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revision 211 by ph10, Thu Aug 9 09:52:43 2007 UTC revision 572 by ph10, Wed Nov 17 17:55:57 2010 UTC
# Line 2  Line 2 
2  This file contains a concatenation of the PCRE man pages, converted to plain  This file contains a concatenation of the PCRE man pages, converted to plain
3  text format for ease of searching with a text editor, or for use on systems  text format for ease of searching with a text editor, or for use on systems
4  that do not have a man page processor. The small individual files that give  that do not have a man page processor. The small individual files that give
5  synopses of each function in the library have not been included. There are  synopses of each function in the library have not been included. Neither has
6  separate text files for the pcregrep and pcretest commands.  the pcredemo program. There are separate text files for the pcregrep and
7    pcretest commands.
8  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
9    
10    
# Line 18  INTRODUCTION Line 19  INTRODUCTION
19    
20         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
21         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
22         just  a  few differences. (Certain features that appeared in Python and         just  a few differences. Some features that appeared in Python and PCRE
23         PCRE before they appeared in Perl are also available using  the  Python         before they appeared in Perl are also available using the  Python  syn-
24         syntax.)         tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25           items, and there is an option for requesting some  minor  changes  that
26         The  current  implementation of PCRE (release 7.x) corresponds approxi-         give better JavaScript compatibility.
27         mately with Perl 5.10, including support for UTF-8 encoded strings  and  
28         Unicode general category properties. However, UTF-8 and Unicode support         The  current implementation of PCRE corresponds approximately with Perl
29         has to be explicitly enabled; it is not the default. The Unicode tables         5.12, including support for UTF-8 encoded strings and  Unicode  general
30         correspond to Unicode release 5.0.0.         category  properties.  However,  UTF-8  and  Unicode  support has to be
31           explicitly enabled; it is not the default. The  Unicode  tables  corre-
32           spond to Unicode release 5.2.0.
33    
34         In  addition to the Perl-compatible matching function, PCRE contains an         In  addition to the Perl-compatible matching function, PCRE contains an
35         alternative matching function that matches the same  compiled  patterns         alternative function that matches the same compiled patterns in a  dif-
36         in  a different way. In certain circumstances, the alternative function         ferent way. In certain circumstances, the alternative function has some
37         has some advantages. For a discussion of the two  matching  algorithms,         advantages.  For a discussion of the two matching algorithms,  see  the
38         see the pcrematching page.         pcrematching page.
39    
40         PCRE  is  written  in C and released as a C library. A number of people         PCRE  is  written  in C and released as a C library. A number of people
41         have written wrappers and interfaces of various kinds.  In  particular,         have written wrappers and interfaces of various kinds.  In  particular,
# Line 52  INTRODUCTION Line 55  INTRODUCTION
55         library is built. The pcre_config() function makes it  possible  for  a         library is built. The pcre_config() function makes it  possible  for  a
56         client  to  discover  which  features are available. The features them-         client  to  discover  which  features are available. The features them-
57         selves are described in the pcrebuild page. Documentation about  build-         selves are described in the pcrebuild page. Documentation about  build-
58         ing  PCRE for various operating systems can be found in the README file         ing  PCRE  for various operating systems can be found in the README and
59         in the source distribution.         NON-UNIX-USE files in the source distribution.
60    
61         The library contains a number of undocumented  internal  functions  and         The library contains a number of undocumented  internal  functions  and
62         data  tables  that  are  used by more than one of the exported external         data  tables  that  are  used by more than one of the exported external
# Line 69  USER DOCUMENTATION Line 72  USER DOCUMENTATION
72         The user documentation for PCRE comprises a number  of  different  sec-         The user documentation for PCRE comprises a number  of  different  sec-
73         tions.  In the "man" format, each of these is a separate "man page". In         tions.  In the "man" format, each of these is a separate "man page". In
74         the HTML format, each is a separate page, linked from the  index  page.         the HTML format, each is a separate page, linked from the  index  page.
75         In  the  plain text format, all the sections are concatenated, for ease         In  the  plain  text format, all the sections, except the pcredemo sec-
76         of searching. The sections are as follows:         tion, are concatenated, for ease of searching. The sections are as fol-
77           lows:
78    
79           pcre              this document           pcre              this document
80           pcre-config       show PCRE installation configuration information           pcre-config       show PCRE installation configuration information
# Line 79  USER DOCUMENTATION Line 83  USER DOCUMENTATION
83           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
84           pcrecompat        discussion of Perl compatibility           pcrecompat        discussion of Perl compatibility
85           pcrecpp           details of the C++ wrapper           pcrecpp           details of the C++ wrapper
86             pcredemo          a demonstration C program that uses PCRE
87           pcregrep          description of the pcregrep command           pcregrep          description of the pcregrep command
88           pcrematching      discussion of the two matching algorithms           pcrematching      discussion of the two matching algorithms
89           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
90           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
91                               regular expressions                               regular expressions
          pcresyntax        quick syntax reference  
92           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
93           pcreposix         the POSIX-compatible C API           pcreposix         the POSIX-compatible C API
94           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
95           pcresample        discussion of the sample program           pcresample        discussion of the pcredemo program
96           pcrestack         discussion of stack usage           pcrestack         discussion of stack usage
97             pcresyntax        quick syntax reference
98           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
99    
100         In  addition,  in the "man" and HTML formats, there is a short page for         In  addition,  in the "man" and HTML formats, there is a short page for
# Line 134  UTF-8 AND UNICODE PROPERTY SUPPORT Line 139  UTF-8 AND UNICODE PROPERTY SUPPORT
139    
140         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8
141         support in the code, and, in addition,  you  must  call  pcre_compile()         support in the code, and, in addition,  you  must  call  pcre_compile()
142         with  the PCRE_UTF8 option flag. When you do this, both the pattern and         with  the  PCRE_UTF8  option  flag,  or the pattern must start with the
143         any subject strings that are matched against it are  treated  as  UTF-8         sequence (*UTF8). When either of these is the case,  both  the  pattern
144         strings instead of just strings of bytes.         and  any  subject  strings  that  are matched against it are treated as
145           UTF-8 strings instead of strings of 1-byte characters.
146    
147         If  you compile PCRE with UTF-8 support, but do not use it at run time,         If you compile PCRE with UTF-8 support, but do not use it at run  time,
148         the library will be a bit bigger, but the additional run time  overhead         the  library will be a bit bigger, but the additional run time overhead
149         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
150         very big.         very big.
151    
152         If PCRE is built with Unicode character property support (which implies         If PCRE is built with Unicode character property support (which implies
153         UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-         UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-
154         ported.  The available properties that can be tested are limited to the         ported.  The available properties that can be tested are limited to the
155         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
156         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,
157         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
158         pcrepattern documentation. Only the short names for properties are sup-         pcrepattern documentation. Only the short names for properties are sup-
159         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-
160         ter}, is not supported.  Furthermore,  in  Perl,  many  properties  may         ter},  is  not  supported.   Furthermore,  in Perl, many properties may
161         optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE         optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE
162         does not support this.         does not support this.
163    
164     Validity of UTF-8 strings     Validity of UTF-8 strings
165    
166         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
167         subjects are (by default) checked for validity on entry to the relevant         subjects are (by default) checked for validity on entry to the relevant
168         functions. From release 7.3 of PCRE, the check is according  the  rules         functions.  From  release 7.3 of PCRE, the check is according the rules
169         of  RFC  3629, which are themselves derived from the Unicode specifica-         of RFC 3629, which are themselves derived from the  Unicode  specifica-
170         tion. Earlier releases of PCRE followed the rules of  RFC  2279,  which         tion.  Earlier  releases  of PCRE followed the rules of RFC 2279, which
171         allows  the  full range of 31-bit values (0 to 0x7FFFFFFF). The current         allows the full range of 31-bit values (0 to 0x7FFFFFFF).  The  current
172         check allows only values in the range U+0 to U+10FFFF, excluding U+D800         check allows only values in the range U+0 to U+10FFFF, excluding U+D800
173         to U+DFFF.         to U+DFFF.
174    
175         The  excluded  code  points are the "Low Surrogate Area" of Unicode, of         The excluded code points are the "Low Surrogate Area"  of  Unicode,  of
176         which the Unicode Standard says this: "The Low Surrogate Area does  not         which  the Unicode Standard says this: "The Low Surrogate Area does not
177         contain  any  character  assignments,  consequently  no  character code         contain any  character  assignments,  consequently  no  character  code
178         charts or namelists are provided for this area. Surrogates are reserved         charts or namelists are provided for this area. Surrogates are reserved
179         for  use  with  UTF-16 and then must be used in pairs." The code points         for use with UTF-16 and then must be used in pairs."  The  code  points
180         that are encoded by UTF-16 pairs  are  available  as  independent  code         that  are  encoded  by  UTF-16  pairs are available as independent code
181         points  in  the  UTF-8  encoding.  (In other words, the whole surrogate         points in the UTF-8 encoding. (In  other  words,  the  whole  surrogate
182         thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)         thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
183    
184         If an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error  return         If  an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error return
185         (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know         (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know
186         that your strings are valid, and therefore want to skip these checks in         that your strings are valid, and therefore want to skip these checks in
187         order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at         order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at
188         compile time or at run time, PCRE assumes that the pattern  or  subject         compile  time  or at run time, PCRE assumes that the pattern or subject
189         it  is  given  (respectively)  contains only valid UTF-8 codes. In this         it is given (respectively) contains only valid  UTF-8  codes.  In  this
190         case, it does not diagnose an invalid UTF-8 string.         case, it does not diagnose an invalid UTF-8 string.
191    
192         If you pass an invalid UTF-8 string  when  PCRE_NO_UTF8_CHECK  is  set,         If  you  pass  an  invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set,
193         what  happens  depends on why the string is invalid. If the string con-         what happens depends on why the string is invalid. If the  string  con-
194         forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a         forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
195         string  of  characters  in  the  range 0 to 0x7FFFFFFF. In other words,         string of characters in the range 0  to  0x7FFFFFFF.  In  other  words,
196         apart from the initial validity test, PCRE (when in UTF-8 mode) handles         apart from the initial validity test, PCRE (when in UTF-8 mode) handles
197         strings  according  to  the more liberal rules of RFC 2279. However, if         strings according to the more liberal rules of RFC  2279.  However,  if
198         the string does not even conform to RFC 2279, the result is  undefined.         the  string does not even conform to RFC 2279, the result is undefined.
199         Your program may crash.         Your program may crash.
200    
201         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
202         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
203         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
204         this situation, you will have to apply your own validity check.         this situation, you will have to apply your own validity check.
205    
206     General comments about UTF-8 mode     General comments about UTF-8 mode
207    
208         1. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a         1.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a
209         two-byte UTF-8 character if the value is greater than 127.         two-byte UTF-8 character if the value is greater than 127.
210    
211         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
212         characters for values greater than \177.         characters for values greater than \177.
213    
214         3. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-         3.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-
215         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
216    
217         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-
218         gle byte.         gle byte.
219    
220         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
221         mode,  but  its  use can lead to some strange effects. This facility is         mode, but its use can lead to some strange effects.  This  facility  is
222         not available in the alternative matching function, pcre_dfa_exec().         not available in the alternative matching function, pcre_dfa_exec().
223    
224         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
225         test  characters of any code value, but the characters that PCRE recog-         test characters of any code value, but, by default, the characters that
226         nizes as digits, spaces, or word characters  remain  the  same  set  as         PCRE  recognizes  as digits, spaces, or word characters remain the same
227         before, all with values less than 256. This remains true even when PCRE         set as before, all with values less than 256. This  remains  true  even
228         includes Unicode property support, because to do otherwise  would  slow         when  PCRE  is built to include Unicode property support, because to do
229         down  PCRE in many common cases. If you really want to test for a wider         otherwise would slow down PCRE in many common cases. Note in particular
230         sense of, say, "digit", you must use Unicode  property  tests  such  as         that this applies to \b and \B, because they are defined in terms of \w
231         \p{Nd}.         and \W. If you really want to test for a wider sense of, say,  "digit",
232           you  can  use  explicit Unicode property tests such as \p{Nd}. Alterna-
233           tively, if you set the PCRE_UCP option,  the  way  that  the  character
234           escapes  work  is changed so that Unicode properties are used to deter-
235           mine which characters match. There are more details in the  section  on
236           generic character types in the pcrepattern documentation.
237    
238         7.  Similarly,  characters that match the POSIX named character classes         7.  Similarly,  characters that match the POSIX named character classes
239         are all low-valued characters.         are all low-valued characters, unless the PCRE_UCP option is set.
240    
241         8. However, the Perl 5.10 horizontal and vertical  whitespace  matching         8. However, the horizontal and  vertical  whitespace  matching  escapes
242         escapes (\h, \H, \v, and \V) do match all the appropriate Unicode char-         (\h,  \H,  \v, and \V) do match all the appropriate Unicode characters,
243         acters.         whether or not PCRE_UCP is set.
244    
245         9. Case-insensitive matching applies only to  characters  whose  values         9. Case-insensitive matching applies only to  characters  whose  values
246         are  less than 128, unless PCRE is built with Unicode property support.         are  less than 128, unless PCRE is built with Unicode property support.
247         Even when Unicode property support is available, PCRE  still  uses  its         Even when Unicode property support is available, PCRE  still  uses  its
248         own  character  tables when checking the case of low-valued characters,         own  character  tables when checking the case of low-valued characters,
249         so as not to degrade performance.  The Unicode property information  is         so as not to degrade performance.  The Unicode property information  is
250         used only for characters with higher values. Even when Unicode property         used only for characters with higher values. Furthermore, PCRE supports
251         support is available, PCRE supports case-insensitive matching only when         case-insensitive matching only  when  there  is  a  one-to-one  mapping
252         there  is  a  one-to-one  mapping between a letter's cases. There are a         between  a letter's cases. There are a small number of many-to-one map-
253         small number of many-to-one mappings in Unicode;  these  are  not  sup-         pings in Unicode; these are not supported by PCRE.
        ported by PCRE.  
254    
255    
256  AUTHOR  AUTHOR
# Line 249  AUTHOR Line 259  AUTHOR
259         University Computing Service         University Computing Service
260         Cambridge CB2 3QH, England.         Cambridge CB2 3QH, England.
261    
262         Putting  an actual email address here seems to have been a spam magnet,         Putting an actual email address here seems to have been a spam  magnet,
263         so I've taken it away. If you want to email me, use  my  two  initials,         so  I've  taken  it away. If you want to email me, use my two initials,
264         followed by the two digits 10, at the domain cam.ac.uk.         followed by the two digits 10, at the domain cam.ac.uk.
265    
266    
267  REVISION  REVISION
268    
269         Last updated: 09 August 2007         Last updated: 13 November 2010
270         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
271  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
272    
273    
274  PCREBUILD(3)                                                      PCREBUILD(3)  PCREBUILD(3)                                                      PCREBUILD(3)
275    
276    
# Line 271  NAME Line 281  NAME
281  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
282    
283         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
284         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
285         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
286         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
287         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
288         directory) can be obtained by running         environments using the GUI facility of cmake-gui if you are using CMake
289           instead of configure to build PCRE.
290    
291           There  is  a  lot more information about building PCRE in non-Unix-like
292           environments in the file called NON_UNIX_USE, which is part of the PCRE
293           distribution.  You  should consult this file as well as the README file
294           if you are building in a non-Unix-like environment.
295    
296           The complete list of options for configure (which includes the standard
297           ones  such  as  the  selection  of  the  installation directory) can be
298           obtained by running
299    
300           ./configure --help           ./configure --help
301    
# Line 300  C++ SUPPORT Line 320  C++ SUPPORT
320    
321  UTF-8 SUPPORT  UTF-8 SUPPORT
322    
323         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 Unicode character strings, add
324    
325           --enable-utf8           --enable-utf8
326    
327         to  the  configure  command.  Of  itself, this does not make PCRE treat         to  the  configure  command.  Of  itself, this does not make PCRE treat
328         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
329         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()
330         function.         or pcre_compile2() functions.
331    
332           If you set --enable-utf8 when compiling in an EBCDIC environment,  PCRE
333           expects its input to be either ASCII or UTF-8 (depending on the runtime
334           option). It is not possible to support both EBCDIC and UTF-8  codes  in
335           the  same  version  of  the  library.  Consequently,  --enable-utf8 and
336           --enable-ebcdic are mutually exclusive.
337    
338    
339  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
# Line 330  UNICODE CHARACTER PROPERTY SUPPORT Line 356  UNICODE CHARACTER PROPERTY SUPPORT
356    
357  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
358    
359         By  default,  PCRE interprets character 10 (linefeed, LF) as indicating         By  default,  PCRE interprets the linefeed (LF) character as indicating
360         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
361         systems. You can compile PCRE to use character 13 (carriage return, CR)         systems.  You  can compile PCRE to use carriage return (CR) instead, by
362         instead, by adding         adding
363    
364           --enable-newline-is-cr           --enable-newline-is-cr
365    
# Line 356  CODE VALUE OF NEWLINE Line 382  CODE VALUE OF NEWLINE
382    
383         causes PCRE to recognize any Unicode newline sequence.         causes PCRE to recognize any Unicode newline sequence.
384    
385         Whatever line ending convention is selected when PCRE is built  can  be         Whatever  line  ending convention is selected when PCRE is built can be
386         overridden  when  the library functions are called. At build time it is         overridden when the library functions are called. At build time  it  is
387         conventional to use the standard for your operating system.         conventional to use the standard for your operating system.
388    
389    
390    WHAT \R MATCHES
391    
392           By  default,  the  sequence \R in a pattern matches any Unicode newline
393           sequence, whatever has been selected as the line  ending  sequence.  If
394           you specify
395    
396             --enable-bsr-anycrlf
397    
398           the  default  is changed so that \R matches only CR, LF, or CRLF. What-
399           ever is selected when PCRE is built can be overridden when the  library
400           functions are called.
401    
402    
403  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
404    
405         The PCRE building process uses libtool to build both shared and  static         The  PCRE building process uses libtool to build both shared and static
406         Unix  libraries by default. You can suppress one of these by adding one         Unix libraries by default. You can suppress one of these by adding  one
407         of         of
408    
409           --disable-shared           --disable-shared
# Line 376  BUILDING SHARED AND STATIC LIBRARIES Line 415  BUILDING SHARED AND STATIC LIBRARIES
415  POSIX MALLOC USAGE  POSIX MALLOC USAGE
416    
417         When PCRE is called through the POSIX interface (see the pcreposix doc-         When PCRE is called through the POSIX interface (see the pcreposix doc-
418         umentation),  additional  working  storage  is required for holding the         umentation), additional working storage is  required  for  holding  the
419         pointers to capturing substrings, because PCRE requires three  integers         pointers  to capturing substrings, because PCRE requires three integers
420         per  substring,  whereas  the POSIX interface provides only two. If the         per substring, whereas the POSIX interface provides only  two.  If  the
421         number of expected substrings is small, the wrapper function uses space         number of expected substrings is small, the wrapper function uses space
422         on the stack, because this is faster than using malloc() for each call.         on the stack, because this is faster than using malloc() for each call.
423         The default threshold above which the stack is no longer used is 10; it         The default threshold above which the stack is no longer used is 10; it
# Line 391  POSIX MALLOC USAGE Line 430  POSIX MALLOC USAGE
430    
431  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
432    
433         Within  a  compiled  pattern,  offset values are used to point from one         Within a compiled pattern, offset values are used  to  point  from  one
434         part to another (for example, from an opening parenthesis to an  alter-         part  to another (for example, from an opening parenthesis to an alter-
435         nation  metacharacter).  By default, two-byte values are used for these         nation metacharacter). By default, two-byte values are used  for  these
436         offsets, leading to a maximum size for a  compiled  pattern  of  around         offsets,  leading  to  a  maximum size for a compiled pattern of around
437         64K.  This  is sufficient to handle all but the most gigantic patterns.         64K. This is sufficient to handle all but the most  gigantic  patterns.
438         Nevertheless, some people do want to process enormous patterns,  so  it         Nevertheless,  some  people do want to process truyl enormous patterns,
439         is  possible  to compile PCRE to use three-byte or four-byte offsets by         so it is possible to compile PCRE to use three-byte or  four-byte  off-
440         adding a setting such as         sets by adding a setting such as
441    
442           --with-link-size=3           --with-link-size=3
443    
444         to the configure command. The value given must be 2,  3,  or  4.  Using         to  the  configure  command.  The value given must be 2, 3, or 4. Using
445         longer  offsets slows down the operation of PCRE because it has to load         longer offsets slows down the operation of PCRE because it has to  load
446         additional bytes when handling them.         additional bytes when handling them.
447    
448    
449  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
450    
451         When matching with the pcre_exec() function, PCRE implements backtrack-         When matching with the pcre_exec() function, PCRE implements backtrack-
452         ing  by  making recursive calls to an internal function called match().         ing by making recursive calls to an internal function  called  match().
453         In environments where the size of the stack is limited,  this  can  se-         In  environments  where  the size of the stack is limited, this can se-
454         verely  limit  PCRE's operation. (The Unix environment does not usually         verely limit PCRE's operation. (The Unix environment does  not  usually
455         suffer from this problem, but it may sometimes be necessary to increase         suffer from this problem, but it may sometimes be necessary to increase
456         the  maximum  stack size.  There is a discussion in the pcrestack docu-         the maximum stack size.  There is a discussion in the  pcrestack  docu-
457         mentation.) An alternative approach to recursion that uses memory  from         mentation.)  An alternative approach to recursion that uses memory from
458         the  heap  to remember data, instead of using recursive function calls,         the heap to remember data, instead of using recursive  function  calls,
459         has been implemented to work round the problem of limited  stack  size.         has  been  implemented to work round the problem of limited stack size.
460         If you want to build a version of PCRE that works this way, add         If you want to build a version of PCRE that works this way, add
461    
462           --disable-stack-for-recursion           --disable-stack-for-recursion
463    
464         to  the  configure  command. With this configuration, PCRE will use the         to the configure command. With this configuration, PCRE  will  use  the
465         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
466         ment  functions. By default these point to malloc() and free(), but you         ment functions. By default these point to malloc() and free(), but  you
467         can replace the pointers so that your own functions are used.         can replace the pointers so that your own functions are used instead.
468    
469         Separate functions are  provided  rather  than  using  pcre_malloc  and         Separate  functions  are  provided  rather  than  using pcre_malloc and
470         pcre_free  because  the  usage  is  very  predictable:  the block sizes         pcre_free because the  usage  is  very  predictable:  the  block  sizes
471         requested are always the same, and  the  blocks  are  always  freed  in         requested  are  always  the  same,  and  the blocks are always freed in
472         reverse  order.  A calling program might be able to implement optimized         reverse order. A calling program might be able to  implement  optimized
473         functions that perform better  than  malloc()  and  free().  PCRE  runs         functions  that  perform  better  than  malloc()  and free(). PCRE runs
474         noticeably more slowly when built in this way. This option affects only         noticeably more slowly when built in this way. This option affects only
475         the  pcre_exec()  function;  it   is   not   relevant   for   the   the         the pcre_exec() function; it is not relevant for pcre_dfa_exec().
        pcre_dfa_exec() function.  
476    
477    
478  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
# Line 496  USING EBCDIC CODE Line 534  USING EBCDIC CODE
534    
535         to the configure command. This setting implies --enable-rebuild-charta-         to the configure command. This setting implies --enable-rebuild-charta-
536         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
537         environment (for example, an IBM mainframe operating system).         environment (for example,  an  IBM  mainframe  operating  system).  The
538           --enable-ebcdic option is incompatible with --enable-utf8.
539    
540    
541    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
542    
543           By default, pcregrep reads all files as plain text. You can build it so
544           that it recognizes files whose names end in .gz or .bz2, and reads them
545           with libz or libbz2, respectively, by adding one or both of
546    
547             --enable-pcregrep-libz
548             --enable-pcregrep-libbz2
549    
550           to the configure command. These options naturally require that the rel-
551           evant libraries are installed on your system. Configuration  will  fail
552           if they are not.
553    
554    
555    PCRETEST OPTION FOR LIBREADLINE SUPPORT
556    
557           If you add
558    
559             --enable-pcretest-libreadline
560    
561           to  the  configure  command,  pcretest  is  linked with the libreadline
562           library, and when its input is from a terminal, it reads it  using  the
563           readline() function. This provides line-editing and history facilities.
564           Note that libreadline is GPL-licensed, so if you distribute a binary of
565           pcretest linked in this way, there may be licensing issues.
566    
567           Setting  this  option  causes  the -lreadline option to be added to the
568           pcretest build. In many operating environments with  a  sytem-installed
569           libreadline this is sufficient. However, in some environments (e.g.  if
570           an unmodified distribution version of readline is in use),  some  extra
571           configuration  may  be necessary. The INSTALL file for libreadline says
572           this:
573    
574             "Readline uses the termcap functions, but does not link with the
575             termcap or curses library itself, allowing applications which link
576             with readline the to choose an appropriate library."
577    
578           If your environment has not been set up so that an appropriate  library
579           is automatically included, you may need to add something like
580    
581             LIBS="-ncurses"
582    
583           immediately before the configure command.
584    
585    
586  SEE ALSO  SEE ALSO
# Line 513  AUTHOR Line 597  AUTHOR
597    
598  REVISION  REVISION
599    
600         Last updated: 30 July 2007         Last updated: 29 September 2009
601         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
602  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
603    
604    
605  PCREMATCHING(3)                                                PCREMATCHING(3)  PCREMATCHING(3)                                                PCREMATCHING(3)
606    
607    
# Line 601  THE ALTERNATIVE MATCHING ALGORITHM Line 685  THE ALTERNATIVE MATCHING ALGORITHM
685         though  it is not implemented as a traditional finite state machine (it         though  it is not implemented as a traditional finite state machine (it
686         keeps multiple states active simultaneously).         keeps multiple states active simultaneously).
687    
688           Although the general principle of this matching algorithm  is  that  it
689           scans  the subject string only once, without backtracking, there is one
690           exception: when a lookaround assertion is encountered,  the  characters
691           following  or  preceding  the  current  point  have to be independently
692           inspected.
693    
694         The scan continues until either the end of the subject is  reached,  or         The scan continues until either the end of the subject is  reached,  or
695         there  are  no more unterminated paths. At this point, terminated paths         there  are  no more unterminated paths. At this point, terminated paths
696         represent the different matching possibilities (if there are none,  the         represent the different matching possibilities (if there are none,  the
697         match  has  failed).   Thus,  if there is more than one possible match,         match  has  failed).   Thus,  if there is more than one possible match,
698         this algorithm finds all of them, and in particular, it finds the long-         this algorithm finds all of them, and in particular, it finds the long-
699         est.  In PCRE, there is an option to stop the algorithm after the first         est.  The  matches are returned in decreasing order of length. There is
700         match (which is necessarily the shortest) has been found.         an option to stop the algorithm after the first match (which is  neces-
701           sarily the shortest) is found.
702    
703         Note that all the matches that are found start at the same point in the         Note that all the matches that are found start at the same point in the
704         subject. If the pattern         subject. If the pattern
705    
706           cat(er(pillar)?)           cat(er(pillar)?)?
707    
708         is  matched  against the string "the caterpillar catchment", the result         is matched against the string "the caterpillar catchment",  the  result
709         will be the three strings "cat", "cater", and "caterpillar" that  start         will  be the three strings "caterpillar", "cater", and "cat" that start
710         at the fourth character of the subject. The algorithm does not automat-         at the fifth character of the subject. The algorithm does not automati-
711         ically move on to find matches that start at later positions.         cally move on to find matches that start at later positions.
712    
713         There are a number of features of PCRE regular expressions that are not         There are a number of features of PCRE regular expressions that are not
714         supported by the alternative matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
715    
716         1.  Because  the  algorithm  finds  all possible matches, the greedy or         1. Because the algorithm finds all  possible  matches,  the  greedy  or
717         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
718         ungreedy quantifiers are treated in exactly the same way. However, pos-         ungreedy quantifiers are treated in exactly the same way. However, pos-
719         sessive quantifiers can make a difference when what follows could  also         sessive  quantifiers can make a difference when what follows could also
720         match what is quantified, for example in a pattern like this:         match what is quantified, for example in a pattern like this:
721    
722           ^a++\w!           ^a++\w!
723    
724         This  pattern matches "aaab!" but not "aaa!", which would be matched by         This pattern matches "aaab!" but not "aaa!", which would be matched  by
725         a non-possessive quantifier. Similarly, if an atomic group is  present,         a  non-possessive quantifier. Similarly, if an atomic group is present,
726         it  is matched as if it were a standalone pattern at the current point,         it is matched as if it were a standalone pattern at the current  point,
727         and the longest match is then "locked in" for the rest of  the  overall         and  the  longest match is then "locked in" for the rest of the overall
728         pattern.         pattern.
729    
730         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
731         is not straightforward to keep track of  captured  substrings  for  the         is  not  straightforward  to  keep track of captured substrings for the
732         different  matching  possibilities,  and  PCRE's implementation of this         different matching possibilities, and  PCRE's  implementation  of  this
733         algorithm does not attempt to do this. This means that no captured sub-         algorithm does not attempt to do this. This means that no captured sub-
734         strings are available.         strings are available.
735    
736         3.  Because no substrings are captured, back references within the pat-         3. Because no substrings are captured, back references within the  pat-
737         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
738    
739         4. For the same reason, conditional expressions that use  a  backrefer-         4.  For  the same reason, conditional expressions that use a backrefer-
740         ence  as  the  condition or test for a specific group recursion are not         ence as the condition or test for a specific group  recursion  are  not
741         supported.         supported.
742    
743         5. Because many paths through the tree may be  active,  the  \K  escape         5.  Because  many  paths  through the tree may be active, the \K escape
744         sequence, which resets the start of the match when encountered (but may         sequence, which resets the start of the match when encountered (but may
745         be on some paths and not on others), is not  supported.  It  causes  an         be  on  some  paths  and not on others), is not supported. It causes an
746         error if encountered.         error if encountered.
747    
748         6.  Callouts  are  supported, but the value of the capture_top field is         6. Callouts are supported, but the value of the  capture_top  field  is
749         always 1, and the value of the capture_last field is always -1.         always 1, and the value of the capture_last field is always -1.
750    
751         7. The \C escape sequence, which (in the standard algorithm) matches  a         7.  The \C escape sequence, which (in the standard algorithm) matches a
752         single  byte, even in UTF-8 mode, is not supported because the alterna-         single byte, even in UTF-8 mode, is not supported because the  alterna-
753         tive algorithm moves through the subject  string  one  character  at  a         tive  algorithm  moves  through  the  subject string one character at a
754         time, for all active paths through the tree.         time, for all active paths through the tree.
755    
756         8.  None  of  the  backtracking control verbs such as (*PRUNE) are sup-         8. Except for (*FAIL), the backtracking control verbs such as  (*PRUNE)
757         ported.         are  not  supported.  (*FAIL)  is supported, and behaves like a failing
758           negative assertion.
759    
760    
761  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
# Line 676  ADVANTAGES OF THE ALTERNATIVE ALGORITHM Line 768  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
768         more than one match using the standard algorithm, you have to do kludgy         more than one match using the standard algorithm, you have to do kludgy
769         things with callouts.         things with callouts.
770    
771         2. There is much better support for partial matching. The  restrictions         2. Because the alternative algorithm  scans  the  subject  string  just
        on  the content of the pattern that apply when using the standard algo-  
        rithm for partial matching do not apply to the  alternative  algorithm.  
        For  non-anchored patterns, the starting position of a partial match is  
        available.  
   
        3. Because the alternative algorithm  scans  the  subject  string  just  
772         once,  and  never  needs to backtrack, it is possible to pass very long         once,  and  never  needs to backtrack, it is possible to pass very long
773         subject strings to the matching function in  several  pieces,  checking         subject strings to the matching function in  several  pieces,  checking
774         for partial matching each time.         for  partial  matching  each time. Although it is possible to do multi-
775           segment matching using the standard algorithm (pcre_exec()), by retain-
776           ing  partially matched substrings, it is more complicated. The pcrepar-
777           tial documentation gives details  of  partial  matching  and  discusses
778           multi-segment matching.
779    
780    
781  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
# Line 711  AUTHOR Line 801  AUTHOR
801    
802  REVISION  REVISION
803    
804         Last updated: 08 August 2007         Last updated: 17 November 2010
805         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
806  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
807    
808    
809  PCREAPI(3)                                                          PCREAPI(3)  PCREAPI(3)                                                          PCREAPI(3)
810    
811    
# Line 819  PCRE API OVERVIEW Line 909  PCRE API OVERVIEW
909         bers for the library.  Applications can use these  to  include  support         bers for the library.  Applications can use these  to  include  support
910         for different releases of PCRE.         for different releases of PCRE.
911    
912           In a Windows environment, if you want to statically link an application
913           program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC
914           before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-
915           loc()   and   pcre_free()   exported   functions   will   be   declared
916           __declspec(dllimport), with unwanted results.
917    
918         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
919         pcre_exec() are used for compiling and matching regular expressions  in         pcre_exec() are used for compiling and matching regular expressions  in
920         a  Perl-compatible  manner. A sample program that demonstrates the sim-         a  Perl-compatible  manner. A sample program that demonstrates the sim-
921         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
922         the  source distribution. The pcresample documentation describes how to         the PCRE source distribution. A listing of this program is given in the
923         run it.         pcredemo documentation, and the pcresample documentation describes  how
924           to compile and run it.
925    
926         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
927         ble,  is  also provided. This uses a different algorithm for the match-         ble, is also provided. This uses a different algorithm for  the  match-
928         ing. The alternative algorithm finds all possible matches (at  a  given         ing.  The  alternative algorithm finds all possible matches (at a given
929         point  in  the subject), and scans the subject just once. However, this         point in the subject), and scans the subject just  once  (unless  there
930         algorithm does not return captured substrings. A description of the two         are  lookbehind  assertions).  However,  this algorithm does not return
931         matching  algorithms and their advantages and disadvantages is given in         captured substrings. A description of the two matching  algorithms  and
932         the pcrematching documentation.         their  advantages  and disadvantages is given in the pcrematching docu-
933           mentation.
934    
935         In addition to the main compiling and  matching  functions,  there  are         In addition to the main compiling and  matching  functions,  there  are
936         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
# Line 908  NEWLINES Line 1006  NEWLINES
1006         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
1007         pattern is compiled, or when it is matched.         pattern is compiled, or when it is matched.
1008    
1009           At compile time, the newline convention can be specified by the options
1010           argument of pcre_compile(), or it can be specified by special  text  at
1011           the start of the pattern itself; this overrides any other settings. See
1012           the pcrepattern page for details of the special character sequences.
1013    
1014         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-
1015         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
1016         newline  convention  affects  the  handling of the dot, circumflex, and         newline convention affects the handling of  the  dot,  circumflex,  and
1017         dollar metacharacters, the handling of #-comments in /x mode, and, when         dollar metacharacters, the handling of #-comments in /x mode, and, when
1018         CRLF  is a recognized line ending sequence, the match position advance-         CRLF is a recognized line ending sequence, the match position  advance-
1019         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
1020         not affect the interpretation of the \n or \r escape sequences.         section on pcre_exec() options below.
1021    
1022           The choice of newline convention does not affect the interpretation  of
1023           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
1024           which is controlled in a similar way, but by separate options.
1025    
1026    
1027  MULTITHREADING  MULTITHREADING
1028    
1029         The  PCRE  functions  can be used in multi-threading applications, with         The PCRE functions can be used in  multi-threading  applications,  with
1030         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
1031         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
1032         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 1075  CHECKING BUILD-TIME OPTIONS
1075         The output is an integer whose value specifies  the  default  character         The output is an integer whose value specifies  the  default  character
1076         sequence  that is recognized as meaning "newline". The four values that         sequence  that is recognized as meaning "newline". The four values that
1077         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,
1078         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
1079         for your operating system.         are returned in EBCDIC environments. The default should normally corre-
1080           spond to the standard sequence for your operating system.
1081    
1082             PCRE_CONFIG_BSR
1083    
1084           The output is an integer whose value indicates what character sequences
1085           the \R escape sequence matches by default. A value of 0 means  that  \R
1086           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1087           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1088           tern is compiled or matched.
1089    
1090           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1091    
1092         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
1093         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
1094         4. Larger values allow larger regular expressions to  be  compiled,  at         4.  Larger  values  allow larger regular expressions to be compiled, at
1095         the  expense  of  slower matching. The default value of 2 is sufficient         the expense of slower matching. The default value of  2  is  sufficient
1096         for all but the most massive patterns, since  it  allows  the  compiled         for  all  but  the  most massive patterns, since it allows the compiled
1097         pattern to be up to 64K in size.         pattern to be up to 64K in size.
1098    
1099           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1100    
1101         The  output  is  an integer that contains the threshold above which the         The output is an integer that contains the threshold  above  which  the
1102         POSIX interface uses malloc() for output vectors. Further  details  are         POSIX  interface  uses malloc() for output vectors. Further details are
1103         given in the pcreposix documentation.         given in the pcreposix documentation.
1104    
1105           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1106    
1107         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-
1108         internal matching function calls in a  pcre_exec()  execution.  Further         ber  of  internal  matching  function calls in a pcre_exec() execution.
1109         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1110    
1111           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1112    
1113         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
1114         recursion when calling the internal matching function in a  pcre_exec()         of   recursion  when  calling  the  internal  matching  function  in  a
1115         execution. Further details are given with pcre_exec() below.         pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1116           below.
1117    
1118           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1119    
# Line 1023  COMPILING A PATTERN Line 1140  COMPILING A PATTERN
1140         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1141         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1142         the  two interfaces is that pcre_compile2() has an additional argument,         the  two interfaces is that pcre_compile2() has an additional argument,
1143         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr, via which a numerical error  code  can  be  returned.  To
1144           avoid  too  much repetition, we refer just to pcre_compile() below, but
1145           the information applies equally to pcre_compile2().
1146    
1147         The pattern is a C string terminated by a binary zero, and is passed in         The pattern is a C string terminated by a binary zero, and is passed in
1148         the  pattern  argument.  A  pointer to a single block of memory that is         the  pattern  argument.  A  pointer to a single block of memory that is
# Line 1040  COMPILING A PATTERN Line 1159  COMPILING A PATTERN
1159    
1160         The options argument contains various bit settings that affect the com-         The options argument contains various bit settings that affect the com-
1161         pilation. It should be zero if no options are required.  The  available         pilation. It should be zero if no options are required.  The  available
1162         options  are  described  below. Some of them, in particular, those that         options  are  described  below. Some of them (in particular, those that
1163         are compatible with Perl, can also be set and  unset  from  within  the         are compatible with Perl, but some others as well) can also be set  and
1164         pattern  (see  the  detailed  description in the pcrepattern documenta-         unset  from  within  the  pattern  (see the detailed description in the
1165         tion). For these options, the contents of the options  argument  speci-         pcrepattern documentation). For those options that can be different  in
1166         fies  their initial settings at the start of compilation and execution.         different  parts  of  the pattern, the contents of the options argument
1167         The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at  the  time         specifies their settings at the start of compilation and execution. The
1168         of matching as well as at compile time.         PCRE_ANCHORED, PCRE_BSR_xxx, and PCRE_NEWLINE_xxx options can be set at
1169           the time of matching as well as at compile time.
1170    
1171         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1172         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and
1173         sets the variable pointed to by errptr to point to a textual error mes-         sets the variable pointed to by errptr to point to a textual error mes-
1174         sage. This is a static string that is part of the library. You must not         sage. This is a static string that is part of the library. You must not
1175         try to free it. The offset from the start of the pattern to the charac-         try to free it. The offset from the start of the pattern  to  the  byte
1176         ter where the error was discovered is placed in the variable pointed to         that was being processed when the error was discovered is placed in the
1177         by  erroffset,  which must not be NULL. If it is, an immediate error is         variable pointed to by erroffset, which must not be NULL. If it is,  an
1178         given.         immediate error is given. Some errors are not detected until checks are
1179           carried out when the whole pattern has been scanned; in this  case  the
1180         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         offset is set to the end of the pattern.
1181         codeptr  argument is not NULL, a non-zero error code number is returned  
1182         via this argument in the event of an error. This is in addition to  the         Note  that  the offset is in bytes, not characters, even in UTF-8 mode.
1183           It may point into the middle of a UTF-8 character  (for  example,  when
1184           PCRE_ERROR_BADUTF8 is returned for an invalid UTF-8 string).
1185    
1186           If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1187           codeptr argument is not NULL, a non-zero error code number is  returned
1188           via  this argument in the event of an error. This is in addition to the
1189         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1190    
1191         If  the  final  argument, tableptr, is NULL, PCRE uses a default set of         If the final argument, tableptr, is NULL, PCRE uses a  default  set  of
1192         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1193         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1194         result of a call to pcre_maketables(). This value is  stored  with  the         result  of  a  call to pcre_maketables(). This value is stored with the
1195         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1196         pointer is passed to it. For more discussion, see the section on locale         pointer is passed to it. For more discussion, see the section on locale
1197         support below.         support below.
1198    
1199         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1200         pile():         pile():
1201    
1202           pcre *re;           pcre *re;
# Line 1083  COMPILING A PATTERN Line 1209  COMPILING A PATTERN
1209             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1210             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1211    
1212         The following names for option bits are defined in  the  pcre.h  header         The  following  names  for option bits are defined in the pcre.h header
1213         file:         file:
1214    
1215           PCRE_ANCHORED           PCRE_ANCHORED
1216    
1217         If this bit is set, the pattern is forced to be "anchored", that is, it         If this bit is set, the pattern is forced to be "anchored", that is, it
1218         is constrained to match only at the first matching point in the  string         is  constrained to match only at the first matching point in the string
1219         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1220         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1221         only way to do it in Perl.         only way to do it in Perl.
1222    
1223           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1224    
1225         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1226         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1227         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1228    
1229             PCRE_BSR_ANYCRLF
1230             PCRE_BSR_UNICODE
1231    
1232           These options (which are mutually exclusive) control what the \R escape
1233           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1234           or to match any Unicode newline sequence. The default is specified when
1235           PCRE is built. It can be overridden from within the pattern, or by set-
1236           ting an option when a compiled pattern is matched.
1237    
1238           PCRE_CASELESS           PCRE_CASELESS
1239    
1240         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
1241         case letters. It is equivalent to Perl's  /i  option,  and  it  can  be         case  letters.  It  is  equivalent  to  Perl's /i option, and it can be
1242         changed  within a pattern by a (?i) option setting. In UTF-8 mode, PCRE         changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
1243         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1244         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1245         with higher values, the concept of case is supported if  PCRE  is  com-         with  higher  values,  the concept of case is supported if PCRE is com-
1246         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1247         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1248         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1249         UTF-8 support.         UTF-8 support.
1250    
1251           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1252    
1253         If this bit is set, a dollar metacharacter in the pattern matches  only         If  this bit is set, a dollar metacharacter in the pattern matches only
1254         at  the  end  of the subject string. Without this option, a dollar also         at the end of the subject string. Without this option,  a  dollar  also
1255         matches immediately before a newline at the end of the string (but  not         matches  immediately before a newline at the end of the string (but not
1256         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1257         if PCRE_MULTILINE is set.  There is no equivalent  to  this  option  in         if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
1258         Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1259    
1260           PCRE_DOTALL           PCRE_DOTALL
1261    
1262         If this bit is set, a dot metacharater in the pattern matches all char-         If this bit is set, a dot metacharacter in the pattern matches a  char-
1263         acters, including those that indicate newline. Without it, a  dot  does         acter of any value, including one that indicates a newline. However, it
1264         not  match  when  the  current position is at a newline. This option is         only ever matches one character, even if newlines are  coded  as  CRLF.
1265         equivalent to Perl's /s option, and it can be changed within a  pattern         Without  this option, a dot does not match when the current position is
1266         by  a (?s) option setting. A negative class such as [^a] always matches         at a newline. This option is equivalent to Perl's /s option, and it can
1267         newline characters, independent of the setting of this option.         be  changed within a pattern by a (?s) option setting. A negative class
1268           such as [^a] always matches newline characters, independent of the set-
1269           ting of this option.
1270    
1271           PCRE_DUPNAMES           PCRE_DUPNAMES
1272    
1273         If this bit is set, names used to identify capturing  subpatterns  need         If  this  bit is set, names used to identify capturing subpatterns need
1274         not be unique. This can be helpful for certain types of pattern when it         not be unique. This can be helpful for certain types of pattern when it
1275         is known that only one instance of the named  subpattern  can  ever  be         is  known  that  only  one instance of the named subpattern can ever be
1276         matched.  There  are  more details of named subpatterns below; see also         matched. There are more details of named subpatterns  below;  see  also
1277         the pcrepattern documentation.         the pcrepattern documentation.
1278    
1279           PCRE_EXTENDED           PCRE_EXTENDED
1280    
1281         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1282         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1283         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1284         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1285         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1286         option,  and  it  can be changed within a pattern by a (?x) option set-         option, and it can be changed within a pattern by a  (?x)  option  set-
1287         ting.         ting.
1288    
1289           Which  characters  are  interpreted  as  newlines  is controlled by the
1290           options passed to pcre_compile() or by a special sequence at the  start
1291           of  the  pattern, as described in the section entitled "Newline conven-
1292           tions" in the pcrepattern documentation. Note that the end of this type
1293           of  comment  is  a  literal  newline  sequence  in  the pattern; escape
1294           sequences that happen to represent a newline do not count.
1295    
1296         This option makes it possible to include  comments  inside  complicated         This option makes it possible to include  comments  inside  complicated
1297         patterns.   Note,  however,  that this applies only to data characters.         patterns.   Note,  however,  that this applies only to data characters.
1298         Whitespace  characters  may  never  appear  within  special   character         Whitespace  characters  may  never  appear  within  special   character
1299         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for example within the sequence (?( that intro-
1300         introduces a conditional subpattern.         duces a conditional subpattern.
1301    
1302           PCRE_EXTRA           PCRE_EXTRA
1303    
# Line 1163  COMPILING A PATTERN Line 1307  COMPILING A PATTERN
1307         letter  that  has  no  special  meaning causes an error, thus reserving         letter  that  has  no  special  meaning causes an error, thus reserving
1308         these combinations for future expansion. By  default,  as  in  Perl,  a         these combinations for future expansion. By  default,  as  in  Perl,  a
1309         backslash  followed by a letter with no special meaning is treated as a         backslash  followed by a letter with no special meaning is treated as a
1310         literal. (Perl can, however, be persuaded to give a warning for  this.)         literal. (Perl can, however, be persuaded to give an error for this, by
1311         There  are  at  present no other features controlled by this option. It         running  it with the -w option.) There are at present no other features
1312         can also be set by a (?X) option setting within a pattern.         controlled by this option. It can also be set by a (?X) option  setting
1313           within a pattern.
1314    
1315           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1316    
1317         If this option is set, an  unanchored  pattern  is  required  to  match         If  this  option  is  set,  an  unanchored pattern is required to match
1318         before  or  at  the  first  newline  in  the subject string, though the         before or at the first  newline  in  the  subject  string,  though  the
1319         matched text may continue over the newline.         matched text may continue over the newline.
1320    
1321             PCRE_JAVASCRIPT_COMPAT
1322    
1323           If this option is set, PCRE's behaviour is changed in some ways so that
1324           it is compatible with JavaScript rather than Perl. The changes  are  as
1325           follows:
1326    
1327           (1)  A  lone  closing square bracket in a pattern causes a compile-time
1328           error, because this is illegal in JavaScript (by default it is  treated
1329           as a data character). Thus, the pattern AB]CD becomes illegal when this
1330           option is set.
1331    
1332           (2) At run time, a back reference to an unset subpattern group  matches
1333           an  empty  string (by default this causes the current matching alterna-
1334           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
1335           set  (assuming  it can find an "a" in the subject), whereas it fails by
1336           default, for Perl compatibility.
1337    
1338           PCRE_MULTILINE           PCRE_MULTILINE
1339    
1340         By default, PCRE treats the subject string as consisting  of  a  single         By default, PCRE treats the subject string as consisting  of  a  single
# Line 1217  COMPILING A PATTERN Line 1379  COMPILING A PATTERN
1379         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1380         cause an error.         cause an error.
1381    
1382         The only time that a line break is specially recognized when  compiling         The only time that a line break in a pattern  is  specially  recognized
1383         a  pattern  is  if  PCRE_EXTENDED  is set, and an unescaped # outside a         when  compiling  is when PCRE_EXTENDED is set. CR and LF are whitespace
1384         character class is encountered. This indicates  a  comment  that  lasts         characters, and so are ignored in this mode. Also, an unescaped #  out-
1385         until  after the next line break sequence. In other circumstances, line         side  a  character class indicates a comment that lasts until after the
1386         break  sequences  are  treated  as  literal  data,   except   that   in         next line break sequence. In other circumstances, line break  sequences
1387         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         in patterns are treated as literal data.
        and are therefore ignored.  
1388    
1389         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
1390         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.
1391    
1392           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1393    
# Line 1236  COMPILING A PATTERN Line 1397  COMPILING A PATTERN
1397         be  used  for  capturing  (and  they acquire numbers in the usual way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
1398         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1399    
1400             PCRE_UCP
1401    
1402           This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
1403           \w,  and  some  of  the POSIX character classes. By default, only ASCII
1404           characters are recognized, but if PCRE_UCP is set,  Unicode  properties
1405           are  used instead to classify characters. More details are given in the
1406           section on generic character types in the pcrepattern page. If you  set
1407           PCRE_UCP,  matching  one of the items it affects takes much longer. The
1408           option is available only if PCRE has been compiled with  Unicode  prop-
1409           erty support.
1410    
1411           PCRE_UNGREEDY           PCRE_UNGREEDY
1412    
1413         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1414         are  not greedy by default, but become greedy if followed by "?". It is         are not greedy by default, but become greedy if followed by "?". It  is
1415         not compatible with Perl. It can also be set by a (?U)  option  setting         not  compatible  with Perl. It can also be set by a (?U) option setting
1416         within the pattern.         within the pattern.
1417    
1418           PCRE_UTF8           PCRE_UTF8
1419    
1420         This  option  causes PCRE to regard both the pattern and the subject as         This option causes PCRE to regard both the pattern and the  subject  as
1421         strings of UTF-8 characters instead of single-byte  character  strings.         strings  of  UTF-8 characters instead of single-byte character strings.
1422         However,  it is available only when PCRE is built to include UTF-8 sup-         However, it is available only when PCRE is built to include UTF-8  sup-
1423         port. If not, the use of this option provokes an error. Details of  how         port.  If not, the use of this option provokes an error. Details of how
1424         this  option  changes the behaviour of PCRE are given in the section on         this option changes the behaviour of PCRE are given in the  section  on
1425         UTF-8 support in the main pcre page.         UTF-8 support in the main pcre page.
1426    
1427           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1428    
1429         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
1430         automatically  checked.  There  is  a  discussion about the validity of         automatically checked. There is a  discussion  about  the  validity  of
1431         UTF-8 strings in the main pcre page. If an invalid  UTF-8  sequence  of         UTF-8  strings  in  the main pcre page. If an invalid UTF-8 sequence of
1432         bytes  is  found,  pcre_compile() returns an error. If you already know         bytes is found, pcre_compile() returns an error. If  you  already  know
1433         that your pattern is valid, and you want to skip this check for perfor-         that your pattern is valid, and you want to skip this check for perfor-
1434         mance  reasons,  you  can set the PCRE_NO_UTF8_CHECK option. When it is         mance reasons, you can set the PCRE_NO_UTF8_CHECK option.  When  it  is
1435         set, the effect of passing an invalid UTF-8  string  as  a  pattern  is         set,  the  effect  of  passing  an invalid UTF-8 string as a pattern is
1436         undefined.  It  may  cause your program to crash. Note that this option         undefined. It may cause your program to crash. Note  that  this  option
1437         can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the         can  also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the
1438         UTF-8 validity checking of subject strings.         UTF-8 validity checking of subject strings.
1439    
1440    
1441  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1442    
1443         The  following  table  lists  the  error  codes than may be returned by         The following table lists the error  codes  than  may  be  returned  by
1444         pcre_compile2(), along with the error messages that may be returned  by         pcre_compile2(),  along with the error messages that may be returned by
1445         both  compiling functions. As PCRE has developed, some error codes have         both compiling functions. As PCRE has developed, some error codes  have
1446         fallen out of use. To avoid confusion, they have not been re-used.         fallen out of use. To avoid confusion, they have not been re-used.
1447    
1448            0  no error            0  no error
# Line 1285  COMPILATION ERROR CODES Line 1457  COMPILATION ERROR CODES
1457            9  nothing to repeat            9  nothing to repeat
1458           10  [this code is not in use]           10  [this code is not in use]
1459           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1460           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1461           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1462           14  missing )           14  missing )
1463           15  reference to non-existent subpattern           15  reference to non-existent subpattern
# Line 1293  COMPILATION ERROR CODES Line 1465  COMPILATION ERROR CODES
1465           17  unknown option bit(s) set           17  unknown option bit(s) set
1466           18  missing ) after comment           18  missing ) after comment
1467           19  [this code is not in use]           19  [this code is not in use]
1468           20  regular expression too large           20  regular expression is too large
1469           21  failed to get memory           21  failed to get memory
1470           22  unmatched parentheses           22  unmatched parentheses
1471           23  internal error: code overflow           23  internal error: code overflow
# Line 1322  COMPILATION ERROR CODES Line 1494  COMPILATION ERROR CODES
1494           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1495           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1496           48  subpattern name is too long (maximum 32 characters)           48  subpattern name is too long (maximum 32 characters)
1497           49  too many named subpatterns (maximum 10,000)           49  too many named subpatterns (maximum 10000)
1498           50  [this code is not in use]           50  [this code is not in use]
1499           51  octal value is greater than \377 (not in UTF-8 mode)           51  octal value is greater than \377 (not in UTF-8 mode)
1500           52  internal error: overran compiling workspace           52  internal error: overran compiling workspace
1501           53  internal  error:  previously-checked  referenced  subpattern  not           53  internal error: previously-checked referenced subpattern
1502         found                 not found
1503           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1504           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1505           56  inconsistent NEWLINE options"           56  inconsistent NEWLINE options
1506           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
1507                 non-zero number                 name/number or by a plain number
1508           58  (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number           58  a numbered reference must not be zero
1509             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1510             60  (*VERB) not recognized
1511             61  number is too big
1512             62  subpattern name expected
1513             63  digit expected after (?+
1514             64  ] is an invalid data character in JavaScript compatibility mode
1515             65  different names for subpatterns of the same number are
1516                   not allowed
1517             66  (*MARK) must have an argument
1518             67  this version of PCRE is not compiled with PCRE_UCP support
1519    
1520           The  numbers  32  and 10000 in errors 48 and 49 are defaults; different
1521           values may be used if the limits were changed when PCRE was built.
1522    
1523    
1524  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1341  STUDYING A PATTERN Line 1526  STUDYING A PATTERN
1526         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1527              const char **errptr);              const char **errptr);
1528    
1529         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
1530         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
1531         matching.  The function pcre_study() takes a pointer to a compiled pat-         matching. The function pcre_study() takes a pointer to a compiled  pat-
1532         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1533         information  that  will  help speed up matching, pcre_study() returns a         information that will help speed up matching,  pcre_study()  returns  a
1534         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
1535         the results of the study.         the results of the study.
1536    
1537         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1538         pcre_exec(). However, a pcre_extra block  also  contains  other  fields         pcre_exec()  or  pcre_dfa_exec(). However, a pcre_extra block also con-
1539         that  can  be  set  by the caller before the block is passed; these are         tains other fields that can be set by the caller before  the  block  is
1540         described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1541    
1542         If studying the pattern does not  produce  any  additional  information         If  studying  the  pattern  does  not  produce  any useful information,
1543         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1544         wants to pass any of the other fields to pcre_exec(), it  must  set  up         wants   to   pass   any   of   the   other  fields  to  pcre_exec()  or
1545         its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1546    
1547         The  second  argument of pcre_study() contains option bits. At present,         The second argument of pcre_study() contains option bits.  At  present,
1548         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1549    
1550         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.
1551         If  studying  succeeds  (even  if no data is returned), the variable it         If studying succeeds (even if no data is  returned),  the  variable  it
1552         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
1553         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
1554         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
1555         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1556    
1557         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 1377  STUDYING A PATTERN Line 1562  STUDYING A PATTERN
1562             0,              /* no options exist */             0,              /* no options exist */
1563             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1564    
1565         At present, studying a pattern is useful only for non-anchored patterns         Studying a pattern does two things: first, a lower bound for the length
1566         that do not have a single fixed starting character. A bitmap of  possi-         of subject string that is needed to match the pattern is computed. This
1567         ble starting bytes is created.         does not mean that there are any strings of that length that match, but
1568           it  does  guarantee that no shorter strings match. The value is used by
1569           pcre_exec() and pcre_dfa_exec() to avoid  wasting  time  by  trying  to
1570           match  strings  that are shorter than the lower bound. You can find out
1571           the value in a calling program via the pcre_fullinfo() function.
1572    
1573           Studying a pattern is also useful for non-anchored patterns that do not
1574           have  a  single fixed starting character. A bitmap of possible starting
1575           bytes is created. This speeds up finding a position in the  subject  at
1576           which to start matching.
1577    
1578           The  two  optimizations  just  described can be disabled by setting the
1579           PCRE_NO_START_OPTIMIZE   option    when    calling    pcre_exec()    or
1580           pcre_dfa_exec().  You  might  want  to do this if your pattern contains
1581           callouts or (*MARK), and you want to make use of  these  facilities  in
1582           cases  where  matching fails. See the discussion of PCRE_NO_START_OPTI-
1583           MIZE below.
1584    
1585    
1586  LOCALE SUPPORT  LOCALE SUPPORT
1587    
1588         PCRE  handles  caseless matching, and determines whether characters are         PCRE handles caseless matching, and determines whether  characters  are
1589         letters, digits, or whatever, by reference to a set of tables,  indexed         letters,  digits, or whatever, by reference to a set of tables, indexed
1590         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
1591         characters with codes less than 128. Higher-valued  codes  never  match         characters  with  codes  less than 128. By default, higher-valued codes
1592         escapes  such  as  \w or \d, but can be tested with \p if PCRE is built         never match escapes such as \w or \d, but they can be tested with \p if
1593         with Unicode character property support. The use of locales  with  Uni-         PCRE  is  built with Unicode character property support. Alternatively,
1594         code  is discouraged. If you are handling characters with codes greater         the PCRE_UCP option can be set at compile  time;  this  causes  \w  and
1595         than 128, you should either use UTF-8 and Unicode, or use locales,  but         friends to use Unicode property support instead of built-in tables. The
1596         not try to mix the two.         use of locales with Unicode is discouraged. If you are handling charac-
1597           ters  with codes greater than 128, you should either use UTF-8 and Uni-
1598           code, or use locales, but not try to mix the two.
1599    
1600         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
1601         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many
1602         applications.  Normally, the internal tables recognize only ASCII char-         applications.  Normally, the internal tables recognize only ASCII char-
1603         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-
1604         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,
1605         which may cause them to be different.         which may cause them to be different.
1606    
1607         The internal tables can always be overridden by tables supplied by  the         The  internal tables can always be overridden by tables supplied by the
1608         application that calls PCRE. These may be created in a different locale         application that calls PCRE. These may be created in a different locale
1609         from the default. As more and more applications change  to  using  Uni-         from  the  default.  As more and more applications change to using Uni-
1610         code, the need for this locale support is expected to die away.         code, the need for this locale support is expected to die away.
1611    
1612         External  tables  are  built by calling the pcre_maketables() function,         External tables are built by calling  the  pcre_maketables()  function,
1613         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
1614         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For
1615         example, to build and use tables that are appropriate  for  the  French         example,  to  build  and use tables that are appropriate for the French
1616         locale  (where  accented  characters  with  values greater than 128 are         locale (where accented characters with  values  greater  than  128  are
1617         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1618    
1619           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1620           tables = pcre_maketables();           tables = pcre_maketables();
1621           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1622    
1623         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;
1624         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".
1625    
1626         When  pcre_maketables()  runs,  the  tables are built in memory that is         When pcre_maketables() runs, the tables are built  in  memory  that  is
1627         obtained via pcre_malloc. It is the caller's responsibility  to  ensure         obtained  via  pcre_malloc. It is the caller's responsibility to ensure
1628         that  the memory containing the tables remains available for as long as         that the memory containing the tables remains available for as long  as
1629         it is needed.         it is needed.
1630    
1631         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
1632         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()
1633         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-
1634         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1635         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1636    
1637         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
1638         the  internal  tables)  to  pcre_exec(). Although not intended for this         the internal tables) to pcre_exec(). Although  not  intended  for  this
1639         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
1640         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
1641         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1642    
# Line 1443  INFORMATION ABOUT A PATTERN Line 1646  INFORMATION ABOUT A PATTERN
1646         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1647              int what, void *where);              int what, void *where);
1648    
1649         The pcre_fullinfo() function returns information about a compiled  pat-         The  pcre_fullinfo() function returns information about a compiled pat-
1650         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1651         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1652    
1653         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled
1654         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
1655         the pattern was not studied. The third argument specifies  which  piece         the  pattern  was not studied. The third argument specifies which piece
1656         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
1657         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
1658         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1659    
1660           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1459  INFORMATION ABOUT A PATTERN Line 1662  INFORMATION ABOUT A PATTERN
1662           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1663           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1664    
1665         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
1666         an simple check against passing an arbitrary memory pointer. Here is  a         an  simple check against passing an arbitrary memory pointer. Here is a
1667         typical  call  of pcre_fullinfo(), to obtain the length of the compiled         typical call of pcre_fullinfo(), to obtain the length of  the  compiled
1668         pattern:         pattern:
1669    
1670           int rc;           int rc;
# Line 1472  INFORMATION ABOUT A PATTERN Line 1675  INFORMATION ABOUT A PATTERN
1675             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1676             &length);         /* where to put the data */             &length);         /* where to put the data */
1677    
1678         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
1679         are as follows:         are as follows:
1680    
1681           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1682    
1683         Return  the  number  of  the highest back reference in the pattern. The         Return the number of the highest back reference  in  the  pattern.  The
1684         fourth argument should point to an int variable. Zero  is  returned  if         fourth  argument  should  point to an int variable. Zero is returned if
1685         there are no back references.         there are no back references.
1686    
1687           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1688    
1689         Return  the  number of capturing subpatterns in the pattern. The fourth         Return the number of capturing subpatterns in the pattern.  The  fourth
1690         argument should point to an int variable.         argument should point to an int variable.
1691    
1692           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1693    
1694         Return a pointer to the internal default character tables within  PCRE.         Return  a pointer to the internal default character tables within PCRE.
1695         The  fourth  argument should point to an unsigned char * variable. This         The fourth argument should point to an unsigned char *  variable.  This
1696         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1697         tion.  External  callers  can  cause PCRE to use its internal tables by         tion. External callers can cause PCRE to use  its  internal  tables  by
1698         passing a NULL table pointer.         passing a NULL table pointer.
1699    
1700           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1701    
1702         Return information about the first byte of any matched  string,  for  a         Return  information  about  the first byte of any matched string, for a
1703         non-anchored  pattern. The fourth argument should point to an int vari-         non-anchored pattern. The fourth argument should point to an int  vari-
1704         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
1705         is still recognized for backwards compatibility.)         is still recognized for backwards compatibility.)
1706    
1707         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
1708         (cat|cow|coyote), its value is returned. Otherwise, if either         (cat|cow|coyote), its value is returned. Otherwise, if either
1709    
1710         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
1711         branch starts with "^", or         branch starts with "^", or
1712    
1713         (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
1714         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1715    
1716         -1 is returned, indicating that the pattern matches only at  the  start         -1  is  returned, indicating that the pattern matches only at the start
1717         of  a  subject string or after any newline within the string. Otherwise         of a subject string or after any newline within the  string.  Otherwise
1718         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1719    
1720           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1721    
1722         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
1723         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
1724         matching string, a pointer to the table is returned. Otherwise NULL  is         matching  string, a pointer to the table is returned. Otherwise NULL is
1725         returned.  The fourth argument should point to an unsigned char * vari-         returned. The fourth argument should point to an unsigned char *  vari-
1726         able.         able.
1727    
1728             PCRE_INFO_HASCRORLF
1729    
1730           Return  1  if  the  pattern  contains any explicit matches for CR or LF
1731           characters, otherwise 0. The fourth argument should  point  to  an  int
1732           variable.  An explicit match is either a literal CR or LF character, or
1733           \r or \n.
1734    
1735           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
1736    
1737         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,
1738         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)
1739         nal option setting changes the local PCRE_DUPNAMES option.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1740    
1741           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1742    
# Line 1538  INFORMATION ABOUT A PATTERN Line 1748  INFORMATION ABOUT A PATTERN
1748         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
1749         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1750    
1751             PCRE_INFO_MINLENGTH
1752    
1753           If the pattern was studied and a minimum length  for  matching  subject
1754           strings  was  computed,  its  value is returned. Otherwise the returned
1755           value is -1. The value is a number of characters, not bytes  (this  may
1756           be  relevant in UTF-8 mode). The fourth argument should point to an int
1757           variable. A non-negative value is a lower bound to the  length  of  any
1758           matching  string.  There  may not be any strings of that length that do
1759           actually match, but every string that does match is at least that long.
1760    
1761           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
1762           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1763           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
# Line 1559  INFORMATION ABOUT A PATTERN Line 1779  INFORMATION ABOUT A PATTERN
1779         a pointer to the first entry of the table  (a  pointer  to  char).  The         a pointer to the first entry of the table  (a  pointer  to  char).  The
1780         first two bytes of each entry are the number of the capturing parenthe-         first two bytes of each entry are the number of the capturing parenthe-
1781         sis, most significant byte first. The rest of the entry is  the  corre-         sis, most significant byte first. The rest of the entry is  the  corre-
1782         sponding  name,  zero  terminated. The names are in alphabetical order.         sponding name, zero terminated.
1783         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-  
1784         theses  numbers.  For  example,  consider the following pattern (assume         The  names are in alphabetical order. Duplicate names may appear if (?|
1785         PCRE_EXTENDED is  set,  so  white  space  -  including  newlines  -  is         is used to create multiple groups with the same number, as described in
1786         ignored):         the  section  on  duplicate subpattern numbers in the pcrepattern page.
1787           Duplicate names for subpatterns with different  numbers  are  permitted
1788           only  if  PCRE_DUPNAMES  is  set. In all cases of duplicate names, they
1789           appear in the table in the order in which they were found in  the  pat-
1790           tern.  In  the  absence  of (?| this is the order of increasing number;
1791           when (?| is used this is not necessarily the case because later subpat-
1792           terns may have lower numbers.
1793    
1794           As  a  simple  example of the name/number table, consider the following
1795           pattern (assume PCRE_EXTENDED is set, so white space -  including  new-
1796           lines - is ignored):
1797    
1798           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1799           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
# Line 1584  INFORMATION ABOUT A PATTERN Line 1814  INFORMATION ABOUT A PATTERN
1814    
1815           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
1816    
1817         Return 1 if the pattern can be used for partial matching, otherwise  0.         Return 1  if  the  pattern  can  be  used  for  partial  matching  with
1818         The  fourth  argument  should point to an int variable. The pcrepartial         pcre_exec(),  otherwise  0.  The fourth argument should point to an int
1819         documentation lists the restrictions that apply to patterns  when  par-         variable. From  release  8.00,  this  always  returns  1,  because  the
1820         tial matching is used.         restrictions  that  previously  applied  to  partial matching have been
1821           lifted. The pcrepartial documentation gives details of  partial  match-
1822           ing.
1823    
1824           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1825    
# Line 1624  INFORMATION ABOUT A PATTERN Line 1856  INFORMATION ABOUT A PATTERN
1856         Return the size of the data block pointed to by the study_data field in         Return the size of the data block pointed to by the study_data field in
1857         a pcre_extra block. That is,  it  is  the  value  that  was  passed  to         a pcre_extra block. That is,  it  is  the  value  that  was  passed  to
1858         pcre_malloc() when PCRE was getting memory into which to place the data         pcre_malloc() when PCRE was getting memory into which to place the data
1859         created by pcre_study(). The fourth argument should point to  a  size_t         created by pcre_study(). If pcre_extra is NULL, or there  is  no  study
1860           data,  zero  is  returned. The fourth argument should point to a size_t
1861         variable.         variable.
1862    
1863    
# Line 1632  OBSOLETE INFO FUNCTION Line 1865  OBSOLETE INFO FUNCTION
1865    
1866         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1867    
1868         The  pcre_info()  function is now obsolete because its interface is too         The pcre_info() function is now obsolete because its interface  is  too
1869         restrictive to return all the available data about a compiled  pattern.         restrictive  to return all the available data about a compiled pattern.
1870         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of
1871         pcre_info() is the number of capturing subpatterns, or one of the  fol-         pcre_info()  is the number of capturing subpatterns, or one of the fol-
1872         lowing negative numbers:         lowing negative numbers:
1873    
1874           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1875           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1876    
1877         If  the  optptr  argument is not NULL, a copy of the options with which         If the optptr argument is not NULL, a copy of the  options  with  which
1878         the pattern was compiled is placed in the integer  it  points  to  (see         the  pattern  was  compiled  is placed in the integer it points to (see
1879         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1880    
1881         If  the  pattern  is  not anchored and the firstcharptr argument is not         If the pattern is not anchored and the  firstcharptr  argument  is  not
1882         NULL, it is used to pass back information about the first character  of         NULL,  it is used to pass back information about the first character of
1883         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1884    
1885    
# Line 1654  REFERENCE COUNTS Line 1887  REFERENCE COUNTS
1887    
1888         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1889    
1890         The  pcre_refcount()  function is used to maintain a reference count in         The pcre_refcount() function is used to maintain a reference  count  in
1891         the data block that contains a compiled pattern. It is provided for the         the data block that contains a compiled pattern. It is provided for the
1892         benefit  of  applications  that  operate  in an object-oriented manner,         benefit of applications that  operate  in  an  object-oriented  manner,
1893         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1894         pattern, but you want to free the block when they are all done.         pattern, but you want to free the block when they are all done.
1895    
1896         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1897         zero.  It is changed only by calling this function, whose action is  to         zero.   It is changed only by calling this function, whose action is to
1898         add  the  adjust  value  (which may be positive or negative) to it. The         add the adjust value (which may be positive or  negative)  to  it.  The
1899         yield of the function is the new value. However, the value of the count         yield of the function is the new value. However, the value of the count
1900         is  constrained to lie between 0 and 65535, inclusive. If the new value         is constrained to lie between 0 and 65535, inclusive. If the new  value
1901         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1902    
1903         Except when it is zero, the reference count is not correctly  preserved         Except  when it is zero, the reference count is not correctly preserved
1904         if  a  pattern  is  compiled on one host and then transferred to a host         if a pattern is compiled on one host and then  transferred  to  a  host
1905         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1906    
1907    
# Line 1680  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1913  MATCHING A PATTERN: THE TRADITIONAL FUNC
1913    
1914         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
1915         compiled pattern, which is passed in the code argument. If the  pattern         compiled pattern, which is passed in the code argument. If the  pattern
1916         has been studied, the result of the study should be passed in the extra         was  studied,  the  result  of  the study should be passed in the extra
1917         argument. This function is the main matching facility of  the  library,         argument. This function is the main matching facility of  the  library,
1918         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
1919         an alternative matching function, which is described below in the  sec-         an alternative matching function, which is described below in the  sec-
# Line 1720  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1953  MATCHING A PATTERN: THE TRADITIONAL FUNC
1953           unsigned long int match_limit_recursion;           unsigned long int match_limit_recursion;
1954           void *callout_data;           void *callout_data;
1955           const unsigned char *tables;           const unsigned char *tables;
1956             unsigned char **mark;
1957    
1958         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
1959         are set. The flag bits are:         are set. The flag bits are:
# Line 1729  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1963  MATCHING A PATTERN: THE TRADITIONAL FUNC
1963           PCRE_EXTRA_MATCH_LIMIT_RECURSION           PCRE_EXTRA_MATCH_LIMIT_RECURSION
1964           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1965           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1966             PCRE_EXTRA_MARK
1967    
1968         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
1969         the  pcre_extra  block  that is returned by pcre_study(), together with         the  pcre_extra  block  that is returned by pcre_study(), together with
# Line 1739  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1974  MATCHING A PATTERN: THE TRADITIONAL FUNC
1974         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
1975         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
1976         match, but which have a very large number  of  possibilities  in  their         match, but which have a very large number  of  possibilities  in  their
1977         search  trees.  The  classic  example  is  the  use of nested unlimited         search  trees. The classic example is a pattern that uses nested unlim-
1978         repeats.         ited repeats.
1979    
1980         Internally, PCRE uses a function called match() which it calls  repeat-         Internally, PCRE uses a function called match() which it calls  repeat-
1981         edly  (sometimes  recursively). The limit set by match_limit is imposed         edly  (sometimes  recursively). The limit set by match_limit is imposed
# Line 1762  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1997  MATCHING A PATTERN: THE TRADITIONAL FUNC
1997         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-
1998         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.
1999    
2000         Limiting  the  recursion  depth  limits the amount of stack that can be         Limiting the recursion depth limits the amount of  stack  that  can  be
2001         used, or, when PCRE has been compiled to use memory on the heap instead         used, or, when PCRE has been compiled to use memory on the heap instead
2002         of the stack, the amount of heap memory that can be used.         of the stack, the amount of heap memory that can be used.
2003    
2004         The  default  value  for  match_limit_recursion can be set when PCRE is         The default value for match_limit_recursion can be  set  when  PCRE  is
2005         built; the default default  is  the  same  value  as  the  default  for         built;  the  default  default  is  the  same  value  as the default for
2006         match_limit.  You can override the default by suppling pcre_exec() with         match_limit. You can override the default by suppling pcre_exec()  with
2007         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and         a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
2008         PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the         PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the
2009         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
2010    
2011         The pcre_callout field is used in conjunction with the  "callout"  fea-         The  callout_data  field is used in conjunction with the "callout" fea-
2012         ture, which is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
2013    
2014         The  tables  field  is  used  to  pass  a  character  tables pointer to         The tables field  is  used  to  pass  a  character  tables  pointer  to
2015         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec();  this overrides the value that is stored with the compiled
2016         pattern.  A  non-NULL value is stored with the compiled pattern only if         pattern. A non-NULL value is stored with the compiled pattern  only  if
2017         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
2018         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
2019         PCRE's internal tables to be used. This facility is  helpful  when  re-         PCRE's  internal  tables  to be used. This facility is helpful when re-
2020         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
2021         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
2022         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
2023         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
2024    
2025           If  PCRE_EXTRA_MARK  is  set in the flags field, the mark field must be
2026           set to point to a char * variable. If the pattern  contains  any  back-
2027           tracking  control verbs such as (*MARK:NAME), and the execution ends up
2028           with a name to pass back, a pointer to the  name  string  (zero  termi-
2029           nated)  is  placed  in  the  variable pointed to by the mark field. The
2030           names are within the compiled pattern; if you wish  to  retain  such  a
2031           name  you must copy it before freeing the memory of a compiled pattern.
2032           If there is no name to pass back, the variable pointed to by  the  mark
2033           field  set  to NULL. For details of the backtracking control verbs, see
2034           the section entitled "Backtracking control" in the pcrepattern documen-
2035           tation.
2036    
2037     Option bits for pcre_exec()     Option bits for pcre_exec()
2038    
2039         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.
2040         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,
2041         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
2042         PCRE_PARTIAL.         PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
2043           PCRE_PARTIAL_HARD.
2044    
2045           PCRE_ANCHORED           PCRE_ANCHORED
2046    
# Line 1801  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2049  MATCHING A PATTERN: THE TRADITIONAL FUNC
2049         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
2050         unachored at matching time.         unachored at matching time.
2051    
2052             PCRE_BSR_ANYCRLF
2053             PCRE_BSR_UNICODE
2054    
2055           These options (which are mutually exclusive) control what the \R escape
2056           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
2057           or to match any Unicode newline sequence. These  options  override  the
2058           choice that was made or defaulted when the pattern was compiled.
2059    
2060           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
2061           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
2062           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
2063           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
2064           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
2065    
2066         These options override  the  newline  definition  that  was  chosen  or         These  options  override  the  newline  definition  that  was chosen or
2067         defaulted  when the pattern was compiled. For details, see the descrip-         defaulted when the pattern was compiled. For details, see the  descrip-
2068         tion of pcre_compile()  above.  During  matching,  the  newline  choice         tion  of  pcre_compile()  above.  During  matching,  the newline choice
2069         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
2070         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
2071         match  failure  for  an  unanchored  pattern.  When  PCRE_NEWLINE_CRLF,         match failure for an unanchored pattern.
2072         PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a  match  attempt  
2073         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
2074         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-
2075         after the CRLF.         rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
2076           explicit  matches  for  CR  or  LF  characters,  the  match position is
2077           advanced by two characters instead of one, in other words, to after the
2078           CRLF.
2079    
2080           The above rule is a compromise that makes the most common cases work as
2081           expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
2082           option is not set), it does not match the string "\r\nA" because, after
2083           failing at the start, it skips both the CR and the LF before  retrying.
2084           However,  the  pattern  [\r\n]A does match that string, because it con-
2085           tains an explicit CR or LF reference, and so advances only by one char-
2086           acter after the first failure.
2087    
2088           An explicit match for CR of LF is either a literal appearance of one of
2089           those characters, or one of the \r or  \n  escape  sequences.  Implicit
2090           matches  such  as [^X] do not count, nor does \s (which includes CR and
2091           LF in the characters that it matches).
2092    
2093           Notwithstanding the above, anomalous effects may still occur when  CRLF
2094           is a valid newline sequence and explicit \r or \n escapes appear in the
2095           pattern.
2096    
2097           PCRE_NOTBOL           PCRE_NOTBOL
2098    
2099         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
2100         the beginning of a line, so the  circumflex  metacharacter  should  not         the  beginning  of  a  line, so the circumflex metacharacter should not
2101         match  before it. Setting this without PCRE_MULTILINE (at compile time)         match before it. Setting this without PCRE_MULTILINE (at compile  time)
2102         causes circumflex never to match. This option affects only  the  behav-         causes  circumflex  never to match. This option affects only the behav-
2103         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
2104    
2105           PCRE_NOTEOL           PCRE_NOTEOL
2106    
2107         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
2108         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
2109         in  multiline mode) a newline immediately before it. Setting this with-         in multiline mode) a newline immediately before it. Setting this  with-
2110         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2111         option  affects only the behaviour of the dollar metacharacter. It does         option affects only the behaviour of the dollar metacharacter. It  does
2112         not affect \Z or \z.         not affect \Z or \z.
2113    
2114           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2115    
2116         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
2117         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
2118         the alternatives match the empty string, the entire  match  fails.  For         the  alternatives  match  the empty string, the entire match fails. For
2119         example, if the pattern         example, if the pattern
2120    
2121           a?b?           a?b?
2122    
2123         is  applied  to  a string not beginning with "a" or "b", it matches the         is applied to a string not beginning with "a" or  "b",  it  matches  an
2124         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
2125         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-
2126         rences of "a" or "b".         rences of "a" or "b".
2127    
2128         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2129         cial  case  of  a  pattern match of the empty string within its split()  
2130         function, and when using the /g modifier. It  is  possible  to  emulate         This  is  like PCRE_NOTEMPTY, except that an empty string match that is
2131         Perl's behaviour after matching a null string by first trying the match         not at the start of  the  subject  is  permitted.  If  the  pattern  is
2132         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then         anchored, such a match can occur only if the pattern contains \K.
2133         if  that  fails by advancing the starting offset (see below) and trying  
2134         an ordinary match again. There is some code that demonstrates how to do         Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or
2135         this in the pcredemo.c sample program.         PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern
2136           match  of  the empty string within its split() function, and when using
2137           the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after
2138           matching a null string by first trying the match again at the same off-
2139           set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that
2140           fails, by advancing the starting offset (see below) and trying an ordi-
2141           nary match again. There is some code that demonstrates how to  do  this
2142           in  the  pcredemo sample program. In the most general case, you have to
2143           check to see if the newline convention recognizes CRLF  as  a  newline,
2144           and  if so, and the current character is CR followed by LF, advance the
2145           starting offset by two characters instead of one.
2146    
2147             PCRE_NO_START_OPTIMIZE
2148    
2149           There are a number of optimizations that pcre_exec() uses at the  start
2150           of  a  match,  in  order to speed up the process. For example, if it is
2151           known that an unanchored match must start with a specific character, it
2152           searches  the  subject  for that character, and fails immediately if it
2153           cannot find it, without actually running the  main  matching  function.
2154           This means that a special item such as (*COMMIT) at the start of a pat-
2155           tern is not considered until after a suitable starting  point  for  the
2156           match  has been found. When callouts or (*MARK) items are in use, these
2157           "start-up" optimizations can cause them to be skipped if the pattern is
2158           never  actually  used.  The start-up optimizations are in effect a pre-
2159           scan of the subject that takes place before the pattern is run.
2160    
2161           The PCRE_NO_START_OPTIMIZE option disables the start-up  optimizations,
2162           possibly  causing  performance  to  suffer,  but ensuring that in cases
2163           where the result is "no match", the callouts do occur, and  that  items
2164           such as (*COMMIT) and (*MARK) are considered at every possible starting
2165           position in the subject  string.   Setting  PCRE_NO_START_OPTIMIZE  can
2166           change the outcome of a matching operation.  Consider the pattern
2167    
2168             (*COMMIT)ABC
2169    
2170           When  this  is  compiled, PCRE records the fact that a match must start
2171           with the character "A". Suppose the subject  string  is  "DEFABC".  The
2172           start-up  optimization  scans along the subject, finds "A" and runs the
2173           first match attempt from there. The (*COMMIT) item means that the  pat-
2174           tern  must  match the current starting position, which in this case, it
2175           does. However, if the same match  is  run  with  PCRE_NO_START_OPTIMIZE
2176           set,  the  initial  scan  along the subject string does not happen. The
2177           first match attempt is run starting  from  "D"  and  when  this  fails,
2178           (*COMMIT)  prevents  any  further  matches  being tried, so the overall
2179           result is "no match". If the pattern is studied,  more  start-up  opti-
2180           mizations  may  be  used. For example, a minimum length for the subject
2181           may be recorded. Consider the pattern
2182    
2183             (*MARK:A)(X|Y)
2184    
2185           The minimum length for a match is one  character.  If  the  subject  is
2186           "ABC",  there  will  be  attempts  to  match "ABC", "BC", "C", and then
2187           finally an empty string.  If the pattern is studied, the final  attempt
2188           does  not take place, because PCRE knows that the subject is too short,
2189           and so the (*MARK) is never encountered.  In this  case,  studying  the
2190           pattern  does  not  affect the overall match result, which is still "no
2191           match", but it does affect the auxiliary information that is returned.
2192    
2193           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2194    
2195         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
2196         UTF-8 string is automatically checked when pcre_exec() is  subsequently         UTF-8  string is automatically checked when pcre_exec() is subsequently
2197         called.   The  value  of  startoffset is also checked to ensure that it         called.  The value of startoffset is also checked  to  ensure  that  it
2198         points to the start of a UTF-8 character. There is a  discussion  about         points  to  the start of a UTF-8 character. There is a discussion about
2199         the  validity  of  UTF-8 strings in the section on UTF-8 support in the         the validity of UTF-8 strings in the section on UTF-8  support  in  the
2200         main pcre page. If  an  invalid  UTF-8  sequence  of  bytes  is  found,         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,
2201         pcre_exec()  returns  the error PCRE_ERROR_BADUTF8. If startoffset con-         pcre_exec() returns  the  error  PCRE_ERROR_BADUTF8  or,  if  PCRE_PAR-
2202         tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.         TIAL_HARD  is set and the problem is a truncated UTF-8 character at the
2203           end of the subject, PCRE_ERROR_SHORTUTF8.  If  startoffset  contains  a
2204           value  that does not point to the start of a UTF-8 character (or to the
2205           end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2206    
2207         If you already know that your subject is valid, and you  want  to  skip         If you already know that your subject is valid, and you  want  to  skip
2208         these    checks    for   performance   reasons,   you   can   set   the         these    checks    for   performance   reasons,   you   can   set   the
# Line 1875  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2210  MATCHING A PATTERN: THE TRADITIONAL FUNC
2210         do  this  for the second and subsequent calls to pcre_exec() if you are         do  this  for the second and subsequent calls to pcre_exec() if you are
2211         making repeated calls to find all  the  matches  in  a  single  subject         making repeated calls to find all  the  matches  in  a  single  subject
2212         string.  However,  you  should  be  sure  that the value of startoffset         string.  However,  you  should  be  sure  that the value of startoffset
2213         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is         points to the start of a UTF-8 character (or the end of  the  subject).
2214         set,  the  effect of passing an invalid UTF-8 string as a subject, or a         When  PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8
2215         value of startoffset that does not point to the start of a UTF-8  char-         string as a subject or an invalid value of  startoffset  is  undefined.
2216         acter, is undefined. Your program may crash.         Your program may crash.
2217    
2218           PCRE_PARTIAL           PCRE_PARTIAL_HARD
2219             PCRE_PARTIAL_SOFT
2220         This  option  turns  on  the  partial  matching feature. If the subject  
2221         string fails to match the pattern, but at some point during the  match-         These  options turn on the partial matching feature. For backwards com-
2222         ing  process  the  end of the subject was reached (that is, the subject         patibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A  partial
2223         partially matches the pattern and the failure to  match  occurred  only         match  occurs if the end of the subject string is reached successfully,
2224         because  there were not enough subject characters), pcre_exec() returns         but there are not enough subject characters to complete the  match.  If
2225         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is         this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
2226         used,  there  are restrictions on what may appear in the pattern. These         matching continues by testing any remaining alternatives.  Only  if  no
2227         are discussed in the pcrepartial documentation.         complete  match  can be found is PCRE_ERROR_PARTIAL returned instead of
2228           PCRE_ERROR_NOMATCH. In other words,  PCRE_PARTIAL_SOFT  says  that  the
2229           caller  is  prepared to handle a partial match, but only if no complete
2230           match can be found.
2231    
2232           If PCRE_PARTIAL_HARD is set, it overrides  PCRE_PARTIAL_SOFT.  In  this
2233           case,  if  a  partial  match  is found, pcre_exec() immediately returns
2234           PCRE_ERROR_PARTIAL, without  considering  any  other  alternatives.  In
2235           other  words, when PCRE_PARTIAL_HARD is set, a partial match is consid-
2236           ered to be more important that an alternative complete match.
2237    
2238           In both cases, the portion of the string that was  inspected  when  the
2239           partial match was found is set as the first matching string. There is a
2240           more detailed discussion of partial and  multi-segment  matching,  with
2241           examples, in the pcrepartial documentation.
2242    
2243     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2244    
2245         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
2246         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.
2247         mode, the byte offset must point to the start  of  a  UTF-8  character.         If  this  is  negative  or  greater  than  the  length  of the subject,
2248         Unlike  the  pattern string, the subject may contain binary zero bytes.         pcre_exec() returns PCRE_ERROR_BADOFFSET. When the starting  offset  is
2249         When the starting offset is zero, the search for a match starts at  the         zero,  the  search  for a match starts at the beginning of the subject,
2250         beginning of the subject, and this is by far the most common case.         and this is by far the most common case. In UTF-8 mode, the byte offset
2251           must  point  to  the start of a UTF-8 character (or the end of the sub-
2252           ject). Unlike the pattern string, the subject may contain  binary  zero
2253           bytes.
2254    
2255         A  non-zero  starting offset is useful when searching for another match         A  non-zero  starting offset is useful when searching for another match
2256         in the same subject by calling pcre_exec() again after a previous  suc-         in the same subject by calling pcre_exec() again after a previous  suc-
# Line 1919  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2271  MATCHING A PATTERN: THE TRADITIONAL FUNC
2271         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
2272         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2273    
2274         If a non-zero starting offset is passed when the pattern  is  anchored,         Finding all the matches in a subject is tricky  when  the  pattern  can
2275           match an empty string. It is possible to emulate Perl's /g behaviour by
2276           first  trying  the  match  again  at  the   same   offset,   with   the
2277           PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED  options,  and  then  if that
2278           fails, advancing the starting  offset  and  trying  an  ordinary  match
2279           again. There is some code that demonstrates how to do this in the pcre-
2280           demo sample program. In the most general case, you have to check to see
2281           if  the newline convention recognizes CRLF as a newline, and if so, and
2282           the current character is CR followed by LF, advance the starting offset
2283           by two characters instead of one.
2284    
2285           If  a  non-zero starting offset is passed when the pattern is anchored,
2286         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
2287         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
2288         subject.         subject.
2289    
2290     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2291    
2292         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
2293         addition, further substrings from the subject  may  be  picked  out  by         addition,  further  substrings  from  the  subject may be picked out by
2294         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2295         this is called "capturing" in what follows, and the  phrase  "capturing         this  is  called "capturing" in what follows, and the phrase "capturing
2296         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-
2297         string. PCRE supports several other kinds of  parenthesized  subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2298         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2299    
2300         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2301         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-
2302         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:
2303         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2304    
2305         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-
2306         strings,  each  substring using a pair of integers. The remaining third         strings, each substring using a pair of integers. The  remaining  third
2307         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-
2308         turing  subpatterns, and is not available for passing back information.         turing subpatterns, and is not available for passing back  information.
2309         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
2310         it is not, it is rounded down.         it is not, it is rounded down.
2311    
2312         When  a  match  is successful, information about captured substrings is         When a match is successful, information about  captured  substrings  is
2313         returned in pairs of integers, starting at the  beginning  of  ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2314         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
2315         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
2316         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
2317         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
2318         tor[1],  identify  the  portion  of  the  subject string matched by the         byte offsets, even in UTF-8 mode. They are not character counts.
2319         entire pattern. The next pair is used for the first  capturing  subpat-  
2320         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
2321         highest numbered pair that has been set. For example, if two substrings         portion  of  the subject string matched by the entire pattern. The next
2322         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
2323         subpatterns, the return value from a successful match is 1,  indicating         returned by pcre_exec() is one more than the highest numbered pair that
2324         that just the first pair of offsets has been set.         has been set.  For example, if two substrings have been  captured,  the
2325           returned  value is 3. If there are no capturing subpatterns, the return
2326           value from a successful match is 1, indicating that just the first pair
2327           of offsets has been set.
2328    
2329         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2330         of the string that it matched that is returned.         of the string that it matched that is returned.
2331    
2332         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,
2333         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
2334         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
2335         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
2336         as NULL and ovecsize as zero. However, if  the  pattern  contains  back         ovecsize as zero. However, if the pattern contains back references  and
2337         references  and  the  ovector is not big enough to remember the related         the  ovector is not big enough to remember the related substrings, PCRE
2338         substrings, PCRE has to get additional memory for use during  matching.         has to get additional memory for use during matching. Thus it  is  usu-
2339         Thus it is usually advisable to supply an ovector.         ally advisable to supply an ovector.
2340    
2341         The  pcre_info()  function  can  be used to find out how many capturing         The pcre_fullinfo() function can be used to find out how many capturing
2342         subpatterns there are in a compiled  pattern.  The  smallest  size  for         subpatterns there are in a compiled  pattern.  The  smallest  size  for
2343         ovector  that  will allow for n captured substrings, in addition to the         ovector  that  will allow for n captured substrings, in addition to the
2344         offsets of the substring matched by the whole pattern, is (n+1)*3.         offsets of the substring matched by the whole pattern, is (n+1)*3.
# Line 1988  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2354  MATCHING A PATTERN: THE TRADITIONAL FUNC
2354         expression are also set to -1. For example,  if  the  string  "abc"  is         expression are also set to -1. For example,  if  the  string  "abc"  is
2355         matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not         matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
2356         matched. The return from the function is 2, because  the  highest  used         matched. The return from the function is 2, because  the  highest  used
2357         capturing subpattern number is 1. However, you can refer to the offsets         capturing  subpattern  number  is 1, and the offsets for for the second
2358         for the second and third capturing subpatterns if  you  wish  (assuming         and third capturing subpatterns (assuming the vector is  large  enough,
2359         the vector is large enough, of course).         of course) are set to -1.
2360    
2361           Note: Elements of ovector that do not correspond to capturing parenthe-
2362           ses in the pattern are never changed. That is, if a pattern contains  n
2363           capturing parentheses, no more than ovector[0] to ovector[2n+1] are set
2364           by pcre_exec(). The other elements retain whatever values  they  previ-
2365           ously had.
2366    
2367         Some  convenience  functions  are  provided for extracting the captured         Some  convenience  functions  are  provided for extracting the captured
2368         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
# Line 2035  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2407  MATCHING A PATTERN: THE TRADITIONAL FUNC
2407         purpose.  If the call via pcre_malloc() fails, this error is given. The         purpose.  If the call via pcre_malloc() fails, this error is given. The
2408         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2409    
2410           This error is also given if pcre_stack_malloc() fails  in  pcre_exec().
2411           This  can happen only when PCRE has been compiled with --disable-stack-
2412           for-recursion.
2413    
2414           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2415    
2416         This error is used by the pcre_copy_substring(),  pcre_get_substring(),         This error is used by the pcre_copy_substring(),  pcre_get_substring(),
# Line 2056  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2432  MATCHING A PATTERN: THE TRADITIONAL FUNC
2432           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2433    
2434         A string that contains an invalid UTF-8 byte sequence was passed  as  a         A string that contains an invalid UTF-8 byte sequence was passed  as  a
2435         subject.         subject.   However,  if  PCRE_PARTIAL_HARD  is set and the problem is a
2436           truncated UTF-8 character at the end of the subject,  PCRE_ERROR_SHORT-
2437           UTF8 is used instead.
2438    
2439           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2440    
2441         The UTF-8 byte sequence that was passed as a subject was valid, but the         The UTF-8 byte sequence that was passed as a subject was valid, but the
2442         value of startoffset did not point to the beginning of a UTF-8  charac-         value of startoffset did not point to the beginning of a UTF-8  charac-
2443         ter.         ter or the end of the subject.
2444    
2445           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2446    
# Line 2071  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2449  MATCHING A PATTERN: THE TRADITIONAL FUNC
2449    
2450           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2451    
2452         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing         This code is no longer in  use.  It  was  formerly  returned  when  the
2453         items  that are not supported for partial matching. See the pcrepartial         PCRE_PARTIAL  option  was used with a compiled pattern containing items
2454         documentation for details of partial matching.         that were  not  supported  for  partial  matching.  From  release  8.00
2455           onwards, there are no restrictions on partial matching.
2456    
2457           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2458    
2459         An unexpected internal error has occurred. This error could  be  caused         An  unexpected  internal error has occurred. This error could be caused
2460         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2461    
2462           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2463    
2464         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.
2465    
2466           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2467    
# Line 2094  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2473  MATCHING A PATTERN: THE TRADITIONAL FUNC
2473    
2474         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2475    
2476             PCRE_ERROR_BADOFFSET      (-24)
2477    
2478           The value of startoffset was negative or greater than the length of the
2479           subject, that is, the value in length.
2480    
2481             PCRE_ERROR_SHORTUTF8      (-25)
2482    
2483           The  subject  string ended with an incomplete (truncated) UTF-8 charac-
2484           ter, and the PCRE_PARTIAL_HARD option was  set.  Without  this  option,
2485           PCRE_ERROR_BADUTF8 is returned in this situation.
2486    
2487         Error numbers -16 to -20 and -22 are not used by pcre_exec().         Error numbers -16 to -20 and -22 are not used by pcre_exec().
2488    
2489    
# Line 2110  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2500  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2500         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2501              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2502    
2503         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
2504         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
2505         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2506         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
2507         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
2508         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
2509         substrings.         substrings.
2510    
2511         A substring that contains a binary zero is correctly extracted and  has         A  substring that contains a binary zero is correctly extracted and has
2512         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
2513         string.  However, you can process such a string  by  referring  to  the         string.   However,  you  can  process such a string by referring to the
2514         length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2515         string().  Unfortunately, the interface to pcre_get_substring_list() is         string().  Unfortunately, the interface to pcre_get_substring_list() is
2516         not  adequate for handling strings containing binary zeros, because the         not adequate for handling strings containing binary zeros, because  the
2517         end of the final string is not independently indicated.         end of the final string is not independently indicated.
2518    
2519         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-
2520         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
2521         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
2522         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2523         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
2524         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2525         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
2526         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
2527         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2528    
2529         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
2530         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
2531         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
2532         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
2533         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
2534         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2535         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2536         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
2537         the terminating zero, or one of these error codes:         the terminating zero, or one of these error codes:
2538    
2539           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2540    
2541         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
2542         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2543    
2544           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2545    
2546         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2547    
2548         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
2549         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
2550         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
2551         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
2552         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
2553         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
2554         error code         error code
2555    
2556           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2557    
2558         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2559    
2560         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
2561         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
2562         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
2563         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2564         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
2565         tive for unset substrings.         tive for unset substrings.
2566    
2567         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2568         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
2569         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2570         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
2571         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.
2572         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-
2573         cial  interface  to  another  programming  language  that  cannot   use         cial   interface  to  another  programming  language  that  cannot  use
2574         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-
2575         vided.         vided.
2576    
2577    
# Line 2200  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2590  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2590              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2591              const char **stringptr);              const char **stringptr);
2592    
2593         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-
2594         ber.  For example, for this pattern         ber.  For example, for this pattern
2595    
2596           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
# Line 2209  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2599  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2599         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
2600         name by calling pcre_get_stringnumber(). The first argument is the com-         name by calling pcre_get_stringnumber(). The first argument is the com-
2601         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
2602         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2603         subpattern of that name.         subpattern of that name.
2604    
2605         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
2606         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
2607         are also two functions that do the whole job.         are also two functions that do the whole job.
2608    
2609         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
2610         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
2611         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
2612         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
2613         differences:         differences:
2614    
2615         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
2616         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
2617         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
2618         name-to-number translation table.         name-to-number translation table.
2619    
2620         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2621         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2622         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
2623         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2624    
2625           Warning: If the pattern uses the (?| feature to set up multiple subpat-
2626           terns with the same number, as described in the  section  on  duplicate
2627           subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2628           distinguish the different subpatterns, because names are  not  included
2629           in  the compiled code. The matching process uses only numbers. For this
2630           reason, the use of different names for subpatterns of the  same  number
2631           causes an error at compile time.
2632    
2633    
2634  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
2635    
2636         int pcre_get_stringtable_entries(const pcre *code,         int pcre_get_stringtable_entries(const pcre *code,
2637              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2638    
2639         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2640         subpatterns  are  not  required  to  be unique. Normally, patterns with         subpatterns are not required to be unique. (Duplicate names are  always
2641         duplicate names are such that in any one match, only one of  the  named         allowed  for subpatterns with the same number, created by using the (?|
2642         subpatterns  participates. An example is shown in the pcrepattern docu-         feature. Indeed, if such subpatterns are named, they  are  required  to
2643         mentation.         use the same names.)
2644    
2645         When   duplicates   are   present,   pcre_copy_named_substring()    and         Normally, patterns with duplicate names are such that in any one match,
2646         pcre_get_named_substring()  return the first substring corresponding to         only one of the named subpatterns participates. An example is shown  in
2647         the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING         the pcrepattern documentation.
2648         (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()  
2649         function returns one of the numbers that are associated with the  name,         When    duplicates   are   present,   pcre_copy_named_substring()   and
2650           pcre_get_named_substring() return the first substring corresponding  to
2651           the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2652           (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2653           function  returns one of the numbers that are associated with the name,
2654         but it is not defined which it is.         but it is not defined which it is.
2655    
2656         If  you want to get full details of all captured substrings for a given         If you want to get full details of all captured substrings for a  given
2657         name, you must use  the  pcre_get_stringtable_entries()  function.  The         name,  you  must  use  the pcre_get_stringtable_entries() function. The
2658         first argument is the compiled pattern, and the second is the name. The         first argument is the compiled pattern, and the second is the name. The
2659         third and fourth are pointers to variables which  are  updated  by  the         third  and  fourth  are  pointers to variables which are updated by the
2660         function. After it has run, they point to the first and last entries in         function. After it has run, they point to the first and last entries in
2661         the name-to-number table  for  the  given  name.  The  function  itself         the  name-to-number  table  for  the  given  name.  The function itself
2662         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2663         there are none. The format of the table is described above in the  sec-         there  are none. The format of the table is described above in the sec-
2664         tion  entitled  Information  about  a  pattern.  Given all the relevant         tion entitled Information about a  pattern.   Given  all  the  relevant
2665         entries for the name, you can extract each of their numbers, and  hence         entries  for the name, you can extract each of their numbers, and hence
2666         the captured data, if any.         the captured data, if any.
2667    
2668    
2669  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
2670    
2671         The  traditional  matching  function  uses a similar algorithm to Perl,         The traditional matching function uses a  similar  algorithm  to  Perl,
2672         which stops when it finds the first match, starting at a given point in         which stops when it finds the first match, starting at a given point in
2673         the  subject.  If you want to find all possible matches, or the longest         the subject. If you want to find all possible matches, or  the  longest
2674         possible match, consider using the alternative matching  function  (see         possible  match,  consider using the alternative matching function (see
2675         below)  instead.  If you cannot use the alternative function, but still         below) instead. If you cannot use the alternative function,  but  still
2676         need to find all possible matches, you can kludge it up by  making  use         need  to  find all possible matches, you can kludge it up by making use
2677         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
2678         tation.         tation.
2679    
2680         What you have to do is to insert a callout right at the end of the pat-         What you have to do is to insert a callout right at the end of the pat-
2681         tern.   When your callout function is called, extract and save the cur-         tern.  When your callout function is called, extract and save the  cur-
2682         rent matched substring. Then return  1,  which  forces  pcre_exec()  to         rent  matched  substring.  Then  return  1, which forces pcre_exec() to
2683         backtrack  and  try other alternatives. Ultimately, when it runs out of         backtrack and try other alternatives. Ultimately, when it runs  out  of
2684         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2685    
2686    
# Line 2289  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2691  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2691              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
2692              int *workspace, int wscount);              int *workspace, int wscount);
2693    
2694         The function pcre_dfa_exec()  is  called  to  match  a  subject  string         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2695         against  a  compiled pattern, using a matching algorithm that scans the         against a compiled pattern, using a matching algorithm that  scans  the
2696         subject string just once, and does not backtrack.  This  has  different         subject  string  just  once, and does not backtrack. This has different
2697         characteristics  to  the  normal  algorithm, and is not compatible with         characteristics to the normal algorithm, and  is  not  compatible  with
2698         Perl. Some of the features of PCRE patterns are not  supported.  Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2699         theless,  there are times when this kind of matching can be useful. For         theless, there are times when this kind of matching can be useful.  For
2700         a discussion of the two matching algorithms, see the pcrematching docu-         a  discussion  of  the  two matching algorithms, and a list of features
2701         mentation.         that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2702           tion.
2703    
2704         The  arguments  for  the  pcre_dfa_exec()  function are the same as for         The  arguments  for  the  pcre_dfa_exec()  function are the same as for
2705         pcre_exec(), plus two extras. The ovector argument is used in a differ-         pcre_exec(), plus two extras. The ovector argument is used in a differ-
# Line 2331  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2734  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2734    
2735         The  unused  bits  of  the options argument for pcre_dfa_exec() must be         The  unused  bits  of  the options argument for pcre_dfa_exec() must be
2736         zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-         zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-
2737         LINE_xxx,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2738         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last         PCRE_NOTEMPTY_ATSTART,      PCRE_NO_UTF8_CHECK,       PCRE_BSR_ANYCRLF,
2739         three of these are the same as for pcre_exec(), so their description is         PCRE_BSR_UNICODE,  PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD, PCRE_PAR-
2740         not repeated here.         TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.  All but  the  last
2741           four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
2742           PCRE_PARTIAL         description is not repeated here.
2743    
2744         This has the same general effect as it does for  pcre_exec(),  but  the           PCRE_PARTIAL_HARD
2745         details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for           PCRE_PARTIAL_SOFT
2746         pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into  
2747         PCRE_ERROR_PARTIAL  if  the  end  of the subject is reached, there have         These have the same general effect as they do for pcre_exec(), but  the
2748         been no complete matches, but there is still at least one matching pos-         details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
2749         sibility.  The portion of the string that provided the partial match is         pcre_dfa_exec(), it returns PCRE_ERROR_PARTIAL if the end of  the  sub-
2750         set as the first matching string.         ject  is  reached  and there is still at least one matching possibility
2751           that requires additional characters. This happens even if some complete
2752           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2753           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2754           of  the  subject  is  reached, there have been no complete matches, but
2755           there is still at least one matching possibility. The  portion  of  the
2756           string  that  was inspected when the longest partial match was found is
2757           set as the first matching string  in  both  cases.   There  is  a  more
2758           detailed  discussion  of partial and multi-segment matching, with exam-
2759           ples, in the pcrepartial documentation.
2760    
2761           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2762    
# Line 2355  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2767  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2767    
2768           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2769    
2770         When  pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option, and         When pcre_dfa_exec() returns a partial match, it is possible to call it
2771         returns a partial match, it is possible to call it  again,  with  addi-         again, with additional subject characters, and have  it  continue  with
2772         tional  subject  characters,  and have it continue with the same match.         the  same match. The PCRE_DFA_RESTART option requests this action; when
2773         The PCRE_DFA_RESTART option requests this action; when it is  set,  the         it is set, the workspace and wscount options must  reference  the  same
2774         workspace  and wscount options must reference the same vector as before         vector  as  before  because data about the match so far is left in them
2775         because data about the match so far is left in  them  after  a  partial         after a partial match. There is more discussion of this facility in the
2776         match.  There  is  more  discussion of this facility in the pcrepartial         pcrepartial documentation.
        documentation.  
2777    
2778     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2779    
2780         When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-         When  pcre_dfa_exec()  succeeds, it may have matched more than one sub-
2781         string in the subject. Note, however, that all the matches from one run         string in the subject. Note, however, that all the matches from one run
2782         of the function start at the same point in  the  subject.  The  shorter         of  the  function  start  at the same point in the subject. The shorter
2783         matches  are all initial substrings of the longer matches. For example,         matches are all initial substrings of the longer matches. For  example,
2784         if the pattern         if the pattern
2785    
2786           <.*>           <.*>
# Line 2384  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2795  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2795           <something> <something else>           <something> <something else>
2796           <something> <something else> <something further>           <something> <something else> <something further>
2797    
2798         On success, the yield of the function is a number  greater  than  zero,         On  success,  the  yield of the function is a number greater than zero,
2799         which  is  the  number of matched substrings. The substrings themselves         which is the number of matched substrings.  The  substrings  themselves
2800         are returned in ovector. Each string uses two elements;  the  first  is         are  returned  in  ovector. Each string uses two elements; the first is
2801         the  offset  to  the start, and the second is the offset to the end. In         the offset to the start, and the second is the offset to  the  end.  In
2802         fact, all the strings have the same start  offset.  (Space  could  have         fact,  all  the  strings  have the same start offset. (Space could have
2803         been  saved by giving this only once, but it was decided to retain some         been saved by giving this only once, but it was decided to retain  some
2804         compatibility with the way pcre_exec() returns data,  even  though  the         compatibility  with  the  way pcre_exec() returns data, even though the
2805         meaning of the strings is different.)         meaning of the strings is different.)
2806    
2807         The strings are returned in reverse order of length; that is, the long-         The strings are returned in reverse order of length; that is, the long-
2808         est matching string is given first. If there were too many  matches  to         est  matching  string is given first. If there were too many matches to
2809         fit  into ovector, the yield of the function is zero, and the vector is         fit into ovector, the yield of the function is zero, and the vector  is
2810         filled with the longest matches.         filled with the longest matches.
2811    
2812     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2813    
2814         The pcre_dfa_exec() function returns a negative number when  it  fails.         The  pcre_dfa_exec()  function returns a negative number when it fails.
2815         Many  of  the  errors  are  the  same as for pcre_exec(), and these are         Many of the errors are the same  as  for  pcre_exec(),  and  these  are
2816         described above.  There are in addition the following errors  that  are         described  above.   There are in addition the following errors that are
2817         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2818    
2819           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2820    
2821         This  return is given if pcre_dfa_exec() encounters an item in the pat-         This return is given if pcre_dfa_exec() encounters an item in the  pat-
2822         tern that it does not support, for instance, the use of \C  or  a  back         tern  that  it  does not support, for instance, the use of \C or a back
2823         reference.         reference.
2824    
2825           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2826    
2827         This  return  is  given  if pcre_dfa_exec() encounters a condition item         This return is given if pcre_dfa_exec()  encounters  a  condition  item
2828         that uses a back reference for the condition, or a test  for  recursion         that  uses  a back reference for the condition, or a test for recursion
2829         in a specific group. These are not supported.         in a specific group. These are not supported.
2830    
2831           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2832    
2833         This  return  is given if pcre_dfa_exec() is called with an extra block         This return is given if pcre_dfa_exec() is called with an  extra  block
2834         that contains a setting of the match_limit field. This is not supported         that contains a setting of the match_limit field. This is not supported
2835         (it is meaningless).         (it is meaningless).
2836    
2837           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2838    
2839         This  return  is  given  if  pcre_dfa_exec()  runs  out of space in the         This return is given if  pcre_dfa_exec()  runs  out  of  space  in  the
2840         workspace vector.         workspace vector.
2841    
2842           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2843    
2844         When a recursive subpattern is processed, the matching  function  calls         When  a  recursive subpattern is processed, the matching function calls
2845         itself  recursively,  using  private vectors for ovector and workspace.         itself recursively, using private vectors for  ovector  and  workspace.
2846         This error is given if the output vector  is  not  large  enough.  This         This  error  is  given  if  the output vector is not large enough. This
2847         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2848    
2849    
2850  SEE ALSO  SEE ALSO
2851    
2852         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
2853         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3),  pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2854    
2855    
2856  AUTHOR  AUTHOR
# Line 2451  AUTHOR Line 2862  AUTHOR
2862    
2863  REVISION  REVISION
2864    
2865         Last updated: 09 August 2007         Last updated: 13 November 2010
2866         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
2867  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2868    
2869    
2870  PCRECALLOUT(3)                                                  PCRECALLOUT(3)  PCRECALLOUT(3)                                                  PCRECALLOUT(3)
2871    
2872    
# Line 2481  PCRE CALLOUTS Line 2892  PCRE CALLOUTS
2892    
2893           (?C1)abc(?C2)def           (?C1)abc(?C2)def
2894    
2895         If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() is         If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() or
2896         called, PCRE automatically  inserts  callouts,  all  with  number  255,         pcre_compile2() is called, PCRE  automatically  inserts  callouts,  all
2897         before  each  item in the pattern. For example, if PCRE_AUTO_CALLOUT is         with  number  255,  before  each  item  in the pattern. For example, if
2898         used with the pattern         PCRE_AUTO_CALLOUT is used with the pattern
2899    
2900           A(\d{2}|--)           A(\d{2}|--)
2901    
# Line 2503  PCRE CALLOUTS Line 2914  PCRE CALLOUTS
2914  MISSING CALLOUTS  MISSING CALLOUTS
2915    
2916         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
2917         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
2918         pattern is         example, if the pattern is
2919    
2920           ab(?C4)cd           ab(?C4)cd
2921    
# Line 2513  MISSING CALLOUTS Line 2924  MISSING CALLOUTS
2924         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
2925         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
2926    
2927           If the pattern is studied, PCRE knows the minimum length of a  matching
2928           string,  and will immediately give a "no match" return without actually
2929           running a match if the subject is not long enough, or,  for  unanchored
2930           patterns, if it has been scanned far enough.
2931    
2932           You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
2933           MIZE option to pcre_exec() or  pcre_dfa_exec().  This  slows  down  the
2934           matching  process,  but  does  ensure that callouts such as the example
2935           above are obeyed.
2936    
2937    
2938  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2939    
# Line 2540  THE CALLOUT INTERFACE Line 2961  THE CALLOUT INTERFACE
2961         version number will change again in future  if  additional  fields  are         version number will change again in future  if  additional  fields  are
2962         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.
2963    
2964         The callout_number field contains the number of the  callout,  as  com-         The  callout_number  field  contains the number of the callout, as com-
2965         piled  into  the pattern (that is, the number after ?C for manual call-         piled into the pattern (that is, the number after ?C for  manual  call-
2966         outs, and 255 for automatically generated callouts).         outs, and 255 for automatically generated callouts).
2967    
2968         The offset_vector field is a pointer to the vector of offsets that  was         The  offset_vector field is a pointer to the vector of offsets that was
2969         passed   by   the   caller  to  pcre_exec()  or  pcre_dfa_exec().  When         passed  by  the  caller  to  pcre_exec()   or   pcre_dfa_exec().   When
2970         pcre_exec() is used, the contents can be inspected in order to  extract         pcre_exec()  is used, the contents can be inspected in order to extract
2971         substrings  that  have  been  matched  so  far,  in the same way as for         substrings that have been matched so  far,  in  the  same  way  as  for
2972         extracting substrings after a match has completed. For  pcre_dfa_exec()         extracting  substrings after a match has completed. For pcre_dfa_exec()
2973         this field is not useful.         this field is not useful.
2974    
2975         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
2976         were passed to pcre_exec().         were passed to pcre_exec().
2977    
2978         The start_match field normally contains the offset within  the  subject         The  start_match  field normally contains the offset within the subject
2979         at  which  the  current  match  attempt started. However, if the escape         at which the current match attempt  started.  However,  if  the  escape
2980         sequence \K has been encountered, this value is changed to reflect  the         sequence  \K has been encountered, this value is changed to reflect the
2981         modified  starting  point.  If the pattern is not anchored, the callout         modified starting point. If the pattern is not  anchored,  the  callout
2982         function may be called several times from the same point in the pattern         function may be called several times from the same point in the pattern
2983         for different starting points in the subject.         for different starting points in the subject.
2984    
2985         The  current_position  field  contains the offset within the subject of         The current_position field contains the offset within  the  subject  of
2986         the current match pointer.         the current match pointer.
2987    
2988         When the pcre_exec() function is used, the capture_top  field  contains         When  the  pcre_exec() function is used, the capture_top field contains
2989         one  more than the number of the highest numbered captured substring so         one more than the number of the highest numbered captured substring  so
2990         far. If no substrings have been captured, the value of  capture_top  is         far.  If  no substrings have been captured, the value of capture_top is
2991         one.  This  is always the case when pcre_dfa_exec() is used, because it         one. This is always the case when pcre_dfa_exec() is used,  because  it
2992         does not support captured substrings.         does not support captured substrings.
2993    
2994         The capture_last field contains the number of the  most  recently  cap-         The  capture_last  field  contains the number of the most recently cap-
2995         tured  substring. If no substrings have been captured, its value is -1.         tured substring. If no substrings have been captured, its value is  -1.
2996         This is always the case when pcre_dfa_exec() is used.         This is always the case when pcre_dfa_exec() is used.
2997    
2998         The callout_data field contains a value that is passed  to  pcre_exec()         The  callout_data  field contains a value that is passed to pcre_exec()
2999         or  pcre_dfa_exec() specifically so that it can be passed back in call-         or pcre_dfa_exec() specifically so that it can be passed back in  call-
3000         outs. It is passed in the pcre_callout field  of  the  pcre_extra  data         outs.  It  is  passed  in the pcre_callout field of the pcre_extra data
3001         structure.  If  no such data was passed, the value of callout_data in a         structure. If no such data was passed, the value of callout_data  in  a
3002         pcre_callout block is NULL. There is a description  of  the  pcre_extra         pcre_callout  block  is  NULL. There is a description of the pcre_extra
3003         structure in the pcreapi documentation.         structure in the pcreapi documentation.
3004    
3005         The  pattern_position field is present from version 1 of the pcre_call-         The pattern_position field is present from version 1 of the  pcre_call-
3006         out structure. It contains the offset to the next item to be matched in         out structure. It contains the offset to the next item to be matched in
3007         the pattern string.         the pattern string.
3008    
3009         The  next_item_length field is present from version 1 of the pcre_call-         The next_item_length field is present from version 1 of the  pcre_call-
3010         out structure. It contains the length of the next item to be matched in         out structure. It contains the length of the next item to be matched in
3011         the  pattern  string. When the callout immediately precedes an alterna-         the pattern string. When the callout immediately precedes  an  alterna-
3012         tion bar, a closing parenthesis, or the end of the pattern, the  length         tion  bar, a closing parenthesis, or the end of the pattern, the length
3013         is  zero.  When the callout precedes an opening parenthesis, the length         is zero. When the callout precedes an opening parenthesis,  the  length
3014         is that of the entire subpattern.         is that of the entire subpattern.
3015    
3016         The pattern_position and next_item_length fields are intended  to  help         The  pattern_position  and next_item_length fields are intended to help
3017         in  distinguishing between different automatic callouts, which all have         in distinguishing between different automatic callouts, which all  have
3018         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
3019    
3020    
3021  RETURN VALUES  RETURN VALUES
3022    
3023         The external callout function returns an integer to PCRE. If the  value         The  external callout function returns an integer to PCRE. If the value
3024         is  zero,  matching  proceeds  as  normal. If the value is greater than         is zero, matching proceeds as normal. If  the  value  is  greater  than
3025         zero, matching fails at the current point, but  the  testing  of  other         zero,  matching  fails  at  the current point, but the testing of other
3026         matching possibilities goes ahead, just as if a lookahead assertion had         matching possibilities goes ahead, just as if a lookahead assertion had
3027         failed. If the value is less than zero, the  match  is  abandoned,  and         failed.  If  the  value  is less than zero, the match is abandoned, and
3028         pcre_exec() (or pcre_dfa_exec()) returns the negative value.         pcre_exec() or pcre_dfa_exec() returns the negative value.
3029    
3030         Negative   values   should   normally   be   chosen  from  the  set  of         Negative  values  should  normally  be   chosen   from   the   set   of
3031         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
3032         dard  "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT is         dard "no  match"  failure.   The  error  number  PCRE_ERROR_CALLOUT  is
3033         reserved for use by callout functions; it will never be  used  by  PCRE         reserved  for  use  by callout functions; it will never be used by PCRE
3034         itself.         itself.
3035    
3036    
# Line 2622  AUTHOR Line 3043  AUTHOR
3043    
3044  REVISION  REVISION
3045    
3046         Last updated: 29 May 2007         Last updated: 29 September 2009
3047         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
3048  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3049    
3050    
3051  PCRECOMPAT(3)                                                    PCRECOMPAT(3)  PCRECOMPAT(3)                                                    PCRECOMPAT(3)
3052    
3053    
# Line 2637  NAME Line 3058  NAME
3058  DIFFERENCES BETWEEN PCRE AND PERL  DIFFERENCES BETWEEN PCRE AND PERL
3059    
3060         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
3061         handle regular expressions. The differences described here  are  mainly         handle regular expressions. The differences  described  here  are  with
3062         with  respect  to  Perl 5.8, though PCRE versions 7.0 and later contain         respect to Perl versions 5.10 and above.
        some features that are expected to be in the forthcoming Perl 5.10.  
3063    
3064         1. PCRE has only a subset of Perl's UTF-8 and Unicode support.  Details         1.  PCRE has only a subset of Perl's UTF-8 and Unicode support. Details
3065         of  what  it does have are given in the section on UTF-8 support in the         of what it does have are given in the section on UTF-8 support  in  the
3066         main pcre page.         main pcre page.
3067    
3068         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl
3069         permits  them,  but they do not mean what you might think. For example,         permits them, but they do not mean what you might think.  For  example,
3070         (?!a){3} does not assert that the next three characters are not "a". It         (?!a){3} does not assert that the next three characters are not "a". It
3071         just asserts that the next character is not "a" three times.         just asserts that the next character is not "a" three times.
3072    
3073         3.  Capturing  subpatterns  that occur inside negative lookahead asser-         3. Capturing subpatterns that occur inside  negative  lookahead  asser-
3074         tions are counted, but their entries in the offsets  vector  are  never         tions  are  counted,  but their entries in the offsets vector are never
3075         set.  Perl sets its numerical variables from any such patterns that are         set. Perl sets its numerical variables from any such patterns that  are
3076         matched before the assertion fails to match something (thereby succeed-         matched before the assertion fails to match something (thereby succeed-
3077         ing),  but  only  if the negative lookahead assertion contains just one         ing), but only if the negative lookahead assertion  contains  just  one
3078         branch.         branch.
3079    
3080         4. Though binary zero characters are supported in the  subject  string,         4.  Though  binary zero characters are supported in the subject string,
3081         they are not allowed in a pattern string because it is passed as a nor-         they are not allowed in a pattern string because it is passed as a nor-
3082         mal C string, terminated by zero. The escape sequence \0 can be used in         mal C string, terminated by zero. The escape sequence \0 can be used in
3083         the pattern to represent a binary zero.         the pattern to represent a binary zero.
3084    
3085         5.  The  following Perl escape sequences are not supported: \l, \u, \L,         5. The following Perl escape sequences are not supported: \l,  \u,  \L,
3086         \U, and \N. In fact these are implemented by Perl's general string-han-         \U, and \N. In fact these are implemented by Perl's general string-han-
3087         dling  and are not part of its pattern matching engine. If any of these         dling and are not part of its pattern matching engine. If any of  these
3088         are encountered by PCRE, an error is generated.         are encountered by PCRE, an error is generated.
3089    
3090         6. The Perl escape sequences \p, \P, and \X are supported only if  PCRE         6.  The Perl escape sequences \p, \P, and \X are supported only if PCRE
3091         is  built  with Unicode character property support. The properties that         is built with Unicode character property support. The  properties  that
3092         can be tested with \p and \P are limited to the general category  prop-         can  be tested with \p and \P are limited to the general category prop-
3093         erties  such  as  Lu and Nd, script names such as Greek or Han, and the         erties such as Lu and Nd, script names such as Greek or  Han,  and  the
3094         derived properties Any and L&.         derived  properties  Any  and  L&. PCRE does support the Cs (surrogate)
3095           property, which Perl does not; the  Perl  documentation  says  "Because
3096           Perl hides the need for the user to understand the internal representa-
3097           tion of Unicode characters, there is no need to implement the  somewhat
3098           messy concept of surrogates."
3099    
3100         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-
3101         ters  in  between  are  treated as literals. This is slightly different         ters in between are treated as literals.  This  is  slightly  different
3102         from Perl in that $ and @ are  also  handled  as  literals  inside  the         from  Perl  in  that  $  and  @ are also handled as literals inside the
3103         quotes.  In Perl, they cause variable interpolation (but of course PCRE         quotes. In Perl, they cause variable interpolation (but of course  PCRE
3104         does not have variables). Note the following examples:         does not have variables). Note the following examples:
3105    
3106             Pattern            PCRE matches      Perl matches             Pattern            PCRE matches      Perl matches
# Line 2686  DIFFERENCES BETWEEN PCRE AND PERL Line 3110  DIFFERENCES BETWEEN PCRE AND PERL
3110             \Qabc\$xyz\E       abc\$xyz          abc\$xyz             \Qabc\$xyz\E       abc\$xyz          abc\$xyz
3111             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
3112    
3113         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
3114         classes.         classes.
3115    
3116         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
3117         constructions. However, there is support for recursive  patterns.  This         constructions.  However,  there is support for recursive patterns. This
3118         is  not available in Perl 5.8, but will be in Perl 5.10. Also, the PCRE         is not available in Perl 5.8, but it is in Perl 5.10.  Also,  the  PCRE
3119         "callout" feature allows an external function to be called during  pat-         "callout"  feature allows an external function to be called during pat-
3120         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
3121    
3122         9.  Subpatterns  that  are  called  recursively or as "subroutines" are         9. Subpatterns that are called  recursively  or  as  "subroutines"  are
3123         always treated as atomic groups in  PCRE.  This  is  like  Python,  but         always  treated  as  atomic  groups  in  PCRE. This is like Python, but
3124         unlike Perl.         unlike Perl. There is a discussion of an example that explains this  in
3125           more  detail  in  the section on recursion differences from Perl in the
3126         10.  There are some differences that are concerned with the settings of         pcrepattern page.
3127         captured strings when part of  a  pattern  is  repeated.  For  example,  
3128         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2         10. There are some differences that are concerned with the settings  of
3129           captured  strings  when  part  of  a  pattern is repeated. For example,
3130           matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2
3131         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
3132    
3133         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),         11.  PCRE's handling of duplicate subpattern numbers and duplicate sub-
3134         (*FAIL),  (*F),  (*COMMIT), (*PRUNE), (*SKIP), and (*THEN), but only in         pattern names is not as general as Perl's. This is a consequence of the
3135         the forms without an  argument.  PCRE  does  not  support  (*MARK).  If         fact the PCRE works internally just with numbers, using an external ta-
3136         (*ACCEPT)  is within capturing parentheses, PCRE does not set that cap-         ble to translate between numbers and names. In  particular,  a  pattern
3137         ture group; this is different to Perl.         such  as  (?|(?<a>A)|(?<b)B),  where the two capturing parentheses have
3138           the same number but different names, is not supported,  and  causes  an
3139         12. PCRE provides some extensions to the Perl regular expression facil-         error  at compile time. If it were allowed, it would not be possible to
3140         ities.   Perl  5.10  will  include new features that are not in earlier         distinguish which parentheses matched, because both names map  to  cap-
3141         versions, some of which (such as named parentheses) have been  in  PCRE         turing subpattern number 1. To avoid this confusing situation, an error
3142         for some time. This list is with respect to Perl 5.10:         is given at compile time.
3143    
3144         (a)  Although  lookbehind  assertions  must match fixed length strings,         12. Perl recognizes comments in some  places  that  PCRE  doesn't,  for
3145         each alternative branch of a lookbehind assertion can match a different         example, between the ( and ? at the start of a subpattern.
3146         length of string. Perl requires them all to have the same length.  
3147           13. PCRE provides some extensions to the Perl regular expression facil-
3148           ities.  Perl 5.10 includes new features that are not  in  earlier  ver-
3149           sions  of  Perl, some of which (such as named parentheses) have been in
3150           PCRE for some time. This list is with respect to Perl 5.10:
3151    
3152           (a) Although lookbehind assertions in  PCRE  must  match  fixed  length
3153           strings,  each alternative branch of a lookbehind assertion can match a
3154           different length of string. Perl requires them all  to  have  the  same
3155           length.
3156    
3157         (b)  If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $         (b)  If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $
3158         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
# Line 2733  DIFFERENCES BETWEEN PCRE AND PERL Line 3168  DIFFERENCES BETWEEN PCRE AND PERL
3168         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be
3169         tried only at the first matching position in the subject string.         tried only at the first matching position in the subject string.
3170    
3171         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
3172         TURE options for pcre_exec() have no Perl equivalents.         and PCRE_NO_AUTO_CAPTURE options for pcre_exec() have no  Perl  equiva-
3173           lents.
3174    
3175         (g) The callout facility is PCRE-specific.         (g)  The  \R escape sequence can be restricted to match only CR, LF, or
3176           CRLF by the PCRE_BSR_ANYCRLF option.
3177    
3178         (h) The partial matching facility is PCRE-specific.         (h) The callout facility is PCRE-specific.
3179    
3180         (i) Patterns compiled by PCRE can be saved and re-used at a later time,         (i) The partial matching facility is PCRE-specific.
3181    
3182           (j) Patterns compiled by PCRE can be saved and re-used at a later time,
3183         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
3184    
3185         (j)  The  alternative  matching function (pcre_dfa_exec()) matches in a         (k)  The  alternative  matching function (pcre_dfa_exec()) matches in a
3186         different way and is not Perl-compatible.         different way and is not Perl-compatible.
3187    
3188           (l) PCRE recognizes some special sequences such as (*CR) at  the  start
3189           of a pattern that set overall options that cannot be changed within the
3190           pattern.
3191    
3192    
3193  AUTHOR  AUTHOR
3194    
# Line 2756  AUTHOR Line 3199  AUTHOR
3199    
3200  REVISION  REVISION
3201    
3202         Last updated: 08 August 2007         Last updated: 31 October 2010
3203         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
3204  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3205    
3206    
3207  PCREPATTERN(3)                                                  PCREPATTERN(3)  PCREPATTERN(3)                                                  PCREPATTERN(3)
3208    
3209    
# Line 2772  PCRE REGULAR EXPRESSION DETAILS Line 3215  PCRE REGULAR EXPRESSION DETAILS
3215    
3216         The  syntax and semantics of the regular expressions that are supported         The  syntax and semantics of the regular expressions that are supported
3217         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-
3218         tax  summary  in  the  pcresyntax  page. Perl's regular expressions are         tax summary in the pcresyntax page. PCRE tries to match Perl syntax and
3219         described in its own documentation, and regular expressions in  general         semantics as closely as it can. PCRE  also  supports  some  alternative
3220         are  covered in a number of books, some of which have copious examples.         regular  expression  syntax (which does not conflict with the Perl syn-
3221         Jeffrey  Friedl's  "Mastering  Regular   Expressions",   published   by         tax) in order to provide some compatibility with regular expressions in
3222         O'Reilly,  covers regular expressions in great detail. This description         Python, .NET, and Oniguruma.
3223         of PCRE's regular expressions is intended as reference material.  
3224           Perl's  regular expressions are described in its own documentation, and
3225           regular expressions in general are covered in a number of  books,  some
3226           of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
3227           Expressions", published by  O'Reilly,  covers  regular  expressions  in
3228           great  detail.  This  description  of  PCRE's  regular  expressions  is
3229           intended as reference material.
3230    
3231         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
3232         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
3233         this, you must build PCRE to  include  UTF-8  support,  and  then  call         this, PCRE must be built to include UTF-8 support, and  you  must  call
3234         pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern         pcre_compile()  or  pcre_compile2() with the PCRE_UTF8 option. There is
3235         matching is mentioned in several places below. There is also a  summary         also a special sequence that can be given at the start of a pattern:
3236         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre  
3237         page.           (*UTF8)
3238    
3239           Starting a pattern with this sequence  is  equivalent  to  setting  the
3240           PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3241           UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3242           below.  There  is  also  a  summary of UTF-8 features in the section on
3243           UTF-8 support in the main pcre page.
3244    
3245           Another special sequence that may appear at the start of a  pattern  or
3246           in combination with (*UTF8) is:
3247    
3248             (*UCP)
3249    
3250           This  has  the  same  effect  as setting the PCRE_UCP option: it causes
3251           sequences such as \d and \w to  use  Unicode  properties  to  determine
3252           character types, instead of recognizing only characters with codes less
3253           than 128 via a lookup table.
3254    
3255         The remainder of this document discusses the  patterns  that  are  sup-         The remainder of this document discusses the  patterns  that  are  sup-
3256         ported  by  PCRE when its main matching function, pcre_exec(), is used.         ported  by  PCRE when its main matching function, pcre_exec(), is used.
# Line 2797  PCRE REGULAR EXPRESSION DETAILS Line 3262  PCRE REGULAR EXPRESSION DETAILS
3262         discussed in the pcrematching page.         discussed in the pcrematching page.
3263    
3264    
3265    NEWLINE CONVENTIONS
3266    
3267           PCRE  supports five different conventions for indicating line breaks in
3268           strings: a single CR (carriage return) character, a  single  LF  (line-
3269           feed) character, the two-character sequence CRLF, any of the three pre-
3270           ceding, or any Unicode newline sequence. The pcreapi page  has  further
3271           discussion  about newlines, and shows how to set the newline convention
3272           in the options arguments for the compiling and matching functions.
3273    
3274           It is also possible to specify a newline convention by starting a  pat-
3275           tern string with one of the following five sequences:
3276    
3277             (*CR)        carriage return
3278             (*LF)        linefeed
3279             (*CRLF)      carriage return, followed by linefeed
3280             (*ANYCRLF)   any of the three above
3281             (*ANY)       all Unicode newline sequences
3282    
3283           These  override  the default and the options given to pcre_compile() or
3284           pcre_compile2(). For example, on a Unix system where LF is the  default
3285           newline sequence, the pattern
3286    
3287             (*CR)a.b
3288    
3289           changes the convention to CR. That pattern matches "a\nb" because LF is
3290           no longer a newline. Note that these special settings,  which  are  not
3291           Perl-compatible,  are  recognized  only at the very start of a pattern,
3292           and that they must be in upper case.  If  more  than  one  of  them  is
3293           present, the last one is used.
3294    
3295           The  newline convention affects the interpretation of the dot metachar-
3296           acter when PCRE_DOTALL is not set, and also the behaviour of  \N.  How-
3297           ever,  it  does  not  affect  what  the  \R escape sequence matches. By
3298           default, this is any Unicode newline sequence, for Perl  compatibility.
3299           However,  this can be changed; see the description of \R in the section
3300           entitled "Newline sequences" below. A change of \R setting can be  com-
3301           bined with a change of newline convention.
3302    
3303    
3304  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
3305    
3306         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 3356  CHARACTERS AND METACHARACTERS
3356                    syntax)                    syntax)
3357           ]      terminates the character class           ]      terminates the character class
3358    
3359         The  following sections describe the use of each of the metacharacters.         The following sections describe the use of each of the metacharacters.
3360    
3361    
3362  BACKSLASH  BACKSLASH
3363    
3364         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3365         a  non-alphanumeric  character,  it takes away any special meaning that         a non-alphanumeric character, it takes away any  special  meaning  that
3366         character may have. This  use  of  backslash  as  an  escape  character         character  may  have.  This  use  of  backslash  as an escape character
3367         applies both inside and outside character classes.         applies both inside and outside character classes.
3368    
3369         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
3370         pattern.  This escaping action applies whether  or  not  the  following         pattern.   This  escaping  action  applies whether or not the following
3371         character  would  otherwise be interpreted as a metacharacter, so it is         character would otherwise be interpreted as a metacharacter, so  it  is
3372         always safe to precede a non-alphanumeric  with  backslash  to  specify         always  safe  to  precede  a non-alphanumeric with backslash to specify
3373         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-
3374         slash, you write \\.         slash, you write \\.
3375    
3376         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in
3377         the  pattern (other than in a character class) and characters between a         the pattern (other than in a character class) and characters between  a
3378         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
3379         ing  backslash  can  be  used to include a whitespace or # character as         ing backslash can be used to include a whitespace  or  #  character  as
3380         part of the pattern.         part of the pattern.
3381    
3382         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-
3383         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-
3384         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
3385         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-
3386         tion. Note the following examples:         tion. Note the following examples:
3387    
3388           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 2888  BACKSLASH Line 3392  BACKSLASH
3392           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
3393           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3394    
3395         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
3396         classes.         classes.  An isolated \E that is not preceded by \Q is ignored.
3397    
3398     Non-printing characters     Non-printing characters
3399    
3400         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-
3401         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
3402         appearance  of non-printing characters, apart from the binary zero that         appearance of non-printing characters, apart from the binary zero  that
3403         terminates a pattern, but when a pattern  is  being  prepared  by  text         terminates  a  pattern,  but  when  a pattern is being prepared by text
3404         editing,  it  is  usually  easier  to  use  one of the following escape         editing, it is  often  easier  to  use  one  of  the  following  escape
3405         sequences than the binary character it represents:         sequences than the binary character it represents:
3406    
3407           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3408           \cx       "control-x", where x is any character           \cx       "control-x", where x is any character
3409           \e        escape (hex 1B)           \e        escape (hex 1B)
3410           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3411           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3412           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3413           \t        tab (hex 09)           \t        tab (hex 09)
3414           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or back reference
3415           \xhh      character with hex code hh           \xhh      character with hex code hh
3416           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh..
3417    
3418         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,
3419         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
3420         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;
3421         becomes hex 7B.         becomes hex 7B.
3422    
3423         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
3424         in upper or lower case). Any number of hexadecimal  digits  may  appear         in  upper  or  lower case). Any number of hexadecimal digits may appear
3425         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
3426         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,
3427         the  maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger         the maximum value in hexadecimal is 7FFFFFFF. Note that this is  bigger
3428         than the largest Unicode code point, which is 10FFFF.         than the largest Unicode code point, which is 10FFFF.
3429    
3430         If characters other than hexadecimal digits appear between \x{  and  },         If  characters  other than hexadecimal digits appear between \x{ and },
3431         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.
3432         Instead, the initial \x will be  interpreted  as  a  basic  hexadecimal         Instead,  the  initial  \x  will  be interpreted as a basic hexadecimal
3433         escape,  with  no  following  digits, giving a character whose value is         escape, with no following digits, giving a  character  whose  value  is
3434         zero.         zero.
3435    
3436         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
3437         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-
3438         dled. For example, \xdc is exactly the same as \x{dc}.         dled. For example, \xdc is exactly the same as \x{dc}.
3439    
3440         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
3441         than  two  digits,  just  those  that  are  present  are used. Thus the         than two digits, just  those  that  are  present  are  used.  Thus  the
3442         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
3443         (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
3444         if the pattern character that follows is itself an octal digit.         if the pattern character that follows is itself an octal digit.
3445    
3446         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-
3447         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
3448         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
3449         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
3450         expression, the entire  sequence  is  taken  as  a  back  reference.  A         expression,  the  entire  sequence  is  taken  as  a  back reference. A
3451         description  of how this works is given later, following the discussion         description of how this works is given later, following the  discussion
3452         of parenthesized subpatterns.         of parenthesized subpatterns.
3453    
3454         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
3455         and  there have not been that many capturing subpatterns, PCRE re-reads         and there have not been that many capturing subpatterns, PCRE  re-reads
3456         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-
3457         erate  a data character. Any subsequent digits stand for themselves. In         erate a data character. Any subsequent digits stand for themselves.  In
3458         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
3459         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
3460         example:         example:
3461    
3462           \040   is another way of writing a space           \040   is another way of writing a space
# Line 2970  BACKSLASH Line 3474  BACKSLASH
3474           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
3475                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
3476    
3477         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
3478         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
3479    
3480         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
3481         inside and outside character classes. In addition, inside  a  character         inside  and  outside character classes. In addition, inside a character
3482         class,  the  sequence \b is interpreted as the backspace character (hex         class, the sequence \b is interpreted as the backspace  character  (hex
3483         08), and the sequences \R and \X are interpreted as the characters  "R"         08).  The sequences \B, \N, \R, and \X are not special inside a charac-
3484         and  "X", respectively. Outside a character class, these sequences have         ter class. Like any  other  unrecognized  escape  sequences,  they  are
3485         different meanings (see below).         treated  as  the  literal characters "B", "N", "R", and "X" by default,
3486           but cause an error if the PCRE_EXTRA option is set. Outside a character
3487           class, these sequences have different meanings.
3488    
3489     Absolute and relative back references     Absolute and relative back references
3490    
3491         The sequence \g followed by an unsigned or a negative  number,  option-         The  sequence  \g followed by an unsigned or a negative number, option-
3492         ally  enclosed  in braces, is an absolute or relative back reference. A         ally enclosed in braces, is an absolute or relative back  reference.  A
3493         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-
3494         cussed later, following the discussion of parenthesized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3495    
3496       Absolute and relative subroutine calls
3497    
3498           For compatibility with Oniguruma, the non-Perl syntax \g followed by  a
3499           name or a number enclosed either in angle brackets or single quotes, is
3500           an alternative syntax for referencing a subpattern as  a  "subroutine".
3501           Details  are  discussed  later.   Note  that  \g{...} (Perl syntax) and
3502           \g<...> (Oniguruma syntax) are not synonymous. The  former  is  a  back
3503           reference; the latter is a subroutine call.
3504    
3505     Generic character types     Generic character types
3506    
3507         Another use of backslash is for specifying generic character types. The         Another use of backslash is for specifying generic character types:
        following are always recognized:  
3508    
3509           \d     any decimal digit           \d     any decimal digit
3510           \D     any character that is not a decimal digit           \D     any character that is not a decimal digit
# Line 3003  BACKSLASH Line 3517  BACKSLASH
3517           \w     any "word" character           \w     any "word" character
3518           \W     any "non-word" character           \W     any "non-word" character
3519    
3520         Each pair of escape sequences partitions the complete set of characters         There is also the single sequence \N, which matches a non-newline char-
3521         into  two disjoint sets. Any given character matches one, and only one,         acter.  This is the same as the "." metacharacter when  PCRE_DOTALL  is
3522         of each pair.         not set.
3523    
3524         These character type sequences can appear both inside and outside char-         Each  pair of lower and upper case escape sequences partitions the com-
3525         acter  classes.  They each match one character of the appropriate type.         plete set of characters into two disjoint  sets.  Any  given  character
3526         If the current matching point is at the end of the subject string,  all         matches  one, and only one, of each pair. The sequences can appear both
3527         of them fail, since there is no character to match.         inside and outside character classes. They each match one character  of
3528           the  appropriate  type.  If the current matching point is at the end of
3529           the subject string, all of them fail, because there is no character  to
3530           match.
3531    
3532         For  compatibility  with Perl, \s does not match the VT character (code         For  compatibility  with Perl, \s does not match the VT character (code
3533         11).  This makes it different from the the POSIX "space" class. The  \s         11).  This makes it different from the the POSIX "space" class. The  \s
# Line 3018  BACKSLASH Line 3535  BACKSLASH
3535         "use locale;" is included in a Perl script, \s may match the VT charac-         "use locale;" is included in a Perl script, \s may match the VT charac-
3536         ter. In PCRE, it never does.         ter. In PCRE, it never does.
3537    
3538         In  UTF-8 mode, characters with values greater than 128 never match \d,         A  "word"  character is an underscore or any character that is a letter
3539         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-         or digit.  By default, the definition of letters  and  digits  is  con-
3540         code  character  property  support is available. These sequences retain         trolled  by PCRE's low-valued character tables, and may vary if locale-
3541         their original meanings from before UTF-8 support was available, mainly         specific matching is taking place (see "Locale support" in the  pcreapi
3542         for efficiency reasons.         page).  For  example,  in  a French locale such as "fr_FR" in Unix-like
3543           systems, or "french" in Windows, some character codes greater than  128
3544         The sequences \h, \H, \v, and \V are Perl 5.10 features. In contrast to         are  used  for  accented letters, and these are then matched by \w. The
3545         the other sequences, these do match certain high-valued  codepoints  in         use of locales with Unicode is discouraged.
3546         UTF-8 mode.  The horizontal space characters are:  
3547           By default, in UTF-8 mode, characters  with  values  greater  than  128
3548           never  match  \d,  \s,  or  \w,  and always match \D, \S, and \W. These
3549           sequences retain their original meanings from before UTF-8 support  was
3550           available,  mainly for efficiency reasons. However, if PCRE is compiled
3551           with Unicode property support, and the PCRE_UCP option is set, the  be-
3552           haviour  is  changed  so  that Unicode properties are used to determine
3553           character types, as follows:
3554    
3555             \d  any character that \p{Nd} matches (decimal digit)
3556             \s  any character that \p{Z} matches, plus HT, LF, FF, CR
3557             \w  any character that \p{L} or \p{N} matches, plus underscore
3558    
3559           The upper case escapes match the inverse sets of characters. Note  that
3560           \d  matches  only decimal digits, whereas \w matches any Unicode digit,
3561           as well as any Unicode letter, and underscore. Note also that  PCRE_UCP
3562           affects  \b,  and  \B  because  they are defined in terms of \w and \W.
3563           Matching these sequences is noticeably slower when PCRE_UCP is set.
3564    
3565           The sequences \h, \H, \v, and \V are features that were added  to  Perl
3566           at  release  5.10. In contrast to the other sequences, which match only
3567           ASCII characters by default, these  always  match  certain  high-valued
3568           codepoints  in UTF-8 mode, whether or not PCRE_UCP is set. The horizon-
3569           tal space characters are:
3570    
3571           U+0009     Horizontal tab           U+0009     Horizontal tab
3572           U+0020     Space           U+0020     Space
# Line 3058  BACKSLASH Line 3598  BACKSLASH
3598           U+2028     Line separator           U+2028     Line separator
3599           U+2029     Paragraph separator           U+2029     Paragraph separator
3600    
        A "word" character is an underscore or any character less than 256 that  
        is a letter or digit. The definition of  letters  and  digits  is  con-  
        trolled  by PCRE's low-valued character tables, and may vary if locale-  
        specific matching is taking place (see "Locale support" in the  pcreapi  
        page).  For  example,  in  a French locale such as "fr_FR" in Unix-like  
        systems, or "french" in Windows, some character codes greater than  128  
        are  used for accented letters, and these are matched by \w. The use of  
        locales with Unicode is discouraged.  
   
3601     Newline sequences     Newline sequences
3602    
3603         Outside a character class, the escape sequence \R matches  any  Unicode         Outside a character class, by default, the escape sequence  \R  matches
3604         newline  sequence. This is a Perl 5.10 feature. In non-UTF-8 mode \R is         any Unicode newline sequence. In non-UTF-8 mode \R is equivalent to the
3605         equivalent to the following:         following:
3606    
3607           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3608    
# Line 3087  BACKSLASH Line 3618  BACKSLASH
3618         rator,  U+2029).   Unicode character property support is not needed for         rator,  U+2029).   Unicode character property support is not needed for
3619         these characters to be recognized.         these characters to be recognized.
3620    
3621         Inside a character class, \R matches the letter "R".         It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3622           the  complete  set  of  Unicode  line  endings)  by  setting the option
3623           PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3624           (BSR is an abbrevation for "backslash R".) This can be made the default
3625           when PCRE is built; if this is the case, the  other  behaviour  can  be
3626           requested  via  the  PCRE_BSR_UNICODE  option.   It is also possible to
3627           specify these settings by starting a pattern string  with  one  of  the
3628           following sequences:
3629    
3630             (*BSR_ANYCRLF)   CR, LF, or CRLF only
3631             (*BSR_UNICODE)   any Unicode newline sequence
3632    
3633           These  override  the default and the options given to pcre_compile() or
3634           pcre_compile2(), but  they  can  be  overridden  by  options  given  to
3635           pcre_exec() or pcre_dfa_exec(). Note that these special settings, which
3636           are not Perl-compatible, are recognized only at the  very  start  of  a
3637           pattern,  and that they must be in upper case. If more than one of them
3638           is present, the last one is used. They can be combined with a change of
3639           newline convention; for example, a pattern can start with:
3640    
3641             (*ANY)(*BSR_ANYCRLF)
3642    
3643           They can also be combined with the (*UTF8) or (*UCP) special sequences.
3644           Inside a character class, \R  is  treated  as  an  unrecognized  escape
3645           sequence, and so matches the letter "R" by default, but causes an error
3646           if PCRE_EXTRA is set.
3647    
3648     Unicode character properties     Unicode character properties
3649    
# Line 3102  BACKSLASH Line 3658  BACKSLASH
3658           \X       an extended Unicode sequence           \X       an extended Unicode sequence
3659    
3660         The property names represented by xx above are limited to  the  Unicode         The property names represented by xx above are limited to  the  Unicode
3661         script names, the general category properties, and "Any", which matches         script names, the general category properties, "Any", which matches any
3662         any character (including newline). Other properties such as "InMusical-         character  (including  newline),  and  some  special  PCRE   properties
3663         Symbols"  are  not  currently supported by PCRE. Note that \P{Any} does         (described  in the next section).  Other Perl properties such as "InMu-
3664         not match any characters, so always causes a match failure.         sicalSymbols" are not currently supported by PCRE.  Note  that  \P{Any}
3665           does not match any characters, so always causes a match failure.
3666    
3667         Sets of Unicode characters are defined as belonging to certain scripts.         Sets of Unicode characters are defined as belonging to certain scripts.
3668         A  character from one of these sets can be matched using a script name.         A character from one of these sets can be matched using a script  name.
3669         For example:         For example:
3670    
3671           \p{Greek}           \p{Greek}
3672           \P{Han}           \P{Han}
3673    
3674         Those that are not part of an identified script are lumped together  as         Those  that are not part of an identified script are lumped together as
3675         "Common". The current list of scripts is:         "Common". The current list of scripts is:
3676    
3677         Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,         Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille,
3678         Buhid,  Canadian_Aboriginal,  Cherokee,  Common,   Coptic,   Cuneiform,         Buginese,  Buhid,  Canadian_Aboriginal, Carian, Cham, Cherokee, Common,
3679         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,         Coptic,  Cuneiform,  Cypriot,  Cyrillic,  Deseret,  Devanagari,   Egyp-
3680         Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew,  Hira-         tian_Hieroglyphs,   Ethiopic,   Georgian,  Glagolitic,  Gothic,  Greek,
3681         gana,  Inherited,  Kannada,  Katakana,  Kharoshthi,  Khmer, Lao, Latin,         Gujarati, Gurmukhi,  Han,  Hangul,  Hanunoo,  Hebrew,  Hiragana,  Impe-
3682         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,         rial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian,
3683         Ogham,  Old_Italic,  Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician,         Javanese, Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer,  Lao,
3684         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,         Latin,  Lepcha,  Limbu,  Linear_B,  Lisu,  Lycian,  Lydian,  Malayalam,
3685         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.         Meetei_Mayek, Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham,  Old_Italic,
3686           Old_Persian,  Old_South_Arabian,  Old_Turkic, Ol_Chiki, Oriya, Osmanya,
3687         Each  character has exactly one general category property, specified by         Phags_Pa, Phoenician, Rejang, Runic,  Samaritan,  Saurashtra,  Shavian,
3688         a two-letter abbreviation. For compatibility with Perl, negation can be         Sinhala,  Sundanese,  Syloti_Nagri,  Syriac, Tagalog, Tagbanwa, Tai_Le,
3689         specified  by  including a circumflex between the opening brace and the         Tai_Tham, Tai_Viet, Tamil, Telugu,  Thaana,  Thai,  Tibetan,  Tifinagh,
3690         property name. For example, \p{^Lu} is the same as \P{Lu}.         Ugaritic, Vai, Yi.
3691    
3692           Each character has exactly one Unicode general category property, spec-
3693           ified by a two-letter abbreviation. For compatibility with Perl,  nega-
3694           tion  can  be  specified  by including a circumflex between the opening
3695           brace and the property name.  For  example,  \p{^Lu}  is  the  same  as
3696           \P{Lu}.
3697    
3698         If only one letter is specified with \p or \P, it includes all the gen-         If only one letter is specified with \p or \P, it includes all the gen-
3699         eral  category properties that start with that letter. In this case, in         eral category properties that start with that letter. In this case,  in
3700         the absence of negation, the curly brackets in the escape sequence  are         the  absence of negation, the curly brackets in the escape sequence are
3701         optional; these two examples have the same effect:         optional; these two examples have the same effect:
3702    
3703           \p{L}           \p{L}
# Line 3186  BACKSLASH Line 3749  BACKSLASH
3749           Zp    Paragraph separator           Zp    Paragraph separator
3750           Zs    Space separator           Zs    Space separator
3751    
3752         The  special property L& is also supported: it matches a character that         The special property L& is also supported: it matches a character  that
3753         has the Lu, Ll, or Lt property, in other words, a letter  that  is  not         has  the  Lu,  Ll, or Lt property, in other words, a letter that is not
3754         classified as a modifier or "other".         classified as a modifier or "other".
3755    
3756         The  Cs  (Surrogate)  property  applies only to characters in the range         The Cs (Surrogate) property applies only to  characters  in  the  range
3757         U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see         U+D800  to  U+DFFF. Such characters are not valid in UTF-8 strings (see
3758         RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-         RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
3759         ing has been turned off (see the discussion  of  PCRE_NO_UTF8_CHECK  in         ing  has  been  turned off (see the discussion of PCRE_NO_UTF8_CHECK in
3760         the pcreapi page).         the pcreapi page). Perl does not support the Cs property.
3761    
3762         The  long  synonyms  for  these  properties that Perl supports (such as         The long synonyms for  property  names  that  Perl  supports  (such  as
3763         \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix         \p{Letter})  are  not  supported by PCRE, nor is it permitted to prefix
3764         any of these properties with "Is".         any of these properties with "Is".
3765    
3766         No character that is in the Unicode table has the Cn (unassigned) prop-         No character that is in the Unicode table has the Cn (unassigned) prop-
3767         erty.  Instead, this property is assumed for any code point that is not         erty.  Instead, this property is assumed for any code point that is not
3768         in the Unicode table.         in the Unicode table.
3769    
3770         Specifying  caseless  matching  does not affect these escape sequences.         Specifying caseless matching does not affect  these  escape  sequences.
3771         For example, \p{Lu} always matches only upper case letters.         For example, \p{Lu} always matches only upper case letters.
3772    
3773         The \X escape matches any number of Unicode  characters  that  form  an         The  \X  escape  matches  any number of Unicode characters that form an
3774         extended Unicode sequence. \X is equivalent to         extended Unicode sequence. \X is equivalent to
3775    
3776           (?>\PM\pM*)           (?>\PM\pM*)
3777    
3778         That  is,  it matches a character without the "mark" property, followed         That is, it matches a character without the "mark"  property,  followed
3779         by zero or more characters with the "mark"  property,  and  treats  the         by  zero  or  more  characters with the "mark" property, and treats the
3780         sequence  as  an  atomic group (see below).  Characters with the "mark"         sequence as an atomic group (see below).  Characters  with  the  "mark"
3781         property are typically accents that  affect  the  preceding  character.         property  are  typically  accents  that affect the preceding character.
3782         None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X         None of them have codepoints less than 256, so  in  non-UTF-8  mode  \X
3783         matches any one character.         matches any one character.
3784    
3785         Matching characters by Unicode property is not fast, because  PCRE  has         Matching  characters  by Unicode property is not fast, because PCRE has
3786         to  search  a  structure  that  contains data for over fifteen thousand         to search a structure that contains  data  for  over  fifteen  thousand
3787         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
3788         \w do not use Unicode properties in PCRE.         \w do not use Unicode properties in PCRE by  default,  though  you  can
3789           make them do so by setting the PCRE_UCP option for pcre_compile() or by
3790           starting the pattern with (*UCP).
3791    
3792       PCRE's additional properties
3793    
3794           As well as the standard Unicode properties described  in  the  previous
3795           section,  PCRE supports four more that make it possible to convert tra-
3796           ditional escape sequences such as \w and \s and POSIX character classes
3797           to use Unicode properties. PCRE uses these non-standard, non-Perl prop-
3798           erties internally when PCRE_UCP is set. They are:
3799    
3800             Xan   Any alphanumeric character
3801             Xps   Any POSIX space character
3802             Xsp   Any Perl space character
3803             Xwd   Any Perl "word" character
3804    
3805           Xan matches characters that have either the L (letter) or the  N  (num-
3806           ber)  property. Xps matches the characters tab, linefeed, vertical tab,
3807           formfeed, or carriage return, and any other character that  has  the  Z
3808           (separator) property.  Xsp is the same as Xps, except that vertical tab
3809           is excluded. Xwd matches the same characters as Xan, plus underscore.
3810    
3811     Resetting the match start     Resetting the match start
3812    
3813         The escape sequence \K, which is a Perl 5.10 feature, causes any previ-         The escape sequence \K causes any previously matched characters not  to
3814         ously matched characters not  to  be  included  in  the  final  matched         be included in the final matched sequence. For example, the pattern:
        sequence. For example, the pattern:  
3815    
3816           foo\Kbar           foo\Kbar
3817    
# Line 3243  BACKSLASH Line 3826  BACKSLASH
3826    
3827         matches "foobar", the first substring is still set to "foo".         matches "foobar", the first substring is still set to "foo".
3828    
3829           Perl documents that the use  of  \K  within  assertions  is  "not  well
3830           defined".  In  PCRE,  \K  is  acted upon when it occurs inside positive
3831           assertions, but is ignored in negative assertions.
3832    
3833     Simple assertions     Simple assertions
3834    
3835         The final use of backslash is for certain simple assertions. An  asser-         The final use of backslash is for certain simple assertions. An  asser-
# Line 3259  BACKSLASH Line 3846  BACKSLASH
3846           \z     matches only at the end of the subject           \z     matches only at the end of the subject
3847           \G     matches at the first matching position in the subject           \G     matches at the first matching position in the subject
3848    
3849         These assertions may not appear in character classes (but note that  \b         Inside a character class, \b has a different meaning;  it  matches  the
3850         has a different meaning, namely the backspace character, inside a char-         backspace  character.  If  any  other  of these assertions appears in a
3851         acter class).         character class, by default it matches the corresponding literal  char-
3852           acter  (for  example,  \B  matches  the  letter  B).  However,  if  the
3853         A word boundary is a position in the subject string where  the  current         PCRE_EXTRA option is set, an "invalid escape sequence" error is  gener-
3854         character  and  the previous character do not both match \w or \W (i.e.         ated instead.
3855         one matches \w and the other matches \W), or the start or  end  of  the  
3856         string if the first or last character matches \w, respectively.         A  word  boundary is a position in the subject string where the current
3857           character and the previous character do not both match \w or  \W  (i.e.
3858           one  matches  \w  and the other matches \W), or the start or end of the
3859           string if the first or last  character  matches  \w,  respectively.  In
3860           UTF-8  mode,  the  meanings  of \w and \W can be changed by setting the