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revision 75 by nigel, Sat Feb 24 21:40:37 2007 UTC revision 77 by nigel, Sat Feb 24 21:40:45 2007 UTC
# Line 6  synopses of each function in the library Line 6  synopses of each function in the library
6  separate text files for the pcregrep and pcretest commands.  separate text files for the pcregrep and pcretest commands.
7  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
8    
 PCRE(3)                                                                PCRE(3)  
   
9    
10    
11  NAME  NAME
12         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
13    
14    
15  INTRODUCTION  INTRODUCTION
16    
17         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
18         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
19         just  a  few  differences.  The current implementation of PCRE (release         just  a  few  differences.  The current implementation of PCRE (release
20         5.x) corresponds approximately with Perl  5.8,  including  support  for         6.x) corresponds approximately with Perl  5.8,  including  support  for
21         UTF-8 encoded strings and Unicode general category properties. However,         UTF-8 encoded strings and Unicode general category properties. However,
22         this support has to be explicitly enabled; it is not the default.         this support has to be explicitly enabled; it is not the default.
23    
24           In addition to the Perl-compatible matching function,  PCRE  also  con-
25           tains  an  alternative matching function that matches the same compiled
26           patterns in a different way. In certain circumstances, the  alternative
27           function  has  some  advantages.  For  a discussion of the two matching
28           algorithms, see the pcrematching page.
29    
30         PCRE is written in C and released as a C library. A  number  of  people         PCRE is written in C and released as a C library. A  number  of  people
31         have  written  wrappers and interfaces of various kinds. A C++ class is         have  written  wrappers and interfaces of various kinds. In particular,
32         included in these contributions, which can  be  found  in  the  Contrib         Google Inc.  have provided a comprehensive C++  wrapper.  This  is  now
33         directory at the primary FTP site, which is:         included as part of the PCRE distribution. The pcrecpp page has details
34           of this interface. Other people's contributions can  be  found  in  the
35           Contrib directory at the primary FTP site, which is:
36    
37         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
38    
# Line 40  INTRODUCTION Line 47  INTRODUCTION
47         ing  PCRE for various operating systems can be found in the README file         ing  PCRE for various operating systems can be found in the README file
48         in the source distribution.         in the source distribution.
49    
50           The library contains a number of undocumented  internal  functions  and
51           data  tables  that  are  used by more than one of the exported external
52           functions, but which are not intended  for  use  by  external  callers.
53           Their  names  all begin with "_pcre_", which hopefully will not provoke
54           any name clashes.
55    
56    
57  USER DOCUMENTATION  USER DOCUMENTATION
58    
# Line 50  USER DOCUMENTATION Line 63  USER DOCUMENTATION
63         of searching. The sections are as follows:         of searching. The sections are as follows:
64    
65           pcre              this document           pcre              this document
66           pcreapi           details of PCRE's native API           pcreapi           details of PCRE's native C API
67           pcrebuild         options for building PCRE           pcrebuild         options for building PCRE
68           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
69           pcrecompat        discussion of Perl compatibility           pcrecompat        discussion of Perl compatibility
70             pcrecpp           details of the C++ wrapper
71           pcregrep          description of the pcregrep command           pcregrep          description of the pcregrep command
72             pcrematching      discussion of the two matching algorithms
73           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
74           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
75                               regular expressions                               regular expressions
76           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
77           pcreposix         the POSIX-compatible API           pcreposix         the POSIX-compatible C API
78           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
79           pcresample        discussion of the sample program           pcresample        discussion of the sample program
80           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
81    
82         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
83         each library function, listing its arguments and results.         each C library function, listing its arguments and results.
84    
85    
86  LIMITATIONS  LIMITATIONS
# Line 90  LIMITATIONS Line 105  LIMITATIONS
105         tern, is 200.         tern, is 200.
106    
107         The  maximum  length of a subject string is the largest positive number         The  maximum  length of a subject string is the largest positive number
108         that an integer variable can hold. However, PCRE uses recursion to han-         that an integer variable can hold. However, when using the  traditional
109         dle  subpatterns  and indefinite repetition. This means that the avail-         matching function, PCRE uses recursion to handle subpatterns and indef-
110         able stack space may limit the size of a subject  string  that  can  be         inite repetition.  This means that the available stack space may  limit
111         processed by certain patterns.         the size of a subject string that can be processed by certain patterns.
112    
113    
114  UTF-8 AND UNICODE PROPERTY SUPPORT  UTF-8 AND UNICODE PROPERTY SUPPORT
115    
116         From  release  3.3,  PCRE  has  had  some support for character strings         From release 3.3, PCRE has  had  some  support  for  character  strings
117         encoded in the UTF-8 format. For release 4.0 this was greatly  extended         encoded  in the UTF-8 format. For release 4.0 this was greatly extended
118         to  cover  most common requirements, and in release 5.0 additional sup-         to cover most common requirements, and in release 5.0  additional  sup-
119         port for Unicode general category properties was added.         port for Unicode general category properties was added.
120    
121         In order process UTF-8 strings, you must build PCRE  to  include  UTF-8         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8
122         support  in  the  code,  and, in addition, you must call pcre_compile()         support in the code, and, in addition,  you  must  call  pcre_compile()
123         with the PCRE_UTF8 option flag. When you do this, both the pattern  and         with  the PCRE_UTF8 option flag. When you do this, both the pattern and
124         any  subject  strings  that are matched against it are treated as UTF-8         any subject strings that are matched against it are  treated  as  UTF-8
125         strings instead of just strings of bytes.         strings instead of just strings of bytes.
126    
127         If you compile PCRE with UTF-8 support, but do not use it at run  time,         If  you compile PCRE with UTF-8 support, but do not use it at run time,
128         the  library will be a bit bigger, but the additional run time overhead         the library will be a bit bigger, but the additional run time  overhead
129         is limited to testing the PCRE_UTF8 flag in several places,  so  should         is  limited  to testing the PCRE_UTF8 flag in several places, so should
130         not be very large.         not be very large.
131    
132         If PCRE is built with Unicode character property support (which implies         If PCRE is built with Unicode character property support (which implies
133         UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-         UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-
134         ported.  The available properties that can be tested are limited to the         ported.  The available properties that can be tested are limited to the
135         general category properties such as Lu for an upper case letter  or  Nd         general  category  properties such as Lu for an upper case letter or Nd
136         for  a decimal number. A full list is given in the pcrepattern documen-         for a decimal number. A full list is given in the pcrepattern  documen-
137         tation. The PCRE library is increased in size by about 90K when Unicode         tation. The PCRE library is increased in size by about 90K when Unicode
138         property support is included.         property support is included.
139    
140         The following comments apply when PCRE is running in UTF-8 mode:         The following comments apply when PCRE is running in UTF-8 mode:
141    
142         1.  When you set the PCRE_UTF8 flag, the strings passed as patterns and         1. When you set the PCRE_UTF8 flag, the strings passed as patterns  and
143         subjects are checked for validity on entry to the  relevant  functions.         subjects  are  checked for validity on entry to the relevant functions.
144         If an invalid UTF-8 string is passed, an error return is given. In some         If an invalid UTF-8 string is passed, an error return is given. In some
145         situations, you may already know  that  your  strings  are  valid,  and         situations,  you  may  already  know  that  your strings are valid, and
146         therefore want to skip these checks in order to improve performance. If         therefore want to skip these checks in order to improve performance. If
147         you set the PCRE_NO_UTF8_CHECK flag at compile time  or  at  run  time,         you  set  the  PCRE_NO_UTF8_CHECK  flag at compile time or at run time,
148         PCRE  assumes  that  the  pattern or subject it is given (respectively)         PCRE assumes that the pattern or subject  it  is  given  (respectively)
149         contains only valid UTF-8 codes. In this case, it does not diagnose  an         contains  only valid UTF-8 codes. In this case, it does not diagnose an
150         invalid  UTF-8 string. If you pass an invalid UTF-8 string to PCRE when         invalid UTF-8 string. If you pass an invalid UTF-8 string to PCRE  when
151         PCRE_NO_UTF8_CHECK is set, the results are undefined. Your program  may         PCRE_NO_UTF8_CHECK  is set, the results are undefined. Your program may
152         crash.         crash.
153    
154         2. In a pattern, the escape sequence \x{...}, where the contents of the         2. In a pattern, the escape sequence \x{...}, where the contents of the
155         braces is a string of hexadecimal digits, is  interpreted  as  a  UTF-8         braces  is  a  string  of hexadecimal digits, is interpreted as a UTF-8
156         character  whose code number is the given hexadecimal number, for exam-         character whose code number is the given hexadecimal number, for  exam-
157         ple: \x{1234}. If a non-hexadecimal digit appears between  the  braces,         ple:  \x{1234}.  If a non-hexadecimal digit appears between the braces,
158         the item is not recognized.  This escape sequence can be used either as         the item is not recognized.  This escape sequence can be used either as
159         a literal, or within a character class.         a literal, or within a character class.
160    
161         3. The original hexadecimal escape sequence, \xhh, matches  a  two-byte         3.  The  original hexadecimal escape sequence, \xhh, matches a two-byte
162         UTF-8 character if the value is greater than 127.         UTF-8 character if the value is greater than 127.
163    
164         4.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-         4. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-
165         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
166    
167         5. The dot metacharacter matches one UTF-8 character instead of a  sin-         5.  The dot metacharacter matches one UTF-8 character instead of a sin-
168         gle byte.         gle byte.
169    
170         6.  The  escape sequence \C can be used to match a single byte in UTF-8         6. The escape sequence \C can be used to match a single byte  in  UTF-8
171         mode, but its use can lead to some strange effects.         mode,  but  its  use can lead to some strange effects. This facility is
172           not available in the alternative matching function, pcre_dfa_exec().
173    
174         7. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly         7. The character escapes \b, \B, \d, \D, \s, \S, \w, and  \W  correctly
175         test  characters of any code value, but the characters that PCRE recog-         test  characters of any code value, but the characters that PCRE recog-
# Line 177  UTF-8 AND UNICODE PROPERTY SUPPORT Line 193  UTF-8 AND UNICODE PROPERTY SUPPORT
193    
194  AUTHOR  AUTHOR
195    
196         Philip Hazel <ph10@cam.ac.uk>         Philip Hazel
197         University Computing Service,         University Computing Service,
198         Cambridge CB2 3QG, England.         Cambridge CB2 3QG, England.
        Phone: +44 1223 334714  
199    
200  Last updated: 09 September 2004         Putting  an actual email address here seems to have been a spam magnet,
201  Copyright (c) 1997-2004 University of Cambridge.         so I've taken it away. If you want to email me, use my initial and sur-
202  -----------------------------------------------------------------------------         name, separated by a dot, at the domain ucs.cam.ac.uk.
203    
204  PCRE(3)                                                                PCRE(3)  Last updated: 07 March 2005
205    Copyright (c) 1997-2005 University of Cambridge.
206    -----------------------------------------------------------------------------
207    
208    
209    
210  NAME  NAME
211         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
212    
213    
214  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
215    
216         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
# Line 287  POSIX MALLOC USAGE Line 305  POSIX MALLOC USAGE
305  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
306    
307         Internally,  PCRE has a function called match(), which it calls repeat-         Internally,  PCRE has a function called match(), which it calls repeat-
308         edly (possibly recursively) when matching a pattern. By controlling the         edly  (possibly  recursively)  when  matching  a   pattern   with   the
309         maximum  number  of  times  this function may be called during a single         pcre_exec()  function.  By controlling the maximum number of times this
310         matching operation, a limit can be placed on the resources  used  by  a         function may be called during a single matching operation, a limit  can
311         single  call  to  pcre_exec(). The limit can be changed at run time, as         be  placed  on  the resources used by a single call to pcre_exec(). The
312         described in the pcreapi documentation. The default is 10 million,  but         limit can be changed at run time, as described in the pcreapi  documen-
313         this can be changed by adding a setting such as         tation.  The default is 10 million, but this can be changed by adding a
314           setting such as
315    
316           --with-match-limit=500000           --with-match-limit=500000
317    
318         to the configure command.         to  the  configure  command.  This  setting  has  no  effect   on   the
319           pcre_dfa_exec() matching function.
320    
321    
322  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
# Line 324  HANDLING VERY LARGE PATTERNS Line 344  HANDLING VERY LARGE PATTERNS
344    
345  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
346    
347         PCRE  implements  backtracking while matching by making recursive calls         When matching with the pcre_exec() function, PCRE implements backtrack-
348         to an internal function called match(). In environments where the  size         ing by making recursive calls to an internal function  called  match().
349         of the stack is limited, this can severely limit PCRE's operation. (The         In  environments  where  the size of the stack is limited, this can se-
350         Unix environment does not usually suffer from this problem.) An  alter-         verely limit PCRE's operation. (The Unix environment does  not  usually
351         native  approach  that  uses  memory  from  the  heap to remember data,         suffer  from  this  problem.)  An alternative approach that uses memory
352         instead of using recursive function calls, has been implemented to work         from the heap to remember data, instead  of  using  recursive  function
353         round  this  problem. If you want to build a version of PCRE that works         calls,  has been implemented to work round this problem. If you want to
354         this way, add         build a version of PCRE that works this way, add
355    
356           --disable-stack-for-recursion           --disable-stack-for-recursion
357    
# Line 342  AVOIDING EXCESSIVE STACK USAGE Line 362  AVOIDING EXCESSIVE STACK USAGE
362         the blocks are always freed in reverse order. A calling  program  might         the blocks are always freed in reverse order. A calling  program  might
363         be  able  to implement optimized functions that perform better than the         be  able  to implement optimized functions that perform better than the
364         standard malloc() and  free()  functions.  PCRE  runs  noticeably  more         standard malloc() and  free()  functions.  PCRE  runs  noticeably  more
365         slowly when built in this way.         slowly when built in this way. This option affects only the pcre_exec()
366           function; it is not relevant for the the pcre_dfa_exec() function.
367    
368    
369  USING EBCDIC CODE  USING EBCDIC CODE
370    
371         PCRE  assumes  by  default that it will run in an environment where the         PCRE assumes by default that it will run in an  environment  where  the
372         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).
373         PCRE  can,  however,  be  compiled  to  run in an EBCDIC environment by         PCRE can, however, be compiled to  run  in  an  EBCDIC  environment  by
374         adding         adding
375    
376           --enable-ebcdic           --enable-ebcdic
377    
378         to the configure command.         to the configure command.
379    
380  Last updated: 09 September 2004  Last updated: 28 February 2005
381  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
382  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
383    
384  PCRE(3)                                                                PCRE(3)  
385    
386    NAME
387           PCRE - Perl-compatible regular expressions
388    
389    
390    PCRE MATCHING ALGORITHMS
391    
392           This document describes the two different algorithms that are available
393           in PCRE for matching a compiled regular expression against a given sub-
394           ject  string.  The  "standard"  algorithm  is  the  one provided by the
395           pcre_exec() function.  This works in the same was  as  Perl's  matching
396           function, and provides a Perl-compatible matching operation.
397    
398           An  alternative  algorithm is provided by the pcre_dfa_exec() function;
399           this operates in a different way, and is not  Perl-compatible.  It  has
400           advantages  and disadvantages compared with the standard algorithm, and
401           these are described below.
402    
403           When there is only one possible way in which a given subject string can
404           match  a pattern, the two algorithms give the same answer. A difference
405           arises, however, when there are multiple possibilities. For example, if
406           the pattern
407    
408             ^<.*>
409    
410           is matched against the string
411    
412             <something> <something else> <something further>
413    
414           there are three possible answers. The standard algorithm finds only one
415           of them, whereas the DFA algorithm finds all three.
416    
417    
418    REGULAR EXPRESSIONS AS TREES
419    
420           The set of strings that are matched by a regular expression can be rep-
421           resented  as  a  tree structure. An unlimited repetition in the pattern
422           makes the tree of infinite size, but it is still a tree.  Matching  the
423           pattern  to a given subject string (from a given starting point) can be
424           thought of as a search of the tree.  There are  two  standard  ways  to
425           search  a  tree: depth-first and breadth-first, and these correspond to
426           the two matching algorithms provided by PCRE.
427    
428    
429    THE STANDARD MATCHING ALGORITHM
430    
431           In the terminology of Jeffrey Friedl's book Mastering  Regular  Expres-
432           sions,  the  standard  algorithm  is  an "NFA algorithm". It conducts a
433           depth-first search of the pattern tree. That is, it  proceeds  along  a
434           single path through the tree, checking that the subject matches what is
435           required. When there is a mismatch, the algorithm  tries  any  alterna-
436           tives  at  the  current point, and if they all fail, it backs up to the
437           previous branch point in the  tree,  and  tries  the  next  alternative
438           branch  at  that  level.  This often involves backing up (moving to the
439           left) in the subject string as well.  The  order  in  which  repetition
440           branches  are  tried  is controlled by the greedy or ungreedy nature of
441           the quantifier.
442    
443           If a leaf node is reached, a matching string has  been  found,  and  at
444           that  point the algorithm stops. Thus, if there is more than one possi-
445           ble match, this algorithm returns the first one that it finds.  Whether
446           this  is the shortest, the longest, or some intermediate length depends
447           on the way the greedy and ungreedy repetition quantifiers are specified
448           in the pattern.
449    
450           Because  it  ends  up  with a single path through the tree, it is rela-
451           tively straightforward for this algorithm to keep  track  of  the  sub-
452           strings  that  are  matched  by portions of the pattern in parentheses.
453           This provides support for capturing parentheses and back references.
454    
455    
456    THE DFA MATCHING ALGORITHM
457    
458           DFA stands for "deterministic finite automaton", but you do not need to
459           understand the origins of that name. This algorithm conducts a breadth-
460           first search of the tree. Starting from the first matching point in the
461           subject,  it scans the subject string from left to right, once, charac-
462           ter by character, and as it does  this,  it  remembers  all  the  paths
463           through the tree that represent valid matches.
464    
465           The  scan  continues until either the end of the subject is reached, or
466           there are no more unterminated paths. At this point,  terminated  paths
467           represent  the different matching possibilities (if there are none, the
468           match has failed).  Thus, if there is more  than  one  possible  match,
469           this algorithm finds all of them, and in particular, it finds the long-
470           est. In PCRE, there is an option to stop the algorithm after the  first
471           match (which is necessarily the shortest) has been found.
472    
473           Note that all the matches that are found start at the same point in the
474           subject. If the pattern
475    
476             cat(er(pillar)?)
477    
478           is matched against the string "the caterpillar catchment",  the  result
479           will  be the three strings "cat", "cater", and "caterpillar" that start
480           at the fourth character of the subject. The algorithm does not automat-
481           ically move on to find matches that start at later positions.
482    
483           There are a number of features of PCRE regular expressions that are not
484           supported by the DFA matching algorithm. They are as follows:
485    
486           1. Because the algorithm finds all  possible  matches,  the  greedy  or
487           ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
488           ungreedy quantifiers are treated in exactly the same way.
489    
490           2. When dealing with multiple paths through the tree simultaneously, it
491           is  not  straightforward  to  keep track of captured substrings for the
492           different matching possibilities, and  PCRE's  implementation  of  this
493           algorithm does not attempt to do this. This means that no captured sub-
494           strings are available.
495    
496           3. Because no substrings are captured, back references within the  pat-
497           tern are not supported, and cause errors if encountered.
498    
499           4.  For  the same reason, conditional expressions that use a backrefer-
500           ence as the condition are not supported.
501    
502           5. Callouts are supported, but the value of the  capture_top  field  is
503           always 1, and the value of the capture_last field is always -1.
504    
505           6.  The \C escape sequence, which (in the standard algorithm) matches a
506           single byte, even in UTF-8 mode, is not supported because the DFA algo-
507           rithm moves through the subject string one character at a time, for all
508           active paths through the tree.
509    
510    
511    ADVANTAGES OF THE DFA ALGORITHM
512    
513           Using the DFA matching algorithm provides the following advantages:
514    
515           1. All possible matches (at a single point in the subject) are automat-
516           ically  found,  and  in particular, the longest match is found. To find
517           more than one match using the standard algorithm, you have to do kludgy
518           things with callouts.
519    
520           2.  There is much better support for partial matching. The restrictions
521           on the content of the pattern that apply when using the standard  algo-
522           rithm  for partial matching do not apply to the DFA algorithm. For non-
523           anchored patterns, the starting position of a partial match  is  avail-
524           able.
525    
526           3.  Because  the  DFA algorithm scans the subject string just once, and
527           never needs to backtrack, it is possible  to  pass  very  long  subject
528           strings  to  the matching function in several pieces, checking for par-
529           tial matching each time.
530    
531    
532    DISADVANTAGES OF THE DFA ALGORITHM
533    
534           The DFA algorithm suffers from a number of disadvantages:
535    
536           1. It is substantially slower than  the  standard  algorithm.  This  is
537           partly  because  it has to search for all possible matches, but is also
538           because it is less susceptible to optimization.
539    
540           2. Capturing parentheses and back references are not supported.
541    
542           3. The "atomic group" feature of PCRE regular expressions is supported,
543           but  does not provide the advantage that it does for the standard algo-
544           rithm.
545    
546    Last updated: 28 February 2005
547    Copyright (c) 1997-2005 University of Cambridge.
548    -----------------------------------------------------------------------------
549    
550    
551    
552  NAME  NAME
553         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
554    
555    
556  PCRE NATIVE API  PCRE NATIVE API
557    
558         #include <pcre.h>         #include <pcre.h>
# Line 375  PCRE NATIVE API Line 561  PCRE NATIVE API
561              const char **errptr, int *erroffset,              const char **errptr, int *erroffset,
562              const unsigned char *tableptr);              const unsigned char *tableptr);
563    
564           pcre *pcre_compile2(const char *pattern, int options,
565                int *errorcodeptr,
566                const char **errptr, int *erroffset,
567                const unsigned char *tableptr);
568    
569         pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options,
570              const char **errptr);              const char **errptr);
571    
# Line 382  PCRE NATIVE API Line 573  PCRE NATIVE API
573              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
574              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
575    
576           int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
577                const char *subject, int length, int startoffset,
578                int options, int *ovector, int ovecsize,
579                int *workspace, int wscount);
580    
581         int pcre_copy_named_substring(const pcre *code,         int pcre_copy_named_substring(const pcre *code,
582              const char *subject, int *ovector,              const char *subject, int *ovector,
583              int stringcount, const char *stringname,              int stringcount, const char *stringname,
# Line 417  PCRE NATIVE API Line 613  PCRE NATIVE API
613    
614         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
615    
616           int pcre_refcount(pcre *code, int adjust);
617    
618         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
619    
620         char *pcre_version(void);         char *pcre_version(void);
# Line 436  PCRE API OVERVIEW Line 634  PCRE API OVERVIEW
634    
635         PCRE has its own native API, which is described in this document. There         PCRE has its own native API, which is described in this document. There
636         is also a set of wrapper functions that correspond to the POSIX regular         is also a set of wrapper functions that correspond to the POSIX regular
637         expression API.  These are described in the pcreposix documentation.         expression  API.  These  are  described in the pcreposix documentation.
638           Both of these APIs define a set of C function calls. A C++  wrapper  is
639           distributed with PCRE. It is documented in the pcrecpp page.
640    
641         The  native  API  function  prototypes  are  defined in the header file         The  native  API  C  function prototypes are defined in the header file
642         pcre.h, and on Unix systems the library itself is  called  libpcre.  It         pcre.h, and on Unix systems the library itself is called  libpcre.   It
643         can normally be accessed by adding -lpcre to the command for linking an         can normally be accessed by adding -lpcre to the command for linking an
644         application  that  uses  PCRE.  The  header  file  defines  the  macros         application  that  uses  PCRE.  The  header  file  defines  the  macros
645         PCRE_MAJOR  and  PCRE_MINOR to contain the major and minor release num-         PCRE_MAJOR  and  PCRE_MINOR to contain the major and minor release num-
646         bers for the library.  Applications can use these  to  include  support         bers for the library.  Applications can use these  to  include  support
647         for different releases of PCRE.         for different releases of PCRE.
648    
649         The  functions  pcre_compile(),  pcre_study(), and pcre_exec() are used         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
650         for compiling and matching regular expressions. A sample  program  that         pcre_exec() are used for compiling and matching regular expressions  in
651         demonstrates  the  simplest  way  of using them is provided in the file         a  Perl-compatible  manner. A sample program that demonstrates the sim-
652         called pcredemo.c in the source distribution. The pcresample documenta-         plest way of using them is provided in the file  called  pcredemo.c  in
653         tion describes how to run it.         the  source distribution. The pcresample documentation describes how to
654           run it.
655         In  addition  to  the  main compiling and matching functions, there are  
656         convenience functions for extracting captured substrings from a matched         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
657         subject string.  They are:         ble,  is  also provided. This uses a different algorithm for the match-
658           ing. This allows it to find all possible matches (at a given  point  in
659           the  subject),  not  just  one. However, this algorithm does not return
660           captured substrings. A description of the two matching  algorithms  and
661           their  advantages  and disadvantages is given in the pcrematching docu-
662           mentation.
663    
664           In addition to the main compiling and  matching  functions,  there  are
665           convenience functions for extracting captured substrings from a subject
666           string that is matched by pcre_exec(). They are:
667    
668           pcre_copy_substring()           pcre_copy_substring()
669           pcre_copy_named_substring()           pcre_copy_named_substring()
# Line 466  PCRE API OVERVIEW Line 675  PCRE API OVERVIEW
675         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
676         to free the memory used for extracted strings.         to free the memory used for extracted strings.
677    
678         The function pcre_maketables() is used to  build  a  set  of  character         The  function  pcre_maketables()  is  used  to build a set of character
679         tables   in  the  current  locale  for  passing  to  pcre_compile()  or         tables  in  the  current  locale   for   passing   to   pcre_compile(),
680         pcre_exec().  This is an optional facility that is  provided  for  spe-         pcre_exec(),  or  pcre_dfa_exec(). This is an optional facility that is
681         cialist use. Most commonly, no special tables are passed, in which case         provided for specialist use.  Most  commonly,  no  special  tables  are
682         internal tables that are generated when PCRE is built are used.         passed,  in  which case internal tables that are generated when PCRE is
683           built are used.
684    
685         The function pcre_fullinfo() is used to find out  information  about  a         The function pcre_fullinfo() is used to find out  information  about  a
686         compiled  pattern; pcre_info() is an obsolete version that returns only         compiled  pattern; pcre_info() is an obsolete version that returns only
# Line 478  PCRE API OVERVIEW Line 688  PCRE API OVERVIEW
688         patibility.   The function pcre_version() returns a pointer to a string         patibility.   The function pcre_version() returns a pointer to a string
689         containing the version of PCRE and its date of release.         containing the version of PCRE and its date of release.
690    
691           The function pcre_refcount() maintains a  reference  count  in  a  data
692           block  containing  a compiled pattern. This is provided for the benefit
693           of object-oriented applications.
694    
695         The global variables pcre_malloc and pcre_free  initially  contain  the         The global variables pcre_malloc and pcre_free  initially  contain  the
696         entry  points  of  the  standard malloc() and free() functions, respec-         entry  points  of  the  standard malloc() and free() functions, respec-
697         tively. PCRE calls the memory management functions via these variables,         tively. PCRE calls the memory management functions via these variables,
# Line 487  PCRE API OVERVIEW Line 701  PCRE API OVERVIEW
701         The global variables pcre_stack_malloc  and  pcre_stack_free  are  also         The global variables pcre_stack_malloc  and  pcre_stack_free  are  also
702         indirections  to  memory  management functions. These special functions         indirections  to  memory  management functions. These special functions
703         are used only when PCRE is compiled to use  the  heap  for  remembering         are used only when PCRE is compiled to use  the  heap  for  remembering
704         data,  instead  of recursive function calls. This is a non-standard way         data, instead of recursive function calls, when running the pcre_exec()
705         of building PCRE, for use in environments  that  have  limited  stacks.         function. This is a non-standard way of building PCRE, for use in envi-
706         Because  of  the greater use of memory management, it runs more slowly.         ronments that have limited stacks. Because of the greater use of memory
707         Separate functions are provided so that special-purpose  external  code         management, it runs more slowly.  Separate functions  are  provided  so
708         can be used for this case. When used, these functions are always called         that  special-purpose  external  code  can  be used for this case. When
709         in a stack-like manner (last obtained, first  freed),  and  always  for         used, these functions are always called in a  stack-like  manner  (last
710         memory blocks of the same size.         obtained,  first freed), and always for memory blocks of the same size.
711    
712         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
713         by the caller to a "callout" function, which PCRE  will  then  call  at         by  the  caller  to  a "callout" function, which PCRE will then call at
714         specified  points during a matching operation. Details are given in the         specified points during a matching operation. Details are given in  the
715         pcrecallout documentation.         pcrecallout documentation.
716    
717    
718  MULTITHREADING  MULTITHREADING
719    
720         The PCRE functions can be used in  multi-threading  applications,  with         The  PCRE  functions  can be used in multi-threading applications, with
721         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
722         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
723         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
724    
725         The compiled form of a regular expression is not altered during  match-         The  compiled form of a regular expression is not altered during match-
726         ing, so the same compiled pattern can safely be used by several threads         ing, so the same compiled pattern can safely be used by several threads
727         at once.         at once.
728    
# Line 516  MULTITHREADING Line 730  MULTITHREADING
730  SAVING PRECOMPILED PATTERNS FOR LATER USE  SAVING PRECOMPILED PATTERNS FOR LATER USE
731    
732         The compiled form of a regular expression can be saved and re-used at a         The compiled form of a regular expression can be saved and re-used at a
733         later  time,  possibly by a different program, and even on a host other         later time, possibly by a different program, and even on a  host  other
734         than the one on which  it  was  compiled.  Details  are  given  in  the         than  the  one  on  which  it  was  compiled.  Details are given in the
735         pcreprecompile documentation.         pcreprecompile documentation.
736    
737    
# Line 525  CHECKING BUILD-TIME OPTIONS Line 739  CHECKING BUILD-TIME OPTIONS
739    
740         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
741    
742         The  function pcre_config() makes it possible for a PCRE client to dis-         The function pcre_config() makes it possible for a PCRE client to  dis-
743         cover which optional features have been compiled into the PCRE library.         cover which optional features have been compiled into the PCRE library.
744         The  pcrebuild documentation has more details about these optional fea-         The pcrebuild documentation has more details about these optional  fea-
745         tures.         tures.
746    
747         The first argument for pcre_config() is an  integer,  specifying  which         The  first  argument  for pcre_config() is an integer, specifying which
748         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
749         into which the information is  placed.  The  following  information  is         into  which  the  information  is  placed. The following information is
750         available:         available:
751    
752           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
753    
754         The  output is an integer that is set to one if UTF-8 support is avail-         The output is an integer that is set to one if UTF-8 support is  avail-
755         able; otherwise it is set to zero.         able; otherwise it is set to zero.
756    
757           PCRE_CONFIG_UNICODE_PROPERTIES           PCRE_CONFIG_UNICODE_PROPERTIES
758    
759         The output is an integer that is set to  one  if  support  for  Unicode         The  output  is  an  integer  that is set to one if support for Unicode
760         character properties is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
761    
762           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
763    
764         The  output  is an integer that is set to the value of the code that is         The output is an integer that is set to the value of the code  that  is
765         used for the newline character. It is either linefeed (10) or  carriage         used  for the newline character. It is either linefeed (10) or carriage
766         return  (13),  and  should  normally be the standard character for your         return (13), and should normally be the  standard  character  for  your
767         operating system.         operating system.
768    
769           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
770    
771         The output is an integer that contains the number  of  bytes  used  for         The  output  is  an  integer that contains the number of bytes used for
772         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
773         4. Larger values allow larger regular expressions to  be  compiled,  at         4.  Larger  values  allow larger regular expressions to be compiled, at
774         the  expense  of  slower matching. The default value of 2 is sufficient         the expense of slower matching. The default value of  2  is  sufficient
775         for all but the most massive patterns, since  it  allows  the  compiled         for  all  but  the  most massive patterns, since it allows the compiled
776         pattern to be up to 64K in size.         pattern to be up to 64K in size.
777    
778           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
779    
780         The  output  is  an integer that contains the threshold above which the         The output is an integer that contains the threshold  above  which  the
781         POSIX interface uses malloc() for output vectors. Further  details  are         POSIX  interface  uses malloc() for output vectors. Further details are
782         given in the pcreposix documentation.         given in the pcreposix documentation.
783    
784           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
785    
786         The output is an integer that gives the default limit for the number of         The output is an integer that gives the default limit for the number of
787         internal matching function calls in a  pcre_exec()  execution.  Further         internal  matching  function  calls in a pcre_exec() execution. Further
788         details are given with pcre_exec() below.         details are given with pcre_exec() below.
789    
790           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
791    
792         The  output  is  an integer that is set to one if internal recursion is         The output is an integer that is set to one if internal recursion  when
793         implemented by recursive function calls that use the stack to  remember         running pcre_exec() is implemented by recursive function calls that use
794         their state. This is the usual way that PCRE is compiled. The output is         the stack to remember their state. This is the usual way that  PCRE  is
795         zero if PCRE was compiled to use blocks of data on the heap instead  of         compiled. The output is zero if PCRE was compiled to use blocks of data
796         recursive   function   calls.   In  this  case,  pcre_stack_malloc  and         on the  heap  instead  of  recursive  function  calls.  In  this  case,
797         pcre_stack_free are called to manage memory blocks on  the  heap,  thus         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory
798         avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
799    
800    
801  COMPILING A PATTERN  COMPILING A PATTERN
# Line 590  COMPILING A PATTERN Line 804  COMPILING A PATTERN
804              const char **errptr, int *erroffset,              const char **errptr, int *erroffset,
805              const unsigned char *tableptr);              const unsigned char *tableptr);
806    
807         The  function  pcre_compile()  is  called  to compile a pattern into an         pcre *pcre_compile2(const char *pattern, int options,
808         internal form. The pattern is a C string terminated by a  binary  zero,              int *errorcodeptr,
809         and  is  passed in the pattern argument. A pointer to a single block of              const char **errptr, int *erroffset,
810         memory that is obtained via pcre_malloc is returned. This contains  the              const unsigned char *tableptr);
811         compiled  code  and  related  data.  The  pcre  type is defined for the  
812         returned block; this is a typedef for a structure  whose  contents  are         Either of the functions pcre_compile() or pcre_compile2() can be called
813         not  externally defined. It is up to the caller to free the memory when         to compile a pattern into an internal form. The only difference between
814         it is no longer required.         the two interfaces is that pcre_compile2() has an additional  argument,
815           errorcodeptr, via which a numerical error code can be returned.
816    
817           The pattern is a C string terminated by a binary zero, and is passed in
818           the pattern argument. A pointer to a single block  of  memory  that  is
819           obtained  via  pcre_malloc is returned. This contains the compiled code
820           and related data. The pcre type is defined for the returned block; this
821           is a typedef for a structure whose contents are not externally defined.
822           It is up to the caller  to  free  the  memory  when  it  is  no  longer
823           required.
824    
825         Although the compiled code of a PCRE regex is relocatable, that is,  it         Although  the compiled code of a PCRE regex is relocatable, that is, it
826         does not depend on memory location, the complete pcre data block is not         does not depend on memory location, the complete pcre data block is not
827         fully relocatable, because it may contain a copy of the tableptr  argu-         fully  relocatable, because it may contain a copy of the tableptr argu-
828         ment, which is an address (see below).         ment, which is an address (see below).
829    
830         The options argument contains independent bits that affect the compila-         The options argument contains independent bits that affect the compila-
831         tion. It should be zero if  no  options  are  required.  The  available         tion.  It  should  be  zero  if  no options are required. The available
832         options  are  described  below. Some of them, in particular, those that         options are described below. Some of them, in  particular,  those  that
833         are compatible with Perl, can also be set and  unset  from  within  the         are  compatible  with  Perl,  can also be set and unset from within the
834         pattern  (see  the  detailed  description in the pcrepattern documenta-         pattern (see the detailed description  in  the  pcrepattern  documenta-
835         tion). For these options, the contents of the options  argument  speci-         tion).  For  these options, the contents of the options argument speci-
836         fies  their initial settings at the start of compilation and execution.         fies their initial settings at the start of compilation and  execution.
837         The PCRE_ANCHORED option can be set at the time of matching as well  as         The  PCRE_ANCHORED option can be set at the time of matching as well as
838         at compile time.         at compile time.
839    
840         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
841         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
842         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-
843         sage. The offset from the start of the pattern to the  character  where         sage.  The  offset from the start of the pattern to the character where
844         the  error  was  discovered  is  placed  in  the variable pointed to by         the error was discovered is  placed  in  the  variable  pointed  to  by
845         erroffset, which must not be NULL. If it  is,  an  immediate  error  is         erroffset,  which  must  not  be  NULL. If it is, an immediate error is
846         given.         given.
847    
848           If pcre_compile2() is used instead of pcre_compile(),  and  the  error-
849           codeptr  argument is not NULL, a non-zero error code number is returned
850           via this argument in the event of an error. This is in addition to  the
851           textual error message. Error codes and messages are listed below.
852    
853         If  the  final  argument, tableptr, is NULL, PCRE uses a default set of         If  the  final  argument, tableptr, is NULL, PCRE uses a default set of
854         character tables that are  built  when  PCRE  is  compiled,  using  the         character tables that are  built  when  PCRE  is  compiled,  using  the
855         default  C  locale.  Otherwise, tableptr must be an address that is the         default  C  locale.  Otherwise, tableptr must be an address that is the
# Line 664  COMPILING A PATTERN Line 892  COMPILING A PATTERN
892    
893         If  this  bit is set, letters in the pattern match both upper and lower         If  this  bit is set, letters in the pattern match both upper and lower
894         case letters. It is equivalent to Perl's  /i  option,  and  it  can  be         case letters. It is equivalent to Perl's  /i  option,  and  it  can  be
895         changed  within  a  pattern  by  a (?i) option setting. When running in         changed  within a pattern by a (?i) option setting. In UTF-8 mode, PCRE
896         UTF-8 mode, case support for high-valued characters is  available  only         always understands the concept of case for characters whose values  are
897         when PCRE is built with Unicode character property support.         less  than 128, so caseless matching is always possible. For characters
898           with higher values, the concept of case is supported if  PCRE  is  com-
899           piled  with Unicode property support, but not otherwise. If you want to
900           use caseless matching for characters 128 and  above,  you  must  ensure
901           that  PCRE  is  compiled  with Unicode property support as well as with
902           UTF-8 support.
903    
904           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
905    
906         If  this bit is set, a dollar metacharacter in the pattern matches only         If this bit is set, a dollar metacharacter in the pattern matches  only
907         at the end of the subject string. Without this option,  a  dollar  also         at  the  end  of the subject string. Without this option, a dollar also
908         matches  immediately before the final character if it is a newline (but         matches immediately before the final character if it is a newline  (but
909         not before any  other  newlines).  The  PCRE_DOLLAR_ENDONLY  option  is         not  before  any  other  newlines).  The  PCRE_DOLLAR_ENDONLY option is
910         ignored if PCRE_MULTILINE is set. There is no equivalent to this option         ignored if PCRE_MULTILINE is set. There is no equivalent to this option
911         in Perl, and no way to set it within a pattern.         in Perl, and no way to set it within a pattern.
912    
913           PCRE_DOTALL           PCRE_DOTALL
914    
915         If this bit is set, a dot metacharater in the pattern matches all char-         If this bit is set, a dot metacharater in the pattern matches all char-
916         acters,  including  newlines.  Without  it, newlines are excluded. This         acters, including newlines. Without it,  newlines  are  excluded.  This
917         option is equivalent to Perl's /s option, and it can be changed  within         option  is equivalent to Perl's /s option, and it can be changed within
918         a  pattern  by  a  (?s)  option  setting. A negative class such as [^a]         a pattern by a (?s) option setting.  A  negative  class  such  as  [^a]
919         always matches a newline character, independent of the setting of  this         always  matches a newline character, independent of the setting of this
920         option.         option.
921    
922           PCRE_EXTENDED           PCRE_EXTENDED
923    
924         If  this  bit  is  set,  whitespace  data characters in the pattern are         If this bit is set, whitespace  data  characters  in  the  pattern  are
925         totally ignored except  when  escaped  or  inside  a  character  class.         totally ignored except when escaped or inside a character class. White-
926         Whitespace  does  not  include the VT character (code 11). In addition,         space does not include the VT character (code 11). In addition, charac-
927         characters between an unescaped # outside a  character  class  and  the         ters between an unescaped # outside a character class and the next new-
928         next newline character, inclusive, are also ignored. This is equivalent         line character, inclusive, are also  ignored.  This  is  equivalent  to
929         to Perl's /x option, and it can be changed within a pattern by  a  (?x)         Perl's  /x  option,  and  it  can be changed within a pattern by a (?x)
930         option setting.         option setting.
931    
932         This  option  makes  it possible to include comments inside complicated         This option makes it possible to include  comments  inside  complicated
933         patterns.  Note, however, that this applies only  to  data  characters.         patterns.   Note,  however,  that this applies only to data characters.
934         Whitespace   characters  may  never  appear  within  special  character         Whitespace  characters  may  never  appear  within  special   character
935         sequences in a pattern, for  example  within  the  sequence  (?(  which         sequences  in  a  pattern,  for  example  within the sequence (?( which
936         introduces a conditional subpattern.         introduces a conditional subpattern.
937    
938           PCRE_EXTRA           PCRE_EXTRA
939    
940         This  option  was invented in order to turn on additional functionality         This option was invented in order to turn on  additional  functionality
941         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
942         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
943         letter that has no special meaning  causes  an  error,  thus  reserving         letter  that  has  no  special  meaning causes an error, thus reserving
944         these  combinations  for  future  expansion.  By default, as in Perl, a         these combinations for future expansion. By  default,  as  in  Perl,  a
945         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
946         literal.  There  are  at  present  no other features controlled by this         literal. There are at present no  other  features  controlled  by  this
947         option. It can also be set by a (?X) option setting within a pattern.         option. It can also be set by a (?X) option setting within a pattern.
948    
949             PCRE_FIRSTLINE
950    
951           If  this  option  is  set,  an  unanchored pattern is required to match
952           before or at the first newline character in the subject string,  though
953           the matched text may continue over the newline.
954    
955           PCRE_MULTILINE           PCRE_MULTILINE
956    
957         By default, PCRE treats the subject string as consisting  of  a  single         By  default,  PCRE  treats the subject string as consisting of a single
958         line  of characters (even if it actually contains newlines). The "start         line of characters (even if it actually contains newlines). The  "start
959         of line" metacharacter (^) matches only at the  start  of  the  string,         of  line"  metacharacter  (^)  matches only at the start of the string,
960         while  the  "end  of line" metacharacter ($) matches only at the end of         while the "end of line" metacharacter ($) matches only at  the  end  of
961         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
962         is set). This is the same as Perl.         is set). This is the same as Perl.
963    
964         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"
965         constructs match immediately following or immediately before  any  new-         constructs  match  immediately following or immediately before any new-
966         line  in the subject string, respectively, as well as at the very start         line in the subject string, respectively, as well as at the very  start
967         and end. This is equivalent to Perl's /m option, and it can be  changed         and  end. This is equivalent to Perl's /m option, and it can be changed
968         within a pattern by a (?m) option setting. If there are no "\n" charac-         within a pattern by a (?m) option setting. If there are no "\n" charac-
969         ters in a subject string, or no occurrences of ^ or  $  in  a  pattern,         ters  in  a  subject  string, or no occurrences of ^ or $ in a pattern,
970         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
971    
972           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
973    
974         If this option is set, it disables the use of numbered capturing paren-         If this option is set, it disables the use of numbered capturing paren-
975         theses in the pattern. Any opening parenthesis that is not followed  by         theses  in the pattern. Any opening parenthesis that is not followed by
976         ?  behaves as if it were followed by ?: but named parentheses can still         ? behaves as if it were followed by ?: but named parentheses can  still
977         be used for capturing (and they acquire  numbers  in  the  usual  way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
978         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
979    
980           PCRE_UNGREEDY           PCRE_UNGREEDY
981    
982         This  option  inverts  the "greediness" of the quantifiers so that they         This option inverts the "greediness" of the quantifiers  so  that  they
983         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
984         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
985         within the pattern.         within the pattern.
986    
987           PCRE_UTF8           PCRE_UTF8
988    
989         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
990         strings  of  UTF-8 characters instead of single-byte character strings.         strings of UTF-8 characters instead of single-byte  character  strings.
991         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-
992         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
993         this option changes the behaviour of PCRE are given in the  section  on         this  option  changes the behaviour of PCRE are given in the section on
994         UTF-8 support in the main pcre page.         UTF-8 support in the main pcre page.
995    
996           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
997    
998         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
999         automatically checked. If an invalid UTF-8 sequence of bytes is  found,         automatically  checked. If an invalid UTF-8 sequence of bytes is found,
1000         pcre_compile()  returns an error. If you already know that your pattern         pcre_compile() returns an error. If you already know that your  pattern
1001         is valid, and you want to skip this check for performance reasons,  you         is  valid, and you want to skip this check for performance reasons, you
1002         can  set  the  PCRE_NO_UTF8_CHECK option. When it is set, the effect of         can set the PCRE_NO_UTF8_CHECK option. When it is set,  the  effect  of
1003         passing an invalid UTF-8 string as a pattern is undefined. It may cause         passing an invalid UTF-8 string as a pattern is undefined. It may cause
1004         your  program  to  crash.   Note that this option can also be passed to         your program to crash.  Note that this option can  also  be  passed  to
1005         pcre_exec(),  to  suppress  the  UTF-8  validity  checking  of  subject         pcre_exec()  and pcre_dfa_exec(), to suppress the UTF-8 validity check-
1006         strings.         ing of subject strings.
1007    
1008    
1009    COMPILATION ERROR CODES
1010    
1011           The following table lists the error  codes  than  may  be  returned  by
1012           pcre_compile2(),  along with the error messages that may be returned by
1013           both compiling functions.
1014    
1015              0  no error
1016              1  \ at end of pattern
1017              2  \c at end of pattern
1018              3  unrecognized character follows \
1019              4  numbers out of order in {} quantifier
1020              5  number too big in {} quantifier
1021              6  missing terminating ] for character class
1022              7  invalid escape sequence in character class
1023              8  range out of order in character class
1024              9  nothing to repeat
1025             10  operand of unlimited repeat could match the empty string
1026             11  internal error: unexpected repeat
1027             12  unrecognized character after (?
1028             13  POSIX named classes are supported only within a class
1029             14  missing )
1030             15  reference to non-existent subpattern
1031             16  erroffset passed as NULL
1032             17  unknown option bit(s) set
1033             18  missing ) after comment
1034             19  parentheses nested too deeply
1035             20  regular expression too large
1036             21  failed to get memory
1037             22  unmatched parentheses
1038             23  internal error: code overflow
1039             24  unrecognized character after (?<
1040             25  lookbehind assertion is not fixed length
1041             26  malformed number after (?(
1042             27  conditional group contains more than two branches
1043             28  assertion expected after (?(
1044             29  (?R or (?digits must be followed by )
1045             30  unknown POSIX class name
1046             31  POSIX collating elements are not supported
1047             32  this version of PCRE is not compiled with PCRE_UTF8 support
1048             33  spare error
1049             34  character value in \x{...} sequence is too large
1050             35  invalid condition (?(0)
1051             36  \C not allowed in lookbehind assertion
1052             37  PCRE does not support \L, \l, \N, \U, or \u
1053             38  number after (?C is > 255
1054             39  closing ) for (?C expected
1055             40  recursive call could loop indefinitely
1056             41  unrecognized character after (?P
1057             42  syntax error after (?P
1058             43  two named groups have the same name
1059             44  invalid UTF-8 string
1060             45  support for \P, \p, and \X has not been compiled
1061             46  malformed \P or \p sequence
1062             47  unknown property name after \P or \p
1063    
1064    
1065  STUDYING A PATTERN  STUDYING A PATTERN
1066    
1067         pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options
1068              const char **errptr);              const char **errptr);
1069    
1070         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
1071         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
1072         matching.  The function pcre_study() takes a pointer to a compiled pat-         matching. The function pcre_study() takes a pointer to a compiled  pat-
1073         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1074         information  that  will  help speed up matching, pcre_study() returns a         information that will help speed up matching,  pcre_study()  returns  a
1075         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
1076         the results of the study.         the results of the study.
1077    
1078         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1079         pcre_exec(). However, a pcre_extra block  also  contains  other  fields         pcre_exec().  However,  a  pcre_extra  block also contains other fields
1080         that  can  be  set  by the caller before the block is passed; these are         that can be set by the caller before the block  is  passed;  these  are
1081         described below in the section on matching a pattern.         described below in the section on matching a pattern.
1082    
1083         If studying the pattern does not produce  any  additional  information,         If  studying  the  pattern  does not produce any additional information
1084         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1085         wants to pass any of the other fields to pcre_exec(), it  must  set  up         wants  to  pass  any of the other fields to pcre_exec(), it must set up
1086         its own pcre_extra block.         its own pcre_extra block.
1087    
1088         The  second  argument of pcre_study() contains option bits. At present,         The second argument of pcre_study() contains option bits.  At  present,
1089         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1090    
1091         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.
1092         If  studying  succeeds  (even  if no data is returned), the variable it         If studying succeeds (even if no data is  returned),  the  variable  it
1093         points to is set to NULL. Otherwise it points to a textual  error  mes-         points  to  is set to NULL. Otherwise it points to a textual error mes-
1094         sage.  You should therefore test the error pointer for NULL after call-         sage. You should therefore test the error pointer for NULL after  call-
1095         ing pcre_study(), to be sure that it has run successfully.         ing pcre_study(), to be sure that it has run successfully.
1096    
1097         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 808  STUDYING A PATTERN Line 1103  STUDYING A PATTERN
1103             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1104    
1105         At present, studying a pattern is useful only for non-anchored patterns         At present, studying a pattern is useful only for non-anchored patterns
1106         that  do not have a single fixed starting character. A bitmap of possi-         that do not have a single fixed starting character. A bitmap of  possi-
1107         ble starting bytes is created.         ble starting bytes is created.
1108    
1109    
1110  LOCALE SUPPORT  LOCALE SUPPORT
1111    
1112         PCRE handles caseless matching, and determines whether  characters  are         PCRE  handles  caseless matching, and determines whether characters are
1113         letters,  digits, or whatever, by reference to a set of tables, indexed         letters digits, or whatever, by reference to a set of  tables,  indexed
1114         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
1115         characters  with  codes  less than 128. Higher-valued codes never match         characters with codes less than 128. Higher-valued  codes  never  match
1116         escapes such as \w or \d, but can be tested with \p if  PCRE  is  built         escapes  such  as  \w or \d, but can be tested with \p if PCRE is built
1117         with Unicode character property support.)         with Unicode character property support.
1118    
1119         An  internal set of tables is created in the default C locale when PCRE         An internal set of tables is created in the default C locale when  PCRE
1120         is built. This is used when the final  argument  of  pcre_compile()  is         is  built.  This  is  used when the final argument of pcre_compile() is
1121         NULL,  and  is  sufficient for many applications. An alternative set of         NULL, and is sufficient for many applications. An  alternative  set  of
1122         tables can, however, be supplied. These may be created in  a  different         tables  can,  however, be supplied. These may be created in a different
1123         locale  from the default. As more and more applications change to using         locale from the default. As more and more applications change to  using
1124         Unicode, the need for this locale support is expected to die away.         Unicode, the need for this locale support is expected to die away.
1125    
1126         External tables are built by calling  the  pcre_maketables()  function,         External  tables  are  built by calling the pcre_maketables() function,
1127         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
1128         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
1129         example,  to  build  and use tables that are appropriate for the French         example, to build and use tables that are appropriate  for  the  French
1130         locale (where accented characters with  values  greater  than  128  are         locale  (where  accented  characters  with  values greater than 128 are
1131         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1132    
1133           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1134           tables = pcre_maketables();           tables = pcre_maketables();
1135           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1136    
1137         When  pcre_maketables()  runs,  the  tables are built in memory that is         When pcre_maketables() runs, the tables are built  in  memory  that  is
1138         obtained via pcre_malloc. It is the caller's responsibility  to  ensure         obtained  via  pcre_malloc. It is the caller's responsibility to ensure
1139         that  the memory containing the tables remains available for as long as         that the memory containing the tables remains available for as long  as
1140         it is needed.         it is needed.
1141    
1142         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
1143         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()
1144         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-
1145         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1146         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1147    
1148         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
1149         the  internal  tables)  to  pcre_exec(). Although not intended for this         the internal tables) to pcre_exec(). Although  not  intended  for  this
1150         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
1151         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
1152         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1153    
# Line 862  INFORMATION ABOUT A PATTERN Line 1157  INFORMATION ABOUT A PATTERN
1157         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1158              int what, void *where);              int what, void *where);
1159    
1160         The pcre_fullinfo() function returns information about a compiled  pat-         The  pcre_fullinfo() function returns information about a compiled pat-
1161         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1162         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1163    
1164         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled
1165         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
1166         the pattern was not studied. The third argument specifies  which  piece         the  pattern  was not studied. The third argument specifies which piece
1167         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
1168         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
1169         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1170    
1171           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 878  INFORMATION ABOUT A PATTERN Line 1173  INFORMATION ABOUT A PATTERN
1173           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1174           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1175    
1176         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
1177         an simple check against passing an arbitrary memory pointer. Here is  a         an  simple check against passing an arbitrary memory pointer. Here is a
1178         typical  call  of pcre_fullinfo(), to obtain the length of the compiled         typical call of pcre_fullinfo(), to obtain the length of  the  compiled
1179         pattern:         pattern:
1180    
1181           int rc;           int rc;
# Line 891  INFORMATION ABOUT A PATTERN Line 1186  INFORMATION ABOUT A PATTERN
1186             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1187             &length);         /* where to put the data */             &length);         /* where to put the data */
1188    
1189         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
1190         are as follows:         are as follows:
1191    
1192           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1193    
1194         Return  the  number  of  the highest back reference in the pattern. The         Return the number of the highest back reference  in  the  pattern.  The
1195         fourth argument should point to an int variable. Zero  is  returned  if         fourth  argument  should  point to an int variable. Zero is returned if
1196         there are no back references.         there are no back references.
1197    
1198           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1199    
1200         Return  the  number of capturing subpatterns in the pattern. The fourth         Return the number of capturing subpatterns in the pattern.  The  fourth
1201         argument should point to an int variable.         argument should point to an int variable.
1202    
1203           PCRE_INFO_DEFAULTTABLES           PCRE_INFO_DEFAULT_TABLES
1204    
1205         Return a pointer to the internal default character tables within  PCRE.         Return  a pointer to the internal default character tables within PCRE.
1206         The  fourth  argument should point to an unsigned char * variable. This         The fourth argument should point to an unsigned char *  variable.  This
1207         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1208         tion.  External  callers  can  cause PCRE to use its internal tables by         tion. External callers can cause PCRE to use  its  internal  tables  by
1209         passing a NULL table pointer.         passing a NULL table pointer.
1210    
1211           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1212    
1213         Return information about the first byte of any matched  string,  for  a         Return  information  about  the first byte of any matched string, for a
1214         non-anchored    pattern.    (This    option    used    to   be   called         non-anchored   pattern.   (This    option    used    to    be    called
1215         PCRE_INFO_FIRSTCHAR; the old name is  still  recognized  for  backwards         PCRE_INFO_FIRSTCHAR;  the  old  name  is still recognized for backwards
1216         compatibility.)         compatibility.)
1217    
1218         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
1219         (cat|cow|coyote), it is returned in the integer pointed  to  by  where.         (cat|cow|coyote),  it  is  returned in the integer pointed to by where.
1220         Otherwise, if either         Otherwise, if either
1221    
1222         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1223         branch starts with "^", or         branch starts with "^", or
1224    
1225         (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
1226         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1227    
1228         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
1229         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
1230         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1231    
1232           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1233    
1234         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
1235         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
1236         matching  string, a pointer to the table is returned. Otherwise NULL is         matching string, a pointer to the table is returned. Otherwise NULL  is
1237         returned. The fourth argument should point to an unsigned char *  vari-         returned.  The fourth argument should point to an unsigned char * vari-
1238         able.         able.
1239    
1240           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1241    
1242         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
1243         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
1244         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1245         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
1246         byte  is  recorded only if it follows something of variable length. For         byte is recorded only if it follows something of variable  length.  For
1247         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
1248         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1249    
# Line 956  INFORMATION ABOUT A PATTERN Line 1251  INFORMATION ABOUT A PATTERN
1251           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1252           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1253    
1254         PCRE  supports the use of named as well as numbered capturing parenthe-         PCRE supports the use of named as well as numbered capturing  parenthe-
1255         ses. The names are just an additional way of identifying the  parenthe-         ses.  The names are just an additional way of identifying the parenthe-
1256         ses,  which  still  acquire  numbers.  A  convenience  function  called         ses,  which  still  acquire  numbers.  A  convenience  function  called
1257         pcre_get_named_substring() is provided  for  extracting  an  individual         pcre_get_named_substring()  is  provided  for  extracting an individual
1258         captured  substring  by  name.  It is also possible to extract the data         captured substring by name. It is also possible  to  extract  the  data
1259         directly, by first converting the name to a number in order  to  access         directly,  by  first converting the name to a number in order to access
1260         the  correct  pointers in the output vector (described with pcre_exec()         the correct pointers in the output vector (described  with  pcre_exec()
1261         below). To do the conversion, you need to use the  name-to-number  map,         below).  To  do the conversion, you need to use the name-to-number map,
1262         which is described by these three values.         which is described by these three values.
1263    
1264         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
1265         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1266         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
1267         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns
1268         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
1269         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-
1270         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-
1271         sponding name, zero terminated. The names are  in  alphabetical  order.         sponding  name,  zero  terminated. The names are in alphabetical order.
1272         For  example,  consider  the following pattern (assume PCRE_EXTENDED is         For example, consider the following pattern  (assume  PCRE_EXTENDED  is
1273         set, so white space - including newlines - is ignored):         set, so white space - including newlines - is ignored):
1274    
1275           (?P<date> (?P<year>(\d\d)?\d\d) -           (?P<date> (?P<year>(\d\d)?\d\d) -
1276           (?P<month>\d\d) - (?P<day>\d\d) )           (?P<month>\d\d) - (?P<day>\d\d) )
1277    
1278         There are four named subpatterns, so the table has  four  entries,  and         There  are  four  named subpatterns, so the table has four entries, and
1279         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,
1280         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1281         as ??:         as ??:
1282    
# Line 990  INFORMATION ABOUT A PATTERN Line 1285  INFORMATION ABOUT A PATTERN
1285           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1286           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1287    
1288         When  writing  code  to  extract  data from named subpatterns using the         When writing code to extract data  from  named  subpatterns  using  the
1289         name-to-number map, remember that the length of each entry is likely to         name-to-number map, remember that the length of each entry is likely to
1290         be different for each compiled pattern.         be different for each compiled pattern.
1291    
1292           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1293    
1294         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
1295         fourth argument should point to an unsigned long  int  variable.  These         fourth  argument  should  point to an unsigned long int variable. These
1296         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1297         by any top-level option settings within the pattern itself.         by any top-level option settings within the pattern itself.
1298    
1299         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
1300         alternatives begin with one of the following:         alternatives begin with one of the following:
1301    
1302           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1015  INFORMATION ABOUT A PATTERN Line 1310  INFORMATION ABOUT A PATTERN
1310    
1311           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1312    
1313         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
1314         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
1315         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
1316         size_t variable.         size_t variable.
# Line 1023  INFORMATION ABOUT A PATTERN Line 1318  INFORMATION ABOUT A PATTERN
1318           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1319    
1320         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
1321         a pcre_extra block. That is,  it  is  the  value  that  was  passed  to         a  pcre_extra  block.  That  is,  it  is  the  value that was passed to
1322         pcre_malloc() when PCRE was getting memory into which to place the data         pcre_malloc() when PCRE was getting memory into which to place the data
1323         created by pcre_study(). The fourth argument should point to  a  size_t         created  by  pcre_study(). The fourth argument should point to a size_t
1324         variable.         variable.
1325    
1326    
# Line 1033  OBSOLETE INFO FUNCTION Line 1328  OBSOLETE INFO FUNCTION
1328    
1329         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1330    
1331         The  pcre_info()  function is now obsolete because its interface is too         The pcre_info() function is now obsolete because its interface  is  too
1332         restrictive to return all the available data about a compiled  pattern.         restrictive  to return all the available data about a compiled pattern.
1333         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of
1334         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-
1335         lowing negative numbers:         lowing negative numbers:
1336    
1337           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1338           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1339    
1340         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
1341         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
1342         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1343    
1344         If  the  pattern  is  not anchored and the firstcharptr argument is not         If the pattern is not anchored and the  firstcharptr  argument  is  not
1345         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
1346         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1347    
1348    
1349  MATCHING A PATTERN  REFERENCE COUNTS
1350    
1351           int pcre_refcount(pcre *code, int adjust);
1352    
1353           The pcre_refcount() function is used to maintain a reference  count  in
1354           the data block that contains a compiled pattern. It is provided for the
1355           benefit of applications that  operate  in  an  object-oriented  manner,
1356           where different parts of the application may be using the same compiled
1357           pattern, but you want to free the block when they are all done.
1358    
1359           When a pattern is compiled, the reference count field is initialized to
1360           zero.   It is changed only by calling this function, whose action is to
1361           add the adjust value (which may be positive or  negative)  to  it.  The
1362           yield of the function is the new value. However, the value of the count
1363           is constrained to lie between 0 and 65535, inclusive. If the new  value
1364           is outside these limits, it is forced to the appropriate limit value.
1365    
1366           Except  when it is zero, the reference count is not correctly preserved
1367           if a pattern is compiled on one host and then  transferred  to  a  host
1368           whose byte-order is different. (This seems a highly unlikely scenario.)
1369    
1370    
1371    MATCHING A PATTERN: THE TRADITIONAL FUNCTION
1372    
1373         int pcre_exec(const pcre *code, const pcre_extra *extra,         int pcre_exec(const pcre *code, const pcre_extra *extra,
1374              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1375              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1376    
1377         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
1378         compiled pattern, which is passed in the code argument. If the  pattern         compiled  pattern, which is passed in the code argument. If the pattern
1379         has been studied, the result of the study should be passed in the extra         has been studied, the result of the study should be passed in the extra
1380         argument.         argument.  This  function is the main matching facility of the library,
1381           and it operates in a Perl-like manner. For specialist use there is also
1382           an  alternative matching function, which is described below in the sec-
1383           tion about the pcre_dfa_exec() function.
1384    
1385         In most applications, the pattern will have been compiled (and  option-         In most applications, the pattern will have been compiled (and  option-
1386         ally  studied)  in the same process that calls pcre_exec(). However, it         ally  studied)  in the same process that calls pcre_exec(). However, it
# Line 1080  MATCHING A PATTERN Line 1400  MATCHING A PATTERN
1400             0,              /* start at offset 0 in the subject */             0,              /* start at offset 0 in the subject */
1401             0,              /* default options */             0,              /* default options */
1402             ovector,        /* vector of integers for substring information */             ovector,        /* vector of integers for substring information */
1403             30);            /* number of elements in the vector  (NOT  size  in             30);            /* number of elements (NOT size in bytes) */
        bytes) */  
1404    
1405     Extra data for pcre_exec()     Extra data for pcre_exec()
1406    
1407         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
1408         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
1409         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-
1410         tional information in it. The fields in a pcre_extra block are as  fol-         tional  information in it. The fields in a pcre_extra block are as fol-
1411         lows:         lows:
1412    
1413           unsigned long int flags;           unsigned long int flags;
# Line 1097  MATCHING A PATTERN Line 1416  MATCHING A PATTERN
1416           void *callout_data;           void *callout_data;
1417           const unsigned char *tables;           const unsigned char *tables;
1418    
1419         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
1420         are set. The flag bits are:         are set. The flag bits are:
1421    
1422           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
# Line 1105  MATCHING A PATTERN Line 1424  MATCHING A PATTERN
1424           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1425           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1426    
1427         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
1428         the  pcre_extra  block  that is returned by pcre_study(), together with         the pcre_extra block that is returned by  pcre_study(),  together  with
1429         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
1430         add  to  the  block by setting the other fields and their corresponding         add to the block by setting the other fields  and  their  corresponding
1431         flag bits.         flag bits.
1432    
1433         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
1434         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
1435         match, but which have a very large number  of  possibilities  in  their         match,  but  which  have  a very large number of possibilities in their
1436         search  trees.  The  classic  example  is  the  use of nested unlimited         search trees. The classic  example  is  the  use  of  nested  unlimited
1437         repeats.         repeats.
1438    
1439         Internally, PCRE uses a function called match() which it calls  repeat-         Internally,  PCRE uses a function called match() which it calls repeat-
1440         edly  (sometimes  recursively).  The  limit is imposed on the number of         edly (sometimes recursively). The limit is imposed  on  the  number  of
1441         times this function is called during a match, which has the  effect  of         times  this  function is called during a match, which has the effect of
1442         limiting  the amount of recursion and backtracking that can take place.         limiting the amount of recursion and backtracking that can take  place.
1443         For patterns that are not anchored, the count starts from zero for each         For patterns that are not anchored, the count starts from zero for each
1444         position in the subject string.         position in the subject string.
1445    
1446         The  default  limit  for the library can be set when PCRE is built; the         The default limit for the library can be set when PCRE  is  built;  the
1447         default default is 10 million, which handles all but the  most  extreme         default  default  is 10 million, which handles all but the most extreme
1448         cases.  You  can  reduce  the  default  by  suppling pcre_exec() with a         cases. You can reduce  the  default  by  suppling  pcre_exec()  with  a
1449         pcre_extra block in which match_limit is set to a  smaller  value,  and         pcre_extra  block  in  which match_limit is set to a smaller value, and
1450         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
1451         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1452    
1453         The pcre_callout field is used in conjunction with the  "callout"  fea-         The  pcre_callout  field is used in conjunction with the "callout" fea-
1454         ture, which is described in the pcrecallout documentation.         ture, which is described in the pcrecallout documentation.
1455    
1456         The  tables  field  is  used  to  pass  a  character  tables pointer to         The tables field  is  used  to  pass  a  character  tables  pointer  to
1457         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec();  this overrides the value that is stored with the compiled
1458         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
1459         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
1460         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
1461         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-
1462         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
1463         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
1464         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
1465         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
1466    
1467     Option bits for pcre_exec()     Option bits for pcre_exec()
1468    
1469         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.
1470         The   only  bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NOTBOL,         The  only  bits  that  may  be  set  are  PCRE_ANCHORED,   PCRE_NOTBOL,
1471         PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.         PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.
1472    
1473           PCRE_ANCHORED           PCRE_ANCHORED
1474    
1475         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first
1476         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or
1477         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
1478         unachored at matching time.         unachored at matching time.
1479    
1480           PCRE_NOTBOL           PCRE_NOTBOL
1481    
1482         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
1483         the beginning of a line, so the  circumflex  metacharacter  should  not         the  beginning  of  a  line, so the circumflex metacharacter should not
1484         match  before it. Setting this without PCRE_MULTILINE (at compile time)         match before it. Setting this without PCRE_MULTILINE (at compile  time)
1485         causes  circumflex  never  to  match.  This  option  affects  only  the         causes  circumflex  never to match. This option affects only the behav-
1486         behaviour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
1487    
1488           PCRE_NOTEOL           PCRE_NOTEOL
1489    
1490         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
1491         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
1492         in  multiline mode) a newline immediately before it. Setting this with-         in multiline mode) a newline immediately before it. Setting this  with-
1493         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
1494         option  affects only the behaviour of the dollar metacharacter. It does         option affects only the behaviour of the dollar metacharacter. It  does
1495         not affect \Z or \z.         not affect \Z or \z.
1496    
1497           PCRE_NOTEMPTY           PCRE_NOTEMPTY
1498    
1499         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
1500         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
1501         the alternatives match the empty string, the entire  match  fails.  For         the  alternatives  match  the empty string, the entire match fails. For
1502         example, if the pattern         example, if the pattern
1503    
1504           a?b?           a?b?
1505    
1506         is  applied  to  a string not beginning with "a" or "b", it matches the         is applied to a string not beginning with "a" or "b",  it  matches  the
1507         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
1508         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-
1509         rences of "a" or "b".         rences of "a" or "b".
1510    
1511         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-
1512         cial  case  of  a  pattern match of the empty string within its split()         cial case of a pattern match of the empty  string  within  its  split()
1513         function, and when using the /g modifier. It  is  possible  to  emulate         function,  and  when  using  the /g modifier. It is possible to emulate
1514         Perl's behaviour after matching a null string by first trying the match         Perl's behaviour after matching a null string by first trying the match
1515         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then
1516         if  that  fails by advancing the starting offset (see below) and trying         if that fails by advancing the starting offset (see below)  and  trying
1517         an ordinary match again. There is some code that demonstrates how to do         an ordinary match again. There is some code that demonstrates how to do
1518         this in the pcredemo.c sample program.         this in the pcredemo.c sample program.
1519    
1520           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1521    
1522         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
1523         UTF-8 string is automatically checked when pcre_exec() is  subsequently         UTF-8  string is automatically checked when pcre_exec() is subsequently
1524         called.   The  value  of  startoffset is also checked to ensure that it         called.  The value of startoffset is also checked  to  ensure  that  it
1525         points to the start of a UTF-8 character. If an invalid UTF-8  sequence         points  to the start of a UTF-8 character. If an invalid UTF-8 sequence
1526         of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If         of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If
1527         startoffset contains an  invalid  value,  PCRE_ERROR_BADUTF8_OFFSET  is         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is
1528         returned.         returned.
1529    
1530         If  you  already  know that your subject is valid, and you want to skip         If you already know that your subject is valid, and you  want  to  skip
1531         these   checks   for   performance   reasons,   you   can    set    the         these    checks    for   performance   reasons,   you   can   set   the
1532         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to
1533         do this for the second and subsequent calls to pcre_exec() if  you  are         do  this  for the second and subsequent calls to pcre_exec() if you are
1534         making  repeated  calls  to  find  all  the matches in a single subject         making repeated calls to find all  the  matches  in  a  single  subject
1535         string. However, you should be  sure  that  the  value  of  startoffset         string.  However,  you  should  be  sure  that the value of startoffset
1536         points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is
1537         set, the effect of passing an invalid UTF-8 string as a subject,  or  a         set,  the  effect of passing an invalid UTF-8 string as a subject, or a
1538         value  of startoffset that does not point to the start of a UTF-8 char-         value of startoffset that does not point to the start of a UTF-8  char-
1539         acter, is undefined. Your program may crash.         acter, is undefined. Your program may crash.
1540    
1541           PCRE_PARTIAL           PCRE_PARTIAL
1542    
1543         This option turns on the  partial  matching  feature.  If  the  subject         This  option  turns  on  the  partial  matching feature. If the subject
1544         string  fails to match the pattern, but at some point during the match-         string fails to match the pattern, but at some point during the  match-
1545         ing process the end of the subject was reached (that  is,  the  subject         ing  process  the  end of the subject was reached (that is, the subject
1546         partially  matches  the  pattern and the failure to match occurred only         partially matches the pattern and the failure to  match  occurred  only
1547         because there were not enough subject characters), pcre_exec()  returns         because  there were not enough subject characters), pcre_exec() returns
1548         PCRE_ERROR_PARTIAL  instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is
1549         used, there are restrictions on what may appear in the  pattern.  These         used,  there  are restrictions on what may appear in the pattern. These
1550         are discussed in the pcrepartial documentation.         are discussed in the pcrepartial documentation.
1551    
1552     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
1553    
1554         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
1555         length in length, and a starting byte offset in startoffset.  In  UTF-8         length  in  length, and a starting byte offset in startoffset. In UTF-8
1556         mode,  the  byte  offset  must point to the start of a UTF-8 character.         mode, the byte offset must point to the start  of  a  UTF-8  character.
1557         Unlike the pattern string, the subject may contain binary  zero  bytes.         Unlike  the  pattern string, the subject may contain binary zero bytes.
1558         When  the starting offset is zero, the search for a match starts at the         When the starting offset is zero, the search for a match starts at  the
1559         beginning of the subject, and this is by far the most common case.         beginning of the subject, and this is by far the most common case.
1560    
1561         A non-zero starting offset is useful when searching for  another  match         A  non-zero  starting offset is useful when searching for another match
1562         in  the same subject by calling pcre_exec() again after a previous suc-         in the same subject by calling pcre_exec() again after a previous  suc-
1563         cess.  Setting startoffset differs from just passing over  a  shortened         cess.   Setting  startoffset differs from just passing over a shortened
1564         string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins         string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins
1565         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
1566    
1567           \Biss\B           \Biss\B
1568    
1569         which finds occurrences of "iss" in the middle of  words.  (\B  matches         which  finds  occurrences  of "iss" in the middle of words. (\B matches
1570         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.)
1571         When applied to the string "Mississipi" the first call  to  pcre_exec()         When  applied  to the string "Mississipi" the first call to pcre_exec()
1572         finds  the  first  occurrence. If pcre_exec() is called again with just         finds the first occurrence. If pcre_exec() is called  again  with  just
1573         the remainder of the subject,  namely  "issipi",  it  does  not  match,         the  remainder  of  the  subject,  namely  "issipi", it does not match,
1574         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
1575         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
1576         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-
1577         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
1578         discover that it is preceded by a letter.         discover that it is preceded by a letter.
1579    
1580         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,
1581         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
1582         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
1583         subject.         subject.
1584    
1585     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
1586    
1587         In general, a pattern matches a certain portion of the subject, and  in         In  general, a pattern matches a certain portion of the subject, and in
1588         addition,  further  substrings  from  the  subject may be picked out by         addition, further substrings from the subject  may  be  picked  out  by
1589         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,
1590         this  is  called "capturing" in what follows, and the phrase "capturing         this is called "capturing" in what follows, and the  phrase  "capturing
1591         subpattern" is used for a fragment of a pattern that picks out  a  sub-         subpattern"  is  used for a fragment of a pattern that picks out a sub-
1592         string.  PCRE  supports several other kinds of parenthesized subpattern         string. PCRE supports several other kinds of  parenthesized  subpattern
1593         that do not cause substrings to be captured.         that do not cause substrings to be captured.
1594    
1595         Captured substrings are returned to the caller via a vector of  integer         Captured  substrings are returned to the caller via a vector of integer
1596         offsets  whose  address is passed in ovector. The number of elements in         offsets whose address is passed in ovector. The number of  elements  in
1597         the vector is passed in ovecsize, which must be a non-negative  number.         the  vector is passed in ovecsize, which must be a non-negative number.
1598         Note: this argument is NOT the size of ovector in bytes.         Note: this argument is NOT the size of ovector in bytes.
1599    
1600         The  first  two-thirds of the vector is used to pass back captured sub-         The first two-thirds of the vector is used to pass back  captured  sub-
1601         strings, each substring using a pair of integers. The  remaining  third         strings,  each  substring using a pair of integers. The remaining third
1602         of  the  vector is used as workspace by pcre_exec() while matching cap-         of the vector is used as workspace by pcre_exec() while  matching  cap-
1603         turing subpatterns, and is not available for passing back  information.         turing  subpatterns, and is not available for passing back information.
1604         The  length passed in ovecsize should always be a multiple of three. If         The length passed in ovecsize should always be a multiple of three.  If
1605         it is not, it is rounded down.         it is not, it is rounded down.
1606    
1607         When a match is successful, information about  captured  substrings  is         When  a  match  is successful, information about captured substrings is
1608         returned  in  pairs  of integers, starting at the beginning of ovector,         returned in pairs of integers, starting at the  beginning  of  ovector,
1609         and continuing up to two-thirds of its length at the  most.  The  first         and  continuing  up  to two-thirds of its length at the most. The first
1610         element of a pair is set to the offset of the first character in a sub-         element of a pair is set to the offset of the first character in a sub-
1611         string, and the second is set to the  offset  of  the  first  character         string,  and  the  second  is  set to the offset of the first character
1612         after  the  end  of  a  substring. The first pair, ovector[0] and ovec-         after the end of a substring. The  first  pair,  ovector[0]  and  ovec-
1613         tor[1], identify the portion of  the  subject  string  matched  by  the         tor[1],  identify  the  portion  of  the  subject string matched by the
1614         entire  pattern.  The next pair is used for the first capturing subpat-         entire pattern. The next pair is used for the first  capturing  subpat-
1615         tern, and so on. The value returned by pcre_exec()  is  the  number  of         tern,  and  so  on.  The value returned by pcre_exec() is the number of
1616         pairs  that  have  been set. If there are no capturing subpatterns, the         pairs that have been set. If there are no  capturing  subpatterns,  the
1617         return value from a successful match is 1,  indicating  that  just  the         return  value  from  a  successful match is 1, indicating that just the
1618         first pair of offsets has been set.         first pair of offsets has been set.
1619    
1620         Some  convenience  functions  are  provided for extracting the captured         Some convenience functions are provided  for  extracting  the  captured
1621         substrings as separate strings. These are described  in  the  following         substrings  as  separate  strings. These are described in the following
1622         section.         section.
1623    
1624         It  is  possible  for  an capturing subpattern number n+1 to match some         It is possible for an capturing subpattern number  n+1  to  match  some
1625         part of the subject when subpattern n has not been  used  at  all.  For         part  of  the  subject  when subpattern n has not been used at all. For
1626         example, if the string "abc" is matched against the pattern (a|(z))(bc)         example, if the string "abc" is matched against the pattern (a|(z))(bc)
1627         subpatterns 1 and 3 are matched, but 2 is not. When this happens,  both         subpatterns  1 and 3 are matched, but 2 is not. When this happens, both
1628         offset values corresponding to the unused subpattern are set to -1.         offset values corresponding to the unused subpattern are set to -1.
1629    
1630         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
1631         of the string that it matched that is returned.         of the string that it matched that is returned.
1632    
1633         If the vector is too small to hold all the captured substring  offsets,         If  the vector is too small to hold all the captured substring offsets,
1634         it is used as far as possible (up to two-thirds of its length), and the         it is used as far as possible (up to two-thirds of its length), and the
1635         function returns a value of zero. In particular, if the substring  off-         function  returns a value of zero. In particular, if the substring off-
1636         sets are not of interest, pcre_exec() may be called with ovector passed         sets are not of interest, pcre_exec() may be called with ovector passed
1637         as NULL and ovecsize as zero. However, if  the  pattern  contains  back         as  NULL  and  ovecsize  as zero. However, if the pattern contains back
1638         references  and  the  ovector is not big enough to remember the related         references and the ovector is not big enough to  remember  the  related
1639         substrings, PCRE has to get additional memory for use during  matching.         substrings,  PCRE has to get additional memory for use during matching.
1640         Thus it is usually advisable to supply an ovector.         Thus it is usually advisable to supply an ovector.
1641    
1642         Note  that  pcre_info() can be used to find out how many capturing sub-         Note that pcre_info() can be used to find out how many  capturing  sub-
1643         patterns there are in a compiled pattern. The smallest size for ovector         patterns there are in a compiled pattern. The smallest size for ovector
1644         that  will  allow for n captured substrings, in addition to the offsets         that will allow for n captured substrings, in addition to  the  offsets
1645         of the substring matched by the whole pattern, is (n+1)*3.         of the substring matched by the whole pattern, is (n+1)*3.
1646    
1647     Return values from pcre_exec()     Return values from pcre_exec()
1648    
1649         If pcre_exec() fails, it returns a negative number. The  following  are         If  pcre_exec()  fails, it returns a negative number. The following are
1650         defined in the header file:         defined in the header file:
1651    
1652           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 1336  MATCHING A PATTERN Line 1655  MATCHING A PATTERN
1655    
1656           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
1657    
1658         Either  code  or  subject  was  passed as NULL, or ovector was NULL and         Either code or subject was passed as NULL,  or  ovector  was  NULL  and
1659         ovecsize was not zero.         ovecsize was not zero.
1660    
1661           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 1345  MATCHING A PATTERN Line 1664  MATCHING A PATTERN
1664    
1665           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
1666    
1667         PCRE stores a 4-byte "magic number" at the start of the compiled  code,         PCRE  stores a 4-byte "magic number" at the start of the compiled code,
1668         to catch the case when it is passed a junk pointer and to detect when a         to catch the case when it is passed a junk pointer and to detect when a
1669         pattern that was compiled in an environment of one endianness is run in         pattern that was compiled in an environment of one endianness is run in
1670         an  environment  with the other endianness. This is the error that PCRE         an environment with the other endianness. This is the error  that  PCRE
1671         gives when the magic number is not present.         gives when the magic number is not present.
1672    
1673           PCRE_ERROR_UNKNOWN_NODE   (-5)           PCRE_ERROR_UNKNOWN_NODE   (-5)
1674    
1675         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
1676         compiled  pattern.  This  error  could be caused by a bug in PCRE or by         compiled pattern. This error could be caused by a bug  in  PCRE  or  by
1677         overwriting of the compiled pattern.         overwriting of the compiled pattern.
1678    
1679           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
1680    
1681         If a pattern contains back references, but the ovector that  is  passed         If  a  pattern contains back references, but the ovector that is passed
1682         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
1683         PCRE gets a block of memory at the start of matching to  use  for  this         PCRE  gets  a  block of memory at the start of matching to use for this
1684         purpose.  If the call via pcre_malloc() fails, this error is given. The         purpose. If the call via pcre_malloc() fails, this error is given.  The
1685         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
1686    
1687           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
1688    
1689         This error is used by the pcre_copy_substring(),  pcre_get_substring(),         This  error is used by the pcre_copy_substring(), pcre_get_substring(),
1690         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
1691         returned by pcre_exec().         returned by pcre_exec().
1692    
1693           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
1694    
1695         The recursion and backtracking limit, as specified by  the  match_limit         The  recursion  and backtracking limit, as specified by the match_limit
1696         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field in a pcre_extra structure (or defaulted)  was  reached.  See  the
1697         description above.         description above.
1698    
1699           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
1700    
1701         This error is never generated by pcre_exec() itself. It is provided for         This error is never generated by pcre_exec() itself. It is provided for
1702         use  by  callout functions that want to yield a distinctive error code.         use by callout functions that want to yield a distinctive  error  code.
1703         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
1704    
1705           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
1706    
1707         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
1708         subject.         subject.
1709    
1710           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
1711    
1712         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 valid, but the
1713         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-
1714         ter.         ter.
1715    
1716           PCRE_ERROR_PARTIAL (-12)           PCRE_ERROR_PARTIAL        (-12)
1717    
1718         The  subject  string did not match, but it did match partially. See the         The subject string did not match, but it did match partially.  See  the
1719         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
1720    
1721           PCRE_ERROR_BAD_PARTIAL (-13)           PCRE_ERROR_BADPARTIAL     (-13)
1722    
1723         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing         The  PCRE_PARTIAL  option  was  used with a compiled pattern containing
1724         items  that are not supported for partial matching. See the pcrepartial         items that are not supported for partial matching. See the  pcrepartial
1725         documentation for details of partial matching.         documentation for details of partial matching.
1726    
1727           PCRE_ERROR_INTERNAL (-14)           PCRE_ERROR_INTERNAL       (-14)
1728    
1729         An unexpected internal error has occurred. This error could  be  caused         An  unexpected  internal error has occurred. This error could be caused
1730         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
1731    
1732           PCRE_ERROR_BADCOUNT (-15)           PCRE_ERROR_BADCOUNT       (-15)
1733    
1734         This  error is given if the value of the ovecsize argument is negative.         This error is given if the value of the ovecsize argument is  negative.
1735    
1736    
1737  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
# Line 1428  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 1747  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
1747         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
1748              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
1749    
1750         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
1751         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
1752         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
1753         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
1754         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
1755         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
1756         substrings. A substring  that  contains  a  binary  zero  is  correctly         substrings.  A  substring  that  contains  a  binary  zero is correctly
1757         extracted  and  has  a further zero added on the end, but the result is         extracted and has a further zero added on the end, but  the  result  is
1758         not, of course, a C string.         not, of course, a C string.
1759    
1760         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-
1761         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
1762         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
1763         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
1764         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
1765         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
1766         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
1767         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
1768         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
1769    
1770         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
1771         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
1772         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
1773         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
1774         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
1775         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
1776         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
1777         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
1778         the terminating zero, or one of         the terminating zero, or one of
1779    
1780           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
1781    
1782         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
1783         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
1784    
1785           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
1786    
1787         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
1788    
1789         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
1790         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
1791         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
1792         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
1793         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
1794         pointer. The yield of the function is zero if all went well, or         pointer. The yield of the function is zero if all went well, or
1795    
1796           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
1797    
1798         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
1799    
1800         When any of these functions encounter a substring that is unset,  which         When  any of these functions encounter a substring that is unset, which
1801         can  happen  when  capturing subpattern number n+1 matches some part of         can happen when capturing subpattern number n+1 matches  some  part  of
1802         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
1803         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
1804         string by inspecting the appropriate offset in ovector, which is  nega-         string  by inspecting the appropriate offset in ovector, which is nega-
1805         tive for unset substrings.         tive for unset substrings.
1806    
1807         The  two convenience functions pcre_free_substring() and pcre_free_sub-         The two convenience functions pcre_free_substring() and  pcre_free_sub-
1808         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
1809         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
1810         tively. They do nothing more than  call  the  function  pointed  to  by         tively.  They  do  nothing  more  than  call the function pointed to by
1811         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.
1812         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-
1813         cial  interface  to  another  programming  language  which  cannot  use         cial  interface  to  another  programming  language  which  cannot  use
1814         pcre_free directly; it is  for  these  cases  that  the  functions  are         pcre_free  directly;  it is for these cases that the functions are pro-
1815         provided.         vided.
1816    
1817    
1818  EXTRACTING CAPTURED SUBSTRINGS BY NAME  EXTRACTING CAPTURED SUBSTRINGS BY NAME
# Line 1511  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 1830  EXTRACTING CAPTURED SUBSTRINGS BY NAME
1830              int stringcount, const char *stringname,              int stringcount, const char *stringname,
1831              const char **stringptr);              const char **stringptr);
1832    
1833         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-
1834         ber.  For example, for this pattern         ber.  For example, for this pattern
1835    
1836           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
1837    
1838         the number of the subpattern called "xxx" is 2. You can find the number         the number of the subpattern called "xxx" is 2. You can find the number
1839         from the name by calling pcre_get_stringnumber(). The first argument is         from the name by calling pcre_get_stringnumber(). The first argument is
1840         the compiled pattern, and the second is the  name.  The  yield  of  the         the  compiled  pattern,  and  the  second is the name. The yield of the
1841         function  is  the  subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if         function is the subpattern number, or  PCRE_ERROR_NOSUBSTRING  (-7)  if
1842         there is no subpattern of that name.         there is no subpattern of that name.
1843    
1844         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
1845         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
1846         are also two functions that do the whole job.         are also two functions that do the whole job.
1847    
1848         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
1849         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
1850         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
1851         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
1852         differences:         differences:
1853    
1854         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
1855         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
1856         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
1857         name-to-number translation table.         name-to-number translation table.
1858    
1859         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
1860         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
1861         ate.         ate.
1862    
 Last updated: 09 September 2004  
 Copyright (c) 1997-2004 University of Cambridge.  
 -----------------------------------------------------------------------------  
1863    
1864  PCRE(3)                                                                PCRE(3)  FINDING ALL POSSIBLE MATCHES
1865    
1866           The traditional matching function uses a  similar  algorithm  to  Perl,
1867           which stops when it finds the first match, starting at a given point in
1868           the subject. If you want to find all possible matches, or  the  longest
1869           possible  match,  consider using the alternative matching function (see
1870           below) instead. If you cannot use the alternative function,  but  still
1871           need  to  find all possible matches, you can kludge it up by making use
1872           of the callout facility, which is described in the pcrecallout documen-
1873           tation.
1874    
1875           What you have to do is to insert a callout right at the end of the pat-
1876           tern.  When your callout function is called, extract and save the  cur-
1877           rent  matched  substring.  Then  return  1, which forces pcre_exec() to
1878           backtrack and try other alternatives. Ultimately, when it runs  out  of
1879           matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
1880    
1881    
1882    MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
1883    
1884           int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
1885                const char *subject, int length, int startoffset,
1886                int options, int *ovector, int ovecsize,
1887                int *workspace, int wscount);
1888    
1889           The  function  pcre_dfa_exec()  is  called  to  match  a subject string
1890           against a compiled pattern, using a "DFA" matching algorithm. This  has
1891           different  characteristics to the normal algorithm, and is not compati-
1892           ble with Perl. Some of the features of PCRE patterns are not supported.
1893           Nevertheless, there are times when this kind of matching can be useful.
1894           For a discussion of the two matching algorithms, see  the  pcrematching
1895           documentation.
1896    
1897           The  arguments  for  the  pcre_dfa_exec()  function are the same as for
1898           pcre_exec(), plus two extras. The ovector argument is used in a differ-
1899           ent  way,  and  this is described below. The other common arguments are
1900           used in the same way as for pcre_exec(), so their  description  is  not
1901           repeated here.
1902    
1903           The  two  additional  arguments provide workspace for the function. The
1904           workspace vector should contain at least 20 elements. It  is  used  for
1905           keeping  track  of  multiple  paths  through  the  pattern  tree.  More
1906           workspace will be needed for patterns and subjects where  there  are  a
1907           lot of possible matches.
1908    
1909           Here is an example of a simple call to pcre_exec():
1910    
1911             int rc;
1912             int ovector[10];
1913             int wspace[20];
1914             rc = pcre_exec(
1915               re,             /* result of pcre_compile() */
1916               NULL,           /* we didn't study the pattern */
1917               "some string",  /* the subject string */
1918               11,             /* the length of the subject string */
1919               0,              /* start at offset 0 in the subject */
1920               0,              /* default options */
1921               ovector,        /* vector of integers for substring information */
1922               10,             /* number of elements (NOT size in bytes) */
1923               wspace,         /* working space vector */
1924               20);            /* number of elements (NOT size in bytes) */
1925    
1926       Option bits for pcre_dfa_exec()
1927    
1928           The  unused  bits  of  the options argument for pcre_dfa_exec() must be
1929           zero. The only bits that may be  set  are  PCRE_ANCHORED,  PCRE_NOTBOL,
1930           PCRE_NOTEOL,     PCRE_NOTEMPTY,    PCRE_NO_UTF8_CHECK,    PCRE_PARTIAL,
1931           PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All  but  the  last  three  of
1932           these  are  the  same  as  for pcre_exec(), so their description is not
1933           repeated here.
1934    
1935             PCRE_PARTIAL
1936    
1937           This has the same general effect as it does for  pcre_exec(),  but  the
1938           details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for
1939           pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into
1940           PCRE_ERROR_PARTIAL  if  the  end  of the subject is reached, there have
1941           been no complete matches, but there is still at least one matching pos-
1942           sibility.  The portion of the string that provided the partial match is
1943           set as the first matching string.
1944    
1945             PCRE_DFA_SHORTEST
1946    
1947           Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
1948           stop  as  soon  as  it  has found one match. Because of the way the DFA
1949           algorithm works, this is necessarily the shortest possible match at the
1950           first possible matching point in the subject string.
1951    
1952             PCRE_DFA_RESTART
1953    
1954           When  pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option, and
1955           returns a partial match, it is possible to call it  again,  with  addi-
1956           tional  subject  characters,  and have it continue with the same match.
1957           The PCRE_DFA_RESTART option requests this action; when it is  set,  the
1958           workspace  and wscount options must reference the same vector as before
1959           because data about the match so far is left in  them  after  a  partial
1960           match.  There  is  more  discussion of this facility in the pcrepartial
1961           documentation.
1962    
1963       Successful returns from pcre_dfa_exec()
1964    
1965           When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-
1966           string in the subject. Note, however, that all the matches from one run
1967           of the function start at the same point in  the  subject.  The  shorter
1968           matches  are all initial substrings of the longer matches. For example,
1969           if the pattern
1970    
1971             <.*>
1972    
1973           is matched against the string
1974    
1975             This is <something> <something else> <something further> no more
1976    
1977           the three matched strings are
1978    
1979             <something>
1980             <something> <something else>
1981             <something> <something else> <something further>
1982    
1983           On success, the yield of the function is a number  greater  than  zero,
1984           which  is  the  number of matched substrings. The substrings themselves
1985           are returned in ovector. Each string uses two elements;  the  first  is
1986           the  offset  to the start, and the second is the offset to the end. All
1987           the strings have the same start offset. (Space could have been saved by
1988           giving  this only once, but it was decided to retain some compatibility
1989           with the way pcre_exec() returns data, even though the meaning  of  the
1990           strings is different.)
1991    
1992           The strings are returned in reverse order of length; that is, the long-
1993           est matching string is given first. If there were too many  matches  to
1994           fit  into ovector, the yield of the function is zero, and the vector is
1995           filled with the longest matches.
1996    
1997       Error returns from pcre_dfa_exec()
1998    
1999           The pcre_dfa_exec() function returns a negative number when  it  fails.
2000           Many  of  the  errors  are  the  same as for pcre_exec(), and these are
2001           described above.  There are in addition the following errors  that  are
2002           specific to pcre_dfa_exec():
2003    
2004             PCRE_ERROR_DFA_UITEM      (-16)
2005    
2006           This  return is given if pcre_dfa_exec() encounters an item in the pat-
2007           tern that it does not support, for instance, the use of \C  or  a  back
2008           reference.
2009    
2010             PCRE_ERROR_DFA_UCOND      (-17)
2011    
2012           This  return is given if pcre_dfa_exec() encounters a condition item in
2013           a pattern that uses a back reference for the  condition.  This  is  not
2014           supported.
2015    
2016             PCRE_ERROR_DFA_UMLIMIT    (-18)
2017    
2018           This  return  is given if pcre_dfa_exec() is called with an extra block
2019           that contains a setting of the match_limit field. This is not supported
2020           (it is meaningless).
2021    
2022             PCRE_ERROR_DFA_WSSIZE     (-19)
2023    
2024           This  return  is  given  if  pcre_dfa_exec()  runs  out of space in the
2025           workspace vector.
2026    
2027             PCRE_ERROR_DFA_RECURSE    (-20)
2028    
2029           When a recursive subpattern is processed, the matching  function  calls
2030           itself  recursively,  using  private vectors for ovector and workspace.
2031           This error is given if the output vector  is  not  large  enough.  This
2032           should be extremely rare, as a vector of size 1000 is used.
2033    
2034    Last updated: 16 May 2005
2035    Copyright (c) 1997-2005 University of Cambridge.
2036    -----------------------------------------------------------------------------
2037    
2038    
2039    
2040  NAME  NAME
2041         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
2042    
2043    
2044  PCRE CALLOUTS  PCRE CALLOUTS
2045    
2046         int (*pcre_callout)(pcre_callout_block *);         int (*pcre_callout)(pcre_callout_block *);
# Line 1606  MISSING CALLOUTS Line 2095  MISSING CALLOUTS
2095  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2096    
2097         During matching, when PCRE reaches a callout point, the external  func-         During matching, when PCRE reaches a callout point, the external  func-
2098         tion  defined  by pcre_callout is called (if it is set). The only argu-         tion  defined by pcre_callout is called (if it is set). This applies to
2099         ment is a pointer to a pcre_callout block. This structure contains  the         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The
2100         following fields:         only  argument  to  the callout function is a pointer to a pcre_callout
2101           block. This structure contains the following fields:
2102    
2103           int          version;           int          version;
2104           int          callout_number;           int          callout_number;
# Line 1623  THE CALLOUT INTERFACE Line 2113  THE CALLOUT INTERFACE
2113           int          pattern_position;           int          pattern_position;
2114           int          next_item_length;           int          next_item_length;
2115    
2116         The  version  field  is an integer containing the version number of the         The version field is an integer containing the version  number  of  the
2117         block format. The initial version was 0; the current version is 1.  The         block  format. The initial version was 0; the current version is 1. The
2118         version  number  will  change  again in future if additional fields are         version number will change again in future  if  additional  fields  are
2119         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.
2120    
2121         The  callout_number  field  contains the number of the callout, as com-         The callout_number field contains the number of the  callout,  as  com-
2122         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-
2123         outs, and 255 for automatically generated callouts).         outs, and 255 for automatically generated callouts).
2124    
2125         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
2126         passed by the caller to pcre_exec(). The contents can be  inspected  in         passed   by   the   caller  to  pcre_exec()  or  pcre_dfa_exec().  When
2127         order  to extract substrings that have been matched so far, in the same         pcre_exec() is used, the contents can be inspected in order to  extract
2128         way as for extracting substrings after a match has completed.         substrings  that  have  been  matched  so  far,  in the same way as for
2129           extracting substrings after a match has completed. For  pcre_dfa_exec()
2130           this field is not useful.
2131    
2132         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
2133         were passed to pcre_exec().         were passed to pcre_exec().
2134    
2135         The  start_match  field contains the offset within the subject at which         The start_match field contains the offset within the subject  at  which
2136         the current match attempt started. If the pattern is not anchored,  the         the  current match attempt started. If the pattern is not anchored, the
2137         callout function may be called several times from the same point in the         callout function may be called several times from the same point in the
2138         pattern for different starting points in the subject.         pattern for different starting points in the subject.
2139    
2140         The current_position field contains the offset within  the  subject  of         The  current_position  field  contains the offset within the subject of
2141         the current match pointer.         the current match pointer.
2142    
2143         The  capture_top field contains one more than the number of the highest         When the pcre_exec() function is used, the capture_top  field  contains
2144         numbered captured substring so far. If no  substrings  have  been  cap-         one  more than the number of the highest numbered captured substring so
2145         tured, the value of capture_top is one.         far. If no substrings have been captured, the value of  capture_top  is
2146           one.  This  is always the case when pcre_dfa_exec() is used, because it
2147         The  capture_last  field  contains the number of the most recently cap-         does not support captured substrings.
2148         tured substring. If no substrings have been captured, its value is  -1.  
2149           The capture_last field contains the number of the  most  recently  cap-
2150         The  callout_data  field contains a value that is passed to pcre_exec()         tured  substring. If no substrings have been captured, its value is -1.
2151         by the caller specifically so that it can be passed back  in  callouts.         This is always the case when pcre_dfa_exec() is used.
2152         It  is  passed  in the pcre_callout field of the pcre_extra data struc-  
2153         ture. If no such data was  passed,  the  value  of  callout_data  in  a         The callout_data field contains a value that is passed  to  pcre_exec()
2154         pcre_callout  block  is  NULL. There is a description of the pcre_extra         or  pcre_dfa_exec() specifically so that it can be passed back in call-
2155           outs. It is passed in the pcre_callout field  of  the  pcre_extra  data
2156           structure.  If  no such data was passed, the value of callout_data in a
2157           pcre_callout block is NULL. There is a description  of  the  pcre_extra
2158         structure in the pcreapi documentation.         structure in the pcreapi documentation.
2159    
2160         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-
2161         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
2162         the pattern string.         the pattern string.
2163    
2164         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-
2165         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
2166         the pattern string. When the callout immediately precedes  an  alterna-         the  pattern  string. When the callout immediately precedes an alterna-
2167         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
2168         is zero. When the callout precedes an opening parenthesis,  the  length         is  zero.  When the callout precedes an opening parenthesis, the length
2169         is that of the entire subpattern.         is that of the entire subpattern.
2170    
2171         The  pattern_position  and next_item_length fields are intended to help         The pattern_position and next_item_length fields are intended  to  help
2172         in distinguishing between different automatic callouts, which all  have         in  distinguishing between different automatic callouts, which all have
2173         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
2174    
2175    
2176  RETURN VALUES  RETURN VALUES
2177    
2178         The  external callout function returns an integer to PCRE. If the value         The external callout function returns an integer to PCRE. If the  value
2179         is zero, matching proceeds as normal. If  the  value  is  greater  than         is  zero,  matching  proceeds  as  normal. If the value is greater than
2180         zero,  matching  fails  at  the current point, but backtracking to test         zero, matching fails at the current point, but  the  testing  of  other
2181         other matching possibilities goes ahead, just as if a lookahead  asser-         matching possibilities goes ahead, just as if a lookahead assertion had
2182         tion  had  failed.  If  the value is less than zero, the match is aban-         failed. If the value is less than zero, the  match  is  abandoned,  and
2183         doned, and pcre_exec() returns the negative value.         pcre_exec() (or pcre_dfa_exec()) returns the negative value.
2184    
2185         Negative  values  should  normally  be   chosen   from   the   set   of         Negative   values   should   normally   be   chosen  from  the  set  of
2186         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
2187         dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is         dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is
2188         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
2189         itself.         itself.
2190    
2191  Last updated: 09 September 2004  Last updated: 28 February 2005
2192  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
2193  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
2194    
 PCRE(3)                                                                PCRE(3)  
   
2195    
2196    
2197  NAME  NAME
2198         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
2199    
2200    
2201  DIFFERENCES BETWEEN PCRE AND PERL  DIFFERENCES BETWEEN PCRE AND PERL
2202    
2203         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
# Line 1808  DIFFERENCES BETWEEN PCRE AND PERL Line 2302  DIFFERENCES BETWEEN PCRE AND PERL
2302         (m) Patterns compiled by PCRE can be saved and re-used at a later time,         (m) Patterns compiled by PCRE can be saved and re-used at a later time,
2303         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
2304    
2305  Last updated: 09 September 2004         (n)  The  alternative  matching function (pcre_dfa_exec()) matches in a
2306  Copyright (c) 1997-2004 University of Cambridge.         different way and is not Perl-compatible.
 -----------------------------------------------------------------------------  
2307    
2308  PCRE(3)                                                                PCRE(3)  Last updated: 28 February 2005
2309    Copyright (c) 1997-2005 University of Cambridge.
2310    -----------------------------------------------------------------------------
2311    
2312    
2313    
2314  NAME  NAME
2315         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
2316    
2317    
2318  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
2319    
2320         The  syntax  and semantics of the regular expressions supported by PCRE         The  syntax  and semantics of the regular expressions supported by PCRE
# Line 1836  PCRE REGULAR EXPRESSION DETAILS Line 2332  PCRE REGULAR EXPRESSION DETAILS
2332         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre
2333         page.         page.
2334    
2335           The remainder of this document discusses the  patterns  that  are  sup-
2336           ported  by  PCRE when its main matching function, pcre_exec(), is used.
2337           From  release  6.0,   PCRE   offers   a   second   matching   function,
2338           pcre_dfa_exec(),  which matches using a different algorithm that is not
2339           Perl-compatible. The advantages and disadvantages  of  the  alternative
2340           function, and how it differs from the normal function, are discussed in
2341           the pcrematching page.
2342    
2343         A regular expression is a pattern that is  matched  against  a  subject         A regular expression is a pattern that is  matched  against  a  subject
2344         string  from  left  to right. Most characters stand for themselves in a         string  from  left  to right. Most characters stand for themselves in a
2345         pattern, and match the corresponding characters in the  subject.  As  a         pattern, and match the corresponding characters in the  subject.  As  a
# Line 1843  PCRE REGULAR EXPRESSION DETAILS Line 2347  PCRE REGULAR EXPRESSION DETAILS
2347    
2348           The quick brown fox           The quick brown fox
2349    
2350         matches  a portion of a subject string that is identical to itself. The         matches a portion of a subject string that is identical to itself. When
2351         power of regular expressions comes from the ability to include alterna-         caseless matching is specified (the PCRE_CASELESS option), letters  are
2352         tives  and repetitions in the pattern. These are encoded in the pattern         matched  independently  of case. In UTF-8 mode, PCRE always understands
2353         by the use of metacharacters, which do not  stand  for  themselves  but         the concept of case for characters whose values are less than  128,  so
2354         instead are interpreted in some special way.         caseless  matching  is always possible. For characters with higher val-
2355           ues, the concept of case is supported if PCRE is compiled with  Unicode
2356         There  are  two different sets of metacharacters: those that are recog-         property  support,  but  not  otherwise.   If  you want to use caseless
2357         nized anywhere in the pattern except within square brackets, and  those         matching for characters 128 and above, you must  ensure  that  PCRE  is
2358         that  are  recognized  in square brackets. Outside square brackets, the         compiled with Unicode property support as well as with UTF-8 support.
2359    
2360           The  power  of  regular  expressions  comes from the ability to include
2361           alternatives and repetitions in the pattern. These are encoded  in  the
2362           pattern by the use of metacharacters, which do not stand for themselves
2363           but instead are interpreted in some special way.
2364    
2365           There are two different sets of metacharacters: those that  are  recog-
2366           nized  anywhere in the pattern except within square brackets, and those
2367           that are recognized in square brackets. Outside  square  brackets,  the
2368         metacharacters are as follows:         metacharacters are as follows:
2369    
2370           \      general escape character with several uses           \      general escape character with several uses
# Line 1870  PCRE REGULAR EXPRESSION DETAILS Line 2383  PCRE REGULAR EXPRESSION DETAILS
2383                  also "possessive quantifier"                  also "possessive quantifier"
2384           {      start min/max quantifier           {      start min/max quantifier
2385    
2386         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
2387         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
2388    
2389           \      general escape character           \      general escape character
# Line 1880  PCRE REGULAR EXPRESSION DETAILS Line 2393  PCRE REGULAR EXPRESSION DETAILS
2393                    syntax)                    syntax)
2394           ]      terminates the character class           ]      terminates the character class
2395    
2396         The  following sections describe the use of each of the metacharacters.         The following sections describe the use of each of the  metacharacters.
2397    
2398    
2399  BACKSLASH  BACKSLASH
2400    
2401         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
2402         a  non-alphanumeric  character,  it takes away any special meaning that         a non-alphanumeric character, it takes away any  special  meaning  that
2403         character may have. This  use  of  backslash  as  an  escape  character         character  may  have.  This  use  of  backslash  as an escape character
2404         applies both inside and outside character classes.         applies both inside and outside character classes.
2405    
2406         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
2407         pattern.  This escaping action applies whether  or  not  the  following         pattern.   This  escaping  action  applies whether or not the following
2408         character  would  otherwise be interpreted as a metacharacter, so it is         character would otherwise be interpreted as a metacharacter, so  it  is
2409         always safe to precede a non-alphanumeric  with  backslash  to  specify         always  safe  to  precede  a non-alphanumeric with backslash to specify
2410         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-
2411         slash, you write \\.         slash, you write \\.
2412    
2413         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in
2414         the  pattern (other than in a character class) and characters between a         the pattern (other than in a character class) and characters between  a
2415         # outside a character class and the next newline character are ignored.         # outside a character class and the next newline character are ignored.
2416         An  escaping backslash can be used to include a whitespace or # charac-         An escaping backslash can be used to include a whitespace or #  charac-
2417         ter as part of the pattern.         ter as part of the pattern.
2418    
2419         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-
2420         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-
2421         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
2422         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-
2423         tion. Note the following examples:         tion. Note the following examples:
2424    
2425           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 1916  BACKSLASH Line 2429  BACKSLASH
2429           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
2430           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
2431    
2432         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
2433         classes.         classes.
2434    
2435     Non-printing characters     Non-printing characters
2436    
2437         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-
2438         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
2439         appearance  of non-printing characters, apart from the binary zero that         appearance of non-printing characters, apart from the binary zero  that
2440         terminates a pattern, but when a pattern  is  being  prepared  by  text         terminates  a  pattern,  but  when  a pattern is being prepared by text
2441         editing,  it  is  usually  easier  to  use  one of the following escape         editing, it is usually easier  to  use  one  of  the  following  escape
2442         sequences than the binary character it represents:         sequences than the binary character it represents:
2443    
2444           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
# Line 1939  BACKSLASH Line 2452  BACKSLASH
2452           \xhh      character with hex code hh           \xhh      character with hex code hh
2453           \x{hhh..} character with hex code hhh... (UTF-8 mode only)           \x{hhh..} character with hex code hhh... (UTF-8 mode only)
2454    
2455         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,
2456         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
2457         inverted.  Thus \cz becomes hex 1A, but \c{ becomes hex 3B,  while  \c;         inverted.   Thus  \cz becomes hex 1A, but \c{ becomes hex 3B, while \c;
2458         becomes hex 7B.         becomes hex 7B.
2459    
2460         After  \x, from zero to two hexadecimal digits are read (letters can be         After \x, from zero to two hexadecimal digits are read (letters can  be
2461         in upper or lower case). In UTF-8 mode, any number of hexadecimal  dig-         in  upper or lower case). In UTF-8 mode, any number of hexadecimal dig-
2462         its  may  appear between \x{ and }, but the value of the character code         its may appear between \x{ and }, but the value of the  character  code
2463         must be less than 2**31 (that is,  the  maximum  hexadecimal  value  is         must  be  less  than  2**31  (that is, the maximum hexadecimal value is
2464         7FFFFFFF).  If  characters other than hexadecimal digits appear between         7FFFFFFF). If characters other than hexadecimal digits  appear  between
2465         \x{ and }, or if there is no terminating }, this form of escape is  not         \x{  and }, or if there is no terminating }, this form of escape is not
2466         recognized. Instead, the initial \x will be interpreted as a basic hex-         recognized. Instead, the initial \x will  be  interpreted  as  a  basic
2467         adecimal escape, with no following digits,  giving  a  character  whose         hexadecimal  escape, with no following digits, giving a character whose
2468         value is zero.         value is zero.
2469    
2470         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
2471         two syntaxes for \x when PCRE is in UTF-8 mode. There is no  difference         two  syntaxes for \x when PCRE is in UTF-8 mode. There is no difference
2472         in  the  way they are handled. For example, \xdc is exactly the same as         in the way they are handled. For example, \xdc is exactly the  same  as
2473         \x{dc}.         \x{dc}.
2474    
2475         After \0 up to two further octal digits are read.  In  both  cases,  if         After  \0  up  to  two further octal digits are read. In both cases, if
2476         there  are fewer than two digits, just those that are present are used.         there are fewer than two digits, just those that are present are  used.
2477         Thus the sequence \0\x\07 specifies two binary zeros followed by a  BEL         Thus  the sequence \0\x\07 specifies two binary zeros followed by a BEL
2478         character  (code  value  7).  Make sure you supply two digits after the         character (code value 7). Make sure you supply  two  digits  after  the
2479         initial zero if the pattern character that follows is itself  an  octal         initial  zero  if the pattern character that follows is itself an octal
2480         digit.         digit.
2481    
2482         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-
2483         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
2484         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
2485         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
2486         expression,  the  entire  sequence  is  taken  as  a  back reference. A         expression, the entire  sequence  is  taken  as  a  back  reference.  A
2487         description of how this works is given later, following the  discussion         description  of how this works is given later, following the discussion
2488         of parenthesized subpatterns.         of parenthesized subpatterns.
2489    
2490         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
2491         and there have not been that many capturing subpatterns, PCRE  re-reads         and  there have not been that many capturing subpatterns, PCRE re-reads
2492         up  to three octal digits following the backslash, and generates a sin-         up to three octal digits following the backslash, and generates a  sin-
2493         gle byte from the least significant 8 bits of the value. Any subsequent         gle byte from the least significant 8 bits of the value. Any subsequent
2494         digits stand for themselves.  For example:         digits stand for themselves.  For example:
2495    
# Line 1995  BACKSLASH Line 2508  BACKSLASH
2508           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
2509                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
2510    
2511         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
2512         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
2513    
2514         All the sequences that define a single byte value  or  a  single  UTF-8         All  the  sequences  that  define a single byte value or a single UTF-8
2515         character (in UTF-8 mode) can be used both inside and outside character         character (in UTF-8 mode) can be used both inside and outside character
2516         classes. In addition, inside a character  class,  the  sequence  \b  is         classes.  In  addition,  inside  a  character class, the sequence \b is
2517         interpreted as the backspace character (hex 08), and the sequence \X is         interpreted as the backspace character (hex 08), and the sequence \X is
2518         interpreted as the character "X".  Outside  a  character  class,  these         interpreted  as  the  character  "X".  Outside a character class, these
2519         sequences have different meanings (see below).         sequences have different meanings (see below).
2520    
2521     Generic character types     Generic character types
2522    
2523         The  third  use of backslash is for specifying generic character types.         The third use of backslash is for specifying generic  character  types.
2524         The following are always recognized:         The following are always recognized:
2525    
2526           \d     any decimal digit           \d     any decimal digit
# Line 2018  BACKSLASH Line 2531  BACKSLASH
2531           \W     any "non-word" character           \W     any "non-word" character
2532    
2533         Each pair of escape sequences partitions the complete set of characters         Each pair of escape sequences partitions the complete set of characters
2534         into  two disjoint sets. Any given character matches one, and only one,         into two disjoint sets. Any given character matches one, and only  one,
2535         of each pair.         of each pair.
2536    
2537         These character type sequences can appear both inside and outside char-         These character type sequences can appear both inside and outside char-
2538         acter  classes.  They each match one character of the appropriate type.         acter classes. They each match one character of the  appropriate  type.
2539         If the current matching point is at the end of the subject string,  all         If  the current matching point is at the end of the subject string, all
2540         of them fail, since there is no character to match.         of them fail, since there is no character to match.
2541    
2542         For  compatibility  with Perl, \s does not match the VT character (code         For compatibility with Perl, \s does not match the VT  character  (code
2543         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
2544         characters are HT (9), LF (10), FF (12), CR (13), and space (32).         characters are HT (9), LF (10), FF (12), CR (13), and space (32).
2545    
2546         A "word" character is an underscore or any character less than 256 that         A "word" character is an underscore or any character less than 256 that
2547         is a letter or digit. The definition of  letters  and  digits  is  con-         is  a  letter  or  digit.  The definition of letters and digits is con-
2548         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-
2549         specific matching is taking place (see "Locale support" in the  pcreapi         specific  matching is taking place (see "Locale support" in the pcreapi
2550         page).  For  example,  in  the  "fr_FR" (French) locale, some character         page). For example, in the  "fr_FR"  (French)  locale,  some  character
2551         codes greater than 128 are used for accented  letters,  and  these  are         codes  greater  than  128  are used for accented letters, and these are
2552         matched by \w.         matched by \w.
2553    
2554         In  UTF-8 mode, characters with values greater than 128 never match \d,         In UTF-8 mode, characters with values greater than 128 never match  \d,
2555         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
2556         code character property support is available.         code character property support is available.
2557    
2558     Unicode character properties     Unicode character properties
2559    
2560         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
2561         tional escape sequences to match generic character types are  available         tional  escape sequences to match generic character types are available
2562         when UTF-8 mode is selected. They are:         when UTF-8 mode is selected. They are:
2563    
2564          \p{xx}   a character with the xx property          \p{xx}   a character with the xx property
2565          \P{xx}   a character without the xx property          \P{xx}   a character without the xx property
2566          \X       an extended Unicode sequence          \X       an extended Unicode sequence
2567    
2568         The  property  names represented by xx above are limited to the Unicode         The property names represented by xx above are limited to  the  Unicode
2569         general category properties. Each character has exactly one such  prop-         general  category properties. Each character has exactly one such prop-
2570         erty,  specified  by  a two-letter abbreviation. For compatibility with         erty, specified by a two-letter abbreviation.  For  compatibility  with
2571         Perl, negation can be specified by including a circumflex  between  the         Perl,  negation  can be specified by including a circumflex between the
2572         opening  brace  and the property name. For example, \p{^Lu} is the same         opening brace and the property name. For example, \p{^Lu} is  the  same
2573         as \P{Lu}.         as \P{Lu}.
2574    
2575         If only one letter is specified with \p or  \P,  it  includes  all  the         If  only  one  letter  is  specified with \p or \P, it includes all the
2576         properties that start with that letter. In this case, in the absence of         properties that start with that letter. In this case, in the absence of
2577         negation, the curly brackets in the escape sequence are optional; these         negation, the curly brackets in the escape sequence are optional; these
2578         two examples have the same effect:         two examples have the same effect:
# Line 2113  BACKSLASH Line 2626  BACKSLASH
2626           Zp    Paragraph separator           Zp    Paragraph separator
2627           Zs    Space separator           Zs    Space separator
2628    
2629         Extended  properties such as "Greek" or "InMusicalSymbols" are not sup-         Extended properties such as "Greek" or "InMusicalSymbols" are not  sup-
2630         ported by PCRE.         ported by PCRE.
2631    
2632         Specifying caseless matching does not affect  these  escape  sequences.         Specifying  caseless  matching  does not affect these escape sequences.
2633         For example, \p{Lu} always matches only upper case letters.         For example, \p{Lu} always matches only upper case letters.
2634    
2635         The  \X  escape  matches  any number of Unicode characters that form an         The \X escape matches any number of Unicode  characters  that  form  an
2636         extended Unicode sequence. \X is equivalent to         extended Unicode sequence. \X is equivalent to
2637    
2638           (?>\PM\pM*)           (?>\PM\pM*)
2639    
2640         That is, it matches a character without the "mark"  property,  followed         That  is,  it matches a character without the "mark" property, followed
2641         by  zero  or  more  characters with the "mark" property, and treats the         by zero or more characters with the "mark"  property,  and  treats  the
2642         sequence as an atomic group (see below).  Characters  with  the  "mark"         sequence  as  an  atomic group (see below).  Characters with the "mark"
2643         property are typically accents that affect the preceding character.         property are typically accents that affect the preceding character.
2644    
2645         Matching  characters  by Unicode property is not fast, because PCRE has         Matching characters by Unicode property is not fast, because  PCRE  has
2646         to search a structure that contains  data  for  over  fifteen  thousand         to  search  a  structure  that  contains data for over fifteen thousand
2647         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
2648         \w do not use Unicode properties in PCRE.         \w do not use Unicode properties in PCRE.
2649    
2650     Simple assertions     Simple assertions
2651    
2652         The fourth use of backslash is for certain simple assertions. An asser-         The fourth use of backslash is for certain simple assertions. An asser-
2653         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
2654         a match, without consuming any characters from the subject string.  The         a  match, without consuming any characters from the subject string. The
2655         use  of subpatterns for more complicated assertions is described below.         use of subpatterns for more complicated assertions is described  below.
2656         The backslashed assertions are:         The backslashed assertions are:
2657    
2658           \b     matches at a word boundary           \b     matches at a word boundary
# Line 2149  BACKSLASH Line 2662  BACKSLASH
2662           \z     matches at end of subject           \z     matches at end of subject
2663           \G     matches at first matching position in subject           \G     matches at first matching position in subject
2664    
2665         These assertions may not appear in character classes (but note that  \b         These  assertions may not appear in character classes (but note that \b
2666         has a different meaning, namely the backspace character, inside a char-         has a different meaning, namely the backspace character, inside a char-
2667         acter class).         acter class).
2668    
2669         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
2670         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.
2671         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
2672         string if the first or last character matches \w, respectively.         string if the first or last character matches \w, respectively.
2673    
2674         The  \A,  \Z,  and \z assertions differ from the traditional circumflex         The \A, \Z, and \z assertions differ from  the  traditional  circumflex
2675         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
2676         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
2677         set. Thus, they are independent of multiline mode. These  three  asser-         set.  Thus,  they are independent of multiline mode. These three asser-
2678         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
2679         affect only the behaviour of the circumflex and dollar  metacharacters.         affect  only the behaviour of the circumflex and dollar metacharacters.
2680         However,  if the startoffset argument of pcre_exec() is non-zero, indi-         However, if the startoffset argument of pcre_exec() is non-zero,  indi-
2681         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
2682         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
2683         that \Z matches before a newline that is  the  last  character  of  the         that  \Z  matches  before  a  newline that is the last character of the
2684         string  as well as at the end of the string, whereas \z matches only at         string as well as at the end of the string, whereas \z matches only  at
2685         the end.         the end.
2686    
2687         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
2688         the  start point of the match, as specified by the startoffset argument         the start point of the match, as specified by the startoffset  argument
2689         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
2690         non-zero.  By calling pcre_exec() multiple times with appropriate argu-         non-zero. By calling pcre_exec() multiple times with appropriate  argu-
2691         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-
2692         mentation where \G can be useful.         mentation where \G can be useful.
2693    
2694         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
2695         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
2696         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
2697         previously matched string was empty. Because PCRE does just  one  match         previously  matched  string was empty. Because PCRE does just one match
2698         at a time, it cannot reproduce this behaviour.         at a time, it cannot reproduce this behaviour.
2699    
2700         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
2701         anchored to the starting match position, and the "anchored" flag is set         anchored to the starting match position, and the "anchored" flag is set
2702         in the compiled regular expression.         in the compiled regular expression.
2703    
# Line 2192  BACKSLASH Line 2705  BACKSLASH
2705  CIRCUMFLEX AND DOLLAR  CIRCUMFLEX AND DOLLAR
2706    
2707         Outside a character class, in the default matching mode, the circumflex         Outside a character class, in the default matching mode, the circumflex
2708         character is an assertion that is true only  if  the  current  matching         character  is  an  assertion  that is true only if the current matching
2709         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-
2710         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
2711         PCRE_MULTILINE  option  is  unset. Inside a character class, circumflex         PCRE_MULTILINE option is unset. Inside a  character  class,  circumflex
2712         has an entirely different meaning (see below).         has an entirely different meaning (see below).
2713    
2714         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
2715         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
2716         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
2717         branch.  If all possible alternatives start with a circumflex, that is,         branch. If all possible alternatives start with a circumflex, that  is,
2718         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-
2719         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
2720         constructs that can cause a pattern to be anchored.)         constructs that can cause a pattern to be anchored.)
2721    
2722         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
2723         matching  point  is  at  the  end of the subject string, or immediately         matching point is at the end of  the  subject  string,  or  immediately
2724         before a newline character that is the last character in the string (by         before a newline character that is the last character in the string (by
2725         default).  Dollar  need  not  be the last character of the pattern if a         default). Dollar need not be the last character of  the  pattern  if  a
2726         number of alternatives are involved, but it should be the last item  in         number  of alternatives are involved, but it should be the last item in
2727         any  branch  in  which  it appears.  Dollar has no special meaning in a         any branch in which it appears.  Dollar has no  special  meaning  in  a
2728         character class.         character class.
2729    
2730         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
2731         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
2732         compile time. This does not affect the \Z assertion.         compile time. This does not affect the \Z assertion.
2733    
2734         The meanings of the circumflex and dollar characters are changed if the         The meanings of the circumflex and dollar characters are changed if the
2735         PCRE_MULTILINE option is set. When this is the case, they match immedi-         PCRE_MULTILINE option is set. When this is the case, they match immedi-
2736         ately after and  immediately  before  an  internal  newline  character,         ately  after  and  immediately  before  an  internal newline character,
2737         respectively,  in addition to matching at the start and end of the sub-         respectively, in addition to matching at the start and end of the  sub-
2738         ject string. For example,  the  pattern  /^abc$/  matches  the  subject         ject  string.  For  example,  the  pattern  /^abc$/ matches the subject
2739         string  "def\nabc"  (where \n represents a newline character) in multi-         string "def\nabc" (where \n represents a newline character)  in  multi-
2740         line mode, but not otherwise.  Consequently, patterns that are anchored         line mode, but not otherwise.  Consequently, patterns that are anchored
2741         in  single line mode because all branches start with ^ are not anchored         in single line mode because all branches start with ^ are not  anchored
2742         in multiline mode, and a match for  circumflex  is  possible  when  the         in  multiline  mode,  and  a  match for circumflex is possible when the
2743         startoffset   argument   of  pcre_exec()  is  non-zero.  The  PCRE_DOL-         startoffset  argument  of  pcre_exec()  is  non-zero.   The   PCRE_DOL-
2744         LAR_ENDONLY option is ignored if PCRE_MULTILINE is set.         LAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
2745    
2746         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
2747         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
2748         start with \A it is always anchored, whether PCRE_MULTILINE is  set  or         start  with  \A it is always anchored, whether PCRE_MULTILINE is set or
2749         not.         not.
2750    
2751    
2752  FULL STOP (PERIOD, DOT)  FULL STOP (PERIOD, DOT)
2753    
2754         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-
2755         ter in the subject, including a non-printing  character,  but  not  (by         ter  in  the  subject,  including a non-printing character, but not (by
2756         default)  newline.   In  UTF-8 mode, a dot matches any UTF-8 character,         default) newline.  In UTF-8 mode, a dot matches  any  UTF-8  character,
2757         which might be more than one byte long, except (by default) newline. If         which might be more than one byte long, except (by default) newline. If
2758         the  PCRE_DOTALL  option  is set, dots match newlines as well. The han-         the PCRE_DOTALL option is set, dots match newlines as  well.  The  han-
2759         dling of dot is entirely independent of the handling of circumflex  and         dling  of dot is entirely independent of the handling of circumflex and
2760         dollar,  the  only  relationship  being  that they both involve newline         dollar, the only relationship being  that  they  both  involve  newline
2761         characters. Dot has no special meaning in a character class.         characters. Dot has no special meaning in a character class.
2762    
2763    
2764  MATCHING A SINGLE BYTE  MATCHING A SINGLE BYTE
2765    
2766         Outside a character class, the escape sequence \C matches any one byte,         Outside a character class, the escape sequence \C matches any one byte,
2767         both  in  and  out of UTF-8 mode. Unlike a dot, it can match a newline.         both in and out of UTF-8 mode. Unlike a dot, it can  match  a  newline.
2768         The feature is provided in Perl in order to match individual  bytes  in         The  feature  is provided in Perl in order to match individual bytes in
2769         UTF-8  mode.  Because  it  breaks  up  UTF-8 characters into individual         UTF-8 mode. Because it  breaks  up  UTF-8  characters  into  individual
2770         bytes, what remains in the string may be a malformed UTF-8 string.  For         bytes,  what remains in the string may be a malformed UTF-8 string. For
2771         this reason, the \C escape sequence is best avoided.         this reason, the \C escape sequence is best avoided.
2772    
2773         PCRE  does  not  allow \C to appear in lookbehind assertions (described         PCRE does not allow \C to appear in  lookbehind  assertions  (described
2774         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-
2775         late the length of the lookbehind.         late the length of the lookbehind.
2776    
2777    
# Line 2267  SQUARE BRACKETS AND CHARACTER CLASSES Line 2780  SQUARE BRACKETS AND CHARACTER CLASSES
2780         An opening square bracket introduces a character class, terminated by a         An opening square bracket introduces a character class, terminated by a
2781         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-
2782         cial. If a closing square bracket is required as a member of the class,         cial. If a closing square bracket is required as a member of the class,
2783         it should be the first data character in the class  (after  an  initial         it  should  be  the first data character in the class (after an initial
2784         circumflex, if present) or escaped with a backslash.         circumflex, if present) or escaped with a backslash.
2785    
2786         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
2787         mode, the character may occupy more than one byte. A matched  character         mode,  the character may occupy more than one byte. A matched character
2788         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
2789         character in the class definition is a circumflex, in  which  case  the         character  in  the  class definition is a circumflex, in which case the
2790         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
2791         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
2792         not the first character, or escape it with a backslash.         not the first character, or escape it with a backslash.
2793    
2794         For  example, the character class [aeiou] matches any lower case vowel,         For example, the character class [aeiou] matches any lower case  vowel,
2795         while [^aeiou] matches any character that is not a  lower  case  vowel.         while  [^aeiou]  matches  any character that is not a lower case vowel.
2796         Note that a circumflex is just a convenient notation for specifying the         Note that a circumflex is just a convenient notation for specifying the
2797         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
2798         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-
2799         sumes a character from the subject string, and therefore  it  fails  if         sumes  a  character  from the subject string, and therefore it fails if
2800         the current pointer is at the end of the string.         the current pointer is at the end of the string.
2801    
2802         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
2803         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
2804         mechanism.         mechanism.
2805    
2806         When  caseless  matching  is set, any letters in a class represent both         When caseless matching is set, any letters in a  class  represent  both
2807         their upper case and lower case versions, so for  example,  a  caseless         their  upper  case  and lower case versions, so for example, a caseless
2808         [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
2809         match "A", whereas a caseful version would. When running in UTF-8 mode,         match  "A", whereas a caseful version would. In UTF-8 mode, PCRE always
2810         PCRE  supports  the  concept of case for characters with values greater         understands the concept of case for characters whose  values  are  less
2811         than 128 only when it is compiled with Unicode property support.         than  128, so caseless matching is always possible. For characters with
2812           higher values, the concept of case is supported  if  PCRE  is  compiled
2813           with  Unicode  property support, but not otherwise.  If you want to use
2814           caseless matching for characters 128 and above, you  must  ensure  that
2815           PCRE  is  compiled  with Unicode property support as well as with UTF-8
2816           support.
2817    
2818         The newline character is never treated in any special way in  character         The newline character is never treated in any special way in  character
2819         classes,  whatever  the  setting  of  the PCRE_DOTALL or PCRE_MULTILINE         classes,  whatever  the  setting  of  the PCRE_DOTALL or PCRE_MULTILINE
# Line 3215  CALLOUTS Line 3733  CALLOUTS
3733         gether. A complete description of the interface to the callout function         gether. A complete description of the interface to the callout function
3734         is given in the pcrecallout documentation.         is given in the pcrecallout documentation.
3735    
3736  Last updated: 09 September 2004  Last updated: 28 February 2005
3737  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
3738  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
3739    
 PCRE(3)                                                                PCRE(3)  
   
3740    
3741    
3742  NAME  NAME
3743         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
3744    
3745    
3746  PARTIAL MATCHING IN PCRE  PARTIAL MATCHING IN PCRE
3747    
3748         In  normal  use  of  PCRE,  if  the  subject  string  that is passed to         In  normal  use  of  PCRE,  if  the  subject  string  that is passed to
3749         pcre_exec() matches as far as it goes, but is too short  to  match  the         pcre_exec() or pcre_dfa_exec() matches as far as it goes,  but  is  too
3750         entire pattern, PCRE_ERROR_NOMATCH is returned. There are circumstances         short  to  match  the  entire  pattern, PCRE_ERROR_NOMATCH is returned.
3751         where it might be helpful to distinguish this case from other cases  in         There are circumstances where it might be helpful to  distinguish  this
3752         which there is no match.         case from other cases in which there is no match.
3753    
3754         Consider, for example, an application where a human is required to type         Consider, for example, an application where a human is required to type
3755         in data for a field with specific formatting requirements.  An  example         in data for a field with specific formatting requirements.  An  example
# Line 3248  PARTIAL MATCHING IN PCRE Line 3765  PARTIAL MATCHING IN PCRE
3765         until the entire string has been entered.         until the entire string has been entered.
3766    
3767         PCRE supports the concept of partial matching by means of the PCRE_PAR-         PCRE supports the concept of partial matching by means of the PCRE_PAR-
3768         TIAL  option,  which  can be set when calling pcre_exec(). When this is         TIAL   option,   which   can   be   set  when  calling  pcre_exec()  or
3769         done,  the   return   code   PCRE_ERROR_NOMATCH   is   converted   into         pcre_dfa_exec(). When this flag is set for pcre_exec(), the return code
3770         PCRE_ERROR_PARTIAL  if  at  any  time  during  the matching process the         PCRE_ERROR_NOMATCH  is converted into PCRE_ERROR_PARTIAL if at any time
3771         entire subject string matched part of the pattern. No captured data  is         during the matching process the last part of the subject string matched
3772         set when this occurs.         part  of  the  pattern. Unfortunately, for non-anchored matching, it is
3773           not possible to obtain the position of the start of the partial  match.
3774           No captured data is set when PCRE_ERROR_PARTIAL is returned.
3775    
3776           When   PCRE_PARTIAL   is  set  for  pcre_dfa_exec(),  the  return  code
3777           PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the  end  of
3778           the  subject is reached, there have been no complete matches, but there
3779           is still at least one matching possibility. The portion of  the  string
3780           that provided the partial match is set as the first matching string.
3781    
3782         Using PCRE_PARTIAL disables one of PCRE's optimizations. PCRE remembers         Using PCRE_PARTIAL disables one of PCRE's optimizations. PCRE remembers
3783         the last literal byte in a pattern, and abandons  matching  immediately         the last literal byte in a pattern, and abandons  matching  immediately
# Line 3263  PARTIAL MATCHING IN PCRE Line 3788  PARTIAL MATCHING IN PCRE
3788  RESTRICTED PATTERNS FOR PCRE_PARTIAL  RESTRICTED PATTERNS FOR PCRE_PARTIAL
3789    
3790         Because of the way certain internal optimizations  are  implemented  in         Because of the way certain internal optimizations  are  implemented  in
3791         PCRE,  the  PCRE_PARTIAL  option  cannot  be  used  with  all patterns.         the  pcre_exec()  function, the PCRE_PARTIAL option cannot be used with
3792         Repeated single characters such as         all patterns. These restrictions do not apply when  pcre_dfa_exec()  is
3793           used.  For pcre_exec(), repeated single characters such as
3794    
3795           a{2,4}           a{2,4}
3796    
# Line 3272  RESTRICTED PATTERNS FOR PCRE_PARTIAL Line 3798  RESTRICTED PATTERNS FOR PCRE_PARTIAL
3798    
3799           \d+           \d+
3800    
3801         are not permitted if the maximum number of occurrences is greater  than         are  not permitted if the maximum number of occurrences is greater than
3802         one.  Optional items such as \d? (where the maximum is one) are permit-         one.  Optional items such as \d? (where the maximum is one) are permit-
3803         ted.  Quantifiers with any values are permitted after  parentheses,  so         ted.   Quantifiers  with any values are permitted after parentheses, so
3804         the invalid examples above can be coded thus:         the invalid examples above can be coded thus:
3805    
3806           (a){2,4}           (a){2,4}
3807           (\d)+           (\d)+
3808    
3809         These  constructions  run more slowly, but for the kinds of application         These constructions run more slowly, but for the kinds  of  application
3810         that are envisaged for this facility, this is not felt to  be  a  major         that  are  envisaged  for this facility, this is not felt to be a major
3811         restriction.         restriction.
3812    
3813         If  PCRE_PARTIAL  is  set  for  a  pattern that does not conform to the         If PCRE_PARTIAL is set for a pattern  that  does  not  conform  to  the
3814         restrictions, pcre_exec() returns the error code  PCRE_ERROR_BADPARTIAL         restrictions,  pcre_exec() returns the error code PCRE_ERROR_BADPARTIAL
3815         (-13).         (-13).
3816    
3817    
3818  EXAMPLE OF PARTIAL MATCHING USING PCRETEST  EXAMPLE OF PARTIAL MATCHING USING PCRETEST
3819    
3820         If  the  escape  sequence  \P  is  present in a pcretest data line, the         If the escape sequence \P is present  in  a  pcretest  data  line,  the
3821         PCRE_PARTIAL flag is used for the match. Here is a run of pcretest that         PCRE_PARTIAL flag is used for the match. Here is a run of pcretest that
3822         uses the date example quoted above:         uses the date example quoted above:
3823    
# Line 3308  EXAMPLE OF PARTIAL MATCHING USING PCRETE Line 3834  EXAMPLE OF PARTIAL MATCHING USING PCRETE
3834           data> jP           data> jP
3835           No match           No match
3836    
3837         The  first  data  string  is  matched completely, so pcretest shows the         The first data string is matched  completely,  so  pcretest  shows  the
3838         matched substrings. The remaining four strings do not  match  the  com-         matched  substrings.  The  remaining four strings do not match the com-
3839         plete pattern, but the first two are partial matches.         plete pattern, but the first two are partial matches.  The  same  test,
3840           using  DFA  matching (by means of the \D escape sequence), produces the
3841           following output:
3842    
3843  Last updated: 08 September 2004             re> /^?(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)$/
3844  Copyright (c) 1997-2004 University of Cambridge.           data> 25jun04\P\D
3845  -----------------------------------------------------------------------------            0: 25jun04
3846             data> 23dec3\P\D
3847             Partial match: 23dec3
3848             data> 3ju\P\D
3849             Partial match: 3ju
3850             data> 3juj\P\D
3851             No match
3852             data> j\P\D
3853             No match
3854    
3855           Notice that in this case the portion of the string that was matched  is
3856           made available.
3857    
3858    
3859    MULTI-SEGMENT MATCHING WITH pcre_dfa_exec()
3860    
3861  PCRE(3)                                                                PCRE(3)         When a partial match has been found using pcre_dfa_exec(), it is possi-
3862           ble to continue the match by  providing  additional  subject  data  and
3863           calling  pcre_dfa_exec() again with the PCRE_DFA_RESTART option and the
3864           same working space (where details of the  previous  partial  match  are
3865           stored).  Here  is  an  example  using  pcretest,  where  the \R escape
3866           sequence sets the PCRE_DFA_RESTART option and the  \D  escape  sequence
3867           requests the use of pcre_dfa_exec():
3868    
3869               re> /^?(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)$/
3870             data> 23ja\P\D
3871             Partial match: 23ja
3872             data> n05\R\D
3873              0: n05
3874    
3875           The  first  call has "23ja" as the subject, and requests partial match-
3876           ing; the second call  has  "n05"  as  the  subject  for  the  continued
3877           (restarted)  match.   Notice  that when the match is complete, only the
3878           last part is shown; PCRE does  not  retain  the  previously  partially-
3879           matched  string. It is up to the calling program to do that if it needs
3880           to.
3881    
3882           This facility can  be  used  to  pass  very  long  subject  strings  to
3883           pcre_dfa_exec(). However, some care is needed for certain types of pat-
3884           tern.
3885    
3886           1. If the pattern contains tests for the beginning or end  of  a  line,
3887           you  need  to pass the PCRE_NOTBOL or PCRE_NOTEOL options, as appropri-
3888           ate, when the subject string for any call does not contain  the  begin-
3889           ning or end of a line.
3890    
3891           2.  If  the  pattern contains backward assertions (including \b or \B),
3892           you need to arrange for some overlap in the subject  strings  to  allow
3893           for  this.  For example, you could pass the subject in chunks that were
3894           500 bytes long, but in a buffer of 700 bytes, with the starting  offset
3895           set to 200 and the previous 200 bytes at the start of the buffer.
3896    
3897           3.  Matching a subject string that is split into multiple segments does
3898           not always produce exactly the same result as matching over one  single
3899           long  string.   The  difference arises when there are multiple matching
3900           possibilities, because a partial match result is given only when  there
3901           are  no  completed  matches  in a call to fBpcre_dfa_exec(). This means
3902           that as soon as the shortest match has been found,  continuation  to  a
3903           new  subject  segment  is  no  longer possible.  Consider this pcretest
3904           example:
3905    
3906               re> /dog(sbody)?/
3907             data> do\P\D
3908             Partial match: do
3909             data> gsb\R\P\D
3910              0: g
3911             data> dogsbody\D
3912              0: dogsbody
3913              1: dog
3914    
3915           The pattern matches the words "dog" or "dogsbody". When the subject  is
3916           presented  in  several  parts  ("do" and "gsb" being the first two) the
3917           match stops when "dog" has been found, and it is not possible  to  con-
3918           tinue.  On  the  other  hand,  if  "dogsbody"  is presented as a single
3919           string, both matches are found.
3920    
3921           Because of this phenomenon, it does not usually make  sense  to  end  a
3922           pattern that is going to be matched in this way with a variable repeat.
3923    
3924    Last updated: 28 February 2005
3925    Copyright (c) 1997-2005 University of Cambridge.
3926    -----------------------------------------------------------------------------
3927    
3928    
3929    
3930  NAME  NAME
3931         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
3932    
3933    
3934  SAVING AND RE-USING PRECOMPILED PCRE PATTERNS  SAVING AND RE-USING PRECOMPILED PCRE PATTERNS
3935    
3936         If  you  are running an application that uses a large number of regular         If  you  are running an application that uses a large number of regular
# Line 3391  SAVING A COMPILED PATTERN Line 3999  SAVING A COMPILED PATTERN
3999  RE-USING A PRECOMPILED PATTERN  RE-USING A PRECOMPILED PATTERN
4000    
4001         Re-using a precompiled pattern is straightforward. Having  reloaded  it         Re-using a precompiled pattern is straightforward. Having  reloaded  it
4002         into main memory, you pass its pointer to pcre_exec() in the usual way.         into   main   memory,   you   pass   its   pointer  to  pcre_exec()  or
4003         This should work even on another host, and even if that  host  has  the         pcre_dfa_exec() in the usual way. This  should  work  even  on  another
4004         opposite endianness to the one where the pattern was compiled.         host,  and  even  if  that  host has the opposite endianness to the one
4005           where the pattern was compiled.
4006         However,  if  you  passed a pointer to custom character tables when the  
4007         pattern was compiled (the tableptr  argument  of  pcre_compile()),  you         However, if you passed a pointer to custom character  tables  when  the
4008         must now pass a similar pointer to pcre_exec(), because the value saved         pattern  was  compiled  (the  tableptr argument of pcre_compile()), you
4009         with the compiled pattern will obviously be  nonsense.  A  field  in  a         must now pass a similar  pointer  to  pcre_exec()  or  pcre_dfa_exec(),
4010         pcre_extra()  block is used to pass this data, as described in the sec-         because  the  value  saved  with the compiled pattern will obviously be
4011         tion on matching a pattern in the pcreapi documentation.         nonsense. A field in a pcre_extra() block is used to pass this data, as
4012           described  in the section on matching a pattern in the pcreapi documen-
4013           tation.
4014    
4015         If you did not provide custom character tables  when  the  pattern  was         If you did not provide custom character tables  when  the  pattern  was
4016         compiled,  the  pointer  in  the compiled pattern is NULL, which causes         compiled,  the  pointer  in  the compiled pattern is NULL, which causes
# Line 3411  RE-USING A PRECOMPILED PATTERN Line 4021  RE-USING A PRECOMPILED PATTERN
4021         your own pcre_extra data block and set the study_data field to point to         your own pcre_extra data block and set the study_data field to point to
4022         the  reloaded  study  data. You must also set the PCRE_EXTRA_STUDY_DATA         the  reloaded  study  data. You must also set the PCRE_EXTRA_STUDY_DATA
4023         bit in the flags field to indicate that study  data  is  present.  Then         bit in the flags field to indicate that study  data  is  present.  Then
4024         pass the pcre_extra block to pcre_exec() in the usual way.         pass  the  pcre_extra  block  to  pcre_exec() or pcre_dfa_exec() in the
4025           usual way.
4026    
4027    
4028  COMPATIBILITY WITH DIFFERENT PCRE RELEASES  COMPATIBILITY WITH DIFFERENT PCRE RELEASES
4029    
4030         The  layout  of the control block that is at the start of the data that         The layout of the control block that is at the start of the  data  that
4031         makes up a compiled pattern was changed for release 5.0.  If  you  have         makes  up  a  compiled pattern was changed for release 5.0. If you have
4032         any  saved  patterns  that  were compiled with previous releases (not a         any saved patterns that were compiled with  previous  releases  (not  a
4033         facility that was previously advertised), you will  have  to  recompile         facility  that  was  previously advertised), you will have to recompile
4034         them  for  release  5.0. However, from now on, it should be possible to         them for release 5.0. However, from now on, it should  be  possible  to
4035         make changes in a compabible manner.         make changes in a compabible manner.
4036    
4037  Last updated: 10 September 2004  Last updated: 28 February 2005
4038  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
4039  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
4040    
 PCRE(3)                                                                PCRE(3)  
   
4041    
4042    
4043  NAME  NAME
4044         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
4045    
4046    
4047  PCRE PERFORMANCE  PCRE PERFORMANCE
4048    
4049         Certain  items  that may appear in regular expression patterns are more         Certain  items  that may appear in regular expression patterns are more
# Line 3469  PCRE PERFORMANCE Line 4079  PCRE PERFORMANCE
4079    
4080         If you are using such a pattern with subject strings that do  not  con-         If you are using such a pattern with subject strings that do  not  con-
4081         tain newlines, the best performance is obtained by setting PCRE_DOTALL,         tain newlines, the best performance is obtained by setting PCRE_DOTALL,
4082         or starting the pattern with ^.* to indicate explicit  anchoring.  That         or starting the pattern with ^.* or ^.*? to indicate  explicit  anchor-
4083         saves  PCRE from having to scan along the subject looking for a newline         ing.  That saves PCRE from having to scan along the subject looking for
4084         to restart at.         a newline to restart at.
4085    
4086         Beware of patterns that contain nested indefinite  repeats.  These  can         Beware of patterns that contain nested indefinite  repeats.  These  can
4087         take  a  long time to run when applied to a string that does not match.         take  a  long time to run when applied to a string that does not match.
# Line 3492  PCRE PERFORMANCE Line 4102  PCRE PERFORMANCE
4102           (a+)*b           (a+)*b
4103    
4104         where a literal character follows. Before  embarking  on  the  standard         where a literal character follows. Before  embarking  on  the  standard
4105         matching  procedure,  PCRE  checks  that  there  is  a "b" later in the         matching  procedure,  PCRE checks that there is a "b" later in the sub-
4106         subject string, and if there is not, it fails  the  match  immediately.         ject string, and if there is not, it fails the match immediately.  How-
4107         However, when there is no following literal this optimization cannot be         ever,  when  there  is no following literal this optimization cannot be
4108         used. You can see the difference by comparing the behaviour of         used. You can see the difference by comparing the behaviour of
4109    
4110           (a+)*\d           (a+)*\d
# Line 3506  PCRE PERFORMANCE Line 4116  PCRE PERFORMANCE
4116         In many cases, the solution to this kind of performance issue is to use         In many cases, the solution to this kind of performance issue is to use
4117         an atomic group or a possessive quantifier.         an atomic group or a possessive quantifier.
4118    
4119  Last updated: 09 September 2004  Last updated: 28 February 2005
4120  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
4121  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
4122    
 PCRE(3)                                                                PCRE(3)  
   
4123    
4124    
4125  NAME  NAME
4126         PCRE - Perl-compatible regular expressions.         PCRE - Perl-compatible regular expressions.
4127    
4128    
4129  SYNOPSIS OF POSIX API  SYNOPSIS OF POSIX API
4130    
4131         #include <pcreposix.h>         #include <pcreposix.h>
# Line 3537  DESCRIPTION Line 4146  DESCRIPTION
4146    
4147         This  set  of  functions provides a POSIX-style API to the PCRE regular         This  set  of  functions provides a POSIX-style API to the PCRE regular
4148         expression package. See the pcreapi documentation for a description  of         expression package. See the pcreapi documentation for a description  of
4149         PCRE's native API, which contains additional functionality.         PCRE's native API, which contains much additional functionality.
4150    
4151         The functions described here are just wrapper functions that ultimately         The functions described here are just wrapper functions that ultimately
4152         call  the  PCRE  native  API.  Their  prototypes  are  defined  in  the         call  the  PCRE  native  API.  Their  prototypes  are  defined  in  the
# Line 3581  COMPILING A PATTERN Line 4190  COMPILING A PATTERN
4190         The argument cflags is either zero, or contains one or more of the bits         The argument cflags is either zero, or contains one or more of the bits
4191         defined by the following macros:         defined by the following macros:
4192    
4193             REG_DOTALL
4194    
4195           The PCRE_DOTALL option is set when the expression is passed for  compi-
4196           lation  to the native function. Note that REG_DOTALL is not part of the
4197           POSIX standard.
4198    
4199           REG_ICASE           REG_ICASE
4200    
4201         The PCRE_CASELESS option is set when the expression is passed for  com-         The PCRE_CASELESS option is set when the expression is passed for  com-
# Line 3692  MEMORY USAGE Line 4307  MEMORY USAGE
4307    
4308  AUTHOR  AUTHOR
4309    
4310         Philip Hazel <ph10@cam.ac.uk>         Philip Hazel
4311         University Computing Service,         University Computing Service,
4312         Cambridge CB2 3QG, England.         Cambridge CB2 3QG, England.
4313    
4314  Last updated: 07 September 2004  Last updated: 28 February 2005
4315  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
4316  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
4317    
4318  PCRE(3)                                                                PCRE(3)  
4319    
4320    NAME
4321           PCRE - Perl-compatible regular expressions.
4322    
4323    
4324    SYNOPSIS OF C++ WRAPPER
4325    
4326           #include <pcrecpp.h>
4327    
4328    
4329    DESCRIPTION
4330    
4331           The  C++  wrapper  for  PCRE was provided by Google Inc. This brief man
4332           page was constructed from the notes in the pcrecpp.h file, which should
4333           be consulted for further details.
4334    
4335    
4336    MATCHING INTERFACE
4337    
4338           The  "FullMatch" operation checks that supplied text matches a supplied
4339           pattern exactly. If pointer arguments are supplied, it  copies  matched
4340           sub-strings that match sub-patterns into them.
4341    
4342             Example: successful match
4343                pcrecpp::RE re("h.*o");
4344                re.FullMatch("hello");
4345    
4346             Example: unsuccessful match (requires full match):
4347                pcrecpp::RE re("e");
4348                !re.FullMatch("hello");
4349    
4350             Example: creating a temporary RE object:
4351                pcrecpp::RE("h.*o").FullMatch("hello");
4352    
4353           You  can pass in a "const char*" or a "string" for "text". The examples
4354           below tend to use a const char*. You can, as in the different  examples
4355           above,  store the RE object explicitly in a variable or use a temporary
4356           RE object. The examples below use one mode or  the  other  arbitrarily.
4357           Either could correctly be used for any of these examples.
4358    
4359           You must supply extra pointer arguments to extract matched subpieces.
4360    
4361             Example: extracts "ruby" into "s" and 1234 into "i"
4362                int i;
4363                string s;
4364                pcrecpp::RE re("(\\w+):(\\d+)");
4365                re.FullMatch("ruby:1234", &s, &i);
4366    
4367             Example: does not try to extract any extra sub-patterns
4368                re.FullMatch("ruby:1234", &s);
4369    
4370             Example: does not try to extract into NULL
4371                re.FullMatch("ruby:1234", NULL, &i);
4372    
4373             Example: integer overflow causes failure
4374                !re.FullMatch("ruby:1234567891234", NULL, &i);
4375    
4376             Example: fails because there aren't enough sub-patterns:
4377                !pcrecpp::RE("\\w+:\\d+").FullMatch("ruby:1234", &s);
4378    
4379             Example: fails because string cannot be stored in integer
4380                !pcrecpp::RE("(.*)").FullMatch("ruby", &i);
4381    
4382           The  provided  pointer  arguments can be pointers to any scalar numeric
4383           type, or one of:
4384    
4385              string        (matched piece is copied to string)
4386              StringPiece   (StringPiece is mutated to point to matched piece)
4387              T             (where "bool T::ParseFrom(const char*, int)" exists)
4388              NULL          (the corresponding matched sub-pattern is not copied)
4389    
4390           The function returns true iff all of the following conditions are  sat-
4391           isfied:
4392    
4393             a. "text" matches "pattern" exactly;
4394    
4395             b. The number of matched sub-patterns is >= number of supplied
4396                pointers;
4397    
4398             c. The "i"th argument has a suitable type for holding the
4399                string captured as the "i"th sub-pattern. If you pass in
4400                NULL for the "i"th argument, or pass fewer arguments than
4401                number of sub-patterns, "i"th captured sub-pattern is
4402                ignored.
4403    
4404           The  matching interface supports at most 16 arguments per call.  If you
4405           need   more,   consider    using    the    more    general    interface
4406           pcrecpp::RE::DoMatch. See pcrecpp.h for the signature for DoMatch.
4407    
4408    
4409    PARTIAL MATCHES
4410    
4411           You  can  use the "PartialMatch" operation when you want the pattern to
4412           match any substring of the text.
4413    
4414             Example: simple search for a string:
4415                pcrecpp::RE("ell").PartialMatch("hello");
4416    
4417             Example: find first number in a string:
4418                int number;
4419                pcrecpp::RE re("(\\d+)");
4420                re.PartialMatch("x*100 + 20", &number);
4421                assert(number == 100);
4422    
4423    
4424    UTF-8 AND THE MATCHING INTERFACE
4425    
4426           By default, pattern and text are plain text, one  byte  per  character.
4427           The  UTF8  flag,  passed  to  the  constructor, causes both pattern and
4428           string to be treated as UTF-8 text, still a byte stream but potentially
4429           multiple  bytes  per character. In practice, the text is likelier to be
4430           UTF-8 than the pattern, but the match returned may depend on  the  UTF8
4431           flag,  so  always use it when matching UTF8 text. For example, "." will
4432           match one byte normally but with UTF8 set may match up to  three  bytes
4433           of a multi-byte character.
4434    
4435             Example:
4436                pcrecpp::RE_Options options;
4437                options.set_utf8();
4438                pcrecpp::RE re(utf8_pattern, options);
4439                re.FullMatch(utf8_string);
4440    
4441             Example: using the convenience function UTF8():
4442                pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8());
4443                re.FullMatch(utf8_string);
4444    
4445           NOTE: The UTF8 flag is ignored if pcre was not configured with the
4446                 --enable-utf8 flag.
4447    
4448    
4449    SCANNING TEXT INCREMENTALLY
4450    
4451           The  "Consume"  operation may be useful if you want to repeatedly match
4452           regular expressions at the front of a string and skip over them as they
4453           match.  This requires use of the "StringPiece" type, which represents a
4454           sub-range of a real string. Like RE,  StringPiece  is  defined  in  the
4455           pcrecpp namespace.
4456    
4457             Example: read lines of the form "var = value" from a string.
4458                string contents = ...;                 // Fill string somehow
4459                pcrecpp::StringPiece input(contents);  // Wrap in a StringPiece
4460    
4461                string var;
4462                int value;
4463                pcrecpp::RE re("(\\w+) = (\\d+)\n");
4464                while (re.Consume(&input, &var, &value)) {
4465                  ...;
4466                }
4467    
4468           Each  successful  call  to  "Consume"  will  set  "var/value", and also
4469           advance "input" so it points past the matched text.
4470    
4471           The "FindAndConsume" operation is similar to  "Consume"  but  does  not
4472           anchor  your  match  at  the  beginning of the string. For example, you
4473           could extract all words from a string by repeatedly calling
4474    
4475             pcrecpp::RE("(\\w+)").FindAndConsume(&input, &word)
4476    
4477    
4478    PARSING HEX/OCTAL/C-RADIX NUMBERS
4479    
4480           By default, if you pass a pointer to a numeric value, the corresponding
4481           text  is  interpreted  as  a  base-10  number. You can instead wrap the
4482           pointer with a call to one of the operators Hex(), Octal(), or CRadix()
4483           to  interpret  the text in another base. The CRadix operator interprets
4484           C-style "0" (base-8) and  "0x"  (base-16)  prefixes,  but  defaults  to
4485           base-10.
4486    
4487             Example:
4488               int a, b, c, d;
4489               pcrecpp::RE re("(.*) (.*) (.*) (.*)");
4490               re.FullMatch("100 40 0100 0x40",
4491                            pcrecpp::Octal(&a), pcrecpp::Hex(&b),
4492                            pcrecpp::CRadix(&c), pcrecpp::CRadix(&d));
4493    
4494           will leave 64 in a, b, c, and d.
4495    
4496    
4497    REPLACING PARTS OF STRINGS
4498    
4499           You  can  replace the first match of "pattern" in "str" with "rewrite".
4500           Within "rewrite", backslash-escaped digits (\1 to \9) can  be  used  to
4501           insert  text  matching  corresponding parenthesized group from the pat-
4502           tern. \0 in "rewrite" refers to the entire matching text. For example:
4503    
4504             string s = "yabba dabba doo";
4505             pcrecpp::RE("b+").Replace("d", &s);
4506    
4507           will leave "s" containing "yada dabba doo". The result is true  if  the
4508           pattern matches and a replacement occurs, false otherwise.
4509    
4510           GlobalReplace  is  like Replace except that it replaces all occurrences
4511           of the pattern in the string with the  rewrite.  Replacements  are  not
4512           subject to re-matching. For example:
4513    
4514             string s = "yabba dabba doo";
4515             pcrecpp::RE("b+").GlobalReplace("d", &s);
4516    
4517           will  leave  "s"  containing  "yada dada doo". It returns the number of
4518           replacements made.
4519    
4520           Extract is like Replace, except that if the pattern matches,  "rewrite"
4521           is  copied into "out" (an additional argument) with substitutions.  The
4522           non-matching portions of "text" are ignored. Returns true iff  a  match
4523           occurred and the extraction happened successfully;  if no match occurs,
4524