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# 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    PCRE(3)                                                                PCRE(3)
11    
12    
13  NAME  NAME
14         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
15    
16    
17  INTRODUCTION  INTRODUCTION
18    
19         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
20         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
21         just  a  few  differences.  The current implementation of PCRE (release         just  a  few  differences.  The current implementation of PCRE (release
22         5.x) corresponds approximately with Perl  5.8,  including  support  for         6.x) corresponds approximately with Perl  5.8,  including  support  for
23         UTF-8 encoded strings and Unicode general category properties. However,         UTF-8 encoded strings and Unicode general category properties. However,
24         this support has to be explicitly enabled; it is not the default.         this support has to be explicitly enabled; it is not the default.
25    
26           In addition to the Perl-compatible matching function,  PCRE  also  con-
27           tains  an  alternative matching function that matches the same compiled
28           patterns in a different way. In certain circumstances, the  alternative
29           function  has  some  advantages.  For  a discussion of the two matching
30           algorithms, see the pcrematching page.
31    
32         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
33         have  written  wrappers and interfaces of various kinds. A C++ class is         have  written  wrappers and interfaces of various kinds. In particular,
34         included in these contributions, which can  be  found  in  the  Contrib         Google Inc.  have provided a comprehensive C++  wrapper.  This  is  now
35         directory at the primary FTP site, which is:         included as part of the PCRE distribution. The pcrecpp page has details
36           of this interface. Other people's contributions can  be  found  in  the
37           Contrib directory at the primary FTP site, which is:
38    
39         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre         ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre
40    
# Line 40  INTRODUCTION Line 49  INTRODUCTION
49         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
50         in the source distribution.         in the source distribution.
51    
52           The library contains a number of undocumented  internal  functions  and
53           data  tables  that  are  used by more than one of the exported external
54           functions, but which are not intended  for  use  by  external  callers.
55           Their  names  all begin with "_pcre_", which hopefully will not provoke
56           any name clashes.
57    
58    
59  USER DOCUMENTATION  USER DOCUMENTATION
60    
# Line 50  USER DOCUMENTATION Line 65  USER DOCUMENTATION
65         of searching. The sections are as follows:         of searching. The sections are as follows:
66    
67           pcre              this document           pcre              this document
68           pcreapi           details of PCRE's native API           pcreapi           details of PCRE's native C API
69           pcrebuild         options for building PCRE           pcrebuild         options for building PCRE
70           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
71           pcrecompat        discussion of Perl compatibility           pcrecompat        discussion of Perl compatibility
72             pcrecpp           details of the C++ wrapper
73           pcregrep          description of the pcregrep command           pcregrep          description of the pcregrep command
74             pcrematching      discussion of the two matching algorithms
75           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
76           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
77                               regular expressions                               regular expressions
78           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
79           pcreposix         the POSIX-compatible API           pcreposix         the POSIX-compatible C API
80           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
81           pcresample        discussion of the sample program           pcresample        discussion of the sample program
82           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
83    
84         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
85         each library function, listing its arguments and results.         each C library function, listing its arguments and results.
86    
87    
88  LIMITATIONS  LIMITATIONS
# Line 90  LIMITATIONS Line 107  LIMITATIONS
107         tern, is 200.         tern, is 200.
108    
109         The  maximum  length of a subject string is the largest positive number         The  maximum  length of a subject string is the largest positive number
110         that an integer variable can hold. However, PCRE uses recursion to han-         that an integer variable can hold. However, when using the  traditional
111         dle  subpatterns  and indefinite repetition. This means that the avail-         matching function, PCRE uses recursion to handle subpatterns and indef-
112         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
113         processed by certain patterns.         the size of a subject string that can be processed by certain patterns.
114    
115    
116  UTF-8 AND UNICODE PROPERTY SUPPORT  UTF-8 AND UNICODE PROPERTY SUPPORT
117    
118         From  release  3.3,  PCRE  has  had  some support for character strings         From release 3.3, PCRE has  had  some  support  for  character  strings
119         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
120         to  cover  most common requirements, and in release 5.0 additional sup-         to cover most common requirements, and in release 5.0  additional  sup-
121         port for Unicode general category properties was added.         port for Unicode general category properties was added.
122    
123         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
124         support  in  the  code,  and, in addition, you must call pcre_compile()         support in the code, and, in addition,  you  must  call  pcre_compile()
125         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
126         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
127         strings instead of just strings of bytes.         strings instead of just strings of bytes.
128    
129         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,
130         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
131         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
132         not be very large.         not be very large.
133    
134         If PCRE is built with Unicode character property support (which implies         If PCRE is built with Unicode character property support (which implies
135         UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-         UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-
136         ported.  The available properties that can be tested are limited to the         ported.  The available properties that can be tested are limited to the
137         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
138         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-
139         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
140         property support is included.         property support is included.
141    
142         The following comments apply when PCRE is running in UTF-8 mode:         The following comments apply when PCRE is running in UTF-8 mode:
143    
144         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
145         subjects are checked for validity on entry to the  relevant  functions.         subjects  are  checked for validity on entry to the relevant functions.
146         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
147         situations, you may already know  that  your  strings  are  valid,  and         situations,  you  may  already  know  that  your strings are valid, and
148         therefore want to skip these checks in order to improve performance. If         therefore want to skip these checks in order to improve performance. If
149         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,
150         PCRE  assumes  that  the  pattern or subject it is given (respectively)         PCRE assumes that the pattern or subject  it  is  given  (respectively)
151         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
152         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
153         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
154         crash.         crash.
155    
156         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
157         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
158         character  whose code number is the given hexadecimal number, for exam-         character whose code number is the given hexadecimal number, for  exam-
159         ple: \x{1234}. If a non-hexadecimal digit appears between  the  braces,         ple:  \x{1234}.  If a non-hexadecimal digit appears between the braces,
160         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
161         a literal, or within a character class.         a literal, or within a character class.
162    
163         3. The original hexadecimal escape sequence, \xhh, matches  a  two-byte         3.  The  original hexadecimal escape sequence, \xhh, matches a two-byte
164         UTF-8 character if the value is greater than 127.         UTF-8 character if the value is greater than 127.
165    
166         4.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-         4. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-
167         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
168    
169         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-
170         gle byte.         gle byte.
171    
172         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
173         mode, but its use can lead to some strange effects.         mode,  but  its  use can lead to some strange effects. This facility is
174           not available in the alternative matching function, pcre_dfa_exec().
175    
176         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
177         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 195  UTF-8 AND UNICODE PROPERTY SUPPORT
195    
196  AUTHOR  AUTHOR
197    
198         Philip Hazel <ph10@cam.ac.uk>         Philip Hazel
199         University Computing Service,         University Computing Service,
200         Cambridge CB2 3QG, England.         Cambridge CB2 3QG, England.
        Phone: +44 1223 334714  
201    
202  Last updated: 09 September 2004         Putting  an actual email address here seems to have been a spam magnet,
203  Copyright (c) 1997-2004 University of Cambridge.         so I've taken it away. If you want to email me, use my initial and sur-
204  -----------------------------------------------------------------------------         name, separated by a dot, at the domain ucs.cam.ac.uk.
205    
206  PCRE(3)                                                                PCRE(3)  Last updated: 07 March 2005
207    Copyright (c) 1997-2005 University of Cambridge.
208    ------------------------------------------------------------------------------
209    
210    
211    PCREBUILD(3)                                                      PCREBUILD(3)
212    
213    
214  NAME  NAME
215         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
216    
217    
218  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
219    
220         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 309  POSIX MALLOC USAGE
309  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
310    
311         Internally,  PCRE has a function called match(), which it calls repeat-         Internally,  PCRE has a function called match(), which it calls repeat-
312         edly (possibly recursively) when matching a pattern. By controlling the         edly  (possibly  recursively)  when  matching  a   pattern   with   the
313         maximum  number  of  times  this function may be called during a single         pcre_exec()  function.  By controlling the maximum number of times this
314         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
315         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
316         described in the pcreapi documentation. The default is 10 million,  but         limit can be changed at run time, as described in the pcreapi  documen-
317         this can be changed by adding a setting such as         tation.  The default is 10 million, but this can be changed by adding a
318           setting such as
319    
320           --with-match-limit=500000           --with-match-limit=500000
321    
322         to the configure command.         to  the  configure  command.  This  setting  has  no  effect   on   the
323           pcre_dfa_exec() matching function.
324    
325    
326  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
# Line 324  HANDLING VERY LARGE PATTERNS Line 348  HANDLING VERY LARGE PATTERNS
348    
349  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
350    
351         PCRE  implements  backtracking while matching by making recursive calls         When matching with the pcre_exec() function, PCRE implements backtrack-
352         to an internal function called match(). In environments where the  size         ing by making recursive calls to an internal function  called  match().
353         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-
354         Unix environment does not usually suffer from this problem.) An  alter-         verely limit PCRE's operation. (The Unix environment does  not  usually
355         native  approach  that  uses  memory  from  the  heap to remember data,         suffer  from  this  problem.)  An alternative approach that uses memory
356         instead of using recursive function calls, has been implemented to work         from the heap to remember data, instead  of  using  recursive  function
357         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
358         this way, add         build a version of PCRE that works this way, add
359    
360           --disable-stack-for-recursion           --disable-stack-for-recursion
361    
# Line 342  AVOIDING EXCESSIVE STACK USAGE Line 366  AVOIDING EXCESSIVE STACK USAGE
366         the blocks are always freed in reverse order. A calling  program  might         the blocks are always freed in reverse order. A calling  program  might
367         be  able  to implement optimized functions that perform better than the         be  able  to implement optimized functions that perform better than the
368         standard malloc() and  free()  functions.  PCRE  runs  noticeably  more         standard malloc() and  free()  functions.  PCRE  runs  noticeably  more
369         slowly when built in this way.         slowly when built in this way. This option affects only the pcre_exec()
370           function; it is not relevant for the the pcre_dfa_exec() function.
371    
372    
373  USING EBCDIC CODE  USING EBCDIC CODE
374    
375         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
376         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).
377         PCRE  can,  however,  be  compiled  to  run in an EBCDIC environment by         PCRE can, however, be compiled to  run  in  an  EBCDIC  environment  by
378         adding         adding
379    
380           --enable-ebcdic           --enable-ebcdic
381    
382         to the configure command.         to the configure command.
383    
384  Last updated: 09 September 2004  Last updated: 28 February 2005
385  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
386  -----------------------------------------------------------------------------  ------------------------------------------------------------------------------
387    
 PCRE(3)                                                                PCRE(3)  
388    
389    PCREMATCHING(3)                                                PCREMATCHING(3)
390    
391    
392  NAME  NAME
393         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
394    
395    
396    PCRE MATCHING ALGORITHMS
397    
398           This document describes the two different algorithms that are available
399           in PCRE for matching a compiled regular expression against a given sub-
400           ject  string.  The  "standard"  algorithm  is  the  one provided by the
401           pcre_exec() function.  This works in the same was  as  Perl's  matching
402           function, and provides a Perl-compatible matching operation.
403    
404           An  alternative  algorithm is provided by the pcre_dfa_exec() function;
405           this operates in a different way, and is not  Perl-compatible.  It  has
406           advantages  and disadvantages compared with the standard algorithm, and
407           these are described below.
408    
409           When there is only one possible way in which a given subject string can
410           match  a pattern, the two algorithms give the same answer. A difference
411           arises, however, when there are multiple possibilities. For example, if
412           the pattern
413    
414             ^<.*>
415    
416           is matched against the string
417    
418             <something> <something else> <something further>
419    
420           there are three possible answers. The standard algorithm finds only one
421           of them, whereas the DFA algorithm finds all three.
422    
423    
424    REGULAR EXPRESSIONS AS TREES
425    
426           The set of strings that are matched by a regular expression can be rep-
427           resented  as  a  tree structure. An unlimited repetition in the pattern
428           makes the tree of infinite size, but it is still a tree.  Matching  the
429           pattern  to a given subject string (from a given starting point) can be
430           thought of as a search of the tree.  There are  two  standard  ways  to
431           search  a  tree: depth-first and breadth-first, and these correspond to
432           the two matching algorithms provided by PCRE.
433    
434    
435    THE STANDARD MATCHING ALGORITHM
436    
437           In the terminology of Jeffrey Friedl's book Mastering  Regular  Expres-
438           sions,  the  standard  algorithm  is  an "NFA algorithm". It conducts a
439           depth-first search of the pattern tree. That is, it  proceeds  along  a
440           single path through the tree, checking that the subject matches what is
441           required. When there is a mismatch, the algorithm  tries  any  alterna-
442           tives  at  the  current point, and if they all fail, it backs up to the
443           previous branch point in the  tree,  and  tries  the  next  alternative
444           branch  at  that  level.  This often involves backing up (moving to the
445           left) in the subject string as well.  The  order  in  which  repetition
446           branches  are  tried  is controlled by the greedy or ungreedy nature of
447           the quantifier.
448    
449           If a leaf node is reached, a matching string has  been  found,  and  at
450           that  point the algorithm stops. Thus, if there is more than one possi-
451           ble match, this algorithm returns the first one that it finds.  Whether
452           this  is the shortest, the longest, or some intermediate length depends
453           on the way the greedy and ungreedy repetition quantifiers are specified
454           in the pattern.
455    
456           Because  it  ends  up  with a single path through the tree, it is rela-
457           tively straightforward for this algorithm to keep  track  of  the  sub-
458           strings  that  are  matched  by portions of the pattern in parentheses.
459           This provides support for capturing parentheses and back references.
460    
461    
462    THE DFA MATCHING ALGORITHM
463    
464           DFA stands for "deterministic finite automaton", but you do not need to
465           understand the origins of that name. This algorithm conducts a breadth-
466           first search of the tree. Starting from the first matching point in the
467           subject,  it scans the subject string from left to right, once, charac-
468           ter by character, and as it does  this,  it  remembers  all  the  paths
469           through the tree that represent valid matches.
470    
471           The  scan  continues until either the end of the subject is reached, or
472           there are no more unterminated paths. At this point,  terminated  paths
473           represent  the different matching possibilities (if there are none, the
474           match has failed).  Thus, if there is more  than  one  possible  match,
475           this algorithm finds all of them, and in particular, it finds the long-
476           est. In PCRE, there is an option to stop the algorithm after the  first
477           match (which is necessarily the shortest) has been found.
478    
479           Note that all the matches that are found start at the same point in the
480           subject. If the pattern
481    
482             cat(er(pillar)?)
483    
484           is matched against the string "the caterpillar catchment",  the  result
485           will  be the three strings "cat", "cater", and "caterpillar" that start
486           at the fourth character of the subject. The algorithm does not automat-
487           ically move on to find matches that start at later positions.
488    
489           There are a number of features of PCRE regular expressions that are not
490           supported by the DFA matching algorithm. They are as follows:
491    
492           1. Because the algorithm finds all  possible  matches,  the  greedy  or
493           ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
494           ungreedy quantifiers are treated in exactly the same way.
495    
496           2. When dealing with multiple paths through the tree simultaneously, it
497           is  not  straightforward  to  keep track of captured substrings for the
498           different matching possibilities, and  PCRE's  implementation  of  this
499           algorithm does not attempt to do this. This means that no captured sub-
500           strings are available.
501    
502           3. Because no substrings are captured, back references within the  pat-
503           tern are not supported, and cause errors if encountered.
504    
505           4.  For  the same reason, conditional expressions that use a backrefer-
506           ence as the condition are not supported.
507    
508           5. Callouts are supported, but the value of the  capture_top  field  is
509           always 1, and the value of the capture_last field is always -1.
510    
511           6.  The \C escape sequence, which (in the standard algorithm) matches a
512           single byte, even in UTF-8 mode, is not supported because the DFA algo-
513           rithm moves through the subject string one character at a time, for all
514           active paths through the tree.
515    
516    
517    ADVANTAGES OF THE DFA ALGORITHM
518    
519           Using the DFA matching algorithm provides the following advantages:
520    
521           1. All possible matches (at a single point in the subject) are automat-
522           ically  found,  and  in particular, the longest match is found. To find
523           more than one match using the standard algorithm, you have to do kludgy
524           things with callouts.
525    
526           2.  There is much better support for partial matching. The restrictions
527           on the content of the pattern that apply when using the standard  algo-
528           rithm  for partial matching do not apply to the DFA algorithm. For non-
529           anchored patterns, the starting position of a partial match  is  avail-
530           able.
531    
532           3.  Because  the  DFA algorithm scans the subject string just once, and
533           never needs to backtrack, it is possible  to  pass  very  long  subject
534           strings  to  the matching function in several pieces, checking for par-
535           tial matching each time.
536    
537    
538    DISADVANTAGES OF THE DFA ALGORITHM
539    
540           The DFA algorithm suffers from a number of disadvantages:
541    
542           1. It is substantially slower than  the  standard  algorithm.  This  is
543           partly  because  it has to search for all possible matches, but is also
544           because it is less susceptible to optimization.
545    
546           2. Capturing parentheses and back references are not supported.
547    
548           3. The "atomic group" feature of PCRE regular expressions is supported,
549           but  does not provide the advantage that it does for the standard algo-
550           rithm.
551    
552    Last updated: 28 February 2005
553    Copyright (c) 1997-2005 University of Cambridge.
554    ------------------------------------------------------------------------------
555    
556    
557    PCREAPI(3)                                                          PCREAPI(3)
558    
559    
560    NAME
561           PCRE - Perl-compatible regular expressions
562    
563    
564  PCRE NATIVE API  PCRE NATIVE API
565    
566         #include <pcre.h>         #include <pcre.h>
# Line 375  PCRE NATIVE API Line 569  PCRE NATIVE API
569              const char **errptr, int *erroffset,              const char **errptr, int *erroffset,
570              const unsigned char *tableptr);              const unsigned char *tableptr);
571    
572           pcre *pcre_compile2(const char *pattern, int options,
573                int *errorcodeptr,
574                const char **errptr, int *erroffset,
575                const unsigned char *tableptr);
576    
577         pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options,
578              const char **errptr);              const char **errptr);
579    
# Line 382  PCRE NATIVE API Line 581  PCRE NATIVE API
581              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
582              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
583    
584           int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
585                const char *subject, int length, int startoffset,
586                int options, int *ovector, int ovecsize,
587                int *workspace, int wscount);
588    
589         int pcre_copy_named_substring(const pcre *code,         int pcre_copy_named_substring(const pcre *code,
590              const char *subject, int *ovector,              const char *subject, int *ovector,
591              int stringcount, const char *stringname,              int stringcount, const char *stringname,
# Line 417  PCRE NATIVE API Line 621  PCRE NATIVE API
621    
622         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
623    
624           int pcre_refcount(pcre *code, int adjust);
625    
626         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
627    
628         char *pcre_version(void);         char *pcre_version(void);
# Line 436  PCRE API OVERVIEW Line 642  PCRE API OVERVIEW
642    
643         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
644         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
645         expression API.  These are described in the pcreposix documentation.         expression  API.  These  are  described in the pcreposix documentation.
646           Both of these APIs define a set of C function calls. A C++  wrapper  is
647           distributed with PCRE. It is documented in the pcrecpp page.
648    
649         The  native  API  function  prototypes  are  defined in the header file         The  native  API  C  function prototypes are defined in the header file
650         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
651         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
652         application  that  uses  PCRE.  The  header  file  defines  the  macros         application  that  uses  PCRE.  The  header  file  defines  the  macros
653         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-
654         bers for the library.  Applications can use these  to  include  support         bers for the library.  Applications can use these  to  include  support
655         for different releases of PCRE.         for different releases of PCRE.
656    
657         The  functions  pcre_compile(),  pcre_study(), and pcre_exec() are used         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
658         for compiling and matching regular expressions. A sample  program  that         pcre_exec() are used for compiling and matching regular expressions  in
659         demonstrates  the  simplest  way  of using them is provided in the file         a  Perl-compatible  manner. A sample program that demonstrates the sim-
660         called pcredemo.c in the source distribution. The pcresample documenta-         plest way of using them is provided in the file  called  pcredemo.c  in
661         tion describes how to run it.         the  source distribution. The pcresample documentation describes how to
662           run it.
663         In  addition  to  the  main compiling and matching functions, there are  
664         convenience functions for extracting captured substrings from a matched         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
665         subject string.  They are:         ble,  is  also provided. This uses a different algorithm for the match-
666           ing. This allows it to find all possible matches (at a given  point  in
667           the  subject),  not  just  one. However, this algorithm does not return
668           captured substrings. A description of the two matching  algorithms  and
669           their  advantages  and disadvantages is given in the pcrematching docu-
670           mentation.
671    
672           In addition to the main compiling and  matching  functions,  there  are
673           convenience functions for extracting captured substrings from a subject
674           string that is matched by pcre_exec(). They are:
675    
676           pcre_copy_substring()           pcre_copy_substring()
677           pcre_copy_named_substring()           pcre_copy_named_substring()
# Line 466  PCRE API OVERVIEW Line 683  PCRE API OVERVIEW
683         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
684         to free the memory used for extracted strings.         to free the memory used for extracted strings.
685    
686         The function pcre_maketables() is used to  build  a  set  of  character         The  function  pcre_maketables()  is  used  to build a set of character
687         tables   in  the  current  locale  for  passing  to  pcre_compile()  or         tables  in  the  current  locale   for   passing   to   pcre_compile(),
688         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
689         cialist use. Most commonly, no special tables are passed, in which case         provided for specialist use.  Most  commonly,  no  special  tables  are
690         internal tables that are generated when PCRE is built are used.         passed,  in  which case internal tables that are generated when PCRE is
691           built are used.
692    
693         The function pcre_fullinfo() is used to find out  information  about  a         The function pcre_fullinfo() is used to find out  information  about  a
694         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 696  PCRE API OVERVIEW
696         patibility.   The function pcre_version() returns a pointer to a string         patibility.   The function pcre_version() returns a pointer to a string
697         containing the version of PCRE and its date of release.         containing the version of PCRE and its date of release.
698    
699           The function pcre_refcount() maintains a  reference  count  in  a  data
700           block  containing  a compiled pattern. This is provided for the benefit
701           of object-oriented applications.
702    
703         The global variables pcre_malloc and pcre_free  initially  contain  the         The global variables pcre_malloc and pcre_free  initially  contain  the
704         entry  points  of  the  standard malloc() and free() functions, respec-         entry  points  of  the  standard malloc() and free() functions, respec-
705         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 709  PCRE API OVERVIEW
709         The global variables pcre_stack_malloc  and  pcre_stack_free  are  also         The global variables pcre_stack_malloc  and  pcre_stack_free  are  also
710         indirections  to  memory  management functions. These special functions         indirections  to  memory  management functions. These special functions
711         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
712         data,  instead  of recursive function calls. This is a non-standard way         data, instead of recursive function calls, when running the pcre_exec()
713         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-
714         Because  of  the greater use of memory management, it runs more slowly.         ronments that have limited stacks. Because of the greater use of memory
715         Separate functions are provided so that special-purpose  external  code         management, it runs more slowly.  Separate functions  are  provided  so
716         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
717         in a stack-like manner (last obtained, first  freed),  and  always  for         used, these functions are always called in a  stack-like  manner  (last
718         memory blocks of the same size.         obtained,  first freed), and always for memory blocks of the same size.
719    
720         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
721         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
722         specified  points during a matching operation. Details are given in the         specified points during a matching operation. Details are given in  the
723         pcrecallout documentation.         pcrecallout documentation.
724    
725    
726  MULTITHREADING  MULTITHREADING
727    
728         The PCRE functions can be used in  multi-threading  applications,  with         The  PCRE  functions  can be used in multi-threading applications, with
729         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
730         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
731         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
732    
733         The compiled form of a regular expression is not altered during  match-         The  compiled form of a regular expression is not altered during match-
734         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
735         at once.         at once.
736    
# Line 516  MULTITHREADING Line 738  MULTITHREADING
738  SAVING PRECOMPILED PATTERNS FOR LATER USE  SAVING PRECOMPILED PATTERNS FOR LATER USE
739    
740         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
741         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
742         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
743         pcreprecompile documentation.         pcreprecompile documentation.
744    
745    
# Line 525  CHECKING BUILD-TIME OPTIONS Line 747  CHECKING BUILD-TIME OPTIONS
747    
748         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
749    
750         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-
751         cover which optional features have been compiled into the PCRE library.         cover which optional features have been compiled into the PCRE library.
752         The  pcrebuild documentation has more details about these optional fea-         The pcrebuild documentation has more details about these optional  fea-
753         tures.         tures.
754    
755         The first argument for pcre_config() is an  integer,  specifying  which         The  first  argument  for pcre_config() is an integer, specifying which
756         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
757         into which the information is  placed.  The  following  information  is         into  which  the  information  is  placed. The following information is
758         available:         available:
759    
760           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
761    
762         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-
763         able; otherwise it is set to zero.         able; otherwise it is set to zero.
764    
765           PCRE_CONFIG_UNICODE_PROPERTIES           PCRE_CONFIG_UNICODE_PROPERTIES
766    
767         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
768         character properties is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
769    
770           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
771    
772         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
773         used for the newline character. It is either linefeed (10) or  carriage         used  for the newline character. It is either linefeed (10) or carriage
774         return  (13),  and  should  normally be the standard character for your         return (13), and should normally be the  standard  character  for  your
775         operating system.         operating system.
776    
777           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
778    
779         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
780         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
781         4. Larger values allow larger regular expressions to  be  compiled,  at         4.  Larger  values  allow larger regular expressions to be compiled, at
782         the  expense  of  slower matching. The default value of 2 is sufficient         the expense of slower matching. The default value of  2  is  sufficient
783         for all but the most massive patterns, since  it  allows  the  compiled         for  all  but  the  most massive patterns, since it allows the compiled
784         pattern to be up to 64K in size.         pattern to be up to 64K in size.
785    
786           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
787    
788         The  output  is  an integer that contains the threshold above which the         The output is an integer that contains the threshold  above  which  the
789         POSIX interface uses malloc() for output vectors. Further  details  are         POSIX  interface  uses malloc() for output vectors. Further details are
790         given in the pcreposix documentation.         given in the pcreposix documentation.
791    
792           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
793    
794         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
795         internal matching function calls in a  pcre_exec()  execution.  Further         internal  matching  function  calls in a pcre_exec() execution. Further
796         details are given with pcre_exec() below.         details are given with pcre_exec() below.
797    
798           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
799    
800         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
801         implemented by recursive function calls that use the stack to  remember         running pcre_exec() is implemented by recursive function calls that use
802         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
803         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
804         recursive   function   calls.   In  this  case,  pcre_stack_malloc  and         on the  heap  instead  of  recursive  function  calls.  In  this  case,
805         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
806         avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
807    
808    
809  COMPILING A PATTERN  COMPILING A PATTERN
# Line 590  COMPILING A PATTERN Line 812  COMPILING A PATTERN
812              const char **errptr, int *erroffset,              const char **errptr, int *erroffset,
813              const unsigned char *tableptr);              const unsigned char *tableptr);
814    
815         The  function  pcre_compile()  is  called  to compile a pattern into an         pcre *pcre_compile2(const char *pattern, int options,
816         internal form. The pattern is a C string terminated by a  binary  zero,              int *errorcodeptr,
817         and  is  passed in the pattern argument. A pointer to a single block of              const char **errptr, int *erroffset,
818         memory that is obtained via pcre_malloc is returned. This contains  the              const unsigned char *tableptr);
        compiled  code  and  related  data.  The  pcre  type is defined for the  
        returned block; this is a typedef for a structure  whose  contents  are  
        not  externally defined. It is up to the caller to free the memory when  
        it is no longer required.  
819    
820         Although the compiled code of a PCRE regex is relocatable, that is,  it         Either of the functions pcre_compile() or pcre_compile2() can be called
821           to compile a pattern into an internal form. The only difference between
822           the two interfaces is that pcre_compile2() has an additional  argument,
823           errorcodeptr, via which a numerical error code can be returned.
824    
825           The pattern is a C string terminated by a binary zero, and is passed in
826           the pattern argument. A pointer to a single block  of  memory  that  is
827           obtained  via  pcre_malloc is returned. This contains the compiled code
828           and related data. The pcre type is defined for the returned block; this
829           is a typedef for a structure whose contents are not externally defined.
830           It is up to the caller  to  free  the  memory  when  it  is  no  longer
831           required.
832    
833           Although  the compiled code of a PCRE regex is relocatable, that is, it
834         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
835         fully relocatable, because it may contain a copy of the tableptr  argu-         fully  relocatable, because it may contain a copy of the tableptr argu-
836         ment, which is an address (see below).         ment, which is an address (see below).
837    
838         The options argument contains independent bits that affect the compila-         The options argument contains independent bits that affect the compila-
839         tion. It should be zero if  no  options  are  required.  The  available         tion.  It  should  be  zero  if  no options are required. The available
840         options  are  described  below. Some of them, in particular, those that         options are described below. Some of them, in  particular,  those  that
841         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
842         pattern  (see  the  detailed  description in the pcrepattern documenta-         pattern (see the detailed description  in  the  pcrepattern  documenta-
843         tion). For these options, the contents of the options  argument  speci-         tion).  For  these options, the contents of the options argument speci-
844         fies  their initial settings at the start of compilation and execution.         fies their initial settings at the start of compilation and  execution.
845         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
846         at compile time.         at compile time.
847    
848         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
849         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
850         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-
851         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
852         the  error  was  discovered  is  placed  in  the variable pointed to by         the error was discovered is  placed  in  the  variable  pointed  to  by
853         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
854         given.         given.
855    
856           If pcre_compile2() is used instead of pcre_compile(),  and  the  error-
857           codeptr  argument is not NULL, a non-zero error code number is returned
858           via this argument in the event of an error. This is in addition to  the
859           textual error message. Error codes and messages are listed below.
860    
861         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
862         character tables that are  built  when  PCRE  is  compiled,  using  the         character tables that are  built  when  PCRE  is  compiled,  using  the
863         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 900  COMPILING A PATTERN
900    
901         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
902         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
903         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
904         UTF-8 mode, case support for high-valued characters is  available  only         always understands the concept of case for characters whose values  are
905         when PCRE is built with Unicode character property support.         less  than 128, so caseless matching is always possible. For characters
906           with higher values, the concept of case is supported if  PCRE  is  com-
907           piled  with Unicode property support, but not otherwise. If you want to
908           use caseless matching for characters 128 and  above,  you  must  ensure
909           that  PCRE  is  compiled  with Unicode property support as well as with
910           UTF-8 support.
911    
912           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
913    
914         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
915         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
916         matches  immediately before the final character if it is a newline (but         matches immediately before the final character if it is a newline  (but
917         not before any  other  newlines).  The  PCRE_DOLLAR_ENDONLY  option  is         not  before  any  other  newlines).  The  PCRE_DOLLAR_ENDONLY option is
918         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
919         in Perl, and no way to set it within a pattern.         in Perl, and no way to set it within a pattern.
920    
921           PCRE_DOTALL           PCRE_DOTALL
922    
923         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-
924         acters,  including  newlines.  Without  it, newlines are excluded. This         acters, including newlines. Without it,  newlines  are  excluded.  This
925         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
926         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]
927         always matches a newline character, independent of the setting of  this         always  matches a newline character, independent of the setting of this
928         option.         option.
929    
930           PCRE_EXTENDED           PCRE_EXTENDED
931    
932         If  this  bit  is  set,  whitespace  data characters in the pattern are         If this bit is set, whitespace  data  characters  in  the  pattern  are
933         totally ignored except  when  escaped  or  inside  a  character  class.         totally ignored except when escaped or inside a character class. White-
934         Whitespace  does  not  include the VT character (code 11). In addition,         space does not include the VT character (code 11). In addition, charac-
935         characters between an unescaped # outside a  character  class  and  the         ters between an unescaped # outside a character class and the next new-
936         next newline character, inclusive, are also ignored. This is equivalent         line character, inclusive, are also  ignored.  This  is  equivalent  to
937         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)
938         option setting.         option setting.
939    
940         This  option  makes  it possible to include comments inside complicated         This option makes it possible to include  comments  inside  complicated
941         patterns.  Note, however, that this applies only  to  data  characters.         patterns.   Note,  however,  that this applies only to data characters.
942         Whitespace   characters  may  never  appear  within  special  character         Whitespace  characters  may  never  appear  within  special   character
943         sequences in a pattern, for  example  within  the  sequence  (?(  which         sequences  in  a  pattern,  for  example  within the sequence (?( which
944         introduces a conditional subpattern.         introduces a conditional subpattern.
945    
946           PCRE_EXTRA           PCRE_EXTRA
947    
948         This  option  was invented in order to turn on additional functionality         This option was invented in order to turn on  additional  functionality
949         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
950         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
951         letter that has no special meaning  causes  an  error,  thus  reserving         letter  that  has  no  special  meaning causes an error, thus reserving
952         these  combinations  for  future  expansion.  By default, as in Perl, a         these combinations for future expansion. By  default,  as  in  Perl,  a
953         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
954         literal.  There  are  at  present  no other features controlled by this         literal. There are at present no  other  features  controlled  by  this
955         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.
956    
957             PCRE_FIRSTLINE
958    
959           If  this  option  is  set,  an  unanchored pattern is required to match
960           before or at the first newline character in the subject string,  though
961           the matched text may continue over the newline.
962    
963           PCRE_MULTILINE           PCRE_MULTILINE
964    
965         By default, PCRE treats the subject string as consisting  of  a  single         By  default,  PCRE  treats the subject string as consisting of a single
966         line  of characters (even if it actually contains newlines). The "start         line of characters (even if it actually contains newlines). The  "start
967         of line" metacharacter (^) matches only at the  start  of  the  string,         of  line"  metacharacter  (^)  matches only at the start of the string,
968         while  the  "end  of line" metacharacter ($) matches only at the end of         while the "end of line" metacharacter ($) matches only at  the  end  of
969         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
970         is set). This is the same as Perl.         is set). This is the same as Perl.
971    
972         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"
973         constructs match immediately following or immediately before  any  new-         constructs  match  immediately following or immediately before any new-
974         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
975         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
976         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-
977         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,
978         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
979    
980           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
981    
982         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-
983         theses in the pattern. Any opening parenthesis that is not followed  by         theses  in the pattern. Any opening parenthesis that is not followed by
984         ?  behaves as if it were followed by ?: but named parentheses can still         ? behaves as if it were followed by ?: but named parentheses can  still
985         be used for capturing (and they acquire  numbers  in  the  usual  way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
986         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
987    
988           PCRE_UNGREEDY           PCRE_UNGREEDY
989    
990         This  option  inverts  the "greediness" of the quantifiers so that they         This option inverts the "greediness" of the quantifiers  so  that  they
991         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
992         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
993         within the pattern.         within the pattern.
994    
995           PCRE_UTF8           PCRE_UTF8
996    
997         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
998         strings  of  UTF-8 characters instead of single-byte character strings.         strings of UTF-8 characters instead of single-byte  character  strings.
999         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-
1000         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
1001         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
1002         UTF-8 support in the main pcre page.         UTF-8 support in the main pcre page.
1003    
1004           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1005    
1006         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
1007         automatically checked. If an invalid UTF-8 sequence of bytes is  found,         automatically  checked. If an invalid UTF-8 sequence of bytes is found,
1008         pcre_compile()  returns an error. If you already know that your pattern         pcre_compile() returns an error. If you already know that your  pattern
1009         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
1010         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
1011         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
1012         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
1013         pcre_exec(),  to  suppress  the  UTF-8  validity  checking  of  subject         pcre_exec()  and pcre_dfa_exec(), to suppress the UTF-8 validity check-
1014         strings.         ing of subject strings.
1015    
1016    
1017    COMPILATION ERROR CODES
1018    
1019           The following table lists the error  codes  than  may  be  returned  by
1020           pcre_compile2(),  along with the error messages that may be returned by
1021           both compiling functions.
1022    
1023              0  no error
1024              1  \ at end of pattern
1025              2  \c at end of pattern
1026              3  unrecognized character follows \
1027              4  numbers out of order in {} quantifier
1028              5  number too big in {} quantifier
1029              6  missing terminating ] for character class
1030              7  invalid escape sequence in character class
1031              8  range out of order in character class
1032              9  nothing to repeat
1033             10  operand of unlimited repeat could match the empty string
1034             11  internal error: unexpected repeat
1035             12  unrecognized character after (?
1036             13  POSIX named classes are supported only within a class
1037             14  missing )
1038             15  reference to non-existent subpattern
1039             16  erroffset passed as NULL
1040             17  unknown option bit(s) set
1041             18  missing ) after comment
1042             19  parentheses nested too deeply
1043             20  regular expression too large
1044             21  failed to get memory
1045             22  unmatched parentheses
1046             23  internal error: code overflow
1047             24  unrecognized character after (?<
1048             25  lookbehind assertion is not fixed length
1049             26  malformed number after (?(
1050             27  conditional group contains more than two branches
1051             28  assertion expected after (?(
1052             29  (?R or (?digits must be followed by )
1053             30  unknown POSIX class name
1054             31  POSIX collating elements are not supported
1055             32  this version of PCRE is not compiled with PCRE_UTF8 support
1056             33  spare error
1057             34  character value in \x{...} sequence is too large
1058             35  invalid condition (?(0)
1059             36  \C not allowed in lookbehind assertion
1060             37  PCRE does not support \L, \l, \N, \U, or \u
1061             38  number after (?C is > 255
1062             39  closing ) for (?C expected
1063             40  recursive call could loop indefinitely
1064             41  unrecognized character after (?P
1065             42  syntax error after (?P
1066             43  two named groups have the same name
1067             44  invalid UTF-8 string
1068             45  support for \P, \p, and \X has not been compiled
1069             46  malformed \P or \p sequence
1070             47  unknown property name after \P or \p
1071    
1072    
1073  STUDYING A PATTERN  STUDYING A PATTERN
1074    
1075         pcre_extra *pcre_study(const pcre *code, int options,         pcre_extra *pcre_study(const pcre *code, int options
1076              const char **errptr);              const char **errptr);
1077    
1078         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
1079         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
1080         matching.  The function pcre_study() takes a pointer to a compiled pat-         matching. The function pcre_study() takes a pointer to a compiled  pat-
1081         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1082         information  that  will  help speed up matching, pcre_study() returns a         information that will help speed up matching,  pcre_study()  returns  a
1083         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
1084         the results of the study.         the results of the study.
1085    
1086         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1087         pcre_exec(). However, a pcre_extra block  also  contains  other  fields         pcre_exec().  However,  a  pcre_extra  block also contains other fields
1088         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
1089         described below in the section on matching a pattern.         described below in the section on matching a pattern.
1090    
1091         If studying the pattern does not produce  any  additional  information,         If  studying  the  pattern  does not produce any additional information
1092         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1093         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
1094         its own pcre_extra block.         its own pcre_extra block.
1095    
1096         The  second  argument of pcre_study() contains option bits. At present,         The second argument of pcre_study() contains option bits.  At  present,
1097         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1098    
1099         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.
1100         If  studying  succeeds  (even  if no data is returned), the variable it         If studying succeeds (even if no data is  returned),  the  variable  it
1101         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-
1102         sage.  You should therefore test the error pointer for NULL after call-         sage. You should therefore test the error pointer for NULL after  call-
1103         ing pcre_study(), to be sure that it has run successfully.         ing pcre_study(), to be sure that it has run successfully.
1104    
1105         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 808  STUDYING A PATTERN Line 1111  STUDYING A PATTERN
1111             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1112    
1113         At present, studying a pattern is useful only for non-anchored patterns         At present, studying a pattern is useful only for non-anchored patterns
1114         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-
1115         ble starting bytes is created.         ble starting bytes is created.
1116    
1117    
1118  LOCALE SUPPORT  LOCALE SUPPORT
1119    
1120         PCRE handles caseless matching, and determines whether  characters  are         PCRE  handles  caseless matching, and determines whether characters are
1121         letters,  digits, or whatever, by reference to a set of tables, indexed         letters digits, or whatever, by reference to a set of  tables,  indexed
1122         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
1123         characters  with  codes  less than 128. Higher-valued codes never match         characters with codes less than 128. Higher-valued  codes  never  match
1124         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
1125         with Unicode character property support.)         with Unicode character property support.
1126    
1127         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
1128         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
1129         NULL,  and  is  sufficient for many applications. An alternative set of         NULL, and is sufficient for many applications. An  alternative  set  of
1130         tables can, however, be supplied. These may be created in  a  different         tables  can,  however, be supplied. These may be created in a different
1131         locale  from the default. As more and more applications change to using         locale from the default. As more and more applications change to  using
1132         Unicode, the need for this locale support is expected to die away.         Unicode, the need for this locale support is expected to die away.
1133    
1134         External tables are built by calling  the  pcre_maketables()  function,         External  tables  are  built by calling the pcre_maketables() function,
1135         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
1136         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
1137         example,  to  build  and use tables that are appropriate for the French         example, to build and use tables that are appropriate  for  the  French
1138         locale (where accented characters with  values  greater  than  128  are         locale  (where  accented  characters  with  values greater than 128 are
1139         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1140    
1141           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1142           tables = pcre_maketables();           tables = pcre_maketables();
1143           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1144    
1145         When  pcre_maketables()  runs,  the  tables are built in memory that is         When pcre_maketables() runs, the tables are built  in  memory  that  is
1146         obtained via pcre_malloc. It is the caller's responsibility  to  ensure         obtained  via  pcre_malloc. It is the caller's responsibility to ensure
1147         that  the memory containing the tables remains available for as long as         that the memory containing the tables remains available for as long  as
1148         it is needed.         it is needed.
1149    
1150         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
1151         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()
1152         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-
1153         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1154         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1155    
1156         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
1157         the  internal  tables)  to  pcre_exec(). Although not intended for this         the internal tables) to pcre_exec(). Although  not  intended  for  this
1158         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
1159         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
1160         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1161    
# Line 862  INFORMATION ABOUT A PATTERN Line 1165  INFORMATION ABOUT A PATTERN
1165         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1166              int what, void *where);              int what, void *where);
1167    
1168         The pcre_fullinfo() function returns information about a compiled  pat-         The  pcre_fullinfo() function returns information about a compiled pat-
1169         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1170         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1171    
1172         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled
1173         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
1174         the pattern was not studied. The third argument specifies  which  piece         the  pattern  was not studied. The third argument specifies which piece
1175         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
1176         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
1177         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1178    
1179           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 878  INFORMATION ABOUT A PATTERN Line 1181  INFORMATION ABOUT A PATTERN
1181           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1182           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1183    
1184         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
1185         an simple check against passing an arbitrary memory pointer. Here is  a         an  simple check against passing an arbitrary memory pointer. Here is a
1186         typical  call  of pcre_fullinfo(), to obtain the length of the compiled         typical call of pcre_fullinfo(), to obtain the length of  the  compiled
1187         pattern:         pattern:
1188    
1189           int rc;           int rc;
# Line 891  INFORMATION ABOUT A PATTERN Line 1194  INFORMATION ABOUT A PATTERN
1194             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1195             &length);         /* where to put the data */             &length);         /* where to put the data */
1196    
1197         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
1198         are as follows:         are as follows:
1199    
1200           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1201    
1202         Return  the  number  of  the highest back reference in the pattern. The         Return the number of the highest back reference  in  the  pattern.  The
1203         fourth argument should point to an int variable. Zero  is  returned  if         fourth  argument  should  point to an int variable. Zero is returned if
1204         there are no back references.         there are no back references.
1205    
1206           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1207    
1208         Return  the  number of capturing subpatterns in the pattern. The fourth         Return the number of capturing subpatterns in the pattern.  The  fourth
1209         argument should point to an int variable.         argument should point to an int variable.
1210    
1211           PCRE_INFO_DEFAULTTABLES           PCRE_INFO_DEFAULT_TABLES
1212    
1213         Return a pointer to the internal default character tables within  PCRE.         Return  a pointer to the internal default character tables within PCRE.
1214         The  fourth  argument should point to an unsigned char * variable. This         The fourth argument should point to an unsigned char *  variable.  This
1215         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1216         tion.  External  callers  can  cause PCRE to use its internal tables by         tion. External callers can cause PCRE to use  its  internal  tables  by
1217         passing a NULL table pointer.         passing a NULL table pointer.
1218    
1219           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1220    
1221         Return information about the first byte of any matched  string,  for  a         Return  information  about  the first byte of any matched string, for a
1222         non-anchored    pattern.    (This    option    used    to   be   called         non-anchored   pattern.   (This    option    used    to    be    called
1223         PCRE_INFO_FIRSTCHAR; the old name is  still  recognized  for  backwards         PCRE_INFO_FIRSTCHAR;  the  old  name  is still recognized for backwards
1224         compatibility.)         compatibility.)
1225    
1226         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
1227         (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.
1228         Otherwise, if either         Otherwise, if either
1229    
1230         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1231         branch starts with "^", or         branch starts with "^", or
1232    
1233         (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
1234         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1235    
1236         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
1237         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
1238         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1239    
1240           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1241    
1242         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
1243         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
1244         matching  string, a pointer to the table is returned. Otherwise NULL is         matching string, a pointer to the table is returned. Otherwise NULL  is
1245         returned. The fourth argument should point to an unsigned char *  vari-         returned.  The fourth argument should point to an unsigned char * vari-
1246         able.         able.
1247    
1248           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1249    
1250         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
1251         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
1252         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1253         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
1254         byte  is  recorded only if it follows something of variable length. For         byte is recorded only if it follows something of variable  length.  For
1255         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
1256         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1257    
# Line 956  INFORMATION ABOUT A PATTERN Line 1259  INFORMATION ABOUT A PATTERN
1259           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1260           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1261    
1262         PCRE  supports the use of named as well as numbered capturing parenthe-         PCRE supports the use of named as well as numbered capturing  parenthe-
1263         ses. The names are just an additional way of identifying the  parenthe-         ses.  The names are just an additional way of identifying the parenthe-
1264         ses,  which  still  acquire  numbers.  A  convenience  function  called         ses,  which  still  acquire  numbers.  A  convenience  function  called
1265         pcre_get_named_substring() is provided  for  extracting  an  individual         pcre_get_named_substring()  is  provided  for  extracting an individual
1266         captured  substring  by  name.  It is also possible to extract the data         captured substring by name. It is also possible  to  extract  the  data
1267         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
1268         the  correct  pointers in the output vector (described with pcre_exec()         the correct pointers in the output vector (described  with  pcre_exec()
1269         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,
1270         which is described by these three values.         which is described by these three values.
1271    
1272         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
1273         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1274         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
1275         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns
1276         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
1277         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-
1278         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-
1279         sponding name, zero terminated. The names are  in  alphabetical  order.         sponding  name,  zero  terminated. The names are in alphabetical order.
1280         For  example,  consider  the following pattern (assume PCRE_EXTENDED is         For example, consider the following pattern  (assume  PCRE_EXTENDED  is
1281         set, so white space - including newlines - is ignored):         set, so white space - including newlines - is ignored):
1282    
1283           (?P<date> (?P<year>(\d\d)?\d\d) -           (?P<date> (?P<year>(\d\d)?\d\d) -
1284           (?P<month>\d\d) - (?P<day>\d\d) )           (?P<month>\d\d) - (?P<day>\d\d) )
1285    
1286         There are four named subpatterns, so the table has  four  entries,  and         There  are  four  named subpatterns, so the table has four entries, and
1287         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,
1288         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1289         as ??:         as ??:
1290    
# Line 990  INFORMATION ABOUT A PATTERN Line 1293  INFORMATION ABOUT A PATTERN
1293           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1294           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1295    
1296         When  writing  code  to  extract  data from named subpatterns using the         When writing code to extract data  from  named  subpatterns  using  the
1297         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
1298         be different for each compiled pattern.         be different for each compiled pattern.
1299    
1300           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1301    
1302         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
1303         fourth argument should point to an unsigned long  int  variable.  These         fourth  argument  should  point to an unsigned long int variable. These
1304         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1305         by any top-level option settings within the pattern itself.         by any top-level option settings within the pattern itself.
1306    
1307         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
1308         alternatives begin with one of the following:         alternatives begin with one of the following:
1309    
1310           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1015  INFORMATION ABOUT A PATTERN Line 1318  INFORMATION ABOUT A PATTERN
1318    
1319           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1320    
1321         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
1322         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
1323         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
1324         size_t variable.         size_t variable.
# Line 1023  INFORMATION ABOUT A PATTERN Line 1326  INFORMATION ABOUT A PATTERN
1326           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1327    
1328         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
1329         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
1330         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
1331         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
1332         variable.         variable.
1333    
1334    
# Line 1033  OBSOLETE INFO FUNCTION Line 1336  OBSOLETE INFO FUNCTION
1336    
1337         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1338    
1339         The  pcre_info()  function is now obsolete because its interface is too         The pcre_info() function is now obsolete because its interface  is  too
1340         restrictive to return all the available data about a compiled  pattern.         restrictive  to return all the available data about a compiled pattern.
1341         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of
1342         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-
1343         lowing negative numbers:         lowing negative numbers:
1344    
1345           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1346           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1347    
1348         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
1349         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
1350         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1351    
1352         If  the  pattern  is  not anchored and the firstcharptr argument is not         If the pattern is not anchored and the  firstcharptr  argument  is  not
1353         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
1354         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1355    
1356    
1357  MATCHING A PATTERN  REFERENCE COUNTS
1358    
1359           int pcre_refcount(pcre *code, int adjust);
1360    
1361           The pcre_refcount() function is used to maintain a reference  count  in
1362           the data block that contains a compiled pattern. It is provided for the
1363           benefit of applications that  operate  in  an  object-oriented  manner,
1364           where different parts of the application may be using the same compiled
1365           pattern, but you want to free the block when they are all done.
1366    
1367           When a pattern is compiled, the reference count field is initialized to
1368           zero.   It is changed only by calling this function, whose action is to
1369           add the adjust value (which may be positive or  negative)  to  it.  The
1370           yield of the function is the new value. However, the value of the count
1371           is constrained to lie between 0 and 65535, inclusive. If the new  value
1372           is outside these limits, it is forced to the appropriate limit value.
1373    
1374           Except  when it is zero, the reference count is not correctly preserved
1375           if a pattern is compiled on one host and then  transferred  to  a  host
1376           whose byte-order is different. (This seems a highly unlikely scenario.)
1377    
1378    
1379    MATCHING A PATTERN: THE TRADITIONAL FUNCTION
1380    
1381         int pcre_exec(const pcre *code, const pcre_extra *extra,         int pcre_exec(const pcre *code, const pcre_extra *extra,
1382              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1383              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1384    
1385         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
1386         compiled pattern, which is passed in the code argument. If the  pattern         compiled  pattern, which is passed in the code argument. If the pattern
1387         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
1388         argument.         argument.  This  function is the main matching facility of the library,
1389           and it operates in a Perl-like manner. For specialist use there is also
1390           an  alternative matching function, which is described below in the sec-
1391           tion about the pcre_dfa_exec() function.
1392    
1393         In most applications, the pattern will have been compiled (and  option-         In most applications, the pattern will have been compiled (and  option-
1394         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 1408  MATCHING A PATTERN
1408             0,              /* start at offset 0 in the subject */             0,              /* start at offset 0 in the subject */
1409             0,              /* default options */             0,              /* default options */
1410             ovector,        /* vector of integers for substring information */             ovector,        /* vector of integers for substring information */
1411             30);            /* number of elements in the vector  (NOT  size  in             30);            /* number of elements (NOT size in bytes) */
        bytes) */  
1412    
1413     Extra data for pcre_exec()     Extra data for pcre_exec()
1414    
1415         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
1416         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
1417         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-
1418         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-
1419         lows:         lows:
1420    
1421           unsigned long int flags;           unsigned long int flags;
# Line 1097  MATCHING A PATTERN Line 1424  MATCHING A PATTERN
1424           void *callout_data;           void *callout_data;
1425           const unsigned char *tables;           const unsigned char *tables;
1426    
1427         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
1428         are set. The flag bits are:         are set. The flag bits are:
1429    
1430           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
# Line 1105  MATCHING A PATTERN Line 1432  MATCHING A PATTERN
1432           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1433           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1434    
1435         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
1436         the  pcre_extra  block  that is returned by pcre_study(), together with         the pcre_extra block that is returned by  pcre_study(),  together  with
1437         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
1438         add  to  the  block by setting the other fields and their corresponding         add to the block by setting the other fields  and  their  corresponding
1439         flag bits.         flag bits.
1440    
1441         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
1442         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
1443         match, but which have a very large number  of  possibilities  in  their         match,  but  which  have  a very large number of possibilities in their
1444         search  trees.  The  classic  example  is  the  use of nested unlimited         search trees. The classic  example  is  the  use  of  nested  unlimited
1445         repeats.         repeats.
1446    
1447         Internally, PCRE uses a function called match() which it calls  repeat-         Internally,  PCRE uses a function called match() which it calls repeat-
1448         edly  (sometimes  recursively).  The  limit is imposed on the number of         edly (sometimes recursively). The limit is imposed  on  the  number  of
1449         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
1450         limiting  the amount of recursion and backtracking that can take place.         limiting the amount of recursion and backtracking that can take  place.
1451         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
1452         position in the subject string.         position in the subject string.
1453    
1454         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
1455         default default is 10 million, which handles all but the  most  extreme         default  default  is 10 million, which handles all but the most extreme
1456         cases.  You  can  reduce  the  default  by  suppling pcre_exec() with a         cases. You can reduce  the  default  by  suppling  pcre_exec()  with  a
1457         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
1458         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
1459         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1460    
1461         The pcre_callout field is used in conjunction with the  "callout"  fea-         The  pcre_callout  field is used in conjunction with the "callout" fea-
1462         ture, which is described in the pcrecallout documentation.         ture, which is described in the pcrecallout documentation.
1463    
1464         The  tables  field  is  used  to  pass  a  character  tables pointer to         The tables field  is  used  to  pass  a  character  tables  pointer  to
1465         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec();  this overrides the value that is stored with the compiled
1466         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
1467         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
1468         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
1469         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-
1470         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
1471         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
1472         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
1473         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
1474    
1475     Option bits for pcre_exec()     Option bits for pcre_exec()
1476    
1477         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.
1478         The   only  bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NOTBOL,         The  only  bits  that  may  be  set  are  PCRE_ANCHORED,   PCRE_NOTBOL,
1479         PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.         PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.
1480    
1481           PCRE_ANCHORED           PCRE_ANCHORED
1482    
1483         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first
1484         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or
1485         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
1486         unachored at matching time.         unachored at matching time.
1487    
1488           PCRE_NOTBOL           PCRE_NOTBOL
1489    
1490         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
1491         the beginning of a line, so the  circumflex  metacharacter  should  not         the  beginning  of  a  line, so the circumflex metacharacter should not
1492         match  before it. Setting this without PCRE_MULTILINE (at compile time)         match before it. Setting this without PCRE_MULTILINE (at compile  time)
1493         causes  circumflex  never  to  match.  This  option  affects  only  the         causes  circumflex  never to match. This option affects only the behav-
1494         behaviour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
1495    
1496           PCRE_NOTEOL           PCRE_NOTEOL
1497    
1498         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
1499         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
1500         in  multiline mode) a newline immediately before it. Setting this with-         in multiline mode) a newline immediately before it. Setting this  with-
1501         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
1502         option  affects only the behaviour of the dollar metacharacter. It does         option affects only the behaviour of the dollar metacharacter. It  does
1503         not affect \Z or \z.         not affect \Z or \z.
1504    
1505           PCRE_NOTEMPTY           PCRE_NOTEMPTY
1506    
1507         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
1508         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
1509         the alternatives match the empty string, the entire  match  fails.  For         the  alternatives  match  the empty string, the entire match fails. For
1510         example, if the pattern         example, if the pattern
1511    
1512           a?b?           a?b?
1513    
1514         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
1515         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
1516         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-
1517         rences of "a" or "b".         rences of "a" or "b".
1518    
1519         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-
1520         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()
1521         function, and when using the /g modifier. It  is  possible  to  emulate         function,  and  when  using  the /g modifier. It is possible to emulate
1522         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
1523         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
1524         if  that  fails by advancing the starting offset (see below) and trying         if that fails by advancing the starting offset (see below)  and  trying
1525         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
1526         this in the pcredemo.c sample program.         this in the pcredemo.c sample program.
1527    
1528           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1529    
1530         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
1531         UTF-8 string is automatically checked when pcre_exec() is  subsequently         UTF-8  string is automatically checked when pcre_exec() is subsequently
1532         called.   The  value  of  startoffset is also checked to ensure that it         called.  The value of startoffset is also checked  to  ensure  that  it
1533         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
1534         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
1535         startoffset contains an  invalid  value,  PCRE_ERROR_BADUTF8_OFFSET  is         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is
1536         returned.         returned.
1537    
1538         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
1539         these   checks   for   performance   reasons,   you   can    set    the         these    checks    for   performance   reasons,   you   can   set   the
1540         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
1541         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
1542         making  repeated  calls  to  find  all  the matches in a single subject         making repeated calls to find all  the  matches  in  a  single  subject
1543         string. However, you should be  sure  that  the  value  of  startoffset         string.  However,  you  should  be  sure  that the value of startoffset
1544         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
1545         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
1546         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-
1547         acter, is undefined. Your program may crash.         acter, is undefined. Your program may crash.
1548    
1549           PCRE_PARTIAL           PCRE_PARTIAL
1550    
1551         This option turns on the  partial  matching  feature.  If  the  subject         This  option  turns  on  the  partial  matching feature. If the subject
1552         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-
1553         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
1554         partially  matches  the  pattern and the failure to match occurred only         partially matches the pattern and the failure to  match  occurred  only
1555         because there were not enough subject characters), pcre_exec()  returns         because  there were not enough subject characters), pcre_exec() returns
1556         PCRE_ERROR_PARTIAL  instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is
1557         used, there are restrictions on what may appear in the  pattern.  These         used,  there  are restrictions on what may appear in the pattern. These
1558         are discussed in the pcrepartial documentation.         are discussed in the pcrepartial documentation.
1559    
1560     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
1561    
1562         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
1563         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
1564         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.
1565         Unlike the pattern string, the subject may contain binary  zero  bytes.         Unlike  the  pattern string, the subject may contain binary zero bytes.
1566         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
1567         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.
1568    
1569         A non-zero starting offset is useful when searching for  another  match         A  non-zero  starting offset is useful when searching for another match
1570         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-
1571         cess.  Setting startoffset differs from just passing over  a  shortened         cess.   Setting  startoffset differs from just passing over a shortened
1572         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
1573         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
1574    
1575           \Biss\B           \Biss\B
1576    
1577         which finds occurrences of "iss" in the middle of  words.  (\B  matches         which  finds  occurrences  of "iss" in the middle of words. (\B matches
1578         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.)
1579         When applied to the string "Mississipi" the first call  to  pcre_exec()         When  applied  to the string "Mississipi" the first call to pcre_exec()
1580         finds  the  first  occurrence. If pcre_exec() is called again with just         finds the first occurrence. If pcre_exec() is called  again  with  just
1581         the remainder of the subject,  namely  "issipi",  it  does  not  match,         the  remainder  of  the  subject,  namely  "issipi", it does not match,
1582         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
1583         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
1584         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-
1585         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
1586         discover that it is preceded by a letter.         discover that it is preceded by a letter.
1587    
1588         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,
1589         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
1590         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
1591         subject.         subject.
1592    
1593     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
1594    
1595         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
1596         addition,  further  substrings  from  the  subject may be picked out by         addition, further substrings from the subject  may  be  picked  out  by
1597         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,
1598         this  is  called "capturing" in what follows, and the phrase "capturing         this is called "capturing" in what follows, and the  phrase  "capturing
1599         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-
1600         string.  PCRE  supports several other kinds of parenthesized subpattern         string. PCRE supports several other kinds of  parenthesized  subpattern
1601         that do not cause substrings to be captured.         that do not cause substrings to be captured.
1602    
1603         Captured substrings are returned to the caller via a vector of  integer         Captured  substrings are returned to the caller via a vector of integer
1604         offsets  whose  address is passed in ovector. The number of elements in         offsets whose address is passed in ovector. The number of  elements  in
1605         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.
1606         Note: this argument is NOT the size of ovector in bytes.         Note: this argument is NOT the size of ovector in bytes.
1607    
1608         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-
1609         strings, each substring using a pair of integers. The  remaining  third         strings,  each  substring using a pair of integers. The remaining third
1610         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-
1611         turing subpatterns, and is not available for passing back  information.         turing  subpatterns, and is not available for passing back information.
1612         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
1613         it is not, it is rounded down.         it is not, it is rounded down.
1614    
1615         When a match is successful, information about  captured  substrings  is         When  a  match  is successful, information about captured substrings is
1616         returned  in  pairs  of integers, starting at the beginning of ovector,         returned in pairs of integers, starting at the  beginning  of  ovector,
1617         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
1618         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-
1619         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
1620         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-
1621         tor[1], identify the portion of  the  subject  string  matched  by  the         tor[1],  identify  the  portion  of  the  subject string matched by the
1622         entire  pattern.  The next pair is used for the first capturing subpat-         entire pattern. The next pair is used for the first  capturing  subpat-
1623         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
1624         pairs  that  have  been set. If there are no capturing subpatterns, the         pairs that have been set. If there are no  capturing  subpatterns,  the
1625         return value from a successful match is 1,  indicating  that  just  the         return  value  from  a  successful match is 1, indicating that just the
1626         first pair of offsets has been set.         first pair of offsets has been set.
1627    
1628         Some  convenience  functions  are  provided for extracting the captured         Some convenience functions are provided  for  extracting  the  captured
1629         substrings as separate strings. These are described  in  the  following         substrings  as  separate  strings. These are described in the following
1630         section.         section.
1631    
1632         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
1633         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
1634         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)
1635         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
1636         offset values corresponding to the unused subpattern are set to -1.         offset values corresponding to the unused subpattern are set to -1.
1637    
1638         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
1639         of the string that it matched that is returned.         of the string that it matched that is returned.
1640    
1641         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,
1642         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
1643         function returns a value of zero. In particular, if the substring  off-         function  returns a value of zero. In particular, if the substring off-
1644         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
1645         as NULL and ovecsize as zero. However, if  the  pattern  contains  back         as  NULL  and  ovecsize  as zero. However, if the pattern contains back
1646         references  and  the  ovector is not big enough to remember the related         references and the ovector is not big enough to  remember  the  related
1647         substrings, PCRE has to get additional memory for use during  matching.         substrings,  PCRE has to get additional memory for use during matching.
1648         Thus it is usually advisable to supply an ovector.         Thus it is usually advisable to supply an ovector.
1649    
1650         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-
1651         patterns there are in a compiled pattern. The smallest size for ovector         patterns there are in a compiled pattern. The smallest size for ovector
1652         that  will  allow for n captured substrings, in addition to the offsets         that will allow for n captured substrings, in addition to  the  offsets
1653         of the substring matched by the whole pattern, is (n+1)*3.         of the substring matched by the whole pattern, is (n+1)*3.
1654    
1655     Return values from pcre_exec()     Return values from pcre_exec()
1656    
1657         If pcre_exec() fails, it returns a negative number. The  following  are         If  pcre_exec()  fails, it returns a negative number. The following are
1658         defined in the header file:         defined in the header file:
1659    
1660           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 1336  MATCHING A PATTERN Line 1663  MATCHING A PATTERN
1663    
1664           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
1665    
1666         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
1667         ovecsize was not zero.         ovecsize was not zero.
1668    
1669           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 1345  MATCHING A PATTERN Line 1672  MATCHING A PATTERN
1672    
1673           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
1674    
1675         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,
1676         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
1677         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
1678         an  environment  with the other endianness. This is the error that PCRE         an environment with the other endianness. This is the error  that  PCRE
1679         gives when the magic number is not present.         gives when the magic number is not present.
1680    
1681           PCRE_ERROR_UNKNOWN_NODE   (-5)           PCRE_ERROR_UNKNOWN_NODE   (-5)
1682    
1683         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
1684         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
1685         overwriting of the compiled pattern.         overwriting of the compiled pattern.
1686    
1687           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
1688    
1689         If a pattern contains back references, but the ovector that  is  passed         If  a  pattern contains back references, but the ovector that is passed
1690         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
1691         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
1692         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
1693         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
1694    
1695           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
1696    
1697         This error is used by the pcre_copy_substring(),  pcre_get_substring(),         This  error is used by the pcre_copy_substring(), pcre_get_substring(),
1698         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
1699         returned by pcre_exec().         returned by pcre_exec().
1700    
1701           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
1702    
1703         The recursion and backtracking limit, as specified by  the  match_limit         The  recursion  and backtracking limit, as specified by the match_limit
1704         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field in a pcre_extra structure (or defaulted)  was  reached.  See  the
1705         description above.         description above.
1706    
1707           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
1708    
1709         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
1710         use  by  callout functions that want to yield a distinctive error code.         use by callout functions that want to yield a distinctive  error  code.
1711         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
1712    
1713           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
1714    
1715         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
1716         subject.         subject.
1717    
1718           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
1719    
1720         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
1721         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-
1722         ter.         ter.
1723    
1724           PCRE_ERROR_PARTIAL (-12)           PCRE_ERROR_PARTIAL        (-12)
1725    
1726         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
1727         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
1728    
1729           PCRE_ERROR_BAD_PARTIAL (-13)           PCRE_ERROR_BADPARTIAL     (-13)
1730    
1731         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing         The  PCRE_PARTIAL  option  was  used with a compiled pattern containing
1732         items  that are not supported for partial matching. See the pcrepartial         items that are not supported for partial matching. See the  pcrepartial
1733         documentation for details of partial matching.         documentation for details of partial matching.
1734    
1735           PCRE_ERROR_INTERNAL (-14)           PCRE_ERROR_INTERNAL       (-14)
1736    
1737         An unexpected internal error has occurred. This error could  be  caused         An  unexpected  internal error has occurred. This error could be caused
1738         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
1739    
1740           PCRE_ERROR_BADCOUNT (-15)           PCRE_ERROR_BADCOUNT       (-15)
1741    
1742         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.
1743    
1744    
1745  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
# Line 1428  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 1755  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
1755         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
1756              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
1757    
1758         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
1759         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
1760         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
1761         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
1762         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
1763         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
1764         substrings. A substring  that  contains  a  binary  zero  is  correctly         substrings.  A  substring  that  contains  a  binary  zero is correctly
1765         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
1766         not, of course, a C string.         not, of course, a C string.
1767    
1768         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-
1769         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
1770         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
1771         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
1772         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
1773         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
1774         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
1775         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
1776         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
1777    
1778         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
1779         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
1780         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
1781         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
1782         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
1783         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
1784         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
1785         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
1786         the terminating zero, or one of         the terminating zero, or one of
1787    
1788           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
1789    
1790         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
1791         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
1792    
1793           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
1794    
1795         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
1796    
1797         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
1798         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
1799         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
1800         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
1801         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
1802         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
1803    
1804           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
1805    
1806         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
1807    
1808         When any of these functions encounter a substring that is unset,  which         When  any of these functions encounter a substring that is unset, which
1809         can  happen  when  capturing subpattern number n+1 matches some part of         can happen when capturing subpattern number n+1 matches  some  part  of
1810         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
1811         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
1812         string by inspecting the appropriate offset in ovector, which is  nega-         string  by inspecting the appropriate offset in ovector, which is nega-
1813         tive for unset substrings.         tive for unset substrings.
1814    
1815         The  two convenience functions pcre_free_substring() and pcre_free_sub-         The two convenience functions pcre_free_substring() and  pcre_free_sub-
1816         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
1817         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
1818         tively. They do nothing more than  call  the  function  pointed  to  by         tively.  They  do  nothing  more  than  call the function pointed to by
1819         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.
1820         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-
1821         cial  interface  to  another  programming  language  which  cannot  use         cial  interface  to  another  programming  language  which  cannot  use
1822         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-
1823         provided.         vided.
1824    
1825    
1826  EXTRACTING CAPTURED SUBSTRINGS BY NAME  EXTRACTING CAPTURED SUBSTRINGS BY NAME
# Line 1511  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 1838  EXTRACTING CAPTURED SUBSTRINGS BY NAME
1838              int stringcount, const char *stringname,              int stringcount, const char *stringname,
1839              const char **stringptr);              const char **stringptr);
1840    
1841         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-
1842         ber.  For example, for this pattern         ber.  For example, for this pattern
1843    
1844           (a+)b(?<xxx>\d+)...           (a+)b(?P<xxx>\d+)...
1845    
1846         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
1847         from the name by calling pcre_get_stringnumber(). The first argument is         from the name by calling pcre_get_stringnumber(). The first argument is
1848         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
1849         function  is  the  subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if         function is the subpattern number, or  PCRE_ERROR_NOSUBSTRING  (-7)  if
1850         there is no subpattern of that name.         there is no subpattern of that name.
1851    
1852         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
1853         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
1854         are also two functions that do the whole job.         are also two functions that do the whole job.
1855    
1856         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
1857         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
1858         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
1859         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
1860         differences:         differences:
1861    
1862         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
1863         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
1864         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
1865         name-to-number translation table.         name-to-number translation table.
1866    
1867         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
1868         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
1869         ate.         ate.
1870    
 Last updated: 09 September 2004  
 Copyright (c) 1997-2004 University of Cambridge.  
 -----------------------------------------------------------------------------  
1871    
1872  PCRE(3)                                                                PCRE(3)  FINDING ALL POSSIBLE MATCHES
1873    
1874           The traditional matching function uses a  similar  algorithm  to  Perl,
1875           which stops when it finds the first match, starting at a given point in
1876           the subject. If you want to find all possible matches, or  the  longest
1877           possible  match,  consider using the alternative matching function (see
1878           below) instead. If you cannot use the alternative function,  but  still
1879           need  to  find all possible matches, you can kludge it up by making use
1880           of the callout facility, which is described in the pcrecallout documen-
1881           tation.
1882    
1883           What you have to do is to insert a callout right at the end of the pat-
1884           tern.  When your callout function is called, extract and save the  cur-
1885           rent  matched  substring.  Then  return  1, which forces pcre_exec() to
1886           backtrack and try other alternatives. Ultimately, when it runs  out  of
1887           matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
1888    
1889    
1890    MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
1891    
1892           int pcre_dfa_exec(const pcre *code, const pcre_extra *extra,
1893                const char *subject, int length, int startoffset,
1894                int options, int *ovector, int ovecsize,
1895                int *workspace, int wscount);
1896    
1897           The  function  pcre_dfa_exec()  is  called  to  match  a subject string
1898           against a compiled pattern, using a "DFA" matching algorithm. This  has
1899           different  characteristics to the normal algorithm, and is not compati-
1900           ble with Perl. Some of the features of PCRE patterns are not supported.
1901           Nevertheless, there are times when this kind of matching can be useful.
1902           For a discussion of the two matching algorithms, see  the  pcrematching
1903           documentation.
1904    
1905           The  arguments  for  the  pcre_dfa_exec()  function are the same as for
1906           pcre_exec(), plus two extras. The ovector argument is used in a differ-
1907           ent  way,  and  this is described below. The other common arguments are
1908           used in the same way as for pcre_exec(), so their  description  is  not
1909           repeated here.
1910    
1911           The  two  additional  arguments provide workspace for the function. The
1912           workspace vector should contain at least 20 elements. It  is  used  for
1913           keeping  track  of  multiple  paths  through  the  pattern  tree.  More
1914           workspace will be needed for patterns and subjects where  there  are  a
1915           lot of possible matches.
1916    
1917           Here is an example of a simple call to pcre_exec():
1918    
1919             int rc;
1920             int ovector[10];
1921             int wspace[20];
1922             rc = pcre_exec(
1923               re,             /* result of pcre_compile() */
1924               NULL,           /* we didn't study the pattern */
1925               "some string",  /* the subject string */
1926               11,             /* the length of the subject string */
1927               0,              /* start at offset 0 in the subject */
1928               0,              /* default options */
1929               ovector,        /* vector of integers for substring information */
1930               10,             /* number of elements (NOT size in bytes) */
1931               wspace,         /* working space vector */
1932               20);            /* number of elements (NOT size in bytes) */
1933    
1934       Option bits for pcre_dfa_exec()
1935    
1936           The  unused  bits  of  the options argument for pcre_dfa_exec() must be
1937           zero. The only bits that may be  set  are  PCRE_ANCHORED,  PCRE_NOTBOL,
1938           PCRE_NOTEOL,     PCRE_NOTEMPTY,    PCRE_NO_UTF8_CHECK,    PCRE_PARTIAL,
1939           PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All  but  the  last  three  of
1940           these  are  the  same  as  for pcre_exec(), so their description is not
1941           repeated here.
1942    
1943             PCRE_PARTIAL
1944    
1945           This has the same general effect as it does for  pcre_exec(),  but  the
1946           details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for
1947           pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into
1948           PCRE_ERROR_PARTIAL  if  the  end  of the subject is reached, there have
1949           been no complete matches, but there is still at least one matching pos-
1950           sibility.  The portion of the string that provided the partial match is
1951           set as the first matching string.
1952    
1953             PCRE_DFA_SHORTEST
1954    
1955           Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
1956           stop  as  soon  as  it  has found one match. Because of the way the DFA
1957           algorithm works, this is necessarily the shortest possible match at the
1958           first possible matching point in the subject string.
1959    
1960             PCRE_DFA_RESTART
1961    
1962           When  pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option, and
1963           returns a partial match, it is possible to call it  again,  with  addi-
1964           tional  subject  characters,  and have it continue with the same match.
1965           The PCRE_DFA_RESTART option requests this action; when it is  set,  the
1966           workspace  and wscount options must reference the same vector as before
1967           because data about the match so far is left in  them  after  a  partial
1968           match.  There  is  more  discussion of this facility in the pcrepartial
1969           documentation.
1970    
1971       Successful returns from pcre_dfa_exec()
1972    
1973           When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-
1974           string in the subject. Note, however, that all the matches from one run
1975           of the function start at the same point in  the  subject.  The  shorter
1976           matches  are all initial substrings of the longer matches. For example,
1977           if the pattern
1978    
1979             <.*>
1980    
1981           is matched against the string
1982    
1983             This is <something> <something else> <something further> no more
1984    
1985           the three matched strings are
1986    
1987             <something>
1988             <something> <something else>
1989             <something> <something else> <something further>
1990    
1991           On success, the yield of the function is a number  greater  than  zero,
1992           which  is  the  number of matched substrings. The substrings themselves
1993           are returned in ovector. Each string uses two elements;  the  first  is
1994           the  offset  to the start, and the second is the offset to the end. All
1995           the strings have the same start offset. (Space could have been saved by
1996           giving  this only once, but it was decided to retain some compatibility
1997           with the way pcre_exec() returns data, even though the meaning  of  the
1998           strings is different.)
1999    
2000           The strings are returned in reverse order of length; that is, the long-
2001           est matching string is given first. If there were too many  matches  to
2002           fit  into ovector, the yield of the function is zero, and the vector is
2003           filled with the longest matches.
2004    
2005       Error returns from pcre_dfa_exec()
2006    
2007           The pcre_dfa_exec() function returns a negative number when  it  fails.
2008           Many  of  the  errors  are  the  same as for pcre_exec(), and these are
2009           described above.  There are in addition the following errors  that  are
2010           specific to pcre_dfa_exec():
2011    
2012             PCRE_ERROR_DFA_UITEM      (-16)
2013    
2014           This  return is given if pcre_dfa_exec() encounters an item in the pat-
2015           tern that it does not support, for instance, the use of \C  or  a  back
2016           reference.
2017    
2018             PCRE_ERROR_DFA_UCOND      (-17)
2019    
2020           This  return is given if pcre_dfa_exec() encounters a condition item in
2021           a pattern that uses a back reference for the  condition.  This  is  not
2022           supported.
2023    
2024             PCRE_ERROR_DFA_UMLIMIT    (-18)
2025    
2026           This  return  is given if pcre_dfa_exec() is called with an extra block
2027           that contains a setting of the match_limit field. This is not supported
2028           (it is meaningless).
2029    
2030             PCRE_ERROR_DFA_WSSIZE     (-19)
2031    
2032           This  return  is  given  if  pcre_dfa_exec()  runs  out of space in the
2033           workspace vector.
2034    
2035             PCRE_ERROR_DFA_RECURSE    (-20)
2036    
2037           When a recursive subpattern is processed, the matching  function  calls
2038           itself  recursively,  using  private vectors for ovector and workspace.
2039           This error is given if the output vector  is  not  large  enough.  This
2040           should be extremely rare, as a vector of size 1000 is used.
2041    
2042    Last updated: 16 May 2005
2043    Copyright (c) 1997-2005 University of Cambridge.
2044    ------------------------------------------------------------------------------
2045    
2046    
2047    PCRECALLOUT(3)                                                  PCRECALLOUT(3)
2048    
2049    
2050  NAME  NAME
2051         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
2052    
2053    
2054  PCRE CALLOUTS  PCRE CALLOUTS
2055    
2056         int (*pcre_callout)(pcre_callout_block *);         int (*pcre_callout)(pcre_callout_block *);
# Line 1606  MISSING CALLOUTS Line 2105  MISSING CALLOUTS
2105  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2106    
2107         During matching, when PCRE reaches a callout point, the external  func-         During matching, when PCRE reaches a callout point, the external  func-
2108         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
2109         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
2110         following fields:         only  argument  to  the callout function is a pointer to a pcre_callout
2111           block. This structure contains the following fields:
2112    
2113           int          version;           int          version;
2114           int          callout_number;           int          callout_number;
# Line 1623  THE CALLOUT INTERFACE Line 2123  THE CALLOUT INTERFACE
2123           int          pattern_position;           int          pattern_position;
2124           int          next_item_length;           int          next_item_length;
2125    
2126         The  version  field  is an integer containing the version number of the         The version field is an integer containing the version  number  of  the
2127         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
2128         version  number  will  change  again in future if additional fields are         version number will change again in future  if  additional  fields  are
2129         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.
2130    
2131         The  callout_number  field  contains the number of the callout, as com-         The callout_number field contains the number of the  callout,  as  com-
2132         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-
2133         outs, and 255 for automatically generated callouts).         outs, and 255 for automatically generated callouts).
2134    
2135         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
2136         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
2137         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
2138         way as for extracting substrings after a match has completed.         substrings  that  have  been  matched  so  far,  in the same way as for
2139           extracting substrings after a match has completed. For  pcre_dfa_exec()
2140           this field is not useful.
2141    
2142         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
2143         were passed to pcre_exec().         were passed to pcre_exec().
2144    
2145         The  start_match  field contains the offset within the subject at which         The start_match field contains the offset within the subject  at  which
2146         the current match attempt started. If the pattern is not anchored,  the         the  current match attempt started. If the pattern is not anchored, the
2147         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
2148         pattern for different starting points in the subject.         pattern for different starting points in the subject.
2149    
2150         The current_position field contains the offset within  the  subject  of         The  current_position  field  contains the offset within the subject of
2151         the current match pointer.         the current match pointer.
2152    
2153         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
2154         numbered captured substring so far. If no  substrings  have  been  cap-         one  more than the number of the highest numbered captured substring so
2155         tured, the value of capture_top is one.         far. If no substrings have been captured, the value of  capture_top  is
2156           one.  This  is always the case when pcre_dfa_exec() is used, because it
2157         The  capture_last  field  contains the number of the most recently cap-         does not support captured substrings.
2158         tured substring. If no substrings have been captured, its value is  -1.  
2159           The capture_last field contains the number of the  most  recently  cap-
2160         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.
2161         by the caller specifically so that it can be passed back  in  callouts.         This is always the case when pcre_dfa_exec() is used.
2162         It  is  passed  in the pcre_callout field of the pcre_extra data struc-  
2163         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()
2164         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-
2165           outs. It is passed in the pcre_callout field  of  the  pcre_extra  data
2166           structure.  If  no such data was passed, the value of callout_data in a
2167           pcre_callout block is NULL. There is a description  of  the  pcre_extra
2168         structure in the pcreapi documentation.         structure in the pcreapi documentation.
2169    
2170         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-
2171         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
2172         the pattern string.         the pattern string.
2173    
2174         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-
2175         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
2176         the pattern string. When the callout immediately precedes  an  alterna-         the  pattern  string. When the callout immediately precedes an alterna-
2177         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
2178         is zero. When the callout precedes an opening parenthesis,  the  length         is  zero.  When the callout precedes an opening parenthesis, the length
2179         is that of the entire subpattern.         is that of the entire subpattern.
2180    
2181         The  pattern_position  and next_item_length fields are intended to help         The pattern_position and next_item_length fields are intended  to  help
2182         in distinguishing between different automatic callouts, which all  have         in  distinguishing between different automatic callouts, which all have
2183         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
2184    
2185    
2186  RETURN VALUES  RETURN VALUES
2187    
2188         The  external callout function returns an integer to PCRE. If the value         The external callout function returns an integer to PCRE. If the  value
2189         is zero, matching proceeds as normal. If  the  value  is  greater  than         is  zero,  matching  proceeds  as  normal. If the value is greater than
2190         zero,  matching  fails  at  the current point, but backtracking to test         zero, matching fails at the current point, but  the  testing  of  other
2191         other matching possibilities goes ahead, just as if a lookahead  asser-         matching possibilities goes ahead, just as if a lookahead assertion had
2192         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
2193         doned, and pcre_exec() returns the negative value.         pcre_exec() (or pcre_dfa_exec()) returns the negative value.
2194    
2195         Negative  values  should  normally  be   chosen   from   the   set   of         Negative   values   should   normally   be   chosen  from  the  set  of
2196         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
2197         dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is         dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is
2198         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
2199         itself.         itself.
2200    
2201  Last updated: 09 September 2004  Last updated: 28 February 2005
2202  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
2203  -----------------------------------------------------------------------------  ------------------------------------------------------------------------------
2204    
 PCRE(3)                                                                PCRE(3)  
2205    
2206    PCRECOMPAT(3)                                                    PCRECOMPAT(3)
2207    
2208    
2209  NAME  NAME
2210         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
2211    
2212    
2213  DIFFERENCES BETWEEN PCRE AND PERL  DIFFERENCES BETWEEN PCRE AND PERL
2214    
2215         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 2314  DIFFERENCES BETWEEN PCRE AND PERL
2314         (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,
2315         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
2316    
2317  Last updated: 09 September 2004         (n)  The  alternative  matching function (pcre_dfa_exec()) matches in a
2318  Copyright (c) 1997-2004 University of Cambridge.         different way and is not Perl-compatible.
 -----------------------------------------------------------------------------  
2319    
2320  PCRE(3)                                                                PCRE(3)  Last updated: 28 February 2005
2321    Copyright (c) 1997-2005 University of Cambridge.
2322    ------------------------------------------------------------------------------
2323    
2324    
2325    PCREPATTERN(3)                                                  PCREPATTERN(3)
2326    
2327    
2328  NAME  NAME
2329         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
2330    
2331    
2332  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
2333    
2334         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 2346  PCRE REGULAR EXPRESSION DETAILS
2346         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
2347         page.         page.
2348    
2349           The remainder of this document discusses the  patterns  that  are  sup-
2350           ported  by  PCRE when its main matching function, pcre_exec(), is used.
2351           From  release  6.0,   PCRE   offers   a   second   matching   function,
2352           pcre_dfa_exec(),  which matches using a different algorithm that is not
2353           Perl-compatible. The advantages and disadvantages  of  the  alternative
2354           function, and how it differs from the normal function, are discussed in
2355           the pcrematching page.
2356    
2357         A regular expression is a pattern that is  matched  against  a  subject         A regular expression is a pattern that is  matched  against  a  subject
2358         string  from  left  to right. Most characters stand for themselves in a         string  from  left  to right. Most characters stand for themselves in a
2359         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 2361  PCRE REGULAR EXPRESSION DETAILS
2361    
2362           The quick brown fox           The quick brown fox
2363    
2364         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
2365         power of regular expressions comes from the ability to include alterna-         caseless matching is specified (the PCRE_CASELESS option), letters  are
2366         tives  and repetitions in the pattern. These are encoded in the pattern         matched  independently  of case. In UTF-8 mode, PCRE always understands
2367         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
2368         instead are interpreted in some special way.         caseless  matching  is always possible. For characters with higher val-
2369           ues, the concept of case is supported if PCRE is compiled with  Unicode
2370         There  are  two different sets of metacharacters: those that are recog-         property  support,  but  not  otherwise.   If  you want to use caseless
2371         nized anywhere in the pattern except within square brackets, and  those         matching for characters 128 and above, you must  ensure  that  PCRE  is
2372         that  are  recognized  in square brackets. Outside square brackets, the         compiled with Unicode property support as well as with UTF-8 support.
2373    
2374           The  power  of  regular  expressions  comes from the ability to include
2375           alternatives and repetitions in the pattern. These are encoded  in  the
2376           pattern by the use of metacharacters, which do not stand for themselves
2377           but instead are interpreted in some special way.
2378    
2379           There are two different sets of metacharacters: those that  are  recog-
2380           nized  anywhere in the pattern except within square brackets, and those
2381           that are recognized in square brackets. Outside  square  brackets,  the
2382         metacharacters are as follows:         metacharacters are as follows:
2383    
2384           \      general escape character with several uses           \      general escape character with several uses
# Line 1870  PCRE REGULAR EXPRESSION DETAILS Line 2397  PCRE REGULAR EXPRESSION DETAILS
2397                  also "possessive quantifier"                  also "possessive quantifier"
2398           {      start min/max quantifier           {      start min/max quantifier
2399    
2400         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
2401         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
2402    
2403           \      general escape character           \      general escape character
# Line 1880  PCRE REGULAR EXPRESSION DETAILS Line 2407  PCRE REGULAR EXPRESSION DETAILS
2407                    syntax)                    syntax)
2408           ]      terminates the character class           ]      terminates the character class
2409    
2410         The  following sections describe the use of each of the metacharacters.         The following sections describe the use of each of the  metacharacters.
2411    
2412    
2413  BACKSLASH  BACKSLASH
2414    
2415         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
2416         a  non-alphanumeric  character,  it takes away any special meaning that         a non-alphanumeric character, it takes away any  special  meaning  that
2417         character may have. This  use  of  backslash  as  an  escape  character         character  may  have.  This  use  of  backslash  as an escape character
2418         applies both inside and outside character classes.         applies both inside and outside character classes.
2419    
2420         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
2421         pattern.  This escaping action applies whether  or  not  the  following         pattern.   This  escaping  action  applies whether or not the following
2422         character  would  otherwise be interpreted as a metacharacter, so it is         character would otherwise be interpreted as a metacharacter, so  it  is
2423         always safe to precede a non-alphanumeric  with  backslash  to  specify         always  safe  to  precede  a non-alphanumeric with backslash to specify
2424         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-
2425         slash, you write \\.         slash, you write \\.
2426    
2427         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in
2428         the  pattern (other than in a character class) and characters between a         the pattern (other than in a character class) and characters between  a
2429         # outside a character class and the next newline character are ignored.         # outside a character class and the next newline character are ignored.
2430         An  escaping backslash can be used to include a whitespace or # charac-         An escaping backslash can be used to include a whitespace or #  charac-
2431         ter as part of the pattern.         ter as part of the pattern.
2432    
2433         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-
2434         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-
2435         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
2436         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-
2437         tion. Note the following examples:         tion. Note the following examples:
2438    
2439           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 1916  BACKSLASH Line 2443  BACKSLASH
2443           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
2444           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
2445    
2446         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
2447         classes.         classes.
2448    
2449     Non-printing characters     Non-printing characters
2450    
2451         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-
2452         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
2453         appearance  of non-printing characters, apart from the binary zero that         appearance of non-printing characters, apart from the binary zero  that
2454         terminates a pattern, but when a pattern  is  being  prepared  by  text         terminates  a  pattern,  but  when  a pattern is being prepared by text
2455         editing,  it  is  usually  easier  to  use  one of the following escape         editing, it is usually easier  to  use  one  of  the  following  escape
2456         sequences than the binary character it represents:         sequences than the binary character it represents:
2457    
2458           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
# Line 1939  BACKSLASH Line 2466  BACKSLASH
2466           \xhh      character with hex code hh           \xhh      character with hex code hh
2467           \x{hhh..} character with hex code hhh... (UTF-8 mode only)           \x{hhh..} character with hex code hhh... (UTF-8 mode only)
2468    
2469         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,
2470         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
2471         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;
2472         becomes hex 7B.         becomes hex 7B.
2473    
2474         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
2475         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-
2476         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
2477         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
2478         7FFFFFFF).  If  characters other than hexadecimal digits appear between         7FFFFFFF). If characters other than hexadecimal digits  appear  between
2479         \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
2480         recognized. Instead, the initial \x will be interpreted as a basic hex-         recognized. Instead, the initial \x will  be  interpreted  as  a  basic
2481         adecimal escape, with no following digits,  giving  a  character  whose         hexadecimal  escape, with no following digits, giving a character whose
2482         value is zero.         value is zero.
2483    
2484         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
2485         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
2486         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
2487         \x{dc}.         \x{dc}.
2488    
2489         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
2490         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.
2491         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
2492         character  (code  value  7).  Make sure you supply two digits after the         character (code value 7). Make sure you supply  two  digits  after  the
2493         initial zero if the pattern character that follows is itself  an  octal         initial  zero  if the pattern character that follows is itself an octal
2494         digit.         digit.
2495    
2496         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-
2497         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
2498         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
2499         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
2500         expression,  the  entire  sequence  is  taken  as  a  back reference. A         expression, the entire  sequence  is  taken  as  a  back  reference.  A
2501         description of how this works is given later, following the  discussion         description  of how this works is given later, following the discussion
2502         of parenthesized subpatterns.         of parenthesized subpatterns.
2503    
2504         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
2505         and there have not been that many capturing subpatterns, PCRE  re-reads         and  there have not been that many capturing subpatterns, PCRE re-reads
2506         up  to three octal digits following the backslash, and generates a sin-         up to three octal digits following the backslash, and generates a  sin-
2507         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
2508         digits stand for themselves.  For example:         digits stand for themselves.  For example:
2509    
# Line 1995  BACKSLASH Line 2522  BACKSLASH
2522           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
2523                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
2524    
2525         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
2526         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
2527    
2528         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
2529         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
2530         classes. In addition, inside a character  class,  the  sequence  \b  is         classes.  In  addition,  inside  a  character class, the sequence \b is
2531         interpreted as the backspace character (hex 08), and the sequence \X is         interpreted as the backspace character (hex 08), and the sequence \X is
2532         interpreted as the character "X".  Outside  a  character  class,  these         interpreted  as  the  character  "X".  Outside a character class, these
2533         sequences have different meanings (see below).         sequences have different meanings (see below).
2534    
2535     Generic character types     Generic character types
2536    
2537         The  third  use of backslash is for specifying generic character types.         The third use of backslash is for specifying generic  character  types.
2538         The following are always recognized:         The following are always recognized:
2539    
2540           \d     any decimal digit           \d     any decimal digit
# Line 2018  BACKSLASH Line 2545  BACKSLASH
2545           \W     any "non-word" character           \W     any "non-word" character
2546    
2547         Each pair of escape sequences partitions the complete set of characters         Each pair of escape sequences partitions the complete set of characters
2548         into  two disjoint sets. Any given character matches one, and only one,         into two disjoint sets. Any given character matches one, and only  one,
2549         of each pair.         of each pair.
2550    
2551         These character type sequences can appear both inside and outside char-         These character type sequences can appear both inside and outside char-
2552         acter  classes.  They each match one character of the appropriate type.         acter classes. They each match one character of the  appropriate  type.
2553         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
2554         of them fail, since there is no character to match.         of them fail, since there is no character to match.
2555    
2556         For  compatibility  with Perl, \s does not match the VT character (code         For compatibility with Perl, \s does not match the VT  character  (code
2557         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
2558         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).
2559    
2560         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
2561         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-
2562         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-
2563         specific matching is taking place (see "Locale support" in the  pcreapi         specific  matching is taking place (see "Locale support" in the pcreapi
2564         page).  For  example,  in  the  "fr_FR" (French) locale, some character         page). For example, in the  "fr_FR"  (French)  locale,  some  character
2565         codes greater than 128 are used for accented  letters,  and  these  are         codes  greater  than  128  are used for accented letters, and these are
2566         matched by \w.         matched by \w.
2567    
2568         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,
2569         \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-
2570         code character property support is available.         code character property support is available.
2571    
2572     Unicode character properties     Unicode character properties
2573    
2574         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
2575         tional escape sequences to match generic character types are  available         tional  escape sequences to match generic character types are available
2576         when UTF-8 mode is selected. They are:         when UTF-8 mode is selected. They are:
2577    
2578          \p{xx}   a character with the xx property          \p{xx}   a character with the xx property
2579          \P{xx}   a character without the xx property          \P{xx}   a character without the xx property
2580          \X       an extended Unicode sequence          \X       an extended Unicode sequence
2581    
2582         The  property  names represented by xx above are limited to the Unicode         The property names represented by xx above are limited to  the  Unicode
2583         general category properties. Each character has exactly one such  prop-         general  category properties. Each character has exactly one such prop-
2584         erty,  specified  by  a two-letter abbreviation. For compatibility with         erty, specified by a two-letter abbreviation.  For  compatibility  with
2585         Perl, negation can be specified by including a circumflex  between  the         Perl,  negation  can be specified by including a circumflex between the
2586         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
2587         as \P{Lu}.         as \P{Lu}.
2588    
2589         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
2590         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
2591         negation, the curly brackets in the escape sequence are optional; these         negation, the curly brackets in the escape sequence are optional; these
2592         two examples have the same effect:         two examples have the same effect:
# Line 2113  BACKSLASH Line 2640  BACKSLASH
2640           Zp    Paragraph separator           Zp    Paragraph separator
2641           Zs    Space separator           Zs    Space separator
2642    
2643         Extended  properties such as "Greek" or "InMusicalSymbols" are not sup-         Extended properties such as "Greek" or "InMusicalSymbols" are not  sup-
2644         ported by PCRE.         ported by PCRE.
2645    
2646         Specifying caseless matching does not affect  these  escape  sequences.         Specifying  caseless  matching  does not affect these escape sequences.
2647         For example, \p{Lu} always matches only upper case letters.         For example, \p{Lu} always matches only upper case letters.
2648    
2649         The  \X  escape  matches  any number of Unicode characters that form an         The \X escape matches any number of Unicode  characters  that  form  an
2650         extended Unicode sequence. \X is equivalent to         extended Unicode sequence. \X is equivalent to
2651    
2652           (?>\PM\pM*)           (?>\PM\pM*)
2653    
2654         That is, it matches a character without the "mark"  property,  followed         That  is,  it matches a character without the "mark" property, followed
2655         by  zero  or  more  characters with the "mark" property, and treats the         by zero or more characters with the "mark"  property,  and  treats  the
2656         sequence as an atomic group (see below).  Characters  with  the  "mark"         sequence  as  an  atomic group (see below).  Characters with the "mark"
2657         property are typically accents that affect the preceding character.         property are typically accents that affect the preceding character.
2658    
2659         Matching  characters  by Unicode property is not fast, because PCRE has         Matching characters by Unicode property is not fast, because  PCRE  has
2660         to search a structure that contains  data  for  over  fifteen  thousand         to  search  a  structure  that  contains data for over fifteen thousand
2661         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
2662         \w do not use Unicode properties in PCRE.         \w do not use Unicode properties in PCRE.
2663    
2664     Simple assertions     Simple assertions
2665    
2666         The fourth use of backslash is for certain simple assertions. An asser-         The fourth use of backslash is for certain simple assertions. An asser-
2667         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
2668         a match, without consuming any characters from the subject string.  The         a  match, without consuming any characters from the subject string. The
2669         use  of subpatterns for more complicated assertions is described below.         use of subpatterns for more complicated assertions is described  below.
2670         The backslashed assertions are:         The backslashed assertions are:
2671    
2672           \b     matches at a word boundary           \b     matches at a word boundary
# Line 2149  BACKSLASH Line 2676  BACKSLASH
2676           \z     matches at end of subject           \z     matches at end of subject
2677           \G     matches at first matching position in subject           \G     matches at first matching position in subject
2678    
2679         These assertions may not appear in character classes (but note that  \b         These  assertions may not appear in character classes (but note that \b
2680         has a different meaning, namely the backspace character, inside a char-         has a different meaning, namely the backspace character, inside a char-
2681         acter class).         acter class).
2682    
2683         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
2684         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.
2685         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
2686         string if the first or last character matches \w, respectively.         string if the first or last character matches \w, respectively.
2687    
2688         The  \A,  \Z,  and \z assertions differ from the traditional circumflex         The \A, \Z, and \z assertions differ from  the  traditional  circumflex
2689         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
2690         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
2691         set. Thus, they are independent of multiline mode. These  three  asser-         set.  Thus,  they are independent of multiline mode. These three asser-
2692         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
2693         affect only the behaviour of the circumflex and dollar  metacharacters.         affect  only the behaviour of the circumflex and dollar metacharacters.
2694         However,  if the startoffset argument of pcre_exec() is non-zero, indi-         However, if the startoffset argument of pcre_exec() is non-zero,  indi-
2695         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
2696         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
2697         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
2698         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
2699         the end.         the end.
2700    
2701         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
2702         the  start point of the match, as specified by the startoffset argument         the start point of the match, as specified by the startoffset  argument
2703         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
2704         non-zero.  By calling pcre_exec() multiple times with appropriate argu-         non-zero. By calling pcre_exec() multiple times with appropriate  argu-
2705         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-
2706         mentation where \G can be useful.         mentation where \G can be useful.
2707    
2708         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
2709         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
2710         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
2711         previously matched string was empty. Because PCRE does just  one  match         previously  matched  string was empty. Because PCRE does just one match
2712         at a time, it cannot reproduce this behaviour.         at a time, it cannot reproduce this behaviour.
2713    
2714         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
2715         anchored to the starting match position, and the "anchored" flag is set         anchored to the starting match position, and the "anchored" flag is set
2716         in the compiled regular expression.         in the compiled regular expression.
2717    
# Line 2192  BACKSLASH Line 2719  BACKSLASH
2719  CIRCUMFLEX AND DOLLAR  CIRCUMFLEX AND DOLLAR
2720    
2721         Outside a character class, in the default matching mode, the circumflex         Outside a character class, in the default matching mode, the circumflex
2722         character is an assertion that is true only  if  the  current  matching         character  is  an  assertion  that is true only if the current matching
2723         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-
2724         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
2725         PCRE_MULTILINE  option  is  unset. Inside a character class, circumflex         PCRE_MULTILINE option is unset. Inside a  character  class,  circumflex
2726         has an entirely different meaning (see below).         has an entirely different meaning (see below).
2727    
2728         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
2729         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
2730         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
2731         branch.  If all possible alternatives start with a circumflex, that is,         branch. If all possible alternatives start with a circumflex, that  is,
2732         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-
2733         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
2734         constructs that can cause a pattern to be anchored.)         constructs that can cause a pattern to be anchored.)
2735    
2736         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
2737         matching  point  is  at  the  end of the subject string, or immediately         matching point is at the end of  the  subject  string,  or  immediately
2738         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
2739         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
2740         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
2741         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
2742         character class.         character class.
2743    
2744         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
2745         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
2746         compile time. This does not affect the \Z assertion.         compile time. This does not affect the \Z assertion.
2747    
2748         The meanings of the circumflex and dollar characters are changed if the         The meanings of the circumflex and dollar characters are changed if the
2749         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-
2750         ately after and  immediately  before  an  internal  newline  character,         ately  after  and  immediately  before  an  internal newline character,
2751         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-
2752         ject string. For example,  the  pattern  /^abc$/  matches  the  subject         ject  string.  For  example,  the  pattern  /^abc$/ matches the subject
2753         string  "def\nabc"  (where \n represents a newline character) in multi-         string "def\nabc" (where \n represents a newline character)  in  multi-
2754         line mode, but not otherwise.  Consequently, patterns that are anchored         line mode, but not otherwise.  Consequently, patterns that are anchored
2755         in  single line mode because all branches start with ^ are not anchored         in single line mode because all branches start with ^ are not  anchored
2756         in multiline mode, and a match for  circumflex  is  possible  when  the         in  multiline  mode,  and  a  match for circumflex is possible when the
2757         startoffset   argument   of  pcre_exec()  is  non-zero.  The  PCRE_DOL-         startoffset  argument  of  pcre_exec()  is  non-zero.   The   PCRE_DOL-
2758         LAR_ENDONLY option is ignored if PCRE_MULTILINE is set.         LAR_ENDONLY option is ignored if PCRE_MULTILINE is set.
2759    
2760         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
2761         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
2762         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
2763         not.         not.
2764    
2765    
2766  FULL STOP (PERIOD, DOT)  FULL STOP (PERIOD, DOT)
2767    
2768         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-
2769         ter in the subject, including a non-printing  character,  but  not  (by         ter  in  the  subject,  including a non-printing character, but not (by
2770         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,
2771         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
2772         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-
2773         dling of dot is entirely independent of the handling of circumflex  and         dling  of dot is entirely independent of the handling of circumflex and
2774         dollar,  the  only  relationship  being  that they both involve newline         dollar, the only relationship being  that  they  both  involve  newline
2775         characters. Dot has no special meaning in a character class.         characters. Dot has no special meaning in a character class.
2776    
2777    
2778  MATCHING A SINGLE BYTE  MATCHING A SINGLE BYTE
2779    
2780         Outside a character class, the escape sequence \C matches any one byte,         Outside a character class, the escape sequence \C matches any one byte,
2781         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.
2782         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
2783         UTF-8  mode.  Because  it  breaks  up  UTF-8 characters into individual         UTF-8 mode. Because it  breaks  up  UTF-8  characters  into  individual
2784         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
2785         this reason, the \C escape sequence is best avoided.         this reason, the \C escape sequence is best avoided.
2786    
2787         PCRE  does  not  allow \C to appear in lookbehind assertions (described         PCRE does not allow \C to appear in  lookbehind  assertions  (described
2788         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-
2789         late the length of the lookbehind.         late the length of the lookbehind.
2790    
2791    
# Line 2267  SQUARE BRACKETS AND CHARACTER CLASSES Line 2794  SQUARE BRACKETS AND CHARACTER CLASSES
2794         An opening square bracket introduces a character class, terminated by a         An opening square bracket introduces a character class, terminated by a
2795         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-
2796         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,
2797         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
2798         circumflex, if present) or escaped with a backslash.         circumflex, if present) or escaped with a backslash.
2799    
2800         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
2801         mode, the character may occupy more than one byte. A matched  character         mode,  the character may occupy more than one byte. A matched character
2802         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
2803         character in the class definition is a circumflex, in  which  case  the         character  in  the  class definition is a circumflex, in which case the
2804         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
2805         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
2806         not the first character, or escape it with a backslash.         not the first character, or escape it with a backslash.
2807    
2808         For  example, the character class [aeiou] matches any lower case vowel,         For example, the character class [aeiou] matches any lower case  vowel,
2809         while [^aeiou] matches any character that is not a  lower  case  vowel.         while  [^aeiou]  matches  any character that is not a lower case vowel.
2810         Note that a circumflex is just a convenient notation for specifying the         Note that a circumflex is just a convenient notation for specifying the
2811         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
2812         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-
2813         sumes a character from the subject string, and therefore  it  fails  if         sumes  a  character  from the subject string, and therefore it fails if
2814         the current pointer is at the end of the string.         the current pointer is at the end of the string.
2815    
2816         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
2817         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
2818         mechanism.         mechanism.
2819    
2820         When  caseless  matching  is set, any letters in a class represent both         When caseless matching is set, any letters in a  class  represent  both
2821         their upper case and lower case versions, so for  example,  a  caseless         their  upper  case  and lower case versions, so for example, a caseless
2822         [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
2823         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
2824         PCRE  supports  the  concept of case for characters with values greater         understands the concept of case for characters whose  values  are  less
2825         than 128 only when it is compiled with Unicode property support.         than  128, so caseless matching is always possible. For characters with
2826           higher values, the concept of case is supported  if  PCRE  is  compiled
2827           with  Unicode  property support, but not otherwise.  If you want to use
2828           caseless matching for characters 128 and above, you  must  ensure  that
2829           PCRE  is  compiled  with Unicode property support as well as with UTF-8
2830           support.
2831    
2832         The newline character is never treated in any special way in  character         The newline character is never treated in any special way in  character
2833         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 3747  CALLOUTS
3747         gether. A complete description of the interface to the callout function         gether. A complete description of the interface to the callout function
3748         is given in the pcrecallout documentation.         is given in the pcrecallout documentation.
3749    
3750  Last updated: 09 September 2004  Last updated: 28 February 2005
3751  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
3752  -----------------------------------------------------------------------------  ------------------------------------------------------------------------------
3753    
 PCRE(3)                                                                PCRE(3)  
3754    
3755    PCREPARTIAL(3)                                                  PCREPARTIAL(3)
3756    
3757    
3758  NAME  NAME
3759         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
3760    
3761    
3762  PARTIAL MATCHING IN PCRE  PARTIAL MATCHING IN PCRE
3763    
3764         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
3765         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
3766         entire pattern, PCRE_ERROR_NOMATCH is returned. There are circumstances         short  to  match  the  entire  pattern, PCRE_ERROR_NOMATCH is returned.
3767         where it might be helpful to distinguish this case from other cases  in         There are circumstances where it might be helpful to  distinguish  this
3768         which there is no match.         case from other cases in which there is no match.
3769    
3770         Consider, for example, an application where a human is required to type         Consider, for example, an application where a human is required to type
3771         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 3781  PARTIAL MATCHING IN PCRE
3781         until the entire string has been entered.         until the entire string has been entered.
3782    
3783         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-
3784         TIAL  option,  which  can be set when calling pcre_exec(). When this is         TIAL   option,   which   can   be   set  when  calling  pcre_exec()  or
3785         done,  the   return   code   PCRE_ERROR_NOMATCH   is   converted   into         pcre_dfa_exec(). When this flag is set for pcre_exec(), the return code
3786         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
3787         entire subject string matched part of the pattern. No captured data  is         during the matching process the last part of the subject string matched
3788         set when this occurs.         part  of  the  pattern. Unfortunately, for non-anchored matching, it is
3789           not possible to obtain the position of the start of the partial  match.
3790           No captured data is set when PCRE_ERROR_PARTIAL is returned.
3791    
3792           When   PCRE_PARTIAL   is  set  for  pcre_dfa_exec(),  the  return  code
3793           PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the  end  of
3794           the  subject is reached, there have been no complete matches, but there
3795           is still at least one matching possibility. The portion of  the  string
3796           that provided the partial match is set as the first matching string.
3797    
3798         Using PCRE_PARTIAL disables one of PCRE's optimizations. PCRE remembers         Using PCRE_PARTIAL disables one of PCRE's optimizations. PCRE remembers
3799         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 3804  PARTIAL MATCHING IN PCRE
3804  RESTRICTED PATTERNS FOR PCRE_PARTIAL  RESTRICTED PATTERNS FOR PCRE_PARTIAL
3805    
3806         Because of the way certain internal optimizations  are  implemented  in         Because of the way certain internal optimizations  are  implemented  in
3807         PCRE,  the  PCRE_PARTIAL  option  cannot  be  used  with  all patterns.         the  pcre_exec()  function, the PCRE_PARTIAL option cannot be used with
3808         Repeated single characters such as         all patterns. These restrictions do not apply when  pcre_dfa_exec()  is
3809           used.  For pcre_exec(), repeated single characters such as
3810    
3811           a{2,4}           a{2,4}
3812    
# Line 3272  RESTRICTED PATTERNS FOR PCRE_PARTIAL Line 3814  RESTRICTED PATTERNS FOR PCRE_PARTIAL
3814    
3815           \d+           \d+
3816    
3817         are not permitted if the maximum number of occurrences is greater  than         are  not permitted if the maximum number of occurrences is greater than
3818         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-
3819         ted.  Quantifiers with any values are permitted after  parentheses,  so         ted.   Quantifiers  with any values are permitted after parentheses, so
3820         the invalid examples above can be coded thus:         the invalid examples above can be coded thus:
3821    
3822           (a){2,4}           (a){2,4}
3823           (\d)+           (\d)+
3824    
3825         These  constructions  run more slowly, but for the kinds of application         These constructions run more slowly, but for the kinds  of  application
3826         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
3827         restriction.         restriction.
3828    
3829         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
3830         restrictions, pcre_exec() returns the error code  PCRE_ERROR_BADPARTIAL         restrictions,  pcre_exec() returns the error code PCRE_ERROR_BADPARTIAL
3831         (-13).         (-13).
3832    
3833    
3834  EXAMPLE OF PARTIAL MATCHING USING PCRETEST  EXAMPLE OF PARTIAL MATCHING USING PCRETEST
3835    
3836         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
3837         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
3838         uses the date example quoted above:         uses the date example quoted above:
3839    
# Line 3308  EXAMPLE OF PARTIAL MATCHING USING PCRETE Line 3850  EXAMPLE OF PARTIAL MATCHING USING PCRETE
3850           data> jP           data> jP
3851           No match           No match
3852    
3853         The  first  data  string  is  matched completely, so pcretest shows the         The first data string is matched  completely,  so  pcretest  shows  the
3854         matched substrings. The remaining four strings do not  match  the  com-         matched  substrings.  The  remaining four strings do not match the com-
3855         plete pattern, but the first two are partial matches.         plete pattern, but the first two are partial matches.  The  same  test,
3856           using  DFA  matching (by means of the \D escape sequence), produces the
3857           following output:
3858    
3859  Last updated: 08 September 2004             re> /^?(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)$/
3860  Copyright (c) 1997-2004 University of Cambridge.           data> 25jun04\P\D
3861  -----------------------------------------------------------------------------            0: 25jun04
3862             data> 23dec3\P\D
3863             Partial match: 23dec3
3864             data> 3ju\P\D
3865             Partial match: 3ju
3866             data> 3juj\P\D
3867             No match
3868             data> j\P\D
3869             No match
3870    
3871           Notice that in this case the portion of the string that was matched  is
3872           made available.
3873    
3874    
3875    MULTI-SEGMENT MATCHING WITH pcre_dfa_exec()
3876    
3877           When a partial match has been found using pcre_dfa_exec(), it is possi-
3878           ble to continue the match by  providing  additional  subject  data  and
3879           calling  pcre_dfa_exec() again with the PCRE_DFA_RESTART option and the
3880           same working space (where details of the  previous  partial  match  are
3881           stored).  Here  is  an  example  using  pcretest,  where  the \R escape
3882           sequence sets the PCRE_DFA_RESTART option and the  \D  escape  sequence
3883           requests the use of pcre_dfa_exec():
3884    
3885               re> /^?(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)$/
3886             data> 23ja\P\D
3887             Partial match: 23ja
3888             data> n05\R\D
3889              0: n05
3890    
3891           The  first  call has "23ja" as the subject, and requests partial match-
3892           ing; the second call  has  "n05"  as  the  subject  for  the  continued
3893           (restarted)  match.   Notice  that when the match is complete, only the
3894           last part is shown; PCRE does  not  retain  the  previously  partially-
3895           matched  string. It is up to the calling program to do that if it needs
3896           to.
3897    
3898           This facility can  be  used  to  pass  very  long  subject  strings  to
3899           pcre_dfa_exec(). However, some care is needed for certain types of pat-
3900           tern.
3901    
3902           1. If the pattern contains tests for the beginning or end  of  a  line,
3903           you  need  to pass the PCRE_NOTBOL or PCRE_NOTEOL options, as appropri-
3904           ate, when the subject string for any call does not contain  the  begin-
3905           ning or end of a line.
3906    
3907           2.  If  the  pattern contains backward assertions (including \b or \B),
3908           you need to arrange for some overlap in the subject  strings  to  allow
3909           for  this.  For example, you could pass the subject in chunks that were
3910           500 bytes long, but in a buffer of 700 bytes, with the starting  offset
3911           set to 200 and the previous 200 bytes at the start of the buffer.
3912    
3913           3.  Matching a subject string that is split into multiple segments does
3914           not always produce exactly the same result as matching over one  single
3915           long  string.   The  difference arises when there are multiple matching
3916           possibilities, because a partial match result is given only when  there
3917           are  no  completed  matches  in a call to fBpcre_dfa_exec(). This means
3918           that as soon as the shortest match has been found,  continuation  to  a
3919           new  subject  segment  is  no  longer possible.  Consider this pcretest
3920           example:
3921    
3922               re> /dog(sbody)?/
3923             data> do\P\D
3924             Partial match: do
3925             data> gsb\R\P\D
3926              0: g
3927             data> dogsbody\D
3928              0: dogsbody
3929              1: dog
3930    
3931           The pattern matches the words "dog" or "dogsbody". When the subject  is
3932           presented  in  several  parts  ("do" and "gsb" being the first two) the
3933           match stops when "dog" has been found, and it is not possible  to  con-
3934           tinue.  On  the  other  hand,  if  "dogsbody"  is presented as a single
3935           string, both matches are found.
3936    
3937           Because of this phenomenon, it does not usually make  sense  to  end  a
3938           pattern that is going to be matched in this way with a variable repeat.
3939    
3940    Last updated: 28 February 2005
3941    Copyright (c) 1997-2005 University of Cambridge.
3942    ------------------------------------------------------------------------------
3943    
 PCRE(3)                                                                PCRE(3)  
3944    
3945    PCREPRECOMPILE(3)                                            PCREPRECOMPILE(3)
3946    
3947    
3948  NAME  NAME
3949         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
3950    
3951    
3952  SAVING AND RE-USING PRECOMPILED PCRE PATTERNS  SAVING AND RE-USING PRECOMPILED PCRE PATTERNS
3953    
3954         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 4017  SAVING A COMPILED PATTERN
4017  RE-USING A PRECOMPILED PATTERN  RE-USING A PRECOMPILED PATTERN
4018    
4019         Re-using a precompiled pattern is straightforward. Having  reloaded  it         Re-using a precompiled pattern is straightforward. Having  reloaded  it
4020         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
4021         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
4022         opposite endianness to the one where the pattern was compiled.         host,  and  even  if  that  host has the opposite endianness to the one
4023           where the pattern was compiled.
4024         However,  if  you  passed a pointer to custom character tables when the  
4025         pattern was compiled (the tableptr  argument  of  pcre_compile()),  you         However, if you passed a pointer to custom character  tables  when  the
4026         must now pass a similar pointer to pcre_exec(), because the value saved         pattern  was  compiled  (the  tableptr argument of pcre_compile()), you
4027         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(),
4028         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
4029         tion on matching a pattern in the pcreapi documentation.         nonsense. A field in a pcre_extra() block is used to pass this data, as
4030           described  in the section on matching a pattern in the pcreapi documen-
4031           tation.
4032    
4033         If you did not provide custom character tables  when  the  pattern  was         If you did not provide custom character tables  when  the  pattern  was
4034         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 4039  RE-USING A PRECOMPILED PATTERN
4039         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
4040         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
4041         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
4042         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
4043           usual way.
4044    
4045    
4046  COMPATIBILITY WITH DIFFERENT PCRE RELEASES  COMPATIBILITY WITH DIFFERENT PCRE RELEASES
4047    
4048         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
4049         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
4050         any  saved  patterns  that  were compiled with previous releases (not a         any saved patterns that were compiled with  previous  releases  (not  a
4051         facility that was previously advertised), you will  have  to  recompile         facility  that  was  previously advertised), you will have to recompile
4052         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
4053         make changes in a compabible manner.         make changes in a compatible manner.
4054    
4055    Last updated: 28 February 2005
4056    Copyright (c) 1997-2005 University of Cambridge.
4057    ------------------------------------------------------------------------------
4058    
 Last updated: 10 September 2004  
 Copyright (c) 1997-2004 University of Cambridge.  
 -----------------------------------------------------------------------------  
   
 PCRE(3)                                                                PCRE(3)  
4059    
4060    PCREPERFORM(3)                                                  PCREPERFORM(3)
4061    
4062    
4063  NAME  NAME
4064         PCRE - Perl-compatible regular expressions         PCRE - Perl-compatible regular expressions
4065    
4066    
4067  PCRE PERFORMANCE  PCRE PERFORMANCE
4068    
4069         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 4099  PCRE PERFORMANCE
4099    
4100         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-
4101         tain newlines, the best performance is obtained by setting PCRE_DOTALL,         tain newlines, the best performance is obtained by setting PCRE_DOTALL,
4102         or starting the pattern with ^.* to indicate explicit  anchoring.  That         or starting the pattern with ^.* or ^.*? to indicate  explicit  anchor-
4103         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
4104         to restart at.         a newline to restart at.
4105    
4106         Beware of patterns that contain nested indefinite  repeats.  These  can         Beware of patterns that contain nested indefinite  repeats.  These  can
4107         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 4122  PCRE PERFORMANCE
4122           (a+)*b           (a+)*b
4123    
4124         where a literal character follows. Before  embarking  on  the  standard         where a literal character follows. Before  embarking  on  the  standard
4125         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-
4126         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-
4127         However, when there is no following literal this optimization cannot be         ever,  when  there  is no following literal this optimization cannot be
4128         used. You can see the difference by comparing the behaviour of         used. You can see the difference by comparing the behaviour of
4129    
4130           (a+)*\d           (a+)*\d
# Line 3506  PCRE PERFORMANCE Line 4136  PCRE PERFORMANCE
4136         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
4137         an atomic group or a possessive quantifier.         an atomic group or a possessive quantifier.
4138    
4139  Last updated: 09 September 2004  Last updated: 28 February 2005
4140  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
4141  -----------------------------------------------------------------------------  ------------------------------------------------------------------------------
4142    
 PCRE(3)                                                                PCRE(3)  
4143    
4144    PCREPOSIX(3)                                                      PCREPOSIX(3)
4145    
4146    
4147  NAME  NAME
4148         PCRE - Perl-compatible regular expressions.         PCRE - Perl-compatible regular expressions.
4149    
4150    
4151  SYNOPSIS OF POSIX API  SYNOPSIS OF POSIX API
4152    
4153         #include <pcreposix.h>         #include <pcreposix.h>
# Line 3537  DESCRIPTION Line 4168  DESCRIPTION
4168    
4169         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
4170         expression package. See the pcreapi documentation for a description  of         expression package. See the pcreapi documentation for a description  of
4171         PCRE's native API, which contains additional functionality.         PCRE's native API, which contains much additional functionality.
4172    
4173         The functions described here are just wrapper functions that ultimately         The functions described here are just wrapper functions that ultimately
4174         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 4212  COMPILING A PATTERN
4212         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
4213         defined by the following macros:         defined by the following macros:
4214    
4215             REG_DOTALL
4216    
4217           The PCRE_DOTALL option is set when the expression is passed for  compi-
4218           lation  to the native function. Note that REG_DOTALL is not part of the
4219           POSIX standard.
4220    
4221           REG_ICASE           REG_ICASE
4222    
4223         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 4329  MEMORY USAGE
4329    
4330  AUTHOR  AUTHOR
4331    
4332         Philip Hazel <ph10@cam.ac.uk>         Philip Hazel
4333         University Computing Service,         University Computing Service,
4334         Cambridge CB2 3QG, England.         Cambridge CB2 3QG, England.
4335    
4336  Last updated: 07 September 2004  Last updated: 28 February 2005
4337  Copyright (c) 1997-2004 University of Cambridge.  Copyright (c) 1997-2005 University of Cambridge.
4338  -----------------------------------------------------------------------------  ------------------------------------------------------------------------------
4339    
 PCRE(3)                                                                PCRE(3)  
4340    
4341    PCRECPP(3)                                                          PCRECPP(3)
4342    
4343    
4344    NAME
4345           PCRE - Perl-compatible regular expressions.
4346    
4347    
4348    SYNOPSIS OF C++ WRAPPER
4349    
4350           #include <pcrecpp.h>
4351    
4352    
4353    DESCRIPTION
4354    
4355           The  C++  wrapper  for PCRE was provided by Google Inc. Some additional
4356           functionality was added by Giuseppe Maxia. This brief man page was con-
4357           structed  from  the  notes  in the pcrecpp.h file, which should be con-
4358           sulted for further details.
4359    
4360    
4361    MATCHING INTERFACE
4362    
4363           The "FullMatch" operation checks that supplied text matches a  supplied
4364           pattern  exactly.  If pointer arguments are supplied, it copies matched
4365           sub-strings that match sub-patterns into them.
4366    
4367             Example: successful match
4368                pcrecpp::RE re("h.*o");
4369                re.FullMatch("hello");
4370    
4371             Example: unsuccessful match (requires full match):
4372                pcrecpp::RE re("e");
4373                !re.FullMatch("hello");
4374    
4375             Example: creating a temporary RE object:
4376                pcrecpp::RE("h.*o").FullMatch("hello");
4377    
4378           You can pass in a "const char*" or a "string" for "text". The  examples
4379           below  tend to use a const char*. You can, as in the different examples
4380           above, store the RE object explicitly in a variable or use a  temporary
4381           RE  object.  The  examples below use one mode or the other arbitrarily.
4382           Either could correctly be used for any of these examples.
4383    
4384           You must supply extra pointer arguments to extract matched subpieces.
4385    
4386             Example: extracts "ruby" into "s" and 1234 into "i"
4387                int i;
4388                string s;
4389                pcrecpp::RE re("(\\w+):(\\d+)");
4390                re.FullMatch("ruby:1234", &s, &i);
4391    
4392             Example: does not try to extract any extra sub-patterns
4393                re.FullMatch("ruby:1234", &s);
4394    
4395             Example: does not try to extract into NULL
4396                re.FullMatch("ruby:1234", NULL, &i);
4397    
4398             Example: integer overflow causes failure
4399                !re.FullMatch("ruby:1234567891234", NULL, &i);
4400    
4401             Example: fails because there aren't enough sub-patterns:
4402                !pcrecpp::RE("\\w+:\\d+").FullMatch("ruby:1234", &s);
4403    
4404             Example: fails because string cannot be stored in integer
4405                !pcrecpp::RE("(.*)").FullMatch("ruby", &i);
4406    
4407           The provided pointer arguments can be pointers to  any  scalar  numeric
4408           type, or one of:
4409    
4410              string        (matched piece is copied to string)
4411              StringPiece   (StringPiece is mutated to point to matched piece)
4412              T             (where "bool T::ParseFrom(const char*, int)" exists)
4413              NULL          (the corresponding matched sub-pattern is not copied)
4414    
4415           The  function returns true iff all of the following conditions are sat-
4416           isfied:
4417    
4418             a. "text" matches "pattern" exactly;
4419    
4420             b. The number of matched sub-patterns is >= number of supplied
4421                pointers;
4422    
4423             c. The "i"th argument has a suitable type for holding the
4424                string captured as the "i"th sub-pattern. If you pass in
4425                NULL for the "i"th argument, or pass fewer arguments than
4426                number of sub-patterns, "i"th captured sub-pattern is
4427                ignored.
4428    
4429           The matching interface supports at most 16 arguments per call.  If  you
4430           need    more,    consider    using    the    more   general   interface
4431           pcrecpp::RE::DoMatch. See pcrecpp.h for the signature for DoMatch.
4432    
4433    
4434    PARTIAL MATCHES
4435    
4436           You can use the "PartialMatch" operation when you want the  pattern  to
4437           match any substring of the text.
4438    
4439             Example: simple search for a string:
4440                pcrecpp::RE("ell").PartialMatch("hello");
4441    
4442             Example: find first number in a string:
4443                int number;
4444                pcrecpp::RE re("(\\d+)");
4445                re.PartialMatch("x*100 + 20", &number);
4446                assert(number == 100);
4447    
4448    
4449    UTF-8 AND THE MATCHING INTERFACE
4450    
4451           By  default,  pattern  and text are plain text, one byte per character.
4452           The UTF8 flag, passed to  the  constructor,  causes  both  pattern  and
4453           string to be treated as UTF-8 text, still a byte stream but potentially
4454           multiple bytes per character. In practice, the text is likelier  to  be
4455           UTF-8  than  the pattern, but the match returned may depend on the UTF8
4456           flag, so always use it when matching UTF8 text. For example,  "."  will
4457           match  one  byte normally but with UTF8 set may match up to three bytes
4458           of a multi-byte character.
4459    
4460             Example:
4461                pcrecpp::RE_Options options;
4462                options.set_utf8();
4463                pcrecpp::RE re(utf8_pattern, options);
4464                re.FullMatch(utf8_string);
4465    
4466             Example: using the convenience function UTF8():
4467                pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8());
4468                re.FullMatch(utf8_string);
4469    
4470           NOTE: The UTF8 flag is ignored if pcre was not configured with the
4471                 --enable-utf8 flag.
4472    
4473    
4474    PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE
4475    
4476           PCRE defines some modifiers to  change  the  behavior  of  the  regular
4477           expression   engine.  The  C++  wrapper  defines  an  auxiliary  class,
4478           RE_Options, as a vehicle to pass such modifiers to  a  RE  class.  Cur-
4479           rently, the following modifiers are supported:
4480    
4481              modifier              description               Perl corresponding
4482    
4483              PCRE_CASELESS         case insensitive match      /i
4484              PCRE_MULTILINE        multiple lines match        /m
4485              PCRE_DOTALL           dot matches newlines        /s
4486              PCRE_DOLLAR_ENDONLY   $ matches only at end       N/A
4487              PCRE_EXTRA            strict escape parsing       N/A
4488              PCRE_EXTENDED         ignore whitespaces          /x
4489              PCRE_UTF8             handles UTF8 chars          built-in
4490              PCRE_UNGREEDY         reverses * and *?           N/A
4491              PCRE_NO_AUTO_CAPTURE  disables capturing parens   N/A (*)
4492    
4493           (*)  Both Perl and PCRE allow non capturing parentheses by means of the
4494           "?:" modifier within the pattern itself. e.g. (?:ab|cd) does  not  cap-
4495           ture, while (ab|cd) does.
4496    
4497           For  a  full  account on how each modifier works, please check the PCRE
4498           API reference page.
4499    
4500           For each modifier, there are two member functions whose  name  is  made
4501           out  of  the  modifier  in  lowercase,  without the "PCRE_" prefix. For
4502           instance, PCRE_CASELESS is handled by
4503    
4504             bool caseless()
4505    
4506           which returns true if the modifier is set, and
4507    
4508             RE_Options & set_caseless(bool)
4509    
4510           which sets or unsets the  modifier.  Moreover,  PCRE_CONFIG_MATCH_LIMIT
4511           can  be accessed through the set_match_limit() and match_limit() member
4512           functions. Setting match_limit to a non-zero value will limit the  exe-
4513           cution  of pcre to keep it from doing bad things like blowing the stack
4514           or taking an eternity to return a result.  A  value  of  5000  is  good
4515           enough  to stop stack blowup in a 2MB thread stack. Setting match_limit
4516           to zero disables match limiting.
4517    
4518           Normally, to pass one or more modifiers to a RE class,  you  declare  a
4519           RE_Options object, set the appropriate options, and pass this object to
4520           a RE constructor. Example:
4521    
4522              RE_options opt;
4523              opt.set_caseless(true);
4524              if (RE("HELLO", opt).PartialMatch("hello world")) ...
4525    
4526           RE_options has two constructors. The default constructor takes no argu-
4527           ments  and creates a set of flags that are off by default. The optional
4528           parameter option_flags is to facilitate transfer of legacy code from  C
4529           programs.  This lets you do
4530    
4531              RE(pattern,
4532                RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str);
4533    
4534           However, new code is better off doing
4535    
4536              RE(pattern,
4537                RE_Options().set_caseless(true).set_multiline(true))
4538                  .PartialMatch(str);
4539    
4540           If you are going to pass one of the most used modifiers, there are some
4541           convenience functions that return a RE_Options class with the appropri-
4542           ate  modifier  already  set: CASELESS(), UTF8(), MULTILINE(), DOTALL(),
4543           and EXTENDED().
4544    
4545           If you need to set several options at once, and you don't  want  to  go
4546           through  the pains of declaring a RE_Options object and setting several
4547           options, there is a parallel method that give you such ability  on  the
4548           fly.  You  can  concatenate several set_xxxxx() member functions, since
4549           each of them returns a reference to its class object. For  example,  to
4550           pass  PCRE_CASELESS, PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one
4551           statement, you may write:
4552    
4553              RE(" ^ xyz \\s+ .* blah$",
4554                RE_Options()
4555                  .set_caseless(true)
4556                  .set_extended(true)
4557                  .set_multiline(true)).PartialMatch(sometext);
4558    
4559    
4560    SCANNING TEXT INCREMENTALLY
4561    
4562           The "Consume" operation may be useful if you want to  repeatedly  match
4563           regular expressions at the front of a string and skip over them as they
4564           match. This requires use of the "StringPiece" type, which represents  a
4565           sub-range  of  a  real  string.  Like RE, StringPiece is defined in the
4566           pcrecpp namespace.
4567    
4568             Example: read lines of the form "var = value" from a string.
4569                string contents = ...;                 // Fill string somehow
4570                pcrecpp::StringPiece input(contents);  // Wrap in a StringPiece
4571    
4572                string var;
4573                int value;
4574                pcrecpp::RE re("(\\w+) = (\\d+)\n");
4575                while (re.Consume(&input, &var, &value)) {
4576                  ...;
4577                }
4578    
4579           Each successful call  to  "Consume"  will  set  "var/value",  and  also
4580           advance "input" so it points past the matched text.
4581    
4582           The  "FindAndConsume"  operation  is  similar to "Consume" but does not
4583           anchor your match at the beginning of  the  string.  For  example,  you
4584           could extract all words from a string by repeatedly calling
4585    
4586             pcrecpp::RE("(\\w+)").FindAndConsume(&input, &word)
4587    
4588    
4589    PARSING HEX/OCTAL/C-RADIX NUMBERS
4590    
4591           By default, if you pass a pointer to a numeric value, the corresponding
4592           text is interpreted as a base-10  number.  You  can  instead  wrap  the
4593           pointer with a call to one of the operators Hex(), Octal(), or CRadix()
4594           to interpret the text in another base. The CRadix  operator  interprets
4595           C-style  "0"  (base-8)  and  "0x"  (base-16)  prefixes, but defaults to
4596           base-10.
4597    
4598             Example:
4599               int a, b, c, d;
4600               pcrecpp::RE re("(.*) (.*) (.*) (.*)");
4601               re.FullMatch("100 40 0100 0x40",
4602                            pcrecpp::Octal(&a), pcrecpp::Hex(&b),
4603                            pcrecpp::CRadix(&c), pcrecpp::CRadix(&d));
4604    
4605           will leave 64 in a, b, c, and d.
4606    
4607    
4608   &nbs