pcreapi man page on Haiku

Man page or keyword search:  
man Server   1409 pages
apropos Keyword Search (all sections)
Output format
Haiku logo
[printable version]

PCREAPI(3)							    PCREAPI(3)

NAME
       PCRE - Perl-compatible regular expressions

PCRE NATIVE API BASIC FUNCTIONS

       #include <pcre.h>

       pcre *pcre_compile(const char *pattern, int options,
	    const char **errptr, int *erroffset,
	    const unsigned char *tableptr);

       pcre *pcre_compile2(const char *pattern, int options,
	    int *errorcodeptr,
	    const char **errptr, int *erroffset,
	    const unsigned char *tableptr);

       pcre_extra *pcre_study(const pcre *code, int options,
	    const char **errptr);

       void pcre_free_study(pcre_extra *extra);

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

       int pcre_copy_named_substring(const pcre *code,
	    const char *subject, int *ovector,
	    int stringcount, const char *stringname,
	    char *buffer, int buffersize);

       int pcre_copy_substring(const char *subject, int *ovector,
	    int stringcount, int stringnumber, char *buffer,
	    int buffersize);

       int pcre_get_named_substring(const pcre *code,
	    const char *subject, int *ovector,
	    int stringcount, const char *stringname,
	    const char **stringptr);

       int pcre_get_stringnumber(const pcre *code,
	    const char *name);

       int pcre_get_stringtable_entries(const pcre *code,
	    const char *name, char **first, char **last);

       int pcre_get_substring(const char *subject, int *ovector,
	    int stringcount, int stringnumber,
	    const char **stringptr);

       int pcre_get_substring_list(const char *subject,
	    int *ovector, int stringcount, const char ***listptr);

       void pcre_free_substring(const char *stringptr);

       void pcre_free_substring_list(const char **stringptr);

       const unsigned char *pcre_maketables(void);

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

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

       int pcre_refcount(pcre *code, int adjust);

       int pcre_config(int what, void *where);

       char *pcre_version(void);

PCRE NATIVE API INDIRECTED FUNCTIONS

       void *(*pcre_malloc)(size_t);

       void (*pcre_free)(void *);

       void *(*pcre_stack_malloc)(size_t);

       void (*pcre_stack_free)(void *);

       int (*pcre_callout)(pcre_callout_block *);

PCRE API OVERVIEW

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

       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
       can normally be accessed by adding -lpcre to the command for linking an
       application  that  uses	PCRE.  The  header  file  defines  the	macros
       PCRE_MAJOR and PCRE_MINOR to contain the major and minor	 release  num‐
       bers  for  the  library.	 Applications can use these to include support
       for different releases of PCRE.

       In a Windows environment, if you want to statically link an application
       program	against	 a  non-dll  pcre.a  file, you must define PCRE_STATIC
       before including pcre.h or pcrecpp.h, because otherwise	the  pcre_mal‐
       loc()   and   pcre_free()   exported   functions	  will	 be   declared
       __declspec(dllimport), with unwanted results.

       The  functions  pcre_compile(),	pcre_compile2(),   pcre_study(),   and
       pcre_exec()  are used for compiling and matching regular expressions in
       a Perl-compatible manner. A sample program that demonstrates  the  sim‐
       plest  way  of  using them is provided in the file called pcredemo.c in
       the PCRE source distribution. A listing of this program is given in the
       pcredemo	 documentation, and the pcresample documentation describes how
       to compile and run it.

       Just-in-time compiler support is an optional feature of PCRE  that  can
       be built in appropriate hardware environments. It greatly speeds up the
       matching performance of	many  patterns.	 Simple	 programs  can	easily
       request	that  it  be  used  if available, by setting an option that is
       ignored when it is not relevant. More complicated programs  might  need
       to     make    use    of	   the	  functions    pcre_jit_stack_alloc(),
       pcre_jit_stack_free(), and pcre_assign_jit_stack() in order to  control
       the  JIT	 code's	 memory	 usage.	  These functions are discussed in the
       pcrejit documentation.

       A second matching function, pcre_dfa_exec(), which is not Perl-compati‐
       ble,  is	 also provided. This uses a different algorithm for the match‐
       ing. The alternative algorithm finds all possible matches (at  a	 given
       point  in  the  subject), and scans the subject just once (unless there
       are lookbehind assertions). However, this  algorithm  does  not	return
       captured	 substrings.  A description of the two matching algorithms and
       their advantages and disadvantages is given in the  pcrematching	 docu‐
       mentation.

       In  addition  to	 the  main compiling and matching functions, there are
       convenience functions for extracting captured substrings from a subject
       string that is matched by pcre_exec(). They are:

	 pcre_copy_substring()
	 pcre_copy_named_substring()
	 pcre_get_substring()
	 pcre_get_named_substring()
	 pcre_get_substring_list()
	 pcre_get_stringnumber()
	 pcre_get_stringtable_entries()

       pcre_free_substring() and pcre_free_substring_list() are also provided,
       to free the memory used for extracted strings.

       The function pcre_maketables() is used to  build	 a  set	 of  character
       tables	in   the   current   locale  for  passing  to  pcre_compile(),
       pcre_exec(), or pcre_dfa_exec(). This is an optional facility  that  is
       provided	 for  specialist  use.	Most  commonly,	 no special tables are
       passed, in which case internal tables that are generated when  PCRE  is
       built are used.

       The  function  pcre_fullinfo()  is used to find out information about a
       compiled pattern; pcre_info() is an obsolete version that returns  only
       some  of	 the available information, but is retained for backwards com‐
       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
       block containing a compiled pattern. This is provided for  the  benefit
       of object-oriented applications.

       The  global  variables  pcre_malloc and pcre_free initially contain the
       entry points of the standard malloc()  and  free()  functions,  respec‐
       tively. PCRE calls the memory management functions via these variables,
       so a calling program can replace them if it  wishes  to	intercept  the
       calls. This should be done before calling any PCRE functions.

       The  global  variables  pcre_stack_malloc  and pcre_stack_free are also
       indirections to memory management functions.  These  special  functions
       are  used  only	when  PCRE is compiled to use the heap for remembering
       data, instead of recursive function calls, when running the pcre_exec()
       function.  See  the  pcrebuild  documentation  for details of how to do
       this. It is a non-standard way of building PCRE, for  use  in  environ‐
       ments  that  have  limited stacks. Because of the greater use of memory
       management, it runs more slowly. Separate  functions  are  provided  so
       that  special-purpose  external	code  can  be used for this case. When
       used, these functions are always called in a  stack-like	 manner	 (last
       obtained,  first freed), and always for memory blocks of the same size.
       There is a discussion about PCRE's stack usage in the  pcrestack	 docu‐
       mentation.

       The global variable pcre_callout initially contains NULL. It can be set
       by the caller to a "callout" function, which PCRE  will	then  call  at
       specified  points during a matching operation. Details are given in the
       pcrecallout documentation.

NEWLINES

       PCRE supports five different conventions for indicating line breaks  in
       strings:	 a  single  CR (carriage return) character, a single LF (line‐
       feed) character, the two-character sequence CRLF, any of the three pre‐
       ceding,	or any Unicode newline sequence. The Unicode newline sequences
       are the three just mentioned, 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 (paragraph separator, U+2029).

       Each of the first three conventions is used by at least	one  operating
       system  as its standard newline sequence. When PCRE is built, a default
       can be specified.  The default default is LF, which is the  Unix	 stan‐
       dard.  When  PCRE  is run, the default can be overridden, either when a
       pattern is compiled, or when it is matched.

       At compile time, the newline convention can be specified by the options
       argument	 of  pcre_compile(), or it can be specified by special text at
       the start of the pattern itself; this overrides any other settings. See
       the pcrepattern page for details of the special character sequences.

       In the PCRE documentation the word "newline" is used to mean "the char‐
       acter or pair of characters that indicate a line break". The choice  of
       newline	convention  affects  the  handling of the dot, circumflex, and
       dollar metacharacters, the handling of #-comments in /x mode, and, when
       CRLF  is a recognized line ending sequence, the match position advance‐
       ment for a non-anchored pattern. There is more detail about this in the
       section on pcre_exec() options below.

       The  choice of newline convention does not affect the interpretation of
       the \n or \r escape sequences, nor does	it  affect  what  \R  matches,
       which is controlled in a similar way, but by separate options.

MULTITHREADING

       The  PCRE  functions  can be used in multi-threading applications, with
       the  proviso  that  the	memory	management  functions  pointed	to  by
       pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
       callout function pointed to by pcre_callout, are shared by all threads.

       The compiled form of a regular expression is not altered during	match‐
       ing, so the same compiled pattern can safely be used by several threads
       at once.

       If the just-in-time optimization feature is being used, it needs	 sepa‐
       rate  memory stack areas for each thread. See the pcrejit documentation
       for more details.

SAVING PRECOMPILED PATTERNS FOR LATER USE

       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
       than the one on which  it  was  compiled.  Details  are	given  in  the
       pcreprecompile  documentation.  However, compiling a regular expression
       with one version of PCRE for use with a different version is not	 guar‐
       anteed to work and may cause crashes.

CHECKING BUILD-TIME OPTIONS

       int pcre_config(int what, void *where);

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

       The first argument for pcre_config() is an  integer,  specifying	 which
       information is required; the second argument is a pointer to a variable
       into which the information is  placed.  The  following  information  is
       available:

	 PCRE_CONFIG_UTF8

       The  output is an integer that is set to one if UTF-8 support is avail‐
       able; otherwise it is set to zero.

	 PCRE_CONFIG_UNICODE_PROPERTIES

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

	 PCRE_CONFIG_JIT

       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.

	 PCRE_CONFIG_NEWLINE

       The output is an integer whose value specifies  the  default  character
       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,
       and  -1	for  ANY.  Though they are derived from ASCII, the same values
       are returned in EBCDIC environments. The default should normally corre‐
       spond to the standard sequence for your operating system.

	 PCRE_CONFIG_BSR

       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
       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‐
       tern is compiled or matched.

	 PCRE_CONFIG_LINK_SIZE

       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
       4.  Larger  values  allow larger regular expressions to be compiled, at
       the expense of slower matching. The default value of  2	is  sufficient
       for  all	 but  the  most massive patterns, since it allows the compiled
       pattern to be up to 64K in size.

	 PCRE_CONFIG_POSIX_MALLOC_THRESHOLD

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

	 PCRE_CONFIG_MATCH_LIMIT

       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.
       Further details are given with pcre_exec() below.

	 PCRE_CONFIG_MATCH_LIMIT_RECURSION

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

	 PCRE_CONFIG_STACKRECURSE

       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
       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
       on  the	heap  instead  of  recursive  function	calls.	In  this case,
       pcre_stack_malloc and  pcre_stack_free  are  called  to	manage	memory
       blocks on the heap, thus avoiding the use of the stack.

COMPILING A PATTERN

       pcre *pcre_compile(const char *pattern, int options,
	    const char **errptr, int *erroffset,
	    const unsigned char *tableptr);

       pcre *pcre_compile2(const char *pattern, int options,
	    int *errorcodeptr,
	    const char **errptr, int *erroffset,
	    const unsigned char *tableptr);

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

       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
       obtained via pcre_malloc is returned. This contains the	compiled  code
       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.
       It is up to the caller to free the memory (via pcre_free) when it is no
       longer required.

       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
       fully relocatable, because it may contain a copy of the tableptr	 argu‐
       ment, which is an address (see below).

       The options argument contains various bit settings that affect the com‐
       pilation. It should be zero if no options are required.	The  available
       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
       unset  from  within  the	 pattern  (see the detailed description in the
       pcrepattern documentation). For those options that can be different  in
       different  parts	 of  the pattern, the contents of the options argument
       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_NO_START_OPT options can be set at the time of matching as well as
       at compile time.

       If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
       if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
       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
       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
       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
       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.

       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.

       If  pcre_compile2()  is	used instead of pcre_compile(), and the error‐
       codeptr argument is not NULL, a non-zero error code number is  returned
       via  this argument in the event of an error. This is in addition to the
       textual error message. Error codes and messages are listed below.

       If the final argument, tableptr, is NULL, PCRE uses a  default  set  of
       character  tables  that	are  built  when  PCRE	is compiled, using the
       default C locale. Otherwise, tableptr must be an address	 that  is  the
       result  of  a  call to pcre_maketables(). This value is stored with the
       compiled pattern, and used again by pcre_exec(), unless	another	 table
       pointer is passed to it. For more discussion, see the section on locale
       support below.

       This code fragment shows a typical straightforward  call	 to  pcre_com‐
       pile():

	 pcre *re;
	 const char *error;
	 int erroffset;
	 re = pcre_compile(
	   "^A.*Z",	     /* the pattern */
	   0,		     /* default options */
	   &error,	     /* for error message */
	   &erroffset,	     /* for error offset */
	   NULL);	     /* use default character tables */

       The  following  names  for option bits are defined in the pcre.h header
       file:

	 PCRE_ANCHORED

       If this bit is set, the pattern is forced to be "anchored", that is, it
       is  constrained to match only at the first matching point in the string
       that is being searched (the "subject string"). This effect can also  be
       achieved	 by appropriate constructs in the pattern itself, which is the
       only way to do it in Perl.

	 PCRE_AUTO_CALLOUT

       If this bit is set, pcre_compile() automatically inserts callout items,
       all  with  number  255, before each pattern item. For discussion of the
       callout facility, see the pcrecallout documentation.

	 PCRE_BSR_ANYCRLF
	 PCRE_BSR_UNICODE

       These options (which are mutually exclusive) control what the \R escape
       sequence	 matches.  The choice is either to match only CR, LF, or CRLF,
       or to match any Unicode newline sequence. The default is specified when
       PCRE is built. It can be overridden from within the pattern, or by set‐
       ting an option when a compiled pattern is matched.

	 PCRE_CASELESS

       If this bit is set, letters in the pattern match both upper  and	 lower
       case  letters.  It  is  equivalent  to  Perl's /i option, and it can be
       changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
       always  understands the concept of case for characters whose values are
       less than 128, so caseless matching is always possible. For  characters
       with  higher  values,  the concept of case is supported if PCRE is com‐
       piled with Unicode property support, but not otherwise. If you want  to
       use  caseless  matching	for  characters 128 and above, you must ensure
       that PCRE is compiled with Unicode property support  as	well  as  with
       UTF-8 support.

	 PCRE_DOLLAR_ENDONLY

       If  this bit is set, a dollar metacharacter in the pattern matches only
       at the end of the subject string. Without this option,  a  dollar  also
       matches	immediately before a newline at the end of the string (but not
       before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
       if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
       Perl, and no way to set it within a pattern.

	 PCRE_DOTALL

       If this bit is set, a dot metacharacter in the pattern matches a	 char‐
       acter of any value, including one that indicates a newline. However, it
       only ever matches one character, even if newlines are  coded  as	 CRLF.
       Without	this option, a dot does not match when the current position is
       at a newline. This option is equivalent to Perl's /s option, and it can
       be  changed within a pattern by a (?s) option setting. A negative class
       such as [^a] always matches newline characters, independent of the set‐
       ting of this option.

	 PCRE_DUPNAMES

       If  this	 bit is set, names used to identify capturing subpatterns need
       not be unique. This can be helpful for certain types of pattern when it
       is  known  that	only  one instance of the named subpattern can ever be
       matched. There are more details of named subpatterns  below;  see  also
       the pcrepattern documentation.

	 PCRE_EXTENDED

       If  this	 bit  is  set,	whitespace  data characters in the pattern are
       totally ignored except when escaped or inside a character class. White‐
       space does not include the VT character (code 11). In addition, charac‐
       ters between an unescaped # outside a character class and the next new‐
       line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
       option, and it can be changed within a pattern by a  (?x)  option  set‐
       ting.

       Which  characters  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 described in the section entitled "Newline conven‐
       tions" in the pcrepattern documentation. Note that the end of this type
       of  comment  is	a  literal  newline  sequence  in  the pattern; escape
       sequences that happen to represent a newline do not count.

       This option makes it possible to include	 comments  inside  complicated
       patterns.   Note,  however,  that this applies only to data characters.
       Whitespace  characters  may  never  appear  within  special   character
       sequences in a pattern, for example within the sequence (?( that intro‐
       duces a conditional subpattern.

	 PCRE_EXTRA

       This option was invented in order to turn on  additional	 functionality
       of  PCRE	 that  is  incompatible with Perl, but it is currently of very
       little use. When set, any backslash in a pattern that is followed by  a
       letter  that  has  no  special  meaning causes an error, thus reserving
       these combinations for future expansion. By  default,  as  in  Perl,  a
       backslash  followed by a letter with no special meaning is treated as a
       literal. (Perl can, however, be persuaded to give an error for this, by
       running	it with the -w option.) There are at present no other features
       controlled by this option. It can also be set by a (?X) option  setting
       within a pattern.

	 PCRE_FIRSTLINE

       If  this	 option	 is  set,  an  unanchored pattern is required to match
       before or at the first  newline	in  the	 subject  string,  though  the
       matched text may continue over the newline.

	 PCRE_JAVASCRIPT_COMPAT

       If this option is set, PCRE's behaviour is changed in some ways so that
       it is compatible with JavaScript rather than Perl. The changes  are  as
       follows:

       (1)  A  lone  closing square bracket in a pattern causes a compile-time
       error, because this is illegal in JavaScript (by default it is  treated
       as a data character). Thus, the pattern AB]CD becomes illegal when this
       option is set.

       (2) At run time, a back reference to an unset subpattern group  matches
       an  empty  string (by default this causes the current matching alterna‐
       tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
       set  (assuming  it can find an "a" in the subject), whereas it fails by
       default, for Perl compatibility.

       (3) \U matches an upper case "U" character; by default \U causes a com‐
       pile time error (Perl uses \U to upper case subsequent characters).

       (4) \u matches a lower case "u" character unless it is followed by four
       hexadecimal digits, in which case the hexadecimal  number  defines  the
       code  point  to match. By default, \u causes a compile time error (Perl
       uses it to upper case the following character).

       (5) \x matches a lower case "x" character unless it is followed by  two
       hexadecimal  digits,  in	 which case the hexadecimal number defines the
       code point to match. By default, as in Perl, a  hexadecimal  number  is
       always expected after \x, but it may have zero, one, or two digits (so,
       for example, \xz matches a binary zero character followed by z).

	 PCRE_MULTILINE

       By default, PCRE treats the subject string as consisting	 of  a	single
       line  of characters (even if it actually contains newlines). The "start
       of line" metacharacter (^) matches only at the  start  of  the  string,
       while  the  "end	 of line" metacharacter ($) matches only at the end of
       the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
       is set). This is the same as Perl.

       When  PCRE_MULTILINE  it	 is set, the "start of line" and "end of line"
       constructs match immediately following or immediately  before  internal
       newlines	 in  the  subject string, respectively, as well as at the very
       start and end. This is equivalent to Perl's /m option, and  it  can  be
       changed within a pattern by a (?m) option setting. If there are no new‐
       lines in a subject string, or no occurrences of ^ or $  in  a  pattern,
       setting PCRE_MULTILINE has no effect.

	 PCRE_NEWLINE_CR
	 PCRE_NEWLINE_LF
	 PCRE_NEWLINE_CRLF
	 PCRE_NEWLINE_ANYCRLF
	 PCRE_NEWLINE_ANY

       These  options  override the default newline definition that was chosen
       when PCRE was built. Setting the first or the second specifies  that  a
       newline	is  indicated  by a single character (CR or LF, respectively).
       Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
       two-character  CRLF  sequence.  Setting	PCRE_NEWLINE_ANYCRLF specifies
       that any of the three preceding sequences should be recognized. Setting
       PCRE_NEWLINE_ANY	 specifies that any Unicode newline sequence should be
       recognized. The Unicode newline sequences are the three just mentioned,
       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
       (paragraph  separator,  U+2029).	 The  last  two are recognized only in
       UTF-8 mode.

       The newline setting in the  options  word  uses	three  bits  that  are
       treated as a number, giving eight possibilities. Currently only six are
       used (default plus the five values above). This means that if  you  set
       more  than one newline option, the combination may or may not be sensi‐
       ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
       PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
       cause an error.

       The only time that a line break in a pattern  is	 specially  recognized
       when  compiling	is when PCRE_EXTENDED is set. CR and LF are whitespace
       characters, and so are ignored in this mode. Also, an unescaped #  out‐
       side  a	character class indicates a comment that lasts until after the
       next line break sequence. In other circumstances, line break  sequences
       in patterns are treated as literal data.

       The newline option that is set at compile time becomes the default that
       is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.

	 PCRE_NO_AUTO_CAPTURE

       If this option is set, it disables the use of numbered capturing paren‐
       theses  in the pattern. Any opening parenthesis that is not followed by
       ? behaves as if it were followed by ?: but named parentheses can	 still
       be  used	 for  capturing	 (and  they acquire numbers in the usual way).
       There is no equivalent of this option in Perl.

	 NO_START_OPTIMIZE

       This is an option that acts at matching time; that is, it is really  an
       option  for  pcre_exec()	 or  pcre_dfa_exec().  If it is set at compile
       time, it is remembered with the compiled pattern and assumed at	match‐
       ing  time.  For	details	 see  the discussion of PCRE_NO_START_OPTIMIZE
       below.

	 PCRE_UCP

       This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
       \w,  and	 some  of  the POSIX character classes. By default, only ASCII
       characters are recognized, but if PCRE_UCP is set,  Unicode  properties
       are  used instead to classify characters. More details are given in the
       section on generic character types in the pcrepattern page. If you  set
       PCRE_UCP,  matching  one of the items it affects takes much longer. The
       option is available only if PCRE has been compiled with	Unicode	 prop‐
       erty support.

	 PCRE_UNGREEDY

       This  option  inverts  the "greediness" of the quantifiers so that they
       are not greedy by default, but become greedy if followed by "?". It  is
       not  compatible	with Perl. It can also be set by a (?U) option setting
       within the pattern.

	 PCRE_UTF8

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

	 PCRE_NO_UTF8_CHECK

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

COMPILATION ERROR CODES

       The following table lists the error  codes  than	 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
       fallen out of use. To avoid confusion, they have not been re-used.

	  0  no error
	  1  \ at end of pattern
	  2  \c at end of pattern
	  3  unrecognized character follows \
	  4  numbers out of order in {} quantifier
	  5  number too big in {} quantifier
	  6  missing terminating ] for character class
	  7  invalid escape sequence in character class
	  8  range out of order in character class
	  9  nothing to repeat
	 10  [this code is not in use]
	 11  internal error: unexpected repeat
	 12  unrecognized character after (? or (?-
	 13  POSIX named classes are supported only within a class
	 14  missing )
	 15  reference to non-existent subpattern
	 16  erroffset passed as NULL
	 17  unknown option bit(s) set
	 18  missing ) after comment
	 19  [this code is not in use]
	 20  regular expression is too large
	 21  failed to get memory
	 22  unmatched parentheses
	 23  internal error: code overflow
	 24  unrecognized character after (?<
	 25  lookbehind assertion is not fixed length
	 26  malformed number or name after (?(
	 27  conditional group contains more than two branches
	 28  assertion expected after (?(
	 29  (?R or (?[+-]digits must be followed by )
	 30  unknown POSIX class name
	 31  POSIX collating elements are not supported
	 32  this version of PCRE is not compiled with PCRE_UTF8 support
	 33  [this code is not in use]
	 34  character value in \x{...} sequence is too large
	 35  invalid condition (?(0)
	 36  \C not allowed in lookbehind assertion
	 37  PCRE does not support \L, \l, \N{name}, \U, or \u
	 38  number after (?C is > 255
	 39  closing ) for (?C expected
	 40  recursive call could loop indefinitely
	 41  unrecognized character after (?P
	 42  syntax error in subpattern name (missing terminator)
	 43  two named subpatterns have the same name
	 44  invalid UTF-8 string
	 45  support for \P, \p, and \X has not been compiled
	 46  malformed \P or \p sequence
	 47  unknown property name after \P or \p
	 48  subpattern name is too long (maximum 32 characters)
	 49  too many named subpatterns (maximum 10000)
	 50  [this code is not in use]
	 51  octal value is greater than \377 (not in UTF-8 mode)
	 52  internal error: overran compiling workspace
	 53  internal error: previously-checked referenced subpattern
	       not found
	 54  DEFINE group contains more than one branch
	 55  repeating a DEFINE group is not allowed
	 56  inconsistent NEWLINE options
	 57  \g is not followed by a braced, angle-bracketed, or quoted
	       name/number or by a plain number
	 58  a numbered reference must not be zero
	 59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
	 60  (*VERB) not recognized
	 61  number is too big
	 62  subpattern name expected
	 63  digit expected after (?+
	 64  ] is an invalid data character in JavaScript compatibility mode
	 65  different names for subpatterns of the same number are
	       not allowed
	 66  (*MARK) must have an argument
	 67  this version of PCRE is not compiled with PCRE_UCP support
	 68  \c must be followed by an ASCII character
	 69  \k is not followed by a braced, angle-bracketed, or quoted name

       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.

STUDYING A PATTERN

       pcre_extra *pcre_study(const pcre *code, int options
	    const char **errptr);

       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
       matching. The function pcre_study() takes a pointer to a compiled  pat‐
       tern as its first argument. If studying the pattern produces additional
       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
       the results of the study.

       The  returned  value  from  pcre_study()	 can  be  passed  directly  to
       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
       passed; these are described below in the section on matching a pattern.

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

       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-
       time compiler is	 available,  the  pattern  is  further	compiled  into
       machine	code  that  executes much faster than the pcre_exec() matching
       function. If the just-in-time compiler is not available, this option is
       ignored. All other bits in the options argument must be zero.

       JIT  compilation	 is  a heavyweight optimization. It can take some time
       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
       study time.  Not all patterns can be optimized by the JIT compiler. For
       those  that cannot be handled, matching automatically falls back to the
       pcre_exec() interpreter. For more details, see the  pcrejit  documenta‐
       tion.

       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
       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
       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.

       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 API for release 8.20. For earlier versions,	the  memory  could  be
       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
       advisable to change to the new function when convenient.

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

	 int rc;
	 pcre *re;
	 pcre_extra *sd;
	 re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
	 sd = pcre_study(
	   re,		   /* result of pcre_compile() */
	   0,		   /* no options */
	   &error);	   /* set to NULL or points to a message */
	 rc = pcre_exec(   /* see below for details of pcre_exec() options */
	   re, sd, "subject", 7, 0, 0, ovector, 30);
	 ...
	 pcre_free_study(sd);
	 pcre_free(re);

       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
       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
       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
       the value in a calling program via the pcre_fullinfo() function.

       Studying a pattern is also useful for non-anchored patterns that do not
       have  a	single fixed starting character. A bitmap of possible starting
       bytes is created. This speeds up finding a position in the  subject  at
       which to start matching.

       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
       with  the  PCRE_STUDY_JIT_COMPILE option, and just-in-time compiling is
       successful.  The	 optimizations	can  be	 disabled   by	 setting   the
       PCRE_NO_START_OPTIMIZE	 option	   when	   calling    pcre_exec()   or
       pcre_dfa_exec(). You might want to do this  if  your  pattern  contains
       callouts	 or (*MARK) (which cannot be handled by the JIT compiler), and
       you want to make use of these facilities in cases where matching fails.
       See the discussion of PCRE_NO_START_OPTIMIZE below.

LOCALE SUPPORT

       PCRE  handles  caseless matching, and determines whether characters are
       letters, digits, or whatever, by reference to a set of tables,  indexed
       by  character  value.  When running in UTF-8 mode, this applies only to
       characters with codes less than 128. By	default,  higher-valued	 codes
       never match escapes such as \w or \d, but they can be tested with \p if
       PCRE is built with Unicode character property  support.	Alternatively,
       the  PCRE_UCP  option  can  be  set at compile time; this causes \w and
       friends to use Unicode property support instead of built-in tables. The
       use of locales with Unicode is discouraged. If you are handling charac‐
       ters with codes greater than 128, you should either use UTF-8 and  Uni‐
       code, or use locales, but not try to mix the two.

       PCRE  contains  an  internal set of tables that are used when the final
       argument of pcre_compile() is  NULL.  These  are	 sufficient  for  many
       applications.  Normally, the internal tables recognize only ASCII char‐
       acters. However, when PCRE is built, it is possible to cause the inter‐
       nal tables to be rebuilt in the default "C" locale of the local system,
       which may cause them to be different.

       The internal tables can always be overridden by tables supplied by  the
       application that calls PCRE. These may be created in a different locale
       from the default. As more and more applications change  to  using  Uni‐
       code, the need for this locale support is expected to die away.

       External	 tables	 are  built by calling the pcre_maketables() function,
       which has no arguments, in the relevant locale. The result can then  be
       passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
       example, to build and use tables that are appropriate  for  the	French
       locale  (where  accented	 characters  with  values greater than 128 are
       treated as letters), the following code could be used:

	 setlocale(LC_CTYPE, "fr_FR");
	 tables = pcre_maketables();
	 re = pcre_compile(..., tables);

       The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
       if you are using Windows, the name for the French locale is "french".

       When  pcre_maketables()	runs,  the  tables are built in memory that is
       obtained via pcre_malloc. It is the caller's responsibility  to	ensure
       that  the memory containing the tables remains available for as long as
       it is needed.

       The pointer that is passed to pcre_compile() is saved with the compiled
       pattern,	 and the same tables are used via this pointer by pcre_study()
       and normally also by pcre_exec(). Thus, by default, for any single pat‐
       tern, compilation, studying and matching all happen in the same locale,
       but different patterns can be compiled in different locales.

       It is possible to pass a table pointer or NULL (indicating the  use  of
       the  internal  tables)  to  pcre_exec(). Although not intended for this
       purpose, this facility could be used to match a pattern in a  different
       locale from the one in which it was compiled. Passing table pointers at
       run time is discussed below in the section on matching a pattern.

INFORMATION ABOUT A PATTERN

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

       The pcre_fullinfo() function returns information about a compiled  pat‐
       tern. It replaces the obsolete pcre_info() function, which is neverthe‐
       less retained for backwards compability (and is documented below).

       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
       the pattern was not studied. The third argument specifies  which	 piece
       of  information	is required, and the fourth argument is a pointer to a
       variable to receive the data. The yield of the  function	 is  zero  for
       success, or one of the following negative numbers:

	 PCRE_ERROR_NULL       the argument code was NULL
			       the argument where was NULL
	 PCRE_ERROR_BADMAGIC   the "magic number" was not found
	 PCRE_ERROR_BADOPTION  the value of what was invalid

       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
       typical	call  of pcre_fullinfo(), to obtain the length of the compiled
       pattern:

	 int rc;
	 size_t length;
	 rc = pcre_fullinfo(
	   re,		     /* result of pcre_compile() */
	   sd,		     /* result of pcre_study(), or NULL */
	   PCRE_INFO_SIZE,   /* what is required */
	   &length);	     /* where to put the data */

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

	 PCRE_INFO_BACKREFMAX

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

	 PCRE_INFO_CAPTURECOUNT

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

	 PCRE_INFO_DEFAULT_TABLES

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

	 PCRE_INFO_FIRSTBYTE

       Return information about the first byte of any matched  string,	for  a
       non-anchored  pattern. The fourth argument should point to an int vari‐
       able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name
       is still recognized for backwards compatibility.)

       If  there  is  a	 fixed first byte, for example, from a pattern such as
       (cat|cow|coyote), its value is returned. Otherwise, if either

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

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

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

	 PCRE_INFO_FIRSTTABLE

       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
       matching string, a pointer to the table is returned. Otherwise NULL  is
       returned.  The fourth argument should point to an unsigned char * vari‐
       able.

	 PCRE_INFO_HASCRORLF

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

	 PCRE_INFO_JCHANGED

       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)
       and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.

	 PCRE_INFO_JIT

       Return  1  if  the  pattern was studied with the PCRE_STUDY_JIT_COMPILE
       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
       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
       compiler could not handle this particular pattern. See the pcrejit doc‐
       umentation for details of what can and cannot be handled.

	 PCRE_INFO_JITSIZE

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

	 PCRE_INFO_LASTLITERAL

       Return  the  value of the rightmost literal byte that must exist in any
       matched string, other than at its  start,  if  such  a  byte  has  been
       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
       byte  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
       /^a\dz\d/ the returned value is -1.

	 PCRE_INFO_MINLENGTH

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

	 PCRE_INFO_NAMECOUNT
	 PCRE_INFO_NAMEENTRYSIZE
	 PCRE_INFO_NAMETABLE

       PCRE  supports the use of named as well as numbered capturing parenthe‐
       ses. The names are just an additional way of identifying the  parenthe‐
       ses, which still acquire numbers. Several convenience functions such as
       pcre_get_named_substring() are provided for  extracting	captured  sub‐
       strings	by  name. It is also possible to extract the data directly, by
       first converting the name to a number in order to  access  the  correct
       pointers in the output vector (described with pcre_exec() below). To do
       the conversion, you need	 to  use  the  name-to-number  map,  which  is
       described by these three values.

       The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
       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
       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
       first two bytes of each entry are the number of the capturing parenthe‐
       sis,  most  significant byte first. The rest of the entry is the corre‐
       sponding name, zero terminated.

       The names are in alphabetical order. Duplicate names may appear if  (?|
       is used to create multiple groups with the same number, as described in
       the section on duplicate subpattern numbers in  the  pcrepattern	 page.
       Duplicate  names	 for  subpatterns with different numbers are permitted
       only if PCRE_DUPNAMES is set. In all cases  of  duplicate  names,  they
       appear  in  the table in the order in which they were found in the pat‐
       tern. In the absence of (?| this is the	order  of  increasing  number;
       when (?| is used this is not necessarily the case because later subpat‐
       terns may have lower numbers.

       As a simple example of the name/number table,  consider	the  following
       pattern	(assume	 PCRE_EXTENDED is set, so white space - including new‐
       lines - is ignored):

	 (?<date> (?<year>(\d\d)?\d\d) -
	 (?<month>\d\d) - (?<day>\d\d) )

       There are four named subpatterns, so the table has  four	 entries,  and
       each  entry  in the table is eight bytes long. The table is as follows,
       with non-printing bytes shows in hexadecimal, and undefined bytes shown
       as ??:

	 00 01 d  a  t	e  00 ??
	 00 05 d  a  y	00 ?? ??
	 00 04 m  o  n	t  h  00
	 00 02 y  e  a	r  00 ??

       When  writing  code  to	extract	 data from named subpatterns using the
       name-to-number map, remember that the length of the entries  is	likely
       to be different for each compiled pattern.

	 PCRE_INFO_OKPARTIAL

       Return  1  if  the  pattern  can	 be  used  for	partial	 matching with
       pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
       variable.  From	release	 8.00,	this  always  returns  1,  because the
       restrictions that previously applied  to	 partial  matching  have  been
       lifted.	The  pcrepartial documentation gives details of partial match‐
       ing.

	 PCRE_INFO_OPTIONS

       Return a copy of the options with which the pattern was	compiled.  The
       fourth  argument	 should	 point to an unsigned long int variable. These
       option bits are those specified in the call to pcre_compile(), modified
       by any top-level option settings at the start of the pattern itself. In
       other words, they are the options that will be in force	when  matching
       starts.	For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
       the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
       and PCRE_EXTENDED.

       A  pattern  is  automatically  anchored by PCRE if all of its top-level
       alternatives begin with one of the following:

	 ^     unless PCRE_MULTILINE is set
	 \A    always
	 \G    always
	 .*    if PCRE_DOTALL is set and there are no back
		 references to the subpattern in which .* appears

       For such patterns, the PCRE_ANCHORED bit is set in the options returned
       by pcre_fullinfo().

	 PCRE_INFO_SIZE

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

	 PCRE_INFO_STUDYSIZE

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

       int pcre_refcount(pcre *code, int adjust);

       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
       benefit	of  applications  that	operate	 in an object-oriented manner,
       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.

       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
       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
       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.

       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
       whose byte-order is different. (This seems a highly unlikely scenario.)

MATCHING A PATTERN: THE TRADITIONAL FUNCTION

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

       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
       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‐
       ments as many times as you like, in order to  match  different  subject
       strings with the same pattern.

       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
       alternative  matching function, which is described below in the section
       about the pcre_dfa_exec() function.

       In most applications, the pattern will have been compiled (and  option‐
       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
       later  in  different processes, possibly even on different hosts. For a
       discussion about this, see the pcreprecompile documentation.

       Here is an example of a simple call to pcre_exec():

	 int rc;
	 int ovector[30];
	 rc = pcre_exec(
	   re,		   /* result of pcre_compile() */
	   NULL,	   /* we didn't study the pattern */
	   "some string",  /* the subject string */
	   11,		   /* the length of the subject string */
	   0,		   /* start at offset 0 in the subject */
	   0,		   /* default options */
	   ovector,	   /* vector of integers for substring information */
	   30);		   /* number of elements (NOT size in bytes) */

   Extra data for pcre_exec()

       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
       return NULL), but you can also create one for yourself, and pass	 addi‐
       tional  information  in it. The pcre_extra block contains the following
       fields (not necessarily in this order):

	 unsigned long int flags;
	 void *study_data;
	 void *executable_jit;
	 unsigned long int match_limit;
	 unsigned long int match_limit_recursion;
	 void *callout_data;
	 const unsigned char *tables;
	 unsigned char **mark;

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

	 PCRE_EXTRA_STUDY_DATA
	 PCRE_EXTRA_EXECUTABLE_JIT
	 PCRE_EXTRA_MATCH_LIMIT
	 PCRE_EXTRA_MATCH_LIMIT_RECURSION
	 PCRE_EXTRA_CALLOUT_DATA
	 PCRE_EXTRA_TABLES
	 PCRE_EXTRA_MARK

       Other  flag  bits should be set to zero. The study_data field and some‐
       times the executable_jit field are set in the pcre_extra block that  is
       returned	 by pcre_study(), together with the appropriate flag bits. You
       should not set these yourself, but you may add to the block by  setting
       the other fields and their corresponding flag bits.

       The match_limit field provides a means of preventing PCRE from using up
       a vast amount of resources when running patterns that are not going  to
       match,  but  which  have	 a very large number of possibilities in their
       search trees. The classic example is a pattern that uses nested	unlim‐
       ited repeats.

       Internally,  pcre_exec() uses a function called match(), which it calls
       repeatedly (sometimes recursively). The limit  set  by  match_limit  is
       imposed	on the number of times this function is called during a match,
       which has the effect of limiting the amount of  backtracking  that  can
       take place. For patterns that are not anchored, the count restarts from
       zero for each position in the subject string.

       When pcre_exec() is called with a pattern that was successfully studied
       with  the  PCRE_STUDY_JIT_COMPILE  option, the way that the matching is
       executed is entirely different. However, there is still the possibility
       of  runaway  matching  that  goes  on  for a very long time, and so the
       match_limit value is also used in this case (but in a different way) to
       limit how long the matching can continue.

       The  default  value  for	 the  limit can be set when PCRE is built; the
       default default is 10 million, which handles all but the	 most  extreme
       cases.  You  can	 override  the	default by suppling pcre_exec() with a
       pcre_extra    block    in    which    match_limit    is	  set,	   and
       PCRE_EXTRA_MATCH_LIMIT  is  set	in  the	 flags	field. If the limit is
       exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.

       The match_limit_recursion field is similar to match_limit, but  instead
       of limiting the total number of times that match() is called, it limits
       the depth of recursion. The recursion depth is a	 smaller  number  than
       the  total number of calls, because not all calls to match() are recur‐
       sive.  This limit is of use only if it is set smaller than match_limit.

       Limiting the recursion depth limits the amount of  machine  stack  that
       can  be used, or, when PCRE has been compiled to use memory on the heap
       instead of the stack, the amount of heap memory that can be used.  This
       limit  is not relevant, and is ignored, if the pattern was successfully
       studied with PCRE_STUDY_JIT_COMPILE.

       The default value for match_limit_recursion can be  set	when  PCRE  is
       built;  the  default  default  is  the  same  value  as the default for
       match_limit. You can override the default by suppling pcre_exec()  with
       a   pcre_extra	block  in  which  match_limit_recursion	 is  set,  and
       PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the	flags  field.  If  the
       limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.

       The  callout_data  field is used in conjunction with the "callout" fea‐
       ture, and is described in the pcrecallout documentation.

       The tables field	 is  used  to  pass  a	character  tables  pointer  to
       pcre_exec();  this overrides the value that is stored with the compiled
       pattern. A non-NULL value is stored with the compiled pattern  only  if
       custom  tables  were  supplied to pcre_compile() via its tableptr argu‐
       ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
       PCRE's  internal	 tables	 to be used. This facility is helpful when re-
       using patterns that have been saved after compiling  with  an  external
       set  of	tables,	 because  the  external tables might be at a different
       address when pcre_exec() is called. See the  pcreprecompile  documenta‐
       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
       set to point to a char * variable. If the pattern  contains  any	 back‐
       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‐
       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
       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
       field  set  to NULL. For details of the backtracking control verbs, see
       the section entitled "Backtracking control" in the pcrepattern documen‐
       tation.

   Option bits for pcre_exec()

       The  unused  bits of the options argument for pcre_exec() must be zero.
       The only bits that may  be  set	are  PCRE_ANCHORED,  PCRE_NEWLINE_xxx,
       PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,	PCRE_NOTEMPTY_ATSTART,
       PCRE_NO_START_OPTIMIZE,	PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
       PCRE_PARTIAL_HARD.

       If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE
       option,	the   only   supported	 options   for	 JIT   execution   are
       PCRE_NO_UTF8_CHECK,   PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,  and
       PCRE_NOTEMPTY_ATSTART. Note in particular that partial matching is  not
       supported.  If an unsupported option is used, JIT execution is disabled
       and the normal interpretive code in pcre_exec() is run.

	 PCRE_ANCHORED

       The PCRE_ANCHORED option limits pcre_exec() to matching	at  the	 first
       matching	 position.  If	a  pattern was compiled with PCRE_ANCHORED, or
       turned out to be anchored by virtue of its contents, it cannot be  made
       unachored at matching time.

	 PCRE_BSR_ANYCRLF
	 PCRE_BSR_UNICODE

       These options (which are mutually exclusive) control what the \R escape
       sequence matches. The choice is either to match only CR, LF,  or	 CRLF,
       or  to  match  any Unicode newline sequence. These options override the
       choice that was made or defaulted when the pattern was compiled.

	 PCRE_NEWLINE_CR
	 PCRE_NEWLINE_LF
	 PCRE_NEWLINE_CRLF
	 PCRE_NEWLINE_ANYCRLF
	 PCRE_NEWLINE_ANY

       These options override  the  newline  definition	 that  was  chosen  or
       defaulted  when the pattern was compiled. For details, see the descrip‐
       tion of pcre_compile()  above.  During  matching,  the  newline	choice
       affects	the  behaviour	of the dot, circumflex, and dollar metacharac‐
       ters. It may also alter the way the match position is advanced after  a
       match failure for an unanchored pattern.

       When  PCRE_NEWLINE_CRLF,	 PCRE_NEWLINE_ANYCRLF,	or PCRE_NEWLINE_ANY is
       set, and a match attempt for an unanchored pattern fails when the  cur‐
       rent  position  is  at  a  CRLF	sequence,  and the pattern contains no
       explicit matches for  CR	 or  LF	 characters,  the  match  position  is
       advanced by two characters instead of one, in other words, to after the
       CRLF.

       The above rule is a compromise that makes the most common cases work as
       expected.  For  example,	 if  the  pattern  is .+A (and the PCRE_DOTALL
       option is not set), it does not match the string "\r\nA" because, after
       failing	at the start, it skips both the CR and the LF before retrying.
       However, the pattern [\r\n]A does match that string,  because  it  con‐
       tains an explicit CR or LF reference, and so advances only by one char‐
       acter after the first failure.

       An explicit match for CR of LF is either a literal appearance of one of
       those  characters,  or  one  of the \r or \n escape sequences. Implicit
       matches such as [^X] do not count, nor does \s (which includes  CR  and
       LF in the characters that it matches).

       Notwithstanding	the above, anomalous effects may still occur when CRLF
       is a valid newline sequence and explicit \r or \n escapes appear in the
       pattern.

	 PCRE_NOTBOL

       This option specifies that first character of the subject string is not
       the beginning of a line, so the	circumflex  metacharacter  should  not
       match  before it. Setting this without PCRE_MULTILINE (at compile time)
       causes circumflex never to match. This option affects only  the	behav‐
       iour of the circumflex metacharacter. It does not affect \A.

	 PCRE_NOTEOL

       This option specifies that the end of the subject string is not the end
       of a line, so the dollar metacharacter should not match it nor  (except
       in  multiline mode) a newline immediately before it. Setting this with‐
       out PCRE_MULTILINE (at compile time) causes dollar never to match. This
       option  affects only the behaviour of the dollar metacharacter. It does
       not affect \Z or \z.

	 PCRE_NOTEMPTY

       An empty string is not considered to be a valid match if this option is
       set.  If	 there are alternatives in the pattern, they are tried. If all
       the alternatives match the empty string, the entire  match  fails.  For
       example, if the pattern

	 a?b?

       is  applied  to	a  string not beginning with "a" or "b", it matches an
       empty string at the start of the subject. With PCRE_NOTEMPTY set,  this
       match is not valid, so PCRE searches further into the string for occur‐
       rences of "a" or "b".

	 PCRE_NOTEMPTY_ATSTART

       This is like PCRE_NOTEMPTY, except that an empty string match  that  is
       not  at	the  start  of	the  subject  is  permitted. If the pattern is
       anchored, such a match can occur only if the pattern contains \K.

       Perl    has    no    direct    equivalent    of	  PCRE_NOTEMPTY	    or
       PCRE_NOTEMPTY_ATSTART,  but  it	does  make a special case of a pattern
       match of the empty string within its split() function, and  when	 using
       the  /g	modifier.  It  is  possible  to emulate Perl's behaviour after
       matching a null string by first trying the match again at the same off‐
       set  with  PCRE_NOTEMPTY_ATSTART	 and  PCRE_ANCHORED,  and then if that
       fails, by advancing the starting offset (see below) and trying an ordi‐
       nary  match  again. There is some code that demonstrates how to do this
       in the pcredemo 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 the current character is CR followed by LF, advance  the
       starting offset by two characters instead of one.

	 PCRE_NO_START_OPTIMIZE

       There  are a number of optimizations that pcre_exec() uses at the start
       of a match, in order to speed up the process. For  example,  if	it  is
       known that an unanchored match must start with a specific character, it
       searches the subject for that character, and fails  immediately	if  it
       cannot  find  it,  without actually running the main matching function.
       This means that a special item such as (*COMMIT) at the start of a pat‐
       tern  is	 not  considered until after a suitable starting point for the
       match has been found. When callouts or (*MARK) items are in use,	 these
       "start-up" optimizations can cause them to be skipped if the pattern is
       never actually used. The start-up optimizations are in  effect  a  pre-
       scan of the subject that takes place before the pattern is run.

       The  PCRE_NO_START_OPTIMIZE option disables the start-up optimizations,
       possibly causing performance to suffer,	but  ensuring  that  in	 cases
       where  the  result is "no match", the callouts do occur, and that items
       such as (*COMMIT) and (*MARK) are considered at every possible starting
       position	 in  the  subject  string. If PCRE_NO_START_OPTIMIZE is set at
       compile time, it cannot be unset at matching time.

       Setting PCRE_NO_START_OPTIMIZE can change the  outcome  of  a  matching
       operation.  Consider the pattern

	 (*COMMIT)ABC

       When  this  is  compiled, PCRE records the fact that a match must start
       with the character "A". Suppose the subject  string  is	"DEFABC".  The
       start-up	 optimization  scans along the subject, finds "A" and runs the
       first match attempt from there. The (*COMMIT) item means that the  pat‐
       tern  must  match the current starting position, which in this case, it
       does. However, if the same match	 is  run  with	PCRE_NO_START_OPTIMIZE
       set,  the  initial  scan	 along the subject string does not happen. The
       first match attempt is run starting  from  "D"  and  when  this	fails,
       (*COMMIT)  prevents  any	 further  matches  being tried, so the overall
       result is "no match". If the pattern is studied,	 more  start-up	 opti‐
       mizations  may  be  used. For example, a minimum length for the subject
       may be recorded. Consider the pattern

	 (*MARK:A)(X|Y)

       The minimum length for a match is one  character.  If  the  subject  is
       "ABC",  there  will  be	attempts  to  match "ABC", "BC", "C", and then
       finally an empty string.	 If the pattern is studied, the final  attempt
       does  not take place, because PCRE knows that the subject is too short,
       and so the (*MARK) is never encountered.	 In this  case,	 studying  the
       pattern	does  not  affect the overall match result, which is still "no
       match", but it does affect the auxiliary information that is returned.

	 PCRE_NO_UTF8_CHECK

       When PCRE_UTF8 is set at compile time, the validity of the subject as a
       UTF-8  string is automatically checked when pcre_exec() is subsequently
       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
       the validity of UTF-8 strings in the section on UTF-8  support  in  the
       main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,
       pcre_exec() returns  the	 error	PCRE_ERROR_BADUTF8  or,	 if  PCRE_PAR‐
       TIAL_HARD  is set and the problem is a truncated UTF-8 character at the
       end of the subject, PCRE_ERROR_SHORTUTF8. In  both  cases,  information
       about  the  precise  nature  of the error may also be returned (see the
       descriptions of these errors in the section entitled Error return  val‐
       ues from pcre_exec() below).  If startoffset contains a value that does
       not point to the start of a UTF-8 character (or to the end of the  sub‐
       ject), PCRE_ERROR_BADUTF8_OFFSET is returned.

       If  you	already	 know that your subject is valid, and you want to skip
       these   checks	for   performance   reasons,   you   can    set	   the
       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
       making  repeated	 calls	to  find  all  the matches in a single subject
       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).
       When PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid	 UTF-8
       string  as  a  subject or an invalid value of startoffset is undefined.
       Your program may crash.

	 PCRE_PARTIAL_HARD
	 PCRE_PARTIAL_SOFT

       These options turn on the partial matching feature. For backwards  com‐
       patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
       match occurs if the end of the subject string is reached	 successfully,
       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,
       matching	 continues  by	testing any remaining alternatives. Only if no
       complete match can be found is PCRE_ERROR_PARTIAL returned  instead  of
       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
       match can be found.

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

       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
       more  detailed  discussion  of partial and multi-segment matching, with
       examples, in the pcrepartial documentation.

   The string to be matched by pcre_exec()

       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.
       If this is  negative  or	 greater  than	the  length  of	 the  subject,
       pcre_exec()  returns  PCRE_ERROR_BADOFFSET. When the starting offset is
       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
       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
       bytes.

       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‐
       cess.  Setting startoffset differs from just passing over  a  shortened
       string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins
       with any kind of lookbehind. For example, consider the pattern

	 \Biss\B

       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.)
       When applied to the string "Mississipi" the first call  to  pcre_exec()
       finds  the  first  occurrence. If pcre_exec() is called again with just
       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
       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‐
       rence of "iss" because it is able to look behind the starting point  to
       discover that it is preceded by a letter.

       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
       first   trying	the   match   again  at	 the  same  offset,  with  the
       PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED	 options,  and	then  if  that
       fails,  advancing  the  starting	 offset	 and  trying an ordinary match
       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
       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
       by two characters instead of one.

       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
       if the pattern does not require the match to be at  the	start  of  the
       subject.

   How pcre_exec() returns captured substrings

       In  general, a pattern matches a certain portion of the subject, and in
       addition, further substrings from the subject  may  be  picked  out  by
       parts  of  the  pattern.	 Following the usage in Jeffrey Friedl's book,
       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‐
       string. PCRE supports several other kinds of  parenthesized  subpattern
       that do not cause substrings to be captured.

       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‐
       tor  is	passed in ovecsize, which must be a non-negative number. Note:
       this argument is NOT the size of ovector in bytes.

       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
       of the vector is used as workspace by pcre_exec() while	matching  cap‐
       turing  subpatterns, and is not available for passing back information.
       The number passed in ovecsize should always be a multiple of three.  If
       it is not, it is rounded down.

       When  a	match  is successful, information about captured substrings is
       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
       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
       character after the end of a substring. Note: these values  are	always
       byte offsets, even in UTF-8 mode. They are not character counts.

       The  first  pair	 of  integers, ovector[0] and ovector[1], identify the
       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
       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
       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
       of offsets has been set.

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

       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
       function	 returns a value of zero. If neither the actual string matched
       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‐
       tern contains back references and the ovector  is  not  big  enough  to
       remember	 the related substrings, PCRE has to get additional memory for
       use during matching. Thus it is usually advisable to supply an  ovector
       of reasonable size.

       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
       match. For example, consider the pattern

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

       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
       captured string, thereby recording a vector overflow, before failing to
       match "c" and backing up	 to  try  the  second  alternative.  The  zero
       return,	however,  does	correctly  indicate that the maximum number of
       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
       than the maximum, a non-zero value is returned.

       The pcre_fullinfo() function can be used to find out how many capturing
       subpatterns  there  are	in  a  compiled pattern. The smallest size for
       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.

       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,
       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
       2  is  not.  When  this happens, both values in the offset pairs corre‐
       sponding to unused subpatterns are set to -1.

       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
       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
       capturing subpattern number is 1, and the offsets for  for  the	second
       and  third  capturing subpatterns (assuming the vector is large enough,
       of course) are set to -1.

       Note: Elements in the first two-thirds of ovector that  do  not	corre‐
       spond  to  capturing parentheses in the pattern are never changed. That
       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
       the first two-thirds) retain whatever values they previously had.

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

   Error return values from pcre_exec()

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

	 PCRE_ERROR_NOMATCH	   (-1)

       The subject string did not match the pattern.

	 PCRE_ERROR_NULL	   (-2)

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

	 PCRE_ERROR_BADOPTION	   (-3)

       An unrecognized bit was set in the options argument.

	 PCRE_ERROR_BADMAGIC	   (-4)

       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
       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
       gives when the magic number is not present.

	 PCRE_ERROR_UNKNOWN_OPCODE (-5)

       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
       overwriting of the compiled pattern.

	 PCRE_ERROR_NOMEMORY	   (-6)

       If  a  pattern contains back references, but the ovector that is passed
       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
       purpose. If the call via pcre_malloc() fails, this error is given.  The
       memory is automatically freed at the end of matching.

       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-
       for-recursion.

	 PCRE_ERROR_NOSUBSTRING	   (-7)

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

	 PCRE_ERROR_MATCHLIMIT	   (-8)

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

	 PCRE_ERROR_CALLOUT	   (-9)

       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.
       See the pcrecallout documentation for details.

	 PCRE_ERROR_BADUTF8	   (-10)

       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
       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‐
       ment,  and  a  reason  code is placed in the second element. The reason
       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‐
       acter  at  the  end  of	the   subject	(reason	  codes	  1   to   5),
       PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.

	 PCRE_ERROR_BADUTF8_OFFSET (-11)

       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
       value  of startoffset did not point to the beginning of a UTF-8 charac‐
       ter or the end of the subject.

	 PCRE_ERROR_PARTIAL	   (-12)

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

	 PCRE_ERROR_BADPARTIAL	   (-13)

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

	 PCRE_ERROR_INTERNAL	   (-14)

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

	 PCRE_ERROR_BADCOUNT	   (-15)

       This error is given if the value of the ovecsize argument is negative.

	 PCRE_ERROR_RECURSIONLIMIT (-21)

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

	 PCRE_ERROR_BADNEWLINE	   (-23)

       An invalid combination of PCRE_NEWLINE_xxx options was given.

	 PCRE_ERROR_BADOFFSET	   (-24)

       The value of startoffset was negative or greater than the length of the
       subject, that is, the value in length.

	 PCRE_ERROR_SHORTUTF8	   (-25)

       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
       option is set.  Information  about  the	failure	 is  returned  as  for
       PCRE_ERROR_BADUTF8.  It	is in fact sufficient to detect this case, but
       this special error code for PCRE_PARTIAL_HARD precedes the  implementa‐
       tion  of returned information; it is retained for backwards compatibil‐
       ity.

	 PCRE_ERROR_RECURSELOOP	   (-26)

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

	 PCRE_ERROR_JIT_STACKLIMIT (-27)

       This error is returned when a pattern  that  was	 successfully  studied
       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
       enough. See the pcrejit documentation for more details.

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

   Reason codes for invalid UTF-8 strings

       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
       offset  of  the	start  of the invalid UTF-8 character is placed in the
       first output vector element (ovector[0]) and a reason code is placed in
       the  second  element  (ovector[1]). The reason codes are given names in
       the pcre.h header file:

	 PCRE_UTF8_ERR1
	 PCRE_UTF8_ERR2
	 PCRE_UTF8_ERR3
	 PCRE_UTF8_ERR4
	 PCRE_UTF8_ERR5

       The string ends with a truncated UTF-8 character;  the  code  specifies
       how  many bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8
       characters to be no longer than 4 bytes, the  encoding  scheme  (origi‐
       nally  defined  by  RFC	2279)  allows  for  up to 6 bytes, and this is
       checked first; hence the possibility of 4 or 5 missing bytes.

	 PCRE_UTF8_ERR6
	 PCRE_UTF8_ERR7
	 PCRE_UTF8_ERR8
	 PCRE_UTF8_ERR9
	 PCRE_UTF8_ERR10

       The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of
       the  character  do  not have the binary value 0b10 (that is, either the
       most significant bit is 0, or the next bit is 1).

	 PCRE_UTF8_ERR11
	 PCRE_UTF8_ERR12

       A character that is valid by the RFC 2279 rules is either 5 or 6	 bytes
       long; these code points are excluded by RFC 3629.

	 PCRE_UTF8_ERR13

       A  4-byte character has a value greater than 0x10fff; these code points
       are excluded by RFC 3629.

	 PCRE_UTF8_ERR14

       A 3-byte character has a value in the  range  0xd800  to	 0xdfff;  this
       range  of code points are reserved by RFC 3629 for use with UTF-16, and
       so are excluded from UTF-8.

	 PCRE_UTF8_ERR15
	 PCRE_UTF8_ERR16
	 PCRE_UTF8_ERR17
	 PCRE_UTF8_ERR18
	 PCRE_UTF8_ERR19

       A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it	 codes
       for  a  value that can be represented by fewer bytes, which is invalid.
       For example, the two bytes 0xc0, 0xae give the value 0x2e,  whose  cor‐
       rect coding uses just one byte.

	 PCRE_UTF8_ERR20

       The two most significant bits of the first byte of a character have the
       binary value 0b10 (that is, the most significant bit is 1 and the  sec‐
       ond  is	0). Such a byte can only validly occur as the second or subse‐
       quent byte of a multi-byte character.

	 PCRE_UTF8_ERR21

       The first byte of a character has the value 0xfe or 0xff. These	values
       can never occur in a valid UTF-8 string.

EXTRACTING CAPTURED SUBSTRINGS BY NUMBER

       int pcre_copy_substring(const char *subject, int *ovector,
	    int stringcount, int stringnumber, char *buffer,
	    int buffersize);

       int pcre_get_substring(const char *subject, int *ovector,
	    int stringcount, int stringnumber,
	    const char **stringptr);

       int pcre_get_substring_list(const char *subject,
	    int *ovector, int stringcount, const char ***listptr);

       Captured	 substrings  can  be  accessed	directly  by using the offsets
       returned by pcre_exec() in  ovector.  For  convenience,	the  functions
       pcre_copy_substring(),	 pcre_get_substring(),	  and	 pcre_get_sub‐
       string_list() are provided for extracting captured substrings  as  new,
       separate,  zero-terminated strings. These functions identify substrings
       by number. The next section describes functions	for  extracting	 named
       substrings.

       A  substring that contains a binary zero is correctly extracted and has
       a further zero added on the end, but the result is not, of course, a  C
       string.	 However,  you	can  process such a string by referring to the
       length that is  returned	 by  pcre_copy_substring()  and	 pcre_get_sub‐
       string().  Unfortunately, the interface to pcre_get_substring_list() is
       not adequate for handling strings containing binary zeros, because  the
       end of the final string is not independently indicated.

       The  first  three  arguments  are the same for all three of these func‐
       tions: subject is the subject string that has  just  been  successfully
       matched, ovector is a pointer to the vector of integer offsets that was
       passed to pcre_exec(), and stringcount is the number of substrings that
       were  captured  by  the match, including the substring that matched the
       entire regular expression. This is the value returned by pcre_exec() if
       it  is greater than zero. If pcre_exec() returned zero, indicating that
       it ran out of space in ovector, the value passed as stringcount	should
       be the number of elements in the vector divided by three.

       The  functions pcre_copy_substring() and pcre_get_substring() extract a
       single substring, whose number is given as  stringnumber.  A  value  of
       zero  extracts  the  substring that matched the entire pattern, whereas
       higher values  extract  the  captured  substrings.  For	pcre_copy_sub‐
       string(),  the  string  is  placed  in buffer, whose length is given by
       buffersize, while for pcre_get_substring() a new	 block	of  memory  is
       obtained	 via  pcre_malloc,  and its address is returned via stringptr.
       The yield of the function is the length of the  string,	not  including
       the terminating zero, or one of these error codes:

	 PCRE_ERROR_NOMEMORY	   (-6)

       The  buffer  was too small for pcre_copy_substring(), or the attempt to
       get memory failed for pcre_get_substring().

	 PCRE_ERROR_NOSUBSTRING	   (-7)

       There is no substring whose number is stringnumber.

       The pcre_get_substring_list()  function	extracts  all  available  sub‐
       strings	and  builds  a list of pointers to them. All this is done in a
       single block of memory that is obtained via pcre_malloc. The address of
       the  memory  block  is returned via listptr, which is also the start of
       the list of string pointers. The end of the list is marked  by  a  NULL
       pointer.	 The  yield  of	 the function is zero if all went well, or the
       error code

	 PCRE_ERROR_NOMEMORY	   (-6)

       if the attempt to get the memory block failed.

       When any of these functions encounter a substring that is unset,	 which
       can  happen  when  capturing subpattern number n+1 matches some part of
       the subject, but subpattern n has not been used at all, they return  an
       empty string. This can be distinguished from a genuine zero-length sub‐
       string by inspecting the appropriate offset in ovector, which is	 nega‐
       tive for unset substrings.

       The  two convenience functions pcre_free_substring() and pcre_free_sub‐
       string_list() can be used to free the memory  returned  by  a  previous
       call  of	 pcre_get_substring()  or  pcre_get_substring_list(),  respec‐
       tively. They do nothing more than  call	the  function  pointed	to  by
       pcre_free,  which  of course could be called directly from a C program.
       However, PCRE is used in some situations where it is linked via a  spe‐
       cial   interface	 to  another  programming  language  that  cannot  use
       pcre_free directly; it is for these cases that the functions  are  pro‐
       vided.

EXTRACTING CAPTURED SUBSTRINGS BY NAME

       int pcre_get_stringnumber(const pcre *code,
	    const char *name);

       int pcre_copy_named_substring(const pcre *code,
	    const char *subject, int *ovector,
	    int stringcount, const char *stringname,
	    char *buffer, int buffersize);

       int pcre_get_named_substring(const pcre *code,
	    const char *subject, int *ovector,
	    int stringcount, const char *stringname,
	    const char **stringptr);

       To  extract a substring by name, you first have to find associated num‐
       ber.  For example, for this pattern

	 (a+)b(?<xxx>\d+)...

       the number of the subpattern called "xxx" is 2. If the name is known to
       be unique (PCRE_DUPNAMES was not set), you can find the number from the
       name by calling pcre_get_stringnumber(). The first argument is the com‐
       piled pattern, and the second is the name. The yield of the function is
       the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if	 there	is  no
       subpattern of that name.

       Given the number, you can extract the substring directly, or use one of
       the functions described in the previous section. For convenience, there
       are also two functions that do the whole job.

       Most    of    the    arguments	of   pcre_copy_named_substring()   and
       pcre_get_named_substring() are the same	as  those  for	the  similarly
       named  functions	 that extract by number. As these are described in the
       previous section, they are not re-described here. There	are  just  two
       differences:

       First,  instead	of a substring number, a substring name is given. Sec‐
       ond, there is an extra argument, given at the start, which is a pointer
       to  the compiled pattern. This is needed in order to gain access to the
       name-to-number translation table.

       These functions call pcre_get_stringnumber(), and if it succeeds,  they
       then  call  pcre_copy_substring() or pcre_get_substring(), as appropri‐
       ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
       behaviour may not be what you want (see the next section).

       Warning: If the pattern uses the (?| feature to set up multiple subpat‐
       terns with the same number, as described in the	section	 on  duplicate
       subpattern  numbers  in	the  pcrepattern page, you cannot use names to
       distinguish the different subpatterns, because names are	 not  included
       in  the compiled code. The matching process uses only numbers. For this
       reason, the use of different names for subpatterns of the  same	number
       causes an error at compile time.

DUPLICATE SUBPATTERN NAMES

       int pcre_get_stringtable_entries(const pcre *code,
	    const char *name, char **first, char **last);

       When  a	pattern	 is  compiled with the PCRE_DUPNAMES option, names for
       subpatterns are not required to be unique. (Duplicate names are	always
       allowed	for subpatterns with the same number, created by using the (?|
       feature. Indeed, if such subpatterns are named, they  are  required  to
       use the same names.)

       Normally, patterns with duplicate names are such that in any one match,
       only one of the named subpatterns participates. An example is shown  in
       the pcrepattern documentation.

       When    duplicates   are	  present,   pcre_copy_named_substring()   and
       pcre_get_named_substring() return the first substring corresponding  to
       the  given  name	 that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
       (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
       function	 returns one of the numbers that are associated with the name,
       but it is not defined which it is.

       If you want to get full details of all captured substrings for a	 given
       name,  you  must	 use  the pcre_get_stringtable_entries() function. The
       first argument is the compiled pattern, and the second is the name. The
       third  and  fourth  are	pointers to variables which are updated by the
       function. After it has run, they point to the first and last entries in
       the  name-to-number  table  for	the  given  name.  The function itself
       returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
       there  are none. The format of the table is described above in the sec‐
       tion entitled Information about a pattern above.	 Given all  the	 rele‐
       vant  entries  for the name, you can extract each of their numbers, and
       hence the captured data, if any.

FINDING ALL POSSIBLE MATCHES

       The traditional matching function uses a	 similar  algorithm  to	 Perl,
       which stops when it finds the first match, starting at a given point in
       the subject. If you want to find all possible matches, or  the  longest
       possible	 match,	 consider using the alternative matching function (see
       below) instead. If you cannot use the alternative function,  but	 still
       need  to	 find all possible matches, you can kludge it up by making use
       of the callout facility, which is described in the pcrecallout documen‐
       tation.

       What you have to do is to insert a callout right at the end of the pat‐
       tern.  When your callout function is called, extract and save the  cur‐
       rent  matched  substring.  Then	return	1, which forces pcre_exec() to
       backtrack and try other alternatives. Ultimately, when it runs  out  of
       matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.

MATCHING A PATTERN: THE ALTERNATIVE FUNCTION

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

       The  function  pcre_dfa_exec()  is  called  to  match  a subject string
       against a compiled pattern, using a matching algorithm that  scans  the
       subject	string	just  once, and does not backtrack. This has different
       characteristics to the normal algorithm, and  is	 not  compatible  with
       Perl.  Some  of the features of PCRE patterns are not supported. Never‐
       theless, there are times when this kind of matching can be useful.  For
       a  discussion  of  the  two matching algorithms, and a list of features
       that pcre_dfa_exec() does not support, see the pcrematching  documenta‐
       tion.

       The  arguments  for  the	 pcre_dfa_exec()  function are the same as for
       pcre_exec(), plus two extras. The ovector argument is used in a differ‐
       ent  way,  and  this is described below. The other common arguments are
       used in the same way as for pcre_exec(), so their  description  is  not
       repeated here.

       The  two	 additional  arguments provide workspace for the function. The
       workspace vector should contain at least 20 elements. It	 is  used  for
       keeping	track  of  multiple  paths  through  the  pattern  tree.  More
       workspace will be needed for patterns and subjects where	 there	are  a
       lot of potential matches.

       Here is an example of a simple call to pcre_dfa_exec():

	 int rc;
	 int ovector[10];
	 int wspace[20];
	 rc = pcre_dfa_exec(
	   re,		   /* result of pcre_compile() */
	   NULL,	   /* we didn't study the pattern */
	   "some string",  /* the subject string */
	   11,		   /* the length of the subject string */
	   0,		   /* start at offset 0 in the subject */
	   0,		   /* default options */
	   ovector,	   /* vector of integers for substring information */
	   10,		   /* number of elements (NOT size in bytes) */
	   wspace,	   /* working space vector */
	   20);		   /* number of elements (NOT size in bytes) */

   Option bits for pcre_dfa_exec()

       The  unused  bits  of  the options argument for pcre_dfa_exec() must be
       zero. The only bits  that  may  be  set	are  PCRE_ANCHORED,  PCRE_NEW‐
       LINE_xxx,	PCRE_NOTBOL,	    PCRE_NOTEOL,	PCRE_NOTEMPTY,
       PCRE_NOTEMPTY_ATSTART,	   PCRE_NO_UTF8_CHECK,	     PCRE_BSR_ANYCRLF,
       PCRE_BSR_UNICODE,  PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD, PCRE_PAR‐
       TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.  All but  the  last
       four  of	 these	are  exactly  the  same	 as  for pcre_exec(), so their
       description is not repeated here.

	 PCRE_PARTIAL_HARD
	 PCRE_PARTIAL_SOFT

       These have the same general effect as they do for pcre_exec(), but  the
       details	are  slightly  different.  When	 PCRE_PARTIAL_HARD  is set for
       pcre_dfa_exec(), it returns PCRE_ERROR_PARTIAL if the end of  the  sub‐
       ject  is	 reached  and there is still at least one matching possibility
       that requires additional characters. This happens even if some complete
       matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
       code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
       of  the	subject	 is  reached, there have been no complete matches, but
       there is still at least one matching possibility. The  portion  of  the
       string  that  was inspected when the longest partial match was found is
       set as the first matching string	 in  both  cases.   There  is  a  more
       detailed	 discussion  of partial and multi-segment matching, with exam‐
       ples, in the pcrepartial documentation.

	 PCRE_DFA_SHORTEST

       Setting the PCRE_DFA_SHORTEST option causes the matching	 algorithm  to
       stop as soon as it has found one match. Because of the way the alterna‐
       tive algorithm works, this is necessarily the shortest  possible	 match
       at the first possible matching point in the subject string.

	 PCRE_DFA_RESTART

       When pcre_dfa_exec() returns a partial match, it is possible to call it
       again, with additional subject characters, and have  it	continue  with
       the  same match. The PCRE_DFA_RESTART option requests this action; when
       it is set, the workspace and wscount options must  reference  the  same
       vector  as  before  because data about the match so far is left in them
       after a partial match. There is more discussion of this facility in the
       pcrepartial documentation.

   Successful returns from pcre_dfa_exec()

       When  pcre_dfa_exec()  succeeds, it may have matched more than one sub‐
       string in the subject. Note, however, that all the matches from one run
       of  the	function  start	 at the same point in the subject. The shorter
       matches are all initial substrings of the longer matches. For  example,
       if the pattern

	 <.*>

       is matched against the string

	 This is <something> <something else> <something further> no more

       the three matched strings are

	 <something>
	 <something> <something else>
	 <something> <something else> <something further>

       On  success,  the  yield of the function is a number greater than zero,
       which is the number of matched substrings.  The	substrings  themselves
       are  returned  in  ovector. Each string uses two elements; the first is
       the offset to the start, and the second is the offset to	 the  end.  In
       fact,  all  the	strings	 have the same start offset. (Space could have
       been saved by giving this only once, but it was decided to retain  some
       compatibility  with  the	 way pcre_exec() returns data, even though the
       meaning of the strings is different.)

       The strings are returned in reverse order of length; that is, the long‐
       est  matching  string is given first. If there were too many matches to
       fit into ovector, the yield of the function is zero, and the vector  is
       filled  with  the  longest matches. Unlike pcre_exec(), pcre_dfa_exec()
       can use the entire ovector for returning matched strings.

   Error returns from pcre_dfa_exec()

       The pcre_dfa_exec() function returns a negative number when  it	fails.
       Many  of	 the  errors  are  the	same as for pcre_exec(), and these are
       described above.	 There are in addition the following errors  that  are
       specific to pcre_dfa_exec():

	 PCRE_ERROR_DFA_UITEM	   (-16)

       This  return is given if pcre_dfa_exec() encounters an item in the pat‐
       tern that it does not support, for instance, the use of \C  or  a  back
       reference.

	 PCRE_ERROR_DFA_UCOND	   (-17)

       This  return  is	 given	if pcre_dfa_exec() encounters a condition item
       that uses a back reference for the condition, or a test	for  recursion
       in a specific group. These are not supported.

	 PCRE_ERROR_DFA_UMLIMIT	   (-18)

       This  return  is given if pcre_dfa_exec() is called with an extra block
       that contains a setting of  the	match_limit  or	 match_limit_recursion
       fields.	This  is  not  supported (these fields are meaningless for DFA
       matching).

	 PCRE_ERROR_DFA_WSSIZE	   (-19)

       This return is given if	pcre_dfa_exec()	 runs  out  of	space  in  the
       workspace vector.

	 PCRE_ERROR_DFA_RECURSE	   (-20)

       When  a	recursive subpattern is processed, the matching function calls
       itself recursively, using private vectors for  ovector  and  workspace.
       This  error  is	given  if  the output vector is not large enough. This
       should be extremely rare, as a vector of size 1000 is used.

SEE ALSO

       pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar‐
       tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).

AUTHOR

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

REVISION

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

								    PCREAPI(3)
[top]

List of man pages available for Haiku

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net