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# Line 18  INTRODUCTION Line 18  INTRODUCTION
18    
19         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
20         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
21         just  a  few differences. (Certain features that appeared in Python and         just  a  few  differences. Certain features that appeared in Python and
22         PCRE before they appeared in Perl are also available using  the  Python         PCRE before they appeared in Perl are also available using  the  Python
23         syntax.)         syntax.  There is also some support for certain .NET and Oniguruma syn-
24           tax items, and there is an option for  requesting  some  minor  changes
25           that give better JavaScript compatibility.
26    
27         The  current  implementation of PCRE (release 7.x) corresponds approxi-         The  current  implementation of PCRE (release 7.x) corresponds approxi-
28         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
# Line 92  USER DOCUMENTATION Line 94  USER DOCUMENTATION
94           pcrestack         discussion of stack usage           pcrestack         discussion of stack usage
95           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
96    
97         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
98         each C library function, listing its arguments and results.         each C library function, listing its arguments and results.
99    
100    
101  LIMITATIONS  LIMITATIONS
102    
103         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
104         never in practice be relevant.         never in practice be relevant.
105    
106         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
107         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
108         process  regular  expressions  that are truly enormous, you can compile         process regular expressions that are truly enormous,  you  can  compile
109         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
110         the  source  distribution and the pcrebuild documentation for details).         the source distribution and the pcrebuild documentation  for  details).
111         In these cases the limit is substantially larger.  However,  the  speed         In  these  cases the limit is substantially larger.  However, the speed
112         of execution is slower.         of execution is slower.
113    
114         All values in repeating quantifiers must be less than 65536.         All values in repeating quantifiers must be less than 65536.
# Line 117  LIMITATIONS Line 119  LIMITATIONS
119         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
120         the maximum number of named subpatterns is 10000.         the maximum number of named subpatterns is 10000.
121    
122         The  maximum  length of a subject string is the largest positive number         The maximum length of a subject string is the largest  positive  number
123         that an integer variable can hold. However, when using the  traditional         that  an integer variable can hold. However, when using the traditional
124         matching function, PCRE uses recursion to handle subpatterns and indef-         matching function, PCRE uses recursion to handle subpatterns and indef-
125         inite repetition.  This means that the available stack space may  limit         inite  repetition.  This means that the available stack space may limit
126         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.
127         For a discussion of stack issues, see the pcrestack documentation.         For a discussion of stack issues, see the pcrestack documentation.
128    
129    
130  UTF-8 AND UNICODE PROPERTY SUPPORT  UTF-8 AND UNICODE PROPERTY SUPPORT
131    
132         From release 3.3, PCRE has  had  some  support  for  character  strings         From  release  3.3,  PCRE  has  had  some support for character strings
133         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
134         to cover most common requirements, and in release 5.0  additional  sup-         to  cover  most common requirements, and in release 5.0 additional sup-
135         port for Unicode general category properties was added.         port for Unicode general category properties was added.
136    
137         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
138         support in the code, and, in addition,  you  must  call  pcre_compile()         support  in  the  code,  and, in addition, you must call pcre_compile()
139         with  the PCRE_UTF8 option flag. When you do this, both the pattern and         with the PCRE_UTF8 option flag. When you do this, both the pattern  and
140         any subject strings that are matched against it are  treated  as  UTF-8         any  subject  strings  that are matched against it are treated as UTF-8
141         strings instead of just strings of bytes.         strings instead of just strings of bytes.
142    
143         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,
144         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
145         is limited to testing the PCRE_UTF8 flag occasionally, so should not be         is limited to testing the PCRE_UTF8 flag occasionally, so should not be
146         very big.         very big.
147    
148         If PCRE is built with Unicode character property support (which implies         If PCRE is built with Unicode character property support (which implies
149         UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-         UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-
150         ported.  The available properties that can be tested are limited to the         ported.  The available properties that can be tested are limited to the
151         general  category  properties such as Lu for an upper case letter or Nd         general category properties such as Lu for an upper case letter  or  Nd
152         for a decimal number, the Unicode script names such as Arabic  or  Han,         for  a  decimal number, the Unicode script names such as Arabic or Han,
153         and  the  derived  properties  Any  and L&. A full list is given in the         and the derived properties Any and L&. A full  list  is  given  in  the
154         pcrepattern documentation. Only the short names for properties are sup-         pcrepattern documentation. Only the short names for properties are sup-
155         ported.  For example, \p{L} matches a letter. Its Perl synonym, \p{Let-         ported. For example, \p{L} matches a letter. Its Perl synonym,  \p{Let-
156         ter}, is not supported.  Furthermore,  in  Perl,  many  properties  may         ter},  is  not  supported.   Furthermore,  in Perl, many properties may
157         optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE         optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE
158         does not support this.         does not support this.
159    
160     Validity of UTF-8 strings     Validity of UTF-8 strings
161    
162         When you set the PCRE_UTF8 flag, the strings  passed  as  patterns  and         When  you  set  the  PCRE_UTF8 flag, the strings passed as patterns and
163         subjects are (by default) checked for validity on entry to the relevant         subjects are (by default) checked for validity on entry to the relevant
164         functions. From release 7.3 of PCRE, the check is according  the  rules         functions.  From  release 7.3 of PCRE, the check is according the rules
165         of  RFC  3629, which are themselves derived from the Unicode specifica-         of RFC 3629, which are themselves derived from the  Unicode  specifica-
166         tion. Earlier releases of PCRE followed the rules of  RFC  2279,  which         tion.  Earlier  releases  of PCRE followed the rules of RFC 2279, which
167         allows  the  full range of 31-bit values (0 to 0x7FFFFFFF). The current         allows the full range of 31-bit values (0 to 0x7FFFFFFF).  The  current
168         check allows only values in the range U+0 to U+10FFFF, excluding U+D800         check allows only values in the range U+0 to U+10FFFF, excluding U+D800
169         to U+DFFF.         to U+DFFF.
170    
171         The  excluded  code  points are the "Low Surrogate Area" of Unicode, of         The excluded code points are the "Low Surrogate Area"  of  Unicode,  of
172         which the Unicode Standard says this: "The Low Surrogate Area does  not         which  the Unicode Standard says this: "The Low Surrogate Area does not
173         contain  any  character  assignments,  consequently  no  character code         contain any  character  assignments,  consequently  no  character  code
174         charts or namelists are provided for this area. Surrogates are reserved         charts or namelists are provided for this area. Surrogates are reserved
175         for  use  with  UTF-16 and then must be used in pairs." The code points         for use with UTF-16 and then must be used in pairs."  The  code  points
176         that are encoded by UTF-16 pairs  are  available  as  independent  code         that  are  encoded  by  UTF-16  pairs are available as independent code
177         points  in  the  UTF-8  encoding.  (In other words, the whole surrogate         points in the UTF-8 encoding. (In  other  words,  the  whole  surrogate
178         thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)         thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
179    
180         If an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error  return         If  an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error return
181         (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know         (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know
182         that your strings are valid, and therefore want to skip these checks in         that your strings are valid, and therefore want to skip these checks in
183         order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at         order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at
184         compile time or at run time, PCRE assumes that the pattern  or  subject         compile  time  or at run time, PCRE assumes that the pattern or subject
185         it  is  given  (respectively)  contains only valid UTF-8 codes. In this         it is given (respectively) contains only valid  UTF-8  codes.  In  this
186         case, it does not diagnose an invalid UTF-8 string.         case, it does not diagnose an invalid UTF-8 string.
187    
188         If you pass an invalid UTF-8 string  when  PCRE_NO_UTF8_CHECK  is  set,         If  you  pass  an  invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set,
189         what  happens  depends on why the string is invalid. If the string con-         what happens depends on why the string is invalid. If the  string  con-
190         forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a         forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
191         string  of  characters  in  the  range 0 to 0x7FFFFFFF. In other words,         string of characters in the range 0  to  0x7FFFFFFF.  In  other  words,
192         apart from the initial validity test, PCRE (when in UTF-8 mode) handles         apart from the initial validity test, PCRE (when in UTF-8 mode) handles
193         strings  according  to  the more liberal rules of RFC 2279. However, if         strings according to the more liberal rules of RFC  2279.  However,  if
194         the string does not even conform to RFC 2279, the result is  undefined.         the  string does not even conform to RFC 2279, the result is undefined.
195         Your program may crash.         Your program may crash.
196    
197         If  you  want  to  process  strings  of  values  in the full range 0 to         If you want to process strings  of  values  in  the  full  range  0  to
198         0x7FFFFFFF, encoded in a UTF-8-like manner as per the old RFC, you  can         0x7FFFFFFF,  encoded in a UTF-8-like manner as per the old RFC, you can
199         set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in         set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in
200         this situation, you will have to apply your own validity check.         this situation, you will have to apply your own validity check.
201    
202     General comments about UTF-8 mode     General comments about UTF-8 mode
203    
204         1. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a         1.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a
205         two-byte UTF-8 character if the value is greater than 127.         two-byte UTF-8 character if the value is greater than 127.
206    
207         2.  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
208         characters for values greater than \177.         characters for values greater than \177.
209    
210         3. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-         3.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-
211         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
212    
213         4.  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-
214         gle byte.         gle byte.
215    
216         5. 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
217         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
218         not available in the alternative matching function, pcre_dfa_exec().         not available in the alternative matching function, pcre_dfa_exec().
219    
220         6. 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
221         test  characters of any code value, but the characters that PCRE recog-         test characters of any code value, but the characters that PCRE  recog-
222         nizes as digits, spaces, or word characters  remain  the  same  set  as         nizes  as  digits,  spaces,  or  word characters remain the same set as
223         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
224         includes Unicode property support, because to do otherwise  would  slow         includes  Unicode  property support, because to do otherwise would slow
225         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
226         sense of, say, "digit", you must use Unicode  property  tests  such  as         sense  of,  say,  "digit",  you must use Unicode property tests such as
227         \p{Nd}.         \p{Nd}. Note that this also applies to \b, because  it  is  defined  in
228           terms of \w and \W.
229    
230         7.  Similarly,  characters that match the POSIX named character classes         7.  Similarly,  characters that match the POSIX named character classes
231         are all low-valued characters.         are all low-valued characters.
# Line 256  AUTHOR Line 259  AUTHOR
259    
260  REVISION  REVISION
261    
262         Last updated: 09 August 2007         Last updated: 18 March 2009
263         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
264  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
265    
266    
# Line 271  NAME Line 274  NAME
274  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
275    
276         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
277         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
278         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
279         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
280         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
281         directory) can be obtained by running         environments using the GUI facility of  CMakeSetup  if  you  are  using
282           CMake instead of configure to build PCRE.
283    
284           The complete list of options for configure (which includes the standard
285           ones such as the  selection  of  the  installation  directory)  can  be
286           obtained by running
287    
288           ./configure --help           ./configure --help
289    
290         The following sections include  descriptions  of  options  whose  names         The  following  sections  include  descriptions  of options whose names
291         begin with --enable or --disable. These settings specify changes to the         begin with --enable or --disable. These settings specify changes to the
292         defaults for the configure command. Because of the way  that  configure         defaults  for  the configure command. Because of the way that configure
293         works,  --enable  and --disable always come in pairs, so the complemen-         works, --enable and --disable always come in pairs, so  the  complemen-
294         tary option always exists as well, but as it specifies the default,  it         tary  option always exists as well, but as it specifies the default, it
295         is not described.         is not described.
296    
297    
# Line 300  C++ SUPPORT Line 308  C++ SUPPORT
308    
309  UTF-8 SUPPORT  UTF-8 SUPPORT
310    
311         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 Unicode character strings, add
312    
313           --enable-utf8           --enable-utf8
314    
315         to  the  configure  command.  Of  itself, this does not make PCRE treat         to the configure command. Of itself, this  does  not  make  PCRE  treat
316         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
317         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()
318         function.         function.
319    
320           If  you set --enable-utf8 when compiling in an EBCDIC environment, PCRE
321           expects its input to be either ASCII or UTF-8 (depending on the runtime
322           option).  It  is not possible to support both EBCDIC and UTF-8 codes in
323           the same  version  of  the  library.  Consequently,  --enable-utf8  and
324           --enable-ebcdic are mutually exclusive.
325    
326    
327  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
328    
329         UTF-8 support allows PCRE to process character values greater than  255         UTF-8  support allows PCRE to process character values greater than 255
330         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-
331         vide any facilities for accessing the properties of such characters. If         vide any facilities for accessing the properties of such characters. If
332         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
333         refer to Unicode character properties, you must add         refer to Unicode character properties, you must add
334    
335           --enable-unicode-properties           --enable-unicode-properties
336    
337         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
338         not explicitly requested it.         not explicitly requested it.
339    
340         Including  Unicode  property  support  adds around 30K of tables to the         Including Unicode property support adds around 30K  of  tables  to  the
341         PCRE library. Only the general category properties such as  Lu  and  Nd         PCRE  library.  Only  the general category properties such as Lu and Nd
342         are supported. Details are given in the pcrepattern documentation.         are supported. Details are given in the pcrepattern documentation.
343    
344    
345  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
346    
347         By  default,  PCRE interprets character 10 (linefeed, LF) as indicating         By default, PCRE interprets the linefeed (LF) character  as  indicating
348         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
349         systems. You can compile PCRE to use character 13 (carriage return, CR)         systems. You can compile PCRE to use carriage return (CR)  instead,  by
350         instead, by adding         adding
351    
352           --enable-newline-is-cr           --enable-newline-is-cr
353    
354         to the  configure  command.  There  is  also  a  --enable-newline-is-lf         to  the  configure  command.  There  is  also  a --enable-newline-is-lf
355         option, which explicitly specifies linefeed as the newline character.         option, which explicitly specifies linefeed as the newline character.
356    
357         Alternatively, you can specify that line endings are to be indicated by         Alternatively, you can specify that line endings are to be indicated by
# Line 349  CODE VALUE OF NEWLINE Line 363  CODE VALUE OF NEWLINE
363    
364           --enable-newline-is-anycrlf           --enable-newline-is-anycrlf
365    
366         which causes PCRE to recognize any of the three sequences  CR,  LF,  or         which  causes  PCRE  to recognize any of the three sequences CR, LF, or
367         CRLF as indicating a line ending. Finally, a fifth option, specified by         CRLF as indicating a line ending. Finally, a fifth option, specified by
368    
369           --enable-newline-is-any           --enable-newline-is-any
# Line 361  CODE VALUE OF NEWLINE Line 375  CODE VALUE OF NEWLINE
375         conventional to use the standard for your operating system.         conventional to use the standard for your operating system.
376    
377    
378    WHAT \R MATCHES
379    
380           By default, the sequence \R in a pattern matches  any  Unicode  newline
381           sequence,  whatever  has  been selected as the line ending sequence. If
382           you specify
383    
384             --enable-bsr-anycrlf
385    
386           the default is changed so that \R matches only CR, LF, or  CRLF.  What-
387           ever  is selected when PCRE is built can be overridden when the library
388           functions are called.
389    
390    
391  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
392    
393         The PCRE building process uses libtool to build both shared and  static         The PCRE building process uses libtool to build both shared and  static
# Line 496  USING EBCDIC CODE Line 523  USING EBCDIC CODE
523    
524         to the configure command. This setting implies --enable-rebuild-charta-         to the configure command. This setting implies --enable-rebuild-charta-
525         bles.  You  should  only  use  it if you know that you are in an EBCDIC         bles.  You  should  only  use  it if you know that you are in an EBCDIC
526         environment (for example, an IBM mainframe operating system).         environment (for example,  an  IBM  mainframe  operating  system).  The
527           --enable-ebcdic option is incompatible with --enable-utf8.
528    
529    
530    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
531    
532           By default, pcregrep reads all files as plain text. You can build it so
533           that it recognizes files whose names end in .gz or .bz2, and reads them
534           with libz or libbz2, respectively, by adding one or both of
535    
536             --enable-pcregrep-libz
537             --enable-pcregrep-libbz2
538    
539           to the configure command. These options naturally require that the rel-
540           evant libraries are installed on your system. Configuration  will  fail
541           if they are not.
542    
543    
544    PCRETEST OPTION FOR LIBREADLINE SUPPORT
545    
546           If you add
547    
548             --enable-pcretest-libreadline
549    
550           to  the  configure  command,  pcretest  is  linked with the libreadline
551           library, and when its input is from a terminal, it reads it  using  the
552           readline() function. This provides line-editing and history facilities.
553           Note that libreadline is GPL-licenced, so if you distribute a binary of
554           pcretest linked in this way, there may be licensing issues.
555    
556           Setting  this  option  causes  the -lreadline option to be added to the
557           pcretest build. In many operating environments with  a  sytem-installed
558           libreadline this is sufficient. However, in some environments (e.g.  if
559           an unmodified distribution version of readline is in use),  some  extra
560           configuration  may  be necessary. The INSTALL file for libreadline says
561           this:
562    
563             "Readline uses the termcap functions, but does not link with the
564             termcap or curses library itself, allowing applications which link
565             with readline the to choose an appropriate library."
566    
567           If your environment has not been set up so that an appropriate  library
568           is automatically included, you may need to add something like
569    
570             LIBS="-ncurses"
571    
572           immediately before the configure command.
573    
574    
575  SEE ALSO  SEE ALSO
# Line 513  AUTHOR Line 586  AUTHOR
586    
587  REVISION  REVISION
588    
589         Last updated: 30 July 2007         Last updated: 17 March 2009
590         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
591  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
592    
593    
# Line 662  THE ALTERNATIVE MATCHING ALGORITHM Line 735  THE ALTERNATIVE MATCHING ALGORITHM
735         tive algorithm moves through the subject  string  one  character  at  a         tive algorithm moves through the subject  string  one  character  at  a
736         time, for all active paths through the tree.         time, for all active paths through the tree.
737    
738         8.  None  of  the  backtracking control verbs such as (*PRUNE) are sup-         8.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)
739         ported.         are not supported. (*FAIL) is supported, and  behaves  like  a  failing
740           negative assertion.
741    
742    
743  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
744    
745         Using the alternative matching algorithm provides the following  advan-         Using  the alternative matching algorithm provides the following advan-
746         tages:         tages:
747    
748         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-
749         ically found, and in particular, the longest match is  found.  To  find         ically  found,  and  in particular, the longest match is found. To find
750         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
751         things with callouts.         things with callouts.
752    
753         2. There is much better support for partial matching. The  restrictions         2.  There is much better support for partial matching. The restrictions
754         on  the content of the pattern that apply when using the standard algo-         on the content of the pattern that apply when using the standard  algo-
755         rithm for partial matching do not apply to the  alternative  algorithm.         rithm  for  partial matching do not apply to the alternative algorithm.
756         For  non-anchored patterns, the starting position of a partial match is         For non-anchored patterns, the starting position of a partial match  is
757         available.         available.
758    
759         3. Because the alternative algorithm  scans  the  subject  string  just         3.  Because  the  alternative  algorithm  scans the subject string just
760         once,  and  never  needs to backtrack, it is possible to pass very long         once, and never needs to backtrack, it is possible to  pass  very  long
761         subject strings to the matching function in  several  pieces,  checking         subject  strings  to  the matching function in several pieces, checking
762         for partial matching each time.         for partial matching each time.
763    
764    
# Line 692  DISADVANTAGES OF THE ALTERNATIVE ALGORIT Line 766  DISADVANTAGES OF THE ALTERNATIVE ALGORIT
766    
767         The alternative algorithm suffers from a number of disadvantages:         The alternative algorithm suffers from a number of disadvantages:
768    
769         1.  It  is  substantially  slower  than the standard algorithm. This is         1. It is substantially slower than  the  standard  algorithm.  This  is
770         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
771         because it is less susceptible to optimization.         because it is less susceptible to optimization.
772    
773         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
# Line 711  AUTHOR Line 785  AUTHOR
785    
786  REVISION  REVISION
787    
788         Last updated: 08 August 2007         Last updated: 19 April 2008
789         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2008 University of Cambridge.
790  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
791    
792    
# Line 824  PCRE API OVERVIEW Line 898  PCRE API OVERVIEW
898         a  Perl-compatible  manner. A sample program that demonstrates the sim-         a  Perl-compatible  manner. A sample program that demonstrates the sim-
899         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
900         the  source distribution. The pcresample documentation describes how to         the  source distribution. The pcresample documentation describes how to
901         run it.         compile and run it.
902    
903         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
904         ble,  is  also provided. This uses a different algorithm for the match-         ble,  is  also provided. This uses a different algorithm for the match-
# Line 908  NEWLINES Line 982  NEWLINES
982         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
983         pattern is compiled, or when it is matched.         pattern is compiled, or when it is matched.
984    
985           At compile time, the newline convention can be specified by the options
986           argument of pcre_compile(), or it can be specified by special  text  at
987           the start of the pattern itself; this overrides any other settings. See
988           the pcrepattern page for details of the special character sequences.
989    
990         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-
991         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
992         newline  convention  affects  the  handling of the dot, circumflex, and         newline convention affects the handling of  the  dot,  circumflex,  and
993         dollar metacharacters, the handling of #-comments in /x mode, and, when         dollar metacharacters, the handling of #-comments in /x mode, and, when
994         CRLF  is a recognized line ending sequence, the match position advance-         CRLF is a recognized line ending sequence, the match position  advance-
995         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
996         not affect the interpretation of the \n or \r escape sequences.         section on pcre_exec() options below.
997    
998           The choice of newline convention does not affect the interpretation  of
999           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
1000           which is controlled in a similar way, but by separate options.
1001    
1002    
1003  MULTITHREADING  MULTITHREADING
1004    
1005         The  PCRE  functions  can be used in multi-threading applications, with         The PCRE functions can be used in  multi-threading  applications,  with
1006         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
1007         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
1008         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
# Line 968  CHECKING BUILD-TIME OPTIONS Line 1051  CHECKING BUILD-TIME OPTIONS
1051         The output is an integer whose value specifies  the  default  character         The output is an integer whose value specifies  the  default  character
1052         sequence  that is recognized as meaning "newline". The four values that         sequence  that is recognized as meaning "newline". The four values that
1053         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
1054         and  -1  for  ANY. The default should normally be the standard sequence         and  -1  for  ANY.  Though they are derived from ASCII, the same values
1055         for your operating system.         are returned in EBCDIC environments. The default should normally corre-
1056           spond to the standard sequence for your operating system.
1057    
1058             PCRE_CONFIG_BSR
1059    
1060           The output is an integer whose value indicates what character sequences
1061           the \R escape sequence matches by default. A value of 0 means  that  \R
1062           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1063           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1064           tern is compiled or matched.
1065    
1066           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1067    
1068         The output is an integer that contains the number  of  bytes  used  for         The  output  is  an  integer that contains the number of bytes used for
1069         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
1070         4. Larger values allow larger regular expressions to  be  compiled,  at         4.  Larger  values  allow larger regular expressions to be compiled, at
1071         the  expense  of  slower matching. The default value of 2 is sufficient         the expense of slower matching. The default value of  2  is  sufficient
1072         for all but the most massive patterns, since  it  allows  the  compiled         for  all  but  the  most massive patterns, since it allows the compiled
1073         pattern to be up to 64K in size.         pattern to be up to 64K in size.
1074    
1075           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1076    
1077         The  output  is  an integer that contains the threshold above which the         The output is an integer that contains the threshold  above  which  the
1078         POSIX interface uses malloc() for output vectors. Further  details  are         POSIX  interface  uses malloc() for output vectors. Further details are
1079         given in the pcreposix documentation.         given in the pcreposix documentation.
1080    
1081           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1082    
1083         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-
1084         internal matching function calls in a  pcre_exec()  execution.  Further         ber  of  internal  matching  function calls in a pcre_exec() execution.
1085         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1086    
1087           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1088    
1089         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
1090         recursion when calling the internal matching function in a  pcre_exec()         of   recursion  when  calling  the  internal  matching  function  in  a
1091         execution. Further details are given with pcre_exec() below.         pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1092           below.
1093    
1094           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1095    
# Line 1100  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 1173  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
# Line 1196  COMPILING A PATTERN Line 1315  COMPILING A PATTERN
1315           PCRE_NEWLINE_ANYCRLF           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_ANYCRLF specifies         two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies
1323         that any of the three preceding sequences should be recognized. Setting         that any of the three preceding sequences should be recognized. Setting
1324         PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be         PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be
1325         recognized. The Unicode newline sequences are the three just mentioned,         recognized. The Unicode newline sequences are the three just mentioned,
1326         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,         plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,
1327         U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS         U+000C),  NEL  (next line, U+0085), LS (line separator, U+2028), and PS
1328         (paragraph  separator,  U+2029).  The  last  two are recognized only in         (paragraph separator, U+2029). The last  two  are  recognized  only  in
1329         UTF-8 mode.         UTF-8 mode.
1330    
1331         The newline setting in the  options  word  uses  three  bits  that  are         The  newline  setting  in  the  options  word  uses three bits that are
1332         treated as a number, giving eight possibilities. Currently only six are         treated as a number, giving eight possibilities. Currently only six are
1333         used (default plus the five values above). This means that if  you  set         used  (default  plus the five values above). This means that if you set
1334         more  than one newline option, the combination may or may not be sensi-         more than one newline option, the combination may or may not be  sensi-
1335         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1336         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and         PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
1337         cause an error.         cause an error.
1338    
1339         The only time that a line break is specially recognized when  compiling         The  only time that a line break is specially recognized when compiling
1340         a  pattern  is  if  PCRE_EXTENDED  is set, and an unescaped # outside a         a pattern is if PCRE_EXTENDED is set, and  an  unescaped  #  outside  a
1341         character class is encountered. This indicates  a  comment  that  lasts         character  class  is  encountered.  This indicates a comment that lasts
1342         until  after the next line break sequence. In other circumstances, line         until after the next line break sequence. In other circumstances,  line
1343         break  sequences  are  treated  as  literal  data,   except   that   in         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 1285  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 1293  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 1322  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  [this code is not in use]           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
# Line 1330  COMPILATION ERROR CODES Line 1449  COMPILATION ERROR CODES
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 name or an optionally braced           57  \g is not followed by a braced, angle-bracketed, or quoted
1454                 non-zero number                 name/number or by a plain number
1455           58  (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number           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 1341  STUDYING A PATTERN Line 1469  STUDYING A PATTERN
1469         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1470              const char **errptr);              const char **errptr);
1471    
1472         If  a  compiled  pattern is going to be used several times, it is worth         If a compiled pattern is going to be used several times,  it  is  worth
1473         spending more time analyzing it in order to speed up the time taken for         spending more time analyzing it in order to speed up the time taken for
1474         matching.  The function pcre_study() takes a pointer to a compiled pat-         matching. The function pcre_study() takes a pointer to a compiled  pat-
1475         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1476         information  that  will  help speed up matching, pcre_study() returns a         information that will help speed up matching,  pcre_study()  returns  a
1477         pointer to a pcre_extra block, in which the study_data field points  to         pointer  to a pcre_extra block, in which the study_data field points to
1478         the results of the study.         the results of the study.
1479    
1480         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1481         pcre_exec(). However, a pcre_extra block  also  contains  other  fields         pcre_exec().  However,  a  pcre_extra  block also contains other fields
1482         that  can  be  set  by the caller before the block is passed; these are         that can be set by the caller before the block  is  passed;  these  are
1483         described below in the section on matching a pattern.         described below in the section on matching a pattern.
1484    
1485         If studying the pattern does not  produce  any  additional  information         If  studying  the  pattern  does not produce any additional information
1486         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1487         wants to pass any of the other fields to pcre_exec(), it  must  set  up         wants  to  pass  any of the other fields to pcre_exec(), it must set up
1488         its own pcre_extra block.         its own pcre_extra block.
1489    
1490         The  second  argument of pcre_study() contains option bits. At present,         The second argument of pcre_study() contains option bits.  At  present,
1491         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1492    
1493         The third argument for pcre_study() is a pointer for an error  message.         The  third argument for pcre_study() is a pointer for an error message.
1494         If  studying  succeeds  (even  if no data is returned), the variable it         If studying succeeds (even if no data is  returned),  the  variable  it
1495         points to is set to NULL. Otherwise it is set to  point  to  a  textual         points  to  is  set  to NULL. Otherwise it is set to point to a textual
1496         error message. This is a static string that is part of the library. You         error message. This is a static string that is part of the library. You
1497         must not try to free it. You should test the  error  pointer  for  NULL         must  not  try  to  free it. You should test the error pointer for NULL
1498         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1499    
1500         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 1378  STUDYING A PATTERN Line 1506  STUDYING A PATTERN
1506             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1507    
1508         At present, studying a pattern is useful only for non-anchored patterns         At present, studying a pattern is useful only for non-anchored patterns
1509         that do not have a single fixed starting character. A bitmap of  possi-         that  do not have a single fixed starting character. A bitmap of possi-
1510         ble starting bytes is created.         ble starting bytes is created.
1511    
1512    
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. If you are handling characters with codes greater         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         than  128, you should either use UTF-8 and Unicode, or use locales, but
1523         not try to mix the two.         not try to mix the two.
1524    
1525         PCRE  contains  an  internal set of tables that are used when the final         PCRE contains an internal set of tables that are used  when  the  final
1526         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many
1527         applications.  Normally, the internal tables recognize only ASCII char-         applications.  Normally, the internal tables recognize only ASCII char-
1528         acters. However, when PCRE is built, it is possible to cause the inter-         acters. However, when PCRE is built, it is possible to cause the inter-
1529         nal tables to be rebuilt in the default "C" locale of the local system,         nal tables to be rebuilt in the default "C" locale of the local system,
1530         which may cause them to be different.         which may cause them to be different.
1531    
1532         The internal tables can always be overridden by tables supplied by  the         The  internal tables can always be overridden by tables supplied by the
1533         application that calls PCRE. These may be created in a different locale         application that calls PCRE. These may be created in a different locale
1534         from the default. As more and more applications change  to  using  Uni-         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.         code, the need for this locale support is expected to die away.
1536    
1537         External  tables  are  built by calling the pcre_maketables() function,         External tables are built by calling  the  pcre_maketables()  function,
1538         which has no arguments, in the relevant locale. The result can then  be         which  has no arguments, in the relevant locale. The result can then be
1539         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For         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         example,  to  build  and use tables that are appropriate for the French
1541         locale  (where  accented  characters  with  values greater than 128 are         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;         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".         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
1554         it is needed.         it is needed.
1555    
1556         The pointer that is passed to pcre_compile() is saved with the compiled         The pointer that is passed to pcre_compile() is saved with the compiled
1557         pattern,  and the same tables are used via this pointer by pcre_study()         pattern, and the same tables are used via this pointer by  pcre_study()
1558         and normally also by pcre_exec(). Thus, by default, for any single pat-         and normally also by pcre_exec(). Thus, by default, for any single pat-
1559         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1560         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1561    
1562         It is possible to pass a table pointer or NULL (indicating the  use  of         It  is  possible to pass a table pointer or NULL (indicating the use of
1563         the  internal  tables)  to  pcre_exec(). Although not intended for this         the internal tables) to pcre_exec(). Although  not  intended  for  this
1564         purpose, this facility could be used to match a pattern in a  different         purpose,  this facility could be used to match a pattern in a different
1565         locale from the one in which it was compiled. Passing table pointers at         locale from the one in which it was compiled. Passing table pointers at
1566         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1567    
# Line 1443  INFORMATION ABOUT A PATTERN Line 1571  INFORMATION ABOUT A PATTERN
1571         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1572              int what, void *where);              int what, void *where);
1573    
1574         The pcre_fullinfo() function returns information about a compiled  pat-         The  pcre_fullinfo() function returns information about a compiled pat-
1575         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1576         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1577    
1578         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled
1579         pattern.  The second argument is the result of pcre_study(), or NULL if         pattern. The second argument is the result of pcre_study(), or NULL  if
1580         the pattern was not studied. The third argument specifies  which  piece         the  pattern  was not studied. The third argument specifies which piece
1581         of  information  is required, and the fourth argument is a pointer to a         of information is required, and the fourth argument is a pointer  to  a
1582         variable to receive the data. The yield of the  function  is  zero  for         variable  to  receive  the  data. The yield of the function is zero for
1583         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1584    
1585           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1459  INFORMATION ABOUT A PATTERN Line 1587  INFORMATION ABOUT A PATTERN
1587           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1588           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1589    
1590         The  "magic  number" is placed at the start of each compiled pattern as         The "magic number" is placed at the start of each compiled  pattern  as
1591         an simple check against passing an arbitrary memory pointer. Here is  a         an  simple check against passing an arbitrary memory pointer. Here is a
1592         typical  call  of pcre_fullinfo(), to obtain the length of the compiled         typical call of pcre_fullinfo(), to obtain the length of  the  compiled
1593         pattern:         pattern:
1594    
1595           int rc;           int rc;
# Line 1472  INFORMATION ABOUT A PATTERN Line 1600  INFORMATION ABOUT A PATTERN
1600             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1601             &length);         /* where to put the data */             &length);         /* where to put the data */
1602    
1603         The possible values for the third argument are defined in  pcre.h,  and         The  possible  values for the third argument are defined in pcre.h, and
1604         are as follows:         are as follows:
1605    
1606           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1607    
1608         Return  the  number  of  the highest back reference in the pattern. The         Return the number of the highest back reference  in  the  pattern.  The
1609         fourth argument should point to an int variable. Zero  is  returned  if         fourth  argument  should  point to an int variable. Zero is returned if
1610         there are no back references.         there are no back references.
1611    
1612           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1613    
1614         Return  the  number of capturing subpatterns in the pattern. The fourth         Return the number of capturing subpatterns in the pattern.  The  fourth
1615         argument should point to an int variable.         argument should point to an int variable.
1616    
1617           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1618    
1619         Return a pointer to the internal default character tables within  PCRE.         Return  a pointer to the internal default character tables within PCRE.
1620         The  fourth  argument should point to an unsigned char * variable. This         The fourth argument should point to an unsigned char *  variable.  This
1621         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1622         tion.  External  callers  can  cause PCRE to use its internal tables by         tion. External callers can cause PCRE to use  its  internal  tables  by
1623         passing a NULL table pointer.         passing a NULL table pointer.
1624    
1625           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1626    
1627         Return information about the first byte of any matched  string,  for  a         Return  information  about  the first byte of any matched string, for a
1628         non-anchored  pattern. The fourth argument should point to an int vari-         non-anchored pattern. The fourth argument should point to an int  vari-
1629         able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name         able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name
1630         is still recognized for backwards compatibility.)         is still recognized for backwards compatibility.)
1631    
1632         If  there  is  a  fixed first byte, for example, from a pattern such as         If there is a fixed first byte, for example, from  a  pattern  such  as
1633         (cat|cow|coyote), its value is returned. Otherwise, if either         (cat|cow|coyote), its value is returned. Otherwise, if either
1634    
1635         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
1636         branch starts with "^", or         branch starts with "^", or
1637    
1638         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
1639         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1640    
1641         -1 is returned, indicating that the pattern matches only at  the  start         -1  is  returned, indicating that the pattern matches only at the start
1642         of  a  subject string or after any newline within the string. Otherwise         of a subject string or after any newline within the  string.  Otherwise
1643         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1644    
1645           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1646    
1647         If the pattern was studied, and this resulted in the construction of  a         If  the pattern was studied, and this resulted in the construction of a
1648         256-bit table indicating a fixed set of bytes for the first byte in any         256-bit table indicating a fixed set of bytes for the first byte in any
1649         matching string, a pointer to the table is returned. Otherwise NULL  is         matching  string, a pointer to the table is returned. Otherwise NULL is
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           PCRE_INFO_JCHANGED
1661    
1662         Return 1 if the (?J) option setting is used in the  pattern,  otherwise         Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,
1663         0. The fourth argument should point to an int variable. The (?J) inter-         otherwise  0. The fourth argument should point to an int variable. (?J)
1664         nal option setting changes the local PCRE_DUPNAMES option.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1665    
1666           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1667    
# Line 1678  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1813  MATCHING A PATTERN: THE TRADITIONAL FUNC
1813              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1814              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1815    
1816         The  function pcre_exec() is called to match a subject string against a         The function pcre_exec() is called to match a subject string against  a
1817         compiled pattern, which is passed in the code argument. If the  pattern         compiled  pattern, which is passed in the code argument. If the pattern
1818         has been studied, the result of the study should be passed in the extra         has been studied, the result of the study should be passed in the extra
1819         argument. This function is the main matching facility of  the  library,         argument.  This  function is the main matching facility of the library,
1820         and it operates in a Perl-like manner. For specialist use there is also         and it operates in a Perl-like manner. For specialist use there is also
1821         an alternative matching function, which is described below in the  sec-         an  alternative matching function, which is described below in the sec-
1822         tion about the pcre_dfa_exec() function.         tion about the pcre_dfa_exec() function.
1823    
1824         In  most applications, the pattern will have been compiled (and option-         In most applications, the pattern will have been compiled (and  option-
1825         ally studied) in the same process that calls pcre_exec().  However,  it         ally  studied)  in the same process that calls pcre_exec(). However, it
1826         is possible to save compiled patterns and study data, and then use them         is possible to save compiled patterns and study data, and then use them
1827         later in different processes, possibly even on different hosts.  For  a         later  in  different processes, possibly even on different hosts. For a
1828         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
1829    
1830         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1708  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1843  MATCHING A PATTERN: THE TRADITIONAL FUNC
1843    
1844     Extra data for pcre_exec()     Extra data for pcre_exec()
1845    
1846         If  the  extra argument is not NULL, it must point to a pcre_extra data         If the extra argument is not NULL, it must point to a  pcre_extra  data
1847         block. The pcre_study() function returns such a block (when it  doesn't         block.  The pcre_study() function returns such a block (when it doesn't
1848         return  NULL), but you can also create one for yourself, and pass addi-         return NULL), but you can also create one for yourself, and pass  addi-
1849         tional information in it. The pcre_extra block contains  the  following         tional  information  in it. The pcre_extra block contains the following
1850         fields (not necessarily in this order):         fields (not necessarily in this order):
1851    
1852           unsigned long int flags;           unsigned long int flags;
# Line 1721  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1856  MATCHING A PATTERN: THE TRADITIONAL FUNC
1856           void *callout_data;           void *callout_data;
1857           const unsigned char *tables;           const unsigned char *tables;
1858    
1859         The  flags  field  is a bitmap that specifies which of the other fields         The flags field is a bitmap that specifies which of  the  other  fields
1860         are set. The flag bits are:         are set. The flag bits are:
1861    
1862           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
# Line 1730  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1865  MATCHING A PATTERN: THE TRADITIONAL FUNC
1865           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1866           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1867    
1868         Other flag bits should be set to zero. The study_data field is  set  in         Other  flag  bits should be set to zero. The study_data field is set in
1869         the  pcre_extra  block  that is returned by pcre_study(), together with         the pcre_extra block that is returned by  pcre_study(),  together  with
1870         the appropriate flag bit. You should not set this yourself, but you may         the appropriate flag bit. You should not set this yourself, but you may
1871         add  to  the  block by setting the other fields and their corresponding         add to the block by setting the other fields  and  their  corresponding
1872         flag bits.         flag bits.
1873    
1874         The match_limit field provides a means of preventing PCRE from using up         The match_limit field provides a means of preventing PCRE from using up
1875         a  vast amount of resources when running patterns that are not going to         a vast amount of resources when running patterns that are not going  to
1876         match, but which have a very large number  of  possibilities  in  their         match,  but  which  have  a very large number of possibilities in their
1877         search  trees.  The  classic  example  is  the  use of nested unlimited         search trees. The classic  example  is  the  use  of  nested  unlimited
1878         repeats.         repeats.
1879    
1880         Internally, PCRE uses a function called match() which it calls  repeat-         Internally,  PCRE uses a function called match() which it calls repeat-
1881         edly  (sometimes  recursively). The limit set by match_limit is imposed         edly (sometimes recursively). The limit set by match_limit  is  imposed
1882         on the number of times this function is called during  a  match,  which         on  the  number  of times this function is called during a match, which
1883         has  the  effect  of  limiting the amount of backtracking that can take         has the effect of limiting the amount of  backtracking  that  can  take
1884         place. For patterns that are not anchored, the count restarts from zero         place. For patterns that are not anchored, the count restarts from zero
1885         for each position in the subject string.         for each position in the subject string.
1886    
1887         The  default  value  for  the  limit can be set when PCRE is built; the         The default value for the limit can be set  when  PCRE  is  built;  the
1888         default default is 10 million, which handles all but the  most  extreme         default  default  is 10 million, which handles all but the most extreme
1889         cases.  You  can  override  the  default by suppling pcre_exec() with a         cases. You can override the default  by  suppling  pcre_exec()  with  a
1890         pcre_extra    block    in    which    match_limit    is    set,     and         pcre_extra     block    in    which    match_limit    is    set,    and
1891         PCRE_EXTRA_MATCH_LIMIT  is  set  in  the  flags  field. If the limit is         PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is
1892         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1893    
1894         The match_limit_recursion field is similar to match_limit, but  instead         The  match_limit_recursion field is similar to match_limit, but instead
1895         of limiting the total number of times that match() is called, it limits         of limiting the total number of times that match() is called, it limits
1896         the depth of recursion. The recursion depth is a  smaller  number  than         the  depth  of  recursion. The recursion depth is a smaller number than
1897         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-
1898         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.
1899    
1900         Limiting  the  recursion  depth  limits the amount of stack that can be         Limiting  the  recursion  depth  limits the amount of stack that can be
# Line 1791  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1926  MATCHING A PATTERN: THE TRADITIONAL FUNC
1926    
1927         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.
1928         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,
1929         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,    PCRE_NO_START_OPTIMIZE,
1930         PCRE_PARTIAL.         PCRE_NO_UTF8_CHECK and PCRE_PARTIAL.
1931    
1932           PCRE_ANCHORED           PCRE_ANCHORED
1933    
# Line 1801  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1936  MATCHING A PATTERN: THE TRADITIONAL FUNC
1936         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
1937         unachored at matching time.         unachored at matching time.
1938    
1939             PCRE_BSR_ANYCRLF
1940             PCRE_BSR_UNICODE
1941    
1942           These options (which are mutually exclusive) control what the \R escape
1943           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1944           or to match any Unicode newline sequence. These  options  override  the
1945           choice that was made or defaulted when the pattern was compiled.
1946    
1947           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
1948           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
1949           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
1950           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1951           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1952    
1953         These options override  the  newline  definition  that  was  chosen  or         These  options  override  the  newline  definition  that  was chosen or
1954         defaulted  when the pattern was compiled. For details, see the descrip-         defaulted when the pattern was compiled. For details, see the  descrip-
1955         tion of pcre_compile()  above.  During  matching,  the  newline  choice         tion  of  pcre_compile()  above.  During  matching,  the newline choice
1956         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
1957         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
1958         match  failure  for  an  unanchored  pattern.  When  PCRE_NEWLINE_CRLF,         match failure for an unanchored pattern.
1959         PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a  match  attempt  
1960         fails  when the current position is at a CRLF sequence, the match posi-         When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
1961         tion is advanced by two characters instead of one, in other  words,  to         set,  and a match attempt for an unanchored pattern fails when the cur-
1962         after the CRLF.         rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
1963           explicit  matches  for  CR  or  LF  characters,  the  match position is
1964           advanced by two characters instead of one, in other words, to after the
1965           CRLF.
1966    
1967           The above rule is a compromise that makes the most common cases work as
1968           expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
1969           option is not set), it does not match the string "\r\nA" because, after
1970           failing at the start, it skips both the CR and the LF before  retrying.
1971           However,  the  pattern  [\r\n]A does match that string, because it con-
1972           tains an explicit CR or LF reference, and so advances only by one char-
1973           acter after the first failure.
1974    
1975           An explicit match for CR of LF is either a literal appearance of one of
1976           those characters, or one of the \r or  \n  escape  sequences.  Implicit
1977           matches  such  as [^X] do not count, nor does \s (which includes CR and
1978           LF in the characters that it matches).
1979    
1980           Notwithstanding the above, anomalous effects may still occur when  CRLF
1981           is a valid newline sequence and explicit \r or \n escapes appear in the
1982           pattern.
1983    
1984           PCRE_NOTBOL           PCRE_NOTBOL
1985    
1986         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
1987         the beginning of a line, so the  circumflex  metacharacter  should  not         the  beginning  of  a  line, so the circumflex metacharacter should not
1988         match  before it. Setting this without PCRE_MULTILINE (at compile time)         match before it. Setting this without PCRE_MULTILINE (at compile  time)
1989         causes circumflex never to match. This option affects only  the  behav-         causes  circumflex  never to match. This option affects only the behav-
1990         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
1991    
1992           PCRE_NOTEOL           PCRE_NOTEOL
1993    
1994         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
1995         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
1996         in  multiline mode) a newline immediately before it. Setting this with-         in multiline mode) a newline immediately before it. Setting this  with-
1997         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
1998         option  affects only the behaviour of the dollar metacharacter. It does         option affects only the behaviour of the dollar metacharacter. It  does
1999         not affect \Z or \z.         not affect \Z or \z.
2000    
2001           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2002    
2003         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
2004         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
2005         the alternatives match the empty string, the entire  match  fails.  For         the  alternatives  match  the empty string, the entire match fails. For
2006         example, if the pattern         example, if the pattern
2007    
2008           a?b?           a?b?
2009    
2010         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
2011         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
2012         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-
2013         rences of "a" or "b".         rences of "a" or "b".
2014    
2015         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-
2016         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()
2017         function, and when using the /g modifier. It  is  possible  to  emulate         function,  and  when  using  the /g modifier. It is possible to emulate
2018         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
2019         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
2020         if  that  fails by advancing the starting offset (see below) and trying         if that fails by advancing the starting offset (see below)  and  trying
2021         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
2022         this in the pcredemo.c sample program.         this in the pcredemo.c sample program.
2023    
2024             PCRE_NO_START_OPTIMIZE
2025    
2026           There are a number of optimizations that pcre_exec() uses at the  start
2027           of  a  match,  in  order to speed up the process. For example, if it is
2028           known that a match must start with a specific  character,  it  searches
2029           the subject for that character, and fails immediately if it cannot find
2030           it, without actually running the main matching function. When  callouts
2031           are  in  use,  these  optimizations  can cause them to be skipped. This
2032           option disables the "start-up" optimizations,  causing  performance  to
2033           suffer, but ensuring that the callouts do occur.
2034    
2035           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2036    
2037         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
# Line 1894  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2068  MATCHING A PATTERN: THE TRADITIONAL FUNC
2068     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2069    
2070         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
2071         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.
2072         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-
2073         Unlike  the  pattern string, the subject may contain binary zero bytes.         acter.  Unlike  the pattern string, the subject may contain binary zero
2074         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
2075         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
2076           case.
2077         A  non-zero  starting offset is useful when searching for another match  
2078         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
2079         cess.   Setting  startoffset differs from just passing over a shortened         in  the same subject by calling pcre_exec() again after a previous suc-
2080         string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins         cess.  Setting startoffset differs from just passing over  a  shortened
2081           string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins
2082         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
2083    
2084           \Biss\B           \Biss\B
2085    
2086         which  finds  occurrences  of "iss" in the middle of words. (\B matches         which finds occurrences of "iss" in the middle of  words.  (\B  matches
2087         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.)
2088         When  applied  to the string "Mississipi" the first call to pcre_exec()         When applied to the string "Mississipi" the first call  to  pcre_exec()
2089         finds the first occurrence. If pcre_exec() is called  again  with  just         finds  the  first  occurrence. If pcre_exec() is called again with just
2090         the  remainder  of  the  subject,  namely  "issipi", it does not match,         the remainder of the subject,  namely  "issipi",  it  does  not  match,
2091         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
2092         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
2093         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-
2094         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
2095         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2096    
2097         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,
2098         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
2099         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
2100         subject.         subject.
2101    
2102     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2103    
2104         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
2105         addition, further substrings from the subject  may  be  picked  out  by         addition,  further  substrings  from  the  subject may be picked out by
2106         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2107         this is called "capturing" in what follows, and the  phrase  "capturing         this  is  called "capturing" in what follows, and the phrase "capturing
2108         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-
2109         string. PCRE supports several other kinds of  parenthesized  subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2110         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2111    
2112         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2113         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-
2114         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:
2115         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2116    
2117         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-
2118         strings,  each  substring using a pair of integers. The remaining third         strings, each substring using a pair of integers. The  remaining  third
2119         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-
2120         turing  subpatterns, and is not available for passing back information.         turing subpatterns, and is not available for passing back  information.
2121         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
2122         it is not, it is rounded down.         it is not, it is rounded down.
2123    
2124         When  a  match  is successful, information about captured substrings is         When a match is successful, information about  captured  substrings  is
2125         returned in pairs of integers, starting at the  beginning  of  ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2126         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
2127         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
2128         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
2129         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
2130         tor[1],  identify  the  portion  of  the  subject string matched by the         byte offsets, even in UTF-8 mode. They are not character counts.
2131         entire pattern. The next pair is used for the first  capturing  subpat-  
2132         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
2133         highest numbered pair that has been set. For example, if two substrings         portion  of  the subject string matched by the entire pattern. The next
2134         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
2135         subpatterns, the return value from a successful match is 1,  indicating         returned by pcre_exec() is one more than the highest numbered pair that
2136         that just the first pair of offsets has been set.         has been set.  For example, if two substrings have been  captured,  the
2137           returned  value is 3. If there are no capturing subpatterns, the return
2138           value from a successful match is 1, indicating that just the first pair
2139           of offsets has been set.
2140    
2141         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2142         of the string that it matched that is returned.         of the string that it matched that is returned.
2143    
2144         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,
2145         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
2146         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
2147         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
2148         as NULL and ovecsize as zero. However, if  the  pattern  contains  back         ovecsize as zero. However, if the pattern contains back references  and
2149         references  and  the  ovector is not big enough to remember the related         the  ovector is not big enough to remember the related substrings, PCRE
2150         substrings, PCRE has to get additional memory for use during  matching.         has to get additional memory for use during matching. Thus it  is  usu-
2151         Thus it is usually advisable to supply an ovector.         ally advisable to supply an ovector.
2152    
2153         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
2154         subpatterns there are in a compiled  pattern.  The  smallest  size  for         subpatterns there are in a compiled  pattern.  The  smallest  size  for
# Line 2082  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2260  MATCHING A PATTERN: THE TRADITIONAL FUNC
2260    
2261           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2262    
2263         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.
2264    
2265           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2266    
2267         The internal recursion limit, as specified by the match_limit_recursion         The internal recursion limit, as specified by the match_limit_recursion
2268         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field in a pcre_extra structure (or defaulted)  was  reached.  See  the
2269         description above.         description above.
2270    
2271           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
# Line 2110  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2288  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2288         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2289              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2290    
2291         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
2292         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
2293         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2294         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
2295         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
2296         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
2297         substrings.         substrings.
2298    
2299         A substring that contains a binary zero is correctly extracted and  has         A  substring that contains a binary zero is correctly extracted and has
2300         a  further zero added on the end, but the result is not, of course, a C         a further zero added on the end, but the result is not, of course, a  C
2301         string.  However, you can process such a string  by  referring  to  the         string.   However,  you  can  process such a string by referring to the
2302         length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2303         string().  Unfortunately, the interface to pcre_get_substring_list() is         string().  Unfortunately, the interface to pcre_get_substring_list() is
2304         not  adequate for handling strings containing binary zeros, because the         not adequate for handling strings containing binary zeros, because  the
2305         end of the final string is not independently indicated.         end of the final string is not independently indicated.
2306    
2307         The first three arguments are the same for all  three  of  these  func-         The  first  three  arguments  are the same for all three of these func-
2308         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
2309         matched, ovector is a pointer to the vector of integer offsets that was         matched, ovector is a pointer to the vector of integer offsets that was
2310         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2311         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
2312         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2313         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
2314         it  ran out of space in ovector, the value passed as stringcount should         it ran out of space in ovector, the value passed as stringcount  should
2315         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2316    
2317         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
2318         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
2319         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
2320         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
2321         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
2322         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2323         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2324         The  yield  of  the function is the length of the string, not including         The yield of the function is the length of the  string,  not  including
2325         the terminating zero, or one of these error codes:         the terminating zero, or one of these error codes:
2326    
2327           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2328    
2329         The buffer was too small for pcre_copy_substring(), or the  attempt  to         The  buffer  was too small for pcre_copy_substring(), or the attempt to
2330         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2331    
2332           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2333    
2334         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2335    
2336         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
2337         strings and builds a list of pointers to them. All this is  done  in  a         strings  and  builds  a list of pointers to them. All this is done in a
2338         single block of memory that is obtained via pcre_malloc. The address of         single block of memory that is obtained via pcre_malloc. The address of
2339         the memory block is returned via listptr, which is also  the  start  of         the  memory  block  is returned via listptr, which is also the start of
2340         the  list  of  string pointers. The end of the list is marked by a NULL         the list of string pointers. The end of the list is marked  by  a  NULL
2341         pointer. The yield of the function is zero if all  went  well,  or  the         pointer.  The  yield  of  the function is zero if all went well, or the
2342         error code         error code
2343    
2344           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2345    
2346         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2347    
2348         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
2349         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
2350         the  subject, but subpattern n has not been used at all, they return an         the subject, but subpattern n has not been used at all, they return  an
2351         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2352         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
2353         tive for unset substrings.         tive for unset substrings.
2354    
2355         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2356         string_list()  can  be  used  to free the memory returned by a previous         string_list() can be used to free the memory  returned  by  a  previous
2357         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2358         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
2359         pcre_free, which of course could be called directly from a  C  program.         pcre_free,  which  of course could be called directly from a C program.
2360         However,  PCRE is used in some situations where it is linked via a spe-         However, PCRE is used in some situations where it is linked via a  spe-
2361         cial  interface  to  another  programming  language  that  cannot   use         cial   interface  to  another  programming  language  that  cannot  use
2362         pcre_free  directly;  it is for these cases that the functions are pro-         pcre_free directly; it is for these cases that the functions  are  pro-
2363         vided.         vided.
2364    
2365    
# Line 2200  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2378  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2378              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2379              const char **stringptr);              const char **stringptr);
2380    
2381         To extract a substring by name, you first have to find associated  num-         To  extract a substring by name, you first have to find associated num-
2382         ber.  For example, for this pattern         ber.  For example, for this pattern
2383    
2384           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
# Line 2209  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2387  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2387         be unique (PCRE_DUPNAMES was not set), you can find the number from the         be unique (PCRE_DUPNAMES was not set), you can find the number from the
2388         name by calling pcre_get_stringnumber(). The first argument is the com-         name by calling pcre_get_stringnumber(). The first argument is the com-
2389         piled pattern, and the second is the name. The yield of the function is         piled pattern, and the second is the name. The yield of the function is
2390         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2391         subpattern of that name.         subpattern of that name.
2392    
2393         Given the number, you can extract the substring directly, or use one of         Given the number, you can extract the substring directly, or use one of
2394         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
2395         are also two functions that do the whole job.         are also two functions that do the whole job.
2396    
2397         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
2398         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
2399         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
2400         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
2401         differences:         differences:
2402    
2403         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
2404         ond, there is an extra argument, given at the start, which is a pointer         ond, there is an extra argument, given at the start, which is a pointer
2405         to the compiled pattern. This is needed in order to gain access to  the         to  the compiled pattern. This is needed in order to gain access to the
2406         name-to-number translation table.         name-to-number translation table.
2407    
2408         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2409         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2410         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the         ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
2411         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2412    
2413           Warning:  If the pattern uses the "(?|" feature to set up multiple sub-
2414           patterns with the same number, you  cannot  use  names  to  distinguish
2415           them, because names are not included in the compiled code. The matching
2416           process uses only numbers.
2417    
2418    
2419  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
2420    
# Line 2439  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2622  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2622  SEE ALSO  SEE ALSO
2623    
2624         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-
2625         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3),  pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2626    
2627    
2628  AUTHOR  AUTHOR
# Line 2451  AUTHOR Line 2634  AUTHOR
2634    
2635  REVISION  REVISION
2636    
2637         Last updated: 09 August 2007         Last updated: 17 March 2009
2638         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
2639  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2640    
2641    
# Line 2503  PCRE CALLOUTS Line 2686  PCRE CALLOUTS
2686  MISSING CALLOUTS  MISSING CALLOUTS
2687    
2688         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
2689         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
2690         pattern is         example, if the pattern is
2691    
2692           ab(?C4)cd           ab(?C4)cd
2693    
# Line 2513  MISSING CALLOUTS Line 2696  MISSING CALLOUTS
2696         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
2697         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
2698    
2699           You can disable these optimizations by passing the  PCRE_NO_START_OPTI-
2700           MIZE  option  to  pcre_exec()  or  pcre_dfa_exec(). This slows down the
2701           matching process, but does ensure that callouts  such  as  the  example
2702           above are obeyed.
2703    
2704    
2705  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2706    
2707         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
2708         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
2709         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
2710         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
2711         block. This structure contains the following fields:         block. This structure contains the following fields:
2712    
2713           int          version;           int          version;
# Line 2535  THE CALLOUT INTERFACE Line 2723  THE CALLOUT INTERFACE
2723           int          pattern_position;           int          pattern_position;
2724           int          next_item_length;           int          next_item_length;
2725    
2726         The version field is an integer containing the version  number  of  the         The  version  field  is an integer containing the version number of the
2727         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
2728         version number will change again in future  if  additional  fields  are         version  number  will  change  again in future if additional fields are
2729         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.
2730    
2731         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 2622  AUTHOR Line 2810  AUTHOR
2810    
2811  REVISION  REVISION
2812    
2813         Last updated: 29 May 2007         Last updated: 15 March 2009
2814         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
2815  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2816    
2817    
# Line 2736  DIFFERENCES BETWEEN PCRE AND PERL Line 2924  DIFFERENCES BETWEEN PCRE AND PERL
2924         (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-
2925         TURE options for pcre_exec() have no Perl equivalents.         TURE options for pcre_exec() have no Perl equivalents.
2926    
2927         (g) The callout facility is PCRE-specific.         (g) The \R escape sequence can be restricted to match only CR,  LF,  or
2928           CRLF by the PCRE_BSR_ANYCRLF option.
2929    
2930         (h) The partial matching facility is PCRE-specific.         (h) The callout facility is PCRE-specific.
2931    
2932         (i) Patterns compiled by PCRE can be saved and re-used at a later time,         (i) The partial matching facility is PCRE-specific.
2933    
2934           (j) Patterns compiled by PCRE can be saved and re-used at a later time,
2935         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
2936    
2937         (j)  The  alternative  matching function (pcre_dfa_exec()) matches in a         (k) The alternative matching function (pcre_dfa_exec())  matches  in  a
2938         different way and is not Perl-compatible.         different way and is not Perl-compatible.
2939    
2940           (l)  PCRE  recognizes some special sequences such as (*CR) at the start
2941           of a pattern that set overall options that cannot be changed within the
2942           pattern.
2943    
2944    
2945  AUTHOR  AUTHOR
2946    
# Line 2756  AUTHOR Line 2951  AUTHOR
2951    
2952  REVISION  REVISION
2953    
2954         Last updated: 08 August 2007         Last updated: 11 September 2007
2955         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2007 University of Cambridge.
2956  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2957    
# Line 2772  PCRE REGULAR EXPRESSION DETAILS Line 2967  PCRE REGULAR EXPRESSION DETAILS
2967    
2968         The  syntax and semantics of the regular expressions that are supported         The  syntax and semantics of the regular expressions that are supported
2969         by PCRE are described in detail below. There is a quick-reference  syn-         by PCRE are described in detail below. There is a quick-reference  syn-
2970         tax  summary  in  the  pcresyntax  page. Perl's regular expressions are         tax summary in the pcresyntax page. PCRE tries to match Perl syntax and
2971         described in its own documentation, and regular expressions in  general         semantics as closely as it can. PCRE  also  supports  some  alternative
2972         are  covered in a number of books, some of which have copious examples.         regular  expression  syntax (which does not conflict with the Perl syn-
2973         Jeffrey  Friedl's  "Mastering  Regular   Expressions",   published   by         tax) in order to provide some compatibility with regular expressions in
2974         O'Reilly,  covers regular expressions in great detail. This description         Python, .NET, and Oniguruma.
2975         of PCRE's regular expressions is intended as reference material.  
2976           Perl's  regular expressions are described in its own documentation, and
2977           regular expressions in general are covered in a number of  books,  some
2978           of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
2979           Expressions", published by  O'Reilly,  covers  regular  expressions  in
2980           great  detail.  This  description  of  PCRE's  regular  expressions  is
2981           intended as reference material.
2982    
2983         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
2984         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
# Line 2797  PCRE REGULAR EXPRESSION DETAILS Line 2998  PCRE REGULAR EXPRESSION DETAILS
2998         discussed in the pcrematching page.         discussed in the pcrematching page.
2999    
3000    
3001    NEWLINE CONVENTIONS
3002    
3003           PCRE  supports five different conventions for indicating line breaks in
3004           strings: a single CR (carriage return) character, a  single  LF  (line-
3005           feed) character, the two-character sequence CRLF, any of the three pre-
3006           ceding, or any Unicode newline sequence. The pcreapi page  has  further
3007           discussion  about newlines, and shows how to set the newline convention
3008           in the options arguments for the compiling and matching functions.
3009    
3010           It is also possible to specify a newline convention by starting a  pat-
3011           tern string with one of the following five sequences:
3012    
3013             (*CR)        carriage return
3014             (*LF)        linefeed
3015             (*CRLF)      carriage return, followed by linefeed
3016             (*ANYCRLF)   any of the three above
3017             (*ANY)       all Unicode newline sequences
3018    
3019           These override the default and the options given to pcre_compile(). For
3020           example, on a Unix system where LF is the default newline sequence, the
3021           pattern
3022    
3023             (*CR)a.b
3024    
3025           changes the convention to CR. That pattern matches "a\nb" because LF is
3026           no longer a newline. Note that these special settings,  which  are  not
3027           Perl-compatible,  are  recognized  only at the very start of a pattern,
3028           and that they must be in upper case.  If  more  than  one  of  them  is
3029           present, the last one is used.
3030    
3031           The  newline  convention  does  not  affect what the \R escape sequence
3032           matches. By default, this is any Unicode  newline  sequence,  for  Perl
3033           compatibility.  However, this can be changed; see the description of \R
3034           in the section entitled "Newline sequences" below. A change of \R  set-
3035           ting can be combined with a change of newline convention.
3036    
3037    
3038  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
3039    
3040         A  regular  expression  is  a pattern that is matched against a subject         A  regular  expression  is  a pattern that is matched against a subject
# Line 2852  CHARACTERS AND METACHARACTERS Line 3090  CHARACTERS AND METACHARACTERS
3090                    syntax)                    syntax)
3091           ]      terminates the character class           ]      terminates the character class
3092    
3093         The  following sections describe the use of each of the metacharacters.         The following sections describe the use of each of the metacharacters.
3094    
3095    
3096  BACKSLASH  BACKSLASH
3097    
3098         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3099         a  non-alphanumeric  character,  it takes away any special meaning that         a non-alphanumeric character, it takes away any  special  meaning  that
3100         character may have. This  use  of  backslash  as  an  escape  character         character  may  have.  This  use  of  backslash  as an escape character
3101         applies both inside and outside character classes.         applies both inside and outside character classes.
3102    
3103         For  example,  if  you want to match a * character, you write \* in the         For example, if you want to match a * character, you write  \*  in  the
3104         pattern.  This escaping action applies whether  or  not  the  following         pattern.   This  escaping  action  applies whether or not the following
3105         character  would  otherwise be interpreted as a metacharacter, so it is         character would otherwise be interpreted as a metacharacter, so  it  is
3106         always safe to precede a non-alphanumeric  with  backslash  to  specify         always  safe  to  precede  a non-alphanumeric with backslash to specify
3107         that  it stands for itself. In particular, if you want to match a back-         that it stands for itself. In particular, if you want to match a  back-
3108         slash, you write \\.         slash, you write \\.
3109    
3110         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in
3111         the  pattern (other than in a character class) and characters between a         the pattern (other than in a character class) and characters between  a
3112         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
3113         ing  backslash  can  be  used to include a whitespace or # character as         ing backslash can be used to include a whitespace  or  #  character  as
3114         part of the pattern.         part of the pattern.
3115    
3116         If you want to remove the special meaning from a  sequence  of  charac-         If  you  want  to remove the special meaning from a sequence of charac-
3117         ters,  you can do so by putting them between \Q and \E. This is differ-         ters, you can do so by putting them between \Q and \E. This is  differ-
3118         ent from Perl in that $ and  @  are  handled  as  literals  in  \Q...\E         ent  from  Perl  in  that  $  and  @ are handled as literals in \Q...\E
3119         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-
3120         tion. Note the following examples:         tion. Note the following examples:
3121    
3122           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 2888  BACKSLASH Line 3126  BACKSLASH
3126           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
3127           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3128    
3129         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
3130         classes.         classes.
3131    
3132     Non-printing characters     Non-printing characters
3133    
3134         A second use of backslash provides a way of encoding non-printing char-         A second use of backslash provides a way of encoding non-printing char-
3135         acters in patterns in a visible manner. There is no restriction on  the         acters  in patterns in a visible manner. There is no restriction on the
3136         appearance  of non-printing characters, apart from the binary zero that         appearance of non-printing characters, apart from the binary zero  that
3137         terminates a pattern, but when a pattern  is  being  prepared  by  text         terminates  a  pattern,  but  when  a pattern is being prepared by text
3138         editing,  it  is  usually  easier  to  use  one of the following escape         editing, it is usually easier  to  use  one  of  the  following  escape
3139         sequences than the binary character it represents:         sequences than the binary character it represents:
3140    
3141           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3142           \cx       "control-x", where x is any character           \cx       "control-x", where x is any character
3143           \e        escape (hex 1B)           \e        escape (hex 1B)
3144           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3145           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3146           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3147           \t        tab (hex 09)           \t        tab (hex 09)
3148           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or backreference
3149           \xhh      character with hex code hh           \xhh      character with hex code hh
3150           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh..
3151    
3152         The precise effect of \cx is as follows: if x is a lower  case  letter,         The  precise  effect of \cx is as follows: if x is a lower case letter,
3153         it  is converted to upper case. Then bit 6 of the character (hex 40) is         it is converted to upper case. Then bit 6 of the character (hex 40)  is
3154         inverted.  Thus \cz becomes hex 1A, but \c{ becomes hex 3B,  while  \c;         inverted.   Thus  \cz becomes hex 1A, but \c{ becomes hex 3B, while \c;
3155         becomes hex 7B.         becomes hex 7B.
3156    
3157         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
3158         in upper or lower case). Any number of hexadecimal  digits  may  appear         in  upper  or  lower case). Any number of hexadecimal digits may appear
3159         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
3160         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,
3161         the  maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger         the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger
3162         than the largest Unicode code point, which is 10FFFF.         than the largest Unicode code point, which is 10FFFF.
3163    
3164         If characters other than hexadecimal digits appear between \x{  and  },         If  characters  other than hexadecimal digits appear between \x{ and },
3165         or if there is no terminating }, this form of escape is not recognized.         or if there is no terminating }, this form of escape is not recognized.
3166         Instead, the initial \x will be  interpreted  as  a  basic  hexadecimal         Instead,  the  initial  \x  will  be interpreted as a basic hexadecimal
3167         escape,  with  no  following  digits, giving a character whose value is         escape, with no following digits, giving a  character  whose  value  is
3168         zero.         zero.
3169    
3170         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
3171         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-
3172         dled. For example, \xdc is exactly the same as \x{dc}.         dled. For example, \xdc is exactly the same as \x{dc}.
3173    
3174         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
3175         than  two  digits,  just  those  that  are  present  are used. Thus the         than two digits, just  those  that  are  present  are  used.  Thus  the
3176         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
3177         (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
3178         if the pattern character that follows is itself an octal digit.         if the pattern character that follows is itself an octal digit.
3179    
3180         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-
3181         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
3182         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
3183         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
3184         expression, the entire  sequence  is  taken  as  a  back  reference.  A         expression,  the  entire  sequence  is  taken  as  a  back reference. A
3185         description  of how this works is given later, following the discussion         description of how this works is given later, following the  discussion
3186         of parenthesized subpatterns.         of parenthesized subpatterns.
3187    
3188         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
3189         and  there have not been that many capturing subpatterns, PCRE re-reads         and there have not been that many capturing subpatterns, PCRE  re-reads
3190         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-
3191         erate  a data character. Any subsequent digits stand for themselves. In         erate a data character. Any subsequent digits stand for themselves.  In
3192         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
3193         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
3194         example:         example:
3195    
3196           \040   is another way of writing a space           \040   is another way of writing a space
# Line 2970  BACKSLASH Line 3208  BACKSLASH
3208           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
3209                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
3210    
3211         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
3212         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
3213    
3214         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
3215         inside and outside character classes. In addition, inside  a  character         inside  and  outside character classes. In addition, inside a character
3216         class,  the  sequence \b is interpreted as the backspace character (hex         class, the sequence \b is interpreted as the backspace  character  (hex
3217         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"
3218         and  "X", respectively. Outside a character class, these sequences have         and "X", respectively. Outside a character class, these sequences  have
3219         different meanings (see below).         different meanings (see below).
3220    
3221     Absolute and relative back references     Absolute and relative back references
3222    
3223         The sequence \g followed by an unsigned or a negative  number,  option-         The  sequence  \g followed by an unsigned or a negative number, option-
3224         ally  enclosed  in braces, is an absolute or relative back reference. A         ally enclosed in braces, is an absolute or relative back  reference.  A
3225         named back reference can be coded as \g{name}. Back references are dis-         named back reference can be coded as \g{name}. Back references are dis-
3226         cussed later, following the discussion of parenthesized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3227    
3228       Absolute and relative subroutine calls
3229    
3230           For compatibility with Oniguruma, the non-Perl syntax \g followed by  a
3231           name or a number enclosed either in angle brackets or single quotes, is
3232           an alternative syntax for referencing a subpattern as  a  "subroutine".
3233           Details  are  discussed  later.   Note  that  \g{...} (Perl syntax) and
3234           \g<...> (Oniguruma syntax) are not synonymous. The  former  is  a  back
3235           reference; the latter is a subroutine call.
3236    
3237     Generic character types     Generic character types
3238    
3239         Another use of backslash is for specifying generic character types. The         Another use of backslash is for specifying generic character types. The
# Line 3022  BACKSLASH Line 3269  BACKSLASH
3269         \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-
3270         code  character  property  support is available. These sequences retain         code  character  property  support is available. These sequences retain
3271         their original meanings from before UTF-8 support was available, mainly         their original meanings from before UTF-8 support was available, mainly
3272         for efficiency reasons.         for  efficiency  reasons. Note that this also affects \b, because it is
3273           defined in terms of \w and \W.
3274    
3275         The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to         The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to
3276         the other sequences, these do match certain high-valued  codepoints  in         the  other  sequences, these do match certain high-valued codepoints in
3277         UTF-8 mode.  The horizontal space characters are:         UTF-8 mode.  The horizontal space characters are:
3278    
3279           U+0009     Horizontal tab           U+0009     Horizontal tab
# Line 3059  BACKSLASH Line 3307  BACKSLASH
3307           U+2029     Paragraph separator           U+2029     Paragraph separator
3308    
3309         A "word" character is an underscore or any character less than 256 that         A "word" character is an underscore or any character less than 256 that
3310         is a letter or digit. The definition of  letters  and  digits  is  con-         is  a  letter  or  digit.  The definition of letters and digits is con-
3311         trolled  by PCRE's low-valued character tables, and may vary if locale-         trolled by PCRE's low-valued character tables, and may vary if  locale-
3312         specific matching is taking place (see "Locale support" in the  pcreapi         specific  matching is taking place (see "Locale support" in the pcreapi
3313         page).  For  example,  in  a French locale such as "fr_FR" in Unix-like         page). For example, in a French locale such  as  "fr_FR"  in  Unix-like
3314         systems, or "french" in Windows, some character codes greater than  128         systems,  or "french" in Windows, some character codes greater than 128
3315         are  used for accented letters, and these are matched by \w. The use of         are used for accented letters, and these are matched by \w. The use  of
3316         locales with Unicode is discouraged.         locales with Unicode is discouraged.
3317    
3318     Newline sequences     Newline sequences
3319    
3320         Outside a character class, the escape sequence \R matches  any  Unicode         Outside  a  character class, by default, the escape sequence \R matches
3321         newline  sequence. This is a Perl 5.10 feature. In non-UTF-8 mode \R is         any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8
3322         equivalent to the following:         mode \R is equivalent to the following:
3323    
3324           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3325    
3326         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
3327         below.  This particular group matches either the two-character sequence         below.  This particular group matches either the two-character sequence
3328         CR followed by LF, or  one  of  the  single  characters  LF  (linefeed,         CR  followed  by  LF,  or  one  of  the single characters LF (linefeed,
3329         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
3330         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
3331         is treated as a single unit that cannot be split.         is treated as a single unit that cannot be split.
3332    
3333         In  UTF-8  mode, two additional characters whose codepoints are greater         In UTF-8 mode, two additional characters whose codepoints  are  greater
3334         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-
3335         rator,  U+2029).   Unicode character property support is not needed for         rator, U+2029).  Unicode character property support is not  needed  for
3336         these characters to be recognized.         these characters to be recognized.
3337    
3338           It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3339           the complete set  of  Unicode  line  endings)  by  setting  the  option
3340           PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3341           (BSR is an abbrevation for "backslash R".) This can be made the default
3342           when  PCRE  is  built;  if this is the case, the other behaviour can be
3343           requested via the PCRE_BSR_UNICODE option.   It  is  also  possible  to
3344           specify  these  settings  by  starting a pattern string with one of the
3345           following sequences:
3346    
3347             (*BSR_ANYCRLF)   CR, LF, or CRLF only
3348             (*BSR_UNICODE)   any Unicode newline sequence
3349    
3350           These override the default and the options given to pcre_compile(), but
3351           they can be overridden by options given to pcre_exec(). Note that these
3352           special settings, which are not Perl-compatible, are recognized only at
3353           the  very  start  of a pattern, and that they must be in upper case. If
3354           more than one of them is present, the last one is  used.  They  can  be
3355           combined  with  a  change of newline convention, for example, a pattern
3356           can start with:
3357    
3358             (*ANY)(*BSR_ANYCRLF)
3359    
3360         Inside a character class, \R matches the letter "R".         Inside a character class, \R matches the letter "R".
3361    
3362     Unicode character properties     Unicode character properties
# Line 3526  POSIX CHARACTER CLASSES Line 3796  POSIX CHARACTER CLASSES
3796    
3797  VERTICAL BAR  VERTICAL BAR
3798    
3799         Vertical  bar characters are used to separate alternative patterns. For         Vertical bar characters are used to separate alternative patterns.  For
3800         example, the pattern         example, the pattern
3801    
3802           gilbert|sullivan           gilbert|sullivan
3803    
3804         matches either "gilbert" or "sullivan". Any number of alternatives  may         matches  either "gilbert" or "sullivan". Any number of alternatives may
3805         appear,  and  an  empty  alternative  is  permitted (matching the empty         appear, and an empty  alternative  is  permitted  (matching  the  empty
3806         string). The matching process tries each alternative in turn, from left         string). The matching process tries each alternative in turn, from left
3807         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
3808         are within a subpattern (defined below), "succeeds" means matching  the         are  within a subpattern (defined below), "succeeds" means matching the
3809         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.
3810    
3811    
3812  INTERNAL OPTION SETTING  INTERNAL OPTION SETTING
3813    
3814         The settings of the  PCRE_CASELESS,  PCRE_MULTILINE,  PCRE_DOTALL,  and         The settings of the  PCRE_CASELESS,  PCRE_MULTILINE,  PCRE_DOTALL,  and
3815         PCRE_EXTENDED  options  can  be  changed  from  within the pattern by a         PCRE_EXTENDED  options  (which are Perl-compatible) can be changed from
3816         sequence of Perl option letters enclosed  between  "(?"  and  ")".  The         within the pattern by  a  sequence  of  Perl  option  letters  enclosed
3817         option letters are         between "(?" and ")".  The option letters are
3818    
3819           i  for PCRE_CASELESS           i  for PCRE_CASELESS
3820           m  for PCRE_MULTILINE           m  for PCRE_MULTILINE
# Line 3558  INTERNAL OPTION SETTING Line 3828  INTERNAL OPTION SETTING
3828         is  also  permitted.  If  a  letter  appears  both before and after the         is  also  permitted.  If  a  letter  appears  both before and after the
3829         hyphen, the option is unset.         hyphen, the option is unset.
3830    
3831           The PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and  PCRE_EXTRA
3832           can  be changed in the same way as the Perl-compatible options by using
3833           the characters J, U and X respectively.
3834    
3835         When an option change occurs at top level (that is, not inside  subpat-         When an option change occurs at top level (that is, not inside  subpat-
3836         tern  parentheses),  the change applies to the remainder of the pattern         tern  parentheses),  the change applies to the remainder of the pattern
3837         that follows.  If the change is placed right at the start of a pattern,         that follows.  If the change is placed right at the start of a pattern,
# Line 3583  INTERNAL OPTION SETTING Line 3857  INTERNAL OPTION SETTING
3857         the effects of option settings happen at compile time. There  would  be         the effects of option settings happen at compile time. There  would  be
3858         some very weird behaviour otherwise.         some very weird behaviour otherwise.
3859    
3860         The  PCRE-specific options PCRE_DUPNAMES, PCRE_UNGREEDY, and PCRE_EXTRA         Note:  There  are  other  PCRE-specific  options that can be set by the
3861         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
3862         the characters J, U and X respectively.         cases  the  pattern  can  contain special leading sequences to override
3863           what the application has set or what has been  defaulted.  Details  are
3864           given in the section entitled "Newline sequences" above.
3865    
3866    
3867  SUBPATTERNS  SUBPATTERNS
# Line 3724  NAMED SUBPATTERNS Line 4000  NAMED SUBPATTERNS
4000         lowest  number  is used. For further details of the interfaces for han-         lowest  number  is used. For further details of the interfaces for han-
4001         dling named subpatterns, see the pcreapi documentation.         dling named subpatterns, see the pcreapi documentation.
4002    
4003           Warning: You cannot use different names to distinguish between two sub-
4004           patterns  with  the same number (see the previous section) because PCRE
4005           uses only the numbers when matching.
4006    
4007    
4008  REPETITION  REPETITION
4009    
# Line 3764  REPETITION Line 4044  REPETITION
4044         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-
4045         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.
4046    
4047         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
4048         individual bytes. Thus, for example, \x{100}{2} matches two UTF-8 char-         individual bytes. Thus, for example, \x{100}{2} matches two UTF-8 char-
4049         acters, each of which is represented by a two-byte sequence. Similarly,         acters, each of which is represented by a two-byte sequence. Similarly,
4050         when Unicode property support is available, \X{3} matches three Unicode         when Unicode property support is available, \X{3} matches three Unicode
4051         extended sequences, each of which may be several bytes long  (and  they         extended  sequences,  each of which may be several bytes long (and they
4052         may be of different lengths).         may be of different lengths).
4053    
4054         The quantifier {0} is permitted, causing the expression to behave as if         The quantifier {0} is permitted, causing the expression to behave as if
4055         the previous item and the quantifier were not present.         the previous item and the quantifier were not present. This may be use-
4056           ful for subpatterns that are referenced as subroutines  from  elsewhere
4057           in the pattern. Items other than subpatterns that have a {0} quantifier
4058           are omitted from the compiled pattern.
4059    
4060         For convenience, the three most common quantifiers have  single-charac-         For convenience, the three most common quantifiers have  single-charac-
4061         ter abbreviations:         ter abbreviations:
# Line 3902  ATOMIC GROUPING AND POSSESSIVE QUANTIFIE Line 4185  ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
4185    
4186           (?>\d+)foo           (?>\d+)foo
4187    
4188         This kind of parenthesis "locks up" the  part of the  pattern  it  con-         This  kind  of  parenthesis "locks up" the  part of the pattern it con-
4189         tains  once  it  has matched, and a failure further into the pattern is         tains once it has matched, and a failure further into  the  pattern  is
4190         prevented from backtracking into it. Backtracking past it  to  previous         prevented  from  backtracking into it. Backtracking past it to previous
4191         items, however, works as normal.         items, however, works as normal.
4192    
4193         An  alternative  description  is that a subpattern of this type matches         An alternative description is that a subpattern of  this  type  matches
4194         the string of characters that an  identical  standalone  pattern  would         the  string  of  characters  that an identical standalone pattern would
4195         match, if anchored at the current point in the subject string.         match, if anchored at the current point in the subject string.
4196    
4197         Atomic grouping subpatterns are not capturing subpatterns. Simple cases         Atomic grouping subpatterns are not capturing subpatterns. Simple cases
4198         such as the above example can be thought of as a maximizing repeat that         such as the above example can be thought of as a maximizing repeat that
4199         must  swallow  everything  it can. So, while both \d+ and \d+? are pre-         must swallow everything it can. So, while both \d+ and  \d+?  are  pre-
4200         pared to adjust the number of digits they match in order  to  make  the         pared  to  adjust  the number of digits they match in order to make the
4201         rest of the pattern match, (?>\d+) can only match an entire sequence of         rest of the pattern match, (?>\d+) can only match an entire sequence of
4202         digits.         digits.
4203    
4204         Atomic groups in general can of course contain arbitrarily  complicated         Atomic  groups in general can of course contain arbitrarily complicated
4205         subpatterns,  and  can  be  nested. However, when the subpattern for an         subpatterns, and can be nested. However, when  the  subpattern  for  an
4206         atomic group is just a single repeated item, as in the example above, a         atomic group is just a single repeated item, as in the example above, a
4207         simpler  notation,  called  a "possessive quantifier" can be used. This         simpler notation, called a "possessive quantifier" can  be  used.  This
4208         consists of an additional + character  following  a  quantifier.  Using         consists  of  an  additional  + character following a quantifier. Using
4209         this notation, the previous example can be rewritten as         this notation, the previous example can be rewritten as
4210    
4211           \d++foo           \d++foo
# Line 3932  ATOMIC GROUPING AND POSSESSIVE QUANTIFIE Line 4215  ATOMIC GROUPING AND POSSESSIVE QUANTIFIE
4215    
4216           (abc|xyz){2,3}+           (abc|xyz){2,3}+
4217    
4218         Possessive  quantifiers  are  always  greedy;  the   setting   of   the         Possessive   quantifiers   are   always  greedy;  the  setting  of  the
4219         PCRE_UNGREEDY option is ignored. They are a convenient notation for the         PCRE_UNGREEDY option is ignored. They are a convenient notation for the
4220         simpler forms of atomic group. However, there is no difference  in  the         simpler  forms  of atomic group. However, there is no difference in the
4221         meaning  of  a  possessive  quantifier and the equivalent atomic group,         meaning of a possessive quantifier and  the  equivalent  atomic  group,
4222         though there may be a performance  difference;  possessive  quantifiers         though  there  may  be a performance difference; possessive quantifiers
4223         should be slightly faster.         should be slightly faster.
4224    
4225         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-
4226         tax.  Jeffrey Friedl originated the idea (and the name)  in  the  first         tax.   Jeffrey  Friedl  originated the idea (and the name) in the first
4227         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
4228         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
4229         found its way into Perl at release 5.10.         found its way into Perl at release 5.10.
4230    
4231         PCRE has an optimization that automatically "possessifies" certain sim-         PCRE has an optimization that automatically "possessifies" certain sim-
4232         ple pattern constructs. For example, the sequence  A+B  is  treated  as         ple  pattern  constructs.  For  example, the sequence A+B is treated as
4233         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
4234         when B must follow.         when B must follow.
4235    
4236         When a pattern contains an unlimited repeat inside  a  subpattern  that         When  a  pattern  contains an unlimited repeat inside a subpattern that
4237         can  itself  be  repeated  an  unlimited number of times, the use of an         can itself be repeated an unlimited number of  times,  the  use  of  an
4238         atomic group is the only way to avoid some  failing  matches  taking  a         atomic  group  is  the  only way to avoid some failing matches taking a
4239         very long time indeed. The pattern         very long time indeed. The pattern
4240    
4241           (\D+|<\d+>)*[!?]           (\D+|<\d+>)*[!?]
4242    
4243         matches  an  unlimited number of substrings that either consist of non-         matches an unlimited number of substrings that either consist  of  non-
4244         digits, or digits enclosed in <>, followed by either ! or  ?.  When  it         digits,  or  digits  enclosed in <>, followed by either ! or ?. When it
4245         matches, it runs quickly. However, if it is applied to         matches, it runs quickly. However, if it is applied to
4246    
4247           aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa           aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
4248    
4249         it  takes  a  long  time  before reporting failure. This is because the         it takes a long time before reporting  failure.  This  is  because  the
4250         string can be divided between the internal \D+ repeat and the  external         string  can be divided between the internal \D+ repeat and the external
4251         *  repeat  in  a  large  number of ways, and all have to be tried. (The         * repeat in a large number of ways, and all  have  to  be  tried.  (The
4252         example uses [!?] rather than a single character at  the  end,  because         example  uses  [!?]  rather than a single character at the end, because
4253         both  PCRE  and  Perl have an optimization that allows for fast failure         both PCRE and Perl have an optimization that allows  for  fast  failure
4254         when a single character is used. They remember the last single  charac-         when  a single character is used. They remember the last single charac-
4255         ter  that  is required for a match, and fail early if it is not present         ter that is required for a match, and fail early if it is  not  present
4256         in the string.) If the pattern is changed so that  it  uses  an  atomic         in  the  string.)  If  the pattern is changed so that it uses an atomic
4257         group, like this:         group, like this:
4258    
4259           ((?>\D+)|<\d+>)*[!?]           ((?>\D+)|<\d+>)*[!?]
4260    
4261         sequences  of non-digits cannot be broken, and failure happens quickly.         sequences of non-digits cannot be broken, and failure happens quickly.
4262    
4263    
4264  BACK REFERENCES  BACK REFERENCES
# Line 4550  SUBPATTERNS AS SUBROUTINES Line 4833  SUBPATTERNS AS SUBROUTINES
4833         processing option does not affect the called subpattern.         processing option does not affect the called subpattern.
4834    
4835    
4836    ONIGURUMA SUBROUTINE SYNTAX
4837    
4838           For  compatibility with Oniguruma, the non-Perl syntax \g followed by a
4839           name or a number enclosed either in angle brackets or single quotes, is
4840           an  alternative  syntax  for  referencing a subpattern as a subroutine,
4841           possibly recursively. Here are two of the examples used above,  rewrit-
4842           ten using this syntax:
4843    
4844             (?<pn> \( ( (?>[^()]+) | \g<pn> )* \) )
4845             (sens|respons)e and \g'1'ibility
4846    
4847           PCRE  supports  an extension to Oniguruma: if a number is preceded by a
4848           plus or a minus sign it is taken as a relative reference. For example:
4849    
4850             (abc)(?i:\g<-1>)
4851    
4852           Note that \g{...} (Perl syntax) and \g<...> (Oniguruma syntax) are  not
4853           synonymous.  The former is a back reference; the latter is a subroutine
4854           call.
4855    
4856    
4857  CALLOUTS  CALLOUTS
4858    
4859         Perl has a feature whereby using the sequence (?{...}) causes arbitrary         Perl has a feature whereby using the sequence (?{...}) causes arbitrary
4860         Perl code to be obeyed in the middle of matching a regular  expression.         Perl  code to be obeyed in the middle of matching a regular expression.
4861         This makes it possible, amongst other things, to extract different sub-         This makes it possible, amongst other things, to extract different sub-
4862         strings that match the same pair of parentheses when there is a repeti-         strings that match the same pair of parentheses when there is a repeti-
4863         tion.         tion.
4864    
4865         PCRE provides a similar feature, but of course it cannot obey arbitrary         PCRE provides a similar feature, but of course it cannot obey arbitrary
4866         Perl code. The feature is called "callout". The caller of PCRE provides         Perl code. The feature is called "callout". The caller of PCRE provides
4867         an  external function by putting its entry point in the global variable         an external function by putting its entry point in the global  variable
4868         pcre_callout.  By default, this variable contains NULL, which  disables         pcre_callout.   By default, this variable contains NULL, which disables
4869         all calling out.         all calling out.
4870    
4871         Within  a  regular  expression,  (?C) indicates the points at which the         Within a regular expression, (?C) indicates the  points  at  which  the
4872         external function is to be called. If you want  to  identify  different         external  function  is  to be called. If you want to identify different
4873         callout  points, you can put a number less than 256 after the letter C.         callout points, you can put a number less than 256 after the letter  C.
4874         The default value is zero.  For example, this pattern has  two  callout         The  default  value is zero.  For example, this pattern has two callout
4875         points:         points:
4876    
4877           (?C1)abc(?C2)def           (?C1)abc(?C2)def
4878    
4879         If the PCRE_AUTO_CALLOUT flag is passed to pcre_compile(), callouts are         If the PCRE_AUTO_CALLOUT flag is passed to pcre_compile(), callouts are
4880         automatically installed before each item in the pattern. They  are  all         automatically  installed  before each item in the pattern. They are all
4881         numbered 255.         numbered 255.
4882    
4883         During matching, when PCRE reaches a callout point (and pcre_callout is         During matching, when PCRE reaches a callout point (and pcre_callout is
4884         set), the external function is called. It is provided with  the  number         set),  the  external function is called. It is provided with the number
4885         of  the callout, the position in the pattern, and, optionally, one item         of the callout, the position in the pattern, and, optionally, one  item
4886         of data originally supplied by the caller of pcre_exec().  The  callout         of  data  originally supplied by the caller of pcre_exec(). The callout
4887         function  may cause matching to proceed, to backtrack, or to fail alto-         function may cause matching to proceed, to backtrack, or to fail  alto-
4888         gether. A complete description of the interface to the callout function         gether. A complete description of the interface to the callout function
4889         is given in the pcrecallout documentation.         is given in the pcrecallout documentation.
4890    
4891    
4892  BACTRACKING CONTROL  BACKTRACKING CONTROL
4893    
4894         Perl  5.10 introduced a number of "Special Backtracking Control Verbs",         Perl 5.10 introduced a number of "Special Backtracking Control  Verbs",
4895         which are described in the Perl documentation as "experimental and sub-         which are described in the Perl documentation as "experimental and sub-
4896         ject  to  change or removal in a future version of Perl". It goes on to         ject to change or removal in a future version of Perl". It goes  on  to
4897         say: "Their usage in production code should be noted to avoid  problems         say:  "Their usage in production code should be noted to avoid problems
4898         during upgrades." The same remarks apply to the PCRE features described         during upgrades." The same remarks apply to the PCRE features described
4899         in this section.         in this section.
4900    
4901         Since these verbs are specifically related to backtracking, they can be         Since  these  verbs  are  specifically related to backtracking, most of
4902         used  only  when  the pattern is to be matched using pcre_exec(), which         them can be  used  only  when  the  pattern  is  to  be  matched  using
4903         uses a backtracking algorithm. They cause an error  if  encountered  by         pcre_exec(), which uses a backtracking algorithm. With the exception of
4904         pcre_dfa_exec().         (*FAIL), which behaves like a failing negative assertion, they cause an
4905           error if encountered by pcre_dfa_exec().
4906    
4907         The  new verbs make use of what was previously invalid syntax: an open-         The  new verbs make use of what was previously invalid syntax: an open-
4908         ing parenthesis followed by an asterisk. In Perl, they are generally of         ing parenthesis followed by an asterisk. In Perl, they are generally of
# Line 4716  AUTHOR Line 5021  AUTHOR
5021    
5022  REVISION  REVISION
5023    
5024         Last updated: 09 August 2007         Last updated: 18 March 2009
5025         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
5026  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
5027    
5028    
# Line 4845  CHARACTER CLASSES Line 5150  CHARACTER CLASSES
5150           [^...]      negative character class           [^...]      negative character class
5151           [x-y]       range (can be used for hex characters)           [x-y]       range (can be used for hex characters)
5152           [[:xxx:]]   positive POSIX named set           [[:xxx:]]   positive POSIX named set
5153           [[^:xxx:]]  negative POSIX named set           [[:^xxx:]]  negative POSIX named set
5154    
5155           alnum       alphanumeric           alnum       alphanumeric
5156           alpha       alphabetic           alpha       alphabetic
# Line 4975  SUBROUTINE REFERENCES (POSSIBLY RECURSIV Line 5280  SUBROUTINE REFERENCES (POSSIBLY RECURSIV
5280           (?-n)          call subpattern by relative number           (?-n)          call subpattern by relative number
5281           (?&name)       call subpattern by name (Perl)           (?&name)       call subpattern by name (Perl)
5282           (?P>name)      call subpattern by name (Python)           (?P>name)      call subpattern by name (Python)
5283             \g<name>       call subpattern by name (Oniguruma)
5284             \g'name'       call subpattern by name (Oniguruma)
5285             \g<n>          call subpattern by absolute number (Oniguruma)
5286             \g'n'          call subpattern by absolute number (Oniguruma)
5287             \g<+n>         call subpattern by relative number (PCRE extension)
5288             \g'+n'         call subpattern by relative number (PCRE extension)
5289             \g<-n>         call subpattern by relative number (PCRE extension)
5290             \g'-n'         call subpattern by relative number (PCRE extension)
5291    
5292    
5293  CONDITIONAL PATTERNS  CONDITIONAL PATTERNS
# Line 5013  BACKTRACKING CONTROL Line 5326  BACKTRACKING CONTROL
5326           (*THEN)        local failure, backtrack to next alternation           (*THEN)        local failure, backtrack to next alternation
5327    
5328    
5329    NEWLINE CONVENTIONS
5330    
5331           These  are  recognized only at the very start of the pattern or after a
5332           (*BSR_...) option.
5333    
5334             (*CR)
5335             (*LF)
5336             (*CRLF)
5337             (*ANYCRLF)
5338             (*ANY)
5339    
5340    
5341    WHAT \R MATCHES
5342    
5343           These are recognized only at the very start of the pattern or  after  a
5344           (*...) option that sets the newline convention.
5345    
5346             (*BSR_ANYCRLF)
5347             (*BSR_UNICODE)
5348    
5349    
5350  CALLOUTS  CALLOUTS
5351    
5352           (?C)      callout           (?C)      callout
# Line 5033  AUTHOR Line 5367  AUTHOR
5367    
5368  REVISION  REVISION
5369    
5370         Last updated: 08 August 2007         Last updated: 09 April 2008
5371         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2008 University of Cambridge.
5372  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
5373    
5374    
# Line 5216  MULTI-SEGMENT MATCHING WITH pcre_dfa_exe Line 5550  MULTI-SEGMENT MATCHING WITH pcre_dfa_exe
5550            0: dogsbody            0: dogsbody
5551            1: dog            1: dog
5552    
5553         The  pattern matches the words "dog" or "dogsbody". When the subject is         The pattern matches the words "dog" or "dogsbody". When the subject  is
5554         presented in several parts ("do" and "gsb" being  the  first  two)  the         presented  in  several  parts  ("do" and "gsb" being the first two) the
5555         match  stops  when "dog" has been found, and it is not possible to con-         match stops when "dog" has been found, and it is not possible  to  con-
5556         tinue. On the other hand,  if  "dogsbody"  is  presented  as  a  single         tinue.  On  the  other  hand,  if  "dogsbody"  is presented as a single
5557         string, both matches are found.         string, both matches are found.
5558    
5559         Because  of  this  phenomenon,  it does not usually make sense to end a         Because of this phenomenon, it does not usually make  sense  to  end  a
5560         pattern that is going to be matched in this way with a variable repeat.         pattern that is going to be matched in this way with a variable repeat.
5561    
5562         4. Patterns that contain alternatives at the top level which do not all         4. Patterns that contain alternatives at the top level which do not all
# Line 5569  DESCRIPTION Line 5903  DESCRIPTION
5903         command  for  linking  an application that uses them. Because the POSIX         command  for  linking  an application that uses them. Because the POSIX
5904         functions call the native ones, it is also necessary to add -lpcre.         functions call the native ones, it is also necessary to add -lpcre.
5905    
5906         I have implemented only those option bits that can be reasonably mapped         I have implemented only those POSIX option bits that can be  reasonably
5907         to PCRE native options. In addition, the option REG_EXTENDED is defined         mapped  to PCRE native options. In addition, the option REG_EXTENDED is
5908         with the value zero. This has no effect, but since  programs  that  are         defined with the value zero. This has no  effect,  but  since  programs
5909         written  to  the  POSIX interface often use it, this makes it easier to         that  are  written  to  the POSIX interface often use it, this makes it
5910         slot in PCRE as a replacement library. Other POSIX options are not even         easier to slot in PCRE as a replacement library.  Other  POSIX  options
5911         defined.         are not even defined.
5912    
5913         When  PCRE  is  called  via these functions, it is only the API that is         When  PCRE  is  called  via these functions, it is only the API that is
5914         POSIX-like in style. The syntax and semantics of  the  regular  expres-         POSIX-like in style. The syntax and semantics of  the  regular  expres-
# Line 5654  COMPILING A PATTERN Line 5988  COMPILING A PATTERN
5988  MATCHING NEWLINE CHARACTERS  MATCHING NEWLINE CHARACTERS
5989    
5990         This area is not simple, because POSIX and Perl take different views of         This area is not simple, because POSIX and Perl take different views of
5991         things.  It is not possible to get PCRE to obey  POSIX  semantics,  but         things.   It  is  not possible to get PCRE to obey POSIX semantics, but
5992         then  PCRE was never intended to be a POSIX engine. The following table         then PCRE was never intended to be a POSIX engine. The following  table
5993         lists the different possibilities for matching  newline  characters  in         lists  the  different  possibilities for matching newline characters in
5994         PCRE:         PCRE:
5995    
5996                                   Default   Change with                                   Default   Change with
# Line 5678  MATCHING NEWLINE CHARACTERS Line 6012  MATCHING NEWLINE CHARACTERS
6012           ^ matches \n in middle     no     REG_NEWLINE           ^ matches \n in middle     no     REG_NEWLINE
6013    
6014         PCRE's behaviour is the same as Perl's, except that there is no equiva-         PCRE's behaviour is the same as Perl's, except that there is no equiva-
6015         lent for PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl,  there  is         lent  for  PCRE_DOLLAR_ENDONLY in Perl. In both PCRE and Perl, there is
6016         no way to stop newline from matching [^a].         no way to stop newline from matching [^a].
6017    
6018         The   default  POSIX  newline  handling  can  be  obtained  by  setting         The  default  POSIX  newline  handling  can  be  obtained  by   setting
6019         PCRE_DOTALL and PCRE_DOLLAR_ENDONLY, but there is no way to  make  PCRE         PCRE_DOTALL  and  PCRE_DOLLAR_ENDONLY, but there is no way to make PCRE
6020         behave exactly as for the REG_NEWLINE action.         behave exactly as for the REG_NEWLINE action.
6021    
6022    
6023  MATCHING A PATTERN  MATCHING A PATTERN
6024    
6025         The  function  regexec()  is  called  to  match a compiled pattern preg         The function regexec() is called  to  match  a  compiled  pattern  preg
6026         against a given string, which is terminated by a zero byte, subject  to         against  a  given string, which is by default terminated by a zero byte
6027         the options in eflags. These can be:         (but see REG_STARTEND below), subject to the options in  eflags.  These
6028           can be:
6029    
6030           REG_NOTBOL           REG_NOTBOL
6031    
6032         The PCRE_NOTBOL option is set when calling the underlying PCRE matching         The PCRE_NOTBOL option is set when calling the underlying PCRE matching
6033         function.         function.
6034    
6035             REG_NOTEMPTY
6036    
6037           The PCRE_NOTEMPTY option is set when calling the underlying PCRE match-
6038           ing function. Note that REG_NOTEMPTY is not part of the POSIX standard.
6039           However, setting this option can give more POSIX-like behaviour in some
6040           situations.
6041    
6042           REG_NOTEOL           REG_NOTEOL
6043    
6044         The PCRE_NOTEOL option is set when calling the underlying PCRE matching         The PCRE_NOTEOL option is set when calling the underlying PCRE matching
6045         function.         function.
6046    
6047             REG_STARTEND
6048    
6049           The string is considered to start at string +  pmatch[0].rm_so  and  to
6050           have  a terminating NUL located at string + pmatch[0].rm_eo (there need
6051           not actually be a NUL at that location), regardless  of  the  value  of
6052           nmatch.  This  is a BSD extension, compatible with but not specified by
6053           IEEE Standard 1003.2 (POSIX.2), and should  be  used  with  caution  in
6054           software intended to be portable to other systems. Note that a non-zero
6055           rm_so does not imply REG_NOTBOL; REG_STARTEND affects only the location
6056           of the string, not how it is matched.
6057    
6058         If  the pattern was compiled with the REG_NOSUB flag, no data about any         If  the pattern was compiled with the REG_NOSUB flag, no data about any
6059         matched strings  is  returned.  The  nmatch  and  pmatch  arguments  of         matched strings  is  returned.  The  nmatch  and  pmatch  arguments  of
6060         regexec() are ignored.         regexec() are ignored.
# Line 5748  AUTHOR Line 6101  AUTHOR
6101    
6102  REVISION  REVISION
6103    
6104         Last updated: 06 March 2007         Last updated: 11 March 2009
6105         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
6106  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
6107    
6108    
# Line 5837  MATCHING INTERFACE Line 6190  MATCHING INTERFACE
6190    
6191           c. The "i"th argument has a suitable type for holding the           c. The "i"th argument has a suitable type for holding the
6192              string captured as the "i"th sub-pattern. If you pass in              string captured as the "i"th sub-pattern. If you pass in
6193              NULL for the "i"th argument, or pass fewer arguments than              void * NULL for the "i"th argument, or a non-void * NULL
6194                of the correct type, or pass fewer arguments than the
6195              number of sub-patterns, "i"th captured sub-pattern is              number of sub-patterns, "i"th captured sub-pattern is
6196              ignored.              ignored.
6197    
# Line 5852  MATCHING INTERFACE Line 6206  MATCHING INTERFACE
6206         need    more,    consider    using    the    more   general   interface         need    more,    consider    using    the    more   general   interface
6207         pcrecpp::RE::DoMatch. See pcrecpp.h for the signature for DoMatch.         pcrecpp::RE::DoMatch. See pcrecpp.h for the signature for DoMatch.
6208    
6209           NOTE: Do not use no_arg, which is used internally to mark the end of  a
6210           list  of optional arguments, as a placeholder for missing arguments, as
6211           this can lead to segfaults.
6212    
6213    
6214  QUOTING METACHARACTERS  QUOTING METACHARACTERS
6215    
# Line 6085  AUTHOR Line 6443  AUTHOR
6443    
6444  REVISION  REVISION
6445    
6446         Last updated: 06 March 2007         Last updated: 17 March 2009
6447  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
6448    
6449    
# Line 6113  PCRE SAMPLE PROGRAM Line 6471  PCRE SAMPLE PROGRAM
6471         bility  of  matching an empty string. Comments in the code explain what         bility  of  matching an empty string. Comments in the code explain what
6472         is going on.         is going on.
6473    
6474         The demonstration program is automatically built if you use  "./config-         If PCRE is installed in the standard include  and  library  directories
6475         ure;make"  to  build PCRE. Otherwise, if PCRE is installed in the stan-         for  your  system, you should be able to compile the demonstration pro-
6476         dard include and library directories for your  system,  you  should  be         gram using this command:
        able to compile the demonstration program using this command:  
6477    
6478           gcc -o pcredemo pcredemo.c -lpcre           gcc -o pcredemo pcredemo.c -lpcre
6479    
6480         If  PCRE is installed elsewhere, you may need to add additional options         If PCRE is installed elsewhere, you may need to add additional  options
6481         to the command line. For example, on a Unix-like system that  has  PCRE         to  the  command line. For example, on a Unix-like system that has PCRE
6482         installed  in  /usr/local,  you  can  compile the demonstration program         installed in /usr/local, you  can  compile  the  demonstration  program
6483         using a command like this:         using a command like this:
6484    
6485           gcc -o pcredemo -I/usr/local/include pcredemo.c \           gcc -o pcredemo -I/usr/local/include pcredemo.c \
6486               -L/usr/local/lib -lpcre               -L/usr/local/lib -lpcre
6487    
6488         Once you have compiled the demonstration program, you  can  run  simple         Once  you  have  compiled the demonstration program, you can run simple
6489         tests like this:         tests like this:
6490    
6491           ./pcredemo 'cat|dog' 'the cat sat on the mat'           ./pcredemo 'cat|dog' 'the cat sat on the mat'
6492           ./pcredemo -g 'cat|dog' 'the dog sat on the cat'           ./pcredemo -g 'cat|dog' 'the dog sat on the cat'
6493    
6494         Note  that  there  is  a  much  more comprehensive test program, called         Note that there is a  much  more  comprehensive  test  program,  called
6495         pcretest, which supports  many  more  facilities  for  testing  regular         pcretest,  which  supports  many  more  facilities  for testing regular
6496         expressions and the PCRE library. The pcredemo program is provided as a         expressions and the PCRE library. The pcredemo program is provided as a
6497         simple coding example.         simple coding example.
6498    
# Line 6143  PCRE SAMPLE PROGRAM Line 6500  PCRE SAMPLE PROGRAM
6500         the standard library directory, you may get an error like this when you         the standard library directory, you may get an error like this when you
6501         try to run pcredemo:         try to run pcredemo:
6502    
6503           ld.so.1: a.out: fatal: libpcre.so.0: open failed:  No  such  file  or           ld.so.1:  a.out:  fatal:  libpcre.so.0:  open failed: No such file or
6504         directory         directory
6505    
6506         This  is  caused  by the way shared library support works on those sys-         This is caused by the way shared library support works  on  those  sys-
6507         tems. You need to add         tems. You need to add
6508    
6509           -R/usr/local/lib           -R/usr/local/lib
# Line 6163  AUTHOR Line 6520  AUTHOR
6520    
6521  REVISION  REVISION
6522    
6523         Last updated: 13 June 2007         Last updated: 23 January 2008
6524         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2008 University of Cambridge.
6525  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
6526  PCRESTACK(3)                                                      PCRESTACK(3)  PCRESTACK(3)                                                      PCRESTACK(3)
6527    
# Line 6230  PCRE DISCUSSION OF STACK USAGE Line 6587  PCRE DISCUSSION OF STACK USAGE
6587         ing long subject strings is to write repeated parenthesized subpatterns         ing long subject strings is to write repeated parenthesized subpatterns
6588         to match more than one character whenever possible.         to match more than one character whenever possible.
6589    
6590       Compiling PCRE to use heap instead of stack
6591    
6592         In environments where stack memory is constrained, you  might  want  to         In environments where stack memory is constrained, you  might  want  to
6593         compile  PCRE to use heap memory instead of stack for remembering back-         compile  PCRE to use heap memory instead of stack for remembering back-
6594         up points. This makes it run a lot more slowly, however. Details of how         up points. This makes it run a lot more slowly, however. Details of how
# Line 6242  PCRE DISCUSSION OF STACK USAGE Line 6601  PCRE DISCUSSION OF STACK USAGE
6601         freed in reverse order, it may be possible to implement customized mem-         freed in reverse order, it may be possible to implement customized mem-
6602         ory handlers that are more efficient than the standard functions.         ory handlers that are more efficient than the standard functions.
6603    
6604       Limiting PCRE's stack usage
6605    
6606           PCRE has an internal counter that can be used to  limit  the  depth  of
6607           recursion,  and  thus cause pcre_exec() to give an error code before it
6608           runs out of stack. By default, the limit is very  large,  and  unlikely
6609           ever  to operate. It can be changed when PCRE is built, and it can also
6610           be set when pcre_exec() is called. For details of these interfaces, see
6611           the pcrebuild and pcreapi documentation.
6612    
6613           As a very rough rule of thumb, you should reckon on about 500 bytes per
6614           recursion. Thus, if you want to limit your  stack  usage  to  8Mb,  you
6615           should  set  the  limit at 16000 recursions. A 64Mb stack, on the other
6616           hand, can support around 128000 recursions. The pcretest  test  program
6617           has a command line option (-S) that can be used to increase the size of
6618           its stack.
6619    
6620       Changing stack size in Unix-like systems
6621    
6622         In Unix-like environments, there is not often a problem with the  stack         In Unix-like environments, there is not often a problem with the  stack
6623         unless  very  long  strings  are  involved, though the default limit on         unless  very  long  strings  are  involved, though the default limit on
6624         stack size varies from system to system. Values from 8Mb  to  64Mb  are         stack size varies from system to system. Values from 8Mb  to  64Mb  are
# Line 6262  PCRE DISCUSSION OF STACK USAGE Line 6639  PCRE DISCUSSION OF STACK USAGE
6639         attempts to increase the soft limit to  100Mb  using  setrlimit().  You         attempts to increase the soft limit to  100Mb  using  setrlimit().  You
6640         must do this before calling pcre_exec().         must do this before calling pcre_exec().
6641    
6642         PCRE  has  an  internal  counter that can be used to limit the depth of     Changing stack size in Mac OS X
        recursion, and thus cause pcre_exec() to give an error code  before  it  
        runs  out  of  stack. By default, the limit is very large, and unlikely  
        ever to operate. It can be changed when PCRE is built, and it can  also  
        be set when pcre_exec() is called. For details of these interfaces, see  
        the pcrebuild and pcreapi documentation.  
6643    
6644         As a very rough rule of thumb, you should reckon on about 500 bytes per         Using setrlimit(), as described above, should also work on Mac OS X. It
6645         recursion.  Thus,  if  you  want  to limit your stack usage to 8Mb, you         is also possible to set a stack size when linking a program. There is a
6646         should set the limit at 16000 recursions. A 64Mb stack,  on  the  other         discussion   about   stack  sizes  in  Mac  OS  X  at  this  web  site:
6647         hand,  can  support around 128000 recursions. The pcretest test program         http://developer.apple.com/qa/qa2005/qa1419.html.
        has a command line option (-S) that can be used to increase the size of  
        its stack.  
6648    
6649    
6650  AUTHOR  AUTHOR
# Line 6286  AUTHOR Line 6656  AUTHOR
6656    
6657  REVISION  REVISION
6658    
6659         Last updated: 05 June 2007         Last updated: 09 July 2008
6660         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2008 University of Cambridge.
6661  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
6662    
6663    

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