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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  CMakeSetup  if  you  are  using
286           CMake instead of configure to build PCRE.
287    
288           The complete list of options for configure (which includes the standard
289           ones such as the  selection  of  the  installation  directory)  can  be
290           obtained by running
291    
292           ./configure --help           ./configure --help
293    
294         The following sections describe certain options whose names begin  with         The  following  sections  include  descriptions  of options whose names
295         --enable  or  --disable. These settings specify changes to the defaults         begin with --enable or --disable. These settings specify changes to the
296         for the configure command. Because of the  way  that  configure  works,         defaults  for  the configure command. Because of the way that configure
297         --enable  and  --disable  always  come  in  pairs, so the complementary         works, --enable and --disable always come in pairs, so  the  complemen-
298         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
299         not described.         is not described.
300    
301    
302  C++ SUPPORT  C++ SUPPORT
# Line 265  C++ SUPPORT Line 312  C++ SUPPORT
312    
313  UTF-8 SUPPORT  UTF-8 SUPPORT
314    
315         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 Unicode character strings, add
316    
317           --enable-utf8           --enable-utf8
318    
319         to  the  configure  command.  Of  itself, this does not make PCRE treat         to the configure command. Of itself, this  does  not  make  PCRE  treat
320         strings as UTF-8. As well as compiling PCRE with this option, you  also         strings  as UTF-8. As well as compiling PCRE with this option, you also
321         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()
322         function.         function.
323    
324           If  you set --enable-utf8 when compiling in an EBCDIC environment, PCRE
325           expects its input to be either ASCII or UTF-8 (depending on the runtime
326           option).  It  is not possible to support both EBCDIC and UTF-8 codes in
327           the same  version  of  the  library.  Consequently,  --enable-utf8  and
328           --enable-ebcdic are mutually exclusive.
329    
330    
331  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
332    
333         UTF-8 support allows PCRE to process character values greater than  255         UTF-8  support allows PCRE to process character values greater than 255
334         in  the  strings that it handles. On its own, however, it does not pro-         in the strings that it handles. On its own, however, it does  not  pro-
335         vide any facilities for accessing the properties of such characters. If         vide any facilities for accessing the properties of such characters. If
336         you  want  to  be able to use the pattern escapes \P, \p, and \X, which         you want to be able to use the pattern escapes \P, \p,  and  \X,  which
337         refer to Unicode character properties, you must add         refer to Unicode character properties, you must add
338    
339           --enable-unicode-properties           --enable-unicode-properties
340    
341         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
342         not explicitly requested it.         not explicitly requested it.
343    
344         Including  Unicode  property  support  adds around 90K of tables to the         Including Unicode property support adds around 30K  of  tables  to  the
345         PCRE library, approximately doubling its size. Only the  general  cate-         PCRE  library.  Only  the general category properties such as Lu and Nd
346         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.  
347    
348    
349  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
350    
351         By default, PCRE interprets character 10 (linefeed, LF)  as  indicating         By default, PCRE interprets the linefeed (LF) character  as  indicating
352         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
353         systems. You can compile PCRE to use character 13 (carriage return, CR)         systems. You can compile PCRE to use carriage return (CR)  instead,  by
354         instead, by adding         adding
355    
356           --enable-newline-is-cr           --enable-newline-is-cr
357    
# Line 313  CODE VALUE OF NEWLINE Line 365  CODE VALUE OF NEWLINE
365    
366         to the configure command. There is a fourth option, specified by         to the configure command. There is a fourth option, specified by
367    
368             --enable-newline-is-anycrlf
369    
370           which  causes  PCRE  to recognize any of the three sequences CR, LF, or
371           CRLF as indicating a line ending. Finally, a fifth option, specified by
372    
373           --enable-newline-is-any           --enable-newline-is-any
374    
375         which causes PCRE to recognize any Unicode newline sequence.         causes PCRE to recognize any Unicode newline sequence.
376    
377         Whatever  line  ending convention is selected when PCRE is built can be         Whatever line ending convention is selected when PCRE is built  can  be
378         overridden when the library functions are called. At build time  it  is         overridden  when  the library functions are called. At build time it is
379         conventional to use the standard for your operating system.         conventional to use the standard for your operating system.
380    
381    
382    WHAT \R MATCHES
383    
384           By default, the sequence \R in a pattern matches  any  Unicode  newline
385           sequence,  whatever  has  been selected as the line ending sequence. If
386           you specify
387    
388             --enable-bsr-anycrlf
389    
390           the default is changed so that \R matches only CR, LF, or  CRLF.  What-
391           ever  is selected when PCRE is built can be overridden when the library
392           functions are called.
393    
394    
395  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
396    
397         The  PCRE building process uses libtool to build both shared and static         The PCRE building process uses libtool to build both shared and  static
398         Unix libraries by default. You can suppress one of these by adding  one         Unix  libraries by default. You can suppress one of these by adding one
399         of         of
400    
401           --disable-shared           --disable-shared
# Line 337  BUILDING SHARED AND STATIC LIBRARIES Line 407  BUILDING SHARED AND STATIC LIBRARIES
407  POSIX MALLOC USAGE  POSIX MALLOC USAGE
408    
409         When PCRE is called through the POSIX interface (see the pcreposix doc-         When PCRE is called through the POSIX interface (see the pcreposix doc-
410         umentation), additional working storage is  required  for  holding  the         umentation),  additional  working  storage  is required for holding the
411         pointers  to capturing substrings, because PCRE requires three integers         pointers to capturing substrings, because PCRE requires three  integers
412         per substring, whereas the POSIX interface provides only  two.  If  the         per  substring,  whereas  the POSIX interface provides only two. If the
413         number of expected substrings is small, the wrapper function uses space         number of expected substrings is small, the wrapper function uses space
414         on the stack, because this is faster than using malloc() for each call.         on the stack, because this is faster than using malloc() for each call.
415         The default threshold above which the stack is no longer used is 10; it         The default threshold above which the stack is no longer used is 10; it
# Line 352  POSIX MALLOC USAGE Line 422  POSIX MALLOC USAGE
422    
423  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
424    
425         Within a compiled pattern, offset values are used  to  point  from  one         Within  a  compiled  pattern,  offset values are used to point from one
426         part  to another (for example, from an opening parenthesis to an alter-         part to another (for example, from an opening parenthesis to an  alter-
427         nation metacharacter). By default, two-byte values are used  for  these         nation  metacharacter).  By default, two-byte values are used for these
428         offsets,  leading  to  a  maximum size for a compiled pattern of around         offsets, leading to a maximum size for a  compiled  pattern  of  around
429         64K. This is sufficient to handle all but the most  gigantic  patterns.         64K.  This  is sufficient to handle all but the most gigantic patterns.
430         Nevertheless,  some  people do want to process enormous patterns, so it         Nevertheless, some people do want to process enormous patterns,  so  it
431         is possible to compile PCRE to use three-byte or four-byte  offsets  by         is  possible  to compile PCRE to use three-byte or four-byte offsets by
432         adding a setting such as         adding a setting such as
433    
434           --with-link-size=3           --with-link-size=3
435    
436         to  the  configure  command.  The value given must be 2, 3, or 4. Using         to the configure command. The value given must be 2,  3,  or  4.  Using
437         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
438         additional bytes when handling them.         additional bytes when handling them.
439    
        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.  
   
440    
441  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
442    
# Line 390  AVOIDING EXCESSIVE STACK USAGE Line 455  AVOIDING EXCESSIVE STACK USAGE
455    
456         to  the  configure  command. With this configuration, PCRE will use the         to  the  configure  command. With this configuration, PCRE will use the
457         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-
458         ment  functions.  Separate  functions are provided because the usage is         ment  functions. By default these point to malloc() and free(), but you
459         very predictable: the block sizes requested are always  the  same,  and         can replace the pointers so that your own functions are used.
460         the  blocks  are always freed in reverse order. A calling program might  
461         be able to implement optimized functions that perform better  than  the         Separate functions are  provided  rather  than  using  pcre_malloc  and
462         standard  malloc()  and  free()  functions.  PCRE  runs noticeably more         pcre_free  because  the  usage  is  very  predictable:  the block sizes
463         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
464         function; it is not relevant for the the pcre_dfa_exec() function.         reverse  order.  A calling program might be able to implement optimized
465           functions that perform better  than  malloc()  and  free().  PCRE  runs
466           noticeably more slowly when built in this way. This option affects only
467           the  pcre_exec()  function;  it   is   not   relevant   for   the   the
468           pcre_dfa_exec() function.
469    
470    
471  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
# Line 429  LIMITING PCRE RESOURCE USAGE Line 498  LIMITING PCRE RESOURCE USAGE
498         time.         time.
499    
500    
501    CREATING CHARACTER TABLES AT BUILD TIME
502    
503           PCRE uses fixed tables for processing characters whose code values  are
504           less  than 256. By default, PCRE is built with a set of tables that are
505           distributed in the file pcre_chartables.c.dist. These  tables  are  for
506           ASCII codes only. If you add
507    
508             --enable-rebuild-chartables
509    
510           to  the  configure  command, the distributed tables are no longer used.
511           Instead, a program called dftables is compiled and  run.  This  outputs
512           the source for new set of tables, created in the default locale of your
513           C runtime system. (This method of replacing the tables does not work if
514           you  are cross compiling, because dftables is run on the local host. If
515           you need to create alternative tables when cross  compiling,  you  will
516           have to do so "by hand".)
517    
518    
519  USING EBCDIC CODE  USING EBCDIC CODE
520    
521         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
522         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
523         PCRE can, however, be compiled to  run  in  an  EBCDIC  environment  by         This  is  the  case for most computer operating systems. PCRE can, how-
524         adding         ever, be compiled to run in an EBCDIC environment by adding
525    
526           --enable-ebcdic           --enable-ebcdic
527    
528         to the configure command.         to the configure command. This setting implies --enable-rebuild-charta-
529           bles.  You  should  only  use  it if you know that you are in an EBCDIC
530           environment (for example,  an  IBM  mainframe  operating  system).  The
531           --enable-ebcdic option is incompatible with --enable-utf8.
532    
533    
534    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
535    
536           By default, pcregrep reads all files as plain text. You can build it so
537           that it recognizes files whose names end in .gz or .bz2, and reads them
538           with libz or libbz2, respectively, by adding one or both of
539    
540             --enable-pcregrep-libz
541             --enable-pcregrep-libbz2
542    
543           to the configure command. These options naturally require that the rel-
544           evant libraries are installed on your system. Configuration  will  fail
545           if they are not.
546    
547    
548    PCRETEST OPTION FOR LIBREADLINE SUPPORT
549    
550           If you add
551    
552             --enable-pcretest-libreadline
553    
554           to  the  configure  command,  pcretest  is  linked with the libreadline
555           library, and when its input is from a terminal, it reads it  using  the
556           readline() function. This provides line-editing and history facilities.
557           Note that libreadline is GPL-licenced, so if you distribute a binary of
558           pcretest linked in this way, there may be licensing issues.
559    
560           Setting  this  option  causes  the -lreadline option to be added to the
561           pcretest build. In many operating environments with  a  sytem-installed
562           libreadline this is sufficient. However, in some environments (e.g.  if
563           an unmodified distribution version of readline is in use),  some  extra
564           configuration  may  be necessary. The INSTALL file for libreadline says
565           this:
566    
567             "Readline uses the termcap functions, but does not link with the
568             termcap or curses library itself, allowing applications which link
569             with readline the to choose an appropriate library."
570    
571           If your environment has not been set up so that an appropriate  library
572           is automatically included, you may need to add something like
573    
574             LIBS="-ncurses"
575    
576           immediately before the configure command.
577    
578    
579  SEE ALSO  SEE ALSO
# Line 455  AUTHOR Line 590  AUTHOR
590    
591  REVISION  REVISION
592    
593         Last updated: 06 March 2007         Last updated: 17 March 2009
594         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
595  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
596    
597    
598  PCREMATCHING(3)                                                PCREMATCHING(3)  PCREMATCHING(3)                                                PCREMATCHING(3)
599    
600    
# Line 508  REGULAR EXPRESSIONS AS TREES Line 643  REGULAR EXPRESSIONS AS TREES
643    
644  THE STANDARD MATCHING ALGORITHM  THE STANDARD MATCHING ALGORITHM
645    
646         In the terminology of Jeffrey Friedl's book Mastering  Regular  Expres-         In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
647         sions,  the  standard  algorithm  is  an "NFA algorithm". It conducts a         sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
648         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
649         single path through the tree, checking that the subject matches what is         single path through the tree, checking that the subject matches what is
650         required. When there is a mismatch, the algorithm  tries  any  alterna-         required. When there is a mismatch, the algorithm  tries  any  alterna-
# Line 591  THE ALTERNATIVE MATCHING ALGORITHM Line 726  THE ALTERNATIVE MATCHING ALGORITHM
726         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
727         supported.         supported.
728    
729         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
730           sequence, which resets the start of the match when encountered (but may
731           be on some paths and not on others), is not  supported.  It  causes  an
732           error if encountered.
733    
734           6.  Callouts  are  supported, but the value of the capture_top field is
735         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.
736    
737         6.  The \C escape sequence, which (in the standard algorithm) matches a         7. The \C escape sequence, which (in the standard algorithm) matches  a
738         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-
739         tive  algorithm  moves  through  the  subject string one character at a         tive algorithm moves through the subject  string  one  character  at  a
740         time, for all active paths through the tree.         time, for all active paths through the tree.
741    
742           8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
743           are not supported. (*FAIL) is supported, and  behaves  like  a  failing
744           negative assertion.
745    
746    
747  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
748    
749         Using the alternative matching algorithm provides the following  advan-         Using  the alternative matching algorithm provides the following advan-
750         tages:         tages:
751    
752         1. All possible matches (at a single point in the subject) are automat-         1. All possible matches (at a single point in the subject) are automat-
753         ically found, and in particular, the longest match is  found.  To  find         ically  found,  and  in particular, the longest match is found. To find
754         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
755         things with callouts.         things with callouts.
756    
757         2. There is much better support for partial matching. The  restrictions         2.  Because  the  alternative  algorithm  scans the subject string just
758         on  the content of the pattern that apply when using the standard algo-         once, and never needs to backtrack, it is possible to  pass  very  long
759         rithm for partial matching do not apply to the  alternative  algorithm.         subject  strings  to  the matching function in several pieces, checking
        For  non-anchored patterns, the starting position of a partial match is  
        available.  
   
        3. Because the alternative algorithm  scans  the  subject  string  just  
        once,  and  never  needs to backtrack, it is possible to pass very long  
        subject strings to the matching function in  several  pieces,  checking  
760         for partial matching each time.         for partial matching each time.
761    
762    
# Line 626  DISADVANTAGES OF THE ALTERNATIVE ALGORIT Line 764  DISADVANTAGES OF THE ALTERNATIVE ALGORIT
764    
765         The alternative algorithm suffers from a number of disadvantages:         The alternative algorithm suffers from a number of disadvantages:
766    
767         1.  It  is  substantially  slower  than the standard algorithm. This is         1. It is substantially slower than  the  standard  algorithm.  This  is
768         partly because it has to search for all possible matches, but  is  also         partly  because  it has to search for all possible matches, but is also
769         because it is less susceptible to optimization.         because it is less susceptible to optimization.
770    
771         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
# Line 645  AUTHOR Line 783  AUTHOR
783    
784  REVISION  REVISION
785    
786         Last updated: 06 March 2007         Last updated: 25 August 2009
787         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
788  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
789    
790    
791  PCREAPI(3)                                                          PCREAPI(3)  PCREAPI(3)                                                          PCREAPI(3)
792    
793    
# Line 757  PCRE API OVERVIEW Line 895  PCRE API OVERVIEW
895         pcre_exec() are used for compiling and matching regular expressions  in         pcre_exec() are used for compiling and matching regular expressions  in
896         a  Perl-compatible  manner. A sample program that demonstrates the sim-         a  Perl-compatible  manner. A sample program that demonstrates the sim-
897         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
898         the  source distribution. The pcresample documentation describes how to         the PCRE source distribution. A listing of this program is given in the
899         run it.         pcredemo documentation, and the pcresample documentation describes  how
900           to compile and run it.
901    
902         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
903         ble,  is  also provided. This uses a different algorithm for the match-         ble, is also provided. This uses a different algorithm for  the  match-
904         ing. The alternative algorithm finds all possible matches (at  a  given         ing.  The  alternative algorithm finds all possible matches (at a given
905         point  in  the subject), and scans the subject just once. However, this         point in the subject), and scans the subject just once.  However,  this
906         algorithm does not return captured substrings. A description of the two         algorithm does not return captured substrings. A description of the two
907         matching  algorithms and their advantages and disadvantages is given in         matching algorithms and their advantages and disadvantages is given  in
908         the pcrematching documentation.         the pcrematching documentation.
909    
910         In addition to the main compiling and  matching  functions,  there  are         In  addition  to  the  main compiling and matching functions, there are
911         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
912         string that is matched by pcre_exec(). They are:         string that is matched by pcre_exec(). They are:
913    
# Line 783  PCRE API OVERVIEW Line 922  PCRE API OVERVIEW
922         pcre_free_substring() and pcre_free_substring_list() are also provided,         pcre_free_substring() and pcre_free_substring_list() are also provided,
923         to free the memory used for extracted strings.         to free the memory used for extracted strings.
924    
925         The  function  pcre_maketables()  is  used  to build a set of character         The function pcre_maketables() is used to  build  a  set  of  character
926         tables  in  the  current  locale   for   passing   to   pcre_compile(),         tables   in   the   current   locale  for  passing  to  pcre_compile(),
927         pcre_exec(),  or  pcre_dfa_exec(). This is an optional facility that is         pcre_exec(), or pcre_dfa_exec(). This is an optional facility  that  is
928         provided for specialist use.  Most  commonly,  no  special  tables  are         provided  for  specialist  use.  Most  commonly,  no special tables are
929         passed,  in  which case internal tables that are generated when PCRE is         passed, in which case internal tables that are generated when  PCRE  is
930         built are used.         built are used.
931    
932         The function pcre_fullinfo() is used to find out  information  about  a         The  function  pcre_fullinfo()  is used to find out information about a
933         compiled  pattern; pcre_info() is an obsolete version that returns only         compiled pattern; pcre_info() is an obsolete version that returns  only
934         some of the available information, but is retained for  backwards  com-         some  of  the available information, but is retained for backwards com-
935         patibility.   The function pcre_version() returns a pointer to a string         patibility.  The function pcre_version() returns a pointer to a  string
936         containing the version of PCRE and its date of release.         containing the version of PCRE and its date of release.
937    
938         The function pcre_refcount() maintains a  reference  count  in  a  data         The  function  pcre_refcount()  maintains  a  reference count in a data
939         block  containing  a compiled pattern. This is provided for the benefit         block containing a compiled pattern. This is provided for  the  benefit
940         of object-oriented applications.         of object-oriented applications.
941    
942         The global variables pcre_malloc and pcre_free  initially  contain  the         The  global  variables  pcre_malloc and pcre_free initially contain the
943         entry  points  of  the  standard malloc() and free() functions, respec-         entry points of the standard malloc()  and  free()  functions,  respec-
944         tively. PCRE calls the memory management functions via these variables,         tively. PCRE calls the memory management functions via these variables,
945         so  a  calling  program  can replace them if it wishes to intercept the         so a calling program can replace them if it  wishes  to  intercept  the
946         calls. This should be done before calling any PCRE functions.         calls. This should be done before calling any PCRE functions.
947    
948         The global variables pcre_stack_malloc  and  pcre_stack_free  are  also         The  global  variables  pcre_stack_malloc  and pcre_stack_free are also
949         indirections  to  memory  management functions. These special functions         indirections to memory management functions.  These  special  functions
950         are used only when PCRE is compiled to use  the  heap  for  remembering         are  used  only  when  PCRE is compiled to use the heap for remembering
951         data, instead of recursive function calls, when running the pcre_exec()         data, instead of recursive function calls, when running the pcre_exec()
952         function. See the pcrebuild documentation for  details  of  how  to  do         function.  See  the  pcrebuild  documentation  for details of how to do
953         this.  It  is  a non-standard way of building PCRE, for use in environ-         this. It is a non-standard way of building PCRE, for  use  in  environ-
954         ments that have limited stacks. Because of the greater  use  of  memory         ments  that  have  limited stacks. Because of the greater use of memory
955         management,  it  runs  more  slowly. Separate functions are provided so         management, it runs more slowly. Separate  functions  are  provided  so
956         that special-purpose external code can be  used  for  this  case.  When         that  special-purpose  external  code  can  be used for this case. When
957         used,  these  functions  are always called in a stack-like manner (last         used, these functions are always called in a  stack-like  manner  (last
958         obtained, first freed), and always for memory blocks of the same  size.         obtained,  first freed), and always for memory blocks of the same size.
959         There  is  a discussion about PCRE's stack usage in the pcrestack docu-         There is a discussion about PCRE's stack usage in the  pcrestack  docu-
960         mentation.         mentation.
961    
962         The global variable pcre_callout initially contains NULL. It can be set         The global variable pcre_callout initially contains NULL. It can be set
963         by  the  caller  to  a "callout" function, which PCRE will then call at         by the caller to a "callout" function, which PCRE  will  then  call  at
964         specified points during a matching operation. Details are given in  the         specified  points during a matching operation. Details are given in the
965         pcrecallout documentation.         pcrecallout documentation.
966    
967    
968  NEWLINES  NEWLINES
969    
970         PCRE  supports four different conventions for indicating line breaks in         PCRE supports five different conventions for indicating line breaks  in
971         strings: a single CR (carriage return) character, a  single  LF  (line-         strings:  a  single  CR (carriage return) character, a single LF (line-
972         feed)  character,  the two-character sequence CRLF, or any Unicode new-         feed) character, the two-character sequence CRLF, any of the three pre-
973         line sequence.  The Unicode newline sequences are the three  just  men-         ceding,  or any Unicode newline sequence. The Unicode newline sequences
974         tioned, plus the single characters VT (vertical tab, U+000B), FF (form-         are the three just mentioned, plus the single characters  VT  (vertical
975         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
976         and PS (paragraph separator, U+2029).         separator, U+2028), and PS (paragraph separator, U+2029).
977    
978         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
979         system as its standard newline sequence. When PCRE is built, a  default         system  as its standard newline sequence. When PCRE is built, a default
980         can  be  specified.  The default default is LF, which is the Unix stan-         can be specified.  The default default is LF, which is the  Unix  stan-
981         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
982         pattern is compiled, or when it is matched.         pattern is compiled, or when it is matched.
983    
984           At compile time, the newline convention can be specified by the options
985           argument  of  pcre_compile(), or it can be specified by special text at
986           the start of the pattern itself; this overrides any other settings. See
987           the pcrepattern page for details of the special character sequences.
988    
989         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-
990         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
991         newline  convention  affects  the  handling of the dot, circumflex, and         newline  convention  affects  the  handling of the dot, circumflex, and
992         dollar metacharacters, the handling of #-comments in /x mode, and, when         dollar metacharacters, the handling of #-comments in /x mode, and, when
993         CRLF  is a recognized line ending sequence, the match position advance-         CRLF  is a recognized line ending sequence, the match position advance-
994         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
995         not affect the interpretation of the \n or \r escape sequences.         section on pcre_exec() options below.
996    
997           The  choice of newline convention does not affect the interpretation of
998           the \n or \r escape sequences, nor does  it  affect  what  \R  matches,
999           which is controlled in a similar way, but by separate options.
1000    
1001    
1002  MULTITHREADING  MULTITHREADING
# Line 858  MULTITHREADING Line 1006  MULTITHREADING
1006         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
1007         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
1008    
1009         The  compiled form of a regular expression is not altered during match-         The compiled form of a regular expression is not altered during  match-
1010         ing, so the same compiled pattern can safely be used by several threads         ing, so the same compiled pattern can safely be used by several threads
1011         at once.         at once.
1012    
# Line 866  MULTITHREADING Line 1014  MULTITHREADING
1014  SAVING PRECOMPILED PATTERNS FOR LATER USE  SAVING PRECOMPILED PATTERNS FOR LATER USE
1015    
1016         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
1017         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
1018         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
1019         pcreprecompile documentation.         pcreprecompile  documentation.  However, compiling a regular expression
1020           with one version of PCRE for use with a different version is not  guar-
1021           anteed to work and may cause crashes.
1022    
1023    
1024  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
1025    
1026         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
1027    
1028         The function pcre_config() makes it possible for a PCRE client to  dis-         The  function pcre_config() makes it possible for a PCRE client to dis-
1029         cover which optional features have been compiled into the PCRE library.         cover which optional features have been compiled into the PCRE library.
1030         The pcrebuild documentation has more details about these optional  fea-         The  pcrebuild documentation has more details about these optional fea-
1031         tures.         tures.
1032    
1033         The  first  argument  for pcre_config() is an integer, specifying which         The first argument for pcre_config() is an  integer,  specifying  which
1034         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
1035         into  which  the  information  is  placed. The following information is         into which the information is  placed.  The  following  information  is
1036         available:         available:
1037    
1038           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
1039    
1040         The output is an integer that is set to one if UTF-8 support is  avail-         The  output is an integer that is set to one if UTF-8 support is avail-
1041         able; otherwise it is set to zero.         able; otherwise it is set to zero.
1042    
1043           PCRE_CONFIG_UNICODE_PROPERTIES           PCRE_CONFIG_UNICODE_PROPERTIES
1044    
1045         The  output  is  an  integer  that is set to one if support for Unicode         The output is an integer that is set to  one  if  support  for  Unicode
1046         character properties is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
1047    
1048           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
1049    
1050         The output is an integer whose value specifies  the  default  character         The  output  is  an integer whose value specifies the default character
1051         sequence  that is recognized as meaning "newline". The four values that         sequence that is recognized as meaning "newline". The four values  that
1052         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,
1053         The default should normally be the standard sequence for your operating         and -1 for ANY.  Though they are derived from ASCII,  the  same  values
1054         system.         are returned in EBCDIC environments. The default should normally corre-
1055           spond to the standard sequence for your operating system.
1056    
1057             PCRE_CONFIG_BSR
1058    
1059           The output is an integer whose value indicates what character sequences
1060           the  \R  escape sequence matches by default. A value of 0 means that \R
1061           matches any Unicode line ending sequence; a value of 1  means  that  \R
1062           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1063           tern is compiled or matched.
1064    
1065           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1066    
# Line 920  CHECKING BUILD-TIME OPTIONS Line 1079  CHECKING BUILD-TIME OPTIONS
1079    
1080           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1081    
1082         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-
1083         internal matching function calls in a  pcre_exec()  execution.  Further         ber of internal matching function calls  in  a  pcre_exec()  execution.
1084         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1085    
1086           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1087    
1088         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
1089         recursion when calling the internal matching function in a  pcre_exec()         of  recursion  when  calling  the  internal  matching  function  in   a
1090         execution. Further details are given with pcre_exec() below.         pcre_exec()  execution.  Further  details  are  given  with pcre_exec()
1091           below.
1092    
1093           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1094    
1095         The  output is an integer that is set to one if internal recursion when         The output is an integer that is set to one if internal recursion  when
1096         running pcre_exec() is implemented by recursive function calls that use         running pcre_exec() is implemented by recursive function calls that use
1097         the  stack  to remember their state. This is the usual way that PCRE is         the stack to remember their state. This is the usual way that  PCRE  is
1098         compiled. The output is zero if PCRE was compiled to use blocks of data         compiled. The output is zero if PCRE was compiled to use blocks of data
1099         on  the  heap  instead  of  recursive  function  calls.  In  this case,         on the  heap  instead  of  recursive  function  calls.  In  this  case,
1100         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory
1101         blocks on the heap, thus avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
1102    
1103    
# Line 954  COMPILING A PATTERN Line 1114  COMPILING A PATTERN
1114    
1115         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1116         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1117         the  two interfaces is that pcre_compile2() has an additional argument,         the two interfaces is that pcre_compile2() has an additional  argument,
1118         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr, via which a numerical error code can be returned.
1119    
1120         The pattern is a C string terminated by a binary zero, and is passed in         The pattern is a C string terminated by a binary zero, and is passed in
1121         the  pattern  argument.  A  pointer to a single block of memory that is         the pattern argument. A pointer to a single block  of  memory  that  is
1122         obtained via pcre_malloc is returned. This contains the  compiled  code         obtained  via  pcre_malloc is returned. This contains the compiled code
1123         and related data. The pcre type is defined for the returned block; this         and related data. The pcre type is defined for the returned block; this
1124         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1125         It is up to the caller to free the memory (via pcre_free) when it is no         It is up to the caller to free the memory (via pcre_free) when it is no
1126         longer required.         longer required.
1127    
1128         Although the compiled code of a PCRE regex is relocatable, that is,  it         Although  the compiled code of a PCRE regex is relocatable, that is, it
1129         does not depend on memory location, the complete pcre data block is not         does not depend on memory location, the complete pcre data block is not
1130         fully relocatable, because it may contain a copy of the tableptr  argu-         fully  relocatable, because it may contain a copy of the tableptr argu-
1131         ment, which is an address (see below).         ment, which is an address (see below).
1132    
1133         The options argument contains various bit settings that affect the com-         The options argument contains various bit settings that affect the com-
1134         pilation. It should be zero if no options are required.  The  available         pilation.  It  should be zero if no options are required. The available
1135         options  are  described  below. Some of them, in particular, those that         options are described below. Some of them (in  particular,  those  that
1136         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
1137         pattern  (see  the  detailed  description in the pcrepattern documenta-         unset from within the pattern (see  the  detailed  description  in  the
1138         tion). For these options, the contents of the options  argument  speci-         pcrepattern  documentation). For those options that can be different in
1139         fies  their initial settings at the start of compilation and execution.         different parts of the pattern, the contents of  the  options  argument
1140         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-
1141         of matching as well as at compile time.         tion. The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at  the
1142           time of matching as well as at compile time.
1143    
1144         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1145         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
# Line 1032  COMPILING A PATTERN Line 1193  COMPILING A PATTERN
1193         all with number 255, before each pattern item. For  discussion  of  the         all with number 255, before each pattern item. For  discussion  of  the
1194         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1195    
1196             PCRE_BSR_ANYCRLF
1197             PCRE_BSR_UNICODE
1198    
1199           These options (which are mutually exclusive) control what the \R escape
1200           sequence matches. The choice is either to match only CR, LF,  or  CRLF,
1201           or to match any Unicode newline sequence. The default is specified when
1202           PCRE is built. It can be overridden from within the pattern, or by set-
1203           ting an option when a compiled pattern is matched.
1204    
1205           PCRE_CASELESS           PCRE_CASELESS
1206    
1207         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
# Line 1105  COMPILING A PATTERN Line 1275  COMPILING A PATTERN
1275         before  or  at  the  first  newline  in  the subject string, though the         before  or  at  the  first  newline  in  the subject string, though the
1276         matched text may continue over the newline.         matched text may continue over the newline.
1277    
1278             PCRE_JAVASCRIPT_COMPAT
1279    
1280           If this option is set, PCRE's behaviour is changed in some ways so that
1281           it  is  compatible with JavaScript rather than Perl. The changes are as
1282           follows:
1283    
1284           (1) A lone closing square bracket in a pattern  causes  a  compile-time
1285           error,  because this is illegal in JavaScript (by default it is treated
1286           as a data character). Thus, the pattern AB]CD becomes illegal when this
1287           option is set.
1288    
1289           (2)  At run time, a back reference to an unset subpattern group matches
1290           an empty string (by default this causes the current  matching  alterna-
1291           tive  to  fail). A pattern such as (\1)(a) succeeds when this option is
1292           set (assuming it can find an "a" in the subject), whereas it  fails  by
1293           default, for Perl compatibility.
1294    
1295           PCRE_MULTILINE           PCRE_MULTILINE
1296    
1297         By default, PCRE treats the subject string as consisting  of  a  single         By  default,  PCRE  treats the subject string as consisting of a single
1298         line  of characters (even if it actually contains newlines). The "start         line of characters (even if it actually contains newlines). The  "start
1299         of line" metacharacter (^) matches only at the  start  of  the  string,         of  line"  metacharacter  (^)  matches only at the start of the string,
1300         while  the  "end  of line" metacharacter ($) matches only at the end of         while the "end of line" metacharacter ($) matches only at  the  end  of
1301         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1302         is set). This is the same as Perl.         is set). This is the same as Perl.
1303    
1304         When  PCRE_MULTILINE  it  is set, the "start of line" and "end of line"         When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"
1305         constructs match immediately following or immediately  before  internal         constructs  match  immediately following or immediately before internal
1306         newlines  in  the  subject string, respectively, as well as at the very         newlines in the subject string, respectively, as well as  at  the  very
1307         start and end. This is equivalent to Perl's /m option, and  it  can  be         start  and  end.  This is equivalent to Perl's /m option, and it can be
1308         changed within a pattern by a (?m) option setting. If there are no new-         changed within a pattern by a (?m) option setting. If there are no new-
1309         lines in a subject string, or no occurrences of ^ or $  in  a  pattern,         lines  in  a  subject string, or no occurrences of ^ or $ in a pattern,
1310         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1311    
1312           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
1313           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
1314           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
1315             PCRE_NEWLINE_ANYCRLF
1316           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1317    
1318         These  options  override the default newline definition that was chosen         These options override the default newline definition that  was  chosen
1319         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
1320         newline  is  indicated  by a single character (CR or LF, respectively).         newline is indicated by a single character (CR  or  LF,  respectively).
1321         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the         Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the
1322         two-character  CRLF  sequence.  Setting PCRE_NEWLINE_ANY specifies that         two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies
1323         any Unicode newline sequence should be recognized. The Unicode  newline         that any of the three preceding sequences should be recognized. Setting
1324         sequences  are  the three just mentioned, plus the single characters VT         PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be
1325         (vertical tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085),         recognized. The Unicode newline sequences are the three just mentioned,
1326         LS  (line separator, U+2028), and PS (paragraph separator, U+2029). The         plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,
1327         last two are recognized only in UTF-8 mode.         U+000C),  NEL  (next line, U+0085), LS (line separator, U+2028), and PS
1328           (paragraph separator, U+2029). The last  two  are  recognized  only  in
1329         The newline setting in the  options  word  uses  three  bits  that  are         UTF-8 mode.
1330         treated  as  a  number, giving eight possibilities. Currently only five  
1331         are used (default plus the four values above). This means that  if  you         The  newline  setting  in  the  options  word  uses three bits that are
1332         set  more  than  one  newline option, the combination may or may not be         treated as a number, giving eight possibilities. Currently only six are
1333         sensible. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is  equiva-         used  (default  plus the five values above). This means that if you set
1334         lent  to PCRE_NEWLINE_CRLF, but other combinations yield unused numbers         more than one newline option, the combination may or may not be  sensi-
1335         and cause an error.         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1336           PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
1337         The only time that a line break is specially recognized when  compiling         cause an error.
1338         a  pattern  is  if  PCRE_EXTENDED  is set, and an unescaped # outside a  
1339         character class is encountered. This indicates  a  comment  that  lasts         The  only time that a line break is specially recognized when compiling
1340         until  after the next line break sequence. In other circumstances, line         a pattern is if PCRE_EXTENDED is set, and  an  unescaped  #  outside  a
1341         break  sequences  are  treated  as  literal  data,   except   that   in         character  class  is  encountered.  This indicates a comment that lasts
1342           until after the next line break sequence. In other circumstances,  line
1343           break   sequences   are   treated  as  literal  data,  except  that  in
1344         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters
1345         and are therefore ignored.         and are therefore ignored.
1346    
1347         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
1348         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.
1349    
1350           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1351    
# Line 1184  COMPILING A PATTERN Line 1374  COMPILING A PATTERN
1374           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1375    
1376         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
1377         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically  checked.  There  is  a  discussion about the validity of
1378         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
1379         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
1380         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-
1381         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
1382         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
1383         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
1384         ing of subject strings.         can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the
1385           UTF-8 validity checking of subject strings.
1386    
1387    
1388  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1389    
1390         The following table lists the error  codes  than  may  be  returned  by         The  following  table  lists  the  error  codes than may be returned by
1391         pcre_compile2(),  along with the error messages that may be returned by         pcre_compile2(), along with the error messages that may be returned  by
1392         both compiling functions. As PCRE has developed, some error codes  have         both  compiling functions. As PCRE has developed, some error codes have
1393         fallen out of use. To avoid confusion, they have not been re-used.         fallen out of use. To avoid confusion, they have not been re-used.
1394    
1395            0  no error            0  no error
# Line 1213  COMPILATION ERROR CODES Line 1404  COMPILATION ERROR CODES
1404            9  nothing to repeat            9  nothing to repeat
1405           10  [this code is not in use]           10  [this code is not in use]
1406           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1407           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1408           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1409           14  missing )           14  missing )
1410           15  reference to non-existent subpattern           15  reference to non-existent subpattern
# Line 1221  COMPILATION ERROR CODES Line 1412  COMPILATION ERROR CODES
1412           17  unknown option bit(s) set           17  unknown option bit(s) set
1413           18  missing ) after comment           18  missing ) after comment
1414           19  [this code is not in use]           19  [this code is not in use]
1415           20  regular expression too large           20  regular expression is too large
1416           21  failed to get memory           21  failed to get memory
1417           22  unmatched parentheses           22  unmatched parentheses
1418           23  internal error: code overflow           23  internal error: code overflow
# Line 1230  COMPILATION ERROR CODES Line 1421  COMPILATION ERROR CODES
1421           26  malformed number or name after (?(           26  malformed number or name after (?(
1422           27  conditional group contains more than two branches           27  conditional group contains more than two branches
1423           28  assertion expected after (?(           28  assertion expected after (?(
1424           29  (?R or (?digits must be followed by )           29  (?R or (?[+-]digits must be followed by )
1425           30  unknown POSIX class name           30  unknown POSIX class name
1426           31  POSIX collating elements are not supported           31  POSIX collating elements are not supported
1427           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 1441  COMPILATION ERROR CODES
1441           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1442           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1443           48  subpattern name is too long (maximum 32 characters)           48  subpattern name is too long (maximum 32 characters)
1444           49  too many named subpatterns (maximum 10,000)           49  too many named subpatterns (maximum 10000)
1445           50  repeated subpattern is too long           50  [this code is not in use]
1446           51  octal value is greater than \377 (not in UTF-8 mode)           51  octal value is greater than \377 (not in UTF-8 mode)
1447           52  internal error: overran compiling workspace           52  internal error: overran compiling workspace
1448           53   internal  error:  previously-checked  referenced  subpattern not           53  internal  error:  previously-checked  referenced  subpattern  not
1449         found         found
1450           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1451           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1452           56  inconsistent NEWLINE options"           56  inconsistent NEWLINE options
1453             57  \g is not followed by a braced, angle-bracketed, or quoted
1454                   name/number or by a plain number
1455             58  a numbered reference must not be zero
1456             59  (*VERB) with an argument is not supported
1457             60  (*VERB) not recognized
1458             61  number is too big
1459             62  subpattern name expected
1460             63  digit expected after (?+
1461             64  ] is an invalid data character in JavaScript compatibility mode
1462    
1463           The  numbers  32  and 10000 in errors 48 and 49 are defaults; different
1464           values may be used if the limits were changed when PCRE was built.
1465    
1466    
1467  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1310  STUDYING A PATTERN Line 1513  STUDYING A PATTERN
1513  LOCALE SUPPORT  LOCALE SUPPORT
1514    
1515         PCRE handles caseless matching, and determines whether  characters  are         PCRE handles caseless matching, and determines whether  characters  are
1516         letters  digits,  or whatever, by reference to a set of tables, indexed         letters,  digits, or whatever, by reference to a set of tables, indexed
1517         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
1518         characters  with  codes  less than 128. Higher-valued codes never match         characters  with  codes  less than 128. Higher-valued codes never match
1519         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
1520         with  Unicode  character property support. The use of locales with Uni-         with  Unicode  character property support. The use of locales with Uni-
1521         code is discouraged.         code is discouraged. If you are handling characters with codes  greater
1522           than  128, you should either use UTF-8 and Unicode, or use locales, but
1523         An internal set of tables is created in the default C locale when  PCRE         not try to mix the two.
1524         is  built.  This  is  used when the final argument of pcre_compile() is  
1525         NULL, and is sufficient for many applications. An  alternative  set  of         PCRE contains an internal set of tables that are used  when  the  final
1526         tables  can,  however, be supplied. These may be created in a different         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many
1527         locale from the default. As more and more applications change to  using         applications.  Normally, the internal tables recognize only ASCII char-
1528         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-
1529           nal tables to be rebuilt in the default "C" locale of the local system,
1530         External  tables  are  built by calling the pcre_maketables() function,         which may cause them to be different.
1531         which has no arguments, in the relevant locale. The result can then  be  
1532         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For         The  internal tables can always be overridden by tables supplied by the
1533         example, to build and use tables that are appropriate  for  the  French         application that calls PCRE. These may be created in a different locale
1534         locale  (where  accented  characters  with  values greater than 128 are         from  the  default.  As more and more applications change to using Uni-
1535           code, the need for this locale support is expected to die away.
1536    
1537           External tables are built by calling  the  pcre_maketables()  function,
1538           which  has no arguments, in the relevant locale. The result can then be
1539           passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For
1540           example,  to  build  and use tables that are appropriate for the French
1541           locale (where accented characters with  values  greater  than  128  are
1542         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1543    
1544           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1545           tables = pcre_maketables();           tables = pcre_maketables();
1546           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1547    
1548           The  locale  name "fr_FR" is used on Linux and other Unix-like systems;
1549           if you are using Windows, the name for the French locale is "french".
1550    
1551         When pcre_maketables() runs, the tables are built  in  memory  that  is         When pcre_maketables() runs, the tables are built  in  memory  that  is
1552         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         obtained  via  pcre_malloc. It is the caller's responsibility to ensure
1553         that the memory containing the tables remains available for as long  as         that the memory containing the tables remains available for as long  as
# Line 1437  INFORMATION ABOUT A PATTERN Line 1650  INFORMATION ABOUT A PATTERN
1650         returned. The fourth argument should point to an unsigned char *  vari-         returned. The fourth argument should point to an unsigned char *  vari-
1651         able.         able.
1652    
1653             PCRE_INFO_HASCRORLF
1654    
1655           Return  1  if  the  pattern  contains any explicit matches for CR or LF
1656           characters, otherwise 0. The fourth argument should  point  to  an  int
1657           variable.  An explicit match is either a literal CR or LF character, or
1658           \r or \n.
1659    
1660             PCRE_INFO_JCHANGED
1661    
1662           Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,
1663           otherwise  0. The fourth argument should point to an int variable. (?J)
1664           and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1665    
1666           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1667    
1668         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
1669         matched string, other than at its  start,  if  such  a  byte  has  been         matched  string,  other  than  at  its  start,  if such a byte has been
1670         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1671         is no such byte, -1 is returned. For anchored patterns, a last  literal         is  no such byte, -1 is returned. For anchored patterns, a last literal
1672         byte  is  recorded only if it follows something of variable length. For         byte is recorded only if it follows something of variable  length.  For
1673         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
1674         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1675    
# Line 1451  INFORMATION ABOUT A PATTERN Line 1677  INFORMATION ABOUT A PATTERN
1677           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1678           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1679    
1680         PCRE  supports the use of named as well as numbered capturing parenthe-         PCRE supports the use of named as well as numbered capturing  parenthe-
1681         ses. The names are just an additional way of identifying the  parenthe-         ses.  The names are just an additional way of identifying the parenthe-
1682         ses, which still acquire numbers. Several convenience functions such as         ses, which still acquire numbers. Several convenience functions such as
1683         pcre_get_named_substring() are provided for  extracting  captured  sub-         pcre_get_named_substring()  are  provided  for extracting captured sub-
1684         strings  by  name. It is also possible to extract the data directly, by         strings by name. It is also possible to extract the data  directly,  by
1685         first converting the name to a number in order to  access  the  correct         first  converting  the  name to a number in order to access the correct
1686         pointers in the output vector (described with pcre_exec() below). To do         pointers in the output vector (described with pcre_exec() below). To do
1687         the conversion, you need  to  use  the  name-to-number  map,  which  is         the  conversion,  you  need  to  use  the  name-to-number map, which is
1688         described by these three values.         described by these three values.
1689    
1690         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
1691         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1692         of  each  entry;  both  of  these  return  an int value. The entry size         of each entry; both of these  return  an  int  value.  The  entry  size
1693         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns
1694         a  pointer  to  the  first  entry of the table (a pointer to char). The         a pointer to the first entry of the table  (a  pointer  to  char).  The
1695         first two bytes of each entry are the number of the capturing parenthe-         first two bytes of each entry are the number of the capturing parenthe-
1696         sis,  most  significant byte first. The rest of the entry is the corre-         sis, most significant byte first. The rest of the entry is  the  corre-
1697         sponding name, zero terminated. The names are  in  alphabetical  order.         sponding  name,  zero  terminated. The names are in alphabetical order.
1698         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-
1699         theses numbers. For example, consider  the  following  pattern  (assume         theses  numbers.  For  example,  consider the following pattern (assume
1700         PCRE_EXTENDED  is  set,  so  white  space  -  including  newlines  - is         PCRE_EXTENDED is  set,  so  white  space  -  including  newlines  -  is
1701         ignored):         ignored):
1702    
1703           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1704           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1705    
1706         There are four named subpatterns, so the table has  four  entries,  and         There  are  four  named subpatterns, so the table has four entries, and
1707         each  entry  in the table is eight bytes long. The table is as follows,         each entry in the table is eight bytes long. The table is  as  follows,
1708         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1709         as ??:         as ??:
1710    
# Line 1487  INFORMATION ABOUT A PATTERN Line 1713  INFORMATION ABOUT A PATTERN
1713           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1714           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1715    
1716         When  writing  code  to  extract  data from named subpatterns using the         When writing code to extract data  from  named  subpatterns  using  the
1717         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
1718         to be different for each compiled pattern.         to be different for each compiled pattern.
1719    
1720             PCRE_INFO_OKPARTIAL
1721    
1722           Return 1 if the pattern can be used for partial matching, otherwise  0.
1723           The fourth argument should point to an int variable. From release 8.00,
1724           this always returns 1, because the restrictions that previously applied
1725           to  partial  matching  have  been lifted. The pcrepartial documentation
1726           gives details of partial matching.
1727    
1728           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1729    
1730         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
1731         fourth argument should point to an unsigned long  int  variable.  These         fourth  argument  should  point to an unsigned long int variable. These
1732         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1733         by any top-level option settings within the pattern itself.         by any top-level option settings at the start of the pattern itself. In
1734           other words, they are the options that will be in force  when  matching
1735           starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
1736           the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1737           and PCRE_EXTENDED.
1738    
1739         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
1740         alternatives begin with one of the following:         alternatives begin with one of the following:
1741    
1742           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1512  INFORMATION ABOUT A PATTERN Line 1750  INFORMATION ABOUT A PATTERN
1750    
1751           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1752    
1753         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
1754         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
1755         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
1756         size_t variable.         size_t variable.
# Line 1520  INFORMATION ABOUT A PATTERN Line 1758  INFORMATION ABOUT A PATTERN
1758           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1759    
1760         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
1761         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
1762         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
1763         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
1764         variable.         variable.
1765    
1766    
# Line 1530  OBSOLETE INFO FUNCTION Line 1768  OBSOLETE INFO FUNCTION
1768    
1769         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1770    
1771         The  pcre_info()  function is now obsolete because its interface is too         The pcre_info() function is now obsolete because its interface  is  too
1772         restrictive to return all the available data about a compiled  pattern.         restrictive  to return all the available data about a compiled pattern.
1773         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of
1774         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-
1775         lowing negative numbers:         lowing negative numbers:
1776    
1777           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1778           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1779    
1780         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
1781         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
1782         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1783    
1784         If  the  pattern  is  not anchored and the firstcharptr argument is not         If the pattern is not anchored and the  firstcharptr  argument  is  not
1785         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
1786         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1787    
1788    
# Line 1552  REFERENCE COUNTS Line 1790  REFERENCE COUNTS
1790    
1791         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1792    
1793         The  pcre_refcount()  function is used to maintain a reference count in         The pcre_refcount() function is used to maintain a reference  count  in
1794         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
1795         benefit  of  applications  that  operate  in an object-oriented manner,         benefit of applications that  operate  in  an  object-oriented  manner,
1796         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1797         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.
1798    
1799         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1800         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
1801         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
1802         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
1803         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
1804         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1805    
1806         Except when it is zero, the reference count is not correctly  preserved         Except  when it is zero, the reference count is not correctly preserved
1807         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
1808         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1809    
1810    
# Line 1660  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1898  MATCHING A PATTERN: THE TRADITIONAL FUNC
1898         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-
1899         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.
1900    
1901         Limiting  the  recursion  depth  limits the amount of stack that can be         Limiting the recursion depth limits the amount of  stack  that  can  be
1902         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
1903         of the stack, the amount of heap memory that can be used.         of the stack, the amount of heap memory that can be used.
1904    
1905         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
1906         built; the default default  is  the  same  value  as  the  default  for         built;  the  default  default  is  the  same  value  as the default for
1907         match_limit.  You can override the default by suppling pcre_exec() with         match_limit. You can override the default by suppling pcre_exec()  with
1908         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and         a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
1909         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
1910         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1911    
1912         The pcre_callout field is used in conjunction with the  "callout"  fea-         The  pcre_callout  field is used in conjunction with the "callout" fea-
1913         ture, which is described in the pcrecallout documentation.         ture, which is described in the pcrecallout documentation.
1914    
1915         The  tables  field  is  used  to  pass  a  character  tables pointer to         The tables field  is  used  to  pass  a  character  tables  pointer  to
1916         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec();  this overrides the value that is stored with the compiled
1917         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
1918         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
1919         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
1920         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-
1921         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
1922         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
1923         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
1924         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
1925    
1926     Option bits for pcre_exec()     Option bits for pcre_exec()
1927    
1928         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.
1929         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,
1930         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,    PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_START_OPTIMIZE,
1931         PCRE_PARTIAL.         PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_SOFT, and PCRE_PARTIAL_HARD.
1932    
1933           PCRE_ANCHORED           PCRE_ANCHORED
1934    
1935         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first
1936         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or
1937         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
1938         unachored at matching time.         unachored at matching time.
1939    
1940             PCRE_BSR_ANYCRLF
1941             PCRE_BSR_UNICODE
1942    
1943           These options (which are mutually exclusive) control what the \R escape
1944           sequence matches. The choice is either to match only CR, LF,  or  CRLF,
1945           or  to  match  any Unicode newline sequence. These options override the
1946           choice that was made or defaulted when the pattern was compiled.
1947    
1948           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
1949           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
1950           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
1951             PCRE_NEWLINE_ANYCRLF
1952           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1953    
1954         These options override  the  newline  definition  that  was  chosen  or         These options override  the  newline  definition  that  was  chosen  or
# Line 1709  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1956  MATCHING A PATTERN: THE TRADITIONAL FUNC
1956         tion of pcre_compile()  above.  During  matching,  the  newline  choice         tion of pcre_compile()  above.  During  matching,  the  newline  choice
1957         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
1958         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
1959         match  failure  for  an  unanchored  pattern. When PCRE_NEWLINE_CRLF or         match failure for an unanchored pattern.
1960         PCRE_NEWLINE_ANY is set, and a match attempt  fails  when  the  current  
1961         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
1962         characters instead of one, in other words, to after the CRLF.         set, and a match attempt for an unanchored pattern fails when the  cur-
1963           rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
1964           explicit matches for  CR  or  LF  characters,  the  match  position  is
1965           advanced by two characters instead of one, in other words, to after the
1966           CRLF.
1967    
1968           The above rule is a compromise that makes the most common cases work as
1969           expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
1970           option is not set), it does not match the string "\r\nA" because, after
1971           failing  at the start, it skips both the CR and the LF before retrying.
1972           However, the pattern [\r\n]A does match that string,  because  it  con-
1973           tains an explicit CR or LF reference, and so advances only by one char-
1974           acter after the first failure.
1975    
1976           An explicit match for CR of LF is either a literal appearance of one of
1977           those  characters,  or  one  of the \r or \n escape sequences. Implicit
1978           matches such as [^X] do not count, nor does \s (which includes  CR  and
1979           LF in the characters that it matches).
1980    
1981           Notwithstanding  the above, anomalous effects may still occur when CRLF
1982           is a valid newline sequence and explicit \r or \n escapes appear in the
1983           pattern.
1984    
1985           PCRE_NOTBOL           PCRE_NOTBOL
1986    
1987         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
1988         the  beginning  of  a  line, so the circumflex metacharacter should not         the beginning of a line, so the  circumflex  metacharacter  should  not
1989         match before it. Setting this without PCRE_MULTILINE (at compile  time)         match  before it. Setting this without PCRE_MULTILINE (at compile time)
1990         causes  circumflex  never to match. This option affects only the behav-         causes circumflex never to match. This option affects only  the  behav-
1991         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
1992    
1993           PCRE_NOTEOL           PCRE_NOTEOL
1994    
1995         This option specifies that the end of the subject string is not the end         This option specifies that the end of the subject string is not the end
1996         of  a line, so the dollar metacharacter should not match it nor (except         of a line, so the dollar metacharacter should not match it nor  (except
1997         in multiline mode) a newline immediately before it. Setting this  with-         in  multiline mode) a newline immediately before it. Setting this with-
1998         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
1999         option affects only the behaviour of the dollar metacharacter. It  does         option  affects only the behaviour of the dollar metacharacter. It does
2000         not affect \Z or \z.         not affect \Z or \z.
2001    
2002           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2003    
2004         An empty string is not considered to be a valid match if this option is         An empty string is not considered to be a valid match if this option is
2005         set. If there are alternatives in the pattern, they are tried.  If  all         set.  If  there are alternatives in the pattern, they are tried. If all
2006         the  alternatives  match  the empty string, the entire match fails. For         the alternatives match the empty string, the entire  match  fails.  For
2007         example, if the pattern         example, if the pattern
2008    
2009           a?b?           a?b?
2010    
2011         is applied to a string not beginning with "a" or "b",  it  matches  the         is  applied  to  a string not beginning with "a" or "b", it matches the
2012         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
2013         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-
2014         rences of "a" or "b".         rences of "a" or "b".
2015    
2016         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-
2017         cial case of a pattern match of the empty  string  within  its  split()         cial  case  of  a  pattern match of the empty string within its split()
2018         function,  and  when  using  the /g modifier. It is possible to emulate         function, and when using the /g modifier. It  is  possible  to  emulate
2019         Perl's behaviour after matching a null string by first trying the match         Perl's behaviour after matching a null string by first trying the match
2020         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then
2021         if that fails by advancing the starting offset (see below)  and  trying         if  that  fails by advancing the starting offset (see below) and trying
2022         an ordinary match again. There is some code that demonstrates how to do         an ordinary match again. There is some code that demonstrates how to do
2023         this in the pcredemo.c sample program.         this in the pcredemo sample program.
2024    
2025             PCRE_NO_START_OPTIMIZE
2026    
2027           There  are a number of optimizations that pcre_exec() uses at the start
2028           of a match, in order to speed up the process. For  example,  if  it  is
2029           known  that  a  match must start with a specific character, it searches
2030           the subject for that character, and fails immediately if it cannot find
2031           it,  without actually running the main matching function. When callouts
2032           are in use, these optimizations can cause  them  to  be  skipped.  This
2033           option  disables  the  "start-up" optimizations, causing performance to
2034           suffer, but ensuring that the callouts do occur.
2035    
2036           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2037    
2038         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
2039         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8  string is automatically checked when pcre_exec() is subsequently
2040         called.  The value of startoffset is also checked  to  ensure  that  it         called.  The value of startoffset is also checked  to  ensure  that  it
2041         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
2042         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
2043         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,
2044         returned.         pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-
2045           tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
2046         If you already know that your subject is valid, and you  want  to  skip  
2047         these    checks    for   performance   reasons,   you   can   set   the         If  you  already  know that your subject is valid, and you want to skip
2048         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to         these   checks   for   performance   reasons,   you   can    set    the
2049         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
2050         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
2051         string.  However,  you  should  be  sure  that the value of startoffset         making  repeated  calls  to  find  all  the matches in a single subject
2052         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
2053         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
2054         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
2055           value  of startoffset that does not point to the start of a UTF-8 char-
2056         acter, is undefined. Your program may crash.         acter, is undefined. Your program may crash.
2057    
2058           PCRE_PARTIAL           PCRE_PARTIAL_HARD
2059             PCRE_PARTIAL_SOFT
2060    
2061         This  option  turns  on  the  partial  matching feature. If the subject         These options turn on the partial matching feature. For backwards  com-
2062         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
2063         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,
2064         partially matches the pattern and the failure to  match  occurred  only         but  there  are not enough subject characters to complete the match. If
2065         because  there were not enough subject characters), pcre_exec() returns         this happens when PCRE_PARTIAL_HARD  is  set,  pcre_exec()  immediately
2066         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is         returns  PCRE_ERROR_PARTIAL.  Otherwise,  if  PCRE_PARTIAL_SOFT is set,
2067         used,  there  are restrictions on what may appear in the pattern. These         matching continues by testing any other alternatives. Only if they  all
2068         are discussed in the pcrepartial documentation.         fail  is  PCRE_ERROR_PARTIAL  returned (instead of PCRE_ERROR_NOMATCH).
2069           The portion of the string that provided the partial match is set as the
2070           first  matching  string.  There  is  a  more detailed discussion in the
2071           pcrepartial documentation.
2072    
2073     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2074    
2075         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
2076         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.
2077         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-
2078         Unlike  the  pattern string, the subject may contain binary zero bytes.         acter.  Unlike  the pattern string, the subject may contain binary zero
2079         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
2080         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
2081           case.
2082         A  non-zero  starting offset is useful when searching for another match  
2083         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
2084         cess.   Setting  startoffset differs from just passing over a shortened         in  the same subject by calling pcre_exec() again after a previous suc-
2085         string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins         cess.  Setting startoffset differs from just passing over  a  shortened
2086           string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins
2087         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
2088    
2089           \Biss\B           \Biss\B
2090    
2091         which  finds  occurrences  of "iss" in the middle of words. (\B matches         which finds occurrences of "iss" in the middle of  words.  (\B  matches
2092         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.)
2093         When  applied  to the string "Mississipi" the first call to pcre_exec()         When applied to the string "Mississipi" the first call  to  pcre_exec()
2094         finds the first occurrence. If pcre_exec() is called  again  with  just         finds  the  first  occurrence. If pcre_exec() is called again with just
2095         the  remainder  of  the  subject,  namely  "issipi", it does not match,         the remainder of the subject,  namely  "issipi",  it  does  not  match,
2096         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
2097         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
2098         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-
2099         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
2100         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2101    
2102         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,
2103         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
2104         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
2105         subject.         subject.
2106    
2107     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2108    
2109         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
2110         addition, further substrings from the subject  may  be  picked  out  by         addition,  further  substrings  from  the  subject may be picked out by
2111         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2112         this is called "capturing" in what follows, and the  phrase  "capturing         this  is  called "capturing" in what follows, and the phrase "capturing
2113         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-
2114         string. PCRE supports several other kinds of  parenthesized  subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2115         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2116    
2117         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2118         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-
2119         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:
2120         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2121    
2122         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-
2123         strings,  each  substring using a pair of integers. The remaining third         strings, each substring using a pair of integers. The  remaining  third
2124         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-
2125         turing  subpatterns, and is not available for passing back information.         turing subpatterns, and is not available for passing back  information.
2126         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
2127         it is not, it is rounded down.         it is not, it is rounded down.
2128    
2129         When  a  match  is successful, information about captured substrings is         When a match is successful, information about  captured  substrings  is
2130         returned in pairs of integers, starting at the  beginning  of  ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2131         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
2132         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
2133         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
2134         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
2135         tor[1],  identify  the  portion  of  the  subject string matched by the         byte offsets, even in UTF-8 mode. They are not character counts.
2136         entire pattern. The next pair is used for the first  capturing  subpat-  
2137         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
2138         highest numbered pair that has been set. For example, if two substrings         portion  of  the subject string matched by the entire pattern. The next
2139         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
2140         subpatterns, the return value from a successful match is 1,  indicating         returned by pcre_exec() is one more than the highest numbered pair that
2141         that just the first pair of offsets has been set.         has been set.  For example, if two substrings have been  captured,  the
2142           returned  value is 3. If there are no capturing subpatterns, the return
2143           value from a successful match is 1, indicating that just the first pair
2144           of offsets has been set.
2145    
2146         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2147         of the string that it matched that is returned.         of the string that it matched that is returned.
2148    
2149         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,
2150         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
2151         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
2152         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
2153         as NULL and ovecsize as zero. However, if  the  pattern  contains  back         ovecsize as zero. However, if the pattern contains back references  and
2154         references  and  the  ovector is not big enough to remember the related         the  ovector is not big enough to remember the related substrings, PCRE
2155         substrings, PCRE has to get additional memory for use during  matching.         has to get additional memory for use during matching. Thus it  is  usu-
2156         Thus it is usually advisable to supply an ovector.         ally advisable to supply an ovector.
2157    
2158         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
2159         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 2254  MATCHING A PATTERN: THE TRADITIONAL FUNC
2254    
2255           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2256    
2257         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing         This code is no longer in  use.  It  was  formerly  returned  when  the
2258         items  that are not supported for partial matching. See the pcrepartial         PCRE_PARTIAL  option  was used with a compiled pattern containing items
2259         documentation for details of partial matching.         that were  not  supported  for  partial  matching.  From  release  8.00
2260           onwards, there are no restrictions on partial matching.
2261    
2262           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2263    
2264         An unexpected internal error has occurred. This error could  be  caused         An  unexpected  internal error has occurred. This error could be caused
2265         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2266    
2267           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2268    
2269         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.
2270    
2271           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2272    
# Line 1985  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2274  MATCHING A PATTERN: THE TRADITIONAL FUNC
2274         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2275         description above.         description above.
2276    
          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.  
   
2277           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
2278    
2279         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2280    
2281         Error numbers -16 to -20 are not used by pcre_exec().         Error numbers -16 to -20 and -22 are not used by pcre_exec().
2282    
2283    
2284  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
# Line 2132  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2413  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2413    
2414         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These  functions call pcre_get_stringnumber(), and if it succeeds, they
2415         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-
2416         ate.         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the
2417           behaviour may not be what you want (see the next section).
2418    
2419           Warning: If the pattern uses the "(?|" feature to set up multiple  sub-
2420           patterns  with  the  same  number,  you cannot use names to distinguish
2421           them, because names are not included in the compiled code. The matching
2422           process uses only numbers.
2423    
2424    
2425  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
# Line 2144  DUPLICATE SUBPATTERN NAMES Line 2431  DUPLICATE SUBPATTERN NAMES
2431         subpatterns are not required to  be  unique.  Normally,  patterns  with         subpatterns are not required to  be  unique.  Normally,  patterns  with
2432         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
2433         subpatterns participates. An example is shown in the pcrepattern  docu-         subpatterns participates. An example is shown in the pcrepattern  docu-
2434         mentation. When duplicates are present, pcre_copy_named_substring() and         mentation.
2435    
2436           When    duplicates   are   present,   pcre_copy_named_substring()   and
2437         pcre_get_named_substring() return the first substring corresponding  to         pcre_get_named_substring() return the first substring corresponding  to
2438         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
2439         returned.  The pcre_get_stringnumber() function returns one of the num-         (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2440         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,
2441         is.         but it is not defined which it is.
2442    
2443         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
2444         name,  you  must  use  the pcre_get_stringtable_entries() function. The         name,  you  must  use  the pcre_get_stringtable_entries() function. The
# Line 2232  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2521  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2521         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
2522         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-
2523         LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,  PCRE_NO_UTF8_CHECK,         LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,  PCRE_NO_UTF8_CHECK,
2524         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last         PCRE_PARTIAL_HARD,     PCRE_PARTIAL_SOFT,     PCRE_DFA_SHORTEST,    and
2525         three of these are the same as for pcre_exec(), so their description is         PCRE_DFA_RESTART. All but the last four of these are exactly  the  same
2526         not repeated here.         as for pcre_exec(), so their description is not repeated here.
2527    
2528           PCRE_PARTIAL           PCRE_PARTIAL_HARD
2529             PCRE_PARTIAL_SOFT
2530         This  has  the  same general effect as it does for pcre_exec(), but the  
2531         details  are  slightly  different.  When  PCRE_PARTIAL   is   set   for         These  have the same general effect as they do for pcre_exec(), but the
2532         pcre_dfa_exec(),  the  return code PCRE_ERROR_NOMATCH is converted into         details are slightly  different.  When  PCRE_PARTIAL_HARD  is  set  for
2533         PCRE_ERROR_PARTIAL if the end of the subject  is  reached,  there  have         pcre_dfa_exec(),  it  returns PCRE_ERROR_PARTIAL if the end of the sub-
2534         been no complete matches, but there is still at least one matching pos-         ject is reached and there is still at least  one  matching  possibility
2535         sibility. The portion of the string that provided the partial match  is         that requires additional characters. This happens even if some complete
2536         set as the first matching string.         matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2537           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2538           of the subject is reached, there have been  no  complete  matches,  but
2539           there  is  still  at least one matching possibility. The portion of the
2540           string that provided the longest partial match  is  set  as  the  first
2541           matching string in both cases.
2542    
2543           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2544    
# Line 2255  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2549  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2549    
2550           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2551    
2552         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
2553         returns  a  partial  match, it is possible to call it again, with addi-         again,  with  additional  subject characters, and have it continue with
2554         tional subject characters, and have it continue with  the  same  match.         the same match. The PCRE_DFA_RESTART option requests this action;  when
2555         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
2556         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
2557         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
2558         match. There is more discussion of this  facility  in  the  pcrepartial         pcrepartial documentation.
        documentation.  
2559    
2560     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2561    
2562         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-
2563         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
2564         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
2565         matches are all initial substrings of the longer matches. For  example,         matches  are all initial substrings of the longer matches. For example,
2566         if the pattern         if the pattern
2567    
2568           <.*>           <.*>
# Line 2284  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2577  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2577           <something> <something else>           <something> <something else>
2578           <something> <something else> <something further>           <something> <something else> <something further>
2579    
2580         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,
2581         which is the number of matched substrings.  The  substrings  themselves         which  is  the  number of matched substrings. The substrings themselves
2582         are  returned  in  ovector. Each string uses two elements; the first is         are returned in ovector. Each string uses two elements;  the  first  is
2583         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
2584         fact,  all  the  strings  have the same start offset. (Space could have         fact, all the strings have the same start  offset.  (Space  could  have
2585         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
2586         compatibility  with  the  way pcre_exec() returns data, even though the         compatibility with the way pcre_exec() returns data,  even  though  the
2587         meaning of the strings is different.)         meaning of the strings is different.)
2588    
2589         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-
2590         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
2591         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
2592         filled with the longest matches.         filled with the longest matches.
2593    
2594     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2595    
2596         The  pcre_dfa_exec()  function returns a negative number when it fails.         The pcre_dfa_exec() function returns a negative number when  it  fails.
2597         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
2598         described  above.   There are in addition the following errors that are         described above.  There are in addition the following errors  that  are
2599         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2600    
2601           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2602    
2603         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-
2604         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
2605         reference.         reference.
2606    
2607           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2608    
2609         This return is given if pcre_dfa_exec()  encounters  a  condition  item         This  return  is  given  if pcre_dfa_exec() encounters a condition item
2610         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
2611         in a specific group. These are not supported.         in a specific group. These are not supported.
2612    
2613           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2614    
2615         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
2616         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
2617         (it is meaningless).         (it is meaningless).
2618    
2619           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2620    
2621         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
2622         workspace vector.         workspace vector.
2623    
2624           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2625    
2626         When  a  recursive subpattern is processed, the matching function calls         When a recursive subpattern is processed, the matching  function  calls
2627         itself recursively, using private vectors for  ovector  and  workspace.         itself  recursively,  using  private vectors for ovector and workspace.
2628         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
2629         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2630    
2631    
2632  SEE ALSO  SEE ALSO
2633    
2634         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-
2635         tial(3),  pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2636    
2637    
2638  AUTHOR  AUTHOR
# Line 2351  AUTHOR Line 2644  AUTHOR
2644    
2645  REVISION  REVISION
2646    
2647         Last updated: 06 March 2007         Last updated: 01 September 2009
2648         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
2649  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2650    
2651    
2652  PCRECALLOUT(3)                                                  PCRECALLOUT(3)  PCRECALLOUT(3)                                                  PCRECALLOUT(3)
2653    
2654    
# Line 2379  PCRE CALLOUTS Line 2672  PCRE CALLOUTS
2672         default value is zero.  For  example,  this  pattern  has  two  callout         default value is zero.  For  example,  this  pattern  has  two  callout
2673         points:         points:
2674    
2675           (?C1)eabc(?C2)def           (?C1)abc(?C2)def
2676    
2677         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
2678         called, PCRE automatically  inserts  callouts,  all  with  number  255,         called, PCRE automatically  inserts  callouts,  all  with  number  255,
# Line 2403  PCRE CALLOUTS Line 2696  PCRE CALLOUTS
2696  MISSING CALLOUTS  MISSING CALLOUTS
2697    
2698         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
2699         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
2700         pattern is         example, if the pattern is
2701    
2702           ab(?C4)cd           ab(?C4)cd
2703    
# Line 2413  MISSING CALLOUTS Line 2706  MISSING CALLOUTS
2706         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
2707         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
2708    
2709           You can disable these optimizations by passing the  PCRE_NO_START_OPTI-
2710           MIZE  option  to  pcre_exec()  or  pcre_dfa_exec(). This slows down the
2711           matching process, but does ensure that callouts  such  as  the  example
2712           above are obeyed.
2713    
2714    
2715  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2716    
2717         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
2718         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
2719         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
2720         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
2721         block. This structure contains the following fields:         block. This structure contains the following fields:
2722    
2723           int          version;           int          version;
# Line 2435  THE CALLOUT INTERFACE Line 2733  THE CALLOUT INTERFACE
2733           int          pattern_position;           int          pattern_position;
2734           int          next_item_length;           int          next_item_length;
2735    
2736         The version field is an integer containing the version  number  of  the         The  version  field  is an integer containing the version number of the
2737         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
2738         version number will change again in future  if  additional  fields  are         version  number  will  change  again in future if additional fields are
2739         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.
2740    
2741         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 2752  THE CALLOUT INTERFACE
2752         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
2753         were passed to pcre_exec().         were passed to pcre_exec().
2754    
2755         The start_match field contains the offset within the subject  at  which         The start_match field normally contains the offset within  the  subject
2756         the  current match attempt started. If the pattern is not anchored, the         at  which  the  current  match  attempt started. However, if the escape
2757         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
2758         pattern for different starting points in the subject.         modified  starting  point.  If the pattern is not anchored, the callout
2759           function may be called several times from the same point in the pattern
2760           for different starting points in the subject.
2761    
2762         The  current_position  field  contains the offset within the subject of         The  current_position  field  contains the offset within the subject of
2763         the current match pointer.         the current match pointer.
# Line 2520  AUTHOR Line 2820  AUTHOR
2820    
2821  REVISION  REVISION
2822    
2823         Last updated: 06 March 2007         Last updated: 15 March 2009
2824         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
2825  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2826    
2827    
2828  PCRECOMPAT(3)                                                    PCRECOMPAT(3)  PCRECOMPAT(3)                                                    PCRECOMPAT(3)
2829    
2830    
# Line 2536  DIFFERENCES BETWEEN PCRE AND PERL Line 2836  DIFFERENCES BETWEEN PCRE AND PERL
2836    
2837         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
2838         handle regular expressions. The differences described here  are  mainly         handle regular expressions. The differences described here  are  mainly
2839         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
2840         tures that are expected to be in the forthcoming Perl 5.10.         some features that are in Perl 5.10.
2841    
2842         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
2843         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 2602  DIFFERENCES BETWEEN PCRE AND PERL Line 2902  DIFFERENCES BETWEEN PCRE AND PERL
2902         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
2903         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
2904    
2905         11. PCRE provides some extensions to the Perl regular expression facil-         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),
2906           (*FAIL),  (*F),  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in
2907           the forms without an  argument.  PCRE  does  not  support  (*MARK).  If
2908           (*ACCEPT)  is within capturing parentheses, PCRE does not set that cap-
2909           ture group; this is different to Perl.
2910    
2911           12. PCRE provides some extensions to the Perl regular expression facil-
2912         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
2913         versions, some of which (such as named parentheses) have been  in  PCRE         versions, some of which (such as named parentheses) have been  in  PCRE
2914         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 2921  DIFFERENCES BETWEEN PCRE AND PERL
2921         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
2922    
2923         (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-
2924         cial  meaning  is  faulted.  Otherwise,  like  Perl,  the  backslash is         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
2925         ignored. (Perl can be made to issue a warning.)         ignored.  (Perl can be made to issue a warning.)
2926    
2927         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-
2928         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 2628  DIFFERENCES BETWEEN PCRE AND PERL Line 2934  DIFFERENCES BETWEEN PCRE AND PERL
2934         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-
2935         TURE options for pcre_exec() have no Perl equivalents.         TURE options for pcre_exec() have no Perl equivalents.
2936    
2937         (g) The callout facility is PCRE-specific.         (g) The \R escape sequence can be restricted to match only CR,  LF,  or
2938           CRLF by the PCRE_BSR_ANYCRLF option.
2939    
2940         (h) The partial matching facility is PCRE-specific.         (h) The callout facility is PCRE-specific.
2941    
2942         (i) Patterns compiled by PCRE can be saved and re-used at a later time,         (i) The partial matching facility is PCRE-specific.
2943    
2944           (j) Patterns compiled by PCRE can be saved and re-used at a later time,
2945         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
2946    
2947         (j)  The  alternative  matching function (pcre_dfa_exec()) matches in a         (k) The alternative matching function (pcre_dfa_exec())  matches  in  a
2948         different way and is not Perl-compatible.         different way and is not Perl-compatible.
2949    
2950           (l)  PCRE  recognizes some special sequences such as (*CR) at the start
2951           of a pattern that set overall options that cannot be changed within the
2952           pattern.
2953    
2954    
2955  AUTHOR  AUTHOR
2956    
# Line 2648  AUTHOR Line 2961  AUTHOR
2961    
2962  REVISION  REVISION
2963    
2964         Last updated: 06 March 2007         Last updated: 25 August 2009
2965         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
2966  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2967    
2968    
2969  PCREPATTERN(3)                                                  PCREPATTERN(3)  PCREPATTERN(3)                                                  PCREPATTERN(3)
2970    
2971    
# Line 2662  NAME Line 2975  NAME
2975    
2976  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
2977    
2978         The  syntax  and semantics of the regular expressions supported by PCRE         The  syntax and semantics of the regular expressions that are supported
2979         are described below. Regular expressions are also described in the Perl         by PCRE are described in detail below. There is a quick-reference  syn-
2980         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
2981         examples.  Jeffrey Friedl's "Mastering Regular Expressions",  published         semantics as closely as it can. PCRE  also  supports  some  alternative
2982         by  O'Reilly, covers regular expressions in great detail. This descrip-         regular  expression  syntax (which does not conflict with the Perl syn-
2983         tion of PCRE's regular expressions is intended as reference material.         tax) in order to provide some compatibility with regular expressions in
2984           Python, .NET, and Oniguruma.
2985    
2986           Perl's  regular expressions are described in its own documentation, and
2987           regular expressions in general are covered in a number of  books,  some
2988           of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
2989           Expressions", published by  O'Reilly,  covers  regular  expressions  in
2990           great  detail.  This  description  of  PCRE's  regular  expressions  is
2991           intended as reference material.
2992    
2993         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
2994         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
2995         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
2996         pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern         pcre_compile()  with  the  PCRE_UTF8  option.  There  is also a special
2997         matching is mentioned in several places below. There is also a  summary         sequence that can be given at the start of a pattern:
2998         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre  
2999         page.           (*UTF8)
3000    
3001           Starting a pattern with this sequence  is  equivalent  to  setting  the
3002           PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3003           UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3004           below.  There  is  also  a  summary of UTF-8 features in the section on
3005           UTF-8 support in the main pcre page.
3006    
3007         The remainder of this document discusses the  patterns  that  are  sup-         The remainder of this document discusses the  patterns  that  are  sup-
3008         ported  by  PCRE when its main matching function, pcre_exec(), is used.         ported  by  PCRE when its main matching function, pcre_exec(), is used.
3009         From  release  6.0,   PCRE   offers   a   second   matching   function,         From  release  6.0,   PCRE   offers   a   second   matching   function,
3010         pcre_dfa_exec(),  which matches using a different algorithm that is not         pcre_dfa_exec(),  which matches using a different algorithm that is not
3011         Perl-compatible. The advantages and disadvantages  of  the  alternative         Perl-compatible. Some of the features discussed below are not available
3012         function, and how it differs from the normal function, are discussed in         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the
3013         the pcrematching page.         alternative function, and how it differs from the normal function,  are
3014           discussed in the pcrematching page.
3015    
3016    
3017    NEWLINE CONVENTIONS
3018    
3019           PCRE  supports five different conventions for indicating line breaks in
3020           strings: a single CR (carriage return) character, a  single  LF  (line-
3021           feed) character, the two-character sequence CRLF, any of the three pre-
3022           ceding, or any Unicode newline sequence. The pcreapi page  has  further
3023           discussion  about newlines, and shows how to set the newline convention
3024           in the options arguments for the compiling and matching functions.
3025    
3026           It is also possible to specify a newline convention by starting a  pat-
3027           tern string with one of the following five sequences:
3028    
3029             (*CR)        carriage return
3030             (*LF)        linefeed
3031             (*CRLF)      carriage return, followed by linefeed
3032             (*ANYCRLF)   any of the three above
3033             (*ANY)       all Unicode newline sequences
3034    
3035           These override the default and the options given to pcre_compile(). For
3036           example, on a Unix system where LF is the default newline sequence, the
3037           pattern
3038    
3039             (*CR)a.b
3040    
3041           changes the convention to CR. That pattern matches "a\nb" because LF is
3042           no longer a newline. Note that these special settings,  which  are  not
3043           Perl-compatible,  are  recognized  only at the very start of a pattern,
3044           and that they must be in upper case.  If  more  than  one  of  them  is
3045           present, the last one is used.
3046    
3047           The  newline  convention  does  not  affect what the \R escape sequence
3048           matches. By default, this is any Unicode  newline  sequence,  for  Perl
3049           compatibility.  However, this can be changed; see the description of \R
3050           in the section entitled "Newline sequences" below. A change of \R  set-
3051           ting can be combined with a change of newline convention.
3052    
3053    
3054  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
3055    
3056         A regular expression is a pattern that is  matched  against  a  subject         A  regular  expression  is  a pattern that is matched against a subject
3057         string  from  left  to right. Most characters stand for themselves in a         string from left to right. Most characters stand for  themselves  in  a
3058         pattern, and match the corresponding characters in the  subject.  As  a         pattern,  and  match  the corresponding characters in the subject. As a
3059         trivial example, the pattern         trivial example, the pattern
3060    
3061           The quick brown fox           The quick brown fox
3062    
3063         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
3064         caseless matching is specified (the PCRE_CASELESS option), letters  are         caseless  matching is specified (the PCRE_CASELESS option), letters are
3065         matched  independently  of case. In UTF-8 mode, PCRE always understands         matched independently of case. In UTF-8 mode, PCRE  always  understands
3066         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
3067         caseless  matching  is always possible. For characters with higher val-         caseless matching is always possible. For characters with  higher  val-
3068         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
3069         property  support,  but  not  otherwise.   If  you want to use caseless         property support, but not otherwise.   If  you  want  to  use  caseless
3070         matching for characters 128 and above, you must  ensure  that  PCRE  is         matching  for  characters  128  and above, you must ensure that PCRE is
3071         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
3072    
3073         The  power  of  regular  expressions  comes from the ability to include         The power of regular expressions comes  from  the  ability  to  include
3074         alternatives and repetitions in the pattern. These are encoded  in  the         alternatives  and  repetitions in the pattern. These are encoded in the
3075         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
3076         but instead are interpreted in some special way.         but instead are interpreted in some special way.
3077    
3078         There are two different sets of metacharacters: those that  are  recog-         There  are  two different sets of metacharacters: those that are recog-
3079         nized  anywhere in the pattern except within square brackets, and those         nized anywhere in the pattern except within square brackets, and  those
3080         that are recognized within square brackets.  Outside  square  brackets,         that  are  recognized  within square brackets. Outside square brackets,
3081         the metacharacters are as follows:         the metacharacters are as follows:
3082    
3083           \      general escape character with several uses           \      general escape character with several uses
# Line 2731  CHARACTERS AND METACHARACTERS Line 3096  CHARACTERS AND METACHARACTERS
3096                  also "possessive quantifier"                  also "possessive quantifier"
3097           {      start min/max quantifier           {      start min/max quantifier
3098    
3099         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
3100         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
3101    
3102           \      general escape character           \      general escape character
# Line 2741  CHARACTERS AND METACHARACTERS Line 3106  CHARACTERS AND METACHARACTERS
3106                    syntax)                    syntax)
3107           ]      terminates the character class           ]      terminates the character class
3108    
3109         The following sections describe the use of each of the  metacharacters.         The following sections describe the use of each of the metacharacters.
3110    
3111    
3112  BACKSLASH  BACKSLASH
# Line 2793  BACKSLASH Line 3158  BACKSLASH
3158           \cx       "control-x", where x is any character           \cx       "control-x", where x is any character
3159           \e        escape (hex 1B)           \e        escape (hex 1B)
3160           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3161           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3162           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3163           \t        tab (hex 09)           \t        tab (hex 09)
3164           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or backreference
# Line 2808  BACKSLASH Line 3173  BACKSLASH
3173         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
3174         in  upper  or  lower case). Any number of hexadecimal digits may appear         in  upper  or  lower case). Any number of hexadecimal digits may appear
3175         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
3176         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,
3177         the maximum hexadecimal value is 7FFFFFFF). If  characters  other  than         the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger
3178         hexadecimal  digits  appear between \x{ and }, or if there is no termi-         than the largest Unicode code point, which is 10FFFF.
3179         nating }, this form of escape is not recognized.  Instead, the  initial  
3180         \x will be interpreted as a basic hexadecimal escape, with no following         If  characters  other than hexadecimal digits appear between \x{ and },
3181         digits, giving a character whose value is zero.         or if there is no terminating }, this form of escape is not recognized.
3182           Instead,  the  initial  \x  will  be interpreted as a basic hexadecimal
3183           escape, with no following digits, giving a  character  whose  value  is
3184           zero.
3185    
3186         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
3187         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-
3188         dled. For example, \xdc is exactly the same as \x{dc}.         dled. For example, \xdc is exactly the same as \x{dc}.
3189    
3190         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
3191         than  two  digits,  just  those  that  are  present  are used. Thus the         than two digits, just  those  that  are  present  are  used.  Thus  the
3192         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
3193         (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
3194         if the pattern character that follows is itself an octal digit.         if the pattern character that follows is itself an octal digit.
3195    
3196         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-
3197         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
3198         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
3199         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
3200         expression, the entire  sequence  is  taken  as  a  back  reference.  A         expression,  the  entire  sequence  is  taken  as  a  back reference. A
3201         description  of how this works is given later, following the discussion         description of how this works is given later, following the  discussion
3202         of parenthesized subpatterns.         of parenthesized subpatterns.
3203    
3204         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
3205         and  there have not been that many capturing subpatterns, PCRE re-reads         and there have not been that many capturing subpatterns, PCRE  re-reads
3206         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-
3207         erate  a data character. Any subsequent digits stand for themselves. In         erate a data character. Any subsequent digits stand for themselves.  In
3208         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
3209         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
3210         example:         example:
3211    
3212           \040   is another way of writing a space           \040   is another way of writing a space
# Line 2856  BACKSLASH Line 3224  BACKSLASH
3224           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
3225                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
3226    
3227         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
3228         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
3229    
3230         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
3231         inside and outside character classes. In addition, inside  a  character         inside  and  outside character classes. In addition, inside a character
3232         class,  the  sequence \b is interpreted as the backspace character (hex         class, the sequence \b is interpreted as the backspace  character  (hex
3233         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"
3234         and  "X", respectively. Outside a character class, these sequences have         and "X", respectively. Outside a character class, these sequences  have
3235         different meanings (see below).         different meanings (see below).
3236    
3237     Absolute and relative back references     Absolute and relative back references
3238    
3239         The sequence \g followed by a positive or negative  number,  optionally         The  sequence  \g followed by an unsigned or a negative number, option-
3240         enclosed  in  braces,  is  an absolute or relative back reference. Back         ally enclosed in braces, is an absolute or relative back  reference.  A
3241         references are discussed later, following the discussion  of  parenthe-         named back reference can be coded as \g{name}. Back references are dis-
3242         sized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3243    
3244       Absolute and relative subroutine calls
3245    
3246           For compatibility with Oniguruma, the non-Perl syntax \g followed by  a
3247           name or a number enclosed either in angle brackets or single quotes, is
3248           an alternative syntax for referencing a subpattern as  a  "subroutine".
3249           Details  are  discussed  later.   Note  that  \g{...} (Perl syntax) and
3250           \g<...> (Oniguruma syntax) are not synonymous. The  former  is  a  back
3251           reference; the latter is a subroutine call.
3252    
3253     Generic character types     Generic character types
3254    
# Line 2880  BACKSLASH Line 3257  BACKSLASH
3257    
3258           \d     any decimal digit           \d     any decimal digit
3259           \D     any character that is not a decimal digit           \D     any character that is not a decimal digit
3260             \h     any horizontal whitespace character
3261             \H     any character that is not a horizontal whitespace character
3262           \s     any whitespace character           \s     any whitespace character
3263           \S     any character that is not a whitespace character           \S     any character that is not a whitespace character
3264             \v     any vertical whitespace character
3265             \V     any character that is not a vertical whitespace character
3266           \w     any "word" character           \w     any "word" character
3267           \W     any "non-word" character           \W     any "non-word" character
3268    
# Line 2896  BACKSLASH Line 3277  BACKSLASH
3277    
3278         For  compatibility  with Perl, \s does not match the VT character (code         For  compatibility  with Perl, \s does not match the VT character (code
3279         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
3280         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
3281         "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-
3282         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.  
3283    
3284         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,
3285         \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-
3286         code  character  property support is available. The use of locales with         code  character  property  support is available. These sequences retain
3287         Unicode is discouraged.         their original meanings from before UTF-8 support was available, mainly
3288           for  efficiency  reasons. Note that this also affects \b, because it is
3289           defined in terms of \w and \W.
3290    
3291           The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to
3292           the  other  sequences, these do match certain high-valued codepoints in
3293           UTF-8 mode.  The horizontal space characters are:
3294    
3295             U+0009     Horizontal tab
3296             U+0020     Space
3297             U+00A0     Non-break space
3298             U+1680     Ogham space mark
3299             U+180E     Mongolian vowel separator
3300             U+2000     En quad
3301             U+2001     Em quad
3302             U+2002     En space
3303             U+2003     Em space
3304             U+2004     Three-per-em space
3305             U+2005     Four-per-em space
3306             U+2006     Six-per-em space
3307             U+2007     Figure space
3308             U+2008     Punctuation space
3309             U+2009     Thin space
3310             U+200A     Hair space
3311             U+202F     Narrow no-break space
3312             U+205F     Medium mathematical space
3313             U+3000     Ideographic space
3314    
3315           The vertical space characters are:
3316    
3317             U+000A     Linefeed
3318             U+000B     Vertical tab
3319             U+000C     Formfeed
3320             U+000D     Carriage return
3321             U+0085     Next line
3322             U+2028     Line separator
3323             U+2029     Paragraph separator
3324    
3325           A "word" character is an underscore or any character less than 256 that
3326           is  a  letter  or  digit.  The definition of letters and digits is con-
3327           trolled by PCRE's low-valued character tables, and may vary if  locale-
3328           specific  matching is taking place (see "Locale support" in the pcreapi
3329           page). For example, in a French locale such  as  "fr_FR"  in  Unix-like
3330           systems,  or "french" in Windows, some character codes greater than 128
3331           are used for accented letters, and these are matched by \w. The use  of
3332           locales with Unicode is discouraged.
3333    
3334     Newline sequences     Newline sequences
3335    
3336         Outside a character class, the escape sequence \R matches  any  Unicode         Outside  a  character class, by default, the escape sequence \R matches
3337         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
3338         equivalent to the following:         mode \R is equivalent to the following:
3339    
3340           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3341    
3342         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
3343         below.  This particular group matches either the two-character sequence         below.  This particular group matches either the two-character sequence
3344         CR followed by LF, or  one  of  the  single  characters  LF  (linefeed,         CR  followed  by  LF,  or  one  of  the single characters LF (linefeed,
3345         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
3346         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
3347         is treated as a single unit that cannot be split.         is treated as a single unit that cannot be split.
3348    
3349         In  UTF-8  mode, two additional characters whose codepoints are greater         In UTF-8 mode, two additional characters whose codepoints  are  greater
3350         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-
3351         rator,  U+2029).   Unicode character property support is not needed for         rator, U+2029).  Unicode character property support is not  needed  for
3352         these characters to be recognized.         these characters to be recognized.
3353    
3354           It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3355           the complete set  of  Unicode  line  endings)  by  setting  the  option
3356           PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3357           (BSR is an abbrevation for "backslash R".) This can be made the default
3358           when  PCRE  is  built;  if this is the case, the other behaviour can be
3359           requested via the PCRE_BSR_UNICODE option.   It  is  also  possible  to
3360           specify  these  settings  by  starting a pattern string with one of the
3361           following sequences:
3362    
3363             (*BSR_ANYCRLF)   CR, LF, or CRLF only
3364             (*BSR_UNICODE)   any Unicode newline sequence
3365    
3366           These override the default and the options given to pcre_compile(), but
3367           they can be overridden by options given to pcre_exec(). Note that these
3368           special settings, which are not Perl-compatible, are recognized only at
3369           the  very  start  of a pattern, and that they must be in upper case. If
3370           more than one of them is present, the last one is  used.  They  can  be
3371           combined  with  a  change of newline convention, for example, a pattern
3372           can start with:
3373    
3374             (*ANY)(*BSR_ANYCRLF)
3375    
3376         Inside a character class, \R matches the letter "R".         Inside a character class, \R matches the letter "R".
3377    
3378     Unicode character properties     Unicode character properties
3379    
3380         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
3381         tional  escape  sequences  to  match character properties are available         tional  escape sequences that match characters with specific properties
3382         when UTF-8 mode is selected. They are:         are available.  When not in UTF-8 mode, these sequences are  of  course
3383           limited  to  testing characters whose codepoints are less than 256, but
3384           they do work in this mode.  The extra escape sequences are:
3385    
3386           \p{xx}   a character with the xx property           \p{xx}   a character with the xx property
3387           \P{xx}   a character without the xx property           \P{xx}   a character without the xx property
# Line 3034  BACKSLASH Line 3476  BACKSLASH
3476         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
3477         classified as a modifier or "other".         classified as a modifier or "other".
3478    
3479           The  Cs  (Surrogate)  property  applies only to characters in the range
3480           U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see
3481           RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
3482           ing has been turned off (see the discussion  of  PCRE_NO_UTF8_CHECK  in
3483           the pcreapi page).
3484    
3485         The  long  synonyms  for  these  properties that Perl supports (such as         The  long  synonyms  for  these  properties that Perl supports (such as
3486         \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
3487         any of these properties with "Is".         any of these properties with "Is".
# Line 3053  BACKSLASH Line 3501  BACKSLASH
3501         That  is,  it matches a character without the "mark" property, followed         That  is,  it matches a character without the "mark" property, followed
3502         by zero or more characters with the "mark"  property,  and  treats  the         by zero or more characters with the "mark"  property,  and  treats  the
3503         sequence  as  an  atomic group (see below).  Characters with the "mark"         sequence  as  an  atomic group (see below).  Characters with the "mark"
3504         property are typically accents that affect the preceding character.         property are typically accents that  affect  the  preceding  character.
3505           None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X
3506           matches any one character.
3507    
3508         Matching characters by Unicode property is not fast, because  PCRE  has         Matching characters by Unicode property is not fast, because  PCRE  has
3509         to  search  a  structure  that  contains data for over fifteen thousand         to  search  a  structure  that  contains data for over fifteen thousand
3510         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
3511         \w do not use Unicode properties in PCRE.         \w do not use Unicode properties in PCRE.
3512    
3513       Resetting the match start
3514    
3515           The escape sequence \K, which is a Perl 5.10 feature, causes any previ-
3516           ously matched characters not  to  be  included  in  the  final  matched
3517           sequence. For example, the pattern:
3518    
3519             foo\Kbar
3520    
3521           matches  "foobar",  but reports that it has matched "bar". This feature
3522           is similar to a lookbehind assertion (described  below).   However,  in
3523           this  case, the part of the subject before the real match does not have
3524           to be of fixed length, as lookbehind assertions do. The use of \K  does
3525           not  interfere  with  the setting of captured substrings.  For example,
3526           when the pattern
3527    
3528             (foo)\Kbar
3529    
3530           matches "foobar", the first substring is still set to "foo".
3531    
3532     Simple assertions     Simple assertions
3533    
3534         The  final use of backslash is for certain simple assertions. An asser-         The final use of backslash is for certain simple assertions. An  asser-
3535         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
3536         a  match, without consuming any characters from the subject string. The         a match, without consuming any characters from the subject string.  The
3537         use of subpatterns for more complicated assertions is described  below.         use  of subpatterns for more complicated assertions is described below.
3538         The backslashed assertions are:         The backslashed assertions are:
3539    
3540           \b     matches at a word boundary           \b     matches at a word boundary
# Line 3076  BACKSLASH Line 3545  BACKSLASH
3545           \z     matches only at the end of the subject           \z     matches only at the end of the subject
3546           \G     matches at the first matching position in the subject           \G     matches at the first matching position in the subject
3547    
3548         These  assertions may not appear in character classes (but note that \b         These assertions may not appear in character classes (but note that  \b
3549         has a different meaning, namely the backspace character, inside a char-         has a different meaning, namely the backspace character, inside a char-
3550         acter class).         acter class).
3551    
3552         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
3553         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.
3554         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
3555         string if the first or last character matches \w, respectively.         string if the first or last character matches \w, respectively.
3556    
3557         The \A, \Z, and \z assertions differ from  the  traditional  circumflex         The  \A,  \Z,  and \z assertions differ from the traditional circumflex
3558         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
3559         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
3560         set.  Thus,  they are independent of multiline mode. These three asser-         set. Thus, they are independent of multiline mode. These  three  asser-
3561         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
3562         affect  only the behaviour of the circumflex and dollar metacharacters.         affect only the behaviour of the circumflex and dollar  metacharacters.
3563         However, if the startoffset argument of pcre_exec() is non-zero,  indi-         However,  if the startoffset argument of pcre_exec() is non-zero, indi-
3564         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
3565         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
3566         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
3567         the very end, whereas \z matches only at the end.         the very end, whereas \z matches only at the end.
3568    
3569         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
3570         the  start point of the match, as specified by the startoffset argument         the start point of the match, as specified by the startoffset  argument
3571         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
3572         non-zero.  By calling pcre_exec() multiple times with appropriate argu-         non-zero. By calling pcre_exec() multiple times with appropriate  argu-
3573         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-
3574         mentation where \G can be useful.         mentation where \G can be useful.
3575    
3576         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
3577         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
3578         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
3579         previously matched string was empty. Because PCRE does just  one  match         previously  matched  string was empty. Because PCRE does just one match
3580         at a time, it cannot reproduce this behaviour.         at a time, it cannot reproduce this behaviour.
3581    
3582         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
3583         anchored to the starting match position, and the "anchored" flag is set         anchored to the starting match position, and the "anchored" flag is set
3584         in the compiled regular expression.         in the compiled regular expression.
3585    
# Line 3118  BACKSLASH Line 3587  BACKSLASH
3587  CIRCUMFLEX AND DOLLAR  CIRCUMFLEX AND DOLLAR
3588    
3589         Outside a character class, in the default matching mode, the circumflex         Outside a character class, in the default matching mode, the circumflex
3590         character is an assertion that is true only  if  the  current  matching         character  is  an  assertion  that is true only if the current matching
3591         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-
3592         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
3593         PCRE_MULTILINE  option  is  unset. Inside a character class, circumflex         PCRE_MULTILINE option is unset. Inside a  character  class,  circumflex
3594         has an entirely different meaning (see below).         has an entirely different meaning (see below).
3595    
3596         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
3597         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
3598         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
3599         branch.  If all possible alternatives start with a circumflex, that is,         branch. If all possible alternatives start with a circumflex, that  is,
3600         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-
3601         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
3602         constructs that can cause a pattern to be anchored.)         constructs that can cause a pattern to be anchored.)
3603    
3604         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
3605         matching  point  is  at  the  end of the subject string, or immediately         matching point is at the end of  the  subject  string,  or  immediately
3606         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
3607         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
3608         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
3609         appears. Dollar has no special meaning in a character class.         appears. Dollar has no special meaning in a character class.
3610    
3611         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
3612         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
3613         compile time. This does not affect the \Z assertion.         compile time. This does not affect the \Z assertion.
3614    
3615         The meanings of the circumflex and dollar characters are changed if the         The meanings of the circumflex and dollar characters are changed if the
3616         PCRE_MULTILINE option is set. When  this  is  the  case,  a  circumflex         PCRE_MULTILINE  option  is  set.  When  this  is the case, a circumflex
3617         matches  immediately after internal newlines as well as at the start of         matches immediately after internal newlines as well as at the start  of
3618         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
3619         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
3620         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
3621         as  the  two-character  sequence CRLF, isolated CR and LF characters do         as the two-character sequence CRLF, isolated CR and  LF  characters  do
3622         not indicate newlines.         not indicate newlines.
3623    
3624         For example, the pattern /^abc$/ matches the subject string  "def\nabc"         For  example, the pattern /^abc$/ matches the subject string "def\nabc"
3625         (where  \n  represents a newline) in multiline mode, but not otherwise.         (where \n represents a newline) in multiline mode, but  not  otherwise.
3626         Consequently, patterns that are anchored in single  line  mode  because         Consequently,  patterns  that  are anchored in single line mode because
3627         all  branches  start  with  ^ are not anchored in multiline mode, and a         all branches start with ^ are not anchored in  multiline  mode,  and  a
3628         match for circumflex is  possible  when  the  startoffset  argument  of         match  for  circumflex  is  possible  when  the startoffset argument of
3629         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
3630         PCRE_MULTILINE is set.         PCRE_MULTILINE is set.
3631    
3632         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
3633         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
3634         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
3635         set.         set.
3636    
3637    
3638  FULL STOP (PERIOD, DOT)  FULL STOP (PERIOD, DOT)
3639    
3640         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-
3641         ter in the subject string except (by default) a character  that  signi-         ter  in  the subject string except (by default) a character that signi-
3642         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
3643         more than one byte long.         more than one byte long.
3644    
3645         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
3646         that  character; when the two-character sequence CRLF is used, dot does         that character; when the two-character sequence CRLF is used, dot  does
3647         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
3648         matches  all characters (including isolated CRs and LFs). When any Uni-         matches all characters (including isolated CRs and LFs). When any  Uni-
3649         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
3650         any of the other line ending characters.         any of the other line ending characters.
3651    
3652         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
3653         PCRE_DOTALL option is set, a dot matches  any  one  character,  without         PCRE_DOTALL  option  is  set,  a dot matches any one character, without
3654         exception. If the two-character sequence CRLF is present in the subject         exception. If the two-character sequence CRLF is present in the subject
3655         string, it takes two dots to match it.         string, it takes two dots to match it.
3656    
3657         The handling of dot is entirely independent of the handling of  circum-         The  handling of dot is entirely independent of the handling of circum-
3658         flex  and  dollar,  the  only relationship being that they both involve         flex and dollar, the only relationship being  that  they  both  involve
3659         newlines. Dot has no special meaning in a character class.         newlines. Dot has no special meaning in a character class.
3660    
3661    
3662  MATCHING A SINGLE BYTE  MATCHING A SINGLE BYTE
3663    
3664         Outside a character class, the escape sequence \C matches any one byte,         Outside a character class, the escape sequence \C matches any one byte,
3665         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
3666         line-ending characters. The feature is provided in  Perl  in  order  to         line-ending  characters.  The  feature  is provided in Perl in order to
3667         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-
3668         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-
3669         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
3670         avoided.         avoided.
3671    
3672         PCRE does not allow \C to appear in  lookbehind  assertions  (described         PCRE  does  not  allow \C to appear in lookbehind assertions (described
3673         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-
3674         late the length of the lookbehind.         late the length of the lookbehind.
3675    
3676    
# Line 3210  SQUARE BRACKETS AND CHARACTER CLASSES Line 3679  SQUARE BRACKETS AND CHARACTER CLASSES
3679         An opening square bracket introduces a character class, terminated by a         An opening square bracket introduces a character class, terminated by a
3680         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-
3681         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,
3682         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
3683         circumflex, if present) or escaped with a backslash.         circumflex, if present) or escaped with a backslash.
3684    
3685         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
3686         mode,  the character may occupy more than one byte. A matched character         mode, the character may occupy more than one byte. A matched  character
3687         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
3688         character  in  the  class definition is a circumflex, in which case the         character in the class definition is a circumflex, in  which  case  the
3689         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
3690         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
3691         not the first character, or escape it with a backslash.         not the first character, or escape it with a backslash.
3692    
3693         For example, the character class [aeiou] matches any lower case  vowel,         For  example, the character class [aeiou] matches any lower case vowel,
3694         while  [^aeiou]  matches  any character that is not a lower case vowel.         while [^aeiou] matches any character that is not a  lower  case  vowel.
3695         Note that a circumflex is just a convenient notation for specifying the         Note that a circumflex is just a convenient notation for specifying the
3696         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
3697         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-
3698         sumes  a  character  from the subject string, and therefore it fails if         sumes a character from the subject string, and therefore  it  fails  if
3699         the current pointer is at the end of the string.         the current pointer is at the end of the string.
3700    
3701         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
3702         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
3703         mechanism.         mechanism.
3704    
3705         When caseless matching is set, any letters in a  class  represent  both         When  caseless  matching  is set, any letters in a class represent both
3706         their  upper  case  and lower case versions, so for example, a caseless         their upper case and lower case versions, so for  example,  a  caseless
3707         [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
3708         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
3709         understands the concept of case for characters whose  values  are  less         understands  the  concept  of case for characters whose values are less
3710         than  128, so caseless matching is always possible. For characters with         than 128, so caseless matching is always possible. For characters  with
3711         higher values, the concept of case is supported  if  PCRE  is  compiled         higher  values,  the  concept  of case is supported if PCRE is compiled
3712         with  Unicode  property support, but not otherwise.  If you want to use         with Unicode property support, but not otherwise.  If you want  to  use
3713         caseless matching for characters 128 and above, you  must  ensure  that         caseless  matching  for  characters 128 and above, you must ensure that
3714         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
3715         support.         support.
3716    
3717         Characters that might indicate line breaks are  never  treated  in  any         Characters  that  might  indicate  line breaks are never treated in any
3718         special  way  when  matching  character  classes,  whatever line-ending         special way  when  matching  character  classes,  whatever  line-ending
3719         sequence is in  use,  and  whatever  setting  of  the  PCRE_DOTALL  and         sequence  is  in  use,  and  whatever  setting  of  the PCRE_DOTALL and
3720         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
3721         of these characters.         of these characters.
3722    
3723         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-
3724         ters  in  a  character  class.  For  example,  [d-m] matches any letter         ters in a character  class.  For  example,  [d-m]  matches  any  letter
3725         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
3726         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
3727         where it cannot be interpreted as indicating a range, typically as  the         where  it cannot be interpreted as indicating a range, typically as the
3728         first or last character in the class.         first or last character in the class.
3729    
3730         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-
3731         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
3732         two  characters ("W" and "-") followed by a literal string "46]", so it         two characters ("W" and "-") followed by a literal string "46]", so  it
3733         would match "W46]" or "-46]". However, if the "]"  is  escaped  with  a         would  match  "W46]"  or  "-46]". However, if the "]" is escaped with a
3734         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-
3735         preted as a class containing a range followed by two other  characters.         preted  as a class containing a range followed by two other characters.
3736         The  octal or hexadecimal representation of "]" can also be used to end         The octal or hexadecimal representation of "]" can also be used to  end
3737         a range.         a range.
3738    
3739         Ranges operate in the collating sequence of character values. They  can         Ranges  operate in the collating sequence of character values. They can
3740         also   be  used  for  characters  specified  numerically,  for  example         also  be  used  for  characters  specified  numerically,  for   example
3741         [\000-\037]. In UTF-8 mode, ranges can include characters whose  values         [\000-\037].  In UTF-8 mode, ranges can include characters whose values
3742         are greater than 255, for example [\x{100}-\x{2ff}].         are greater than 255, for example [\x{100}-\x{2ff}].
3743    
3744         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,
3745         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
3746         to  [][\\^_`wxyzabc],  matched  caselessly,  and  in non-UTF-8 mode, if         to [][\\^_`wxyzabc], matched caselessly,  and  in  non-UTF-8  mode,  if
3747         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
3748         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
3749         concept of case for characters with values greater than 128  only  when         concept  of  case for characters with values greater than 128 only when
3750         it is compiled with Unicode property support.         it is compiled with Unicode property support.
3751    
3752         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
3753         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
3754         class. For example, [\dABCDEF] matches any hexadecimal digit. A circum-         class. For example, [\dABCDEF] matches any hexadecimal digit. A circum-
3755         flex can conveniently be used with the upper case  character  types  to         flex  can  conveniently  be used with the upper case character types to
3756         specify  a  more  restricted  set of characters than the matching lower         specify a more restricted set of characters  than  the  matching  lower
3757         case type. For example, the class [^\W_] matches any letter  or  digit,         case  type.  For example, the class [^\W_] matches any letter or digit,
3758         but not underscore.         but not underscore.
3759    
3760         The  only  metacharacters  that are recognized in character classes are         The only metacharacters that are recognized in  character  classes  are
3761         backslash, hyphen (only where it can be  interpreted  as  specifying  a         backslash,  hyphen  (only  where  it can be interpreted as specifying a
3762         range),  circumflex  (only  at the start), opening square bracket (only         range), circumflex (only at the start), opening  square  bracket  (only
3763         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
3764         next  section),  and  the  terminating closing square bracket. However,         next section), and the terminating  closing  square  bracket.  However,
3765         escaping other non-alphanumeric characters does no harm.         escaping other non-alphanumeric characters does no harm.
3766    
3767    
3768  POSIX CHARACTER CLASSES  POSIX CHARACTER CLASSES
3769    
3770         Perl supports the POSIX notation for character classes. This uses names         Perl supports the POSIX notation for character classes. This uses names
3771         enclosed  by  [: and :] within the enclosing square brackets. PCRE also         enclosed by [: and :] within the enclosing square brackets.  PCRE  also
3772         supports this notation. For example,         supports this notation. For example,
3773    
3774           [01[:alpha:]%]           [01[:alpha:]%]
# Line 3322  POSIX CHARACTER CLASSES Line 3791  POSIX CHARACTER CLASSES
3791           word     "word" characters (same as \w)           word     "word" characters (same as \w)
3792           xdigit   hexadecimal digits           xdigit   hexadecimal digits
3793    
3794         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),
3795         and space (32). Notice that this list includes the VT  character  (code         and  space  (32). Notice that this list includes the VT character (code
3796         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
3797         Perl compatibility).         Perl compatibility).
3798    
3799         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
3800         from  Perl  5.8. Another Perl extension is negation, which is indicated         from Perl 5.8. Another Perl extension is negation, which  is  indicated
3801         by a ^ character after the colon. For example,         by a ^ character after the colon. For example,
3802    
3803           [12[:^digit:]]           [12[:^digit:]]
3804    
3805         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
3806         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but         POSIX syntax [.ch.] and [=ch=] where "ch" is a "collating element", but
3807         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.
3808    
# Line 3353  VERTICAL BAR Line 3822  VERTICAL BAR
3822         string). The matching process tries each alternative in turn, from left         string). The matching process tries each alternative in turn, from left
3823         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
3824         are  within a subpattern (defined below), "succeeds" means matching the         are  within a subpattern (defined below), "succeeds" means matching the
3825         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.
3826    
3827    
3828  INTERNAL OPTION SETTING  INTERNAL OPTION SETTING
3829    
3830         The  settings  of  the  PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and         The settings of the  PCRE_CASELESS,  PCRE_MULTILINE,  PCRE_DOTALL,  and
3831         PCRE_EXTENDED options can be changed  from  within  the  pattern  by  a         PCRE_EXTENDED  options  (which are Perl-compatible) can be changed from
3832         sequence  of  Perl  option  letters  enclosed between "(?" and ")". The         within the pattern by  a  sequence  of  Perl  option  letters  enclosed
3833         option letters are         between "(?" and ")".  The option letters are
3834    
3835           i  for PCRE_CASELESS           i  for PCRE_CASELESS
3836           m  for PCRE_MULTILINE           m  for PCRE_MULTILINE
# Line 3370  INTERNAL OPTION SETTING Line 3839  INTERNAL OPTION SETTING
3839    
3840         For example, (?im) sets caseless, multiline matching. It is also possi-         For example, (?im) sets caseless, multiline matching. It is also possi-
3841         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
3842         combined setting and unsetting such as (?im-sx), which sets  PCRE_CASE-         combined  setting and unsetting such as (?im-sx), which sets PCRE_CASE-
3843         LESS  and PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED,         LESS and PCRE_MULTILINE while unsetting PCRE_DOTALL and  PCRE_EXTENDED,
3844         is also permitted. If a  letter  appears  both  before  and  after  the         is  also  permitted.  If  a  letter  appears  both before and after the
3845         hyphen, the option is unset.         hyphen, the option is unset.
3846    
3847         When  an option change occurs at top level (that is, not inside subpat-         The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA
3848         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
3849         that follows.  If the change is placed right at the start of a pattern,         the characters J, U and X respectively.
3850         PCRE extracts it into the global options (and it will therefore show up  
3851         in data extracted by the pcre_fullinfo() function).         When one of these option changes occurs at  top  level  (that  is,  not
3852           inside  subpattern parentheses), the change applies to the remainder of
3853           the pattern that follows. If the change is placed right at the start of
3854           a pattern, PCRE extracts it into the global options (and it will there-
3855           fore show up in data extracted by the pcre_fullinfo() function).
3856    
3857         An  option  change  within a subpattern (see below for a description of         An option change within a subpattern (see below for  a  description  of
3858         subpatterns) affects only that part of the current pattern that follows         subpatterns) affects only that part of the current pattern that follows
3859         it, so         it, so
3860    
3861           (a(?i)b)c           (a(?i)b)c
3862    
3863         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
3864         used).  By this means, options can be made to have  different  settings         used).   By  this means, options can be made to have different settings
3865         in  different parts of the pattern. Any changes made in one alternative         in different parts of the pattern. Any changes made in one  alternative
3866         do carry on into subsequent branches within the  same  subpattern.  For         do  carry  on  into subsequent branches within the same subpattern. For
3867         example,         example,
3868    
3869           (a(?i)b|c)           (a(?i)b|c)
3870    
3871         matches  "ab",  "aB",  "c",  and "C", even though when matching "C" the         matches "ab", "aB", "c", and "C", even though  when  matching  "C"  the
3872         first branch is abandoned before the option setting.  This  is  because         first  branch  is  abandoned before the option setting. This is because
3873         the  effects  of option settings happen at compile time. There would be         the effects of option settings happen at compile time. There  would  be
3874         some very weird behaviour otherwise.         some very weird behaviour otherwise.
3875    
3876         The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA         Note:  There  are  other  PCRE-specific  options that can be set by the
3877         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
3878         the characters J, U and X respectively.         cases the pattern can contain special leading sequences such as (*CRLF)
3879           to override what the application has set or what  has  been  defaulted.
3880           Details  are  given  in the section entitled "Newline sequences" above.
3881           There is also the (*UTF8) leading sequence that  can  be  used  to  set
3882           UTF-8 mode; this is equivalent to setting the PCRE_UTF8 option.
3883    
3884    
3885  SUBPATTERNS  SUBPATTERNS
# Line 3414  SUBPATTERNS Line 3891  SUBPATTERNS
3891    
3892           cat(aract|erpillar|)           cat(aract|erpillar|)
3893    
3894         matches  one  of the words "cat", "cataract", or "caterpillar". Without         matches one of the words "cat", "cataract", or  "caterpillar".  Without
3895         the parentheses, it would match  "cataract",  "erpillar"  or  an  empty         the  parentheses,  it  would  match  "cataract", "erpillar" or an empty
3896         string.         string.
3897    
3898         2.  It  sets  up  the  subpattern as a capturing subpattern. This means         2. It sets up the subpattern as  a  capturing  subpattern.  This  means
3899         that, when the whole pattern  matches,  that  portion  of  the  subject         that,  when  the  whole  pattern  matches,  that portion of the subject
3900         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
3901         ovector argument of pcre_exec(). Opening parentheses are  counted  from         ovector  argument  of pcre_exec(). Opening parentheses are counted from
3902         left  to  right  (starting  from 1) to obtain numbers for the capturing         left to right (starting from 1) to obtain  numbers  for  the  capturing
3903         subpatterns.         subpatterns.
3904    
3905         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-
3906         tern         tern
3907    
3908           the ((red|white) (king|queen))           the ((red|white) (king|queen))
# Line 3433  SUBPATTERNS Line 3910  SUBPATTERNS
3910         the captured substrings are "red king", "red", and "king", and are num-         the captured substrings are "red king", "red", and "king", and are num-
3911         bered 1, 2, and 3, respectively.         bered 1, 2, and 3, respectively.
3912    
3913         The fact that plain parentheses fulfil  two  functions  is  not  always         The  fact  that  plain  parentheses  fulfil two functions is not always
3914         helpful.   There are often times when a grouping subpattern is required         helpful.  There are often times when a grouping subpattern is  required
3915         without a capturing requirement. If an opening parenthesis is  followed         without  a capturing requirement. If an opening parenthesis is followed
3916         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-
3917         ing, and is not counted when computing the  number  of  any  subsequent         ing,  and  is  not  counted when computing the number of any subsequent
3918         capturing  subpatterns. For example, if the string "the white queen" is         capturing subpatterns. For example, if the string "the white queen"  is
3919         matched against the pattern         matched against the pattern
3920    
3921           the ((?:red|white) (king|queen))           the ((?:red|white) (king|queen))
# Line 3446  SUBPATTERNS Line 3923  SUBPATTERNS
3923         the captured substrings are "white queen" and "queen", and are numbered         the captured substrings are "white queen" and "queen", and are numbered
3924         1 and 2. The maximum number of capturing subpatterns is 65535.         1 and 2. The maximum number of capturing subpatterns is 65535.
3925    
3926         As  a  convenient shorthand, if any option settings are required at the         As a convenient shorthand, if any option settings are required  at  the
3927         start of a non-capturing subpattern,  the  option  letters  may  appear         start  of  a  non-capturing  subpattern,  the option letters may appear
3928         between the "?" and the ":". Thus the two patterns         between the "?" and the ":". Thus the two patterns
3929    
3930           (?i:saturday|sunday)           (?i:saturday|sunday)
3931           (?:(?i)saturday|sunday)           (?:(?i)saturday|sunday)
3932    
3933         match exactly the same set of strings. Because alternative branches are         match exactly the same set of strings. Because alternative branches are
3934         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
3935         the  subpattern is reached, an option setting in one branch does affect         the subpattern is reached, an option setting in one branch does  affect
3936         subsequent branches, so the above patterns match "SUNDAY"  as  well  as         subsequent  branches,  so  the above patterns match "SUNDAY" as well as
3937         "Saturday".         "Saturday".
3938    
3939    
3940    DUPLICATE SUBPATTERN NUMBERS
3941    
3942           Perl 5.10 introduced a feature whereby each alternative in a subpattern
3943           uses  the same numbers for its capturing parentheses. Such a subpattern
3944           starts with (?| and is itself a non-capturing subpattern. For  example,
3945           consider this pattern:
3946    
3947             (?|(Sat)ur|(Sun))day
3948    
3949           Because  the two alternatives are inside a (?| group, both sets of cap-
3950           turing parentheses are numbered one. Thus, when  the  pattern  matches,
3951           you  can  look  at captured substring number one, whichever alternative
3952           matched. This construct is useful when you want to  capture  part,  but
3953           not all, of one of a number of alternatives. Inside a (?| group, paren-
3954           theses are numbered as usual, but the number is reset at the  start  of
3955           each  branch. The numbers of any capturing buffers that follow the sub-
3956           pattern start after the highest number used in any branch. The  follow-
3957           ing  example  is taken from the Perl documentation.  The numbers under-
3958           neath show in which buffer the captured content will be stored.
3959    
3960             # before  ---------------branch-reset----------- after
3961             / ( a )  (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x
3962             # 1            2         2  3        2     3     4
3963    
3964           A backreference or a recursive call to  a  numbered  subpattern  always
3965           refers to the first one in the pattern with the given number.
3966    
3967           An  alternative approach to using this "branch reset" feature is to use
3968           duplicate named subpatterns, as described in the next section.
3969    
3970    
3971  NAMED SUBPATTERNS  NAMED SUBPATTERNS
3972    
3973         Identifying  capturing  parentheses  by number is simple, but it can be         Identifying capturing parentheses by number is simple, but  it  can  be
3974         very hard to keep track of the numbers in complicated  regular  expres-         very  hard  to keep track of the numbers in complicated regular expres-
3975         sions.  Furthermore,  if  an  expression  is  modified, the numbers may         sions. Furthermore, if an  expression  is  modified,  the  numbers  may
3976         change. To help with this difficulty, PCRE supports the naming of  sub-         change.  To help with this difficulty, PCRE supports the naming of sub-
3977         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
3978         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
3979         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-
3980         tax.         tax.
3981    
3982         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>...)
3983         or  (?'name'...)  as in Perl, or (?P<name>...) as in Python. References         or (?'name'...) as in Perl, or (?P<name>...) as in  Python.  References
3984         to capturing parentheses from other parts of the pattern, such as back-         to capturing parentheses from other parts of the pattern, such as back-
3985         references,  recursion,  and conditions, can be made by name as well as         references, recursion, and conditions, can be made by name as  well  as
3986         by number.         by number.
3987    
3988         Names consist of up to  32  alphanumeric  characters  and  underscores.         Names  consist  of  up  to  32 alphanumeric characters and underscores.
3989         Named  capturing  parentheses  are  still  allocated numbers as well as         Named capturing parentheses are still  allocated  numbers  as  well  as
3990         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
3991         function calls for extracting the name-to-number translation table from         function calls for extracting the name-to-number translation table from
3992         a compiled pattern. There is also a convenience function for extracting         a compiled pattern. There is also a convenience function for extracting
3993         a captured substring by name.         a captured substring by name.
3994    
3995         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
3996         to relax this constraint by setting the PCRE_DUPNAMES option at compile         to relax this constraint by setting the PCRE_DUPNAMES option at compile
3997         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
3998         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
3999         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
4000         both cases you want to extract the abbreviation. This pattern (ignoring         both cases you want to extract the abbreviation. This pattern (ignoring
4001         the line breaks) does the job:         the line breaks) does the job:
4002    
# Line 3498  NAMED SUBPATTERNS Line 4006  NAMED SUBPATTERNS
4006           (?<DN>Thu)(?:rsday)?|           (?<DN>Thu)(?:rsday)?|
4007           (?<DN>Sat)(?:urday)?           (?<DN>Sat)(?:urday)?
4008    
4009         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
4010         match.  The convenience  function  for  extracting  the  data  by  name         match.  (An alternative way of solving this problem is to use a "branch
4011         returns  the  substring  for  the first (and in this example, the only)         reset" subpattern, as described in the previous section.)
4012         subpattern of that name that matched.  This  saves  searching  to  find  
4013         which  numbered  subpattern  it  was. If you make a reference to a non-         The convenience function for extracting the data by  name  returns  the
4014         unique named subpattern from elsewhere in the  pattern,  the  one  that         substring  for  the first (and in this example, the only) subpattern of
4015         corresponds  to  the  lowest number is used. For further details of the         that name that matched. This saves searching  to  find  which  numbered
4016         interfaces for handling named subpatterns, see the  pcreapi  documenta-         subpattern  it  was. If you make a reference to a non-unique named sub-
4017         tion.         pattern from elsewhere in the pattern, the one that corresponds to  the
4018           lowest  number  is used. For further details of the interfaces for han-
4019           dling named subpatterns, see the pcreapi documentation.
4020    
4021           Warning: You cannot use different names to distinguish between two sub-
4022           patterns  with  the same number (see the previous section) because PCRE
4023           uses only the numbers when matching.
4024    
4025    
4026  REPETITION  REPETITION
4027    
4028         Repetition  is  specified  by  quantifiers, which can follow any of the         Repetition is specified by quantifiers, which can  follow  any  of  the
4029         following items:         following items:
4030    
4031           a literal data character           a literal data character
# Line 3524  REPETITION Line 4038  REPETITION
4038           a back reference (see next section)           a back reference (see next section)
4039           a parenthesized subpattern (unless it is an assertion)           a parenthesized subpattern (unless it is an assertion)
4040    
4041         The general repetition quantifier specifies a minimum and maximum  num-         The  general repetition quantifier specifies a minimum and maximum num-
4042         ber  of  permitted matches, by giving the two numbers in curly brackets         ber of permitted matches, by giving the two numbers in  curly  brackets
4043         (braces), separated by a comma. The numbers must be  less  than  65536,         (braces),  separated  by  a comma. The numbers must be less than 65536,
4044         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:
4045    
4046           z{2,4}           z{2,4}
4047    
4048         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
4049         special character. If the second number is omitted, but  the  comma  is         special  character.  If  the second number is omitted, but the comma is
4050         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
4051         are both omitted, the quantifier specifies an exact number of  required         are  both omitted, the quantifier specifies an exact number of required
4052         matches. Thus         matches. Thus
4053    
4054           [aeiou]{3,}           [aeiou]{3,}
# Line 3543  REPETITION Line 4057  REPETITION
4057    
4058           \d{8}           \d{8}
4059    
4060         matches  exactly  8  digits. An opening curly bracket that appears in a         matches exactly 8 digits. An opening curly bracket that  appears  in  a
4061         position where a quantifier is not allowed, or one that does not  match         position  where a quantifier is not allowed, or one that does not match
4062         the  syntax of a quantifier, is taken as a literal character. For exam-         the syntax of a quantifier, is taken as a literal character. For  exam-
4063         ple, {,6} is not a quantifier, but a literal string of four characters.         ple, {,6} is not a quantifier, but a literal string of four characters.
4064    
4065         In  UTF-8  mode,  quantifiers  apply to UTF-8 characters rather than to         In  UTF-8  mode,  quantifiers  apply to UTF-8 characters rather than to
# Line 3556  REPETITION Line 4070  REPETITION
4070         may be of different lengths).         may be of different lengths).
4071    
4072         The quantifier {0} is permitted, causing the expression to behave as if         The quantifier {0} is permitted, causing the expression to behave as if
4073         the previous item and the quantifier were not present.         the previous item and the quantifier were not present. This may be use-
4074           ful for subpatterns that are referenced as subroutines  from  elsewhere
4075           in the pattern. Items other than subpatterns that have a {0} quantifier
4076           are omitted from the compiled pattern.
4077    
4078         For  convenience, the three most common quantifiers have single-charac-         For convenience, the three most common quantifiers have  single-charac-
4079         ter abbreviations:         ter abbreviations:
4080    
4081           *    is equivalent to {0,}           *    is equivalent to {0,}
4082           +    is equivalent to {1,}           +    is equivalent to {1,}
4083           ?    is equivalent to {0,1}           ?    is equivalent to {0,1}
4084    
4085         It is possible to construct infinite loops by  following  a  subpattern         It  is  possible  to construct infinite loops by following a subpattern
4086         that can match no characters with a quantifier that has no upper limit,         that can match no characters with a quantifier that has no upper limit,
4087         for example:         for example:
4088    
4089           (a?)*           (a?)*
4090    
4091         Earlier versions of Perl and PCRE used to give an error at compile time         Earlier versions of Perl and PCRE used to give an error at compile time
4092         for  such  patterns. However, because there are cases where this can be         for such patterns. However, because there are cases where this  can  be
4093         useful, such patterns are now accepted, but if any  repetition  of  the         useful,  such  patterns  are now accepted, but if any repetition of the
4094         subpattern  does in fact match no characters, the loop is forcibly bro-         subpattern does in fact match no characters, the loop is forcibly  bro-
4095         ken.         ken.
4096    
4097         By default, the quantifiers are "greedy", that is, they match  as  much         By  default,  the quantifiers are "greedy", that is, they match as much
4098         as  possible  (up  to  the  maximum number of permitted times), without         as possible (up to the maximum  number  of  permitted  times),  without
4099         causing the rest of the pattern to fail. The classic example  of  where         causing  the  rest of the pattern to fail. The classic example of where
4100         this gives problems is in trying to match comments in C programs. These         this gives problems is in trying to match comments in C programs. These
4101         appear between /* and */ and within the comment,  individual  *  and  /         appear  between  /*  and  */ and within the comment, individual * and /
4102         characters  may  appear. An attempt to match C comments by applying the         characters may appear. An attempt to match C comments by  applying  the
4103         pattern         pattern
4104    
4105           /\*.*\*/           /\*.*\*/
# Line 3591  REPETITION Line 4108  REPETITION
4108    
4109           /* first comment */  not comment  /* second comment */           /* first comment */  not comment  /* second comment */
4110    
4111         fails, because it matches the entire string owing to the greediness  of         fails,  because it matches the entire string owing to the greediness of
4112         the .*  item.         the .*  item.
4113    
4114         However,  if  a quantifier is followed by a question mark, it ceases to         However, if a quantifier is followed by a question mark, it  ceases  to
4115         be greedy, and instead matches the minimum number of times possible, so         be greedy, and instead matches the minimum number of times possible, so
4116         the pattern         the pattern
4117    
4118           /\*.*?\*/           /\*.*?\*/
4119    
4120         does  the  right  thing with the C comments. The meaning of the various         does the right thing with the C comments. The meaning  of  the  various
4121         quantifiers is not otherwise changed,  just  the  preferred  number  of         quantifiers  is  not  otherwise  changed,  just the preferred number of
4122         matches.   Do  not  confuse this use of question mark with its use as a         matches.  Do not confuse this use of question mark with its  use  as  a
4123         quantifier in its own right. Because it has two uses, it can  sometimes         quantifier  in its own right. Because it has two uses, it can sometimes
4124         appear doubled, as in         appear doubled, as in
4125    
4126           \d??\d           \d??\d
# Line 3611  REPETITION Line 4128  REPETITION
4128         which matches one digit by preference, but can match two if that is the         which matches one digit by preference, but can match two if that is the
4129         only way the rest of the pattern matches.         only way the rest of the pattern matches.
4130    
4131         If the PCRE_UNGREEDY option is set (an option that is not available  in         If  the PCRE_UNGREEDY option is set (an option that is not available in
4132         Perl),  the  quantifiers are not greedy by default, but individual ones         Perl), the quantifiers are not greedy by default, but  individual  ones
4133         can be made greedy by following them with a  question  mark.  In  other         can  be  made  greedy  by following them with a question mark. In other
4134         words, it inverts the default behaviour.         words, it inverts the default behaviour.
4135    
4136         When  a  parenthesized  subpattern  is quantified with a minimum repeat         When a parenthesized subpattern is quantified  with  a  minimum  repeat
4137         count that is greater than 1 or with a limited maximum, more memory  is         count  that is greater than 1 or with a limited maximum, more memory is
4138         required  for  the  compiled  pattern, in proportion to the size of the         required for the compiled pattern, in proportion to  the  size  of  the
4139         minimum or maximum.         minimum or maximum.
4140    
4141         If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equiv-         If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equiv-
4142         alent  to  Perl's  /s) is set, thus allowing the dot to match newlines,         alent to Perl's /s) is set, thus allowing the dot  to  match  newlines,
4143         the pattern is implicitly anchored, because whatever  follows  will  be         the  pattern  is  implicitly anchored, because whatever follows will be
4144         tried  against every character position in the subject string, so there         tried against every character position in the subject string, so  there
4145         is no point in retrying the overall match at  any  position  after  the         is  no  point  in  retrying the overall match at any position after the
4146         first.  PCRE  normally treats such a pattern as though it were preceded         first. PCRE normally treats such a pattern as though it  were  preceded
4147         by \A.         by \A.
4148    
4149         In cases where it is known that the subject  string  contains  no  new-         In  cases  where  it  is known that the subject string contains no new-
4150         lines,  it  is  worth setting PCRE_DOTALL in order to obtain this opti-         lines, it is worth setting PCRE_DOTALL in order to  obtain  this  opti-
4151         mization, or alternatively using ^ to indicate anchoring explicitly.         mization, or alternatively using ^ to indicate anchoring explicitly.
4152    
4153         However, there is one situation where the optimization cannot be  used.         However,  there is one situation where the optimization cannot be used.
4154         When  .*   is  inside  capturing  parentheses that are the subject of a         When .*  is inside capturing parentheses that  are  the  subject  of  a
4155         backreference elsewhere in the pattern, a match at the start  may  fail         backreference  elsewhere  in the pattern, a match at the start may fail
4156         where a later one succeeds. Consider, for example:         where a later one succeeds. Consider, for example:
4157    
4158           (.*)abc\1           (.*)abc\1
4159    
4160         If  the subject is "xyz123abc123" the match point is the fourth charac-         If the subject is "xyz123abc123" the match point is the fourth  charac-
4161         ter. For this reason, such a pattern is not implicitly anchored.         ter. For this reason, such a pattern is not implicitly anchored.
4162    
4163         When a capturing subpattern is repeated, the value captured is the sub-         When a capturing subpattern is repeated, the value captured is the sub-
# Line 3649  REPETITION Line 4166  REPETITION
4166           (tweedle[dume]{3}\s*)+           (tweedle[dume]{3}\s*)+
4167    
4168         has matched "tweedledum tweedledee" the value of the captured substring         has matched "tweedledum tweedledee" the value of the captured substring
4169         is "tweedledee". However, if there are  nested  capturing  subpatterns,         is  "tweedledee".  However,  if there are nested capturing subpatterns,
4170         the  corresponding captured values may have been set in previous itera-         the corresponding captured values may have been set in previous  itera-
4171         tions. For example, after         tions. For example, after
4172    
4173           /(a|(b))+/           /(a|(b))+/
# Line 3660  REPETITION Line 4177  REPETITION
4177    
4178  ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS  ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS
4179    
4180         With both maximizing ("greedy") and minimizing ("ungreedy"  or  "lazy")         With  both  maximizing ("greedy") and minimizing ("ungreedy" or "lazy")
4181         repetition,  failure  of what follows normally causes the repeated item         repetition, failure of what follows normally causes the  repeated  item
4182         to be re-evaluated to see if a different number of repeats  allows  the         to  be  re-evaluated to see if a different number of repeats allows the
4183         rest  of  the pattern to match. Sometimes it is useful to prevent this,         rest of the pattern to match. Sometimes it is useful to  prevent  this,
4184         either to change the nature of the match, or to cause it  fail  earlier         either  to  change the nature of the match, or to cause it fail earlier
4185         than  it otherwise might, when the author of the pattern knows there is         than it otherwise might, when the author of the pattern knows there  is
4186         no point in carrying on.         no point in carrying on.
4187    
4188         Consider, for example, the pattern \d+foo when applied to  the  subject         Consider,  for  example, the pattern \d+foo when applied to the subject
4189         line         line
4190    
4191           123456bar           123456bar
4192    
4193         After matching all 6 digits and then failing to match "foo", the normal         After matching all 6 digits and then failing to match "foo", the normal
4194         action of the matcher is to try again with only 5 digits  matching  the         action  of  the matcher is to try again with only 5 digits matching the
4195         \d+  item,  and  then  with  4,  and  so on, before ultimately failing.         \d+ item, and then with  4,  and  so  on,  before  ultimately  failing.
4196         "Atomic grouping" (a term taken from Jeffrey  Friedl's  book)  provides         "Atomic  grouping"  (a  term taken from Jeffrey Friedl's book) provides
4197         the  means for specifying that once a subpattern has matched, it is not         the means for specifying that once a subpattern has matched, it is  not
4198         to be re-evaluated in this way.         to be re-evaluated in this way.
4199    
4200         If we use atomic grouping for the previous example, the  matcher  gives         If  we  use atomic grouping for the previous example, the matcher gives
4201         up  immediately  on failing to match "foo" the first time. The notation         up immediately on failing to match "foo" the first time.  The  notation
4202         is a kind of special parenthesis, starting with (?> as in this example:         is a kind of special parenthesis, starting with (?> as in this example:
4203    
4204           (?>\d+)foo           (?>\d+)foo
# Line 3711  ATOMIC GROUPING AND POSSESSIVE QUANTIFIE Line 4228  ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
4228    
4229           \d++foo           \d++foo
4230    
4231         Possessive  quantifiers  are  always  greedy;  the   setting   of   the         Note that a possessive quantifier can be used with an entire group, for
4232           example:
4233    
4234             (abc|xyz){2,3}+
4235    
4236           Possessive   quantifiers   are   always  greedy;  the  setting  of  the
4237         PCRE_UNGREEDY option is ignored. They are a convenient notation for the         PCRE_UNGREEDY option is ignored. They are a convenient notation for the
4238         simpler forms of atomic group. However, there is no difference  in  the         simpler  forms  of atomic group. However, there is no difference in the
4239         meaning  of  a  possessive  quantifier and the equivalent atomic group,         meaning of a possessive quantifier and  the  equivalent  atomic  group,
4240         though there may be a performance  difference;  possessive  quantifiers         though  there  may  be a performance difference; possessive quantifiers
4241         should be slightly faster.         should be slightly faster.
4242    
4243         The  possessive  quantifier syntax is an extension to the Perl 5.8 syn-         The possessive quantifier syntax is an extension to the Perl  5.8  syn-
4244         tax.  Jeffrey Friedl originated the idea (and the name)  in  the  first         tax.   Jeffrey  Friedl  originated the idea (and the name) in the first
4245         edition of his book. Mike McCloskey liked it, so implemented it when he         edition of his book. Mike McCloskey liked it, so implemented it when he
4246         built Sun's Java package, and PCRE copied it from there. It  ultimately         built  Sun's Java package, and PCRE copied it from there. It ultimately
4247         found its way into Perl at release 5.10.         found its way into Perl at release 5.10.
4248    
4249         PCRE has an optimization that automatically "possessifies" certain sim-         PCRE has an optimization that automatically "possessifies" certain sim-
4250         ple pattern constructs. For example, the sequence  A+B  is  treated  as         ple  pattern  constructs.  For  example, the sequence A+B is treated as
4251         A++B  because  there is no point in backtracking into a sequence of A's         A++B because there is no point in backtracking into a sequence  of  A's
4252         when B must follow.         when B must follow.
4253    
4254         When a pattern contains an unlimited repeat inside  a  subpattern  that         Whe