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revision 172 by ph10, Tue Jun 5 10:40:13 2007 UTC revision 567 by ph10, Sat Nov 6 17:10:00 2010 UTC
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2  This file contains a concatenation of the PCRE man pages, converted to plain  This file contains a concatenation of the PCRE man pages, converted to plain
3  text format for ease of searching with a text editor, or for use on systems  text format for ease of searching with a text editor, or for use on systems
4  that do not have a man page processor. The small individual files that give  that do not have a man page processor. The small individual files that give
5  synopses of each function in the library have not been included. There are  synopses of each function in the library have not been included. Neither has
6  separate text files for the pcregrep and pcretest commands.  the pcredemo program. There are separate text files for the pcregrep and
7    pcretest commands.
8  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
9    
10    
# Line 18  INTRODUCTION Line 19  INTRODUCTION
19    
20         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
21         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
22         just  a  few differences. (Certain features that appeared in Python and         just  a few differences. Some features that appeared in Python and PCRE
23         PCRE before they appeared in Perl are also available using  the  Python         before they appeared in Perl are also available using the  Python  syn-
24         syntax.)         tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25           items, and there is an option for requesting some  minor  changes  that
26         The  current  implementation of PCRE (release 7.x) corresponds approxi-         give better JavaScript compatibility.
27         mately with Perl 5.10, including support for UTF-8 encoded strings  and  
28         Unicode general category properties. However, UTF-8 and Unicode support         The  current implementation of PCRE corresponds approximately with Perl
29         has to be explicitly enabled; it is not the default. The Unicode tables         5.10/5.11, including support for UTF-8 encoded strings and Unicode gen-
30         correspond to Unicode release 5.0.0.         eral  category properties. However, UTF-8 and Unicode support has to be
31           explicitly enabled; it is not the default. The  Unicode  tables  corre-
32           spond to Unicode release 5.2.0.
33    
34         In  addition to the Perl-compatible matching function, PCRE contains an         In  addition to the Perl-compatible matching function, PCRE contains an
35         alternative matching function that matches the same  compiled  patterns         alternative function that matches the same compiled patterns in a  dif-
36         in  a different way. In certain circumstances, the alternative function         ferent way. In certain circumstances, the alternative function has some
37         has some advantages. For a discussion of the two  matching  algorithms,         advantages.  For a discussion of the two matching algorithms,  see  the
38         see the pcrematching page.         pcrematching page.
39    
40         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
41         have written wrappers and interfaces of various kinds.  In  particular,         have written wrappers and interfaces of various kinds.  In  particular,
# Line 45  INTRODUCTION Line 48  INTRODUCTION
48    
49         Details of exactly which Perl regular expression features are  and  are         Details of exactly which Perl regular expression features are  and  are
50         not supported by PCRE are given in separate documents. See the pcrepat-         not supported by PCRE are given in separate documents. See the pcrepat-
51         tern and pcrecompat pages.         tern and pcrecompat pages. There is a syntax summary in the  pcresyntax
52           page.
53    
54         Some features of PCRE can be included, excluded, or  changed  when  the         Some  features  of  PCRE can be included, excluded, or changed when the
55         library  is  built.  The pcre_config() function makes it possible for a         library is built. The pcre_config() function makes it  possible  for  a
56         client to discover which features are  available.  The  features  them-         client  to  discover  which  features are available. The features them-
57         selves  are described in the pcrebuild page. Documentation about build-         selves are described in the pcrebuild page. Documentation about  build-
58         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 and
59         in the source distribution.         NON-UNIX-USE files in the source distribution.
60    
61         The  library  contains  a number of undocumented internal functions and         The library contains a number of undocumented  internal  functions  and
62         data tables that are used by more than one  of  the  exported  external         data  tables  that  are  used by more than one of the exported external
63         functions,  but  which  are  not  intended for use by external callers.         functions, but which are not intended  for  use  by  external  callers.
64         Their names all begin with "_pcre_", which hopefully will  not  provoke         Their  names  all begin with "_pcre_", which hopefully will not provoke
65         any name clashes. In some environments, it is possible to control which         any name clashes. In some environments, it is possible to control which
66         external symbols are exported when a shared library is  built,  and  in         external  symbols  are  exported when a shared library is built, and in
67         these cases the undocumented symbols are not exported.         these cases the undocumented symbols are not exported.
68    
69    
70  USER DOCUMENTATION  USER DOCUMENTATION
71    
72         The  user  documentation  for PCRE comprises a number of different sec-         The user documentation for PCRE comprises a number  of  different  sec-
73         tions. In the "man" format, each of these is a separate "man page".  In         tions.  In the "man" format, each of these is a separate "man page". In
74         the  HTML  format, each is a separate page, linked from the index page.         the HTML format, each is a separate page, linked from the  index  page.
75         In the plain text format, all the sections are concatenated,  for  ease         In  the  plain  text format, all the sections, except the pcredemo sec-
76         of searching. The sections are as follows:         tion, are concatenated, for ease of searching. The sections are as fol-
77           lows:
78    
79           pcre              this document           pcre              this document
80           pcre-config       show PCRE installation configuration information           pcre-config       show PCRE installation configuration information
# Line 78  USER DOCUMENTATION Line 83  USER DOCUMENTATION
83           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
84           pcrecompat        discussion of Perl compatibility           pcrecompat        discussion of Perl compatibility
85           pcrecpp           details of the C++ wrapper           pcrecpp           details of the C++ wrapper
86             pcredemo          a demonstration C program that uses PCRE
87           pcregrep          description of the pcregrep command           pcregrep          description of the pcregrep command
88           pcrematching      discussion of the two matching algorithms           pcrematching      discussion of the two matching algorithms
89           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
# Line 86  USER DOCUMENTATION Line 92  USER DOCUMENTATION
92           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
93           pcreposix         the POSIX-compatible C API           pcreposix         the POSIX-compatible C API
94           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
95           pcresample        discussion of the sample program           pcresample        discussion of the pcredemo program
96           pcrestack         discussion of stack usage           pcrestack         discussion of stack usage
97             pcresyntax        quick syntax reference
98           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
99    
100         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
101         each C library function, listing its arguments and results.         each C library function, listing its arguments and results.
102    
103    
104  LIMITATIONS  LIMITATIONS
105    
106         There  are some size limitations in PCRE but it is hoped that they will         There are some size limitations in PCRE but it is hoped that they  will
107         never in practice be relevant.         never in practice be relevant.
108    
109         The maximum length of a compiled pattern is 65539 (sic) bytes  if  PCRE         The  maximum  length of a compiled pattern is 65539 (sic) bytes if PCRE
110         is compiled with the default internal linkage size of 2. If you want to         is compiled with the default internal linkage size of 2. If you want to
111         process regular expressions that are truly enormous,  you  can  compile         process  regular  expressions  that are truly enormous, you can compile
112         PCRE  with  an  internal linkage size of 3 or 4 (see the README file in         PCRE with an internal linkage size of 3 or 4 (see the  README  file  in
113         the source distribution and the pcrebuild documentation  for  details).         the  source  distribution and the pcrebuild documentation for details).
114         In  these  cases the limit is substantially larger.  However, the speed         In these cases the limit is substantially larger.  However,  the  speed
115         of execution is slower.         of execution is slower.
116    
117         All values in repeating quantifiers must be less than 65536. The  maxi-         All values in repeating quantifiers must be less than 65536.
        mum  compiled  length  of  subpattern  with an explicit repeat count is  
        30000 bytes. The maximum number of capturing subpatterns is 65535.  
118    
119         There is no limit to the number of parenthesized subpatterns, but there         There is no limit to the number of parenthesized subpatterns, but there
120         can be no more than 65535 capturing subpatterns.         can be no more than 65535 capturing subpatterns.
# Line 117  LIMITATIONS Line 122  LIMITATIONS
122         The maximum length of name for a named subpattern is 32 characters, and         The maximum length of name for a named subpattern is 32 characters, and
123         the maximum number of named subpatterns is 10000.         the maximum number of named subpatterns is 10000.
124    
125         The maximum length of a subject string is the largest  positive  number         The  maximum  length of a subject string is the largest positive number
126         that  an integer variable can hold. However, when using the traditional         that an integer variable can hold. However, when using the  traditional
127         matching function, PCRE uses recursion to handle subpatterns and indef-         matching function, PCRE uses recursion to handle subpatterns and indef-
128         inite  repetition.  This means that the available stack space may limit         inite repetition.  This means that the available stack space may  limit
129         the size of a subject string that can be processed by certain patterns.         the size of a subject string that can be processed by certain patterns.
130         For a discussion of stack issues, see the pcrestack documentation.         For a discussion of stack issues, see the pcrestack documentation.
131    
132    
133  UTF-8 AND UNICODE PROPERTY SUPPORT  UTF-8 AND UNICODE PROPERTY SUPPORT
134    
135         From  release  3.3,  PCRE  has  had  some support for character strings         From release 3.3, PCRE has  had  some  support  for  character  strings
136         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
137         to  cover  most common requirements, and in release 5.0 additional sup-         to cover most common requirements, and in release 5.0  additional  sup-
138         port for Unicode general category properties was added.         port for Unicode general category properties was added.
139    
140         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
141         support  in  the  code,  and, in addition, you must call pcre_compile()         support in the code, and, in addition,  you  must  call  pcre_compile()
142         with the PCRE_UTF8 option flag. When you do this, both the pattern  and         with  the  PCRE_UTF8  option  flag,  or the pattern must start with the
143         any  subject  strings  that are matched against it are treated as UTF-8         sequence (*UTF8). When either of these is the case,  both  the  pattern
144         strings instead of just strings of bytes.         and  any  subject  strings  that  are matched against it are treated as
145           UTF-8 strings instead of strings of 1-byte characters.
146    
147         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,
148         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
# Line 155  UTF-8 AND UNICODE PROPERTY SUPPORT Line 161  UTF-8 AND UNICODE PROPERTY SUPPORT
161         optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE         optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE
162         does not support this.         does not support this.
163    
164         The following comments apply when PCRE is running in UTF-8 mode:     Validity of UTF-8 strings
165    
166           When  you  set  the  PCRE_UTF8 flag, the strings passed as patterns and
167           subjects are (by default) checked for validity on entry to the relevant
168           functions.  From  release 7.3 of PCRE, the check is according the rules
169           of RFC 3629, which are themselves derived from the  Unicode  specifica-
170           tion.  Earlier  releases  of PCRE followed the rules of RFC 2279, which
171           allows the full range of 31-bit values (0 to 0x7FFFFFFF).  The  current
172           check allows only values in the range U+0 to U+10FFFF, excluding U+D800
173           to U+DFFF.
174    
175           The excluded code points are the "Low Surrogate Area"  of  Unicode,  of
176           which  the Unicode Standard says this: "The Low Surrogate Area does not
177           contain any  character  assignments,  consequently  no  character  code
178           charts or namelists are provided for this area. Surrogates are reserved
179           for use with UTF-16 and then must be used in pairs."  The  code  points
180           that  are  encoded  by  UTF-16  pairs are available as independent code
181           points in the UTF-8 encoding. (In  other  words,  the  whole  surrogate
182           thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
183    
184           If  an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error return
185           (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know
186           that your strings are valid, and therefore want to skip these checks in
187           order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at
188           compile  time  or at run time, PCRE assumes that the pattern or subject
189           it is given (respectively) contains only valid  UTF-8  codes.  In  this
190           case, it does not diagnose an invalid UTF-8 string.
191    
192           If  you  pass  an  invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set,
193           what happens depends on why the string is invalid. If the  string  con-
194           forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
195           string of characters in the range 0  to  0x7FFFFFFF.  In  other  words,
196           apart from the initial validity test, PCRE (when in UTF-8 mode) handles
197           strings according to the more liberal rules of RFC  2279.  However,  if
198           the  string does not even conform to RFC 2279, the result is undefined.
199           Your program may crash.
200    
201           If you want to process strings  of  values  in  the  full  range  0  to
202           0x7FFFFFFF,  encoded in a UTF-8-like manner as per the old RFC, you can
203           set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in
204           this situation, you will have to apply your own validity check.
205    
206         1.  When you set the PCRE_UTF8 flag, the strings passed as patterns and     General comments about UTF-8 mode
        subjects are checked for validity on entry to the  relevant  functions.  
        If an invalid UTF-8 string is passed, an error return is given. In some  
        situations, you may already know  that  your  strings  are  valid,  and  
        therefore want to skip these checks in order to improve performance. If  
        you set the PCRE_NO_UTF8_CHECK flag at compile time  or  at  run  time,  
        PCRE  assumes  that  the  pattern or subject it is given (respectively)  
        contains only valid UTF-8 codes. In this case, it does not diagnose  an  
        invalid  UTF-8 string. If you pass an invalid UTF-8 string to PCRE when  
        PCRE_NO_UTF8_CHECK is set, the results are undefined. Your program  may  
        crash.  
207    
208         2.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a         1.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a
209         two-byte UTF-8 character if the value is greater than 127.         two-byte UTF-8 character if the value is greater than 127.
210    
211         3. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8         2. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8
212         characters for values greater than \177.         characters for values greater than \177.
213    
214         4.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-         3.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-
215         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
216    
217         5. The dot metacharacter matches one UTF-8 character instead of a  sin-         4. The dot metacharacter matches one UTF-8 character instead of a  sin-
218         gle byte.         gle byte.
219    
220         6.  The  escape sequence \C can be used to match a single byte in UTF-8         5.  The  escape sequence \C can be used to match a single byte in UTF-8
221         mode, but its use can lead to some strange effects.  This  facility  is         mode, but its use can lead to some strange effects.  This  facility  is
222         not available in the alternative matching function, pcre_dfa_exec().         not available in the alternative matching function, pcre_dfa_exec().
223    
224         7.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly         6.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly
225         test characters of any code value, but the characters that PCRE  recog-         test characters of any code value, but, by default, the characters that
226         nizes  as  digits,  spaces,  or  word characters remain the same set as         PCRE  recognizes  as digits, spaces, or word characters remain the same
227         before, all with values less than 256. This remains true even when PCRE         set as before, all with values less than 256. This  remains  true  even
228         includes  Unicode  property support, because to do otherwise would slow         when  PCRE  is built to include Unicode property support, because to do
229         down PCRE in many common cases. If you really want to test for a  wider         otherwise would slow down PCRE in many common cases. Note in particular
230         sense  of,  say,  "digit",  you must use Unicode property tests such as         that this applies to \b and \B, because they are defined in terms of \w
231         \p{Nd}.         and \W. If you really want to test for a wider sense of, say,  "digit",
232           you  can  use  explicit Unicode property tests such as \p{Nd}. Alterna-
233         8. Similarly, characters that match the POSIX named  character  classes         tively, if you set the PCRE_UCP option,  the  way  that  the  character
234         are all low-valued characters.         escapes  work  is changed so that Unicode properties are used to deter-
235           mine which characters match. There are more details in the  section  on
236         9.  Case-insensitive  matching  applies only to characters whose values         generic character types in the pcrepattern documentation.
237         are less than 128, unless PCRE is built with Unicode property  support.  
238         Even  when  Unicode  property support is available, PCRE still uses its         7.  Similarly,  characters that match the POSIX named character classes
239         own character tables when checking the case of  low-valued  characters,         are all low-valued characters, unless the PCRE_UCP option is set.
240         so  as not to degrade performance.  The Unicode property information is  
241           8. However, the Perl 5.10 horizontal and vertical  whitespace  matching
242           escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-
243           acters, whether or not PCRE_UCP is set.
244    
245           9. Case-insensitive matching applies only to  characters  whose  values
246           are  less than 128, unless PCRE is built with Unicode property support.
247           Even when Unicode property support is available, PCRE  still  uses  its
248           own  character  tables when checking the case of low-valued characters,
249           so as not to degrade performance.  The Unicode property information  is
250         used only for characters with higher values. Even when Unicode property         used only for characters with higher values. Even when Unicode property
251         support is available, PCRE supports case-insensitive matching only when         support is available, PCRE supports case-insensitive matching only when
252         there is a one-to-one mapping between a letter's  cases.  There  are  a         there  is  a  one-to-one  mapping between a letter's cases. There are a
253         small  number  of  many-to-one  mappings in Unicode; these are not sup-         small number of many-to-one mappings in Unicode;  these  are  not  sup-
254         ported by PCRE.         ported by PCRE.
255    
256    
# Line 215  AUTHOR Line 260  AUTHOR
260         University Computing Service         University Computing Service
261         Cambridge CB2 3QH, England.         Cambridge CB2 3QH, England.
262    
263         Putting an actual email address here seems to have been a spam  magnet,         Putting  an actual email address here seems to have been a spam magnet,
264         so  I've  taken  it away. If you want to email me, use my two initials,         so I've taken it away. If you want to email me, use  my  two  initials,
265         followed by the two digits 10, at the domain cam.ac.uk.         followed by the two digits 10, at the domain cam.ac.uk.
266    
267    
268  REVISION  REVISION
269    
270         Last updated: 18 April 2007         Last updated: 22 October 2010
271         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
272  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
273    
274    
275  PCREBUILD(3)                                                      PCREBUILD(3)  PCREBUILD(3)                                                      PCREBUILD(3)
276    
277    
# Line 237  NAME Line 282  NAME
282  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
283    
284         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
285         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
286         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
287         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
288         includes  the  standard  ones such as the selection of the installation         the  same  options  can be selected in both Unix-like and non-Unix-like
289         directory) can be obtained by running         environments using the GUI facility of cmake-gui if you are using CMake
290           instead of configure to build PCRE.
291    
292           There  is  a  lot more information about building PCRE in non-Unix-like
293           environments in the file called NON_UNIX_USE, which is part of the PCRE
294           distribution.  You  should consult this file as well as the README file
295           if you are building in a non-Unix-like environment.
296    
297           The complete list of options for configure (which includes the standard
298           ones  such  as  the  selection  of  the  installation directory) can be
299           obtained by running
300    
301           ./configure --help           ./configure --help
302    
# Line 266  C++ SUPPORT Line 321  C++ SUPPORT
321    
322  UTF-8 SUPPORT  UTF-8 SUPPORT
323    
324         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 Unicode character strings, add
325    
326           --enable-utf8           --enable-utf8
327    
328         to  the  configure  command.  Of  itself, this does not make PCRE treat         to  the  configure  command.  Of  itself, this does not make PCRE treat
329         strings as UTF-8. As well as compiling PCRE with this option, you  also         strings as UTF-8. As well as compiling PCRE with this option, you  also
330         have  have to set the PCRE_UTF8 option when you call the pcre_compile()         have  have to set the PCRE_UTF8 option when you call the pcre_compile()
331         function.         or pcre_compile2() functions.
332    
333           If you set --enable-utf8 when compiling in an EBCDIC environment,  PCRE
334           expects its input to be either ASCII or UTF-8 (depending on the runtime
335           option). It is not possible to support both EBCDIC and UTF-8  codes  in
336           the  same  version  of  the  library.  Consequently,  --enable-utf8 and
337           --enable-ebcdic are mutually exclusive.
338    
339    
340  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
# Line 296  UNICODE CHARACTER PROPERTY SUPPORT Line 357  UNICODE CHARACTER PROPERTY SUPPORT
357    
358  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
359    
360         By  default,  PCRE interprets character 10 (linefeed, LF) as indicating         By  default,  PCRE interprets the linefeed (LF) character as indicating
361         the end of a line. This is the normal newline  character  on  Unix-like         the end of a line. This is the normal newline  character  on  Unix-like
362         systems. You can compile PCRE to use character 13 (carriage return, CR)         systems.  You  can compile PCRE to use carriage return (CR) instead, by
363         instead, by adding         adding
364    
365           --enable-newline-is-cr           --enable-newline-is-cr
366    
# Line 322  CODE VALUE OF NEWLINE Line 383  CODE VALUE OF NEWLINE
383    
384         causes PCRE to recognize any Unicode newline sequence.         causes PCRE to recognize any Unicode newline sequence.
385    
386         Whatever line ending convention is selected when PCRE is built  can  be         Whatever  line  ending convention is selected when PCRE is built can be
387         overridden  when  the library functions are called. At build time it is         overridden when the library functions are called. At build time  it  is
388         conventional to use the standard for your operating system.         conventional to use the standard for your operating system.
389    
390    
391    WHAT \R MATCHES
392    
393           By  default,  the  sequence \R in a pattern matches any Unicode newline
394           sequence, whatever has been selected as the line  ending  sequence.  If
395           you specify
396    
397             --enable-bsr-anycrlf
398    
399           the  default  is changed so that \R matches only CR, LF, or CRLF. What-
400           ever is selected when PCRE is built can be overridden when the  library
401           functions are called.
402    
403    
404  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
405    
406         The PCRE building process uses libtool to build both shared and  static         The  PCRE building process uses libtool to build both shared and static
407         Unix  libraries by default. You can suppress one of these by adding one         Unix libraries by default. You can suppress one of these by adding  one
408         of         of
409    
410           --disable-shared           --disable-shared
# Line 342  BUILDING SHARED AND STATIC LIBRARIES Line 416  BUILDING SHARED AND STATIC LIBRARIES
416  POSIX MALLOC USAGE  POSIX MALLOC USAGE
417    
418         When PCRE is called through the POSIX interface (see the pcreposix doc-         When PCRE is called through the POSIX interface (see the pcreposix doc-
419         umentation),  additional  working  storage  is required for holding the         umentation), additional working storage is  required  for  holding  the
420         pointers to capturing substrings, because PCRE requires three  integers         pointers  to capturing substrings, because PCRE requires three integers
421         per  substring,  whereas  the POSIX interface provides only two. If the         per substring, whereas the POSIX interface provides only  two.  If  the
422         number of expected substrings is small, the wrapper function uses space         number of expected substrings is small, the wrapper function uses space
423         on the stack, because this is faster than using malloc() for each call.         on the stack, because this is faster than using malloc() for each call.
424         The default threshold above which the stack is no longer used is 10; it         The default threshold above which the stack is no longer used is 10; it
# Line 357  POSIX MALLOC USAGE Line 431  POSIX MALLOC USAGE
431    
432  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
433    
434         Within  a  compiled  pattern,  offset values are used to point from one         Within a compiled pattern, offset values are used  to  point  from  one
435         part to another (for example, from an opening parenthesis to an  alter-         part  to another (for example, from an opening parenthesis to an alter-
436         nation  metacharacter).  By default, two-byte values are used for these         nation metacharacter). By default, two-byte values are used  for  these
437         offsets, leading to a maximum size for a  compiled  pattern  of  around         offsets,  leading  to  a  maximum size for a compiled pattern of around
438         64K.  This  is sufficient to handle all but the most gigantic patterns.         64K. This is sufficient to handle all but the most  gigantic  patterns.
439         Nevertheless, some people do want to process enormous patterns,  so  it         Nevertheless,  some  people do want to process truyl enormous patterns,
440         is  possible  to compile PCRE to use three-byte or four-byte offsets by         so it is possible to compile PCRE to use three-byte or  four-byte  off-
441         adding a setting such as         sets by adding a setting such as
442    
443           --with-link-size=3           --with-link-size=3
444    
445         to the configure command. The value given must be 2,  3,  or  4.  Using         to  the  configure  command.  The value given must be 2, 3, or 4. Using
446         longer  offsets slows down the operation of PCRE because it has to load         longer offsets slows down the operation of PCRE because it has to  load
447         additional bytes when handling them.         additional bytes when handling them.
448    
449    
450  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
451    
452         When matching with the pcre_exec() function, PCRE implements backtrack-         When matching with the pcre_exec() function, PCRE implements backtrack-
453         ing  by  making recursive calls to an internal function called match().         ing by making recursive calls to an internal function  called  match().
454         In environments where the size of the stack is limited,  this  can  se-         In  environments  where  the size of the stack is limited, this can se-
455         verely  limit  PCRE's operation. (The Unix environment does not usually         verely limit PCRE's operation. (The Unix environment does  not  usually
456         suffer from this problem, but it may sometimes be necessary to increase         suffer from this problem, but it may sometimes be necessary to increase
457         the  maximum  stack size.  There is a discussion in the pcrestack docu-         the maximum stack size.  There is a discussion in the  pcrestack  docu-
458         mentation.) An alternative approach to recursion that uses memory  from         mentation.)  An alternative approach to recursion that uses memory from
459         the  heap  to remember data, instead of using recursive function calls,         the heap to remember data, instead of using recursive  function  calls,
460         has been implemented to work round the problem of limited  stack  size.         has  been  implemented to work round the problem of limited stack size.
461         If you want to build a version of PCRE that works this way, add         If you want to build a version of PCRE that works this way, add
462    
463           --disable-stack-for-recursion           --disable-stack-for-recursion
464    
465         to  the  configure  command. With this configuration, PCRE will use the         to the configure command. With this configuration, PCRE  will  use  the
466         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
467         ment  functions.  Separate  functions are provided because the usage is         ment functions. By default these point to malloc() and free(), but  you
468         very predictable: the block sizes requested are always  the  same,  and         can replace the pointers so that your own functions are used instead.
469         the  blocks  are always freed in reverse order. A calling program might  
470         be able to implement optimized functions that perform better  than  the         Separate  functions  are  provided  rather  than  using pcre_malloc and
471         standard  malloc()  and  free()  functions.  PCRE  runs noticeably more         pcre_free because the  usage  is  very  predictable:  the  block  sizes
472         slowly when built in this way. This option affects only the pcre_exec()         requested  are  always  the  same,  and  the blocks are always freed in
473         function; it is not relevant for the the pcre_dfa_exec() function.         reverse order. A calling program might be able to  implement  optimized
474           functions  that  perform  better  than  malloc()  and free(). PCRE runs
475           noticeably more slowly when built in this way. This option affects only
476           the pcre_exec() function; it is not relevant for pcre_dfa_exec().
477    
478    
479  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
# Line 451  USING EBCDIC CODE Line 528  USING EBCDIC CODE
528    
529         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
530         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
531         PCRE  can,  however,  be  compiled  to  run in an EBCDIC environment by         This  is  the  case for most computer operating systems. PCRE can, how-
532         adding         ever, be compiled to run in an EBCDIC environment by adding
533    
534           --enable-ebcdic           --enable-ebcdic
535    
536         to the configure command. This setting implies --enable-rebuild-charta-         to the configure command. This setting implies --enable-rebuild-charta-
537         bles.         bles.  You  should  only  use  it if you know that you are in an EBCDIC
538           environment (for example,  an  IBM  mainframe  operating  system).  The
539           --enable-ebcdic option is incompatible with --enable-utf8.
540    
541    
542    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
543    
544           By default, pcregrep reads all files as plain text. You can build it so
545           that it recognizes files whose names end in .gz or .bz2, and reads them
546           with libz or libbz2, respectively, by adding one or both of
547    
548             --enable-pcregrep-libz
549             --enable-pcregrep-libbz2
550    
551           to the configure command. These options naturally require that the rel-
552           evant libraries are installed on your system. Configuration  will  fail
553           if they are not.
554    
555    
556    PCRETEST OPTION FOR LIBREADLINE SUPPORT
557    
558           If you add
559    
560             --enable-pcretest-libreadline
561    
562           to  the  configure  command,  pcretest  is  linked with the libreadline
563           library, and when its input is from a terminal, it reads it  using  the
564           readline() function. This provides line-editing and history facilities.
565           Note that libreadline is GPL-licensed, so if you distribute a binary of
566           pcretest linked in this way, there may be licensing issues.
567    
568           Setting  this  option  causes  the -lreadline option to be added to the
569           pcretest build. In many operating environments with  a  sytem-installed
570           libreadline this is sufficient. However, in some environments (e.g.  if
571           an unmodified distribution version of readline is in use),  some  extra
572           configuration  may  be necessary. The INSTALL file for libreadline says
573           this:
574    
575             "Readline uses the termcap functions, but does not link with the
576             termcap or curses library itself, allowing applications which link
577             with readline the to choose an appropriate library."
578    
579           If your environment has not been set up so that an appropriate  library
580           is automatically included, you may need to add something like
581    
582             LIBS="-ncurses"
583    
584           immediately before the configure command.
585    
586    
587  SEE ALSO  SEE ALSO
# Line 474  AUTHOR Line 598  AUTHOR
598    
599  REVISION  REVISION
600    
601         Last updated: 16 April 2007         Last updated: 29 September 2009
602         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
603  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
604    
605    
606  PCREMATCHING(3)                                                PCREMATCHING(3)  PCREMATCHING(3)                                                PCREMATCHING(3)
607    
608    
# Line 562  THE ALTERNATIVE MATCHING ALGORITHM Line 686  THE ALTERNATIVE MATCHING ALGORITHM
686         though  it is not implemented as a traditional finite state machine (it         though  it is not implemented as a traditional finite state machine (it
687         keeps multiple states active simultaneously).         keeps multiple states active simultaneously).
688    
689           Although the general principle of this matching algorithm  is  that  it
690           scans  the subject string only once, without backtracking, there is one
691           exception: when a lookaround assertion is encountered,  the  characters
692           following  or  preceding  the  current  point  have to be independently
693           inspected.
694    
695         The scan continues until either the end of the subject is  reached,  or         The scan continues until either the end of the subject is  reached,  or
696         there  are  no more unterminated paths. At this point, terminated paths         there  are  no more unterminated paths. At this point, terminated paths
697         represent the different matching possibilities (if there are none,  the         represent the different matching possibilities (if there are none,  the
698         match  has  failed).   Thus,  if there is more than one possible match,         match  has  failed).   Thus,  if there is more than one possible match,
699         this algorithm finds all of them, and in particular, it finds the long-         this algorithm finds all of them, and in particular, it finds the long-
700         est.  In PCRE, there is an option to stop the algorithm after the first         est.  There  is  an  option to stop the algorithm after the first match
701         match (which is necessarily the shortest) has been found.         (which is necessarily the shortest) is found.
702    
703         Note that all the matches that are found start at the same point in the         Note that all the matches that are found start at the same point in the
704         subject. If the pattern         subject. If the pattern
# Line 618  THE ALTERNATIVE MATCHING ALGORITHM Line 748  THE ALTERNATIVE MATCHING ALGORITHM
748         6.  Callouts  are  supported, but the value of the capture_top field is         6.  Callouts  are  supported, but the value of the capture_top field is
749         always 1, and the value of the capture_last field is always -1.         always 1, and the value of the capture_last field is always -1.
750    
751         7.  The \C escape sequence, which (in the standard algorithm) matches a         7. The \C escape sequence, which (in the standard algorithm) matches  a
752         single  byte, even in UTF-8 mode, is not supported because the alterna-         single  byte, even in UTF-8 mode, is not supported because the alterna-
753         tive algorithm moves through the subject  string  one  character  at  a         tive algorithm moves through the subject  string  one  character  at  a
754         time, for all active paths through the tree.         time, for all active paths through the tree.
755    
756           8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
757           are not supported. (*FAIL) is supported, and  behaves  like  a  failing
758           negative assertion.
759    
760    
761  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
762    
# Line 634  ADVANTAGES OF THE ALTERNATIVE ALGORITHM Line 768  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
768         more than one match using the standard algorithm, you have to do kludgy         more than one match using the standard algorithm, you have to do kludgy
769         things with callouts.         things with callouts.
770    
771         2.  There is much better support for partial matching. The restrictions         2.  Because  the  alternative  algorithm  scans the subject string just
        on the content of the pattern that apply when using the standard  algo-  
        rithm  for  partial matching do not apply to the alternative algorithm.  
        For non-anchored patterns, the starting position of a partial match  is  
        available.  
   
        3.  Because  the  alternative  algorithm  scans the subject string just  
772         once, and never needs to backtrack, it is possible to  pass  very  long         once, and never needs to backtrack, it is possible to  pass  very  long
773         subject  strings  to  the matching function in several pieces, checking         subject  strings  to  the matching function in several pieces, checking
774         for partial matching each time.         for partial matching each time. It  is  possible  to  do  multi-segment
775           matching using pcre_exec() (by retaining partially matched substrings),
776           but it is more complicated. The pcrepartial documentation gives details
777           of partial matching and discusses multi-segment matching.
778    
779    
780  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
781    
782         The alternative algorithm suffers from a number of disadvantages:         The alternative algorithm suffers from a number of disadvantages:
783    
784         1. It is substantially slower than  the  standard  algorithm.  This  is         1.  It  is  substantially  slower  than the standard algorithm. This is
785         partly  because  it has to search for all possible matches, but is also         partly because it has to search for all possible matches, but  is  also
786         because it is less susceptible to optimization.         because it is less susceptible to optimization.
787    
788         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
# Line 669  AUTHOR Line 800  AUTHOR
800    
801  REVISION  REVISION
802    
803         Last updated: 29 May 2007         Last updated: 22 October 2010
804         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
805  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
806    
807    
808  PCREAPI(3)                                                          PCREAPI(3)  PCREAPI(3)                                                          PCREAPI(3)
809    
810    
# Line 777  PCRE API OVERVIEW Line 908  PCRE API OVERVIEW
908         bers for the library.  Applications can use these  to  include  support         bers for the library.  Applications can use these  to  include  support
909         for different releases of PCRE.         for different releases of PCRE.
910    
911           In a Windows environment, if you want to statically link an application
912           program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC
913           before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-
914           loc()   and   pcre_free()   exported   functions   will   be   declared
915           __declspec(dllimport), with unwanted results.
916    
917         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
918         pcre_exec() are used for compiling and matching regular expressions  in         pcre_exec() are used for compiling and matching regular expressions  in
919         a  Perl-compatible  manner. A sample program that demonstrates the sim-         a  Perl-compatible  manner. A sample program that demonstrates the sim-
920         plest way of using them is provided in the file  called  pcredemo.c  in         plest way of using them is provided in the file  called  pcredemo.c  in
921         the  source distribution. The pcresample documentation describes how to         the PCRE source distribution. A listing of this program is given in the
922         run it.         pcredemo documentation, and the pcresample documentation describes  how
923           to compile and run it.
924    
925         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
926         ble,  is  also provided. This uses a different algorithm for the match-         ble, is also provided. This uses a different algorithm for  the  match-
927         ing. The alternative algorithm finds all possible matches (at  a  given         ing.  The  alternative algorithm finds all possible matches (at a given
928         point  in  the subject), and scans the subject just once. However, this         point in the subject), and scans the subject just  once  (unless  there
929         algorithm does not return captured substrings. A description of the two         are  lookbehind  assertions).  However,  this algorithm does not return
930         matching  algorithms and their advantages and disadvantages is given in         captured substrings. A description of the two matching  algorithms  and
931         the pcrematching documentation.         their  advantages  and disadvantages is given in the pcrematching docu-
932           mentation.
933    
934         In addition to the main compiling and  matching  functions,  there  are         In addition to the main compiling and  matching  functions,  there  are
935         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
# Line 866  NEWLINES Line 1005  NEWLINES
1005         dard. When PCRE is run, the default can be overridden,  either  when  a         dard. When PCRE is run, the default can be overridden,  either  when  a
1006         pattern is compiled, or when it is matched.         pattern is compiled, or when it is matched.
1007    
1008           At compile time, the newline convention can be specified by the options
1009           argument of pcre_compile(), or it can be specified by special  text  at
1010           the start of the pattern itself; this overrides any other settings. See
1011           the pcrepattern page for details of the special character sequences.
1012    
1013         In the PCRE documentation the word "newline" is used to mean "the char-         In the PCRE documentation the word "newline" is used to mean "the char-
1014         acter or pair of characters that indicate a line break". The choice  of         acter  or pair of characters that indicate a line break". The choice of
1015         newline  convention  affects  the  handling of the dot, circumflex, and         newline convention affects the handling of  the  dot,  circumflex,  and
1016         dollar metacharacters, the handling of #-comments in /x mode, and, when         dollar metacharacters, the handling of #-comments in /x mode, and, when
1017         CRLF  is a recognized line ending sequence, the match position advance-         CRLF is a recognized line ending sequence, the match position  advance-
1018         ment for a non-anchored pattern. The choice of newline convention  does         ment for a non-anchored pattern. There is more detail about this in the
1019         not affect the interpretation of the \n or \r escape sequences.         section on pcre_exec() options below.
1020    
1021           The choice of newline convention does not affect the interpretation  of
1022           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
1023           which is controlled in a similar way, but by separate options.
1024    
1025    
1026  MULTITHREADING  MULTITHREADING
1027    
1028         The  PCRE  functions  can be used in multi-threading applications, with         The PCRE functions can be used in  multi-threading  applications,  with
1029         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
1030         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
1031         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
# Line 926  CHECKING BUILD-TIME OPTIONS Line 1074  CHECKING BUILD-TIME OPTIONS
1074         The output is an integer whose value specifies  the  default  character         The output is an integer whose value specifies  the  default  character
1075         sequence  that is recognized as meaning "newline". The four values that         sequence  that is recognized as meaning "newline". The four values that
1076         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
1077         and  -1  for  ANY. The default should normally be the standard sequence         and  -1  for  ANY.  Though they are derived from ASCII, the same values
1078         for your operating system.         are returned in EBCDIC environments. The default should normally corre-
1079           spond to the standard sequence for your operating system.
1080    
1081             PCRE_CONFIG_BSR
1082    
1083           The output is an integer whose value indicates what character sequences
1084           the \R escape sequence matches by default. A value of 0 means  that  \R
1085           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1086           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1087           tern is compiled or matched.
1088    
1089           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1090    
1091         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
1092         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
1093         4. Larger values allow larger regular expressions to  be  compiled,  at         4.  Larger  values  allow larger regular expressions to be compiled, at
1094         the  expense  of  slower matching. The default value of 2 is sufficient         the expense of slower matching. The default value of  2  is  sufficient
1095         for all but the most massive patterns, since  it  allows  the  compiled         for  all  but  the  most massive patterns, since it allows the compiled
1096         pattern to be up to 64K in size.         pattern to be up to 64K in size.
1097    
1098           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1099    
1100         The  output  is  an integer that contains the threshold above which the         The output is an integer that contains the threshold  above  which  the
1101         POSIX interface uses malloc() for output vectors. Further  details  are         POSIX  interface  uses malloc() for output vectors. Further details are
1102         given in the pcreposix documentation.         given in the pcreposix documentation.
1103    
1104           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1105    
1106         The output is an integer that gives the default limit for the number of         The output is a long integer that gives the default limit for the  num-
1107         internal matching function calls in a  pcre_exec()  execution.  Further         ber  of  internal  matching  function calls in a pcre_exec() execution.
1108         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1109    
1110           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1111    
1112         The  output is an integer that gives the default limit for the depth of         The output is a long integer that gives the default limit for the depth
1113         recursion when calling the internal matching function in a  pcre_exec()         of   recursion  when  calling  the  internal  matching  function  in  a
1114         execution. Further details are given with pcre_exec() below.         pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1115           below.
1116    
1117           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1118    
# Line 981  COMPILING A PATTERN Line 1139  COMPILING A PATTERN
1139         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1140         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1141         the  two interfaces is that pcre_compile2() has an additional argument,         the  two interfaces is that pcre_compile2() has an additional argument,
1142         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr, via which a numerical error  code  can  be  returned.  To
1143           avoid  too  much repetition, we refer just to pcre_compile() below, but
1144           the information applies equally to pcre_compile2().
1145    
1146         The pattern is a C string terminated by a binary zero, and is passed in         The pattern is a C string terminated by a binary zero, and is passed in
1147         the  pattern  argument.  A  pointer to a single block of memory that is         the  pattern  argument.  A  pointer to a single block of memory that is
# Line 998  COMPILING A PATTERN Line 1158  COMPILING A PATTERN
1158    
1159         The options argument contains various bit settings that affect the com-         The options argument contains various bit settings that affect the com-
1160         pilation. It should be zero if no options are required.  The  available         pilation. It should be zero if no options are required.  The  available
1161         options  are  described  below. Some of them, in particular, those that         options  are  described  below. Some of them (in particular, those that
1162         are compatible with Perl, can also be set and  unset  from  within  the         are compatible with Perl, but some others as well) can also be set  and
1163         pattern  (see  the  detailed  description in the pcrepattern documenta-         unset  from  within  the  pattern  (see the detailed description in the
1164         tion). For these options, the contents of the options  argument  speci-         pcrepattern documentation). For those options that can be different  in
1165         fies  their initial settings at the start of compilation and execution.         different  parts  of  the pattern, the contents of the options argument
1166         The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at  the  time         specifies their settings at the start of compilation and execution. The
1167         of matching as well as at compile time.         PCRE_ANCHORED, PCRE_BSR_xxx, and PCRE_NEWLINE_xxx options can be set at
1168           the time of matching as well as at compile time.
1169    
1170         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1171         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1172         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-
1173         sage. This is a static string that is part of the library. You must not         sage. This is a static string that is part of the library. You must not
1174         try to free it. The offset from the start of the pattern to the charac-         try to free it. The byte offset from the start of the  pattern  to  the
1175         ter where the error was discovered is placed in the variable pointed to         character  that  was  being  processed when the error was discovered is
1176         by  erroffset,  which must not be NULL. If it is, an immediate error is         placed in the variable pointed to by erroffset, which must not be NULL.
1177         given.         If  it  is,  an  immediate error is given. Some errors are not detected
1178           until checks are carried out when the whole pattern has  been  scanned;
1179         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         in this case the offset is set to the end of the pattern.
1180         codeptr  argument is not NULL, a non-zero error code number is returned  
1181         via this argument in the event of an error. This is in addition to  the         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1182           codeptr argument is not NULL, a non-zero error code number is  returned
1183           via  this argument in the event of an error. This is in addition to the
1184         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1185    
1186         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
1187         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1188         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1189         result of a call to pcre_maketables(). This value is  stored  with  the         result  of  a  call to pcre_maketables(). This value is stored with the
1190         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1191         pointer is passed to it. For more discussion, see the section on locale         pointer is passed to it. For more discussion, see the section on locale
1192         support below.         support below.
1193    
1194         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1195         pile():         pile():
1196    
1197           pcre *re;           pcre *re;
# Line 1041  COMPILING A PATTERN Line 1204  COMPILING A PATTERN
1204             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1205             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1206    
1207         The following names for option bits are defined in  the  pcre.h  header         The  following  names  for option bits are defined in the pcre.h header
1208         file:         file:
1209    
1210           PCRE_ANCHORED           PCRE_ANCHORED
1211    
1212         If this bit is set, the pattern is forced to be "anchored", that is, it         If this bit is set, the pattern is forced to be "anchored", that is, it
1213         is constrained to match only at the first matching point in the  string         is  constrained to match only at the first matching point in the string
1214         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1215         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1216         only way to do it in Perl.         only way to do it in Perl.
1217    
1218           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1219    
1220         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1221         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1222         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1223    
1224             PCRE_BSR_ANYCRLF
1225             PCRE_BSR_UNICODE
1226    
1227           These options (which are mutually exclusive) control what the \R escape
1228           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1229           or to match any Unicode newline sequence. The default is specified when
1230           PCRE is built. It can be overridden from within the pattern, or by set-
1231           ting an option when a compiled pattern is matched.
1232    
1233           PCRE_CASELESS           PCRE_CASELESS
1234    
1235         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
1236         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
1237         changed  within a pattern by a (?i) option setting. In UTF-8 mode, PCRE         changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
1238         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1239         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1240         with higher values, the concept of case is supported if  PCRE  is  com-         with  higher  values,  the concept of case is supported if PCRE is com-
1241         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1242         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1243         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1244         UTF-8 support.         UTF-8 support.
1245    
1246           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1247    
1248         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
1249         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
1250         matches immediately before a newline at the end of the string (but  not         matches  immediately before a newline at the end of the string (but not
1251         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1252         if PCRE_MULTILINE is set.  There is no equivalent  to  this  option  in         if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
1253         Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1254    
1255           PCRE_DOTALL           PCRE_DOTALL
1256    
1257         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-
1258         acters, including those that indicate newline. Without it, a  dot  does         acters,  including  those that indicate newline. Without it, a dot does
1259         not  match  when  the  current position is at a newline. This option is         not match when the current position is at a  newline.  This  option  is
1260         equivalent to Perl's /s option, and it can be changed within a  pattern         equivalent  to Perl's /s option, and it can be changed within a pattern
1261         by  a (?s) option setting. A negative class such as [^a] always matches         by a (?s) option setting. A negative class such as [^a] always  matches
1262         newline characters, independent of the setting of this option.         newline characters, independent of the setting of this option.
1263    
1264           PCRE_DUPNAMES           PCRE_DUPNAMES
1265    
1266         If this bit is set, names used to identify capturing  subpatterns  need         If  this  bit is set, names used to identify capturing subpatterns need
1267         not be unique. This can be helpful for certain types of pattern when it         not be unique. This can be helpful for certain types of pattern when it
1268         is known that only one instance of the named  subpattern  can  ever  be         is  known  that  only  one instance of the named subpattern can ever be
1269         matched.  There  are  more details of named subpatterns below; see also         matched. There are more details of named subpatterns  below;  see  also
1270         the pcrepattern documentation.         the pcrepattern documentation.
1271    
1272           PCRE_EXTENDED           PCRE_EXTENDED
1273    
1274         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1275         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1276         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1277         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1278         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1279         option,  and  it  can be changed within a pattern by a (?x) option set-         option, and it can be changed within a pattern by a  (?x)  option  set-
1280         ting.         ting.
1281    
1282         This option makes it possible to include  comments  inside  complicated         This  option  makes  it possible to include comments inside complicated
1283         patterns.   Note,  however,  that this applies only to data characters.         patterns.  Note, however, that this applies only  to  data  characters.
1284         Whitespace  characters  may  never  appear  within  special   character         Whitespace   characters  may  never  appear  within  special  character
1285         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for  example  within  the  sequence  (?(  which
1286         introduces a conditional subpattern.         introduces a conditional subpattern.
1287    
1288           PCRE_EXTRA           PCRE_EXTRA
1289    
1290         This option was invented in order to turn on  additional  functionality         This  option  was invented in order to turn on additional functionality
1291         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
1292         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
1293         letter  that  has  no  special  meaning causes an error, thus reserving         letter that has no special meaning  causes  an  error,  thus  reserving
1294         these combinations for future expansion. By  default,  as  in  Perl,  a         these  combinations  for  future  expansion.  By default, as in Perl, a
1295         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
1296         literal. (Perl can, however, be persuaded to give a warning for  this.)         literal. (Perl can, however, be persuaded to give an error for this, by
1297         There  are  at  present no other features controlled by this option. It         running it with the -w option.) There are at present no other  features
1298         can also be set by a (?X) option setting within a pattern.         controlled  by this option. It can also be set by a (?X) option setting
1299           within a pattern.
1300    
1301           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1302    
# Line 1131  COMPILING A PATTERN Line 1304  COMPILING A PATTERN
1304         before  or  at  the  first  newline  in  the subject string, though the         before  or  at  the  first  newline  in  the subject string, though the
1305         matched text may continue over the newline.         matched text may continue over the newline.
1306    
1307             PCRE_JAVASCRIPT_COMPAT
1308    
1309           If this option is set, PCRE's behaviour is changed in some ways so that
1310           it  is  compatible with JavaScript rather than Perl. The changes are as
1311           follows:
1312    
1313           (1) A lone closing square bracket in a pattern  causes  a  compile-time
1314           error,  because this is illegal in JavaScript (by default it is treated
1315           as a data character). Thus, the pattern AB]CD becomes illegal when this
1316           option is set.
1317    
1318           (2)  At run time, a back reference to an unset subpattern group matches
1319           an empty string (by default this causes the current  matching  alterna-
1320           tive  to  fail). A pattern such as (\1)(a) succeeds when this option is
1321           set (assuming it can find an "a" in the subject), whereas it  fails  by
1322           default, for Perl compatibility.
1323    
1324           PCRE_MULTILINE           PCRE_MULTILINE
1325    
1326         By default, PCRE treats the subject string as consisting  of  a  single         By  default,  PCRE  treats the subject string as consisting of a single
1327         line  of characters (even if it actually contains newlines). The "start         line of characters (even if it actually contains newlines). The  "start
1328         of line" metacharacter (^) matches only at the  start  of  the  string,         of  line"  metacharacter  (^)  matches only at the start of the string,
1329         while  the  "end  of line" metacharacter ($) matches only at the end of         while the "end of line" metacharacter ($) matches only at  the  end  of
1330         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1331         is set). This is the same as Perl.         is set). This is the same as Perl.
1332    
1333         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"
1334         constructs match immediately following or immediately  before  internal         constructs  match  immediately following or immediately before internal
1335         newlines  in  the  subject string, respectively, as well as at the very         newlines in the subject string, respectively, as well as  at  the  very
1336         start and end. This is equivalent to Perl's /m option, and  it  can  be         start  and  end.  This is equivalent to Perl's /m option, and it can be
1337         changed within a pattern by a (?m) option setting. If there are no new-         changed within a pattern by a (?m) option setting. If there are no new-
1338         lines in a subject string, or no occurrences of ^ or $  in  a  pattern,         lines  in  a  subject string, or no occurrences of ^ or $ in a pattern,
1339         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1340    
1341           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 1154  COMPILING A PATTERN Line 1344  COMPILING A PATTERN
1344           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1345           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1346    
1347         These  options  override the default newline definition that was chosen         These options override the default newline definition that  was  chosen
1348         when PCRE was built. Setting the first or the second specifies  that  a         when  PCRE  was built. Setting the first or the second specifies that a
1349         newline  is  indicated  by a single character (CR or LF, respectively).         newline is indicated by a single character (CR  or  LF,  respectively).
1350         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the         Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the
1351         two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies         two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies
1352         that any of the three preceding sequences should be recognized. Setting         that any of the three preceding sequences should be recognized. Setting
1353         PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be         PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be
1354         recognized. The Unicode newline sequences are the three just mentioned,         recognized. The Unicode newline sequences are the three just mentioned,
1355         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,         plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,
1356         U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS         U+000C),  NEL  (next line, U+0085), LS (line separator, U+2028), and PS
1357         (paragraph  separator,  U+2029).  The  last  two are recognized only in         (paragraph separator, U+2029). The last  two  are  recognized  only  in
1358         UTF-8 mode.         UTF-8 mode.
1359    
1360         The newline setting in the  options  word  uses  three  bits  that  are         The  newline  setting  in  the  options  word  uses three bits that are
1361         treated as a number, giving eight possibilities. Currently only six are         treated as a number, giving eight possibilities. Currently only six are
1362         used (default plus the five values above). This means that if  you  set         used  (default  plus the five values above). This means that if you set
1363         more  than one newline option, the combination may or may not be sensi-         more than one newline option, the combination may or may not be  sensi-
1364         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1365         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and         PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
1366         cause an error.         cause an error.
1367    
1368         The only time that a line break is specially recognized when  compiling         The  only time that a line break is specially recognized when compiling
1369         a  pattern  is  if  PCRE_EXTENDED  is set, and an unescaped # outside a         a pattern is if PCRE_EXTENDED is set, and  an  unescaped  #  outside  a
1370         character class is encountered. This indicates  a  comment  that  lasts         character  class  is  encountered.  This indicates a comment that lasts
1371         until  after the next line break sequence. In other circumstances, line         until after the next line break sequence. In other circumstances,  line
1372         break  sequences  are  treated  as  literal  data,   except   that   in         break   sequences   are   treated  as  literal  data,  except  that  in
1373         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
1374         and are therefore ignored.         and are therefore ignored.
1375    
1376         The newline option that is set at compile time becomes the default that         The newline option that is set at compile time becomes the default that
1377         is  used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.         is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
1378    
1379           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1380    
# Line 1194  COMPILING A PATTERN Line 1384  COMPILING A PATTERN
1384         be  used  for  capturing  (and  they acquire numbers in the usual way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
1385         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1386    
1387             PCRE_UCP
1388    
1389           This option changes the way PCRE processes \b, \d, \s, \w, and some  of
1390           the POSIX character classes. By default, only ASCII characters are rec-
1391           ognized, but if PCRE_UCP is set, Unicode properties are used instead to
1392           classify  characters.  More details are given in the section on generic
1393           character types in the pcrepattern page. If you set PCRE_UCP,  matching
1394           one  of the items it affects takes much longer. The option is available
1395           only if PCRE has been compiled with Unicode property support.
1396    
1397           PCRE_UNGREEDY           PCRE_UNGREEDY
1398    
1399         This option inverts the "greediness" of the quantifiers  so  that  they         This option inverts the "greediness" of the quantifiers  so  that  they
# Line 1213  COMPILING A PATTERN Line 1413  COMPILING A PATTERN
1413           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1414    
1415         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
1416         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically  checked.  There  is  a  discussion about the validity of
1417         pcre_compile() returns an error. If you already know that your  pattern         UTF-8 strings in the main pcre page. If an invalid  UTF-8  sequence  of
1418         is  valid, and you want to skip this check for performance reasons, you         bytes  is  found,  pcre_compile() returns an error. If you already know
1419         can set the PCRE_NO_UTF8_CHECK option. When it is set,  the  effect  of         that your pattern is valid, and you want to skip this check for perfor-
1420         passing an invalid UTF-8 string as a pattern is undefined. It may cause         mance  reasons,  you  can set the PCRE_NO_UTF8_CHECK option. When it is
1421         your program to crash.  Note that this option can  also  be  passed  to         set, the effect of passing an invalid UTF-8  string  as  a  pattern  is
1422         pcre_exec()  and pcre_dfa_exec(), to suppress the UTF-8 validity check-         undefined.  It  may  cause your program to crash. Note that this option
1423         ing of subject strings.         can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the
1424           UTF-8 validity checking of subject strings.
1425    
1426    
1427  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1428    
1429         The following table lists the error  codes  than  may  be  returned  by         The  following  table  lists  the  error  codes than may be returned by
1430         pcre_compile2(),  along with the error messages that may be returned by         pcre_compile2(), along with the error messages that may be returned  by
1431         both compiling functions. As PCRE has developed, some error codes  have         both  compiling functions. As PCRE has developed, some error codes have
1432         fallen out of use. To avoid confusion, they have not been re-used.         fallen out of use. To avoid confusion, they have not been re-used.
1433    
1434            0  no error            0  no error
# Line 1242  COMPILATION ERROR CODES Line 1443  COMPILATION ERROR CODES
1443            9  nothing to repeat            9  nothing to repeat
1444           10  [this code is not in use]           10  [this code is not in use]
1445           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1446           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1447           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1448           14  missing )           14  missing )
1449           15  reference to non-existent subpattern           15  reference to non-existent subpattern
# Line 1250  COMPILATION ERROR CODES Line 1451  COMPILATION ERROR CODES
1451           17  unknown option bit(s) set           17  unknown option bit(s) set
1452           18  missing ) after comment           18  missing ) after comment
1453           19  [this code is not in use]           19  [this code is not in use]
1454           20  regular expression too large           20  regular expression is too large
1455           21  failed to get memory           21  failed to get memory
1456           22  unmatched parentheses           22  unmatched parentheses
1457           23  internal error: code overflow           23  internal error: code overflow
# Line 1259  COMPILATION ERROR CODES Line 1460  COMPILATION ERROR CODES
1460           26  malformed number or name after (?(           26  malformed number or name after (?(
1461           27  conditional group contains more than two branches           27  conditional group contains more than two branches
1462           28  assertion expected after (?(           28  assertion expected after (?(
1463           29  (?R or (?digits must be followed by )           29  (?R or (?[+-]digits must be followed by )
1464           30  unknown POSIX class name           30  unknown POSIX class name
1465           31  POSIX collating elements are not supported           31  POSIX collating elements are not supported
1466           32  this version of PCRE is not compiled with PCRE_UTF8 support           32  this version of PCRE is not compiled with PCRE_UTF8 support
# Line 1279  COMPILATION ERROR CODES Line 1480  COMPILATION ERROR CODES
1480           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1481           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1482           48  subpattern name is too long (maximum 32 characters)           48  subpattern name is too long (maximum 32 characters)
1483           49  too many named subpatterns (maximum 10,000)           49  too many named subpatterns (maximum 10000)
1484           50  repeated subpattern is too long           50  [this code is not in use]
1485           51  octal value is greater than \377 (not in UTF-8 mode)           51  octal value is greater than \377 (not in UTF-8 mode)
1486           52  internal error: overran compiling workspace           52  internal error: overran compiling workspace
1487           53   internal  error:  previously-checked  referenced  subpattern not           53  internal error: previously-checked referenced subpattern
1488         found                 not found
1489           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1490           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1491           56  inconsistent NEWLINE options"           56  inconsistent NEWLINE options
1492             57  \g is not followed by a braced, angle-bracketed, or quoted
1493                   name/number or by a plain number
1494             58  a numbered reference must not be zero
1495             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1496             60  (*VERB) not recognized
1497             61  number is too big
1498             62  subpattern name expected
1499             63  digit expected after (?+
1500             64  ] is an invalid data character in JavaScript compatibility mode
1501             65  different names for subpatterns of the same number are
1502                   not allowed
1503             66  (*MARK) must have an argument
1504             67  this version of PCRE is not compiled with PCRE_UCP support
1505    
1506           The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
1507           values may be used if the limits were changed when PCRE was built.
1508    
1509    
1510  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1295  STUDYING A PATTERN Line 1512  STUDYING A PATTERN
1512         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1513              const char **errptr);              const char **errptr);
1514    
1515         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
1516         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
1517         matching. The function pcre_study() takes a pointer to a compiled  pat-         matching.  The function pcre_study() takes a pointer to a compiled pat-
1518         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1519         information that will help speed up matching,  pcre_study()  returns  a         information  that  will  help speed up matching, pcre_study() returns a
1520         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
1521         the results of the study.         the results of the study.
1522    
1523         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1524         pcre_exec().  However,  a  pcre_extra  block also contains other fields         pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-
1525         that can be set by the caller before the block  is  passed;  these  are         tains  other  fields  that can be set by the caller before the block is
1526         described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1527    
1528         If  studying  the  pattern  does not produce any additional information         If studying the  pattern  does  not  produce  any  useful  information,
1529         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1530         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()   or
1531         its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1532    
1533         The second argument of pcre_study() contains option bits.  At  present,         The  second  argument of pcre_study() contains option bits. At present,
1534         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1535    
1536         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.
1537         If studying succeeds (even if no data is  returned),  the  variable  it         If  studying  succeeds  (even  if no data is returned), the variable it
1538         points  to  is  set  to NULL. Otherwise it is set to point to a textual         points to is set to NULL. Otherwise it is set to  point  to  a  textual
1539         error message. This is a static string that is part of the library. You         error message. This is a static string that is part of the library. You
1540         must  not  try  to  free it. You should test the error pointer for NULL         must not try to free it. You should test the  error  pointer  for  NULL
1541         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1542    
1543         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 1331  STUDYING A PATTERN Line 1548  STUDYING A PATTERN
1548             0,              /* no options exist */             0,              /* no options exist */
1549             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1550    
1551         At present, studying a pattern is useful only for non-anchored patterns         Studying a pattern does two things: first, a lower bound for the length
1552         that  do not have a single fixed starting character. A bitmap of possi-         of subject string that is needed to match the pattern is computed. This
1553         ble starting bytes is created.         does not mean that there are any strings of that length that match, but
1554           it does guarantee that no shorter strings match. The value is  used  by
1555           pcre_exec()  and  pcre_dfa_exec()  to  avoid  wasting time by trying to
1556           match strings that are shorter than the lower bound. You can  find  out
1557           the value in a calling program via the pcre_fullinfo() function.
1558    
1559           Studying a pattern is also useful for non-anchored patterns that do not
1560           have a single fixed starting character. A bitmap of  possible  starting
1561           bytes  is  created. This speeds up finding a position in the subject at
1562           which to start matching.
1563    
1564           The two optimizations just described can be  disabled  by  setting  the
1565           PCRE_NO_START_OPTIMIZE    option    when    calling    pcre_exec()   or
1566           pcre_dfa_exec(). You might want to do this  if  your  pattern  contains
1567           callouts,  or  make  use of (*MARK), and you make use of these in cases
1568           where matching fails.  See  the  discussion  of  PCRE_NO_START_OPTIMIZE
1569           below.
1570    
1571    
1572  LOCALE SUPPORT  LOCALE SUPPORT
1573    
1574         PCRE handles caseless matching, and determines whether  characters  are         PCRE  handles  caseless matching, and determines whether characters are
1575         letters,  digits, or whatever, by reference to a set of tables, indexed         letters, digits, or whatever, by reference to a set of tables,  indexed
1576         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
1577         characters  with  codes  less than 128. Higher-valued codes never match         characters with codes less than 128. By  default,  higher-valued  codes
1578         escapes such as \w or \d, but can be tested with \p if  PCRE  is  built         never match escapes such as \w or \d, but they can be tested with \p if
1579         with  Unicode  character property support. The use of locales with Uni-         PCRE is built with Unicode character property  support.  Alternatively,
1580         code is discouraged. If you are handling characters with codes  greater         the  PCRE_UCP  option  can  be  set at compile time; this causes \w and
1581         than  128, you should either use UTF-8 and Unicode, or use locales, but         friends to use Unicode property support instead of built-in tables. The
1582         not try to mix the two.         use of locales with Unicode is discouraged. If you are handling charac-
1583           ters with codes greater than 128, you should either use UTF-8 and  Uni-
1584           code, or use locales, but not try to mix the two.
1585    
1586         PCRE contains an internal set of tables that are used  when  the  final         PCRE  contains  an  internal set of tables that are used when the final
1587         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
1588         applications.  Normally, the internal tables recognize only ASCII char-         applications.  Normally, the internal tables recognize only ASCII char-
1589         acters. However, when PCRE is built, it is possible to cause the inter-         acters. However, when PCRE is built, it is possible to cause the inter-
1590         nal tables to be rebuilt in the default "C" locale of the local system,         nal tables to be rebuilt in the default "C" locale of the local system,
1591         which may cause them to be different.         which may cause them to be different.
1592    
1593         The  internal tables can always be overridden by tables supplied by the         The internal tables can always be overridden by tables supplied by  the
1594         application that calls PCRE. These may be created in a different locale         application that calls PCRE. These may be created in a different locale
1595         from  the  default.  As more and more applications change to using Uni-         from the default. As more and more applications change  to  using  Uni-
1596         code, the need for this locale support is expected to die away.         code, the need for this locale support is expected to die away.
1597    
1598         External tables are built by calling  the  pcre_maketables()  function,         External  tables  are  built by calling the pcre_maketables() function,
1599         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
1600         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
1601         example,  to  build  and use tables that are appropriate for the French         example, to build and use tables that are appropriate  for  the  French
1602         locale (where accented characters with  values  greater  than  128  are         locale  (where  accented  characters  with  values greater than 128 are
1603         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1604    
1605           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1606           tables = pcre_maketables();           tables = pcre_maketables();
1607           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1608    
1609         The  locale  name "fr_FR" is used on Linux and other Unix-like systems;         The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
1610         if you are using Windows, the name for the French locale is "french".         if you are using Windows, the name for the French locale is "french".
1611    
1612         When pcre_maketables() runs, the tables are built  in  memory  that  is         When  pcre_maketables()  runs,  the  tables are built in memory that is
1613         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         obtained via pcre_malloc. It is the caller's responsibility  to  ensure
1614         that the memory containing the tables remains available for as long  as         that  the memory containing the tables remains available for as long as
1615         it is needed.         it is needed.
1616    
1617         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
1618         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()
1619         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-
1620         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1621         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1622    
1623         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
1624         the internal tables) to pcre_exec(). Although  not  intended  for  this         the  internal  tables)  to  pcre_exec(). Although not intended for this
1625         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
1626         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
1627         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1628    
# Line 1397  INFORMATION ABOUT A PATTERN Line 1632  INFORMATION ABOUT A PATTERN
1632         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1633              int what, void *where);              int what, void *where);
1634    
1635         The  pcre_fullinfo() function returns information about a compiled pat-         The pcre_fullinfo() function returns information about a compiled  pat-
1636         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1637         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1638    
1639         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
1640         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
1641         the  pattern  was not studied. The third argument specifies which piece         the pattern was not studied. The third argument specifies  which  piece
1642         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
1643         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
1644         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1645    
1646           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1413  INFORMATION ABOUT A PATTERN Line 1648  INFORMATION ABOUT A PATTERN
1648           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1649           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1650    
1651         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
1652         an  simple check against passing an arbitrary memory pointer. Here is a         an simple check against passing an arbitrary memory pointer. Here is  a
1653         typical call of pcre_fullinfo(), to obtain the length of  the  compiled         typical  call  of pcre_fullinfo(), to obtain the length of the compiled
1654         pattern:         pattern:
1655    
1656           int rc;           int rc;
# Line 1426  INFORMATION ABOUT A PATTERN Line 1661  INFORMATION ABOUT A PATTERN
1661             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1662             &length);         /* where to put the data */             &length);         /* where to put the data */
1663    
1664         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
1665         are as follows:         are as follows:
1666    
1667           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1668    
1669         Return the number of the highest back reference  in  the  pattern.  The         Return  the  number  of  the highest back reference in the pattern. The
1670         fourth  argument  should  point to an int variable. Zero is returned if         fourth argument should point to an int variable. Zero  is  returned  if
1671         there are no back references.         there are no back references.
1672    
1673           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1674    
1675         Return the number of capturing subpatterns in the pattern.  The  fourth         Return  the  number of capturing subpatterns in the pattern. The fourth
1676         argument should point to an int variable.         argument should point to an int variable.
1677    
1678           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1679    
1680         Return  a pointer to the internal default character tables within PCRE.         Return a pointer to the internal default character tables within  PCRE.
1681         The fourth argument should point to an unsigned char *  variable.  This         The  fourth  argument should point to an unsigned char * variable. This
1682         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1683         tion. External callers can cause PCRE to use  its  internal  tables  by         tion.  External  callers  can  cause PCRE to use its internal tables by
1684         passing a NULL table pointer.         passing a NULL table pointer.
1685    
1686           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1687    
1688         Return  information  about  the first byte of any matched string, for a         Return information about the first byte of any matched  string,  for  a
1689         non-anchored pattern. The fourth argument should point to an int  vari-         non-anchored  pattern. The fourth argument should point to an int vari-
1690         able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name         able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name
1691         is still recognized for backwards compatibility.)         is still recognized for backwards compatibility.)
1692    
1693         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
1694         (cat|cow|coyote), its value is returned. Otherwise, if either         (cat|cow|coyote), its value is returned. Otherwise, if either
1695    
1696         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1697         branch starts with "^", or         branch starts with "^", or
1698    
1699         (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
1700         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1701    
1702         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
1703         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
1704         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1705    
1706           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1707    
1708         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
1709         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
1710         matching  string, a pointer to the table is returned. Otherwise NULL is         matching string, a pointer to the table is returned. Otherwise NULL  is
1711         returned. The fourth argument should point to an unsigned char *  vari-         returned.  The fourth argument should point to an unsigned char * vari-
1712         able.         able.
1713    
1714             PCRE_INFO_HASCRORLF
1715    
1716           Return 1 if the pattern contains any explicit  matches  for  CR  or  LF
1717           characters,  otherwise  0.  The  fourth argument should point to an int
1718           variable. An explicit match is either a literal CR or LF character,  or
1719           \r or \n.
1720    
1721           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
1722    
1723         Return  1  if the (?J) option setting is used in the pattern, otherwise         Return  1  if  the (?J) or (?-J) option setting is used in the pattern,
1724         0. The fourth argument should point to an int variable. The (?J) inter-         otherwise 0. The fourth argument should point to an int variable.  (?J)
1725         nal option setting changes the local PCRE_DUPNAMES value.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1726    
1727           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1728    
# Line 1492  INFORMATION ABOUT A PATTERN Line 1734  INFORMATION ABOUT A PATTERN
1734         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
1735         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1736    
1737             PCRE_INFO_MINLENGTH
1738    
1739           If  the  pattern  was studied and a minimum length for matching subject
1740           strings was computed, its value is  returned.  Otherwise  the  returned
1741           value  is  -1. The value is a number of characters, not bytes (this may
1742           be relevant in UTF-8 mode). The fourth argument should point to an  int
1743           variable.  A  non-negative  value is a lower bound to the length of any
1744           matching string. There may not be any strings of that  length  that  do
1745           actually match, but every string that does match is at least that long.
1746    
1747           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
1748           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1749           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
# Line 1513  INFORMATION ABOUT A PATTERN Line 1765  INFORMATION ABOUT A PATTERN
1765         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
1766         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-
1767         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-
1768         sponding name, zero terminated. The names are  in  alphabetical  order.         sponding name, zero terminated.
1769         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-  
1770         theses numbers. For example, consider  the  following  pattern  (assume         The names are in alphabetical order. Duplicate names may appear if  (?|
1771         PCRE_EXTENDED  is  set,  so  white  space  -  including  newlines  - is         is used to create multiple groups with the same number, as described in
1772         ignored):         the section on duplicate subpattern numbers in  the  pcrepattern  page.
1773           Duplicate  names  for  subpatterns with different numbers are permitted
1774           only if PCRE_DUPNAMES is set. In all cases  of  duplicate  names,  they
1775           appear  in  the table in the order in which they were found in the pat-
1776           tern. In the absence of (?| this is the  order  of  increasing  number;
1777           when (?| is used this is not necessarily the case because later subpat-
1778           terns may have lower numbers.
1779    
1780           As a simple example of the name/number table,  consider  the  following
1781           pattern  (assume  PCRE_EXTENDED is set, so white space - including new-
1782           lines - is ignored):
1783    
1784           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1785           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
# Line 1538  INFORMATION ABOUT A PATTERN Line 1800  INFORMATION ABOUT A PATTERN
1800    
1801           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
1802    
1803         Return  1 if the pattern can be used for partial matching, otherwise 0.         Return  1  if  the  pattern  can  be  used  for  partial  matching with
1804         The fourth argument should point to an int  variable.  The  pcrepartial         pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
1805         documentation  lists  the restrictions that apply to patterns when par-         variable.  From  release  8.00,  this  always  returns  1,  because the
1806         tial matching is used.         restrictions that previously applied  to  partial  matching  have  been
1807           lifted.  The  pcrepartial documentation gives details of partial match-
1808           ing.
1809    
1810           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1811    
1812         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
1813         fourth  argument  should  point to an unsigned long int variable. These         fourth  argument  should  point to an unsigned long int variable. These
1814         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1815         by any top-level option settings within the pattern itself.         by any top-level option settings at the start of the pattern itself. In
1816           other words, they are the options that will be in force  when  matching
1817           starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
1818           the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1819           and PCRE_EXTENDED.
1820    
1821         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
1822         alternatives begin with one of the following:         alternatives begin with one of the following:
# Line 1574  INFORMATION ABOUT A PATTERN Line 1842  INFORMATION ABOUT A PATTERN
1842         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
1843         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
1844         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
1845         created  by  pcre_study(). The fourth argument should point to a size_t         created  by  pcre_study().  If pcre_extra is NULL, or there is no study
1846           data, zero is returned. The fourth argument should point  to  a  size_t
1847         variable.         variable.
1848    
1849    
# Line 1582  OBSOLETE INFO FUNCTION Line 1851  OBSOLETE INFO FUNCTION
1851    
1852         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1853    
1854         The pcre_info() function is now obsolete because its interface  is  too         The  pcre_info()  function is now obsolete because its interface is too
1855         restrictive  to return all the available data about a compiled pattern.         restrictive to return all the available data about a compiled  pattern.
1856         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of
1857         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-
1858         lowing negative numbers:         lowing negative numbers:
1859    
1860           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1861           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1862    
1863         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
1864         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
1865         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1866    
1867         If the pattern is not anchored and the  firstcharptr  argument  is  not         If  the  pattern  is  not anchored and the firstcharptr argument is not
1868         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
1869         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1870    
1871    
# Line 1604  REFERENCE COUNTS Line 1873  REFERENCE COUNTS
1873    
1874         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1875    
1876         The pcre_refcount() function is used to maintain a reference  count  in         The  pcre_refcount()  function is used to maintain a reference count in
1877         the data block that contains a compiled pattern. It is provided for the         the data block that contains a compiled pattern. It is provided for the
1878         benefit of applications that  operate  in  an  object-oriented  manner,         benefit  of  applications  that  operate  in an object-oriented manner,
1879         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1880         pattern, but you want to free the block when they are all done.         pattern, but you want to free the block when they are all done.
1881    
1882         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1883         zero.   It is changed only by calling this function, whose action is to         zero.  It is changed only by calling this function, whose action is  to
1884         add the adjust value (which may be positive or  negative)  to  it.  The         add  the  adjust  value  (which may be positive or negative) to it. The
1885         yield of the function is the new value. However, the value of the count         yield of the function is the new value. However, the value of the count
1886         is constrained to lie between 0 and 65535, inclusive. If the new  value         is  constrained to lie between 0 and 65535, inclusive. If the new value
1887         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1888    
1889         Except  when it is zero, the reference count is not correctly preserved         Except when it is zero, the reference count is not correctly  preserved
1890         if a pattern is compiled on one host and then  transferred  to  a  host         if  a  pattern  is  compiled on one host and then transferred to a host
1891         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1892    
1893    
# Line 1630  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1899  MATCHING A PATTERN: THE TRADITIONAL FUNC
1899    
1900         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
1901         compiled  pattern, which is passed in the code argument. If the pattern         compiled  pattern, which is passed in the code argument. If the pattern
1902         has been studied, the result of the study should be passed in the extra         was studied, the result of the study should  be  passed  in  the  extra
1903         argument.  This  function is the main matching facility of the library,         argument.  This  function is the main matching facility of the library,
1904         and it operates in a Perl-like manner. For specialist use there is also         and it operates in a Perl-like manner. For specialist use there is also
1905         an  alternative matching function, which is described below in the sec-         an  alternative matching function, which is described below in the sec-
# Line 1670  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1939  MATCHING A PATTERN: THE TRADITIONAL FUNC
1939           unsigned long int match_limit_recursion;           unsigned long int match_limit_recursion;
1940           void *callout_data;           void *callout_data;
1941           const unsigned char *tables;           const unsigned char *tables;
1942             unsigned char **mark;
1943    
1944         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
1945         are set. The flag bits are:         are set. The flag bits are:
# Line 1679  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1949  MATCHING A PATTERN: THE TRADITIONAL FUNC
1949           PCRE_EXTRA_MATCH_LIMIT_RECURSION           PCRE_EXTRA_MATCH_LIMIT_RECURSION
1950           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1951           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1952             PCRE_EXTRA_MARK
1953    
1954         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
1955         the pcre_extra block that is returned by  pcre_study(),  together  with         the pcre_extra block that is returned by  pcre_study(),  together  with
# Line 1689  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1960  MATCHING A PATTERN: THE TRADITIONAL FUNC
1960         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
1961         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
1962         match,  but  which  have  a very large number of possibilities in their         match,  but  which  have  a very large number of possibilities in their
1963         search trees. The classic  example  is  the  use  of  nested  unlimited         search trees. The classic example is a pattern that uses nested  unlim-
1964         repeats.         ited repeats.
1965    
1966         Internally,  PCRE uses a function called match() which it calls repeat-         Internally,  PCRE uses a function called match() which it calls repeat-
1967         edly (sometimes recursively). The limit set by match_limit  is  imposed         edly (sometimes recursively). The limit set by match_limit  is  imposed
# Line 1712  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1983  MATCHING A PATTERN: THE TRADITIONAL FUNC
1983         the total number of calls, because not all calls to match() are  recur-         the total number of calls, because not all calls to match() are  recur-
1984         sive.  This limit is of use only if it is set smaller than match_limit.         sive.  This limit is of use only if it is set smaller than match_limit.
1985    
1986         Limiting the recursion depth limits the amount of  stack  that  can  be         Limiting  the  recursion  depth  limits the amount of stack that can be
1987         used, or, when PCRE has been compiled to use memory on the heap instead         used, or, when PCRE has been compiled to use memory on the heap instead
1988         of the stack, the amount of heap memory that can be used.         of the stack, the amount of heap memory that can be used.
1989    
1990         The default value for match_limit_recursion can be  set  when  PCRE  is         The  default  value  for  match_limit_recursion can be set when PCRE is
1991         built;  the  default  default  is  the  same  value  as the default for         built; the default default  is  the  same  value  as  the  default  for
1992         match_limit. You can override the default by suppling pcre_exec()  with         match_limit.  You can override the default by suppling pcre_exec() with
1993         a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and
1994         PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the         PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the
1995         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1996    
1997         The  pcre_callout  field is used in conjunction with the "callout" fea-         The callout_data field is used in conjunction with the  "callout"  fea-
1998         ture, which is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
1999    
2000         The tables field  is  used  to  pass  a  character  tables  pointer  to         The  tables  field  is  used  to  pass  a  character  tables pointer to
2001         pcre_exec();  this overrides the value that is stored with the compiled         pcre_exec(); this overrides the value that is stored with the  compiled
2002         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
2003         custom  tables  were  supplied to pcre_compile() via its tableptr argu-         custom tables were supplied to pcre_compile() via  its  tableptr  argu-
2004         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
2005         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-
2006         using patterns that have been saved after compiling  with  an  external         using  patterns  that  have been saved after compiling with an external
2007         set  of  tables,  because  the  external tables might be at a different         set of tables, because the external tables  might  be  at  a  different
2008         address when pcre_exec() is called. See the  pcreprecompile  documenta-         address  when  pcre_exec() is called. See the pcreprecompile documenta-
2009         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
2010    
2011           If PCRE_EXTRA_MARK is set in the flags field, the mark  field  must  be
2012           set  to  point  to a char * variable. If the pattern contains any back-
2013           tracking control verbs such as (*MARK:NAME), and the execution ends  up
2014           with  a  name  to  pass back, a pointer to the name string (zero termi-
2015           nated) is placed in the variable pointed to  by  the  mark  field.  The
2016           names  are  within  the  compiled pattern; if you wish to retain such a
2017           name you must copy it before freeing the memory of a compiled  pattern.
2018           If  there  is no name to pass back, the variable pointed to by the mark
2019           field set to NULL. For details of the backtracking control  verbs,  see
2020           the section entitled "Backtracking control" in the pcrepattern documen-
2021           tation.
2022    
2023     Option bits for pcre_exec()     Option bits for pcre_exec()
2024    
2025         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.
2026         The only bits that may  be  set  are  PCRE_ANCHORED,  PCRE_NEWLINE_xxx,         The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
2027         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,   PCRE_NOTEOL,    PCRE_NOTEMPTY,    PCRE_NOTEMPTY_ATSTART,
2028         PCRE_PARTIAL.         PCRE_NO_START_OPTIMIZE,   PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,  and
2029           PCRE_PARTIAL_HARD.
2030    
2031           PCRE_ANCHORED           PCRE_ANCHORED
2032    
# Line 1751  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2035  MATCHING A PATTERN: THE TRADITIONAL FUNC
2035         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
2036         unachored at matching time.         unachored at matching time.
2037    
2038             PCRE_BSR_ANYCRLF
2039             PCRE_BSR_UNICODE
2040    
2041           These options (which are mutually exclusive) control what the \R escape
2042           sequence matches. The choice is either to match only CR, LF,  or  CRLF,
2043           or  to  match  any Unicode newline sequence. These options override the
2044           choice that was made or defaulted when the pattern was compiled.
2045    
2046           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
2047           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
2048           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
2049           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
2050           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
2051    
2052         These  options  override  the  newline  definition  that  was chosen or         These options override  the  newline  definition  that  was  chosen  or
2053         defaulted when the pattern was compiled. For details, see the  descrip-         defaulted  when the pattern was compiled. For details, see the descrip-
2054         tion  of  pcre_compile()  above.  During  matching,  the newline choice         tion of pcre_compile()  above.  During  matching,  the  newline  choice
2055         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
2056         ters.  It may also alter the way the match position is advanced after a         ters. It may also alter the way the match position is advanced after  a
2057         match  failure  for  an  unanchored  pattern.  When  PCRE_NEWLINE_CRLF,         match failure for an unanchored pattern.
2058         PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY is set, and a match attempt  
2059         fails when the current position is at a CRLF sequence, the match  posi-         When  PCRE_NEWLINE_CRLF,  PCRE_NEWLINE_ANYCRLF,  or PCRE_NEWLINE_ANY is
2060         tion  is  advanced by two characters instead of one, in other words, to         set, and a match attempt for an unanchored pattern fails when the  cur-
2061         after the CRLF.         rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
2062           explicit matches for  CR  or  LF  characters,  the  match  position  is
2063           advanced by two characters instead of one, in other words, to after the
2064           CRLF.
2065    
2066           The above rule is a compromise that makes the most common cases work as
2067           expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
2068           option is not set), it does not match the string "\r\nA" because, after
2069           failing  at the start, it skips both the CR and the LF before retrying.
2070           However, the pattern [\r\n]A does match that string,  because  it  con-
2071           tains an explicit CR or LF reference, and so advances only by one char-
2072           acter after the first failure.
2073    
2074           An explicit match for CR of LF is either a literal appearance of one of
2075           those  characters,  or  one  of the \r or \n escape sequences. Implicit
2076           matches such as [^X] do not count, nor does \s (which includes  CR  and
2077           LF in the characters that it matches).
2078    
2079           Notwithstanding  the above, anomalous effects may still occur when CRLF
2080           is a valid newline sequence and explicit \r or \n escapes appear in the
2081           pattern.
2082    
2083           PCRE_NOTBOL           PCRE_NOTBOL
2084    
2085         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
2086         the  beginning  of  a  line, so the circumflex metacharacter should not         the beginning of a line, so the  circumflex  metacharacter  should  not
2087         match before it. Setting this without PCRE_MULTILINE (at compile  time)         match  before it. Setting this without PCRE_MULTILINE (at compile time)
2088         causes  circumflex  never to match. This option affects only the behav-         causes circumflex never to match. This option affects only  the  behav-
2089         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
2090    
2091           PCRE_NOTEOL           PCRE_NOTEOL
2092    
2093         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
2094         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
2095         in multiline mode) a newline immediately before it. Setting this  with-         in  multiline mode) a newline immediately before it. Setting this with-
2096         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2097         option affects only the behaviour of the dollar metacharacter. It  does         option  affects only the behaviour of the dollar metacharacter. It does
2098         not affect \Z or \z.         not affect \Z or \z.
2099    
2100           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2101    
2102         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
2103         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
2104         the  alternatives  match  the empty string, the entire match fails. For         the alternatives match the empty string, the entire  match  fails.  For
2105         example, if the pattern         example, if the pattern
2106    
2107           a?b?           a?b?
2108    
2109         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 an
2110         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
2111         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-
2112         rences of "a" or "b".         rences of "a" or "b".
2113    
2114         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2115         cial case of a pattern match of the empty  string  within  its  split()  
2116         function,  and  when  using  the /g modifier. It is possible to emulate         This is like PCRE_NOTEMPTY, except that an empty string match  that  is
2117         Perl's behaviour after matching a null string by first trying the match         not  at  the  start  of  the  subject  is  permitted. If the pattern is
2118         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then         anchored, such a match can occur only if the pattern contains \K.
2119         if that fails by advancing the starting offset (see below)  and  trying  
2120         an ordinary match again. There is some code that demonstrates how to do         Perl    has    no    direct    equivalent    of    PCRE_NOTEMPTY     or
2121         this in the pcredemo.c sample program.         PCRE_NOTEMPTY_ATSTART,  but  it  does  make a special case of a pattern
2122           match of the empty string within its split() function, and  when  using
2123           the  /g  modifier.  It  is  possible  to emulate Perl's behaviour after
2124           matching a null string by first trying the match again at the same off-
2125           set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that
2126           fails, by advancing the starting offset (see below) and trying an ordi-
2127           nary  match  again. There is some code that demonstrates how to do this
2128           in the pcredemo sample program. In the most general case, you  have  to
2129           check  to  see  if the newline convention recognizes CRLF as a newline,
2130           and if so, and the current character is CR followed by LF, advance  the
2131           starting offset by two characters instead of one.
2132    
2133             PCRE_NO_START_OPTIMIZE
2134    
2135           There  are a number of optimizations that pcre_exec() uses at the start
2136           of a match, in order to speed up the process. For  example,  if  it  is
2137           known that an unanchored match must start with a specific character, it
2138           searches the subject for that character, and fails  immediately  if  it
2139           cannot  find  it,  without actually running the main matching function.
2140           This means that a special item such as (*COMMIT) at the start of a pat-
2141           tern  is  not  considered until after a suitable starting point for the
2142           match has been found. When callouts or (*MARK) items are in use,  these
2143           "start-up" optimizations can cause them to be skipped if the pattern is
2144           never actually used. The start-up optimizations are in  effect  a  pre-
2145           scan of the subject that takes place before the pattern is run.
2146    
2147           The  PCRE_NO_START_OPTIMIZE option disables the start-up optimizations,
2148           possibly causing performance to suffer,  but  ensuring  that  in  cases
2149           where  the  result is "no match", the callouts do occur, and that items
2150           such as (*COMMIT) and (*MARK) are considered at every possible starting
2151           position  in  the  subject  string.  Setting PCRE_NO_START_OPTIMIZE can
2152           change the outcome of a matching operation.  Consider the pattern
2153    
2154             (*COMMIT)ABC
2155    
2156           When this is compiled, PCRE records the fact that a  match  must  start
2157           with  the  character  "A".  Suppose the subject string is "DEFABC". The
2158           start-up optimization scans along the subject, finds "A" and  runs  the
2159           first  match attempt from there. The (*COMMIT) item means that the pat-
2160           tern must match the current starting position, which in this  case,  it
2161           does.  However,  if  the  same match is run with PCRE_NO_START_OPTIMIZE
2162           set, the initial scan along the subject string  does  not  happen.  The
2163           first  match  attempt  is  run  starting  from "D" and when this fails,
2164           (*COMMIT) prevents any further matches  being  tried,  so  the  overall
2165           result  is  "no  match". If the pattern is studied, more start-up opti-
2166           mizations may be used. For example, a minimum length  for  the  subject
2167           may be recorded. Consider the pattern
2168    
2169             (*MARK:A)(X|Y)
2170    
2171           The  minimum  length  for  a  match is one character. If the subject is
2172           "ABC", there will be attempts to  match  "ABC",  "BC",  "C",  and  then
2173           finally  an empty string.  If the pattern is studied, the final attempt
2174           does not take place, because PCRE knows that the subject is too  short,
2175           and  so  the  (*MARK) is never encountered.  In this case, studying the
2176           pattern does not affect the overall match result, which  is  still  "no
2177           match", but it does affect the auxiliary information that is returned.
2178    
2179           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2180    
2181         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
2182         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8 string is automatically checked when pcre_exec() is  subsequently
2183         called.  The value of startoffset is also checked  to  ensure  that  it         called.   The  value  of  startoffset is also checked to ensure that it
2184         points  to the start of a UTF-8 character. If an invalid UTF-8 sequence         points to the start of a UTF-8 character. There is a  discussion  about
2185         of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If         the  validity  of  UTF-8 strings in the section on UTF-8 support in the
2186         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is         main pcre page. If  an  invalid  UTF-8  sequence  of  bytes  is  found,
2187         returned.         pcre_exec()  returns  the error PCRE_ERROR_BADUTF8. If startoffset con-
2188           tains a value that does not point to the start of a UTF-8 character (or
2189         If you already know that your subject is valid, and you  want  to  skip         to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2190         these    checks    for   performance   reasons,   you   can   set   the  
2191         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to         If  you  already  know that your subject is valid, and you want to skip
2192         do  this  for the second and subsequent calls to pcre_exec() if you are         these   checks   for   performance   reasons,   you   can    set    the
2193         making repeated calls to find all  the  matches  in  a  single  subject         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
2194         string.  However,  you  should  be  sure  that the value of startoffset         do this for the second and subsequent calls to pcre_exec() if  you  are
2195         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is         making  repeated  calls  to  find  all  the matches in a single subject
2196         set,  the  effect of passing an invalid UTF-8 string as a subject, or a         string. However, you should be  sure  that  the  value  of  startoffset
2197         value of startoffset that does not point to the start of a UTF-8  char-         points  to  the start of a UTF-8 character (or the end of the subject).
2198         acter, is undefined. Your program may crash.         When PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid  UTF-8
2199           string  as  a  subject or an invalid value of startoffset is undefined.
2200           PCRE_PARTIAL         Your program may crash.
2201    
2202         This  option  turns  on  the  partial  matching feature. If the subject           PCRE_PARTIAL_HARD
2203         string fails to match the pattern, but at some point during the  match-           PCRE_PARTIAL_SOFT
2204         ing  process  the  end of the subject was reached (that is, the subject  
2205         partially matches the pattern and the failure to  match  occurred  only         These options turn on the partial matching feature. For backwards  com-
2206         because  there were not enough subject characters), pcre_exec() returns         patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
2207         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is         match occurs if the end of the subject string is reached  successfully,
2208         used,  there  are restrictions on what may appear in the pattern. These         but  there  are not enough subject characters to complete the match. If
2209         are discussed in the pcrepartial documentation.         this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
2210           matching  continues  by  testing any remaining alternatives. Only if no
2211           complete match can be found is PCRE_ERROR_PARTIAL returned  instead  of
2212           PCRE_ERROR_NOMATCH.  In  other  words,  PCRE_PARTIAL_SOFT says that the
2213           caller is prepared to handle a partial match, but only if  no  complete
2214           match can be found.
2215    
2216           If  PCRE_PARTIAL_HARD  is  set, it overrides PCRE_PARTIAL_SOFT. In this
2217           case, if a partial match  is  found,  pcre_exec()  immediately  returns
2218           PCRE_ERROR_PARTIAL,  without  considering  any  other  alternatives. In
2219           other words, when PCRE_PARTIAL_HARD is set, a partial match is  consid-
2220           ered to be more important that an alternative complete match.
2221    
2222           In  both  cases,  the portion of the string that was inspected when the
2223           partial match was found is set as the first matching string. There is a
2224           more  detailed  discussion  of partial and multi-segment matching, with
2225           examples, in the pcrepartial documentation.
2226    
2227     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2228    
2229         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
2230         length  in  length, and a starting byte offset in startoffset. In UTF-8         length (in bytes) in length, and a starting byte offset in startoffset.
2231         mode, the byte offset must point to the start  of  a  UTF-8  character.         If this is  negative  or  greater  than  the  length  of  the  subject,
2232         Unlike  the  pattern string, the subject may contain binary zero bytes.         pcre_exec() returns PCRE_ERROR_BADOFFSET.
2233         When the starting offset is zero, the search for a match starts at  the  
2234         beginning of the subject, and this is by far the most common case.         In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-
2235           acter (or the end of the subject). Unlike the pattern string, the  sub-
2236           ject  may  contain binary zero bytes. When the starting offset is zero,
2237           the search for a match starts at the beginning of the subject, and this
2238           is by far the most common case.
2239    
2240         A  non-zero  starting offset is useful when searching for another match         A  non-zero  starting offset is useful when searching for another match
2241         in the same subject by calling pcre_exec() again after a previous  suc-         in the same subject by calling pcre_exec() again after a previous  suc-
# Line 1868  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2256  MATCHING A PATTERN: THE TRADITIONAL FUNC
2256         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
2257         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2258    
2259         If a non-zero starting offset is passed when the pattern  is  anchored,         Finding all the matches in a subject is tricky  when  the  pattern  can
2260           match an empty string. It is possible to emulate Perl's /g behaviour by
2261           first  trying  the  match  again  at  the   same   offset,   with   the
2262           PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED  options,  and  then  if that
2263           fails, advancing the starting  offset  and  trying  an  ordinary  match
2264           again. There is some code that demonstrates how to do this in the pcre-
2265           demo sample program. In the most general case, you have to check to see
2266           if  the newline convention recognizes CRLF as a newline, and if so, and
2267           the current character is CR followed by LF, advance the starting offset
2268           by two characters instead of one.
2269    
2270           If  a  non-zero starting offset is passed when the pattern is anchored,
2271         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
2272         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
2273         subject.         subject.
2274    
2275     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2276    
2277         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
2278         addition, further substrings from the subject  may  be  picked  out  by         addition,  further  substrings  from  the  subject may be picked out by
2279         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2280         this is called "capturing" in what follows, and the  phrase  "capturing         this  is  called "capturing" in what follows, and the phrase "capturing
2281         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-
2282         string. PCRE supports several other kinds of  parenthesized  subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2283         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2284    
2285         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2286         offsets whose address is passed in ovector. The number of  elements  in         whose  address is passed in ovector. The number of elements in the vec-
2287         the  vector is passed in ovecsize, which must be a non-negative number.         tor is passed in ovecsize, which must be a non-negative  number.  Note:
2288         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2289    
2290         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-
2291         strings,  each  substring using a pair of integers. The remaining third         strings, each substring using a pair of integers. The  remaining  third
2292         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-
2293         turing  subpatterns, and is not available for passing back information.         turing subpatterns, and is not available for passing back  information.
2294         The length passed in ovecsize should always be a multiple of three.  If         The  number passed in ovecsize should always be a multiple of three. If
2295         it is not, it is rounded down.         it is not, it is rounded down.
2296    
2297         When  a  match  is successful, information about captured substrings is         When a match is successful, information about  captured  substrings  is
2298         returned in pairs of integers, starting at the  beginning  of  ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2299         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
2300         element of a pair is set to the offset of the first character in a sub-         element  of  each pair is set to the byte offset of the first character
2301         string,  and  the  second  is  set to the offset of the first character         in a substring, and the second is set to the byte offset of  the  first
2302         after the end of a substring. The  first  pair,  ovector[0]  and  ovec-         character  after  the end of a substring. Note: these values are always
2303         tor[1],  identify  the  portion  of  the  subject string matched by the         byte offsets, even in UTF-8 mode. They are not character counts.
2304         entire pattern. The next pair is used for the first  capturing  subpat-  
2305         tern, and so on. The value returned by pcre_exec() is one more than the         The first pair of integers, ovector[0]  and  ovector[1],  identify  the
2306         highest numbered pair that has been set. For example, if two substrings         portion  of  the subject string matched by the entire pattern. The next
2307         have  been captured, the returned value is 3. If there are no capturing         pair is used for the first capturing subpattern, and so on.  The  value
2308         subpatterns, the return value from a successful match is 1,  indicating         returned by pcre_exec() is one more than the highest numbered pair that
2309         that just the first pair of offsets has been set.         has been set.  For example, if two substrings have been  captured,  the
2310           returned  value is 3. If there are no capturing subpatterns, the return
2311           value from a successful match is 1, indicating that just the first pair
2312           of offsets has been set.
2313    
2314         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2315         of the string that it matched that is returned.         of the string that it matched that is returned.
2316    
2317         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,
2318         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
2319         function returns a value of zero. In particular, if the substring  off-         function returns a value of zero. If the substring offsets are  not  of
2320         sets are not of interest, pcre_exec() may be called with ovector passed         interest,  pcre_exec()  may  be  called with ovector passed as NULL and
2321         as NULL and ovecsize as zero. However, if  the  pattern  contains  back         ovecsize as zero. However, if the pattern contains back references  and
2322         references  and  the  ovector is not big enough to remember the related         the  ovector is not big enough to remember the related substrings, PCRE
2323         substrings, PCRE has to get additional memory for use during  matching.         has to get additional memory for use during matching. Thus it  is  usu-
2324         Thus it is usually advisable to supply an ovector.         ally advisable to supply an ovector.
2325    
2326         The  pcre_info()  function  can  be used to find out how many capturing         The pcre_fullinfo() function can be used to find out how many capturing
2327         subpatterns there are in a compiled  pattern.  The  smallest  size  for         subpatterns there are in a compiled  pattern.  The  smallest  size  for
2328         ovector  that  will allow for n captured substrings, in addition to the         ovector  that  will allow for n captured substrings, in addition to the
2329         offsets of the substring matched by the whole pattern, is (n+1)*3.         offsets of the substring matched by the whole pattern, is (n+1)*3.
# Line 1984  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2386  MATCHING A PATTERN: THE TRADITIONAL FUNC
2386         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
2387         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2388    
2389           This error is also given if pcre_stack_malloc() fails  in  pcre_exec().
2390           This  can happen only when PCRE has been compiled with --disable-stack-
2391           for-recursion.
2392    
2393           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2394    
2395         This error is used by the pcre_copy_substring(),  pcre_get_substring(),         This error is used by the pcre_copy_substring(),  pcre_get_substring(),
# Line 2020  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2426  MATCHING A PATTERN: THE TRADITIONAL FUNC
2426    
2427           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2428    
2429         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing         This code is no longer in  use.  It  was  formerly  returned  when  the
2430         items  that are not supported for partial matching. See the pcrepartial         PCRE_PARTIAL  option  was used with a compiled pattern containing items
2431         documentation for details of partial matching.         that were  not  supported  for  partial  matching.  From  release  8.00
2432           onwards, there are no restrictions on partial matching.
2433    
2434           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2435    
2436         An unexpected internal error has occurred. This error could  be  caused         An  unexpected  internal error has occurred. This error could be caused
2437         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2438    
2439           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2440    
2441         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.
2442    
2443           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2444    
# Line 2039  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2446  MATCHING A PATTERN: THE TRADITIONAL FUNC
2446         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2447         description above.         description above.
2448    
          PCRE_ERROR_NULLWSLIMIT    (-22)  
   
        When a group that can match an empty  substring  is  repeated  with  an  
        unbounded  upper  limit, the subject position at the start of the group  
        must be remembered, so that a test for an empty string can be made when  
        the  end  of the group is reached. Some workspace is required for this;  
        if it runs out, this error is given.  
   
2449           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
2450    
2451         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2452    
2453         Error numbers -16 to -20 are not used by pcre_exec().           PCRE_ERROR_BADOFFSET      (-24)
2454    
2455           The value of startoffset was negative or greater than the length of the
2456           subject, that is, the value in length.
2457    
2458           Error numbers -16 to -20 and -22 are not used by pcre_exec().
2459    
2460    
2461  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
# Line 2067  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2471  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2471         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2472              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2473    
2474         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
2475         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
2476         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2477         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
2478         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
2479         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
2480         substrings.         substrings.
2481    
2482         A substring that contains a binary zero is correctly extracted and  has         A  substring that contains a binary zero is correctly extracted and has
2483         a  further zero added on the end, but the result is not, of course, a C         a further zero added on the end, but the result is not, of course, a  C
2484         string.  However, you can process such a string  by  referring  to  the         string.   However,  you  can  process such a string by referring to the
2485         length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2486         string().  Unfortunately, the interface to pcre_get_substring_list() is         string().  Unfortunately, the interface to pcre_get_substring_list() is
2487         not  adequate for handling strings containing binary zeros, because the         not adequate for handling strings containing binary zeros, because  the
2488         end of the final string is not independently indicated.         end of the final string is not independently indicated.
2489    
2490         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-
2491         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
2492         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
2493         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2494         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
2495         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2496         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
2497         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
2498         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2499    
2500         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
2501         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
2502         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
2503         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
2504         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
2505         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2506         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2507         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
2508         the terminating zero, or one of these error codes:         the terminating zero, or one of these error codes:
2509    
2510           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2511    
2512         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
2513         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2514    
2515           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2516    
2517         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2518    
2519         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
2520         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
2521         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
2522         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
2523         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
2524         pointer. The yield of the function is zero if all  went  well,  or  the         pointer.  The  yield  of  the function is zero if all went well, or the
2525         error code         error code
2526    
2527           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2528    
2529         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2530    
2531         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
2532         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
2533         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
2534         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2535         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
2536         tive for unset substrings.         tive for unset substrings.
2537    
2538         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2539         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
2540         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2541         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
2542         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.
2543         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-
2544         cial  interface  to  another  programming  language  that  cannot   use         cial   interface  to  another  programming  language  that  cannot  use
2545         pcre_free  directly;  it is for these cases that the functions are pro-         pcre_free directly; it is for these cases that the functions  are  pro-
2546         vided.         vided.
2547    
2548    
# Line 2157  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2561  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2561              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2562              const char **stringptr);              const char **stringptr);
2563    
2564         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-
2565         ber.  For example, for this pattern         ber.  For example, for this pattern
2566    
2567           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
# Line 2166  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2570  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2570         be unique (PCRE_DUPNAMES was not set), you can find the number from the         be unique (PCRE_DUPNAMES was not set), you can find the number from the
2571         name by calling pcre_get_stringnumber(). The first argument is the com-         name by calling pcre_get_stringnumber(). The first argument is the com-
2572         piled pattern, and the second is the name. The yield of the function is         piled pattern, and the second is the name. The yield of the function is
2573         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2574         subpattern of that name.         subpattern of that name.
2575    
2576         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
2577         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
2578         are also two functions that do the whole job.         are also two functions that do the whole job.
2579    
2580         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
2581         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
2582         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
2583         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
2584         differences:         differences:
2585    
2586         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
2587         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
2588         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
2589         name-to-number translation table.         name-to-number translation table.
2590    
2591         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2592         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2593         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the         ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
2594         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2595    
2596           Warning: If the pattern uses the (?| feature to set up multiple subpat-
2597           terns with the same number, as described in the  section  on  duplicate
2598           subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2599           distinguish the different subpatterns, because names are  not  included
2600           in  the compiled code. The matching process uses only numbers. For this
2601           reason, the use of different names for subpatterns of the  same  number
2602           causes an error at compile time.
2603    
2604    
2605  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
2606    
2607         int pcre_get_stringtable_entries(const pcre *code,         int pcre_get_stringtable_entries(const pcre *code,
2608              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2609    
2610         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2611         subpatterns  are  not  required  to  be unique. Normally, patterns with         subpatterns are not required to be unique. (Duplicate names are  always
2612         duplicate names are such that in any one match, only one of  the  named         allowed  for subpatterns with the same number, created by using the (?|
2613         subpatterns  participates. An example is shown in the pcrepattern docu-         feature. Indeed, if such subpatterns are named, they  are  required  to
2614         mentation. When duplicates are present, pcre_copy_named_substring() and         use the same names.)
        pcre_get_named_substring()  return the first substring corresponding to  
        the given name that is set.  If  none  are  set,  an  empty  string  is  
        returned.  The pcre_get_stringnumber() function returns one of the num-  
        bers that are associated with the name, but it is not defined which  it  
        is.  
2615    
2616         If  you want to get full details of all captured substrings for a given         Normally, patterns with duplicate names are such that in any one match,
2617         name, you must use  the  pcre_get_stringtable_entries()  function.  The         only one of the named subpatterns participates. An example is shown  in
2618           the pcrepattern documentation.
2619    
2620           When    duplicates   are   present,   pcre_copy_named_substring()   and
2621           pcre_get_named_substring() return the first substring corresponding  to
2622           the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2623           (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2624           function  returns one of the numbers that are associated with the name,
2625           but it is not defined which it is.
2626    
2627           If you want to get full details of all captured substrings for a  given
2628           name,  you  must  use  the pcre_get_stringtable_entries() function. The
2629         first argument is the compiled pattern, and the second is the name. The         first argument is the compiled pattern, and the second is the name. The
2630         third and fourth are pointers to variables which  are  updated  by  the         third  and  fourth  are  pointers to variables which are updated by the
2631         function. After it has run, they point to the first and last entries in         function. After it has run, they point to the first and last entries in
2632         the name-to-number table  for  the  given  name.  The  function  itself         the  name-to-number  table  for  the  given  name.  The function itself
2633         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2634         there are none. The format of the table is described above in the  sec-         there  are none. The format of the table is described above in the sec-
2635         tion  entitled  Information  about  a  pattern.  Given all the relevant         tion entitled Information about a  pattern.   Given  all  the  relevant
2636         entries for the name, you can extract each of their numbers, and  hence         entries  for the name, you can extract each of their numbers, and hence
2637         the captured data, if any.         the captured data, if any.
2638    
2639    
2640  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
2641    
2642         The  traditional  matching  function  uses a similar algorithm to Perl,         The traditional matching function uses a  similar  algorithm  to  Perl,
2643         which stops when it finds the first match, starting at a given point in         which stops when it finds the first match, starting at a given point in
2644         the  subject.  If you want to find all possible matches, or the longest         the subject. If you want to find all possible matches, or  the  longest
2645         possible match, consider using the alternative matching  function  (see         possible  match,  consider using the alternative matching function (see
2646         below)  instead.  If you cannot use the alternative function, but still         below) instead. If you cannot use the alternative function,  but  still
2647         need to find all possible matches, you can kludge it up by  making  use         need  to  find all possible matches, you can kludge it up by making use
2648         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
2649         tation.         tation.
2650    
2651         What you have to do is to insert a callout right at the end of the pat-         What you have to do is to insert a callout right at the end of the pat-
2652         tern.   When your callout function is called, extract and save the cur-         tern.  When your callout function is called, extract and save the  cur-
2653         rent matched substring. Then return  1,  which  forces  pcre_exec()  to         rent  matched  substring.  Then  return  1, which forces pcre_exec() to
2654         backtrack  and  try other alternatives. Ultimately, when it runs out of         backtrack and try other alternatives. Ultimately, when it runs  out  of
2655         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2656    
2657    
# Line 2244  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2662  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2662              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
2663              int *workspace, int wscount);              int *workspace, int wscount);
2664    
2665         The function pcre_dfa_exec()  is  called  to  match  a  subject  string         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2666         against  a  compiled pattern, using a matching algorithm that scans the         against a compiled pattern, using a matching algorithm that  scans  the
2667         subject string just once, and does not backtrack.  This  has  different         subject  string  just  once, and does not backtrack. This has different
2668         characteristics  to  the  normal  algorithm, and is not compatible with         characteristics to the normal algorithm, and  is  not  compatible  with
2669         Perl. Some of the features of PCRE patterns are not  supported.  Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2670         theless,  there are times when this kind of matching can be useful. For         theless, there are times when this kind of matching can be useful.  For
2671         a discussion of the two matching algorithms, see the pcrematching docu-         a  discussion  of  the  two matching algorithms, and a list of features
2672         mentation.         that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2673           tion.
2674    
2675         The  arguments  for  the  pcre_dfa_exec()  function are the same as for         The  arguments  for  the  pcre_dfa_exec()  function are the same as for
2676         pcre_exec(), plus two extras. The ovector argument is used in a differ-         pcre_exec(), plus two extras. The ovector argument is used in a differ-
# Line 2286  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2705  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2705    
2706         The  unused  bits  of  the options argument for pcre_dfa_exec() must be         The  unused  bits  of  the options argument for pcre_dfa_exec() must be
2707         zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-         zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-
2708         LINE_xxx,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2709         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last         PCRE_NOTEMPTY_ATSTART,      PCRE_NO_UTF8_CHECK,       PCRE_BSR_ANYCRLF,
2710         three of these are the same as for pcre_exec(), so their description is         PCRE_BSR_UNICODE,  PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD, PCRE_PAR-
2711         not repeated here.         TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.  All but  the  last
2712           four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
2713           PCRE_PARTIAL         description is not repeated here.
2714    
2715         This has the same general effect as it does for  pcre_exec(),  but  the           PCRE_PARTIAL_HARD
2716         details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for           PCRE_PARTIAL_SOFT
2717         pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into  
2718         PCRE_ERROR_PARTIAL  if  the  end  of the subject is reached, there have         These have the same general effect as they do for pcre_exec(), but  the
2719         been no complete matches, but there is still at least one matching pos-         details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
2720         sibility.  The portion of the string that provided the partial match is         pcre_dfa_exec(), it returns PCRE_ERROR_PARTIAL if the end of  the  sub-
2721         set as the first matching string.         ject  is  reached  and there is still at least one matching possibility
2722           that requires additional characters. This happens even if some complete
2723           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2724           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2725           of  the  subject  is  reached, there have been no complete matches, but
2726           there is still at least one matching possibility. The  portion  of  the
2727           string  that  was inspected when the longest partial match was found is
2728           set as the first matching string  in  both  cases.   There  is  a  more
2729           detailed  discussion  of partial and multi-segment matching, with exam-
2730           ples, in the pcrepartial documentation.
2731    
2732           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2733    
# Line 2310  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2738  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2738    
2739           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2740    
2741         When  pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option, and         When pcre_dfa_exec() returns a partial match, it is possible to call it
2742         returns a partial match, it is possible to call it  again,  with  addi-         again, with additional subject characters, and have  it  continue  with
2743         tional  subject  characters,  and have it continue with the same match.         the  same match. The PCRE_DFA_RESTART option requests this action; when
2744         The PCRE_DFA_RESTART option requests this action; when it is  set,  the         it is set, the workspace and wscount options must  reference  the  same
2745         workspace  and wscount options must reference the same vector as before         vector  as  before  because data about the match so far is left in them
2746         because data about the match so far is left in  them  after  a  partial         after a partial match. There is more discussion of this facility in the
2747         match.  There  is  more  discussion of this facility in the pcrepartial         pcrepartial documentation.
        documentation.  
2748    
2749     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2750    
2751         When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-         When  pcre_dfa_exec()  succeeds, it may have matched more than one sub-
2752         string in the subject. Note, however, that all the matches from one run         string in the subject. Note, however, that all the matches from one run
2753         of the function start at the same point in  the  subject.  The  shorter         of  the  function  start  at the same point in the subject. The shorter
2754         matches  are all initial substrings of the longer matches. For example,         matches are all initial substrings of the longer matches. For  example,
2755         if the pattern         if the pattern
2756    
2757           <.*>           <.*>
# Line 2339  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2766  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2766           <something> <something else>           <something> <something else>
2767           <something> <something else> <something further>           <something> <something else> <something further>
2768    
2769         On success, the yield of the function is a number  greater  than  zero,         On  success,  the  yield of the function is a number greater than zero,
2770         which  is  the  number of matched substrings. The substrings themselves         which is the number of matched substrings.  The  substrings  themselves
2771         are returned in ovector. Each string uses two elements;  the  first  is         are  returned  in  ovector. Each string uses two elements; the first is
2772         the  offset  to  the start, and the second is the offset to the end. In         the offset to the start, and the second is the offset to  the  end.  In
2773         fact, all the strings have the same start  offset.  (Space  could  have         fact,  all  the  strings  have the same start offset. (Space could have
2774         been  saved by giving this only once, but it was decided to retain some         been saved by giving this only once, but it was decided to retain  some
2775         compatibility with the way pcre_exec() returns data,  even  though  the         compatibility  with  the  way pcre_exec() returns data, even though the
2776         meaning of the strings is different.)         meaning of the strings is different.)
2777    
2778         The strings are returned in reverse order of length; that is, the long-         The strings are returned in reverse order of length; that is, the long-
2779         est matching string is given first. If there were too many  matches  to         est  matching  string is given first. If there were too many matches to
2780         fit  into ovector, the yield of the function is zero, and the vector is         fit into ovector, the yield of the function is zero, and the vector  is
2781         filled with the longest matches.         filled with the longest matches.
2782    
2783     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2784    
2785         The pcre_dfa_exec() function returns a negative number when  it  fails.         The  pcre_dfa_exec()  function returns a negative number when it fails.
2786         Many  of  the  errors  are  the  same as for pcre_exec(), and these are         Many of the errors are the same  as  for  pcre_exec(),  and  these  are
2787         described above.  There are in addition the following errors  that  are         described  above.   There are in addition the following errors that are
2788         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2789    
2790           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2791    
2792         This  return is given if pcre_dfa_exec() encounters an item in the pat-         This return is given if pcre_dfa_exec() encounters an item in the  pat-
2793         tern that it does not support, for instance, the use of \C  or  a  back         tern  that  it  does not support, for instance, the use of \C or a back
2794         reference.         reference.
2795    
2796           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2797    
2798         This  return  is  given  if pcre_dfa_exec() encounters a condition item         This return is given if pcre_dfa_exec()  encounters  a  condition  item
2799         that uses a back reference for the condition, or a test  for  recursion         that  uses  a back reference for the condition, or a test for recursion
2800         in a specific group. These are not supported.         in a specific group. These are not supported.
2801    
2802           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2803    
2804         This  return  is given if pcre_dfa_exec() is called with an extra block         This return is given if pcre_dfa_exec() is called with an  extra  block
2805         that contains a setting of the match_limit field. This is not supported         that contains a setting of the match_limit field. This is not supported
2806         (it is meaningless).         (it is meaningless).
2807    
2808           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2809    
2810         This  return  is  given  if  pcre_dfa_exec()  runs  out of space in the         This return is given if  pcre_dfa_exec()  runs  out  of  space  in  the
2811         workspace vector.         workspace vector.
2812    
2813           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2814    
2815         When a recursive subpattern is processed, the matching  function  calls         When  a  recursive subpattern is processed, the matching function calls
2816         itself  recursively,  using  private vectors for ovector and workspace.         itself recursively, using private vectors for  ovector  and  workspace.
2817         This error is given if the output vector  is  not  large  enough.  This         This  error  is  given  if  the output vector is not large enough. This
2818         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2819    
2820    
2821  SEE ALSO  SEE ALSO
2822    
2823         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
2824         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3),  pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2825    
2826    
2827  AUTHOR  AUTHOR
# Line 2406  AUTHOR Line 2833  AUTHOR
2833    
2834  REVISION  REVISION
2835    
2836         Last updated: 04 June 2007         Last updated: 06 November 2010
2837         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
2838  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2839    
2840    
2841  PCRECALLOUT(3)                                                  PCRECALLOUT(3)  PCRECALLOUT(3)                                                  PCRECALLOUT(3)
2842    
2843    
# Line 2436  PCRE CALLOUTS Line 2863  PCRE CALLOUTS
2863    
2864           (?C1)abc(?C2)def           (?C1)abc(?C2)def
2865    
2866         If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() is         If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() or
2867         called, PCRE automatically  inserts  callouts,  all  with  number  255,         pcre_compile2() is called, PCRE  automatically  inserts  callouts,  all
2868         before  each  item in the pattern. For example, if PCRE_AUTO_CALLOUT is         with  number  255,  before  each  item  in the pattern. For example, if
2869         used with the pattern         PCRE_AUTO_CALLOUT is used with the pattern
2870    
2871           A(\d{2}|--)           A(\d{2}|--)
2872    
# Line 2458  PCRE CALLOUTS Line 2885  PCRE CALLOUTS
2885  MISSING CALLOUTS  MISSING CALLOUTS
2886    
2887         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
2888         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
2889         pattern is         example, if the pattern is
2890    
2891           ab(?C4)cd           ab(?C4)cd
2892    
# Line 2468  MISSING CALLOUTS Line 2895  MISSING CALLOUTS
2895         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
2896         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
2897    
2898           If the pattern is studied, PCRE knows the minimum length of a  matching
2899           string,  and will immediately give a "no match" return without actually
2900           running a match if the subject is not long enough, or,  for  unanchored
2901           patterns, if it has been scanned far enough.
2902    
2903           You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
2904           MIZE option to pcre_exec() or  pcre_dfa_exec().  This  slows  down  the
2905           matching  process,  but  does  ensure that callouts such as the example
2906           above are obeyed.
2907    
2908    
2909  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2910    
# Line 2495  THE CALLOUT INTERFACE Line 2932  THE CALLOUT INTERFACE
2932         version number will change again in future  if  additional  fields  are         version number will change again in future  if  additional  fields  are
2933         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.
2934    
2935         The callout_number field contains the number of the  callout,  as  com-         The  callout_number  field  contains the number of the callout, as com-
2936         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-
2937         outs, and 255 for automatically generated callouts).         outs, and 255 for automatically generated callouts).
2938    
2939         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
2940         passed   by   the   caller  to  pcre_exec()  or  pcre_dfa_exec().  When         passed  by  the  caller  to  pcre_exec()   or   pcre_dfa_exec().   When
2941         pcre_exec() is used, the contents can be inspected in order to  extract         pcre_exec()  is used, the contents can be inspected in order to extract
2942         substrings  that  have  been  matched  so  far,  in the same way as for         substrings that have been matched so  far,  in  the  same  way  as  for
2943         extracting substrings after a match has completed. For  pcre_dfa_exec()         extracting  substrings after a match has completed. For pcre_dfa_exec()
2944         this field is not useful.         this field is not useful.
2945    
2946         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
2947         were passed to pcre_exec().         were passed to pcre_exec().
2948    
2949         The start_match field normally contains the offset within  the  subject         The  start_match  field normally contains the offset within the subject
2950         at  which  the  current  match  attempt started. However, if the escape         at which the current match attempt  started.  However,  if  the  escape
2951         sequence \K has been encountered, this value is changed to reflect  the         sequence  \K has been encountered, this value is changed to reflect the
2952         modified  starting  point.  If the pattern is not anchored, the callout         modified starting point. If the pattern is not  anchored,  the  callout
2953         function may be called several times from the same point in the pattern         function may be called several times from the same point in the pattern
2954         for different starting points in the subject.         for different starting points in the subject.
2955    
2956         The  current_position  field  contains the offset within the subject of         The current_position field contains the offset within  the  subject  of
2957         the current match pointer.         the current match pointer.
2958    
2959         When the pcre_exec() function is used, the capture_top  field  contains         When  the  pcre_exec() function is used, the capture_top field contains
2960         one  more than the number of the highest numbered captured substring so         one more than the number of the highest numbered captured substring  so
2961         far. If no substrings have been captured, the value of  capture_top  is         far.  If  no substrings have been captured, the value of capture_top is
2962         one.  This  is always the case when pcre_dfa_exec() is used, because it         one. This is always the case when pcre_dfa_exec() is used,  because  it
2963         does not support captured substrings.         does not support captured substrings.
2964    
2965         The capture_last field contains the number of the  most  recently  cap-         The  capture_last  field  contains the number of the most recently cap-
2966         tured  substring. If no substrings have been captured, its value is -1.         tured substring. If no substrings have been captured, its value is  -1.
2967         This is always the case when pcre_dfa_exec() is used.         This is always the case when pcre_dfa_exec() is used.
2968    
2969         The callout_data field contains a value that is passed  to  pcre_exec()         The  callout_data  field contains a value that is passed to pcre_exec()
2970         or  pcre_dfa_exec() specifically so that it can be passed back in call-         or pcre_dfa_exec() specifically so that it can be passed back in  call-
2971         outs. It is passed in the pcre_callout field  of  the  pcre_extra  data         outs.  It  is  passed  in the pcre_callout field of the pcre_extra data
2972         structure.  If  no such data was passed, the value of callout_data in a         structure. If no such data was passed, the value of callout_data  in  a
2973         pcre_callout block is NULL. There is a description  of  the  pcre_extra         pcre_callout  block  is  NULL. There is a description of the pcre_extra
2974         structure in the pcreapi documentation.         structure in the pcreapi documentation.
2975    
2976         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-
2977         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
2978         the pattern string.         the pattern string.
2979    
2980         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-
2981         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
2982         the  pattern  string. When the callout immediately precedes an alterna-         the pattern string. When the callout immediately precedes  an  alterna-
2983         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
2984         is  zero.  When the callout precedes an opening parenthesis, the length         is zero. When the callout precedes an opening parenthesis,  the  length
2985         is that of the entire subpattern.         is that of the entire subpattern.
2986    
2987         The pattern_position and next_item_length fields are intended  to  help         The  pattern_position  and next_item_length fields are intended to help
2988         in  distinguishing between different automatic callouts, which all have         in distinguishing between different automatic callouts, which all  have
2989         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
2990    
2991    
2992  RETURN VALUES  RETURN VALUES
2993    
2994         The external callout function returns an integer to PCRE. If the  value         The  external callout function returns an integer to PCRE. If the value
2995         is  zero,  matching  proceeds  as  normal. If the value is greater than         is zero, matching proceeds as normal. If  the  value  is  greater  than
2996         zero, matching fails at the current point, but  the  testing  of  other         zero,  matching  fails  at  the current point, but the testing of other
2997         matching possibilities goes ahead, just as if a lookahead assertion had         matching possibilities goes ahead, just as if a lookahead assertion had
2998         failed. If the value is less than zero, the  match  is  abandoned,  and         failed.  If  the  value  is less than zero, the match is abandoned, and
2999         pcre_exec() (or pcre_dfa_exec()) returns the negative value.         pcre_exec() or pcre_dfa_exec() returns the negative value.
3000    
3001         Negative   values   should   normally   be   chosen  from  the  set  of         Negative  values  should  normally  be   chosen   from   the   set   of
3002         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
3003         dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is         dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is
3004         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
3005         itself.         itself.
3006    
3007    
# Line 2577  AUTHOR Line 3014  AUTHOR
3014    
3015  REVISION  REVISION
3016    
3017         Last updated: 29 May 2007         Last updated: 29 September 2009
3018         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
3019  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3020    
3021    
3022  PCRECOMPAT(3)                                                    PCRECOMPAT(3)  PCRECOMPAT(3)                                                    PCRECOMPAT(3)
3023    
3024    
# Line 2592  NAME Line 3029  NAME
3029  DIFFERENCES BETWEEN PCRE AND PERL  DIFFERENCES BETWEEN PCRE AND PERL
3030    
3031         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
3032         handle regular expressions. The differences described here  are  mainly         handle regular expressions. The differences  described  here  are  with
3033         with  respect  to  Perl 5.8, though PCRE version 7.0 contains some fea-         respect to Perl versions 5.10 and above.
        tures that are expected to be in the forthcoming Perl 5.10.  
3034    
3035         1. PCRE has only a subset of Perl's UTF-8 and Unicode support.  Details         1.  PCRE has only a subset of Perl's UTF-8 and Unicode support. Details
3036         of  what  it does have are given in the section on UTF-8 support in the         of what it does have are given in the section on UTF-8 support  in  the
3037         main pcre page.         main pcre page.
3038    
3039         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl
3040         permits  them,  but they do not mean what you might think. For example,         permits them, but they do not mean what you might think.  For  example,
3041         (?!a){3} does not assert that the next three characters are not "a". It         (?!a){3} does not assert that the next three characters are not "a". It
3042         just asserts that the next character is not "a" three times.         just asserts that the next character is not "a" three times.
3043    
3044         3.  Capturing  subpatterns  that occur inside negative lookahead asser-         3. Capturing subpatterns that occur inside  negative  lookahead  asser-
3045         tions are counted, but their entries in the offsets  vector  are  never         tions  are  counted,  but their entries in the offsets vector are never
3046         set.  Perl sets its numerical variables from any such patterns that are         set. Perl sets its numerical variables from any such patterns that  are
3047         matched before the assertion fails to match something (thereby succeed-         matched before the assertion fails to match something (thereby succeed-
3048         ing),  but  only  if the negative lookahead assertion contains just one         ing), but only if the negative lookahead assertion  contains  just  one
3049         branch.         branch.
3050    
3051         4. Though binary zero characters are supported in the  subject  string,         4.  Though  binary zero characters are supported in the subject string,
3052         they are not allowed in a pattern string because it is passed as a nor-         they are not allowed in a pattern string because it is passed as a nor-
3053         mal C string, terminated by zero. The escape sequence \0 can be used in         mal C string, terminated by zero. The escape sequence \0 can be used in
3054         the pattern to represent a binary zero.         the pattern to represent a binary zero.
3055    
3056         5.  The  following Perl escape sequences are not supported: \l, \u, \L,         5. The following Perl escape sequences are not supported: \l,  \u,  \L,
3057         \U, and \N. In fact these are implemented by Perl's general string-han-         \U, and \N. In fact these are implemented by Perl's general string-han-
3058         dling  and are not part of its pattern matching engine. If any of these         dling and are not part of its pattern matching engine. If any of  these
3059         are encountered by PCRE, an error is generated.         are encountered by PCRE, an error is generated.
3060    
3061         6. The Perl escape sequences \p, \P, and \X are supported only if  PCRE         6.  The Perl escape sequences \p, \P, and \X are supported only if PCRE
3062         is  built  with Unicode character property support. The properties that         is built with Unicode character property support. The  properties  that
3063         can be tested with \p and \P are limited to the general category  prop-         can  be tested with \p and \P are limited to the general category prop-
3064         erties  such  as  Lu and Nd, script names such as Greek or Han, and the         erties such as Lu and Nd, script names such as Greek or  Han,  and  the
3065         derived properties Any and L&.         derived  properties  Any  and  L&. PCRE does support the Cs (surrogate)
3066           property, which Perl does not; the  Perl  documentation  says  "Because
3067           Perl hides the need for the user to understand the internal representa-
3068           tion of Unicode characters, there is no need to implement the  somewhat
3069           messy concept of surrogates."
3070    
3071         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-
3072         ters  in  between  are  treated as literals. This is slightly different         ters in between are treated as literals.  This  is  slightly  different
3073         from Perl in that $ and @ are  also  handled  as  literals  inside  the         from  Perl  in  that  $  and  @ are also handled as literals inside the
3074         quotes.  In Perl, they cause variable interpolation (but of course PCRE         quotes. In Perl, they cause variable interpolation (but of course  PCRE
3075         does not have variables). Note the following examples:         does not have variables). Note the following examples:
3076    
3077             Pattern            PCRE matches      Perl matches             Pattern            PCRE matches      Perl matches
# Line 2641  DIFFERENCES BETWEEN PCRE AND PERL Line 3081  DIFFERENCES BETWEEN PCRE AND PERL
3081             \Qabc\$xyz\E       abc\$xyz          abc\$xyz             \Qabc\$xyz\E       abc\$xyz          abc\$xyz
3082             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
3083    
3084         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
3085         classes.         classes.
3086    
3087         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
3088         constructions. However, there is support for recursive  patterns.  This         constructions.  However,  there is support for recursive patterns. This
3089         is  not available in Perl 5.8, but will be in Perl 5.10. Also, the PCRE         is not available in Perl 5.8, but it is in Perl 5.10.  Also,  the  PCRE
3090         "callout" feature allows an external function to be called during  pat-         "callout"  feature allows an external function to be called during pat-
3091         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
3092    
3093         9.  Subpatterns  that  are  called  recursively or as "subroutines" are         9. Subpatterns that are called  recursively  or  as  "subroutines"  are
3094         always treated as atomic groups in  PCRE.  This  is  like  Python,  but         always  treated  as  atomic  groups  in  PCRE. This is like Python, but
3095         unlike Perl.         unlike Perl. There is a discussion of an example that explains this  in
3096           more  detail  in  the section on recursion differences from Perl in the
3097         10.  There are some differences that are concerned with the settings of         pcrepattern page.
3098         captured strings when part of  a  pattern  is  repeated.  For  example,  
3099         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2         10. There are some differences that are concerned with the settings  of
3100           captured  strings  when  part  of  a  pattern is repeated. For example,
3101           matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2
3102         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
3103    
3104         11. PCRE provides some extensions to the Perl regular expression facil-         11.  PCRE's handling of duplicate subpattern numbers and duplicate sub-
3105         ities.   Perl  5.10  will  include new features that are not in earlier         pattern names is not as general as Perl's. This is a consequence of the
3106         versions, some of which (such as named parentheses) have been  in  PCRE         fact the PCRE works internally just with numbers, using an external ta-
3107         for some time. This list is with respect to Perl 5.10:         ble to translate between numbers and names. In  particular,  a  pattern
3108           such  as  (?|(?<a>A)|(?<b)B),  where the two capturing parentheses have
3109         (a)  Although  lookbehind  assertions  must match fixed length strings,         the same number but different names, is not supported,  and  causes  an
3110         each alternative branch of a lookbehind assertion can match a different         error  at compile time. If it were allowed, it would not be possible to
3111         length of string. Perl requires them all to have the same length.         distinguish which parentheses matched, because both names map  to  cap-
3112           turing subpattern number 1. To avoid this confusing situation, an error
3113           is given at compile time.
3114    
3115           12. Perl recognizes comments in some  places  that  PCRE  doesn't,  for
3116           example, between the ( and ? at the start of a subpattern.
3117    
3118           13. PCRE provides some extensions to the Perl regular expression facil-
3119           ities.  Perl 5.10 includes new features that are not  in  earlier  ver-
3120           sions  of  Perl, some of which (such as named parentheses) have been in
3121           PCRE for some time. This list is with respect to Perl 5.10:
3122    
3123           (a) Although lookbehind assertions in  PCRE  must  match  fixed  length
3124           strings,  each alternative branch of a lookbehind assertion can match a
3125           different length of string. Perl requires them all  to  have  the  same
3126           length.
3127    
3128         (b)  If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $         (b)  If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $
3129         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
3130    
3131         (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe-         (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe-
3132         cial  meaning  is  faulted.  Otherwise,  like  Perl,  the  backslash is         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
3133         ignored. (Perl can be made to issue a warning.)         ignored.  (Perl can be made to issue a warning.)
3134    
3135         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-
3136         fiers is inverted, that is, by default they are not greedy, but if fol-         fiers is inverted, that is, by default they are not greedy, but if fol-
# Line 2682  DIFFERENCES BETWEEN PCRE AND PERL Line 3139  DIFFERENCES BETWEEN PCRE AND PERL
3139         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be
3140         tried only at the first matching position in the subject string.         tried only at the first matching position in the subject string.
3141    
3142         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
3143         TURE options for pcre_exec() have no Perl equivalents.         and PCRE_NO_AUTO_CAPTURE options for pcre_exec() have no  Perl  equiva-
3144           lents.
3145    
3146         (g) The callout facility is PCRE-specific.         (g)  The  \R escape sequence can be restricted to match only CR, LF, or
3147           CRLF by the PCRE_BSR_ANYCRLF option.
3148    
3149         (h) The partial matching facility is PCRE-specific.         (h) The callout facility is PCRE-specific.
3150    
3151         (i) Patterns compiled by PCRE can be saved and re-used at a later time,         (i) The partial matching facility is PCRE-specific.
3152    
3153           (j) Patterns compiled by PCRE can be saved and re-used at a later time,
3154         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
3155    
3156         (j)  The  alternative  matching function (pcre_dfa_exec()) matches in a         (k)  The  alternative  matching function (pcre_dfa_exec()) matches in a
3157         different way and is not Perl-compatible.         different way and is not Perl-compatible.
3158    
3159           (l) PCRE recognizes some special sequences such as (*CR) at  the  start
3160           of a pattern that set overall options that cannot be changed within the
3161           pattern.
3162    
3163    
3164  AUTHOR  AUTHOR
3165    
# Line 2705  AUTHOR Line 3170  AUTHOR
3170    
3171  REVISION  REVISION
3172    
3173         Last updated: 06 March 2007         Last updated: 31 October 2010
3174         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
3175  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3176    
3177    
3178  PCREPATTERN(3)                                                  PCREPATTERN(3)  PCREPATTERN(3)                                                  PCREPATTERN(3)
3179    
3180    
# Line 2719  NAME Line 3184  NAME
3184    
3185  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
3186    
3187         The  syntax  and semantics of the regular expressions supported by PCRE         The  syntax and semantics of the regular expressions that are supported
3188         are described below. Regular expressions are also described in the Perl         by PCRE are described in detail below. There is a quick-reference  syn-
3189         documentation  and  in  a  number  of books, some of which have copious         tax summary in the pcresyntax page. PCRE tries to match Perl syntax and
3190         examples.  Jeffrey Friedl's "Mastering Regular Expressions",  published         semantics as closely as it can. PCRE  also  supports  some  alternative
3191         by  O'Reilly, covers regular expressions in great detail. This descrip-         regular  expression  syntax (which does not conflict with the Perl syn-
3192         tion of PCRE's regular expressions is intended as reference material.         tax) in order to provide some compatibility with regular expressions in
3193           Python, .NET, and Oniguruma.
3194    
3195           Perl's  regular expressions are described in its own documentation, and
3196           regular expressions in general are covered in a number of  books,  some
3197           of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
3198           Expressions", published by  O'Reilly,  covers  regular  expressions  in
3199           great  detail.  This  description  of  PCRE's  regular  expressions  is
3200           intended as reference material.
3201    
3202         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
3203         However,  there is now also support for UTF-8 character strings. To use         However,  there is now also support for UTF-8 character strings. To use
3204         this, you must build PCRE to  include  UTF-8  support,  and  then  call         this, PCRE must be built to include UTF-8 support, and  you  must  call
3205         pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern         pcre_compile()  or  pcre_compile2() with the PCRE_UTF8 option. There is
3206         matching is mentioned in several places below. There is also a  summary         also a special sequence that can be given at the start of a pattern:
3207         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre  
3208         page.           (*UTF8)
3209    
3210           Starting a pattern with this sequence  is  equivalent  to  setting  the
3211           PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3212           UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3213           below.  There  is  also  a  summary of UTF-8 features in the section on
3214           UTF-8 support in the main pcre page.
3215    
3216           Another special sequence that may appear at the start of a  pattern  or
3217           in combination with (*UTF8) is:
3218    
3219             (*UCP)
3220    
3221           This  has  the  same  effect  as setting the PCRE_UCP option: it causes
3222           sequences such as \d and \w to  use  Unicode  properties  to  determine
3223           character types, instead of recognizing only characters with codes less
3224           than 128 via a lookup table.
3225    
3226         The remainder of this document discusses the  patterns  that  are  sup-         The remainder of this document discusses the  patterns  that  are  sup-
3227         ported  by  PCRE when its main matching function, pcre_exec(), is used.         ported  by  PCRE when its main matching function, pcre_exec(), is used.
# Line 2744  PCRE REGULAR EXPRESSION DETAILS Line 3233  PCRE REGULAR EXPRESSION DETAILS
3233         discussed in the pcrematching page.         discussed in the pcrematching page.
3234    
3235    
3236    NEWLINE CONVENTIONS
3237    
3238           PCRE  supports five different conventions for indicating line breaks in
3239           strings: a single CR (carriage return) character, a  single  LF  (line-
3240           feed) character, the two-character sequence CRLF, any of the three pre-
3241           ceding, or any Unicode newline sequence. The pcreapi page  has  further
3242           discussion  about newlines, and shows how to set the newline convention
3243           in the options arguments for the compiling and matching functions.
3244    
3245           It is also possible to specify a newline convention by starting a  pat-
3246           tern string with one of the following five sequences:
3247    
3248             (*CR)        carriage return
3249             (*LF)        linefeed
3250             (*CRLF)      carriage return, followed by linefeed
3251             (*ANYCRLF)   any of the three above
3252             (*ANY)       all Unicode newline sequences
3253    
3254           These  override  the default and the options given to pcre_compile() or
3255           pcre_compile2(). For example, on a Unix system where LF is the  default
3256           newline sequence, the pattern
3257    
3258             (*CR)a.b
3259    
3260           changes the convention to CR. That pattern matches "a\nb" because LF is
3261           no longer a newline. Note that these special settings,  which  are  not
3262           Perl-compatible,  are  recognized  only at the very start of a pattern,
3263           and that they must be in upper case.  If  more  than  one  of  them  is
3264           present, the last one is used.
3265    
3266           The  newline convention affects the interpretation of the dot metachar-
3267           acter when PCRE_DOTALL is not set, and also the behaviour of  \N.  How-
3268           ever,  it  does  not  affect  what  the  \R escape sequence matches. By
3269           default, this is any Unicode newline sequence, for Perl  compatibility.
3270           However,  this can be changed; see the description of \R in the section
3271           entitled "Newline sequences" below. A change of \R setting can be  com-
3272           bined with a change of newline convention.
3273    
3274    
3275  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
3276    
3277         A  regular  expression  is  a pattern that is matched against a subject         A  regular  expression  is  a pattern that is matched against a subject
# Line 2799  CHARACTERS AND METACHARACTERS Line 3327  CHARACTERS AND METACHARACTERS
3327                    syntax)                    syntax)
3328           ]      terminates the character class           ]      terminates the character class
3329    
3330         The  following sections describe the use of each of the metacharacters.         The following sections describe the use of each of the metacharacters.
3331    
3332    
3333  BACKSLASH  BACKSLASH
3334    
3335         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3336         a  non-alphanumeric  character,  it takes away any special meaning that         a non-alphanumeric character, it takes away any  special  meaning  that
3337         character may have. This  use  of  backslash  as  an  escape  character         character  may  have.  This  use  of  backslash  as an escape character
3338         applies both inside and outside character classes.         applies both inside and outside character classes.
3339    
3340         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
3341         pattern.  This escaping action applies whether  or  not  the  following         pattern.   This  escaping  action  applies whether or not the following
3342         character  would  otherwise be interpreted as a metacharacter, so it is         character would otherwise be interpreted as a metacharacter, so  it  is
3343         always safe to precede a non-alphanumeric  with  backslash  to  specify         always  safe  to  precede  a non-alphanumeric with backslash to specify
3344         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-
3345         slash, you write \\.         slash, you write \\.
3346    
3347         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in
3348         the  pattern (other than in a character class) and characters between a         the pattern (other than in a character class) and characters between  a
3349         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
3350         ing  backslash  can  be  used to include a whitespace or # character as         ing backslash can be used to include a whitespace  or  #  character  as
3351         part of the pattern.         part of the pattern.
3352    
3353         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-
3354         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-
3355         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
3356         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-
3357         tion. Note the following examples:         tion. Note the following examples:
3358    
3359           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 2835  BACKSLASH Line 3363  BACKSLASH
3363           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
3364           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3365    
3366         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
3367         classes.         classes.  An isolated \E that is not preceded by \Q is ignored.
3368    
3369     Non-printing characters     Non-printing characters
3370    
3371         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-
3372         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
3373         appearance  of non-printing characters, apart from the binary zero that         appearance of non-printing characters, apart from the binary zero  that
3374         terminates a pattern, but when a pattern  is  being  prepared  by  text         terminates  a  pattern,  but  when  a pattern is being prepared by text
3375         editing,  it  is  usually  easier  to  use  one of the following escape         editing, it is  often  easier  to  use  one  of  the  following  escape
3376         sequences than the binary character it represents:         sequences than the binary character it represents:
3377    
3378           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3379           \cx       "control-x", where x is any character           \cx       "control-x", where x is any character
3380           \e        escape (hex 1B)           \e        escape (hex 1B)
3381           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3382           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3383           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3384           \t        tab (hex 09)           \t        tab (hex 09)
3385           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or back reference
3386           \xhh      character with hex code hh           \xhh      character with hex code hh
3387           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh..
3388    
3389         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,
3390         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
3391         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;
3392         becomes hex 7B.         becomes hex 7B.
3393    
3394         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
3395         in upper or lower case). Any number of hexadecimal  digits  may  appear         in  upper  or  lower case). Any number of hexadecimal digits may appear
3396         between  \x{  and  },  but the value of the character code must be less         between \x{ and }, but the value of the character  code  must  be  less
3397         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode (that is,         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,
3398         the  maximum  hexadecimal  value is 7FFFFFFF). If characters other than         the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger
3399         hexadecimal digits appear between \x{ and }, or if there is  no  termi-         than the largest Unicode code point, which is 10FFFF.
3400         nating  }, this form of escape is not recognized.  Instead, the initial  
3401         \x will be interpreted as a basic hexadecimal escape, with no following         If  characters  other than hexadecimal digits appear between \x{ and },
3402         digits, giving a character whose value is zero.         or if there is no terminating }, this form of escape is not recognized.
3403           Instead,  the  initial  \x  will  be interpreted as a basic hexadecimal
3404           escape, with no following digits, giving a  character  whose  value  is
3405           zero.
3406    
3407         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
3408         two syntaxes for \x. There is no difference in the way  they  are  han-         two syntaxes for \x. There is no difference in the way  they  are  han-
# Line 2920  BACKSLASH Line 3451  BACKSLASH
3451         All the sequences that define a single character value can be used both         All the sequences that define a single character value can be used both
3452         inside  and  outside character classes. In addition, inside a character         inside  and  outside character classes. In addition, inside a character
3453         class, the sequence \b is interpreted as the backspace  character  (hex         class, the sequence \b is interpreted as the backspace  character  (hex
3454         08),  and the sequences \R and \X are interpreted as the characters "R"         08).  The sequences \B, \N, \R, and \X are not special inside a charac-
3455         and "X", respectively. Outside a character class, these sequences  have         ter class. Like any  other  unrecognized  escape  sequences,  they  are
3456         different meanings (see below).         treated  as  the  literal characters "B", "N", "R", and "X" by default,
3457           but cause an error if the PCRE_EXTRA option is set. Outside a character
3458           class, these sequences have different meanings.
3459    
3460     Absolute and relative back references     Absolute and relative back references
3461    
3462         The  sequence  \g followed by a positive or negative number, optionally         The  sequence  \g followed by an unsigned or a negative number, option-
3463         enclosed in braces, is an absolute or relative back reference. A  named         ally enclosed in braces, is an absolute or relative back  reference.  A
3464         back  reference can be coded as \g{name}. Back references are discussed         named back reference can be coded as \g{name}. Back references are dis-
3465         later, following the discussion of parenthesized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3466    
3467       Absolute and relative subroutine calls
3468    
3469           For compatibility with Oniguruma, the non-Perl syntax \g followed by  a
3470           name or a number enclosed either in angle brackets or single quotes, is
3471           an alternative syntax for referencing a subpattern as  a  "subroutine".
3472           Details  are  discussed  later.   Note  that  \g{...} (Perl syntax) and
3473           \g<...> (Oniguruma syntax) are not synonymous. The  former  is  a  back
3474           reference; the latter is a subroutine call.
3475    
3476     Generic character types     Generic character types
3477    
3478         Another use of backslash is for specifying generic character types. The         Another use of backslash is for specifying generic character types:
        following are always recognized:  
3479    
3480           \d     any decimal digit           \d     any decimal digit
3481           \D     any character that is not a decimal digit           \D     any character that is not a decimal digit
3482             \h     any horizontal whitespace character
3483             \H     any character that is not a horizontal whitespace character
3484           \s     any whitespace character           \s     any whitespace character
3485           \S     any character that is not a whitespace character           \S     any character that is not a whitespace character
3486             \v     any vertical whitespace character
3487             \V     any character that is not a vertical whitespace character
3488           \w     any "word" character           \w     any "word" character
3489           \W     any "non-word" character           \W     any "non-word" character
3490    
3491         Each pair of escape sequences partitions the complete set of characters         There is also the single sequence \N, which matches a non-newline char-
3492         into two disjoint sets. Any given character matches one, and only  one,         acter.  This is the same as the "." metacharacter when  PCRE_DOTALL  is
3493         of each pair.         not set.
3494    
3495         These character type sequences can appear both inside and outside char-         Each  pair of lower and upper case escape sequences partitions the com-
3496         acter classes. They each match one character of the  appropriate  type.         plete set of characters into two disjoint  sets.  Any  given  character
3497         If  the current matching point is at the end of the subject string, all         matches  one, and only one, of each pair. The sequences can appear both
3498         of them fail, since there is no character to match.         inside and outside character classes. They each match one character  of
3499           the  appropriate  type.  If the current matching point is at the end of
3500         For compatibility with Perl, \s does not match the VT  character  (code         the subject string, all of them fail, because there is no character  to
3501         11).   This makes it different from the the POSIX "space" class. The \s         match.
3502         characters are HT (9), LF (10), FF (12), CR (13), and space  (32).  (If  
3503           For  compatibility  with Perl, \s does not match the VT character (code
3504           11).  This makes it different from the the POSIX "space" class. The  \s
3505           characters  are  HT  (9), LF (10), FF (12), CR (13), and space (32). If
3506         "use locale;" is included in a Perl script, \s may match the VT charac-         "use locale;" is included in a Perl script, \s may match the VT charac-
3507         ter. In PCRE, it never does.)         ter. In PCRE, it never does.
3508    
3509         A "word" character is an underscore or any character less than 256 that         A  "word"  character is an underscore or any character that is a letter
3510         is  a  letter  or  digit.  The definition of letters and digits is con-         or digit.  By default, the definition of letters  and  digits  is  con-
3511         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-
3512         specific  matching is taking place (see "Locale support" in the pcreapi         specific matching is taking place (see "Locale support" in the  pcreapi
3513         page). For example, in a French locale such  as  "fr_FR"  in  Unix-like         page).  For  example,  in  a French locale such as "fr_FR" in Unix-like
3514         systems,  or "french" in Windows, some character codes greater than 128         systems, or "french" in Windows, some character codes greater than  128
3515         are used for accented letters, and these are matched by \w.         are  used  for  accented letters, and these are then matched by \w. The
3516           use of locales with Unicode is discouraged.
3517         In UTF-8 mode, characters with values greater than 128 never match  \d,  
3518         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-         By default, in UTF-8 mode, characters  with  values  greater  than  128
3519         code character property support is available. The use of  locales  with         never  match  \d,  \s,  or  \w,  and always match \D, \S, and \W. These
3520         Unicode is discouraged.         sequences retain their original meanings from before UTF-8 support  was
3521           available,  mainly for efficiency reasons. However, if PCRE is compiled
3522           with Unicode property support, and the PCRE_UCP option is set, the  be-
3523           haviour  is  changed  so  that Unicode properties are used to determine
3524           character types, as follows:
3525    
3526             \d  any character that \p{Nd} matches (decimal digit)
3527             \s  any character that \p{Z} matches, plus HT, LF, FF, CR
3528             \w  any character that \p{L} or \p{N} matches, plus underscore
3529    
3530           The upper case escapes match the inverse sets of characters. Note  that
3531           \d  matches  only decimal digits, whereas \w matches any Unicode digit,
3532           as well as any Unicode letter, and underscore. Note also that  PCRE_UCP
3533           affects  \b,  and  \B  because  they are defined in terms of \w and \W.
3534           Matching these sequences is noticeably slower when PCRE_UCP is set.
3535    
3536           The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to
3537           the  other  sequences,  which  match  only ASCII characters by default,
3538           these always  match  certain  high-valued  codepoints  in  UTF-8  mode,
3539           whether or not PCRE_UCP is set. The horizontal space characters are:
3540    
3541             U+0009     Horizontal tab
3542             U+0020     Space
3543             U+00A0     Non-break space
3544             U+1680     Ogham space mark
3545             U+180E     Mongolian vowel separator
3546             U+2000     En quad
3547             U+2001     Em quad
3548             U+2002     En space
3549             U+2003     Em space
3550             U+2004     Three-per-em space
3551             U+2005     Four-per-em space
3552             U+2006     Six-per-em space
3553             U+2007     Figure space
3554             U+2008     Punctuation space
3555             U+2009     Thin space
3556             U+200A     Hair space
3557             U+202F     Narrow no-break space
3558             U+205F     Medium mathematical space
3559             U+3000     Ideographic space
3560    
3561           The vertical space characters are:
3562    
3563             U+000A     Linefeed
3564             U+000B     Vertical tab
3565             U+000C     Formfeed
3566             U+000D     Carriage return
3567             U+0085     Next line
3568             U+2028     Line separator
3569             U+2029     Paragraph separator
3570    
3571     Newline sequences     Newline sequences
3572    
3573         Outside  a  character class, the escape sequence \R matches any Unicode         Outside  a  character class, by default, the escape sequence \R matches
3574         newline sequence. This is an extension to Perl. In non-UTF-8 mode \R is         any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8
3575         equivalent to the following:         mode \R is equivalent to the following:
3576    
3577           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3578    
# Line 2991  BACKSLASH Line 3588  BACKSLASH
3588         rator, U+2029).  Unicode character property support is not  needed  for         rator, U+2029).  Unicode character property support is not  needed  for
3589         these characters to be recognized.         these characters to be recognized.
3590    
3591         Inside a character class, \R matches the letter "R".         It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3592           the complete set  of  Unicode  line  endings)  by  setting  the  option
3593           PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3594           (BSR is an abbrevation for "backslash R".) This can be made the default
3595           when  PCRE  is  built;  if this is the case, the other behaviour can be
3596           requested via the PCRE_BSR_UNICODE option.   It  is  also  possible  to
3597           specify  these  settings  by  starting a pattern string with one of the
3598           following sequences:
3599    
3600             (*BSR_ANYCRLF)   CR, LF, or CRLF only
3601             (*BSR_UNICODE)   any Unicode newline sequence
3602    
3603           These override the default and the options given to  pcre_compile()  or
3604           pcre_compile2(),  but  they  can  be  overridden  by  options  given to
3605           pcre_exec() or pcre_dfa_exec(). Note that these special settings, which
3606           are  not  Perl-compatible,  are  recognized only at the very start of a
3607           pattern, and that they must be in upper case. If more than one of  them
3608           is present, the last one is used. They can be combined with a change of
3609           newline convention; for example, a pattern can start with:
3610    
3611             (*ANY)(*BSR_ANYCRLF)
3612    
3613           They can also be combined with the (*UTF8) or (*UCP) special sequences.
3614           Inside  a  character  class,  \R  is  treated as an unrecognized escape
3615           sequence, and so matches the letter "R" by default, but causes an error
3616           if PCRE_EXTRA is set.
3617    
3618     Unicode character properties     Unicode character properties
3619    
3620         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
3621         tional escape sequences to match  character  properties  are  available         tional escape sequences that match characters with specific  properties
3622         when UTF-8 mode is selected. They are:         are  available.   When not in UTF-8 mode, these sequences are of course
3623           limited to testing characters whose codepoints are less than  256,  but
3624           they do work in this mode.  The extra escape sequences are:
3625    
3626           \p{xx}   a character with the xx property           \p{xx}   a character with the xx property
3627           \P{xx}   a character without the xx property           \P{xx}   a character without the xx property
3628           \X       an extended Unicode sequence           \X       an extended Unicode sequence
3629    
3630         The  property  names represented by xx above are limited to the Unicode         The  property  names represented by xx above are limited to the Unicode
3631         script names, the general category properties, and "Any", which matches         script names, the general category properties, "Any", which matches any
3632         any character (including newline). Other properties such as "InMusical-         character   (including  newline),  and  some  special  PCRE  properties
3633         Symbols" are not currently supported by PCRE. Note  that  \P{Any}  does         (described in the next section).  Other Perl properties such as  "InMu-
3634         not match any characters, so always causes a match failure.         sicalSymbols"  are  not  currently supported by PCRE. Note that \P{Any}
3635           does not match any characters, so always causes a match failure.
3636    
3637         Sets of Unicode characters are defined as belonging to certain scripts.         Sets of Unicode characters are defined as belonging to certain scripts.
3638         A character from one of these sets can be matched using a script  name.         A  character from one of these sets can be matched using a script name.
3639         For example:         For example:
3640    
3641           \p{Greek}           \p{Greek}
3642           \P{Han}           \P{Han}
3643    
3644         Those  that are not part of an identified script are lumped together as         Those that are not part of an identified script are lumped together  as
3645         "Common". The current list of scripts is:         "Common". The current list of scripts is:
3646    
3647         Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,         Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille,
3648         Buhid,   Canadian_Aboriginal,   Cherokee,  Common,  Coptic,  Cuneiform,         Buginese, Buhid, Canadian_Aboriginal, Carian, Cham,  Cherokee,  Common,
3649         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,         Coptic,   Cuneiform,  Cypriot,  Cyrillic,  Deseret,  Devanagari,  Egyp-
3650         Gothic,  Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hira-         tian_Hieroglyphs,  Ethiopic,  Georgian,  Glagolitic,   Gothic,   Greek,
3651         gana, Inherited, Kannada,  Katakana,  Kharoshthi,  Khmer,  Lao,  Latin,         Gujarati,  Gurmukhi,  Han,  Hangul,  Hanunoo,  Hebrew,  Hiragana, Impe-
3652         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,         rial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian,
3653         Ogham, Old_Italic, Old_Persian, Oriya, Osmanya,  Phags_Pa,  Phoenician,         Javanese,  Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Lao,
3654         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,         Latin,  Lepcha,  Limbu,  Linear_B,  Lisu,  Lycian,  Lydian,  Malayalam,
3655         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.         Meetei_Mayek,  Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham, Old_Italic,
3656           Old_Persian, Old_South_Arabian, Old_Turkic, Ol_Chiki,  Oriya,  Osmanya,
3657         Each character has exactly one general category property, specified  by         Phags_Pa,  Phoenician,  Rejang,  Runic, Samaritan, Saurashtra, Shavian,
3658         a two-letter abbreviation. For compatibility with Perl, negation can be         Sinhala, Sundanese, Syloti_Nagri, Syriac,  Tagalog,  Tagbanwa,  Tai_Le,
3659         specified by including a circumflex between the opening brace  and  the         Tai_Tham,  Tai_Viet,  Tamil,  Telugu,  Thaana, Thai, Tibetan, Tifinagh,
3660         property name. For example, \p{^Lu} is the same as \P{Lu}.         Ugaritic, Vai, Yi.
3661    
3662           Each character has exactly one Unicode general category property, spec-
3663           ified  by a two-letter abbreviation. For compatibility with Perl, nega-
3664           tion can be specified by including a  circumflex  between  the  opening
3665           brace  and  the  property  name.  For  example,  \p{^Lu} is the same as
3666           \P{Lu}.
3667    
3668         If only one letter is specified with \p or \P, it includes all the gen-         If only one letter is specified with \p or \P, it includes all the gen-
3669         eral category properties that start with that letter. In this case,  in         eral  category properties that start with that letter. In this case, in
3670         the  absence of negation, the curly brackets in the escape sequence are         the absence of negation, the curly brackets in the escape sequence  are
3671         optional; these two examples have the same effect:         optional; these two examples have the same effect:
3672    
3673           \p{L}           \p{L}
# Line 3088  BACKSLASH Line 3719  BACKSLASH
3719           Zp    Paragraph separator           Zp    Paragraph separator
3720           Zs    Space separator           Zs    Space separator
3721    
3722         The special property L& is also supported: it matches a character  that         The  special property L& is also supported: it matches a character that
3723         has  the  Lu,  Ll, or Lt property, in other words, a letter that is not         has the Lu, Ll, or Lt property, in other words, a letter  that  is  not
3724         classified as a modifier or "other".         classified as a modifier or "other".
3725    
3726         The long synonyms for these properties  that  Perl  supports  (such  as         The  Cs  (Surrogate)  property  applies only to characters in the range
3727         \p{Letter})  are  not  supported by PCRE, nor is it permitted to prefix         U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see
3728           RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
3729           ing has been turned off (see the discussion  of  PCRE_NO_UTF8_CHECK  in
3730           the pcreapi page). Perl does not support the Cs property.
3731    
3732           The  long  synonyms  for  property  names  that  Perl supports (such as
3733           \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix
3734         any of these properties with "Is".         any of these properties with "Is".
3735    
3736         No character that is in the Unicode table has the Cn (unassigned) prop-         No character that is in the Unicode table has the Cn (unassigned) prop-
3737         erty.  Instead, this property is assumed for any code point that is not         erty.  Instead, this property is assumed for any code point that is not
3738         in the Unicode table.         in the Unicode table.
3739    
3740         Specifying caseless matching does not affect  these  escape  sequences.         Specifying  caseless  matching  does not affect these escape sequences.
3741         For example, \p{Lu} always matches only upper case letters.         For example, \p{Lu} always matches only upper case letters.
3742    
3743         The  \X  escape  matches  any number of Unicode characters that form an         The \X escape matches any number of Unicode  characters  that  form  an
3744         extended Unicode sequence. \X is equivalent to         extended Unicode sequence. \X is equivalent to
3745    
3746           (?>\PM\pM*)           (?>\PM\pM*)
3747    
3748         That is, it matches a character without the "mark"  property,  followed         That  is,  it matches a character without the "mark" property, followed
3749         by  zero  or  more  characters with the "mark" property, and treats the         by zero or more characters with the "mark"  property,  and  treats  the
3750         sequence as an atomic group (see below).  Characters  with  the  "mark"         sequence  as  an  atomic group (see below).  Characters with the "mark"
3751         property are typically accents that affect the preceding character.         property are typically accents that  affect  the  preceding  character.
3752           None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X
3753           matches any one character.
3754    
3755         Matching  characters  by Unicode property is not fast, because PCRE has         Matching characters by Unicode property is not fast, because  PCRE  has
3756         to search a structure that contains  data  for  over  fifteen  thousand         to  search  a  structure  that  contains data for over fifteen thousand
3757         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
3758         \w do not use Unicode properties in PCRE.         \w  do  not  use  Unicode properties in PCRE by default, though you can
3759           make them do so by setting the PCRE_UCP option for pcre_compile() or by
3760           starting the pattern with (*UCP).
3761    
3762       PCRE's additional properties
3763    
3764           As  well  as  the standard Unicode properties described in the previous
3765           section, PCRE supports four more that make it possible to convert  tra-
3766           ditional escape sequences such as \w and \s and POSIX character classes
3767           to use Unicode properties. PCRE uses these non-standard, non-Perl prop-
3768           erties internally when PCRE_UCP is set. They are:
3769    
3770             Xan   Any alphanumeric character
3771             Xps   Any POSIX space character
3772             Xsp   Any Perl space character
3773             Xwd   Any Perl "word" character
3774    
3775           Xan  matches  characters that have either the L (letter) or the N (num-
3776           ber) property. Xps matches the characters tab, linefeed, vertical  tab,
3777           formfeed,  or  carriage  return, and any other character that has the Z
3778           (separator) property.  Xsp is the same as Xps, except that vertical tab
3779           is excluded. Xwd matches the same characters as Xan, plus underscore.
3780    
3781     Resetting the match start     Resetting the match start
3782    
3783         The escape sequence \K, which is a Perl 5.10 feature, causes any previ-         The escape sequence \K, which is a Perl 5.10 feature, causes any previ-
3784         ously  matched  characters  not  to  be  included  in the final matched         ously matched characters not  to  be  included  in  the  final  matched
3785         sequence. For example, the pattern:         sequence. For example, the pattern:
3786    
3787           foo\Kbar           foo\Kbar
3788    
3789         matches "foobar", but reports that it has matched "bar".  This  feature         matches  "foobar",  but reports that it has matched "bar". This feature
3790         is  similar  to  a lookbehind assertion (described below).  However, in         is similar to a lookbehind assertion (described  below).   However,  in
3791         this case, the part of the subject before the real match does not  have         this  case, the part of the subject before the real match does not have
3792         to  be of fixed length, as lookbehind assertions do. The use of \K does         to be of fixed length, as lookbehind assertions do. The use of \K  does
3793         not interfere with the setting of captured  substrings.   For  example,         not  interfere  with  the setting of captured substrings.  For example,
3794         when the pattern         when the pattern
3795    
3796           (foo)\Kbar           (foo)\Kbar
3797    
3798         matches "foobar", the first substring is still set to "foo".         matches "foobar", the first substring is still set to "foo".
3799    
3800           Perl documents that the use  of  \K  within  assertions  is  "not  well
3801           defined".  In  PCRE,  \K  is  acted upon when it occurs inside positive
3802           assertions, but is ignored in negative asse