained from the heap.


MATCHING A PATTERN: THE ALTERNATIVE FUNCTION	MATCHING A PATTERN: THE ALTERNATIVE FUNCTION

int pcre_dfa_exec(const pcre code, const pcre_extra extra,	int pcre_dfa_exec(const pcre code, const pcre_extra extra,
Line 2991 MATCHING A PATTERN: THE ALTERNATIVE FUNCTION	Line 3455 MATCHING A PATTERN: THE ALTERNATIVE FUNCTION

SEE ALSO	SEE ALSO

pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-	pcre16(3), pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematch-
tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).	ing(3), pcrepartial(3), pcreposix(3), pcreprecompile(3), pcresample(3),
	pcrestack(3).


AUTHOR	AUTHOR
Line 3004 AUTHOR	Line 3469 AUTHOR

REVISION	REVISION

Last updated: 02 December 2011	Last updated: 21 January 2012
Copyright (c) 1997-2011 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------


Line 3020 PCRE CALLOUTS	Line 3485 PCRE CALLOUTS

int (pcre_callout)(pcre_callout_block );	int (pcre_callout)(pcre_callout_block );

	int (pcre16_callout)(pcre16_callout_block );

PCRE provides a feature called "callout", which is a means of temporar-	PCRE provides a feature called "callout", which is a means of temporar-
ily passing control to the caller of PCRE in the middle of pattern	ily passing control to the caller of PCRE in the middle of pattern
matching. The caller of PCRE provides an external function by putting	matching. The caller of PCRE provides an external function by putting
its entry point in the global variable pcre_callout. By default, this	its entry point in the global variable pcre_callout (pcre16_callout for
variable contains NULL, which disables all calling out.	the 16-bit library). By default, this variable contains NULL, which
	disables all calling out.

Within a regular expression, (?C) indicates the points at which the	Within a regular expression, (?C) indicates the points at which the
external function is to be called. Different callout points can be	external function is to be called. Different callout points can be
identified by putting a number less than 256 after the letter C. The	identified by putting a number less than 256 after the letter C. The
default value is zero. For example, this pattern has two callout	default value is zero. For example, this pattern has two callout
points:	points:

(?C1)abc(?C2)def	(?C1)abc(?C2)def

If the PCRE_AUTO_CALLOUT option bit is set when pcre_compile() or	If the PCRE_AUTO_CALLOUT option bit is set when a pattern is compiled,
pcre_compile2() is called, PCRE automatically inserts callouts, all	PCRE automatically inserts callouts, all with number 255, before each
with number 255, before each item in the pattern. For example, if	item in the pattern. For example, if PCRE_AUTO_CALLOUT is used with the
PCRE_AUTO_CALLOUT is used with the pattern	pattern

A(\d{2}\|--)	A(\d{2}\|--)

Line 3045 PCRE CALLOUTS	Line 3513 PCRE CALLOUTS

(?C255)A(?C255)((?C255)\d{2}(?C255)\|(?C255)-(?C255)-(?C255))(?C255)	(?C255)A(?C255)((?C255)\d{2}(?C255)\|(?C255)-(?C255)-(?C255))(?C255)

Notice that there is a callout before and after each parenthesis and	Notice that there is a callout before and after each parenthesis and
alternation bar. Automatic callouts can be used for tracking the	alternation bar. Automatic callouts can be used for tracking the
progress of pattern matching. The pcretest command has an option that	progress of pattern matching. The pcretest command has an option that
sets automatic callouts; when it is used, the output indicates how the	sets automatic callouts; when it is used, the output indicates how the
pattern is matched. This is useful information when you are trying to	pattern is matched. This is useful information when you are trying to
optimize the performance of a particular pattern.	optimize the performance of a particular pattern.

The use of callouts in a pattern makes it ineligible for optimization	The use of callouts in a pattern makes it ineligible for optimization
by the just-in-time compiler. Studying such a pattern with the	by the just-in-time compiler. Studying such a pattern with the
PCRE_STUDY_JIT_COMPILE option always fails.	PCRE_STUDY_JIT_COMPILE option always fails.


MISSING CALLOUTS	MISSING CALLOUTS

You should be aware that, because of optimizations in the way PCRE	You should be aware that, because of optimizations in the way PCRE
matches patterns by default, callouts sometimes do not happen. For	matches patterns by default, callouts sometimes do not happen. For
example, if the pattern is	example, if the pattern is

ab(?C4)cd	ab(?C4)cd

PCRE knows that any matching string must contain the letter "d". If the	PCRE knows that any matching string must contain the letter "d". If the
subject string is "abyz", the lack of "d" means that matching doesn't	subject string is "abyz", the lack of "d" means that matching doesn't
ever start, and the callout is never reached. However, with "abyd",	ever start, and the callout is never reached. However, with "abyd",
though the result is still no match, the callout is obeyed.	though the result is still no match, the callout is obeyed.

If the pattern is studied, PCRE knows the minimum length of a matching	If the pattern is studied, PCRE knows the minimum length of a matching
string, and will immediately give a "no match" return without actually	string, and will immediately give a "no match" return without actually
running a match if the subject is not long enough, or, for unanchored	running a match if the subject is not long enough, or, for unanchored
patterns, if it has been scanned far enough.	patterns, if it has been scanned far enough.

You can disable these optimizations by passing the PCRE_NO_START_OPTI-	You can disable these optimizations by passing the PCRE_NO_START_OPTI-
MIZE option to pcre_compile(), pcre_exec(), or pcre_dfa_exec(), or by	MIZE option to the matching function, or by starting the pattern with
starting the pattern with (*NO_START_OPT). This slows down the matching	(*NO_START_OPT). This slows down the matching process, but does ensure
process, but does ensure that callouts such as the example above are	that callouts such as the example above are obeyed.
obeyed.


THE CALLOUT INTERFACE	THE CALLOUT INTERFACE

During matching, when PCRE reaches a callout point, the external func-	During matching, when PCRE reaches a callout point, the external func-
tion defined by pcre_callout is called (if it is set). This applies to	tion defined by pcre_callout or pcre16_callout is called (if it is
both the pcre_exec() and the pcre_dfa_exec() matching functions. The	set). This applies to both normal and DFA matching. The only argument
only argument to the callout function is a pointer to a pcre_callout	to the callout function is a pointer to a pcre_callout or pcre16_call-
block. This structure contains the following fields:	out block. These structures contains the following fields:

int version;	int version;
int callout_number;	int callout_number;
int *offset_vector;	int *offset_vector;
const char *subject;	const char *subject; (8-bit version)
int subject_length;	PCRE_SPTR16 subject; (16-bit version)
int start_match;	int subject_length;
int current_position;	int start_match;
int capture_top;	int current_position;
int capture_last;	int capture_top;
void *callout_data;	int capture_last;
int pattern_position;	void *callout_data;
int next_item_length;
const unsigned char *mark;	int next_item_length;
	const unsigned char *mark; (8-bit version)
	const PCRE_UCHAR16 *mark; (16-bit version)

The version field is an integer containing the version number of the	The version field is an integer containing the version number of the
block format. The initial version was 0; the current version is 2. The	block format. The initial version was 0; the current version is 2. The
Line 3114 THE CALLOUT INTERFACE	Line 3583 THE CALLOUT INTERFACE
outs, and 255 for automatically generated callouts).	outs, and 255 for automatically generated callouts).

The offset_vector field is a pointer to the vector of offsets that was	The offset_vector field is a pointer to the vector of offsets that was
passed by the caller to pcre_exec() or pcre_dfa_exec(). When	passed by the caller to the matching function. When pcre_exec() or
pcre_exec() is used, the contents can be inspected in order to extract	pcre16_exec() is used, the contents can be inspected, in order to
substrings that have been matched so far, in the same way as for	extract substrings that have been matched so far, in the same way as
extracting substrings after a match has completed. For pcre_dfa_exec()	for extracting substrings after a match has completed. For the DFA
this field is not useful.	matching functions, this field is not useful.

The subject and subject_length fields contain copies of the values that	The subject and subject_length fields contain copies of the values that
were passed to pcre_exec().	were passed to the matching function.

The start_match field normally contains the offset within the subject	The start_match field normally contains the offset within the subject
at which the current match attempt started. However, if the escape	at which the current match attempt started. However, if the escape
Line 3133 THE CALLOUT INTERFACE	Line 3602 THE CALLOUT INTERFACE
The current_position field contains the offset within the subject of	The current_position field contains the offset within the subject of
the current match pointer.	the current match pointer.

When the pcre_exec() function is used, the capture_top field contains	When the pcre_exec() or pcre16_exec() is used, the capture_top field
one more than the number of the highest numbered captured substring so	contains one more than the number of the highest numbered captured sub-
far. If no substrings have been captured, the value of capture_top is	string so far. If no substrings have been captured, the value of cap-
one. This is always the case when pcre_dfa_exec() is used, because it	ture_top is one. This is always the case when the DFA functions are
does not support captured substrings.	used, because they do not support captured substrings.

The capture_last field contains the number of the most recently cap-	The capture_last field contains the number of the most recently cap-
tured substring. If no substrings have been captured, its value is -1.	tured substring. If no substrings have been captured, its value is -1.
This is always the case when pcre_dfa_exec() is used.	This is always the case for the DFA matching functions.

The callout_data field contains a value that is passed to pcre_exec()	The callout_data field contains a value that is passed to a matching
or pcre_dfa_exec() specifically so that it can be passed back in call-	function specifically so that it can be passed back in callouts. It is
outs. It is passed in the pcre_callout field of the pcre_extra data	passed in the callout_data field of a pcre_extra or pcre16_extra data
structure. If no such data was passed, the value of callout_data in a	structure. If no such data was passed, the value of callout_data in a
pcre_callout block is NULL. There is a description of the pcre_extra	callout block is NULL. There is a description of the pcre_extra struc-
structure in the pcreapi documentation.	ture in the pcreapi documentation.

The pattern_position field is present from version 1 of the pcre_call-	The pattern_position field is present from version 1 of the callout
out structure. It contains the offset to the next item to be matched in	structure. It contains the offset to the next item to be matched in the
the pattern string.	pattern string.

The next_item_length field is present from version 1 of the pcre_call-	The next_item_length field is present from version 1 of the callout
out structure. It contains the length of the next item to be matched in	structure. It contains the length of the next item to be matched in the
the pattern string. When the callout immediately precedes an alterna-	pattern string. When the callout immediately precedes an alternation
tion bar, a closing parenthesis, or the end of the pattern, the length	bar, a closing parenthesis, or the end of the pattern, the length is
is zero. When the callout precedes an opening parenthesis, the length	zero. When the callout precedes an opening parenthesis, the length is
is that of the entire subpattern.	that of the entire subpattern.

The pattern_position and next_item_length fields are intended to help	The pattern_position and next_item_length fields are intended to help
in distinguishing between different automatic callouts, which all have	in distinguishing between different automatic callouts, which all have
the same callout number. However, they are set for all callouts.	the same callout number. However, they are set for all callouts.

The mark field is present from version 2 of the pcre_callout structure.	The mark field is present from version 2 of the callout structure. In
In callouts from pcre_exec() it contains a pointer to the zero-termi-	callouts from pcre_exec() or pcre16_exec() it contains a pointer to the
nated name of the most recently passed (MARK), (PRUNE), or (*THEN)	zero-terminated name of the most recently passed (MARK), (PRUNE), or
item in the match, or NULL if no such items have been passed. Instances	(*THEN) item in the match, or NULL if no such items have been passed.
of (PRUNE) or (THEN) without a name do not obliterate a previous	Instances of (PRUNE) or (THEN) without a name do not obliterate a
(*MARK). In callouts from pcre_dfa_exec() this field always contains	previous (*MARK). In callouts from the DFA matching functions this
NULL.	field always contains NULL.


RETURN VALUES	RETURN VALUES
Line 3180 RETURN VALUES	Line 3649 RETURN VALUES
is zero, matching proceeds as normal. If the value is greater than	is zero, matching proceeds as normal. If the value is greater than
zero, matching fails at the current point, but the testing of other	zero, matching fails at the current point, but the testing of other
matching possibilities goes ahead, just as if a lookahead assertion had	matching possibilities goes ahead, just as if a lookahead assertion had
failed. If the value is less than zero, the match is abandoned, and	failed. If the value is less than zero, the match is abandoned, the
pcre_exec() or pcre_dfa_exec() returns the negative value.	matching function returns the negative value.

Negative values should normally be chosen from the set of	Negative values should normally be chosen from the set of
PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-	PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
Line 3199 AUTHOR	Line 3668 AUTHOR

REVISION	REVISION

Last updated: 30 November 2011	Last updated: 08 Janurary 2012
Copyright (c) 1997-2011 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------


Line 3217 DIFFERENCES BETWEEN PCRE AND PERL	Line 3686 DIFFERENCES BETWEEN PCRE AND PERL
handle regular expressions. The differences described here are with	handle regular expressions. The differences described here are with
respect to Perl versions 5.10 and above.	respect to Perl versions 5.10 and above.

1. PCRE has only a subset of Perl's UTF-8 and Unicode support. Details	1. PCRE has only a subset of Perl's Unicode support. Details of what it
of what it does have are given in the pcreunicode page.	does have are given in the pcreunicode page.

2. PCRE allows repeat quantifiers only on parenthesized assertions, but	2. PCRE allows repeat quantifiers only on parenthesized assertions, but
they do not mean what you might think. For example, (?!a){3} does not	they do not mean what you might think. For example, (?!a){3} does not
Line 3356 DIFFERENCES BETWEEN PCRE AND PERL	Line 3825 DIFFERENCES BETWEEN PCRE AND PERL
even on different hosts that have the other endianness. However, this	even on different hosts that have the other endianness. However, this
does not apply to optimized data created by the just-in-time compiler.	does not apply to optimized data created by the just-in-time compiler.

(k) The alternative matching function (pcre_dfa_exec()) matches in a	(k) The alternative matching functions (pcre_dfa_exec() and
different way and is not Perl-compatible.	pcre16_dfa_exec()) match in a different way and are not Perl-compati-
	ble.

(l) PCRE recognizes some special sequences such as (*CR) at the start	(l) PCRE recognizes some special sequences such as (*CR) at the start
of a pattern that set overall options that cannot be changed within the	of a pattern that set overall options that cannot be changed within the
pattern.	pattern.

Line 3373 AUTHOR	Line 3843 AUTHOR

REVISION	REVISION

Last updated: 14 November 2011	Last updated: 08 Januray 2012
Copyright (c) 1997-2011 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------


Line 3403 PCRE REGULAR EXPRESSION DETAILS	Line 3873 PCRE REGULAR EXPRESSION DETAILS
intended as reference material.	intended as reference material.

The original operation of PCRE was on strings of one-byte characters.	The original operation of PCRE was on strings of one-byte characters.
However, there is now also support for UTF-8 character strings. To use	However, there is now also support for UTF-8 strings in the original
this, PCRE must be built to include UTF-8 support, and you must call	library, and a second library that supports 16-bit and UTF-16 character
pcre_compile() or pcre_compile2() with the PCRE_UTF8 option. There is	strings. To use these features, PCRE must be built to include appropri-
also a special sequence that can be given at the start of a pattern:	ate support. When using UTF strings you must either call the compiling
	function with the PCRE_UTF8 or PCRE_UTF16 option, or the pattern must
	start with one of these special sequences:

(*UTF8)	(*UTF8)
	(*UTF16)

Starting a pattern with this sequence is equivalent to setting the	Starting a pattern with such a sequence is equivalent to setting the
PCRE_UTF8 option. This feature is not Perl-compatible. How setting	relevant option. This feature is not Perl-compatible. How setting a UTF
UTF-8 mode affects pattern matching is mentioned in several places	mode affects pattern matching is mentioned in several places below.
below. There is also a summary of UTF-8 features in the pcreunicode	There is also a summary of features in the pcreunicode page.
page.

Another special sequence that may appear at the start of a pattern or	Another special sequence that may appear at the start of a pattern or
in combination with (*UTF8) is:	in combination with (UTF8) or (UTF16) is:

(*UCP)	(*UCP)

This has the same effect as setting the PCRE_UCP option: it causes	This has the same effect as setting the PCRE_UCP option: it causes
sequences such as \d and \w to use Unicode properties to determine	sequences such as \d and \w to use Unicode properties to determine
character types, instead of recognizing only characters with codes less	character types, instead of recognizing only characters with codes less
than 128 via a lookup table.	than 128 via a lookup table.

If a pattern starts with (*NO_START_OPT), it has the same effect as	If a pattern sta If a pattern sta
setting the PCRE_NO_START_OPTIMIZE option either at compile or matching	setting the PCRE_NO_START_OPTIMIZE option either at compile or matching
time. There are also some more of these special sequences that are con-	time. There are also some more of these special sequences that are con-
cerned with the handling of newlines; they are described below.	cerned with the handling of newlines; they are described below.

The remainder of this document discusses the patterns that are sup-	The remainder of this document discusses the patterns that are sup-
ported by PCRE when its main matching function, pcre_exec(), is used.	ported by PCRE when one its main matching functions, pcre_exec()
From release 6.0, PCRE offers a second matching function,	(8-bit) or pcre16_exec() (16-bit), is used. PCRE also has alternative
pcre_dfa_exec(), which matches using a different algorithm that is not	matching functions, pcre_dfa_exec() and pcre16_dfa_exec(), which match
Perl-compatible. Some of the features discussed below are not available	using a different algorithm that is not Perl-compatible. Some of the
when pcre_dfa_exec() is used. The advantages and disadvantages of the	features discussed below are not available when DFA matching is used.
alternative function, and how it differs from the normal function, are	The advantages and disadvantages of the alternative functions, and how
discussed in the pcrematching page.	they differ from the normal functions, are discussed in the pcrematch-
	ing page.


NEWLINE CONVENTIONS	NEWLINE CONVENTIONS
Line 3459 NEWLINE CONVENTIONS	Line 3932 NEWLINE CONVENTIONS
(*ANYCRLF) any of the three above	(*ANYCRLF) any of the three above
(*ANY) all Unicode newline sequences	(*ANY) all Unicode newline sequences

These override the default and the options given to pcre_compile() or	These override the default and the options given to the compiling func-
pcre_compile2(). For example, on a Unix system where LF is the default	tion. For example, on a Unix system where LF is the default newline
newline sequence, the pattern	sequence, the pattern

(*CR)a.b	(*CR)a.b

Line 3491 CHARACTERS AND METACHARACTERS	Line 3964 CHARACTERS AND METACHARACTERS

matches a portion of a subject string that is identical to itself. When	matches a portion of a subject string that is identical to itself. When
caseless matching is specified (the PCRE_CASELESS option), letters are	caseless matching is specified (the PCRE_CASELESS option), letters are
matched independently of case. In UTF-8 mode, PCRE always understands	matched independently of case. In a UTF mode, PCRE always understands
the concept of case for characters whose values are less than 128, so	the concept of case for characters whose values are less than 128, so
caseless matching is always possible. For characters with higher val-	caseless matching is always possible. For characters with higher val-
ues, the concept of case is supported if PCRE is compiled with Unicode	ues, the concept of case is supported if PCRE is compiled with Unicode
property support, but not otherwise. If you want to use caseless	property support, but not otherwise. If you want to use caseless
matching for characters 128 and above, you must ensure that PCRE is	matching for characters 128 and above, you must ensure that PCRE is
compiled with Unicode property support as well as with UTF-8 support.	compiled with Unicode property support as well as with UTF support.

The power of regular expressions comes from the ability to include	The power of regular expressions comes from the ability to include
alternatives and repetitions in the pattern. These are encoded in the	alternatives and repetitions in the pattern. These are encoded in the
Line 3552 BACKSLASH	Line 4025 BACKSLASH
that it stands for itself. In particular, if you want to match a back-	that it stands for itself. In particular, if you want to match a back-
slash, you write \\.	slash, you write \\.

In UTF-8 mode, only ASCII numbers and letters have any special meaning	In a UTF mode, only ASCII numbers and letters have any special meaning
after a backslash. All other characters (in particular, those whose	after a backslash. All other characters (in particular, those whose
codepoints are greater than 127) are treated as literals.	codepoints are greater than 127) are treated as literals.

Line 3608 BACKSLASH	Line 4081 BACKSLASH
inverted. Thus \cz becomes hex 1A (z is 7A), but \c{ becomes hex 3B ({	inverted. Thus \cz becomes hex 1A (z is 7A), but \c{ becomes hex 3B ({
is 7B), while \c; becomes hex 7B (; is 3B). If the byte following \c	is 7B), while \c; becomes hex 7B (; is 3B). If the byte following \c
has a value greater than 127, a compile-time error occurs. This locks	has a value greater than 127, a compile-time error occurs. This locks
out non-ASCII characters in both byte mode and UTF-8 mode. (When PCRE	out non-ASCII characters in all modes. (When PCRE is compiled in EBCDIC
is compiled in EBCDIC mode, all byte values are valid. A lower case	mode, all byte values are valid. A lower case letter is converted to
letter is converted to upper case, and then the 0xc0 bits are flipped.)	upper case, and then the 0xc0 bits are flipped.)

By default, after \x, from zero to two hexadecimal digits are read	By default, after \x, from zero to two hexadecimal digits are read
(letters can be in upper or lower case). Any number of hexadecimal dig-	(letters can be in upper or lower case). Any number of hexadecimal dig-
its may appear between \x{ and }, but the value of the character code	its may appear between \x{ and }, but the character code is constrained
must be less than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8	as follows:
mode. That is, the maximum value in hexadecimal is 7FFFFFFF. Note that
this is bigger than the largest Unicode code point, which is 10FFFF.

If characters other than hexadecimal digits appear between \x{ and },	or if there is no terminating }, this form of escape is not recognized.
	8-bit UTF-8 mode less than 0x10ffff and a valid codepoint
	16-bit non-UTF mode less than 0x10000
	16-bit UTF-16 mode less than 0x10ffff and a valid codepoint

	Invalid Unicode codepoints are the range 0xd800 to 0xdfff (the so-
	called "surrogate" codepoints).

	If characters other than hexadecimal digits appear between \x{ and },
or if there is no terminating }, this form of escape is not recognized.	or if there is no terminating }, this form of escape is not recognized.
Instead, the initial \x will be interpreted as a basic hexadecimal	Instead, the initial \x will be interpreted as a basic hexadecimal
escape, with no following digits, giving a character whose value is	escape, with no following digits, giving a character whose value is
zero.	zero.

If the PCRE_JAVASCRIPT_COMPAT option is set, the interpretation of \x	If the PCRE_JAVASCRIPT_COMPAT option is set, the interpretation of \x
is as just described only when it is followed by two hexadecimal dig-	is as just described only when it is followed by two hexadecimal dig-
its. Otherwise, it matches a literal "x" character. In JavaScript	its. Otherwise, it matches a literal "x" character. In JavaScript
mode, support for code points greater than 256 is provided by \u, which	mode, support for code points greater than 256 is provided by \u, which
must be followed by four hexadecimal digits; otherwise it matches a	must be followed by four hexadecimal digits; otherwise it matches a
literal "u" character.	literal "u" character.

Characters whose value is less than 256 can be defined by either of the	Characters whose value is less than 256 can be defined by either of the
two syntaxes for \x (or by \u in JavaScript mode). There is no differ-	two syntaxes for \x (or by \u in JavaScript mode). There is no differ-
ence in the way they are handled. For example, \xdc is exactly the same	ence in the way they are handled. For example, \xdc is exactly the same
as \x{dc} (or \u00dc in JavaScript mode).	as \x{dc} (or \u00dc in JavaScript mode).

After \0 up to two further octal digits are read. If there are fewer	After \0 up to two further octal digits are read. If there are fewer
than two digits, just those that are present are used. Thus the	than two digits, just those that are present are used. Thus the
sequence \0\x\07 specifies two binary zeros followed by a BEL character	sequence \0\x\07 specifies two binary zeros followed by a BEL character
(code value 7). Make sure you supply two digits after the initial zero	(code value 7). Make sure you supply two digits after the initial zero
if the pattern character that follows is itself an octal digit.	if the pattern character that follows is itself an octal digit.

The handling of a backslash followed by a digit other than 0 is compli-	The handling of a backslash followed by a digit other than 0 is compli-
cated. Outside a character class, PCRE reads it and any following dig-	cated. Outside a character class, PCRE reads it and any following dig-
its as a decimal number. If the number is less than 10, or if there	its as a decimal number. If the number is less its as a decimal number. If the number is less than 10, or if there
have been at least that many previous capturing left parentheses in the	have been at least that many previous capturing left parentheses in the
expression, the entire sequence is taken as a back reference. A	expression, the entire sequence is taken as a back reference. A
description of how this works is given later, following the discussion	description of how this works is given later, following the discussion
of parenthesized subpatterns.	of parenthesized subpatterns.

Inside a character class, or if the decimal number is greater than 9	Inside a character class, or if the decimal number is greater than 9
and there have not been that many capturing subpatterns, PCRE re-reads	and there have not been that many capturing subpatterns, PCRE re-reads
up to three octal digits following the backslash, and uses them to gen-	up to three octal digits following the backslash, and uses them to gen-
erate a data character. Any subsequent digits stand for themselves. In	erate a data character. Any subsequent digits stand for themselves. The
non-UTF-8 mode, the value of a character specified in octal must be	value of the character is constrained in the same way as characters
less than \400. In UTF-8 mode, values up to \777 are permitted. For	specified in hexadecimal. For example:
example:

\040 is another way of writing a space	\040 is another way of writing a space
\40 is the same, provided there are fewer than 40	\40 is the same, provided there are fewer than 40
Line 3670 BACKSLASH	Line 4148 BACKSLASH
\113 might be a back reference, otherwise the	\113 might be a back reference, otherwise the
character with octal code 113	character with octal code 113
\377 might be a back reference, otherwise	\377 might be a back reference, otherwise
the byte consisting entirely of 1 bits	the value 255 (decimal)
\81 is either a back reference, or a binary zero	\81 is either a back reference, or a binary zero
followed by the two characters "8" and "1"	followed by the two characters "8" and "1"

Line 3755 BACKSLASH	Line 4233 BACKSLASH
are used for accented letters, and these are then matched by \w. The	are used for accented letters, and these are then matched by \w. The
use of locales with Unicode is discouraged.	use of locales with Unicode is discouraged.

By default, in UTF-8 mode, characters with values greater than 128	By default, in a UTF mode, characters with values greater than 128
never match \d, \s, or \w, and always match \D, \S, and \W. These	never match \d, \s, or \w, and always match \D, \S, and \W. These
sequences retain their original meanings from before UTF-8 support was	sequences retain their original meanings from before UTF support was
available, mainly for efficiency reasons. However, if PCRE is compiled	available, mainly for efficiency reasons. However, if PCRE is compiled
with Unicode property support, and the PCRE_UCP option is set, the be-	with Unicode property support, and the PCRE_UCP option is set, the be-
haviour is changed so that Unicode properties are used to determine	haviour is changed so that Unicode properties are used to determine
Line 3776 BACKSLASH	Line 4254 BACKSLASH
The sequences \h, \H, \v, and \V are features that were added to Perl	The sequences \h, \H, \v, and \V are features that were added to Perl
at release 5.10. In contrast to the other sequences, which match only	at release 5.10. In contrast to the other sequences, which match only
ASCII characters by default, these always match certain high-valued	ASCII characters by default, these always match certain high-valued
codepoints in UTF-8 mode, whether or not PCRE_UCP is set. The horizon-	codepoints, whether or not PCRE_UCP is set. The horizontal space char-
tal space characters are:	acters are:

U+0009 Horizontal tab	U+0009 Horizontal tab
U+0020 Space	U+0020 Space
Line 3809 BACKSLASH	Line 4287 BACKSLASH
U+2028 Line separator	U+2028 Line separator
U+2029 Paragraph separator	U+2029 Paragraph separator

	In 8-bit, non-UTF-8 mode, only the characters with codepoints less than
	256 are relevant.

Newline sequences	Newline sequences

Outside a character class, by default, the escape sequence \R matches	Outside a character class, by default, the escape sequence \R matches
any Unicode newline sequence. In non-UTF-8 mode \R is equivalent to the	any Unicode newline sequence. In 8-bit non-UTF-8 mode \R is equivalent
following:	to the following:

(?>\r\n\|\n\|\x0b\|\f\|\r\|\x85)	(?>\r\n\|\n\|\x0b\|\f\|\r\|\x85)

This is an example of an "atomic group", details of which are given	This is an example of an "atomic group", details of which are given
below. This particular group matches either the two-character sequence	below. This particular group matches either the two-character sequence
CR followed by LF, or one of the single characters LF (linefeed,	CR followed by LF, or one of CR followed by LF, or one of the single characters LF (linefeed,
U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage	U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage
return, U+000D), or NEL (next line, U+0085). The two-character sequence	return, U+000D), or NEL (next line, U+0085). The two-character sequence
is treated as a single unit that cannot be split.	is treated as a single unit that cannot be split.

In UTF-8 mode, two additional characters whose codepoints are greater	In other modes, two additional characters whose codepoints are greater
than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-	than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
rator, U+2029). Unicode character property support is not needed for	rator, U+2029). Unicode character property support is not needed for
these characters to be recognized.	these characters to be recognized.

It is possible to restrict \R to match only CR, LF, or CRLF (instead of	It is possible to restrict \R to match only CR, LF, or CRLF (instead of
the complete set of Unicode line endings) by setting the option	the complete set of Unicode line endings) by setting the option
PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.	PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
(BSR is an abbrevation for "backslash R".) This can be made the default	(BSR is an abbrevation for "backslash R".) This can be made the default
when PCRE is built; if this is the case, the other behaviour can be	when PCRE is built; if this is the case, the other behaviour can be
requested via the PCRE_BSR_UNICODE option. It is also possible to	requested via the PCRE_BSR_UNICODE option. It is also possible to
specify these settings by starting a pattern string with one of the	specify these settings by starting a pattern string with one of the
following sequences:	following sequences:

(*BSR_ANYCRLF) CR, LF, or CRLF only	(*BSR_ANYCRLF) CR, LF, or CRLF only
(*BSR_UNICODE) any Unicode newline sequence	(*BSR_UNICODE) any Unicode newline sequence

These override the default and the options given to pcre_compile() or	These override the default and the options given to the compiling func-
pcre_compile2(), but they can be overridden by options given to	tion, but they can themselves be overridden by options given to a
pcre_exec() or pcre_dfa_exec(). Note that these special settings, which	matching function. Note that these special settings, which are not
are not Perl-compatible, are recognized only at the very start of a	Perl-compatible, are recognized only at the very start of a pattern,
pattern, and that they must be in upper case. If more than one of them	and that they must be in upper case. If more than one of them is
is present, the last one is used. They can be combined with a change of	present, the last one is used. They can be combined with a change of
newline convention; for example, a pattern can start with:	newline convention; for example, a pattern can start with:

(ANY)(BSR_ANYCRLF)	(ANY)(BSR_ANYCRLF)

They can also be combined with the (UTF8) or (UCP) special sequences.	They can also be combined with the (UTF8), (UTF16), or (*UCP) special
Inside a character class, \R is treated as an unrecognized escape	sequences. Inside a character class, \R is treated as an unrecognized
sequence, and so matches the letter "R" by default, but causes an error	escape sequence, and so matches the letter "R" by default, but causes
if PCRE_EXTRA is set.	an error if PCRE_EXTRA is set.

Unicode character properties	Unicode character properties

When PCRE is built with Unicode character property support, three addi-	When PCRE is built with Unicode character property support, three addi-
tional escape sequences that match characters with specific properties	tional escape sequences that match characters with specific properties
are available. When not in UTF-8 mode, these sequences are of course	are available. When in 8-bit non-UTF-8 mode, these sequences are of
limited to testing characters whose codepoints are less than 256, but	course limited to testing characters whose codepoints are less than
they do work in this mode. The extra escape sequences are:	256, but they do work in this mode. The extra escape sequences are:

\p{xx} a character with the xx property	\p{xx} a character with the xx property
\P{xx} a character without the xx property	\P{xx} a character without the xx property
\X an extended Unicode sequence	\X an extended Unicode sequence

The property names represented by xx above are limited to the Unicode	The property names represented by xx above are limited to the Unicode
script names, the general category properties, "Any", which matches any	script names, the general category properties, "Any", which matches any
character (including newline), and some special PCRE properties	character (including newline), and some special PCRE properties
(described in the next section). Other Perl properties such as "InMu-	(described in the next section). Other Perl properties such as "InMu-
sicalSymbols" are not currently supported by PCRE. Note that \P{Any}	sicalSymbols" are not currently supported by PCRE. Note that \P{Any}
does not match any characters, so always causes a match failure.	does not match any characters, so always causes a match failure.

Sets of Unicode characters are defined as belonging to certain scripts.	Sets of Unicode characters are defined as belonging to certain scripts.
A character from one of these sets can be matched using a script name.	A character from one of these sets can be matched using a script name.
For example:	For example:

\p{Greek}	\p{Greek}
\P{Han}	\P{Han}

Those that are not part of an identified script are lumped together as	Those that are not part of an identified script are lumped together as
"Common". The current list of scripts is:	"Common". The current list of scripts is:

Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille,	Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille,
Buginese, Buhid, Canadian_Aboriginal, Carian, Cham, Cherokee, Common,	Buginese, Buhid, Canadian_Aboriginal, Carian, Cham, Cherokee, Common,
Coptic, Cuneiform, Cypriot, Cyrillic, Deseret, Devanagari, Egyp-	Coptic, Cuneiform, Cypriot, Cyrillic, Deseret, Devanagari, Egyp-
tian_Hieroglyphs, Ethiopic, Georgian, Glagolitic, Gothic, Greek,	tian_Hieroglyphs, Ethiopic, Georgian, Glagolitic, Gothic, Greek,
Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hiragana, Impe-	Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hiragana, Impe-
rial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian,	rial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian,
Javanese, Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Lao,	Javanese, Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Lao,
Latin, Lepcha, Limbu, Linear_B, Lisu, Lycian, Lydian, Malayalam,	Latin, Lepcha, Limbu, Linear_B, Lisu, Lycian, Lydian, Malayalam,
Meetei_Mayek, Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham, Old_Italic,	Meetei_Mayek, Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham, Old_Italic,
Old_Persian, Old_South_Arabian, Old_Turkic, Ol_Chiki, Oriya, Osmanya,	Old_Persian, Old_South_Arabian, Old_Turkic, Ol_Chiki, Oriya, Osmanya,
Phags_Pa, Phoenician, Rejang, Runic, Samaritan, Saurashtra, Shavian,	Phags_Pa, Phoenician, Rejang, Runic, Samaritan, Saurashtra, Shavian,
Sinhala, Sundanese, Syloti_Nagri, Syriac, Tagalog, Tagbanwa, Tai_Le,	Sinhala, Sundanese, Syloti_Nagri, Syriac, Tagalog, Tagbanwa, Tai_Le,
Tai_Tham, Tai_Viet, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh,	Tai_Tham, Tai_Viet, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh,
Ugaritic, Vai, Yi.	Ugaritic, Vai, Yi.

Each character has exactly one Unicode general category property, spec-	Each character has exactly one Unicode general category property, spec-
ified by a two-letter abbreviation. For compatibility with Perl, nega-	ified by a two-letter abbreviation. For compatibility with Perl, nega-
tion can be specified by including a circumflex between the opening	tion can be specified by including a circumflex between the opening
brace and the property name. For example, \p{^Lu} is the same as	brace and the property name. For example, \p{^Lu} is the same as
\P{Lu}.	\P{Lu}.

If only one letter is specified with \p or \P, it includes all the gen-	If only one letter is specified with \p or \P, it includes all the gen-
eral category properties that start with that letter. In this case, in	eral category properties that start with that letter. In this case, in
the absence of negation, the curly brackets in the escape sequence are	the absence of negation, the curly brackets in the escape sequence are
optional; these two examples have the same effect:	optional; these two examples have the same effect:

\p{L}	\p{L}
Line 3960 BACKSLASH	Line 4441 BACKSLASH
Zp Paragraph separator	Zp Paragraph separator
Zs Space separator	Zs Space separator

The special property L& is also supported: it matches a character that	The special property L& is also supported: it matches a character that
has the Lu, Ll, or Lt property, in other words, a letter that is not	has the Lu, Ll, or Lt property, in other words, a letter that is not
classified as a modifier or "other".	classified as a modifier or "other".

The Cs (Surrogate) property applies only to characters in the range	The Cs (Surrogate) property applies only to characters in the range
U+D800 to U+DFFF. Such characters are not valid in UTF-8 strings (see	U+D800 to U+DFFF. Such characters are not valid in Unicode strings and
RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-	so cannot be tested by PCRE, unless UTF validity checking has been
ing has been turned off (see the discussion of PCRE_NO_UTF8_CHECK in	turned off (see the discussion of PCRE_NO_UTF8_CHECK and
the pcreapi page). Perl does not support the Cs property.	PCRE_NO_UTF16_CHECK in the pcreapi page). Perl does not support the Cs
	property.

The long synonyms for property names that Perl supports (such as	The long synonyms for property names that Perl supports (such as
\p{Letter}) are not supported by PCRE, nor is it permitted to prefix	\p{Letter}) are not supported by PCRE, nor is it permitted to prefix
Line 3990 BACKSLASH	Line 4472 BACKSLASH
by zero or more characters with the "mark" property, and treats the	by zero or more characters with the "mark" property, and treats the
sequence as an atomic group (see below). Characters with the "mark"	sequence as an atomic group (see below). Characters with the "mark"
property are typically accents that affect the preceding character.	property are typically accents that affect the preceding character.
None of them have codepoints less than 256, so in non-UTF-8 mode \X	None of them have codepoints less than 256, so in 8-bit non-UTF-8 mode
matches any one character.	\X matches any one character.

Note that recent versions of Perl have changed \X to match what Unicode	Note that recent versions of Perl have changed \X to match what Unicode
calls an "extended grapheme cluster", which has a more complicated def-	calls an "extended grapheme cluster", which has a more complicated def-
Line 4001 BACKSLASH	Line 4483 BACKSLASH
to search a structure that contains data for over fifteen thousand	to search a structure that contains data for over fifteen thousand
characters. That is why the traditional escape sequences such as \d and	characters. That is why the traditional escape sequences such as \d and
\w do not use Unicode properties in PCRE by default, though you can	\w do not use Unicode properties in PCRE by default, though you can
make them do so by setting the PCRE_UCP option for pcre_compile() or by	make them do so by setting the PCRE_UCP option or by starting the pat-
starting the pattern with (*UCP).	tern with (*UCP).

PCRE's additional properties	PCRE's additional properties

Line 4071 BACKSLASH	Line 4553 BACKSLASH
A word boundary is a position in the subject string where the current	A word boundary is a position in the subject string where the current
character and the previous character do not both match \w or \W (i.e.	character and the previous character do not both match \w or \W (i.e.
one matches \w and the other matches \W), or the start or end of the	one matches \w and the other matches \W), or the start or end of the
string if the first or last character matches \w, respectively. In	string if the first or last character matches \w, respectively. In a
UTF-8 mode, the meanings of \w and \W can be changed by setting the	UTF mode, the meanings of \w and \W can be changed by setting the
PCRE_UCP option. When this is done, it also affects \b and \B. Neither	PCRE_UCP option. When this is done, it also affects \b and \B. Neither
PCRE nor Perl has a separate "start of word" or "end of word" metase-	PCRE nor Perl has a separate "start of word" or "end of word" metase-
quence. However, whatever follows \b normally determines which it is.	quence. However, whatever follows \b normally determines which it is.
Line 4163 FULL STOP (PERIOD, DOT) AND \N	Line 4645 FULL STOP (PERIOD, DOT) AND \N

Outside a character class, a dot in the pattern matches any one charac-	Outside a character class, a dot in the pattern matches any one charac-
ter in the subject string except (by default) a character that signi-	ter in the subject string except (by default) a character that signi-
fies the end of a line. In UTF-8 mode, the matched character may be	fies the end of a line.
more than one byte long.

When a line ending is defined as a single character, dot never matches	When a line ending is defined as a single character, dot never matches
that character; when the two-character sequence CRLF is used, dot does	that character; when the two-character sequence CRLF is used, dot does
not match CR if it is immediately followed by LF, but otherwise it	not match CR if it is immediately followed by LF, but otherwise it
matches all characters (including isolated CRs and LFs). When any Uni-	matches all characters (including isolated CRs and LFs). When any Uni-
code line endings are being recognized, dot does not match CR or LF or	code line endings are being recognized, dot does not match CR or LF or
any of the other line ending characters.	any of the other line ending characters.

The behaviour of dot with regard to newlines can be changed. If the	The behaviour of dot with regard to newlines can be changed. If the
PCRE_DOTALL option is set, a dot matches any one character, without	PCRE_DOTALL option is set, a dot matches any one character, without
exception. If the two-character sequence CRLF is present in the subject	exception. If the two-character sequence CRLF is present in the subject
string, it takes two dots to match it.	string, it takes two dots to match it.

The handling of dot is entirely independent of the handling of circum-	The handling of dot is entirely independent of the handling of circum-
flex and dollar, the only relationship being that they both involve	flex and dollar, the only relationship being that they both involve
newlines. Dot has no special meaning in a character class.	newlines. Dot has no special meaning in a character class.

The escape sequence \N behaves like a dot, except that it is not	The escape sequence \N behaves like a dot, except that it is not
affected by the PCRE_DOTALL option. In other words, it matches any	affected by the PCRE_DOTALL option. In other words, it matches any
character except one that signifies the end of a line. Perl also uses	character except one that signifies the end of a line. Perl also uses
\N to match characters by name; PCRE does not support this.	\N to match characters by name; PCRE does not support this.


MATCHING A SINGLE BYTE	MATCHING A SINGLE DATA UNIT

Outside a character class, the escape sequence \C matches any one byte,	Outside a character class, the escape sequence \C matches any one data
both in and out of UTF-8 mode. Unlike a dot, it always matches line-	unit, whether or not a UTF mode is set. In the 8-bit library, one data
ending characters. The feature is provided in Perl in order to match	unit is one byte; in the 16-bit library it is a 16-bit unit. Unlike a
individual bytes in UTF-8 mode, but it is unclear how it can usefully	dot, \C always matches line-ending characters. The feature is provided
be used. Because \C breaks up characters into individual bytes, match-	in Perl in order to match individual bytes in UTF-8 mode, but it is
ing one byte with \C in UTF-8 mode means that the rest of the string	unclear how it can usefully be used. Because \C breaks up characters
may start with a malformed UTF-8 character. This has undefined results,	into individual data units, matching one unit with \C in a UTF mode
because PCRE assumes that it is dealing with valid UTF-8 strings (and	means that the rest of the string may start with a malformed UTF char-
by default it checks this at the start of processing unless the	acter. This has undefined results, because PCRE assumes that it is
PCRE_NO_UTF8_CHECK option is used).	dealing with valid UTF strings (and by default it checks this at the
	start of processing unless the PCRE_NO_UTF8_CHECK option is used).

PCRE does not allow \C to appear in lookbehind assertions (described	PCRE does not allow \C to appear in lookbehind assertions (described
below) in UTF-8 mode, because this would make it impossible to calcu-	below) in a UTF mode, because this would make it impossible to calcu-
late the length of the lookbehind.	late the length of the lookbehind.

In general, the \C escape sequence is best avoided in UTF-8 mode. How-	In general, the \C escape sequence is best avoided. However, one way of
ever, one way of using it that avoids the problem of malformed UTF-8	using it that avoids the problem of malformed UTF characters is to use
characters is to use a lookahead to check the length of the next char-	a lookahead to check the length of the next character, as in this pat-
acter, as in this pattern (ignore white space and line breaks):	tern, which could be used with a UTF-8 string (ignore white space and
	line breaks):

(?\| (?=[\x00-\x7f])(\C) \|	(?\| (?=[\x00-\x7f])(\C) \|
(?=[\x80-\x{7ff}])(\C)(\C) \|	(?=[\x80-\x{7ff}])(\C)(\C) \|
(?=[\x{800}-\x{ffff}])(\C)(\C)(\C) \|	(?=[\x{800}-\x{ffff}])(\C)(\C)(\C) \|
(?=[\x{10000}-\x{1fffff}])(\C)(\C)(\C)(\C))	(?=[\x{10000}-\x{1fffff}])(\C)(\C)(\C)(\C))

A group that starts with (?\| resets the capturing parentheses numbers	A group that starts with (?\| resets the capturing parentheses numbers
in each alternative (see "Duplicate Subpattern Numbers" below). The	in each alternative (see "Duplicate Subpattern Numbers" below). The
assertions at the start of each branch check the next UTF-8 character	assertions at the start of each branch check the next UTF-8 character
for values whose encoding uses 1, 2, 3, or 4 bytes, respectively. The	for values whose encoding uses 1, 2, 3, or 4 bytes, respectively. The
character's individual bytes are then captured by the appropriate num-	character's individual bytes are then captured by the appropriate num-
ber of groups.	ber of groups.


Line 4229 SQUARE BRACKETS AND CHARACTER CLASSES	Line 4712 SQUARE BRACKETS AND CHARACTER CLASSES
closing square bracket. A closing square bracket on its own is not spe-	closing square bracket. A closing square bracket on its own is not spe-
cial by default. However, if the PCRE_JAVASCRIPT_COMPAT option is set,	cial by default. However, if the PCRE_JAVASCRIPT_COMPAT option is set,
a lone closing square bracket causes a compile-time error. If a closing	a lone closing square bracket causes a compile-time error. If a closing
square bracket is required as a member of the class, it should be the	square bracket is required as a member of the class, it should be the
first data character in the class (after an initial circumflex, if	first data character in the class (after an initial circumflex, if
present) or escaped with a backslash.	present) or escaped with a backslash.

A character class matches a single character in the subject. In UTF-8	A character class matches a single character in the subject. In a UTF
mode, the character may be more than one byte long. A matched character	mode, the character may be more than one data unit long. A matched
must be in the set of characters defined by the class, unless the first	character must be in the set of characters defined by the class, unless
character in the class definition is a circumflex, in which case the	the first character in the class definition is a circumflex, in which
subject character must not be in the set defined by the class. If a	case the subject character must not be in the set defined by the class.
circumflex is actually required as a member of the class, ensure it is	If a circumflex is actually required as a member of the class, ensure
not the first character, or escape it with a backslash.	it is not the first character, or escape it with a backslash.

For example, the character class [aeiou] matches any lower case vowel,	For example, the character class [aeiou] matches any lower case vowel,
while [^aeiou] matches any character that is not a lower case vowel.	while [^aeiou] matches any character that is not a lower case vowel.
Note that a circumflex is just a convenient notation for specifying the	Note that a circumflex is just a convenient notation for specifying the
characters that are in the class by enumerating those that are not. A	characters that are in the class by enumerating those that are not. A
class that starts with a circumflex is not an assertion; it still con-	class that starts with a circumflex is not an assertion; it still con-
sumes a character from the subject string, and therefore it fails if	sumes a character from the subject string, and therefore it fails if
the current pointer is at the end of the string.	the current pointer is at the end of the string.

In UTF-8 mode, characters with values greater than 255 can be included	In UTF-8 (UTF-16) mode, characters with values greater than 255
in a class as a literal string of bytes, or by using the \x{ escaping	(0xffff) can be included in a class as a literal string of data units,
mechanism.	or by using the \x{ escaping mechanism.

When caseless matching is set, any letters in a class represent both	When caseless matching is set, any letters in a class represent both
their upper case and lower case versions, so for example, a caseless	their upper case and lower case versions, so for example, a caseless
[aeiou] matches "A" as well as "a", and a caseless [^aeiou] does not	[aeiou] matches "A" as well as "a", and a caseless [^aeiou] does not
match "A", whereas a caseful version would. In UTF-8 mode, PCRE always	match "A", whereas a caseful version would. In a UTF mode, PCRE always
understands the concept of case for characters whose values are less	understands the concept of case for characters whose values are less
than 128, so caseless matching is always possible. For characters with	than 128, so caseless matching is always possible. For characters with
higher values, the concept of case is supported if PCRE is compiled	higher values, the concept of case is supported if PCRE is compiled
with Unicode property support, but not otherwise. If you want to use	with Unicode property support, but not otherwise. If you want to use
caseless matching in UTF8-mode for characters 128 and above, you must	caseless matching in a UTF mode for characters 128 and above, you must
ensure that PCRE is compiled with Unicode property support as well as	ensure that PCRE is compiled with Unicode property support as well as
with UTF-8 support.	with UTF support.

Characters that might indicate line breaks are never treated in any	Characters that might indicate line breaks are never treated in any
special way when matching character classes, whatever line-ending	special way when matching character classes, whatever line-ending
sequence is in use, and whatever setting of the PCRE_DOTALL and	sequence is in use, and whatever setting of the PCRE_DOTALL and
PCRE_MULTILINE options is used. A class such as [^a] always matches one	PCRE_MULTILINE options is used. A class such as [^a] always matches one
of these characters.	of these characters.

The minus (hyphen) character can be used to specify a range of charac-	The minus (hyphen) character can be used to specify a range of charac-
ters in a character class. For example, [d-m] matches any letter	ters in a character class. For example, [d-m] matches any letter
between d and m, inclusive. If a minus character is required in a	between d and m, inclusive. If a minus character is required in a
class, it must be escaped with a backslash or appear in a position	class, it must be escaped with a backslash or appear in a position
where it cannot be interpreted as indicating a range, typically as the	where it cannot be interpreted as indicating a range, typically as the
first or last character in the class.	first or last character in the class.

It is not possible to have the literal character "]" as the end charac-	It is not possible to have the literal character "]" as the end charac-
ter of a range. A pattern such as [W-]46] is interpreted as a class of	ter of a range. A pattern such as [W-]46] is interpreted as a class of
two characters ("W" and "-") followed by a literal string "46]", so it	two characters ("W" and "-") followed by a literal string "46]", so it
would match "W46]" or "-46]". However, if the "]" is escaped with a	would match "W46]" or "-46]". However, if the "]" is escaped with a
backslash it is interpreted as the end of range, so [W-\]46] is inter-	backslash it is interpreted as the end of range, so [W-\]46] is inter-
preted as a class containing a range followed by two other characters.	preted as a class containing a range followed by two other characters.
The octal or hexadecimal representation of "]" can also be used to end	The octal or hexadecimal representation of "]" can also be used to end
a range.	a range.

Ranges operate in the collating sequence of character values. They can	Ranges operate in the collating sequence of character values. They can
also be used for characters specified numerically, for example	also be used for characters specified numerically, for example
[\000-\037]. In UTF-8 mode, ranges can include characters whose values	[\000-\037]. Ranges can include any characters that are valid for the
are greater than 255, for example [\x{100}-\x{2ff}].	current mode.

If a range that includes letters is used when caseless matching is set,	If a range that includes letters is used when caseless matching is set,
it matches the letters in either case. For example, [W-c] is equivalent	it matches the letters in either case. For example, [W-c] is equivalent
to [][\\^_`wxyzabc], matched caselessly, and in non-UTF-8 mode, if	to [][\\^_`wxyzabc], matched caselessly, and in a non-UTF mode, if
character tables for a French locale are in use, [\xc8-\xcb] matches	character tables for a French locale are in use, [\xc8-\xcb] matches
accented E characters in both cases. In UTF-8 mode, PCRE supports the	accented E characters in both cases. In UTF modes, PCRE supports the
concept of case for characters with values greater than 128 only when	concept of case for characters with values greater than 128 only when
it is compiled with Unicode property support.	it is compiled with Unicode property support.

The character escape sequences \d, \D, \h, \H, \p, \P, \s, \S, \v, \V,	The character escape sequences \d, \D, \h, \H, \p, \P, \s, \S, \v, \V,
\w, and \W may appear in a character class, and add the characters that	\w, and \W may appear in a character class, and add the characters that
they match to the class. For example, [\dABCDEF] matches any hexadeci-	they match to the class. For example, [\dABCDEF] matches any hexadeci-
mal digit. In UTF-8 mode, the PCRE_UCP option affects the meanings of	mal digit. In UTF modes, the PCRE_UCP option affects the meanings of
\d, \s, \w and their upper case partners, just as it does when they	\d, \s, \w and their upper case partners, just as it does when they
appear outside a character class, as described in the section entitled	appear outside a character class, as described in the section entitled
"Generic character types" above. The escape sequence \b has a different	"Generic character types" above. The escape sequence \b has a different
meaning inside a character class; it matches the backspace character.	meaning inside a character class; it matches the backspace character.
The sequences \B, \N, \R, and \X are not special inside a character	The sequences \B, \N, \R, and \X are not special inside a character
class. Like any other unrecognized escape sequences, they are treated	class. Like any other unrecognized escape sequences, they are treated
as the literal characters "B", "N", "R", and "X" by default, but cause	as the literal characters "B", "N", "R", and "X" by default, but cause
an error if the PCRE_EXTRA option is set.	an error if the PCRE_EXTRA option is set.

A circumflex can conveniently be used with the upper case character	A circumflex can conveniently be used with the upper case character
types to specify a more restricted set of characters than the matching	types to specify a more restricted set of characters than the matching
lower case type. For example, the class [^\W_] matches any letter or	lower case type. For example, the class [^\W_] matches any letter or
digit, but not underscore, whereas [\w] includes underscore. A positive	digit, but not underscore, whereas [\w] includes underscore. A positive
character class should be read as "something OR something OR ..." and a	character class should be read as "something OR something OR ..." and a
negative class as "NOT something AND NOT something AND NOT ...".	negative class as "NOT something AND NOT something AND NOT ...".

The only metacharacters that are recognized in character classes are	The only metacharacters that are recognized in character classes are
backslash, hyphen (only where it can be interpreted as specifying a	backslash, hyphen (only where it can be interpreted as specifying a
range), circumflex (only at the start), opening square bracket (only	range), circumflex (only at the start), opening square bracket (only
when it can be interpreted as introducing a POSIX class name - see the	when it can be interpreted as introducing a POSIX class name - see the
next section), and the terminating closing square bracket. However,	next section), and the terminating closing square bracket. However,
escaping other non-alphanumeric characters does no harm.	escaping other non-alphanumeric characters does no harm.


POSIX CHARACTER CLASSES	POSIX CHARACTER CLASSES

Perl supports the POSIX notation for character classes. This uses names	Perl supports the POSIX notation for character classes. This uses names
enclosed by [: and :] within the enclosing square brackets. PCRE also	enclosed by [: and :] within the enclosing square brackets. PCRE also
supports this notation. For example,	supports this notation. For example,

[01[:alpha:]%]	[01[:alpha:]%]
Line 4354 POSIX CHARACTER CLASSES	Line 4837 POSIX CHARACTER CLASSES
word "word" characters (same as \w)	word "word" characters (same as \w)
xdigit hexadecimal digits	xdigit hexadecimal digits

The "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13),	The "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13),
and space (32). Notice that this list includes the VT character (code	and space (32). Notice that this list includes the VT character (code
11). This makes "space" different to \s, which does not include VT (for	11). This makes "space" different to \s, which does not include VT (for
Perl compatibility).	Perl compatibility).

The name "word" is a Perl extension, and "blank" is a GNU extension	The name "word" is a Perl extension, and "blank" is a GNU extension
from Perl 5.8. Another Perl extension is negation, which is indicated	from Perl 5.8. Another Perl extension is negation, which is indicated
by a ^ character after the colon. For example,	by a ^ character after the colon. For example,

[12[:^digit:]]	[12[:^digit:]]

matches "1", "2", or any non-digit. PCRE (and Perl) also recognize the	matches "1", "2", or any non-digit. PCRE (and Perl) also recognize the
POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but	POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but
these are not supported, and an error is given if they are encountered.	these are not supported, and an error is given if they are encountered.

By default, in UTF-8 mode, characters with values greater than 128 do	By default, in UTF modes, characters with values greater than 128 do
not match any of the POSIX character classes. However, if the PCRE_UCP	not match any of the POSIX character classes. However, if the PCRE_UCP
option is passed to pcre_compile(), some of the classes are changed so	option is passed to pcre_compile(), some of the classes are changed so
that Unicode character properties are used. This is achieved by replac-	that Unicode character properties are used. This is achieved by replac-
ing the POSIX classes by other sequences, as follows:	ing the POSIX classes by other sequences, as follows:

Line 4384 POSIX CHARACTER CLASSES	Line 4867 POSIX CHARACTER CLASSES
[:upper:] becomes \p{Lu}	[:upper:] becomes \p{Lu}
[:word:] becomes \p{Xwd}	[:word:] becomes \p{Xwd}

Negated versions, such as [:^alpha:] use \P instead of \p. The other	Negated versions, such as [:^alpha:] use \P instead of \p. The other
POSIX classes are unchanged, and match only characters with code points	POSIX classes are unchanged, and match only characters with code points
less than 128.	less than 128.


VERTICAL BAR	VERTICAL BAR

Vertical bar characters are used to separate alternative patterns. For	Vertical bar characters are used to separate alternative patterns. For
example, the pattern	example, the pattern

gilbert\|sullivan	gilbert\|sullivan

matches either "gilbert" or "sullivan". Any number of alternatives may	matches either "gilbert" or "sullivan". Any number of alternatives may
appear, and an empty alternative is permitted (matching the empty	appear, and an empty alternative is permitted (matching the empty
string). The matching process tries each alternative in turn, from left	string). The matching process tries each alternative in turn, from left
to right, and the first one that succeeds is used. If the alternatives	to right, and the first one that succeeds is used. If the alternatives
are within a subpattern (defined below), "succeeds" means matching the	are within a subpattern (defined below), "succeeds" means matching the
rest of the main pattern as well as the alternative in the subpattern.	rest of the main pattern as well as the alternative in the subpattern.


INTERNAL OPTION SETTING	INTERNAL OPTION SETTING

The settings of the PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and	The settings of the PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and
PCRE_EXTENDED options (which are Perl-compatible) can be changed from	PCRE_EXTENDED options (which are Perl-compatible) can be changed from
within the pattern by a sequence of Perl option letters enclosed	within the pattern by a sequence of Perl option letters enclosed
between "(?" and ")". The option letters are	between "(?" and ")". The option letters are

i for PCRE_CASELESS	i for PCRE_CASELESS
Line 4418 INTERNAL OPTION SETTING	Line 4901 INTERNAL OPTION SETTING

For example, (?im) sets caseless, multiline matching. It is also possi-	For example, (?im) sets caseless, multiline matching. It is also possi-
ble to unset these options by preceding the letter with a hyphen, and a	ble to unset these options by preceding the letter with a hyphen, and a
combined setting and unsetting such as (?im-sx), which sets PCRE_CASE-	combined setting and unsetting such as (?im-sx), which sets PCRE_CASE-
LESS and PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED,	LESS and PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED,
is also permitted. If a letter appears both before and after the	is also permitted. If a letter appears both before and after the
hyphen, the option is unset.	hyphen, the option is unset.

The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA	The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA
can be changed in the same way as the Perl-compatible options by using	can be changed in the same way as the Perl-compatible options by using
the characters J, U and X respectively.	the characters J, U and X respectively.

When one of these option changes occurs at top level (that is, not	When one of these option changes occurs at top level (that is, not
inside subpattern parentheses), the change applies to the remainder of	inside subpattern parentheses), the change applies to the remainder of
the pattern that follows. If the change is placed right at the start of	the pattern that follows. If the change is placed right at the start of
a pattern, PCRE extracts it into the global options (and it will there-	a pattern, PCRE extracts it into the global options (and it will there-
fore show up in data extracted by the pcre_fullinfo() function).	fore show up in data extracted by the pcre_fullinfo() function).

An option change within a subpattern (see below for a description of	An option change within a subpattern (see below for a description of
subpatterns) affects only that part of the subpattern that follows it,	subpatterns) affects only that part of the subpattern that follows it,
so	so

(a(?i)b)c	(a(?i)b)c

matches abc and aBc and no other strings (assuming PCRE_CASELESS is not	matches abc and aBc and no other strings (assuming PCRE_CASELESS is not
used). By this means, options can be made to have different settings	used). By this means, options can be made to have different settings
in different parts of the pattern. Any changes made in one alternative	in different parts of the pattern. Any changes made in one alternative
do carry on into subsequent branches within the same subpattern. For	do carry on into subsequent branches within the same subpattern. For
example,	example,

(a(?i)b\|c)	(a(?i)b\|c)

matches "ab", "aB", "c", and "C", even though when matching "C" the	matches "ab", "aB", "c", and "C", even though when matching "C" the
first branch is abandoned before the option setting. This is because	first branch is abandoned before the option setting. This is because
the effects of option settings happen at compile time. There would be	the effects of option settings happen at compile time. There would be
some very weird behaviour otherwise.	some very weird behaviour otherwise.

Note: There are other PCRE-specific options that can be set by the	Note: There are other PCRE-specific options that can be set by the
application when the compile or match functions are called. In some	application when the compiling or matching functions are called. In
cases the pattern can contain special leading sequences such as (*CRLF)	some cases the pattern can contain special leading sequences such as
to override what the application has set or what has been defaulted.	(*CRLF) to override what the application has set or what has been
Details are given in the section entitled "Newline sequences" above.	defaulted. Details are given in the section entitled "Newline
There are also the (UTF8) and (UCP) leading sequences that can be	sequences" above. There are also the (UTF8), (UTF16), and (*UCP)
used to set UTF-8 and Unicode property modes; they are equivalent to	leading sequences that can be used to set UTF and Unicode property
setting the PCRE_UTF8 and the PCRE_UCP options, respectively.	modes; they are equivalent to setting the PCRE_UTF8, PCRE_UTF16, and
	the PCRE_UCP options, respectively.


SUBPATTERNS	SUBPATTERNS
Line 4477 SUBPATTERNS	Line 4961 SUBPATTERNS
2. It sets up the subpattern as a capturing subpattern. This means	2. It sets up the subpattern as a capturing subpattern. This means
that, when the whole pattern matches, that portion of the subject	that, when the whole pattern matches, that portion of the subject
string that matched the subpattern is passed back to the caller via the	string that matched the subpattern is passed back to the caller via the
ovector argument of pcre_exec(). Opening parentheses are counted from	ovector argument of the matching function. (This applies only to the
left to right (starting from 1) to obtain numbers for the capturing	traditional matching functions; the DFA matching functions do not sup-
subpatterns. For example, if the string "the red king" is matched	port capturing.)
against the pattern

	Opening parentheses are counted from left to right (starting from 1) to
	obtain numbers for the capturing subpatterns. For example, if the
	string "the red king" is matched against the pattern

the ((red\|white) (king\|queen))	the ((red\|white) (king\|queen))

the captured substrings are "red king", "red", and "king", and are num-	the captured substrings are "red king", "red", and "king", and are num-
bered 1, 2, and 3, respectively.	bered 1, 2, and 3, respectively.

The fact that plain parentheses fulfil two functions is not always	The fact that plain parentheses fulfil two functions is not always
helpful. There are often times when a grouping subpattern is required	helpful. There are often times when a grouping subpattern is required
without a capturing requirement. If an opening parenthesis is followed	without a capturing requirement. If an opening parenthesis is followed
by a question mark and a colon, the subpattern does not do any captur-	by a question mark and a colon, the subpattern does not do any captur-
ing, and is not counted when computing the number of any subsequent	ing, and is not counted when computing the number of any subsequent
capturing subpatterns. For example, if the string "the white queen" is	capturing subpatterns. For example, if the string "the white queen" is
matched against the pattern	matched against the pattern

the ((?:red\|white) (king\|queen))	the ((?:red\|white) (king\|queen))
Line 4500 SUBPATTERNS	Line 4987 SUBPATTERNS
the captured substrings are "white queen" and "queen", and are numbered	the captured substrings are "white queen" and "queen", and are numbered
1 and 2. The maximum number of capturing subpatterns is 65535.	1 and 2. The maximum number of capturing subpatterns is 65535.

As a convenient shorthand, if any option settings are required at the	As a convenient shorthand, if any option settings are required at the
start of a non-capturing subpattern, the option letters may appear	start of a non-capturing subpattern, the option letters may appear
between the "?" and the ":". Thus the two patterns	between the "?" and the ":". Thus the two patterns

(?i:saturday\|sunday)	(?i:saturday\|sunday)
(?:(?i)saturday\|sunday)	(?:(?i)saturday\|sunday)

match exactly the same set of strings. Because alternative branches are	match exactly the same set of strings. Because alternative branches are
tried from left to right, and options are not reset until the end of	tried from left to right, and options are not reset until the end of
the subpattern is reached, an option setting in one branch does affect	the subpattern is reached, an option setting in one branch does affect
subsequent branches, so the above patterns match "SUNDAY" as well as	subsequent branches, so the above patterns match "SUNDAY" as well as
"Saturday".	"Saturday".


DUPLICATE SUBPATTERN NUMBERS	DUPLICATE SUBPATTERN NUMBERS

Perl 5.10 introduced a feature whereby each alternative in a subpattern	Perl 5.10 introduced a feature whereby each alternative in a subpattern
uses the same numbers for its capturing parentheses. Such a subpattern	uses the same numbers for its capturing parentheses. Such a subpattern
starts with (?\| and is itself a non-capturing subpattern. For example,	starts with (?\| and is itself a non-capturing subpattern. For example,
consider this pattern:	consider this pattern:

(?\|(Sat)ur\|(Sun))day	(?\|(Sat)ur\|(Sun))day

Because the two alternatives are inside a (?\| group, both sets of cap-	Because the two alternatives are inside a (?\| group, both sets of cap-
turing parentheses are numbered one. Thus, when the pattern matches,	turing parentheses are numbered one. Thus, when the pattern matches,
you can look at captured substring number one, whichever alternative	you can look at captured substring number one, whichever alternative
matched. This construct is useful when you want to capture part, but	matched. This construct is useful when you want to capture part, but
not all, of one of a number of alternatives. Inside a (?\| group, paren-	not all, of one of a number of alternatives. Inside a (?\| group, paren-
theses are numbered as usual, but the number is reset at the start of	theses are numbered as usual, but the number is reset at the start of
each branch. The numbers of any capturing parentheses that follow the	each branch. The numbers of any capturing parentheses that follow the
subpattern start after the highest number used in any branch. The fol-	subpattern start after the highest number used in any branch. The fol-
lowing example is taken from the Perl documentation. The numbers under-	lowing example is taken from the Perl documentation. The numbers under-
neath show in which buffer the captured content will be stored.	neath show in which buffer the captured content will be stored.

Line 4538 DUPLICATE SUBPATTERN NUMBERS	Line 5025 DUPLICATE SUBPATTERN NUMBERS
/ ( a ) (?\| x ( y ) z \| (p (q) r) \| (t) u (v) ) ( z ) /x	/ ( a ) (?\| x ( y ) z \| (p (q) r) \| (t) u (v) ) ( z ) /x
# 1 2 2 3 2 3 4	# 1 2 2 3 2 3 4

A back reference to a numbered subpattern uses the most recent value	A back reference to a numbered subpattern uses the most recent value
that is set for that number by any subpattern. The following pattern	that is set for that number by any subpattern. The following pattern
matches "abcabc" or "defdef":	matches "abcabc" or "defdef":

/(?\|(abc)\|(def))\1/	/(?\|(abc)\|(def))\1/

In contrast, a subroutine call to a numbered subpattern always refers	In contrast, a subroutine call to a numbered subpattern always refers
to the first one in the pattern with the given number. The following	to the first one in the pattern with the given number. The following
pattern matches "abcabc" or "defabc":	pattern matches "abcabc" or "defabc":

/(?\|(abc)\|(def))(?1)/	/(?\|(abc)\|(def))(?1)/

If a condition test for a subpattern's having matched refers to a non-	If a condition test for a subpattern's having matched refers to a non-
unique number, the test is true if any of the subpatterns of that num-	unique number, the test is true if any of the subpatterns of that num-
ber have matched.	ber have matched.

An alternative approach to using this "branch reset" feature is to use	An alternative approach to using this "branch reset" feature is to use
duplicate named subpatterns, as described in the next section.	duplicate named subpatterns, as described in the next section.


NAMED SUBPATTERNS	NAMED SUBPATTERNS

Identifying capturing parentheses by number is simple, but it can be	Identifying capturing parentheses by number is simple, but it can be
very hard to keep track of the numbers in complicated regular expres-	very hard to keep track of the numbers in complicated regular expres-
sions. Furthermore, if an expression is modified, the numbers may	sions. Furthermore, if an expression is modified, the numbers may
change. To help with this difficulty, PCRE supports the naming of sub-	change. To help with this difficulty, PCRE supports the naming of sub-
patterns. This feature was not added to Perl until release 5.10. Python	patterns. This feature was not added to Perl until release 5.10. Python
had the feature earlier, and PCRE introduced it at release 4.0, using	had the feature earlier, and PCRE introduced it at release 4.0, using
the Python syntax. PCRE now supports both the Perl and the Python syn-	the Python syntax. PCRE now supports both the Perl and the Python syn-
tax. Perl allows identically numbered subpatterns to have different	tax. Perl allows identically numbered subpatterns to have different
names, but PCRE does not.	names, but PCRE does not.

In PCRE, a subpattern can be named in one of three ways: (?<name>...)	In PCRE, a subpattern can be named in one of three ways: (?<name>...)
or (?'name'...) as in Perl, or (?P<name>...) as in Python. References	or (?'name'...) as in Perl, or (?P<name>...) as in Python. References
to capturing parentheses from other parts of the pattern, such as back	to capturing parentheses from other parts of the pattern, such as back
references, recursion, and conditions, can be made by name as well as	references, recursion, and conditions, can be made by name as well as
by number.	by number.

Names consist of up to 32 alphanumeric characters and underscores.	Names consist of up to 32 alphanumeric characters and underscores.
Named capturing parentheses are still allocated numbers as well as	Named capturing parentheses are still allocated numbers as well as
names, exactly as if the names were not present. The PCRE API provides	names, exactly as if the names were not present. The PCRE API provides
function calls for extracting the name-to-number translation table from	function calls for extracting the name-to-number translation table from
a compiled pattern. There is also a convenience function for extracting	a compiled pattern. There is also a convenience function for extracting
a captured substring by name.	a captured substring by name.

By default, a name must be unique within a pattern, but it is possible	By default, a name must be unique within a pattern, but it is possible
to relax this constraint by setting the PCRE_DUPNAMES option at compile	to relax this constraint by setting the PCRE_DUPNAMES option at compile
time. (Duplicate names are also always permitted for subpatterns with	time. (Duplicate names are also always permitted for subpatterns with
the same number, set up as described in the previous section.) Dupli-	the same number, set up as described in the previous section.) Dupli-
cate names can be useful for patterns where only one instance of the	cate names can be useful for patterns where only one instance of the
named parentheses can match. Suppose you want to match the name of a	named parentheses can match. Suppose you want to match the name of a
weekday, either as a 3-letter abbreviation or as the full name, and in	weekday, either as a 3-letter abbreviation or as the full name, and in
both cases you want to extract the abbreviation. This pattern (ignoring	both cases you want to extract the abbreviation. This pattern (ignoring
the line breaks) does the job:	the line breaks) does the job:

Line 4599 NAMED SUBPATTERNS	Line 5086 NAMED SUBPATTERNS
(?<DN>Thu)(?:rsday)?\|	(?<DN>Thu)(?:rsday)?\|
(?<DN>Sat)(?:urday)?	(?<DN>Sat)(?:urday)?

There are five capturing substrings, but only one is ever set after a	There are five capturing substrings, but only one is ever set after a
match. (An alternative way of solving this problem is to use a "branch	match. (An alternative way of solving this problem is to use a "branch
reset" subpattern, as described in the previous section.)	reset" subpattern, as described in the previous section.)

The convenience function for extracting the data by name returns the	The convenience function for extracting the data by name returns the
substring for the first (and in this example, the only) subpattern of	substring for the first (and in this example, the only) subpattern of
that name that matched. This saves searching to find which numbered	that name that matched. This saves searching to find which numbered
subpattern it was.	subpattern it was.

If you make a back reference to a non-unique named subpattern from	If you make a back reference to a non-unique named subpattern from
elsewhere in the pattern, the one that corresponds to the first occur-	elsewhere in the pattern, the one that corresponds to the first occur-
rence of the name is used. In the absence of duplicate numbers (see the	rence of the name is used. In the absence of duplicate numbers (see the
previous section) this is the one with the lowest number. If you use a	previous section) this is the one with the lowest number. If you use a
named reference in a condition test (see the section about conditions	named reference in a condition test (see the section about conditions
below), either to check whether a subpattern has matched, or to check	below), either to check whether a subpattern has matched, or to check
for recursion, all subpatterns with the same name are tested. If the	for recursion, all subpatterns with the same name are tested. If the
condition is true for any one of them, the overall condition is true.	condition is true for any one of them, the overall condition is true.
This is the same behaviour as testing by number. For further details of	This is the same behaviour as testing by number. For further details of
the interfaces for handling named subpatterns, see the pcreapi documen-	the interfaces for handling named subpatterns, see the pcreapi documen-
tation.	tation.

Warning: You cannot use different names to distinguish between two sub-	Warning: You cannot use different names to distinguish between two sub-
patterns with the same number because PCRE uses only the numbers when	patterns with the same number because PCRE uses only the numbers when
matching. For this reason, an error is given at compile time if differ-	matching. For this reason, an error is given at compile time if differ-
ent names are given to subpatterns with the same number. However, you	ent names are given to subpatterns with the same number. However, you
can give the same name to subpatterns with the same number, even when	can give the same name to subpatterns with the same number, even when
PCRE_DUPNAMES is not set.	PCRE_DUPNAMES is not set.


REPETITION	REPETITION

Repetition is specified by quantifiers, which can follow any of the	Repetition is specified by quantifiers, which can follow any of the
following items:	following items:

a literal data character	a literal data character
the dot metacharacter	the dot metacharacter
the \C escape sequence	the \C escape sequence
the \X escape sequence (in UTF-8 mode with Unicode properties)	the \X escape sequence
the \R escape sequence	the \R escape sequence
an escape such as \d or \pL that matches a single character	an escape such as \d or \pL that matches a single character
a character class	a character class
Line 4644 REPETITION	Line 5131 REPETITION
a parenthesized subpattern (including assertions)	a parenthesized subpattern (including assertions)
a subroutine call to a subpattern (recursive or otherwise)	a subroutine call to a subpattern (recursive or otherwise)

The general repetition quantifier specifies a minimum and maximum num-	The general repetition quantifier specifies a minimum and maximum num-
ber of permitted matches, by giving the two numbers in curly brackets	ber of permitted matches, by giving the two numbers in curly brackets
(braces), separated by a comma. The numbers must be less than 65536,	(braces), separated by a comma. The numbers must be less than 65536,
and the first must be less than or equal to the second. For example:	and the first must be less than or equal to the second. For example:

z{2,4}	z{2,4}

matches "zz", "zzz", or "zzzz". A closing brace on its own is not a	matches "zz", "zzz", or "zzzz". A closing brace on its own is not a
special character. If the second number is omitted, but the comma is	special character. If the second number is omitted, but the comma is
present, there is no upper limit; if the second number and the comma	present, there is no upper limit; if the second number and the comma
are both omitted, the quantifier specifies an exact number of required	are both omitted, the quantifier specifies an exact number of required
matches. Thus	matches. Thus

[aeiou]{3,}	[aeiou]{3,}
Line 4663 REPETITION	Line 5150 REPETITION

\d{8}	\d{8}

matches exactly 8 digits. An opening curly bracket that appears in a	matches exactly 8 digits. An opening curly bracket that appears in a
position where a quantifier is not allowed, or one that does not match	position where a quantifier is not allowed, or one that does not match
the syntax of a quantifier, is taken as a literal character. For exam-	the syntax of a quantifier, is taken as a literal character. For exam-
ple, {,6} is not a quantifier, but a literal string of four characters.	ple, {,6} is not a quantifier, but a literal string of four characters.

In UTF-8 mode, quantifiers apply to UTF-8 characters rather than to	In UTF modes, quantifiers apply to characters rather than to individual
individual bytes. Thus, for example, \x{100}{2} matches two UTF-8 char-	data units. Thus, for example, \x{100}{2} matches two characters, each
acters, each of which is represented by a two-byte sequence. Similarly,	of which is represented by a two-byte sequence in a UTF-8 string. Simi-
when Unicode property support is available, \X{3} matches three Unicode	larly, \X{3} matches three Unicode extended sequences, each of which
extended sequences, each of which may be several bytes long (and they	may be several data units long (and they may be of different lengths).
may be of different lengths).

The quantifier {0} is permitted, causing the expression to behave as if	The quantifier {0} is permitted, causing the expression to behave as if
the previous item and the quantifier were not present. This may be use-	the previous item and the quantifier were not present. This may be use-
Line 5109 ASSERTIONS	Line 5595 ASSERTIONS
then try to match. If there are insufficient characters before the cur-	then try to match. If there are insufficient characters before the cur-
rent position, the assertion fails.	rent position, the assertion fails.

In UTF-8 mode, PCRE does not allow the \C escape (which matches a sin-	In a UTF mode, PCRE does not allow the \C escape (which matches a sin-
gle byte, even in UTF-8 mode) to appear in lookbehind assertions,	gle data unit even in a UTF mode) to appear in lookbehind assertions,
because it makes it impossible to calculate the length of the lookbe-	because it makes it impossible to calculate the length of the lookbe-
hind. The \X and \R escapes, which can match different numbers of	hind. The \X and \R escapes, which can match different numbers of data
bytes, are also not permitted.	units, are also not permitted.

"Subroutine" calls (see below) such as (?2) or (?&X) are permitted in	"Subroutine" calls (see below) such as (?2) or (?&X) are permitted in
lookbehinds, as long as the subpattern matches a fixed-length string.	lookbehinds, as long as the subpattern matches a fixed-length string.
Line 5338 COMMENTS	Line 5824 COMMENTS
comment, which in this case continues to immediately after the next	comment, which in this case continues to immediately after the next
newline character or character sequence in the pattern. Which charac-	newline character or character sequence in the pattern. Which charac-
ters are interpreted as newlines is controlled by the options passed to	ters are interpreted as newlines is controlled by the options passed to
pcre_compile() or by a special sequence at the start of the pattern, as	a compiling function or by a special sequence at the start of the pat-
described in the section entitled "Newline conventions" above. Note	tern, as described in the section entitled "Newline conventions" above.
that the end of this type of comment is a literal newline sequence in	Note that the end of this type of comment is a literal newline sequence
the pattern; escape sequences that happen to represent a newline do not	in the pattern; escape sequences that happen to represent a newline do
count. For example, consider this pattern when PCRE_EXTENDED is set,	not count. For example, consider this pattern when PCRE_EXTENDED is
and the default newline convention is in force:	set, and the default newline convention is in force:

abc #comment \n still comment	abc #comment \n still comment

Line 5636 CALLOUTS	Line 6122 CALLOUTS
PCRE provides a similar feature, but of course it cannot obey arbitrary	PCRE provides a similar feature, but of course it cannot obey arbitrary
Perl code. The feature is called "callout". The caller of PCRE provides	Perl code. The feature is called "callout". The caller of PCRE provides
an external function by putting its entry point in the global variable	an external function by putting its entry point in the global variable
pcre_callout. By default, this variable contains NULL, which disables	pcre_callout (8-bit library) or pcre16_callout (16-bit library). By
all calling out.	default, this variable contains NULL, which disables all calling out.

Within a regular expression, (?C) indicates the points at which the	Within a regular expression, (?C) indicates the points at which the
external function is to be called. If you want to identify different	external function is to be called. If you want to identify different
Line 5647 CALLOUTS	Line 6133 CALLOUTS

(?C1)abc(?C2)def	(?C1)abc(?C2)def

If the PCRE_AUTO_CALLOUT flag is passed to pcre_compile(), callouts are	If the PCRE_AUTO_CALLOUT flag is passed to a compiling function, call-
automatically installed before each item in the pattern. They are all	outs are automatically installed before each item in the pattern. They
numbered 255.	are all numbered 255.

During matching, when PCRE reaches a callout point (and pcre_callout is	During matching, when PCRE reaches a callout point, the external func-
set), the external function is called. It is provided with the number	tion is called. It is provided with the number of the callout, the
of the callout, the position in the pattern, and, optionally, one item	position in the pattern, and, optionally, one item of data originally
of data originally supplied by the caller of pcre_exec(). The callout	supplied by the caller of the matching function. The callout function
function may cause matching to proceed, to backtrack, or to fail alto-	may cause matching to proceed, to backtrack, or to fail altogether. A
gether. A complete description of the interface to the callout function	complete description of the interface to the callout function is given
is given in the pcrecallout documentation.	in the pcrecallout documentation.


BACKTRACKING CONTROL	BACKTRACKING CONTROL
Line 5670 BACKTRACKING CONTROL	Line 6156 BACKTRACKING CONTROL
in this section.	in this section.

Since these verbs are specifically related to backtracking, most of	Since these verbs are specifically related to backtracking, most of
them can be used only when the pattern is to be matched using	them can be used only when the pattern is to be matched using one of
pcre_exec(), which uses a backtracking algorithm. With the exception of	the traditional matching functions, which use a backtracking algorithm.
(*FAIL), which behaves like a failing negative assertion, they cause an	With the exception of (*FAIL), which behaves like a failing negative
error if encountered by pcre_dfa_exec().	assertion, they cause an error if encountered by a DFA matching func-
	tion.

If any of these verbs are used in an assertion or in a subpattern that	If any of these verbs are used in an assertion or in a subpattern that
is called as a subroutine (whether or not recursively), their effect is	is called as a subroutine (whether or not recursively), their effect is
confined to that subpattern; it does not extend to the surrounding pat-	confined to that subpattern; it does not extend to the surrounding pat-
tern, with one exception: the name from a (MARK), (PRUNE), or (*THEN)	tern, with one exception: the name from a (MARK), (PRUNE), or (*THEN)
that is encountered in a successful positive assertion is passed back	that is encountered in a successful positive assertion is passed back
when a match succeeds (compare capturing parentheses in assertions).	when a match succeeds (compare capturing parentheses in assertions).
Note that such subpatterns are processed as anchored at the point where	Note that such subpatterns are processed as anchored at the point where
they are tested. Note also that Perl's treatment of subroutines is dif-	they are tested. Note also that Perl's treatment of subroutines is dif-
ferent in some cases.	ferent in some cases.

The new verbs make use of what was previously invalid syntax: an open-	The new verbs make use of what was previously invalid syntax: an open-
ing parenthesis followed by an asterisk. They are generally of the form	ing parenthesis followed by an asterisk. They are generally of the form
(VERB) or (VERB:NAME). Some may take either form, with differing be-	(VERB) or (VERB:NAME). Some may take either form, with differing be-
haviour, depending on whether or not an argument is present. A name is	haviour, depending on whether or not an argument is present. A name is
any sequence of characters that does not include a closing parenthesis.	any sequence of characters that does not include a closing parenthesis.
If the name is empty, that is, if the closing parenthesis immediately	If the name is empty, that is, if the closing parenthesis immediately
follows the colon, the effect is as if the colon were not there. Any	follows the colon, the effect is as if the colon were not there. Any
number of these verbs may occur in a pattern.	number of these verbs may occur in a pattern.

PCRE contains some optimizations that are used to speed up matching by	PCRE contains some optimizations that are used to speed up matching by
running some checks at the start of each match attempt. For example, it	running some checks at the start of each match attempt. For example, it
may know the minimum length of matching subject, or that a particular	may know the minimum length of matching subject, or that a particular
character must be present. When one of these optimizations suppresses	character must be present. When one of these optimizations suppresses
the running of a match, any included backtracking verbs will not, of	the running of a match, any included backtracking verbs will not, of
course, be processed. You can suppress the start-of-match optimizations	course, be processed. You can suppress the start-of-match optimizations
by setting the PCRE_NO_START_OPTIMIZE option when calling pcre_com-	by setting the PCRE_NO_START_OPTIMIZE opt by setting the PCRE_NO_START_OPTIMIZE option when calling pcre_com-
pile() or pcre_exec(), or by starting the pattern with (*NO_START_OPT).	pile() or pcre_exec(), or by starting the pattern with (*NO_START_OPT).

Experiments with Perl suggest that it too has similar optimizations,	Experiments with Perl suggest that it too has similar optimizations,
sometimes leading to anomalous results.	sometimes leading to anomalous results.

Verbs that act immediately	Verbs that act immediately

The following verbs act as soon as they are encountered. They may not	The following verbs act as soon as they are encountered. Th The following verbs act as soon as they are encountered. They may not
be followed by a name.	be followed by a name.

(*ACCEPT)	(*ACCEPT)

This verb causes the match to end successfully, skipping the remainder	This verb causes the match to end successfully, skipping the remainder
of the pattern. However, when it is inside a subpattern that is called	of the pattern. However, when it is inside a subpattern that is called
as a subroutine, only that subpattern is ended successfully. Matching	as a subroutine, only that subpattern is ended successfully. Matching
then continues at the outer level. If (*ACCEPT) is inside capturing	then continues at the outer level. If (*ACCEPT) is inside capturing
parentheses, the data so far is captured. For example:	parentheses, the data so far is captured. For example:

A((?:A\|B(*ACCEPT)\|C)D)	A((?:A\|B(*ACCEPT)\|C)D)

This matches "AB", "AAD", or "ACD"; when it matches "AB", "B" is cap-	This matches "AB", "AAD", or "ACD"; when it matches "AB", "B" is cap-
tured by the outer parentheses.	tured by the outer parentheses.

(FAIL) or (F)	(FAIL) or (F)

This verb causes a matching failure, forcing backtracking to occur. It	This verb causes a matching failure, forcing backtracking to occur. It
is equivalent to (?!) but easier to read. The Perl documentation notes	is equivalent to (?!) but easier to read. The Perl documentation notes
that it is probably useful only when combined with (?{}) or (??{}).	that it is probably useful only when combined with (?{}) or (??{}).
Those are, of course, Perl features that are not present in PCRE. The	Those are, of course, Perl features that are not present in PCRE. The
nearest equivalent is the callout feature, as for example in this pat-	nearest equivalent is the callout feature, as for example in this pat-
tern:	tern:

a+(?C)(*FAIL)	a+(?C)(*FAIL)

A match with the string "aaaa" always fails, but the callout is taken	A match with the string "aaaa" always fails, but the callout is taken
before each backtrack happens (in this example, 10 times).	before each backtrack happens (in this example, 10 times).

Recording which path was taken	Recording which path was taken

There is one verb whose main purpose is to track how a match was	There is one verb whose main purpose is to track how a match was
arrived at, though it also has a secondary use in conjunction with	arrived at, though it also has a secondary use in conjunction with
advancing the match starting point (see (*SKIP) below).	advancing the match starting point (see (*SKIP) below).

(MARK:NAME) or (:NAME)	(MARK:NAME) or (:NAME)

A name is always required with this verb. There may be as many	A name is always required with this verb. There may be as many
instances of (*MARK) as you like in a pattern, and their names do not	instances of (*MARK) as you like in a pattern, and their names do not
have to be unique.	have to be unique.

When a match succeeds, the name of the last-encountered (*MARK) on the	When a match succeeds, the name of the last-encountered (*MARK) on the
matching path is passed back to the caller via the pcre_extra data	matching path is passed back to the caller as described in the section
structure, as described in the section on pcre_extra in the pcreapi	entitled "Extra data for pcre_exec()" in the pcreapi documentation.
documentation. Here is an example of pcretest output, where the /K mod-	Here is an example of pcretest output, where the /K modifier requests
ifier requests the retrieval and outputting of (*MARK) data:	the retrieval and outputting of (*MARK) data:

re> /X(MARK:A)Y\|X(MARK:B)Z/K	re> /X(MARK:A)Y\|X(MARK:B)Z/K
data> XY	data> XY
Line 5765 BACKTRACKING CONTROL	Line 6252 BACKTRACKING CONTROL
MK: B	MK: B

The (*MARK) name is tagged with "MK:" in this output, and in this exam-	The (*MARK) name is tagged with "MK:" in this output, and in this exam-
ple it indicates which of the two alternatives matched. This is a more	ple it indicates which of the two alternatives matched. This is a more
efficient way of obtaining this information than putting each alterna-	efficient way of obtaining this information than putting each alterna-
tive in its own capturing parentheses.	tive in its own capturing parentheses.

If (*MARK) is encountered in a positive assertion, its name is recorded	If (*MARK) is encountered in a positive assertion, its name is recorded
and passed back if it is the last-encountered. This does not happen for	and passed back if it is the last-encountered. This does not happen for
negative assertions.	negative assertions.

After a partial match or a failed match, the name of the last encoun-	After a partial match or a failed match, the name of the last encoun-
tered (*MARK) in the entire match process is returned. For example:	tered (*MARK) in the entire match process is returned. For example:

re> /X(MARK:A)Y\|X(MARK:B)Z/K	re> /X(MARK:A)Y\|X(MARK:B)Z/K
data> XP	data> XP
No match, mark = B	No match, mark = B

Note that in this unanchored example the mark is retained from the	Note that in this unanchored example the mark is retained from the
match attempt that started at the letter "X". Subsequent match attempts	match attempt that started at the letter "X". Subsequent match attempts
starting at "P" and then with an empty string do not get as far as the	starting at "P" and then with an empty string do not get as far as the
(*MARK) item, but nevertheless do not reset it.	(*MARK) item, but nevertheless do not reset it.

Verbs that act after backtracking	Verbs that act after backtracking

The following verbs do nothing when they are encountered. Matching con-	The following verbs do nothing when they are encountered. Matching con-
tinues with what follows, but if there is no subsequent match, causing	tinues with what follows, but if there is no subsequent match, causing
a backtrack to the verb, a failure is forced. That is, backtracking	a backtrack to the verb, a failure is forced. That is, backtracking
cannot pass to the left of the verb. However, when one of these verbs	cannot pass to the left of the verb. However, when one of these verbs
appears inside an atomic group, its effect is confined to that group,	appears inside an atomic group, its effect is confined to that group,
because once the group has been matched, there is never any backtrack-	because once the group has been matched, there is never any backtrack-
ing into it. In this situation, backtracking can "jump back" to the	ing into it. In this situation, backtracking can "jump back" to the
left of the entire atomic group. (Remember also, as stated above, that	left of the entire atomic group. (Remember also, as stated above, that
this localization also applies in subroutine calls and assertions.)	this localization also applies in subroutine calls and assertions.)

These verbs differ in exactly what kind of failure occurs when back-	These verbs differ in exactly what kind of failure occurs when back-
tracking reaches them.	tracking reaches them.

(*COMMIT)	(*COMMIT)

This verb, which may not be followed by a name, causes the whole match	This verb, which may not be followed by a name, causes the whole match
to fail outright if the rest of the pattern does not match. Even if the	to fail outright if the rest of the pattern does not match. Even if the
pattern is unanchored, no further attempts to find a match by advancing	pattern is unanchored, no further attempts to find a match by advancing
the starting point take place. Once (*COMMIT) has been passed,	the starting point take place. Once (*COMMIT) has been passed,
pcre_exec() is committed to finding a match at the current starting	pcre_exec() is committed to finding a match at the current starting
point, or not at all. For example:	point, or not at all. For example:

a+(*COMMIT)b	a+(*COMMIT)b

This matches "xxaab" but not "aacaab". It can be thought of as a kind	This matches "xxaab" but not "aacaab". It can be thought of as a kind
of dynamic anchor, or "I've started, so I must finish." The name of the	of dynamic anchor, or "I've started, so I must finish." The name of the
most recently passed (MARK) in the path is passed back when (COMMIT)	most recently passed (MARK) in the path is passed back when (COMMIT)
forces a match failure.	forces a match failure.

Note that (*COMMIT) at the start of a pattern is not the same as an	Note that (*COMMIT) at the start of a pattern is not the same as an
anchor, unless PCRE's start-of-match optimizations are turned off, as	anchor, unless PCRE's start-of-match optimizations are turned off, as
shown in this pcretest example:	shown in this pcretest example:

re> /(*COMMIT)abc/	re> /(*COMMIT)abc/
Line 5826 BACKTRACKING CONTROL	Line 6313 BACKTRACKING CONTROL
xyzabc\Y	xyzabc\Y
No match	No match

PCRE knows that any match must start with "a", so the optimization	PCRE knows that any match must start with "a", so the optimization
skips along the subject to "a" before running the first match attempt,	skips along the subject to "a" before running the first match attempt,
which succeeds. When the optimization is disabled by the \Y escape in	which succeeds. When the optimization is disabled by the \Y escape in
the second subject, the match starts at "x" and so the (*COMMIT) causes	the second subject, the match starts at "x" and so the (*COMMIT) causes
it to fail without trying any other starting points.	it to fail without trying any other starting points.

(PRUNE) or (PRUNE:NAME)	(PRUNE) or (PRUNE:NAME)

This verb causes the match to fail at the current starting position in	This verb causes the match to fail at the current starting position in
the subject if the rest of the pattern does not match. If the pattern	the subject if the rest of the pattern does not match. If the pattern
is unanchored, the normal "bumpalong" advance to the next starting	is unanchored, the normal "bumpalong" advance to the next starting
character then happens. Backtracking can occur as usual to the left of	character then happens. Backtracking can occur as usual to the left of
(*PRUNE), before it is reached, or when matching to the right of	(*PRUNE), before it is reached, or when matching to the right of
(*PRUNE), but if there is no match to the right, backtracking cannot	(*PRUNE), but if there is no match to the right, backtracking cannot
cross (PRUNE). In simple cases, the use of (PRUNE) is just an alter-	cross (PRUNE). In simple cases, the use of (PRUNE) is just an alter-
native to an atomic group or possessive quantifier, but there are some	native to an atomic group or possessive quantifier, but there are some
uses of (*PRUNE) that cannot be expressed in any other way. The behav-	uses of (*PRUNE) that cannot be expressed in any other way. The behav-
iour of (PRUNE:NAME) is the same as (MARK:NAME)(*PRUNE). In an	iour of (PRUNE:NAME) is the same as (MARK:NAME)(*PRUNE). In an
anchored pattern (PRUNE) has the same effect as (COMMIT).	anchored pattern (PRUNE) has the same effect as (COMMIT).

(*SKIP)	(*SKIP)

This verb, when given without a name, is like (*PRUNE), except that if	This verb, when given without a name, is like (*PRUNE), except that if
the pattern is unanchored, the "bumpalong" advance is not to the next	the pattern is unanchored, the "bumpalong" advance is not to the next
character, but to the position in the subject where (*SKIP) was encoun-	character, but to the position in the subject where (*SKIP) was encoun-
tered. (*SKIP) signifies that whatever text was matched leading up to	tered. (*SKIP) signifies that whatever text was matched leading up to
it cannot be part of a successful match. Consider:	it cannot be part of a successful match. Consider:

a+(*SKIP)b	a+(*SKIP)b

If the subject is "aaaac...", after the first match attempt fails	If the subject is "aaaac...", after the first match attempt fails
(starting at the first character in the string), the starting point	(starting at the first character in the string), the starting point
skips on to start the next attempt at "c". Note that a possessive quan-	skips on to start the next attempt at "c". Note that a possessive quan-
tifer does not have the same effect as this example; although it would	tifer does not have the same effect as this example; although it would
suppress backtracking during the first match attempt, the second	suppress backtracking during the first match attempt, the second
attempt would start at the second character instead of skipping on to	attempt would start at the second character instead of skipping on to
"c".	"c".

(*SKIP:NAME)	(*SKIP:NAME)

When (*SKIP) has an associated name, its behaviour is modified. If the	When (*SKIP) has an associated name, its behaviour is modified. If the
following pattern fails to match, the previous path through the pattern	following pattern fails to match, the previous path through the pattern
is searched for the most recent (*MARK) that has the same name. If one	is searched for the most recent (*MARK) that has the same name. If one
is found, the "bumpalong" advance is to the subject position that cor-	is found, the "bumpalong" advance is to the subject position that cor-
responds to that (MARK) instead of to where (SKIP) was encountered.	responds to that (MARK) instead of to where (SKIP) was encountered.
If no (MARK) with a matching name is found, the (SKIP) is ignored.	If no (MARK) with a matching name is found, the (SKIP) is ignored.

(THEN) or (THEN:NAME)	(THEN) or (THEN:NAME)

This verb causes a skip to the next innermost alternative if the rest	This verb causes a skip to the next innermost alternative if the rest
of the pattern does not match. That is, it cancels pending backtrack-	of the pattern does not match. That is, it cancels pending backtrack-
ing, but only within the current alternative. Its name comes from the	ing, but only within the current alternative. Its name comes from the
observation that it can be used for a pattern-based if-then-else block:	observation that it can be used for a pattern-based if-then-else block:

( COND1 (THEN) FOO \| COND2 (THEN) BAR \| COND3 (*THEN) BAZ ) ...	( COND1 (THEN) FOO \| COND2 (THEN) BAR \| COND3 (*THEN) BAZ ) ...

If the COND1 pattern matches, FOO is tried (and possibly further items	If the COND1 pattern matches, FOO is tried (and possibly further items
after the end of the group if FOO succeeds); on failure, the matcher	after the end of the group if FOO succeeds); on failure, the matcher
skips to the second alternative and tries COND2, without backtracking	skips to the second alternative and tries COND2, without backtracking
into COND1. The behaviour of (*THEN:NAME) is exactly the same as	into COND1. The behaviour of (*THEN:NAME) is exactly the same as
(MARK:NAME)(THEN). If (*THEN) is not inside an alternation, it acts	(MARK:NAME)(THEN). If (*THEN) is not inside an alternation, it acts
like (*PRUNE).	like (*PRUNE).

Note that a subpattern that does not contain a \| character is just a	Note that a subpattern that does not contain a \| character is just a
part of the enclosing alternative; it is not a nested alternation with	part of the enclosing alternative; it is not a nested alternation with
only one alternative. The effect of (*THEN) extends beyond such a sub-	only one alternative. The effect of (*THEN) extends beyond such a sub-
pattern to the enclosing alternative. Consider this pattern, where A,	pattern to the enclosing alternative. Consider this pattern, where A,
B, etc. are complex pattern fragments that do not contain any \| charac-	B, etc. are complex pattern fragments that do not contain any \| charac-
ters at this level:	ters at this level:

A (B(*THEN)C) \| D	A (B(*THEN)C) \| D

If A and B are matched, but there is a failure in C, matching does not	If A and B are matched, but there is a failure in C, matching does not
backtrack into A; instead it moves to the next alternative, that is, D.	backtrack into A; instead it moves to the next alternative, that is, D.
However, if the subpattern containing (*THEN) is given an alternative,	However, if the subpattern containing (*THEN) is given an alternative,
it behaves differently:	it behaves differently:

A (B(THEN)C \| (FAIL)) \| D	A (B(THEN)C \| (FAIL)) \| D

The effect of (*THEN) is now confined to the inner subpattern. After a	The effect of (*THEN) is now confined to the inner subpattern. After a
failure in C, matching moves to (*FAIL), which causes the whole subpat-	failure in C, matching moves to (*FAIL), which causes the whole subpat-
tern to fail because there are no more alternatives to try. In this	tern to fail because there are no more alternatives to try. In this
case, matching does now backtrack into A.	case, matching does now backtrack into A.

Note also that a conditional subpattern is not considered as having two	Note also that a conditional subpattern is not considered as having two
alternatives, because only one is ever used. In other words, the \|	alternatives, because only one is ever used. In other words, the \|
character in a conditional subpattern has a different meaning. Ignoring	character in a conditional subpattern has a different meaning. Ignoring
white space, consider:	white space, consider:

^.? (?(?=a) a \| b(THEN)c )	^.? (?(?=a) a \| b(THEN)c )

If the subject is "ba", this pattern does not match. Because .*? is	If the subject is "ba", this pattern does not match. Because .*? is
ungreedy, it initially matches zero characters. The condition (?=a)	ungreedy, it initially matches zero characters. The condition (?=a)
then fails, the character "b" is matched, but "c" is not. At this	then fails, the character "b" is matched, but "c" is not. At this
point, matching does not backtrack to .*? as might perhaps be expected	point, matching does not backtrack to .*? as might perhaps be expected
from the presence of the \| character. The conditional subpattern is	from the presence of the \| character. The conditional subpattern is
part of the single alternative that comprises the whole pattern, and so	part of the single alternative that comprises the whole pattern, and so
the match fails. (If there was a backtrack into .*?, allowing it to	the match fails. (If there was a backtrack into .*?, allowing it to
match "b", the match would succeed.)	match "b", the match would succeed.)

The verbs just described provide four different "strengths" of control	The verbs just described provide four different "strengths" of control
when subsequent matching fails. (*THEN) is the weakest, carrying on the	when subsequent matching fails. (*THEN) is the weakest, carrying on the
match at the next alternative. (*PRUNE) comes next, failing the match	match at the next alternative. (*PRUNE) comes next, failing the match
at the current starting position, but allowing an advance to the next	at the current starting position, but allowing an advance to the next
character (for an unanchored pattern). (*SKIP) is similar, except that	character (for an unanchored pattern). (*SKIP) is similar, except that
the advance may be more than one character. (*COMMIT) is the strongest,	the advance may be more than one character. (*COMMIT) is the strongest,
causing the entire match to fail.	causing the entire match to fail.

Line 5940 BACKTRACKING CONTROL	Line 6427 BACKTRACKING CONTROL

(A(COMMIT)B(THEN)C\|D)	(A(COMMIT)B(THEN)C\|D)

Once A has matched, PCRE is committed to this match, at the current	Once A has matched, PCRE is committed to this match, at the current
starting position. If subsequently B matches, but C does not, the nor-	starting position. If subsequently B matches, but C does not, the nor-
mal (*THEN) action of trying the next alternative (that is, D) does not	mal (*THEN) action of trying the next alternative (that is, D) does not
happen because (*COMMIT) overrides.	happen because (*COMMIT) overrides.


SEE ALSO	SEE ALSO

pcreapi(3), pcrecallout(3), pcrematching(3), pcresyntax(3), pcre(3).	pcreapi(3), pcrecallout(3), pcrematching(3), pcresyntax(3), pcre(3),
	pcre16(3).


AUTHOR	AUTHOR
Line 5960 AUTHOR	Line 6448 AUTHOR

REVISION	REVISION

Last updated: 29 November 2011	Last updated: 09 January 2012
Copyright (c) 1997-2011 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------


Line 5976 PCRE REGULAR EXPRESSION SYNTAX SUMMARY	Line 6464 PCRE REGULAR EXPRESSION SYNTAX SUMMARY

The full syntax and semantics of the regular expressions that are sup-	The full syntax and semantics of the regular expressions that are sup-
ported by PCRE are described in the pcrepattern documentation. This	ported by PCRE are described in the pcrepattern documentation. This
document contains just a quick-reference summary of the syntax.	document contains a quick-reference summary of the syntax.


QUOTING	QUOTING
Line 6003 CHARACTER TYPES	Line 6491 CHARACTER TYPES

. any character except newline;	. any character except newline;
in dotall mode, any character whatsoever	in dotall mode, any character whatsoever
\C one byte, even in UTF-8 mode (best avoided)	\C one data unit, even in UTF mode (best avoided)
\d a decimal digit	\d a decimal digit
\D a character that is not a decimal digit	\D a character that is not a decimal digit
\h a horizontal whitespace character	\h a horizontal whitespace character
Line 6021 CHARACTER TYPES	Line 6509 CHARACTER TYPES
\X an extended Unicode sequence	\X an extended Unicode sequence

In PCRE, by default, \d, \D, \s, \S, \w, and \W recognize only ASCII	In PCRE, by default, \d, \D, \s, \S, \w, and \W recognize only ASCII
characters, even in UTF-8 mode. However, this can be changed by setting	characters, even in a UTF mode. However, this can be changed by setting
the PCRE_UCP option.	the PCRE_UCP option.


Line 6208 OPTION SETTING	Line 6696 OPTION SETTING
one of the newline-setting options with similar syntax:	one of the newline-setting options with similar syntax:

(*NO_START_OPT) no start-match optimization (PCRE_NO_START_OPTIMIZE)	(*NO_START_OPT) no start-match optimization (PCRE_NO_START_OPTIMIZE)
(*UTF8) set UTF-8 mode (PCRE_UTF8)	(*UTF8) set UTF-8 mode: 8-bit library (PCRE_UTF8)
	(*UTF16) set UTF-16 mode: 16-bit library (PCRE_UTF16)
(*UCP) set PCRE_UCP (use Unicode properties for \d etc)	(*UCP) set PCRE_UCP (use Unicode properties for \d etc)


Line 6277 BACKTRACKING CONTROL	Line 6766 BACKTRACKING CONTROL

(*ACCEPT) force successful match	(*ACCEPT) force successful match
(FAIL) force backtrack; synonym (F)	(FAIL) force backtrack; synonym (F)
	(MARK:NAME) set name to be passed back; synonym (:NAME)

The following act only when a subsequent match failure causes a back-	The following act only when a subsequent match failure causes a back-
track to reach them. They all force a match failure, but they differ in	track to reach them. They all force a match failure, but they differ in
Line 6285 BACKTRACKING CONTROL	Line 6775 BACKTRACKING CONTROL

(*COMMIT) overall failure, no advance of starting point	(*COMMIT) overall failure, no advance of starting point
(*PRUNE) advance to next starting character	(*PRUNE) advance to next starting character
(*SKIP) advance start to current matching position	(PRUNE:NAME) equivalent to (MARK:NAME)(*PRUNE)
	(*SKIP) advance to current matching position
	(*SKIP:NAME) advance to position corresponding to an earlier
	(MARK:NAME); if not found, the (SKIP) is ignored
(*THEN) local failure, backtrack to next alternation	(*THEN) local failure, backtrack to next alternation
	(THEN:NAME) equivalent to (MARK:NAME)(*THEN)


NEWLINE CONVENTIONS	NEWLINE CONVENTIONS

These are recognized only at the very start of the pattern or after a	These are recognized only at the very start of the pattern or after a
(BSR_...) or (UTF8) or (*UCP) option.	(BSR_...), (UTF8), (UTF16) or (UCP) option.

(*CR) carriage return only	(*CR) carriage return only
(*LF) linefeed only	(*LF) linefeed only
Line 6304 NEWLINE CONVENTIONS	Line 6798 NEWLINE CONVENTIONS
WHAT \R MATCHES	WHAT \R MATCHES

These are recognized only at the very start of the pattern or after a	These are recognized only at the very start of the pattern or after a
(*...) option that sets the newline convention or UTF-8 or UCP mode.	(*...) option that sets the newline convention or a UTF or UCP mode.

(*BSR_ANYCRLF) CR, LF, or CRLF	(*BSR_ANYCRLF) CR, LF, or CRLF
(*BSR_UNICODE) any Unicode newline sequence	(*BSR_UNICODE) any Unicode newline sequence
Line 6330 AUTHOR	Line 6824 AUTHOR

REVISION	REVISION

Last updated: 21 November 2010	Last updated: 10 January 2012
Copyright (c) 1997-2010 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------


Line 6342 NAME	Line 6836 NAME
PCRE - Perl-compatible regular expressions	PCRE - Perl-compatible regular expressions


UTF-8 AND UNICODE PROPERTY SUPPORT	UTF-8, UTF-16, AND UNICODE PROPERTY SUPPORT

In order process UTF-8 strings, you must build PCRE to include UTF-8	From Release 8.30, in addition to its previous UTF-8 support, PCRE also
support in the code, and, in addition, you must call pcre_compile()	supports UTF-16 by means of a separate 16-bit library. This can be
with the PCRE_UTF8 option flag, or the pattern must start with the	built as well as, or instead of, the 8-bit library.
sequence (*UTF8). When either of these is the case, both the pattern
and any subject strings that are matched against it are treated as
UTF-8 strings instead of strings of 1-byte characters. PCRE does not
support any other formats (in particular, it does not support UTF-16).

If you compile PCRE with UTF-8 support, but do not use it at run time,
	UTF-8 SUPPORT

	In order process UTF-8 strings, you must build PCRE's 8-bit library
	with UTF support, and, in addition, you must call pcre_compile() with
	the PCRE_UTF8 option flag, or the pattern must start with the sequence
	(*UTF8). When either of these is the case, both the pattern and any
	subject strings that are matched against it are treated as UTF-8
	strings instead of strings of 1-byte characters.


	UTF-16 SUPPORT

	In order process UTF-16 strings, you must build PCRE's 16-bit library
	with UTF support, and, in addition, you must call pcre16_compile() with
	the PCRE_UTF16 option flag, or the pattern must start with the sequence
	(*UTF16). When either of these is the case, both the pattern and any
	subject strings that are matched against it are treated as UTF-16
	strings instead of strings of 16-bit characters.


	UTF SUPPORT OVERHEAD

	If you compile PCRE with UTF support, but do not use it at run time,
the library will be a bit bigger, but the additional run time overhead	the library will be a bit bigger, but the additional run time overhead
is limited to testing the PCRE_UTF8 flag occasionally, so should not be	is limited to testing the PCRE_UTF8/16 flag occasionally, so should not
very big.	be very big.


	UNICODE PROPERTY SUPPORT

If PCRE is built with Unicode character property support (which implies	If PCRE is built with Unicode character property support (which implies
UTF-8 support), the escape sequences \p{..}, \P{..}, and \X are sup-	UTF support), the escape sequences \p{..}, \P{..}, and \X can be used.
ported. The available properties that can be tested are limited to the	The available properties that can be tested are limited to the general
general category properties such as Lu for an upper case letter or Nd	category properties such as Lu for an upper case letter or Nd for a
for a decimal number, the Unicode script names such as Arabic or Han,	decimal number, the Unicode script names such as Arabic or Han, and the
and the derived properties Any and L&. A full list is given in the	derived properties Any and L&. A full list is given in the pcrepattern
pcrepattern documentation. Only the short names for properties are sup-	documentation. Only the short names for properties are supported. For
ported. For example, \p{L} matches a letter. Its Perl synonym, \p{Let-	example, \p{L} matches a letter. Its Perl synonym, \p{Letter}, is not
ter}, is not supported. Furthermore, in Perl, many properties may	supported. Furthermore, in Perl, many properties may optionally be
optionally be prefixed by "Is", for compatibility with Perl 5.6. PCRE	prefixed by "Is", for compatibility with Perl 5.6. PCRE does not sup-
does not support this.	port this.

Validity of UTF-8 strings	Validity of UTF-8 strings

When you set the PCRE_UTF8 flag, the strings passed as patterns and	When you set the PCRE_UTF8 flag, the byte strings passed as patterns
subjects are (by default) checked for validity on entry to the relevant	and subjects are (by default) checked for validity on entry to the rel-
functions. From release 7.3 of PCRE, the check is according the rules	evant functions. From release 7.3 of PCRE, the check is according the
of RFC 3629, which are themselves derived from the Unicode specifica-	rules of RFC 3629, which are themselves derived from the Unicode speci-
tion. Earlier releases of PCRE followed the rules of RFC 2279, which	fication. Earlier releases of PCRE followed the rules of RFC 2279,
allows the full range of 31-bit values (0 to 0x7FFFFFFF). The current	which allows the full range of 31-bit values (0 to 0x7FFFFFFF). The
check allows only values in the range U+0 to U+10FFFF, excluding U+D800	current check allows only values in the range U+0 to U+10FFFF, exclud-
to U+DFFF.	ing U+D800 to U+DFFF.

The excluded code points are the "Low Surrogate Area" of Unicode, of	The excluded code points are the "Surrogate Area" of Unicode. They are
which the Unicode Standard says this: "The Low Surrogate Area does not	reserved for use by UTF-16, where they are used in pairs to encode
contain any character assignments, consequently no character code	codepoints with values greater than 0xFFFF. The code points that are
charts or namelists are provided for this area. Surrogates are reserved	encoded by UTF-16 pairs are available independently in the UTF-8 encod-
for use with UTF-16 and then must be used in pairs." The code points	ing. (In other words, the whole surrogate thing is a fudge for UTF-16
that are encoded by UTF-16 pairs are available as independent code	which unfortunately messes up UTF-8.)
points in the UTF-8 encoding. (In other words, the whole surrogate
thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)

If an invalid UTF-8 string is passed to PCRE, an error return is given.	If an invalid UTF-8 string is passed to PCRE, an error return is given.
At compile time, the only additional information is the offset to the	At compile time, the only additional information is the offset to the
Line 6420 UTF-8 AND UNICODE PROPERTY SUPPORT	Line 6934 UTF-8 AND UNICODE PROPERTY SUPPORT
this situation, you will have to apply your own validity check, and	this situation, you will have to apply your own validity check, and
avoid the use of JIT optimization.	avoid the use of JIT optimization.

General comments about UTF-8 mode	Validity of UTF-16 strings

1. An unbraced hexadecimal escape sequence (such as \xb3) matches a	When you set the PCRE_UTF16 flag, the strings of 16-bit data units that
two-byte UTF-8 character if the value is greater than 127.	are passed as patterns and subjects are (by default) checked for valid-
	ity on entry to the relevant functions. Values other than those in the
	surrogate range U+D800 to U+DFFF are independent code points. Values in
	the surrogate range must be used in pairs in the correct manner.

2. Octal numbers up to \777 are recognized, and match two-byte UTF-8	If an invalid UTF-16 string is passed to PCRE, an error return is
characters for values greater than \177.	given. At compile time, the only additional information is the offset
	to the first data unit of the failing character. The runtime functions
	pcre16_exec() and pcre16_dfa_exec() also pass back this information, as
	well as a more detailed reason code if the caller has provided memory
	in which to do this.

3. Repeat quantifiers apply to complete UTF-8 characters, not to indi-	In some situations, you may already know that your strings are valid,
vidual bytes, for example: \x{100}{3}.	and therefore want to skip these checks in order to improve perfor-
	mance. If you set the PCRE_NO_UTF16_CHECK flag at compile time or at
	run time, PCRE assumes that the pattern or subject it is given (respec-
	tively) contains only valid UTF-16 sequences. In this case, it does not
	diagnose an invalid UTF-16 string.

4. The dot metacharacter matches one UTF-8 character instead of a sin-	General comments about UTF modes
gle byte.

5. The escape sequence \C can be used to match a single byte in UTF-8	1. Codepoints less than 256 can be specified by either braced or
mode, but its use can lead to some strange effects because it breaks up	unbraced hexadecimal escape sequences (for example, \x{b3} or \xb3).
multibyte characters (see the description of \C in the pcrepattern doc-	Larger values have to use braced sequences.
umentation). The use of \C is not supported in the alternative matching
function pcre_dfa_exec(), nor is it supported in UTF-8 mode by the JIT
optimization of pcre_exec(). If JIT optimization is requested for a
UTF-8 pattern that contains \C, it will not succeed, and so the match-
ing will be carried out by the normal interpretive function.

	2. Octal numbers up to \777 are recognized, and in UTF-8 mode, they
	match two-byte characters for values greater than \177.

	3. Repeat quantifiers apply to complete UTF characters, not to individ-
	ual data units, for example: \x{100}{3}.

	4. The dot metacharacter matches one UTF character instead of a single
	data unit.

	5. The escape sequence \C can be used to match a single byte in UTF-8
	mode, or a single 16-bit data unit in UTF-16 mode, but its use can lead
	to some strange effects because it breaks up multi-unit characters (see
	the description of \C in the pcrepattern documentation). The use of \C
	is not supported in the alternative matching function
	pcre[16]_dfa_exec(), nor is it supported in UTF mode by the JIT opti-
	mization of pcre[16]_exec(). If JIT optimization is requested for a UTF
	pattern that contains \C, it will not succeed, and so the matching will
	be carried out by the normal interpretive function.

6. The character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly	6. The character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly
test characters of any code value, but, by default, the characters that	test characters of any code value, but, by default, the characters that
PCRE recognizes as digits, spaces, or word characters remain the same	PCRE recognizes as digits, spaces, or word characters remain the same
set as before, all with values less than 256. This remains true even	set as in non-UTF mode, all with values less than 256. This remains
when PCRE is built to include Unicode property support, because to do	true even when PCRE is built to include Unicode property support,
otherwise would slow down PCRE in many common cases. Note in particular	because to do otherwise would slow down PCRE in many common cases. Note
that this applies to \b and \B, because they are defined in terms of \w	in particular that this applies to \b and \B, because they are defined
and \W. If you really want to test for a wider sense of, say, "digit",	in terms of \w and \W. If you really want to test for a wider sense of,
you can use explicit Unicode property tests such as \p{Nd}. Alterna-	say, "digit", you can use explicit Unicode property tests such as
tively, if you set the PCRE_UCP option, the way that the character	\p{Nd}. Alternatively, if you set the PCRE_UCP option, the way that the
escapes work is changed so that Unicode properties are used to deter-	character escapes work is changed so that Unicode properties are used
mine which characters match. There are more details in the section on	to determine which characters match. There are more details in the sec-
generic character types in the pcrepattern documentation.	tion on generic character types in the pcrepattern documentation.

7. Similarly, characters that match the POSIX named character classes	7. Similarly, characters that match the POSIX named character classes
are all low-valued characters, unless the PCRE_UCP option is set.	are all low-valued characters, unless the PCRE_UCP option is set.
Line 6484 AUTHOR	Line 7022 AUTHOR

REVISION	REVISION

Last updated: 19 October 2011	Last updated: 13 January 2012
Copyright (c) 1997-2011 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------


Line 6502 PCRE JUST-IN-TIME COMPILER SUPPORT	Line 7040 PCRE JUST-IN-TIME COMPILER SUPPORT
speed up pattern matching. However, it comes at the cost of extra pro-	speed up pattern matching. However, it comes at the cost of extra pro-
cessing before the match is performed. Therefore, it is of most benefit	cessing before the match is performed. Therefore, it is of most benefit
when the same pattern is going to be matched many times. This does not	when the same pattern is going to be matched many times. This does not
necessarily mean many calls of pcre_exec(); if the pattern is not	necessarily mean many calls of a matching function; if the pattern is
anchored, matching attempts may take place many times at various posi-	not anchored, matching attempts may take place many times at various
tions in the subject, even for a single call to pcre_exec(). If the	positions in the subject, even for a single call. Therefore, if the
subject string is very long, it may still pay to use JIT for one-off	subject string is very long, it may still pay to use JIT for one-off
matches.	matches.

JIT support applies only to the traditional matching function,	JIT support applies only to the traditional Perl-compatible matching
pcre_exec(). It does not apply when pcre_dfa_exec() is being used. The	function. It does not apply when the DFA matching function is being
code for this support was written by Zoltan Herczeg.	used. The code for this support was written by Zoltan Herczeg.


	8-BIT and 16-BIT SUPPORT

	JIT support is available for both the 8-bit and 16-bit PCRE libraries.
	To keep this documentation simple, only the 8-bit interface is
	described in what follows. If you are using the 16-bit library, substi-
	tute the 16-bit functions and 16-bit structures (for example,
	pcre16_jit_stack instead of pcre_jit_stack).


AVAILABILITY OF JIT SUPPORT	AVAILABILITY OF JIT SUPPORT

JIT support is an optional feature of PCRE. The "configure" option	JIT support is an optional feature of PCRE. The "configure" option
Line 6523 AVAILABILITY OF JIT SUPPORT	Line 7070 AVAILABILITY OF JIT SUPPORT
ARM v5, v7, and Thumb2	ARM v5, v7, and Thumb2
Intel x86 32-bit and 64-bit	Intel x86 32-bit and 64-bit
MIPS 32-bit	MIPS 32-bit
Power PC 32-bit and 64-bit (experimental)	Power PC 32-bit and 64-bit

The Power PC support is designated as experimental because it has not	The Power PC support is designated as experimental because it has not
been fully tested. If --enable-jit is set on an unsupported platform,	been fully tested. If --enable-jit is set on an unsupported platform,
Line 6831 AUTHOR	Line 7378 AUTHOR

REVISION	REVISION

Last updated: 26 November 2011	Last updated: 08 January 2012
Copyright (c) 1997-2011 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------


Line 6845 NAME	Line 7392 NAME

PARTIAL MATCHING IN PCRE	PARTIAL MATCHING IN PCRE

In normal use of PCRE, if the subject string that is passed to	In normal use of PCRE, if the subject string that is passed to a match-
pcre_exec() or pcre_dfa_exec() matches as far as it goes, but is too	ing function matches as far as it goes, but is too short to match the
short to match the entire pattern, PCRE_ERROR_NOMATCH is returned.	entire pattern, PCRE_ERROR_NOMATCH is returned. There are circumstances
There are circumstances where it might be helpful to distinguish this	where it might be helpful to distinguish this case from other cases in
case from other cases in which there is no match.	which there is no match.

Consider, for example, an application where a human is required to type	Consider, for example, an application where a human is required to type
in data for a field with specific formatting requirements. An example	in data for a field with specific formatting requirements. An example
Line 6867 PARTIAL MATCHING IN PCRE	Line 7414 PARTIAL MATCHING IN PCRE
available at once.	available at once.

PCRE supports partial matching by means of the PCRE_PARTIAL_SOFT and	PCRE supports partial matching by means of the PCRE_PARTIAL_SOFT and
PCRE_PARTIAL_HARD options, which can be set when calling pcre_exec() or	PCRE_PARTIAL_HARD options, which can be set when calling any of the
pcre_dfa_exec(). For backwards compatibility, PCRE_PARTIAL is a synonym	matching functions. For backwards compatibility, PCRE_PARTIAL is a syn-
for PCRE_PARTIAL_SOFT. The essential difference between the two options	onym for PCRE_PARTIAL_SOFT. The essential difference between the two
is whether or not a partial match is preferred to an alternative com-	options is whether or not a partial match is preferred to an alterna-
plete match, though the details differ between the two matching func-	tive complete match, though the details differ between the two types of
tions. If both options are set, PCRE_PARTIAL_HARD takes precedence.	matching function. If both options are set, PCRE_PARTIAL_HARD takes
	precedence.

Setting a partial matching option for pcre_exec() disables the use of	Setting a partial matching option disables the use of any just-in-time
any just-in-time code that was set up by calling pcre_study() with the	code that was set up by studying the compiled pattern with the
PCRE_STUDY_JIT_COMPILE option. It also disables two of PCRE's standard	PCRE_STUDY_JIT_COMPILE option. It also disables two of PCRE's standard
optimizations. PCRE remembers the last literal byte in a pattern, and	optimizations. PCRE remembers the last literal data unit in a pattern,
abandons matching immediately if such a byte is not present in the sub-	and abandons matching immediately if it is not present in the subject
ject string. This optimization cannot be used for a subject string that	string. This optimization cannot be used for a subject string that
might match only partially. If the pattern was studied, PCRE knows the	might match only partially. If the pattern was studied, PCRE knows the
minimum length of a matching string, and does not bother to run the	minimum length of a matching string, and does not bother to run the
matching function on shorter strings. This optimization is also dis-	matching function on shorter strings. This optimization is also dis-
abled for partial matching.	abled for partial matching.


PARTIAL MATCHING USING pcre_exec()	PARTIAL MATCHING USING pcre_exec() OR pcre16_exec()

A partial match occurs during a call to pcre_exec() when the end of the	A partial match occurs during a call to pcre_exec() or pcre16_exec()
subject string is reached successfully, but matching cannot continue	when the end of the subject string is reached successfully, but match-
because more characters are needed. However, at least one character in	ing cannot continue because more characters are needed. However, at
the subject must have been inspected. This character need not form part	least one character in the subject must have been inspected. This char-
of the final matched string; lookbehind assertions and the \K escape	acter need not form part of the final matched string; lookbehind asser-
sequence provide ways of inspecting characters before the start of a	tions and the \K escape sequence provide ways of inspecting characters
matched substring. The requirement for inspecting at least one charac-	before the start of a matched substring. The requirement for inspecting
ter exists because an empty string can always be matched; without such	at least one character exists because an empty string can always be
a restriction there would always be a partial match of an empty string	matched; without such a restriction there would always be a partial
at the end of the subject.	match of an empty string at the end of the subject.

If there are at least two slots in the offsets vector when pcre_exec()	If there are at least two slots in the offsets vector when a partial
returns with a partial match, the first slot is set to the offset of	match is returned, the first slot is set to the offset of the earliest
the earliest character that was inspected when the partial match was	character that was inspected. For convenience, the second offset points
found. For convenience, the second offset points to the end of the sub-	to the end of the subject so that a substring can easily be identified.
ject so that a substring can easily be identified.

For the majority of patterns, the first offset identifies the start of	For the majority of patterns, the first offset identifies the start of
the partially matched string. However, for patterns that contain look-	the partially matched string. However, for patterns that contain look-
Line 6920 PARTIAL MATCHING USING pcre_exec()	Line 7467 PARTIAL MATCHING USING pcre_exec()
What happens when a partial match is identified depends on which of the	What happens when a partial match is identified depends on which of the
two partial matching options are set.	two partial matching options are set.

PCRE_PARTIAL_SOFT with pcre_exec()	PCRE_PARTIAL_SOFT WITH pcre_exec() OR pcre16_exec()

If PCRE_PARTIAL_SOFT is set when pcre_exec() identifies a partial	If PCRE_PARTIAL_SOFT is set when pcre_exec() or pcre16_exec() identi-
match, the partial match is remembered, but matching continues as nor-	fies a partial match, the partial match is remembered, but matching
mal, and other alternatives in the pattern are tried. If no complete	continues as normal, and other alternatives in the pattern are tried.
match can be found, pcre_exec() returns PCRE_ERROR_PARTIAL instead of	If no complete match can be found, PCRE_ERROR_PARTIAL is returned
PCRE_ERROR_NOMATCH.	instead of PCRE_ERROR_NOMATCH.

This option is "soft" because it prefers a complete match over a par-	This option is "soft" because it prefers a complete match over a par-
tial match. All the various matching items in a pattern behave as if	tial match. All the various matching items in a pattern behave as if
Line 6946 PARTIAL MATCHING USING pcre_exec()	Line 7493 PARTIAL MATCHING USING pcre_exec()
(In this example, there are two partial matches, because "dog" on its	(In this example, there are two partial matches, because "dog" on its
own partially matches the second alternative.)	own partially matches the second alternative.)

PCRE_PARTIAL_HARD with pcre_exec()	PCRE_PARTIAL_HARD WITH pcre_exec() OR pcre16_exec()

If PCRE_PARTIAL_HARD is set for pcre_exec(), it returns PCRE_ERROR_PAR-	If PCRE_PARTIAL_HARD is set for pcre_exec() or pcre16_exec(),
TIAL as soon as a partial match is found, without continuing to search	PCRE_ERROR_PARTIAL is returned as soon as a partial match is found,
for possible complete matches. This option is "hard" because it prefers	without continuing to search for possible complete matches. This option
an earlier partial match over a later complete match. For this reason,	is "hard" because it prefers an earlier partial match over a later com-
the assumption is made that the end of the supplied subject string may	plete match. For this reason, the assumption is made that the end of
not be the true end of the available data, and so, if \z, \Z, \b, \B,	the supplied subject string may not be the true end of the available
or $ are encountered at the end of the subject, the result is	data, and so, if \z, \Z, \b, \B, or $ are encountered at the end of the
PCRE_ERROR_PARTIAL.	subject, the result is PCRE_ERROR_PARTIAL, provided that at least one
	character in the subject has been inspected.

Setting PCRE_PARTIAL_HARD also affects the way pcre_exec() checks UTF-8	Setting PCRE_PARTIAL_HARD also affects the way UTF-8 and UTF-16 subject
subject strings for validity. Normally, an invalid UTF-8 sequence	strings are checked for validity. Normally, an invalid sequence causes
causes the error PCRE_ERROR_BADUTF8. However, in the special case of a	the error PCRE_ERROR_BADUTF8 or PCRE_ERROR_BADUTF16. However, in the
truncated UTF-8 character at the end of the subject, PCRE_ERROR_SHORT-	special case of a truncated character at the end of the subject,
UTF8 is returned when PCRE_PARTIAL_HARD is set.	PCRE_ERROR_SHORTUTF8 or PCRE_ERROR_SHORTUTF16 is returned when
	PCRE_PARTIAL_HARD is set.

Comparing hard and soft partial matching	Comparing hard and soft partial matching

Line 6979 PARTIAL MATCHING USING pcre_exec()	Line 7528 PARTIAL MATCHING USING pcre_exec()

/dog(sbody)??/	/dog(sbody)??/

In this case the result is always a complete match because pcre_exec()	In this case the result is always a complete match because that is
finds that first, and it never continues after finding a match. It	found first, and matching never continues after finding a complete
might be easier to follow this explanation by thinking of the two pat-	match. It might be easier to follow this explanation by thinking of the
terns like this:	two patterns like this:

/dog(sbody)?/ is the same as /dogsbody\|dog/	/dog(sbody)?/ is the same as /dogsbody\|dog/
/dog(sbody)??/ is the same as /dog\|dogsbody/	/dog(sbody)??/ is the same as /dog\|dogsbody/

The second pattern will never match "dogsbody" when pcre_exec() is	The second pattern will never match "dogsbody", because it will always
used, because it will always find the shorter match first.	find the shorter match first.


PARTIAL MATCHING USING pcre_dfa_exec()	PARTIAL MATCHING USING pcre_dfa_exec() OR pcre16_dfa_exec()

The pcre_dfa_exec() function moves along the subject string character	The DFA functions move along the subject string character by character,
by character, without backtracking, searching for all possible matches	without backtracking, searching for all possible matches simultane-
simultaneously. If the end of the subject is reached before the end of	ously. If the end of the subject is reached before the end of the pat-
the pattern, there is the possibility of a partial match, again pro-	tern, there is the possibility of a partial match, again provided that
vided that at least one character has been inspected.	at least one character has been inspected.

When PCRE_PARTIAL_SOFT is set, PCRE_ERROR_PARTIAL is returned only if	When PCRE_PARTIAL_SOFT is set, PCRE_ERROR_PARTIAL is returned only if
there have been no complete matches. Otherwise, the complete matches	there have been no complete matches. Otherwise, the complete matches
Line 7007 PARTIAL MATCHING USING pcre_dfa_exec()	Line 7556 PARTIAL MATCHING USING pcre_dfa_exec()
the first matching string, provided there are at least two slots in the	the first matching string, provided there are at least two slots in the
offsets vector.	offsets vector.

Because pcre_dfa_exec() always searches for all possible matches, and	Because the DFA functions always search for all possible matches, and
there is no difference between greedy and ungreedy repetition, its be-	there is no difference between greedy and ungreedy repetition, their
haviour is different from pcre_exec when PCRE_PARTIAL_HARD is set. Con-	behaviour is different from the standard functions when PCRE_PAR-
sider the string "dog" matched against the ungreedy pattern shown	TIAL_HARD is set. Consider the string "dog" matched against the
above:	ungreedy pattern shown above:

/dog(sbody)??/	/dog(sbody)??/

Whereas pcre_exec() stops as soon as it finds the complete match for	Whereas the standard functions stop as soon as they find the complete
"dog", pcre_dfa_exec() also finds the partial match for "dogsbody", and	match for "dog", the DFA functions also find the partial match for
so returns that when PCRE_PARTIAL_HARD is set.	"dogsbody", and so return that when PCRE_PARTIAL_HARD is set.


PARTIAL MATCHING AND WORD BOUNDARIES	PARTIAL MATCHING AND WORD BOUNDARIES
Line 7031 PARTIAL MATCHING AND WORD BOUNDARIES	Line 7580 PARTIAL MATCHING AND WORD BOUNDARIES
This matches "cat", provided there is a word boundary at either end. If	This matches "cat", provided there is a word boundary at either end. If
the subject string is "the cat", the comparison of the final "t" with a	the subject string is "the cat", the comparison of the final "t" with a
following character cannot take place, so a partial match is found.	following character cannot take place, so a partial match is found.
However, pcre_exec() carries on with normal matching, which matches \b	However, normal matching carries on, and \b matches at the end of the
at the end of the subject when the last character is a letter, thus	subject when the last character is a letter, so a complete match is
finding a complete match. The result, therefore, is not PCRE_ERROR_PAR-	found. The result, therefore, is not PCRE_ERROR_PARTIAL. Using
TIAL. The same thing happens with pcre_dfa_exec(), because it also	PCRE_PARTIAL_HARD in this case does yield PCRE_ERROR_PARTIAL, because
finds the complete match.	then the partial match takes precedence.

Using PCRE_PARTIAL_HARD in this case does yield PCRE_ERROR_PARTIAL,
because then the partial match takes precedence.


FORMERLY RESTRICTED PATTERNS	FORMERLY RESTRICTED PATTERNS

For releases of PCRE prior to 8.00, because of the way certain internal	For releases of PCRE prior to 8.00, because of the way certain internal
optimizations were implemented in the pcre_exec() function, the	optimizations were implemented in the pcre_exec() function, the
PCRE_PARTIAL option (predecessor of PCRE_PARTIAL_SOFT) could not be	PCRE_PARTIAL option (predecessor of PCRE_PARTIAL_SOFT) could not be
used with all patterns. From release 8.00 onwards, the restrictions no	used with all patterns. From release 8.00 onwards, the restrictions no
longer apply, and partial matching with pcre_exec() can be requested	longer apply, and partial matching with can be requested for any pat-
for any pattern.	tern.

Items that were formerly restricted were repeated single characters and	Items that were formerly restricted were repeated single characters and
repeated metasequences. If PCRE_PARTIAL was set for a pattern that did	repeated metasequences. If PCRE_PARTIAL was set for a pattern that did
not conform to the restrictions, pcre_exec() returned the error code	not conform to the restrictions, pcre_exec() returned the error code
PCRE_ERROR_BADPARTIAL (-13). This error code is no longer in use. The	PCRE_ERROR_BADPARTIAL (-13). This error code is no longer in use. The
PCRE_INFO_OKPARTIAL call to pcre_fullinfo() to find out if a compiled	PCRE_INFO_OKPARTIAL call to pcre_fullinfo() to find out if a compiled
pattern can be used for partial matching now always returns 1.	pattern can be used for partial matching now always returns 1.


EXAMPLE OF PARTIAL MATCHING USING PCRETEST	EXAMPLE OF PARTIAL MATCHING USING PCRETEST

If the escape sequence \P is present in a pcretest data line, the	If the escape sequence \P is present in a pcretest data line, the
PCRE_PARTIAL_SOFT option is used for the match. Here is a run of	PCRE_PARTIAL_SOFT option is used for the match. Here is a run of
pcretest that uses the date example quoted above:	pcretest that uses the date example quoted above:

re> /^\d?\d(jan\|feb\|mar\|apr\|may\|jun\|jul\|aug\|sep\|oct\|nov\|dec)\d\d$/	re> /^\d?\d(jan\|feb\|mar\|apr\|may\|jun\|jul\|aug\|sep\|oct\|nov\|dec)\d\d$/
Line 7077 EXAMPLE OF PARTIAL MATCHING USING PCRETEST	Line 7623 EXAMPLE OF PARTIAL MATCHING USING PCRETEST
data> j\P	data> j\P
No match	No match

The first data string is matched completely, so pcretest shows the	The first data string is matched completely, so pcretest shows the
matched substrings. The remaining four strings do not match the com-	matched substrings. The remaining four strings do not match the com-
plete pattern, but the first two are partial matches. Similar output is	plete pattern, but the first two are partial matches. Similar output is
obtained when pcre_dfa_exec() is used.	obtained if DFA matching is used.

If the escape sequence \P is present more than once in a pcretest data	If the escape sequence \P is present more than once in a pcretest data
line, the PCRE_PARTIAL_HARD option is set for the match.	line, the PCRE_PARTIAL_HARD option is set for the match.


MULTI-SEGMENT MATCHING WITH pcre_dfa_exec()	MULTI-SEGMENT MATCHING WITH pcre_dfa_exec() OR pcre16_dfa_exec()

When a partial match has been found using pcre_dfa_exec(), it is possi-	When a partial match has been found using a DFA matching function, it
ble to continue the match by providing additional subject data and	is possible to continue the match by providing additional subject data
calling pcre_dfa_exec() again with the same compiled regular expres-	and calling the function again with the same compiled regular expres-
sion, this time setting the PCRE_DFA_RESTART option. You must pass the	sion, this time setting the PCRE_DFA_RESTART option. You must pass the
same working space as before, because this is where details of the pre-	same working space as before, because this is where details of the pre-
vious partial match are stored. Here is an example using pcretest,	vious partial match are stored. Here is an example using pcretest,
using the \R escape sequence to set the PCRE_DFA_RESTART option (\D	using the \R escape sequence to set the PCRE_DFA_RESTART option (\D
specifies the use of pcre_dfa_exec()):	specifies the use of the DFA matching function):

re> /^\d?\d(jan\|feb\|mar\|apr\|may\|jun\|jul\|aug\|sep\|oct\|nov\|dec)\d\d$/	re> /^\d?\d(jan\|feb\|mar\|apr\|may\|jun\|jul\|aug\|sep\|oct\|nov\|dec)\d\d$/
data> 23ja\P\D	data> 23ja\P\D
Line 7103 MULTI-SEGMENT MATCHING WITH pcre_dfa_exec()	Line 7649 MULTI-SEGMENT MATCHING WITH pcre_dfa_exec()
data> n05\R\D	data> n05\R\D
0: n05	0: n05

The first call has "23ja" as the subject, and requests partial match-	The first call has "23ja" as the subject, and requests partial match-
ing; the second call has "n05" as the subject for the continued	ing; the second call has "n05" as the subject for the continued
(restarted) match. Notice that when the match is complete, only the	(restarted) match. Notice that when the match is complete, only the
last part is shown; PCRE does not retain the previously partially-	last part is shown; PCRE does not retain the previously partially-
matched string. It is up to the calling program to do that if it needs	matched string. It is up to the calling program to do that if it needs
to.	to.

You can set the PCRE_PARTIAL_SOFT or PCRE_PARTIAL_HARD options with	You can set the PCRE_PARTIAL_SOFT or PCRE_PARTIAL_HARD options with
PCRE_DFA_RESTART to continue partial matching over multiple segments.	PCRE_DFA_RESTART to continue partial matching over multiple segments.
This facility can be used to pass very long subject strings to	This facility can be used to pass very long subject strings to the DFA
pcre_dfa_exec().	matching functions.


MULTI-SEGMENT MATCHING WITH pcre_exec()	MULTI-SEGMENT MATCHING WITH pcre_exec() OR pcre16_exec()

From release 8.00, pcre_exec() can also be used to do multi-segment	From release 8.00, the standard matching functions can also be used to
matching. Unlike pcre_dfa_exec(), it is not possible to restart the	do multi-segment matching. Unlike the DFA functions, it is not possible
previous match with a new segment of data. Instead, new data must be	to restart the previous match with a new segment of data. Instead, new
added to the previous subject string, and the entire match re-run,	data must be added to the previous subject string, and the entire match
starting from the point where the partial match occurred. Earlier data	re-run, starting from the point where the partial match occurred. Ear-
can be discarded. It is best to use PCRE_PARTIAL_HARD in this situa-	lier data can be discarded.
tion, because it does not treat the end of a segment as the end of the
subject when matching \z, \Z, \b, \B, and $. Consider an unanchored
pattern that matches dates:

	It is best to use PCRE_PARTIAL_HARD in this situation, because it does
	not treat the end of a segment as the end of the subject when matching
	\z, \Z, \b, \B, and $. Consider an unanchored pattern that matches
	dates:

re> /\d?\d(jan\|feb\|mar\|apr\|may\|jun\|jul\|aug\|sep\|oct\|nov\|dec)\d\d/	re> /\d?\d(jan\|feb\|mar\|apr\|may\|jun\|jul\|aug\|sep\|oct\|nov\|dec)\d\d/
data> The date is 23ja\P\P	data> The date is 23ja\P\P
Partial match: 23ja	Partial match: 23ja

At this stage, an application could discard the text preceding "23ja",	At this stage, an application could discard the text preceding "23ja",
add on text from the next segment, and call pcre_exec() again. Unlike	add on text from the next segment, and call the matching function
pcre_dfa_exec(), the entire matching string must always be available,	again. Unlike the DFA matching functions the entire matching string
and the complete matching process occurs for each call, so more memory	must always be available, and the complete matching process occurs for
and more processing time is needed.	each call, so more memory and more processing time is needed.

Note: If the pattern contains lookbehind assertions, or \K, or starts	Note: If the pattern contains lookbehind assertions, or \K, or starts
with \b or \B, the string that is returned for a partial match will	with \b or \B, the string that is returned for a partial match includes
include characters that precede the partially matched string itself,	characters that precede the partially matched string itself, because
because these must be retained when adding on more characters for a	these must be retained when adding on more characters for a subsequent
subsequent matching attempt.	matching attempt.


ISSUES WITH MULTI-SEGMENT MATCHING	ISSUES WITH MULTI-SEGMENT MATCHING
Line 7151 ISSUES WITH MULTI-SEGMENT MATCHING	Line 7699 ISSUES WITH MULTI-SEGMENT MATCHING
whichever matching function is used.	whichever matching function is used.

1. If the pattern contains a test for the beginning of a line, you need	1. If the pattern contains a test for the beginning of a line, you need
to pass the PCRE_NOTBOL option when the subject string for any call	to pass the PCRE_NOTBOL option when the subject string for any call
does start at the beginning of a line. There is also a PCRE_NOTEOL	does start at the beginning of a line. There is also a PCRE_NOTEOL
option, but in practice when doing multi-segment matching you should be	option, but in practice when doing multi-segment matching you should be
using PCRE_PARTIAL_HARD, which includes the effect of PCRE_NOTEOL.	using PCRE_PARTIAL_HARD, which includes the effect of PCRE_NOTEOL.

2. Lookbehind assertions at the start of a pattern are catered for in	2. Lookbehind assertions at the start of a pattern are catered for in
the offsets that are returned for a partial match. However, in theory,	the offsets that are returned for a partial match. However, in theory,
a lookbehind assertion later in the pattern could require even earlier	a lookbehind assertion later in the pattern could require even earlier
characters to be inspected, and it might not have been reached when a	characters to be inspected, and it might not have been reached when a
partial match occurs. This is probably an extremely unlikely case; you	partial match occurs. This is probably an extremely unlikely case; you
could guard against it to a certain extent by always including extra	could guard against it to a certain extent by always including extra
characters at the start.	characters at the start.

3. Matching a subject string that is split into multiple segments may	3. Matching a subject string that is split into multiple segments may
not always produce exactly the same result as matching over one single	not always produce exactly the same result as matching over one single
long string, especially when PCRE_PARTIAL_SOFT is used. The section	long string, especially when PCRE_PARTIAL_SOFT is used. The section
"Partial Matching and Word Boundaries" above describes an issue that	"Partial Matching and Word Boundaries" above describes an issue that
arises if the pattern ends with \b or \B. Another kind of difference	arises if the pattern ends with \b or \B. Another kind of difference
may occur when there are multiple matching possibilities, because (for	may occur when there are multiple matching possibilities, because (for
PCRE_PARTIAL_SOFT) a partial match result is given only when there are	PCRE_PARTIAL_SOFT) a partial match result is given only when there are
no completed matches. This means that as soon as the shortest match has	no completed matches. This means that as soon as the shortest match has
been found, continuation to a new subject segment is no longer possi-	been found, continuation to a new subject segment is no longer possi-
ble. Consider again this pcretest example:	ble. Consider again this pcretest example:

re> /dog(sbody)?/	re> /dog(sbody)?/
Line 7186 ISSUES WITH MULTI-SEGMENT MATCHING	Line 7734 ISSUES WITH MULTI-SEGMENT MATCHING
0: dogsbody	0: dogsbody
1: dog	1: dog

The first data line passes the string "dogsb" to pcre_exec(), setting	The first data line passes the string "dogsb" to a standard matching
the PCRE_PARTIAL_SOFT option. Although the string is a partial match	function, setting the PCRE_PARTIAL_SOFT option. Although the string is
for "dogsbody", the result is not PCRE_ERROR_PARTIAL, because the	a partial match for "dogsbody", the result is not PCRE_ERROR_PARTIAL,
shorter string "dog" is a complete match. Similarly, when the subject	because the shorter string "dog" is a complete match. Similarly, when
is presented to pcre_dfa_exec() in several parts ("do" and "gsb" being	the subject is presented to a DFA matching function in several parts
the first two) the match stops when "dog" has been found, and it is not	("do" and "gsb" being the first two) the match stops when "dog" has
possible to continue. On the other hand, if "dogsbody" is presented as	been found, and it is not possible to continue. On the other hand, if
a single string, pcre_dfa_exec() finds both matches.	"dogsbody" is presented as a single string, a DFA matching function
	finds both matches.

Because of these problems, it is best to use PCRE_PARTIAL_HARD when	Because of these problems, it is best to use PCRE_PARTIAL_HARD when
matching multi-segment data. The example above then behaves differ-	matching multi-segment data. The example above then behaves differ-
Line 7209 ISSUES WITH MULTI-SEGMENT MATCHING	Line 7758 ISSUES WITH MULTI-SEGMENT MATCHING

4. Patterns that contain alternatives at the top level which do not all	4. Patterns that contain alternatives at the top level which do not all
start with the same pattern item may not work as expected when	start with the same pattern item may not work as expected when
PCRE_DFA_RESTART is used with pcre_dfa_exec(). For example, consider	PCRE_DFA_RESTART is used. For example, consider this pattern:
this pattern:

1234\|3789	1234\|3789

If the first part of the subject is "ABC123", a partial match of the	If the first part of the subject is "ABC123", a partial match of the
first alternative is found at offset 3. There is no partial match for	first alternative is found at offset 3. There is no partial match for
the second alternative, because such a match does not start at the same	the second alternative, because such a match does not start at the same
point in the subject string. Attempting to continue with the string	point in the subject string. Attempting to continue with the string
"7890" does not yield a match because only those alternatives that	"7890" does not yield a match because only those alternatives that
match at one point in the subject are remembered. The problem arises	match at one point in the subject are remembered. The problem arises
because the start of the second alternative matches within the first	because the start of the second alternative matches within the first
alternative. There is no problem with anchored patterns or patterns	alternative. There is no problem with anchored patterns or patterns
such as:	such as:

1234\|ABCD	1234\|ABCD

where no string can be a partial match for both alternatives. This is	where no string can be a partial match for both alternatives. This is
not a problem if pcre_exec() is used, because the entire match has to	not a problem if a standard matching function is used, because the
be rerun each time:	entire match has to be rerun each time:

re> /1234\|3789/	re> /1234\|3789/
data> ABC123\P\P	data> ABC123\P\P
Line 7237 ISSUES WITH MULTI-SEGMENT MATCHING	Line 7785 ISSUES WITH MULTI-SEGMENT MATCHING
0: 3789	0: 3789

Of course, instead of using PCRE_DFA_RESTART, the same technique of re-	Of course, instead of using PCRE_DFA_RESTART, the same technique of re-
running the entire match can also be used with pcre_dfa_exec(). Another	running the entire match can also be used with the DFA matching func-
possibility is to work with two buffers. If a partial match at offset n	tions. Another possibility is to work with two buffers. If a partial
in the first buffer is followed by "no match" when PCRE_DFA_RESTART is	match at offset n in the first buffer is followed by "no match" when
used on the second buffer, you can then try a new match starting at	PCRE_DFA_RESTART is used on the second buffer, you can then try a new
offset n+1 in the first buffer.	match starting at offset n+1 in the first buffer.


AUTHOR	AUTHOR
Line 7253 AUTHOR	Line 7801 AUTHOR

REVISION	REVISION

Last updated: 26 August 2011	Last updated: 21 January 2012
Copyright (c) 1997-2011 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------


Line 7273 SAVING AND RE-USING PRECOMPILED PCRE PATTERNS	Line 7821 SAVING AND RE-USING PRECOMPILED PCRE PATTERNS
run. If you are not using any private character tables (see the	run. If you are not using any private character tables (see the
pcre_maketables() documentation), this is relatively straightforward.	pcre_maketables() documentation), this is relatively straightforward.
If you are using private tables, it is a little bit more complicated.	If you are using private tables, it is a little bit more complicated.
However, if you are using the just-in-time optimization feature of	However, if you are using the just-in-time optimization feature, it is
pcre_study(), it is not possible to save and reload the JIT data.	not possible to save and reload the JIT data.

If you save compiled patterns to a file, you can copy them to a differ-	If you save compiled patterns to a file, you can copy them to a differ-
ent host and run them there. This works even if the new host has the	ent host and run them there. If the two hosts have different endianness
opposite endianness to the one on which the patterns were compiled.	(byte order), you should run the pcre[16]_pattern_to_host_byte_order()
There may be a small performance penalty, but it should be insignifi-	function on the new host before trying to match the pattern. The match-
cant. However, compiling regular expressions with one version of PCRE	ing functions return PCRE_ERROR_BADENDIANNESS if they detect a pattern
for use with a different version is not guaranteed to work and may	with the wrong endianness.
cause crashes, and saving and restoring a compiled pattern loses any
JIT optimization data.

	Compiling regular expressions with one version of PCRE for use with a
	different version is not guaranteed to work and may cause crashes, and
	saving and restoring a compiled pattern loses any JIT optimization
	data.


SAVING A COMPILED PATTERN	SAVING A COMPILED PATTERN

The value returned by pcre_compile() points to a single block of memory	The value returned by pcre[16]_compile() points to a single block of
that holds the compiled pattern and associated data. You can find the	memory that holds the compiled pattern and associated data. You can
length of this block in bytes by calling pcre_fullinfo() with an argu-	find the length of this block in bytes by calling pcre[16]_fullinfo()
ment of PCRE_INFO_SIZE. You can then save the data in any appropriate	with an argument of PCRE_INFO_SIZE. You can then save the data in any
manner. Here is sample code that compiles a pattern and writes it to a	appropriate manner. Here is sample code for the 8-bit library that com-
file. It assumes that the variable fd refers to a file that is open for	piles a pattern and writes it to a file. It assumes that the variable
output:	fd refers to a file that is open for output:

int erroroffset, rc, size;	int erroroffset, rc, size;
char *error;	char *error;
Line 7307 SAVING A COMPILED PATTERN	Line 7858 SAVING A COMPILED PATTERN
rc = fwrite(re, 1, size, fd);	rc = fwrite(re, 1, size, fd);
if (rc != size) { ... handle errors ... }	if (rc != size) { ... handle errors ... }

In this example, the bytes that comprise the compiled pattern are	In this example, the bytes that comprise the compiled pattern are
copied exactly. Note that this is binary data that may contain any of	copied exactly. Note that this is binary data that may contain any of
the 256 possible byte values. On systems that make a distinction	the 256 possible byte values. On systems that make a distinction
between binary and non-binary data, be sure that the file is opened for	between binary and non-binary data, be sure that the file is opened for
binary output.	binary output.

If you want to write more than one pattern to a file, you will have to	If you want to write more than one pattern to a file, you will have to
devise a way of separating them. For binary data, preceding each pat-	devise a way of separating them. For binary data, preceding each pat-
tern with its length is probably the most straightforward approach.	tern with its length is probably the most straightforward approach.
Another possibility is to write out the data in hexadecimal instead of	Another possibility is to write out the data in hexadecimal instead of
binary, one pattern to a line.	binary, one pattern to a line.

Saving compiled patterns in a file is only one possible way of storing	Saving compiled patterns in a file is only one possible way of storing
them for later use. They could equally well be saved in a database, or	them for later use. They could equally well be saved in a database, or
in the memory of some daemon process that passes them via sockets to	in the memory of some daemon process that passes them via sockets to
the processes that want them.	the processes that want them.

If the pattern has been studied, it is also possible to save the normal	If the pattern has been studied, it is also possible to save the normal
study data in a similar way to the compiled pattern itself. However, if	study data in a similar way to the compiled pattern itself. However, if
the PCRE_STUDY_JIT_COMPILE was used, the just-in-time data that is cre-	the PCRE_STUDY_JIT_COMPILE was used, the just-in-time data that is cre-
ated cannot be saved because it is too dependent on the current envi-	ated cannot be saved because it is too dependent on the current envi-
ronment. When studying generates additional information, pcre_study()	ronment. When studying generates additional information,
returns a pointer to a pcre_extra data block. Its format is defined in	pcre[16]_study() returns a pointer to a pcre[16]_extra data block. Its
the section on matching a pattern in the pcreapi documentation. The	format is defined in the section on matching a pattern in the pcreapi
study_data field points to the binary study data, and this is what you	documentation. The study_data field points to the binary study data,
must save (not the pcre_extra block itself). The length of the study	and this is what you must save (not the pcre[16]_extra block itself).
data can be obtained by calling pcre_fullinfo() with an argument of	The length of the study data can be obtained by calling
PCRE_INFO_STUDYSIZE. Remember to check that pcre_study() did return a	pcre[16]_fullinfo() with an argument of PCRE_INFO_STUDYSIZE. Remember
non-NULL value before trying to save the study data.	to check that pcre[16]_study() did return a non-NULL value before try-
	ing to save the study data.


RE-USING A PRECOMPILED PATTERN	RE-USING A PRECOMPILED PATTERN

Re-using a precompiled pattern is straightforward. Having reloaded it	Re-using a precompiled pattern is straightforward. Having reloaded it
into main memory, you pass its pointer to pcre_exec() or	into main memory, called pcre[16]_pattern_to_host_byte_order() if nec-
pcre_dfa_exec() in the usual way. This should work even on another	essary, you pass its pointer to pcre[16]_exec() or pcre[16]_dfa_exec()
host, and even if that host has the opposite endianness to the one	in the usual way.
where the pattern was compiled.

However, if you passed a pointer to custom character tables when the	However, if you passed a pointer to custom character tables when the
pattern was compiled (the tableptr argument of pcre_compile()), you	pattern was compiled (the tableptr argument of pcre[16]_compile()), you
must now pass a similar pointer to pcre_exec() or pcre_dfa_exec(),	must now pass a similar pointer to pcre[16]_exec() or
because the value saved with the compiled pattern will obviously be	pcre[16]_dfa_exec(), because the value saved with the compiled pattern
nonsense. A field in a pcre_extra() block is used to pass this data, as	will obviously be nonsense. A field in a pcre[16]_extra() block is used
described in the section on matching a pattern in the pcreapi documen-	to pass this data, as described in the section on matching a pattern in
tation.	the pcreapi documentation.

If you did not provide custom character tables when the pattern was	If you did not provide custom character tables when the pattern was
compiled, the pointer in the compiled pattern is NULL, which causes	compiled, the pointer in the compiled pattern is NULL, which causes the
pcre_exec() to use PCRE's internal tables. Thus, you do not need to	matching functions to use PCRE's internal tables. Thus, you do not need
take any special action at run time in this case.	to take any special action at run time in this case.

If you saved study data with the compiled pattern, you need to create	If you saved study data with the compiled pattern, you need to create
your own pcre_extra data block and set the study_data field to point to	your own pcre[16]_extra data block and set the study_data field to
the reloaded study data. You must also set the PCRE_EXTRA_STUDY_DATA	point to the reloaded study data. You must also set the
bit in the flags field to indicate that study data is present. Then	PCRE_EXTRA_STUDY_DATA bit in the flags field to indicate that study
pass the pcre_extra block to pcre_exec() or pcre_dfa_exec() in the	data is present. Then pass the pcre[16]_extra block to the matching
usual way. If the pattern was studied for just-in-time optimization,	function in the usual way. If the pattern was studied for just-in-time
that data cannot be saved, and so is lost by a save/restore cycle.	optimization, that data cannot be saved, and so is lost by a
	save/restore cycle.


COMPATIBILITY WITH DIFFERENT PCRE RELEASES	COMPATIBILITY WITH DIFFERENT PCRE RELEASES
Line 7384 AUTHOR	Line 7936 AUTHOR

REVISION	REVISION

Last updated: 26 August 2011	Last updated: 10 January 2012
Copyright (c) 1997-2011 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------


Line 7405 PCRE PERFORMANCE	Line 7957 PCRE PERFORMANCE

COMPILED PATTERN MEMORY USAGE	COMPILED PATTERN MEMORY USAGE

Patterns are compiled by PCRE into a reasonably efficient byte code, so	Patterns are compiled by PCRE into a reasonably efficient interpretive
that most simple patterns do not use much memory. However, there is one	code, so that most simple patterns do not use much memory. However,
case where the memory usage of a compiled pattern can be unexpectedly	there is one case where the memory usage of a compiled pattern can be
large. If a parenthesized subpattern has a quantifier with a minimum	unexpectedly large. If a parenthesized subpattern has a quantifier with
greater than 1 and/or a limited maximum, the whole subpattern is	a minimum greater than 1 and/or a limited maximum, the whole subpattern
repeated in the compiled code. For example, the pattern	is repeated in the compiled code. For example, the pattern

(abc\|def){2,4}	(abc\|def){2,4}

Line 7428 COMPILED PATTERN MEMORY USAGE	Line 7980 COMPILED PATTERN MEMORY USAGE

((ab){1,1000}c){1,3}	((ab){1,1000}c){1,3}

uses 51K bytes when compiled. When PCRE is compiled with its default	uses 51K bytes when compiled using the 8-bit library. When PCRE is com-
internal pointer size of two bytes, the size limit on a compiled pat-	piled with its default internal pointer size of two bytes, the size
tern is 64K, and this is reached with the above pattern if the outer	limit on a compiled pattern is 64K data units, and this is reached with
repetition is increased from 3 to 4. PCRE can be compiled to use larger	the above pattern if the outer repetition is increased from 3 to 4.
internal pointers and thus handle larger compiled patterns, but it is	PCRE can be compiled to use larger internal pointers and thus handle
better to try to rewrite your pattern to use less memory if you can.	larger compiled patterns, but it is better to try to rewrite your pat-
	tern to use less memory if you can.

One way of reducing the memory usage for such patterns is to make use	One way of reducing the memory usage for such patterns is to make use
of PCRE's "subroutine" facility. Re-writing the above pattern as	of PCRE's "subroutine" facility. Re-writing the above pattern as

((ab)(?2){0,999}c)(?1){0,2}	((ab)(?2){0,999}c)(?1){0,2}

reduces the memory requirements to 18K, and indeed it remains under 20K	reduces the memory requirements to 18K, and indeed it remains under 20K
even with the outer repetition increased to 100. However, this pattern	even with the outer repetition increased to 100. However, this pattern
is not exactly equivalent, because the "subroutine" calls are treated	is not exactly equivalent, because the "subroutine" calls are treated
as atomic groups into which there can be no backtracking if there is a	as atomic groups into which there can be no backtracking if there is a
subsequent matching failure. Therefore, PCRE cannot do this kind of	subsequent matching failure. Therefore, PCRE cannot do this kind of
rewriting automatically. Furthermore, there is a noticeable loss of	rewriting automatically. Furthermore, there is a noticeable loss of
speed when executing the modified pattern. Nevertheless, if the atomic	speed when executing the modified pattern. Nevertheless, if the atomic
grouping is not a problem and the loss of speed is acceptable, this	grouping is not a problem and the loss of speed is acceptable, this
kind of rewriting will allow you to process patterns that PCRE cannot	kind of rewriting will allow you to process patterns that PCRE cannot
otherwise handle.	otherwise handle.


STACK USAGE AT RUN TIME	STACK USAGE AT RUN TIME

When pcre_exec() is used for matching, certain kinds of pattern can	When pcre_exec() or pcre16_exec() is used for matching, certain kinds
cause it to use large amounts of the process stack. In some environ-	of pattern can cause it to use large amounts of the process stack. In
ments the default process stack is quite small, and if it runs out the	some environments the default process stack is quite small, and if it
result is often SIGSEGV. This issue is probably the most frequently	runs out the result is often SIGSEGV. This issue is probably the most
raised problem with PCRE. Rewriting your pattern can often help. The	frequently raised problem with PCRE. Rewriting your pattern can often
pcrestack documentation discusses this issue in detail.	help. The pcrestack documentation discusses this issue in detail.


PROCESSING TIME	PROCESSING TIME

Certain items in regular expression patterns are processed more effi-	Certain items in regular expression patterns are processed more effi-
ciently than others. It is more efficient to use a character class like	ciently than others. It is more efficient to use a character class like
[aeiou] than a set of single-character alternatives such as	[aeiou] than a set of single-character alternatives such as
(a\|e\|i\|o\|u). In general, the simplest construction that provides the	(a\|e\|i\|o\|u). In general, the simplest construction that provides the
required behaviour is usually the most efficient. Jeffrey Friedl's book	required behaviour is usually the most efficient. Jeffrey Friedl's book
contains a lot of useful general discussion about optimizing regular	contains a lot of useful general discussion about optimizing regular
expressions for efficient performance. This document contains a few	expressions for efficient performance. This document contains a few
observations about PCRE.	observations about PCRE.

Using Unicode character properties (the \p, \P, and \X escapes) is	Using Unicode character properties (the \p, \P, and \X escapes) is
slow, because PCRE has to scan a structure that contains data for over	slow, because PCRE has to scan a structure that contains data for over
fifteen thousand characters whenever it needs a character's property.	fifteen thousand characters whenever it needs a character's property.
If you can find an alternative pattern that does not use character	If you can find an alternative pattern that does not use character
properties, it will probably be faster.	properties, it will probably be faster.

By default, the escape sequences \b, \d, \s, and \w, and the POSIX	By default, the escape sequences \b, \d, \s, and \w, and the POSIX
character classes such as [:alpha:] do not use Unicode properties,	character classes such as [:alpha:] do not use Unicode properties,
partly for backwards compatibility, and partly for performance reasons.	partly for backwards compatibility, and partly for performance reasons.
However, you can set PCRE_UCP if you want Unicode character properties	However, you can set PCRE_UCP if you want Unicode character properties
to be used. This can double the matching time for items such as \d,	to be used. This can double the matching time for items such as \d,
when matched with pcre_exec(); the performance loss is less with	when matched with a traditional matching function; the performance loss
pcre_dfa_exec(), and in both cases there is not much difference for \b.	is less with a DFA matching function, and in both cases there is not
	much difference for \b.

When a pattern begins with .* not in parentheses, or in parentheses	When a pattern begins with .* not in parentheses, or in parentheses
that are not the subject of a backreference, and the PCRE_DOTALL option	that are not the subject of a backreference, and the PCRE_DOTALL option
Line 7552 AUTHOR	Line 8106 AUTHOR

REVISION	REVISION

Last updated: 16 May 2010	Last updated: 09 January 2012
Copyright (c) 1997-2010 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------


Line 7582 SYNOPSIS OF POSIX API	Line 8136 SYNOPSIS OF POSIX API

DESCRIPTION	DESCRIPTION

This set of functions provides a POSIX-style API to the PCRE regular	This set of functions provides a POSIX-style API for the PCRE regular
expression package. See the pcreapi documentation for a description of	expression 8-bit library. See the pcreapi documentation for a descrip-
PCRE's native API, which contains much additional functionality.	tion of PCRE's native API, which contains much additional functional-
	ity. There is no POSIX-style wrapper for PCRE's 16-bit library.

The functions described here are just wrapper functions that ultimately	The functions described here are just wrapper functions that ultimately
call the PCRE native API. Their prototypes are defined in the	call the PCRE native API. Their prototypes are defined in the
pcreposix.h header file, and on Unix systems the library itself is	pcreposix.h header file, and on Unix systems the library itself is
called pcreposix.a, so can be accessed by adding -lpcreposix to the	called pcreposix.a, so can be accessed by adding -lpcreposix to the
command for linking an application that uses them. Because the POSIX	command for linking an application that uses them. Because the POSIX
functions call the native ones, it is also necessary to add -lpcre.	functions call the native ones, it is also necessary to add -lpcre.

I have implemented only those POSIX option bits that can be reasonably	I have implemented only those POSIX option bits that can be reasonably
mapped to PCRE native options. In addition, the option REG_EXTENDED is	mapped to PCRE native options. In addition, the option REG_EXTENDED is
defined with the value zero. This has no effect, but since programs	defined with the value zero. This has no effect, but since programs
that are written to the POSIX interface often use it, this makes it	that are written to the POSIX interface often use it, this makes it
easier to slot in PCRE as a replacement library. Other POSIX options	easier to slot in PCRE as a replacement library. Other POSIX options
are not even defined.	are not even defined.

There are also some other options that are not defined by POSIX. These	There are also some other options that are not defined by POSIX. These
have been added at the request of users who want to make use of certain	have been added at the request of users who want to make use of certain
PCRE-specific features via the POSIX calling interface.	PCRE-specific features via the POSIX calling interface.

When PCRE is called via these functions, it is only the API that is	When PCRE is called via these functions, it is only the API that is
POSIX-like in style. The syntax and semantics of the regular expres-	POSIX-like in style. The syntax and semantics of the regular expres-
sions themselves are still those of Perl, subject to the setting of	sions themselves are still those of Perl, subject to the setting of
various PCRE options, as described below. "POSIX-like in style" means	various PCRE options, as described below. "POSIX-like in style" means
that the API approximates to the POSIX definition; it is not fully	that the API approximates to the POSIX definition; it is not fully
POSIX-compatible, and in multi-byte encoding domains it is probably	POSIX-compatible, and in multi-byte encoding domains it is probably
even less compatible.	even less compatible.

The header for these functions is supplied as pcreposix.h to avoid any	The header for these functions is supplied as pcreposix.h to avoid any
potential clash with other POSIX libraries. It can, of course, be	potential clash with other POSIX libraries. It can, of course, be
renamed or aliased as regex.h, which is the "correct" name. It provides	renamed or aliased as regex.h, which is the "correct" name. It provides
two structure types, regex_t for compiled internal forms, and reg-	two structure types, regex_t for compiled internal forms, and reg-
match_t for returning captured substrings. It also defines some con-	match_t for returning captured substrings. It also defines some con-
stants whose names start with "REG_"; these are used for setting	stants whose names start with "REG_"; these are used for setting
options and identifying error codes.	options and identifying error codes.


COMPILING A PATTERN	COMPILING A PATTERN

The function regcomp() is called to compile a pattern into an internal	The function regcomp() is called to compile a pattern into an internal
form. The pattern is a C string terminated by a binary zero, and is	form. The pattern is a C string terminated by a binary zero, and is
passed in the argument pattern. The preg argument is a pointer to a	passed in the argument pattern. The preg argument is a pointer to a
regex_t structure that is used as a base for storing information about	regex_t structure that is used as a base for storing information about
the compiled regular expression.	the compiled regular expression.

The argument cflags is either zero, or contains one or more of the bits	The argument cflags is either zero, or contains one or more of the bits
Line 7640 COMPILING A PATTERN	Line 8195 COMPILING A PATTERN

REG_ICASE	REG_ICASE

The PCRE_CASELESS option is set when the regular expression is passed	The PCRE_CASELESS option is set when the regular expression is passed
for compilation to the native function.	for compilation to the native function.

REG_NEWLINE	REG_NEWLINE

The PCRE_MULTILINE option is set when the regular expression is passed	The PCRE_MULTILINE option is set when the regular expression is passed
for compilation to the native function. Note that this does not mimic	for compilation to the native function. Note that this does not mimic
the defined POSIX behaviour for REG_NEWLINE (see the following sec-	the defined POSIX behaviour for REG_NEWLINE (see the following sec-
tion).	tion).

REG_NOSUB	REG_NOSUB

The PCRE_NO_AUTO_CAPTURE option is set when the regular expression is	The PCRE_NO_AUTO_CAPTURE option is set when the regul The PCRE_NO_AUTO_CAPTURE option is set when the regular expression is
passed for compilation to the native function. In addition, when a pat-	passed for compilation to the native function. In addition, when a pat-
tern that is compiled with this flag is passed to regexec() for match-	tern that is compiled with this flag is passed to regexec() for match-
ing, the nmatch and pmatch arguments are ignored, and no captured	ing, the nmatch and pmatch arguments are ignored, and no captured
strings are returned.	strings are returned.

REG_UCP	REG_UCP

The PCRE_UCP option is set when the regular expression is passed for	The PCRE_UCP option is set when the regular expression is passed for
compilation to the native function. This causes PCRE to use Unicode	compilation to the native function. This causes PCRE to use Unicode
properties when matchine \d, \w, etc., instead of just recognizing	properties when matchine \d, \w, etc., instead of just recognizing
ASCII values. Note that REG_UTF8 is not part of the POSIX standard.	ASCII values. Note that REG_UTF8 is not part of the POSIX standard.

REG_UNGREEDY	REG_UNGREEDY

The PCRE_UNGREEDY option is set when the regular expression is passed	The PCRE_UNGREEDY option is set when the regular expression is passed
for compilation to the native function. Note that REG_UNGREEDY is not	for compilation to the native function. Note that REG_UNGREEDY is not
part of the POSIX standard.	part of the POSIX standard.

REG_UTF8	REG_UTF8

The PCRE_UTF8 option is set when the regular expression is passed for	The PCRE_UTF8 option is set when the regular expression is passed for
compilation to the native function. This causes the pattern itself and	compilation to the native function. This causes the pattern itself and
all data strings used for matching it to be treated as UTF-8 strings.	all data strings used for matching it to be treated as UTF-8 strings.
Note that REG_UTF8 is not part of the POSIX standard.	Note that REG_UTF8 is not part of the POSIX standard.

In the absence of these flags, no options are passed to the native	In the absence of these flags, no options are passed to the native
function. This means the the regex is compiled with PCRE default	function. This means the the regex is compiled with PCRE default
semantics. In particular, the way it handles newline characters in the	semantics. In particular, the way it handles newline characters in the
subject string is the Perl way, not the POSIX way. Note that setting	subject string is the Perl way, not the POSIX way. Note that setting
PCRE_MULTILINE has only some of the effects specified for REG_NEWLINE.	PCRE_MULTILINE has only some of the effects specified for REG_NEWLINE.
It does not affect the way newlines are matched by . (they are not) or	It does not affect the way newlines are matched by . (they are not) or
by a negative class such as [^a] (they are).	by a negative class such as [^a] (they are).

The yield of regcomp() is zero on success, and non-zero otherwise. The	The yield of regcomp() is zero on success, and non-zero otherwise. The
preg structure is filled in on success, and one member of the structure	preg structure is filled in on success, and one member of the structure
is public: re_nsub contains the number of capturing subpatterns in the	is public: re_nsub contains the number of capturing subpatterns in the
regular expression. Various error codes are defined in the header file.	regular expression. Various error codes are defined in the header file.

NOTE: If the yield of regcomp() is non-zero, you must not attempt to	NOTE: If the yield of regcomp() is non-zero, you must not attempt to
use the contents of the preg structure. If, for example, you pass it to	use the contents of the preg structure. If, for example, you pass it to
regexec(), the result is undefined and your program is likely to crash.	regexec(), the result is undefined and your program is likely to crash.

Line 7699 COMPILING A PATTERN	Line 8254 COMPILING A PATTERN
MATCHING NEWLINE CHARACTERS	MATCHING NEWLINE CHARACTERS

This area is not simple, because POSIX and Perl take different views of	This area is not simple, because POSIX and Perl take different views of
things. It is not possible to get PCRE to obey POSIX semantics, but	things. It is not possible to get PCRE to obey POSIX semantics, but
then PCRE was never intended to be a POSIX engine. The following table	then PCRE was never intended to be a POSIX engine. The following table
lists the different possibilities for matching newline characters in	lists the different possibilities for matching newline characters in
PCRE:	PCRE:

Default Change with	Default Change with
Line 7723 MATCHING NEWLINE CHARACTERS	Line 8278 MATCHING NEWLINE CHARACTERS
^ matches \n in middle no REG_NEWLINE	^ matches \n in middle no REG_NEWLINE

PCRE's behaviour is the same as Perl's, except that there is no equiva-	PCRE's behaviour is the same as Perl's, except that there is no equiva-
lent for PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl, there is	lent for PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl, there is
no way to stop newline from matching [^a].	no way to stop newline from matching [^a].

The default POSIX newline handling can be obtained by setting	The default POSIX newline handling can be obtained by setting
PCRE_DOTALL and PCRE_DOLLAR_ENDONLY, but there is no way to make PCRE	PCRE_DOTALL and PCRE_DOLLAR_ENDONLY, but there is no way to make PCRE
behave exactly as for the REG_NEWLINE action.	behave exactly as for the REG_NEWLINE action.


MATCHING A PATTERN	MATCHING A PATTERN

The function regexec() is called to match a compiled pattern preg	The function regexec() is called to match a compiled pattern preg
against a given string, which is by default terminated by a zero byte	against a given string, which is by default terminated by a zero byte
(but see REG_STARTEND below), subject to the options in eflags. These	(but see REG_STARTEND below), subject to the options in eflags. These
can be:	can be:

REG_NOTBOL	REG_NOTBOL
Line 7757 MATCHING A PATTERN	Line 8312 MATCHING A PATTERN

REG_STARTEND	REG_STARTEND

The string is considered to start at string + pmatch[0].rm_so and to	The string is considered to start at string + pmatch[0].rm_so and to
have a terminating NUL located at string + pmatch[0].rm_eo (there need	have a terminating NUL located at string + pmatch[0].rm_eo (there need
not actually be a NUL at that location), regardless of the value of	not actually be a NUL at that location), regardless of the value of
nmatch. This is a BSD extension, compatible with but not specified by	nmatch. This is a BSD extension, compatible with but not specified by
IEEE Standard 1003.2 (POSIX.2), and should be used with caution in	IEEE Standard 1003.2 (POSIX.2), and should be used with caution in
software intended to be portable to other systems. Note that a non-zero	software intended to be portable to other systems. Note that a non-zero
rm_so does not imply REG_NOTBOL; REG_STARTEND affects only the location	rm_so does not imply REG_NOTBOL; REG_STARTEND affects only the location
of the string, not how it is matched.	of the string, not how it is matched.

If the pattern was compiled with the REG_NOSUB flag, no data about any	If the pattern was compiled with the REG_NOSUB flag, no data about any
matched strings is returned. The nmatch and pmatch arguments of	matched strings is returned. The nmatch and pmatch arguments of
regexec() are ignored.	regexec() are ignored.

If the value of nmatch is zero, or if the value pmatch is NULL, no data	If the value of nmatch is zero, or if the value pmatch is NULL, no data
Line 7775 MATCHING A PATTERN	Line 8330 MATCHING A PATTERN

Otherwise,the portion of the string that was matched, and also any cap-	Otherwise,the portion of the string that was matched, and also any cap-
tured substrings, are returned via the pmatch argument, which points to	tured substrings, are returned via the pmatch argument, which points to
an array of nmatch structures of type regmatch_t, containing the mem-	an array of nmatch structures of type regmatch_t, containing the mem-
bers rm_so and rm_eo. These contain the offset to the first character	bers rm_so and rm_eo. These contain the offset to the first character
of each substring and the offset to the first character after the end	of each substring and the offset to the first character after the end
of each substring, respectively. The 0th element of the vector relates	of each substring, respectively. The 0th element of the vector relates
to the entire portion of string that was matched; subsequent elements	to the entire portion of string that was matched; subsequent elements
relate to the capturing subpatterns of the regular expression. Unused	relate to the capturing subpatterns of the regular expression. Unused
entries in the array have both structure members set to -1.	entries in the array have both structure members set to -1.

A successful match yields a zero return; various error codes are	A successful match yields a zero return; various error codes are
defined in the header file, of which REG_NOMATCH is the "expected"	defined in the header file, of which REG_NOMATCH is the "expected"
failure code.	failure code.


ERROR MESSAGES	ERROR MESSAGES

The regerror() function maps a non-zero errorcode from either regcomp()	The regerror() function maps a non-zero errorcode from either regcomp()
or regexec() to a printable message. If preg is not NULL, the error	or regexec() to or regexec() to a printable message. If preg is not NULL, the error
should have arisen from the use of that structure. A message terminated	should have arisen from the use of that structure. A message terminated
by a binary zero is placed in errbuf. The length of the message,	by a binary zero is placed in errbuf. The length of the message,
including the zero, is limited to errbuf_size. The yield of the func-	including the zero, is limited to errbuf_size. The yield of the func-
tion is the size of buffer needed to hold the whole message.	tion is the size of buffer needed to hold the whole message.


MEMORY USAGE	MEMORY USAGE

Compiling a regular expression causes memory to be allocated and asso-	Compiling a regular expression causes memory to be allocated and asso-
ciated with the preg structure. The function regfree() frees all such	ciated with the preg structure. The function regfree() frees all such
memory, after which preg may no longer be used as a compiled expres-	memory, after which preg may no longer be used as a compiled expres-
sion.	sion.


Line 7815 AUTHOR	Line 8370 AUTHOR

REVISION	REVISION

Last updated: 16 May 2010	Last updated: 09 January 2012
Copyright (c) 1997-2010 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------


Line 7837 DESCRIPTION	Line 8392 DESCRIPTION
The C++ wrapper for PCRE was provided by Google Inc. Some additional	The C++ wrapper for PCRE was provided by Google Inc. Some additional
functionality was added by Giuseppe Maxia. This brief man page was con-	functionality was added by Giuseppe Maxia. This brief man page was con-
structed from the notes in the pcrecpp.h file, which should be con-	structed from the notes in the pcrecpp.h file, which should be con-
sulted for further details.	sulted for further details. Note that the C++ wrapper supports only the
	original 8-bit PCRE library. There is no 16-bit support at present.


MATCHING INTERFACE	MATCHING INTERFACE

The "FullMatch" operation checks that supplied text matches a supplied	The "FullMatch" operation checks that supplied text matches a supplied
pattern exactly. If pointer arguments are supplied, it copies matched	pattern exactly. If pointer arguments are supplied, it copies matched
sub-strings that match sub-patterns into them.	sub-strings that match sub-patterns into them.

Example: successful match	Example: successful match
Line 7857 MATCHING INTERFACE	Line 8413 MATCHING INTERFACE
Example: creating a temporary RE object:	Example: creating a temporary RE object:
pcrecpp::RE("h.*o").FullMatch("hello");	pcrecpp::RE("h.*o").FullMatch("hello");

You can pass in a "const char*" or a "string" for "text". The examples	You can pass in a "const char*" or a "string" for "text". The examples
below tend to use a const char*. You can, as in the different examples	below tend to use a const char*. You can, as in the different examples
above, store the RE object explicitly in a variable or use a temporary	above, store the RE object explicitly in a variable or use a temporary
RE object. The examples below use one mode or the other arbitrarily.	RE object. The examples below use one mode or the other arbitrarily.
Either could correctly be used for any of these examples.	Either could correctly be used for any of these examples.

You must supply extra pointer arguments to extract matched subpieces.	You must supply extra pointer arguments to extract matched subpieces.
Line 7886 MATCHING INTERFACE	Line 8442 MATCHING INTERFACE
Example: fails because string cannot be stored in integer	Example: fails because string cannot be stored in integer
!pcrecpp::RE("(.*)").FullMatch("ruby", &i);	!pcrecpp::RE("(.*)").FullMatch("ruby", &i);

The provided pointer arguments can be pointers to any scalar numeric	The provided point The provided point
type, or one of:	type, or one of:

string (matched piece is copied to string)	string (matched piece is copied to string)
Line 7894 MATCHING INTERFACE	Line 8450 MATCHING INTERFACE
T (where "bool T::ParseFrom(const char*, int)" exists)	T (where "bool T::ParseFrom(const char*, int)" exists)
NULL (the corresponding matched sub-pattern is not copied)	NULL (the corresponding matched sub-pattern is not copied)

The function returns true iff all of the following conditions are sat-	The function returns true iff all of the following conditions are sat-
isfied:	isfied:

a. "text" matches "pattern" exactly;	a. "text" matches "pattern" exactly;
Line 7909 MATCHING INTERFACE	Line 8465 MATCHING INTERFACE
number of sub-patterns, "i"th captured sub-pattern is	number of sub-patterns, "i"th captured sub-pattern is
ignored.	ignored.

CAVEAT: An optional sub-pattern that does not exist in the matched	CAVEAT: An optional sub-pattern that does not exist in the matched
string is assigned the empty string. Therefore, the following will	string is assigned the empty string. Therefore, the following will
return false (because the empty string is not a valid number):	return false (because the empty string is not a valid number):

int number;	int number;
pcrecpp::RE::FullMatch("abc", "[a-z]+(\\d+)?", &number);	pcrecpp::RE::FullMatch("abc", "[a-z]+(\\d+)?", &number);

The matching interface supports at most 16 arguments per call. If you	The matching interface supports at most 16 arguments per call. If you
need more, consider using the more general interface	need more, consider using the more general interface
pcrecpp::RE::DoMatch. See pcrecpp.h for the signature for DoMatch.	pcrecpp::RE::DoMatch. See pcrecpp.h for the signature for DoMatch.

NOTE: Do not use no_arg, which is used internally to mark the end of a	NOTE: Do not use no_arg, which is used internally to mark the end of a
list of optional arguments, as a placeholder for missing arguments, as	list of optional arguments, as a placeholder for missing arguments, as
this can lead to segfaults.	this can lead to segfaults.


QUOTING METACHARACTERS	QUOTING METACHARACTERS

You can use the "QuoteMeta" operation to insert backslashes before all	You can use the "QuoteMeta" operation to insert backslashes before all
potentially meaningful characters in a string. The returned string,	potentially meaningful characters in a string. The returned string,
used as a regular expression, will exactly match the original string.	used as a regular expression, will exactly match the original string.

Example:	Example:
string quoted = RE::QuoteMeta(unquoted);	string quoted = RE::QuoteMeta(unquoted);

Note that it's legal to escape a character even if it has no special	Note that it's legal to escape a character even if it has no special
meaning in a regular expression -- so this function does that. (This	meaning in a regular expression -- so this function does that. (This
also makes it identical to the perl function of the same name; see	also makes it identical to the perl function of the same name; see
"perldoc -f quotemeta".) For example, "1.5-2.0?" becomes	"perldoc -f quotemeta".) For example, "1.5-2.0?" becomes
"1\.5\-2\.0\?".	"1\.5\-2\.0\?".


PARTIAL MATCHES	PARTIAL MATCHES

You can use the "PartialMatch" operation when you want the pattern to	You can use the "PartialMatch" operation when you want t You can use the "PartialMatch" operation when you want the pattern to
match any substring of the text.	match any substring of the text.

Example: simple search for a string:	Example: simple search for a string:
Line 7958 PARTIAL MATCHES	Line 8514 PARTIAL MATCHES

UTF-8 AND THE MATCHING INTERFACE	UTF-8 AND THE MATCHING INTERFACE

By default, pattern and text are plain text, one byte per character.	By default, pattern and text are plain text, one byte per character.
The UTF8 flag, passed to the constructor, causes both pattern and	The UTF8 flag, passed to the constructor, causes both pattern and
string to be treated as UTF-8 text, still a byte stream but potentially	string to be treated as UTF-8 text, still a byte stream but potentially
multiple bytes per character. In practice, the text is likelier to be	multiple bytes per character. In practice, the text is likelier to be
UTF-8 than the pattern, but the match returned may depend on the UTF8	UTF-8 than the pattern, but the match returned may depend on the UTF8
flag, so always use it when matching UTF8 text. For example, "." will	flag, so always use it when matching UTF8 text. For example, "." will
match one byte normally but with UTF8 set may match up to three bytes	match one byte normally but with UTF8 set may match up to three bytes
of a multi-byte character.	of a multi-byte character.

Example:	Example:
Line 7983 UTF-8 AND THE MATCHING INTERFACE	Line 8539 UTF-8 AND THE MATCHING INTERFACE

PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE	PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE

PCRE defines some modifiers to change the behavior of the regular	PCRE defines some modifiers to change the behavior of the regular
expression engine. The C++ wrapper defines an auxiliary class,	expression engine. The C++ wrapper defines an auxiliary class,
RE_Options, as a vehicle to pass such modifiers to a RE class. Cur-	RE_Options, as a vehicle to pass such modifiers to a RE class. Cur-
rently, the following modifiers are supported:	rently, the following modifiers are supported:

modifier description Perl corresponding	modifier description Perl corresponding
Line 8000 PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE	Line 8556 PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE
PCRE_UNGREEDY reverses * and *? N/A	PCRE_UNGREEDY reverses * and *? N/A
PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*)	PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*)

(*) Both Perl and PCRE allow non capturing parentheses by means of the	(*) Both Perl and PCRE allow non capturing parentheses by means of the
"?:" modifier within the pattern itself. e.g. (?:ab\|cd) does not cap-	"?:" modifier within the pattern itself. e.g. (?:ab\|cd) does not cap-
ture, while (ab\|cd) does.	ture, while (ab\|cd) does.

For a full account on how each modifier works, please check the PCRE	For a full account on how each modifier works, please check the PCRE
API reference page.	API reference page.

For each modifier, there are two member functions whose name is made	For each modifier, there are two member functions whose name is made
out of the modifier in lowercase, without the "PCRE_" prefix. For	out of the modifier in lowercase, without the "PCRE_" prefix. For
instance, PCRE_CASELESS is handled by	instance, PCRE_CASELESS is handled by

bool caseless()	bool caseless()
Line 8018 PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE	Line 8574 PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE
RE_Options & set_caseless(bool)	RE_Options & set_caseless(bool)

which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can	which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can
be accessed through the set_match_limit() and match_limit() member	be accessed through the set_match_limit() and match_limit() member
functions. Setting match_limit to a non-zero value will limit the exe-	functions. Setting match_limit to a non-zero value will limit the exe-
cution of pcre to keep it from doing bad things like blowing the stack	cution of pcre to keep it from doing bad things like blowing the stack
or taking an eternity to return a result. A value of 5000 is good	or taking an eternity to return a result. A value of 5000 is good
enough to stop stack blowup in a 2MB thread stack. Setting match_limit	enough to stop stack blowup in a 2MB thread stack. Setting match_limit
to zero disables match limiting. Alternatively, you can call	to zero disables match limiting. Alternatively, you can call
match_limit_recursion() which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to	match_limit_recursion() which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to
limit how much PCRE recurses. match_limit() limits the number of	limit how much PCRE recurses. match_limit() limits the number of
matches PCRE does; match_limit_recursion() limits the depth of internal	matches PCRE does; match_limit_recursion() limits the depth of internal
recursion, and therefore the amount of stack that is used.	recursion, and therefore the amount of stack that is used.

Normally, to pass one or more modifiers to a RE class, you declare a	Normally, to pass one or more modifiers to a RE class, you declare a
RE_Options object, set the appropriate options, and pass this object to	RE_Options object, set the appropriate options, and pass this object to
a RE constructor. Example:	a RE constructor. Example:

Line 8038 PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE	Line 8594 PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE
if (RE("HELLO", opt).PartialMatch("hello world")) ...	if (RE("HELLO", opt).PartialMatch("hello world")) ...

RE_options has two constructors. The default constructor takes no argu-	RE_options has two constructors. The default constructor takes no argu-
ments and creates a set of flags that are off by default. The optional	ments and creates a set of flags that are off by default. The optional
parameter option_flags is to facilitate transfer of legacy code from C	parameter option_flags is to facilitate transfer of legacy code from C
programs. This lets you do	programs. This lets you do

RE(pattern,	RE(pattern,
Line 8053 PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE	Line 8609 PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE

If you are going to pass one of the most used modifiers, there are some	If you are going to pass one of the most used modifiers, there are some
convenience functions that return a RE_Options class with the appropri-	convenience functions that return a RE_Options class with the appropri-
ate modifier already set: CASELESS(), UTF8(), MULTILINE(), DOTALL(),	ate modifier already set: CASELESS(), UTF8(), MULTILINE(), DOTALL(),
and EXTENDED().	and EXTENDED().

If you need to set several options at once, and you don't want to go	If you need to set several options at once, and you don't want to go
through the pains of declaring a RE_Options object and setting several	through the pains of declaring a RE_Options object and setting several
options, there is a parallel method that give you such ability on the	options, there is a parallel method that give you such ability on the
fly. You can concatenate several set_xxxxx() member functions, since	fly. You can concatenate several set_xxxxx() member functions, since
each of them returns a reference to its class object. For example, to	each of them returns a reference to its class object. For example, to
pass PCRE_CASELESS, PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one	pass PCRE_CASELESS, PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one
statement, you may write:	statement, you may write:

RE(" ^ xyz \\s+ .* blah$",	RE(" ^ xyz \\s+ .* blah$",
Line 8073 PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE	Line 8629 PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE

SCANNING TEXT INCREMENTALLY	SCANNING TEXT INCREMENTALLY

The "Consume" operation may be useful if you want to repeatedly match	The "Consume" operation may be useful if you want to repeatedl The "Consume" operation may be useful if you want to repeatedl
regular expressions at the front of a string and skip over them as they	regular expressions at the front of a string and skip over them as they
match. This requires use of the "StringPiece" type, which represents a	match. This requires use of the "StringPiece" type, which represents a
sub-range of a real string. Like RE, StringPiece is defined in the	sub-range of a real string. Like RE, StringPiece is defined in the
pcrecpp namespace.	pcrecpp namespace.

Example: read lines of the form "var = value" from a string.	Example: read lines of the form "var = value" from a string.
Line 8090 SCANNING TEXT INCREMENTALLY	Line 8646 SCANNING TEXT INCREMENTALLY
...;	...;
}	}

Each successful call to "Consume" will set "var/value", and also	Each successful call to "Consume" will set "var/value", and also
advance "input" so it points past the matched text.	advance "input" so it points past the matched text.

The "FindAndConsume" operation is similar to "Consume" but does not	The "FindAndConsume" operation is similar to "Consume" but does not
anchor your match at the beginning of the string. For example, you	anchor your match at the beginning of the string. For example, you
could extract all words from a string by repeatedly calling	could extract all words from a string by repeatedly calling

pcrecpp::RE("(\\w+)").FindAndConsume(&input, &word)	pcrecpp::RE("(\\w+)").FindAndConsume(&input, &word)
Line 8103 SCANNING TEXT INCREMENTALLY	Line 8659 SCANNING TEXT INCREMENTALLY
PARSING HEX/OCTAL/C-RADIX NUMBERS	PARSING HEX/OCTAL/C-RADIX NUMBERS

By default, if you pass a pointer to a numeric value, the corresponding	By default, if you pass a pointer to a numeric value, the corresponding
text is interpreted as a base-10 number. You can instead wrap the	text is interpreted as a base-10 number. You can instead wrap the
pointer with a call to one of the operators Hex(), Octal(), or CRadix()	pointer with a call to one of the operators Hex(), Octal(), or CRadix()
to interpret the text in another base. The CRadix operator interprets	to interpret the text in another base. The CRadix operator interprets
C-style "0" (base-8) and "0x" (base-16) prefixes, but defaults to	C-style "0" (base-8) and "0x" (base-16) prefixes, but defaults to
base-10.	base-10.

Example:	Example:
Line 8121 PARSING HEX/OCTAL/C-RADIX NUMBERS	Line 8677 PARSING HEX/OCTAL/C-RADIX NUMBERS

REPLACING PARTS OF STRINGS	REPLACING PARTS OF STRINGS

You can replace the first match of "pattern" in "str" with "rewrite".	You can replace the first match of "pattern" in "str" with "rewrite".
Within "rewrite", backslash-escaped digits (\1 to \9) can be used to	Within "rewrite", backslash-escaped digits (\1 to \9) can be used to
insert text matching corresponding parenthesized group from the pat-	insert text matching corresponding parenthesized group from the pat-
tern. \0 in "rewrite" refers to the entire matching text. For example:	tern. \0 in "rewrite" refers to the entire matching text. For example:

string s = "yabba dabba doo";	string s = "yabba dabba doo";
pcrecpp::RE("b+").Replace("d", &s);	pcrecpp::RE("b+").Replace("d", &s);

will leave "s" containing "yada dabba doo". The result is true if the	will leave "s" containing "yada dabba doo". The result is true if the
pattern matches and a replacement occurs, false otherwise.	pattern matches and a replacement occurs, false otherwise.

GlobalReplace is like Replace except that it replaces all occurrences	GlobalReplace is like Replace except that it replaces all occurrences
of the pattern in the string with the rewrite. Replacements are not	of the pattern in the string with the rewrite. Replacements are not
subject to re-matching. For example:	subject to re-matching. For example:

string s = "yabba dabba doo";	string s = "yabba dabba doo";
pcrecpp::RE("b+").GlobalReplace("d", &s);	pcrecpp::RE("b+").GlobalReplace("d", &s);

will leave "s" containing "yada dada doo". It returns the number of	will leave "s" containing "yada dada doo". It returns the number of
replacements made.	replacements made.

Extract is like Replace, except that if the pattern matches, "rewrite"	Extract is like Replace, except that if the pattern matches, "rewrite"
is copied into "out" (an additional argument) with substitutions. The	is copied into "out" (an additional argument) with substitutions. The
non-matching portions of "text" are ignored. Returns true iff a match	non-matching portions of "text" are ignored. Returns true iff a match
occurred and the extraction happened successfully; if no match occurs,	occurred and the extraction happened successfully; if no match occurs,
the string is left unaffected.	the string is left unaffected.

Line 8157 AUTHOR	Line 8713 AUTHOR

REVISION	REVISION

Last updated: 17 March 2009	Last updated: 08 January 2012
Minor typo fixed: 25 July 2011
------------------------------------------------------------------------------	------------------------------------------------------------------------------


Line 8177 PCRE SAMPLE PROGRAM	Line 8732 PCRE SAMPLE PROGRAM
do not have a copy of the PCRE distribution, you can save this listing	do not have a copy of the PCRE distribution, you can save this listing
to re-create pcredemo.c.	to re-create pcredemo.c.

The program compiles the regular expression that is its first argument,	The demonstration program, which uses the original PCRE 8-bit library,
and matches it against the subject string in its second argument. No	compiles the regular expression that is its first argument, and matches
PCRE options are set, and default character tables are used. If match-	it against the subject string in its second argument. No PCRE options
ing succeeds, the program outputs the portion of the subject that	are set, and default character tables are used. If matching succeeds,
matched, together with the contents of any captured substrings.	the program outputs the portion of the subject that matched, together
	with the contents of any captured substrings.

If the -g option is given on the command line, the program then goes on	If the -g option is given on the command line, the program then goes on
to check for further matches of the same regular expression in the same	to check for further matches of the same regular expression in the same
subject string. The logic is a little bit tricky because of the possi-	subject string. The logic is a little bit tricky because of the possi-
bility of matching an empty string. Comments in the code explain what	bility of matching an empty string. Comments in the code explain what
is going on.	is going on.

If PCRE is installed in the standard include and library directories	If PCRE is installed in the standard include and library directories
for your operating system, you should be able to compile the demonstra-	for your operating system, you should be able to compile the demonstra-
tion program using this command:	tion program using this command:

gcc -o pcredemo pcredemo.c -lpcre	gcc -o pcredemo pcredemo.c -lpcre

If PCRE is installed elsewhere, you may need to add additional options	If PCRE is installed elsewhere, you may need to add additional options
to the command line. For example, on a Unix-like system that has PCRE	to the command line. For example, on a Unix-like system that has PCRE
installed in /usr/local, you can compile the demonstration program	installed in /usr/local, you can compile the demonstration program
using a command like this:	using a command like this:

gcc -o pcredemo -I/usr/local/include pcredemo.c \	gcc -o pcredemo -I/usr/local/include pcredemo.c \
-L/usr/local/lib -lpcre	-L/usr/local/lib -lpcre

In a Windows environment, if you want to statically link the program	In a Windows environment, if you want to statica In a Windows environment, if you want to statically link the program
against a non-dll pcre.a file, you must uncomment the line that defines	against a non-dll pcre.a file, you must uncomment the line that defines
PCRE_STATIC before including pcre.h, because otherwise the pcre_mal-	PCRE_STATIC before including pcre.h, because otherwise the pcre_mal-
loc() and pcre_free() exported functions will be declared	loc() and pcre_free() exported functions will be declared
__declspec(dllimport), with unwanted results.	__declspec(dllimport), with unwanted results.

Once you have compiled and linked the demonstration program, you can	Once you have compiled and linked the demonstration program, you can
run simple tests like this:	run simple tests like this:

./pcredemo 'cat\|dog' 'the cat sat on the mat'	./pcredemo 'cat\|dog' 'the cat sat on the mat'
./pcredemo -g 'cat\|dog' 'the dog sat on the cat'	./pcredemo -g 'cat\|dog' 'the dog sat on the cat'

Note that there is a much more comprehensive test program, called	Note that there is a much more comprehensive test program, called
pcretest, which supports many more facilities for testing regular	pcretest, which supports many more facilities for testing regular
expressions and the PCRE library. The pcredemo program is provided as a	expressions and both PCRE libraries. The pcredemo program is provided
simple coding example.	as a simple coding example.

If you try to run pcredemo when PCRE is not installed in the standard	If you try to run pcredemo when PCRE is not installed in the standard
library directory, you may get an error like this on some operating	library directory, you may get an error like this on some operating
systems (e.g. Solaris):	systems (e.g. Solaris):

ld.so.1: a.out: fatal: libpcre.so.0: open failed: No such file or	ld.so.1: a.out: fatal: libpcre.so.0: open failed: No such file or
directory	directory

This is caused by the way shared library support works on those sys-	This is caused by the way shared library support works on those sys-
tems. You need to add	tems. You need to add

-R/usr/local/lib	-R/usr/local/lib
Line 8244 AUTHOR	Line 8800 AUTHOR

REVISION	REVISION

Last updated: 17 November 2010	Last updated: 10 January 2012
Copyright (c) 1997-2010 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------
PCRELIMITS(3) PCRELIMITS(3)	PCRELIMITS(3) PCRELIMITS(3)

Line 8259 SIZE AND OTHER LIMITATIONS	Line 8815 SIZE AND OTHER LIMITATIONS
There are some size limitations in PCRE but it is hoped that they will	There are some size limitations in PCRE but it is hoped that they will
never in practice be relevant.	never in practice be relevant.

The maximum length of a compiled pattern is 65539 (sic) bytes if PCRE	The maximum length of a compiled pattern is approximately 64K data
is compiled with the default internal linkage size of 2. If you want to	units (bytes for the 8-bit library, 16-bit units for the 16-bit
process regular expressions that are truly enormous, you can compile	library) if PCRE is compiled with the default internal linkage size of
PCRE with an internal linkage size of 3 or 4 (see the README file in	2 bytes. If you want to process regular expressions that are truly
the source distribution and the pcrebuild documentation for details).	enormous, you can compile PCRE with an internal linkage size of 3 or 4
In these cases the limit is substantially larger. However, the speed	(when building the 16-bit library, 3 is rounded up to 4). See the
of execution is slower.	README file in the source distribution and the pcrebuild documentation
	for details. In these cases the limit is substantially larger. How-
	ever, the speed of execution is slower.

All values in repeating quantifiers must be less than 65536.	All values in repeating quantifiers must be less than 65536.

Line 8298 AUTHOR	Line 8856 AUTHOR

REVISION	REVISION

Last updated: 30 November 2011	Last updated: 08 January 2012
Copyright (c) 1997-2011 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------


Line 8312 NAME	Line 8870 NAME

PCRE DISCUSSION OF STACK USAGE	PCRE DISCUSSION OF STACK USAGE

When you call pcre_exec(), it makes use of an internal function called	When you call pcre[16]_exec(), it makes use of an internal function
match(). This calls itself recursively at branch points in the pattern,	called match(). This calls itself recursively at branch points in the
in order to remember the state of the match so that it can back up and	pattern, in order to remember the state of the match so that it can
try a different alternative if the first one fails. As matching pro-	back up and try a different alternative if the first one fails. As
ceeds deeper and deeper into the tree of possibilities, the recursion	matching proceeds deeper and deeper into the tree of possibilities, the
depth increases. The match() function is also called in other circum-	recursion depth increases. The match() function is also called in other
stances, for example, whenever a parenthesized sub-pattern is entered,	circumstances, for example, whenever a parenthesized sub-pattern is
and in certain cases of repetition.	entered, and in certain cases of repetition.

Not all calls of match() increase the recursion depth; for an item such	Not all calls of match() increase the recursion depth; for an item such
as a* it may be called several times at the same level, after matching	as a* it may be called several times at the same level, after matching
Line 8328 PCRE DISCUSSION OF STACK USAGE	Line 8886 PCRE DISCUSSION OF STACK USAGE
result of the current call (a "tail recursion"), the function is just	result of the current call (a "tail recursion"), the function is just
restarted instead.	restarted instead.

The above comments apply when pcre_exec() is run in its normal inter-	The above comments apply when pcre[16]_exec() is run in its normal
pretive manner. If the pattern was studied with the PCRE_STUDY_JIT_COM-	interpretive manner. If the pattern was studied with the
PILE option, and just-in-time compiling was successful, and the options	PCRE_STUDY_JIT_COMPILE option, and just-in-time compiling was success-
passed to pcre_exec() were not incompatible, the matching process uses	ful, and the options passed to pcre[16]_exec() were not incompatible,
the JIT-compiled code instead of the match() function. In this case,	the matching process uses the JIT-compiled code instead of the match()
the memory requirements are handled entirely differently. See the pcre-	function. In this case, the memory requirements are handled entirely
jit documentation for details.	differently. See the pcrejit documentation for details.

The pcre_dfa_exec() function operates in an entirely different way, and	The pcre[16]_dfa_exec() function operates in an entirely different way,
uses recursion only when there is a regular expression recursion or	and uses recursion only when there is a regular expression recursion or
subroutine call in the pattern. This includes the processing of asser-	subroutine call in the pattern. This includes the processing of asser-
tion and "once-only" subpatterns, which are handled like subroutine	tion and "once-only" subpatterns, which are handled like subroutine
calls. Normally, these are never very deep, and the limit on the com-	calls. Normally, these are never very deep, and the limit on the com-
plexity of pcre_dfa_exec() is controlled by the amount of workspace it	plexity of pcre[16]_dfa_exec() is controlled by the amount of workspace
is given. However, it is possible to write patterns with runaway infi-	it is given. However, it is possible to write patterns with runaway
nite recursions; such patterns will cause pcre_dfa_exec() to run out of	infinite recursions; such patterns will cause pcre[16]_dfa_exec() to
stack. At present, there is no protection against this.	run out of stack. At present, there is no protection against this.

The comments that follow do NOT apply to pcre_dfa_exec(); they are rel-	The comments that follow do NOT apply to pcre[16]_dfa_exec(); they are
evant only for pcre_exec() without the JIT optimization.	relevant only for pcre[16]_exec() without the JIT optimization.

Reducing pcre_exec()'s stack usage	Reducing pcre[16]_exec()'s stack usage

Each time that match() is actually called recursively, it uses memory	Each time that match() is actually called recursively, it uses memory
from the process stack. For certain kinds of pattern and data, very	from the process stack. For certain kinds of pattern and data, very
Line 8382 PCRE DISCUSSION OF STACK USAGE	Line 8940 PCRE DISCUSSION OF STACK USAGE
ing long subject strings is to write repeated parenthesized subpatterns	ing long subject strings is to write repeated parenthesized subpatterns
to match more than one character whenever possible.	to match more than one character whenever possible.

Compiling PCRE to use heap instead of stack for pcre_exec()	Compiling PCRE to use heap instead of stack for pcre[16]_exec()

In environments where stack memory is constrained, you might want to	In environments where stack memory is constrained, you might want to
compile PCRE to use heap memory instead of stack for remembering back-	compile PCRE to use heap memory instead of stack for remembering back-
up points when pcre_exec() is running. This makes it run a lot more	up points when pcre[16]_exec() is running. This makes it run a lot more
slowly, however. Details of how to do this are given in the pcrebuild	slowly, however. Details of how to do this are given in the pcrebuild
documentation. When built in this way, instead of using the stack, PCRE	documentation. When built in this way, instead of using the stack, PCRE
obtains and frees memory by calling the functions that are pointed to	obtains and frees memory by calling the functions that are pointed to
by the pcre_stack_malloc and pcre_stack_free variables. By default,	by the pcre[16]_stack_malloc and pcre[16]_stack_free variables. By
these point to malloc() and free(), but you can replace the pointers to	default, these point to malloc() and free(), but you can replace the
cause PCRE to use your own functions. Since the block sizes are always	pointers to cause PCRE to use your own functions. Since the block sizes
the same, and are always freed in reverse order, it may be possible to	are always the same, and are always freed in reverse order, it may be
implement customized memory handlers that are more efficient than the	possible to implement customized memory handlers that are more effi-
standard functions.	cient than the standard functions.

Limiting pcre_exec()'s stack usage	Limiting pcre[16]_exec()'s stack usage

You can set limits on the number of times that match() is called, both	You can set limits on the number of times that match() is called, both
in total and recursively. If a limit is exceeded, pcre_exec() returns	in total and recursively. If a limit is exceeded, pcre[16]_exec()
an error code. Setting suitable limits should prevent it from running	returns an error code. Setting suitable limits should prevent it from
out of stack. The default values of the limits are very large, and	running out of stack. The default values of the limits are very large,
unlikely ever to operate. They can be changed when PCRE is built, and	and unlikely ever to operate. They can be changed when PCRE is built,
they can also be set when pcre_exec() is called. For details of these	and they can also be set when pcre[16]_exec() is called. For details of
interfaces, see the pcrebuild documentation and the section on extra	these interfaces, see the pcrebuild documentation and the section on
data for pcre_exec() in the pcreapi documentation.	extra data for pcre[16]_exec() in the pcreapi documentation.

As a very rough rule of thumb, you should reckon on about 500 bytes per	As a very rough rule of thumb, you should reckon on about 500 bytes per
recursion. Thus, if you want to limit your stack usage to 8Mb, you	recursion. Thus, if you want to limit your stack usage to 8Mb, you
Line 8417 PCRE DISCUSSION OF STACK USAGE	Line 8975 PCRE DISCUSSION OF STACK USAGE
option (-S) that can be used to increase the size of its stack. As long	option (-S) that can be used to increase the size of its stack. As long
as the stack is large enough, another option (-M) can be used to find	as the stack is large enough, another option (-M) can be used to find
the smallest limits that allow a particular pattern to match a given	the smallest limits that allow a particular pattern to match a given
subject string. This is done by calling pcre_exec() repeatedly with	subject string. This is done by calling pcre[16]_exec() repeatedly with
different limits.	different limits.

	Obtaining an estimate of stack usage

	The actual amount of stack used per recursion can vary quite a lot,
	depending on the compiler that was used to build PCRE and the optimiza-
	tion or debugging options that were set for it. The rule of thumb value
	of 500 bytes mentioned above may be larger or smaller than what is
	actually needed. A better approximation can be obtained by running this
	command:

	pcretest -m -C

	The -C option causes pcretest to output information about the options
	with which PCRE was compiled. When -m is also given (before -C), infor-
	mation about stack use is given in a line like this:

	Match recursion uses stack: approximate frame size = 640 bytes

	The value is approximate because some recursions need a bit more (up to
	perhaps 16 more bytes).

	If the above command is given when PCRE is compiled to use the heap
	instead of the stack for recursion, the value that is output is the
	size of each block that is obtained from the heap.

Changing stack size in Unix-like systems	Changing stack size in Unix-like systems

In Unix-like environments, there is not often a problem with the stack	In Unix-like environments, there is not often a problem with the stack
Line 8440 PCRE DISCUSSION OF STACK USAGE	Line 9022 PCRE DISCUSSION OF STACK USAGE

This reads the current limits (soft and hard) using getrlimit(), then	This reads the current limits (soft and hard) using getrlimit(), then
attempts to increase the soft limit to 100Mb using setrlimit(). You	attempts to increase the soft limit to 100Mb using setrlimit(). You
must do this before calling pcre_exec().	must do this before calling pcre[16]_exec().

Changing stack size in Mac OS X	Changing stack size in Mac OS X

Line 8459 AUTHOR	Line 9041 AUTHOR

REVISION	REVISION

Last updated: 26 August 2011	Last updated: 21 January 2012
Copyright (c) 1997-2011 University of Cambridge.	Copyright (c) 1997-2012 University of Cambridge.
------------------------------------------------------------------------------	------------------------------------------------------------------------------

FreeBSD-CVSweb <freebsd-cvsweb@FreeBSD.org>

Removed from v.1.1.1.1
changed lines
	Added in v.1.1.1.2