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# Line 26  INTRODUCTION Line 26  INTRODUCTION
26         give better JavaScript compatibility.         give better JavaScript compatibility.
27    
28         The  current implementation of PCRE corresponds approximately with Perl         The  current implementation of PCRE corresponds approximately with Perl
29         5.10/5.11, including support for UTF-8 encoded strings and Unicode gen-         5.12, including support for UTF-8 encoded strings and  Unicode  general
30         eral  category properties. However, UTF-8 and Unicode support has to be         category  properties.  However,  UTF-8  and  Unicode  support has to be
31         explicitly enabled; it is not the default. The  Unicode  tables  corre-         explicitly enabled; it is not the default. The  Unicode  tables  corre-
32         spond to Unicode release 5.2.0.         spond to Unicode release 6.0.0.
33    
34         In  addition to the Perl-compatible matching function, PCRE contains an         In  addition to the Perl-compatible matching function, PCRE contains an
35         alternative function that matches the same compiled patterns in a  dif-         alternative function that matches the same compiled patterns in a  dif-
# Line 85  USER DOCUMENTATION Line 85  USER DOCUMENTATION
85           pcrecpp           details of the C++ wrapper           pcrecpp           details of the C++ wrapper
86           pcredemo          a demonstration C program that uses PCRE           pcredemo          a demonstration C program that uses PCRE
87           pcregrep          description of the pcregrep command           pcregrep          description of the pcregrep command
88             pcrejit           discussion of the just-in-time optimization support
89             pcrelimits        details of size and other limits
90           pcrematching      discussion of the two matching algorithms           pcrematching      discussion of the two matching algorithms
91           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
92           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
# Line 96  USER DOCUMENTATION Line 98  USER DOCUMENTATION
98           pcrestack         discussion of stack usage           pcrestack         discussion of stack usage
99           pcresyntax        quick syntax reference           pcresyntax        quick syntax reference
100           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
101             pcreunicode       discussion of Unicode and UTF-8 support
102    
103         In  addition,  in the "man" and HTML formats, there is a short page for         In  addition,  in the "man" and HTML formats, there is a short page for
104         each C library function, listing its arguments and results.         each C library function, listing its arguments and results.
105    
106    
 LIMITATIONS  
   
        There are some size limitations in PCRE but it is hoped that they  will  
        never in practice be relevant.  
   
        The  maximum  length of a compiled pattern is 65539 (sic) bytes if PCRE  
        is compiled with the default internal linkage size of 2. If you want to  
        process  regular  expressions  that are truly enormous, you can compile  
        PCRE with an internal linkage size of 3 or 4 (see the  README  file  in  
        the  source  distribution and the pcrebuild documentation for details).  
        In these cases the limit is substantially larger.  However,  the  speed  
        of execution is slower.  
   
        All values in repeating quantifiers must be less than 65536.  
   
        There is no limit to the number of parenthesized subpatterns, but there  
        can be no more than 65535 capturing subpatterns.  
   
        The maximum length of name for a named subpattern is 32 characters, and  
        the maximum number of named subpatterns is 10000.  
   
        The  maximum  length of a subject string is the largest positive number  
        that an integer variable can hold. However, when using the  traditional  
        matching function, PCRE uses recursion to handle subpatterns and indef-  
        inite repetition.  This means that the available stack space may  limit  
        the size of a subject string that can be processed by certain patterns.  
        For a discussion of stack issues, see the pcrestack documentation.  
   
   
 UTF-8 AND UNICODE PROPERTY SUPPORT  
   
        From release 3.3, PCRE has  had  some  support  for  character  strings  
        encoded  in the UTF-8 format. For release 4.0 this was greatly extended  
        to cover most common requirements, and in release 5.0  additional  sup-  
        port for Unicode general category properties was added.  
   
        In  order  process  UTF-8 strings, you must build PCRE to include UTF-8  
        support in the code, and, in addition,  you  must  call  pcre_compile()  
        with  the  PCRE_UTF8  option  flag,  or the pattern must start with the  
        sequence (*UTF8). When either of these is the case,  both  the  pattern  
        and  any  subject  strings  that  are matched against it are treated as  
        UTF-8 strings instead of strings of 1-byte characters.  
   
        If you compile PCRE with UTF-8 support, but do not use it at run  time,  
        the  library will be a bit bigger, but the additional run time overhead  
        is limited to testing the PCRE_UTF8 flag occasionally, so should not be  
        very big.  
   
        If PCRE is built with Unicode character property support (which implies  
        UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-  
        ported.  The available properties that can be tested are limited to the  
        general category properties such as Lu for an upper case letter  or  Nd  
        for  a  decimal number, the Unicode script names such as Arabic or Han,  
        and the derived properties Any and L&. A full  list  is  given  in  the  
        pcrepattern documentation. Only the short names for properties are sup-  
        ported. For example, \p{L} matches a letter. Its Perl synonym,  \p{Let-  
        ter},  is  not  supported.   Furthermore,  in Perl, many properties may  
        optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE  
        does not support this.  
   
    Validity of UTF-8 strings  
   
        When  you  set  the  PCRE_UTF8 flag, the strings passed as patterns and  
        subjects are (by default) checked for validity on entry to the relevant  
        functions.  From  release 7.3 of PCRE, the check is according the rules  
        of RFC 3629, which are themselves derived from the  Unicode  specifica-  
        tion.  Earlier  releases  of PCRE followed the rules of RFC 2279, which  
        allows the full range of 31-bit values (0 to 0x7FFFFFFF).  The  current  
        check allows only values in the range U+0 to U+10FFFF, excluding U+D800  
        to U+DFFF.  
   
        The excluded code points are the "Low Surrogate Area"  of  Unicode,  of  
        which  the Unicode Standard says this: "The Low Surrogate Area does not  
        contain any  character  assignments,  consequently  no  character  code  
        charts or namelists are provided for this area. Surrogates are reserved  
        for use with UTF-16 and then must be used in pairs."  The  code  points  
        that  are  encoded  by  UTF-16  pairs are available as independent code  
        points in the UTF-8 encoding. (In  other  words,  the  whole  surrogate  
        thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)  
   
        If  an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error return  
        (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know  
        that your strings are valid, and therefore want to skip these checks in  
        order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at  
        compile  time  or at run time, PCRE assumes that the pattern or subject  
        it is given (respectively) contains only valid  UTF-8  codes.  In  this  
        case, it does not diagnose an invalid UTF-8 string.  
   
        If  you  pass  an  invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set,  
        what happens depends on why the string is invalid. If the  string  con-  
        forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a  
        string of characters in the range 0  to  0x7FFFFFFF.  In  other  words,  
        apart from the initial validity test, PCRE (when in UTF-8 mode) handles  
        strings according to the more liberal rules of RFC  2279.  However,  if  
        the  string does not even conform to RFC 2279, the result is undefined.  
        Your program may crash.  
   
        If you want to process strings  of  values  in  the  full  range  0  to  
        0x7FFFFFFF,  encoded in a UTF-8-like manner as per the old RFC, you can  
        set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in  
        this situation, you will have to apply your own validity check.  
   
    General comments about UTF-8 mode  
   
        1.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a  
        two-byte UTF-8 character if the value is greater than 127.  
   
        2. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8  
        characters for values greater than \177.  
   
        3.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-  
        vidual bytes, for example: \x{100}{3}.  
   
        4. The dot metacharacter matches one UTF-8 character instead of a  sin-  
        gle byte.  
   
        5.  The  escape sequence \C can be used to match a single byte in UTF-8  
        mode, but its use can lead to some strange effects.  This  facility  is  
        not available in the alternative matching function, pcre_dfa_exec().  
   
        6.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly  
        test characters of any code value, but, by default, the characters that  
        PCRE  recognizes  as digits, spaces, or word characters remain the same  
        set as before, all with values less than 256. This  remains  true  even  
        when  PCRE  is built to include Unicode property support, because to do  
        otherwise would slow down PCRE in many common  cases.  Note  that  this  
        also applies to \b, because it is defined in terms of \w and \W. If you  
        really want to test for a wider sense of, say,  "digit",  you  can  use  
        explicit  Unicode property tests such as \p{Nd}.  Alternatively, if you  
        set the PCRE_UCP option, the way that the  character  escapes  work  is  
        changed  so that Unicode properties are used to determine which charac-  
        ters match. There are more details in the section on generic  character  
        types in the pcrepattern documentation.  
   
        7.  Similarly,  characters that match the POSIX named character classes  
        are all low-valued characters, unless the PCRE_UCP option is set.  
   
        8. However, the Perl 5.10 horizontal and vertical  whitespace  matching  
        escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-  
        acters, whether or not PCRE_UCP is set.  
   
        9. Case-insensitive matching applies only to  characters  whose  values  
        are  less than 128, unless PCRE is built with Unicode property support.  
        Even when Unicode property support is available, PCRE  still  uses  its  
        own  character  tables when checking the case of low-valued characters,  
        so as not to degrade performance.  The Unicode property information  is  
        used only for characters with higher values. Even when Unicode property  
        support is available, PCRE supports case-insensitive matching only when  
        there  is  a  one-to-one  mapping between a letter's cases. There are a  
        small number of many-to-one mappings in Unicode;  these  are  not  sup-  
        ported by PCRE.  
   
   
107  AUTHOR  AUTHOR
108    
109         Philip Hazel         Philip Hazel
110         University Computing Service         University Computing Service
111         Cambridge CB2 3QH, England.         Cambridge CB2 3QH, England.
112    
113         Putting  an actual email address here seems to have been a spam magnet,         Putting an actual email address here seems to have been a spam  magnet,
114         so I've taken it away. If you want to email me, use  my  two  initials,         so  I've  taken  it away. If you want to email me, use my two initials,
115         followed by the two digits 10, at the domain cam.ac.uk.         followed by the two digits 10, at the domain cam.ac.uk.
116    
117    
118  REVISION  REVISION
119    
120         Last updated: 12 May 2010         Last updated: 24 August 2011
121         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
122  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
123    
124    
# Line 308  PCRE BUILD-TIME OPTIONS Line 158  PCRE BUILD-TIME OPTIONS
158         is not described.         is not described.
159    
160    
161    BUILDING SHARED AND STATIC LIBRARIES
162    
163           The  PCRE building process uses libtool to build both shared and static
164           Unix libraries by default. You can suppress one of these by adding  one
165           of
166    
167             --disable-shared
168             --disable-static
169    
170           to the configure command, as required.
171    
172    
173  C++ SUPPORT  C++ SUPPORT
174    
175         By default, the configure script will search for a C++ compiler and C++         By default, the configure script will search for a C++ compiler and C++
# Line 355  UNICODE CHARACTER PROPERTY SUPPORT Line 217  UNICODE CHARACTER PROPERTY SUPPORT
217         are supported. Details are given in the pcrepattern documentation.         are supported. Details are given in the pcrepattern documentation.
218    
219    
220    JUST-IN-TIME COMPILER SUPPORT
221    
222           Just-in-time compiler support is included in the build by specifying
223    
224             --enable-jit
225    
226           This  support  is available only for certain hardware architectures. If
227           this option is set for an  unsupported  architecture,  a  compile  time
228           error  occurs.   See  the pcrejit documentation for a discussion of JIT
229           usage. When JIT support is enabled, pcregrep automatically makes use of
230           it, unless you add
231    
232             --disable-pcregrep-jit
233    
234           to the "configure" command.
235    
236    
237  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
238    
239         By  default,  PCRE interprets the linefeed (LF) character as indicating         By  default,  PCRE interprets the linefeed (LF) character as indicating
# Line 401  WHAT \R MATCHES Line 280  WHAT \R MATCHES
280         functions are called.         functions are called.
281    
282    
 BUILDING SHARED AND STATIC LIBRARIES  
   
        The  PCRE building process uses libtool to build both shared and static  
        Unix libraries by default. You can suppress one of these by adding  one  
        of  
   
          --disable-shared  
          --disable-static  
   
        to the configure command, as required.  
   
   
283  POSIX MALLOC USAGE  POSIX MALLOC USAGE
284    
285         When PCRE is called through the POSIX interface (see the pcreposix doc-         When PCRE is called through the POSIX interface (see the pcreposix doc-
# Line 553  PCREGREP OPTIONS FOR COMPRESSED FILE SUP Line 420  PCREGREP OPTIONS FOR COMPRESSED FILE SUP
420         if they are not.         if they are not.
421    
422    
423    PCREGREP BUFFER SIZE
424    
425           pcregrep  uses  an internal buffer to hold a "window" on the file it is
426           scanning, in order to be able to output "before" and "after" lines when
427           it  finds  a match. The size of the buffer is controlled by a parameter
428           whose default value is 20K. The buffer itself is three times this size,
429           but because of the way it is used for holding "before" lines, the long-
430           est line that is guaranteed to be processable is  the  parameter  size.
431           You can change the default parameter value by adding, for example,
432    
433             --with-pcregrep-bufsize=50K
434    
435           to the configure command. The caller of pcregrep can, however, override
436           this value by specifying a run-time option.
437    
438    
439  PCRETEST OPTION FOR LIBREADLINE SUPPORT  PCRETEST OPTION FOR LIBREADLINE SUPPORT
440    
441         If you add         If you add
442    
443           --enable-pcretest-libreadline           --enable-pcretest-libreadline
444    
445         to  the  configure  command,  pcretest  is  linked with the libreadline         to the configure command,  pcretest  is  linked  with  the  libreadline
446         library, and when its input is from a terminal, it reads it  using  the         library,  and  when its input is from a terminal, it reads it using the
447         readline() function. This provides line-editing and history facilities.         readline() function. This provides line-editing and history facilities.
448         Note that libreadline is GPL-licensed, so if you distribute a binary of         Note that libreadline is GPL-licensed, so if you distribute a binary of
449         pcretest linked in this way, there may be licensing issues.         pcretest linked in this way, there may be licensing issues.
450    
451         Setting  this  option  causes  the -lreadline option to be added to the         Setting this option causes the -lreadline option to  be  added  to  the
452         pcretest build. In many operating environments with  a  sytem-installed         pcretest  build.  In many operating environments with a sytem-installed
453         libreadline this is sufficient. However, in some environments (e.g.  if         libreadline this is sufficient. However, in some environments (e.g.  if
454         an unmodified distribution version of readline is in use),  some  extra         an  unmodified  distribution version of readline is in use), some extra
455         configuration  may  be necessary. The INSTALL file for libreadline says         configuration may be necessary. The INSTALL file for  libreadline  says
456         this:         this:
457    
458           "Readline uses the termcap functions, but does not link with the           "Readline uses the termcap functions, but does not link with the
459           termcap or curses library itself, allowing applications which link           termcap or curses library itself, allowing applications which link
460           with readline the to choose an appropriate library."           with readline the to choose an appropriate library."
461    
462         If your environment has not been set up so that an appropriate  library         If  your environment has not been set up so that an appropriate library
463         is automatically included, you may need to add something like         is automatically included, you may need to add something like
464    
465           LIBS="-ncurses"           LIBS="-ncurses"
# Line 598  AUTHOR Line 481  AUTHOR
481    
482  REVISION  REVISION
483    
484         Last updated: 29 September 2009         Last updated: 06 September 2011
485         Copyright (c) 1997-2009 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
486  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
487    
488    
# Line 697  THE ALTERNATIVE MATCHING ALGORITHM Line 580  THE ALTERNATIVE MATCHING ALGORITHM
580         represent the different matching possibilities (if there are none,  the         represent the different matching possibilities (if there are none,  the
581         match  has  failed).   Thus,  if there is more than one possible match,         match  has  failed).   Thus,  if there is more than one possible match,
582         this algorithm finds all of them, and in particular, it finds the long-         this algorithm finds all of them, and in particular, it finds the long-
583         est.  There  is  an  option to stop the algorithm after the first match         est.  The  matches are returned in decreasing order of length. There is
584         (which is necessarily the shortest) is found.         an option to stop the algorithm after the first match (which is  neces-
585           sarily the shortest) is found.
586    
587         Note that all the matches that are found start at the same point in the         Note that all the matches that are found start at the same point in the
588         subject. If the pattern         subject. If the pattern
589    
590           cat(er(pillar)?)           cat(er(pillar)?)?
591    
592         is  matched  against the string "the caterpillar catchment", the result         is matched against the string "the caterpillar catchment",  the  result
593         will be the three strings "cat", "cater", and "caterpillar" that  start         will  be the three strings "caterpillar", "cater", and "cat" that start
594         at the fourth character of the subject. The algorithm does not automat-         at the fifth character of the subject. The algorithm does not automati-
595         ically move on to find matches that start at later positions.         cally move on to find matches that start at later positions.
596    
597         There are a number of features of PCRE regular expressions that are not         There are a number of features of PCRE regular expressions that are not
598         supported by the alternative matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
599    
600         1.  Because  the  algorithm  finds  all possible matches, the greedy or         1. Because the algorithm finds all  possible  matches,  the  greedy  or
601         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
602         ungreedy quantifiers are treated in exactly the same way. However, pos-         ungreedy quantifiers are treated in exactly the same way. However, pos-
603         sessive quantifiers can make a difference when what follows could  also         sessive  quantifiers can make a difference when what follows could also
604         match what is quantified, for example in a pattern like this:         match what is quantified, for example in a pattern like this:
605    
606           ^a++\w!           ^a++\w!
607    
608         This  pattern matches "aaab!" but not "aaa!", which would be matched by         This pattern matches "aaab!" but not "aaa!", which would be matched  by
609         a non-possessive quantifier. Similarly, if an atomic group is  present,         a  non-possessive quantifier. Similarly, if an atomic group is present,
610         it  is matched as if it were a standalone pattern at the current point,         it is matched as if it were a standalone pattern at the current  point,
611         and the longest match is then "locked in" for the rest of  the  overall         and  the  longest match is then "locked in" for the rest of the overall
612         pattern.         pattern.
613    
614         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
615         is not straightforward to keep track of  captured  substrings  for  the         is  not  straightforward  to  keep track of captured substrings for the
616         different  matching  possibilities,  and  PCRE's implementation of this         different matching possibilities, and  PCRE's  implementation  of  this
617         algorithm does not attempt to do this. This means that no captured sub-         algorithm does not attempt to do this. This means that no captured sub-
618         strings are available.         strings are available.
619    
620         3.  Because no substrings are captured, back references within the pat-         3. Because no substrings are captured, back references within the  pat-
621         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
622    
623         4. For the same reason, conditional expressions that use  a  backrefer-         4.  For  the same reason, conditional expressions that use a backrefer-
624         ence  as  the  condition or test for a specific group recursion are not         ence as the condition or test for a specific group  recursion  are  not
625         supported.         supported.
626    
627         5. Because many paths through the tree may be  active,  the  \K  escape         5.  Because  many  paths  through the tree may be active, the \K escape
628         sequence, which resets the start of the match when encountered (but may         sequence, which resets the start of the match when encountered (but may
629         be on some paths and not on others), is not  supported.  It  causes  an         be  on  some  paths  and not on others), is not supported. It causes an
630         error if encountered.         error if encountered.
631    
632         6.  Callouts  are  supported, but the value of the capture_top field is         6. Callouts are supported, but the value of the  capture_top  field  is
633         always 1, and the value of the capture_last field is always -1.         always 1, and the value of the capture_last field is always -1.
634    
635         7. The \C escape sequence, which (in the standard algorithm) matches  a         7.  The \C escape sequence, which (in the standard algorithm) matches a
636         single  byte, even in UTF-8 mode, is not supported because the alterna-         single byte, even in UTF-8  mode,  is  not  supported  in  UTF-8  mode,
637         tive algorithm moves through the subject  string  one  character  at  a         because  the alternative algorithm moves through the subject string one
638         time, for all active paths through the tree.         character at a time, for all active paths through the tree.
639    
640         8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)         8. Except for (*FAIL), the backtracking control verbs such as  (*PRUNE)
641         are not supported. (*FAIL) is supported, and  behaves  like  a  failing         are  not  supported.  (*FAIL)  is supported, and behaves like a failing
642         negative assertion.         negative assertion.
643    
644    
645  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
646    
647         Using  the alternative matching algorithm provides the following advan-         Using the alternative matching algorithm provides the following  advan-
648         tages:         tages:
649    
650         1. All possible matches (at a single point in the subject) are automat-         1. All possible matches (at a single point in the subject) are automat-
651         ically  found,  and  in particular, the longest match is found. To find         ically found, and in particular, the longest match is  found.  To  find
652         more than one match using the standard algorithm, you have to do kludgy         more than one match using the standard algorithm, you have to do kludgy
653         things with callouts.         things with callouts.
654    
655         2.  Because  the  alternative  algorithm  scans the subject string just         2. Because the alternative algorithm  scans  the  subject  string  just
656         once, and never needs to backtrack, it is possible to  pass  very  long         once,  and  never  needs to backtrack, it is possible to pass very long
657         subject  strings  to  the matching function in several pieces, checking         subject strings to the matching function in  several  pieces,  checking
658         for partial matching each time.  The  pcrepartial  documentation  gives         for  partial  matching  each time. Although it is possible to do multi-
659         details of partial matching.         segment matching using the standard algorithm (pcre_exec()), by retain-
660           ing  partially matched substrings, it is more complicated. The pcrepar-
661           tial documentation gives details  of  partial  matching  and  discusses
662           multi-segment matching.
663    
664    
665  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
# Line 798  AUTHOR Line 685  AUTHOR
685    
686  REVISION  REVISION
687    
688         Last updated: 29 September 2009         Last updated: 19 November 2011
689         Copyright (c) 1997-2009 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
690  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
691    
692    
# Line 810  NAME Line 697  NAME
697         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
698    
699    
700  PCRE NATIVE API  PCRE NATIVE API BASIC FUNCTIONS
701    
702         #include <pcre.h>         #include <pcre.h>
703    
# Line 826  PCRE NATIVE API Line 713  PCRE NATIVE API
713         pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options,
714              const char **errptr);              const char **errptr);
715    
716           void pcre_free_study(pcre_extra *extra);
717    
718         int pcre_exec(const pcre *code, const pcre_extra *extra,         int pcre_exec(const pcre *code, const pcre_extra *extra,
719              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
720              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
721    
722    
723    PCRE NATIVE API AUXILIARY FUNCTIONS
724    
725           pcre_jit_stack *pcre_jit_stack_alloc(int startsize, int maxsize);
726    
727           void pcre_jit_stack_free(pcre_jit_stack *stack);
728    
729           void pcre_assign_jit_stack(pcre_extra *extra,
730                pcre_jit_callback callback, void *data);
731    
732         int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,         int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
733              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
734              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
# Line 879  PCRE NATIVE API Line 778  PCRE NATIVE API
778    
779         char *pcre_version(void);         char *pcre_version(void);
780    
781    
782    PCRE NATIVE API INDIRECTED FUNCTIONS
783    
784         void *(*pcre_malloc)(size_t);         void *(*pcre_malloc)(size_t);
785    
786         void (*pcre_free)(void *);         void (*pcre_free)(void *);
# Line 894  PCRE API OVERVIEW Line 796  PCRE API OVERVIEW
796    
797         PCRE has its own native API, which is described in this document. There         PCRE has its own native API, which is described in this document. There
798         are also some wrapper functions that correspond to  the  POSIX  regular         are also some wrapper functions that correspond to  the  POSIX  regular
799         expression  API.  These  are  described in the pcreposix documentation.         expression  API,  but they do not give access to all the functionality.
800         Both of these APIs define a set of C function calls. A C++  wrapper  is         They are described in the pcreposix documentation. Both of  these  APIs
801         distributed with PCRE. It is documented in the pcrecpp page.         define  a  set  of  C function calls. A C++ wrapper is also distributed
802           with PCRE. It is documented in the pcrecpp page.
803    
804         The  native  API  C  function prototypes are defined in the header file         The native API C function prototypes are defined  in  the  header  file
805         pcre.h, and on Unix systems the library itself is called  libpcre.   It         pcre.h,  and  on Unix systems the library itself is called libpcre.  It
806         can normally be accessed by adding -lpcre to the command for linking an         can normally be accessed by adding -lpcre to the command for linking an
807         application  that  uses  PCRE.  The  header  file  defines  the  macros         application  that  uses  PCRE.  The  header  file  defines  the  macros
808         PCRE_MAJOR  and  PCRE_MINOR to contain the major and minor release num-         PCRE_MAJOR and PCRE_MINOR to contain the major and minor  release  num-
809         bers for the library.  Applications can use these  to  include  support         bers  for  the  library.  Applications can use these to include support
810         for different releases of PCRE.         for different releases of PCRE.
811    
812         In a Windows environment, if you want to statically link an application         In a Windows environment, if you want to statically link an application
813         program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC         program  against  a  non-dll  pcre.a  file, you must define PCRE_STATIC
814         before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-         before including pcre.h or pcrecpp.h, because otherwise  the  pcre_mal-
815         loc()   and   pcre_free()   exported   functions   will   be   declared         loc()   and   pcre_free()   exported   functions   will   be   declared
816         __declspec(dllimport), with unwanted results.         __declspec(dllimport), with unwanted results.
817    
818         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and         The  functions  pcre_compile(),  pcre_compile2(),   pcre_study(),   and
819         pcre_exec() are used for compiling and matching regular expressions  in         pcre_exec()  are used for compiling and matching regular expressions in
820         a  Perl-compatible  manner. A sample program that demonstrates the sim-         a Perl-compatible manner. A sample program that demonstrates  the  sim-
821         plest way of using them is provided in the file  called  pcredemo.c  in         plest  way  of  using them is provided in the file called pcredemo.c in
822         the PCRE source distribution. A listing of this program is given in the         the PCRE source distribution. A listing of this program is given in the
823         pcredemo documentation, and the pcresample documentation describes  how         pcredemo  documentation, and the pcresample documentation describes how
824         to compile and run it.         to compile and run it.
825    
826           Just-in-time compiler support is an optional feature of PCRE  that  can
827           be built in appropriate hardware environments. It greatly speeds up the
828           matching performance of  many  patterns.  Simple  programs  can  easily
829           request  that  it  be  used  if available, by setting an option that is
830           ignored when it is not relevant. More complicated programs  might  need
831           to     make    use    of    the    functions    pcre_jit_stack_alloc(),
832           pcre_jit_stack_free(), and pcre_assign_jit_stack() in order to  control
833           the  JIT  code's  memory  usage.   These functions are discussed in the
834           pcrejit documentation.
835    
836         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
837         ble, is also provided. This uses a different algorithm for  the  match-         ble,  is  also provided. This uses a different algorithm for the match-
838         ing.  The  alternative algorithm finds all possible matches (at a given         ing. The alternative algorithm finds all possible matches (at  a  given
839         point in the subject), and scans the subject just  once  (unless  there         point  in  the  subject), and scans the subject just once (unless there
840         are  lookbehind  assertions).  However,  this algorithm does not return         are lookbehind assertions). However, this  algorithm  does  not  return
841         captured substrings. A description of the two matching  algorithms  and         captured  substrings.  A description of the two matching algorithms and
842         their  advantages  and disadvantages is given in the pcrematching docu-         their advantages and disadvantages is given in the  pcrematching  docu-
843         mentation.         mentation.
844    
845         In addition to the main compiling and  matching  functions,  there  are         In  addition  to  the  main compiling and matching functions, there are
846         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
847         string that is matched by pcre_exec(). They are:         string that is matched by pcre_exec(). They are:
848    
# Line 944  PCRE API OVERVIEW Line 857  PCRE API OVERVIEW
857         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
858         to free the memory used for extracted strings.         to free the memory used for extracted strings.
859    
860         The  function  pcre_maketables()  is  used  to build a set of character         The function pcre_maketables() is used to  build  a  set  of  character
861         tables  in  the  current  locale   for   passing   to   pcre_compile(),         tables   in   the   current   locale  for  passing  to  pcre_compile(),
862         pcre_exec(),  or  pcre_dfa_exec(). This is an optional facility that is         pcre_exec(), or pcre_dfa_exec(). This is an optional facility  that  is
863         provided for specialist use.  Most  commonly,  no  special  tables  are         provided  for  specialist  use.  Most  commonly,  no special tables are
864         passed,  in  which case internal tables that are generated when PCRE is         passed, in which case internal tables that are generated when  PCRE  is
865         built are used.         built are used.
866    
867         The function pcre_fullinfo() is used to find out  information  about  a         The  function  pcre_fullinfo()  is used to find out information about a
868         compiled  pattern; pcre_info() is an obsolete version that returns only         compiled pattern; pcre_info() is an obsolete version that returns  only
869         some of the available information, but is retained for  backwards  com-         some  of  the available information, but is retained for backwards com-
870         patibility.   The function pcre_version() returns a pointer to a string         patibility.  The function pcre_version() returns a pointer to a  string
871         containing the version of PCRE and its date of release.         containing the version of PCRE and its date of release.
872    
873         The function pcre_refcount() maintains a  reference  count  in  a  data         The  function  pcre_refcount()  maintains  a  reference count in a data
874         block  containing  a compiled pattern. This is provided for the benefit         block containing a compiled pattern. This is provided for  the  benefit
875         of object-oriented applications.         of object-oriented applications.
876    
877         The global variables pcre_malloc and pcre_free  initially  contain  the         The  global  variables  pcre_malloc and pcre_free initially contain the
878         entry  points  of  the  standard malloc() and free() functions, respec-         entry points of the standard malloc()  and  free()  functions,  respec-
879         tively. PCRE calls the memory management functions via these variables,         tively. PCRE calls the memory management functions via these variables,
880         so  a  calling  program  can replace them if it wishes to intercept the         so a calling program can replace them if it  wishes  to  intercept  the
881         calls. This should be done before calling any PCRE functions.         calls. This should be done before calling any PCRE functions.
882    
883         The global variables pcre_stack_malloc  and  pcre_stack_free  are  also         The  global  variables  pcre_stack_malloc  and pcre_stack_free are also
884         indirections  to  memory  management functions. These special functions         indirections to memory management functions.  These  special  functions
885         are used only when PCRE is compiled to use  the  heap  for  remembering         are  used  only  when  PCRE is compiled to use the heap for remembering
886         data, instead of recursive function calls, when running the pcre_exec()         data, instead of recursive function calls, when running the pcre_exec()
887         function. See the pcrebuild documentation for  details  of  how  to  do         function.  See  the  pcrebuild  documentation  for details of how to do
888         this.  It  is  a non-standard way of building PCRE, for use in environ-         this. It is a non-standard way of building PCRE, for  use  in  environ-
889         ments that have limited stacks. Because of the greater  use  of  memory         ments  that  have  limited stacks. Because of the greater use of memory
890         management,  it  runs  more  slowly. Separate functions are provided so         management, it runs more slowly. Separate  functions  are  provided  so
891         that special-purpose external code can be  used  for  this  case.  When         that  special-purpose  external  code  can  be used for this case. When
892         used,  these  functions  are always called in a stack-like manner (last         used, these functions are always called in a  stack-like  manner  (last
893         obtained, first freed), and always for memory blocks of the same  size.         obtained,  first freed), and always for memory blocks of the same size.
894         There  is  a discussion about PCRE's stack usage in the pcrestack docu-         There is a discussion about PCRE's stack usage in the  pcrestack  docu-
895         mentation.         mentation.
896    
897         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
898         by  the  caller  to  a "callout" function, which PCRE will then call at         by the caller to a "callout" function, which PCRE  will  then  call  at
899         specified points during a matching operation. Details are given in  the         specified  points during a matching operation. Details are given in the
900         pcrecallout documentation.         pcrecallout documentation.
901    
902    
903  NEWLINES  NEWLINES
904    
905         PCRE  supports five different conventions for indicating line breaks in         PCRE supports five different conventions for indicating line breaks  in
906         strings: a single CR (carriage return) character, a  single  LF  (line-         strings:  a  single  CR (carriage return) character, a single LF (line-
907         feed) character, the two-character sequence CRLF, any of the three pre-         feed) character, the two-character sequence CRLF, any of the three pre-
908         ceding, or any Unicode newline sequence. The Unicode newline  sequences         ceding,  or any Unicode newline sequence. The Unicode newline sequences
909         are  the  three just mentioned, plus the single characters VT (vertical         are the three just mentioned, plus the single characters  VT  (vertical
910         tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line         tab,  U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line
911         separator, U+2028), and PS (paragraph separator, U+2029).         separator, U+2028), and PS (paragraph separator, U+2029).
912    
913         Each  of  the first three conventions is used by at least one operating         Each of the first three conventions is used by at least  one  operating
914         system as its standard newline sequence. When PCRE is built, a  default         system  as its standard newline sequence. When PCRE is built, a default
915         can  be  specified.  The default default is LF, which is the Unix stan-         can be specified.  The default default is LF, which is the  Unix  stan-
916         dard. When PCRE is run, the default can be overridden,  either  when  a         dard.  When  PCRE  is run, the default can be overridden, either when a
917         pattern is compiled, or when it is matched.         pattern is compiled, or when it is matched.
918    
919         At compile time, the newline convention can be specified by the options         At compile time, the newline convention can be specified by the options
920         argument of pcre_compile(), or it can be specified by special  text  at         argument  of  pcre_compile(), or it can be specified by special text at
921         the start of the pattern itself; this overrides any other settings. See         the start of the pattern itself; this overrides any other settings. See
922         the pcrepattern page for details of the special character sequences.         the pcrepattern page for details of the special character sequences.
923    
924         In the PCRE documentation the word "newline" is used to mean "the char-         In the PCRE documentation the word "newline" is used to mean "the char-
925         acter  or pair of characters that indicate a line break". The choice of         acter or pair of characters that indicate a line break". The choice  of
926         newline convention affects the handling of  the  dot,  circumflex,  and         newline  convention  affects  the  handling of the dot, circumflex, and
927         dollar metacharacters, the handling of #-comments in /x mode, and, when         dollar metacharacters, the handling of #-comments in /x mode, and, when
928         CRLF is a recognized line ending sequence, the match position  advance-         CRLF  is a recognized line ending sequence, the match position advance-
929         ment for a non-anchored pattern. There is more detail about this in the         ment for a non-anchored pattern. There is more detail about this in the
930         section on pcre_exec() options below.         section on pcre_exec() options below.
931    
932         The choice of newline convention does not affect the interpretation  of         The  choice of newline convention does not affect the interpretation of
933         the  \n  or  \r  escape  sequences, nor does it affect what \R matches,         the \n or \r escape sequences, nor does  it  affect  what  \R  matches,
934         which is controlled in a similar way, but by separate options.         which is controlled in a similar way, but by separate options.
935    
936    
937  MULTITHREADING  MULTITHREADING
938    
939         The PCRE functions can be used in  multi-threading  applications,  with         The  PCRE  functions  can be used in multi-threading applications, with
940         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
941         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
942         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
943    
944         The  compiled form of a regular expression is not altered during match-         The compiled form of a regular expression is not altered during  match-
945         ing, so the same compiled pattern can safely be used by several threads         ing, so the same compiled pattern can safely be used by several threads
946         at once.         at once.
947    
948           If the just-in-time optimization feature is being used, it needs  sepa-
949           rate  memory stack areas for each thread. See the pcrejit documentation
950           for more details.
951    
952    
953  SAVING PRECOMPILED PATTERNS FOR LATER USE  SAVING PRECOMPILED PATTERNS FOR LATER USE
954    
955         The compiled form of a regular expression can be saved and re-used at a         The compiled form of a regular expression can be saved and re-used at a
956         later time, possibly by a different program, and even on a  host  other         later  time,  possibly by a different program, and even on a host other
957         than  the  one  on  which  it  was  compiled.  Details are given in the         than the one on which  it  was  compiled.  Details  are  given  in  the
958         pcreprecompile documentation. However, compiling a  regular  expression         pcreprecompile  documentation.  However, compiling a regular expression
959         with  one version of PCRE for use with a different version is not guar-         with one version of PCRE for use with a different version is not  guar-
960         anteed to work and may cause crashes.         anteed to work and may cause crashes.
961    
962    
# Line 1047  CHECKING BUILD-TIME OPTIONS Line 964  CHECKING BUILD-TIME OPTIONS
964    
965         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
966    
967         The function pcre_config() makes it possible for a PCRE client to  dis-         The  function pcre_config() makes it possible for a PCRE client to dis-
968         cover which optional features have been compiled into the PCRE library.         cover which optional features have been compiled into the PCRE library.
969         The pcrebuild documentation has more details about these optional  fea-         The  pcrebuild documentation has more details about these optional fea-
970         tures.         tures.
971    
972         The  first  argument  for pcre_config() is an integer, specifying which         The first argument for pcre_config() is an  integer,  specifying  which
973         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
974         into  which  the  information  is  placed. The following information is         into which the information is  placed.  The  following  information  is
975         available:         available:
976    
977           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
978    
979         The output is an integer that is set to one if UTF-8 support is  avail-         The  output is an integer that is set to one if UTF-8 support is avail-
980         able; otherwise it is set to zero.         able; otherwise it is set to zero.
981    
982           PCRE_CONFIG_UNICODE_PROPERTIES           PCRE_CONFIG_UNICODE_PROPERTIES
983    
984         The  output  is  an  integer  that is set to one if support for Unicode         The output is an integer that is set to  one  if  support  for  Unicode
985         character properties is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
986    
987             PCRE_CONFIG_JIT
988    
989           The output is an integer that is set to one if support for just-in-time
990           compiling is available; otherwise it is set to zero.
991    
992           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
993    
994         The output is an integer whose value specifies  the  default  character         The output is an integer whose value specifies  the  default  character
# Line 1162  COMPILING A PATTERN Line 1084  COMPILING A PATTERN
1084         pcrepattern documentation). For those options that can be different  in         pcrepattern documentation). For those options that can be different  in
1085         different  parts  of  the pattern, the contents of the options argument         different  parts  of  the pattern, the contents of the options argument
1086         specifies their settings at the start of compilation and execution. The         specifies their settings at the start of compilation and execution. The
1087         PCRE_ANCHORED, PCRE_BSR_xxx, and PCRE_NEWLINE_xxx options can be set at         PCRE_ANCHORED,  PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK, and
1088         the time of matching as well as at compile time.         PCRE_NO_START_OPT options can be set at the time of matching as well as
1089           at compile time.
1090    
1091         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1092         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
1093         sets the variable pointed to by errptr to point to a textual error mes-         sets the variable pointed to by errptr to point to a textual error mes-
1094         sage. This is a static string that is part of the library. You must not         sage. This is a static string that is part of the library. You must not
1095         try to free it. The byte offset from the start of the  pattern  to  the         try  to  free it. Normally, the offset from the start of the pattern to
1096         character  that  was  being  processed when the error was discovered is         the byte that was being processed when  the  error  was  discovered  is
1097         placed in the variable pointed to by erroffset, which must not be NULL.         placed  in the variable pointed to by erroffset, which must not be NULL
1098         If  it  is,  an  immediate error is given. Some errors are not detected         (if it is, an immediate error is given). However, for an invalid  UTF-8
1099         until checks are carried out when the whole pattern has  been  scanned;         string,  the offset is that of the first byte of the failing character.
1100         in this case the offset is set to the end of the pattern.         Also, some errors are not detected until checks are  carried  out  when
1101           the  whole  pattern  has been scanned; in these cases the offset passed
1102           back is the length of the pattern.
1103    
1104           Note that the offset is in bytes, not characters, even in  UTF-8  mode.
1105           It may sometimes point into the middle of a UTF-8 character.
1106    
1107         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1108         codeptr argument is not NULL, a non-zero error code number is  returned         codeptr argument is not NULL, a non-zero error code number is  returned
# Line 1252  COMPILING A PATTERN Line 1180  COMPILING A PATTERN
1180    
1181           PCRE_DOTALL           PCRE_DOTALL
1182    
1183         If this bit is set, a dot metacharater in the pattern matches all char-         If this bit is set, a dot metacharacter in the pattern matches a  char-
1184         acters,  including  those that indicate newline. Without it, a dot does         acter of any value, including one that indicates a newline. However, it
1185         not match when the current position is at a  newline.  This  option  is         only ever matches one character, even if newlines are  coded  as  CRLF.
1186         equivalent  to Perl's /s option, and it can be changed within a pattern         Without  this option, a dot does not match when the current position is
1187         by a (?s) option setting. A negative class such as [^a] always  matches         at a newline. This option is equivalent to Perl's /s option, and it can
1188         newline characters, independent of the setting of this option.         be  changed within a pattern by a (?s) option setting. A negative class
1189           such as [^a] always matches newline characters, independent of the set-
1190           ting of this option.
1191    
1192           PCRE_DUPNAMES           PCRE_DUPNAMES
1193    
# Line 1277  COMPILING A PATTERN Line 1207  COMPILING A PATTERN
1207         option, and it can be changed within a pattern by a  (?x)  option  set-         option, and it can be changed within a pattern by a  (?x)  option  set-
1208         ting.         ting.
1209    
1210         This  option  makes  it possible to include comments inside complicated         Which  characters  are  interpreted  as  newlines  is controlled by the
1211         patterns.  Note, however, that this applies only  to  data  characters.         options passed to pcre_compile() or by a special sequence at the  start
1212         Whitespace   characters  may  never  appear  within  special  character         of  the  pattern, as described in the section entitled "Newline conven-
1213         sequences in a pattern, for  example  within  the  sequence  (?(  which         tions" in the pcrepattern documentation. Note that the end of this type
1214         introduces a conditional subpattern.         of  comment  is  a  literal  newline  sequence  in  the pattern; escape
1215           sequences that happen to represent a newline do not count.
1216    
1217           This option makes it possible to include  comments  inside  complicated
1218           patterns.   Note,  however,  that this applies only to data characters.
1219           Whitespace  characters  may  never  appear  within  special   character
1220           sequences in a pattern, for example within the sequence (?( that intro-
1221           duces a conditional subpattern.
1222    
1223           PCRE_EXTRA           PCRE_EXTRA
1224    
1225         This  option  was invented in order to turn on additional functionality         This option was invented in order to turn on  additional  functionality
1226         of PCRE that is incompatible with Perl, but it  is  currently  of  very         of  PCRE  that  is  incompatible with Perl, but it is currently of very
1227         little  use. When set, any backslash in a pattern that is followed by a         little use. When set, any backslash in a pattern that is followed by  a
1228         letter that has no special meaning  causes  an  error,  thus  reserving         letter  that  has  no  special  meaning causes an error, thus reserving
1229         these  combinations  for  future  expansion.  By default, as in Perl, a         these combinations for future expansion. By  default,  as  in  Perl,  a
1230         backslash followed by a letter with no special meaning is treated as  a         backslash  followed by a letter with no special meaning is treated as a
1231         literal. (Perl can, however, be persuaded to give an error for this, by         literal. (Perl can, however, be persuaded to give an error for this, by
1232         running it with the -w option.) There are at present no other  features         running  it with the -w option.) There are at present no other features
1233         controlled  by this option. It can also be set by a (?X) option setting         controlled by this option. It can also be set by a (?X) option  setting
1234         within a pattern.         within a pattern.
1235    
1236           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1237    
1238         If this option is set, an  unanchored  pattern  is  required  to  match         If  this  option  is  set,  an  unanchored pattern is required to match
1239         before  or  at  the  first  newline  in  the subject string, though the         before or at the first  newline  in  the  subject  string,  though  the
1240         matched text may continue over the newline.         matched text may continue over the newline.
1241    
1242           PCRE_JAVASCRIPT_COMPAT           PCRE_JAVASCRIPT_COMPAT
1243    
1244         If this option is set, PCRE's behaviour is changed in some ways so that         If this option is set, PCRE's behaviour is changed in some ways so that
1245         it  is  compatible with JavaScript rather than Perl. The changes are as         it is compatible with JavaScript rather than Perl. The changes  are  as
1246         follows:         follows:
1247    
1248         (1) A lone closing square bracket in a pattern  causes  a  compile-time         (1)  A  lone  closing square bracket in a pattern causes a compile-time
1249         error,  because this is illegal in JavaScript (by default it is treated         error, because this is illegal in JavaScript (by default it is  treated
1250         as a data character). Thus, the pattern AB]CD becomes illegal when this         as a data character). Thus, the pattern AB]CD becomes illegal when this
1251         option is set.         option is set.
1252    
1253         (2)  At run time, a back reference to an unset subpattern group matches         (2) At run time, a back reference to an unset subpattern group  matches
1254         an empty string (by default this causes the current  matching  alterna-         an  empty  string (by default this causes the current matching alterna-
1255         tive  to  fail). A pattern such as (\1)(a) succeeds when this option is         tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
1256         set (assuming it can find an "a" in the subject), whereas it  fails  by         set  (assuming  it can find an "a" in the subject), whereas it fails by
1257         default, for Perl compatibility.         default, for Perl compatibility.
1258    
1259           (3) \U matches an upper case "U" character; by default \U causes a com-
1260           pile time error (Perl uses \U to upper case subsequent characters).
1261    
1262           (4) \u matches a lower case "u" character unless it is followed by four
1263           hexadecimal digits, in which case the hexadecimal  number  defines  the
1264           code  point  to match. By default, \u causes a compile time error (Perl
1265           uses it to upper case the following character).
1266    
1267           (5) \x matches a lower case "x" character unless it is followed by  two
1268           hexadecimal  digits,  in  which case the hexadecimal number defines the
1269           code point to match. By default, as in Perl, a  hexadecimal  number  is
1270           always expected after \x, but it may have zero, one, or two digits (so,
1271           for example, \xz matches a binary zero character followed by z).
1272    
1273           PCRE_MULTILINE           PCRE_MULTILINE
1274    
1275         By  default,  PCRE  treats the subject string as consisting of a single         By default, PCRE treats the subject string as consisting  of  a  single
1276         line of characters (even if it actually contains newlines). The  "start         line  of characters (even if it actually contains newlines). The "start
1277         of  line"  metacharacter  (^)  matches only at the start of the string,         of line" metacharacter (^) matches only at the  start  of  the  string,
1278         while the "end of line" metacharacter ($) matches only at  the  end  of         while  the  "end  of line" metacharacter ($) matches only at the end of
1279         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1280         is set). This is the same as Perl.         is set). This is the same as Perl.
1281    
1282         When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"         When  PCRE_MULTILINE  it  is set, the "start of line" and "end of line"
1283         constructs  match  immediately following or immediately before internal         constructs match immediately following or immediately  before  internal
1284         newlines in the subject string, respectively, as well as  at  the  very         newlines  in  the  subject string, respectively, as well as at the very
1285         start  and  end.  This is equivalent to Perl's /m option, and it can be         start and end. This is equivalent to Perl's /m option, and  it  can  be
1286         changed within a pattern by a (?m) option setting. If there are no new-         changed within a pattern by a (?m) option setting. If there are no new-
1287         lines  in  a  subject string, or no occurrences of ^ or $ in a pattern,         lines in a subject string, or no occurrences of ^ or $  in  a  pattern,
1288         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1289    
1290           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 1342  COMPILING A PATTERN Line 1293  COMPILING A PATTERN
1293           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1294           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1295    
1296         These options override the default newline definition that  was  chosen         These  options  override the default newline definition that was chosen
1297         when  PCRE  was built. Setting the first or the second specifies that a         when PCRE was built. Setting the first or the second specifies  that  a
1298         newline is indicated by a single character (CR  or  LF,  respectively).         newline  is  indicated  by a single character (CR or LF, respectively).
1299         Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
1300         two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies         two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
1301         that any of the three preceding sequences should be recognized. Setting         that any of the three preceding sequences should be recognized. Setting
1302         PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be         PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
1303         recognized. The Unicode newline sequences are the three just mentioned,         recognized. The Unicode newline sequences are the three just mentioned,
1304         plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,
1305         U+000C),  NEL  (next line, U+0085), LS (line separator, U+2028), and PS         U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS
1306         (paragraph separator, U+2029). The last  two  are  recognized  only  in         (paragraph  separator,  U+2029).  The  last  two are recognized only in
1307         UTF-8 mode.         UTF-8 mode.
1308    
1309         The  newline  setting  in  the  options  word  uses three bits that are         The newline setting in the  options  word  uses  three  bits  that  are
1310         treated as a number, giving eight possibilities. Currently only six are         treated as a number, giving eight possibilities. Currently only six are
1311         used  (default  plus the five values above). This means that if you set         used (default plus the five values above). This means that if  you  set
1312         more than one newline option, the combination may or may not be  sensi-         more  than one newline option, the combination may or may not be sensi-
1313         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1314         PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1315         cause an error.         cause an error.
1316    
1317         The  only time that a line break is specially recognized when compiling         The only time that a line break in a pattern  is  specially  recognized
1318         a pattern is if PCRE_EXTENDED is set, and  an  unescaped  #  outside  a         when  compiling  is when PCRE_EXTENDED is set. CR and LF are whitespace
1319         character  class  is  encountered.  This indicates a comment that lasts         characters, and so are ignored in this mode. Also, an unescaped #  out-
1320         until after the next line break sequence. In other circumstances,  line         side  a  character class indicates a comment that lasts until after the
1321         break   sequences   are   treated  as  literal  data,  except  that  in         next line break sequence. In other circumstances, line break  sequences
1322         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         in patterns are treated as literal data.
        and are therefore ignored.  
1323    
1324         The newline option that is set at compile time becomes the default that         The newline option that is set at compile time becomes the default that
1325         is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.         is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
# Line 1382  COMPILING A PATTERN Line 1332  COMPILING A PATTERN
1332         be  used  for  capturing  (and  they acquire numbers in the usual way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
1333         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1334    
1335             NO_START_OPTIMIZE
1336    
1337           This is an option that acts at matching time; that is, it is really  an
1338           option  for  pcre_exec()  or  pcre_dfa_exec().  If it is set at compile
1339           time, it is remembered with the compiled pattern and assumed at  match-
1340           ing  time.  For  details  see  the discussion of PCRE_NO_START_OPTIMIZE
1341           below.
1342    
1343           PCRE_UCP           PCRE_UCP
1344    
1345         This option changes the way PCRE processes \b, \d, \s, \w, and some  of         This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
1346         the POSIX character classes. By default, only ASCII characters are rec-         \w,  and  some  of  the POSIX character classes. By default, only ASCII
1347         ognized, but if PCRE_UCP is set, Unicode properties are used instead to         characters are recognized, but if PCRE_UCP is set,  Unicode  properties
1348         classify  characters.  More details are given in the section on generic         are  used instead to classify characters. More details are given in the
1349         character types in the pcrepattern page. If you set PCRE_UCP,  matching         section on generic character types in the pcrepattern page. If you  set
1350         one  of the items it affects takes much longer. The option is available         PCRE_UCP,  matching  one of the items it affects takes much longer. The
1351         only if PCRE has been compiled with Unicode property support.         option is available only if PCRE has been compiled with  Unicode  prop-
1352           erty support.
1353    
1354           PCRE_UNGREEDY           PCRE_UNGREEDY
1355    
1356         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1357         are  not greedy by default, but become greedy if followed by "?". It is         are not greedy by default, but become greedy if followed by "?". It  is
1358         not compatible with Perl. It can also be set by a (?U)  option  setting         not  compatible  with Perl. It can also be set by a (?U) option setting
1359         within the pattern.         within the pattern.
1360    
1361           PCRE_UTF8           PCRE_UTF8
1362    
1363         This  option  causes PCRE to regard both the pattern and the subject as         This option causes PCRE to regard both the pattern and the  subject  as
1364         strings of UTF-8 characters instead of single-byte  character  strings.         strings  of  UTF-8 characters instead of single-byte character strings.
1365         However,  it is available only when PCRE is built to include UTF-8 sup-         However, it is available only when PCRE is built to include UTF-8  sup-
1366         port. If not, the use of this option provokes an error. Details of  how         port.  If not, the use of this option provokes an error. Details of how
1367         this  option  changes the behaviour of PCRE are given in the section on         this option changes the behaviour of PCRE are given in the  pcreunicode
1368         UTF-8 support in the main pcre page.         page.
1369    
1370           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1371    
1372         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
1373         automatically  checked.  There  is  a  discussion about the validity of         automatically checked. There is a  discussion  about  the  validity  of
1374         UTF-8 strings in the main pcre page. If an invalid  UTF-8  sequence  of         UTF-8  strings  in  the main pcre page. If an invalid UTF-8 sequence of
1375         bytes  is  found,  pcre_compile() returns an error. If you already know         bytes is found, pcre_compile() returns an error. If  you  already  know
1376         that your pattern is valid, and you want to skip this check for perfor-         that your pattern is valid, and you want to skip this check for perfor-
1377         mance  reasons,  you  can set the PCRE_NO_UTF8_CHECK option. When it is         mance reasons, you can set the PCRE_NO_UTF8_CHECK option.  When  it  is
1378         set, the effect of passing an invalid UTF-8  string  as  a  pattern  is         set,  the  effect  of  passing  an invalid UTF-8 string as a pattern is
1379         undefined.  It  may  cause your program to crash. Note that this option         undefined. It may cause your program to crash. Note  that  this  option
1380         can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the         can  also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the
1381         UTF-8 validity checking of subject strings.         UTF-8 validity checking of subject strings.
1382    
1383    
1384  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1385    
1386         The  following  table  lists  the  error  codes than may be returned by         The following table lists the error  codes  than  may  be  returned  by
1387         pcre_compile2(), along with the error messages that may be returned  by         pcre_compile2(),  along with the error messages that may be returned by
1388         both  compiling functions. As PCRE has developed, some error codes have         both compiling functions. As PCRE has developed, some error codes  have
1389         fallen out of use. To avoid confusion, they have not been re-used.         fallen out of use. To avoid confusion, they have not been re-used.
1390    
1391            0  no error            0  no error
# Line 1466  COMPILATION ERROR CODES Line 1425  COMPILATION ERROR CODES
1425           34  character value in \x{...} sequence is too large           34  character value in \x{...} sequence is too large
1426           35  invalid condition (?(0)           35  invalid condition (?(0)
1427           36  \C not allowed in lookbehind assertion           36  \C not allowed in lookbehind assertion
1428           37  PCRE does not support \L, \l, \N, \U, or \u           37  PCRE does not support \L, \l, \N{name}, \U, or \u
1429           38  number after (?C is > 255           38  number after (?C is > 255
1430           39  closing ) for (?C expected           39  closing ) for (?C expected
1431           40  recursive call could loop indefinitely           40  recursive call could loop indefinitely
# Line 1500  COMPILATION ERROR CODES Line 1459  COMPILATION ERROR CODES
1459                 not allowed                 not allowed
1460           66  (*MARK) must have an argument           66  (*MARK) must have an argument
1461           67  this version of PCRE is not compiled with PCRE_UCP support           67  this version of PCRE is not compiled with PCRE_UCP support
1462             68  \c must be followed by an ASCII character
1463             69  \k is not followed by a braced, angle-bracketed, or quoted name
1464    
1465         The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different         The  numbers  32  and 10000 in errors 48 and 49 are defaults; different
1466         values may be used if the limits were changed when PCRE was built.         values may be used if the limits were changed when PCRE was built.
1467    
1468    
# Line 1510  STUDYING A PATTERN Line 1471  STUDYING A PATTERN
1471         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1472              const char **errptr);              const char **errptr);
1473    
1474         If  a  compiled  pattern is going to be used several times, it is worth         If a compiled pattern is going to be used several times,  it  is  worth
1475         spending more time analyzing it in order to speed up the time taken for         spending more time analyzing it in order to speed up the time taken for
1476         matching.  The function pcre_study() takes a pointer to a compiled pat-         matching. The function pcre_study() takes a pointer to a compiled  pat-
1477         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1478         information  that  will  help speed up matching, pcre_study() returns a         information that will help speed up matching,  pcre_study()  returns  a
1479         pointer to a pcre_extra block, in which the study_data field points  to         pointer  to a pcre_extra block, in which the study_data field points to
1480         the results of the study.         the results of the study.
1481    
1482         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1483         pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-         pcre_exec()  or  pcre_dfa_exec(). However, a pcre_extra block also con-
1484         tains  other  fields  that can be set by the caller before the block is         tains other fields that can be set by the caller before  the  block  is
1485         passed; these are described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1486    
1487         If studying the  pattern  does  not  produce  any  useful  information,         If  studying  the  pattern  does  not  produce  any useful information,
1488         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1489         wants  to  pass  any  of   the   other   fields   to   pcre_exec()   or         wants   to   pass   any   of   the   other  fields  to  pcre_exec()  or
1490         pcre_dfa_exec(), it must set up its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1491    
1492         The  second  argument of pcre_study() contains option bits. At present,         The second argument of pcre_study() contains option bits. There is only
1493         no options are defined, and this argument should always be zero.         one  option:  PCRE_STUDY_JIT_COMPILE.  If this is set, and the just-in-
1494           time compiler is  available,  the  pattern  is  further  compiled  into
1495           machine  code  that  executes much faster than the pcre_exec() matching
1496           function. If the just-in-time compiler is not available, this option is
1497           ignored. All other bits in the options argument must be zero.
1498    
1499           JIT  compilation  is  a heavyweight optimization. It can take some time
1500           for patterns to be analyzed, and for one-off matches  and  simple  pat-
1501           terns  the benefit of faster execution might be offset by a much slower
1502           study time.  Not all patterns can be optimized by the JIT compiler. For
1503           those  that cannot be handled, matching automatically falls back to the
1504           pcre_exec() interpreter. For more details, see the  pcrejit  documenta-
1505           tion.
1506    
1507         The third argument for pcre_study() is a pointer for an error  message.         The  third argument for pcre_study() is a pointer for an error message.
1508         If  studying  succeeds  (even  if no data is returned), the variable it         If studying succeeds (even if no data is  returned),  the  variable  it
1509         points to is set to NULL. Otherwise it is set to  point  to  a  textual         points  to  is  set  to NULL. Otherwise it is set to point to a textual
1510         error message. This is a static string that is part of the library. You         error message. This is a static string that is part of the library. You
1511         must not try to free it. You should test the  error  pointer  for  NULL         must  not  try  to  free it. You should test the error pointer for NULL
1512         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1513    
1514         This is a typical call to pcre_study():         When you are finished with a pattern, you can free the memory used  for
1515           the study data by calling pcre_free_study(). This function was added to
1516           the API for release 8.20. For earlier versions,  the  memory  could  be
1517           freed  with  pcre_free(), just like the pattern itself. This will still
1518           work in cases where PCRE_STUDY_JIT_COMPILE  is  not  used,  but  it  is
1519           advisable to change to the new function when convenient.
1520    
1521           pcre_extra *pe;         This  is  a typical way in which pcre_study() is used (except that in a
1522           pe = pcre_study(         real application there should be tests for errors):
1523    
1524             int rc;
1525             pcre *re;
1526             pcre_extra *sd;
1527             re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
1528             sd = pcre_study(
1529             re,             /* result of pcre_compile() */             re,             /* result of pcre_compile() */
1530             0,              /* no options exist */             0,              /* no options */
1531             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1532             rc = pcre_exec(   /* see below for details of pcre_exec() options */
1533               re, sd, "subject", 7, 0, 0, ovector, 30);
1534             ...
1535             pcre_free_study(sd);
1536             pcre_free(re);
1537    
1538         Studying a pattern does two things: first, a lower bound for the length         Studying a pattern does two things: first, a lower bound for the length
1539         of subject string that is needed to match the pattern is computed. This         of subject string that is needed to match the pattern is computed. This
1540         does not mean that there are any strings of that length that match, but         does not mean that there are any strings of that length that match, but
1541         it does guarantee that no shorter strings match. The value is  used  by         it  does  guarantee that no shorter strings match. The value is used by
1542         pcre_exec()  and  pcre_dfa_exec()  to  avoid  wasting time by trying to         pcre_exec() and pcre_dfa_exec() to avoid  wasting  time  by  trying  to
1543         match strings that are shorter than the lower bound. You can  find  out         match  strings  that are shorter than the lower bound. You can find out
1544         the value in a calling program via the pcre_fullinfo() function.         the value in a calling program via the pcre_fullinfo() function.
1545    
1546         Studying a pattern is also useful for non-anchored patterns that do not         Studying a pattern is also useful for non-anchored patterns that do not
1547         have a single fixed starting character. A bitmap of  possible  starting         have  a  single fixed starting character. A bitmap of possible starting
1548         bytes  is  created. This speeds up finding a position in the subject at         bytes is created. This speeds up finding a position in the  subject  at
1549         which to start matching.         which to start matching.
1550    
1551         The two optimizations just described can be  disabled  by  setting  the         These  two optimizations apply to both pcre_exec() and pcre_dfa_exec().
1552           However, they are not used by pcre_exec()  if  pcre_study()  is  called
1553           with  the  PCRE_STUDY_JIT_COMPILE option, and just-in-time compiling is
1554           successful.  The  optimizations  can  be  disabled   by   setting   the
1555         PCRE_NO_START_OPTIMIZE    option    when    calling    pcre_exec()   or         PCRE_NO_START_OPTIMIZE    option    when    calling    pcre_exec()   or
1556         pcre_dfa_exec(). You might want to do this  if  your  pattern  contains         pcre_dfa_exec(). You might want to do this  if  your  pattern  contains
1557         callouts,  or  make  use of (*MARK), and you make use of these in cases         callouts  or (*MARK) (which cannot be handled by the JIT compiler), and
1558         where matching fails.  See  the  discussion  of  PCRE_NO_START_OPTIMIZE         you want to make use of these facilities in cases where matching fails.
1559         below.         See the discussion of PCRE_NO_START_OPTIMIZE below.
1560    
1561    
1562  LOCALE SUPPORT  LOCALE SUPPORT
# Line 1655  INFORMATION ABOUT A PATTERN Line 1647  INFORMATION ABOUT A PATTERN
1647           size_t length;           size_t length;
1648           rc = pcre_fullinfo(           rc = pcre_fullinfo(
1649             re,               /* result of pcre_compile() */             re,               /* result of pcre_compile() */
1650             pe,               /* result of pcre_study(), or NULL */             sd,               /* result of pcre_study(), or NULL */
1651             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1652             &length);         /* where to put the data */             &length);         /* where to put the data */
1653    
# Line 1722  INFORMATION ABOUT A PATTERN Line 1714  INFORMATION ABOUT A PATTERN
1714         otherwise 0. The fourth argument should point to an int variable.  (?J)         otherwise 0. The fourth argument should point to an int variable.  (?J)
1715         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1716    
1717             PCRE_INFO_JIT
1718    
1719           Return  1  if  the  pattern was studied with the PCRE_STUDY_JIT_COMPILE
1720           option, and just-in-time compiling was successful. The fourth  argument
1721           should  point  to  an  int variable. A return value of 0 means that JIT
1722           support is not available in this version of PCRE, or that  the  pattern
1723           was not studied with the PCRE_STUDY_JIT_COMPILE option, or that the JIT
1724           compiler could not handle this particular pattern. See the pcrejit doc-
1725           umentation for details of what can and cannot be handled.
1726    
1727             PCRE_INFO_JITSIZE
1728    
1729           If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE
1730           option, return the size of the  JIT  compiled  code,  otherwise  return
1731           zero. The fourth argument should point to a size_t variable.
1732    
1733           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1734    
1735         Return  the  value of the rightmost literal byte that must exist in any         Return  the  value of the rightmost literal byte that must exist in any
# Line 1830  INFORMATION ABOUT A PATTERN Line 1838  INFORMATION ABOUT A PATTERN
1838    
1839           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1840    
1841         Return  the  size  of the compiled pattern, that is, the value that was         Return  the  size  of  the compiled pattern. The fourth argument should
1842         passed as the argument to pcre_malloc() when PCRE was getting memory in         point to a size_t variable. This value does not include the size of the
1843         which to place the compiled data. The fourth argument should point to a         pcre  structure  that  is returned by pcre_compile(). The value that is
1844         size_t variable.         passed as the argument to pcre_malloc() when pcre_compile() is  getting
1845           memory  in  which  to  place the compiled data is the value returned by
1846           this option plus the size of the pcre structure.  Studying  a  compiled
1847           pattern, with or without JIT, does not alter the value returned by this
1848           option.
1849    
1850           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1851    
1852         Return the size of the data block pointed to by the study_data field in         Return the size of the data block pointed to by the study_data field in
1853         a  pcre_extra  block.  That  is,  it  is  the  value that was passed to         a  pcre_extra  block. If pcre_extra is NULL, or there is no study data,
1854         pcre_malloc() when PCRE was getting memory into which to place the data         zero is returned. The fourth argument should point to  a  size_t  vari-
1855         created  by  pcre_study().  If pcre_extra is NULL, or there is no study         able.   The  study_data field is set by pcre_study() to record informa-
1856         data, zero is returned. The fourth argument should point  to  a  size_t         tion that will speed up matching (see the section entitled "Studying  a
1857         variable.         pattern" above). The format of the study_data block is private, but its
1858           length is made available via this option so that it can  be  saved  and
1859           restored (see the pcreprecompile documentation for details).
1860    
1861    
1862  OBSOLETE INFO FUNCTION  OBSOLETE INFO FUNCTION
# Line 1898  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1912  MATCHING A PATTERN: THE TRADITIONAL FUNC
1912         The function pcre_exec() is called to match a subject string against  a         The function pcre_exec() is called to match a subject string against  a
1913         compiled  pattern, which is passed in the code argument. If the pattern         compiled  pattern, which is passed in the code argument. If the pattern
1914         was studied, the result of the study should  be  passed  in  the  extra         was studied, the result of the study should  be  passed  in  the  extra
1915         argument.  This  function is the main matching facility of the library,         argument.  You  can call pcre_exec() with the same code and extra argu-
1916         and it operates in a Perl-like manner. For specialist use there is also         ments as many times as you like, in order to  match  different  subject
1917         an  alternative matching function, which is described below in the sec-         strings with the same pattern.
1918         tion about the pcre_dfa_exec() function.  
1919           This  function  is  the  main  matching facility of the library, and it
1920           operates in a Perl-like manner. For specialist use  there  is  also  an
1921           alternative  matching function, which is described below in the section
1922           about the pcre_dfa_exec() function.
1923    
1924         In most applications, the pattern will have been compiled (and  option-         In most applications, the pattern will have been compiled (and  option-
1925         ally  studied)  in the same process that calls pcre_exec(). However, it         ally  studied)  in the same process that calls pcre_exec(). However, it
# Line 1933  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1951  MATCHING A PATTERN: THE TRADITIONAL FUNC
1951    
1952           unsigned long int flags;           unsigned long int flags;
1953           void *study_data;           void *study_data;
1954             void *executable_jit;
1955           unsigned long int match_limit;           unsigned long int match_limit;
1956           unsigned long int match_limit_recursion;           unsigned long int match_limit_recursion;
1957           void *callout_data;           void *callout_data;
# Line 1943  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1962  MATCHING A PATTERN: THE TRADITIONAL FUNC
1962         are set. The flag bits are:         are set. The flag bits are:
1963    
1964           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
1965             PCRE_EXTRA_EXECUTABLE_JIT
1966           PCRE_EXTRA_MATCH_LIMIT           PCRE_EXTRA_MATCH_LIMIT
1967           PCRE_EXTRA_MATCH_LIMIT_RECURSION           PCRE_EXTRA_MATCH_LIMIT_RECURSION
1968           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1969           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1970           PCRE_EXTRA_MARK           PCRE_EXTRA_MARK
1971    
1972         Other  flag  bits should be set to zero. The study_data field is set in         Other  flag  bits should be set to zero. The study_data field and some-
1973         the pcre_extra block that is returned by  pcre_study(),  together  with         times the executable_jit field are set in the pcre_extra block that  is
1974         the appropriate flag bit. You should not set this yourself, but you may         returned  by pcre_study(), together with the appropriate flag bits. You
1975         add to the block by setting the other fields  and  their  corresponding         should not set these yourself, but you may add to the block by  setting
1976         flag bits.         the other fields and their corresponding flag bits.
1977    
1978         The match_limit field provides a means of preventing PCRE from using up         The match_limit field provides a means of preventing PCRE from using up
1979         a vast amount of resources when running patterns that are not going  to         a vast amount of resources when running patterns that are not going  to
# Line 1961  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1981  MATCHING A PATTERN: THE TRADITIONAL FUNC
1981         search trees. The classic example is a pattern that uses nested  unlim-         search trees. The classic example is a pattern that uses nested  unlim-
1982         ited repeats.         ited repeats.
1983    
1984         Internally,  PCRE uses a function called match() which it calls repeat-         Internally,  pcre_exec() uses a function called match(), which it calls
1985         edly (sometimes recursively). The limit set by match_limit  is  imposed         repeatedly (sometimes recursively). The limit  set  by  match_limit  is
1986         on  the  number  of times this function is called during a match, which         imposed  on the number of times this function is called during a match,
1987         has the effect of limiting the amount of  backtracking  that  can  take         which has the effect of limiting the amount of  backtracking  that  can
1988         place. For patterns that are not anchored, the count restarts from zero         take place. For patterns that are not anchored, the count restarts from
1989         for each position in the subject string.         zero for each position in the subject string.
1990    
1991         The default value for the limit can be set  when  PCRE  is  built;  the         When pcre_exec() is called with a pattern that was successfully studied
1992         default  default  is 10 million, which handles all but the most extreme         with  the  PCRE_STUDY_JIT_COMPILE  option, the way that the matching is
1993         cases. You can override the default  by  suppling  pcre_exec()  with  a         executed is entirely different. However, there is still the possibility
1994         pcre_extra     block    in    which    match_limit    is    set,    and         of  runaway  matching  that  goes  on  for a very long time, and so the
1995         PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is         match_limit value is also used in this case (but in a different way) to
1996           limit how long the matching can continue.
1997    
1998           The  default  value  for  the  limit can be set when PCRE is built; the
1999           default default is 10 million, which handles all but the  most  extreme
2000           cases.  You  can  override  the  default by suppling pcre_exec() with a
2001           pcre_extra    block    in    which    match_limit    is    set,     and
2002           PCRE_EXTRA_MATCH_LIMIT  is  set  in  the  flags  field. If the limit is
2003         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
2004    
2005         The  match_limit_recursion field is similar to match_limit, but instead         The match_limit_recursion field is similar to match_limit, but  instead
2006         of limiting the total number of times that match() is called, it limits         of limiting the total number of times that match() is called, it limits
2007         the  depth  of  recursion. The recursion depth is a smaller number than         the depth of recursion. The recursion depth is a  smaller  number  than
2008         the total number of calls, because not all calls to match() are  recur-         the  total number of calls, because not all calls to match() are recur-
2009         sive.  This limit is of use only if it is set smaller than match_limit.         sive.  This limit is of use only if it is set smaller than match_limit.
2010    
2011         Limiting  the  recursion  depth  limits the amount of stack that can be         Limiting the recursion depth limits the amount of  machine  stack  that
2012         used, or, when PCRE has been compiled to use memory on the heap instead         can  be used, or, when PCRE has been compiled to use memory on the heap
2013         of the stack, the amount of heap memory that can be used.         instead of the stack, the amount of heap memory that can be used.  This
2014           limit  is not relevant, and is ignored, if the pattern was successfully
2015         The  default  value  for  match_limit_recursion can be set when PCRE is         studied with PCRE_STUDY_JIT_COMPILE.
2016         built; the default default  is  the  same  value  as  the  default  for  
2017         match_limit.  You can override the default by suppling pcre_exec() with         The default value for match_limit_recursion can be  set  when  PCRE  is
2018         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and         built;  the  default  default  is  the  same  value  as the default for
2019         PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the         match_limit. You can override the default by suppling pcre_exec()  with
2020           a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
2021           PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
2022         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
2023    
2024         The callout_data field is used in conjunction with the  "callout"  fea-         The  callout_data  field is used in conjunction with the "callout" fea-
2025         ture, and is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
2026    
2027         The  tables  field  is  used  to  pass  a  character  tables pointer to         The tables field  is  used  to  pass  a  character  tables  pointer  to
2028         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec();  this overrides the value that is stored with the compiled
2029         pattern.  A  non-NULL value is stored with the compiled pattern only if         pattern. A non-NULL value is stored with the compiled pattern  only  if
2030         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
2031         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
2032         PCRE's internal tables to be used. This facility is  helpful  when  re-         PCRE's  internal  tables  to be used. This facility is helpful when re-
2033         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
2034         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
2035         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
2036         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
2037    
2038         If PCRE_EXTRA_MARK is set in the flags field, the mark  field  must  be         If  PCRE_EXTRA_MARK  is  set in the flags field, the mark field must be
2039         set  to  point  to a char * variable. If the pattern contains any back-         set to point to a char * variable. If the pattern  contains  any  back-
2040         tracking control verbs such as (*MARK:NAME), and the execution ends  up         tracking  control verbs such as (*MARK:NAME), and the execution ends up
2041         with  a  name  to  pass back, a pointer to the name string (zero termi-         with a name to pass back, a pointer to the  name  string  (zero  termi-
2042         nated) is placed in the variable pointed to  by  the  mark  field.  The         nated)  is  placed  in  the  variable pointed to by the mark field. The
2043         names  are  within  the  compiled pattern; if you wish to retain such a         names are within the compiled pattern; if you wish  to  retain  such  a
2044         name you must copy it before freeing the memory of a compiled  pattern.         name  you must copy it before freeing the memory of a compiled pattern.
2045         If  there  is no name to pass back, the variable pointed to by the mark         If there is no name to pass back, the variable pointed to by  the  mark
2046         field set to NULL. For details of the backtracking control  verbs,  see         field  set  to NULL. For details of the backtracking control verbs, see
2047         the section entitled "Backtracking control" in the pcrepattern documen-         the section entitled "Backtracking control" in the pcrepattern documen-
2048         tation.         tation.
2049    
2050     Option bits for pcre_exec()     Option bits for pcre_exec()
2051    
2052         The unused bits of the options argument for pcre_exec() must  be  zero.         The  unused  bits of the options argument for pcre_exec() must be zero.
2053         The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,         The only bits that may  be  set  are  PCRE_ANCHORED,  PCRE_NEWLINE_xxx,
2054         PCRE_NOTBOL,   PCRE_NOTEOL,    PCRE_NOTEMPTY,    PCRE_NOTEMPTY_ATSTART,         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
2055         PCRE_NO_START_OPTIMIZE,   PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,  and         PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
2056         PCRE_PARTIAL_HARD.         PCRE_PARTIAL_HARD.
2057    
2058           If the pattern was successfully studied with the PCRE_STUDY_JIT_COMPILE
2059           option,  the   only   supported   options   for   JIT   execution   are
2060           PCRE_NO_UTF8_CHECK,   PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,  and
2061           PCRE_NOTEMPTY_ATSTART. Note in particular that partial matching is  not
2062           supported.  If an unsupported option is used, JIT execution is disabled
2063           and the normal interpretive code in pcre_exec() is run.
2064    
2065           PCRE_ANCHORED           PCRE_ANCHORED
2066    
2067         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first
# Line 2123  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2159  MATCHING A PATTERN: THE TRADITIONAL FUNC
2159         set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that         set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that
2160         fails, by advancing the starting offset (see below) and trying an ordi-         fails, by advancing the starting offset (see below) and trying an ordi-
2161         nary  match  again. There is some code that demonstrates how to do this         nary  match  again. There is some code that demonstrates how to do this
2162         in the pcredemo sample program.         in the pcredemo sample program. In the most general case, you  have  to
2163           check  to  see  if the newline convention recognizes CRLF as a newline,
2164           and if so, and the current character is CR followed by LF, advance  the
2165           starting offset by two characters instead of one.
2166    
2167           PCRE_NO_START_OPTIMIZE           PCRE_NO_START_OPTIMIZE
2168    
2169         There are a number of optimizations that pcre_exec() uses at the  start         There  are a number of optimizations that pcre_exec() uses at the start
2170         of  a  match,  in  order to speed up the process. For example, if it is         of a match, in order to speed up the process. For  example,  if  it  is
2171         known that an unanchored match must start with a specific character, it         known that an unanchored match must start with a specific character, it
2172         searches  the  subject  for that character, and fails immediately if it         searches the subject for that character, and fails  immediately  if  it
2173         cannot find it, without actually running the  main  matching  function.         cannot  find  it,  without actually running the main matching function.
2174         This means that a special item such as (*COMMIT) at the start of a pat-         This means that a special item such as (*COMMIT) at the start of a pat-
2175         tern is not considered until after a suitable starting  point  for  the         tern  is  not  considered until after a suitable starting point for the
2176         match  has been found. When callouts or (*MARK) items are in use, these         match has been found. When callouts or (*MARK) items are in use,  these
2177         "start-up" optimizations can cause them to be skipped if the pattern is         "start-up" optimizations can cause them to be skipped if the pattern is
2178         never  actually  used.  The start-up optimizations are in effect a pre-         never actually used. The start-up optimizations are in  effect  a  pre-
2179         scan of the subject that takes place before the pattern is run.         scan of the subject that takes place before the pattern is run.
2180    
2181         The PCRE_NO_START_OPTIMIZE option disables the start-up  optimizations,         The  PCRE_NO_START_OPTIMIZE option disables the start-up optimizations,
2182         possibly  causing  performance  to  suffer,  but ensuring that in cases         possibly causing performance to suffer,  but  ensuring  that  in  cases
2183         where the result is "no match", the callouts do occur, and  that  items         where  the  result is "no match", the callouts do occur, and that items
2184         such as (*COMMIT) and (*MARK) are considered at every possible starting         such as (*COMMIT) and (*MARK) are considered at every possible starting
2185         position in the subject  string.   Setting  PCRE_NO_START_OPTIMIZE  can         position  in  the  subject  string. If PCRE_NO_START_OPTIMIZE is set at
2186         change the outcome of a matching operation.  Consider the pattern         compile time, it cannot be unset at matching time.
2187    
2188           Setting PCRE_NO_START_OPTIMIZE can change the  outcome  of  a  matching
2189           operation.  Consider the pattern
2190    
2191           (*COMMIT)ABC           (*COMMIT)ABC
2192    
# Line 2179  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2221  MATCHING A PATTERN: THE TRADITIONAL FUNC
2221         points  to  the start of a UTF-8 character. There is a discussion about         points  to  the start of a UTF-8 character. There is a discussion about
2222         the validity of UTF-8 strings in the section on UTF-8  support  in  the         the validity of UTF-8 strings in the section on UTF-8  support  in  the
2223         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,
2224         pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-         pcre_exec() returns  the  error  PCRE_ERROR_BADUTF8  or,  if  PCRE_PAR-
2225         tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.         TIAL_HARD  is set and the problem is a truncated UTF-8 character at the
2226           end of the subject, PCRE_ERROR_SHORTUTF8. In  both  cases,  information
2227           about  the  precise  nature  of the error may also be returned (see the
2228           descriptions of these errors in the section entitled Error return  val-
2229           ues from pcre_exec() below).  If startoffset contains a value that does
2230           not point to the start of a UTF-8 character (or to the end of the  sub-
2231           ject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2232    
2233         If  you  already  know that your subject is valid, and you want to skip         If  you  already  know that your subject is valid, and you want to skip
2234         these   checks   for   performance   reasons,   you   can    set    the         these   checks   for   performance   reasons,   you   can    set    the
# Line 2188  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2236  MATCHING A PATTERN: THE TRADITIONAL FUNC
2236         do this for the second and subsequent calls to pcre_exec() if  you  are         do this for the second and subsequent calls to pcre_exec() if  you  are
2237         making  repeated  calls  to  find  all  the matches in a single subject         making  repeated  calls  to  find  all  the matches in a single subject
2238         string. However, you should be  sure  that  the  value  of  startoffset         string. However, you should be  sure  that  the  value  of  startoffset
2239         points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is         points  to  the start of a UTF-8 character (or the end of the subject).
2240         set, the effect of passing an invalid UTF-8 string as a subject,  or  a         When PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid  UTF-8
2241         value  of startoffset that does not point to the start of a UTF-8 char-         string  as  a  subject or an invalid value of startoffset is undefined.
2242         acter, is undefined. Your program may crash.         Your program may crash.
2243    
2244           PCRE_PARTIAL_HARD           PCRE_PARTIAL_HARD
2245           PCRE_PARTIAL_SOFT           PCRE_PARTIAL_SOFT
# Line 2200  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2248  MATCHING A PATTERN: THE TRADITIONAL FUNC
2248         patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial         patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
2249         match occurs if the end of the subject string is reached  successfully,         match occurs if the end of the subject string is reached  successfully,
2250         but  there  are not enough subject characters to complete the match. If         but  there  are not enough subject characters to complete the match. If
2251         this happens when PCRE_PARTIAL_HARD  is  set,  pcre_exec()  immediately         this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
2252         returns  PCRE_ERROR_PARTIAL.  Otherwise,  if  PCRE_PARTIAL_SOFT is set,         matching  continues  by  testing any remaining alternatives. Only if no
2253         matching continues by testing any other alternatives. Only if they  all         complete match can be found is PCRE_ERROR_PARTIAL returned  instead  of
2254         fail  is  PCRE_ERROR_PARTIAL  returned (instead of PCRE_ERROR_NOMATCH).         PCRE_ERROR_NOMATCH.  In  other  words,  PCRE_PARTIAL_SOFT says that the
2255         The portion of the string that was inspected when the partial match was         caller is prepared to handle a partial match, but only if  no  complete
2256         found  is  set  as  the first matching string. There is a more detailed         match can be found.
2257         discussion in the pcrepartial documentation.  
2258           If  PCRE_PARTIAL_HARD  is  set, it overrides PCRE_PARTIAL_SOFT. In this
2259           case, if a partial match  is  found,  pcre_exec()  immediately  returns
2260           PCRE_ERROR_PARTIAL,  without  considering  any  other  alternatives. In
2261           other words, when PCRE_PARTIAL_HARD is set, a partial match is  consid-
2262           ered to be more important that an alternative complete match.
2263    
2264           In  both  cases,  the portion of the string that was inspected when the
2265           partial match was found is set as the first matching string. There is a
2266           more  detailed  discussion  of partial and multi-segment matching, with
2267           examples, in the pcrepartial documentation.
2268    
2269     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2270    
2271         The subject string is passed to pcre_exec() as a pointer in subject,  a         The subject string is passed to pcre_exec() as a pointer in subject,  a
2272         length (in bytes) in length, and a starting byte offset in startoffset.         length (in bytes) in length, and a starting byte offset in startoffset.
2273         In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-         If this is  negative  or  greater  than  the  length  of  the  subject,
2274         acter.  Unlike  the pattern string, the subject may contain binary zero         pcre_exec()  returns  PCRE_ERROR_BADOFFSET. When the starting offset is
2275         bytes. When the starting offset is zero, the search for a match  starts         zero, the search for a match starts at the beginning  of  the  subject,
2276         at  the  beginning  of  the subject, and this is by far the most common         and this is by far the most common case. In UTF-8 mode, the byte offset
2277         case.         must point to the start of a UTF-8 character (or the end  of  the  sub-
2278           ject).  Unlike  the pattern string, the subject may contain binary zero
2279           bytes.
2280    
2281         A non-zero starting offset is useful when searching for  another  match         A non-zero starting offset is useful when searching for  another  match
2282         in  the same subject by calling pcre_exec() again after a previous suc-         in  the same subject by calling pcre_exec() again after a previous suc-
# Line 2237  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2297  MATCHING A PATTERN: THE TRADITIONAL FUNC
2297         rence of "iss" because it is able to look behind the starting point  to         rence of "iss" because it is able to look behind the starting point  to
2298         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2299    
2300         If  a  non-zero starting offset is passed when the pattern is anchored,         Finding  all  the  matches  in a subject is tricky when the pattern can
2301           match an empty string. It is possible to emulate Perl's /g behaviour by
2302           first   trying   the   match   again  at  the  same  offset,  with  the
2303           PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED  options,  and  then  if  that
2304           fails,  advancing  the  starting  offset  and  trying an ordinary match
2305           again. There is some code that demonstrates how to do this in the pcre-
2306           demo sample program. In the most general case, you have to check to see
2307           if the newline convention recognizes CRLF as a newline, and if so,  and
2308           the current character is CR followed by LF, advance the starting offset
2309           by two characters instead of one.
2310    
2311           If a non-zero starting offset is passed when the pattern  is  anchored,
2312         one attempt to match at the given offset is made. This can only succeed         one attempt to match at the given offset is made. This can only succeed
2313         if  the  pattern  does  not require the match to be at the start of the         if the pattern does not require the match to be at  the  start  of  the
2314         subject.         subject.
2315    
2316     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2317    
2318         In general, a pattern matches a certain portion of the subject, and  in         In  general, a pattern matches a certain portion of the subject, and in
2319         addition,  further  substrings  from  the  subject may be picked out by         addition, further substrings from the subject  may  be  picked  out  by
2320         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,
2321         this  is  called "capturing" in what follows, and the phrase "capturing         this is called "capturing" in what follows, and the  phrase  "capturing
2322         subpattern" is used for a fragment of a pattern that picks out  a  sub-         subpattern"  is  used for a fragment of a pattern that picks out a sub-
2323         string.  PCRE  supports several other kinds of parenthesized subpattern         string. PCRE supports several other kinds of  parenthesized  subpattern
2324         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2325    
2326         Captured substrings are returned to the caller via a vector of integers         Captured substrings are returned to the caller via a vector of integers
2327         whose  address is passed in ovector. The number of elements in the vec-         whose address is passed in ovector. The number of elements in the  vec-
2328         tor is passed in ovecsize, which must be a non-negative  number.  Note:         tor  is  passed in ovecsize, which must be a non-negative number. Note:
2329         this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2330    
2331         The  first  two-thirds of the vector is used to pass back captured sub-         The first two-thirds of the vector is used to pass back  captured  sub-
2332         strings, each substring using a pair of integers. The  remaining  third         strings,  each  substring using a pair of integers. The remaining third
2333         of  the  vector is used as workspace by pcre_exec() while matching cap-         of the vector is used as workspace by pcre_exec() while  matching  cap-
2334         turing subpatterns, and is not available for passing back  information.         turing  subpatterns, and is not available for passing back information.
2335         The  number passed in ovecsize should always be a multiple of three. If         The number passed in ovecsize should always be a multiple of three.  If
2336         it is not, it is rounded down.         it is not, it is rounded down.
2337    
2338         When a match is successful, information about  captured  substrings  is         When  a  match  is successful, information about captured substrings is
2339         returned  in  pairs  of integers, starting at the beginning of ovector,         returned in pairs of integers, starting at the  beginning  of  ovector,
2340         and continuing up to two-thirds of its length at the  most.  The  first         and  continuing  up  to two-thirds of its length at the most. The first
2341         element  of  each pair is set to the byte offset of the first character         element of each pair is set to the byte offset of the  first  character
2342         in a substring, and the second is set to the byte offset of  the  first         in  a  substring, and the second is set to the byte offset of the first
2343         character  after  the end of a substring. Note: these values are always         character after the end of a substring. Note: these values  are  always
2344         byte offsets, even in UTF-8 mode. They are not character counts.         byte offsets, even in UTF-8 mode. They are not character counts.
2345    
2346         The first pair of integers, ovector[0]  and  ovector[1],  identify  the         The  first  pair  of  integers, ovector[0] and ovector[1], identify the
2347         portion  of  the subject string matched by the entire pattern. The next         portion of the subject string matched by the entire pattern.  The  next
2348         pair is used for the first capturing subpattern, and so on.  The  value         pair  is  used for the first capturing subpattern, and so on. The value
2349         returned by pcre_exec() is one more than the highest numbered pair that         returned by pcre_exec() is one more than the highest numbered pair that
2350         has been set.  For example, if two substrings have been  captured,  the         has  been  set.  For example, if two substrings have been captured, the
2351         returned  value is 3. If there are no capturing subpatterns, the return         returned value is 3. If there are no capturing subpatterns, the  return
2352         value from a successful match is 1, indicating that just the first pair         value from a successful match is 1, indicating that just the first pair
2353         of offsets has been set.         of offsets has been set.
2354    
2355         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2356         of the string that it matched that is returned.         of the string that it matched that is returned.
2357    
2358         If the vector is too small to hold all the captured substring  offsets,         If  the vector is too small to hold all the captured substring offsets,
2359         it is used as far as possible (up to two-thirds of its length), and the         it is used as far as possible (up to two-thirds of its length), and the
2360         function returns a value of zero. If the substring offsets are  not  of         function  returns a value of zero. If neither the actual string matched
2361         interest,  pcre_exec()  may  be  called with ovector passed as NULL and         not any captured substrings are of interest, pcre_exec() may be  called
2362         ovecsize as zero. However, if the pattern contains back references  and         with  ovector passed as NULL and ovecsize as zero. However, if the pat-
2363         the  ovector is not big enough to remember the related substrings, PCRE         tern contains back references and the ovector  is  not  big  enough  to
2364         has to get additional memory for use during matching. Thus it  is  usu-         remember  the related substrings, PCRE has to get additional memory for
2365         ally advisable to supply an ovector.         use during matching. Thus it is usually advisable to supply an  ovector
2366           of reasonable size.
2367    
2368           There  are  some  cases where zero is returned (indicating vector over-
2369           flow) when in fact the vector is exactly the right size for  the  final
2370           match. For example, consider the pattern
2371    
2372             (a)(?:(b)c|bd)
2373    
2374           If  a  vector of 6 elements (allowing for only 1 captured substring) is
2375           given with subject string "abd", pcre_exec() will try to set the second
2376           captured string, thereby recording a vector overflow, before failing to
2377           match "c" and backing up  to  try  the  second  alternative.  The  zero
2378           return,  however,  does  correctly  indicate that the maximum number of
2379           slots (namely 2) have been filled. In similar cases where there is tem-
2380           porary  overflow,  but  the final number of used slots is actually less
2381           than the maximum, a non-zero value is returned.
2382    
2383         The pcre_fullinfo() function can be used to find out how many capturing         The pcre_fullinfo() function can be used to find out how many capturing
2384         subpatterns there are in a compiled  pattern.  The  smallest  size  for         subpatterns  there  are  in  a  compiled pattern. The smallest size for
2385         ovector  that  will allow for n captured substrings, in addition to the         ovector that will allow for n captured substrings, in addition  to  the
2386         offsets of the substring matched by the whole pattern, is (n+1)*3.         offsets of the substring matched by the whole pattern, is (n+1)*3.
2387    
2388         It is possible for capturing subpattern number n+1 to match  some  part         It  is  possible for capturing subpattern number n+1 to match some part
2389         of the subject when subpattern n has not been used at all. For example,         of the subject when subpattern n has not been used at all. For example,
2390         if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the         if  the  string  "abc"  is  matched against the pattern (a|(z))(bc) the
2391         return from the function is 4, and subpatterns 1 and 3 are matched, but         return from the function is 4, and subpatterns 1 and 3 are matched, but
2392         2 is not. When this happens, both values in  the  offset  pairs  corre-         2  is  not.  When  this happens, both values in the offset pairs corre-
2393         sponding to unused subpatterns are set to -1.         sponding to unused subpatterns are set to -1.
2394    
2395         Offset  values  that correspond to unused subpatterns at the end of the         Offset values that correspond to unused subpatterns at the end  of  the
2396         expression are also set to -1. For example,  if  the  string  "abc"  is         expression  are  also  set  to  -1. For example, if the string "abc" is
2397         matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not         matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are  not
2398         matched. The return from the function is 2, because  the  highest  used         matched.  The  return  from the function is 2, because the highest used
2399         capturing subpattern number is 1. However, you can refer to the offsets         capturing subpattern number is 1, and the offsets for  for  the  second
2400         for the second and third capturing subpatterns if  you  wish  (assuming         and  third  capturing subpatterns (assuming the vector is large enough,
2401         the vector is large enough, of course).         of course) are set to -1.
2402    
2403           Note: Elements in the first two-thirds of ovector that  do  not  corre-
2404           spond  to  capturing parentheses in the pattern are never changed. That
2405           is, if a pattern contains n capturing parentheses, no more  than  ovec-
2406           tor[0]  to ovector[2n+1] are set by pcre_exec(). The other elements (in
2407           the first two-thirds) retain whatever values they previously had.
2408    
2409         Some  convenience  functions  are  provided for extracting the captured         Some convenience functions are provided  for  extracting  the  captured
2410         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
2411    
2412     Error return values from pcre_exec()     Error return values from pcre_exec()
2413    
2414         If pcre_exec() fails, it returns a negative number. The  following  are         If  pcre_exec()  fails, it returns a negative number. The following are
2415         defined in the header file:         defined in the header file:
2416    
2417           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 2327  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2420  MATCHING A PATTERN: THE TRADITIONAL FUNC
2420    
2421           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2422    
2423         Either  code  or  subject  was  passed as NULL, or ovector was NULL and         Either code or subject was passed as NULL,  or  ovector  was  NULL  and
2424         ovecsize was not zero.         ovecsize was not zero.
2425    
2426           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 2336  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2429  MATCHING A PATTERN: THE TRADITIONAL FUNC
2429    
2430           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2431    
2432         PCRE stores a 4-byte "magic number" at the start of the compiled  code,         PCRE  stores a 4-byte "magic number" at the start of the compiled code,
2433         to catch the case when it is passed a junk pointer and to detect when a         to catch the case when it is passed a junk pointer and to detect when a
2434         pattern that was compiled in an environment of one endianness is run in         pattern that was compiled in an environment of one endianness is run in
2435         an  environment  with the other endianness. This is the error that PCRE         an environment with the other endianness. This is the error  that  PCRE
2436         gives when the magic number is not present.         gives when the magic number is not present.
2437    
2438           PCRE_ERROR_UNKNOWN_OPCODE (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2439    
2440         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2441         compiled  pattern.  This  error  could be caused by a bug in PCRE or by         compiled pattern. This error could be caused by a bug  in  PCRE  or  by
2442         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2443    
2444           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2445    
2446         If a pattern contains back references, but the ovector that  is  passed         If  a  pattern contains back references, but the ovector that is passed
2447         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2448         PCRE gets a block of memory at the start of matching to  use  for  this         PCRE  gets  a  block of memory at the start of matching to use for this
2449         purpose.  If the call via pcre_malloc() fails, this error is given. The         purpose. If the call via pcre_malloc() fails, this error is given.  The
2450         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2451    
2452         This error is also given if pcre_stack_malloc() fails  in  pcre_exec().         This  error  is also given if pcre_stack_malloc() fails in pcre_exec().
2453         This  can happen only when PCRE has been compiled with --disable-stack-         This can happen only when PCRE has been compiled with  --disable-stack-
2454         for-recursion.         for-recursion.
2455    
2456           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2457    
2458         This error is used by the pcre_copy_substring(),  pcre_get_substring(),         This  error is used by the pcre_copy_substring(), pcre_get_substring(),
2459         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2460         returned by pcre_exec().         returned by pcre_exec().
2461    
2462           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2463    
2464         The backtracking limit, as specified by  the  match_limit  field  in  a         The  backtracking  limit,  as  specified  by the match_limit field in a
2465         pcre_extra  structure  (or  defaulted) was reached. See the description         pcre_extra structure (or defaulted) was reached.  See  the  description
2466         above.         above.
2467    
2468           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2469    
2470         This error is never generated by pcre_exec() itself. It is provided for         This error is never generated by pcre_exec() itself. It is provided for
2471         use  by  callout functions that want to yield a distinctive error code.         use by callout functions that want to yield a distinctive  error  code.
2472         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2473    
2474           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2475    
2476         A string that contains an invalid UTF-8 byte sequence was passed  as  a         A  string  that contains an invalid UTF-8 byte sequence was passed as a
2477         subject.         subject, and the PCRE_NO_UTF8_CHECK option was not set. If the size  of
2478           the  output  vector  (ovecsize)  is  at least 2, the byte offset to the
2479           start of the the invalid UTF-8 character is placed in  the  first  ele-
2480           ment,  and  a  reason  code is placed in the second element. The reason
2481           codes are listed in the following section.  For backward compatibility,
2482           if  PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8 char-
2483           acter  at  the  end  of  the   subject   (reason   codes   1   to   5),
2484           PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2485    
2486           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2487    
2488         The UTF-8 byte sequence that was passed as a subject was valid, but the         The  UTF-8  byte  sequence that was passed as a subject was checked and
2489         value of startoffset did not point to the beginning of a UTF-8  charac-         found to be valid (the PCRE_NO_UTF8_CHECK option was not set), but  the
2490         ter.         value  of startoffset did not point to the beginning of a UTF-8 charac-
2491           ter or the end of the subject.
2492    
2493           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2494    
2495         The  subject  string did not match, but it did match partially. See the         The subject string did not match, but it did match partially.  See  the
2496         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
2497    
2498           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2499    
2500         This code is no longer in  use.  It  was  formerly  returned  when  the         This  code  is  no  longer  in  use.  It was formerly returned when the
2501         PCRE_PARTIAL  option  was used with a compiled pattern containing items         PCRE_PARTIAL option was used with a compiled pattern  containing  items
2502         that were  not  supported  for  partial  matching.  From  release  8.00         that  were  not  supported  for  partial  matching.  From  release 8.00
2503         onwards, there are no restrictions on partial matching.         onwards, there are no restrictions on partial matching.
2504    
2505           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2506    
2507         An  unexpected  internal error has occurred. This error could be caused         An unexpected internal error has occurred. This error could  be  caused
2508         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2509    
2510           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
# Line 2413  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2514  MATCHING A PATTERN: THE TRADITIONAL FUNC
2514           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2515    
2516         The internal recursion limit, as specified by the match_limit_recursion         The internal recursion limit, as specified by the match_limit_recursion
2517         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field in a pcre_extra structure (or defaulted)  was  reached.  See  the
2518         description above.         description above.
2519    
2520           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
2521    
2522         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2523    
2524             PCRE_ERROR_BADOFFSET      (-24)
2525    
2526           The value of startoffset was negative or greater than the length of the
2527           subject, that is, the value in length.
2528    
2529             PCRE_ERROR_SHORTUTF8      (-25)
2530    
2531           This error is returned instead of PCRE_ERROR_BADUTF8 when  the  subject
2532           string  ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD
2533           option is set.  Information  about  the  failure  is  returned  as  for
2534           PCRE_ERROR_BADUTF8.  It  is in fact sufficient to detect this case, but
2535           this special error code for PCRE_PARTIAL_HARD precedes the  implementa-
2536           tion  of returned information; it is retained for backwards compatibil-
2537           ity.
2538    
2539             PCRE_ERROR_RECURSELOOP    (-26)
2540    
2541           This error is returned when pcre_exec() detects a recursion loop within
2542           the  pattern. Specifically, it means that either the whole pattern or a
2543           subpattern has been called recursively for the second time at the  same
2544           position in the subject string. Some simple patterns that might do this
2545           are detected and faulted at compile time, but more  complicated  cases,
2546           in particular mutual recursions between two different subpatterns, can-
2547           not be detected until run time.
2548    
2549             PCRE_ERROR_JIT_STACKLIMIT (-27)
2550    
2551           This error is returned when a pattern  that  was  successfully  studied
2552           using  the PCRE_STUDY_JIT_COMPILE option is being matched, but the mem-
2553           ory available for  the  just-in-time  processing  stack  is  not  large
2554           enough. See the pcrejit documentation for more details.
2555    
2556         Error numbers -16 to -20 and -22 are not used by pcre_exec().         Error numbers -16 to -20 and -22 are not used by pcre_exec().
2557    
2558       Reason codes for invalid UTF-8 strings
2559    
2560           When pcre_exec() returns either PCRE_ERROR_BADUTF8 or PCRE_ERROR_SHORT-
2561           UTF8, and the size of the output vector (ovecsize) is at least  2,  the
2562           offset  of  the  start  of the invalid UTF-8 character is placed in the
2563           first output vector element (ovector[0]) and a reason code is placed in
2564           the  second  element  (ovector[1]). The reason codes are given names in
2565           the pcre.h header file:
2566    
2567             PCRE_UTF8_ERR1
2568             PCRE_UTF8_ERR2
2569             PCRE_UTF8_ERR3
2570             PCRE_UTF8_ERR4
2571             PCRE_UTF8_ERR5
2572    
2573           The string ends with a truncated UTF-8 character;  the  code  specifies
2574           how  many bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8
2575           characters to be no longer than 4 bytes, the  encoding  scheme  (origi-
2576           nally  defined  by  RFC  2279)  allows  for  up to 6 bytes, and this is
2577           checked first; hence the possibility of 4 or 5 missing bytes.
2578    
2579             PCRE_UTF8_ERR6
2580             PCRE_UTF8_ERR7
2581             PCRE_UTF8_ERR8
2582             PCRE_UTF8_ERR9
2583             PCRE_UTF8_ERR10
2584    
2585           The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of
2586           the  character  do  not have the binary value 0b10 (that is, either the
2587           most significant bit is 0, or the next bit is 1).
2588    
2589             PCRE_UTF8_ERR11
2590             PCRE_UTF8_ERR12
2591    
2592           A character that is valid by the RFC 2279 rules is either 5 or 6  bytes
2593           long; these code points are excluded by RFC 3629.
2594    
2595             PCRE_UTF8_ERR13
2596    
2597           A  4-byte character has a value greater than 0x10fff; these code points
2598           are excluded by RFC 3629.
2599    
2600             PCRE_UTF8_ERR14
2601    
2602           A 3-byte character has a value in the  range  0xd800  to  0xdfff;  this
2603           range  of code points are reserved by RFC 3629 for use with UTF-16, and
2604           so are excluded from UTF-8.
2605    
2606             PCRE_UTF8_ERR15
2607             PCRE_UTF8_ERR16
2608             PCRE_UTF8_ERR17
2609             PCRE_UTF8_ERR18
2610             PCRE_UTF8_ERR19
2611    
2612           A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it  codes
2613           for  a  value that can be represented by fewer bytes, which is invalid.
2614           For example, the two bytes 0xc0, 0xae give the value 0x2e,  whose  cor-
2615           rect coding uses just one byte.
2616    
2617             PCRE_UTF8_ERR20
2618    
2619           The two most significant bits of the first byte of a character have the
2620           binary value 0b10 (that is, the most significant bit is 1 and the  sec-
2621           ond  is  0). Such a byte can only validly occur as the second or subse-
2622           quent byte of a multi-byte character.
2623    
2624             PCRE_UTF8_ERR21
2625    
2626           The first byte of a character has the value 0xfe or 0xff. These  values
2627           can never occur in a valid UTF-8 string.
2628    
2629    
2630  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2631    
# Line 2436  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2640  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2640         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2641              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2642    
2643         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
2644         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
2645         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2646         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
2647         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
2648         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
2649         substrings.         substrings.
2650    
2651         A substring that contains a binary zero is correctly extracted and  has         A  substring that contains a binary zero is correctly extracted and has
2652         a  further zero added on the end, but the result is not, of course, a C         a further zero added on the end, but the result is not, of course, a  C
2653         string.  However, you can process such a string  by  referring  to  the         string.   However,  you  can  process such a string by referring to the
2654         length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2655         string().  Unfortunately, the interface to pcre_get_substring_list() is         string().  Unfortunately, the interface to pcre_get_substring_list() is
2656         not  adequate for handling strings containing binary zeros, because the         not adequate for handling strings containing binary zeros, because  the
2657         end of the final string is not independently indicated.         end of the final string is not independently indicated.
2658    
2659         The first three arguments are the same for all  three  of  these  func-         The  first  three  arguments  are the same for all three of these func-
2660         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
2661         matched, ovector is a pointer to the vector of integer offsets that was         matched, ovector is a pointer to the vector of integer offsets that was
2662         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2663         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
2664         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2665         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
2666         it  ran out of space in ovector, the value passed as stringcount should         it ran out of space in ovector, the value passed as stringcount  should
2667         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2668    
2669         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
2670         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
2671         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
2672         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
2673         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
2674         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2675         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2676         The  yield  of  the function is the length of the string, not including         The yield of the function is the length of the  string,  not  including
2677         the terminating zero, or one of these error codes:         the terminating zero, or one of these error codes:
2678    
2679           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2680    
2681         The buffer was too small for pcre_copy_substring(), or the  attempt  to         The  buffer  was too small for pcre_copy_substring(), or the attempt to
2682         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2683    
2684           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2685    
2686         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2687    
2688         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
2689         strings and builds a list of pointers to them. All this is  done  in  a         strings  and  builds  a list of pointers to them. All this is done in a
2690         single block of memory that is obtained via pcre_malloc. The address of         single block of memory that is obtained via pcre_malloc. The address of
2691         the memory block is returned via listptr, which is also  the  start  of         the  memory  block  is returned via listptr, which is also the start of
2692         the  list  of  string pointers. The end of the list is marked by a NULL         the list of string pointers. The end of the list is marked  by  a  NULL
2693         pointer. The yield of the function is zero if all  went  well,  or  the         pointer.  The  yield  of  the function is zero if all went well, or the
2694         error code         error code
2695    
2696           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2697    
2698         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2699    
2700         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
2701         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
2702         the  subject, but subpattern n has not been used at all, they return an         the subject, but subpattern n has not been used at all, they return  an
2703         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2704         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
2705         tive for unset substrings.         tive for unset substrings.
2706    
2707         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2708         string_list()  can  be  used  to free the memory returned by a previous         string_list() can be used to free the memory  returned  by  a  previous
2709         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2710         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
2711         pcre_free, which of course could be called directly from a  C  program.         pcre_free,  which  of course could be called directly from a C program.
2712         However,  PCRE is used in some situations where it is linked via a spe-         However, PCRE is used in some situations where it is linked via a  spe-
2713         cial  interface  to  another  programming  language  that  cannot   use         cial   interface  to  another  programming  language  that  cannot  use
2714         pcre_free  directly;  it is for these cases that the functions are pro-         pcre_free directly; it is for these cases that the functions  are  pro-
2715         vided.         vided.
2716    
2717    
# Line 2526  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2730  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2730              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2731              const char **stringptr);              const char **stringptr);
2732    
2733         To extract a substring by name, you first have to find associated  num-         To  extract a substring by name, you first have to find associated num-
2734         ber.  For example, for this pattern         ber.  For example, for this pattern
2735    
2736           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
# Line 2535  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2739  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2739         be unique (PCRE_DUPNAMES was not set), you can find the number from the         be unique (PCRE_DUPNAMES was not set), you can find the number from the
2740         name by calling pcre_get_stringnumber(). The first argument is the com-         name by calling pcre_get_stringnumber(). The first argument is the com-
2741         piled pattern, and the second is the name. The yield of the function is         piled pattern, and the second is the name. The yield of the function is
2742         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2743         subpattern of that name.         subpattern of that name.
2744    
2745         Given the number, you can extract the substring directly, or use one of         Given the number, you can extract the substring directly, or use one of
2746         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
2747         are also two functions that do the whole job.         are also two functions that do the whole job.
2748    
2749         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
2750         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
2751         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
2752         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
2753         differences:         differences:
2754    
2755         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
2756         ond, there is an extra argument, given at the start, which is a pointer         ond, there is an extra argument, given at the start, which is a pointer
2757         to the compiled pattern. This is needed in order to gain access to  the         to  the compiled pattern. This is needed in order to gain access to the
2758         name-to-number translation table.         name-to-number translation table.
2759    
2760         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2761         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2762         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the         ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
2763         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2764    
2765         Warning: If the pattern uses the (?| feature to set up multiple subpat-         Warning: If the pattern uses the (?| feature to set up multiple subpat-
2766         terns  with  the  same number, as described in the section on duplicate         terns with the same number, as described in the  section  on  duplicate
2767         subpattern numbers in the pcrepattern page, you  cannot  use  names  to         subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2768         distinguish  the  different subpatterns, because names are not included         distinguish the different subpatterns, because names are  not  included
2769         in the compiled code. The matching process uses only numbers. For  this         in  the compiled code. The matching process uses only numbers. For this
2770         reason,  the  use of different names for subpatterns of the same number         reason, the use of different names for subpatterns of the  same  number
2771         causes an error at compile time.         causes an error at compile time.
2772    
2773    
# Line 2572  DUPLICATE SUBPATTERN NAMES Line 2776  DUPLICATE SUBPATTERN NAMES
2776         int pcre_get_stringtable_entries(const pcre *code,         int pcre_get_stringtable_entries(const pcre *code,
2777              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2778    
2779         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2780         subpatterns  are not required to be unique. (Duplicate names are always         subpatterns are not required to be unique. (Duplicate names are  always
2781         allowed for subpatterns with the same number, created by using the  (?|         allowed  for subpatterns with the same number, created by using the (?|
2782         feature.  Indeed,  if  such subpatterns are named, they are required to         feature. Indeed, if such subpatterns are named, they  are  required  to
2783         use the same names.)         use the same names.)
2784    
2785         Normally, patterns with duplicate names are such that in any one match,         Normally, patterns with duplicate names are such that in any one match,
2786         only  one of the named subpatterns participates. An example is shown in         only one of the named subpatterns participates. An example is shown  in
2787         the pcrepattern documentation.         the pcrepattern documentation.
2788    
2789         When   duplicates   are   present,   pcre_copy_named_substring()    and         When    duplicates   are   present,   pcre_copy_named_substring()   and
2790         pcre_get_named_substring()  return the first substring corresponding to         pcre_get_named_substring() return the first substring corresponding  to
2791         the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING         the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2792         (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()         (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2793         function returns one of the numbers that are associated with the  name,         function  returns one of the numbers that are associated with the name,
2794         but it is not defined which it is.         but it is not defined which it is.
2795    
2796         If  you want to get full details of all captured substrings for a given         If you want to get full details of all captured substrings for a  given
2797         name, you must use  the  pcre_get_stringtable_entries()  function.  The         name,  you  must  use  the pcre_get_stringtable_entries() function. The
2798         first argument is the compiled pattern, and the second is the name. The         first argument is the compiled pattern, and the second is the name. The
2799         third and fourth are pointers to variables which  are  updated  by  the         third  and  fourth  are  pointers to variables which are updated by the
2800         function. After it has run, they point to the first and last entries in         function. After it has run, they point to the first and last entries in
2801         the name-to-number table  for  the  given  name.  The  function  itself         the  name-to-number  table  for  the  given  name.  The function itself
2802         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2803         there are none. The format of the table is described above in the  sec-         there  are none. The format of the table is described above in the sec-
2804         tion  entitled  Information  about  a  pattern.  Given all the relevant         tion entitled Information about a pattern above.  Given all  the  rele-
2805         entries for the name, you can extract each of their numbers, and  hence         vant  entries  for the name, you can extract each of their numbers, and
2806         the captured data, if any.         hence the captured data, if any.
2807    
2808    
2809  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
2810    
2811         The  traditional  matching  function  uses a similar algorithm to Perl,         The traditional matching function uses a  similar  algorithm  to  Perl,
2812         which stops when it finds the first match, starting at a given point in         which stops when it finds the first match, starting at a given point in
2813         the  subject.  If you want to find all possible matches, or the longest         the subject. If you want to find all possible matches, or  the  longest
2814         possible match, consider using the alternative matching  function  (see         possible  match,  consider using the alternative matching function (see
2815         below)  instead.  If you cannot use the alternative function, but still         below) instead. If you cannot use the alternative function,  but  still
2816         need to find all possible matches, you can kludge it up by  making  use         need  to  find all possible matches, you can kludge it up by making use
2817         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
2818         tation.         tation.
2819    
2820         What you have to do is to insert a callout right at the end of the pat-         What you have to do is to insert a callout right at the end of the pat-
2821         tern.   When your callout function is called, extract and save the cur-         tern.  When your callout function is called, extract and save the  cur-
2822         rent matched substring. Then return  1,  which  forces  pcre_exec()  to         rent  matched  substring.  Then  return  1, which forces pcre_exec() to
2823         backtrack  and  try other alternatives. Ultimately, when it runs out of         backtrack and try other alternatives. Ultimately, when it runs  out  of
2824         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2825    
2826    
# Line 2627  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2831  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2831              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
2832              int *workspace, int wscount);              int *workspace, int wscount);
2833    
2834         The function pcre_dfa_exec()  is  called  to  match  a  subject  string         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2835         against  a  compiled pattern, using a matching algorithm that scans the         against a compiled pattern, using a matching algorithm that  scans  the
2836         subject string just once, and does not backtrack.  This  has  different         subject  string  just  once, and does not backtrack. This has different
2837         characteristics  to  the  normal  algorithm, and is not compatible with         characteristics to the normal algorithm, and  is  not  compatible  with
2838         Perl. Some of the features of PCRE patterns are not  supported.  Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2839         theless,  there are times when this kind of matching can be useful. For         theless, there are times when this kind of matching can be useful.  For
2840         a discussion of the two matching algorithms, and  a  list  of  features         a  discussion  of  the  two matching algorithms, and a list of features
2841         that  pcre_dfa_exec() does not support, see the pcrematching documenta-         that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2842         tion.         tion.
2843    
2844         The arguments for the pcre_dfa_exec() function  are  the  same  as  for         The  arguments  for  the  pcre_dfa_exec()  function are the same as for
2845         pcre_exec(), plus two extras. The ovector argument is used in a differ-         pcre_exec(), plus two extras. The ovector argument is used in a differ-
2846         ent way, and this is described below. The other  common  arguments  are         ent  way,  and  this is described below. The other common arguments are
2847         used  in  the  same way as for pcre_exec(), so their description is not         used in the same way as for pcre_exec(), so their  description  is  not
2848         repeated here.         repeated here.
2849    
2850         The two additional arguments provide workspace for  the  function.  The         The  two  additional  arguments provide workspace for the function. The
2851         workspace  vector  should  contain at least 20 elements. It is used for         workspace vector should contain at least 20 elements. It  is  used  for
2852         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2853         workspace  will  be  needed for patterns and subjects where there are a         workspace will be needed for patterns and subjects where  there  are  a
2854         lot of potential matches.         lot of potential matches.
2855    
2856         Here is an example of a simple call to pcre_dfa_exec():         Here is an example of a simple call to pcre_dfa_exec():
# Line 2668  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2872  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2872    
2873     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2874    
2875         The unused bits of the options argument  for  pcre_dfa_exec()  must  be         The  unused  bits  of  the options argument for pcre_dfa_exec() must be
2876         zero.  The  only  bits  that  may  be  set are PCRE_ANCHORED, PCRE_NEW-         zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-
2877         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2878         PCRE_NOTEMPTY_ATSTART,       PCRE_NO_UTF8_CHECK,      PCRE_BSR_ANYCRLF,         PCRE_NOTEMPTY_ATSTART,      PCRE_NO_UTF8_CHECK,       PCRE_BSR_ANYCRLF,
2879         PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD,  PCRE_PAR-         PCRE_BSR_UNICODE,  PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD, PCRE_PAR-
2880         TIAL_SOFT,  PCRE_DFA_SHORTEST,  and PCRE_DFA_RESTART.  All but the last         TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.  All but  the  last
2881         four of these are  exactly  the  same  as  for  pcre_exec(),  so  their         four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
2882         description is not repeated here.         description is not repeated here.
2883    
2884           PCRE_PARTIAL_HARD           PCRE_PARTIAL_HARD
2885           PCRE_PARTIAL_SOFT           PCRE_PARTIAL_SOFT
2886    
2887         These  have the same general effect as they do for pcre_exec(), but the         These have the same general effect as they do for pcre_exec(), but  the
2888         details are slightly  different.  When  PCRE_PARTIAL_HARD  is  set  for         details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
2889         pcre_dfa_exec(),  it  returns PCRE_ERROR_PARTIAL if the end of the sub-         pcre_dfa_exec(), it returns PCRE_ERROR_PARTIAL if the end of  the  sub-
2890         ject is reached and there is still at least  one  matching  possibility         ject  is  reached  and there is still at least one matching possibility
2891         that requires additional characters. This happens even if some complete         that requires additional characters. This happens even if some complete
2892         matches have also been found. When PCRE_PARTIAL_SOFT is set, the return         matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2893         code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end         code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2894         of the subject is reached, there have been  no  complete  matches,  but         of  the  subject  is  reached, there have been no complete matches, but
2895         there  is  still  at least one matching possibility. The portion of the         there is still at least one matching possibility. The  portion  of  the
2896         string that was inspected when the longest partial match was  found  is         string  that  was inspected when the longest partial match was found is
2897         set as the first matching string in both cases.         set as the first matching string  in  both  cases.   There  is  a  more
2898           detailed  discussion  of partial and multi-segment matching, with exam-
2899           ples, in the pcrepartial documentation.
2900    
2901           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2902    
2903         Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
2904         stop as soon as it has found one match. Because of the way the alterna-         stop as soon as it has found one match. Because of the way the alterna-
2905         tive  algorithm  works, this is necessarily the shortest possible match         tive algorithm works, this is necessarily the shortest  possible  match
2906         at the first possible matching point in the subject string.         at the first possible matching point in the subject string.
2907    
2908           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2909    
2910         When pcre_dfa_exec() returns a partial match, it is possible to call it         When pcre_dfa_exec() returns a partial match, it is possible to call it
2911         again,  with  additional  subject characters, and have it continue with         again, with additional subject characters, and have  it  continue  with
2912         the same match. The PCRE_DFA_RESTART option requests this action;  when         the  same match. The PCRE_DFA_RESTART option requests this action; when
2913         it  is  set,  the workspace and wscount options must reference the same         it is set, the workspace and wscount options must  reference  the  same
2914         vector as before because data about the match so far is  left  in  them         vector  as  before  because data about the match so far is left in them
2915         after a partial match. There is more discussion of this facility in the         after a partial match. There is more discussion of this facility in the
2916         pcrepartial documentation.         pcrepartial documentation.
2917    
2918     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2919    
2920         When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-         When  pcre_dfa_exec()  succeeds, it may have matched more than one sub-
2921         string in the subject. Note, however, that all the matches from one run         string in the subject. Note, however, that all the matches from one run
2922         of the function start at the same point in  the  subject.  The  shorter         of  the  function  start  at the same point in the subject. The shorter
2923         matches  are all initial substrings of the longer matches. For example,         matches are all initial substrings of the longer matches. For  example,
2924         if the pattern         if the pattern
2925    
2926           <.*>           <.*>
# Line 2729  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2935  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2935           <something> <something else>           <something> <something else>
2936           <something> <something else> <something further>           <something> <something else> <something further>
2937    
2938         On success, the yield of the function is a number  greater  than  zero,         On  success,  the  yield of the function is a number greater than zero,
2939         which  is  the  number of matched substrings. The substrings themselves         which is the number of matched substrings.  The  substrings  themselves
2940         are returned in ovector. Each string uses two elements;  the  first  is         are  returned  in  ovector. Each string uses two elements; the first is
2941         the  offset  to  the start, and the second is the offset to the end. In         the offset to the start, and the second is the offset to  the  end.  In
2942         fact, all the strings have the same start  offset.  (Space  could  have         fact,  all  the  strings  have the same start offset. (Space could have
2943         been  saved by giving this only once, but it was decided to retain some         been saved by giving this only once, but it was decided to retain  some
2944         compatibility with the way pcre_exec() returns data,  even  though  the         compatibility  with  the  way pcre_exec() returns data, even though the
2945         meaning of the strings is different.)         meaning of the strings is different.)
2946    
2947         The strings are returned in reverse order of length; that is, the long-         The strings are returned in reverse order of length; that is, the long-
2948         est matching string is given first. If there were too many  matches  to         est  matching  string is given first. If there were too many matches to
2949         fit  into ovector, the yield of the function is zero, and the vector is         fit into ovector, the yield of the function is zero, and the vector  is
2950         filled with the longest matches.         filled  with  the  longest matches. Unlike pcre_exec(), pcre_dfa_exec()
2951           can use the entire ovector for returning matched strings.
2952    
2953     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2954    
# Line 2765  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2972  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2972           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2973    
2974         This  return  is given if pcre_dfa_exec() is called with an extra block         This  return  is given if pcre_dfa_exec() is called with an extra block
2975         that contains a setting of the match_limit field. This is not supported         that contains a setting of  the  match_limit  or  match_limit_recursion
2976         (it is meaningless).         fields.  This  is  not  supported (these fields are meaningless for DFA
2977           matching).
2978    
2979           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2980    
2981         This  return  is  given  if  pcre_dfa_exec()  runs  out of space in the         This return is given if  pcre_dfa_exec()  runs  out  of  space  in  the
2982         workspace vector.         workspace vector.
2983    
2984           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2985    
2986         When a recursive subpattern is processed, the matching  function  calls         When  a  recursive subpattern is processed, the matching function calls
2987         itself  recursively,  using  private vectors for ovector and workspace.         itself recursively, using private vectors for  ovector  and  workspace.
2988         This error is given if the output vector  is  not  large  enough.  This         This  error  is  given  if  the output vector is not large enough. This
2989         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2990    
2991    
2992  SEE ALSO  SEE ALSO
2993    
2994         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
2995         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2996    
2997    
# Line 2796  AUTHOR Line 3004  AUTHOR
3004    
3005  REVISION  REVISION
3006    
3007         Last updated: 21 June 2010         Last updated: 02 December 2011
3008         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3009  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3010    
3011    
# Line 2844  PCRE CALLOUTS Line 3052  PCRE CALLOUTS
3052         pattern is matched. This is useful information when you are  trying  to         pattern is matched. This is useful information when you are  trying  to
3053         optimize the performance of a particular pattern.         optimize the performance of a particular pattern.
3054    
3055           The  use  of callouts in a pattern makes it ineligible for optimization
3056           by  the  just-in-time  compiler.  Studying  such  a  pattern  with  the
3057           PCRE_STUDY_JIT_COMPILE option always fails.
3058    
3059    
3060  MISSING CALLOUTS  MISSING CALLOUTS
3061    
# Line 2864  MISSING CALLOUTS Line 3076  MISSING CALLOUTS
3076         patterns, if it has been scanned far enough.         patterns, if it has been scanned far enough.
3077    
3078         You  can disable these optimizations by passing the PCRE_NO_START_OPTI-         You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
3079         MIZE option to pcre_exec() or  pcre_dfa_exec().  This  slows  down  the         MIZE option to pcre_compile(), pcre_exec(), or pcre_dfa_exec(),  or  by
3080         matching  process,  but  does  ensure that callouts such as the example         starting the pattern with (*NO_START_OPT). This slows down the matching
3081         above are obeyed.         process, but does ensure that callouts such as the  example  above  are
3082           obeyed.
3083    
3084    
3085  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
3086    
3087         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
3088         tion  defined by pcre_callout is called (if it is set). This applies to         tion defined by pcre_callout is called (if it is set). This applies  to
3089         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
3090         only  argument  to  the callout function is a pointer to a pcre_callout         only argument to the callout function is a pointer  to  a  pcre_callout
3091         block. This structure contains the following fields:         block. This structure contains the following fields:
3092    
3093           int          version;           int         version;
3094           int          callout_number;           int         callout_number;
3095           int         *offset_vector;           int        *offset_vector;
3096           const char  *subject;           const char *subject;
3097           int          subject_length;           int         subject_length;
3098           int          start_match;           int         start_match;
3099           int          current_position;           int         current_position;
3100           int          capture_top;           int         capture_top;
3101           int          capture_last;           int         capture_last;
3102           void        *callout_data;           void       *callout_data;
3103           int          pattern_position;           int         pattern_position;
3104           int          next_item_length;           int         next_item_length;
3105             const unsigned char *mark;
3106         The version field is an integer containing the version  number  of  the  
3107         block  format. The initial version was 0; the current version is 1. The         The  version  field  is an integer containing the version number of the
3108         version number will change again in future  if  additional  fields  are         block format. The initial version was 0; the current version is 2.  The
3109           version  number  will  change  again in future if additional fields are
3110         added, but the intention is never to remove any of the existing fields.         added, but the intention is never to remove any of the existing fields.
3111    
3112         The  callout_number  field  contains the number of the callout, as com-         The callout_number field contains the number of the  callout,  as  com-
3113         piled into the pattern (that is, the number after ?C for  manual  call-         piled  into  the pattern (that is, the number after ?C for manual call-
3114         outs, and 255 for automatically generated callouts).         outs, and 255 for automatically generated callouts).
3115    
3116         The  offset_vector field is a pointer to the vector of offsets that was         The offset_vector field is a pointer to the vector of offsets that  was
3117         passed  by  the  caller  to  pcre_exec()   or   pcre_dfa_exec().   When         passed   by   the   caller  to  pcre_exec()  or  pcre_dfa_exec().  When
3118         pcre_exec()  is used, the contents can be inspected in order to extract         pcre_exec() is used, the contents can be inspected in order to  extract
3119         substrings that have been matched so  far,  in  the  same  way  as  for         substrings  that  have  been  matched  so  far,  in the same way as for
3120         extracting  substrings after a match has completed. For pcre_dfa_exec()         extracting substrings after a match has completed. For  pcre_dfa_exec()
3121         this field is not useful.         this field is not useful.
3122    
3123         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
3124         were passed to pcre_exec().         were passed to pcre_exec().
3125    
3126         The  start_match  field normally contains the offset within the subject         The start_match field normally contains the offset within  the  subject
3127         at which the current match attempt  started.  However,  if  the  escape         at  which  the  current  match  attempt started. However, if the escape
3128         sequence  \K has been encountered, this value is changed to reflect the         sequence \K has been encountered, this value is changed to reflect  the
3129         modified starting point. If the pattern is not  anchored,  the  callout         modified  starting  point.  If the pattern is not anchored, the callout
3130         function may be called several times from the same point in the pattern         function may be called several times from the same point in the pattern
3131         for different starting points in the subject.         for different starting points in the subject.
3132    
3133         The current_position field contains the offset within  the  subject  of         The  current_position  field  contains the offset within the subject of
3134         the current match pointer.         the current match pointer.
3135    
3136         When  the  pcre_exec() function is used, the capture_top field contains         When the pcre_exec() function is used, the capture_top  field  contains
3137         one more than the number of the highest numbered captured substring  so         one  more than the number of the highest numbered captured substring so
3138         far.  If  no substrings have been captured, the value of capture_top is         far. If no substrings have been captured, the value of  capture_top  is
3139         one. This is always the case when pcre_dfa_exec() is used,  because  it         one.  This  is always the case when pcre_dfa_exec() is used, because it
3140         does not support captured substrings.         does not support captured substrings.
3141    
3142         The  capture_last  field  contains the number of the most recently cap-         The capture_last field contains the number of the  most  recently  cap-
3143         tured substring. If no substrings have been captured, its value is  -1.         tured  substring. If no substrings have been captured, its value is -1.
3144         This is always the case when pcre_dfa_exec() is used.         This is always the case when pcre_dfa_exec() is used.
3145    
3146         The  callout_data  field contains a value that is passed to pcre_exec()         The callout_data field contains a value that is passed  to  pcre_exec()
3147         or pcre_dfa_exec() specifically so that it can be passed back in  call-         or  pcre_dfa_exec() specifically so that it can be passed back in call-
3148         outs.  It  is  passed  in the pcre_callout field of the pcre_extra data         outs. It is passed in the pcre_callout field  of  the  pcre_extra  data
3149         structure. If no such data was passed, the value of callout_data  in  a         structure.  If  no such data was passed, the value of callout_data in a
3150         pcre_callout  block  is  NULL. There is a description of the pcre_extra         pcre_callout block is NULL. There is a description  of  the  pcre_extra
3151         structure in the pcreapi documentation.         structure in the pcreapi documentation.
3152    
3153         The pattern_position field is present from version 1 of the  pcre_call-         The  pattern_position field is present from version 1 of the pcre_call-
3154         out structure. It contains the offset to the next item to be matched in         out structure. It contains the offset to the next item to be matched in
3155         the pattern string.         the pattern string.
3156    
3157         The next_item_length field is present from version 1 of the  pcre_call-         The  next_item_length field is present from version 1 of the pcre_call-
3158         out structure. It contains the length of the next item to be matched in         out structure. It contains the length of the next item to be matched in
3159         the pattern string. When the callout immediately precedes  an  alterna-         the  pattern  string. When the callout immediately precedes an alterna-
3160         tion  bar, a closing parenthesis, or the end of the pattern, the length         tion bar, a closing parenthesis, or the end of the pattern, the  length
3161         is zero. When the callout precedes an opening parenthesis,  the  length         is  zero.  When the callout precedes an opening parenthesis, the length
3162         is that of the entire subpattern.         is that of the entire subpattern.
3163    
3164         The  pattern_position  and next_item_length fields are intended to help         The pattern_position and next_item_length fields are intended  to  help
3165         in distinguishing between different automatic callouts, which all  have         in  distinguishing between different automatic callouts, which all have
3166         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
3167    
3168           The mark field is present from version 2 of the pcre_callout structure.
3169           In  callouts  from pcre_exec() it contains a pointer to the zero-termi-
3170           nated name of the most recently passed (*MARK),  (*PRUNE),  or  (*THEN)
3171           item in the match, or NULL if no such items have been passed. Instances
3172           of (*PRUNE) or (*THEN) without a name  do  not  obliterate  a  previous
3173           (*MARK).  In  callouts  from pcre_dfa_exec() this field always contains
3174           NULL.
3175    
3176    
3177  RETURN VALUES  RETURN VALUES
3178    
3179         The  external callout function returns an integer to PCRE. If the value         The external callout function returns an integer to PCRE. If the  value
3180         is zero, matching proceeds as normal. If  the  value  is  greater  than         is  zero,  matching  proceeds  as  normal. If the value is greater than
3181         zero,  matching  fails  at  the current point, but the testing of other         zero, matching fails at the current point, but  the  testing  of  other
3182         matching possibilities goes ahead, just as if a lookahead assertion had         matching possibilities goes ahead, just as if a lookahead assertion had
3183         failed.  If  the  value  is less than zero, the match is abandoned, and         failed. If the value is less than zero, the  match  is  abandoned,  and
3184         pcre_exec() or pcre_dfa_exec() returns the negative value.         pcre_exec() or pcre_dfa_exec() returns the negative value.
3185    
3186         Negative  values  should  normally  be   chosen   from   the   set   of         Negative   values   should   normally   be   chosen  from  the  set  of
3187         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
3188         dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is         dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is
3189         reserved  for  use  by callout functions; it will never be used by PCRE         reserved for use by callout functions; it will never be  used  by  PCRE
3190         itself.         itself.
3191    
3192    
# Line 2977  AUTHOR Line 3199  AUTHOR
3199    
3200  REVISION  REVISION
3201    
3202         Last updated: 29 September 2009         Last updated: 30 November 2011
3203         Copyright (c) 1997-2009 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3204  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3205    
3206    
# Line 2993  DIFFERENCES BETWEEN PCRE AND PERL Line 3215  DIFFERENCES BETWEEN PCRE AND PERL
3215    
3216         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
3217         handle regular expressions. The differences  described  here  are  with         handle regular expressions. The differences  described  here  are  with
3218         respect to Perl 5.10/5.11.         respect to Perl versions 5.10 and above.
3219    
3220         1.  PCRE has only a subset of Perl's UTF-8 and Unicode support. Details         1.  PCRE has only a subset of Perl's UTF-8 and Unicode support. Details
3221         of what it does have are given in the section on UTF-8 support  in  the         of what it does have are given in the pcreunicode page.
        main pcre page.  
3222    
3223         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         2. PCRE allows repeat quantifiers only on parenthesized assertions, but
3224         permits them, but they do not mean what you might think.  For  example,         they  do  not mean what you might think. For example, (?!a){3} does not
3225         (?!a){3} does not assert that the next three characters are not "a". It         assert that the next three characters are not "a". It just asserts that
3226         just asserts that the next character is not "a" three times.         the next character is not "a" three times (in principle: PCRE optimizes
3227           this to run the assertion just once). Perl allows repeat quantifiers on
3228         3. Capturing subpatterns that occur inside  negative  lookahead  asser-         other assertions such as \b, but these do not seem to have any use.
3229         tions  are  counted,  but their entries in the offsets vector are never  
3230         set. Perl sets its numerical variables from any such patterns that  are         3.  Capturing  subpatterns  that occur inside negative lookahead asser-
3231           tions are counted, but their entries in the offsets  vector  are  never
3232           set.  Perl sets its numerical variables from any such patterns that are
3233         matched before the assertion fails to match something (thereby succeed-         matched before the assertion fails to match something (thereby succeed-
3234         ing), but only if the negative lookahead assertion  contains  just  one         ing),  but  only  if the negative lookahead assertion contains just one
3235         branch.         branch.
3236    
3237         4.  Though  binary zero characters are supported in the subject string,         4. Though binary zero characters are supported in the  subject  string,
3238         they are not allowed in a pattern string because it is passed as a nor-         they are not allowed in a pattern string because it is passed as a nor-
3239         mal C string, terminated by zero. The escape sequence \0 can be used in         mal C string, terminated by zero. The escape sequence \0 can be used in
3240         the pattern to represent a binary zero.         the pattern to represent a binary zero.
3241    
3242         5. The following Perl escape sequences are not supported: \l,  \u,  \L,         5.  The  following Perl escape sequences are not supported: \l, \u, \L,
3243         \U, and \N. In fact these are implemented by Perl's general string-han-         \U, and \N when followed by a character name or Unicode value.  (\N  on
3244         dling and are not part of its pattern matching engine. If any of  these         its own, matching a non-newline character, is supported.) In fact these
3245         are encountered by PCRE, an error is generated.         are implemented by Perl's general string-handling and are not  part  of
3246           its  pattern  matching engine. If any of these are encountered by PCRE,
3247         6.  The Perl escape sequences \p, \P, and \X are supported only if PCRE         an error is generated by default. However, if the  PCRE_JAVASCRIPT_COM-
3248         is built with Unicode character property support. The  properties  that         PAT  option  is set, \U and \u are interpreted as JavaScript interprets
3249         can  be tested with \p and \P are limited to the general category prop-         them.
3250         erties such as Lu and Nd, script names such as Greek or  Han,  and  the  
3251         derived  properties  Any  and  L&. PCRE does support the Cs (surrogate)         6. The Perl escape sequences \p, \P, and \X are supported only if  PCRE
3252         property, which Perl does not; the  Perl  documentation  says  "Because         is  built  with Unicode character property support. The properties that
3253           can be tested with \p and \P are limited to the general category  prop-
3254           erties  such  as  Lu and Nd, script names such as Greek or Han, and the
3255           derived properties Any and L&. PCRE does  support  the  Cs  (surrogate)
3256           property,  which  Perl  does  not; the Perl documentation says "Because
3257         Perl hides the need for the user to understand the internal representa-         Perl hides the need for the user to understand the internal representa-
3258         tion of Unicode characters, there is no need to implement the  somewhat         tion  of Unicode characters, there is no need to implement the somewhat
3259         messy concept of surrogates."         messy concept of surrogates."
3260    
3261         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7. PCRE implements a simpler version of \X than Perl, which changed  to
3262           make  \X  match what Unicode calls an "extended grapheme cluster". This
3263           is more complicated than an extended Unicode sequence,  which  is  what
3264           PCRE matches.
3265    
3266           8. PCRE does support the \Q...\E escape for quoting substrings. Charac-
3267         ters in between are treated as literals.  This  is  slightly  different         ters in between are treated as literals.  This  is  slightly  different
3268         from  Perl  in  that  $  and  @ are also handled as literals inside the         from  Perl  in  that  $  and  @ are also handled as literals inside the
3269         quotes. In Perl, they cause variable interpolation (but of course  PCRE         quotes. In Perl, they cause variable interpolation (but of course  PCRE
# Line 3047  DIFFERENCES BETWEEN PCRE AND PERL Line 3279  DIFFERENCES BETWEEN PCRE AND PERL
3279         The  \Q...\E  sequence  is recognized both inside and outside character         The  \Q...\E  sequence  is recognized both inside and outside character
3280         classes.         classes.
3281    
3282         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})         9. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
3283         constructions.  However,  there is support for recursive patterns. This         constructions.  However,  there is support for recursive patterns. This
3284         is not available in Perl 5.8, but it is in Perl 5.10.  Also,  the  PCRE         is not available in Perl 5.8, but it is in Perl 5.10.  Also,  the  PCRE
3285         "callout"  feature allows an external function to be called during pat-         "callout"  feature allows an external function to be called during pat-
3286         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
3287    
3288         9. Subpatterns that are called  recursively  or  as  "subroutines"  are         10. Subpatterns that are called as subroutines (whether or  not  recur-
3289         always  treated  as  atomic  groups  in  PCRE. This is like Python, but         sively)  are  always  treated  as  atomic  groups in PCRE. This is like
3290         unlike Perl. There is a discussion of an example that explains this  in         Python, but unlike Perl.  Captured values that are set outside  a  sub-
3291         more  detail  in  the section on recursion differences from Perl in the         routine  call  can  be  reference from inside in PCRE, but not in Perl.
3292         pcrepattern page.         There is a discussion that explains these differences in more detail in
3293           the section on recursion differences from Perl in the pcrepattern page.
3294         10. There are some differences that are concerned with the settings  of  
3295         captured  strings  when  part  of  a  pattern is repeated. For example,         11.  If  (*THEN)  is present in a group that is called as a subroutine,
3296         matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2         its action is limited to that group, even if the group does not contain
3297           any | characters.
3298    
3299           12.  There are some differences that are concerned with the settings of
3300           captured strings when part of  a  pattern  is  repeated.  For  example,
3301           matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
3302         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
3303    
3304         11.  PCRE's handling of duplicate subpattern numbers and duplicate sub-         13. PCRE's handling of duplicate subpattern numbers and duplicate  sub-
3305         pattern names is not as general as Perl's. This is a consequence of the         pattern names is not as general as Perl's. This is a consequence of the
3306         fact the PCRE works internally just with numbers, using an external ta-         fact the PCRE works internally just with numbers, using an external ta-
3307         ble to translate between numbers and names. In  particular,  a  pattern         ble  to  translate  between numbers and names. In particular, a pattern
3308         such  as  (?|(?<a>A)|(?<b)B),  where the two capturing parentheses have         such as (?|(?<a>A)|(?<b)B), where the two  capturing  parentheses  have
3309         the same number but different names, is not supported,  and  causes  an         the  same  number  but different names, is not supported, and causes an
3310         error  at compile time. If it were allowed, it would not be possible to         error at compile time. If it were allowed, it would not be possible  to
3311         distinguish which parentheses matched, because both names map  to  cap-         distinguish  which  parentheses matched, because both names map to cap-
3312         turing subpattern number 1. To avoid this confusing situation, an error         turing subpattern number 1. To avoid this confusing situation, an error
3313         is given at compile time.         is given at compile time.
3314    
3315         12. PCRE provides some extensions to the Perl regular expression facil-         14.  Perl  recognizes  comments  in some places that PCRE does not, for
3316           example, between the ( and ? at the start of a subpattern.  If  the  /x
3317           modifier  is set, Perl allows whitespace between ( and ? but PCRE never
3318           does, even if the PCRE_EXTENDED option is set.
3319    
3320           15. PCRE provides some extensions to the Perl regular expression facil-
3321         ities.   Perl  5.10  includes new features that are not in earlier ver-         ities.   Perl  5.10  includes new features that are not in earlier ver-
3322         sions of Perl, some of which (such as named parentheses) have  been  in         sions of Perl, some of which (such as named parentheses) have  been  in
3323         PCRE for some time. This list is with respect to Perl 5.10:         PCRE for some time. This list is with respect to Perl 5.10:
# Line 3111  DIFFERENCES BETWEEN PCRE AND PERL Line 3353  DIFFERENCES BETWEEN PCRE AND PERL
3353         (i) The partial matching facility is PCRE-specific.         (i) The partial matching facility is PCRE-specific.
3354    
3355         (j) Patterns compiled by PCRE can be saved and re-used at a later time,         (j) Patterns compiled by PCRE can be saved and re-used at a later time,
3356         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.  However,  this
3357           does not apply to optimized data created by the just-in-time compiler.
3358    
3359         (k) The alternative matching function (pcre_dfa_exec())  matches  in  a         (k)  The  alternative  matching function (pcre_dfa_exec()) matches in a
3360         different way and is not Perl-compatible.         different way and is not Perl-compatible.
3361    
3362         (l)  PCRE  recognizes some special sequences such as (*CR) at the start         (l) PCRE recognizes some special sequences such as (*CR) at  the  start
3363         of a pattern that set overall options that cannot be changed within the         of a pattern that set overall options that cannot be changed within the
3364         pattern.         pattern.
3365    
# Line 3130  AUTHOR Line 3373  AUTHOR
3373    
3374  REVISION  REVISION
3375    
3376         Last updated: 12 May 2010         Last updated: 14 November 2011
3377         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3378  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3379    
3380    
# Line 3170  PCRE REGULAR EXPRESSION DETAILS Line 3413  PCRE REGULAR EXPRESSION DETAILS
3413         Starting a pattern with this sequence  is  equivalent  to  setting  the         Starting a pattern with this sequence  is  equivalent  to  setting  the
3414         PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting         PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3415         UTF-8 mode affects pattern matching  is  mentioned  in  several  places         UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3416         below.  There  is  also  a  summary of UTF-8 features in the section on         below.  There  is  also  a summary of UTF-8 features in the pcreunicode
3417         UTF-8 support in the main pcre page.         page.
3418    
3419         Another special sequence that may appear at the start of a  pattern  or         Another special sequence that may appear at the start of a  pattern  or
3420         in combination with (*UTF8) is:         in combination with (*UTF8) is:
# Line 3183  PCRE REGULAR EXPRESSION DETAILS Line 3426  PCRE REGULAR EXPRESSION DETAILS
3426         character types, instead of recognizing only characters with codes less         character types, instead of recognizing only characters with codes less
3427         than 128 via a lookup table.         than 128 via a lookup table.
3428    
3429         The remainder of this document discusses the  patterns  that  are  sup-         If a pattern starts with (*NO_START_OPT), it has  the  same  effect  as
3430         ported  by  PCRE when its main matching function, pcre_exec(), is used.         setting the PCRE_NO_START_OPTIMIZE option either at compile or matching
3431         From  release  6.0,   PCRE   offers   a   second   matching   function,         time. There are also some more of these special sequences that are con-
3432         pcre_dfa_exec(),  which matches using a different algorithm that is not         cerned with the handling of newlines; they are described below.
3433    
3434           The  remainder  of  this  document discusses the patterns that are sup-
3435           ported by PCRE when its main matching function, pcre_exec(),  is  used.
3436           From   release   6.0,   PCRE   offers   a   second  matching  function,
3437           pcre_dfa_exec(), which matches using a different algorithm that is  not
3438         Perl-compatible. Some of the features discussed below are not available         Perl-compatible. Some of the features discussed below are not available
3439         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the         when pcre_dfa_exec() is used. The advantages and disadvantages  of  the
3440         alternative function, and how it differs from the normal function,  are         alternative  function, and how it differs from the normal function, are
3441         discussed in the pcrematching page.         discussed in the pcrematching page.
3442    
3443    
3444  NEWLINE CONVENTIONS  NEWLINE CONVENTIONS
3445    
3446         PCRE  supports five different conventions for indicating line breaks in         PCRE supports five different conventions for indicating line breaks  in
3447         strings: a single CR (carriage return) character, a  single  LF  (line-         strings:  a  single  CR (carriage return) character, a single LF (line-
3448         feed) character, the two-character sequence CRLF, any of the three pre-         feed) character, the two-character sequence CRLF, any of the three pre-
3449         ceding, or any Unicode newline sequence. The pcreapi page  has  further         ceding,  or  any Unicode newline sequence. The pcreapi page has further
3450         discussion  about newlines, and shows how to set the newline convention         discussion about newlines, and shows how to set the newline  convention
3451         in the options arguments for the compiling and matching functions.         in the options arguments for the compiling and matching functions.
3452    
3453         It is also possible to specify a newline convention by starting a  pat-         It  is also possible to specify a newline convention by starting a pat-
3454         tern string with one of the following five sequences:         tern string with one of the following five sequences:
3455    
3456           (*CR)        carriage return           (*CR)        carriage return
# Line 3211  NEWLINE CONVENTIONS Line 3459  NEWLINE CONVENTIONS
3459           (*ANYCRLF)   any of the three above           (*ANYCRLF)   any of the three above
3460           (*ANY)       all Unicode newline sequences           (*ANY)       all Unicode newline sequences
3461    
3462         These  override  the default and the options given to pcre_compile() or         These override the default and the options given to  pcre_compile()  or
3463         pcre_compile2(). For example, on a Unix system where LF is the  default         pcre_compile2().  For example, on a Unix system where LF is the default
3464         newline sequence, the pattern         newline sequence, the pattern
3465    
3466           (*CR)a.b           (*CR)a.b
3467    
3468         changes the convention to CR. That pattern matches "a\nb" because LF is         changes the convention to CR. That pattern matches "a\nb" because LF is
3469         no longer a newline. Note that these special settings,  which  are  not         no  longer  a  newline. Note that these special settings, which are not
3470         Perl-compatible,  are  recognized  only at the very start of a pattern,         Perl-compatible, are recognized only at the very start  of  a  pattern,
3471         and that they must be in upper case.  If  more  than  one  of  them  is         and  that  they  must  be  in  upper  case. If more than one of them is
3472         present, the last one is used.         present, the last one is used.
3473    
3474         The  newline convention affects the interpretation of the dot metachar-         The newline convention affects the interpretation of the dot  metachar-
3475         acter when PCRE_DOTALL is not set, and also the behaviour of  \N.  How-         acter  when  PCRE_DOTALL is not set, and also the behaviour of \N. How-
3476         ever,  it  does  not  affect  what  the  \R escape sequence matches. By         ever, it does not affect  what  the  \R  escape  sequence  matches.  By
3477         default, this is any Unicode newline sequence, for Perl  compatibility.         default,  this is any Unicode newline sequence, for Perl compatibility.
3478         However,  this can be changed; see the description of \R in the section         However, this can be changed; see the description of \R in the  section
3479         entitled "Newline sequences" below. A change of \R setting can be  com-         entitled  "Newline sequences" below. A change of \R setting can be com-
3480         bined with a change of newline convention.         bined with a change of newline convention.
3481    
3482    
3483  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
3484    
3485         A  regular  expression  is  a pattern that is matched against a subject         A regular expression is a pattern that is  matched  against  a  subject
3486         string from left to right. Most characters stand for  themselves  in  a         string  from  left  to right. Most characters stand for themselves in a
3487         pattern,  and  match  the corresponding characters in the subject. As a         pattern, and match the corresponding characters in the  subject.  As  a
3488         trivial example, the pattern         trivial example, the pattern
3489    
3490           The quick brown fox           The quick brown fox
3491    
3492         matches a portion of a subject string that is identical to itself. When         matches a portion of a subject string that is identical to itself. When
3493         caseless  matching is specified (the PCRE_CASELESS option), letters are         caseless matching is specified (the PCRE_CASELESS option), letters  are
3494         matched independently of case. In UTF-8 mode, PCRE  always  understands         matched  independently  of case. In UTF-8 mode, PCRE always understands
3495         the  concept  of case for characters whose values are less than 128, so         the concept of case for characters whose values are less than  128,  so
3496         caseless matching is always possible. For characters with  higher  val-         caseless  matching  is always possible. For characters with higher val-
3497         ues,  the concept of case is supported if PCRE is compiled with Unicode         ues, the concept of case is supported if PCRE is compiled with  Unicode
3498         property support, but not otherwise.   If  you  want  to  use  caseless         property  support,  but  not  otherwise.   If  you want to use caseless
3499         matching  for  characters  128  and above, you must ensure that PCRE is         matching for characters 128 and above, you must  ensure  that  PCRE  is
3500         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
3501    
3502         The power of regular expressions comes  from  the  ability  to  include         The  power  of  regular  expressions  comes from the ability to include
3503         alternatives  and  repetitions in the pattern. These are encoded in the         alternatives and repetitions in the pattern. These are encoded  in  the
3504         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
3505         but instead are interpreted in some special way.         but instead are interpreted in some special way.
3506    
3507         There  are  two different sets of metacharacters: those that are recog-         There are two different sets of metacharacters: those that  are  recog-
3508         nized anywhere in the pattern except within square brackets, and  those         nized  anywhere in the pattern except within square brackets, and those
3509         that  are  recognized  within square brackets. Outside square brackets,         that are recognized within square brackets.  Outside  square  brackets,
3510         the metacharacters are as follows:         the metacharacters are as follows:
3511    
3512           \      general escape character with several uses           \      general escape character with several uses
# Line 3277  CHARACTERS AND METACHARACTERS Line 3525  CHARACTERS AND METACHARACTERS
3525                  also "possessive quantifier"                  also "possessive quantifier"
3526           {      start min/max quantifier           {      start min/max quantifier
3527    
3528         Part of a pattern that is in square brackets  is  called  a  "character         Part  of  a  pattern  that is in square brackets is called a "character
3529         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
3530    
3531           \      general escape character           \      general escape character
# Line 3293  CHARACTERS AND METACHARACTERS Line 3541  CHARACTERS AND METACHARACTERS
3541  BACKSLASH  BACKSLASH
3542    
3543         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3544         a non-alphanumeric character, it takes away any  special  meaning  that         a character that is not a number or a letter, it takes away any special
3545         character  may  have.  This  use  of  backslash  as an escape character         meaning that character may have. This use of  backslash  as  an  escape
3546         applies both inside and outside character classes.         character applies both inside and outside character classes.
3547    
3548         For example, if you want to match a * character, you write  \*  in  the         For  example,  if  you want to match a * character, you write \* in the
3549         pattern.   This  escaping  action  applies whether or not the following         pattern.  This escaping action applies whether  or  not  the  following
3550         character would otherwise be interpreted as a metacharacter, so  it  is         character  would  otherwise be interpreted as a metacharacter, so it is
3551         always  safe  to  precede  a non-alphanumeric with backslash to specify         always safe to precede a non-alphanumeric  with  backslash  to  specify
3552         that it stands for itself. In particular, if you want to match a  back-         that  it stands for itself. In particular, if you want to match a back-
3553         slash, you write \\.         slash, you write \\.
3554    
3555         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in         In UTF-8 mode, only ASCII numbers and letters have any special  meaning
3556         the pattern (other than in a character class) and characters between  a         after  a  backslash.  All  other characters (in particular, those whose
3557           codepoints are greater than 127) are treated as literals.
3558    
3559           If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
3560           the  pattern (other than in a character class) and characters between a
3561         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
3562         ing backslash can be used to include a whitespace  or  #  character  as         ing  backslash  can  be  used to include a whitespace or # character as
3563         part of the pattern.         part of the pattern.
3564    
3565         If  you  want  to remove the special meaning from a sequence of charac-         If you want to remove the special meaning from a  sequence  of  charac-
3566         ters, you can do so by putting them between \Q and \E. This is  differ-         ters,  you can do so by putting them between \Q and \E. This is differ-
3567         ent  from  Perl  in  that  $  and  @ are handled as literals in \Q...\E         ent from Perl in that $ and  @  are  handled  as  literals  in  \Q...\E
3568         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-
3569         tion. Note the following examples:         tion. Note the following examples:
3570    
3571           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 3323  BACKSLASH Line 3575  BACKSLASH
3575           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
3576           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3577    
3578         The  \Q...\E  sequence  is recognized both inside and outside character         The \Q...\E sequence is recognized both inside  and  outside  character
3579         classes.         classes.   An  isolated \E that is not preceded by \Q is ignored. If \Q
3580           is not followed by \E later in the pattern, the literal  interpretation
3581           continues  to  the  end  of  the pattern (that is, \E is assumed at the
3582           end). If the isolated \Q is inside a character class,  this  causes  an
3583           error, because the character class is not terminated.
3584    
3585     Non-printing characters     Non-printing characters
3586    
3587         A second use of backslash provides a way of encoding non-printing char-         A second use of backslash provides a way of encoding non-printing char-
3588         acters  in patterns in a visible manner. There is no restriction on the         acters in patterns in a visible manner. There is no restriction on  the
3589         appearance of non-printing characters, apart from the binary zero  that         appearance  of non-printing characters, apart from the binary zero that
3590         terminates  a  pattern,  but  when  a pattern is being prepared by text         terminates a pattern, but when a pattern  is  being  prepared  by  text
3591         editing, it is  often  easier  to  use  one  of  the  following  escape         editing,  it  is  often  easier  to  use  one  of  the following escape
3592         sequences than the binary character it represents:         sequences than the binary character it represents:
3593    
3594           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3595           \cx       "control-x", where x is any character           \cx       "control-x", where x is any ASCII character
3596           \e        escape (hex 1B)           \e        escape (hex 1B)
3597           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3598           \n        linefeed (hex 0A)           \n        linefeed (hex 0A)
# Line 3344  BACKSLASH Line 3600  BACKSLASH
3600           \t        tab (hex 09)           \t        tab (hex 09)
3601           \ddd      character with octal code ddd, or back reference           \ddd      character with octal code ddd, or back reference
3602           \xhh      character with hex code hh           \xhh      character with hex code hh
3603           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh.. (non-JavaScript mode)
3604             \uhhhh    character with hex code hhhh (JavaScript mode only)
3605    
3606         The  precise  effect of \cx is as follows: if x is a lower case letter,         The precise effect of \cx is as follows: if x is a lower  case  letter,
3607         it is converted to upper case. Then bit 6 of the character (hex 40)  is         it  is converted to upper case. Then bit 6 of the character (hex 40) is
3608         inverted.   Thus  \cz becomes hex 1A, but \c{ becomes hex 3B, while \c;         inverted.  Thus \cz becomes hex 1A (z is 7A), but \c{ becomes hex 3B ({
3609         becomes hex 7B.         is  7B),  while  \c; becomes hex 7B (; is 3B). If the byte following \c
3610           has a value greater than 127, a compile-time error occurs.  This  locks
3611         After \x, from zero to two hexadecimal digits are read (letters can  be         out  non-ASCII  characters in both byte mode and UTF-8 mode. (When PCRE
3612         in  upper  or  lower case). Any number of hexadecimal digits may appear         is compiled in EBCDIC mode, all byte values are  valid.  A  lower  case
3613         between \x{ and }, but the value of the character  code  must  be  less         letter is converted to upper case, and then the 0xc0 bits are flipped.)
3614         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,  
3615         the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger         By  default,  after  \x,  from  zero to two hexadecimal digits are read
3616         than the largest Unicode code point, which is 10FFFF.         (letters can be in upper or lower case). Any number of hexadecimal dig-
3617           its  may  appear between \x{ and }, but the value of the character code
3618           must be less than 256 in non-UTF-8 mode, and less than 2**31  in  UTF-8
3619           mode.  That is, the maximum value in hexadecimal is 7FFFFFFF. Note that
3620           this is bigger than the largest Unicode code point, which is 10FFFF.
3621    
3622         If  characters  other than hexadecimal digits appear between \x{ and },         If characters other than hexadecimal digits appear between \x{  and  },
3623         or if there is no terminating }, this form of escape is not recognized.         or if there is no terminating }, this form of escape is not recognized.
3624         Instead,  the  initial  \x  will  be interpreted as a basic hexadecimal         Instead, the initial \x will be  interpreted  as  a  basic  hexadecimal
3625         escape, with no following digits, giving a  character  whose  value  is         escape,  with  no  following  digits, giving a character whose value is
3626         zero.         zero.
3627    
3628           If the PCRE_JAVASCRIPT_COMPAT option is set, the interpretation  of  \x
3629           is  as  just described only when it is followed by two hexadecimal dig-
3630           its.  Otherwise, it matches a  literal  "x"  character.  In  JavaScript
3631           mode, support for code points greater than 256 is provided by \u, which
3632           must be followed by four hexadecimal digits;  otherwise  it  matches  a
3633           literal "u" character.
3634    
3635         Characters whose value is less than 256 can be defined by either of the         Characters whose value is less than 256 can be defined by either of the
3636         two syntaxes for \x. There is no difference in the way  they  are  han-         two syntaxes for \x (or by \u in JavaScript mode). There is no  differ-
3637         dled. For example, \xdc is exactly the same as \x{dc}.         ence in the way they are handled. For example, \xdc is exactly the same
3638           as \x{dc} (or \u00dc in JavaScript mode).
3639    
3640         After  \0  up  to two further octal digits are read. If there are fewer         After \0 up to two further octal digits are read. If  there  are  fewer
3641         than two digits, just  those  that  are  present  are  used.  Thus  the         than  two  digits,  just  those  that  are  present  are used. Thus the
3642         sequence \0\x\07 specifies two binary zeros followed by a BEL character         sequence \0\x\07 specifies two binary zeros followed by a BEL character
3643         (code value 7). Make sure you supply two digits after the initial  zero         (code  value 7). Make sure you supply two digits after the initial zero
3644         if the pattern character that follows is itself an octal digit.         if the pattern character that follows is itself an octal digit.
3645    
3646         The handling of a backslash followed by a digit other than 0 is compli-         The handling of a backslash followed by a digit other than 0 is compli-
3647         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
3648         its  as  a  decimal  number. If the number is less than 10, or if there         its as a decimal number. If the number is less than  10,  or  if  there
3649         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
3650         expression,  the  entire  sequence  is  taken  as  a  back reference. A         expression, the entire  sequence  is  taken  as  a  back  reference.  A
3651         description of how this works is given later, following the  discussion         description  of how this works is given later, following the discussion
3652         of parenthesized subpatterns.         of parenthesized subpatterns.
3653    
3654         Inside  a  character  class, or if the decimal number is greater than 9         Inside a character class, or if the decimal number is  greater  than  9
3655         and there have not been that many capturing subpatterns, PCRE  re-reads         and  there have not been that many capturing subpatterns, PCRE re-reads
3656         up to three octal digits following the backslash, and uses them to gen-         up to three octal digits following the backslash, and uses them to gen-
3657         erate a data character. Any subsequent digits stand for themselves.  In         erate  a data character. Any subsequent digits stand for themselves. In
3658         non-UTF-8  mode,  the  value  of a character specified in octal must be         non-UTF-8 mode, the value of a character specified  in  octal  must  be
3659         less than \400. In UTF-8 mode, values up to  \777  are  permitted.  For         less  than  \400.  In  UTF-8 mode, values up to \777 are permitted. For
3660         example:         example:
3661    
3662           \040   is another way of writing a space           \040   is another way of writing a space
# Line 3405  BACKSLASH Line 3674  BACKSLASH
3674           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
3675                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
3676    
3677         Note  that  octal  values of 100 or greater must not be introduced by a         Note that octal values of 100 or greater must not be  introduced  by  a
3678         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
3679    
3680         All the sequences that define a single character value can be used both         All the sequences that define a single character value can be used both
3681         inside  and  outside character classes. In addition, inside a character         inside and outside character classes. In addition, inside  a  character
3682         class, the sequence \b is interpreted as the backspace  character  (hex         class, \b is interpreted as the backspace character (hex 08).
3683         08).  The sequences \B, \N, \R, and \X are not special inside a charac-  
3684         ter class. Like any  other  unrecognized  escape  sequences,  they  are         \N  is not allowed in a character class. \B, \R, and \X are not special
3685         treated  as  the  literal characters "B", "N", "R", and "X" by default,         inside a character class. Like  other  unrecognized  escape  sequences,
3686         but cause an error if the PCRE_EXTRA option is set. Outside a character         they  are  treated  as  the  literal  characters  "B",  "R", and "X" by
3687         class, these sequences have different meanings.         default, but cause an error if the PCRE_EXTRA option is set. Outside  a
3688           character class, these sequences have different meanings.
3689    
3690       Unsupported escape sequences
3691    
3692           In  Perl, the sequences \l, \L, \u, and \U are recognized by its string
3693           handler and used  to  modify  the  case  of  following  characters.  By
3694           default,  PCRE does not support these escape sequences. However, if the
3695           PCRE_JAVASCRIPT_COMPAT option is set, \U matches a "U"  character,  and
3696           \u can be used to define a character by code point, as described in the
3697           previous section.
3698    
3699     Absolute and relative back references     Absolute and relative back references
3700    
3701         The  sequence  \g followed by an unsigned or a negative number, option-         The sequence \g followed by an unsigned or a negative  number,  option-
3702         ally enclosed in braces, is an absolute or relative back  reference.  A         ally  enclosed  in braces, is an absolute or relative back reference. A
3703         named back reference can be coded as \g{name}. Back references are dis-         named back reference can be coded as \g{name}. Back references are dis-
3704         cussed later, following the discussion of parenthesized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3705    
3706     Absolute and relative subroutine calls     Absolute and relative subroutine calls
3707    
3708         For compatibility with Oniguruma, the non-Perl syntax \g followed by  a         For  compatibility with Oniguruma, the non-Perl syntax \g followed by a
3709         name or a number enclosed either in angle brackets or single quotes, is         name or a number enclosed either in angle brackets or single quotes, is
3710         an alternative syntax for referencing a subpattern as  a  "subroutine".         an  alternative  syntax for referencing a subpattern as a "subroutine".
3711         Details  are  discussed  later.   Note  that  \g{...} (Perl syntax) and         Details are discussed later.   Note  that  \g{...}  (Perl  syntax)  and
3712         \g<...> (Oniguruma syntax) are not synonymous. The  former  is  a  back         \g<...>  (Oniguruma  syntax)  are  not synonymous. The former is a back
3713         reference; the latter is a subroutine call.         reference; the latter is a subroutine call.
3714    
3715     Generic character types     Generic character types
# Line 3449  BACKSLASH Line 3728  BACKSLASH
3728           \W     any "non-word" character           \W     any "non-word" character
3729    
3730         There is also the single sequence \N, which matches a non-newline char-         There is also the single sequence \N, which matches a non-newline char-
3731         acter.  This is the same as the "." metacharacter when  PCRE_DOTALL  is         acter.   This  is the same as the "." metacharacter when PCRE_DOTALL is
3732         not set.         not set. Perl also uses \N to match characters by name; PCRE  does  not
3733           support this.
3734    
3735         Each  pair of lower and upper case escape sequences partitions the com-         Each  pair of lower and upper case escape sequences partitions the com-
3736         plete set of characters into two disjoint  sets.  Any  given  character         plete set of characters into two disjoint  sets.  Any  given  character
# Line 3493  BACKSLASH Line 3773  BACKSLASH
3773         affects  \b,  and  \B  because  they are defined in terms of \w and \W.         affects  \b,  and  \B  because  they are defined in terms of \w and \W.
3774         Matching these sequences is noticeably slower when PCRE_UCP is set.         Matching these sequences is noticeably slower when PCRE_UCP is set.
3775    
3776         The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to         The sequences \h, \H, \v, and \V are features that were added  to  Perl
3777         the  other  sequences,  which  match  only ASCII characters by default,         at  release  5.10. In contrast to the other sequences, which match only
3778         these always  match  certain  high-valued  codepoints  in  UTF-8  mode,         ASCII characters by default, these  always  match  certain  high-valued
3779         whether or not PCRE_UCP is set. The horizontal space characters are:         codepoints  in UTF-8 mode, whether or not PCRE_UCP is set. The horizon-
3780           tal space characters are:
3781    
3782           U+0009     Horizontal tab           U+0009     Horizontal tab
3783           U+0020     Space           U+0020     Space
# Line 3530  BACKSLASH Line 3811  BACKSLASH
3811    
3812     Newline sequences     Newline sequences
3813    
3814         Outside  a  character class, by default, the escape sequence \R matches         Outside a character class, by default, the escape sequence  \R  matches
3815         any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8         any Unicode newline sequence. In non-UTF-8 mode \R is equivalent to the
3816         mode \R is equivalent to the following:         following:
3817    
3818           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3819    
3820         This  is  an  example  of an "atomic group", details of which are given         This is an example of an "atomic group", details  of  which  are  given
3821         below.  This particular group matches either the two-character sequence         below.  This particular group matches either the two-character sequence
3822         CR  followed  by  LF,  or  one  of  the single characters LF (linefeed,         CR followed by LF, or  one  of  the  single  characters  LF  (linefeed,
3823         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage
3824         return, U+000D), or NEL (next line, U+0085). The two-character sequence         return, U+000D), or NEL (next line, U+0085). The two-character sequence
3825         is treated as a single unit that cannot be split.         is treated as a single unit that cannot be split.
3826    
3827         In UTF-8 mode, two additional characters whose codepoints  are  greater         In  UTF-8  mode, two additional characters whose codepoints are greater
3828         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
3829         rator, U+2029).  Unicode character property support is not  needed  for         rator,  U+2029).   Unicode character property support is not needed for
3830         these characters to be recognized.         these characters to be recognized.
3831    
3832         It is possible to restrict \R to match only CR, LF, or CRLF (instead of         It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3833         the complete set  of  Unicode  line  endings)  by  setting  the  option         the  complete  set  of  Unicode  line  endings)  by  setting the option
3834         PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.         PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3835         (BSR is an abbrevation for "backslash R".) This can be made the default         (BSR is an abbrevation for "backslash R".) This can be made the default
3836         when  PCRE  is  built;  if this is the case, the other behaviour can be         when PCRE is built; if this is the case, the  other  behaviour  can  be
3837         requested via the PCRE_BSR_UNICODE option.   It  is  also  possible  to         requested  via  the  PCRE_BSR_UNICODE  option.   It is also possible to
3838         specify  these  settings  by  starting a pattern string with one of the         specify these settings by starting a pattern string  with  one  of  the
3839         following sequences:         following sequences:
3840    
3841           (*BSR_ANYCRLF)   CR, LF, or CRLF only           (*BSR_ANYCRLF)   CR, LF, or CRLF only
3842           (*BSR_UNICODE)   any Unicode newline sequence           (*BSR_UNICODE)   any Unicode newline sequence
3843    
3844         These override the default and the options given to  pcre_compile()  or         These  override  the default and the options given to pcre_compile() or
3845         pcre_compile2(),  but  they  can  be  overridden  by  options  given to         pcre_compile2(), but  they  can  be  overridden  by  options  given  to
3846         pcre_exec() or pcre_dfa_exec(). Note that these special settings, which         pcre_exec() or pcre_dfa_exec(). Note that these special settings, which
3847         are  not  Perl-compatible,  are  recognized only at the very start of a         are not Perl-compatible, are recognized only at the  very  start  of  a
3848         pattern, and that they must be in upper case. If more than one of  them         pattern,  and that they must be in upper case. If more than one of them
3849         is present, the last one is used. They can be combined with a change of         is present, the last one is used. They can be combined with a change of
3850         newline convention; for example, a pattern can start with:         newline convention; for example, a pattern can start with:
3851    
3852           (*ANY)(*BSR_ANYCRLF)           (*ANY)(*BSR_ANYCRLF)
3853    
3854         They can also be combined with the (*UTF8) or (*UCP) special sequences.         They can also be combined with the (*UTF8) or (*UCP) special sequences.
3855         Inside  a  character  class,  \R  is  treated as an unrecognized escape         Inside a character class, \R  is  treated  as  an  unrecognized  escape
3856         sequence, and so matches the letter "R" by default, but causes an error         sequence, and so matches the letter "R" by default, but causes an error
3857         if PCRE_EXTRA is set.         if PCRE_EXTRA is set.
3858    
3859     Unicode character properties     Unicode character properties
3860    
3861         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
3862         tional escape sequences that match characters with specific  properties         tional  escape sequences that match characters with specific properties
3863         are  available.   When not in UTF-8 mode, these sequences are of course         are available.  When not in UTF-8 mode, these sequences are  of  course
3864         limited to testing characters whose codepoints are less than  256,  but         limited  to  testing characters whose codepoints are less than 256, but
3865         they do work in this mode.  The extra escape sequences are:         they do work in this mode.  The extra escape sequences are:
3866    
3867           \p{xx}   a character with the xx property           \p{xx}   a character with the xx property
3868           \P{xx}   a character without the xx property           \P{xx}   a character without the xx property
3869           \X       an extended Unicode sequence           \X       an extended Unicode sequence
3870    
3871         The  property  names represented by xx above are limited to the Unicode         The property names represented by xx above are limited to  the  Unicode
3872         script names, the general category properties, "Any", which matches any         script names, the general category properties, "Any", which matches any
3873         character   (including  newline),  and  some  special  PCRE  properties         character  (including  newline),  and  some  special  PCRE   properties
3874         (described in the next section).  Other Perl properties such as  "InMu-         (described  in the next section).  Other Perl properties such as "InMu-
3875         sicalSymbols"  are  not  currently supported by PCRE. Note that \P{Any}         sicalSymbols" are not currently supported by PCRE.  Note  that  \P{Any}
3876         does not match any characters, so always causes a match failure.         does not match any characters, so always causes a match failure.
3877    
3878         Sets of Unicode characters are defined as belonging to certain scripts.         Sets of Unicode characters are defined as belonging to certain scripts.
3879         A  character from one of these sets can be matched using a script name.         A character from one of these sets can be matched using a script  name.
3880         For example:         For example:
3881    
3882           \p{Greek}           \p{Greek}
3883           \P{Han}           \P{Han}
3884    
3885         Those that are not part of an identified script are lumped together  as         Those  that are not part of an identified script are lumped together as
3886         "Common". The current list of scripts is:         "Common". The current list of scripts is:
3887    
3888         Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille,         Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille,
3889         Buginese, Buhid, Canadian_Aboriginal, Carian, Cham,  Cherokee,  Common,         Buginese,  Buhid,  Canadian_Aboriginal, Carian, Cham, Cherokee, Common,
3890         Coptic,   Cuneiform,  Cypriot,  Cyrillic,  Deseret,  Devanagari,  Egyp-         Coptic,  Cuneiform,  Cypriot,  Cyrillic,  Deseret,  Devanagari,   Egyp-
3891         tian_Hieroglyphs,  Ethiopic,  Georgian,  Glagolitic,   Gothic,   Greek,         tian_Hieroglyphs,   Ethiopic,   Georgian,  Glagolitic,  Gothic,  Greek,
3892         Gujarati,  Gurmukhi,  Han,  Hangul,  Hanunoo,  Hebrew,  Hiragana, Impe-         Gujarati, Gurmukhi,  Han,  Hangul,  Hanunoo,  Hebrew,  Hiragana,  Impe-
3893         rial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian,         rial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian,
3894         Javanese,  Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Lao,         Javanese, Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer,  Lao,
3895         Latin,  Lepcha,  Limbu,  Linear_B,  Lisu,  Lycian,  Lydian,  Malayalam,         Latin,  Lepcha,  Limbu,  Linear_B,  Lisu,  Lycian,  Lydian,  Malayalam,
3896         Meetei_Mayek,  Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham, Old_Italic,         Meetei_Mayek, Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham,  Old_Italic,
3897         Old_Persian, Old_South_Arabian, Old_Turkic, Ol_Chiki,  Oriya,  Osmanya,         Old_Persian,  Old_South_Arabian,  Old_Turkic, Ol_Chiki, Oriya, Osmanya,
3898         Phags_Pa,  Phoenician,  Rejang,  Runic, Samaritan, Saurashtra, Shavian,         Phags_Pa, Phoenician, Rejang, Runic,  Samaritan,  Saurashtra,  Shavian,
3899         Sinhala, Sundanese, Syloti_Nagri, Syriac,  Tagalog,  Tagbanwa,  Tai_Le,         Sinhala,  Sundanese,  Syloti_Nagri,  Syriac, Tagalog, Tagbanwa, Tai_Le,
3900         Tai_Tham,  Tai_Viet,  Tamil,  Telugu,  Thaana, Thai, Tibetan, Tifinagh,         Tai_Tham, Tai_Viet, Tamil, Telugu,  Thaana,  Thai,  Tibetan,  Tifinagh,
3901         Ugaritic, Vai, Yi.         Ugaritic, Vai, Yi.
3902    
3903         Each character has exactly one Unicode general category property, spec-         Each character has exactly one Unicode general category property, spec-
3904         ified  by a two-letter abbreviation. For compatibility with Perl, nega-         ified by a two-letter abbreviation. For compatibility with Perl,  nega-
3905         tion can be specified by including a  circumflex  between  the  opening         tion  can  be  specified  by including a circumflex between the opening
3906         brace  and  the  property  name.  For  example,  \p{^Lu} is the same as         brace and the property name.  For  example,  \p{^Lu}  is  the  same  as
3907         \P{Lu}.         \P{Lu}.
3908    
3909         If only one letter is specified with \p or \P, it includes all the gen-         If only one letter is specified with \p or \P, it includes all the gen-
3910         eral  category properties that start with that letter. In this case, in         eral category properties that start with that letter. In this case,  in
3911         the absence of negation, the curly brackets in the escape sequence  are         the  absence of negation, the curly brackets in the escape sequence are
3912         optional; these two examples have the same effect:         optional; these two examples have the same effect:
3913    
3914           \p{L}           \p{L}
# Line 3679  BACKSLASH Line 3960  BACKSLASH
3960           Zp    Paragraph separator           Zp    Paragraph separator
3961           Zs    Space separator           Zs    Space separator
3962    
3963         The  special property L& is also supported: it matches a character that         The special property L& is also supported: it matches a character  that
3964         has the Lu, Ll, or Lt property, in other words, a letter  that  is  not         has  the  Lu,  Ll, or Lt property, in other words, a letter that is not
3965         classified as a modifier or "other".         classified as a modifier or "other".
3966    
3967         The  Cs  (Surrogate)  property  applies only to characters in the range         The Cs (Surrogate) property applies only to  characters  in  the  range
3968         U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see         U+D800  to  U+DFFF. Such characters are not valid in UTF-8 strings (see
3969         RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-         RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
3970         ing has been turned off (see the discussion  of  PCRE_NO_UTF8_CHECK  in         ing  has  been  turned off (see the discussion of PCRE_NO_UTF8_CHECK in
3971         the pcreapi page). Perl does not support the Cs property.         the pcreapi page). Perl does not support the Cs property.
3972    
3973         The  long  synonyms  for  property  names  that  Perl supports (such as         The long synonyms for  property  names  that  Perl  supports  (such  as
3974         \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix         \p{Letter})  are  not  supported by PCRE, nor is it permitted to prefix
3975         any of these properties with "Is".         any of these properties with "Is".
3976    
3977         No character that is in the Unicode table has the Cn (unassigned) prop-         No character that is in the Unicode table has the Cn (unassigned) prop-
3978         erty.  Instead, this property is assumed for any code point that is not         erty.  Instead, this property is assumed for any code point that is not
3979         in the Unicode table.         in the Unicode table.
3980    
3981         Specifying  caseless  matching  does not affect these escape sequences.         Specifying caseless matching does not affect  these  escape  sequences.
3982         For example, \p{Lu} always matches only upper case letters.         For example, \p{Lu} always matches only upper case letters.
3983    
3984         The \X escape matches any number of Unicode  characters  that  form  an         The  \X  escape  matches  any number of Unicode characters that form an
3985         extended Unicode sequence. \X is equivalent to         extended Unicode sequence. \X is equivalent to
3986    
3987           (?>\PM\pM*)           (?>\PM\pM*)
3988    
3989         That  is,  it matches a character without the "mark" property, followed         That is, it matches a character without the "mark"  property,  followed
3990         by zero or more characters with the "mark"  property,  and  treats  the         by  zero  or  more  characters with the "mark" property, and treats the
3991         sequence  as  an  atomic group (see below).  Characters with the "mark"         sequence as an atomic group (see below).  Characters  with  the  "mark"
3992         property are typically accents that  affect  the  preceding  character.         property  are  typically  accents  that affect the preceding character.
3993         None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X         None of them have codepoints less than 256, so  in  non-UTF-8  mode  \X
3994         matches any one character.         matches any one character.
3995    
3996         Matching characters by Unicode property is not fast, because  PCRE  has         Note that recent versions of Perl have changed \X to match what Unicode
3997         to  search  a  structure  that  contains data for over fifteen thousand         calls an "extended grapheme cluster", which has a more complicated def-
3998           inition.
3999    
4000           Matching  characters  by Unicode property is not fast, because PCRE has
4001           to search a structure that contains  data  for  over  fifteen  thousand
4002         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
4003         \w  do  not  use  Unicode properties in PCRE by default, though you can         \w do not use Unicode properties in PCRE by  default,  though  you  can
4004         make them do so by setting the PCRE_UCP option for pcre_compile() or by         make them do so by setting the PCRE_UCP option for pcre_compile() or by
4005         starting the pattern with (*UCP).         starting the pattern with (*UCP).
4006    
4007     PCRE's additional properties     PCRE's additional properties
4008    
4009         As  well  as  the standard Unicode properties described in the previous         As well as the standard Unicode properties described  in  the  previous
4010         section, PCRE supports four more that make it possible to convert  tra-         section,  PCRE supports four more that make it possible to convert tra-
4011         ditional escape sequences such as \w and \s and POSIX character classes         ditional escape sequences such as \w and \s and POSIX character classes
4012         to use Unicode properties. PCRE uses these non-standard, non-Perl prop-         to use Unicode properties. PCRE uses these non-standard, non-Perl prop-
4013         erties internally when PCRE_UCP is set. They are:         erties internally when PCRE_UCP is set. They are:
# Line 3732  BACKSLASH Line 4017  BACKSLASH
4017           Xsp   Any Perl space character           Xsp   Any Perl space character
4018           Xwd   Any Perl "word" character           Xwd   Any Perl "word" character
4019    
4020         Xan  matches  characters that have either the L (letter) or the N (num-         Xan matches characters that have either the L (letter) or the  N  (num-
4021         ber) property. Xps matches the characters tab, linefeed, vertical  tab,         ber)  property. Xps matches the characters tab, linefeed, vertical tab,
4022         formfeed,  or  carriage  return, and any other character that has the Z         formfeed, or carriage return, and any other character that  has  the  Z
4023         (separator) property.  Xsp is the same as Xps, except that vertical tab         (separator) property.  Xsp is the same as Xps, except that vertical tab
4024         is excluded. Xwd matches the same characters as Xan, plus underscore.         is excluded. Xwd matches the same characters as Xan, plus underscore.
4025    
4026     Resetting the match start     Resetting the match start
4027    
4028         The escape sequence \K, which is a Perl 5.10 feature, causes any previ-         The escape sequence \K causes any previously matched characters not  to
4029         ously matched characters not  to  be  included  in  the  final  matched         be included in the final matched sequence. For example, the pattern:
        sequence. For example, the pattern:  
4030    
4031           foo\Kbar           foo\Kbar
4032    
# Line 3898  FULL STOP (PERIOD, DOT) AND \N Line 4182  FULL STOP (PERIOD, DOT) AND \N
4182         flex and dollar, the only relationship being  that  they  both  involve         flex and dollar, the only relationship being  that  they  both  involve
4183         newlines. Dot has no special meaning in a character class.         newlines. Dot has no special meaning in a character class.
4184    
4185         The escape sequence \N always behaves as a dot does when PCRE_DOTALL is         The  escape  sequence  \N  behaves  like  a  dot, except that it is not
4186         not set. In other words, it matches any one character except  one  that         affected by the PCRE_DOTALL option. In  other  words,  it  matches  any
4187         signifies the end of a line.         character  except  one that signifies the end of a line. Perl also uses
4188           \N to match characters by name; PCRE does not support this.
4189    
4190    
4191  MATCHING A SINGLE BYTE  MATCHING A SINGLE BYTE
4192    
4193         Outside a character class, the escape sequence \C matches any one byte,         Outside a character class, the escape sequence \C matches any one byte,
4194         both in and out of UTF-8 mode. Unlike a  dot,  it  always  matches  any         both  in  and  out of UTF-8 mode. Unlike a dot, it always matches line-
4195         line-ending  characters.  The  feature  is provided in Perl in order to         ending characters. The feature is provided in Perl in  order  to  match
4196         match individual bytes in UTF-8 mode. Because it breaks up UTF-8  char-         individual  bytes  in UTF-8 mode, but it is unclear how it can usefully
4197         acters  into individual bytes, what remains in the string may be a mal-         be used. Because \C breaks up characters into individual bytes,  match-
4198         formed UTF-8 string. For this reason, the \C escape  sequence  is  best         ing  one  byte  with \C in UTF-8 mode means that the rest of the string
4199         avoided.         may start with a malformed UTF-8 character. This has undefined results,
4200           because  PCRE  assumes that it is dealing with valid UTF-8 strings (and
4201           by default it checks  this  at  the  start  of  processing  unless  the
4202           PCRE_NO_UTF8_CHECK option is used).
4203    
4204         PCRE  does  not  allow \C to appear in lookbehind assertions (described         PCRE  does  not  allow \C to appear in lookbehind assertions (described
4205         below), because in UTF-8 mode this would make it impossible  to  calcu-         below) in UTF-8 mode, because this would make it impossible  to  calcu-
4206         late the length of the lookbehind.         late the length of the lookbehind.
4207    
4208           In  general, the \C escape sequence is best avoided in UTF-8 mode. How-
4209           ever, one way of using it that avoids the problem  of  malformed  UTF-8
4210           characters  is to use a lookahead to check the length of the next char-
4211           acter, as in this pattern (ignore white space and line breaks):
4212    
4213             (?| (?=[\x00-\x7f])(\C) |
4214                 (?=[\x80-\x{7ff}])(\C)(\C) |
4215                 (?=[\x{800}-\x{ffff}])(\C)(\C)(\C) |
4216                 (?=[\x{10000}-\x{1fffff}])(\C)(\C)(\C)(\C))
4217    
4218           A group that starts with (?| resets the capturing  parentheses  numbers
4219           in  each  alternative  (see  "Duplicate Subpattern Numbers" below). The
4220           assertions at the start of each branch check the next  UTF-8  character
4221           for  values  whose encoding uses 1, 2, 3, or 4 bytes, respectively. The
4222           character's individual bytes are then captured by the appropriate  num-
4223           ber of groups.
4224    
4225    
4226  SQUARE BRACKETS AND CHARACTER CLASSES  SQUARE BRACKETS AND CHARACTER CLASSES
4227    
# Line 3995  SQUARE BRACKETS AND CHARACTER CLASSES Line 4300  SQUARE BRACKETS AND CHARACTER CLASSES
4300         concept  of  case for characters with values greater than 128 only when         concept  of  case for characters with values greater than 128 only when
4301         it is compiled with Unicode property support.         it is compiled with Unicode property support.
4302    
4303         The character types \d, \D, \h, \H, \p, \P, \s, \S, \v, \V, \w, and  \W         The character escape sequences \d, \D, \h, \H, \p, \P, \s, \S, \v,  \V,
4304         may  also appear in a character class, and add the characters that they         \w, and \W may appear in a character class, and add the characters that
4305         match to the class. For example,  [\dABCDEF]  matches  any  hexadecimal         they match to the class. For example, [\dABCDEF] matches any  hexadeci-
4306         digit.  A circumflex can conveniently be used with the upper case char-         mal  digit.  In UTF-8 mode, the PCRE_UCP option affects the meanings of
4307         acter types to specify a more restricted set  of  characters  than  the         \d, \s, \w and their upper case partners, just as  it  does  when  they
4308         matching  lower  case  type.  For example, the class [^\W_] matches any         appear  outside a character class, as described in the section entitled
4309         letter or digit, but not underscore.         "Generic character types" above. The escape sequence \b has a different
4310           meaning  inside  a character class; it matches the backspace character.
4311           The sequences \B, \N, \R, and \X are not  special  inside  a  character
4312           class.  Like  any other unrecognized escape sequences, they are treated
4313           as the literal characters "B", "N", "R", and "X" by default, but  cause
4314           an error if the PCRE_EXTRA option is set.
4315    
4316           A  circumflex  can  conveniently  be used with the upper case character
4317           types to specify a more restricted set of characters than the  matching
4318           lower  case  type.  For example, the class [^\W_] matches any letter or
4319           digit, but not underscore, whereas [\w] includes underscore. A positive
4320           character class should be read as "something OR something OR ..." and a
4321           negative class as "NOT something AND NOT something AND NOT ...".
4322    
4323         The only metacharacters that are recognized in  character  classes  are         The only metacharacters that are recognized in  character  classes  are
4324         backslash,  hyphen  (only  where  it can be interpreted as specifying a         backslash,  hyphen  (only  where  it can be interpreted as specifying a
# Line 4117  INTERNAL OPTION SETTING Line 4434  INTERNAL OPTION SETTING
4434         fore show up in data extracted by the pcre_fullinfo() function).         fore show up in data extracted by the pcre_fullinfo() function).
4435    
4436         An  option  change  within a subpattern (see below for a description of         An  option  change  within a subpattern (see below for a description of
4437         subpatterns) affects only that part of the current pattern that follows         subpatterns) affects only that part of the subpattern that follows  it,
4438         it, so         so
4439    
4440           (a(?i)b)c           (a(?i)b)c
4441    
# Line 4154  SUBPATTERNS Line 4471  SUBPATTERNS
4471    
4472           cat(aract|erpillar|)           cat(aract|erpillar|)
4473    
4474         matches one of the words "cat", "cataract", or  "caterpillar".  Without         matches "cataract", "caterpillar", or "cat". Without  the  parentheses,
4475         the  parentheses,  it  would  match  "cataract", "erpillar" or an empty         it would match "cataract", "erpillar" or an empty string.
        string.  
4476    
4477         2. It sets up the subpattern as  a  capturing  subpattern.  This  means         2.  It  sets  up  the  subpattern as a capturing subpattern. This means
4478         that,  when  the  whole  pattern  matches,  that portion of the subject         that, when the whole pattern  matches,  that  portion  of  the  subject
4479         string that matched the subpattern is passed back to the caller via the         string that matched the subpattern is passed back to the caller via the
4480         ovector  argument  of pcre_exec(). Opening parentheses are counted from         ovector argument of pcre_exec(). Opening parentheses are  counted  from
4481         left to right (starting from 1) to obtain  numbers  for  the  capturing         left  to  right  (starting  from 1) to obtain numbers for the capturing
4482         subpatterns.         subpatterns. For example, if the  string  "the  red  king"  is  matched
4483           against the pattern
        For  example,  if the string "the red king" is matched against the pat-  
        tern  
4484    
4485           the ((red|white) (king|queen))           the ((red|white) (king|queen))
4486    
4487         the captured substrings are "red king", "red", and "king", and are num-         the captured substrings are "red king", "red", and "king", and are num-
4488         bered 1, 2, and 3, respectively.         bered 1, 2, and 3, respectively.
4489    
4490         The  fact  that  plain  parentheses  fulfil two functions is not always         The fact that plain parentheses fulfil  two  functions  is  not  always
4491         helpful.  There are often times when a grouping subpattern is  required         helpful.   There are often times when a grouping subpattern is required
4492         without  a capturing requirement. If an opening parenthesis is followed         without a capturing requirement. If an opening parenthesis is  followed
4493         by a question mark and a colon, the subpattern does not do any  captur-         by  a question mark and a colon, the subpattern does not do any captur-
4494         ing,  and  is  not  counted when computing the number of any subsequent         ing, and is not counted when computing the  number  of  any  subsequent
4495         capturing subpatterns. For example, if the string "the white queen"  is         capturing  subpatterns. For example, if the string "the white queen" is
4496         matched against the pattern         matched against the pattern
4497    
4498           the ((?:red|white) (king|queen))           the ((?:red|white) (king|queen))
# Line 4186  SUBPATTERNS Line 4500  SUBPATTERNS
4500         the captured substrings are "white queen" and "queen", and are numbered         the captured substrings are "white queen" and "queen", and are numbered
4501         1 and 2. The maximum number of capturing subpatterns is 65535.         1 and 2. The maximum number of capturing subpatterns is 65535.
4502    
4503         As a convenient shorthand, if any option settings are required  at  the         As  a  convenient shorthand, if any option settings are required at the
4504         start  of  a  non-capturing  subpattern,  the option letters may appear         start of a non-capturing subpattern,  the  option  letters  may  appear
4505         between the "?" and the ":". Thus the two patterns         between the "?" and the ":". Thus the two patterns
4506    
4507           (?i:saturday|sunday)           (?i:saturday|sunday)
4508           (?:(?i)saturday|sunday)           (?:(?i)saturday|sunday)
4509    
4510         match exactly the same set of strings. Because alternative branches are         match exactly the same set of strings. Because alternative branches are
4511         tried  from  left  to right, and options are not reset until the end of         tried from left to right, and options are not reset until  the  end  of
4512         the subpattern is reached, an option setting in one branch does  affect         the  subpattern is reached, an option setting in one branch does affect
4513         subsequent  branches,  so  the above patterns match "SUNDAY" as well as         subsequent branches, so the above patterns match "SUNDAY"  as  well  as
4514         "Saturday".         "Saturday".
4515    
4516    
4517  DUPLICATE SUBPATTERN NUMBERS  DUPLICATE SUBPATTERN NUMBERS
4518    
4519         Perl 5.10 introduced a feature whereby each alternative in a subpattern         Perl 5.10 introduced a feature whereby each alternative in a subpattern
4520         uses  the same numbers for its capturing parentheses. Such a subpattern         uses the same numbers for its capturing parentheses. Such a  subpattern
4521         starts with (?| and is itself a non-capturing subpattern. For  example,         starts  with (?| and is itself a non-capturing subpattern. For example,
4522         consider this pattern:         consider this pattern:
4523    
4524           (?|(Sat)ur|(Sun))day           (?|(Sat)ur|(Sun))day
4525    
4526         Because  the two alternatives are inside a (?| group, both sets of cap-         Because the two alternatives are inside a (?| group, both sets of  cap-
4527         turing parentheses are numbered one. Thus, when  the  pattern  matches,         turing  parentheses  are  numbered one. Thus, when the pattern matches,
4528         you  can  look  at captured substring number one, whichever alternative         you can look at captured substring number  one,  whichever  alternative
4529         matched. This construct is useful when you want to  capture  part,  but         matched.  This  construct  is useful when you want to capture part, but
4530         not all, of one of a number of alternatives. Inside a (?| group, paren-         not all, of one of a number of alternatives. Inside a (?| group, paren-
4531         theses are numbered as usual, but the number is reset at the  start  of         theses  are  numbered as usual, but the number is reset at the start of
4532         each  branch. The numbers of any capturing buffers that follow the sub-         each branch. The numbers of any capturing parentheses that  follow  the
4533         pattern start after the highest number used in any branch. The  follow-         subpattern  start after the highest number used in any branch. The fol-
4534         ing  example  is taken from the Perl documentation.  The numbers under-         lowing example is taken from the Perl documentation. The numbers under-
4535         neath show in which buffer the captured content will be stored.         neath show in which buffer the captured content will be stored.
4536    
4537           # before  ---------------branch-reset----------- after           # before  ---------------branch-reset----------- after
4538           / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x           / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x
4539           # 1            2         2  3        2     3     4           # 1            2         2  3        2     3     4
4540    
4541         A back reference to a numbered subpattern uses the  most  recent  value         A  back  reference  to a numbered subpattern uses the most recent value
4542         that  is  set  for that number by any subpattern. The following pattern         that is set for that number by any subpattern.  The  following  pattern
4543         matches "abcabc" or "defdef":         matches "abcabc" or "defdef":
4544    
4545           /(?|(abc)|(def))\1/           /(?|(abc)|(def))\1/
4546    
4547         In contrast, a recursive or "subroutine" call to a numbered  subpattern         In  contrast,  a subroutine call to a numbered subpattern always refers
4548         always  refers  to  the first one in the pattern with the given number.         to the first one in the pattern with the given  number.  The  following
4549         The following pattern matches "abcabc" or "defabc":         pattern matches "abcabc" or "defabc":
4550    
4551           /(?|(abc)|(def))(?1)/           /(?|(abc)|(def))(?1)/
4552    
4553         If a condition test for a subpattern's having matched refers to a  non-         If  a condition test for a subpattern's having matched refers to a non-
4554         unique  number, the test is true if any of the subpatterns of that num-         unique number, the test is true if any of the subpatterns of that  num-
4555         ber have matched.         ber have matched.
4556    
4557         An alternative approach to using this "branch reset" feature is to  use         An  alternative approach to using this "branch reset" feature is to use
4558         duplicate named subpatterns, as described in the next section.         duplicate named subpatterns, as described in the next section.
4559    
4560    
4561  NAMED SUBPATTERNS  NAMED SUBPATTERNS
4562    
4563         Identifying  capturing  parentheses  by number is simple, but it can be         Identifying capturing parentheses by number is simple, but  it  can  be
4564         very hard to keep track of the numbers in complicated  regular  expres-         very  hard  to keep track of the numbers in complicated regular expres-
4565         sions.  Furthermore,  if  an  expression  is  modified, the numbers may         sions. Furthermore, if an  expression  is  modified,  the  numbers  may
4566         change. To help with this difficulty, PCRE supports the naming of  sub-         change.  To help with this difficulty, PCRE supports the naming of sub-
4567         patterns. This feature was not added to Perl until release 5.10. Python         patterns. This feature was not added to Perl until release 5.10. Python
4568         had the feature earlier, and PCRE introduced it at release  4.0,  using         had  the  feature earlier, and PCRE introduced it at release 4.0, using
4569         the  Python syntax. PCRE now supports both the Perl and the Python syn-         the Python syntax. PCRE now supports both the Perl and the Python  syn-
4570         tax. Perl allows identically numbered  subpatterns  to  have  different         tax.  Perl  allows  identically  numbered subpatterns to have different
4571         names, but PCRE does not.         names, but PCRE does not.
4572    
4573         In  PCRE,  a subpattern can be named in one of three ways: (?<name>...)         In PCRE, a subpattern can be named in one of three  ways:  (?<name>...)
4574         or (?'name'...) as in Perl, or (?P<name>...) as in  Python.  References         or  (?'name'...)  as in Perl, or (?P<name>...) as in Python. References