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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. Certain features that appeared in Python and
23         PCRE before they appeared in Perl are also available using  the  Python         PCRE before they appeared in Perl are also available using  the  Python
24         syntax.)         syntax.  There is also some support for certain .NET and Oniguruma syn-
25           tax items, and there is an option for  requesting  some  minor  changes
26           that give better JavaScript compatibility.
27    
28         The  current  implementation of PCRE (release 7.x) corresponds approxi-         The  current implementation of PCRE (release 8.xx) corresponds approxi-
29         mately with Perl 5.10, including support for UTF-8 encoded strings  and         mately with Perl 5.10, including support for UTF-8 encoded strings  and
30         Unicode general category properties. However, UTF-8 and Unicode support         Unicode general category properties. However, UTF-8 and Unicode support
31         has to be explicitly enabled; it is not the default. The Unicode tables         has to be explicitly enabled; it is not the default. The Unicode tables
32         correspond to Unicode release 5.0.0.         correspond to Unicode release 5.1.
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 matching function that matches the same  compiled  patterns
# 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 file
59         in the source distribution.         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
81           pcreapi           details of PCRE's native C API           pcreapi           details of PCRE's native C API
82           pcrebuild         options for building PCRE           pcrebuild         options for building PCRE
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
90           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
91                               regular expressions                               regular expressions
92             pcresyntax        quick syntax reference
93           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
94           pcreposix         the POSIX-compatible C API           pcreposix         the POSIX-compatible C API
95           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
96           pcresample        discussion of the sample program           pcresample        discussion of the pcredemo program
97           pcrestack         discussion of stack usage           pcrestack         discussion of stack usage
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 116  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 just strings of bytes.
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 154  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 the characters that PCRE  recog-
226         nizes  as  digits,  spaces,  or  word characters remain the same set as         nizes  as  digits,  spaces,  or  word characters remain the same set as
227         before, all with values less than 256. This remains true even when PCRE         before, all with values less than 256. This remains true even when PCRE
228         includes  Unicode  property support, because to do otherwise would slow         includes  Unicode  property support, because to do otherwise would slow
229         down PCRE in many common cases. If you really want to test for a  wider         down PCRE in many common cases. If you really want to test for a  wider
230         sense  of,  say,  "digit",  you must use Unicode property tests such as         sense  of,  say,  "digit",  you must use Unicode property tests such as
231         \p{Nd}.         \p{Nd}. Note that this also applies to \b, because  it  is  defined  in
232           terms of \w and \W.
233    
234         8. Similarly, characters that match the POSIX named  character  classes         7.  Similarly,  characters that match the POSIX named character classes
235         are all low-valued characters.         are all low-valued characters.
236    
237         9.  Case-insensitive  matching  applies only to characters whose values         8. However, the Perl 5.10 horizontal and vertical  whitespace  matching
238         are less than 128, unless PCRE is built with Unicode property  support.         escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-
239         Even  when  Unicode  property support is available, PCRE still uses its         acters.
240         own character tables when checking the case of  low-valued  characters,  
241         so  as not to degrade performance.  The Unicode property information is         9. Case-insensitive matching applies only to  characters  whose  values
242           are  less than 128, unless PCRE is built with Unicode property support.
243           Even when Unicode property support is available, PCRE  still  uses  its
244           own  character  tables when checking the case of low-valued characters,
245           so as not to degrade performance.  The Unicode property information  is
246         used only for characters with higher values. Even when Unicode property         used only for characters with higher values. Even when Unicode property
247         support is available, PCRE supports case-insensitive matching only when         support is available, PCRE supports case-insensitive matching only when
248         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
249         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-
250         ported by PCRE.         ported by PCRE.
251    
252    
# Line 214  AUTHOR Line 256  AUTHOR
256         University Computing Service         University Computing Service
257         Cambridge CB2 3QH, England.         Cambridge CB2 3QH, England.
258    
259         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,
260         so I've taken it away. If you want to email me, use my initial and sur-         so I've taken it away. If you want to email me, use  my  two  initials,
261         name, separated by a dot, at the domain ucs.cam.ac.uk.         followed by the two digits 10, at the domain cam.ac.uk.
262    
263    
264  REVISION  REVISION
265    
266         Last updated: 06 March 2007         Last updated: 01 September 2009
267         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
268  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
269    
270    
271  PCREBUILD(3)                                                      PCREBUILD(3)  PCREBUILD(3)                                                      PCREBUILD(3)
272    
273    
# Line 236  NAME Line 278  NAME
278  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
279    
280         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
281         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
282         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
283         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
284         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
285         directory) can be obtained by running         environments using the GUI facility of cmake-gui if you are using CMake
286           instead of configure to build PCRE.
287    
288           There  is  a  lot more information about building PCRE in non-Unix-like
289           environments in the file called NON_UNIX_USE, which is part of the PCRE
290           distribution.  You  should consult this file as well as the README file
291           if you are building in a non-Unix-like environment.
292    
293           The complete list of options for configure (which includes the standard
294           ones  such  as  the  selection  of  the  installation directory) can be
295           obtained by running
296    
297           ./configure --help           ./configure --help
298    
299         The following sections describe certain options whose names begin  with         The following sections include  descriptions  of  options  whose  names
300         --enable  or  --disable. These settings specify changes to the defaults         begin with --enable or --disable. These settings specify changes to the
301         for the configure command. Because of the  way  that  configure  works,         defaults for the configure command. Because of the way  that  configure
302         --enable  and  --disable  always  come  in  pairs, so the complementary         works,  --enable  and --disable always come in pairs, so the complemen-
303         option always exists as well, but as it specifies the  default,  it  is         tary option always exists as well, but as it specifies the default,  it
304         not described.         is not described.
305    
306    
307  C++ SUPPORT  C++ SUPPORT
# Line 265  C++ SUPPORT Line 317  C++ SUPPORT
317    
318  UTF-8 SUPPORT  UTF-8 SUPPORT
319    
320         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 Unicode character strings, add
321    
322           --enable-utf8           --enable-utf8
323    
# Line 274  UTF-8 SUPPORT Line 326  UTF-8 SUPPORT
326         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()
327         function.         function.
328    
329           If you set --enable-utf8 when compiling in an EBCDIC environment,  PCRE
330           expects its input to be either ASCII or UTF-8 (depending on the runtime
331           option). It is not possible to support both EBCDIC and UTF-8  codes  in
332           the  same  version  of  the  library.  Consequently,  --enable-utf8 and
333           --enable-ebcdic are mutually exclusive.
334    
335    
336  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
337    
# Line 288  UNICODE CHARACTER PROPERTY SUPPORT Line 346  UNICODE CHARACTER PROPERTY SUPPORT
346         to the configure command. This implies UTF-8 support, even if you  have         to the configure command. This implies UTF-8 support, even if you  have
347         not explicitly requested it.         not explicitly requested it.
348    
349         Including  Unicode  property  support  adds around 90K of tables to the         Including  Unicode  property  support  adds around 30K of tables to the
350         PCRE library, approximately doubling its size. Only the  general  cate-         PCRE library. Only the general category properties such as  Lu  and  Nd
351         gory  properties  such as Lu and Nd are supported. Details are given in         are supported. Details are given in the pcrepattern documentation.
        the pcrepattern documentation.  
352    
353    
354  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
355    
356         By default, PCRE interprets character 10 (linefeed, LF)  as  indicating         By  default,  PCRE interprets the linefeed (LF) character as indicating
357         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
358         systems. You can compile PCRE to use character 13 (carriage return, CR)         systems.  You  can compile PCRE to use carriage return (CR) instead, by
359         instead, by adding         adding
360    
361           --enable-newline-is-cr           --enable-newline-is-cr
362    
363         to  the  configure  command.  There  is  also  a --enable-newline-is-lf         to the  configure  command.  There  is  also  a  --enable-newline-is-lf
364         option, which explicitly specifies linefeed as the newline character.         option, which explicitly specifies linefeed as the newline character.
365    
366         Alternatively, you can specify that line endings are to be indicated by         Alternatively, you can specify that line endings are to be indicated by
# Line 313  CODE VALUE OF NEWLINE Line 370  CODE VALUE OF NEWLINE
370    
371         to the configure command. There is a fourth option, specified by         to the configure command. There is a fourth option, specified by
372    
373             --enable-newline-is-anycrlf
374    
375           which causes PCRE to recognize any of the three sequences  CR,  LF,  or
376           CRLF as indicating a line ending. Finally, a fifth option, specified by
377    
378           --enable-newline-is-any           --enable-newline-is-any
379    
380         which causes PCRE to recognize any Unicode newline sequence.         causes PCRE to recognize any Unicode newline sequence.
381    
382         Whatever  line  ending convention is selected when PCRE is built can be         Whatever  line  ending convention is selected when PCRE is built can be
383         overridden when the library functions are called. At build time  it  is         overridden when the library functions are called. At build time  it  is
384         conventional to use the standard for your operating system.         conventional to use the standard for your operating system.
385    
386    
387    WHAT \R MATCHES
388    
389           By  default,  the  sequence \R in a pattern matches any Unicode newline
390           sequence, whatever has been selected as the line  ending  sequence.  If
391           you specify
392    
393             --enable-bsr-anycrlf
394    
395           the  default  is changed so that \R matches only CR, LF, or CRLF. What-
396           ever is selected when PCRE is built can be overridden when the  library
397           functions are called.
398    
399    
400  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
401    
402         The  PCRE building process uses libtool to build both shared and static         The  PCRE building process uses libtool to build both shared and static
# Line 367  HANDLING VERY LARGE PATTERNS Line 442  HANDLING VERY LARGE PATTERNS
442         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
443         additional bytes when handling them.         additional bytes when handling them.
444    
        If  you  build  PCRE with an increased link size, test 2 (and test 5 if  
        you are using UTF-8) will fail. Part of the output of these tests is  a  
        representation  of the compiled pattern, and this changes with the link  
        size.  
   
445    
446  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
447    
448         When matching with the pcre_exec() function, PCRE implements backtrack-         When matching with the pcre_exec() function, PCRE implements backtrack-
449         ing  by  making recursive calls to an internal function called match().         ing by making recursive calls to an internal function  called  match().
450         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-
451         verely  limit  PCRE's operation. (The Unix environment does not usually         verely limit PCRE's operation. (The Unix environment does  not  usually
452         suffer from this problem, but it may sometimes be necessary to increase         suffer from this problem, but it may sometimes be necessary to increase
453         the  maximum  stack size.  There is a discussion in the pcrestack docu-         the maximum stack size.  There is a discussion in the  pcrestack  docu-
454         mentation.) An alternative approach to recursion that uses memory  from         mentation.)  An alternative approach to recursion that uses memory from
455         the  heap  to remember data, instead of using recursive function calls,         the heap to remember data, instead of using recursive  function  calls,
456         has been implemented to work round the problem of limited  stack  size.         has  been  implemented to work round the problem of limited stack size.
457         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
458    
459           --disable-stack-for-recursion           --disable-stack-for-recursion
460    
461         to  the  configure  command. With this configuration, PCRE will use the         to the configure command. With this configuration, PCRE  will  use  the
462         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
463         ment  functions.  Separate  functions are provided because the usage is         ment functions. By default these point to malloc() and free(), but  you
464         very predictable: the block sizes requested are always  the  same,  and         can replace the pointers so that your own functions are used.
465         the  blocks  are always freed in reverse order. A calling program might  
466         be able to implement optimized functions that perform better  than  the         Separate  functions  are  provided  rather  than  using pcre_malloc and
467         standard  malloc()  and  free()  functions.  PCRE  runs noticeably more         pcre_free because the  usage  is  very  predictable:  the  block  sizes
468         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
469         function; it is not relevant for the the pcre_dfa_exec() function.         reverse order. A calling program might be able to  implement  optimized
470           functions  that  perform  better  than  malloc()  and free(). PCRE runs
471           noticeably more slowly when built in this way. This option affects only
472           the   pcre_exec()   function;   it   is   not   relevant  for  the  the
473           pcre_dfa_exec() function.
474    
475    
476  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
477    
478         Internally,  PCRE has a function called match(), which it calls repeat-         Internally, PCRE has a function called match(), which it calls  repeat-
479         edly  (sometimes  recursively)  when  matching  a  pattern   with   the         edly   (sometimes   recursively)  when  matching  a  pattern  with  the
480         pcre_exec()  function.  By controlling the maximum number of times this         pcre_exec() function. By controlling the maximum number of  times  this
481         function may be called during a single matching operation, a limit  can         function  may be called during a single matching operation, a limit can
482         be  placed  on  the resources used by a single call to pcre_exec(). The         be placed on the resources used by a single call  to  pcre_exec().  The
483         limit can be changed at run time, as described in the pcreapi  documen-         limit  can be changed at run time, as described in the pcreapi documen-
484         tation.  The default is 10 million, but this can be changed by adding a         tation. The default is 10 million, but this can be changed by adding  a
485         setting such as         setting such as
486    
487           --with-match-limit=500000           --with-match-limit=500000
488    
489         to  the  configure  command.  This  setting  has  no  effect   on   the         to   the   configure  command.  This  setting  has  no  effect  on  the
490         pcre_dfa_exec() matching function.         pcre_dfa_exec() matching function.
491    
492         In  some  environments  it is desirable to limit the depth of recursive         In some environments it is desirable to limit the  depth  of  recursive
493         calls of match() more strictly than the total number of calls, in order         calls of match() more strictly than the total number of calls, in order
494         to  restrict  the maximum amount of stack (or heap, if --disable-stack-         to restrict the maximum amount of stack (or heap,  if  --disable-stack-
495         for-recursion is specified) that is used. A second limit controls this;         for-recursion is specified) that is used. A second limit controls this;
496         it  defaults  to  the  value  that is set for --with-match-limit, which         it defaults to the value that  is  set  for  --with-match-limit,  which
497         imposes no additional constraints. However, you can set a  lower  limit         imposes  no  additional constraints. However, you can set a lower limit
498         by adding, for example,         by adding, for example,
499    
500           --with-match-limit-recursion=10000           --with-match-limit-recursion=10000
501    
502         to  the  configure  command.  This  value can also be overridden at run         to the configure command. This value can  also  be  overridden  at  run
503         time.         time.
504    
505    
506    CREATING CHARACTER TABLES AT BUILD TIME
507    
508           PCRE  uses fixed tables for processing characters whose code values are
509           less than 256. By default, PCRE is built with a set of tables that  are
510           distributed  in  the  file pcre_chartables.c.dist. These tables are for
511           ASCII codes only. If you add
512    
513             --enable-rebuild-chartables
514    
515           to the configure command, the distributed tables are  no  longer  used.
516           Instead,  a  program  called dftables is compiled and run. This outputs
517           the source for new set of tables, created in the default locale of your
518           C runtime system. (This method of replacing the tables does not work if
519           you are cross compiling, because dftables is run on the local host.  If
520           you  need  to  create alternative tables when cross compiling, you will
521           have to do so "by hand".)
522    
523    
524  USING EBCDIC CODE  USING EBCDIC CODE
525    
526         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
527         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).
528         PCRE can, however, be compiled to  run  in  an  EBCDIC  environment  by         This is the case for most computer operating systems.  PCRE  can,  how-
529         adding         ever, be compiled to run in an EBCDIC environment by adding
530    
531           --enable-ebcdic           --enable-ebcdic
532    
533         to the configure command.         to the configure command. This setting implies --enable-rebuild-charta-
534           bles. You should only use it if you know that  you  are  in  an  EBCDIC
535           environment  (for  example,  an  IBM  mainframe  operating system). The
536           --enable-ebcdic option is incompatible with --enable-utf8.
537    
538    
539    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
540    
541           By default, pcregrep reads all files as plain text. You can build it so
542           that it recognizes files whose names end in .gz or .bz2, and reads them
543           with libz or libbz2, respectively, by adding one or both of
544    
545             --enable-pcregrep-libz
546             --enable-pcregrep-libbz2
547    
548           to the configure command. These options naturally require that the rel-
549           evant  libraries  are installed on your system. Configuration will fail
550           if they are not.
551    
552    
553    PCRETEST OPTION FOR LIBREADLINE SUPPORT
554    
555           If you add
556    
557             --enable-pcretest-libreadline
558    
559           to the configure command,  pcretest  is  linked  with  the  libreadline
560           library,  and  when its input is from a terminal, it reads it using the
561           readline() function. This provides line-editing and history facilities.
562           Note that libreadline is GPL-licenced, so if you distribute a binary of
563           pcretest linked in this way, there may be licensing issues.
564    
565           Setting this option causes the -lreadline option to  be  added  to  the
566           pcretest  build.  In many operating environments with a sytem-installed
567           libreadline this is sufficient. However, in some environments (e.g.  if
568           an  unmodified  distribution version of readline is in use), some extra
569           configuration may be necessary. The INSTALL file for  libreadline  says
570           this:
571    
572             "Readline uses the termcap functions, but does not link with the
573             termcap or curses library itself, allowing applications which link
574             with readline the to choose an appropriate library."
575    
576           If  your environment has not been set up so that an appropriate library
577           is automatically included, you may need to add something like
578    
579             LIBS="-ncurses"
580    
581           immediately before the configure command.
582    
583    
584  SEE ALSO  SEE ALSO
# Line 455  AUTHOR Line 595  AUTHOR
595    
596  REVISION  REVISION
597    
598         Last updated: 06 March 2007         Last updated: 06 September 2009
599         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
600  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
601    
602    
603  PCREMATCHING(3)                                                PCREMATCHING(3)  PCREMATCHING(3)                                                PCREMATCHING(3)
604    
605    
# Line 508  REGULAR EXPRESSIONS AS TREES Line 648  REGULAR EXPRESSIONS AS TREES
648    
649  THE STANDARD MATCHING ALGORITHM  THE STANDARD MATCHING ALGORITHM
650    
651         In the terminology of Jeffrey Friedl's book Mastering  Regular  Expres-         In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
652         sions,  the  standard  algorithm  is  an "NFA algorithm". It conducts a         sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
653         depth-first search of the pattern tree. That is, it  proceeds  along  a         depth-first search of the pattern tree. That is, it  proceeds  along  a
654         single path through the tree, checking that the subject matches what is         single path through the tree, checking that the subject matches what is
655         required. When there is a mismatch, the algorithm  tries  any  alterna-         required. When there is a mismatch, the algorithm  tries  any  alterna-
# Line 561  THE ALTERNATIVE MATCHING ALGORITHM Line 701  THE ALTERNATIVE MATCHING ALGORITHM
701         at the fourth character of the subject. The algorithm does not automat-         at the fourth character of the subject. The algorithm does not automat-
702         ically move on to find matches that start at later positions.         ically move on to find matches that start at later positions.
703    
704           Although the general principle of this matching algorithm  is  that  it
705           scans  the subject string only once, without backtracking, there is one
706           exception: when a lookbehind assertion is  encountered,  the  preceding
707           characters have to be re-inspected.
708    
709         There are a number of features of PCRE regular expressions that are not         There are a number of features of PCRE regular expressions that are not
710         supported by the alternative matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
711    
712         1.  Because  the  algorithm  finds  all possible matches, the greedy or         1. Because the algorithm finds all  possible  matches,  the  greedy  or
713         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
714         ungreedy quantifiers are treated in exactly the same way. However, pos-         ungreedy quantifiers are treated in exactly the same way. However, pos-
715         sessive quantifiers can make a difference when what follows could  also         sessive  quantifiers can make a difference when what follows could also
716         match what is quantified, for example in a pattern like this:         match what is quantified, for example in a pattern like this:
717    
718           ^a++\w!           ^a++\w!
719    
720         This  pattern matches "aaab!" but not "aaa!", which would be matched by         This pattern matches "aaab!" but not "aaa!", which would be matched  by
721         a non-possessive quantifier. Similarly, if an atomic group is  present,         a  non-possessive quantifier. Similarly, if an atomic group is present,
722         it  is matched as if it were a standalone pattern at the current point,         it is matched as if it were a standalone pattern at the current  point,
723         and the longest match is then "locked in" for the rest of  the  overall         and  the  longest match is then "locked in" for the rest of the overall
724         pattern.         pattern.
725    
726         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
727         is not straightforward to keep track of  captured  substrings  for  the         is  not  straightforward  to  keep track of captured substrings for the
728         different  matching  possibilities,  and  PCRE's implementation of this         different matching possibilities, and  PCRE's  implementation  of  this
729         algorithm does not attempt to do this. This means that no captured sub-         algorithm does not attempt to do this. This means that no captured sub-
730         strings are available.         strings are available.
731    
732         3.  Because no substrings are captured, back references within the pat-         3. Because no substrings are captured, back references within the  pat-
733         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
734    
735         4. For the same reason, conditional expressions that use  a  backrefer-         4.  For  the same reason, conditional expressions that use a backrefer-
736         ence  as  the  condition or test for a specific group recursion are not         ence as the condition or test for a specific group  recursion  are  not
737         supported.         supported.
738    
739         5. Callouts are supported, but the value of the  capture_top  field  is         5.  Because  many  paths  through the tree may be active, the \K escape
740           sequence, which resets the start of the match when encountered (but may
741           be  on  some  paths  and not on others), is not supported. It causes an
742           error if encountered.
743    
744           6. Callouts are supported, but the value of the  capture_top  field  is
745         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.
746    
747         6.  The \C escape sequence, which (in the standard algorithm) matches a         7.  The \C escape sequence, which (in the standard algorithm) matches a
748         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-
749         tive  algorithm  moves  through  the  subject string one character at a         tive  algorithm  moves  through  the  subject string one character at a
750         time, for all active paths through the tree.         time, for all active paths through the tree.
751    
752           8. Except for (*FAIL), the backtracking control verbs such as  (*PRUNE)
753           are  not  supported.  (*FAIL)  is supported, and behaves like a failing
754           negative assertion.
755    
756    
757  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
758    
# Line 610  ADVANTAGES OF THE ALTERNATIVE ALGORITHM Line 764  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
764         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
765         things with callouts.         things with callouts.
766    
767         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  
768         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
769         subject strings to the matching function in  several  pieces,  checking         subject strings to the matching function in  several  pieces,  checking
770         for partial matching each time.         for partial matching each time.
# Line 645  AUTHOR Line 793  AUTHOR
793    
794  REVISION  REVISION
795    
796         Last updated: 06 March 2007         Last updated: 05 September 2009
797         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
798  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
799    
800    
801  PCREAPI(3)                                                          PCREAPI(3)  PCREAPI(3)                                                          PCREAPI(3)
802    
803    
# Line 757  PCRE API OVERVIEW Line 905  PCRE API OVERVIEW
905         pcre_exec() are used for compiling and matching regular expressions  in         pcre_exec() are used for compiling and matching regular expressions  in
906         a  Perl-compatible  manner. A sample program that demonstrates the sim-         a  Perl-compatible  manner. A sample program that demonstrates the sim-
907         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
908         the  source distribution. The pcresample documentation describes how to         the PCRE source distribution. A listing of this program is given in the
909         run it.         pcredemo documentation, and the pcresample documentation describes  how
910           to compile and run it.
911    
912         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
913         ble,  is  also provided. This uses a different algorithm for the match-         ble, is also provided. This uses a different algorithm for  the  match-
914         ing. The alternative algorithm finds all possible matches (at  a  given         ing.  The  alternative algorithm finds all possible matches (at a given
915         point  in  the subject), and scans the subject just once. However, this         point in the subject), and scans the subject just  once  (unless  there
916         algorithm does not return captured substrings. A description of the two         are  lookbehind  assertions).  However,  this algorithm does not return
917         matching  algorithms and their advantages and disadvantages is given in         captured substrings. A description of the two matching  algorithms  and
918         the pcrematching documentation.         their  advantages  and disadvantages is given in the pcrematching docu-
919           mentation.
920    
921         In addition to the main compiling and  matching  functions,  there  are         In addition to the main compiling and  matching  functions,  there  are
922         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
# Line 828  PCRE API OVERVIEW Line 978  PCRE API OVERVIEW
978    
979  NEWLINES  NEWLINES
980    
981         PCRE  supports four different conventions for indicating line breaks in         PCRE  supports five different conventions for indicating line breaks in
982         strings: a single CR (carriage return) character, a  single  LF  (line-         strings: a single CR (carriage return) character, a  single  LF  (line-
983         feed)  character,  the two-character sequence CRLF, or any Unicode new-         feed) character, the two-character sequence CRLF, any of the three pre-
984         line sequence.  The Unicode newline sequences are the three  just  men-         ceding, or any Unicode newline sequence. The Unicode newline  sequences
985         tioned, plus the single characters VT (vertical tab, U+000B), FF (form-         are  the  three just mentioned, plus the single characters VT (vertical
986         feed, U+000C), NEL (next line, U+0085), LS  (line  separator,  U+2028),         tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line
987         and PS (paragraph separator, U+2029).         separator, U+2028), and PS (paragraph separator, U+2029).
988    
989         Each  of  the first three conventions is used by at least one operating         Each  of  the first three conventions is used by at least one operating
990         system as its standard newline sequence. When PCRE is built, a  default         system as its standard newline sequence. When PCRE is built, a  default
# Line 842  NEWLINES Line 992  NEWLINES
992         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
993         pattern is compiled, or when it is matched.         pattern is compiled, or when it is matched.
994    
995           At compile time, the newline convention can be specified by the options
996           argument of pcre_compile(), or it can be specified by special  text  at
997           the start of the pattern itself; this overrides any other settings. See
998           the pcrepattern page for details of the special character sequences.
999    
1000         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-
1001         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
1002         newline  convention  affects  the  handling of the dot, circumflex, and         newline convention affects the handling of  the  dot,  circumflex,  and
1003         dollar metacharacters, the handling of #-comments in /x mode, and, when         dollar metacharacters, the handling of #-comments in /x mode, and, when
1004         CRLF  is a recognized line ending sequence, the match position advance-         CRLF is a recognized line ending sequence, the match position  advance-
1005         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
1006         not affect the interpretation of the \n or \r escape sequences.         section on pcre_exec() options below.
1007    
1008           The choice of newline convention does not affect the interpretation  of
1009           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
1010           which is controlled in a similar way, but by separate options.
1011    
1012    
1013  MULTITHREADING  MULTITHREADING
1014    
1015         The  PCRE  functions  can be used in multi-threading applications, with         The PCRE functions can be used in  multi-threading  applications,  with
1016         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
1017         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
1018         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 868  SAVING PRECOMPILED PATTERNS FOR LATER US Line 1027  SAVING PRECOMPILED PATTERNS FOR LATER US
1027         The compiled form of a regular expression can be saved and re-used at a         The compiled form of a regular expression can be saved and re-used at a
1028         later time, possibly by a different program, and even on a  host  other         later time, possibly by a different program, and even on a  host  other
1029         than  the  one  on  which  it  was  compiled.  Details are given in the         than  the  one  on  which  it  was  compiled.  Details are given in the
1030         pcreprecompile documentation.         pcreprecompile documentation. However, compiling a  regular  expression
1031           with  one version of PCRE for use with a different version is not guar-
1032           anteed to work and may cause crashes.
1033    
1034    
1035  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
# Line 899  CHECKING BUILD-TIME OPTIONS Line 1060  CHECKING BUILD-TIME OPTIONS
1060    
1061         The output is an integer whose value specifies  the  default  character         The output is an integer whose value specifies  the  default  character
1062         sequence  that is recognized as meaning "newline". The four values that         sequence  that is recognized as meaning "newline". The four values that
1063         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, and -1 for ANY.         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
1064         The default should normally be the standard sequence for your operating         and  -1  for  ANY.  Though they are derived from ASCII, the same values
1065         system.         are returned in EBCDIC environments. The default should normally corre-
1066           spond to the standard sequence for your operating system.
1067    
1068             PCRE_CONFIG_BSR
1069    
1070           The output is an integer whose value indicates what character sequences
1071           the \R escape sequence matches by default. A value of 0 means  that  \R
1072           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1073           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1074           tern is compiled or matched.
1075    
1076           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1077    
1078         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
1079         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
1080         4. Larger values allow larger regular expressions to  be  compiled,  at         4.  Larger  values  allow larger regular expressions to be compiled, at
1081         the  expense  of  slower matching. The default value of 2 is sufficient         the expense of slower matching. The default value of  2  is  sufficient
1082         for all but the most massive patterns, since  it  allows  the  compiled         for  all  but  the  most massive patterns, since it allows the compiled
1083         pattern to be up to 64K in size.         pattern to be up to 64K in size.
1084    
1085           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1086    
1087         The  output  is  an integer that contains the threshold above which the         The output is an integer that contains the threshold  above  which  the
1088         POSIX interface uses malloc() for output vectors. Further  details  are         POSIX  interface  uses malloc() for output vectors. Further details are
1089         given in the pcreposix documentation.         given in the pcreposix documentation.
1090    
1091           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1092    
1093         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-
1094         internal matching function calls in a  pcre_exec()  execution.  Further         ber  of  internal  matching  function calls in a pcre_exec() execution.
1095         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1096    
1097           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1098    
1099         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
1100         recursion when calling the internal matching function in a  pcre_exec()         of   recursion  when  calling  the  internal  matching  function  in  a
1101         execution. Further details are given with pcre_exec() below.         pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1102           below.
1103    
1104           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1105    
# Line 972  COMPILING A PATTERN Line 1143  COMPILING A PATTERN
1143    
1144         The options argument contains various bit settings that affect the com-         The options argument contains various bit settings that affect the com-
1145         pilation. It should be zero if no options are required.  The  available         pilation. It should be zero if no options are required.  The  available
1146         options  are  described  below. Some of them, in particular, those that         options  are  described  below. Some of them (in particular, those that
1147         are compatible with Perl, can also be set and  unset  from  within  the         are compatible with Perl, but also some others) can  also  be  set  and
1148         pattern  (see  the  detailed  description in the pcrepattern documenta-         unset  from  within  the  pattern  (see the detailed description in the
1149         tion). For these options, the contents of the options  argument  speci-         pcrepattern documentation). For those options that can be different  in
1150         fies  their initial settings at the start of compilation and execution.         different  parts  of  the pattern, the contents of the options argument
1151         The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at  the  time         specifies their initial settings at the start of compilation and execu-
1152         of matching as well as at compile time.         tion.  The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at the
1153           time of matching as well as at compile time.
1154    
1155         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1156         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1157         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-
1158         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
1159         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
1160         ter where the error was discovered is placed in the variable pointed to         character  that  was  being  processes when the error was discovered is
1161         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.
1162         given.         If  it  is,  an  immediate error is given. Some errors are not detected
1163           until checks are carried out when the whole pattern has  been  scanned;
1164         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.
1165         codeptr  argument is not NULL, a non-zero error code number is returned  
1166         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-
1167           codeptr argument is not NULL, a non-zero error code number is  returned
1168           via  this argument in the event of an error. This is in addition to the
1169         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1170    
1171         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
1172         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1173         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1174         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
1175         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1176         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
1177         support below.         support below.
1178    
1179         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1180         pile():         pile():
1181    
1182           pcre *re;           pcre *re;
# Line 1015  COMPILING A PATTERN Line 1189  COMPILING A PATTERN
1189             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1190             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1191    
1192         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
1193         file:         file:
1194    
1195           PCRE_ANCHORED           PCRE_ANCHORED
1196    
1197         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
1198         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
1199         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1200         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1201         only way to do it in Perl.         only way to do it in Perl.
1202    
1203           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1204    
1205         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1206         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1207         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1208    
1209             PCRE_BSR_ANYCRLF
1210             PCRE_BSR_UNICODE
1211    
1212           These options (which are mutually exclusive) control what the \R escape
1213           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1214           or to match any Unicode newline sequence. The default is specified when
1215           PCRE is built. It can be overridden from within the pattern, or by set-
1216           ting an option when a compiled pattern is matched.
1217    
1218           PCRE_CASELESS           PCRE_CASELESS
1219    
1220         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
1221         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
1222         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
1223         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1224         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1225         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-
1226         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1227         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1228         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1229         UTF-8 support.         UTF-8 support.
1230    
1231           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1232    
1233         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
1234         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
1235         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
1236         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1237         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
1238         Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1239    
1240           PCRE_DOTALL           PCRE_DOTALL
1241    
1242         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-
1243         acters, including those that indicate newline. Without it, a  dot  does         acters,  including  those that indicate newline. Without it, a dot does
1244         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
1245         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
1246         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
1247         newline characters, independent of the setting of this option.         newline characters, independent of the setting of this option.
1248    
1249           PCRE_DUPNAMES           PCRE_DUPNAMES
1250    
1251         If this bit is set, names used to identify capturing  subpatterns  need         If  this  bit is set, names used to identify capturing subpatterns need
1252         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
1253         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
1254         matched.  There  are  more details of named subpatterns below; see also         matched. There are more details of named subpatterns  below;  see  also
1255         the pcrepattern documentation.         the pcrepattern documentation.
1256    
1257           PCRE_EXTENDED           PCRE_EXTENDED
1258    
1259         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1260         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1261         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1262         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1263         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1264         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-
1265         ting.         ting.
1266    
1267         This option makes it possible to include  comments  inside  complicated         This  option  makes  it possible to include comments inside complicated
1268         patterns.   Note,  however,  that this applies only to data characters.         patterns.  Note, however, that this applies only  to  data  characters.
1269         Whitespace  characters  may  never  appear  within  special   character         Whitespace   characters  may  never  appear  within  special  character
1270         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for  example  within  the  sequence  (?(  which
1271         introduces a conditional subpattern.         introduces a conditional subpattern.
1272    
1273           PCRE_EXTRA           PCRE_EXTRA
1274    
1275         This option was invented in order to turn on  additional  functionality         This  option  was invented in order to turn on additional functionality
1276         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
1277         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
1278         letter  that  has  no  special  meaning causes an error, thus reserving         letter that has no special meaning  causes  an  error,  thus  reserving
1279         these combinations for future expansion. By  default,  as  in  Perl,  a         these  combinations  for  future  expansion.  By default, as in Perl, a
1280         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
1281         literal. (Perl can, however, be persuaded to give a warning for  this.)         literal.  (Perl can, however, be persuaded to give a warning for this.)
1282         There  are  at  present no other features controlled by this option. It         There are at present no other features controlled by  this  option.  It
1283         can also be set by a (?X) option setting within a pattern.         can also be set by a (?X) option setting within a pattern.
1284    
1285           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1286    
1287         If this option is set, an  unanchored  pattern  is  required  to  match         If  this  option  is  set,  an  unanchored pattern is required to match
1288         before  or  at  the  first  newline  in  the subject string, though the         before or at the first  newline  in  the  subject  string,  though  the
1289         matched text may continue over the newline.         matched text may continue over the newline.
1290    
1291             PCRE_JAVASCRIPT_COMPAT
1292    
1293           If this option is set, PCRE's behaviour is changed in some ways so that
1294           it is compatible with JavaScript rather than Perl. The changes  are  as
1295           follows:
1296    
1297           (1)  A  lone  closing square bracket in a pattern causes a compile-time
1298           error, because this is illegal in JavaScript (by default it is  treated
1299           as a data character). Thus, the pattern AB]CD becomes illegal when this
1300           option is set.
1301    
1302           (2) At run time, a back reference to an unset subpattern group  matches
1303           an  empty  string (by default this causes the current matching alterna-
1304           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
1305           set  (assuming  it can find an "a" in the subject), whereas it fails by
1306           default, for Perl compatibility.
1307    
1308           PCRE_MULTILINE           PCRE_MULTILINE
1309    
1310         By default, PCRE treats the subject string as consisting  of  a  single         By default, PCRE treats the subject string as consisting  of  a  single
# Line 1125  COMPILING A PATTERN Line 1325  COMPILING A PATTERN
1325           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
1326           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
1327           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
1328             PCRE_NEWLINE_ANYCRLF
1329           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1330    
1331         These  options  override the default newline definition that was chosen         These  options  override the default newline definition that was chosen
1332         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
1333         newline  is  indicated  by a single character (CR or LF, respectively).         newline  is  indicated  by a single character (CR or LF, respectively).
1334         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
1335         two-character  CRLF  sequence.  Setting PCRE_NEWLINE_ANY specifies that         two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
1336         any Unicode newline sequence should be recognized. The Unicode  newline         that any of the three preceding sequences should be recognized. Setting
1337         sequences  are  the three just mentioned, plus the single characters VT         PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
1338         (vertical tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085),         recognized. The Unicode newline sequences are the three just mentioned,
1339         LS  (line separator, U+2028), and PS (paragraph separator, U+2029). The         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,
1340         last two are recognized only in UTF-8 mode.         U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS
1341           (paragraph  separator,  U+2029).  The  last  two are recognized only in
1342           UTF-8 mode.
1343    
1344         The newline setting in the  options  word  uses  three  bits  that  are         The newline setting in the  options  word  uses  three  bits  that  are
1345         treated  as  a  number, giving eight possibilities. Currently only five         treated as a number, giving eight possibilities. Currently only six are
1346         are used (default plus the four values above). This means that  if  you         used (default plus the five values above). This means that if  you  set
1347         set  more  than  one  newline option, the combination may or may not be         more  than one newline option, the combination may or may not be sensi-
1348         sensible. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is  equiva-         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1349         lent  to PCRE_NEWLINE_CRLF, but other combinations yield unused numbers         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1350         and cause an error.         cause an error.
1351    
1352         The only time that a line break is specially recognized when  compiling         The only time that a line break is specially recognized when  compiling
1353         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
# Line 1155  COMPILING A PATTERN Line 1358  COMPILING A PATTERN
1358         and are therefore ignored.         and are therefore ignored.
1359    
1360         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
1361         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.
1362    
1363           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1364    
1365         If this option is set, it disables the use of numbered capturing paren-         If this option is set, it disables the use of numbered capturing paren-
1366         theses  in the pattern. Any opening parenthesis that is not followed by         theses in the pattern. Any opening parenthesis that is not followed  by
1367         ? behaves as if it were followed by ?: but named parentheses can  still         ?  behaves as if it were followed by ?: but named parentheses can still
1368         be  used  for  capturing  (and  they acquire numbers in the usual way).         be used for capturing (and they acquire  numbers  in  the  usual  way).
1369         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1370    
1371           PCRE_UNGREEDY           PCRE_UNGREEDY
1372    
1373         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1374         are  not greedy by default, but become greedy if followed by "?". It is         are not greedy by default, but become greedy if followed by "?". It  is
1375         not compatible with Perl. It can also be set by a (?U)  option  setting         not  compatible  with Perl. It can also be set by a (?U) option setting
1376         within the pattern.         within the pattern.
1377    
1378           PCRE_UTF8           PCRE_UTF8
1379    
1380         This  option  causes PCRE to regard both the pattern and the subject as         This option causes PCRE to regard both the pattern and the  subject  as
1381         strings of UTF-8 characters instead of single-byte  character  strings.         strings  of  UTF-8 characters instead of single-byte character strings.
1382         However,  it is available only when PCRE is built to include UTF-8 sup-         However, it is available only when PCRE is built to include UTF-8  sup-
1383         port. If not, the use of this option provokes an error. Details of  how         port.  If not, the use of this option provokes an error. Details of how
1384         this  option  changes the behaviour of PCRE are given in the section on         this option changes the behaviour of PCRE are given in the  section  on
1385         UTF-8 support in the main pcre page.         UTF-8 support in the main pcre page.
1386    
1387           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1388    
1389         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
1390         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically checked. There is a  discussion  about  the  validity  of
1391         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
1392         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
1393         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-
1394         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
1395         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
1396         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
1397         ing of subject strings.         can  also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the
1398           UTF-8 validity checking of subject strings.
1399    
1400    
1401  COMPILATION ERROR CODES  COMPILATION ERROR CODES
# Line 1213  COMPILATION ERROR CODES Line 1417  COMPILATION ERROR CODES
1417            9  nothing to repeat            9  nothing to repeat
1418           10  [this code is not in use]           10  [this code is not in use]
1419           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1420           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1421           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1422           14  missing )           14  missing )
1423           15  reference to non-existent subpattern           15  reference to non-existent subpattern
# Line 1221  COMPILATION ERROR CODES Line 1425  COMPILATION ERROR CODES
1425           17  unknown option bit(s) set           17  unknown option bit(s) set
1426           18  missing ) after comment           18  missing ) after comment
1427           19  [this code is not in use]           19  [this code is not in use]
1428           20  regular expression too large           20  regular expression is too large
1429           21  failed to get memory           21  failed to get memory
1430           22  unmatched parentheses           22  unmatched parentheses
1431           23  internal error: code overflow           23  internal error: code overflow
# Line 1230  COMPILATION ERROR CODES Line 1434  COMPILATION ERROR CODES
1434           26  malformed number or name after (?(           26  malformed number or name after (?(
1435           27  conditional group contains more than two branches           27  conditional group contains more than two branches
1436           28  assertion expected after (?(           28  assertion expected after (?(
1437           29  (?R or (?digits must be followed by )           29  (?R or (?[+-]digits must be followed by )
1438           30  unknown POSIX class name           30  unknown POSIX class name
1439           31  POSIX collating elements are not supported           31  POSIX collating elements are not supported
1440           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 1250  COMPILATION ERROR CODES Line 1454  COMPILATION ERROR CODES
1454           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1455           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1456           48  subpattern name is too long (maximum 32 characters)           48  subpattern name is too long (maximum 32 characters)
1457           49  too many named subpatterns (maximum 10,000)           49  too many named subpatterns (maximum 10000)
1458           50  repeated subpattern is too long           50  [this code is not in use]
1459           51  octal value is greater than \377 (not in UTF-8 mode)           51  octal value is greater than \377 (not in UTF-8 mode)
1460           52  internal error: overran compiling workspace           52  internal error: overran compiling workspace
1461           53   internal  error:  previously-checked  referenced  subpattern not           53   internal  error:  previously-checked  referenced  subpattern not
1462         found         found
1463           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1464           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1465           56  inconsistent NEWLINE options"           56  inconsistent NEWLINE options
1466             57  \g is not followed by a braced, angle-bracketed, or quoted
1467                   name/number or by a plain number
1468             58  a numbered reference must not be zero
1469             59  (*VERB) with an argument is not supported
1470             60  (*VERB) not recognized
1471             61  number is too big
1472             62  subpattern name expected
1473             63  digit expected after (?+
1474             64  ] is an invalid data character in JavaScript compatibility mode
1475    
1476           The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
1477           values may be used if the limits were changed when PCRE was built.
1478    
1479    
1480  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1266  STUDYING A PATTERN Line 1482  STUDYING A PATTERN
1482         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1483              const char **errptr);              const char **errptr);
1484    
1485         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
1486         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
1487         matching. The function pcre_study() takes a pointer to a compiled  pat-         matching.  The function pcre_study() takes a pointer to a compiled pat-
1488         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1489         information that will help speed up matching,  pcre_study()  returns  a         information  that  will  help speed up matching, pcre_study() returns a
1490         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
1491         the results of the study.         the results of the study.
1492    
1493         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1494         pcre_exec().  However,  a  pcre_extra  block also contains other fields         pcre_exec(). However, a pcre_extra block  also  contains  other  fields
1495         that can be set by the caller before the block  is  passed;  these  are         that  can  be  set  by the caller before the block is passed; these are
1496         described below in the section on matching a pattern.         described below in the section on matching a pattern.
1497    
1498         If  studying  the  pattern  does not produce any additional information         If studying the pattern does not  produce  any  additional  information
1499         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1500         wants  to  pass  any of the other fields to pcre_exec(), it must set up         wants to pass any of the other fields to pcre_exec(), it  must  set  up
1501         its own pcre_extra block.         its own pcre_extra block.
1502    
1503         The second argument of pcre_study() contains option bits.  At  present,         The  second  argument of pcre_study() contains option bits. At present,
1504         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1505    
1506         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.
1507         If studying succeeds (even if no data is  returned),  the  variable  it         If  studying  succeeds  (even  if no data is returned), the variable it
1508         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
1509         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
1510         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
1511         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1512    
1513         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 1303  STUDYING A PATTERN Line 1519  STUDYING A PATTERN
1519             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1520    
1521         At present, studying a pattern is useful only for non-anchored patterns         At present, studying a pattern is useful only for non-anchored patterns
1522         that  do not have a single fixed starting character. A bitmap of possi-         that do not have a single fixed starting character. A bitmap of  possi-
1523         ble starting bytes is created.         ble starting bytes is created.
1524    
1525    
1526  LOCALE SUPPORT  LOCALE SUPPORT
1527    
1528         PCRE handles caseless matching, and determines whether  characters  are         PCRE  handles  caseless matching, and determines whether characters are
1529         letters  digits,  or whatever, by reference to a set of tables, indexed         letters, digits, or whatever, by reference to a set of tables,  indexed
1530         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
1531         characters  with  codes  less than 128. Higher-valued codes never match         characters with codes less than 128. Higher-valued  codes  never  match
1532         escapes such as \w or \d, but can be tested with \p if  PCRE  is  built         escapes  such  as  \w or \d, but can be tested with \p if PCRE is built
1533         with  Unicode  character property support. The use of locales with Uni-         with Unicode character property support. The use of locales  with  Uni-
1534         code is discouraged.         code  is discouraged. If you are handling characters with codes greater
1535           than 128, you should either use UTF-8 and Unicode, or use locales,  but
1536         An internal set of tables is created in the default C locale when  PCRE         not try to mix the two.
1537         is  built.  This  is  used when the final argument of pcre_compile() is  
1538         NULL, and is sufficient for many applications. An  alternative  set  of         PCRE  contains  an  internal set of tables that are used when the final
1539         tables  can,  however, be supplied. These may be created in a different         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
1540         locale from the default. As more and more applications change to  using         applications.  Normally, the internal tables recognize only ASCII char-
1541         Unicode, the need for this locale support is expected to die away.         acters. However, when PCRE is built, it is possible to cause the inter-
1542           nal tables to be rebuilt in the default "C" locale of the local system,
1543           which may cause them to be different.
1544    
1545           The internal tables can always be overridden by tables supplied by  the
1546           application that calls PCRE. These may be created in a different locale
1547           from the default. As more and more applications change  to  using  Uni-
1548           code, the need for this locale support is expected to die away.
1549    
1550         External  tables  are  built by calling the pcre_maketables() function,         External  tables  are  built by calling the pcre_maketables() function,
1551         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
# Line 1335  LOCALE SUPPORT Line 1558  LOCALE SUPPORT
1558           tables = pcre_maketables();           tables = pcre_maketables();
1559           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1560    
1561         When pcre_maketables() runs, the tables are built  in  memory  that  is         The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
1562         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         if you are using Windows, the name for the French locale is "french".
1563         that the memory containing the tables remains available for as long  as  
1564           When  pcre_maketables()  runs,  the  tables are built in memory that is
1565           obtained via pcre_malloc. It is the caller's responsibility  to  ensure
1566           that  the memory containing the tables remains available for as long as
1567         it is needed.         it is needed.
1568    
1569         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
1570         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()
1571         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-
1572         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1573         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1574    
1575         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
1576         the internal tables) to pcre_exec(). Although  not  intended  for  this         the  internal  tables)  to  pcre_exec(). Although not intended for this
1577         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
1578         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
1579         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1580    
# Line 1358  INFORMATION ABOUT A PATTERN Line 1584  INFORMATION ABOUT A PATTERN
1584         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1585              int what, void *where);              int what, void *where);
1586    
1587         The  pcre_fullinfo() function returns information about a compiled pat-         The pcre_fullinfo() function returns information about a compiled  pat-
1588         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1589         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1590    
1591         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
1592         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
1593         the  pattern  was not studied. The third argument specifies which piece         the pattern was not studied. The third argument specifies  which  piece
1594         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
1595         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
1596         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1597    
1598           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1374  INFORMATION ABOUT A PATTERN Line 1600  INFORMATION ABOUT A PATTERN
1600           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1601           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1602    
1603         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
1604         an  simple check against passing an arbitrary memory pointer. Here is a         an simple check against passing an arbitrary memory pointer. Here is  a
1605         typical call of pcre_fullinfo(), to obtain the length of  the  compiled         typical  call  of pcre_fullinfo(), to obtain the length of the compiled
1606         pattern:         pattern:
1607    
1608           int rc;           int rc;
# Line 1387  INFORMATION ABOUT A PATTERN Line 1613  INFORMATION ABOUT A PATTERN
1613             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1614             &length);         /* where to put the data */             &length);         /* where to put the data */
1615    
1616         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
1617         are as follows:         are as follows:
1618    
1619           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1620    
1621         Return the number of the highest back reference  in  the  pattern.  The         Return  the  number  of  the highest back reference in the pattern. The
1622         fourth  argument  should  point to an int variable. Zero is returned if         fourth argument should point to an int variable. Zero  is  returned  if
1623         there are no back references.         there are no back references.
1624    
1625           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1626    
1627         Return the number of capturing subpatterns in the pattern.  The  fourth         Return  the  number of capturing subpatterns in the pattern. The fourth
1628         argument should point to an int variable.         argument should point to an int variable.
1629    
1630           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1631    
1632         Return  a pointer to the internal default character tables within PCRE.         Return a pointer to the internal default character tables within  PCRE.
1633         The fourth argument should point to an unsigned char *  variable.  This         The  fourth  argument should point to an unsigned char * variable. This
1634         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1635         tion. External callers can cause PCRE to use  its  internal  tables  by         tion.  External  callers  can  cause PCRE to use its internal tables by
1636         passing a NULL table pointer.         passing a NULL table pointer.
1637    
1638           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1639    
1640         Return  information  about  the first byte of any matched string, for a         Return information about the first byte of any matched  string,  for  a
1641         non-anchored pattern. The fourth argument should point to an int  vari-         non-anchored  pattern. The fourth argument should point to an int vari-
1642         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
1643         is still recognized for backwards compatibility.)         is still recognized for backwards compatibility.)
1644    
1645         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
1646         (cat|cow|coyote), its value is returned. Otherwise, if either         (cat|cow|coyote), its value is returned. Otherwise, if either
1647    
1648         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1649         branch starts with "^", or         branch starts with "^", or
1650    
1651         (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
1652         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1653    
1654         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
1655         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
1656         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1657    
1658           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1659    
1660         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
1661         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
1662         matching  string, a pointer to the table is returned. Otherwise NULL is         matching string, a pointer to the table is returned. Otherwise NULL  is
1663         returned. The fourth argument should point to an unsigned char *  vari-         returned.  The fourth argument should point to an unsigned char * vari-
1664         able.         able.
1665    
1666             PCRE_INFO_HASCRORLF
1667    
1668           Return 1 if the pattern contains any explicit  matches  for  CR  or  LF
1669           characters,  otherwise  0.  The  fourth argument should point to an int
1670           variable. An explicit match is either a literal CR or LF character,  or
1671           \r or \n.
1672    
1673             PCRE_INFO_JCHANGED
1674    
1675           Return  1  if  the (?J) or (?-J) option setting is used in the pattern,
1676           otherwise 0. The fourth argument should point to an int variable.  (?J)
1677           and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1678    
1679           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1680    
1681         Return  the  value of the rightmost literal byte that must exist in any         Return  the  value of the rightmost literal byte that must exist in any
# Line 1491  INFORMATION ABOUT A PATTERN Line 1730  INFORMATION ABOUT A PATTERN
1730         name-to-number map, remember that the length of the entries  is  likely         name-to-number map, remember that the length of the entries  is  likely
1731         to be different for each compiled pattern.         to be different for each compiled pattern.
1732    
1733             PCRE_INFO_OKPARTIAL
1734    
1735           Return  1  if  the  pattern  can  be  used  for  partial  matching with
1736           pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
1737           variable.  From  release  8.00,  this  always  returns  1,  because the
1738           restrictions that previously applied  to  partial  matching  have  been
1739           lifted.  The  pcrepartial documentation gives details of partial match-
1740           ing.
1741    
1742           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1743    
1744         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
1745         fourth argument should point to an unsigned long  int  variable.  These         fourth  argument  should  point to an unsigned long int variable. These
1746         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1747         by any top-level option settings within the pattern itself.         by any top-level option settings at the start of the pattern itself. In
1748           other words, they are the options that will be in force  when  matching
1749           starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
1750           the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1751           and PCRE_EXTENDED.
1752    
1753         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
1754         alternatives begin with one of the following:         alternatives begin with one of the following:
1755    
1756           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1512  INFORMATION ABOUT A PATTERN Line 1764  INFORMATION ABOUT A PATTERN
1764    
1765           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1766    
1767         Return the size of the compiled pattern, that is, the  value  that  was         Return  the  size  of the compiled pattern, that is, the value that was
1768         passed as the argument to pcre_malloc() when PCRE was getting memory in         passed as the argument to pcre_malloc() when PCRE was getting memory in
1769         which to place the compiled data. The fourth argument should point to a         which to place the compiled data. The fourth argument should point to a
1770         size_t variable.         size_t variable.
# Line 1520  INFORMATION ABOUT A PATTERN Line 1772  INFORMATION ABOUT A PATTERN
1772           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1773    
1774         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
1775         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
1776         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
1777         created by pcre_study(). The fourth argument should point to  a  size_t         created  by  pcre_study(). The fourth argument should point to a size_t
1778         variable.         variable.
1779    
1780    
# Line 1530  OBSOLETE INFO FUNCTION Line 1782  OBSOLETE INFO FUNCTION
1782    
1783         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1784    
1785         The  pcre_info()  function is now obsolete because its interface is too         The pcre_info() function is now obsolete because its interface  is  too
1786         restrictive to return all the available data about a compiled  pattern.         restrictive  to return all the available data about a compiled pattern.
1787         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of
1788         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-
1789         lowing negative numbers:         lowing negative numbers:
1790    
1791           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1792           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1793    
1794         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
1795         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
1796         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1797    
1798         If  the  pattern  is  not anchored and the firstcharptr argument is not         If the pattern is not anchored and the  firstcharptr  argument  is  not
1799         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
1800         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1801    
1802    
# Line 1552  REFERENCE COUNTS Line 1804  REFERENCE COUNTS
1804    
1805         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1806    
1807         The  pcre_refcount()  function is used to maintain a reference count in         The pcre_refcount() function is used to maintain a reference  count  in
1808         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
1809         benefit  of  applications  that  operate  in an object-oriented manner,         benefit of applications that  operate  in  an  object-oriented  manner,
1810         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1811         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.
1812    
1813         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1814         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
1815         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
1816         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
1817         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
1818         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1819    
1820         Except when it is zero, the reference count is not correctly  preserved         Except  when it is zero, the reference count is not correctly preserved
1821         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
1822         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1823    
1824    
# Line 1660  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1912  MATCHING A PATTERN: THE TRADITIONAL FUNC
1912         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-
1913         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.
1914    
1915         Limiting  the  recursion  depth  limits the amount of stack that can be         Limiting the recursion depth limits the amount of  stack  that  can  be
1916         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
1917         of the stack, the amount of heap memory that can be used.         of the stack, the amount of heap memory that can be used.
1918    
1919         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
1920         built; the default default  is  the  same  value  as  the  default  for         built;  the  default  default  is  the  same  value  as the default for
1921         match_limit.  You can override the default by suppling pcre_exec() with         match_limit. You can override the default by suppling pcre_exec()  with
1922         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and         a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
1923         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
1924         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1925    
1926         The pcre_callout field is used in conjunction with the  "callout"  fea-         The  callout_data  field is used in conjunction with the "callout" fea-
1927         ture, which is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
1928    
1929         The  tables  field  is  used  to  pass  a  character  tables pointer to         The tables field  is  used  to  pass  a  character  tables  pointer  to
1930         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec();  this overrides the value that is stored with the compiled
1931         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
1932         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
1933         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
1934         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-
1935         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
1936         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
1937         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
1938         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
1939    
1940     Option bits for pcre_exec()     Option bits for pcre_exec()
1941    
1942         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.
1943         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,
1944         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
1945         PCRE_PARTIAL.         PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
1946           PCRE_PARTIAL_HARD.
1947    
1948           PCRE_ANCHORED           PCRE_ANCHORED
1949    
# Line 1699  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1952  MATCHING A PATTERN: THE TRADITIONAL FUNC
1952         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
1953         unachored at matching time.         unachored at matching time.
1954    
1955             PCRE_BSR_ANYCRLF
1956             PCRE_BSR_UNICODE
1957    
1958           These options (which are mutually exclusive) control what the \R escape
1959           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1960           or to match any Unicode newline sequence. These  options  override  the
1961           choice that was made or defaulted when the pattern was compiled.
1962    
1963           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
1964           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
1965           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
1966             PCRE_NEWLINE_ANYCRLF
1967           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1968    
1969         These options override  the  newline  definition  that  was  chosen  or         These  options  override  the  newline  definition  that  was chosen or
1970         defaulted  when the pattern was compiled. For details, see the descrip-         defaulted when the pattern was compiled. For details, see the  descrip-
1971         tion of pcre_compile()  above.  During  matching,  the  newline  choice         tion  of  pcre_compile()  above.  During  matching,  the newline choice
1972         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
1973         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
1974         match  failure  for  an  unanchored  pattern. When PCRE_NEWLINE_CRLF or         match failure for an unanchored pattern.
1975         PCRE_NEWLINE_ANY is set, and a match attempt  fails  when  the  current  
1976         position  is  at a CRLF sequence, the match position is advanced by two         When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
1977         characters instead of one, in other words, to after the CRLF.         set,  and a match attempt for an unanchored pattern fails when the cur-
1978           rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
1979           explicit  matches  for  CR  or  LF  characters,  the  match position is
1980           advanced by two characters instead of one, in other words, to after the
1981           CRLF.
1982    
1983           The above rule is a compromise that makes the most common cases work as
1984           expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
1985           option is not set), it does not match the string "\r\nA" because, after
1986           failing at the start, it skips both the CR and the LF before  retrying.
1987           However,  the  pattern  [\r\n]A does match that string, because it con-
1988           tains an explicit CR or LF reference, and so advances only by one char-
1989           acter after the first failure.
1990    
1991           An explicit match for CR of LF is either a literal appearance of one of
1992           those characters, or one of the \r or  \n  escape  sequences.  Implicit
1993           matches  such  as [^X] do not count, nor does \s (which includes CR and
1994           LF in the characters that it matches).
1995    
1996           Notwithstanding the above, anomalous effects may still occur when  CRLF
1997           is a valid newline sequence and explicit \r or \n escapes appear in the
1998           pattern.
1999    
2000           PCRE_NOTBOL           PCRE_NOTBOL
2001    
# Line 1740  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2023  MATCHING A PATTERN: THE TRADITIONAL FUNC
2023    
2024           a?b?           a?b?
2025    
2026         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
2027         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
2028         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-
2029         rences of "a" or "b".         rences of "a" or "b".
2030    
2031         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2032         cial case of a pattern match of the empty  string  within  its  split()  
2033         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
2034         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
2035         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.
2036         if that fails by advancing the starting offset (see below)  and  trying  
2037         an ordinary match again. There is some code that demonstrates how to do         Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or
2038         this in the pcredemo.c sample program.         PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern
2039           match  of  the empty string within its split() function, and when using
2040           the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after
2041           matching a null string by first trying the match again at the same off-
2042           set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that
2043           fails, by advancing the starting offset (see below) and trying an ordi-
2044           nary match again. There is some code that demonstrates how to  do  this
2045           in the pcredemo sample program.
2046    
2047             PCRE_NO_START_OPTIMIZE
2048    
2049           There  are a number of optimizations that pcre_exec() uses at the start
2050           of a match, in order to speed up the process. For  example,  if  it  is
2051           known  that  a  match must start with a specific character, it searches
2052           the subject for that character, and fails immediately if it cannot find
2053           it,  without actually running the main matching function. When callouts
2054           are in use, these optimizations can cause  them  to  be  skipped.  This
2055           option  disables  the  "start-up" optimizations, causing performance to
2056           suffer, but ensuring that the callouts do occur.
2057    
2058           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2059    
2060         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
2061         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8  string is automatically checked when pcre_exec() is subsequently
2062         called.  The value of startoffset is also checked  to  ensure  that  it         called.  The value of startoffset is also checked  to  ensure  that  it
2063         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
2064         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
2065         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,
2066         returned.         pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-
2067           tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
2068         If you already know that your subject is valid, and you  want  to  skip  
2069         these    checks    for   performance   reasons,   you   can   set   the         If  you  already  know that your subject is valid, and you want to skip
2070         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to         these   checks   for   performance   reasons,   you   can    set    the
2071         do  this  for the second and subsequent calls to pcre_exec() if you are         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to
2072         making repeated calls to find all  the  matches  in  a  single  subject         do this for the second and subsequent calls to pcre_exec() if  you  are
2073         string.  However,  you  should  be  sure  that the value of startoffset         making  repeated  calls  to  find  all  the matches in a single subject
2074         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is         string. However, you should be  sure  that  the  value  of  startoffset
2075         set,  the  effect of passing an invalid UTF-8 string as a subject, or a         points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is
2076         value of startoffset that does not point to the start of a UTF-8  char-         set, the effect of passing an invalid UTF-8 string as a subject,  or  a
2077           value  of startoffset that does not point to the start of a UTF-8 char-
2078         acter, is undefined. Your program may crash.         acter, is undefined. Your program may crash.
2079    
2080           PCRE_PARTIAL           PCRE_PARTIAL_HARD
2081             PCRE_PARTIAL_SOFT
2082    
2083         This  option  turns  on  the  partial  matching feature. If the subject         These options turn on the partial matching feature. For backwards  com-
2084         string fails to match the pattern, but at some point during the  match-         patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial
2085         ing  process  the  end of the subject was reached (that is, the subject         match occurs if the end of the subject string is reached  successfully,
2086         partially matches the pattern and the failure to  match  occurred  only         but  there  are not enough subject characters to complete the match. If
2087         because  there were not enough subject characters), pcre_exec() returns         this happens when PCRE_PARTIAL_HARD  is  set,  pcre_exec()  immediately
2088         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is         returns  PCRE_ERROR_PARTIAL.  Otherwise,  if  PCRE_PARTIAL_SOFT is set,
2089         used,  there  are restrictions on what may appear in the pattern. These         matching continues by testing any other alternatives. Only if they  all
2090         are discussed in the pcrepartial documentation.         fail  is  PCRE_ERROR_PARTIAL  returned (instead of PCRE_ERROR_NOMATCH).
2091           The portion of the string that was inspected when the partial match was
2092           found  is  set  as  the first matching string. There is a more detailed
2093           discussion in the pcrepartial documentation.
2094    
2095     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2096    
2097         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
2098         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.
2099         mode, the byte offset must point to the start  of  a  UTF-8  character.         In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-
2100         Unlike  the  pattern string, the subject may contain binary zero bytes.         acter.  Unlike  the pattern string, the subject may contain binary zero
2101         When the starting offset is zero, the search for a match starts at  the         bytes. When the starting offset is zero, the search for a match  starts
2102         beginning of the subject, and this is by far the most common case.         at  the  beginning  of  the subject, and this is by far the most common
2103           case.
2104         A  non-zero  starting offset is useful when searching for another match  
2105         in the same subject by calling pcre_exec() again after a previous  suc-         A non-zero starting offset is useful when searching for  another  match
2106         cess.   Setting  startoffset differs from just passing over a shortened         in  the same subject by calling pcre_exec() again after a previous suc-
2107         string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins         cess.  Setting startoffset differs from just passing over  a  shortened
2108           string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins
2109         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
2110    
2111           \Biss\B           \Biss\B
2112    
2113         which  finds  occurrences  of "iss" in the middle of words. (\B matches         which finds occurrences of "iss" in the middle of  words.  (\B  matches
2114         only if the current position in the subject is not  a  word  boundary.)         only  if  the  current position in the subject is not a word boundary.)
2115         When  applied  to the string "Mississipi" the first call to pcre_exec()         When applied to the string "Mississipi" the first call  to  pcre_exec()
2116         finds the first occurrence. If pcre_exec() is called  again  with  just         finds  the  first  occurrence. If pcre_exec() is called again with just
2117         the  remainder  of  the  subject,  namely  "issipi", it does not match,         the remainder of the subject,  namely  "issipi",  it  does  not  match,
2118         because \B is always false at the start of the subject, which is deemed         because \B is always false at the start of the subject, which is deemed
2119         to  be  a  word  boundary. However, if pcre_exec() is passed the entire         to be a word boundary. However, if pcre_exec()  is  passed  the  entire
2120         string again, but with startoffset set to 4, it finds the second occur-         string again, but with startoffset set to 4, it finds the second occur-
2121         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
2122         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2123    
2124         If a non-zero starting offset is passed when the pattern  is  anchored,         If  a  non-zero starting offset is passed when the pattern is anchored,
2125         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
2126         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
2127         subject.         subject.
2128    
2129     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2130    
2131         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
2132         addition, further substrings from the subject  may  be  picked  out  by         addition,  further  substrings  from  the  subject may be picked out by
2133         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2134         this is called "capturing" in what follows, and the  phrase  "capturing         this  is  called "capturing" in what follows, and the phrase "capturing
2135         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-
2136         string. PCRE supports several other kinds of  parenthesized  subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2137         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2138    
2139         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2140         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-
2141         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:
2142         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2143    
2144         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-
2145         strings,  each  substring using a pair of integers. The remaining third         strings, each substring using a pair of integers. The  remaining  third
2146         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-
2147         turing  subpatterns, and is not available for passing back information.         turing subpatterns, and is not available for passing back  information.
2148         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
2149         it is not, it is rounded down.         it is not, it is rounded down.
2150    
2151         When  a  match  is successful, information about captured substrings is         When a match is successful, information about  captured  substrings  is
2152         returned in pairs of integers, starting at the  beginning  of  ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2153         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
2154         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
2155         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
2156         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
2157         tor[1],  identify  the  portion  of  the  subject string matched by the         byte offsets, even in UTF-8 mode. They are not character counts.
2158         entire pattern. The next pair is used for the first  capturing  subpat-  
2159         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
2160         highest numbered pair that has been set. For example, if two substrings         portion  of  the subject string matched by the entire pattern. The next
2161         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
2162         subpatterns, the return value from a successful match is 1,  indicating         returned by pcre_exec() is one more than the highest numbered pair that
2163         that just the first pair of offsets has been set.         has been set.  For example, if two substrings have been  captured,  the
2164           returned  value is 3. If there are no capturing subpatterns, the return
2165           value from a successful match is 1, indicating that just the first pair
2166           of offsets has been set.
2167    
2168         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2169         of the string that it matched that is returned.         of the string that it matched that is returned.
2170    
2171         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,
2172         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
2173         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
2174         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
2175         as NULL and ovecsize as zero. However, if  the  pattern  contains  back         ovecsize as zero. However, if the pattern contains back references  and
2176         references  and  the  ovector is not big enough to remember the related         the  ovector is not big enough to remember the related substrings, PCRE
2177         substrings, PCRE has to get additional memory for use during  matching.         has to get additional memory for use during matching. Thus it  is  usu-
2178         Thus it is usually advisable to supply an ovector.         ally advisable to supply an ovector.
2179    
2180         The  pcre_info()  function  can  be used to find out how many capturing         The  pcre_info()  function  can  be used to find out how many capturing
2181         subpatterns there are in a compiled  pattern.  The  smallest  size  for         subpatterns there are in a compiled  pattern.  The  smallest  size  for
# Line 1966  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2276  MATCHING A PATTERN: THE TRADITIONAL FUNC
2276    
2277           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2278    
2279         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing         This code is no longer in  use.  It  was  formerly  returned  when  the
2280         items  that are not supported for partial matching. See the pcrepartial         PCRE_PARTIAL  option  was used with a compiled pattern containing items
2281         documentation for details of partial matching.         that were  not  supported  for  partial  matching.  From  release  8.00
2282           onwards, there are no restrictions on partial matching.
2283    
2284           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2285    
2286         An unexpected internal error has occurred. This error could  be  caused         An  unexpected  internal error has occurred. This error could be caused
2287         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2288    
2289           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2290    
2291         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.
2292    
2293           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2294    
# Line 1985  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2296  MATCHING A PATTERN: THE TRADITIONAL FUNC
2296         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2297         description above.         description above.
2298    
          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.  
   
2299           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
2300    
2301         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2302    
2303         Error numbers -16 to -20 are not used by pcre_exec().         Error numbers -16 to -20 and -22 are not used by pcre_exec().
2304    
2305    
2306  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
# Line 2132  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2435  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2435    
2436         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These  functions call pcre_get_stringnumber(), and if it succeeds, they
2437         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-
2438         ate.         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the
2439           behaviour may not be what you want (see the next section).
2440    
2441           Warning: If the pattern uses the "(?|" feature to set up multiple  sub-
2442           patterns  with  the  same  number,  you cannot use names to distinguish
2443           them, because names are not included in the compiled code. The matching
2444           process uses only numbers.
2445    
2446    
2447  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
# Line 2144  DUPLICATE SUBPATTERN NAMES Line 2453  DUPLICATE SUBPATTERN NAMES
2453         subpatterns are not required to  be  unique.  Normally,  patterns  with         subpatterns are not required to  be  unique.  Normally,  patterns  with
2454         duplicate  names  are such that in any one match, only one of the named         duplicate  names  are such that in any one match, only one of the named
2455         subpatterns participates. An example is shown in the pcrepattern  docu-         subpatterns participates. An example is shown in the pcrepattern  docu-
2456         mentation. When duplicates are present, pcre_copy_named_substring() and         mentation.
2457    
2458           When    duplicates   are   present,   pcre_copy_named_substring()   and
2459         pcre_get_named_substring() return the first substring corresponding  to         pcre_get_named_substring() return the first substring corresponding  to
2460         the  given  name  that  is  set.  If  none  are set, an empty string is         the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2461         returned.  The pcre_get_stringnumber() function returns one of the num-         (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2462         bers  that are associated with the name, but it is not defined which it         function  returns one of the numbers that are associated with the name,
2463         is.         but it is not defined which it is.
2464    
2465         If you want to get full details of all captured substrings for a  given         If you want to get full details of all captured substrings for a  given
2466         name,  you  must  use  the pcre_get_stringtable_entries() function. The         name,  you  must  use  the pcre_get_stringtable_entries() function. The
# Line 2195  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2506  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2506         characteristics to the normal algorithm, and  is  not  compatible  with         characteristics to the normal algorithm, and  is  not  compatible  with
2507         Perl.  Some  of the features of PCRE patterns are not supported. Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2508         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
2509         a discussion of the two matching algorithms, see the pcrematching docu-         a  discussion  of  the  two matching algorithms, and a list of features
2510         mentation.         that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2511           tion.
2512    
2513         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
2514         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-
2515         ent way, and this is described below. The other  common  arguments  are         ent  way,  and  this is described below. The other common arguments are
2516         used  in  the  same way as for pcre_exec(), so their description is not         used in the same way as for pcre_exec(), so their  description  is  not
2517         repeated here.         repeated here.
2518    
2519         The two additional arguments provide workspace for  the  function.  The         The  two  additional  arguments provide workspace for the function. The
2520         workspace  vector  should  contain at least 20 elements. It is used for         workspace vector should contain at least 20 elements. It  is  used  for
2521         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2522         workspace  will  be  needed for patterns and subjects where there are a         workspace will be needed for patterns and subjects where  there  are  a
2523         lot of potential matches.         lot of potential matches.
2524    
2525         Here is an example of a simple call to pcre_dfa_exec():         Here is an example of a simple call to pcre_dfa_exec():
# Line 2229  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2541  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2541    
2542     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2543    
2544         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
2545         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-
2546         LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,  PCRE_NO_UTF8_CHECK,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2547         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last         PCRE_NOTEMPTY_ATSTART, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PAR-
2548         three of these are the same as for pcre_exec(), so their description is         TIAL_SOFT,  PCRE_DFA_SHORTEST,  and  PCRE_DFA_RESTART. All but the last
2549         not repeated here.         four of these are  exactly  the  same  as  for  pcre_exec(),  so  their
2550           description is not repeated here.
2551           PCRE_PARTIAL  
2552             PCRE_PARTIAL_HARD
2553         This  has  the  same general effect as it does for pcre_exec(), but the           PCRE_PARTIAL_SOFT
2554         details  are  slightly  different.  When  PCRE_PARTIAL   is   set   for  
2555         pcre_dfa_exec(),  the  return code PCRE_ERROR_NOMATCH is converted into         These  have the same general effect as they do for pcre_exec(), but the
2556         PCRE_ERROR_PARTIAL if the end of the subject  is  reached,  there  have         details are slightly  different.  When  PCRE_PARTIAL_HARD  is  set  for
2557         been no complete matches, but there is still at least one matching pos-         pcre_dfa_exec(),  it  returns PCRE_ERROR_PARTIAL if the end of the sub-
2558         sibility. The portion of the string that provided the partial match  is         ject is reached and there is still at least  one  matching  possibility
2559         set as the first matching string.         that requires additional characters. This happens even if some complete
2560           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2561           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2562           of the subject is reached, there have been  no  complete  matches,  but
2563           there  is  still  at least one matching possibility. The portion of the
2564           string that was inspected when the longest partial match was  found  is
2565           set as the first matching string in both cases.
2566    
2567           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2568    
# Line 2255  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2573  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2573    
2574           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2575    
2576         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
2577         returns  a  partial  match, it is possible to call it again, with addi-         again,  with  additional  subject characters, and have it continue with
2578         tional subject characters, and have it continue with  the  same  match.         the same match. The PCRE_DFA_RESTART option requests this action;  when
2579         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
2580         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
2581         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
2582         match. There is more discussion of this  facility  in  the  pcrepartial         pcrepartial documentation.
        documentation.  
2583    
2584     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2585    
2586         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-
2587         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
2588         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
2589         matches are all initial substrings of the longer matches. For  example,         matches  are all initial substrings of the longer matches. For example,
2590         if the pattern         if the pattern
2591    
2592           <.*>           <.*>
# Line 2284  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2601  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2601           <something> <something else>           <something> <something else>
2602           <something> <something else> <something further>           <something> <something else> <something further>
2603    
2604         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,
2605         which is the number of matched substrings.  The  substrings  themselves         which  is  the  number of matched substrings. The substrings themselves
2606         are  returned  in  ovector. Each string uses two elements; the first is         are returned in ovector. Each string uses two elements;  the  first  is
2607         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
2608         fact,  all  the  strings  have the same start offset. (Space could have         fact, all the strings have the same start  offset.  (Space  could  have
2609         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
2610         compatibility  with  the  way pcre_exec() returns data, even though the         compatibility with the way pcre_exec() returns data,  even  though  the
2611         meaning of the strings is different.)         meaning of the strings is different.)
2612    
2613         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-
2614         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
2615         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
2616         filled with the longest matches.         filled with the longest matches.
2617    
2618     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2619    
2620         The  pcre_dfa_exec()  function returns a negative number when it fails.         The pcre_dfa_exec() function returns a negative number when  it  fails.
2621         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
2622         described  above.   There are in addition the following errors that are         described above.  There are in addition the following errors  that  are
2623         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2624    
2625           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2626    
2627         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-
2628         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
2629         reference.         reference.
2630    
2631           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2632    
2633         This return is given if pcre_dfa_exec()  encounters  a  condition  item         This  return  is  given  if pcre_dfa_exec() encounters a condition item
2634         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
2635         in a specific group. These are not supported.         in a specific group. These are not supported.
2636    
2637           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2638    
2639         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
2640         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
2641         (it is meaningless).         (it is meaningless).
2642    
2643           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2644    
2645         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
2646         workspace vector.         workspace vector.
2647    
2648           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2649    
2650         When  a  recursive subpattern is processed, the matching function calls         When a recursive subpattern is processed, the matching  function  calls
2651         itself recursively, using private vectors for  ovector  and  workspace.         itself  recursively,  using  private vectors for ovector and workspace.
2652         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
2653         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2654    
2655    
2656  SEE ALSO  SEE ALSO
2657    
2658         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-
2659         tial(3),  pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2660    
2661    
2662  AUTHOR  AUTHOR
# Line 2351  AUTHOR Line 2668  AUTHOR
2668    
2669  REVISION  REVISION
2670    
2671         Last updated: 06 March 2007         Last updated: 22 September 2009
2672         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
2673  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2674    
2675    
2676  PCRECALLOUT(3)                                                  PCRECALLOUT(3)  PCRECALLOUT(3)                                                  PCRECALLOUT(3)
2677    
2678    
# Line 2379  PCRE CALLOUTS Line 2696  PCRE CALLOUTS
2696         default value is zero.  For  example,  this  pattern  has  two  callout         default value is zero.  For  example,  this  pattern  has  two  callout
2697         points:         points:
2698    
2699           (?C1)eabc(?C2)def           (?C1)abc(?C2)def
2700    
2701         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() is
2702         called, PCRE automatically  inserts  callouts,  all  with  number  255,         called, PCRE automatically  inserts  callouts,  all  with  number  255,
# Line 2403  PCRE CALLOUTS Line 2720  PCRE CALLOUTS
2720  MISSING CALLOUTS  MISSING CALLOUTS
2721    
2722         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
2723         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
2724         pattern is         example, if the pattern is
2725    
2726           ab(?C4)cd           ab(?C4)cd
2727    
# Line 2413  MISSING CALLOUTS Line 2730  MISSING CALLOUTS
2730         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
2731         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
2732    
2733           You can disable these optimizations by passing the  PCRE_NO_START_OPTI-
2734           MIZE  option  to  pcre_exec()  or  pcre_dfa_exec(). This slows down the
2735           matching process, but does ensure that callouts  such  as  the  example
2736           above are obeyed.
2737    
2738    
2739  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2740    
2741         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
2742         tion  defined by pcre_callout is called (if it is set). This applies to         tion defined by pcre_callout is called (if it is set). This applies  to
2743         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
2744         only  argument  to  the callout function is a pointer to a pcre_callout         only argument to the callout function is a pointer  to  a  pcre_callout
2745         block. This structure contains the following fields:         block. This structure contains the following fields:
2746    
2747           int          version;           int          version;
# Line 2435  THE CALLOUT INTERFACE Line 2757  THE CALLOUT INTERFACE
2757           int          pattern_position;           int          pattern_position;
2758           int          next_item_length;           int          next_item_length;
2759    
2760         The version field is an integer containing the version  number  of  the         The  version  field  is an integer containing the version number of the
2761         block  format. The initial version was 0; the current version is 1. The         block format. The initial version was 0; the current version is 1.  The
2762         version number will change again in future  if  additional  fields  are         version  number  will  change  again in future if additional fields are
2763         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.
2764    
2765         The callout_number field contains the number of the  callout,  as  com-         The callout_number field contains the number of the  callout,  as  com-
# Line 2454  THE CALLOUT INTERFACE Line 2776  THE CALLOUT INTERFACE
2776         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
2777         were passed to pcre_exec().         were passed to pcre_exec().
2778    
2779         The start_match field contains the offset within the subject  at  which         The start_match field normally contains the offset within  the  subject
2780         the  current match attempt started. If the pattern is not anchored, the         at  which  the  current  match  attempt started. However, if the escape
2781         callout function may be called several times from the same point in the         sequence \K has been encountered, this value is changed to reflect  the
2782         pattern for different starting points in the subject.         modified  starting  point.  If the pattern is not anchored, the callout
2783           function may be called several times from the same point in the pattern
2784           for different starting points in the subject.
2785    
2786         The  current_position  field  contains the offset within the subject of         The  current_position  field  contains the offset within the subject of
2787         the current match pointer.         the current match pointer.
# Line 2520  AUTHOR Line 2844  AUTHOR
2844    
2845  REVISION  REVISION
2846    
2847         Last updated: 06 March 2007         Last updated: 15 March 2009
2848         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
2849  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2850    
2851    
2852  PCRECOMPAT(3)                                                    PCRECOMPAT(3)  PCRECOMPAT(3)                                                    PCRECOMPAT(3)
2853    
2854    
# Line 2536  DIFFERENCES BETWEEN PCRE AND PERL Line 2860  DIFFERENCES BETWEEN PCRE AND PERL
2860    
2861         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
2862         handle regular expressions. The differences described here  are  mainly         handle regular expressions. The differences described here  are  mainly
2863         with  respect  to  Perl 5.8, though PCRE version 7.0 contains some fea-         with  respect  to  Perl 5.8, though PCRE versions 7.0 and later contain
2864         tures that are expected to be in the forthcoming Perl 5.10.         some features that are in Perl 5.10.
2865    
2866         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
2867         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
# Line 2569  DIFFERENCES BETWEEN PCRE AND PERL Line 2893  DIFFERENCES BETWEEN PCRE AND PERL
2893         is  built  with Unicode character property support. The properties that         is  built  with Unicode character property support. The properties that
2894         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-
2895         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
2896         derived properties Any and L&.         derived properties Any and L&. PCRE does  support  the  Cs  (surrogate)
2897           property,  which  Perl  does  not; the Perl documentation says "Because
2898           Perl hides the need for the user to understand the internal representa-
2899           tion  of Unicode characters, there is no need to implement the somewhat
2900           messy concept of surrogates."
2901    
2902         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-
2903         ters  in  between  are  treated as literals. This is slightly different         ters  in  between  are  treated as literals. This is slightly different
# Line 2589  DIFFERENCES BETWEEN PCRE AND PERL Line 2917  DIFFERENCES BETWEEN PCRE AND PERL
2917    
2918         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
2919         constructions. However, there is support for recursive  patterns.  This         constructions. However, there is support for recursive  patterns.  This
2920         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
2921         "callout" feature allows an external function to be called during  pat-         "callout" feature allows an external function to be called during  pat-
2922         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
2923    
2924         9.  Subpatterns  that  are  called  recursively or as "subroutines" are         9.  Subpatterns  that  are  called  recursively or as "subroutines" are
2925         always treated as atomic groups in  PCRE.  This  is  like  Python,  but         always treated as atomic groups in  PCRE.  This  is  like  Python,  but
2926         unlike Perl.         unlike  Perl. There is a discussion of an example that explains this in
2927           more detail in the section on recursion differences from  Perl  in  the
2928           pcrecompat page.
2929    
2930         10.  There are some differences that are concerned with the settings of         10.  There are some differences that are concerned with the settings of
2931         captured strings when part of  a  pattern  is  repeated.  For  example,         captured strings when part of  a  pattern  is  repeated.  For  example,
2932         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
2933         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
2934    
2935         11. PCRE provides some extensions to the Perl regular expression facil-         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),
2936           (*FAIL),  (*F),  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in
2937           the forms without an argument. PCRE does not support (*MARK).
2938    
2939           12. PCRE provides some extensions to the Perl regular expression facil-
2940         ities.   Perl  5.10  will  include new features that are not in earlier         ities.   Perl  5.10  will  include new features that are not in earlier
2941         versions, some of which (such as named parentheses) have been  in  PCRE         versions, some of which (such as named parentheses) have been  in  PCRE
2942         for some time. This list is with respect to Perl 5.10:         for some time. This list is with respect to Perl 5.10:
# Line 2615  DIFFERENCES BETWEEN PCRE AND PERL Line 2949  DIFFERENCES BETWEEN PCRE AND PERL
2949         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
2950    
2951         (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-
2952         cial  meaning  is  faulted.  Otherwise,  like  Perl,  the  backslash is         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
2953         ignored. (Perl can be made to issue a warning.)         ignored.  (Perl can be made to issue a warning.)
2954    
2955         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-
2956         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 2625  DIFFERENCES BETWEEN PCRE AND PERL Line 2959  DIFFERENCES BETWEEN PCRE AND PERL
2959         (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
2960         tried only at the first matching position in the subject string.         tried only at the first matching position in the subject string.
2961    
2962         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
2963         TURE options for pcre_exec() have no Perl equivalents.         and PCRE_NO_AUTO_CAPTURE options for pcre_exec() have no  Perl  equiva-
2964           lents.
2965    
2966           (g)  The  \R escape sequence can be restricted to match only CR, LF, or
2967           CRLF by the PCRE_BSR_ANYCRLF option.
2968    
2969         (g) The callout facility is PCRE-specific.         (h) The callout facility is PCRE-specific.
2970    
2971         (h) The partial matching facility is PCRE-specific.         (i) The partial matching facility is PCRE-specific.
2972    
2973         (i) Patterns compiled by PCRE can be saved and re-used at a later time,         (j) Patterns compiled by PCRE can be saved and re-used at a later time,
2974         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
2975    
2976         (j)  The  alternative  matching function (pcre_dfa_exec()) matches in a         (k)  The  alternative  matching function (pcre_dfa_exec()) matches in a
2977         different way and is not Perl-compatible.         different way and is not Perl-compatible.
2978    
2979           (l) PCRE recognizes some special sequences such as (*CR) at  the  start
2980           of a pattern that set overall options that cannot be changed within the
2981           pattern.
2982    
2983    
2984  AUTHOR  AUTHOR
2985    
# Line 2648  AUTHOR Line 2990  AUTHOR
2990    
2991  REVISION  REVISION
2992    
2993         Last updated: 06 March 2007         Last updated: 18 September 2009
2994         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
2995  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2996    
2997    
2998  PCREPATTERN(3)                                                  PCREPATTERN(3)  PCREPATTERN(3)                                                  PCREPATTERN(3)
2999    
3000    
# Line 2662  NAME Line 3004  NAME
3004    
3005  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
3006    
3007         The  syntax  and semantics of the regular expressions supported by PCRE         The  syntax and semantics of the regular expressions that are supported
3008         are described below. Regular expressions are also described in the Perl         by PCRE are described in detail below. There is a quick-reference  syn-
3009         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
3010         examples.  Jeffrey Friedl's "Mastering Regular Expressions",  published         semantics as closely as it can. PCRE  also  supports  some  alternative
3011         by  O'Reilly, covers regular expressions in great detail. This descrip-         regular  expression  syntax (which does not conflict with the Perl syn-
3012         tion of PCRE's regular expressions is intended as reference material.         tax) in order to provide some compatibility with regular expressions in
3013           Python, .NET, and Oniguruma.
3014    
3015           Perl's  regular expressions are described in its own documentation, and
3016           regular expressions in general are covered in a number of  books,  some
3017           of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
3018           Expressions", published by  O'Reilly,  covers  regular  expressions  in
3019           great  detail.  This  description  of  PCRE's  regular  expressions  is
3020           intended as reference material.
3021    
3022         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
3023         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
3024         this, you must build PCRE to  include  UTF-8  support,  and  then  call         this, you must build PCRE to  include  UTF-8  support,  and  then  call
3025         pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern         pcre_compile()  with  the  PCRE_UTF8  option.  There  is also a special
3026         matching is mentioned in several places below. There is also a  summary         sequence that can be given at the start of a pattern:
3027         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre  
3028         page.           (*UTF8)
3029    
3030           Starting a pattern with this sequence  is  equivalent  to  setting  the
3031           PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3032           UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3033           below.  There  is  also  a  summary of UTF-8 features in the section on
3034           UTF-8 support in the main pcre page.
3035    
3036         The remainder of this document discusses the  patterns  that  are  sup-         The remainder of this document discusses the  patterns  that  are  sup-
3037         ported  by  PCRE when its main matching function, pcre_exec(), is used.         ported  by  PCRE when its main matching function, pcre_exec(), is used.
3038         From  release  6.0,   PCRE   offers   a   second   matching   function,         From  release  6.0,   PCRE   offers   a   second   matching   function,
3039         pcre_dfa_exec(),  which matches using a different algorithm that is not         pcre_dfa_exec(),  which matches using a different algorithm that is not
3040         Perl-compatible. The advantages and disadvantages  of  the  alternative         Perl-compatible. Some of the features discussed below are not available
3041         function, and how it differs from the normal function, are discussed in         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the
3042         the pcrematching page.         alternative function, and how it differs from the normal function,  are
3043           discussed in the pcrematching page.
3044    
3045    
3046    NEWLINE CONVENTIONS
3047    
3048           PCRE  supports five different conventions for indicating line breaks in
3049           strings: a single CR (carriage return) character, a  single  LF  (line-
3050           feed) character, the two-character sequence CRLF, any of the three pre-
3051           ceding, or any Unicode newline sequence. The pcreapi page  has  further
3052           discussion  about newlines, and shows how to set the newline convention
3053           in the options arguments for the compiling and matching functions.
3054    
3055           It is also possible to specify a newline convention by starting a  pat-
3056           tern string with one of the following five sequences:
3057    
3058             (*CR)        carriage return
3059             (*LF)        linefeed
3060             (*CRLF)      carriage return, followed by linefeed
3061             (*ANYCRLF)   any of the three above
3062             (*ANY)       all Unicode newline sequences
3063    
3064           These override the default and the options given to pcre_compile(). For
3065           example, on a Unix system where LF is the default newline sequence, the
3066           pattern
3067    
3068             (*CR)a.b
3069    
3070           changes the convention to CR. That pattern matches "a\nb" because LF is
3071           no longer a newline. Note that these special settings,  which  are  not
3072           Perl-compatible,  are  recognized  only at the very start of a pattern,
3073           and that they must be in upper case.  If  more  than  one  of  them  is
3074           present, the last one is used.
3075    
3076           The  newline  convention  does  not  affect what the \R escape sequence
3077           matches. By default, this is any Unicode  newline  sequence,  for  Perl
3078           compatibility.  However, this can be changed; see the description of \R
3079           in the section entitled "Newline sequences" below. A change of \R  set-
3080           ting can be combined with a change of newline convention.
3081    
3082    
3083  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
3084    
3085         A regular expression is a pattern that is  matched  against  a  subject         A  regular  expression  is  a pattern that is matched against a subject
3086         string  from  left  to right. Most characters stand for themselves in a         string from left to right. Most characters stand for  themselves  in  a
3087         pattern, and match the corresponding characters in the  subject.  As  a         pattern,  and  match  the corresponding characters in the subject. As a
3088         trivial example, the pattern         trivial example, the pattern
3089    
3090           The quick brown fox           The quick brown fox
3091    
3092         matches a portion of a subject string that is identical to itself. When         matches a portion of a subject string that is identical to itself. When
3093         caseless matching is specified (the PCRE_CASELESS option), letters  are         caseless  matching is specified (the PCRE_CASELESS option), letters are
3094         matched  independently  of case. In UTF-8 mode, PCRE always understands         matched independently of case. In UTF-8 mode, PCRE  always  understands
3095         the concept of case for characters whose values are less than  128,  so         the  concept  of case for characters whose values are less than 128, so
3096         caseless  matching  is always possible. For characters with higher val-         caseless matching is always possible. For characters with  higher  val-
3097         ues, the concept of case is supported if PCRE is compiled with  Unicode         ues,  the concept of case is supported if PCRE is compiled with Unicode
3098         property  support,  but  not  otherwise.   If  you want to use caseless         property support, but not otherwise.   If  you  want  to  use  caseless
3099         matching for characters 128 and above, you must  ensure  that  PCRE  is         matching  for  characters  128  and above, you must ensure that PCRE is
3100         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
3101    
3102         The  power  of  regular  expressions  comes from the ability to include         The power of regular expressions comes  from  the  ability  to  include
3103         alternatives and repetitions in the pattern. These are encoded  in  the         alternatives  and  repetitions in the pattern. These are encoded in the
3104         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
3105         but instead are interpreted in some special way.         but instead are interpreted in some special way.
3106    
3107         There are two different sets of metacharacters: those that  are  recog-         There  are  two different sets of metacharacters: those that are recog-
3108         nized  anywhere in the pattern except within square brackets, and those         nized anywhere in the pattern except within square brackets, and  those
3109         that are recognized within square brackets.  Outside  square  brackets,         that  are  recognized  within square brackets. Outside square brackets,
3110         the metacharacters are as follows:         the metacharacters are as follows:
3111    
3112           \      general escape character with several uses           \      general escape character with several uses
# Line 2731  CHARACTERS AND METACHARACTERS Line 3125  CHARACTERS AND METACHARACTERS
3125                  also "possessive quantifier"                  also "possessive quantifier"
3126           {      start min/max quantifier           {      start min/max quantifier
3127    
3128         Part  of  a  pattern  that is in square brackets is called a "character         Part of a pattern that is in square brackets  is  called  a  "character
3129         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
3130    
3131           \      general escape character           \      general escape character
# Line 2741  CHARACTERS AND METACHARACTERS Line 3135  CHARACTERS AND METACHARACTERS
3135                    syntax)                    syntax)
3136           ]      terminates the character class           ]      terminates the character class
3137    
3138         The following sections describe the use of each of the  metacharacters.         The following sections describe the use of each of the metacharacters.
3139    
3140    
3141  BACKSLASH  BACKSLASH
# Line 2793  BACKSLASH Line 3187  BACKSLASH
3187           \cx       "control-x", where x is any character           \cx       "control-x", where x is any character
3188           \e        escape (hex 1B)           \e        escape (hex 1B)
3189           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3190           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3191           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3192           \t        tab (hex 09)           \t        tab (hex 09)
3193           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or backreference
# Line 2808  BACKSLASH Line 3202  BACKSLASH
3202         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
3203         in  upper  or  lower case). Any number of hexadecimal digits may appear         in  upper  or  lower case). Any number of hexadecimal digits may appear
3204         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
3205         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,
3206         the maximum hexadecimal value is 7FFFFFFF). If  characters  other  than         the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger
3207         hexadecimal  digits  appear between \x{ and }, or if there is no termi-         than the largest Unicode code point, which is 10FFFF.
3208         nating }, this form of escape is not recognized.  Instead, the  initial  
3209         \x will be interpreted as a basic hexadecimal escape, with no following         If  characters  other than hexadecimal digits appear between \x{ and },
3210         digits, giving a character whose value is zero.         or if there is no terminating }, this form of escape is not recognized.
3211           Instead,  the  initial  \x  will  be interpreted as a basic hexadecimal
3212           escape, with no following digits, giving a  character  whose  value  is
3213           zero.
3214    
3215         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
3216         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-
3217         dled. For example, \xdc is exactly the same as \x{dc}.         dled. For example, \xdc is exactly the same as \x{dc}.
3218    
3219         After \0 up to two further octal digits are read. If  there  are  fewer         After  \0  up  to two further octal digits are read. If there are fewer
3220         than  two  digits,  just  those  that  are  present  are used. Thus the         than two digits, just  those  that  are  present  are  used.  Thus  the
3221         sequence \0\x\07 specifies two binary zeros followed by a BEL character         sequence \0\x\07 specifies two binary zeros followed by a BEL character
3222         (code  value 7). Make sure you supply two digits after the initial zero         (code value 7). Make sure you supply two digits after the initial  zero
3223         if the pattern character that follows is itself an octal digit.         if the pattern character that follows is itself an octal digit.
3224    
3225         The handling of a backslash followed by a digit other than 0 is compli-         The handling of a backslash followed by a digit other than 0 is compli-
3226         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
3227         its as a decimal number. If the number is less than  10,  or  if  there         its  as  a  decimal  number. If the number is less than 10, or if there
3228         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
3229         expression, the entire  sequence  is  taken  as  a  back  reference.  A         expression,  the  entire  sequence  is  taken  as  a  back reference. A
3230         description  of how this works is given later, following the discussion         description of how this works is given later, following the  discussion
3231         of parenthesized subpatterns.         of parenthesized subpatterns.
3232    
3233         Inside a character class, or if the decimal number is  greater  than  9         Inside  a  character  class, or if the decimal number is greater than 9
3234         and  there have not been that many capturing subpatterns, PCRE re-reads         and there have not been that many capturing subpatterns, PCRE  re-reads
3235         up to three octal digits following the backslash, and uses them to gen-         up to three octal digits following the backslash, and uses them to gen-
3236         erate  a data character. Any subsequent digits stand for themselves. In         erate a data character. Any subsequent digits stand for themselves.  In
3237         non-UTF-8 mode, the value of a character specified  in  octal  must  be         non-UTF-8  mode,  the  value  of a character specified in octal must be
3238         less  than  \400.  In  UTF-8 mode, values up to \777 are permitted. For         less than \400. In UTF-8 mode, values up to  \777  are  permitted.  For
3239         example:         example:
3240    
3241           \040   is another way of writing a space           \040   is another way of writing a space
# Line 2856  BACKSLASH Line 3253  BACKSLASH
3253           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
3254                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
3255    
3256         Note that octal values of 100 or greater must not be  introduced  by  a         Note  that  octal  values of 100 or greater must not be introduced by a
3257         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
3258    
3259         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
3260         inside and outside character classes. In addition, inside  a  character         inside  and  outside character classes. In addition, inside a character
3261         class,  the  sequence \b is interpreted as the backspace character (hex         class, the sequence \b is interpreted as the backspace  character  (hex
3262         08), and the sequences \R and \X are interpreted as the characters  "R"         08),  and the sequences \R and \X are interpreted as the characters "R"
3263         and  "X", respectively. Outside a character class, these sequences have         and "X", respectively. Outside a character class, these sequences  have
3264         different meanings (see below).         different meanings (see below).
3265    
3266     Absolute and relative back references     Absolute and relative back references
3267    
3268         The sequence \g followed by a positive or negative  number,  optionally         The  sequence  \g followed by an unsigned or a negative number, option-
3269         enclosed  in  braces,  is  an absolute or relative back reference. Back         ally enclosed in braces, is an absolute or relative back  reference.  A
3270         references are discussed later, following the discussion  of  parenthe-         named back reference can be coded as \g{name}. Back references are dis-
3271         sized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3272    
3273       Absolute and relative subroutine calls
3274    
3275           For compatibility with Oniguruma, the non-Perl syntax \g followed by  a
3276           name or a number enclosed either in angle brackets or single quotes, is
3277           an alternative syntax for referencing a subpattern as  a  "subroutine".
3278           Details  are  discussed  later.   Note  that  \g{...} (Perl syntax) and
3279           \g<...> (Oniguruma syntax) are not synonymous. The  former  is  a  back
3280           reference; the latter is a subroutine call.
3281    
3282     Generic character types     Generic character types
3283    
# Line 2880  BACKSLASH Line 3286  BACKSLASH
3286    
3287           \d     any decimal digit           \d     any decimal digit
3288           \D     any character that is not a decimal digit           \D     any character that is not a decimal digit
3289             \h     any horizontal whitespace character
3290             \H     any character that is not a horizontal whitespace character
3291           \s     any whitespace character           \s     any whitespace character
3292           \S     any character that is not a whitespace character           \S     any character that is not a whitespace character
3293             \v     any vertical whitespace character
3294             \V     any character that is not a vertical whitespace character
3295           \w     any "word" character           \w     any "word" character
3296           \W     any "non-word" character           \W     any "non-word" character
3297    
# Line 2896  BACKSLASH Line 3306  BACKSLASH
3306    
3307         For  compatibility  with Perl, \s does not match the VT character (code         For  compatibility  with Perl, \s does not match the VT character (code
3308         11).  This makes it different from the the POSIX "space" class. The  \s         11).  This makes it different from the the POSIX "space" class. The  \s
3309         characters  are  HT (9), LF (10), FF (12), CR (13), and space (32). (If         characters  are  HT  (9), LF (10), FF (12), CR (13), and space (32). If
3310         "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-
3311         ter. In PCRE, it never does.)         ter. In PCRE, it never does.
   
        A "word" character is an underscore or any character less than 256 that  
        is a letter or digit. The definition of  letters  and  digits  is  con-  
        trolled  by PCRE's low-valued character tables, and may vary if locale-  
        specific matching is taking place (see "Locale support" in the  pcreapi  
        page).  For  example,  in  the  "fr_FR" (French) locale, some character  
        codes greater than 128 are used for accented  letters,  and  these  are  
        matched by \w.  
3312    
3313         In  UTF-8 mode, characters with values greater than 128 never match \d,         In  UTF-8 mode, characters with values greater than 128 never match \d,
3314         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-
3315         code  character  property support is available. The use of locales with         code  character  property  support is available. These sequences retain
3316         Unicode is discouraged.         their original meanings from before UTF-8 support was available, mainly
3317           for  efficiency  reasons. Note that this also affects \b, because it is
3318           defined in terms of \w and \W.
3319    
3320           The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to
3321           the  other  sequences, these do match certain high-valued codepoints in
3322           UTF-8 mode.  The horizontal space characters are:
3323    
3324             U+0009     Horizontal tab
3325             U+0020     Space
3326             U+00A0     Non-break space
3327             U+1680     Ogham space mark
3328             U+180E     Mongolian vowel separator
3329             U+2000     En quad
3330             U+2001     Em quad
3331             U+2002     En space
3332             U+2003     Em space
3333             U+2004     Three-per-em space
3334             U+2005     Four-per-em space
3335             U+2006     Six-per-em space
3336             U+2007     Figure space
3337             U+2008     Punctuation space
3338             U+2009     Thin space
3339             U+200A     Hair space
3340             U+202F     Narrow no-break space
3341             U+205F     Medium mathematical space
3342             U+3000     Ideographic space
3343    
3344           The vertical space characters are:
3345    
3346             U+000A     Linefeed
3347             U+000B     Vertical tab
3348             U+000C     Formfeed
3349             U+000D     Carriage return
3350             U+0085     Next line
3351             U+2028     Line separator
3352             U+2029     Paragraph separator
3353    
3354           A "word" character is an underscore or any character less than 256 that
3355           is  a  letter  or  digit.  The definition of letters and digits is con-
3356           trolled by PCRE's low-valued character tables, and may vary if  locale-
3357           specific  matching is taking place (see "Locale support" in the pcreapi
3358           page). For example, in a French locale such  as  "fr_FR"  in  Unix-like
3359           systems,  or "french" in Windows, some character codes greater than 128
3360           are used for accented letters, and these are matched by \w. The use  of
3361           locales with Unicode is discouraged.
3362    
3363     Newline sequences     Newline sequences
3364    
3365         Outside a character class, the escape sequence \R matches  any  Unicode         Outside  a  character class, by default, the escape sequence \R matches
3366         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
3367         equivalent to the following:         mode \R is equivalent to the following:
3368    
3369           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3370    
3371         This is an example of an "atomic group", details  of  which  are  given         This  is  an  example  of an "atomic group", details of which are given
3372         below.  This particular group matches either the two-character sequence         below.  This particular group matches either the two-character sequence
3373         CR followed by LF, or  one  of  the  single  characters  LF  (linefeed,         CR  followed  by  LF,  or  one  of  the single characters LF (linefeed,
3374         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage
3375         return, U+000D), or NEL (next line, U+0085). The two-character sequence         return, U+000D), or NEL (next line, U+0085). The two-character sequence
3376         is treated as a single unit that cannot be split.         is treated as a single unit that cannot be split.
3377    
3378         In  UTF-8  mode, two additional characters whose codepoints are greater         In UTF-8 mode, two additional characters whose codepoints  are  greater
3379         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
3380         rator,  U+2029).   Unicode character property support is not needed for         rator, U+2029).  Unicode character property support is not  needed  for
3381         these characters to be recognized.         these characters to be recognized.
3382    
3383           It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3384           the complete set  of  Unicode  line  endings)  by  setting  the  option
3385           PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3386           (BSR is an abbrevation for "backslash R".) This can be made the default
3387           when  PCRE  is  built;  if this is the case, the other behaviour can be
3388           requested via the PCRE_BSR_UNICODE option.   It  is  also  possible  to
3389           specify  these  settings  by  starting a pattern string with one of the
3390           following sequences:
3391    
3392             (*BSR_ANYCRLF)   CR, LF, or CRLF only
3393             (*BSR_UNICODE)   any Unicode newline sequence
3394    
3395           These override the default and the options given to pcre_compile(), but
3396           they can be overridden by options given to pcre_exec(). Note that these
3397           special settings, which are not Perl-compatible, are recognized only at
3398           the  very  start  of a pattern, and that they must be in upper case. If
3399           more than one of them is present, the last one is  used.  They  can  be
3400           combined  with  a  change of newline convention, for example, a pattern
3401           can start with:
3402    
3403             (*ANY)(*BSR_ANYCRLF)
3404    
3405         Inside a character class, \R matches the letter "R".         Inside a character class, \R matches the letter "R".
3406    
3407     Unicode character properties     Unicode character properties
3408    
3409         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
3410         tional  escape  sequences  to  match character properties are available         tional  escape sequences that match characters with specific properties
3411         when UTF-8 mode is selected. They are:         are available.  When not in UTF-8 mode, these sequences are  of  course
3412           limited  to  testing characters whose codepoints are less than 256, but
3413           they do work in this mode.  The extra escape sequences are:
3414    
3415           \p{xx}   a character with the xx property           \p{xx}   a character with the xx property
3416           \P{xx}   a character without the xx property           \P{xx}   a character without the xx property
# Line 3034  BACKSLASH Line 3505  BACKSLASH
3505         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
3506         classified as a modifier or "other".         classified as a modifier or "other".
3507    
3508         The  long  synonyms  for  these  properties that Perl supports (such as         The  Cs  (Surrogate)  property  applies only to characters in the range
3509           U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see
3510           RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
3511           ing has been turned off (see the discussion  of  PCRE_NO_UTF8_CHECK  in
3512           the pcreapi page). Perl does not support the Cs property.
3513    
3514           The  long  synonyms  for  property  names  that  Perl supports (such as
3515         \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix         \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix
3516         any of these properties with "Is".         any of these properties with "Is".
3517    
# Line 3053  BACKSLASH Line 3530  BACKSLASH
3530         That  is,  it matches a character without the "mark" property, followed         That  is,  it matches a character without the "mark" property, followed
3531         by zero or more characters with the "mark"  property,  and  treats  the         by zero or more characters with the "mark"  property,  and  treats  the
3532         sequence  as  an  atomic group (see below).  Characters with the "mark"         sequence  as  an  atomic group (see below).  Characters with the "mark"
3533         property are typically accents that affect the preceding character.         property are typically accents that  affect  the  preceding  character.
3534           None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X
3535           matches any one character.
3536    
3537         Matching characters by Unicode property is not fast, because  PCRE  has         Matching characters by Unicode property is not fast, because  PCRE  has
3538         to  search  a  structure  that  contains data for over fifteen thousand         to  search  a  structure  that  contains data for over fifteen thousand
3539         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
3540         \w do not use Unicode properties in PCRE.         \w do not use Unicode properties in PCRE.
3541    
3542       Resetting the match start
3543    
3544           The escape sequence \K, which is a Perl 5.10 feature, causes any previ-
3545           ously matched characters not  to  be  included  in  the  final  matched
3546           sequence. For example, the pattern:
3547    
3548             foo\Kbar
3549    
3550           matches  "foobar",  but reports that it has matched "bar". This feature
3551           is similar to a lookbehind assertion (described  below).   However,  in
3552           this  case, the part of the subject before the real match does not have
3553           to be of fixed length, as lookbehind assertions do. The use of \K  does
3554           not  interfere  with  the setting of captured substrings.  For example,
3555           when the pattern
3556    
3557             (foo)\Kbar
3558    
3559           matches "foobar", the first substring is still set to "foo".
3560    
3561     Simple assertions     Simple assertions
3562    
3563         The  final use of backslash is for certain simple assertions. An asser-         The final use of backslash is for certain simple assertions. An  asser-
3564         tion specifies a condition that has to be met at a particular point  in         tion  specifies a condition that has to be met at a particular point in
3565         a  match, without consuming any characters from the subject string. The         a match, without consuming any characters from the subject string.  The
3566         use of subpatterns for more complicated assertions is described  below.         use  of subpatterns for more complicated assertions is described below.
3567         The backslashed assertions are:         The backslashed assertions are:
3568    
3569           \b     matches at a word boundary           \b     matches at a word boundary
# Line 3076  BACKSLASH Line 3574  BACKSLASH
3574           \z     matches only at the end of the subject           \z     matches only at the end of the subject
3575           \G     matches at the first matching position in the subject           \G     matches at the first matching position in the subject
3576    
3577         These  assertions may not appear in character classes (but note that \b         These assertions may not appear in character classes (but note that  \b
3578         has a different meaning, namely the backspace character, inside a char-         has a different meaning, namely the backspace character, inside a char-
3579         acter class).         acter class).
3580    
3581         A  word  boundary is a position in the subject string where the current         A word boundary is a position in the subject string where  the  current
3582         character and the previous character do not both match \w or  \W  (i.e.         character  and  the previous character do not both match \w or \W (i.e.
3583         one  matches  \w  and the other matches \W), or the start or end of the         one matches \w and the other matches \W), or the start or  end  of  the
3584         string if the first or last character matches \w, respectively.         string if the first or last character matches \w, respectively.
3585    
3586         The \A, \Z, and \z assertions differ from  the  traditional  circumflex         The  \A,  \Z,  and \z assertions differ from the traditional circumflex
3587         and dollar (described in the next section) in that they only ever match         and dollar (described in the next section) in that they only ever match
3588         at the very start and end of the subject string, whatever  options  are         at  the  very start and end of the subject string, whatever options are
3589         set.  Thus,  they are independent of multiline mode. These three asser-         set. Thus, they are independent of multiline mode. These  three  asser-
3590         tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which         tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which
3591         affect  only the behaviour of the circumflex and dollar metacharacters.         affect only the behaviour of the circumflex and dollar  metacharacters.
3592         However, if the startoffset argument of pcre_exec() is non-zero,  indi-         However,  if the startoffset argument of pcre_exec() is non-zero, indi-
3593         cating that matching is to start at a point other than the beginning of         cating that matching is to start at a point other than the beginning of
3594         the subject, \A can never match. The difference between \Z  and  \z  is         the  subject,  \A  can never match. The difference between \Z and \z is
3595         that \Z matches before a newline at the end of the string as well as at         that \Z matches before a newline at the end of the string as well as at
3596         the very end, whereas \z matches only at the end.         the very end, whereas \z matches only at the end.
3597    
3598         The \G assertion is true only when the current matching position is  at         The  \G assertion is true only when the current matching position is at
3599         the  start point of the match, as specified by the startoffset argument         the start point of the match, as specified by the startoffset  argument
3600         of pcre_exec(). It differs from \A when the  value  of  startoffset  is         of  pcre_exec().  It  differs  from \A when the value of startoffset is
3601         non-zero.  By calling pcre_exec() multiple times with appropriate argu-         non-zero. By calling pcre_exec() multiple times with appropriate  argu-
3602         ments, you can mimic Perl's /g option, and it is in this kind of imple-         ments, you can mimic Perl's /g option, and it is in this kind of imple-
3603         mentation where \G can be useful.         mentation where \G can be useful.
3604    
3605         Note,  however,  that  PCRE's interpretation of \G, as the start of the         Note, however, that PCRE's interpretation of \G, as the  start  of  the
3606         current match, is subtly different from Perl's, which defines it as the         current match, is subtly different from Perl's, which defines it as the
3607         end  of  the  previous  match. In Perl, these can be different when the         end of the previous match. In Perl, these can  be  different  when  the
3608         previously matched string was empty. Because PCRE does just  one  match         previously  matched  string was empty. Because PCRE does just one match
3609         at a time, it cannot reproduce this behaviour.         at a time, it cannot reproduce this behaviour.
3610    
3611         If  all  the alternatives of a pattern begin with \G, the expression is         If all the alternatives of a pattern begin with \G, the  expression  is
3612         anchored to the starting match position, and the "anchored" flag is set         anchored to the starting match position, and the "anchored" flag is set
3613         in the compiled regular expression.         in the compiled regular expression.
3614    
# Line 3118  BACKSLASH Line 3616  BACKSLASH
3616  CIRCUMFLEX AND DOLLAR  CIRCUMFLEX AND DOLLAR
3617    
3618         Outside a character class, in the default matching mode, the circumflex         Outside a character class, in the default matching mode, the circumflex
3619         character is an assertion that is true only  if  the  current  matching         character  is  an  assertion  that is true only if the current matching
3620         point  is  at the start of the subject string. If the startoffset argu-         point is at the start of the subject string. If the  startoffset  argu-
3621         ment of pcre_exec() is non-zero, circumflex  can  never  match  if  the         ment  of  pcre_exec()  is  non-zero,  circumflex can never match if the
3622         PCRE_MULTILINE  option  is  unset. Inside a character class, circumflex         PCRE_MULTILINE option is unset. Inside a  character  class,  circumflex
3623         has an entirely different meaning (see below).         has an entirely different meaning (see below).
3624    
3625         Circumflex need not be the first character of the pattern if  a  number         Circumflex  need  not be the first character of the pattern if a number
3626         of  alternatives are involved, but it should be the first thing in each         of alternatives are involved, but it should be the first thing in  each
3627         alternative in which it appears if the pattern is ever  to  match  that         alternative  in  which  it appears if the pattern is ever to match that
3628         branch.  If all possible alternatives start with a circumflex, that is,         branch. If all possible alternatives start with a circumflex, that  is,
3629         if the pattern is constrained to match only at the start  of  the  sub-         if  the  pattern  is constrained to match only at the start of the sub-
3630         ject,  it  is  said  to be an "anchored" pattern. (There are also other         ject, it is said to be an "anchored" pattern.  (There  are  also  other
3631         constructs that can cause a pattern to be anchored.)         constructs that can cause a pattern to be anchored.)
3632    
3633         A dollar character is an assertion that is true  only  if  the  current         A  dollar  character  is  an assertion that is true only if the current
3634         matching  point  is  at  the  end of the subject string, or immediately         matching point is at the end of  the  subject  string,  or  immediately
3635         before a newline at the end of the string (by default). Dollar need not         before a newline at the end of the string (by default). Dollar need not
3636         be  the  last  character of the pattern if a number of alternatives are         be the last character of the pattern if a number  of  alternatives  are
3637         involved, but it should be the last item in  any  branch  in  which  it         involved,  but  it  should  be  the last item in any branch in which it
3638         appears. Dollar has no special meaning in a character class.         appears. Dollar has no special meaning in a character class.
3639    
3640         The  meaning  of  dollar  can be changed so that it matches only at the         The meaning of dollar can be changed so that it  matches  only  at  the
3641         very end of the string, by setting the  PCRE_DOLLAR_ENDONLY  option  at         very  end  of  the string, by setting the PCRE_DOLLAR_ENDONLY option at
3642         compile time. This does not affect the \Z assertion.         compile time. This does not affect the \Z assertion.
3643    
3644         The meanings of the circumflex and dollar characters are changed if the         The meanings of the circumflex and dollar characters are changed if the
3645         PCRE_MULTILINE option is set. When  this  is  the  case,  a  circumflex         PCRE_MULTILINE  option  is  set.  When  this  is the case, a circumflex
3646         matches  immediately after internal newlines as well as at the start of         matches immediately after internal newlines as well as at the start  of
3647         the subject string. It does not match after a  newline  that  ends  the         the  subject  string.  It  does not match after a newline that ends the
3648         string.  A dollar matches before any newlines in the string, as well as         string. A dollar matches before any newlines in the string, as well  as
3649         at the very end, when PCRE_MULTILINE is set. When newline is  specified         at  the very end, when PCRE_MULTILINE is set. When newline is specified
3650         as  the  two-character  sequence CRLF, isolated CR and LF characters do         as the two-character sequence CRLF, isolated CR and  LF  characters  do
3651         not indicate newlines.         not indicate newlines.
3652    
3653         For example, the pattern /^abc$/ matches the subject string  "def\nabc"         For  example, the pattern /^abc$/ matches the subject string "def\nabc"
3654         (where  \n  represents a newline) in multiline mode, but not otherwise.         (where \n represents a newline) in multiline mode, but  not  otherwise.
3655         Consequently, patterns that are anchored in single  line  mode  because         Consequently,  patterns  that  are anchored in single line mode because
3656         all  branches  start  with  ^ are not anchored in multiline mode, and a         all branches start with ^ are not anchored in  multiline  mode,  and  a
3657         match for circumflex is  possible  when  the  startoffset  argument  of         match  for  circumflex  is  possible  when  the startoffset argument of
3658         pcre_exec()  is  non-zero. The PCRE_DOLLAR_ENDONLY option is ignored if         pcre_exec() is non-zero. The PCRE_DOLLAR_ENDONLY option is  ignored  if
3659         PCRE_MULTILINE is set.         PCRE_MULTILINE is set.
3660    
3661         Note that the sequences \A, \Z, and \z can be used to match  the  start         Note  that  the sequences \A, \Z, and \z can be used to match the start
3662         and  end of the subject in both modes, and if all branches of a pattern         and end of the subject in both modes, and if all branches of a  pattern
3663         start with \A it is always anchored, whether or not  PCRE_MULTILINE  is         start  with  \A it is always anchored, whether or not PCRE_MULTILINE is
3664         set.         set.
3665    
3666    
3667  FULL STOP (PERIOD, DOT)  FULL STOP (PERIOD, DOT)
3668    
3669         Outside a character class, a dot in the pattern matches any one charac-         Outside a character class, a dot in the pattern matches any one charac-
3670         ter in the subject string except (by default) a character  that  signi-         ter  in  the subject string except (by default) a character that signi-
3671         fies  the  end  of  a line. In UTF-8 mode, the matched character may be         fies the end of a line. In UTF-8 mode, the  matched  character  may  be
3672         more than one byte long.         more than one byte long.
3673    
3674         When a line ending is defined as a single character, dot never  matches         When  a line ending is defined as a single character, dot never matches
3675         that  character; when the two-character sequence CRLF is used, dot does         that character; when the two-character sequence CRLF is used, dot  does
3676         not match CR if it is immediately followed  by  LF,  but  otherwise  it         not  match  CR  if  it  is immediately followed by LF, but otherwise it
3677         matches  all characters (including isolated CRs and LFs). When any Uni-         matches all characters (including isolated CRs and LFs). When any  Uni-
3678         code line endings are being recognized, dot does not match CR or LF  or         code  line endings are being recognized, dot does not match CR or LF or
3679         any of the other line ending characters.         any of the other line ending characters.
3680    
3681         The  behaviour  of  dot  with regard to newlines can be changed. If the         The behaviour of dot with regard to newlines can  be  changed.  If  the
3682         PCRE_DOTALL option is set, a dot matches  any  one  character,  without         PCRE_DOTALL  option  is  set,  a dot matches any one character, without
3683         exception. If the two-character sequence CRLF is present in the subject         exception. If the two-character sequence CRLF is present in the subject
3684         string, it takes two dots to match it.         string, it takes two dots to match it.
3685    
3686         The handling of dot is entirely independent of the handling of  circum-         The  handling of dot is entirely independent of the handling of circum-
3687         flex  and  dollar,  the  only relationship being that they both involve         flex and dollar, the only relationship being  that  they  both  involve
3688         newlines. Dot has no special meaning in a character class.         newlines. Dot has no special meaning in a character class.
3689    
3690    
3691  MATCHING A SINGLE BYTE  MATCHING A SINGLE BYTE
3692    
3693         Outside a character class, the escape sequence \C matches any one byte,         Outside a character class, the escape sequence \C matches any one byte,
3694         both  in  and  out  of  UTF-8 mode. Unlike a dot, it always matches any         both in and out of UTF-8 mode. Unlike a  dot,  it  always  matches  any
3695         line-ending characters. The feature is provided in  Perl  in  order  to         line-ending  characters.  The  feature  is provided in Perl in order to
3696         match  individual bytes in UTF-8 mode. Because it breaks up UTF-8 char-         match individual bytes in UTF-8 mode. Because it breaks up UTF-8  char-
3697         acters into individual bytes, what remains in the string may be a  mal-         acters  into individual bytes, what remains in the string may be a mal-
3698         formed  UTF-8  string.  For this reason, the \C escape sequence is best         formed UTF-8 string. For this reason, the \C escape  sequence  is  best
3699         avoided.         avoided.
3700    
3701         PCRE does not allow \C to appear in  lookbehind  assertions  (described         PCRE  does  not  allow \C to appear in lookbehind assertions (described
3702         below),  because  in UTF-8 mode this would make it impossible to calcu-         below), because in UTF-8 mode this would make it impossible  to  calcu-
3703         late the length of the lookbehind.         late the length of the lookbehind.
3704    
3705    
# Line 3210  SQUARE BRACKETS AND CHARACTER CLASSES Line 3708  SQUARE BRACKETS AND CHARACTER CLASSES
3708         An opening square bracket introduces a character class, terminated by a         An opening square bracket introduces a character class, terminated by a
3709         closing square bracket. A closing square bracket on its own is not spe-         closing square bracket. A closing square bracket on its own is not spe-
3710         cial. If a closing square bracket is required as a member of the class,         cial. If a closing square bracket is required as a member of the class,
3711         it  should  be  the first data character in the class (after an initial         it should be the first data character in the class  (after  an  initial
3712         circumflex, if present) or escaped with a backslash.         circumflex, if present) or escaped with a backslash.
3713    
3714         A character class matches a single character in the subject.  In  UTF-8         A  character  class matches a single character in the subject. In UTF-8
3715         mode,  the character may occupy more than one byte. A matched character         mode, the character may occupy more than one byte. A matched  character
3716         must be in the set of characters defined by the class, unless the first         must be in the set of characters defined by the class, unless the first
3717         character  in  the  class definition is a circumflex, in which case the         character in the class definition is a circumflex, in  which  case  the
3718         subject character must not be in the set defined by  the  class.  If  a         subject  character  must  not  be in the set defined by the class. If a
3719         circumflex  is actually required as a member of the class, ensure it is         circumflex is actually required as a member of the class, ensure it  is
3720         not the first character, or escape it with a backslash.         not the first character, or escape it with a backslash.
3721    
3722         For example, the character class [aeiou] matches any lower case  vowel,         For  example, the character class [aeiou] matches any lower case vowel,
3723         while  [^aeiou]  matches  any character that is not a lower case vowel.         while [^aeiou] matches any character that is not a  lower  case  vowel.
3724         Note that a circumflex is just a convenient notation for specifying the         Note that a circumflex is just a convenient notation for specifying the
3725         characters  that  are in the class by enumerating those that are not. A         characters that are in the class by enumerating those that are  not.  A
3726         class that starts with a circumflex is not an assertion: it still  con-         class  that starts with a circumflex is not an assertion: it still con-
3727         sumes  a  character  from the subject string, and therefore it fails if         sumes a character from the subject string, and therefore  it  fails  if
3728         the current pointer is at the end of the string.         the current pointer is at the end of the string.
3729    
3730         In UTF-8 mode, characters with values greater than 255 can be  included         In  UTF-8 mode, characters with values greater than 255 can be included
3731         in  a  class as a literal string of bytes, or by using the \x{ escaping         in a class as a literal string of bytes, or by using the  \x{  escaping
3732         mechanism.         mechanism.
3733    
3734         When caseless matching is set, any letters in a  class  represent  both         When  caseless  matching  is set, any letters in a class represent both
3735         their  upper  case  and lower case versions, so for example, a caseless         their upper case and lower case versions, so for  example,  a  caseless
3736         [aeiou] matches "A" as well as "a", and a caseless  [^aeiou]  does  not         [aeiou]  matches  "A"  as well as "a", and a caseless [^aeiou] does not
3737         match  "A", whereas a caseful version would. In UTF-8 mode, PCRE always         match "A", whereas a caseful version would. In UTF-8 mode, PCRE  always
3738         understands the concept of case for characters whose  values  are  less         understands  the  concept  of case for characters whose values are less
3739         than  128, so caseless matching is always possible. For characters with         than 128, so caseless matching is always possible. For characters  with
3740         higher values, the concept of case is supported  if  PCRE  is  compiled         higher  values,  the  concept  of case is supported if PCRE is compiled
3741         with  Unicode  property support, but not otherwise.  If you want to use         with Unicode property support, but not otherwise.  If you want  to  use
3742         caseless matching for characters 128 and above, you  must  ensure  that         caseless  matching  for  characters 128 and above, you must ensure that
3743         PCRE  is  compiled  with Unicode property support as well as with UTF-8         PCRE is compiled with Unicode property support as well  as  with  UTF-8
3744         support.         support.
3745    
3746         Characters that might indicate line breaks are  never  treated  in  any         Characters  that  might  indicate  line breaks are never treated in any
3747         special  way  when  matching  character  classes,  whatever line-ending         special way  when  matching  character  classes,  whatever  line-ending
3748         sequence is in  use,  and  whatever  setting  of  the  PCRE_DOTALL  and         sequence  is  in  use,  and  whatever  setting  of  the PCRE_DOTALL and
3749         PCRE_MULTILINE options is used. A class such as [^a] always matches one         PCRE_MULTILINE options is used. A class such as [^a] always matches one
3750         of these characters.         of these characters.
3751    
3752         The minus (hyphen) character can be used to specify a range of  charac-         The  minus (hyphen) character can be used to specify a range of charac-
3753         ters  in  a  character  class.  For  example,  [d-m] matches any letter         ters in a character  class.  For  example,  [d-m]  matches  any  letter
3754         between d and m, inclusive. If a  minus  character  is  required  in  a         between  d  and  m,  inclusive.  If  a minus character is required in a
3755         class,  it  must  be  escaped  with a backslash or appear in a position         class, it must be escaped with a backslash  or  appear  in  a  position
3756         where it cannot be interpreted as indicating a range, typically as  the         where  it cannot be interpreted as indicating a range, typically as the
3757         first or last character in the class.         first or last character in the class.
3758    
3759         It is not possible to have the literal character "]" as the end charac-         It is not possible to have the literal character "]" as the end charac-
3760         ter of a range. A pattern such as [W-]46] is interpreted as a class  of         ter  of a range. A pattern such as [W-]46] is interpreted as a class of
3761         two  characters ("W" and "-") followed by a literal string "46]", so it         two characters ("W" and "-") followed by a literal string "46]", so  it
3762         would match "W46]" or "-46]". However, if the "]"  is  escaped  with  a         would  match  "W46]"  or  "-46]". However, if the "]" is escaped with a
3763         backslash  it is interpreted as the end of range, so [W-\]46] is inter-         backslash it is interpreted as the end of range, so [W-\]46] is  inter-
3764         preted as a class containing a range followed by two other  characters.         preted  as a class containing a range followed by two other characters.
3765         The  octal or hexadecimal representation of "]" can also be used to end         The octal or hexadecimal representation of "]" can also be used to  end
3766         a range.         a range.
3767    
3768         Ranges operate in the collating sequence of character values. They  can         Ranges  operate in the collating sequence of character values. They can
3769         also   be  used  for  characters  specified  numerically,  for  example         also  be  used  for  characters  specified  numerically,  for   example
3770         [\000-\037]. In UTF-8 mode, ranges can include characters whose  values         [\000-\037].  In UTF-8 mode, ranges can include characters whose values
3771         are greater than 255, for example [\x{100}-\x{2ff}].         are greater than 255, for example [\x{100}-\x{2ff}].
3772    
3773         If a range that includes letters is used when caseless matching is set,         If a range that includes letters is used when caseless matching is set,
3774         it matches the letters in either case. For example, [W-c] is equivalent         it matches the letters in either case. For example, [W-c] is equivalent
3775         to  [][\\^_`wxyzabc],  matched  caselessly,  and  in non-UTF-8 mode, if         to [][\\^_`wxyzabc], matched caselessly,  and  in  non-UTF-8  mode,  if
3776         character tables for the "fr_FR" locale are in use, [\xc8-\xcb] matches         character  tables  for  a French locale are in use, [\xc8-\xcb] matches
3777         accented  E  characters in both cases. In UTF-8 mode, PCRE supports the         accented E characters in both cases. In UTF-8 mode, PCRE  supports  the
3778         concept of case for characters with values greater than 128  only  when         concept  of  case for characters with values greater than 128 only when
3779         it is compiled with Unicode property support.         it is compiled with Unicode property support.
3780    
3781         The  character types \d, \D, \p, \P, \s, \S, \w, and \W may also appear         The character types \d, \D, \p, \P, \s, \S, \w, and \W may also  appear
3782         in a character class, and add the characters that  they  match  to  the         in  a  character  class,  and add the characters that they match to the
3783         class. For example, [\dABCDEF] matches any hexadecimal digit. A circum-         class. For example, [\dABCDEF] matches any hexadecimal digit. A circum-
3784         flex can conveniently be used with the upper case  character  types  to         flex  can  conveniently  be used with the upper case character types to
3785         specify  a  more  restricted  set of characters than the matching lower         specify a more restricted set of characters  than  the  matching  lower
3786         case type. For example, the class [^\W_] matches any letter  or  digit,         case  type.  For example, the class [^\W_] matches any letter or digit,
3787         but not underscore.         but not underscore.
3788    
3789         The  only  metacharacters  that are recognized in character classes are         The only metacharacters that are recognized in  character  classes  are
3790         backslash, hyphen (only where it can be  interpreted  as  specifying  a         backslash,  hyphen  (only  where  it can be interpreted as specifying a
3791         range),  circumflex  (only  at the start), opening square bracket (only         range), circumflex (only at the start), opening  square  bracket  (only
3792         when it can be interpreted as introducing a POSIX class name - see  the         when  it can be interpreted as introducing a POSIX class name - see the
3793         next  section),  and  the  terminating closing square bracket. However,         next section), and the terminating  closing  square  bracket.  However,
3794         escaping other non-alphanumeric characters does no harm.         escaping other non-alphanumeric characters does no harm.
3795    
3796    
3797  POSIX CHARACTER CLASSES  POSIX CHARACTER CLASSES
3798    
3799         Perl supports the POSIX notation for character classes. This uses names         Perl supports the POSIX notation for character classes. This uses names
3800         enclosed  by  [: and :] within the enclosing square brackets. PCRE also         enclosed by [: and :] within the enclosing square brackets.  PCRE  also
3801         supports this notation. For example,         supports this notation. For example,
3802    
3803           [01[:alpha:]%]           [01[:alpha:]%]
# Line 3322  POSIX CHARACTER CLASSES Line 3820  POSIX CHARACTER CLASSES
3820           word     "word" characters (same as \w)           word     "word" characters (same as \w)
3821           xdigit   hexadecimal digits           xdigit   hexadecimal digits
3822    
3823         The  "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13),         The "space" characters are HT (9), LF (10), VT (11), FF (12), CR  (13),
3824         and space (32). Notice that this list includes the VT  character  (code         and  space  (32). Notice that this list includes the VT character (code
3825         11). This makes "space" different to \s, which does not include VT (for         11). This makes "space" different to \s, which does not include VT (for
3826         Perl compatibility).         Perl compatibility).
3827    
3828         The name "word" is a Perl extension, and "blank"  is  a  GNU  extension         The  name  "word"  is  a Perl extension, and "blank" is a GNU extension
3829         from  Perl  5.8. Another Perl extension is negation, which is indicated         from Perl 5.8. Another Perl extension is negation, which  is  indicated
3830         by a ^ character after the colon. For example,         by a ^ character after the colon. For example,
3831    
3832           [12[:^digit:]]           [12[:^digit:]]
3833    
3834         matches "1", "2", or any non-digit. PCRE (and Perl) also recognize  the         matches  "1", "2", or any non-digit. PCRE (and Perl) also recognize the
3835         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but
3836         these are not supported, and an error is given if they are encountered.         these are not supported, and an error is given if they are encountered.
3837    
# Line 3353  VERTICAL BAR Line 3851  VERTICAL BAR
3851         string). The matching process tries each alternative in turn, from left         string). The matching process tries each alternative in turn, from left
3852         to right, and the first one that succeeds is used. If the  alternatives         to right, and the first one that succeeds is used. If the  alternatives
3853         are  within a subpattern (defined below), "succeeds" means matching the         are  within a subpattern (defined below), "succeeds" means matching the
3854         rest of the main pattern as well as the alternative in the  subpattern.         rest of the main pattern as well as the alternative in the subpattern.
3855    
3856    
3857  INTERNAL OPTION SETTING  INTERNAL OPTION SETTING
3858    
3859         The  settings  of  the  PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and         The settings of the  PCRE_CASELESS,  PCRE_MULTILINE,  PCRE_DOTALL,  and
3860         PCRE_EXTENDED options can be changed  from  within  the  pattern  by  a         PCRE_EXTENDED  options  (which are Perl-compatible) can be changed from
3861         sequence  of  Perl  option  letters  enclosed between "(?" and ")". The         within the pattern by  a  sequence  of  Perl  option  letters  enclosed
3862         option letters are         between "(?" and ")".  The option letters are
3863    
3864           i  for PCRE_CASELESS           i  for PCRE_CASELESS
3865           m  for PCRE_MULTILINE           m  for PCRE_MULTILINE
# Line 3370  INTERNAL OPTION SETTING Line 3868  INTERNAL OPTION SETTING
3868    
3869         For example, (?im) sets caseless, multiline matching. It is also possi-         For example, (?im) sets caseless, multiline matching. It is also possi-
3870         ble to unset these options by preceding the letter with a hyphen, and a         ble to unset these options by preceding the letter with a hyphen, and a
3871         combined setting and unsetting such as (?im-sx), which sets  PCRE_CASE-         combined  setting and unsetting such as (?im-sx), which sets PCRE_CASE-
3872         LESS  and PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED,         LESS and PCRE_MULTILINE while unsetting PCRE_DOTALL and  PCRE_EXTENDED,
3873         is also permitted. If a  letter  appears  both  before  and  after  the         is  also  permitted.  If  a  letter  appears  both before and after the
3874         hyphen, the option is unset.         hyphen, the option is unset.
3875    
3876         When  an option change occurs at top level (that is, not inside subpat-         The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA
3877         tern parentheses), the change applies to the remainder of  the  pattern         can  be changed in the same way as the Perl-compatible options by using
3878         that follows.  If the change is placed right at the start of a pattern,         the characters J, U and X respectively.
3879         PCRE extracts it into the global options (and it will therefore show up  
3880         in data extracted by the pcre_fullinfo() function).         When one of these option changes occurs at  top  level  (that  is,  not
3881           inside  subpattern parentheses), the change applies to the remainder of
3882           the pattern that follows. If the change is placed right at the start of
3883           a pattern, PCRE extracts it into the global options (and it will there-
3884           fore show up in data extracted by the pcre_fullinfo() function).
3885    
3886         An  option  change  within a subpattern (see below for a description of         An option change within a subpattern (see below for  a  description  of
3887         subpatterns) affects only that part of the current pattern that follows         subpatterns) affects only that part of the current pattern that follows
3888         it, so         it, so
3889    
3890           (a(?i)b)c           (a(?i)b)c
3891    
3892         matches abc and aBc and no other strings (assuming PCRE_CASELESS is not         matches abc and aBc and no other strings (assuming PCRE_CASELESS is not
3893         used).  By this means, options can be made to have  different  settings         used).   By  this means, options can be made to have different settings
3894         in  different parts of the pattern. Any changes made in one alternative         in different parts of the pattern. Any changes made in one  alternative
3895         do carry on into subsequent branches within the  same  subpattern.  For         do  carry  on  into subsequent branches within the same subpattern. For
3896         example,         example,
3897    
3898           (a(?i)b|c)           (a(?i)b|c)
3899    
3900         matches  "ab",  "aB",  "c",  and "C", even though when matching "C" the         matches "ab", "aB", "c", and "C", even though  when  matching  "C"  the
3901         first branch is abandoned before the option setting.  This  is  because         first  branch  is  abandoned before the option setting. This is because
3902         the  effects  of option settings happen at compile time. There would be         the effects of option settings happen at compile time. There  would  be
3903         some very weird behaviour otherwise.         some very weird behaviour otherwise.
3904    
3905         The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA         Note:  There  are  other  PCRE-specific  options that can be set by the
3906         can  be changed in the same way as the Perl-compatible options by using         application when the compile or match functions  are  called.  In  some
3907         the characters J, U and X respectively.         cases the pattern can contain special leading sequences such as (*CRLF)
3908           to override what the application has set or what  has  been  defaulted.
3909           Details  are  given  in the section entitled "Newline sequences" above.
3910           There is also the (*UTF8) leading sequence that  can  be  used  to  set
3911           UTF-8 mode; this is equivalent to setting the PCRE_UTF8 option.
3912    
3913    
3914  SUBPATTERNS  SUBPATTERNS
# Line 3414  SUBPATTERNS Line 3920  SUBPATTERNS
3920    
3921           cat(aract|erpillar|)           cat(aract|erpillar|)
3922    
3923         matches  one  of the words "cat", "cataract", or "caterpillar". Without         matches one of the words "cat", "cataract", or  "caterpillar".  Without
3924         the parentheses, it would match  "cataract",  "erpillar"  or  an  empty         the  parentheses,  it  would  match  "cataract", "erpillar" or an empty
3925         string.         string.
3926    
3927         2.  It  sets  up  the  subpattern as a capturing subpattern. This means         2. It sets up the subpattern as  a  capturing  subpattern.  This  means
3928         that, when the whole pattern  matches,  that  portion  of  the  subject         that,  when  the  whole  pattern  matches,  that portion of the subject
3929         string that matched the subpattern is passed back to the caller via the         string that matched the subpattern is passed back to the caller via the
3930         ovector argument of pcre_exec(). Opening parentheses are  counted  from         ovector  argument  of pcre_exec(). Opening parentheses are counted from
3931         left  to  right  (starting  from 1) to obtain numbers for the capturing         left to right (starting from 1) to obtain  numbers  for  the  capturing
3932         subpatterns.         subpatterns.
3933    
3934         For example, if the string "the red king" is matched against  the  pat-         For  example,  if the string "the red king" is matched against the pat-
3935         tern         tern
3936    
3937           the ((red|white) (king|queen))           the ((red|white) (king|queen))
# Line 3433  SUBPATTERNS Line 3939  SUBPATTERNS
3939         the captured substrings are "red king", "red", and "king", and are num-         the captured substrings are "red king", "red", and "king", and are num-
3940         bered 1, 2, and 3, respectively.         bered 1, 2, and 3, respectively.
3941    
3942         The fact that plain parentheses fulfil  two  functions  is  not  always         The  fact  that  plain  parentheses  fulfil two functions is not always
3943         helpful.   There are often times when a grouping subpattern is required         helpful.  There are often times when a grouping subpattern is  required
3944         without a capturing requirement. If an opening parenthesis is  followed         without  a capturing requirement. If an opening parenthesis is followed
3945         by  a question mark and a colon, the subpattern does not do any captur-         by a question mark and a colon, the subpattern does not do any  captur-
3946         ing, and is not counted when computing the  number  of  any  subsequent         ing,  and  is  not  counted when computing the number of any subsequent
3947         capturing  subpatterns. For example, if the string "the white queen" is         capturing subpatterns. For example, if the string "the white queen"  is
3948         matched against the pattern         matched against the pattern
3949    
3950           the ((?:red|white) (king|queen))           the ((?:red|white) (king|queen))
# Line 3446  SUBPATTERNS Line 3952  SUBPATTERNS
3952         the captured substrings are "white queen" and "queen", and are numbered         the captured substrings are "white queen" and "queen", and are numbered
3953         1 and 2. The maximum number of capturing subpatterns is 65535.         1 and 2. The maximum number of capturing subpatterns is 65535.
3954    
3955         As  a  convenient shorthand, if any option settings are required at the         As a convenient shorthand, if any option settings are required  at  the
3956         start of a non-capturing subpattern,  the  option  letters  may  appear         start  of  a  non-capturing  subpattern,  the option letters may appear
3957         between the "?" and the ":". Thus the two patterns         between the "?" and the ":". Thus the two patterns
3958    
3959           (?i:saturday|sunday)           (?i:saturday|sunday)
3960           (?:(?i)saturday|sunday)           (?:(?i)saturday|sunday)
3961    
3962         match exactly the same set of strings. Because alternative branches are         match exactly the same set of strings. Because alternative branches are
3963         tried from left to right, and options are not reset until  the  end  of         tried  from  left  to right, and options are not reset until the end of
3964         the  subpattern is reached, an option setting in one branch does affect         the subpattern is reached, an option setting in one branch does  affect
3965         subsequent branches, so the above patterns match "SUNDAY"  as  well  as         subsequent  branches,  so  the above patterns match "SUNDAY" as well as
3966         "Saturday".         "Saturday".
3967    
3968    
3969    DUPLICATE SUBPATTERN NUMBERS
3970    
3971           Perl 5.10 introduced a feature whereby each alternative in a subpattern
3972           uses  the same numbers for its capturing parentheses. Such a subpattern
3973           starts with (?| and is itself a non-capturing subpattern. For  example,
3974           consider this pattern:
3975    
3976             (?|(Sat)ur|(Sun))day
3977    
3978           Because  the two alternatives are inside a (?| group, both sets of cap-
3979           turing parentheses are numbered one. Thus, when  the  pattern  matches,
3980           you  can  look  at captured substring number one, whichever alternative
3981           matched. This construct is useful when you want to  capture  part,  but
3982           not all, of one of a number of alternatives. Inside a (?| group, paren-
3983           theses are numbered as usual, but the number is reset at the  start  of
3984           each  branch. The numbers of any capturing buffers that follow the sub-
3985           pattern start after the highest number used in any branch. The  follow-
3986           ing  example  is taken from the Perl documentation.  The numbers under-
3987           neath show in which buffer the captured content will be stored.
3988    
3989             # before  ---------------branch-reset----------- after
3990             / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x
3991             # 1            2         2  3        2     3     4
3992    
3993           A backreference or a recursive call to  a  numbered  subpattern  always
3994           refers to the first one in the pattern with the given number.
3995    
3996           An  alternative approach to using this "branch reset" feature is to use
3997           duplicate named subpatterns, as described in the next section.
3998    
3999    
4000  NAMED SUBPATTERNS  NAMED SUBPATTERNS
4001    
4002         Identifying  capturing  parentheses  by number is simple, but it can be         Identifying capturing parentheses by number is simple, but  it  can  be
4003         very hard to keep track of the numbers in complicated  regular  expres-         very  hard  to keep track of the numbers in complicated regular expres-
4004         sions.  Furthermore,  if  an  expression  is  modified, the numbers may         sions. Furthermore, if an  expression  is  modified,  the  numbers  may
4005         change. To help with this difficulty, PCRE supports the naming of  sub-         change.  To help with this difficulty, PCRE supports the naming of sub-
4006         patterns. This feature was not added to Perl until release 5.10. Python         patterns. This feature was not added to Perl until release 5.10. Python
4007         had the feature earlier, and PCRE introduced it at release  4.0,  using         had  the  feature earlier, and PCRE introduced it at release 4.0, using
4008         the  Python syntax. PCRE now supports both the Perl and the Python syn-         the Python syntax. PCRE now supports both the Perl and the Python  syn-
4009         tax.         tax.
4010    
4011         In PCRE, a subpattern can be named in one of three  ways:  (?<name>...)         In  PCRE,  a subpattern can be named in one of three ways: (?<name>...)
4012         or  (?'name'...)  as in Perl, or (?P<name>...) as in Python. References         or (?'name'...) as in Perl, or (?P<name>...) as in  Python.  References
4013         to capturing parentheses from other parts of the pattern, such as back-         to capturing parentheses from other parts of the pattern, such as back-
4014         references,  recursion,  and conditions, can be made by name as well as         references, recursion, and conditions, can be made by name as  well  as
4015         by number.         by number.
4016    
4017         Names consist of up to  32  alphanumeric  characters  and  underscores.         Names  consist  of  up  to  32 alphanumeric characters and underscores.
4018         Named  capturing  parentheses  are  still  allocated numbers as well as         Named capturing parentheses are still  allocated  numbers  as  well  as
4019         names, exactly as if the names were not present. The PCRE API  provides         names,  exactly as if the names were not present. The PCRE API provides
4020         function calls for extracting the name-to-number translation table from         function calls for extracting the name-to-number translation table from
4021         a compiled pattern. There is also a convenience function for extracting         a compiled pattern. There is also a convenience function for extracting
4022         a captured substring by name.         a captured substring by name.
4023    
4024         By  default, a name must be unique within a pattern, but it is possible         By default, a name must be unique within a pattern, but it is  possible
4025         to relax this constraint by setting the PCRE_DUPNAMES option at compile         to relax this constraint by setting the PCRE_DUPNAMES option at compile
4026         time.  This  can  be useful for patterns where only one instance of the         time. This can be useful for patterns where only one  instance  of  the
4027         named parentheses can match. Suppose you want to match the  name  of  a         named  parentheses  can  match. Suppose you want to match the name of a
4028         weekday,  either as a 3-letter abbreviation or as the full name, and in         weekday, either as a 3-letter abbreviation or as the full name, and  in
4029         both cases you want to extract the abbreviation. This pattern (ignoring         both cases you want to extract the abbreviation. This pattern (ignoring
4030         the line breaks) does the job:         the line breaks) does the job:
4031    
# Line 3498  NAMED SUBPATTERNS Line 4035  NAMED SUBPATTERNS
4035           (?<DN>Thu)(?:rsday)?|           (?<DN>Thu)(?:rsday)?|
4036           (?<DN>Sat)(?:urday)?           (?<DN>Sat)(?:urday)?
4037    
4038         There  are  five capturing substrings, but only one is ever set after a         There are five capturing substrings, but only one is ever set  after  a
4039         match.  The convenience  function  for  extracting  the  data  by  name         match.  (An alternative way of solving this problem is to use a "branch
4040         returns  the  substring  for  the first (and in this example, the only)         reset" subpattern, as described in the previous section.)
4041         subpattern of that name that matched.  This  saves  searching  to  find  
4042         which  numbered  subpattern  it  was. If you make a reference to a non-         The convenience function for extracting the data by  name  returns  the
4043         unique named subpattern from elsewhere in the  pattern,  the  one  that         substring  for  the first (and in this example, the only) subpattern of
4044         corresponds  to  the  lowest number is used. For further details of the         that name that matched. This saves searching  to  find  which  numbered
4045         interfaces for handling named subpatterns, see the  pcreapi  documenta-         subpattern  it  was. If you make a reference to a non-unique named sub-
4046         tion.         pattern from elsewhere in the pattern, the one that corresponds to  the
4047           lowest  number  is used. For further details of the interfaces for han-
4048           dling named subpatterns, see the pcreapi documentation.
4049    
4050           Warning: You cannot use different names to distinguish between two sub-
4051           patterns  with  the same number (see the previous section) because PCRE
4052           uses only the numbers when matching.
4053    
4054    
4055  REPETITION  REPETITION
4056    
4057         Repetition  is  specified  by  quantifiers, which can follow any of the         Repetition is specified by quantifiers, which can  follow  any  of  the
4058         following items:         following items:
4059    
4060           a literal data character           a literal data character
# Line 3524  REPETITION Line 4067  REPETITION
4067           a back reference (see next section)           a back reference (see next section)
4068           a parenthesized subpattern (unless it is an assertion)           a parenthesized subpattern (unless it is an assertion)
4069    
4070         The general repetition quantifier specifies a minimum and maximum  num-         The  general repetition quantifier specifies a minimum and maximum num-
4071         ber  of  permitted matches, by giving the two numbers in curly brackets         ber of permitted matches, by giving the two numbers in  curly  brackets
4072         (braces), separated by a comma. The numbers must be  less  than  65536,         (braces),  separated  by  a comma. The numbers must be less than 65536,
4073         and the first must be less than or equal to the second. For example:         and the first must be less than or equal to the second. For example:
4074    
4075           z{2,4}           z{2,4}
4076    
4077         matches  "zz",  "zzz",  or  "zzzz". A closing brace on its own is not a         matches "zz", "zzz", or "zzzz". A closing brace on its  own  is  not  a
4078         special character. If the second number is omitted, but  the  comma  is         special  character.  If  the second number is omitted, but the comma is
4079         present,  there  is  no upper limit; if the second number and the comma         present, there is no upper limit; if the second number  and  the  comma
4080         are both omitted, the quantifier specifies an exact number of  required         are  both omitted, the quantifier specifies an exact number of required
4081         matches. Thus         matches. Thus
4082    
4083           [aeiou]{3,}           [aeiou]{3,}
# Line 3543  REPETITION Line 4086