/[pcre]/code/trunk/doc/pcre.txt
ViewVC logotype

Diff of /code/trunk/doc/pcre.txt

Parent Directory Parent Directory | Revision Log Revision Log | View Patch Patch

revision 548 by ph10, Fri Jun 25 14:42:00 2010 UTC revision 678 by ph10, Sun Aug 28 15:23:03 2011 UTC
# 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    
125  PCREBUILD(3)                                                      PCREBUILD(3)  PCREBUILD(3)                                                      PCREBUILD(3)
126    
127    
# 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 401  WHAT \R MATCHES Line 263  WHAT \R MATCHES
263         functions are called.         functions are called.
264    
265    
 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.  
   
   
266  POSIX MALLOC USAGE  POSIX MALLOC USAGE
267    
268         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 403  PCREGREP OPTIONS FOR COMPRESSED FILE SUP
403         if they are not.         if they are not.
404    
405    
406    PCREGREP BUFFER SIZE
407    
408           pcregrep  uses  an internal buffer to hold a "window" on the file it is
409           scanning, in order to be able to output "before" and "after" lines when
410           it  finds  a match. The size of the buffer is controlled by a parameter
411           whose default value is 20K. The buffer itself is three times this size,
412           but because of the way it is used for holding "before" lines, the long-
413           est line that is guaranteed to be processable is  the  parameter  size.
414           You can change the default parameter value by adding, for example,
415    
416             --with-pcregrep-bufsize=50K
417    
418           to the configure command. The caller of pcregrep can, however, override
419           this value by specifying a run-time option.
420    
421    
422  PCRETEST OPTION FOR LIBREADLINE SUPPORT  PCRETEST OPTION FOR LIBREADLINE SUPPORT
423    
424         If you add         If you add
425    
426           --enable-pcretest-libreadline           --enable-pcretest-libreadline
427    
428         to  the  configure  command,  pcretest  is  linked with the libreadline         to the configure command,  pcretest  is  linked  with  the  libreadline
429         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
430         readline() function. This provides line-editing and history facilities.         readline() function. This provides line-editing and history facilities.
431         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
432         pcretest linked in this way, there may be licensing issues.         pcretest linked in this way, there may be licensing issues.
433    
434         Setting  this  option  causes  the -lreadline option to be added to the         Setting this option causes the -lreadline option to  be  added  to  the
435         pcretest build. In many operating environments with  a  sytem-installed         pcretest  build.  In many operating environments with a sytem-installed
436         libreadline this is sufficient. However, in some environments (e.g.  if         libreadline this is sufficient. However, in some environments (e.g.  if
437         an unmodified distribution version of readline is in use),  some  extra         an  unmodified  distribution version of readline is in use), some extra
438         configuration  may  be necessary. The INSTALL file for libreadline says         configuration may be necessary. The INSTALL file for  libreadline  says
439         this:         this:
440    
441           "Readline uses the termcap functions, but does not link with the           "Readline uses the termcap functions, but does not link with the
442           termcap or curses library itself, allowing applications which link           termcap or curses library itself, allowing applications which link
443           with readline the to choose an appropriate library."           with readline the to choose an appropriate library."
444    
445         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
446         is automatically included, you may need to add something like         is automatically included, you may need to add something like
447    
448           LIBS="-ncurses"           LIBS="-ncurses"
# Line 598  AUTHOR Line 464  AUTHOR
464    
465  REVISION  REVISION
466    
467         Last updated: 29 September 2009         Last updated: 02 August 2011
468         Copyright (c) 1997-2009 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
469  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
470    
471    
472  PCREMATCHING(3)                                                PCREMATCHING(3)  PCREMATCHING(3)                                                PCREMATCHING(3)
473    
474    
# Line 697  THE ALTERNATIVE MATCHING ALGORITHM Line 563  THE ALTERNATIVE MATCHING ALGORITHM
563         represent the different matching possibilities (if there are none,  the         represent the different matching possibilities (if there are none,  the
564         match  has  failed).   Thus,  if there is more than one possible match,         match  has  failed).   Thus,  if there is more than one possible match,
565         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-
566         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
567         (which is necessarily the shortest) is found.         an option to stop the algorithm after the first match (which is  neces-
568           sarily the shortest) is found.
569    
570         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
571         subject. If the pattern         subject. If the pattern
572    
573           cat(er(pillar)?)           cat(er(pillar)?)?
574    
575         is  matched  against the string "the caterpillar catchment", the result         is matched against the string "the caterpillar catchment",  the  result
576         will be the three strings "cat", "cater", and "caterpillar" that  start         will  be the three strings "caterpillar", "cater", and "cat" that start
577         at the fourth character of the subject. The algorithm does not automat-         at the fifth character of the subject. The algorithm does not automati-
578         ically move on to find matches that start at later positions.         cally move on to find matches that start at later positions.
579    
580         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
581         supported by the alternative matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
582    
583         1.  Because  the  algorithm  finds  all possible matches, the greedy or         1. Because the algorithm finds all  possible  matches,  the  greedy  or
584         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
585         ungreedy quantifiers are treated in exactly the same way. However, pos-         ungreedy quantifiers are treated in exactly the same way. However, pos-
586         sessive quantifiers can make a difference when what follows could  also         sessive  quantifiers can make a difference when what follows could also
587         match what is quantified, for example in a pattern like this:         match what is quantified, for example in a pattern like this:
588    
589           ^a++\w!           ^a++\w!
590    
591         This  pattern matches "aaab!" but not "aaa!", which would be matched by         This pattern matches "aaab!" but not "aaa!", which would be matched  by
592         a non-possessive quantifier. Similarly, if an atomic group is  present,         a  non-possessive quantifier. Similarly, if an atomic group is present,
593         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,
594         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
595         pattern.         pattern.
596    
597         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
598         is not straightforward to keep track of  captured  substrings  for  the         is  not  straightforward  to  keep track of captured substrings for the
599         different  matching  possibilities,  and  PCRE's implementation of this         different matching possibilities, and  PCRE's  implementation  of  this
600         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-
601         strings are available.         strings are available.
602    
603         3.  Because no substrings are captured, back references within the pat-         3. Because no substrings are captured, back references within the  pat-
604         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
605    
606         4. For the same reason, conditional expressions that use  a  backrefer-         4.  For  the same reason, conditional expressions that use a backrefer-
607         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
608         supported.         supported.
609    
610         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
611         sequence, which resets the start of the match when encountered (but may         sequence, which resets the start of the match when encountered (but may
612         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
613         error if encountered.         error if encountered.
614    
615         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
616         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.
617    
618         7. The \C escape sequence, which (in the standard algorithm) matches  a         7.  The \C escape sequence, which (in the standard algorithm) matches a
619         single  byte, even in UTF-8 mode, is not supported because the alterna-         single byte, even in UTF-8 mode, is not supported because the  alterna-
620         tive algorithm moves through the subject  string  one  character  at  a         tive  algorithm  moves  through  the  subject string one character at a
621         time, for all active paths through the tree.         time, for all active paths through the tree.
622    
623         8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)         8. Except for (*FAIL), the backtracking control verbs such as  (*PRUNE)
624         are not supported. (*FAIL) is supported, and  behaves  like  a  failing         are  not  supported.  (*FAIL)  is supported, and behaves like a failing
625         negative assertion.         negative assertion.
626    
627    
628  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
629    
630         Using  the alternative matching algorithm provides the following advan-         Using the alternative matching algorithm provides the following  advan-
631         tages:         tages:
632    
633         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-
634         ically  found,  and  in particular, the longest match is found. To find         ically found, and in particular, the longest match is  found.  To  find
635         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
636         things with callouts.         things with callouts.
637    
638         2.  Because  the  alternative  algorithm  scans the subject string just         2. Because the alternative algorithm  scans  the  subject  string  just
639         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
640         subject  strings  to  the matching function in several pieces, checking         subject strings to the matching function in  several  pieces,  checking
641         for partial matching each time.  The  pcrepartial  documentation  gives         for  partial  matching  each time. Although it is possible to do multi-
642         details of partial matching.         segment matching using the standard algorithm (pcre_exec()), by retain-
643           ing  partially matched substrings, it is more complicated. The pcrepar-
644           tial documentation gives details  of  partial  matching  and  discusses
645           multi-segment matching.
646    
647    
648  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
# Line 798  AUTHOR Line 668  AUTHOR
668    
669  REVISION  REVISION
670    
671         Last updated: 29 September 2009         Last updated: 17 November 2010
672         Copyright (c) 1997-2009 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
673  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
674    
675    
676  PCREAPI(3)                                                          PCREAPI(3)  PCREAPI(3)                                                          PCREAPI(3)
677    
678    
# Line 1162  COMPILING A PATTERN Line 1032  COMPILING A PATTERN
1032         pcrepattern documentation). For those options that can be different  in         pcrepattern documentation). For those options that can be different  in
1033         different  parts  of  the pattern, the contents of the options argument         different  parts  of  the pattern, the contents of the options argument
1034         specifies their settings at the start of compilation and execution. The         specifies their settings at the start of compilation and execution. The
1035         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
1036         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
1037           at compile time.
1038    
1039         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1040         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
1041         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-
1042         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
1043         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
1044         character  that  was  being  processed when the error was discovered is         the byte that was being processed when  the  error  was  discovered  is
1045         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
1046         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
1047         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.
1048         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
1049           the  whole  pattern  has been scanned; in these cases the offset passed
1050           back is the length of the pattern.
1051    
1052           Note that the offset is in bytes, not characters, even in  UTF-8  mode.
1053           It may sometimes point into the middle of a UTF-8 character.
1054    
1055         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1056         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 1128  COMPILING A PATTERN
1128    
1129           PCRE_DOTALL           PCRE_DOTALL
1130    
1131         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-
1132         acters,  including  those that indicate newline. Without it, a dot does         acter of any value, including one that indicates a newline. However, it
1133         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.
1134         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
1135         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
1136         newline characters, independent of the setting of this option.         be  changed within a pattern by a (?s) option setting. A negative class
1137           such as [^a] always matches newline characters, independent of the set-
1138           ting of this option.
1139    
1140           PCRE_DUPNAMES           PCRE_DUPNAMES
1141    
# Line 1277  COMPILING A PATTERN Line 1155  COMPILING A PATTERN
1155         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-
1156         ting.         ting.
1157    
1158         This  option  makes  it possible to include comments inside complicated         Which  characters  are  interpreted  as  newlines  is controlled by the
1159         patterns.  Note, however, that this applies only  to  data  characters.         options passed to pcre_compile() or by a special sequence at the  start
1160         Whitespace   characters  may  never  appear  within  special  character         of  the  pattern, as described in the section entitled "Newline conven-
1161         sequences in a pattern, for  example  within  the  sequence  (?(  which         tions" in the pcrepattern documentation. Note that the end of this type
1162         introduces a conditional subpattern.         of  comment  is  a  literal  newline  sequence  in  the pattern; escape
1163           sequences that happen to represent a newline do not count.
1164    
1165           This option makes it possible to include  comments  inside  complicated
1166           patterns.   Note,  however,  that this applies only to data characters.
1167           Whitespace  characters  may  never  appear  within  special   character
1168           sequences in a pattern, for example within the sequence (?( that intro-
1169           duces a conditional subpattern.
1170    
1171           PCRE_EXTRA           PCRE_EXTRA
1172    
1173         This  option  was invented in order to turn on additional functionality         This option was invented in order to turn on  additional  functionality
1174         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
1175         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
1176         letter that has no special meaning  causes  an  error,  thus  reserving         letter  that  has  no  special  meaning causes an error, thus reserving
1177         these  combinations  for  future  expansion.  By default, as in Perl, a         these combinations for future expansion. By  default,  as  in  Perl,  a
1178         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
1179         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
1180         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
1181         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
1182         within a pattern.         within a pattern.
1183    
1184           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1185    
1186         If this option is set, an  unanchored  pattern  is  required  to  match         If  this  option  is  set,  an  unanchored pattern is required to match
1187         before  or  at  the  first  newline  in  the subject string, though the         before or at the first  newline  in  the  subject  string,  though  the
1188         matched text may continue over the newline.         matched text may continue over the newline.
1189    
1190           PCRE_JAVASCRIPT_COMPAT           PCRE_JAVASCRIPT_COMPAT
1191    
1192         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
1193         it  is  compatible with JavaScript rather than Perl. The changes are as         it is compatible with JavaScript rather than Perl. The changes  are  as
1194         follows:         follows:
1195    
1196         (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
1197         error,  because this is illegal in JavaScript (by default it is treated         error, because this is illegal in JavaScript (by default it is  treated
1198         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
1199         option is set.         option is set.
1200    
1201         (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
1202         an empty string (by default this causes the current  matching  alterna-         an  empty  string (by default this causes the current matching alterna-
1203         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
1204         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
1205         default, for Perl compatibility.         default, for Perl compatibility.
1206    
1207           PCRE_MULTILINE           PCRE_MULTILINE
1208    
1209         By  default,  PCRE  treats the subject string as consisting of a single         By default, PCRE treats the subject string as consisting  of  a  single
1210         line of characters (even if it actually contains newlines). The  "start         line  of characters (even if it actually contains newlines). The "start
1211         of  line"  metacharacter  (^)  matches only at the start of the string,         of line" metacharacter (^) matches only at the  start  of  the  string,
1212         while the "end of line" metacharacter ($) matches only at  the  end  of         while  the  "end  of line" metacharacter ($) matches only at the end of
1213         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1214         is set). This is the same as Perl.         is set). This is the same as Perl.
1215    
1216         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"
1217         constructs  match  immediately following or immediately before internal         constructs match immediately following or immediately  before  internal
1218         newlines in the subject string, respectively, as well as  at  the  very         newlines  in  the  subject string, respectively, as well as at the very
1219         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
1220         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-
1221         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,
1222         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1223    
1224           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 1342  COMPILING A PATTERN Line 1227  COMPILING A PATTERN
1227           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1228           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1229    
1230         These options override the default newline definition that  was  chosen         These  options  override the default newline definition that was chosen
1231         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
1232         newline is indicated by a single character (CR  or  LF,  respectively).         newline  is  indicated  by a single character (CR or LF, respectively).
1233         Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
1234         two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies         two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
1235         that any of the three preceding sequences should be recognized. Setting         that any of the three preceding sequences should be recognized. Setting
1236         PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be         PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
1237         recognized. The Unicode newline sequences are the three just mentioned,         recognized. The Unicode newline sequences are the three just mentioned,
1238         plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,
1239         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
1240         (paragraph separator, U+2029). The last  two  are  recognized  only  in         (paragraph  separator,  U+2029).  The  last  two are recognized only in
1241         UTF-8 mode.         UTF-8 mode.
1242    
1243         The  newline  setting  in  the  options  word  uses three bits that are         The newline setting in the  options  word  uses  three  bits  that  are
1244         treated as a number, giving eight possibilities. Currently only six are         treated as a number, giving eight possibilities. Currently only six are
1245         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
1246         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-
1247         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
1248         PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1249         cause an error.         cause an error.
1250    
1251         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
1252         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
1253         character  class  is  encountered.  This indicates a comment that lasts         characters, and so are ignored in this mode. Also, an unescaped #  out-
1254         until after the next line break sequence. In other circumstances,  line         side  a  character class indicates a comment that lasts until after the
1255         break   sequences   are   treated  as  literal  data,  except  that  in         next line break sequence. In other circumstances, line break  sequences
1256         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         in patterns are treated as literal data.
        and are therefore ignored.  
1257    
1258         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
1259         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 1266  COMPILING A PATTERN
1266         be  used  for  capturing  (and  they acquire numbers in the usual way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
1267         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1268    
1269             NO_START_OPTIMIZE
1270    
1271           This is an option that acts at matching time; that is, it is really  an
1272           option  for  pcre_exec()  or  pcre_dfa_exec().  If it is set at compile
1273           time, it is remembered with the compiled pattern and assumed at  match-
1274           ing  time.  For  details  see  the discussion of PCRE_NO_START_OPTIMIZE
1275           below.
1276    
1277           PCRE_UCP           PCRE_UCP
1278    
1279         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,
1280         the POSIX character classes. By default, only ASCII characters are rec-         \w,  and  some  of  the POSIX character classes. By default, only ASCII
1281         ognized, but if PCRE_UCP is set, Unicode properties are used instead to         characters are recognized, but if PCRE_UCP is set,  Unicode  properties
1282         classify  characters.  More details are given in the section on generic         are  used instead to classify characters. More details are given in the
1283         character types in the pcrepattern page. If you set PCRE_UCP,  matching         section on generic character types in the pcrepattern page. If you  set
1284         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
1285         only if PCRE has been compiled with Unicode property support.         option is available only if PCRE has been compiled with  Unicode  prop-
1286           erty support.
1287    
1288           PCRE_UNGREEDY           PCRE_UNGREEDY
1289    
1290         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1291         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
1292         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
1293         within the pattern.         within the pattern.
1294    
1295           PCRE_UTF8           PCRE_UTF8
1296    
1297         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
1298         strings of UTF-8 characters instead of single-byte  character  strings.         strings  of  UTF-8 characters instead of single-byte character strings.
1299         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-
1300         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
1301         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
1302         UTF-8 support in the main pcre page.         page.
1303    
1304           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1305    
1306         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
1307         automatically  checked.  There  is  a  discussion about the validity of         automatically checked. There is a  discussion  about  the  validity  of
1308         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
1309         bytes  is  found,  pcre_compile() returns an error. If you already know         bytes is found, pcre_compile() returns an error. If  you  already  know
1310         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-
1311         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
1312         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
1313         undefined.  It  may  cause your program to crash. Note that this option         undefined. It may cause your program to crash. Note  that  this  option
1314         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
1315         UTF-8 validity checking of subject strings.         UTF-8 validity checking of subject strings.
1316    
1317    
1318  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1319    
1320         The  following  table  lists  the  error  codes than may be returned by         The following table lists the error  codes  than  may  be  returned  by
1321         pcre_compile2(), along with the error messages that may be returned  by         pcre_compile2(),  along with the error messages that may be returned by
1322         both  compiling functions. As PCRE has developed, some error codes have         both compiling functions. As PCRE has developed, some error codes  have
1323         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.
1324    
1325            0  no error            0  no error
# Line 1466  COMPILATION ERROR CODES Line 1359  COMPILATION ERROR CODES
1359           34  character value in \x{...} sequence is too large           34  character value in \x{...} sequence is too large
1360           35  invalid condition (?(0)           35  invalid condition (?(0)
1361           36  \C not allowed in lookbehind assertion           36  \C not allowed in lookbehind assertion
1362           37  PCRE does not support \L, \l, \N, \U, or \u           37  PCRE does not support \L, \l, \N{name}, \U, or \u
1363           38  number after (?C is > 255           38  number after (?C is > 255
1364           39  closing ) for (?C expected           39  closing ) for (?C expected
1365           40  recursive call could loop indefinitely           40  recursive call could loop indefinitely
# Line 1500  COMPILATION ERROR CODES Line 1393  COMPILATION ERROR CODES
1393                 not allowed                 not allowed
1394           66  (*MARK) must have an argument           66  (*MARK) must have an argument
1395           67  this version of PCRE is not compiled with PCRE_UCP support           67  this version of PCRE is not compiled with PCRE_UCP support
1396             68  \c must be followed by an ASCII character
1397             69  \k is not followed by a braced, angle-bracketed, or quoted name
1398    
1399         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
1400         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.
1401    
1402    
# Line 1510  STUDYING A PATTERN Line 1405  STUDYING A PATTERN
1405         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1406              const char **errptr);              const char **errptr);
1407    
1408         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
1409         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
1410         matching.  The function pcre_study() takes a pointer to a compiled pat-         matching. The function pcre_study() takes a pointer to a compiled  pat-
1411         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1412         information  that  will  help speed up matching, pcre_study() returns a         information that will help speed up matching,  pcre_study()  returns  a
1413         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
1414         the results of the study.         the results of the study.
1415    
1416         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1417         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-
1418         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
1419         passed; these are described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1420    
1421         If studying the  pattern  does  not  produce  any  useful  information,         If  studying  the  pattern  does  not  produce  any useful information,
1422         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1423         wants  to  pass  any  of   the   other   fields   to   pcre_exec()   or         wants   to   pass   any   of   the   other  fields  to  pcre_exec()  or
1424         pcre_dfa_exec(), it must set up its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1425    
1426         The  second  argument of pcre_study() contains option bits. At present,         The second argument of pcre_study() contains option bits.  At  present,
1427         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1428    
1429         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.
1430         If  studying  succeeds  (even  if no data is returned), the variable it         If studying succeeds (even if no data is  returned),  the  variable  it
1431         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
1432         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
1433         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
1434         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1435    
1436         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 1549  STUDYING A PATTERN Line 1444  STUDYING A PATTERN
1444         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
1445         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
1446         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
1447         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
1448         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
1449         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
1450         the value in a calling program via the pcre_fullinfo() function.         the value in a calling program via the pcre_fullinfo() function.
1451    
1452         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
1453         have a single fixed starting character. A bitmap of  possible  starting         have  a  single fixed starting character. A bitmap of possible starting
1454         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
1455         which to start matching.         which to start matching.
1456    
1457         The two optimizations just described can be  disabled  by  setting  the         The  two  optimizations  just  described can be disabled by setting the
1458         PCRE_NO_START_OPTIMIZE    option    when    calling    pcre_exec()   or         PCRE_NO_START_OPTIMIZE   option    when    calling    pcre_exec()    or
1459         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
1460         callouts,  or  make  use of (*MARK), and you make use of these in cases         callouts or (*MARK), and you want to make use of  these  facilities  in
1461         where matching fails.  See  the  discussion  of  PCRE_NO_START_OPTIMIZE         cases  where  matching fails. See the discussion of PCRE_NO_START_OPTI-
1462         below.         MIZE below.
1463    
1464    
1465  LOCALE SUPPORT  LOCALE SUPPORT
1466    
1467         PCRE  handles  caseless matching, and determines whether characters are         PCRE handles caseless matching, and determines whether  characters  are
1468         letters, digits, or whatever, by reference to a set of tables,  indexed         letters,  digits, or whatever, by reference to a set of tables, indexed
1469         by  character  value.  When running in UTF-8 mode, this applies only to         by character value. When running in UTF-8 mode, this  applies  only  to
1470         characters with codes less than 128. By  default,  higher-valued  codes         characters  with  codes  less than 128. By default, higher-valued codes
1471         never match escapes such as \w or \d, but they can be tested with \p if         never match escapes such as \w or \d, but they can be tested with \p if
1472         PCRE is built with Unicode character property  support.  Alternatively,         PCRE  is  built with Unicode character property support. Alternatively,
1473         the  PCRE_UCP  option  can  be  set at compile time; this causes \w and         the PCRE_UCP option can be set at compile  time;  this  causes  \w  and
1474         friends to use Unicode property support instead of built-in tables. The         friends to use Unicode property support instead of built-in tables. The
1475         use of locales with Unicode is discouraged. If you are handling charac-         use of locales with Unicode is discouraged. If you are handling charac-
1476         ters with codes greater than 128, you should either use UTF-8 and  Uni-         ters  with codes greater than 128, you should either use UTF-8 and Uni-
1477         code, or use locales, but not try to mix the two.         code, or use locales, but not try to mix the two.
1478    
1479         PCRE  contains  an  internal set of tables that are used when the final         PCRE contains an internal set of tables that are used  when  the  final
1480         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many
1481         applications.  Normally, the internal tables recognize only ASCII char-         applications.  Normally, the internal tables recognize only ASCII char-
1482         acters. However, when PCRE is built, it is possible to cause the inter-         acters. However, when PCRE is built, it is possible to cause the inter-
1483         nal tables to be rebuilt in the default "C" locale of the local system,         nal tables to be rebuilt in the default "C" locale of the local system,
1484         which may cause them to be different.         which may cause them to be different.
1485    
1486         The internal tables can always be overridden by tables supplied by  the         The  internal tables can always be overridden by tables supplied by the
1487         application that calls PCRE. These may be created in a different locale         application that calls PCRE. These may be created in a different locale
1488         from the default. As more and more applications change  to  using  Uni-         from  the  default.  As more and more applications change to using Uni-
1489         code, the need for this locale support is expected to die away.         code, the need for this locale support is expected to die away.
1490    
1491         External  tables  are  built by calling the pcre_maketables() function,         External tables are built by calling  the  pcre_maketables()  function,
1492         which has no arguments, in the relevant locale. The result can then  be         which  has no arguments, in the relevant locale. The result can then be
1493         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For
1494         example, to build and use tables that are appropriate  for  the  French         example,  to  build  and use tables that are appropriate for the French
1495         locale  (where  accented  characters  with  values greater than 128 are         locale (where accented characters with  values  greater  than  128  are
1496         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1497    
1498           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1499           tables = pcre_maketables();           tables = pcre_maketables();
1500           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1501    
1502         The locale name "fr_FR" is used on Linux and other  Unix-like  systems;         The  locale  name "fr_FR" is used on Linux and other Unix-like systems;
1503         if you are using Windows, the name for the French locale is "french".         if you are using Windows, the name for the French locale is "french".
1504    
1505         When  pcre_maketables()  runs,  the  tables are built in memory that is         When pcre_maketables() runs, the tables are built  in  memory  that  is
1506         obtained via pcre_malloc. It is the caller's responsibility  to  ensure         obtained  via  pcre_malloc. It is the caller's responsibility to ensure
1507         that  the memory containing the tables remains available for as long as         that the memory containing the tables remains available for as long  as
1508         it is needed.         it is needed.
1509    
1510         The pointer that is passed to pcre_compile() is saved with the compiled         The pointer that is passed to pcre_compile() is saved with the compiled
1511         pattern,  and the same tables are used via this pointer by pcre_study()         pattern, and the same tables are used via this pointer by  pcre_study()
1512         and normally also by pcre_exec(). Thus, by default, for any single pat-         and normally also by pcre_exec(). Thus, by default, for any single pat-
1513         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1514         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1515    
1516         It is possible to pass a table pointer or NULL (indicating the  use  of         It  is  possible to pass a table pointer or NULL (indicating the use of
1517         the  internal  tables)  to  pcre_exec(). Although not intended for this         the internal tables) to pcre_exec(). Although  not  intended  for  this
1518         purpose, this facility could be used to match a pattern in a  different         purpose,  this facility could be used to match a pattern in a different
1519         locale from the one in which it was compiled. Passing table pointers at         locale from the one in which it was compiled. Passing table pointers at
1520         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1521    
# Line 1630  INFORMATION ABOUT A PATTERN Line 1525  INFORMATION ABOUT A PATTERN
1525         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1526              int what, void *where);              int what, void *where);
1527    
1528         The pcre_fullinfo() function returns information about a compiled  pat-         The  pcre_fullinfo() function returns information about a compiled pat-
1529         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1530         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1531    
1532         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled
1533         pattern.  The second argument is the result of pcre_study(), or NULL if         pattern. The second argument is the result of pcre_study(), or NULL  if
1534         the pattern was not studied. The third argument specifies  which  piece         the  pattern  was not studied. The third argument specifies which piece
1535         of  information  is required, and the fourth argument is a pointer to a         of information is required, and the fourth argument is a pointer  to  a
1536         variable to receive the data. The yield of the  function  is  zero  for         variable  to  receive  the  data. The yield of the function is zero for
1537         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1538    
1539           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1646  INFORMATION ABOUT A PATTERN Line 1541  INFORMATION ABOUT A PATTERN
1541           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1542           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1543    
1544         The  "magic  number" is placed at the start of each compiled pattern as         The "magic number" is placed at the start of each compiled  pattern  as
1545         an simple check against passing an arbitrary memory pointer. Here is  a         an  simple check against passing an arbitrary memory pointer. Here is a
1546         typical  call  of pcre_fullinfo(), to obtain the length of the compiled         typical call of pcre_fullinfo(), to obtain the length of  the  compiled
1547         pattern:         pattern:
1548    
1549           int rc;           int rc;
# Line 1659  INFORMATION ABOUT A PATTERN Line 1554  INFORMATION ABOUT A PATTERN
1554             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1555             &length);         /* where to put the data */             &length);         /* where to put the data */
1556    
1557         The possible values for the third argument are defined in  pcre.h,  and         The  possible  values for the third argument are defined in pcre.h, and
1558         are as follows:         are as follows:
1559    
1560           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1561    
1562         Return  the  number  of  the highest back reference in the pattern. The         Return the number of the highest back reference  in  the  pattern.  The
1563         fourth argument should point to an int variable. Zero  is  returned  if         fourth  argument  should  point to an int variable. Zero is returned if
1564         there are no back references.         there are no back references.
1565    
1566           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1567    
1568         Return  the  number of capturing subpatterns in the pattern. The fourth         Return the number of capturing subpatterns in the pattern.  The  fourth
1569         argument should point to an int variable.         argument should point to an int variable.
1570    
1571           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1572    
1573         Return a pointer to the internal default character tables within  PCRE.         Return  a pointer to the internal default character tables within PCRE.
1574         The  fourth  argument should point to an unsigned char * variable. This         The fourth argument should point to an unsigned char *  variable.  This
1575         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1576         tion.  External  callers  can  cause PCRE to use its internal tables by         tion. External callers can cause PCRE to use  its  internal  tables  by
1577         passing a NULL table pointer.         passing a NULL table pointer.
1578    
1579           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1580    
1581         Return information about the first byte of any matched  string,  for  a         Return  information  about  the first byte of any matched string, for a
1582         non-anchored  pattern. The fourth argument should point to an int vari-         non-anchored pattern. The fourth argument should point to an int  vari-
1583         able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name         able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name
1584         is still recognized for backwards compatibility.)         is still recognized for backwards compatibility.)
1585    
1586         If  there  is  a  fixed first byte, for example, from a pattern such as         If there is a fixed first byte, for example, from  a  pattern  such  as
1587         (cat|cow|coyote), its value is returned. Otherwise, if either         (cat|cow|coyote), its value is returned. Otherwise, if either
1588    
1589         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
1590         branch starts with "^", or         branch starts with "^", or
1591    
1592         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
1593         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1594    
1595         -1 is returned, indicating that the pattern matches only at  the  start         -1  is  returned, indicating that the pattern matches only at the start
1596         of  a  subject string or after any newline within the string. Otherwise         of a subject string or after any newline within the  string.  Otherwise
1597         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1598    
1599           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1600    
1601         If the pattern was studied, and this resulted in the construction of  a         If  the pattern was studied, and this resulted in the construction of a
1602         256-bit table indicating a fixed set of bytes for the first byte in any         256-bit table indicating a fixed set of bytes for the first byte in any
1603         matching string, a pointer to the table is returned. Otherwise NULL  is         matching  string, a pointer to the table is returned. Otherwise NULL is
1604         returned.  The fourth argument should point to an unsigned char * vari-         returned. The fourth argument should point to an unsigned char *  vari-
1605         able.         able.
1606    
1607           PCRE_INFO_HASCRORLF           PCRE_INFO_HASCRORLF
1608    
1609         Return 1 if the pattern contains any explicit  matches  for  CR  or  LF         Return  1  if  the  pattern  contains any explicit matches for CR or LF
1610         characters,  otherwise  0.  The  fourth argument should point to an int         characters, otherwise 0. The fourth argument should  point  to  an  int
1611         variable. An explicit match is either a literal CR or LF character,  or         variable.  An explicit match is either a literal CR or LF character, or
1612         \r or \n.         \r or \n.
1613    
1614           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
1615    
1616         Return  1  if  the (?J) or (?-J) option setting is used in the pattern,         Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,
1617         otherwise 0. The fourth argument should point to an int variable.  (?J)         otherwise  0. The fourth argument should point to an int variable. (?J)
1618         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1619    
1620           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1621    
1622         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
1623         matched string, other than at its  start,  if  such  a  byte  has  been         matched  string,  other  than  at  its  start,  if such a byte has been
1624         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1625         is no such byte, -1 is returned. For anchored patterns, a last  literal         is  no such byte, -1 is returned. For anchored patterns, a last literal
1626         byte  is  recorded only if it follows something of variable length. For         byte is recorded only if it follows something of variable  length.  For
1627         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
1628         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1629    
1630           PCRE_INFO_MINLENGTH           PCRE_INFO_MINLENGTH
1631    
1632         If  the  pattern  was studied and a minimum length for matching subject         If the pattern was studied and a minimum length  for  matching  subject
1633         strings was computed, its value is  returned.  Otherwise  the  returned         strings  was  computed,  its  value is returned. Otherwise the returned
1634         value  is  -1. The value is a number of characters, not bytes (this may         value is -1. The value is a number of characters, not bytes  (this  may
1635         be relevant in UTF-8 mode). The fourth argument should point to an  int         be  relevant in UTF-8 mode). The fourth argument should point to an int
1636         variable.  A  non-negative  value is a lower bound to the length of any         variable. A non-negative value is a lower bound to the  length  of  any
1637         matching string. There may not be any strings of that  length  that  do         matching  string.  There  may not be any strings of that length that do
1638         actually match, but every string that does match is at least that long.         actually match, but every string that does match is at least that long.
1639    
1640           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
1641           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1642           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1643    
1644         PCRE  supports the use of named as well as numbered capturing parenthe-         PCRE supports the use of named as well as numbered capturing  parenthe-
1645         ses. The names are just an additional way of identifying the  parenthe-         ses.  The names are just an additional way of identifying the parenthe-
1646         ses, which still acquire numbers. Several convenience functions such as         ses, which still acquire numbers. Several convenience functions such as
1647         pcre_get_named_substring() are provided for  extracting  captured  sub-         pcre_get_named_substring()  are  provided  for extracting captured sub-
1648         strings  by  name. It is also possible to extract the data directly, by         strings by name. It is also possible to extract the data  directly,  by
1649         first converting the name to a number in order to  access  the  correct         first  converting  the  name to a number in order to access the correct
1650         pointers in the output vector (described with pcre_exec() below). To do         pointers in the output vector (described with pcre_exec() below). To do
1651         the conversion, you need  to  use  the  name-to-number  map,  which  is         the  conversion,  you  need  to  use  the  name-to-number map, which is
1652         described by these three values.         described by these three values.
1653    
1654         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
1655         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1656         of  each  entry;  both  of  these  return  an int value. The entry size         of each entry; both of these  return  an  int  value.  The  entry  size
1657         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns
1658         a  pointer  to  the  first  entry of the table (a pointer to char). The         a pointer to the first entry of the table  (a  pointer  to  char).  The
1659         first two bytes of each entry are the number of the capturing parenthe-         first two bytes of each entry are the number of the capturing parenthe-
1660         sis,  most  significant byte first. The rest of the entry is the corre-         sis, most significant byte first. The rest of the entry is  the  corre-
1661         sponding name, zero terminated.         sponding name, zero terminated.
1662    
1663         The names are in alphabetical order. Duplicate names may appear if  (?|         The  names are in alphabetical order. Duplicate names may appear if (?|
1664         is used to create multiple groups with the same number, as described in         is used to create multiple groups with the same number, as described in
1665         the section on duplicate subpattern numbers in  the  pcrepattern  page.         the  section  on  duplicate subpattern numbers in the pcrepattern page.
1666         Duplicate  names  for  subpatterns with different numbers are permitted         Duplicate names for subpatterns with different  numbers  are  permitted
1667         only if PCRE_DUPNAMES is set. In all cases  of  duplicate  names,  they         only  if  PCRE_DUPNAMES  is  set. In all cases of duplicate names, they
1668         appear  in  the table in the order in which they were found in the pat-         appear in the table in the order in which they were found in  the  pat-
1669         tern. In the absence of (?| this is the  order  of  increasing  number;         tern.  In  the  absence  of (?| this is the order of increasing number;
1670         when (?| is used this is not necessarily the case because later subpat-         when (?| is used this is not necessarily the case because later subpat-
1671         terns may have lower numbers.         terns may have lower numbers.
1672    
1673         As a simple example of the name/number table,  consider  the  following         As  a  simple  example of the name/number table, consider the following
1674         pattern  (assume  PCRE_EXTENDED is set, so white space - including new-         pattern (assume PCRE_EXTENDED is set, so white space -  including  new-
1675         lines - is ignored):         lines - is ignored):
1676    
1677           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1678           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1679    
1680         There are four named subpatterns, so the table has  four  entries,  and         There  are  four  named subpatterns, so the table has four entries, and
1681         each  entry  in the table is eight bytes long. The table is as follows,         each entry in the table is eight bytes long. The table is  as  follows,
1682         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1683         as ??:         as ??:
1684    
# Line 1792  INFORMATION ABOUT A PATTERN Line 1687  INFORMATION ABOUT A PATTERN
1687           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1688           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1689    
1690         When  writing  code  to  extract  data from named subpatterns using the         When writing code to extract data  from  named  subpatterns  using  the
1691         name-to-number map, remember that the length of the entries  is  likely         name-to-number  map,  remember that the length of the entries is likely
1692         to be different for each compiled pattern.         to be different for each compiled pattern.
1693    
1694           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
1695    
1696         Return  1  if  the  pattern  can  be  used  for  partial  matching with         Return 1  if  the  pattern  can  be  used  for  partial  matching  with
1697         pcre_exec(), otherwise 0. The fourth argument should point  to  an  int         pcre_exec(),  otherwise  0.  The fourth argument should point to an int
1698         variable.  From  release  8.00,  this  always  returns  1,  because the         variable. From  release  8.00,  this  always  returns  1,  because  the
1699         restrictions that previously applied  to  partial  matching  have  been         restrictions  that  previously  applied  to  partial matching have been
1700         lifted.  The  pcrepartial documentation gives details of partial match-         lifted. The pcrepartial documentation gives details of  partial  match-
1701         ing.         ing.
1702    
1703           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1704    
1705         Return a copy of the options with which the pattern was  compiled.  The         Return  a  copy of the options with which the pattern was compiled. The
1706         fourth  argument  should  point to an unsigned long int variable. These         fourth argument should point to an unsigned long  int  variable.  These
1707         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1708         by any top-level option settings at the start of the pattern itself. In         by any top-level option settings at the start of the pattern itself. In
1709         other words, they are the options that will be in force  when  matching         other  words,  they are the options that will be in force when matching
1710         starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with         starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with
1711         the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,         the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,
1712         and PCRE_EXTENDED.         and PCRE_EXTENDED.
1713    
1714         A  pattern  is  automatically  anchored by PCRE if all of its top-level         A pattern is automatically anchored by PCRE if  all  of  its  top-level
1715         alternatives begin with one of the following:         alternatives begin with one of the following:
1716    
1717           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1830  INFORMATION ABOUT A PATTERN Line 1725  INFORMATION ABOUT A PATTERN
1725    
1726           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1727    
1728         Return  the  size  of the compiled pattern, that is, the value that was         Return the size of the compiled pattern, that is, the  value  that  was
1729         passed as the argument to pcre_malloc() when PCRE was getting memory in         passed as the argument to pcre_malloc() when PCRE was getting memory in
1730         which to place the compiled data. The fourth argument should point to a         which to place the compiled data. The fourth argument should point to a
1731         size_t variable.         size_t variable.
# Line 1838  INFORMATION ABOUT A PATTERN Line 1733  INFORMATION ABOUT A PATTERN
1733           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1734    
1735         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
1736         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,
1737         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-
1738         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-
1739         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
1740         variable.         pattern" above). The format of the study_data block is private, but its
1741           length  is  made  available via this option so that it can be saved and
1742           restored (see the pcreprecompile documentation for details).
1743    
1744    
1745  OBSOLETE INFO FUNCTION  OBSOLETE INFO FUNCTION
1746    
1747         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1748    
1749         The  pcre_info()  function is now obsolete because its interface is too         The pcre_info() function is now obsolete because its interface  is  too
1750         restrictive to return all the available data about a compiled  pattern.         restrictive  to return all the available data about a compiled pattern.
1751         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of
1752         pcre_info() is the number of capturing subpatterns, or one of the  fol-         pcre_info()  is the number of capturing subpatterns, or one of the fol-
1753         lowing negative numbers:         lowing negative numbers:
1754    
1755           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1756           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1757    
1758         If  the  optptr  argument is not NULL, a copy of the options with which         If the optptr argument is not NULL, a copy of the  options  with  which
1759         the pattern was compiled is placed in the integer  it  points  to  (see         the  pattern  was  compiled  is placed in the integer it points to (see
1760         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1761    
1762         If  the  pattern  is  not anchored and the firstcharptr argument is not         If the pattern is not anchored and the  firstcharptr  argument  is  not
1763         NULL, it is used to pass back information about the first character  of         NULL,  it is used to pass back information about the first character of
1764         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1765    
1766    
# Line 1871  REFERENCE COUNTS Line 1768  REFERENCE COUNTS
1768    
1769         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1770    
1771         The  pcre_refcount()  function is used to maintain a reference count in         The pcre_refcount() function is used to maintain a reference  count  in
1772         the data block that contains a compiled pattern. It is provided for the         the data block that contains a compiled pattern. It is provided for the
1773         benefit  of  applications  that  operate  in an object-oriented manner,         benefit of applications that  operate  in  an  object-oriented  manner,
1774         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1775         pattern, but you want to free the block when they are all done.         pattern, but you want to free the block when they are all done.
1776    
1777         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1778         zero.  It is changed only by calling this function, whose action is  to         zero.   It is changed only by calling this function, whose action is to
1779         add  the  adjust  value  (which may be positive or negative) to it. The         add the adjust value (which may be positive or  negative)  to  it.  The
1780         yield of the function is the new value. However, the value of the count         yield of the function is the new value. However, the value of the count
1781         is  constrained to lie between 0 and 65535, inclusive. If the new value         is constrained to lie between 0 and 65535, inclusive. If the new  value
1782         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1783    
1784         Except when it is zero, the reference count is not correctly  preserved         Except  when it is zero, the reference count is not correctly preserved
1785         if  a  pattern  is  compiled on one host and then transferred to a host         if a pattern is compiled on one host and then  transferred  to  a  host
1786         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1787    
1788    
# Line 1895  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1792  MATCHING A PATTERN: THE TRADITIONAL FUNC
1792              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1793              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1794    
1795         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
1796         compiled  pattern, which is passed in the code argument. If the pattern         compiled pattern, which is passed in the code argument. If the  pattern
1797         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
1798         argument.  This  function is the main matching facility of the library,         argument. This function is the main matching facility of  the  library,
1799         and it operates in a Perl-like manner. For specialist use there is also         and it operates in a Perl-like manner. For specialist use there is also
1800         an  alternative matching function, which is described below in the sec-         an alternative matching function, which is described below in the  sec-
1801         tion about the pcre_dfa_exec() function.         tion about the pcre_dfa_exec() function.
1802    
1803         In most applications, the pattern will have been compiled (and  option-         In  most applications, the pattern will have been compiled (and option-
1804         ally  studied)  in the same process that calls pcre_exec(). However, it         ally studied) in the same process that calls pcre_exec().  However,  it
1805         is possible to save compiled patterns and study data, and then use them         is possible to save compiled patterns and study data, and then use them
1806         later  in  different processes, possibly even on different hosts. For a         later in different processes, possibly even on different hosts.  For  a
1807         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
1808    
1809         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1925  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1822  MATCHING A PATTERN: THE TRADITIONAL FUNC
1822    
1823     Extra data for pcre_exec()     Extra data for pcre_exec()
1824    
1825         If the extra argument is not NULL, it must point to a  pcre_extra  data         If  the  extra argument is not NULL, it must point to a pcre_extra data
1826         block.  The pcre_study() function returns such a block (when it doesn't         block. The pcre_study() function returns such a block (when it  doesn't
1827         return NULL), but you can also create one for yourself, and pass  addi-         return  NULL), but you can also create one for yourself, and pass addi-
1828         tional  information  in it. The pcre_extra block contains the following         tional information in it. The pcre_extra block contains  the  following
1829         fields (not necessarily in this order):         fields (not necessarily in this order):
1830    
1831           unsigned long int flags;           unsigned long int flags;
# Line 1939  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1836  MATCHING A PATTERN: THE TRADITIONAL FUNC
1836           const unsigned char *tables;           const unsigned char *tables;
1837           unsigned char **mark;           unsigned char **mark;
1838    
1839         The flags field is a bitmap that specifies which of  the  other  fields         The  flags  field  is a bitmap that specifies which of the other fields
1840         are set. The flag bits are:         are set. The flag bits are:
1841    
1842           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
# Line 1949  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1846  MATCHING A PATTERN: THE TRADITIONAL FUNC
1846           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1847           PCRE_EXTRA_MARK           PCRE_EXTRA_MARK
1848    
1849         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 is  set  in
1850         the pcre_extra block that is returned by  pcre_study(),  together  with         the  pcre_extra  block  that is returned by pcre_study(), together with
1851         the appropriate flag bit. You should not set this yourself, but you may         the appropriate flag bit. You should not set this yourself, but you may
1852         add to the block by setting the other fields  and  their  corresponding         add  to  the  block by setting the other fields and their corresponding
1853         flag bits.         flag bits.
1854    
1855         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
1856         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
1857         match,  but  which  have  a very large number of possibilities in their         match, but which have a very large number  of  possibilities  in  their
1858         search trees. The classic example is a pattern that uses nested  unlim-         search  trees. The classic example is a pattern that uses nested unlim-
1859         ited repeats.         ited repeats.
1860    
1861         Internally,  PCRE uses a function called match() which it calls repeat-         Internally, PCRE uses a function called match() which it calls  repeat-
1862         edly (sometimes recursively). The limit set by match_limit  is  imposed         edly  (sometimes  recursively). The limit set by match_limit is imposed
1863         on  the  number  of times this function is called during a match, which         on the number of times this function is called during  a  match,  which
1864         has the effect of limiting the amount of  backtracking  that  can  take         has  the  effect  of  limiting the amount of backtracking that can take
1865         place. For patterns that are not anchored, the count restarts from zero         place. For patterns that are not anchored, the count restarts from zero
1866         for each position in the subject string.         for each position in the subject string.
1867    
1868         The default value for the limit can be set  when  PCRE  is  built;  the         The  default  value  for  the  limit can be set when PCRE is built; the
1869         default  default  is 10 million, which handles all but the most extreme         default default is 10 million, which handles all but the  most  extreme
1870         cases. You can override the default  by  suppling  pcre_exec()  with  a         cases.  You  can  override  the  default by suppling pcre_exec() with a
1871         pcre_extra     block    in    which    match_limit    is    set,    and         pcre_extra    block    in    which    match_limit    is    set,     and
1872         PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is         PCRE_EXTRA_MATCH_LIMIT  is  set  in  the  flags  field. If the limit is
1873         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1874    
1875         The  match_limit_recursion field is similar to match_limit, but instead         The match_limit_recursion field is similar to match_limit, but  instead
1876         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
1877         the  depth  of  recursion. The recursion depth is a smaller number than         the depth of recursion. The recursion depth is a  smaller  number  than
1878         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-
1879         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.
1880    
1881         Limiting  the  recursion  depth  limits the amount of stack that can be         Limiting the recursion depth limits the amount of  stack  that  can  be
1882         used, or, when PCRE has been compiled to use memory on the heap instead         used, or, when PCRE has been compiled to use memory on the heap instead
1883         of the stack, the amount of heap memory that can be used.         of the stack, the amount of heap memory that can be used.
1884    
1885         The  default  value  for  match_limit_recursion can be set when PCRE is         The default value for match_limit_recursion can be  set  when  PCRE  is
1886         built; the default default  is  the  same  value  as  the  default  for         built;  the  default  default  is  the  same  value  as the default for
1887         match_limit.  You can override the default by suppling pcre_exec() with         match_limit. You can override the default by suppling pcre_exec()  with
1888         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and         a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
1889         PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the         PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
1890         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1891    
1892         The callout_data field is used in conjunction with the  "callout"  fea-         The  callout_data  field is used in conjunction with the "callout" fea-
1893         ture, and is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
1894    
1895         The  tables  field  is  used  to  pass  a  character  tables pointer to         The tables field  is  used  to  pass  a  character  tables  pointer  to
1896         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec();  this overrides the value that is stored with the compiled
1897         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
1898         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
1899         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
1900         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-
1901         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
1902         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
1903         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
1904         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
1905    
1906         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
1907         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-
1908         tracking control verbs such as (*MARK:NAME), and the execution ends  up         tracking  control verbs such as (*MARK:NAME), and the execution ends up
1909         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-
1910         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
1911         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
1912         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.
1913         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
1914         field set to NULL. For details of the backtracking control  verbs,  see         field  set  to NULL. For details of the backtracking control verbs, see
1915         the section entitled "Backtracking control" in the pcrepattern documen-         the section entitled "Backtracking control" in the pcrepattern documen-
1916         tation.         tation.
1917    
1918     Option bits for pcre_exec()     Option bits for pcre_exec()
1919    
1920         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.
1921         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,
1922         PCRE_NOTBOL,   PCRE_NOTEOL,    PCRE_NOTEMPTY,    PCRE_NOTEMPTY_ATSTART,         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
1923         PCRE_NO_START_OPTIMIZE,   PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,  and         PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
1924         PCRE_PARTIAL_HARD.         PCRE_PARTIAL_HARD.
1925    
1926           PCRE_ANCHORED           PCRE_ANCHORED
1927    
1928         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first
1929         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or
1930         turned out to be anchored by virtue of its contents, it cannot be  made         turned  out to be anchored by virtue of its contents, it cannot be made
1931         unachored at matching time.         unachored at matching time.
1932    
1933           PCRE_BSR_ANYCRLF           PCRE_BSR_ANYCRLF
1934           PCRE_BSR_UNICODE           PCRE_BSR_UNICODE
1935    
1936         These options (which are mutually exclusive) control what the \R escape         These options (which are mutually exclusive) control what the \R escape
1937         sequence matches. The choice is either to match only CR, LF,  or  CRLF,         sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1938         or  to  match  any Unicode newline sequence. These options override the         or to match any Unicode newline sequence. These  options  override  the
1939         choice that was made or defaulted when the pattern was compiled.         choice that was made or defaulted when the pattern was compiled.
1940    
1941           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 2047  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1944  MATCHING A PATTERN: THE TRADITIONAL FUNC
1944           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1945           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1946    
1947         These options override  the  newline  definition  that  was  chosen  or         These  options  override  the  newline  definition  that  was chosen or
1948         defaulted  when the pattern was compiled. For details, see the descrip-         defaulted when the pattern was compiled. For details, see the  descrip-
1949         tion of pcre_compile()  above.  During  matching,  the  newline  choice         tion  of  pcre_compile()  above.  During  matching,  the newline choice
1950         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
1951         ters. It may also alter the way the match position is advanced after  a         ters.  It may also alter the way the match position is advanced after a
1952         match failure for an unanchored pattern.         match failure for an unanchored pattern.
1953    
1954         When  PCRE_NEWLINE_CRLF,  PCRE_NEWLINE_ANYCRLF,  or PCRE_NEWLINE_ANY is         When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
1955         set, and a match attempt for an unanchored pattern fails when the  cur-         set,  and a match attempt for an unanchored pattern fails when the cur-
1956         rent  position  is  at  a  CRLF  sequence,  and the pattern contains no         rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
1957         explicit matches for  CR  or  LF  characters,  the  match  position  is         explicit  matches  for  CR  or  LF  characters,  the  match position is
1958         advanced by two characters instead of one, in other words, to after the         advanced by two characters instead of one, in other words, to after the
1959         CRLF.         CRLF.
1960    
1961         The above rule is a compromise that makes the most common cases work as         The above rule is a compromise that makes the most common cases work as
1962         expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL         expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
1963         option is not set), it does not match the string "\r\nA" because, after         option is not set), it does not match the string "\r\nA" because, after
1964         failing  at the start, it skips both the CR and the LF before retrying.         failing at the start, it skips both the CR and the LF before  retrying.
1965         However, the pattern [\r\n]A does match that string,  because  it  con-         However,  the  pattern  [\r\n]A does match that string, because it con-
1966         tains an explicit CR or LF reference, and so advances only by one char-         tains an explicit CR or LF reference, and so advances only by one char-
1967         acter after the first failure.         acter after the first failure.
1968    
1969         An explicit match for CR of LF is either a literal appearance of one of         An explicit match for CR of LF is either a literal appearance of one of
1970         those  characters,  or  one  of the \r or \n escape sequences. Implicit         those characters, or one of the \r or  \n  escape  sequences.  Implicit
1971         matches such as [^X] do not count, nor does \s (which includes  CR  and         matches  such  as [^X] do not count, nor does \s (which includes CR and
1972         LF in the characters that it matches).         LF in the characters that it matches).
1973    
1974         Notwithstanding  the above, anomalous effects may still occur when CRLF         Notwithstanding the above, anomalous effects may still occur when  CRLF
1975         is a valid newline sequence and explicit \r or \n escapes appear in the         is a valid newline sequence and explicit \r or \n escapes appear in the
1976         pattern.         pattern.
1977    
1978           PCRE_NOTBOL           PCRE_NOTBOL
1979    
1980         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
1981         the beginning of a line, so the  circumflex  metacharacter  should  not         the  beginning  of  a  line, so the circumflex metacharacter should not
1982         match  before it. Setting this without PCRE_MULTILINE (at compile time)         match before it. Setting this without PCRE_MULTILINE (at compile  time)
1983         causes circumflex never to match. This option affects only  the  behav-         causes  circumflex  never to match. This option affects only the behav-
1984         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
1985    
1986           PCRE_NOTEOL           PCRE_NOTEOL
1987    
1988         This option specifies that the end of the subject string is not the end         This option specifies that the end of the subject string is not the end
1989         of a line, so the dollar metacharacter should not match it nor  (except         of  a line, so the dollar metacharacter should not match it nor (except
1990         in  multiline mode) a newline immediately before it. Setting this with-         in multiline mode) a newline immediately before it. Setting this  with-
1991         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
1992         option  affects only the behaviour of the dollar metacharacter. It does         option affects only the behaviour of the dollar metacharacter. It  does
1993         not affect \Z or \z.         not affect \Z or \z.
1994    
1995           PCRE_NOTEMPTY           PCRE_NOTEMPTY
1996    
1997         An empty string is not considered to be a valid match if this option is         An empty string is not considered to be a valid match if this option is
1998         set.  If  there are alternatives in the pattern, they are tried. If all         set. If there are alternatives in the pattern, they are tried.  If  all
1999         the alternatives match the empty string, the entire  match  fails.  For         the  alternatives  match  the empty string, the entire match fails. For
2000         example, if the pattern         example, if the pattern
2001    
2002           a?b?           a?b?
2003    
2004         is  applied  to  a  string not beginning with "a" or "b", it matches an         is applied to a string not beginning with "a" or  "b",  it  matches  an
2005         empty string at the start of the subject. With PCRE_NOTEMPTY set,  this         empty  string at the start of the subject. With PCRE_NOTEMPTY set, this
2006         match is not valid, so PCRE searches further into the string for occur-         match is not valid, so PCRE searches further into the string for occur-
2007         rences of "a" or "b".         rences of "a" or "b".
2008    
2009           PCRE_NOTEMPTY_ATSTART           PCRE_NOTEMPTY_ATSTART
2010    
2011         This is like PCRE_NOTEMPTY, except that an empty string match  that  is         This  is  like PCRE_NOTEMPTY, except that an empty string match that is
2012         not  at  the  start  of  the  subject  is  permitted. If the pattern is         not at the start of  the  subject  is  permitted.  If  the  pattern  is
2013         anchored, such a match can occur only if the pattern contains \K.         anchored, such a match can occur only if the pattern contains \K.
2014    
2015         Perl    has    no    direct    equivalent    of    PCRE_NOTEMPTY     or         Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or
2016         PCRE_NOTEMPTY_ATSTART,  but  it  does  make a special case of a pattern         PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern
2017         match of the empty string within its split() function, and  when  using         match  of  the empty string within its split() function, and when using
2018         the  /g  modifier.  It  is  possible  to emulate Perl's behaviour after         the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after
2019         matching a null string by first trying the match again at the same off-         matching a null string by first trying the match again at the same off-
2020         set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that         set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that
2021         fails, by advancing the starting offset (see below) and trying an ordi-         fails, by advancing the starting offset (see below) and trying an ordi-
2022         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
2023         in the pcredemo sample program.         in  the  pcredemo sample program. In the most general case, you have to
2024           check to see if the newline convention recognizes CRLF  as  a  newline,
2025           and  if so, and the current character is CR followed by LF, advance the
2026           starting offset by two characters instead of one.
2027    
2028           PCRE_NO_START_OPTIMIZE           PCRE_NO_START_OPTIMIZE
2029    
# Line 2143  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2043  MATCHING A PATTERN: THE TRADITIONAL FUNC
2043         possibly  causing  performance  to  suffer,  but ensuring that in cases         possibly  causing  performance  to  suffer,  but ensuring that in cases
2044         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
2045         such as (*COMMIT) and (*MARK) are considered at every possible starting         such as (*COMMIT) and (*MARK) are considered at every possible starting
2046         position in the subject  string.   Setting  PCRE_NO_START_OPTIMIZE  can         position in the subject string. If  PCRE_NO_START_OPTIMIZE  is  set  at
2047         change the outcome of a matching operation.  Consider the pattern         compile time, it cannot be unset at matching time.
2048    
2049           Setting  PCRE_NO_START_OPTIMIZE  can  change  the outcome of a matching
2050           operation.  Consider the pattern
2051    
2052           (*COMMIT)ABC           (*COMMIT)ABC
2053    
2054         When  this  is  compiled, PCRE records the fact that a match must start         When this is compiled, PCRE records the fact that a  match  must  start
2055         with the character "A". Suppose the subject  string  is  "DEFABC".  The         with  the  character  "A".  Suppose the subject string is "DEFABC". The
2056         start-up  optimization  scans along the subject, finds "A" and runs the         start-up optimization scans along the subject, finds "A" and  runs  the
2057         first match attempt from there. The (*COMMIT) item means that the  pat-         first  match attempt from there. The (*COMMIT) item means that the pat-
2058         tern  must  match the current starting position, which in this case, it         tern must match the current starting position, which in this  case,  it
2059         does. However, if the same match  is  run  with  PCRE_NO_START_OPTIMIZE         does.  However,  if  the  same match is run with PCRE_NO_START_OPTIMIZE
2060         set,  the  initial  scan  along the subject string does not happen. The         set, the initial scan along the subject string  does  not  happen.  The
2061         first match attempt is run starting  from  "D"  and  when  this  fails,         first  match  attempt  is  run  starting  from "D" and when this fails,
2062         (*COMMIT)  prevents  any  further  matches  being tried, so the overall         (*COMMIT) prevents any further matches  being  tried,  so  the  overall
2063         result is "no match". If the pattern is studied,  more  start-up  opti-         result  is  "no  match". If the pattern is studied, more start-up opti-
2064         mizations  may  be  used. For example, a minimum length for the subject         mizations may be used. For example, a minimum length  for  the  subject
2065         may be recorded. Consider the pattern         may be recorded. Consider the pattern
2066    
2067           (*MARK:A)(X|Y)           (*MARK:A)(X|Y)
2068    
2069         The minimum length for a match is one  character.  If  the  subject  is         The  minimum  length  for  a  match is one character. If the subject is
2070         "ABC",  there  will  be  attempts  to  match "ABC", "BC", "C", and then         "ABC", there will be attempts to  match  "ABC",  "BC",  "C",  and  then
2071         finally an empty string.  If the pattern is studied, the final  attempt         finally  an empty string.  If the pattern is studied, the final attempt
2072         does  not take place, because PCRE knows that the subject is too short,         does not take place, because PCRE knows that the subject is too  short,
2073         and so the (*MARK) is never encountered.  In this  case,  studying  the         and  so  the  (*MARK) is never encountered.  In this case, studying the
2074         pattern  does  not  affect the overall match result, which is still "no         pattern does not affect the overall match result, which  is  still  "no
2075         match", but it does affect the auxiliary information that is returned.         match", but it does affect the auxiliary information that is returned.
2076    
2077           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2078    
2079         When PCRE_UTF8 is set at compile time, the validity of the subject as a         When PCRE_UTF8 is set at compile time, the validity of the subject as a
2080         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8 string is automatically checked when pcre_exec() is  subsequently
2081         called.  The value of startoffset is also checked  to  ensure  that  it         called.   The  value  of  startoffset is also checked to ensure that it
2082         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
2083         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
2084         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,
2085         pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-         pcre_exec()  returns  the  error  PCRE_ERROR_BADUTF8  or,  if PCRE_PAR-
2086         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
2087           end  of  the  subject, PCRE_ERROR_SHORTUTF8. In both cases, information
2088         If  you  already  know that your subject is valid, and you want to skip         about the precise nature of the error may also  be  returned  (see  the
2089         these   checks   for   performance   reasons,   you   can    set    the         descriptions  of these errors in the section entitled Error return val-
2090         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to         ues from pcre_exec() below).  If startoffset contains a value that does
2091         do this for the second and subsequent calls to pcre_exec() if  you  are         not  point to the start of a UTF-8 character (or to the end of the sub-
2092         making  repeated  calls  to  find  all  the matches in a single subject         ject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2093         string. However, you should be  sure  that  the  value  of  startoffset  
2094         points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is         If you already know that your subject is valid, and you  want  to  skip
2095         set, the effect of passing an invalid UTF-8 string as a subject,  or  a         these    checks    for   performance   reasons,   you   can   set   the
2096         value  of startoffset that does not point to the start of a UTF-8 char-         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to
2097         acter, is undefined. Your program may crash.         do  this  for the second and subsequent calls to pcre_exec() if you are
2098           making repeated calls to find all  the  matches  in  a  single  subject
2099           string.  However,  you  should  be  sure  that the value of startoffset
2100           points to the start of a UTF-8 character (or the end of  the  subject).
2101           When  PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8
2102           string as a subject or an invalid value of  startoffset  is  undefined.
2103           Your program may crash.
2104    
2105           PCRE_PARTIAL_HARD           PCRE_PARTIAL_HARD
2106           PCRE_PARTIAL_SOFT           PCRE_PARTIAL_SOFT
2107    
2108         These options turn on the partial matching feature. For backwards  com-         These  options turn on the partial matching feature. For backwards com-
2109         patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial         patibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A  partial
2110         match occurs if the end of the subject string is reached  successfully,         match  occurs if the end of the subject string is reached successfully,
2111         but  there  are not enough subject characters to complete the match. If         but there are not enough subject characters to complete the  match.  If
2112         this happens when PCRE_PARTIAL_HARD  is  set,  pcre_exec()  immediately         this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
2113         returns  PCRE_ERROR_PARTIAL.  Otherwise,  if  PCRE_PARTIAL_SOFT is set,         matching continues by testing any remaining alternatives.  Only  if  no
2114         matching continues by testing any other alternatives. Only if they  all         complete  match  can be found is PCRE_ERROR_PARTIAL returned instead of
2115         fail  is  PCRE_ERROR_PARTIAL  returned (instead of PCRE_ERROR_NOMATCH).         PCRE_ERROR_NOMATCH. In other words,  PCRE_PARTIAL_SOFT  says  that  the
2116         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
2117         found  is  set  as  the first matching string. There is a more detailed         match can be found.
2118         discussion in the pcrepartial documentation.  
2119           If PCRE_PARTIAL_HARD is set, it overrides  PCRE_PARTIAL_SOFT.  In  this
2120           case,  if  a  partial  match  is found, pcre_exec() immediately returns
2121           PCRE_ERROR_PARTIAL, without  considering  any  other  alternatives.  In
2122           other  words, when PCRE_PARTIAL_HARD is set, a partial match is consid-
2123           ered to be more important that an alternative complete match.
2124    
2125           In both cases, the portion of the string that was  inspected  when  the
2126           partial match was found is set as the first matching string. There is a
2127           more detailed discussion of partial and  multi-segment  matching,  with
2128           examples, in the pcrepartial documentation.
2129    
2130     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2131    
2132         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
2133         length (in bytes) in length, and a starting byte offset in startoffset.         length (in bytes) in length, and a starting byte offset in startoffset.
2134         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,
2135         acter.  Unlike  the pattern string, the subject may contain binary zero         pcre_exec() returns PCRE_ERROR_BADOFFSET. When the starting  offset  is
2136         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,
2137         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
2138         case.         must  point  to  the start of a UTF-8 character (or the end of the sub-
2139           ject). Unlike the pattern string, the subject may contain  binary  zero
2140         A non-zero starting offset is useful when searching for  another  match         bytes.
2141         in  the same subject by calling pcre_exec() again after a previous suc-  
2142         cess.  Setting startoffset differs from just passing over  a  shortened         A  non-zero  starting offset is useful when searching for another match
2143         string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins         in the same subject by calling pcre_exec() again after a previous  suc-
2144           cess.   Setting  startoffset differs from just passing over a shortened
2145           string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins
2146         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
2147    
2148           \Biss\B           \Biss\B
2149    
2150         which finds occurrences of "iss" in the middle of  words.  (\B  matches         which  finds  occurrences  of "iss" in the middle of words. (\B matches
2151         only  if  the  current position in the subject is not a word boundary.)         only if the current position in the subject is not  a  word  boundary.)
2152         When applied to the string "Mississipi" the first call  to  pcre_exec()         When  applied  to the string "Mississipi" the first call to pcre_exec()
2153         finds  the  first  occurrence. If pcre_exec() is called again with just         finds the first occurrence. If pcre_exec() is called  again  with  just
2154         the remainder of the subject,  namely  "issipi",  it  does  not  match,         the  remainder  of  the  subject,  namely  "issipi", it does not match,
2155         because \B is always false at the start of the subject, which is deemed         because \B is always false at the start of the subject, which is deemed
2156         to be a word boundary. However, if pcre_exec()  is  passed  the  entire         to  be  a  word  boundary. However, if pcre_exec() is passed the entire
2157         string again, but with startoffset set to 4, it finds the second occur-         string again, but with startoffset set to 4, it finds the second occur-
2158         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
2159         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2160    
2161           Finding all the matches in a subject is tricky  when  the  pattern  can
2162           match an empty string. It is possible to emulate Perl's /g behaviour by
2163           first  trying  the  match  again  at  the   same   offset,   with   the
2164           PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED  options,  and  then  if that
2165           fails, advancing the starting  offset  and  trying  an  ordinary  match
2166           again. There is some code that demonstrates how to do this in the pcre-
2167           demo sample program. In the most general case, you have to check to see
2168           if  the newline convention recognizes CRLF as a newline, and if so, and
2169           the current character is CR followed by LF, advance the starting offset
2170           by two characters instead of one.
2171    
2172         If  a  non-zero starting offset is passed when the pattern is anchored,         If  a  non-zero starting offset is passed when the pattern is anchored,
2173         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
2174         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
# Line 2309  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2241  MATCHING A PATTERN: THE TRADITIONAL FUNC
2241         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
2242         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
2243         matched. The return from the function is 2, because  the  highest  used         matched. The return from the function is 2, because  the  highest  used
2244         capturing subpattern number is 1. However, you can refer to the offsets         capturing  subpattern  number  is 1, and the offsets for for the second
2245         for the second and third capturing subpatterns if  you  wish  (assuming         and third capturing subpatterns (assuming the vector is  large  enough,
2246         the vector is large enough, of course).         of course) are set to -1.
2247    
2248           Note: Elements of ovector that do not correspond to capturing parenthe-
2249           ses in the pattern are never changed. That is, if a pattern contains  n
2250           capturing parentheses, no more than ovector[0] to ovector[2n+1] are set
2251           by pcre_exec(). The other elements retain whatever values  they  previ-
2252           ously had.
2253    
2254         Some  convenience  functions  are  provided for extracting the captured         Some  convenience  functions  are  provided for extracting the captured
2255         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
# Line 2381  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2319  MATCHING A PATTERN: THE TRADITIONAL FUNC
2319           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2320    
2321         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
2322         subject.         subject,  and the PCRE_NO_UTF8_CHECK option was not set. If the size of
2323           the output vector (ovecsize) is at least 2,  the  byte  offset  to  the
2324           start  of  the  the invalid UTF-8 character is placed in the first ele-
2325           ment, and a reason code is placed in the  second  element.  The  reason
2326           codes are listed in the following section.  For backward compatibility,
2327           if PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8  char-
2328           acter   at   the   end   of   the   subject  (reason  codes  1  to  5),
2329           PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2330    
2331           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2332    
2333         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
2334           found  to be valid (the PCRE_NO_UTF8_CHECK option was not set), but the
2335         value of startoffset did not point to the beginning of a UTF-8  charac-         value of startoffset did not point to the beginning of a UTF-8  charac-
2336         ter.         ter or the end of the subject.
2337    
2338           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2339    
# Line 2420  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2366  MATCHING A PATTERN: THE TRADITIONAL FUNC
2366    
2367         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2368    
2369             PCRE_ERROR_BADOFFSET      (-24)
2370    
2371           The value of startoffset was negative or greater than the length of the
2372           subject, that is, the value in length.
2373    
2374             PCRE_ERROR_SHORTUTF8      (-25)
2375    
2376           This  error  is returned instead of PCRE_ERROR_BADUTF8 when the subject
2377           string ends with a truncated UTF-8 character and the  PCRE_PARTIAL_HARD
2378           option  is  set.   Information  about  the  failure  is returned as for
2379           PCRE_ERROR_BADUTF8. It is in fact sufficient to detect this  case,  but
2380           this  special error code for PCRE_PARTIAL_HARD precedes the implementa-
2381           tion of returned information; it is retained for backwards  compatibil-
2382           ity.
2383    
2384             PCRE_ERROR_RECURSELOOP    (-26)
2385    
2386           This error is returned when pcre_exec() detects a recursion loop within
2387           the pattern. Specifically, it means that either the whole pattern or  a
2388           subpattern  has been called recursively for the second time at the same
2389           position in the subject string. Some simple patterns that might do this
2390           are  detected  and faulted at compile time, but more complicated cases,
2391           in particular mutual recursions between two different subpatterns, can-
2392           not be detected until run time.
2393    
2394         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().
2395    
2396       Reason codes for invalid UTF-8 strings
2397    
2398           When pcre_exec() returns either PCRE_ERROR_BADUTF8 or PCRE_ERROR_SHORT-
2399           UTF8, and the size of the output vector (ovecsize) is at least  2,  the
2400           offset  of  the  start  of the invalid UTF-8 character is placed in the
2401           first output vector element (ovector[0]) and a reason code is placed in
2402           the  second  element  (ovector[1]). The reason codes are given names in
2403           the pcre.h header file:
2404    
2405             PCRE_UTF8_ERR1
2406             PCRE_UTF8_ERR2
2407             PCRE_UTF8_ERR3
2408             PCRE_UTF8_ERR4
2409             PCRE_UTF8_ERR5
2410    
2411           The string ends with a truncated UTF-8 character;  the  code  specifies
2412           how  many bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8
2413           characters to be no longer than 4 bytes, the  encoding  scheme  (origi-
2414           nally  defined  by  RFC  2279)  allows  for  up to 6 bytes, and this is
2415           checked first; hence the possibility of 4 or 5 missing bytes.
2416    
2417             PCRE_UTF8_ERR6
2418             PCRE_UTF8_ERR7
2419             PCRE_UTF8_ERR8
2420             PCRE_UTF8_ERR9
2421             PCRE_UTF8_ERR10
2422    
2423           The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of
2424           the  character  do  not have the binary value 0b10 (that is, either the
2425           most significant bit is 0, or the next bit is 1).
2426    
2427             PCRE_UTF8_ERR11
2428             PCRE_UTF8_ERR12
2429    
2430           A character that is valid by the RFC 2279 rules is either 5 or 6  bytes
2431           long; these code points are excluded by RFC 3629.
2432    
2433             PCRE_UTF8_ERR13
2434    
2435           A  4-byte character has a value greater than 0x10fff; these code points
2436           are excluded by RFC 3629.
2437    
2438             PCRE_UTF8_ERR14
2439    
2440           A 3-byte character has a value in the  range  0xd800  to  0xdfff;  this
2441           range  of code points are reserved by RFC 3629 for use with UTF-16, and
2442           so are excluded from UTF-8.
2443    
2444             PCRE_UTF8_ERR15
2445             PCRE_UTF8_ERR16
2446             PCRE_UTF8_ERR17
2447             PCRE_UTF8_ERR18
2448             PCRE_UTF8_ERR19
2449    
2450           A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it  codes
2451           for  a  value that can be represented by fewer bytes, which is invalid.
2452           For example, the two bytes 0xc0, 0xae give the value 0x2e,  whose  cor-
2453           rect coding uses just one byte.
2454    
2455             PCRE_UTF8_ERR20
2456    
2457           The two most significant bits of the first byte of a character have the
2458           binary value 0b10 (that is, the most significant bit is 1 and the  sec-
2459           ond  is  0). Such a byte can only validly occur as the second or subse-
2460           quent byte of a multi-byte character.
2461    
2462             PCRE_UTF8_ERR21
2463    
2464           The first byte of a character has the value 0xfe or 0xff. These  values
2465           can never occur in a valid UTF-8 string.
2466    
2467    
2468  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2469    
# Line 2436  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2478  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2478         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2479              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2480    
2481         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
2482         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
2483         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2484         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
2485         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
2486         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
2487         substrings.         substrings.
2488    
2489         A substring that contains a binary zero is correctly extracted and  has         A  substring that contains a binary zero is correctly extracted and has
2490         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
2491         string.  However, you can process such a string  by  referring  to  the         string.   However,  you  can  process such a string by referring to the
2492         length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2493         string().  Unfortunately, the interface to pcre_get_substring_list() is         string().  Unfortunately, the interface to pcre_get_substring_list() is
2494         not  adequate for handling strings containing binary zeros, because the         not adequate for handling strings containing binary zeros, because  the
2495         end of the final string is not independently indicated.         end of the final string is not independently indicated.
2496    
2497         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-
2498         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
2499         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
2500         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2501         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
2502         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2503         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
2504         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
2505         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2506    
2507         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
2508         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
2509         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
2510         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
2511         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
2512         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2513         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2514         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
2515         the terminating zero, or one of these error codes:         the terminating zero, or one of these error codes:
2516    
2517           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2518    
2519         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
2520         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2521    
2522           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2523    
2524         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2525    
2526         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
2527         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
2528         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
2529         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
2530         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
2531         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
2532         error code         error code
2533    
2534           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2535    
2536         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2537    
2538         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
2539         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
2540         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
2541         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2542         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
2543         tive for unset substrings.         tive for unset substrings.
2544    
2545         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2546         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
2547         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2548         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
2549         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.
2550         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-
2551         cial  interface  to  another  programming  language  that  cannot   use         cial   interface  to  another  programming  language  that  cannot  use
2552         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-
2553         vided.         vided.
2554    
2555    
# Line 2526  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2568  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2568              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2569              const char **stringptr);              const char **stringptr);
2570    
2571         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-
2572         ber.  For example, for this pattern         ber.  For example, for this pattern
2573    
2574           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
# Line 2535  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2577  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2577         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
2578         name by calling pcre_get_stringnumber(). The first argument is the com-         name by calling pcre_get_stringnumber(). The first argument is the com-
2579         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
2580         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2581         subpattern of that name.         subpattern of that name.
2582    
2583         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
2584         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
2585         are also two functions that do the whole job.         are also two functions that do the whole job.
2586    
2587         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
2588         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
2589         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
2590         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
2591         differences:         differences:
2592    
2593         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
2594         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
2595         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
2596         name-to-number translation table.         name-to-number translation table.
2597    
2598         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2599         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2600         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
2601         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2602    
2603         Warning: If the pattern uses the (?| feature to set up multiple subpat-         Warning: If the pattern uses the (?| feature to set up multiple subpat-
2604         terns  with  the  same number, as described in the section on duplicate         terns with the same number, as described in the  section  on  duplicate
2605         subpattern numbers in the pcrepattern page, you  cannot  use  names  to         subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2606         distinguish  the  different subpatterns, because names are not included         distinguish the different subpatterns, because names are  not  included
2607         in the compiled code. The matching process uses only numbers. For  this         in  the compiled code. The matching process uses only numbers. For this
2608         reason,  the  use of different names for subpatterns of the same number         reason, the use of different names for subpatterns of the  same  number
2609         causes an error at compile time.         causes an error at compile time.
2610    
2611    
# Line 2572  DUPLICATE SUBPATTERN NAMES Line 2614  DUPLICATE SUBPATTERN NAMES
2614         int pcre_get_stringtable_entries(const pcre *code,         int pcre_get_stringtable_entries(const pcre *code,
2615              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2616    
2617         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2618         subpatterns  are not required to be unique. (Duplicate names are always         subpatterns are not required to be unique. (Duplicate names are  always
2619         allowed for subpatterns with the same number, created by using the  (?|         allowed  for subpatterns with the same number, created by using the (?|
2620         feature.  Indeed,  if  such subpatterns are named, they are required to         feature. Indeed, if such subpatterns are named, they  are  required  to
2621         use the same names.)         use the same names.)
2622    
2623         Normally, patterns with duplicate names are such that in any one match,         Normally, patterns with duplicate names are such that in any one match,
2624         only  one of the named subpatterns participates. An example is shown in         only one of the named subpatterns participates. An example is shown  in
2625         the pcrepattern documentation.         the pcrepattern documentation.
2626    
2627         When   duplicates   are   present,   pcre_copy_named_substring()    and         When    duplicates   are   present,   pcre_copy_named_substring()   and
2628         pcre_get_named_substring()  return the first substring corresponding to         pcre_get_named_substring() return the first substring corresponding  to
2629         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
2630         (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()         (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2631         function returns one of the numbers that are associated with the  name,         function  returns one of the numbers that are associated with the name,
2632         but it is not defined which it is.         but it is not defined which it is.
2633    
2634         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
2635         name, you must use  the  pcre_get_stringtable_entries()  function.  The         name,  you  must  use  the pcre_get_stringtable_entries() function. The
2636         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
2637         third and fourth are pointers to variables which  are  updated  by  the         third  and  fourth  are  pointers to variables which are updated by the
2638         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
2639         the name-to-number table  for  the  given  name.  The  function  itself         the  name-to-number  table  for  the  given  name.  The function itself
2640         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2641         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-
2642         tion  entitled  Information  about  a  pattern.  Given all the relevant         tion entitled Information about a pattern above.  Given all  the  rele-
2643         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
2644         the captured data, if any.         hence the captured data, if any.
2645    
2646    
2647  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
2648    
2649         The  traditional  matching  function  uses a similar algorithm to Perl,         The traditional matching function uses a  similar  algorithm  to  Perl,
2650         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
2651         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
2652         possible match, consider using the alternative matching  function  (see         possible  match,  consider using the alternative matching function (see
2653         below)  instead.  If you cannot use the alternative function, but still         below) instead. If you cannot use the alternative function,  but  still
2654         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
2655         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
2656         tation.         tation.
2657    
2658         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-
2659         tern.   When your callout function is called, extract and save the cur-         tern.  When your callout function is called, extract and save the  cur-
2660         rent matched substring. Then return  1,  which  forces  pcre_exec()  to         rent  matched  substring.  Then  return  1, which forces pcre_exec() to
2661         backtrack  and  try other alternatives. Ultimately, when it runs out of         backtrack and try other alternatives. Ultimately, when it runs  out  of
2662         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2663    
2664    
# Line 2627  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2669  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2669              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
2670              int *workspace, int wscount);              int *workspace, int wscount);
2671    
2672         The function pcre_dfa_exec()  is  called  to  match  a  subject  string         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2673         against  a  compiled pattern, using a matching algorithm that scans the         against a compiled pattern, using a matching algorithm that  scans  the
2674         subject string just once, and does not backtrack.  This  has  different         subject  string  just  once, and does not backtrack. This has different
2675         characteristics  to  the  normal  algorithm, and is not compatible with         characteristics to the normal algorithm, and  is  not  compatible  with
2676         Perl. Some of the features of PCRE patterns are not  supported.  Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2677         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
2678         a discussion of the two matching algorithms, and  a  list  of  features         a  discussion  of  the  two matching algorithms, and a list of features
2679         that  pcre_dfa_exec() does not support, see the pcrematching documenta-         that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2680         tion.         tion.
2681    
2682         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
2683         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-
2684         ent way, and this is described below. The other  common  arguments  are         ent  way,  and  this is described below. The other common arguments are
2685         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
2686         repeated here.         repeated here.
2687    
2688         The two additional arguments provide workspace for  the  function.  The         The  two  additional  arguments provide workspace for the function. The
2689         workspace  vector  should  contain at least 20 elements. It is used for         workspace vector should contain at least 20 elements. It  is  used  for
2690         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2691         workspace  will  be  needed for patterns and subjects where there are a         workspace will be needed for patterns and subjects where  there  are  a
2692         lot of potential matches.         lot of potential matches.
2693    
2694         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 2710  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2710    
2711     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2712    
2713         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
2714         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-
2715         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2716         PCRE_NOTEMPTY_ATSTART,       PCRE_NO_UTF8_CHECK,      PCRE_BSR_ANYCRLF,         PCRE_NOTEMPTY_ATSTART,      PCRE_NO_UTF8_CHECK,       PCRE_BSR_ANYCRLF,
2717         PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD,  PCRE_PAR-         PCRE_BSR_UNICODE,  PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD, PCRE_PAR-
2718         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
2719         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
2720         description is not repeated here.         description is not repeated here.
2721    
2722           PCRE_PARTIAL_HARD           PCRE_PARTIAL_HARD
2723           PCRE_PARTIAL_SOFT           PCRE_PARTIAL_SOFT
2724    
2725         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
2726         details are slightly  different.  When  PCRE_PARTIAL_HARD  is  set  for         details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
2727         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-
2728         ject is reached and there is still at least  one  matching  possibility         ject  is  reached  and there is still at least one matching possibility
2729         that requires additional characters. This happens even if some complete         that requires additional characters. This happens even if some complete
2730         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
2731         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
2732         of the subject is reached, there have been  no  complete  matches,  but         of  the  subject  is  reached, there have been no complete matches, but
2733         there  is  still  at least one matching possibility. The portion of the         there is still at least one matching possibility. The  portion  of  the
2734         string that was inspected when the longest partial match was  found  is         string  that  was inspected when the longest partial match was found is
2735         set as the first matching string in both cases.         set as the first matching string  in  both  cases.   There  is  a  more
2736           detailed  discussion  of partial and multi-segment matching, with exam-
2737           ples, in the pcrepartial documentation.
2738    
2739           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2740    
2741         Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
2742         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-
2743         tive  algorithm  works, this is necessarily the shortest possible match         tive algorithm works, this is necessarily the shortest  possible  match
2744         at the first possible matching point in the subject string.         at the first possible matching point in the subject string.
2745    
2746           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2747    
2748         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
2749         again,  with  additional  subject characters, and have it continue with         again, with additional subject characters, and have  it  continue  with
2750         the same match. The PCRE_DFA_RESTART option requests this action;  when         the  same match. The PCRE_DFA_RESTART option requests this action; when
2751         it  is  set,  the workspace and wscount options must reference the same         it is set, the workspace and wscount options must  reference  the  same
2752         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
2753         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
2754         pcrepartial documentation.         pcrepartial documentation.
2755    
2756     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2757    
2758         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-
2759         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
2760         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
2761         matches  are all initial substrings of the longer matches. For example,         matches are all initial substrings of the longer matches. For  example,
2762         if the pattern         if the pattern
2763    
2764           <.*>           <.*>
# Line 2729  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2773  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2773           <something> <something else>           <something> <something else>
2774           <something> <something else> <something further>           <something> <something else> <something further>
2775    
2776         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,
2777         which  is  the  number of matched substrings. The substrings themselves         which is the number of matched substrings.  The  substrings  themselves
2778         are returned in ovector. Each string uses two elements;  the  first  is         are  returned  in  ovector. Each string uses two elements; the first is
2779         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
2780         fact, all the strings have the same start  offset.  (Space  could  have         fact,  all  the  strings  have the same start offset. (Space could have
2781         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
2782         compatibility with the way pcre_exec() returns data,  even  though  the         compatibility  with  the  way pcre_exec() returns data, even though the
2783         meaning of the strings is different.)         meaning of the strings is different.)
2784    
2785         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-
2786         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
2787         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
2788         filled with the longest matches.         filled with the longest matches.
2789    
2790     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2791    
2792         The pcre_dfa_exec() function returns a negative number when  it  fails.         The  pcre_dfa_exec()  function returns a negative number when it fails.
2793         Many  of  the  errors  are  the  same as for pcre_exec(), and these are         Many of the errors are the same  as  for  pcre_exec(),  and  these  are
2794         described above.  There are in addition the following errors  that  are         described  above.   There are in addition the following errors that are
2795         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2796    
2797           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2798    
2799         This  return is given if pcre_dfa_exec() encounters an item in the pat-         This return is given if pcre_dfa_exec() encounters an item in the  pat-
2800         tern that it does not support, for instance, the use of \C  or  a  back         tern  that  it  does not support, for instance, the use of \C or a back
2801         reference.         reference.
2802    
2803           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2804    
2805         This  return  is  given  if pcre_dfa_exec() encounters a condition item         This return is given if pcre_dfa_exec()  encounters  a  condition  item
2806         that uses a back reference for the condition, or a test  for  recursion         that  uses  a back reference for the condition, or a test for recursion
2807         in a specific group. These are not supported.         in a specific group. These are not supported.
2808    
2809           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2810    
2811         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
2812         that contains a setting of the match_limit field. This is not supported         that contains a setting of the match_limit field. This is not supported
2813         (it is meaningless).         (it is meaningless).
2814    
2815           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2816    
2817         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
2818         workspace vector.         workspace vector.
2819    
2820           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2821    
2822         When a recursive subpattern is processed, the matching  function  calls         When  a  recursive subpattern is processed, the matching function calls
2823         itself  recursively,  using  private vectors for ovector and workspace.         itself recursively, using private vectors for  ovector  and  workspace.
2824         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
2825         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2826    
2827    
2828  SEE ALSO  SEE ALSO
2829    
2830         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
2831         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2832    
2833    
# Line 2796  AUTHOR Line 2840  AUTHOR
2840    
2841  REVISION  REVISION
2842    
2843         Last updated: 21 June 2010         Last updated: 13 August 2011
2844         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
2845  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2846    
2847    
2848  PCRECALLOUT(3)                                                  PCRECALLOUT(3)  PCRECALLOUT(3)                                                  PCRECALLOUT(3)
2849    
2850    
# Line 2864  MISSING CALLOUTS Line 2908  MISSING CALLOUTS
2908         patterns, if it has been scanned far enough.         patterns, if it has been scanned far enough.
2909    
2910         You  can disable these optimizations by passing the PCRE_NO_START_OPTI-         You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
2911         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
2912         matching  process,  but  does  ensure that callouts such as the example         starting the pattern with (*NO_START_OPT). This slows down the matching
2913         above are obeyed.         process, but does ensure that callouts such as the  example  above  are
2914           obeyed.
2915    
2916    
2917  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2918    
2919         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
2920         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
2921         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
2922         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
2923         block. This structure contains the following fields:         block. This structure contains the following fields:
2924    
2925           int          version;           int         version;
2926           int          callout_number;           int         callout_number;
2927           int         *offset_vector;           int        *offset_vector;
2928           const char  *subject;           const char *subject;
2929           int          subject_length;           int         subject_length;
2930           int          start_match;           int         start_match;
2931           int          current_position;           int         current_position;
2932           int          capture_top;           int         capture_top;
2933           int          capture_last;           int         capture_last;
2934           void        *callout_data;           void       *callout_data;
2935           int          pattern_position;           int         pattern_position;
2936           int          next_item_length;           int         next_item_length;
2937             const unsigned char *mark;
2938         The version field is an integer containing the version  number  of  the  
2939         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
2940         version number will change again in future  if  additional  fields  are         block format. The initial version was 0; the current version is 2.  The
2941           version  number  will  change  again in future if additional fields are
2942         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.
2943    
2944         The  callout_number  field  contains the number of the callout, as com-         The callout_number field contains the number of the  callout,  as  com-
2945         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-
2946         outs, and 255 for automatically generated callouts).         outs, and 255 for automatically generated callouts).
2947    
2948         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
2949         passed  by  the  caller  to  pcre_exec()   or   pcre_dfa_exec().   When         passed   by   the   caller  to  pcre_exec()  or  pcre_dfa_exec().  When
2950         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
2951         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
2952         extracting  substrings after a match has completed. For pcre_dfa_exec()         extracting substrings after a match has completed. For  pcre_dfa_exec()
2953         this field is not useful.         this field is not useful.
2954    
2955         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
2956         were passed to pcre_exec().         were passed to pcre_exec().
2957    
2958         The  start_match  field normally contains the offset within the subject         The start_match field normally contains the offset within  the  subject
2959         at which the current match attempt  started.  However,  if  the  escape         at  which  the  current  match  attempt started. However, if the escape
2960         sequence  \K has been encountered, this value is changed to reflect the         sequence \K has been encountered, this value is changed to reflect  the
2961         modified starting point. If the pattern is not  anchored,  the  callout         modified  starting  point.  If the pattern is not anchored, the callout
2962         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
2963         for different starting points in the subject.         for different starting points in the subject.
2964    
2965         The current_position field contains the offset within  the  subject  of         The  current_position  field  contains the offset within the subject of
2966         the current match pointer.         the current match pointer.
2967    
2968         When  the  pcre_exec() function is used, the capture_top field contains         When the pcre_exec() function is used, the capture_top  field  contains
2969         one more than the number of the highest numbered captured substring  so         one  more than the number of the highest numbered captured substring so
2970         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
2971         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
2972         does not support captured substrings.         does not support captured substrings.
2973    
2974         The  capture_last  field  contains the number of the most recently cap-         The capture_last field contains the number of the  most  recently  cap-
2975         tured substring. If no substrings have been captured, its value is  -1.         tured  substring. If no substrings have been captured, its value is -1.
2976         This is always the case when pcre_dfa_exec() is used.         This is always the case when pcre_dfa_exec() is used.
2977    
2978         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()
2979         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-
2980         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
2981         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
2982         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
2983         structure in the pcreapi documentation.         structure in the pcreapi documentation.
2984    
2985         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-
2986         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
2987         the pattern string.         the pattern string.
2988    
2989         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-
2990         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
2991         the pattern string. When the callout immediately precedes  an  alterna-         the  pattern  string. When the callout immediately precedes an alterna-
2992         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
2993         is zero. When the callout precedes an opening parenthesis,  the  length         is  zero.  When the callout precedes an opening parenthesis, the length
2994         is that of the entire subpattern.         is that of the entire subpattern.
2995    
2996         The  pattern_position  and next_item_length fields are intended to help         The pattern_position and next_item_length fields are intended  to  help
2997         in distinguishing between different automatic callouts, which all  have         in  distinguishing between different automatic callouts, which all have
2998         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
2999    
3000           The mark field is present from version 2 of the pcre_callout structure.
3001           In  callouts  from pcre_exec() it contains a pointer to the zero-termi-
3002           nated name of the most recently passed (*MARK) item in  the  match,  or
3003           NULL if there are no (*MARK)s in the current matching path. In callouts
3004           from pcre_dfa_exec() this field always contains NULL.
3005    
3006    
3007  RETURN VALUES  RETURN VALUES
3008    
3009         The  external callout function returns an integer to PCRE. If the value         The external callout function returns an integer to PCRE. If the  value
3010         is zero, matching proceeds as normal. If  the  value  is  greater  than         is  zero,  matching  proceeds  as  normal. If the value is greater than
3011         zero,  matching  fails  at  the current point, but the testing of other         zero, matching fails at the current point, but  the  testing  of  other
3012         matching possibilities goes ahead, just as if a lookahead assertion had         matching possibilities goes ahead, just as if a lookahead assertion had
3013         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
3014         pcre_exec() or pcre_dfa_exec() returns the negative value.         pcre_exec() or pcre_dfa_exec() returns the negative value.
3015    
3016         Negative  values  should  normally  be   chosen   from   the   set   of         Negative   values   should   normally   be   chosen  from  the  set  of
3017         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
3018         dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is         dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is
3019         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
3020         itself.         itself.
3021    
3022    
# Line 2977  AUTHOR Line 3029  AUTHOR
3029    
3030  REVISION  REVISION
3031    
3032         Last updated: 29 September 2009         Last updated: 31 July 2011
3033         Copyright (c) 1997-2009 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3034  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3035    
3036    
3037  PCRECOMPAT(3)                                                    PCRECOMPAT(3)  PCRECOMPAT(3)                                                    PCRECOMPAT(3)
3038    
3039    
# Line 2993  DIFFERENCES BETWEEN PCRE AND PERL Line 3045  DIFFERENCES BETWEEN PCRE AND PERL
3045    
3046         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
3047         handle regular expressions. The differences  described  here  are  with         handle regular expressions. The differences  described  here  are  with
3048         respect to Perl 5.10/5.11.         respect to Perl versions 5.10 and above.
3049    
3050         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
3051         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.  
3052    
3053         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         2. PCRE allows repeat quantifiers only on parenthesized assertions, but
3054         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
3055         (?!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
3056         just asserts that the next character is not "a" three times.         the next character is not "a" three times (in principle: PCRE optimizes
3057           this to run the assertion just once). Perl allows repeat quantifiers on
3058         3. Capturing subpatterns that occur inside  negative  lookahead  asser-         other assertions such as \b, but these do not seem to have any use.
3059         tions  are  counted,  but their entries in the offsets vector are never  
3060         set. Perl sets its numerical variables from any such patterns that  are         3.  Capturing  subpatterns  that occur inside negative lookahead asser-
3061           tions are counted, but their entries in the offsets  vector  are  never
3062           set.  Perl sets its numerical variables from any such patterns that are
3063         matched before the assertion fails to match something (thereby succeed-         matched before the assertion fails to match something (thereby succeed-
3064         ing), but only if the negative lookahead assertion  contains  just  one         ing),  but  only  if the negative lookahead assertion contains just one
3065         branch.         branch.
3066    
3067         4.  Though  binary zero characters are supported in the subject string,         4. Though binary zero characters are supported in the  subject  string,
3068         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-
3069         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
3070         the pattern to represent a binary zero.         the pattern to represent a binary zero.
3071    
3072         5. The following Perl escape sequences are not supported: \l,  \u,  \L,         5.  The  following Perl escape sequences are not supported: \l, \u, \L,
3073         \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
3074         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
3075         are encountered by PCRE, an error is generated.         are implemented by Perl's general string-handling and are not  part  of
3076           its  pattern  matching engine. If any of these are encountered by PCRE,
3077         6.  The Perl escape sequences \p, \P, and \X are supported only if PCRE         an error is generated.
3078         is built with Unicode character property support. The  properties  that  
3079         can  be tested with \p and \P are limited to the general category prop-         6. The Perl escape sequences \p, \P, and \X are supported only if  PCRE
3080         erties such as Lu and Nd, script names such as Greek or  Han,  and  the         is  built  with Unicode character property support. The properties that
3081         derived  properties  Any  and  L&. PCRE does support the Cs (surrogate)         can be tested with \p and \P are limited to the general category  prop-
3082         property, which Perl does not; the  Perl  documentation  says  "Because         erties  such  as  Lu and Nd, script names such as Greek or Han, and the
3083           derived properties Any and L&. PCRE does  support  the  Cs  (surrogate)
3084           property,  which  Perl  does  not; the Perl documentation says "Because
3085         Perl hides the need for the user to understand the internal representa-         Perl hides the need for the user to understand the internal representa-
3086         tion of Unicode characters, there is no need to implement the  somewhat         tion  of Unicode characters, there is no need to implement the somewhat
3087         messy concept of surrogates."         messy concept of surrogates."
3088    
3089         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
3090           make  \X  match what Unicode calls an "extended grapheme cluster". This
3091           is more complicated than an extended Unicode sequence,  which  is  what
3092           PCRE matches.
3093    
3094           8. PCRE does support the \Q...\E escape for quoting substrings. Charac-
3095         ters in between are treated as literals.  This  is  slightly  different         ters in between are treated as literals.  This  is  slightly  different
3096         from  Perl  in  that  $  and  @ are also handled as literals inside the         from  Perl  in  that  $  and  @ are also handled as literals inside the
3097         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 3107  DIFFERENCES BETWEEN PCRE AND PERL
3107         The  \Q...\E  sequence  is recognized both inside and outside character         The  \Q...\E  sequence  is recognized both inside and outside character
3108         classes.         classes.
3109    
3110         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})         9. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
3111         constructions.  However,  there is support for recursive patterns. This         constructions.  However,  there is support for recursive patterns. This
3112         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
3113         "callout"  feature allows an external function to be called during pat-         "callout"  feature allows an external function to be called during pat-
3114         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
3115    
3116         9. Subpatterns that are called  recursively  or  as  "subroutines"  are         10. Subpatterns that are called recursively  or  as  "subroutines"  are
3117         always  treated  as  atomic  groups  in  PCRE. This is like Python, but         always  treated  as  atomic  groups  in  PCRE. This is like Python, but
3118         unlike Perl. There is a discussion of an example that explains this  in         unlike Perl. There is a discussion of an example that explains this  in
3119         more  detail  in  the section on recursion differences from Perl in the         more  detail  in  the section on recursion differences from Perl in the
3120         pcrepattern page.         pcrepattern page.
3121    
3122         10. There are some differences that are concerned with the settings  of         11. There are some differences that are concerned with the settings  of
3123         captured  strings  when  part  of  a  pattern is repeated. For example,         captured  strings  when  part  of  a  pattern is repeated. For example,
3124         matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2         matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2
3125         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
3126    
3127         11.  PCRE's handling of duplicate subpattern numbers and duplicate sub-         12.  PCRE's handling of duplicate subpattern numbers and duplicate sub-
3128         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
3129         fact the PCRE works internally just with numbers, using an external ta-         fact the PCRE works internally just with numbers, using an external ta-
3130         ble to translate between numbers and names. In  particular,  a  pattern         ble to translate between numbers and names. In  particular,  a  pattern
# Line 3075  DIFFERENCES BETWEEN PCRE AND PERL Line 3135  DIFFERENCES BETWEEN PCRE AND PERL
3135         turing subpattern number 1. To avoid this confusing situation, an error         turing subpattern number 1. To avoid this confusing situation, an error
3136         is given at compile time.         is given at compile time.
3137    
3138         12. PCRE provides some extensions to the Perl regular expression facil-         13. Perl recognizes comments in some places that  PCRE  does  not,  for
3139         ities.   Perl  5.10  includes new features that are not in earlier ver-         example,  between  the  ( and ? at the start of a subpattern. If the /x
3140         sions of Perl, some of which (such as named parentheses) have  been  in         modifier is set, Perl allows whitespace between ( and ? but PCRE  never
3141           does, even if the PCRE_EXTENDED option is set.
3142    
3143           14. PCRE provides some extensions to the Perl regular expression facil-
3144           ities.  Perl 5.10 includes new features that are not  in  earlier  ver-
3145           sions  of  Perl, some of which (such as named parentheses) have been in
3146         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:
3147    
3148         (a)  Although  lookbehind  assertions  in  PCRE must match fixed length         (a) Although lookbehind assertions in  PCRE  must  match  fixed  length
3149         strings, each alternative branch of a lookbehind assertion can match  a         strings,  each alternative branch of a lookbehind assertion can match a
3150         different  length  of  string.  Perl requires them all to have the same         different length of string. Perl requires them all  to  have  the  same
3151         length.         length.
3152    
3153         (b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the  $         (b)  If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $
3154         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
3155    
3156         (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe-         (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe-
3157         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
3158         ignored.  (Perl can be made to issue a warning.)         ignored.  (Perl can be made to issue a warning.)
3159    
3160         (d)  If  PCRE_UNGREEDY is set, the greediness of the repetition quanti-         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-
3161         fiers is inverted, that is, by default they are not greedy, but if fol-         fiers is inverted, that is, by default they are not greedy, but if fol-
3162         lowed by a question mark they are.         lowed by a question mark they are.
3163    
# Line 3100  DIFFERENCES BETWEEN PCRE AND PERL Line 3165  DIFFERENCES BETWEEN PCRE AND PERL
3165         tried only at the first matching position in the subject string.         tried only at the first matching position in the subject string.
3166    
3167         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
3168         and  PCRE_NO_AUTO_CAPTURE  options for pcre_exec() have no Perl equiva-         and PCRE_NO_AUTO_CAPTURE options for pcre_exec() have no  Perl  equiva-
3169         lents.         lents.
3170    
3171         (g) The \R escape sequence can be restricted to match only CR,  LF,  or         (g)  The  \R escape sequence can be restricted to match only CR, LF, or
3172         CRLF by the PCRE_BSR_ANYCRLF option.         CRLF by the PCRE_BSR_ANYCRLF option.
3173    
3174         (h) The callout facility is PCRE-specific.         (h) The callout facility is PCRE-specific.
# Line 3113  DIFFERENCES BETWEEN PCRE AND PERL Line 3178  DIFFERENCES BETWEEN PCRE AND PERL
3178         (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,
3179         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
3180    
3181         (k) The alternative matching function (pcre_dfa_exec())  matches  in  a         (k)  The  alternative  matching function (pcre_dfa_exec()) matches in a
3182         different way and is not Perl-compatible.         different way and is not Perl-compatible.
3183    
3184         (l)  PCRE  recognizes some special sequences such as (*CR) at the start         (l) PCRE recognizes some special sequences such as (*CR) at  the  start
3185         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
3186         pattern.         pattern.
3187    
# Line 3130  AUTHOR Line 3195  AUTHOR
3195    
3196  REVISION  REVISION
3197    
3198         Last updated: 12 May 2010         Last updated: 24 August 2011
3199         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3200  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3201    
3202    
3203  PCREPATTERN(3)                                                  PCREPATTERN(3)  PCREPATTERN(3)                                                  PCREPATTERN(3)
3204    
3205    
# Line 3170  PCRE REGULAR EXPRESSION DETAILS Line 3235  PCRE REGULAR EXPRESSION DETAILS
3235         Starting a pattern with this sequence  is  equivalent  to  setting  the         Starting a pattern with this sequence  is  equivalent  to  setting  the
3236         PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting         PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3237         UTF-8 mode affects pattern matching  is  mentioned  in  several  places         UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3238         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
3239         UTF-8 support in the main pcre page.         page.
3240    
3241         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
3242         in combination with (*UTF8) is:         in combination with (*UTF8) is:
# Line 3183  PCRE REGULAR EXPRESSION DETAILS Line 3248  PCRE REGULAR EXPRESSION DETAILS
3248         character types, instead of recognizing only characters with codes less         character types, instead of recognizing only characters with codes less
3249         than 128 via a lookup table.         than 128 via a lookup table.
3250    
3251         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
3252         ported  by  PCRE when its main matching function, pcre_exec(), is used.         setting the PCRE_NO_START_OPTIMIZE option either at compile or matching
3253         From  release  6.0,   PCRE   offers   a   second   matching   function,         time. There are also some more of these special sequences that are con-
3254         pcre_dfa_exec(),  which matches using a different algorithm that is not         cerned with the handling of newlines; they are described below.
3255    
3256           The  remainder  of  this  document discusses the patterns that are sup-
3257           ported by PCRE when its main matching function, pcre_exec(),  is  used.
3258           From   release   6.0,   PCRE   offers   a   second  matching  function,
3259           pcre_dfa_exec(), which matches using a different algorithm that is  not
3260         Perl-compatible. Some of the features discussed below are not available         Perl-compatible. Some of the features discussed below are not available
3261         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the         when pcre_dfa_exec() is used. The advantages and disadvantages  of  the
3262         alternative function, and how it differs from the normal function,  are         alternative  function, and how it differs from the normal function, are
3263         discussed in the pcrematching page.         discussed in the pcrematching page.
3264    
3265    
3266  NEWLINE CONVENTIONS  NEWLINE CONVENTIONS
3267    
3268         PCRE  supports five different conventions for indicating line breaks in         PCRE supports five different conventions for indicating line breaks  in
3269         strings: a single CR (carriage return) character, a  single  LF  (line-         strings:  a  single  CR (carriage return) character, a single LF (line-
3270         feed) character, the two-character sequence CRLF, any of the three pre-         feed) character, the two-character sequence CRLF, any of the three pre-
3271         ceding, or any Unicode newline sequence. The pcreapi page  has  further         ceding,  or  any Unicode newline sequence. The pcreapi page has further
3272         discussion  about newlines, and shows how to set the newline convention         discussion about newlines, and shows how to set the newline  convention
3273         in the options arguments for the compiling and matching functions.         in the options arguments for the compiling and matching functions.
3274    
3275         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-
3276         tern string with one of the following five sequences:         tern string with one of the following five sequences:
3277    
3278           (*CR)        carriage return           (*CR)        carriage return
# Line 3211  NEWLINE CONVENTIONS Line 3281  NEWLINE CONVENTIONS
3281           (*ANYCRLF)   any of the three above           (*ANYCRLF)   any of the three above
3282           (*ANY)       all Unicode newline sequences           (*ANY)       all Unicode newline sequences
3283    
3284         These  override  the default and the options given to pcre_compile() or         These override the default and the options given to  pcre_compile()  or
3285         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
3286         newline sequence, the pattern         newline sequence, the pattern
3287    
3288           (*CR)a.b           (*CR)a.b
3289    
3290         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
3291         no longer a newline. Note that these special settings,  which  are  not         no  longer  a  newline. Note that these special settings, which are not
3292         Perl-compatible,  are  recognized  only at the very start of a pattern,         Perl-compatible, are recognized only at the very start  of  a  pattern,
3293         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
3294         present, the last one is used.         present, the last one is used.
3295    
3296         The  newline convention affects the interpretation of the dot metachar-         The newline convention affects the interpretation of the dot  metachar-
3297         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-
3298         ever,  it  does  not  affect  what  the  \R escape sequence matches. By         ever, it does not affect  what  the  \R  escape  sequence  matches.  By
3299         default, this is any Unicode newline sequence, for Perl  compatibility.         default,  this is any Unicode newline sequence, for Perl compatibility.
3300         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
3301         entitled "Newline sequences" below. A change of \R setting can be  com-         entitled  "Newline sequences" below. A change of \R setting can be com-
3302         bined with a change of newline convention.         bined with a change of newline convention.
3303    
3304    
3305  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
3306    
3307         A  regular  expression  is  a pattern that is matched against a subject         A regular expression is a pattern that is  matched  against  a  subject
3308         string from left to right. Most characters stand for  themselves  in  a         string  from  left  to right. Most characters stand for themselves in a
3309         pattern,  and  match  the corresponding characters in the subject. As a         pattern, and match the corresponding characters in the  subject.  As  a
3310         trivial example, the pattern         trivial example, the pattern
3311    
3312           The quick brown fox           The quick brown fox
3313    
3314         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
3315         caseless  matching is specified (the PCRE_CASELESS option), letters are         caseless matching is specified (the PCRE_CASELESS option), letters  are
3316         matched independently of case. In UTF-8 mode, PCRE  always  understands         matched  independently  of case. In UTF-8 mode, PCRE always understands
3317         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
3318         caseless matching is always possible. For characters with  higher  val-         caseless  matching  is always possible. For characters with higher val-
3319         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
3320         property support, but not otherwise.   If  you  want  to  use  caseless         property  support,  but  not  otherwise.   If  you want to use caseless
3321         matching  for  characters  128  and above, you must ensure that PCRE is         matching for characters 128 and above, you must  ensure  that  PCRE  is
3322         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
3323    
3324         The power of regular expressions comes  from  the  ability  to  include         The  power  of  regular  expressions  comes from the ability to include
3325         alternatives  and  repetitions in the pattern. These are encoded in the         alternatives and repetitions in the pattern. These are encoded  in  the
3326         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
3327         but instead are interpreted in some special way.         but instead are interpreted in some special way.
3328    
3329         There  are  two different sets of metacharacters: those that are recog-         There are two different sets of metacharacters: those that  are  recog-
3330         nized anywhere in the pattern except within square brackets, and  those         nized  anywhere in the pattern except within square brackets, and those
3331         that  are  recognized  within square brackets. Outside square brackets,         that are recognized within square brackets.  Outside  square  brackets,
3332         the metacharacters are as follows:         the metacharacters are as follows:
3333    
3334           \      general escape character with several uses           \      general escape character with several uses
# Line 3277  CHARACTERS AND METACHARACTERS Line 3347  CHARACTERS AND METACHARACTERS
3347                  also "possessive quantifier"                  also "possessive quantifier"
3348           {      start min/max quantifier           {      start min/max quantifier
3349    
3350         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
3351         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
3352    
3353           \      general escape character           \      general escape character
# Line 3293  CHARACTERS AND METACHARACTERS Line 3363  CHARACTERS AND METACHARACTERS
3363  BACKSLASH  BACKSLASH
3364    
3365         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3366         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
3367         character  may  have.  This  use  of  backslash  as an escape character         meaning that character may have. This use of  backslash  as  an  escape
3368         applies both inside and outside character classes.         character applies both inside and outside character classes.
3369    
3370         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
3371         pattern.   This  escaping  action  applies whether or not the following         pattern.  This escaping action applies whether  or  not  the  following
3372         character would otherwise be interpreted as a metacharacter, so  it  is         character  would  otherwise be interpreted as a metacharacter, so it is
3373         always  safe  to  precede  a non-alphanumeric with backslash to specify         always safe to precede a non-alphanumeric  with  backslash  to  specify
3374         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-
3375         slash, you write \\.         slash, you write \\.
3376    
3377         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
3378         the pattern (other than in a character class) and characters between  a         after  a  backslash.  All  other characters (in particular, those whose
3379           codepoints are greater than 127) are treated as literals.
3380    
3381           If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
3382           the  pattern (other than in a character class) and characters between a
3383         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
3384         ing backslash can be used to include a whitespace  or  #  character  as         ing  backslash  can  be  used to include a whitespace or # character as
3385         part of the pattern.         part of the pattern.
3386    
3387         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-
3388         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-
3389         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
3390         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-
3391         tion. Note the following examples:         tion. Note the following examples:
3392    
3393           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 3323  BACKSLASH Line 3397  BACKSLASH
3397           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
3398           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3399    
3400         The  \Q...\E  sequence  is recognized both inside and outside character         The \Q...\E sequence is recognized both inside  and  outside  character
3401         classes.         classes.   An  isolated \E that is not preceded by \Q is ignored. If \Q
3402           is not followed by \E later in the pattern, the literal  interpretation
3403           continues  to  the  end  of  the pattern (that is, \E is assumed at the
3404           end). If the isolated \Q is inside a character class,  this  causes  an
3405           error, because the character class is not terminated.
3406    
3407     Non-printing characters     Non-printing characters
3408    
3409         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-
3410         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
3411         appearance of non-printing characters, apart from the binary zero  that         appearance  of non-printing characters, apart from the binary zero that
3412         terminates  a  pattern,  but  when  a pattern is being prepared by text         terminates a pattern, but when a pattern  is  being  prepared  by  text
3413         editing, it is  often  easier  to  use  one  of  the  following  escape         editing,  it  is  often  easier  to  use  one  of  the following escape
3414         sequences than the binary character it represents:         sequences than the binary character it represents:
3415    
3416           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3417           \cx       "control-x", where x is any character           \cx       "control-x", where x is any ASCII character
3418           \e        escape (hex 1B)           \e        escape (hex 1B)
3419           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3420           \n        linefeed (hex 0A)           \n        linefeed (hex 0A)
# Line 3346  BACKSLASH Line 3424  BACKSLASH
3424           \xhh      character with hex code hh           \xhh      character with hex code hh
3425           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh..
3426    
3427         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,
3428         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
3429         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 ({
3430         becomes hex 7B.         is  7B),  while  \c; becomes hex 7B (; is 3B). If the byte following \c
3431           has a value greater than 127, a compile-time error occurs.  This  locks
3432         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
3433         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
3434         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.)
3435    
3436           After  \x, from zero to two hexadecimal digits are read (letters can be
3437           in upper or lower case). Any number of hexadecimal  digits  may  appear
3438           between  \x{  and  },  but the value of the character code must be less
3439         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,
3440         the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger         the  maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger
3441         than the largest Unicode code point, which is 10FFFF.         than the largest Unicode code point, which is 10FFFF.
3442    
3443         If  characters  other than hexadecimal digits appear between \x{ and },         If characters other than hexadecimal digits appear between \x{  and  },
3444         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.
3445         Instead,  the  initial  \x  will  be interpreted as a basic hexadecimal         Instead, the initial \x will be  interpreted  as  a  basic  hexadecimal
3446         escape, with no following digits, giving a  character  whose  value  is         escape,  with  no  following  digits, giving a character whose value is
3447         zero.         zero.
3448    
3449         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
3450         two syntaxes for \x. There is no difference in the way  they  are  han-         two  syntaxes  for  \x. There is no difference in the way they are han-
3451         dled. For example, \xdc is exactly the same as \x{dc}.         dled. For example, \xdc is exactly the same as \x{dc}.
3452    
3453         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
3454         than two digits, just  those  that  are  present  are  used.  Thus  the         than  two  digits,  just  those  that  are  present  are used. Thus the
3455         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
3456         (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
3457         if the pattern character that follows is itself an octal digit.         if the pattern character that follows is itself an octal digit.
3458    
3459         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-
3460         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
3461         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
3462         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
3463         expression,  the  entire  sequence  is  taken  as  a  back reference. A         expression, the entire  sequence  is  taken  as  a  back  reference.  A
3464         description of how this works is given later, following the  discussion         description  of how this works is given later, following the discussion
3465         of parenthesized subpatterns.         of parenthesized subpatterns.
3466    
3467         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
3468         and there have not been that many capturing subpatterns, PCRE  re-reads         and  there have not been that many capturing subpatterns, PCRE re-reads
3469         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-
3470         erate a data character. Any subsequent digits stand for themselves.  In         erate  a data character. Any subsequent digits stand for themselves. In
3471         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
3472         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
3473         example:         example:
3474    
3475           \040   is another way of writing a space           \040   is another way of writing a space
# Line 3405  BACKSLASH Line 3487  BACKSLASH
3487           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
3488                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
3489    
3490         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
3491         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
3492    
3493         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
3494         inside  and  outside character classes. In addition, inside a character         inside and outside character classes. In addition, inside  a  character
3495         class, the sequence \b is interpreted as the backspace  character  (hex         class,  the  sequence \b is interpreted as the backspace character (hex
3496         08).  The sequences \B, \N, \R, and \X are not special inside a charac-         08). The sequences \B, \N, \R, and \X are not special inside a  charac-
3497         ter class. Like any  other  unrecognized  escape  sequences,  they  are         ter  class.  Like  any  other  unrecognized  escape sequences, they are
3498         treated  as  the  literal characters "B", "N", "R", and "X" by default,         treated as the literal characters "B", "N", "R", and  "X"  by  default,
3499         but cause an error if the PCRE_EXTRA option is set. Outside a character         but cause an error if the PCRE_EXTRA option is set. Outside a character
3500         class, these sequences have different meanings.         class, these sequences have different meanings.
3501    
3502     Absolute and relative back references     Absolute and relative back references
3503    
3504         The  sequence  \g followed by an unsigned or a negative number, option-         The sequence \g followed by an unsigned or a negative  number,  option-
3505         ally enclosed in braces, is an absolute or relative back  reference.  A         ally  enclosed  in braces, is an absolute or relative back reference. A
3506         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-
3507         cussed later, following the discussion of parenthesized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3508    
3509     Absolute and relative subroutine calls     Absolute and relative subroutine calls
3510    
3511         For compatibility with Oniguruma, the non-Perl syntax \g followed by  a         For  compatibility with Oniguruma, the non-Perl syntax \g followed by a
3512         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
3513         an alternative syntax for referencing a subpattern as  a  "subroutine".         an  alternative  syntax for referencing a subpattern as a "subroutine".
3514         Details  are  discussed  later.   Note  that  \g{...} (Perl syntax) and         Details are discussed later.   Note  that  \g{...}  (Perl  syntax)  and
3515         \g<...> (Oniguruma syntax) are not synonymous. The  former  is  a  back         \g<...>  (Oniguruma  syntax)  are  not synonymous. The former is a back
3516         reference; the latter is a subroutine call.         reference; the latter is a subroutine call.
3517    
3518     Generic character types     Generic character types
# Line 3449  BACKSLASH Line 3531  BACKSLASH
3531           \W     any "non-word" character           \W     any "non-word" character
3532    
3533         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-
3534         acter.  This is the same as the "." metacharacter when  PCRE_DOTALL  is         acter.   This  is the same as the "." metacharacter when PCRE_DOTALL is
3535         not set.         not set.
3536    
3537         Each  pair of lower and upper case escape sequences partitions the com-         Each pair of lower and upper case escape sequences partitions the  com-
3538         plete set of characters into two disjoint  sets.  Any  given  character         plete  set  of  characters  into two disjoint sets. Any given character
3539         matches  one, and only one, of each pair. The sequences can appear both         matches one, and only one, of each pair. The sequences can appear  both
3540         inside and outside character classes. They each match one character  of         inside  and outside character classes. They each match one character of
3541         the  appropriate  type.  If the current matching point is at the end of         the appropriate type. If the current matching point is at  the  end  of
3542         the subject string, all of them fail, because there is no character  to         the  subject string, all of them fail, because there is no character to
3543         match.         match.
3544    
3545         For  compatibility  with Perl, \s does not match the VT character (code         For compatibility with Perl, \s does not match the VT  character  (code
3546         11).  This makes it different from the the POSIX "space" class. The  \s         11).   This makes it different from the the POSIX "space" class. The \s
3547         characters  are  HT  (9), LF (10), FF (12), CR (13), and space (32). If         characters are HT (9), LF (10), FF (12), CR (13), and  space  (32).  If
3548         "use locale;" is included in a Perl script, \s may match the VT charac-         "use locale;" is included in a Perl script, \s may match the VT charac-
3549         ter. In PCRE, it never does.         ter. In PCRE, it never does.
3550    
3551         A  "word"  character is an underscore or any character that is a letter         A "word" character is an underscore or any character that is  a  letter
3552         or digit.  By default, the definition of letters  and  digits  is  con-         or  digit.   By  default,  the definition of letters and digits is con-
3553         trolled  by PCRE's low-valued character tables, and may vary if locale-         trolled by PCRE's low-valued character tables, and may vary if  locale-
3554         specific matching is taking place (see "Locale support" in the  pcreapi         specific  matching is taking place (see "Locale support" in the pcreapi
3555         page).  For  example,  in  a French locale such as "fr_FR" in Unix-like         page). For example, in a French locale such  as  "fr_FR"  in  Unix-like
3556         systems, or "french" in Windows, some character codes greater than  128         systems,  or "french" in Windows, some character codes greater than 128
3557         are  used  for  accented letters, and these are then matched by \w. The         are used for accented letters, and these are then matched  by  \w.  The
3558         use of locales with Unicode is discouraged.         use of locales with Unicode is discouraged.
3559    
3560         By default, in UTF-8 mode, characters  with  values  greater  than  128         By  default,  in  UTF-8  mode,  characters with values greater than 128
3561         never  match  \d,  \s,  or  \w,  and always match \D, \S, and \W. These         never match \d, \s, or \w, and always  match  \D,  \S,  and  \W.  These
3562         sequences retain their original meanings from before UTF-8 support  was         sequences  retain their original meanings from before UTF-8 support was
3563         available,  mainly for efficiency reasons. However, if PCRE is compiled         available, mainly for efficiency reasons. However, if PCRE is  compiled
3564         with Unicode property support, and the PCRE_UCP option is set, the  be-         with  Unicode property support, and the PCRE_UCP option is set, the be-
3565         haviour  is  changed  so  that Unicode properties are used to determine         haviour is changed so that Unicode properties  are  used  to  determine
3566         character types, as follows:         character types, as follows:
3567    
3568           \d  any character that \p{Nd} matches (decimal digit)           \d  any character that \p{Nd} matches (decimal digit)
3569           \s  any character that \p{Z} matches, plus HT, LF, FF, CR           \s  any character that \p{Z} matches, plus HT, LF, FF, CR
3570           \w  any character that \p{L} or \p{N} matches, plus underscore           \w  any character that \p{L} or \p{N} matches, plus underscore
3571    
3572         The upper case escapes match the inverse sets of characters. Note  that         The  upper case escapes match the inverse sets of characters. Note that
3573         \d  matches  only decimal digits, whereas \w matches any Unicode digit,         \d matches only decimal digits, whereas \w matches any  Unicode  digit,
3574         as well as any Unicode letter, and underscore. Note also that  PCRE_UCP         as  well as any Unicode letter, and underscore. Note also that PCRE_UCP
3575         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.
3576         Matching these sequences is noticeably slower when PCRE_UCP is set.         Matching these sequences is noticeably slower when PCRE_UCP is set.
3577    
3578         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
3579         the  other  sequences,  which  match  only ASCII characters by default,         at release 5.10. In contrast to the other sequences, which  match  only
3580         these always  match  certain  high-valued  codepoints  in  UTF-8  mode,         ASCII  characters  by  default,  these always match certain high-valued
3581         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-
3582           tal space characters are:
3583    
3584           U+0009     Horizontal tab           U+0009     Horizontal tab
3585           U+0020     Space           U+0020     Space
# Line 3531  BACKSLASH Line 3614  BACKSLASH
3614     Newline sequences     Newline sequences
3615    
3616         Outside  a  character class, by default, the escape sequence \R matches         Outside  a  character class, by default, the escape sequence \R matches
3617         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
3618         mode \R is equivalent to the following:         following:
3619    
3620           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3621    
# Line 3712  BACKSLASH Line 3795  BACKSLASH
3795         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
3796         matches any one character.         matches any one character.
3797    
3798           Note that recent versions of Perl have changed \X to match what Unicode
3799           calls an "extended grapheme cluster", which has a more complicated def-
3800           inition.
3801    
3802         Matching characters by Unicode property is not fast, because  PCRE  has         Matching characters by Unicode property is not fast, because  PCRE  has
3803         to  search  a  structure  that  contains data for over fifteen thousand         to  search  a  structure  that  contains data for over fifteen thousand
3804         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
# Line 3740  BACKSLASH Line 3827  BACKSLASH
3827    
3828     Resetting the match start     Resetting the match start
3829    
3830         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
3831         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:  
3832    
3833           foo\Kbar           foo\Kbar
3834    
3835         matches  "foobar",  but reports that it has matched "bar". This feature         matches "foobar", but reports that it has matched "bar".  This  feature
3836         is similar to a lookbehind assertion (described  below).   However,  in         is  similar  to  a lookbehind assertion (described below).  However, in
3837         this  case, the part of the subject before the real match does not have         this case, the part of the subject before the real match does not  have
3838         to be of fixed length, as lookbehind assertions do. The use of \K  does         to  be of fixed length, as lookbehind assertions do. The use of \K does
3839         not  interfere  with  the setting of captured substrings.  For example,         not interfere with the setting of captured  substrings.   For  example,
3840         when the pattern         when the pattern
3841    
3842           (foo)\Kbar           (foo)\Kbar
3843    
3844         matches "foobar", the first substring is still set to "foo".         matches "foobar", the first substring is still set to "foo".
3845    
3846         Perl documents that the use  of  \K  within  assertions  is  "not  well         Perl  documents  that  the  use  of  \K  within assertions is "not well
3847         defined".  In  PCRE,  \K  is  acted upon when it occurs inside positive         defined". In PCRE, \K is acted upon  when  it  occurs  inside  positive
3848         assertions, but is ignored in negative assertions.         assertions, but is ignored in negative assertions.
3849    
3850     Simple assertions     Simple assertions
3851    
3852         The final use of backslash is for certain simple assertions. An  asser-         The  final use of backslash is for certain simple assertions. An asser-
3853         tion  specifies a condition that has to be met at a particular point in         tion specifies a condition that has to be met at a particular point  in
3854         a match, without consuming any characters from the subject string.  The         a  match, without consuming any characters from the subject string. The
3855         use  of subpatterns for more complicated assertions is described below.         use of subpatterns for more complicated assertions is described  below.
3856         The backslashed assertions are:         The backslashed assertions are:
3857    
3858           \b     matches at a word boundary           \b     matches at a word boundary
# Line 3777  BACKSLASH Line 3863  BACKSLASH
3863           \z     matches only at the end of the subject           \z     matches only at the end of the subject
3864           \G     matches at the first matching position in the subject           \G     matches at the first matching position in the subject
3865    
3866         Inside a character class, \b has a different meaning;  it  matches  the         Inside  a  character  class, \b has a different meaning; it matches the
3867         backspace  character.  If  any  other  of these assertions appears in a         backspace character. If any other of  these  assertions  appears  in  a
3868         character class, by default it matches the corresponding literal  char-         character  class, by default it matches the corresponding literal char-
3869         acter  (for  example,  \B  matches  the  letter  B).  However,  if  the         acter  (for  example,  \B  matches  the  letter  B).  However,  if  the
3870         PCRE_EXTRA option is set, an "invalid escape sequence" error is  gener-         PCRE_EXTRA  option is set, an "invalid escape sequence" error is gener-
3871         ated instead.         ated instead.
3872    
3873         A  word  boundary is a position in the subject string where the current         A word boundary is a position in the subject string where  the  current
3874         character and the previous character do not both match \w or  \W  (i.e.         character  and  the previous character do not both match \w or \W (i.e.
3875         one  matches  \w  and the other matches \W), or the start or end of the         one matches \w and the other matches \W), or the start or  end  of  the
3876         string if the first or last  character  matches  \w,  respectively.  In         string  if  the  first  or  last character matches \w, respectively. In
3877         UTF-8  mode,  the  meanings  of \w and \W can be changed by setting the         UTF-8 mode, the meanings of \w and \W can be  changed  by  setting  the
3878         PCRE_UCP option. When this is done, it also affects \b and \B.  Neither         PCRE_UCP  option. When this is done, it also affects \b and \B. Neither
3879         PCRE  nor  Perl has a separate "start of word" or "end of word" metase-         PCRE nor Perl has a separate "start of word" or "end of  word"  metase-
3880         quence. However, whatever follows \b normally determines which  it  is.         quence.  However,  whatever follows \b normally determines which it is.
3881         For example, the fragment \ba matches "a" at the start of a word.         For example, the fragment \ba matches "a" at the start of a word.
3882    
3883         The  \A,  \Z,  and \z assertions differ from the traditional circumflex         The \A, \Z, and \z assertions differ from  the  traditional  circumflex
3884         and dollar (described in the next section) in that they only ever match         and dollar (described in the next section) in that they only ever match
3885         at  the  very start and end of the subject string, whatever options are         at the very start and end of the subject string, whatever  options  are
3886         set. Thus, they are independent of multiline mode. These  three  asser-         set.  Thus,  they are independent of multiline mode. These three asser-
3887         tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which         tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which
3888         affect only the behaviour of the circumflex and dollar  metacharacters.         affect  only the behaviour of the circumflex and dollar metacharacters.
3889         However,  if the startoffset argument of pcre_exec() is non-zero, indi-         However, if the startoffset argument of pcre_exec() is non-zero,  indi-
3890         cating that matching is to start at a point other than the beginning of         cating that matching is to start at a point other than the beginning of
3891         the  subject,  \A  can never match. The difference between \Z and \z is         the subject, \A can never match. The difference between \Z  and  \z  is
3892         that \Z matches before a newline at the end of the string as well as at         that \Z matches before a newline at the end of the string as well as at
3893         the very end, whereas \z matches only at the end.         the very end, whereas \z matches only at the end.
3894    
3895         The  \G assertion is true only when the current matching position is at         The \G assertion is true only when the current matching position is  at
3896         the start point of the match, as specified by the startoffset  argument         the  start point of the match, as specified by the startoffset argument
3897         of  pcre_exec().  It  differs  from \A when the value of startoffset is         of pcre_exec(). It differs from \A when the  value  of  startoffset  is
3898         non-zero. By calling pcre_exec() multiple times with appropriate  argu-         non-zero.  By calling pcre_exec() multiple times with appropriate argu-
3899         ments, you can mimic Perl's /g option, and it is in this kind of imple-         ments, you can mimic Perl's /g option, and it is in this kind of imple-
3900         mentation where \G can be useful.         mentation where \G can be useful.
3901    
3902         Note, however, that PCRE's interpretation of \G, as the  start  of  the         Note,  however,  that  PCRE's interpretation of \G, as the start of the
3903         current match, is subtly different from Perl's, which defines it as the         current match, is subtly different from Perl's, which defines it as the
3904         end of the previous match. In Perl, these can  be  different  when  the         end  of  the  previous  match. In Perl, these can be different when the
3905         previously  matched  string was empty. Because PCRE does just one match         previously matched string was empty. Because PCRE does just  one  match
3906         at a time, it cannot reproduce this behaviour.         at a time, it cannot reproduce this behaviour.
3907    
3908         If all the alternatives of a pattern begin with \G, the  expression  is         If  all  the alternatives of a pattern begin with \G, the expression is
3909         anchored to the starting match position, and the "anchored" flag is set         anchored to the starting match position, and the "anchored" flag is set
3910         in the compiled regular expression.         in the compiled regular expression.
3911    
# Line 3827  BACKSLASH Line 3913  BACKSLASH
3913  CIRCUMFLEX AND DOLLAR  CIRCUMFLEX AND DOLLAR
3914    
3915         Outside a character class, in the default matching mode, the circumflex         Outside a character class, in the default matching mode, the circumflex
3916         character  is  an  assertion  that is true only if the current matching         character is an assertion that is true only  if  the  current  matching
3917         point is at the start of the subject string. If the  startoffset  argu-         point  is  at the start of the subject string. If the startoffset argu-
3918         ment  of  pcre_exec()  is  non-zero,  circumflex can never match if the         ment of pcre_exec() is non-zero, circumflex  can  never  match  if  the
3919         PCRE_MULTILINE option is unset. Inside a  character  class,  circumflex         PCRE_MULTILINE  option  is  unset. Inside a character class, circumflex
3920         has an entirely different meaning (see below).         has an entirely different meaning (see below).
3921    
3922         Circumflex  need  not be the first character of the pattern if a number         Circumflex need not be the first character of the pattern if  a  number
3923         of alternatives are involved, but it should be the first thing in  each         of  alternatives are involved, but it should be the first thing in each
3924         alternative  in  which  it appears if the pattern is ever to match that         alternative in which it appears if the pattern is ever  to  match  that
3925         branch. If all possible alternatives start with a circumflex, that  is,         branch.  If all possible alternatives start with a circumflex, that is,
3926         if  the  pattern  is constrained to match only at the start of the sub-         if the pattern is constrained to match only at the start  of  the  sub-
3927         ject, it is said to be an "anchored" pattern.  (There  are  also  other         ject,  it  is  said  to be an "anchored" pattern. (There are also other
3928         constructs that can cause a pattern to be anchored.)         constructs that can cause a pattern to be anchored.)
3929    
3930         A  dollar  character  is  an assertion that is true only if the current         A dollar character is an assertion that is true  only  if  the  current
3931         matching point is at the end of  the  subject  string,  or  immediately         matching  point  is  at  the  end of the subject string, or immediately
3932         before a newline at the end of the string (by default). Dollar need not         before a newline at the end of the string (by default). Dollar need not
3933         be the last character of the pattern if a number  of  alternatives  are         be  the  last  character of the pattern if a number of alternatives are
3934         involved,  but  it  should  be  the last item in any branch in which it         involved, but it should be the last item in  any  branch  in  which  it
3935         appears. Dollar has no special meaning in a character class.         appears. Dollar has no special meaning in a character class.
3936    
3937         The meaning of dollar can be changed so that it  matches  only  at  the         The  meaning  of  dollar  can be changed so that it matches only at the
3938         very  end  of  the string, by setting the PCRE_DOLLAR_ENDONLY option at         very end of the string, by setting the  PCRE_DOLLAR_ENDONLY  option  at
3939         compile time. This does not affect the \Z assertion.         compile time. This does not affect the \Z assertion.
3940    
3941         The meanings of the circumflex and dollar characters are changed if the         The meanings of the circumflex and dollar characters are changed if the
3942         PCRE_MULTILINE  option  is  set.  When  this  is the case, a circumflex         PCRE_MULTILINE option is set. When  this  is  the  case,  a  circumflex
3943         matches immediately after internal newlines as well as at the start  of         matches  immediately after internal newlines as well as at the start of
3944         the  subject  string.  It  does not match after a newline that ends the         the subject string. It does not match after a  newline  that  ends  the
3945         string. A dollar matches before any newlines in the string, as well  as         string.  A dollar matches before any newlines in the string, as well as
3946         at  the very end, when PCRE_MULTILINE is set. When newline is specified         at the very end, when PCRE_MULTILINE is set. When newline is  specified
3947         as the two-character sequence CRLF, isolated CR and  LF  characters  do         as  the  two-character  sequence CRLF, isolated CR and LF characters do
3948         not indicate newlines.         not indicate newlines.
3949    
3950         For  example, the pattern /^abc$/ matches the subject string "def\nabc"         For example, the pattern /^abc$/ matches the subject string  "def\nabc"
3951         (where \n represents a newline) in multiline mode, but  not  otherwise.         (where  \n  represents a newline) in multiline mode, but not otherwise.
3952         Consequently,  patterns  that  are anchored in single line mode because         Consequently, patterns that are anchored in single  line  mode  because
3953         all branches start with ^ are not anchored in  multiline  mode,  and  a         all  branches  start  with  ^ are not anchored in multiline mode, and a
3954         match  for  circumflex  is  possible  when  the startoffset argument of         match for circumflex is  possible  when  the  startoffset  argument  of
3955         pcre_exec() is non-zero. The PCRE_DOLLAR_ENDONLY option is  ignored  if         pcre_exec()  is  non-zero. The PCRE_DOLLAR_ENDONLY option is ignored if
3956         PCRE_MULTILINE is set.         PCRE_MULTILINE is set.
3957    
3958         Note  that  the sequences \A, \Z, and \z can be used to match the start         Note that the sequences \A, \Z, and \z can be used to match  the  start
3959         and end of the subject in both modes, and if all branches of a  pattern         and  end of the subject in both modes, and if all branches of a pattern
3960         start  with  \A it is always anchored, whether or not PCRE_MULTILINE is         start with \A it is always anchored, whether or not  PCRE_MULTILINE  is
3961         set.         set.
3962    
3963    
3964  FULL STOP (PERIOD, DOT) AND \N  FULL STOP (PERIOD, DOT) AND \N
3965    
3966         Outside a character class, a dot in the pattern matches any one charac-         Outside a character class, a dot in the pattern matches any one charac-
3967         ter  in  the subject string except (by default) a character that signi-         ter in the subject string except (by default) a character  that  signi-
3968         fies the end of a line. In UTF-8 mode, the  matched  character  may  be         fies  the  end  of  a line. In UTF-8 mode, the matched character may be
3969         more than one byte long.         more than one byte long.
3970    
3971         When  a line ending is defined as a single character, dot never matches         When a line ending is defined as a single character, dot never  matches
3972         that character; when the two-character sequence CRLF is used, dot  does         that  character; when the two-character sequence CRLF is used, dot does
3973         not  match  CR  if  it  is immediately followed by LF, but otherwise it         not match CR if it is immediately followed  by  LF,  but  otherwise  it
3974         matches all characters (including isolated CRs and LFs). When any  Uni-         matches  all characters (including isolated CRs and LFs). When any Uni-
3975         code  line endings are being recognized, dot does not match CR or LF or         code line endings are being recognized, dot does not match CR or LF  or
3976         any of the other line ending characters.         any of the other line ending characters.
3977    
3978         The behaviour of dot with regard to newlines can  be  changed.  If  the         The  behaviour  of  dot  with regard to newlines can be changed. If the
3979         PCRE_DOTALL  option  is  set,  a dot matches any one character, without         PCRE_DOTALL option is set, a dot matches  any  one  character,  without
3980         exception. If the two-character sequence CRLF is present in the subject         exception. If the two-character sequence CRLF is present in the subject
3981         string, it takes two dots to match it.         string, it takes two dots to match it.
3982    
3983         The  handling of dot is entirely independent of the handling of circum-         The handling of dot is entirely independent of the handling of  circum-
3984         flex and dollar, the only relationship being  that  they  both  involve         flex  and  dollar,  the  only relationship being that they both involve
3985         newlines. Dot has no special meaning in a character class.         newlines. Dot has no special meaning in a character class.
3986    
3987         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
3988         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
3989         signifies the end of a line.         character except one that signifies the end of a line.
3990    
3991    
3992  MATCHING A SINGLE BYTE  MATCHING A SINGLE BYTE
3993    
3994         Outside a character class, the escape sequence \C matches any one byte,         Outside a character class, the escape sequence \C matches any one byte,
3995         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 any
3996         line-ending  characters.  The  feature  is provided in Perl in order to         line-ending characters. The feature is provided in  Perl  in  order  to
3997         match individual bytes in UTF-8 mode. Because it breaks up UTF-8  char-         match  individual bytes in UTF-8 mode. Because it breaks up UTF-8 char-
3998         acters  into individual bytes, what remains in the string may be a mal-         acters into individual bytes, the rest of the string may start  with  a
3999         formed UTF-8 string. For this reason, the \C escape  sequence  is  best         malformed  UTF-8  character. For this reason, the \C escape sequence is
4000         avoided.         best avoided.
4001    
4002         PCRE  does  not  allow \C to appear in lookbehind assertions (described         PCRE does not allow \C to appear in  lookbehind  assertions  (described
4003         below), because in UTF-8 mode this would make it impossible  to  calcu-         below),  because  in UTF-8 mode this would make it impossible to calcu-
4004         late the length of the lookbehind.         late the length of the lookbehind.
4005    
4006    
# Line 3924  SQUARE BRACKETS AND CHARACTER CLASSES Line 4010  SQUARE BRACKETS AND CHARACTER CLASSES
4010         closing square bracket. A closing square bracket on its own is not spe-         closing square bracket. A closing square bracket on its own is not spe-
4011         cial by default.  However, if the PCRE_JAVASCRIPT_COMPAT option is set,         cial by default.  However, if the PCRE_JAVASCRIPT_COMPAT option is set,
4012         a lone closing square bracket causes a compile-time error. If a closing         a lone closing square bracket causes a compile-time error. If a closing
4013         square  bracket  is required as a member of the class, it should be the         square bracket is required as a member of the class, it should  be  the
4014         first data character in the class  (after  an  initial  circumflex,  if         first  data  character  in  the  class (after an initial circumflex, if
4015         present) or escaped with a backslash.         present) or escaped with a backslash.
4016    
4017         A  character  class matches a single character in the subject. In UTF-8         A character class matches a single character in the subject.  In  UTF-8
4018         mode, the character may be more than one byte long. A matched character         mode, the character may be more than one byte long. A matched character
4019         must be in the set of characters defined by the class, unless the first         must be in the set of characters defined by the class, unless the first
4020         character in the class definition is a circumflex, in  which  case  the         character  in  the  class definition is a circumflex, in which case the
4021         subject  character  must  not  be in the set defined by the class. If a         subject character must not be in the set defined by  the  class.  If  a
4022         circumflex is actually required as a member of the class, ensure it  is         circumflex  is actually required as a member of the class, ensure it is
4023         not the first character, or escape it with a backslash.         not the first character, or escape it with a backslash.
4024    
4025         For  example, the character class [aeiou] matches any lower case vowel,         For example, the character class [aeiou] matches any lower case  vowel,
4026         while [^aeiou] matches any character that is not a  lower  case  vowel.         while  [^aeiou]  matches  any character that is not a lower case vowel.
4027         Note that a circumflex is just a convenient notation for specifying the         Note that a circumflex is just a convenient notation for specifying the
4028         characters that are in the class by enumerating those that are  not.  A         characters  that  are in the class by enumerating those that are not. A
4029         class  that starts with a circumflex is not an assertion; it still con-         class that starts with a circumflex is not an assertion; it still  con-
4030         sumes a character from the subject string, and therefore  it  fails  if         sumes  a  character  from the subject string, and therefore it fails if
4031         the current pointer is at the end of the string.         the current pointer is at the end of the string.
4032    
4033         In  UTF-8 mode, characters with values greater than 255 can be included         In UTF-8 mode, characters with values greater than 255 can be  included
4034         in a class as a literal string of bytes, or by using the  \x{  escaping         in  a  class as a literal string of bytes, or by using the \x{ escaping
4035         mechanism.         mechanism.
4036    
4037         When  caseless  matching  is set, any letters in a class represent both         When caseless matching is set, any letters in a  class  represent  both
4038         their upper case and lower case versions, so for  example,  a  caseless         their  upper  case  and lower case versions, so for example, a caseless
4039         [aeiou]  matches  "A"  as well as "a", and a caseless [^aeiou] does not         [aeiou] matches "A" as well as "a", and a caseless  [^aeiou]  does  not
4040         match "A", whereas a caseful version would. In UTF-8 mode, PCRE  always         match  "A", whereas a caseful version would. In UTF-8 mode, PCRE always
4041         understands  the  concept  of case for characters whose values are less         understands the concept of case for characters whose  values  are  less
4042         than 128, so caseless matching is always possible. For characters  with         than  128, so caseless matching is always possible. For characters with
4043         higher  values,  the  concept  of case is supported if PCRE is compiled         higher values, the concept of case is supported  if  PCRE  is  compiled
4044         with Unicode property support, but not otherwise.  If you want  to  use         with  Unicode  property support, but not otherwise.  If you want to use
4045         caseless  matching  in UTF8-mode for characters 128 and above, you must         caseless matching in UTF8-mode for characters 128 and above,  you  must
4046         ensure that PCRE is compiled with Unicode property support as  well  as         ensure  that  PCRE is compiled with Unicode property support as well as
4047         with UTF-8 support.         with UTF-8 support.
4048    
4049         Characters  that  might  indicate  line breaks are never treated in any         Characters that might indicate line breaks are  never  treated  in  any
4050         special way  when  matching  character  classes,  whatever  line-ending         special  way  when  matching  character  classes,  whatever line-ending
4051         sequence  is  in  use,  and  whatever  setting  of  the PCRE_DOTALL and         sequence is in  use,  and  whatever  setting  of  the  PCRE_DOTALL  and
4052         PCRE_MULTILINE options is used. A class such as [^a] always matches one         PCRE_MULTILINE options is used. A class such as [^a] always matches one
4053         of these characters.         of these characters.
4054    
4055         The  minus (hyphen) character can be used to specify a range of charac-         The minus (hyphen) character can be used to specify a range of  charac-
4056         ters in a character  class.  For  example,  [d-m]  matches  any  letter         ters  in  a  character  class.  For  example,  [d-m] matches any letter
4057         between  d  and  m,  inclusive.  If  a minus character is required in a         between d and m, inclusive. If a  minus  character  is  required  in  a
4058         class, it must be escaped with a backslash  or  appear  in  a  position         class,  it  must  be  escaped  with a backslash or appear in a position
4059         where  it cannot be interpreted as indicating a range, typically as the         where it cannot be interpreted as indicating a range, typically as  the
4060         first or last character in the class.         first or last character in the class.
4061    
4062         It is not possible to have the literal character "]" as the end charac-         It is not possible to have the literal character "]" as the end charac-
4063         ter  of a range. A pattern such as [W-]46] is interpreted as a class of         ter of a range. A pattern such as [W-]46] is interpreted as a class  of
4064         two characters ("W" and "-") followed by a literal string "46]", so  it         two  characters ("W" and "-") followed by a literal string "46]", so it
4065         would  match  "W46]"  or  "-46]". However, if the "]" is escaped with a         would match "W46]" or "-46]". However, if the "]"  is  escaped  with  a
4066         backslash it is interpreted as the end of range, so [W-\]46] is  inter-         backslash  it is interpreted as the end of range, so [W-\]46] is inter-
4067         preted  as a class containing a range followed by two other characters.         preted as a class containing a range followed by two other  characters.
4068         The octal or hexadecimal representation of "]" can also be used to  end         The  octal or hexadecimal representation of "]" can also be used to end
4069         a range.         a range.
4070    
4071         Ranges  operate in the collating sequence of character values. They can         Ranges operate in the collating sequence of character values. They  can
4072         also  be  used  for  characters  specified  numerically,  for   example         also   be  used  for  characters  specified  numerically,  for  example
4073         [\000-\037].  In UTF-8 mode, ranges can include characters whose values         [\000-\037]. In UTF-8 mode, ranges can include characters whose  values
4074         are greater than 255, for example [\x{100}-\x{2ff}].         are greater than 255, for example [\x{100}-\x{2ff}].
4075    
4076         If a range that includes letters is used when caseless matching is set,         If a range that includes letters is used when caseless matching is set,
4077         it matches the letters in either case. For example, [W-c] is equivalent         it matches the letters in either case. For example, [W-c] is equivalent
4078         to [][\\^_`wxyzabc], matched caselessly,  and  in  non-UTF-8  mode,  if         to  [][\\^_`wxyzabc],  matched  caselessly,  and  in non-UTF-8 mode, if
4079         character  tables  for  a French locale are in use, [\xc8-\xcb] matches         character tables for a French locale are in  use,  [\xc8-\xcb]  matches
4080         accented E characters in both cases. In UTF-8 mode, PCRE  supports  the         accented  E  characters in both cases. In UTF-8 mode, PCRE supports the
4081         concept  of  case for characters with values greater than 128 only when         concept of case for characters with values greater than 128  only  when
4082         it is compiled with Unicode property support.         it is compiled with Unicode property support.
4083    
4084         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,
4085         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
4086         match to the class. For example,  [\dABCDEF]  matches  any  hexadecimal         they  match to the class. For example, [\dABCDEF] matches any hexadeci-
4087         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
4088         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
4089         matching  lower  case  type.  For example, the class [^\W_] matches any         appear outside a character class, as described in the section  entitled
4090         letter or digit, but not underscore.         "Generic character types" above. The escape sequence \b has a different
4091           meaning inside a character class; it matches the  backspace  character.
4092         The only metacharacters that are recognized in  character  classes  are         The  sequences  \B,  \N,  \R, and \X are not special inside a character
4093         backslash,  hyphen  (only  where  it can be interpreted as specifying a         class. Like any other unrecognized escape sequences, they  are  treated
4094         range), circumflex (only at the start), opening  square  bracket  (only         as  the literal characters "B", "N", "R", and "X" by default, but cause
4095         when  it can be interpreted as introducing a POSIX class name - see the         an error if the PCRE_EXTRA option is set.
4096         next section), and the terminating  closing  square  bracket.  However,  
4097           A circumflex can conveniently be used with  the  upper  case  character
4098           types  to specify a more restricted set of characters than the matching
4099           lower case type.  For example, the class [^\W_] matches any  letter  or
4100           digit, but not underscore, whereas [\w] includes underscore. A positive
4101           character class should be read as "something OR something OR ..." and a
4102           negative class as "NOT something AND NOT something AND NOT ...".
4103    
4104           The  only  metacharacters  that are recognized in character classes are
4105           backslash, hyphen (only where it can be  interpreted  as  specifying  a
4106           range),  circumflex  (only  at the start), opening square bracket (only
4107           when it can be interpreted as introducing a POSIX class name - see  the
4108           next  section),  and  the  terminating closing square bracket. However,
4109         escaping other non-alphanumeric characters does no harm.         escaping other non-alphanumeric characters does no harm.
4110    
4111    
4112  POSIX CHARACTER CLASSES  POSIX CHARACTER CLASSES
4113    
4114         Perl supports the POSIX notation for character classes. This uses names         Perl supports the POSIX notation for character classes. This uses names
4115         enclosed by [: and :] within the enclosing square brackets.  PCRE  also         enclosed  by  [: and :] within the enclosing square brackets. PCRE also
4116         supports this notation. For example,         supports this notation. For example,
4117    
4118           [01[:alpha:]%]           [01[:alpha:]%]
# Line 4037  POSIX CHARACTER CLASSES Line 4135  POSIX CHARACTER CLASSES
4135           word     "word" characters (same as \w)           word     "word" characters (same as \w)
4136           xdigit   hexadecimal digits           xdigit   hexadecimal digits
4137    
4138         The "space" characters are HT (9), LF (10), VT (11), FF (12), CR  (13),         The  "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13),
4139         and  space  (32). Notice that this list includes the VT character (code         and space (32). Notice that this list includes the VT  character  (code
4140         11). This makes "space" different to \s, which does not include VT (for         11). This makes "space" different to \s, which does not include VT (for
4141         Perl compatibility).         Perl compatibility).
4142    
4143         The  name  "word"  is  a Perl extension, and "blank" is a GNU extension         The name "word" is a Perl extension, and "blank"  is  a  GNU  extension
4144         from Perl 5.8. Another Perl extension is negation, which  is  indicated         from  Perl  5.8. Another Perl extension is negation, which is indicated
4145         by a ^ character after the colon. For example,         by a ^ character after the colon. For example,
4146    
4147           [12[:^digit:]]           [12[:^digit:]]
4148    
4149         matches  "1", "2", or any non-digit. PCRE (and Perl) also recognize the         matches "1", "2", or any non-digit. PCRE (and Perl) also recognize  the
4150         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but
4151         these are not supported, and an error is given if they are encountered.         these are not supported, and an error is given if they are encountered.
4152    
4153         By  default,  in UTF-8 mode, characters with values greater than 128 do         By default, in UTF-8 mode, characters with values greater than  128  do
4154         not match any of the POSIX character classes. However, if the  PCRE_UCP         not  match any of the POSIX character classes. However, if the PCRE_UCP
4155         option  is passed to pcre_compile(), some of the classes are changed so         option is passed to pcre_compile(), some of the classes are changed  so
4156         that Unicode character properties are used. This is achieved by replac-         that Unicode character properties are used. This is achieved by replac-
4157         ing the POSIX classes by other sequences, as follows:         ing the POSIX classes by other sequences, as follows:
4158    
# Line 4067  POSIX CHARACTER CLASSES Line 4165  POSIX CHARACTER CLASSES
4165           [:upper:]  becomes  \p{Lu}           [:upper:]  becomes  \p{Lu}
4166           [:word:]   becomes  \p{Xwd}           [:word:]   becomes  \p{Xwd}
4167    
4168         Negated  versions,  such  as [:^alpha:] use \P instead of \p. The other         Negated versions, such as [:^alpha:] use \P instead of  \p.  The  other
4169         POSIX classes are unchanged, and match only characters with code points         POSIX classes are unchanged, and match only characters with code points
4170         less than 128.         less than 128.
4171    
4172    
4173  VERTICAL BAR  VERTICAL BAR
4174    
4175         Vertical  bar characters are used to separate alternative patterns. For         Vertical bar characters are used to separate alternative patterns.  For
4176         example, the pattern         example, the pattern
4177    
4178           gilbert|sullivan           gilbert|sullivan
4179    
4180         matches either "gilbert" or "sullivan". Any number of alternatives  may         matches  either "gilbert" or "sullivan". Any number of alternatives may
4181         appear,  and  an  empty  alternative  is  permitted (matching the empty         appear, and an empty  alternative  is  permitted  (matching  the  empty
4182         string). The matching process tries each alternative in turn, from left         string). The matching process tries each alternative in turn, from left
4183         to  right, and the first one that succeeds is used. If the alternatives         to right, and the first one that succeeds is used. If the  alternatives
4184         are within a subpattern (defined below), "succeeds" means matching  the         are  within a subpattern (defined below), "succeeds" means matching the
4185         rest of the main pattern as well as the alternative in the subpattern.         rest of the main pattern as well as the alternative in the subpattern.
4186    
4187    
4188  INTERNAL OPTION SETTING  INTERNAL OPTION SETTING
4189    
4190         The  settings  of  the  PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and         The settings of the  PCRE_CASELESS,  PCRE_MULTILINE,  PCRE_DOTALL,  and
4191         PCRE_EXTENDED options (which are Perl-compatible) can be  changed  from         PCRE_EXTENDED  options  (which are Perl-compatible) can be changed from
4192         within  the  pattern  by  a  sequence  of  Perl option letters enclosed         within the pattern by  a  sequence  of  Perl  option  letters  enclosed
4193         between "(?" and ")".  The option letters are         between "(?" and ")".  The option letters are
4194    
4195           i  for PCRE_CASELESS           i  for PCRE_CASELESS
# Line 4101  INTERNAL OPTION SETTING Line 4199  INTERNAL OPTION SETTING
4199    
4200         For example, (?im) sets caseless, multiline matching. It is also possi-         For example, (?im) sets caseless, multiline matching. It is also possi-
4201         ble to unset these options by preceding the letter with a hyphen, and a         ble to unset these options by preceding the letter with a hyphen, and a
4202         combined setting and unsetting such as (?im-sx), which sets  PCRE_CASE-         combined  setting and unsetting such as (?im-sx), which sets PCRE_CASE-
4203         LESS  and PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED,         LESS and PCRE_MULTILINE while unsetting PCRE_DOTALL and  PCRE_EXTENDED,
4204         is also permitted. If a  letter  appears  both  before  and  after  the         is  also  permitted.  If  a  letter  appears  both before and after the
4205         hyphen, the option is unset.         hyphen, the option is unset.
4206    
4207         The  PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA         The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA
4208         can be changed in the same way as the Perl-compatible options by  using         can  be changed in the same way as the Perl-compatible options by using
<