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# 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.  There is also some support for certain .NET and Oniguruma syn-         tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25         tax items, and there is an option for  requesting  some  minor  changes         items, and there is an option for requesting some  minor  changes  that
26         that give better JavaScript compatibility.         give better JavaScript compatibility.
27    
28         The  current  implementation of PCRE (release 7.x) corresponds approxi-         The  current implementation of PCRE corresponds approximately with Perl
29         mately with Perl 5.10, including support for UTF-8 encoded strings  and         5.12, including support for UTF-8 encoded strings and  Unicode  general
30         Unicode general category properties. However, UTF-8 and Unicode support         category  properties.  However,  UTF-8  and  Unicode  support has to be
31         has to be explicitly enabled; it is not the default. The Unicode tables         explicitly enabled; it is not the default. The  Unicode  tables  corre-
32         correspond to Unicode release 5.0.0.         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 54  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 71  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 81  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 136  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 251  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: 12 April 2008         Last updated: 13 November 2010
270         Copyright (c) 1997-2008 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 277  PCRE BUILD-TIME OPTIONS Line 285  PCRE BUILD-TIME OPTIONS
285         script,  where the optional features are selected or deselected by pro-         script,  where the optional features are selected or deselected by pro-
286         viding options to configure before running the make  command.  However,         viding options to configure before running the make  command.  However,
287         the  same  options  can be selected in both Unix-like and non-Unix-like         the  same  options  can be selected in both Unix-like and non-Unix-like
288         environments using the GUI facility of  CMakeSetup  if  you  are  using         environments using the GUI facility of cmake-gui if you are using CMake
289         CMake instead of configure to build PCRE.         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         The complete list of options for configure (which includes the standard
297         ones such as the  selection  of  the  installation  directory)  can  be         ones  such  as  the  selection  of  the  installation directory) can be
298         obtained by running         obtained by running
299    
300           ./configure --help           ./configure --help
301    
302         The  following  sections  include  descriptions  of options whose names         The following sections include  descriptions  of  options  whose  names
303         begin with --enable or --disable. These settings specify changes to the         begin with --enable or --disable. These settings specify changes to the
304         defaults  for  the configure command. Because of the way that configure         defaults for the configure command. Because of the way  that  configure
305         works, --enable and --disable always come in pairs, so  the  complemen-         works,  --enable  and --disable always come in pairs, so the complemen-
306         tary  option always exists as well, but as it specifies the default, it         tary option always exists as well, but as it specifies the default,  it
307         is not described.         is not described.
308    
309    
# Line 307  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
340    
341         UTF-8  support allows PCRE to process character values greater than 255         UTF-8 support allows PCRE to process character values greater than  255
342         in the strings that it handles. On its own, however, it does  not  pro-         in  the  strings that it handles. On its own, however, it does not pro-
343         vide any facilities for accessing the properties of such characters. If         vide any facilities for accessing the properties of such characters. If
344         you want to be able to use the pattern escapes \P, \p,  and  \X,  which         you  want  to  be able to use the pattern escapes \P, \p, and \X, which
345         refer to Unicode character properties, you must add         refer to Unicode character properties, you must add
346    
347           --enable-unicode-properties           --enable-unicode-properties
348    
349         to  the configure command. This implies UTF-8 support, even if you have         to the configure command. This implies UTF-8 support, even if you  have
350         not explicitly requested it.         not explicitly requested it.
351    
352         Including Unicode property support adds around 30K  of  tables  to  the         Including  Unicode  property  support  adds around 30K of tables to the
353         PCRE  library.  Only  the general category properties such as Lu and Nd         PCRE library. Only the general category properties such as  Lu  and  Nd
354         are supported. Details are given in the pcrepattern documentation.         are supported. Details are given in the pcrepattern documentation.
355    
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    
366         to  the  configure  command.  There  is  also  a --enable-newline-is-lf         to the  configure  command.  There  is  also  a  --enable-newline-is-lf
367         option, which explicitly specifies linefeed as the newline character.         option, which explicitly specifies linefeed as the newline character.
368    
369         Alternatively, you can specify that line endings are to be indicated by         Alternatively, you can specify that line endings are to be indicated by
# Line 356  CODE VALUE OF NEWLINE Line 375  CODE VALUE OF NEWLINE
375    
376           --enable-newline-is-anycrlf           --enable-newline-is-anycrlf
377    
378         which  causes  PCRE  to recognize any of the three sequences CR, LF, or         which causes PCRE to recognize any of the three sequences  CR,  LF,  or
379         CRLF as indicating a line ending. Finally, a fifth option, specified by         CRLF as indicating a line ending. Finally, a fifth option, specified by
380    
381           --enable-newline-is-any           --enable-newline-is-any
# Line 416  HANDLING VERY LARGE PATTERNS Line 435  HANDLING VERY LARGE PATTERNS
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    
# Line 445  AVOIDING EXCESSIVE STACK USAGE Line 464  AVOIDING EXCESSIVE STACK USAGE
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
# Line 453  AVOIDING EXCESSIVE STACK USAGE Line 472  AVOIDING EXCESSIVE STACK USAGE
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
479    
480         Internally, PCRE has a function called match(), which it calls  repeat-         Internally,  PCRE has a function called match(), which it calls repeat-
481         edly   (sometimes   recursively)  when  matching  a  pattern  with  the         edly  (sometimes  recursively)  when  matching  a  pattern   with   the
482         pcre_exec() function. By controlling the maximum number of  times  this         pcre_exec()  function.  By controlling the maximum number of times this
483         function  may be called during a single matching operation, a limit can         function may be called during a single matching operation, a limit  can
484         be placed on the resources used by a single call  to  pcre_exec().  The         be  placed  on  the resources used by a single call to pcre_exec(). The
485         limit  can be changed at run time, as described in the pcreapi documen-         limit can be changed at run time, as described in the pcreapi  documen-
486         tation. The default is 10 million, but this can be changed by adding  a         tation.  The default is 10 million, but this can be changed by adding a
487         setting such as         setting such as
488    
489           --with-match-limit=500000           --with-match-limit=500000
490    
491         to   the   configure  command.  This  setting  has  no  effect  on  the         to  the  configure  command.  This  setting  has  no  effect   on   the
492         pcre_dfa_exec() matching function.         pcre_dfa_exec() matching function.
493    
494         In some environments it is desirable to limit the  depth  of  recursive         In  some  environments  it is desirable to limit the depth of recursive
495         calls of match() more strictly than the total number of calls, in order         calls of match() more strictly than the total number of calls, in order
496         to restrict the maximum amount of stack (or heap,  if  --disable-stack-         to  restrict  the maximum amount of stack (or heap, if --disable-stack-
497         for-recursion is specified) that is used. A second limit controls this;         for-recursion is specified) that is used. A second limit controls this;
498         it defaults to the value that  is  set  for  --with-match-limit,  which         it  defaults  to  the  value  that is set for --with-match-limit, which
499         imposes  no  additional constraints. However, you can set a lower limit         imposes no additional constraints. However, you can set a  lower  limit
500         by adding, for example,         by adding, for example,
501    
502           --with-match-limit-recursion=10000           --with-match-limit-recursion=10000
503    
504         to the configure command. This value can  also  be  overridden  at  run         to  the  configure  command.  This  value can also be overridden at run
505         time.         time.
506    
507    
508  CREATING CHARACTER TABLES AT BUILD TIME  CREATING CHARACTER TABLES AT BUILD TIME
509    
510         PCRE  uses fixed tables for processing characters whose code values are         PCRE uses fixed tables for processing characters whose code values  are
511         less than 256. By default, PCRE is built with a set of tables that  are         less  than 256. By default, PCRE is built with a set of tables that are
512         distributed  in  the  file pcre_chartables.c.dist. These tables are for         distributed in the file pcre_chartables.c.dist. These  tables  are  for
513         ASCII codes only. If you add         ASCII codes only. If you add
514    
515           --enable-rebuild-chartables           --enable-rebuild-chartables
516    
517         to the configure command, the distributed tables are  no  longer  used.         to  the  configure  command, the distributed tables are no longer used.
518         Instead,  a  program  called dftables is compiled and run. This outputs         Instead, a program called dftables is compiled and  run.  This  outputs
519         the source for new set of tables, created in the default locale of your         the source for new set of tables, created in the default locale of your
520         C runtime system. (This method of replacing the tables does not work if         C runtime system. (This method of replacing the tables does not work if
521         you are cross compiling, because dftables is run on the local host.  If         you  are cross compiling, because dftables is run on the local host. If
522         you  need  to  create alternative tables when cross compiling, you will         you need to create alternative tables when cross  compiling,  you  will
523         have to do so "by hand".)         have to do so "by hand".)
524    
525    
526  USING EBCDIC CODE  USING EBCDIC CODE
527    
528         PCRE assumes by default that it will run in an  environment  where  the         PCRE  assumes  by  default that it will run in an environment where the
529         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
530         This is the case for most computer operating systems.  PCRE  can,  how-         This  is  the  case for most computer operating systems. PCRE can, how-
531         ever, be compiled to run in an EBCDIC environment by adding         ever, be compiled to run in an EBCDIC environment by adding
532    
533           --enable-ebcdic           --enable-ebcdic
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  PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
# Line 542  PCRETEST OPTION FOR LIBREADLINE SUPPORT Line 561  PCRETEST OPTION FOR LIBREADLINE SUPPORT
561         to  the  configure  command,  pcretest  is  linked with the libreadline         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         library, and when its input is from a terminal, it reads it  using  the
563         readline() function. This provides line-editing and history facilities.         readline() function. This provides line-editing and history facilities.
564         Note that libreadline is GPL-licenced, so if you distribute a binary of         Note that libreadline is GPL-licensed, so if you distribute a binary of
565         pcretest linked in this way, there may be licensing issues.         pcretest linked in this way, there may be licensing issues.
566    
567         Setting  this  option  causes  the -lreadline option to be added to the         Setting  this  option  causes  the -lreadline option to be added to the
# Line 578  AUTHOR Line 597  AUTHOR
597    
598  REVISION  REVISION
599    
600         Last updated: 13 April 2008         Last updated: 29 September 2009
601         Copyright (c) 1997-2008 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 666  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.  Except for (*FAIL), the backtracking control verbs such as (*PRUNE)         8. Except for (*FAIL), the backtracking control verbs such as  (*PRUNE)
757         are not supported. (*FAIL) is supported, and  behaves  like  a  failing         are  not  supported.  (*FAIL)  is supported, and behaves like a failing
758         negative assertion.         negative assertion.
759    
760    
761  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
762    
763         Using  the alternative matching algorithm provides the following advan-         Using the alternative matching algorithm provides the following  advan-
764         tages:         tages:
765    
766         1. All possible matches (at a single point in the subject) are automat-         1. All possible matches (at a single point in the subject) are automat-
767         ically  found,  and  in particular, the longest match is found. To find         ically found, and in particular, the longest match is  found.  To  find
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
772         on the content of the pattern that apply when using the standard  algo-         once,  and  never  needs to backtrack, it is possible to pass very long
773         rithm  for  partial matching do not apply to the alternative algorithm.         subject strings to the matching function in  several  pieces,  checking
774         For non-anchored patterns, the starting position of a partial match  is         for  partial  matching  each time. Although it is possible to do multi-
775         available.         segment matching using the standard algorithm (pcre_exec()), by retain-
776           ing  partially matched substrings, it is more complicated. The pcrepar-
777         3.  Because  the  alternative  algorithm  scans the subject string just         tial documentation gives details  of  partial  matching  and  discusses
778         once, and never needs to backtrack, it is possible to  pass  very  long         multi-segment matching.
        subject  strings  to  the matching function in several pieces, checking  
        for partial matching each time.  
779    
780    
781  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
782    
783         The alternative algorithm suffers from a number of disadvantages:         The alternative algorithm suffers from a number of disadvantages:
784    
785         1. It is substantially slower than  the  standard  algorithm.  This  is         1.  It  is  substantially  slower  than the standard algorithm. This is
786         partly  because  it has to search for all possible matches, but is also         partly because it has to search for all possible matches, but  is  also
787         because it is less susceptible to optimization.         because it is less susceptible to optimization.
788    
789         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
# Line 777  AUTHOR Line 801  AUTHOR
801    
802  REVISION  REVISION
803    
804         Last updated: 19 April 2008         Last updated: 17 November 2010
805         Copyright (c) 1997-2008 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 885  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         compile and 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 999  MULTITHREADING Line 1031  MULTITHREADING
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.
1033    
1034         The compiled form of a regular expression is not altered during  match-         The  compiled form of a regular expression is not altered during match-
1035         ing, so the same compiled pattern can safely be used by several threads         ing, so the same compiled pattern can safely be used by several threads
1036         at once.         at once.
1037    
# Line 1007  MULTITHREADING Line 1039  MULTITHREADING
1039  SAVING PRECOMPILED PATTERNS FOR LATER USE  SAVING PRECOMPILED PATTERNS FOR LATER USE
1040    
1041         The compiled form of a regular expression can be saved and re-used at a         The compiled form of a regular expression can be saved and re-used at a
1042         later  time,  possibly by a different program, and even on a host other         later time, possibly by a different program, and even on a  host  other
1043         than the one on which  it  was  compiled.  Details  are  given  in  the         than  the  one  on  which  it  was  compiled.  Details are given in the
1044         pcreprecompile  documentation.  However, compiling a regular expression         pcreprecompile documentation. However, compiling a  regular  expression
1045         with one version of PCRE for use with a different version is not  guar-         with  one version of PCRE for use with a different version is not guar-
1046         anteed to work and may cause crashes.         anteed to work and may cause crashes.
1047    
1048    
# Line 1018  CHECKING BUILD-TIME OPTIONS Line 1050  CHECKING BUILD-TIME OPTIONS
1050    
1051         int pcre_config(int what, void *where);         int pcre_config(int what, void *where);
1052    
1053         The  function pcre_config() makes it possible for a PCRE client to dis-         The function pcre_config() makes it possible for a PCRE client to  dis-
1054         cover which optional features have been compiled into the PCRE library.         cover which optional features have been compiled into the PCRE library.
1055         The  pcrebuild documentation has more details about these optional fea-         The pcrebuild documentation has more details about these optional  fea-
1056         tures.         tures.
1057    
1058         The first argument for pcre_config() is an  integer,  specifying  which         The  first  argument  for pcre_config() is an integer, specifying which
1059         information is required; the second argument is a pointer to a variable         information is required; the second argument is a pointer to a variable
1060         into which the information is  placed.  The  following  information  is         into  which  the  information  is  placed. The following information is
1061         available:         available:
1062    
1063           PCRE_CONFIG_UTF8           PCRE_CONFIG_UTF8
1064    
1065         The  output is an integer that is set to one if UTF-8 support is avail-         The output is an integer that is set to one if UTF-8 support is  avail-
1066         able; otherwise it is set to zero.         able; otherwise it is set to zero.
1067    
1068           PCRE_CONFIG_UNICODE_PROPERTIES           PCRE_CONFIG_UNICODE_PROPERTIES
1069    
1070         The output is an integer that is set to  one  if  support  for  Unicode         The  output  is  an  integer  that is set to one if support for Unicode
1071         character properties is available; otherwise it is set to zero.         character properties is available; otherwise it is set to zero.
1072    
1073           PCRE_CONFIG_NEWLINE           PCRE_CONFIG_NEWLINE
1074    
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           PCRE_CONFIG_BSR
1083    
# Line 1071  CHECKING BUILD-TIME OPTIONS Line 1104  CHECKING BUILD-TIME OPTIONS
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    
1120         The output is an integer that is set to one if internal recursion  when         The  output is an integer that is set to one if internal recursion when
1121         running pcre_exec() is implemented by recursive function calls that use         running pcre_exec() is implemented by recursive function calls that use
1122         the stack to remember their state. This is the usual way that  PCRE  is         the  stack  to remember their state. This is the usual way that PCRE is
1123         compiled. The output is zero if PCRE was compiled to use blocks of data         compiled. The output is zero if PCRE was compiled to use blocks of data
1124         on the  heap  instead  of  recursive  function  calls.  In  this  case,         on  the  heap  instead  of  recursive  function  calls.  In  this case,
1125         pcre_stack_malloc  and  pcre_stack_free  are  called  to  manage memory         pcre_stack_malloc and  pcre_stack_free  are  called  to  manage  memory
1126         blocks on the heap, thus avoiding the use of the stack.         blocks on the heap, thus avoiding the use of the stack.
1127    
1128    
# Line 1105  COMPILING A PATTERN Line 1139  COMPILING A PATTERN
1139    
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
1149         obtained  via  pcre_malloc is returned. This contains the compiled code         obtained via pcre_malloc is returned. This contains the  compiled  code
1150         and related data. The pcre type is defined for the returned block; this         and related data. The pcre type is defined for the returned block; this
1151         is a typedef for a structure whose contents are not externally defined.         is a typedef for a structure whose contents are not externally defined.
1152         It is up to the caller to free the memory (via pcre_free) when it is no         It is up to the caller to free the memory (via pcre_free) when it is no
1153         longer required.         longer required.
1154    
1155         Although  the compiled code of a PCRE regex is relocatable, that is, it         Although the compiled code of a PCRE regex is relocatable, that is,  it
1156         does not depend on memory location, the complete pcre data block is not         does not depend on memory location, the complete pcre data block is not
1157         fully  relocatable, because it may contain a copy of the tableptr argu-         fully relocatable, because it may contain a copy of the tableptr  argu-
1158         ment, which is an address (see below).         ment, which is an address (see below).
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, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK, and
1169           PCRE_NO_START_OPT options can be set at the time of matching as well as
1170           at compile time.
1171    
1172         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1173         if  compilation  of  a  pattern fails, pcre_compile() returns NULL, and         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
1174         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-
1175         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
1176         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
1177         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
1178         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
1179         given.         immediate error is given. Some errors are not detected until checks are
1180           carried  out  when the whole pattern has been scanned; in this case the
1181         If  pcre_compile2()  is  used instead of pcre_compile(), and the error-         offset is set to the end of the pattern.
1182         codeptr argument is not NULL, a non-zero error code number is  returned  
1183         via  this argument in the event of an error. This is in addition to the         Note that the offset is in bytes, not characters, even in  UTF-8  mode.
1184           It  may  point  into the middle of a UTF-8 character (for example, when
1185           PCRE_ERROR_BADUTF8 is returned for an invalid UTF-8 string).
1186    
1187           If pcre_compile2() is used instead of pcre_compile(),  and  the  error-
1188           codeptr  argument is not NULL, a non-zero error code number is returned
1189           via this argument in the event of an error. This is in addition to  the
1190         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1191    
1192         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
1193         character  tables  that  are  built  when  PCRE  is compiled, using the         character tables that are  built  when  PCRE  is  compiled,  using  the
1194         default C locale. Otherwise, tableptr must be an address  that  is  the         default  C  locale.  Otherwise, tableptr must be an address that is the
1195         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
1196         compiled pattern, and used again by pcre_exec(), unless  another  table         compiled  pattern,  and used again by pcre_exec(), unless another table
1197         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
1198         support below.         support below.
1199    
1200         This code fragment shows a typical straightforward  call  to  pcre_com-         This  code  fragment  shows a typical straightforward call to pcre_com-
1201         pile():         pile():
1202    
1203           pcre *re;           pcre *re;
# Line 1166  COMPILING A PATTERN Line 1210  COMPILING A PATTERN
1210             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1211             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1212    
1213         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
1214         file:         file:
1215    
1216           PCRE_ANCHORED           PCRE_ANCHORED
1217    
1218         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
1219         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
1220         that is being searched (the "subject string"). This effect can also  be         that  is being searched (the "subject string"). This effect can also be
1221         achieved  by appropriate constructs in the pattern itself, which is the         achieved by appropriate constructs in the pattern itself, which is  the
1222         only way to do it in Perl.         only way to do it in Perl.
1223    
1224           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1225    
1226         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1227         all  with  number  255, before each pattern item. For discussion of the         all with number 255, before each pattern item. For  discussion  of  the
1228         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1229    
1230           PCRE_BSR_ANYCRLF           PCRE_BSR_ANYCRLF
1231           PCRE_BSR_UNICODE           PCRE_BSR_UNICODE
1232    
1233         These options (which are mutually exclusive) control what the \R escape         These options (which are mutually exclusive) control what the \R escape
1234         sequence  matches.  The choice is either to match only CR, LF, or CRLF,         sequence matches. The choice is either to match only CR, LF,  or  CRLF,
1235         or to match any Unicode newline sequence. The default is specified when         or to match any Unicode newline sequence. The default is specified when
1236         PCRE is built. It can be overridden from within the pattern, or by set-         PCRE is built. It can be overridden from within the pattern, or by set-
1237         ting an option when a compiled pattern is matched.         ting an option when a compiled pattern is matched.
1238    
1239           PCRE_CASELESS           PCRE_CASELESS
1240    
1241         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
1242         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
1243         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
1244         always  understands the concept of case for characters whose values are         always understands the concept of case for characters whose values  are
1245         less than 128, so caseless matching is always possible. For  characters         less  than 128, so caseless matching is always possible. For characters
1246         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-
1247         piled with Unicode property support, but not otherwise. If you want  to         piled  with Unicode property support, but not otherwise. If you want to
1248         use  caseless  matching  for  characters 128 and above, you must ensure         use caseless matching for characters 128 and  above,  you  must  ensure
1249         that PCRE is compiled with Unicode property support  as  well  as  with         that  PCRE  is  compiled  with Unicode property support as well as with
1250         UTF-8 support.         UTF-8 support.
1251    
1252           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1253    
1254         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
1255         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
1256         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
1257         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored
1258         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
1259         Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1260    
1261           PCRE_DOTALL           PCRE_DOTALL
1262    
1263         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-
1264         acters,  including  those that indicate newline. Without it, a dot does         acter of any value, including one that indicates a newline. However, it
1265         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.
1266         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
1267         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
1268         newline characters, independent of the setting of this option.         be changed within a pattern by a (?s) option setting. A negative  class
1269           such as [^a] always matches newline characters, independent of the set-
1270           ting of this option.
1271    
1272           PCRE_DUPNAMES           PCRE_DUPNAMES
1273    
1274         If  this  bit is set, names used to identify capturing subpatterns need         If this bit is set, names used to identify capturing  subpatterns  need
1275         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
1276         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
1277         matched. There are more details of named subpatterns  below;  see  also         matched.  There  are  more details of named subpatterns below; see also
1278         the pcrepattern documentation.         the pcrepattern documentation.
1279    
1280           PCRE_EXTENDED           PCRE_EXTENDED
1281    
1282         If  this  bit  is  set,  whitespace  data characters in the pattern are         If this bit is set, whitespace  data  characters  in  the  pattern  are
1283         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1284         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1285         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1286         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x
1287         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-
1288         ting.         ting.
1289    
1290           Which characters are interpreted  as  newlines  is  controlled  by  the
1291           options  passed to pcre_compile() or by a special sequence at the start
1292           of the pattern, as described in the section entitled  "Newline  conven-
1293           tions" in the pcrepattern documentation. Note that the end of this type
1294           of comment is  a  literal  newline  sequence  in  the  pattern;  escape
1295           sequences that happen to represent a newline do not count.
1296    
1297         This  option  makes  it possible to include comments inside complicated         This  option  makes  it possible to include comments inside complicated
1298         patterns.  Note, however, that this applies only  to  data  characters.         patterns.  Note, however, that this applies only  to  data  characters.
1299         Whitespace   characters  may  never  appear  within  special  character         Whitespace   characters  may  never  appear  within  special  character
1300         sequences in a pattern, for  example  within  the  sequence  (?(  which         sequences in a pattern, for example within the sequence (?( that intro-
1301         introduces a conditional subpattern.         duces a conditional subpattern.
1302    
1303           PCRE_EXTRA           PCRE_EXTRA
1304    
# Line 1255  COMPILING A PATTERN Line 1308  COMPILING A PATTERN
1308         letter that has no special meaning  causes  an  error,  thus  reserving         letter that has no special meaning  causes  an  error,  thus  reserving
1309         these  combinations  for  future  expansion.  By default, as in Perl, a         these  combinations  for  future  expansion.  By default, as in Perl, a
1310         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
1311         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
1312         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
1313         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
1314           within a pattern.
1315    
1316           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1317    
1318         If  this  option  is  set,  an  unanchored pattern is required to match         If this option is set, an  unanchored  pattern  is  required  to  match
1319         before or at the first  newline  in  the  subject  string,  though  the         before  or  at  the  first  newline  in  the subject string, though the
1320         matched text may continue over the newline.         matched text may continue over the newline.
1321    
1322           PCRE_JAVASCRIPT_COMPAT           PCRE_JAVASCRIPT_COMPAT
1323    
1324         If this option is set, PCRE's behaviour is changed in some ways so that         If this option is set, PCRE's behaviour is changed in some ways so that
1325         it is compatible with JavaScript rather than Perl. The changes  are  as         it  is  compatible with JavaScript rather than Perl. The changes are as
1326         follows:         follows:
1327    
1328         (1)  A  lone  closing square bracket in a pattern causes a compile-time         (1) A lone closing square bracket in a pattern  causes  a  compile-time
1329         error, because this is illegal in JavaScript (by default it is  treated         error,  because this is illegal in JavaScript (by default it is treated
1330         as a data character). Thus, the pattern AB]CD becomes illegal when this         as a data character). Thus, the pattern AB]CD becomes illegal when this
1331         option is set.         option is set.
1332    
1333         (2) At run time, a back reference to an unset subpattern group  matches         (2)  At run time, a back reference to an unset subpattern group matches
1334         an  empty  string (by default this causes the current matching alterna-         an empty string (by default this causes the current  matching  alterna-
1335         tive to fail). A pattern such as (\1)(a) succeeds when this  option  is         tive  to  fail). A pattern such as (\1)(a) succeeds when this option is
1336         set  (assuming  it can find an "a" in the subject), whereas it fails by         set (assuming it can find an "a" in the subject), whereas it  fails  by
1337         default, for Perl compatibility.         default, for Perl compatibility.
1338    
1339           PCRE_MULTILINE           PCRE_MULTILINE
1340    
1341         By default, PCRE treats the subject string as consisting  of  a  single         By  default,  PCRE  treats the subject string as consisting of a single
1342         line  of characters (even if it actually contains newlines). The "start         line of characters (even if it actually contains newlines). The  "start
1343         of line" metacharacter (^) matches only at the  start  of  the  string,         of  line"  metacharacter  (^)  matches only at the start of the string,
1344         while  the  "end  of line" metacharacter ($) matches only at the end of         while the "end of line" metacharacter ($) matches only at  the  end  of
1345         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1346         is set). This is the same as Perl.         is set). This is the same as Perl.
1347    
1348         When  PCRE_MULTILINE  it  is set, the "start of line" and "end of line"         When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"
1349         constructs match immediately following or immediately  before  internal         constructs  match  immediately following or immediately before internal
1350         newlines  in  the  subject string, respectively, as well as at the very         newlines in the subject string, respectively, as well as  at  the  very
1351         start and end. This is equivalent to Perl's /m option, and  it  can  be         start  and  end.  This is equivalent to Perl's /m option, and it can be
1352         changed within a pattern by a (?m) option setting. If there are no new-         changed within a pattern by a (?m) option setting. If there are no new-
1353         lines in a subject string, or no occurrences of ^ or $  in  a  pattern,         lines  in  a  subject string, or no occurrences of ^ or $ in a pattern,
1354         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1355    
1356           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 1305  COMPILING A PATTERN Line 1359  COMPILING A PATTERN
1359           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1360           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1361    
1362         These  options  override the default newline definition that was chosen         These options override the default newline definition that  was  chosen
1363         when PCRE was built. Setting the first or the second specifies  that  a         when  PCRE  was built. Setting the first or the second specifies that a
1364         newline  is  indicated  by a single character (CR or LF, respectively).         newline is indicated by a single character (CR  or  LF,  respectively).
1365         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the         Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the
1366         two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies         two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies
1367         that any of the three preceding sequences should be recognized. Setting         that any of the three preceding sequences should be recognized. Setting
1368         PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be         PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be
1369         recognized. The Unicode newline sequences are the three just mentioned,         recognized. The Unicode newline sequences are the three just mentioned,
1370         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,         plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,
1371         U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS         U+000C),  NEL  (next line, U+0085), LS (line separator, U+2028), and PS
1372         (paragraph  separator,  U+2029).  The  last  two are recognized only in         (paragraph separator, U+2029). The last  two  are  recognized  only  in
1373         UTF-8 mode.         UTF-8 mode.
1374    
1375         The newline setting in the  options  word  uses  three  bits  that  are         The  newline  setting  in  the  options  word  uses three bits that are
1376         treated as a number, giving eight possibilities. Currently only six are         treated as a number, giving eight possibilities. Currently only six are
1377         used (default plus the five values above). This means that if  you  set         used  (default  plus the five values above). This means that if you set
1378         more  than one newline option, the combination may or may not be sensi-         more than one newline option, the combination may or may not be  sensi-
1379         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1380         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and         PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
1381         cause an error.         cause an error.
1382    
1383         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
1384         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
1385         character class is encountered. This indicates  a  comment  that  lasts         characters,  and so are ignored in this mode. Also, an unescaped # out-
1386         until  after the next line break sequence. In other circumstances, line         side a character class indicates a comment that lasts until  after  the
1387         break  sequences  are  treated  as  literal  data,   except   that   in         next  line break sequence. In other circumstances, line break sequences
1388         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         in patterns are treated as literal data.
        and are therefore ignored.  
1389    
1390         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
1391         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.
1392    
1393           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1394    
1395         If this option is set, it disables the use of numbered capturing paren-         If this option is set, it disables the use of numbered capturing paren-
1396         theses  in the pattern. Any opening parenthesis that is not followed by         theses in the pattern. Any opening parenthesis that is not followed  by
1397         ? behaves as if it were followed by ?: but named parentheses can  still         ?  behaves as if it were followed by ?: but named parentheses can still
1398         be  used  for  capturing  (and  they acquire numbers in the usual way).         be used for capturing (and they acquire  numbers  in  the  usual  way).
1399         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1400    
1401             NO_START_OPTIMIZE
1402    
1403           This  is an option that acts at matching time; that is, it is really an
1404           option for pcre_exec() or pcre_dfa_exec(). If  it  is  set  at  compile
1405           time,  it is remembered with the compiled pattern and assumed at match-
1406           ing time. For details  see  the  discussion  of  PCRE_NO_START_OPTIMIZE
1407           below.
1408    
1409             PCRE_UCP
1410    
1411           This  option changes the way PCRE processes \B, \b, \D, \d, \S, \s, \W,
1412           \w, and some of the POSIX character classes.  By  default,  only  ASCII
1413           characters  are  recognized, but if PCRE_UCP is set, Unicode properties
1414           are used instead to classify characters. More details are given in  the
1415           section  on generic character types in the pcrepattern page. If you set
1416           PCRE_UCP, matching one of the items it affects takes much  longer.  The
1417           option  is  available only if PCRE has been compiled with Unicode prop-
1418           erty support.
1419    
1420           PCRE_UNGREEDY           PCRE_UNGREEDY
1421    
1422         This option inverts the "greediness" of the quantifiers  so  that  they         This option inverts the "greediness" of the quantifiers  so  that  they
# Line 1435  COMPILATION ERROR CODES Line 1507  COMPILATION ERROR CODES
1507           50  [this code is not in use]           50  [this code is not in use]
1508           51  octal value is greater than \377 (not in UTF-8 mode)           51  octal value is greater than \377 (not in UTF-8 mode)
1509           52  internal error: overran compiling workspace           52  internal error: overran compiling workspace
1510           53  internal  error:  previously-checked  referenced  subpattern  not           53  internal error: previously-checked referenced subpattern
1511         found                 not found
1512           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1513           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1514           56  inconsistent NEWLINE options           56  inconsistent NEWLINE options
1515           57  \g is not followed by a braced, angle-bracketed, or quoted           57  \g is not followed by a braced, angle-bracketed, or quoted
1516                 name/number or by a plain number                 name/number or by a plain number
1517           58  a numbered reference must not be zero           58  a numbered reference must not be zero
1518           59  (*VERB) with an argument is not supported           59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1519           60  (*VERB) not recognized           60  (*VERB) not recognized
1520           61  number is too big           61  number is too big
1521           62  subpattern name expected           62  subpattern name expected
1522           63  digit expected after (?+           63  digit expected after (?+
1523           64  ] is an invalid data character in JavaScript compatibility mode           64  ] is an invalid data character in JavaScript compatibility mode
1524             65  different names for subpatterns of the same number are
1525                   not allowed
1526             66  (*MARK) must have an argument
1527             67  this version of PCRE is not compiled with PCRE_UCP support
1528    
1529         The  numbers  32  and 10000 in errors 48 and 49 are defaults; different         The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
1530         values may be used if the limits were changed when PCRE was built.         values may be used if the limits were changed when PCRE was built.
1531    
1532    
# Line 1459  STUDYING A PATTERN Line 1535  STUDYING A PATTERN
1535         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1536              const char **errptr);              const char **errptr);
1537    
1538         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
1539         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
1540         matching. The function pcre_study() takes a pointer to a compiled  pat-         matching.  The function pcre_study() takes a pointer to a compiled pat-
1541         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1542         information that will help speed up matching,  pcre_study()  returns  a         information  that  will  help speed up matching, pcre_study() returns a
1543         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
1544         the results of the study.         the results of the study.
1545    
1546         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1547         pcre_exec().  However,  a  pcre_extra  block also contains other fields         pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-
1548         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
1549         described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1550    
1551         If  studying  the  pattern  does not produce any additional information         If studying the  pattern  does  not  produce  any  useful  information,
1552         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1553         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
1554         its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1555    
1556         The second argument of pcre_study() contains option bits.  At  present,         The  second  argument of pcre_study() contains option bits. At present,
1557         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1558    
1559         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.
1560         If studying succeeds (even if no data is  returned),  the  variable  it         If  studying  succeeds  (even  if no data is returned), the variable it
1561         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
1562         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
1563         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
1564         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1565    
1566         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 1495  STUDYING A PATTERN Line 1571  STUDYING A PATTERN
1571             0,              /* no options exist */             0,              /* no options exist */
1572             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1573    
1574         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
1575         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
1576         ble starting bytes is created.         does not mean that there are any strings of that length that match, but
1577           it does guarantee that no shorter strings match. The value is  used  by
1578           pcre_exec()  and  pcre_dfa_exec()  to  avoid  wasting time by trying to
1579           match strings that are shorter than the lower bound. You can  find  out
1580           the value in a calling program via the pcre_fullinfo() function.
1581    
1582           Studying a pattern is also useful for non-anchored patterns that do not
1583           have a single fixed starting character. A bitmap of  possible  starting
1584           bytes  is  created. This speeds up finding a position in the subject at
1585           which to start matching.
1586    
1587           The two optimizations just described can be  disabled  by  setting  the
1588           PCRE_NO_START_OPTIMIZE    option    when    calling    pcre_exec()   or
1589           pcre_dfa_exec(). You might want to do this  if  your  pattern  contains
1590           callouts  or  (*MARK),  and you want to make use of these facilities in
1591           cases where matching fails. See the discussion  of  PCRE_NO_START_OPTI-
1592           MIZE below.
1593    
1594    
1595  LOCALE SUPPORT  LOCALE SUPPORT
1596    
1597         PCRE handles caseless matching, and determines whether  characters  are         PCRE  handles  caseless matching, and determines whether characters are
1598         letters,  digits, or whatever, by reference to a set of tables, indexed         letters, digits, or whatever, by reference to a set of tables,  indexed
1599         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
1600         characters  with  codes  less than 128. Higher-valued codes never match         characters with codes less than 128. By  default,  higher-valued  codes
1601         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
1602         with  Unicode  character property support. The use of locales with Uni-         PCRE is built with Unicode character property  support.  Alternatively,
1603         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
1604         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
1605         not try to mix the two.         use of locales with Unicode is discouraged. If you are handling charac-
1606           ters with codes greater than 128, you should either use UTF-8 and  Uni-
1607           code, or use locales, but not try to mix the two.
1608    
1609         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
1610         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
1611         applications.  Normally, the internal tables recognize only ASCII char-         applications.  Normally, the internal tables recognize only ASCII char-
1612         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-
1613         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,
1614         which may cause them to be different.         which may cause them to be different.
1615    
1616         The  internal tables can always be overridden by tables supplied by the         The internal tables can always be overridden by tables supplied by  the
1617         application that calls PCRE. These may be created in a different locale         application that calls PCRE. These may be created in a different locale
1618         from  the  default.  As more and more applications change to using Uni-         from the default. As more and more applications change  to  using  Uni-
1619         code, the need for this locale support is expected to die away.         code, the need for this locale support is expected to die away.
1620    
1621         External tables are built by calling  the  pcre_maketables()  function,         External  tables  are  built by calling the pcre_maketables() function,
1622         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
1623         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
1624         example,  to  build  and use tables that are appropriate for the French         example, to build and use tables that are appropriate  for  the  French
1625         locale (where accented characters with  values  greater  than  128  are         locale  (where  accented  characters  with  values greater than 128 are
1626         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1627    
1628           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1629           tables = pcre_maketables();           tables = pcre_maketables();
1630           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1631    
1632         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;
1633         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".
1634    
1635         When pcre_maketables() runs, the tables are built  in  memory  that  is         When  pcre_maketables()  runs,  the  tables are built in memory that is
1636         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         obtained via pcre_malloc. It is the caller's responsibility  to  ensure
1637         that the memory containing the tables remains available for as long  as         that  the memory containing the tables remains available for as long as
1638         it is needed.         it is needed.
1639    
1640         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
1641         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()
1642         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-
1643         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1644         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1645    
1646         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
1647         the internal tables) to pcre_exec(). Although  not  intended  for  this         the  internal  tables)  to  pcre_exec(). Although not intended for this
1648         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
1649         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
1650         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1651    
# Line 1561  INFORMATION ABOUT A PATTERN Line 1655  INFORMATION ABOUT A PATTERN
1655         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1656              int what, void *where);              int what, void *where);
1657    
1658         The  pcre_fullinfo() function returns information about a compiled pat-         The pcre_fullinfo() function returns information about a compiled  pat-
1659         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1660         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1661    
1662         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
1663         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
1664         the  pattern  was not studied. The third argument specifies which piece         the pattern was not studied. The third argument specifies  which  piece
1665         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
1666         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
1667         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1668    
1669           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1577  INFORMATION ABOUT A PATTERN Line 1671  INFORMATION ABOUT A PATTERN
1671           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1672           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1673    
1674         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
1675         an  simple check against passing an arbitrary memory pointer. Here is a         an simple check against passing an arbitrary memory pointer. Here is  a
1676         typical call of pcre_fullinfo(), to obtain the length of  the  compiled         typical  call  of pcre_fullinfo(), to obtain the length of the compiled
1677         pattern:         pattern:
1678    
1679           int rc;           int rc;
# Line 1590  INFORMATION ABOUT A PATTERN Line 1684  INFORMATION ABOUT A PATTERN
1684             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1685             &length);         /* where to put the data */             &length);         /* where to put the data */
1686    
1687         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
1688         are as follows:         are as follows:
1689    
1690           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1691    
1692         Return the number of the highest back reference  in  the  pattern.  The         Return  the  number  of  the highest back reference in the pattern. The
1693         fourth  argument  should  point to an int variable. Zero is returned if         fourth argument should point to an int variable. Zero  is  returned  if
1694         there are no back references.         there are no back references.
1695    
1696           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1697    
1698         Return the number of capturing subpatterns in the pattern.  The  fourth         Return  the  number of capturing subpatterns in the pattern. The fourth
1699         argument should point to an int variable.         argument should point to an int variable.
1700    
1701           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1702    
1703         Return  a pointer to the internal default character tables within PCRE.         Return a pointer to the internal default character tables within  PCRE.
1704         The fourth argument should point to an unsigned char *  variable.  This         The  fourth  argument should point to an unsigned char * variable. This
1705         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1706         tion. External callers can cause PCRE to use  its  internal  tables  by         tion.  External  callers  can  cause PCRE to use its internal tables by
1707         passing a NULL table pointer.         passing a NULL table pointer.
1708    
1709           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1710    
1711         Return  information  about  the first byte of any matched string, for a         Return information about the first byte of any matched  string,  for  a
1712         non-anchored pattern. The fourth argument should point to an int  vari-         non-anchored  pattern. The fourth argument should point to an int vari-
1713         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
1714         is still recognized for backwards compatibility.)         is still recognized for backwards compatibility.)
1715    
1716         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
1717         (cat|cow|coyote), its value is returned. Otherwise, if either         (cat|cow|coyote), its value is returned. Otherwise, if either
1718    
1719         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1720         branch starts with "^", or         branch starts with "^", or
1721    
1722         (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
1723         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1724    
1725         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
1726         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
1727         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1728    
1729           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1730    
1731         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
1732         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
1733         matching  string, a pointer to the table is returned. Otherwise NULL is         matching string, a pointer to the table is returned. Otherwise NULL  is
1734         returned. The fourth argument should point to an unsigned char *  vari-         returned.  The fourth argument should point to an unsigned char * vari-
1735         able.         able.
1736    
1737           PCRE_INFO_HASCRORLF           PCRE_INFO_HASCRORLF
1738    
1739         Return  1  if  the  pattern  contains any explicit matches for CR or LF         Return 1 if the pattern contains any explicit  matches  for  CR  or  LF
1740         characters, otherwise 0. The fourth argument should  point  to  an  int         characters,  otherwise  0.  The  fourth argument should point to an int
1741         variable.  An explicit match is either a literal CR or LF character, or         variable. An explicit match is either a literal CR or LF character,  or
1742         \r or \n.         \r or \n.
1743    
1744           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
1745    
1746         Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,         Return  1  if  the (?J) or (?-J) option setting is used in the pattern,
1747         otherwise  0. The fourth argument should point to an int variable. (?J)         otherwise 0. The fourth argument should point to an int variable.  (?J)
1748         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1749    
1750           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1751    
1752         Return the value of the rightmost literal byte that must exist  in  any         Return  the  value of the rightmost literal byte that must exist in any
1753         matched  string,  other  than  at  its  start,  if such a byte has been         matched string, other than at its  start,  if  such  a  byte  has  been
1754         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1755         is  no such byte, -1 is returned. For anchored patterns, a last literal         is no such byte, -1 is returned. For anchored patterns, a last  literal
1756         byte is recorded only if it follows something of variable  length.  For         byte  is  recorded only if it follows something of variable length. For
1757         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
1758         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1759    
1760             PCRE_INFO_MINLENGTH
1761    
1762           If  the  pattern  was studied and a minimum length for matching subject
1763           strings was computed, its value is  returned.  Otherwise  the  returned
1764           value  is  -1. The value is a number of characters, not bytes (this may
1765           be relevant in UTF-8 mode). The fourth argument should point to an  int
1766           variable.  A  non-negative  value is a lower bound to the length of any
1767           matching string. There may not be any strings of that  length  that  do
1768           actually match, but every string that does match is at least that long.
1769    
1770           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
1771           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1772           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1773    
1774         PCRE supports the use of named as well as numbered capturing  parenthe-         PCRE  supports the use of named as well as numbered capturing parenthe-
1775         ses.  The names are just an additional way of identifying the parenthe-         ses. The names are just an additional way of identifying the  parenthe-
1776         ses, which still acquire numbers. Several convenience functions such as         ses, which still acquire numbers. Several convenience functions such as
1777         pcre_get_named_substring()  are  provided  for extracting captured sub-         pcre_get_named_substring() are provided for  extracting  captured  sub-
1778         strings by name. It is also possible to extract the data  directly,  by         strings  by  name. It is also possible to extract the data directly, by
1779         first  converting  the  name to a number in order to access the correct         first converting the name to a number in order to  access  the  correct
1780         pointers in the output vector (described with pcre_exec() below). To do         pointers in the output vector (described with pcre_exec() below). To do
1781         the  conversion,  you  need  to  use  the  name-to-number map, which is         the conversion, you need  to  use  the  name-to-number  map,  which  is
1782         described by these three values.         described by these three values.
1783    
1784         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
1785         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1786         of each entry; both of these  return  an  int  value.  The  entry  size         of  each  entry;  both  of  these  return  an int value. The entry size
1787         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns
1788         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
1789         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-
1790         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-
1791         sponding  name,  zero  terminated. The names are in alphabetical order.         sponding name, zero terminated.
1792         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-  
1793         theses  numbers.  For  example,  consider the following pattern (assume         The names are in alphabetical order. Duplicate names may appear if  (?|
1794         PCRE_EXTENDED is  set,  so  white  space  -  including  newlines  -  is         is used to create multiple groups with the same number, as described in
1795         ignored):         the section on duplicate subpattern numbers in  the  pcrepattern  page.
1796           Duplicate  names  for  subpatterns with different numbers are permitted
1797           only if PCRE_DUPNAMES is set. In all cases  of  duplicate  names,  they
1798           appear  in  the table in the order in which they were found in the pat-
1799           tern. In the absence of (?| this is the  order  of  increasing  number;
1800           when (?| is used this is not necessarily the case because later subpat-
1801           terns may have lower numbers.
1802    
1803           As a simple example of the name/number table,  consider  the  following
1804           pattern  (assume  PCRE_EXTENDED is set, so white space - including new-
1805           lines - is ignored):
1806    
1807           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1808           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1809    
1810         There  are  four  named subpatterns, so the table has four entries, and         There are four named subpatterns, so the table has  four  entries,  and
1811         each entry in the table is eight bytes long. The table is  as  follows,         each  entry  in the table is eight bytes long. The table is as follows,
1812         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1813         as ??:         as ??:
1814    
# Line 1703  INFORMATION ABOUT A PATTERN Line 1817  INFORMATION ABOUT A PATTERN
1817           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1818           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1819    
1820         When writing code to extract data  from  named  subpatterns  using  the         When  writing  code  to  extract  data from named subpatterns using the
1821         name-to-number  map,  remember that the length of the entries is likely         name-to-number map, remember that the length of the entries  is  likely
1822         to be different for each compiled pattern.         to be different for each compiled pattern.
1823    
1824           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
1825    
1826         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
1827         The  fourth  argument  should point to an int variable. The pcrepartial         pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
1828         documentation lists the restrictions that apply to patterns  when  par-         variable.  From  release  8.00,  this  always  returns  1,  because the
1829         tial matching is used.         restrictions that previously applied  to  partial  matching  have  been
1830           lifted.  The  pcrepartial documentation gives details of partial match-
1831           ing.
1832    
1833           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1834    
1835         Return  a  copy of the options with which the pattern was compiled. The         Return a copy of the options with which the pattern was  compiled.  The
1836         fourth argument should point to an unsigned long  int  variable.  These         fourth  argument  should  point to an unsigned long int variable. These
1837         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1838         by any top-level option settings at the start of the pattern itself. In         by any top-level option settings at the start of the pattern itself. In
1839         other  words,  they are the options that will be in force when matching         other words, they are the options that will be in force  when  matching
1840         starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with         starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
1841         the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,         the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1842         and PCRE_EXTENDED.         and PCRE_EXTENDED.
1843    
1844         A pattern is automatically anchored by PCRE if  all  of  its  top-level         A  pattern  is  automatically  anchored by PCRE if all of its top-level
1845         alternatives begin with one of the following:         alternatives begin with one of the following:
1846    
1847           ^     unless PCRE_MULTILINE is set           ^     unless PCRE_MULTILINE is set
# Line 1739  INFORMATION ABOUT A PATTERN Line 1855  INFORMATION ABOUT A PATTERN
1855    
1856           PCRE_INFO_SIZE           PCRE_INFO_SIZE
1857    
1858         Return the size of the compiled pattern, that is, the  value  that  was         Return  the  size  of the compiled pattern, that is, the value that was
1859         passed as the argument to pcre_malloc() when PCRE was getting memory in         passed as the argument to pcre_malloc() when PCRE was getting memory in
1860         which to place the compiled data. The fourth argument should point to a         which to place the compiled data. The fourth argument should point to a
1861         size_t variable.         size_t variable.
# Line 1747  INFORMATION ABOUT A PATTERN Line 1863  INFORMATION ABOUT A PATTERN
1863           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1864    
1865         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
1866         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
1867         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
1868         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
1869           data, zero is returned. The fourth argument should point  to  a  size_t
1870         variable.         variable.
1871    
1872    
# Line 1803  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1920  MATCHING A PATTERN: THE TRADITIONAL FUNC
1920              const char *subject, int length, int startoffset,              const char *subject, int length, int startoffset,
1921              int options, int *ovector, int ovecsize);              int options, int *ovector, int ovecsize);
1922    
1923         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
1924         compiled pattern, which is passed in the code argument. If the  pattern         compiled  pattern, which is passed in the code argument. If the pattern
1925         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
1926         argument. This function is the main matching facility of  the  library,         argument.  This  function is the main matching facility of the library,
1927         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
1928         an alternative matching function, which is described below in the  sec-         an  alternative matching function, which is described below in the sec-
1929         tion about the pcre_dfa_exec() function.         tion about the pcre_dfa_exec() function.
1930    
1931         In  most applications, the pattern will have been compiled (and option-         In most applications, the pattern will have been compiled (and  option-
1932         ally studied) in the same process that calls pcre_exec().  However,  it         ally  studied)  in the same process that calls pcre_exec(). However, it
1933         is possible to save compiled patterns and study data, and then use them         is possible to save compiled patterns and study data, and then use them
1934         later in different processes, possibly even on different hosts.  For  a         later  in  different processes, possibly even on different hosts. For a
1935         discussion about this, see the pcreprecompile documentation.         discussion about this, see the pcreprecompile documentation.
1936    
1937         Here is an example of a simple call to pcre_exec():         Here is an example of a simple call to pcre_exec():
# Line 1833  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1950  MATCHING A PATTERN: THE TRADITIONAL FUNC
1950    
1951     Extra data for pcre_exec()     Extra data for pcre_exec()
1952    
1953         If  the  extra argument is not NULL, it must point to a pcre_extra data         If the extra argument is not NULL, it must point to a  pcre_extra  data
1954         block. The pcre_study() function returns such a block (when it  doesn't         block.  The pcre_study() function returns such a block (when it doesn't
1955         return  NULL), but you can also create one for yourself, and pass addi-         return NULL), but you can also create one for yourself, and pass  addi-
1956         tional information in it. The pcre_extra block contains  the  following         tional  information  in it. The pcre_extra block contains the following
1957         fields (not necessarily in this order):         fields (not necessarily in this order):
1958    
1959           unsigned long int flags;           unsigned long int flags;
# Line 1845  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1962  MATCHING A PATTERN: THE TRADITIONAL FUNC
1962           unsigned long int match_limit_recursion;           unsigned long int match_limit_recursion;
1963           void *callout_data;           void *callout_data;
1964           const unsigned char *tables;           const unsigned char *tables;
1965             unsigned char **mark;
1966    
1967         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
1968         are set. The flag bits are:         are set. The flag bits are:
1969    
1970           PCRE_EXTRA_STUDY_DATA           PCRE_EXTRA_STUDY_DATA
# Line 1854  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1972  MATCHING A PATTERN: THE TRADITIONAL FUNC
1972           PCRE_EXTRA_MATCH_LIMIT_RECURSION           PCRE_EXTRA_MATCH_LIMIT_RECURSION
1973           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1974           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1975             PCRE_EXTRA_MARK
1976    
1977         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
1978         the  pcre_extra  block  that is returned by pcre_study(), together with         the pcre_extra block that is returned by  pcre_study(),  together  with
1979         the appropriate flag bit. You should not set this yourself, but you may         the appropriate flag bit. You should not set this yourself, but you may
1980         add  to  the  block by setting the other fields and their corresponding         add to the block by setting the other fields  and  their  corresponding
1981         flag bits.         flag bits.
1982    
1983         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
1984         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
1985         match, but which have a very large number  of  possibilities  in  their         match,  but  which  have  a very large number of possibilities in their
1986         search  trees.  The  classic  example  is  the  use of nested unlimited         search trees. The classic example is a pattern that uses nested  unlim-
1987         repeats.         ited repeats.
1988    
1989         Internally, PCRE uses a function called match() which it calls  repeat-         Internally,  PCRE uses a function called match() which it calls repeat-
1990         edly  (sometimes  recursively). The limit set by match_limit is imposed         edly (sometimes recursively). The limit set by match_limit  is  imposed
1991         on the number of times this function is called during  a  match,  which         on  the  number  of times this function is called during a match, which
1992         has  the  effect  of  limiting the amount of backtracking that can take         has the effect of limiting the amount of  backtracking  that  can  take
1993         place. For patterns that are not anchored, the count restarts from zero         place. For patterns that are not anchored, the count restarts from zero
1994         for each position in the subject string.         for each position in the subject string.
1995    
1996         The  default  value  for  the  limit can be set when PCRE is built; the         The default value for the limit can be set  when  PCRE  is  built;  the
1997         default default is 10 million, which handles all but the  most  extreme         default  default  is 10 million, which handles all but the most extreme
1998         cases.  You  can  override  the  default by suppling pcre_exec() with a         cases. You can override the default  by  suppling  pcre_exec()  with  a
1999         pcre_extra    block    in    which    match_limit    is    set,     and         pcre_extra     block    in    which    match_limit    is    set,    and
2000         PCRE_EXTRA_MATCH_LIMIT  is  set  in  the  flags  field. If the limit is         PCRE_EXTRA_MATCH_LIMIT is set in the  flags  field.  If  the  limit  is
2001         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.         exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
2002    
2003         The match_limit_recursion field is similar to match_limit, but  instead         The  match_limit_recursion field is similar to match_limit, but instead
2004         of limiting the total number of times that match() is called, it limits         of limiting the total number of times that match() is called, it limits
2005         the depth of recursion. The recursion depth is a  smaller  number  than         the  depth  of  recursion. The recursion depth is a smaller number than
2006         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-
2007         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.
2008    
2009         Limiting  the  recursion  depth  limits the amount of stack that can be         Limiting  the  recursion  depth  limits the amount of stack that can be
# Line 1898  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2017  MATCHING A PATTERN: THE TRADITIONAL FUNC
2017         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
2018         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
2019    
2020         The pcre_callout field is used in conjunction with the  "callout"  fea-         The callout_data field is used in conjunction with the  "callout"  fea-
2021         ture, which is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
2022    
2023         The  tables  field  is  used  to  pass  a  character  tables pointer to         The  tables  field  is  used  to  pass  a  character  tables pointer to
2024         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec(); this overrides the value that is stored with the  compiled
# Line 1912  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2031  MATCHING A PATTERN: THE TRADITIONAL FUNC
2031         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address  when  pcre_exec() is called. See the pcreprecompile documenta-
2032         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
2033    
2034           If PCRE_EXTRA_MARK is set in the flags field, the mark  field  must  be
2035           set  to  point  to a char * variable. If the pattern contains any back-
2036           tracking control verbs such as (*MARK:NAME), and the execution ends  up
2037           with  a  name  to  pass back, a pointer to the name string (zero termi-
2038           nated) is placed in the variable pointed to  by  the  mark  field.  The
2039           names  are  within  the  compiled pattern; if you wish to retain such a
2040           name you must copy it before freeing the memory of a compiled  pattern.
2041           If  there  is no name to pass back, the variable pointed to by the mark
2042           field set to NULL. For details of the backtracking control  verbs,  see
2043           the section entitled "Backtracking control" in the pcrepattern documen-
2044           tation.
2045    
2046     Option bits for pcre_exec()     Option bits for pcre_exec()
2047    
2048         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.
2049         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,
2050         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,   PCRE_NOTEOL,    PCRE_NOTEMPTY,    PCRE_NOTEMPTY_ATSTART,
2051         PCRE_PARTIAL.         PCRE_NO_START_OPTIMIZE,   PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,  and
2052           PCRE_PARTIAL_HARD.
2053    
2054           PCRE_ANCHORED           PCRE_ANCHORED
2055    
2056         The  PCRE_ANCHORED  option  limits pcre_exec() to matching at the first         The PCRE_ANCHORED option limits pcre_exec() to matching  at  the  first
2057         matching position. If a pattern was  compiled  with  PCRE_ANCHORED,  or         matching  position.  If  a  pattern was compiled with PCRE_ANCHORED, or
2058         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
2059         unachored at matching time.         unachored at matching time.
2060    
2061           PCRE_BSR_ANYCRLF           PCRE_BSR_ANYCRLF
2062           PCRE_BSR_UNICODE           PCRE_BSR_UNICODE
2063    
2064         These options (which are mutually exclusive) control what the \R escape         These options (which are mutually exclusive) control what the \R escape
2065         sequence  matches.  The choice is either to match only CR, LF, or CRLF,         sequence matches. The choice is either to match only CR, LF,  or  CRLF,
2066         or to match any Unicode newline sequence. These  options  override  the         or  to  match  any Unicode newline sequence. These options override the
2067         choice that was made or defaulted when the pattern was compiled.         choice that was made or defaulted when the pattern was compiled.
2068    
2069           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 1940  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2072  MATCHING A PATTERN: THE TRADITIONAL FUNC
2072           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
2073           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
2074    
2075         These  options  override  the  newline  definition  that  was chosen or         These options override  the  newline  definition  that  was  chosen  or
2076         defaulted when the pattern was compiled. For details, see the  descrip-         defaulted  when the pattern was compiled. For details, see the descrip-
2077         tion  of  pcre_compile()  above.  During  matching,  the newline choice         tion of pcre_compile()  above.  During  matching,  the  newline  choice
2078         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
2079         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
2080         match failure for an unanchored pattern.         match failure for an unanchored pattern.
2081    
2082         When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is         When  PCRE_NEWLINE_CRLF,  PCRE_NEWLINE_ANYCRLF,  or PCRE_NEWLINE_ANY is
2083         set,  and a match attempt for an unanchored pattern fails when the cur-         set, and a match attempt for an unanchored pattern fails when the  cur-
2084         rent position is at a  CRLF  sequence,  and  the  pattern  contains  no         rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
2085         explicit  matches  for  CR  or  LF  characters,  the  match position is         explicit matches for  CR  or  LF  characters,  the  match  position  is
2086         advanced by two characters instead of one, in other words, to after the         advanced by two characters instead of one, in other words, to after the
2087         CRLF.         CRLF.
2088    
2089         The above rule is a compromise that makes the most common cases work as         The above rule is a compromise that makes the most common cases work as
2090         expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL         expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
2091         option is not set), it does not match the string "\r\nA" because, after         option is not set), it does not match the string "\r\nA" because, after
2092         failing at the start, it skips both the CR and the LF before  retrying.         failing  at the start, it skips both the CR and the LF before retrying.
2093         However,  the  pattern  [\r\n]A does match that string, because it con-         However, the pattern [\r\n]A does match that string,  because  it  con-
2094         tains an explicit CR or LF reference, and so advances only by one char-         tains an explicit CR or LF reference, and so advances only by one char-
2095         acter after the first failure.         acter after the first failure.
2096    
2097         An explicit match for CR of LF is either a literal appearance of one of         An explicit match for CR of LF is either a literal appearance of one of
2098         those characters, or one of the \r or  \n  escape  sequences.  Implicit         those  characters,  or  one  of the \r or \n escape sequences. Implicit
2099         matches  such  as [^X] do not count, nor does \s (which includes CR and         matches such as [^X] do not count, nor does \s (which includes  CR  and
2100         LF in the characters that it matches).         LF in the characters that it matches).
2101    
2102         Notwithstanding the above, anomalous effects may still occur when  CRLF         Notwithstanding  the above, anomalous effects may still occur when CRLF
2103         is a valid newline sequence and explicit \r or \n escapes appear in the         is a valid newline sequence and explicit \r or \n escapes appear in the
2104         pattern.         pattern.
2105    
2106           PCRE_NOTBOL           PCRE_NOTBOL
2107    
2108         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
2109         the  beginning  of  a  line, so the circumflex metacharacter should not         the beginning of a line, so the  circumflex  metacharacter  should  not
2110         match before it. Setting this without PCRE_MULTILINE (at compile  time)         match  before it. Setting this without PCRE_MULTILINE (at compile time)
2111         causes  circumflex  never to match. This option affects only the behav-         causes circumflex never to match. This option affects only  the  behav-
2112         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
2113    
2114           PCRE_NOTEOL           PCRE_NOTEOL
2115    
2116         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
2117         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
2118         in multiline mode) a newline immediately before it. Setting this  with-         in  multiline mode) a newline immediately before it. Setting this with-
2119         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2120         option affects only the behaviour of the dollar metacharacter. It  does         option  affects only the behaviour of the dollar metacharacter. It does
2121         not affect \Z or \z.         not affect \Z or \z.
2122    
2123           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2124    
2125         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
2126         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
2127         the  alternatives  match  the empty string, the entire match fails. For         the alternatives match the empty string, the entire  match  fails.  For
2128         example, if the pattern         example, if the pattern
2129    
2130           a?b?           a?b?
2131    
2132         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
2133         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
2134         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-
2135         rences of "a" or "b".         rences of "a" or "b".
2136    
2137         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2138         cial case of a pattern match of the empty  string  within  its  split()  
2139         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
2140         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
2141         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.
2142         if that fails by advancing the starting offset (see below)  and  trying  
2143         an ordinary match again. There is some code that demonstrates how to do         Perl    has    no    direct    equivalent    of    PCRE_NOTEMPTY     or
2144         this in the pcredemo.c sample program.         PCRE_NOTEMPTY_ATSTART,  but  it  does  make a special case of a pattern
2145           match of the empty string within its split() function, and  when  using
2146           the  /g  modifier.  It  is  possible  to emulate Perl's behaviour after
2147           matching a null string by first trying the match again at the same off-
2148           set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that
2149           fails, by advancing the starting offset (see below) and trying an ordi-
2150           nary  match  again. There is some code that demonstrates how to do this
2151           in the pcredemo sample program. In the most general case, you  have  to
2152           check  to  see  if the newline convention recognizes CRLF as a newline,
2153           and if so, and the current character is CR followed by LF, advance  the
2154           starting offset by two characters instead of one.
2155    
2156             PCRE_NO_START_OPTIMIZE
2157    
2158           There  are a number of optimizations that pcre_exec() uses at the start
2159           of a match, in order to speed up the process. For  example,  if  it  is
2160           known that an unanchored match must start with a specific character, it
2161           searches the subject for that character, and fails  immediately  if  it
2162           cannot  find  it,  without actually running the main matching function.
2163           This means that a special item such as (*COMMIT) at the start of a pat-
2164           tern  is  not  considered until after a suitable starting point for the
2165           match has been found. When callouts or (*MARK) items are in use,  these
2166           "start-up" optimizations can cause them to be skipped if the pattern is
2167           never actually used. The start-up optimizations are in  effect  a  pre-
2168           scan of the subject that takes place before the pattern is run.
2169    
2170           The  PCRE_NO_START_OPTIMIZE option disables the start-up optimizations,
2171           possibly causing performance to suffer,  but  ensuring  that  in  cases
2172           where  the  result is "no match", the callouts do occur, and that items
2173           such as (*COMMIT) and (*MARK) are considered at every possible starting
2174           position  in  the  subject  string. If PCRE_NO_START_OPTIMIZE is set at
2175           compile time, it cannot be unset at matching time.
2176    
2177           Setting PCRE_NO_START_OPTIMIZE can change the  outcome  of  a  matching
2178           operation.  Consider the pattern
2179    
2180             (*COMMIT)ABC
2181    
2182           When  this  is  compiled, PCRE records the fact that a match must start
2183           with the character "A". Suppose the subject  string  is  "DEFABC".  The
2184           start-up  optimization  scans along the subject, finds "A" and runs the
2185           first match attempt from there. The (*COMMIT) item means that the  pat-
2186           tern  must  match the current starting position, which in this case, it
2187           does. However, if the same match  is  run  with  PCRE_NO_START_OPTIMIZE
2188           set,  the  initial  scan  along the subject string does not happen. The
2189           first match attempt is run starting  from  "D"  and  when  this  fails,
2190           (*COMMIT)  prevents  any  further  matches  being tried, so the overall
2191           result is "no match". If the pattern is studied,  more  start-up  opti-
2192           mizations  may  be  used. For example, a minimum length for the subject
2193           may be recorded. Consider the pattern
2194    
2195             (*MARK:A)(X|Y)
2196    
2197           The minimum length for a match is one  character.  If  the  subject  is
2198           "ABC",  there  will  be  attempts  to  match "ABC", "BC", "C", and then
2199           finally an empty string.  If the pattern is studied, the final  attempt
2200           does  not take place, because PCRE knows that the subject is too short,
2201           and so the (*MARK) is never encountered.  In this  case,  studying  the
2202           pattern  does  not  affect the overall match result, which is still "no
2203           match", but it does affect the auxiliary information that is returned.
2204    
2205           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2206    
# Line 2019  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2210  MATCHING A PATTERN: THE TRADITIONAL FUNC
2210         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
2211         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
2212         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,
2213         pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-         pcre_exec() returns  the  error  PCRE_ERROR_BADUTF8  or,  if  PCRE_PAR-
2214         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
2215           end of the subject, PCRE_ERROR_SHORTUTF8.  If  startoffset  contains  a
2216           value  that does not point to the start of a UTF-8 character (or to the
2217           end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2218    
2219           If you already know that your subject is valid, and you  want  to  skip
2220           these    checks    for   performance   reasons,   you   can   set   the
2221           PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to
2222           do  this  for the second and subsequent calls to pcre_exec() if you are
2223           making repeated calls to find all  the  matches  in  a  single  subject
2224           string.  However,  you  should  be  sure  that the value of startoffset
2225           points to the start of a UTF-8 character (or the end of  the  subject).
2226           When  PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8
2227           string as a subject or an invalid value of  startoffset  is  undefined.
2228           Your program may crash.
2229    
2230         If  you  already  know that your subject is valid, and you want to skip           PCRE_PARTIAL_HARD
2231         these   checks   for   performance   reasons,   you   can    set    the           PCRE_PARTIAL_SOFT
2232         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to  
2233         do this for the second and subsequent calls to pcre_exec() if  you  are         These  options turn on the partial matching feature. For backwards com-
2234         making  repeated  calls  to  find  all  the matches in a single subject         patibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A  partial
2235         string. However, you should be  sure  that  the  value  of  startoffset         match  occurs if the end of the subject string is reached successfully,
2236         points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is         but there are not enough subject characters to complete the  match.  If
2237         set, the effect of passing an invalid UTF-8 string as a subject,  or  a         this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
2238         value  of startoffset that does not point to the start of a UTF-8 char-         matching continues by testing any remaining alternatives.  Only  if  no
2239         acter, is undefined. Your program may crash.         complete  match  can be found is PCRE_ERROR_PARTIAL returned instead of
2240           PCRE_ERROR_NOMATCH. In other words,  PCRE_PARTIAL_SOFT  says  that  the
2241           PCRE_PARTIAL         caller  is  prepared to handle a partial match, but only if no complete
2242           match can be found.
2243         This option turns on the  partial  matching  feature.  If  the  subject  
2244         string  fails to match the pattern, but at some point during the match-         If PCRE_PARTIAL_HARD is set, it overrides  PCRE_PARTIAL_SOFT.  In  this
2245         ing process the end of the subject was reached (that  is,  the  subject         case,  if  a  partial  match  is found, pcre_exec() immediately returns
2246         partially  matches  the  pattern and the failure to match occurred only         PCRE_ERROR_PARTIAL, without  considering  any  other  alternatives.  In
2247         because there were not enough subject characters), pcre_exec()  returns         other  words, when PCRE_PARTIAL_HARD is set, a partial match is consid-
2248         PCRE_ERROR_PARTIAL  instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL is         ered to be more important that an alternative complete match.
2249         used, there are restrictions on what may appear in the  pattern.  These  
2250         are discussed in the pcrepartial documentation.         In both cases, the portion of the string that was  inspected  when  the
2251           partial match was found is set as the first matching string. There is a
2252           more detailed discussion of partial and  multi-segment  matching,  with
2253           examples, in the pcrepartial documentation.
2254    
2255     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2256    
2257         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
2258         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.
2259         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,
2260         Unlike the pattern string, the subject may contain binary  zero  bytes.         pcre_exec() returns PCRE_ERROR_BADOFFSET. When the starting  offset  is
2261         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,
2262         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
2263           must  point  to  the start of a UTF-8 character (or the end of the sub-
2264         A non-zero starting offset is useful when searching for  another  match         ject). Unlike the pattern string, the subject may contain  binary  zero
2265         in  the same subject by calling pcre_exec() again after a previous suc-         bytes.
2266         cess.  Setting startoffset differs from just passing over  a  shortened  
2267         string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins         A  non-zero  starting offset is useful when searching for another match
2268           in the same subject by calling pcre_exec() again after a previous  suc-
2269           cess.   Setting  startoffset differs from just passing over a shortened
2270           string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins
2271         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
2272    
2273           \Biss\B           \Biss\B
2274    
2275         which finds occurrences of "iss" in the middle of  words.  (\B  matches         which  finds  occurrences  of "iss" in the middle of words. (\B matches
2276         only  if  the  current position in the subject is not a word boundary.)         only if the current position in the subject is not  a  word  boundary.)
2277         When applied to the string "Mississipi" the first call  to  pcre_exec()         When  applied  to the string "Mississipi" the first call to pcre_exec()
2278         finds  the  first  occurrence. If pcre_exec() is called again with just         finds the first occurrence. If pcre_exec() is called  again  with  just
2279         the remainder of the subject,  namely  "issipi",  it  does  not  match,         the  remainder  of  the  subject,  namely  "issipi", it does not match,
2280         because \B is always false at the start of the subject, which is deemed         because \B is always false at the start of the subject, which is deemed
2281         to be a word boundary. However, if pcre_exec()  is  passed  the  entire         to  be  a  word  boundary. However, if pcre_exec() is passed the entire
2282         string again, but with startoffset set to 4, it finds the second occur-         string again, but with startoffset set to 4, it finds the second occur-
2283         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
2284         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2285    
2286           Finding all the matches in a subject is tricky  when  the  pattern  can
2287           match an empty string. It is possible to emulate Perl's /g behaviour by
2288           first  trying  the  match  again  at  the   same   offset,   with   the
2289           PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED  options,  and  then  if that
2290           fails, advancing the starting  offset  and  trying  an  ordinary  match
2291           again. There is some code that demonstrates how to do this in the pcre-
2292           demo sample program. In the most general case, you have to check to see
2293           if  the newline convention recognizes CRLF as a newline, and if so, and
2294           the current character is CR followed by LF, advance the starting offset
2295           by two characters instead of one.
2296    
2297         If  a  non-zero starting offset is passed when the pattern is anchored,         If  a  non-zero starting offset is passed when the pattern is anchored,
2298         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
2299         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
# Line 2087  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2309  MATCHING A PATTERN: THE TRADITIONAL FUNC
2309         string.  PCRE  supports several other kinds of parenthesized subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2310         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2311    
2312         Captured substrings are returned to the caller via a vector of  integer         Captured substrings are returned to the caller via a vector of integers
2313         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-
2314         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:
2315         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2316    
2317         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-
2318         strings, each substring using a pair of integers. The  remaining  third         strings, each substring using a pair of integers. The  remaining  third
2319         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-
2320         turing subpatterns, and is not available for passing back  information.         turing subpatterns, and is not available for passing back  information.
2321         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
2322         it is not, it is rounded down.         it is not, it is rounded down.
2323    
2324         When a match is successful, information about  captured  substrings  is         When a match is successful, information about  captured  substrings  is
2325         returned  in  pairs  of integers, starting at the beginning of ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2326         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
2327         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
2328         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
2329         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
2330         tor[1], identify the portion of  the  subject  string  matched  by  the         byte offsets, even in UTF-8 mode. They are not character counts.
2331         entire  pattern.  The next pair is used for the first capturing subpat-  
2332         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
2333         highest numbered pair that has been set. For example, if two substrings         portion  of  the subject string matched by the entire pattern. The next
2334         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
2335         subpatterns,  the return value from a successful match is 1, indicating         returned by pcre_exec() is one more than the highest numbered pair that
2336         that just the first pair of offsets has been set.         has been set.  For example, if two substrings have been  captured,  the
2337           returned  value is 3. If there are no capturing subpatterns, the return
2338           value from a successful match is 1, indicating that just the first pair
2339           of offsets has been set.
2340    
2341         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2342         of the string that it matched that is returned.         of the string that it matched that is returned.
2343    
2344         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,
2345         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
2346         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
2347         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
2348         as  NULL  and  ovecsize  as zero. However, if the pattern contains back         ovecsize as zero. However, if the pattern contains back references  and
2349         references and the ovector is not big enough to  remember  the  related         the  ovector is not big enough to remember the related substrings, PCRE
2350         substrings,  PCRE has to get additional memory for use during matching.         has to get additional memory for use during matching. Thus it  is  usu-
2351         Thus it is usually advisable to supply an ovector.         ally advisable to supply an ovector.
2352    
2353         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
2354         subpatterns  there  are  in  a  compiled pattern. The smallest size for         subpatterns there are in a compiled  pattern.  The  smallest  size  for
2355         ovector that will allow for n captured substrings, in addition  to  the         ovector  that  will allow for n captured substrings, in addition to the
2356         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.
2357    
2358         It  is  possible for capturing subpattern number n+1 to match some part         It is possible for capturing subpattern number n+1 to match  some  part
2359         of the subject when subpattern n has not been used at all. For example,         of the subject when subpattern n has not been used at all. For example,
2360         if  the  string  "abc"  is  matched against the pattern (a|(z))(bc) the         if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the
2361         return from the function is 4, and subpatterns 1 and 3 are matched, but         return from the function is 4, and subpatterns 1 and 3 are matched, but
2362         2  is  not.  When  this happens, both values in the offset pairs corre-         2 is not. When this happens, both values in  the  offset  pairs  corre-
2363         sponding to unused subpatterns are set to -1.         sponding to unused subpatterns are set to -1.
2364    
2365         Offset values that correspond to unused subpatterns at the end  of  the         Offset  values  that correspond to unused subpatterns at the end of the
2366         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
2367         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
2368         matched.  The  return  from the function is 2, because the highest used         matched. The return from the function is 2, because  the  highest  used
2369         capturing subpattern number is 1. However, you can refer to the offsets         capturing  subpattern  number  is 1, and the offsets for for the second
2370         for  the  second  and third capturing subpatterns if you wish (assuming         and third capturing subpatterns (assuming the vector is  large  enough,
2371         the vector is large enough, of course).         of course) are set to -1.
2372    
2373           Note: Elements of ovector that do not correspond to capturing parenthe-
2374           ses in the pattern are never changed. That is, if a pattern contains  n
2375           capturing parentheses, no more than ovector[0] to ovector[2n+1] are set
2376           by pcre_exec(). The other elements retain whatever values  they  previ-
2377           ously had.
2378    
2379         Some convenience functions are provided  for  extracting  the  captured         Some  convenience  functions  are  provided for extracting the captured
2380         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
2381    
2382     Error return values from pcre_exec()     Error return values from pcre_exec()
2383    
2384         If  pcre_exec()  fails, it returns a negative number. The following are         If pcre_exec() fails, it returns a negative number. The  following  are
2385         defined in the header file:         defined in the header file:
2386    
2387           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 2159  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2390  MATCHING A PATTERN: THE TRADITIONAL FUNC
2390    
2391           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2392    
2393         Either code or subject was passed as NULL,  or  ovector  was  NULL  and         Either  code  or  subject  was  passed as NULL, or ovector was NULL and
2394         ovecsize was not zero.         ovecsize was not zero.
2395    
2396           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 2168  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2399  MATCHING A PATTERN: THE TRADITIONAL FUNC
2399    
2400           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2401    
2402         PCRE  stores a 4-byte "magic number" at the start of the compiled code,         PCRE stores a 4-byte "magic number" at the start of the compiled  code,
2403         to catch the case when it is passed a junk pointer and to detect when a         to catch the case when it is passed a junk pointer and to detect when a
2404         pattern that was compiled in an environment of one endianness is run in         pattern that was compiled in an environment of one endianness is run in
2405         an environment with the other endianness. This is the error  that  PCRE         an  environment  with the other endianness. This is the error that PCRE
2406         gives when the magic number is not present.         gives when the magic number is not present.
2407    
2408           PCRE_ERROR_UNKNOWN_OPCODE (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2409    
2410         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2411         compiled pattern. This error could be caused by a bug  in  PCRE  or  by         compiled  pattern.  This  error  could be caused by a bug in PCRE or by
2412         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2413    
2414           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2415    
2416         If  a  pattern contains back references, but the ovector that is passed         If a pattern contains back references, but the ovector that  is  passed
2417         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2418         PCRE  gets  a  block of memory at the start of matching to use for this         PCRE gets a block of memory at the start of matching to  use  for  this
2419         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
2420         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2421    
2422           This error is also given if pcre_stack_malloc() fails  in  pcre_exec().
2423           This  can happen only when PCRE has been compiled with --disable-stack-
2424           for-recursion.
2425    
2426           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2427    
2428         This  error is used by the pcre_copy_substring(), pcre_get_substring(),         This error is used by the pcre_copy_substring(),  pcre_get_substring(),
2429         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2430         returned by pcre_exec().         returned by pcre_exec().
2431    
2432           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2433    
2434         The  backtracking  limit,  as  specified  by the match_limit field in a         The backtracking limit, as specified by  the  match_limit  field  in  a
2435         pcre_extra structure (or defaulted) was reached.  See  the  description         pcre_extra  structure  (or  defaulted) was reached. See the description
2436         above.         above.
2437    
2438           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2439    
2440         This error is never generated by pcre_exec() itself. It is provided for         This error is never generated by pcre_exec() itself. It is provided for
2441         use by callout functions that want to yield a distinctive  error  code.         use  by  callout functions that want to yield a distinctive error code.
2442         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2443    
2444           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2445    
2446         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
2447         subject.         subject.   However,  if  PCRE_PARTIAL_HARD  is set and the problem is a
2448           truncated UTF-8 character at the end of the subject,  PCRE_ERROR_SHORT-
2449           UTF8 is used instead.
2450    
2451           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2452    
2453         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
2454         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-
2455         ter.         ter or the end of the subject.
2456    
2457           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2458    
2459         The subject string did not match, but it did match partially.  See  the         The  subject  string did not match, but it did match partially. See the
2460         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
2461    
2462           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2463    
2464         The  PCRE_PARTIAL  option  was  used with a compiled pattern containing         This code is no longer in  use.  It  was  formerly  returned  when  the
2465         items that are not supported for partial matching. See the  pcrepartial         PCRE_PARTIAL  option  was used with a compiled pattern containing items
2466         documentation for details of partial matching.         that were  not  supported  for  partial  matching.  From  release  8.00
2467           onwards, there are no restrictions on partial matching.
2468    
2469           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2470    
# Line 2235  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2473  MATCHING A PATTERN: THE TRADITIONAL FUNC
2473    
2474           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2475    
2476         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.
2477    
2478           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2479    
2480         The internal recursion limit, as specified by the match_limit_recursion         The internal recursion limit, as specified by the match_limit_recursion
2481         field in a pcre_extra structure (or defaulted)  was  reached.  See  the         field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2482         description above.         description above.
2483    
2484           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
2485    
2486         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2487    
2488             PCRE_ERROR_BADOFFSET      (-24)
2489    
2490           The value of startoffset was negative or greater than the length of the
2491           subject, that is, the value in length.
2492    
2493             PCRE_ERROR_SHORTUTF8      (-25)
2494    
2495           The  subject  string ended with an incomplete (truncated) UTF-8 charac-
2496           ter, and the PCRE_PARTIAL_HARD option was  set.  Without  this  option,
2497           PCRE_ERROR_BADUTF8 is returned in this situation.
2498    
2499         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().
2500    
2501    
# Line 2385  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2634  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2634         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
2635         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2636    
2637           Warning: If the pattern uses the (?| feature to set up multiple subpat-
2638           terns with the same number, as described in the  section  on  duplicate
2639           subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2640           distinguish the different subpatterns, because names are  not  included
2641           in  the compiled code. The matching process uses only numbers. For this
2642           reason, the use of different names for subpatterns of the  same  number
2643           causes an error at compile time.
2644    
2645    
2646  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
2647    
# Line 2392  DUPLICATE SUBPATTERN NAMES Line 2649  DUPLICATE SUBPATTERN NAMES
2649              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2650    
2651         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2652         subpatterns are not required to  be  unique.  Normally,  patterns  with         subpatterns are not required to be unique. (Duplicate names are  always
2653         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 (?|
2654         subpatterns participates. An example is shown in the pcrepattern  docu-         feature. Indeed, if such subpatterns are named, they  are  required  to
2655         mentation.         use the same names.)
2656    
2657           Normally, patterns with duplicate names are such that in any one match,
2658           only one of the named subpatterns participates. An example is shown  in
2659           the pcrepattern documentation.
2660    
2661         When    duplicates   are   present,   pcre_copy_named_substring()   and         When    duplicates   are   present,   pcre_copy_named_substring()   and
2662         pcre_get_named_substring() return the first substring corresponding  to         pcre_get_named_substring() return the first substring corresponding  to
# Line 2448  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2709  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2709         characteristics to the normal algorithm, and  is  not  compatible  with         characteristics to the normal algorithm, and  is  not  compatible  with
2710         Perl.  Some  of the features of PCRE patterns are not supported. Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2711         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
2712         a discussion of the two matching algorithms, see the pcrematching docu-         a  discussion  of  the  two matching algorithms, and a list of features
2713         mentation.         that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2714           tion.
2715    
2716         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
2717         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-
2718         ent way, and this is described below. The other  common  arguments  are         ent  way,  and  this is described below. The other common arguments are
2719         used  in  the  same way as for pcre_exec(), so their description is not         used in the same way as for pcre_exec(), so their  description  is  not
2720         repeated here.         repeated here.
2721    
2722         The two additional arguments provide workspace for  the  function.  The         The  two  additional  arguments provide workspace for the function. The
2723         workspace  vector  should  contain at least 20 elements. It is used for         workspace vector should contain at least 20 elements. It  is  used  for
2724         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2725         workspace  will  be  needed for patterns and subjects where there are a         workspace will be needed for patterns and subjects where  there  are  a
2726         lot of potential matches.         lot of potential matches.
2727    
2728         Here is an example of a simple call to pcre_dfa_exec():         Here is an example of a simple call to pcre_dfa_exec():
# Line 2482  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2744  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2744    
2745     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2746    
2747         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
2748         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-
2749         LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,  PCRE_NO_UTF8_CHECK,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2750         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last         PCRE_NOTEMPTY_ATSTART,      PCRE_NO_UTF8_CHECK,       PCRE_BSR_ANYCRLF,
2751         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-
2752         not repeated here.         TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.  All but  the  last
2753           four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
2754           PCRE_PARTIAL         description is not repeated here.
2755    
2756         This  has  the  same general effect as it does for pcre_exec(), but the           PCRE_PARTIAL_HARD
2757         details  are  slightly  different.  When  PCRE_PARTIAL   is   set   for           PCRE_PARTIAL_SOFT
2758         pcre_dfa_exec(),  the  return code PCRE_ERROR_NOMATCH is converted into  
2759         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
2760         been no complete matches, but there is still at least one matching pos-         details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
2761         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-
2762         set as the first matching string.         ject  is  reached  and there is still at least one matching possibility
2763           that requires additional characters. This happens even if some complete
2764           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2765           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2766           of  the  subject  is  reached, there have been no complete matches, but
2767           there is still at least one matching possibility. The  portion  of  the
2768           string  that  was inspected when the longest partial match was found is
2769           set as the first matching string  in  both  cases.   There  is  a  more
2770           detailed  discussion  of partial and multi-segment matching, with exam-
2771           ples, in the pcrepartial documentation.
2772    
2773           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2774    
2775         Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
2776         stop as soon as it has found one match. Because of the way the alterna-         stop as soon as it has found one match. Because of the way the alterna-
2777         tive  algorithm  works, this is necessarily the shortest possible match         tive algorithm works, this is necessarily the shortest  possible  match
2778         at the first possible matching point in the subject string.         at the first possible matching point in the subject string.
2779    
2780           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2781    
2782         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
2783         returns  a  partial  match, it is possible to call it again, with addi-         again, with additional subject characters, and have  it  continue  with
2784         tional subject characters, and have it continue with  the  same  match.         the  same match. The PCRE_DFA_RESTART option requests this action; when
2785         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
2786         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
2787         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
2788         match. There is more discussion of this  facility  in  the  pcrepartial         pcrepartial documentation.
        documentation.  
2789    
2790     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2791    
# Line 2592  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2862  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2862  SEE ALSO  SEE ALSO
2863    
2864         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
2865         tial(3),  pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2866    
2867    
2868  AUTHOR  AUTHOR
# Line 2604  AUTHOR Line 2874  AUTHOR
2874    
2875  REVISION  REVISION
2876    
2877         Last updated: 12 April 2008         Last updated: 21 November 2010
2878         Copyright (c) 1997-2008 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
2879  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2880    
2881    
2882  PCRECALLOUT(3)                                                  PCRECALLOUT(3)  PCRECALLOUT(3)                                                  PCRECALLOUT(3)
2883    
2884    
# Line 2634  PCRE CALLOUTS Line 2904  PCRE CALLOUTS
2904    
2905           (?C1)abc(?C2)def           (?C1)abc(?C2)def
2906    
2907         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
2908         called, PCRE automatically  inserts  callouts,  all  with  number  255,         pcre_compile2() is called, PCRE  automatically  inserts  callouts,  all
2909         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
2910         used with the pattern         PCRE_AUTO_CALLOUT is used with the pattern
2911    
2912           A(\d{2}|--)           A(\d{2}|--)
2913    
# Line 2656  PCRE CALLOUTS Line 2926  PCRE CALLOUTS
2926  MISSING CALLOUTS  MISSING CALLOUTS
2927    
2928         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
2929         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
2930         pattern is         example, if the pattern is
2931    
2932           ab(?C4)cd           ab(?C4)cd
2933    
# Line 2666  MISSING CALLOUTS Line 2936  MISSING CALLOUTS
2936         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
2937         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
2938    
2939           If the pattern is studied, PCRE knows the minimum length of a  matching
2940           string,  and will immediately give a "no match" return without actually
2941           running a match if the subject is not long enough, or,  for  unanchored
2942           patterns, if it has been scanned far enough.
2943    
2944           You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
2945           MIZE option to pcre_compile(), pcre_exec(), or pcre_dfa_exec(),  or  by
2946           starting the pattern with (*NO_START_OPT). This slows down the matching
2947           process, but does ensure that callouts such as the  example  above  are
2948           obeyed.
2949    
2950    
2951  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2952    
2953         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
2954         tion  defined by pcre_callout is called (if it is set). This applies to         tion defined by pcre_callout is called (if it is set). This applies  to
2955         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
2956         only  argument  to  the callout function is a pointer to a pcre_callout         only argument to the callout function is a pointer  to  a  pcre_callout
2957         block. This structure contains the following fields:         block. This structure contains the following fields:
2958    
2959           int          version;           int          version;
# Line 2688  THE CALLOUT INTERFACE Line 2969  THE CALLOUT INTERFACE
2969           int          pattern_position;           int          pattern_position;
2970           int          next_item_length;           int          next_item_length;
2971    
2972         The version field is an integer containing the version  number  of  the         The  version  field  is an integer containing the version number of the
2973         block  format. The initial version was 0; the current version is 1. The         block format. The initial version was 0; the current version is 1.  The
2974         version number will change again in future  if  additional  fields  are         version  number  will  change  again in future if additional fields are
2975         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.
2976    
2977         The callout_number field contains the number of the  callout,  as  com-         The callout_number field contains the number of the  callout,  as  com-
# Line 2757  RETURN VALUES Line 3038  RETURN VALUES
3038         zero, matching fails at the current point, but  the  testing  of  other         zero, matching fails at the current point, but  the  testing  of  other
3039         matching possibilities goes ahead, just as if a lookahead assertion had         matching possibilities goes ahead, just as if a lookahead assertion had
3040         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
3041         pcre_exec() (or pcre_dfa_exec()) returns the negative value.         pcre_exec() or pcre_dfa_exec() returns the negative value.
3042    
3043         Negative   values   should   normally   be   chosen  from  the  set  of         Negative   values   should   normally   be   chosen  from  the  set  of
3044         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
# Line 2775  AUTHOR Line 3056  AUTHOR
3056    
3057  REVISION  REVISION
3058    
3059         Last updated: 29 May 2007         Last updated: 21 November 2010
3060         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
3061  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3062    
3063    
3064  PCRECOMPAT(3)                                                    PCRECOMPAT(3)  PCRECOMPAT(3)                                                    PCRECOMPAT(3)
3065    
3066    
# Line 2790  NAME Line 3071  NAME
3071  DIFFERENCES BETWEEN PCRE AND PERL  DIFFERENCES BETWEEN PCRE AND PERL
3072    
3073         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
3074         handle regular expressions. The differences described here  are  mainly         handle regular expressions. The differences  described  here  are  with
3075         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.  
3076    
3077         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
3078         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
3079         main pcre page.         main pcre page.
3080    
3081         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl
3082         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,
3083         (?!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
3084         just asserts that the next character is not "a" three times.         just asserts that the next character is not "a" three times.
3085    
3086         3.  Capturing  subpatterns  that occur inside negative lookahead asser-         3. Capturing subpatterns that occur inside  negative  lookahead  asser-
3087         tions are counted, but their entries in the offsets  vector  are  never         tions  are  counted,  but their entries in the offsets vector are never
3088         set.  Perl sets its numerical variables from any such patterns that are         set. Perl sets its numerical variables from any such patterns that  are
3089         matched before the assertion fails to match something (thereby succeed-         matched before the assertion fails to match something (thereby succeed-
3090         ing),  but  only  if the negative lookahead assertion contains just one         ing), but only if the negative lookahead assertion  contains  just  one
3091         branch.         branch.
3092    
3093         4. Though binary zero characters are supported in the  subject  string,         4.  Though  binary zero characters are supported in the subject string,
3094         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-
3095         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
3096         the pattern to represent a binary zero.         the pattern to represent a binary zero.
3097    
3098         5.  The  following Perl escape sequences are not supported: \l, \u, \L,         5. The following Perl escape sequences are not supported: \l,  \u,  \L,
3099         \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-
3100         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
3101         are encountered by PCRE, an error is generated.         are encountered by PCRE, an error is generated.
3102    
3103         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
3104         is  built  with Unicode character property support. The properties that         is built with Unicode character property support. The  properties  that
3105         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-
3106         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
3107         derived properties Any and L&.         derived  properties  Any  and  L&. PCRE does support the Cs (surrogate)
3108           property, which Perl does not; the  Perl  documentation  says  "Because
3109           Perl hides the need for the user to understand the internal representa-
3110           tion of Unicode characters, there is no need to implement the  somewhat
3111           messy concept of surrogates."
3112    
3113         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-
3114         ters  in  between  are  treated as literals. This is slightly different         ters in between are treated as literals.  This  is  slightly  different
3115         from Perl in that $ and @ are  also  handled  as  literals  inside  the         from  Perl  in  that  $  and  @ are also handled as literals inside the
3116         quotes.  In Perl, they cause variable interpolation (but of course PCRE         quotes. In Perl, they cause variable interpolation (but of course  PCRE
3117         does not have variables). Note the following examples:         does not have variables). Note the following examples:
3118    
3119             Pattern            PCRE matches      Perl matches             Pattern            PCRE matches      Perl matches
# Line 2839  DIFFERENCES BETWEEN PCRE AND PERL Line 3123  DIFFERENCES BETWEEN PCRE AND PERL
3123             \Qabc\$xyz\E       abc\$xyz          abc\$xyz             \Qabc\$xyz\E       abc\$xyz          abc\$xyz
3124             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
3125    
3126         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
3127         classes.         classes.
3128    
3129         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
3130         constructions. However, there is support for recursive  patterns.  This         constructions.  However,  there is support for recursive patterns. This
3131         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
3132         "callout" feature allows an external function to be called during  pat-         "callout"  feature allows an external function to be called during pat-
3133         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
3134    
3135         9.  Subpatterns  that  are  called  recursively or as "subroutines" are         9. Subpatterns that are called  recursively  or  as  "subroutines"  are
3136         always treated as atomic groups in  PCRE.  This  is  like  Python,  but         always  treated  as  atomic  groups  in  PCRE. This is like Python, but
3137         unlike Perl.         unlike Perl. There is a discussion of an example that explains this  in
3138           more  detail  in  the section on recursion differences from Perl in the
3139         10.  There are some differences that are concerned with the settings of         pcrepattern page.
3140         captured strings when part of  a  pattern  is  repeated.  For  example,  
3141         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2         10. There are some differences that are concerned with the settings  of
3142           captured  strings  when  part  of  a  pattern is repeated. For example,
3143           matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2
3144         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
3145    
3146         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),         11.  PCRE's handling of duplicate subpattern numbers and duplicate sub-
3147         (*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
3148         the forms without an  argument.  PCRE  does  not  support  (*MARK).  If         fact the PCRE works internally just with numbers, using an external ta-
3149         (*ACCEPT)  is within capturing parentheses, PCRE does not set that cap-         ble to translate between numbers and names. In  particular,  a  pattern
3150         ture group; this is different to Perl.         such  as  (?|(?<a>A)|(?<b)B),  where the two capturing parentheses have
3151           the same number but different names, is not supported,  and  causes  an
3152         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
3153         ities.   Perl  5.10  will  include new features that are not in earlier         distinguish which parentheses matched, because both names map  to  cap-
3154         versions, some of which (such as named parentheses) have been  in  PCRE         turing subpattern number 1. To avoid this confusing situation, an error
3155         for some time. This list is with respect to Perl 5.10:         is given at compile time.
3156    
3157         (a)  Although  lookbehind  assertions  must match fixed length strings,         12. Perl recognizes comments in some  places  that  PCRE  doesn't,  for
3158         each alternative branch of a lookbehind assertion can match a different         example, between the ( and ? at the start of a subpattern.
3159         length of string. Perl requires them all to have the same length.  
3160           13. PCRE provides some extensions to the Perl regular expression facil-
3161           ities.  Perl 5.10 includes new features that are not  in  earlier  ver-
3162           sions  of  Perl, some of which (such as named parentheses) have been in
3163           PCRE for some time. This list is with respect to Perl 5.10:
3164    
3165           (a) Although lookbehind assertions in  PCRE  must  match  fixed  length
3166           strings,  each alternative branch of a lookbehind assertion can match a
3167           different length of string. Perl requires them all  to  have  the  same
3168           length.
3169    
3170         (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 $
3171         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
# Line 2886  DIFFERENCES BETWEEN PCRE AND PERL Line 3181  DIFFERENCES BETWEEN PCRE AND PERL
3181         (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
3182         tried only at the first matching position in the subject string.         tried only at the first matching position in the subject string.
3183    
3184         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
3185         TURE options for pcre_exec() have no Perl equivalents.         and PCRE_NO_AUTO_CAPTURE options for pcre_exec() have no  Perl  equiva-
3186           lents.
3187    
3188         (g) The \R escape sequence can be restricted to match only CR,  LF,  or         (g)  The  \R escape sequence can be restricted to match only CR, LF, or
3189         CRLF by the PCRE_BSR_ANYCRLF option.         CRLF by the PCRE_BSR_ANYCRLF option.
3190    
3191         (h) The callout facility is PCRE-specific.         (h) The callout facility is PCRE-specific.
# Line 2899  DIFFERENCES BETWEEN PCRE AND PERL Line 3195  DIFFERENCES BETWEEN PCRE AND PERL
3195         (j) Patterns compiled by PCRE can be saved and re-used at a later time,         (j) Patterns compiled by PCRE can be saved and re-used at a later time,
3196         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
3197    
3198         (k) The alternative matching function (pcre_dfa_exec())  matches  in  a         (k)  The  alternative  matching function (pcre_dfa_exec()) matches in a
3199         different way and is not Perl-compatible.         different way and is not Perl-compatible.
3200    
3201         (l)  PCRE  recognizes some special sequences such as (*CR) at the start         (l) PCRE recognizes some special sequences such as (*CR) at  the  start
3202         of a pattern that set overall options that cannot be changed within the         of a pattern that set overall options that cannot be changed within the
3203         pattern.         pattern.
3204    
# Line 2916  AUTHOR Line 3212  AUTHOR
3212    
3213  REVISION  REVISION
3214    
3215         Last updated: 11 September 2007         Last updated: 31 October 2010
3216         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
3217  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3218    
3219    
3220  PCREPATTERN(3)                                                  PCREPATTERN(3)  PCREPATTERN(3)                                                  PCREPATTERN(3)
3221    
3222    
# Line 2947  PCRE REGULAR EXPRESSION DETAILS Line 3243  PCRE REGULAR EXPRESSION DETAILS
3243    
3244         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
3245         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
3246         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
3247         pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern         pcre_compile()  or  pcre_compile2() with the PCRE_UTF8 option. There is
3248         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:
3249         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre  
3250         page.           (*UTF8)
3251    
3252           Starting a pattern with this sequence  is  equivalent  to  setting  the
3253           PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3254           UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3255           below.  There  is  also  a  summary of UTF-8 features in the section on
3256           UTF-8 support in the main pcre page.
3257    
3258           Another special sequence that may appear at the start of a  pattern  or
3259           in combination with (*UTF8) is:
3260    
3261             (*UCP)
3262    
3263         The remainder of this document discusses the  patterns  that  are  sup-         This  has  the  same  effect  as setting the PCRE_UCP option: it causes
3264         ported  by  PCRE when its main matching function, pcre_exec(), is used.         sequences such as \d and \w to  use  Unicode  properties  to  determine
3265         From  release  6.0,   PCRE   offers   a   second   matching   function,         character types, instead of recognizing only characters with codes less
3266         pcre_dfa_exec(),  which matches using a different algorithm that is not         than 128 via a lookup table.
3267    
3268           If a pattern starts with (*NO_START_OPT), it has  the  same  effect  as
3269           setting the PCRE_NO_START_OPTIMIZE option either at compile or matching
3270           time. There are also some more of these special sequences that are con-
3271           cerned with the handling of newlines; they are described below.
3272    
3273           The  remainder  of  this  document discusses the patterns that are sup-
3274           ported by PCRE when its main matching function, pcre_exec(),  is  used.
3275           From   release   6.0,   PCRE   offers   a   second  matching  function,
3276           pcre_dfa_exec(), which matches using a different algorithm that is  not
3277         Perl-compatible. Some of the features discussed below are not available         Perl-compatible. Some of the features discussed below are not available
3278         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the         when pcre_dfa_exec() is used. The advantages and disadvantages  of  the
3279         alternative function, and how it differs from the normal function,  are         alternative  function, and how it differs from the normal function, are
3280         discussed in the pcrematching page.         discussed in the pcrematching page.
3281    
3282    
3283  NEWLINE CONVENTIONS  NEWLINE CONVENTIONS
3284    
3285         PCRE  supports five different conventions for indicating line breaks in         PCRE supports five different conventions for indicating line breaks  in
3286         strings: a single CR (carriage return) character, a  single  LF  (line-         strings:  a  single  CR (carriage return) character, a single LF (line-
3287         feed) character, the two-character sequence CRLF, any of the three pre-         feed) character, the two-character sequence CRLF, any of the three pre-
3288         ceding, or any Unicode newline sequence. The pcreapi page  has  further         ceding,  or  any Unicode newline sequence. The pcreapi page has further
3289         discussion  about newlines, and shows how to set the newline convention         discussion about newlines, and shows how to set the newline  convention
3290         in the options arguments for the compiling and matching functions.         in the options arguments for the compiling and matching functions.
3291    
3292         It is also possible to specify a newline convention by starting a  pat-         It  is also possible to specify a newline convention by starting a pat-
3293         tern string with one of the following five sequences:         tern string with one of the following five sequences:
3294    
3295           (*CR)        carriage return           (*CR)        carriage return
# Line 2981  NEWLINE CONVENTIONS Line 3298  NEWLINE CONVENTIONS
3298           (*ANYCRLF)   any of the three above           (*ANYCRLF)   any of the three above
3299           (*ANY)       all Unicode newline sequences           (*ANY)       all Unicode newline sequences
3300    
3301         These override the default and the options given to pcre_compile(). For         These override the default and the options given to  pcre_compile()  or
3302         example, on a Unix system where LF is the default newline sequence, the         pcre_compile2().  For example, on a Unix system where LF is the default
3303         pattern         newline sequence, the pattern
3304    
3305           (*CR)a.b           (*CR)a.b
3306    
3307         changes the convention to CR. That pattern matches "a\nb" because LF is         changes the convention to CR. That pattern matches "a\nb" because LF is
3308         no longer a newline. Note that these special settings,  which  are  not         no  longer  a  newline. Note that these special settings, which are not
3309         Perl-compatible,  are  recognized  only at the very start of a pattern,         Perl-compatible, are recognized only at the very start  of  a  pattern,
3310         and that they must be in upper case.  If  more  than  one  of  them  is         and  that  they  must  be  in  upper  case. If more than one of them is
3311         present, the last one is used.         present, the last one is used.
3312    
3313         The  newline  convention  does  not  affect what the \R escape sequence         The newline convention affects the interpretation of the dot  metachar-
3314         matches. By default, this is any Unicode  newline  sequence,  for  Perl         acter  when  PCRE_DOTALL is not set, and also the behaviour of \N. How-
3315         compatibility.  However, this can be changed; see the description of \R         ever, it does not affect  what  the  \R  escape  sequence  matches.  By
3316         in the section entitled "Newline sequences" below. A change of \R  set-         default,  this is any Unicode newline sequence, for Perl compatibility.
3317         ting can be combined with a change of newline convention.         However, this can be changed; see the description of \R in the  section
3318           entitled  "Newline sequences" below. A change of \R setting can be com-
3319           bined with a change of newline convention.
3320    
3321    
3322  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
3323    
3324         A  regular  expression  is  a pattern that is matched against a subject         A regular expression is a pattern that is  matched  against  a  subject
3325         string from left to right. Most characters stand for  themselves  in  a         string  from  left  to right. Most characters stand for themselves in a
3326         pattern,  and  match  the corresponding characters in the subject. As a         pattern, and match the corresponding characters in the  subject.  As  a
3327         trivial example, the pattern         trivial example, the pattern
3328    
3329           The quick brown fox           The quick brown fox
3330    
3331         matches a portion of a subject string that is identical to itself. When         matches a portion of a subject string that is identical to itself. When
3332         caseless  matching is specified (the PCRE_CASELESS option), letters are         caseless matching is specified (the PCRE_CASELESS option), letters  are
3333         matched independently of case. In UTF-8 mode, PCRE  always  understands         matched  independently  of case. In UTF-8 mode, PCRE always understands
3334         the  concept  of case for characters whose values are less than 128, so         the concept of case for characters whose values are less than  128,  so
3335         caseless matching is always possible. For characters with  higher  val-         caseless  matching  is always possible. For characters with higher val-
3336         ues,  the concept of case is supported if PCRE is compiled with Unicode         ues, the concept of case is supported if PCRE is compiled with  Unicode
3337         property support, but not otherwise.   If  you  want  to  use  caseless         property  support,  but  not  otherwise.   If  you want to use caseless
3338         matching  for  characters  128  and above, you must ensure that PCRE is         matching for characters 128 and above, you must  ensure  that  PCRE  is
3339         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
3340    
3341         The power of regular expressions comes  from  the  ability  to  include         The  power  of  regular  expressions  comes from the ability to include
3342         alternatives  and  repetitions in the pattern. These are encoded in the         alternatives and repetitions in the pattern. These are encoded  in  the
3343         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
3344         but instead are interpreted in some special way.         but instead are interpreted in some special way.
3345    
3346         There  are  two different sets of metacharacters: those that are recog-         There are two different sets of metacharacters: those that  are  recog-
3347         nized anywhere in the pattern except within square brackets, and  those         nized  anywhere in the pattern except within square brackets, and those
3348         that  are  recognized  within square brackets. Outside square brackets,         that are recognized within square brackets.  Outside  square  brackets,
3349         the metacharacters are as follows:         the metacharacters are as follows:
3350    
3351           \      general escape character with several uses           \      general escape character with several uses
# Line 3045  CHARACTERS AND METACHARACTERS Line 3364  CHARACTERS AND METACHARACTERS
3364                  also "possessive quantifier"                  also "possessive quantifier"
3365           {      start min/max quantifier           {      start min/max quantifier
3366    
3367         Part of a pattern that is in square brackets  is  called  a  "character         Part  of  a  pattern  that is in square brackets is called a "character
3368         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
3369    
3370           \      general escape character           \      general escape character
# Line 3055  CHARACTERS AND METACHARACTERS Line 3374  CHARACTERS AND METACHARACTERS
3374                    syntax)                    syntax)
3375           ]      terminates the character class           ]      terminates the character class
3376    
3377         The  following sections describe the use of each of the metacharacters.         The following sections describe the use of each of the metacharacters.
3378    
3379    
3380  BACKSLASH  BACKSLASH
3381    
3382         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3383         a  non-alphanumeric  character,  it takes away any special meaning that         a character that is not a number or a letter, it takes away any special
3384         character may have. This  use  of  backslash  as  an  escape  character         meaning that character may have. This use of  backslash  as  an  escape
3385         applies both inside and outside character classes.         character applies both inside and outside character classes.
3386    
3387         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
3388         pattern.  This escaping action applies whether  or  not  the  following         pattern.  This escaping action applies whether  or  not  the  following
# Line 3072  BACKSLASH Line 3391  BACKSLASH
3391         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-
3392         slash, you write \\.         slash, you write \\.
3393    
3394           In UTF-8 mode, only ASCII numbers and letters have any special  meaning
3395           after  a  backslash.  All  other characters (in particular, those whose
3396           codepoints are greater than 127) are treated as literals.
3397    
3398         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
3399         the  pattern (other than in a character class) and characters between a         the  pattern (other than in a character class) and characters between a
3400         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
# Line 3092  BACKSLASH Line 3415  BACKSLASH
3415           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3416    
3417         The \Q...\E sequence is recognized both inside  and  outside  character         The \Q...\E sequence is recognized both inside  and  outside  character
3418         classes.         classes.  An isolated \E that is not preceded by \Q is ignored.
3419    
3420     Non-printing characters     Non-printing characters
3421    
# Line 3100  BACKSLASH Line 3423  BACKSLASH
3423         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
3424         appearance  of non-printing characters, apart from the binary zero that         appearance  of non-printing characters, apart from the binary zero that
3425         terminates a pattern, but when a pattern  is  being  prepared  by  text         terminates a pattern, but when a pattern  is  being  prepared  by  text
3426         editing,  it  is  usually  easier  to  use  one of the following escape         editing,  it  is  often  easier  to  use  one  of  the following escape
3427         sequences than the binary character it represents:         sequences than the binary character it represents:
3428    
3429           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3430           \cx       "control-x", where x is any character           \cx       "control-x", where x is any ASCII character
3431           \e        escape (hex 1B)           \e        escape (hex 1B)
3432           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3433           \n        linefeed (hex 0A)           \n        linefeed (hex 0A)
3434           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3435           \t        tab (hex 09)           \t        tab (hex 09)
3436           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or back reference
3437           \xhh      character with hex code hh           \xhh      character with hex code hh
3438           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh..
3439    
3440         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,
3441         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
3442         inverted.  Thus \cz becomes hex 1A, but \c{ becomes hex 3B,  while  \c;         inverted.  Thus \cz becomes hex 1A (z is 7A), but \c{ becomes hex 3B ({
3443         becomes hex 7B.         is  7B),  while  \c; becomes hex 7B (; is 3B). If the byte following \c
3444           has a value greater than 127, a compile-time error occurs.  This  locks
3445           out  non-ASCII  characters in both byte mode and UTF-8 mode. (When PCRE
3446           is compiled in EBCDIC mode, all byte values are  valid.  A  lower  case
3447           letter is converted to upper case, and then the 0xc0 bits are flipped.)
3448    
3449         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
3450         in upper or lower case). Any number of hexadecimal  digits  may  appear         in upper or lower case). Any number of hexadecimal  digits  may  appear
# Line 3179  BACKSLASH Line 3506  BACKSLASH
3506         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
3507         inside and outside character classes. In addition, inside  a  character         inside and outside character classes. In addition, inside  a  character
3508         class,  the  sequence \b is interpreted as the backspace character (hex         class,  the  sequence \b is interpreted as the backspace character (hex
3509         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-
3510         and  "X", respectively. Outside a character class, these sequences have         ter  class.  Like  any  other  unrecognized  escape sequences, they are
3511         different meanings (see below).         treated as the literal characters "B", "N", "R", and  "X"  by  default,
3512           but cause an error if the PCRE_EXTRA option is set. Outside a character
3513           class, these sequences have different meanings.
3514    
3515     Absolute and relative back references     Absolute and relative back references
3516    
# Line 3201  BACKSLASH Line 3530  BACKSLASH
3530    
3531     Generic character types     Generic character types
3532    
3533         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:  
3534    
3535           \d     any decimal digit           \d     any decimal digit
3536           \D     any character that is not a decimal digit           \D     any character that is not a decimal digit
# Line 3215  BACKSLASH Line 3543  BACKSLASH
3543           \w     any "word" character           \w     any "word" character
3544           \W     any "non-word" character           \W     any "non-word" character
3545    
3546         Each pair of escape sequences partitions the complete set of characters         There is also the single sequence \N, which matches a non-newline char-
3547         into two disjoint sets. Any given character matches one, and only  one,         acter.   This  is the same as the "." metacharacter when PCRE_DOTALL is
3548         of each pair.         not set.
3549    
3550         These character type sequences can appear both inside and outside char-         Each pair of lower and upper case escape sequences partitions the  com-
3551         acter classes. They each match one character of the  appropriate  type.         plete  set  of  characters  into two disjoint sets. Any given character
3552         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
3553         of them fail, since there is no character to match.         inside  and outside character classes. They each match one character of
3554           the appropriate type. If the current matching point is at  the  end  of
3555           the  subject string, all of them fail, because there is no character to
3556           match.
3557    
3558         For compatibility with Perl, \s does not match the VT  character  (code         For compatibility with Perl, \s does not match the VT  character  (code
3559         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 3230  BACKSLASH Line 3561  BACKSLASH
3561         "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-
3562         ter. In PCRE, it never does.         ter. In PCRE, it never does.
3563    
3564         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
3565         \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-
3566         code character property support is available.  These  sequences  retain         trolled by PCRE's low-valued character tables, and may vary if  locale-
3567         their original meanings from before UTF-8 support was available, mainly         specific  matching is taking place (see "Locale support" in the pcreapi
3568         for efficiency reasons.         page). For example, in a French locale such  as  "fr_FR"  in  Unix-like
3569           systems,  or "french" in Windows, some character codes greater than 128
3570         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
3571         the  other  sequences, these do match certain high-valued codepoints in         use of locales with Unicode is discouraged.
3572         UTF-8 mode.  The horizontal space characters are:  
3573           By  default,  in  UTF-8  mode,  characters with values greater than 128
3574           never match \d, \s, or \w, and always  match  \D,  \S,  and  \W.  These
3575           sequences  retain their original meanings from before UTF-8 support was
3576           available, mainly for efficiency reasons. However, if PCRE is  compiled
3577           with  Unicode property support, and the PCRE_UCP option is set, the be-
3578           haviour is changed so that Unicode properties  are  used  to  determine
3579           character types, as follows:
3580    
3581             \d  any character that \p{Nd} matches (decimal digit)
3582             \s  any character that \p{Z} matches, plus HT, LF, FF, CR
3583             \w  any character that \p{L} or \p{N} matches, plus underscore
3584    
3585           The  upper case escapes match the inverse sets of characters. Note that
3586           \d matches only decimal digits, whereas \w matches any  Unicode  digit,
3587           as  well as any Unicode letter, and underscore. Note also that PCRE_UCP
3588           affects \b, and \B because they are defined in  terms  of  \w  and  \W.
3589           Matching these sequences is noticeably slower when PCRE_UCP is set.
3590    
3591           The  sequences  \h, \H, \v, and \V are features that were added to Perl
3592           at release 5.10. In contrast to the other sequences, which  match  only
3593           ASCII  characters  by  default,  these always match certain high-valued
3594           codepoints in UTF-8 mode, whether or not PCRE_UCP is set. The  horizon-
3595           tal space characters are:
3596    
3597           U+0009     Horizontal tab           U+0009     Horizontal tab
3598           U+0020     Space           U+0020     Space
# Line 3270  BACKSLASH Line 3624  BACKSLASH
3624           U+2028     Line separator           U+2028     Line separator
3625           U+2029     Paragraph separator           U+2029     Paragraph separator
3626    
        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.  
   
3627     Newline sequences     Newline sequences
3628    
3629         Outside  a  character class, by default, the escape sequence \R matches         Outside  a  character class, by default, the escape sequence \R matches
3630         any Unicode newline sequence. This is a Perl 5.10 feature. In non-UTF-8         any Unicode newline sequence. In non-UTF-8 mode \R is equivalent to the
3631         mode \R is equivalent to the following:         following:
3632    
3633           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3634    
# Line 3311  BACKSLASH Line 3656  BACKSLASH
3656           (*BSR_ANYCRLF)   CR, LF, or CRLF only           (*BSR_ANYCRLF)   CR, LF, or CRLF only
3657           (*BSR_UNICODE)   any Unicode newline sequence           (*BSR_UNICODE)   any Unicode newline sequence
3658    
3659         These override the default and the options given to pcre_compile(), but         These override the default and the options given to  pcre_compile()  or
3660         they can be overridden by options given to pcre_exec(). Note that these         pcre_compile2(),  but  they  can  be  overridden  by  options  given to
3661         special settings, which are not Perl-compatible, are recognized only at         pcre_exec() or pcre_dfa_exec(). Note that these special settings, which
3662         the  very  start  of a pattern, and that they must be in upper case. If         are  not  Perl-compatible,  are  recognized only at the very start of a
3663         more than one of them is present, the last one is  used.  They  can  be         pattern, and that they must be in upper case. If more than one of  them
3664         combined  with  a  change of newline convention, for example, a pattern         is present, the last one is used. They can be combined with a change of
3665         can start with:         newline convention; for example, a pattern can start with:
3666    
3667           (*ANY)(*BSR_ANYCRLF)           (*ANY)(*BSR_ANYCRLF)
3668    
3669         Inside a character class, \R matches the letter "R".         They can also be combined with the (*UTF8) or (*UCP) special sequences.
3670           Inside  a  character  class,  \R  is  treated as an unrecognized escape
3671           sequence, and so matches the letter "R" by default, but causes an error
3672           if PCRE_EXTRA is set.
3673    
3674     Unicode character properties     Unicode character properties
3675    
3676         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
3677         tional  escape sequences that match characters with specific properties         tional escape sequences that match characters with specific  properties
3678         are available.  When not in UTF-8 mode, these sequences are  of  course         are  available.   When not in UTF-8 mode, these sequences are of course
3679         limited  to  testing characters whose codepoints are less than 256, but         limited to testing characters whose codepoints are less than  256,  but
3680         they do work in this mode.  The extra escape sequences are:         they do work in this mode.  The extra escape sequences are:
3681    
3682           \p{xx}   a character with the xx property           \p{xx}   a character with the xx property
3683           \P{xx}   a character without the xx property           \P{xx}   a character without the xx property
3684           \X       an extended Unicode sequence           \X       an extended Unicode sequence
3685    
3686         The property names represented by xx above are limited to  the  Unicode         The  property  names represented by xx above are limited to the Unicode
3687         script names, the general category properties, and "Any", which matches         script names, the general category properties, "Any", which matches any
3688         any character (including newline). Other properties such as "InMusical-         character   (including  newline),  and  some  special  PCRE  properties
3689         Symbols"  are  not  currently supported by PCRE. Note that \P{Any} does         (described in the next section).  Other Perl properties such as  "InMu-
3690         not match any characters, so always causes a match failure.         sicalSymbols"  are  not  currently supported by PCRE. Note that \P{Any}
3691           does not match any characters, so always causes a match failure.
3692    
3693         Sets of Unicode characters are defined as belonging to certain scripts.         Sets of Unicode characters are defined as belonging to certain scripts.
3694         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.
# Line 3351  BACKSLASH Line 3700  BACKSLASH
3700         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
3701         "Common". The current list of scripts is:         "Common". The current list of scripts is:
3702    
3703         Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,         Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille,
3704         Buhid,  Canadian_Aboriginal,  Cherokee,  Common,   Coptic,   Cuneiform,         Buginese, Buhid, Canadian_Aboriginal, Carian, Cham,  Cherokee,  Common,
3705         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,         Coptic,   Cuneiform,  Cypriot,  Cyrillic,  Deseret,  Devanagari,  Egyp-
3706         Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew,  Hira-         tian_Hieroglyphs,  Ethiopic,  Georgian,  Glagolitic,   Gothic,   Greek,
3707         gana,  Inherited,  Kannada,  Katakana,  Kharoshthi,  Khmer, Lao, Latin,         Gujarati,  Gurmukhi,  Han,  Hangul,  Hanunoo,  Hebrew,  Hiragana, Impe-
3708         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,         rial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian,
3709         Ogham,  Old_Italic,  Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician,         Javanese,  Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Lao,
3710         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,         Latin,  Lepcha,  Limbu,  Linear_B,  Lisu,  Lycian,  Lydian,  Malayalam,
3711         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.         Meetei_Mayek,  Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham, Old_Italic,
3712           Old_Persian, Old_South_Arabian, Old_Turkic, Ol_Chiki,  Oriya,  Osmanya,
3713         Each  character has exactly one general category property, specified by         Phags_Pa,  Phoenician,  Rejang,  Runic, Samaritan, Saurashtra, Shavian,
3714         a two-letter abbreviation. For compatibility with Perl, negation can be         Sinhala, Sundanese, Syloti_Nagri, Syriac,  Tagalog,  Tagbanwa,  Tai_Le,
3715         specified  by  including a circumflex between the opening brace and the         Tai_Tham,  Tai_Viet,  Tamil,  Telugu,  Thaana, Thai, Tibetan, Tifinagh,
3716         property name. For example, \p{^Lu} is the same as \P{Lu}.         Ugaritic, Vai, Yi.
3717    
3718           Each character has exactly one Unicode general category property, spec-
3719           ified  by a two-letter abbreviation. For compatibility with Perl, nega-
3720           tion can be specified by including a  circumflex  between  the  opening
3721           brace  and  the  property  name.  For  example,  \p{^Lu} is the same as
3722           \P{Lu}.
3723    
3724         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-
3725         eral  category properties that start with that letter. In this case, in         eral  category properties that start with that letter. In this case, in
# Line 3428  BACKSLASH Line 3783  BACKSLASH
3783         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
3784         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-
3785         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
3786         the pcreapi page).         the pcreapi page). Perl does not support the Cs property.
3787    
3788         The  long  synonyms  for  these  properties that Perl supports (such as         The  long  synonyms  for  property  names  that  Perl supports (such as
3789         \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
3790         any of these properties with "Is".         any of these properties with "Is".
3791    
# Line 3456  BACKSLASH Line 3811  BACKSLASH
3811         Matching characters by Unicode property is not fast, because  PCRE  has         Matching characters by Unicode property is not fast, because  PCRE  has
3812         to  search  a  structure  that  contains data for over fifteen thousand         to  search  a  structure  that  contains data for over fifteen thousand
3813         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
3814         \w do not use Unicode properties in PCRE.         \w  do  not  use  Unicode properties in PCRE by default, though you can
3815           make them do so by setting the PCRE_UCP option for pcre_compile() or by
3816           starting the pattern with (*UCP).
3817    
3818       PCRE's additional properties
3819    
3820           As  well  as  the standard Unicode properties described in the previous
3821           section, PCRE supports four more that make it possible to convert  tra-
3822           ditional escape sequences such as \w and \s and POSIX character classes
3823           to use Unicode properties. PCRE uses these non-standard, non-Perl prop-
3824           erties internally when PCRE_UCP is set. They are:
3825    
3826             Xan   Any alphanumeric character
3827             Xps   Any POSIX space character
3828             Xsp   Any Perl space character
3829             Xwd   Any Perl "word" character
3830    
3831           Xan  matches  characters that have either the L (letter) or the N (num-
3832           ber) property. Xps matches the characters tab, linefeed, vertical  tab,
3833           formfeed,  or  carriage  return, and any other character that has the Z
3834           (separator) property.  Xsp is the same as Xps, except that vertical tab
3835           is excluded. Xwd matches the same characters as Xan, plus underscore.
3836    
3837     Resetting the match start     Resetting the match start
3838    
3839         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
3840         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:  
3841    
3842           foo\Kbar           foo\Kbar
3843    
3844         matches  "foobar",  but reports that it has matched "bar". This feature         matches "foobar", but reports that it has matched "bar".  This  feature
3845         is similar to a lookbehind assertion (described  below).   However,  in         is  similar  to  a lookbehind assertion (described below).  However, in
3846         this  case, the part of the subject before the real match does not have         this case, the part of the subject before the real match does not  have
3847         to be of fixed length, as lookbehind assertions do. The use of \K  does         to  be of fixed length, as lookbehind assertions do. The use of \K does
3848         not  interfere  with  the setting of captured substrings.  For example,         not interfere with the setting of captured  substrings.   For  example,
3849         when the pattern         when the pattern
3850    
3851           (foo)\Kbar           (foo)\Kbar
3852    
3853         matches "foobar", the first substring is still set to "foo".         matches "foobar", the first substring is still set to "foo".
3854    
3855           Perl  documents  that  the  use  of  \K  within assertions is "not well
3856           defined". In PCRE, \K is acted upon  when  it  occurs  inside  positive
3857           assertions, but is ignored in negative assertions.
3858    
3859     Simple assertions     Simple assertions
3860    
3861         The final use of backslash is for certain simple assertions. An  asser-         The  final use of backslash is for certain simple assertions. An asser-
3862         tion  specifies a condition that has to be met at a particular point in         tion specifies a condition that has to be met at a particular point  in
3863         a match, without consuming any characters from the subject string.  The         a  match, without consuming any characters from the subject string. The
3864         use  of subpatterns for more complicated assertions is described below.         use of subpatterns for more complicated assertions is described  below.
3865         The backslashed assertions are:         The backslashed assertions are:
3866    
3867           \b     matches at a word boundary           \b     matches at a word boundary
# Line 3493  BACKSLASH Line 3872  BACKSLASH
3872           \z     matches only at the end of the subject           \z     matches only at the end of the subject
3873           \G     matches at the first matching position in the subject           \G     matches at the first matching position in the subject
3874    
3875         These assertions may not appear in character classes (but note that  \b         Inside  a  character  class, \b has a different meaning; it matches the
3876         has a different meaning, namely the backspace character, inside a char-         backspace character. If any other of  these  assertions  appears  in  a
3877         acter class).         character  class, by default it matches the corresponding literal char-
3878           acter  (for  example,  \B  matches  the  letter  B).  However,  if  the
3879           PCRE_EXTRA  option is set, an "invalid escape sequence" error is gener-
3880           ated instead.
3881    
3882         A word boundary is a position in the subject string where  the  current         A word boundary is a position in the subject string where  the  current
3883         character  and  the previous character do not both match \w or \W (i.e.         character  and  the previous character do not both match \w or \W (i.e.
3884         one matches \w and the other matches \W), or the start or  end  of  the         one matches \w and the other matches \W), or the start or  end  of  the
3885         string if the first or last character matches \w, respectively.         string  if  the  first  or  last character matches \w, respectively. In
3886           UTF-8 mode, the meanings of \w and \W can be  changed  by  setting  the
3887           PCRE_UCP  option. When this is done, it also affects \b and \B. Neither
3888           PCRE nor Perl has a separate "start of word" or "end of  word"  metase-
3889           quence.  However,  whatever follows \b normally determines which it is.
3890           For example, the fragment \ba matches "a" at the start of a word.
3891    
3892         The  \A,  \Z,  and \z assertions differ from the traditional circumflex         The \A, \Z, and \z assertions differ from  the  traditional  circumflex
3893         and dollar (described in the next section) in that they only ever match         and dollar (described in the next section) in that they only ever match
3894         at  the  very start and end of the subject string, whatever options are         at the very start and end of the subject string, whatever  options  are
3895         set. Thus, they are independent of multiline mode. These  three  asser-         set.  Thus,  they are independent of multiline mode. These three asser-
3896         tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which         tions are not affected by the PCRE_NOTBOL or PCRE_NOTEOL options, which
3897         affect only the behaviour of the circumflex and dollar  metacharacters.         affect  only the behaviour of the circumflex and dollar metacharacters.
3898         However,  if the startoffset argument of pcre_exec() is non-zero, indi-         However, if the startoffset argument of pcre_exec() is non-zero,  indi-
3899         cating that matching is to start at a point other than the beginning of         cating that matching is to start at a point other than the beginning of
3900         the  subject,  \A  can never match. The difference between \Z and \z is         the subject, \A can never match. The difference between \Z  and  \z  is
3901         that \Z matches before a newline at the end of the string as well as at         that \Z matches before a newline at the end of the string as well as at
3902         the very end, whereas \z matches only at the end.         the very end, whereas \z matches only at the end.
3903    
3904         The  \G assertion is true only when the current matching position is at         The \G assertion is true only when the current matching position is  at
3905         the start point of the match, as specified by the startoffset  argument         the  start point of the match, as specified by the startoffset argument
3906         of  pcre_exec().  It  differs  from \A when the value of startoffset is         of pcre_exec(). It differs from \A when the  value  of  startoffset  is
3907         non-zero. By calling pcre_exec() multiple times with appropriate  argu-         non-zero.  By calling pcre_exec() multiple times with appropriate argu-
3908         ments, you can mimic Perl's /g option, and it is in this kind of imple-         ments, you can mimic Perl's /g option, and it is in this kind of imple-
3909         mentation where \G can be useful.         mentation where \G can be useful.
3910    
3911         Note, however, that PCRE's interpretation of \G, as the  start  of  the         Note,  however,  that  PCRE's interpretation of \G, as the start of the
3912         current match, is subtly different from Perl's, which defines it as the         current match, is subtly different from Perl's, which defines it as the
3913         end of the previous match. In Perl, these can  be  different  when  the         end  of  the  previous  match. In Perl, these can be different when the
3914         previously  matched  string was empty. Because PCRE does just one match         previously matched string was empty. Because PCRE does just  one  match
3915         at a time, it cannot reproduce this behaviour.         at a time, it cannot reproduce this behaviour.
3916    
3917         If all the alternatives of a pattern begin with \G, the  expression  is         If  all  the alternatives of a pattern begin with \G, the expression is
3918         anchored to the starting match position, and the "anchored" flag is set         anchored to the starting match position, and the "anchored" flag is set
3919         in the compiled regular expression.         in the compiled regular expression.
3920    
# Line 3535  BACKSLASH Line 3922  BACKSLASH
3922  CIRCUMFLEX AND DOLLAR  CIRCUMFLEX AND DOLLAR
3923    
3924         Outside a character class, in the default matching mode, the circumflex         Outside a character class, in the default matching mode, the circumflex
3925         character  is  an  assertion  that is true only if the current matching         character is an assertion that is true only  if  the  current  matching
3926         point is at the start of the subject string. If the  startoffset  argu-         point  is  at the start of the subject string. If the startoffset argu-
3927         ment  of  pcre_exec()  is  non-zero,  circumflex can never match if the         ment of pcre_exec() is non-zero, circumflex  can  never  match  if  the
3928         PCRE_MULTILINE option is unset. Inside a  character  class,  circumflex         PCRE_MULTILINE  option  is  unset. Inside a character class, circumflex
3929         has an entirely different meaning (see below).         has an entirely different meaning (see below).
3930    
3931         Circumflex  need  not be the first character of the pattern if a number         Circumflex need not be the first character of the pattern if  a  number
3932         of alternatives are involved, but it should be the first thing in  each         of  alternatives are involved, but it should be the first thing in each
3933         alternative  in  which  it appears if the pattern is ever to match that         alternative in which it appears if the pattern is ever  to  match  that
3934         branch. If all possible alternatives start with a circumflex, that  is,         branch.  If all possible alternatives start with a circumflex, that is,
3935         if  the  pattern  is constrained to match only at the start of the sub-         if the pattern is constrained to match only at the start  of  the  sub-
3936         ject, it is said to be an "anchored" pattern.  (There  are  also  other         ject,  it  is  said  to be an "anchored" pattern. (There are also other
3937         constructs that can cause a pattern to be anchored.)         constructs that can cause a pattern to be anchored.)
3938    
3939         A  dollar  character  is  an assertion that is true only if the current         A dollar character is an assertion that is true  only  if  the  current
3940         matching point is at the end of  the  subject  string,  or  immediately         matching  point  is  at  the  end of the subject string, or immediately
3941         before a newline at the end of the string (by default). Dollar need not         before a newline at the end of the string (by default). Dollar need not
3942         be the last character of the pattern if a number  of  alternatives  are         be  the  last  character of the pattern if a number of alternatives are
3943         involved,  but  it  should  be  the last item in any branch in which it         involved, but it should be the last item in  any  branch  in  which  it
3944         appears. Dollar has no special meaning in a character class.         appears. Dollar has no special meaning in a character class.
3945    
3946         The meaning of dollar can be changed so that it  matches  only  at  the         The  meaning  of  dollar  can be changed so that it matches only at the
3947         very  end  of  the string, by setting the PCRE_DOLLAR_ENDONLY option at         very end of the string, by setting the  PCRE_DOLLAR_ENDONLY  option  at
3948         compile time. This does not affect the \Z assertion.         compile time. This does not affect the \Z assertion.
3949    
3950         The meanings of the circumflex and dollar characters are changed if the         The meanings of the circumflex and dollar characters are changed if the
3951         PCRE_MULTILINE  option  is  set.  When  this  is the case, a circumflex         PCRE_MULTILINE option is set. When  this  is  the  case,  a  circumflex
3952         matches immediately after internal newlines as well as at the start  of         matches  immediately after internal newlines as well as at the start of
3953         the  subject  string.  It  does not match after a newline that ends the         the subject string. It does not match after a  newline  that  ends  the
3954         string. A dollar matches before any newlines in the string, as well  as         string.  A dollar matches before any newlines in the string, as well as
3955         at  the very end, when PCRE_MULTILINE is set. When newline is specified         at the very end, when PCRE_MULTILINE is set. When newline is  specified
3956         as the two-character sequence CRLF, isolated CR and  LF  characters  do         as  the  two-character  sequence CRLF, isolated CR and LF characters do
3957         not indicate newlines.         not indicate newlines.
3958    
3959         For  example, the pattern /^abc$/ matches the subject string "def\nabc"         For example, the pattern /^abc$/ matches the subject string  "def\nabc"
3960         (where \n represents a newline) in multiline mode, but  not  otherwise.         (where  \n  represents a newline) in multiline mode, but not otherwise.
3961         Consequently,  patterns  that  are anchored in single line mode because         Consequently, patterns that are anchored in single  line  mode  because
3962         all branches start with ^ are not anchored in  multiline  mode,  and  a         all  branches  start  with  ^ are not anchored in multiline mode, and a
3963         match  for  circumflex  is  possible  when  the startoffset argument of         match for circumflex is  possible  when  the  startoffset  argument  of
3964         pcre_exec() is non-zero. The PCRE_DOLLAR_ENDONLY option is  ignored  if         pcre_exec()  is  non-zero. The PCRE_DOLLAR_ENDONLY option is ignored if
3965         PCRE_MULTILINE is set.         PCRE_MULTILINE is set.
3966    
3967         Note  that  the sequences \A, \Z, and \z can be used to match the start         Note that the sequences \A, \Z, and \z can be used to match  the  start
3968         and end of the subject in both modes, and if all branches of a  pattern         and  end of the subject in both modes, and if all branches of a pattern
3969         start  with  \A it is always anchored, whether or not PCRE_MULTILINE is         start with \A it is always anchored, whether or not  PCRE_MULTILINE  is
3970         set.         set.
3971    
3972    
3973  FULL STOP (PERIOD, DOT)  FULL STOP (PERIOD, DOT) AND \N
3974    
3975         Outside a character class, a dot in the pattern matches any one charac-         Outside a character class, a dot in the pattern matches any one charac-
3976         ter  in  the subject string except (by default) a character that signi-         ter in the subject string except (by default) a character  that  signi-
3977         fies the end of a line. In UTF-8 mode, the  matched  character  may  be         fies  the  end  of  a line. In UTF-8 mode, the matched character may be
3978         more than one byte long.         more than one byte long.
3979    
3980         When  a line ending is defined as a single character, dot never matches         When a line ending is defined as a single character, dot never  matches
3981         that character; when the two-character sequence CRLF is used, dot  does         that  character; when the two-character sequence CRLF is used, dot does
3982         not  match  CR  if  it  is immediately followed by LF, but otherwise it         not match CR if it is immediately followed  by  LF,  but  otherwise  it
3983         matches all characters (including isolated CRs and LFs). When any  Uni-         matches  all characters (including isolated CRs and LFs). When any Uni-
3984         code  line endings are being recognized, dot does not match CR or LF or         code line endings are being recognized, dot does not match CR or LF  or
3985         any of the other line ending characters.         any of the other line ending characters.
3986    
3987         The behaviour of dot with regard to newlines can  be  changed.  If  the         The  behaviour  of  dot  with regard to newlines can be changed. If the
3988         PCRE_DOTALL  option  is  set,  a dot matches any one character, without         PCRE_DOTALL option is set, a dot matches  any  one  character,  without
3989         exception. If the two-character sequence CRLF is present in the subject         exception. If the two-character sequence CRLF is present in the subject
3990         string, it takes two dots to match it.         string, it takes two dots to match it.
3991    
3992         The  handling of dot is entirely independent of the handling of circum-         The handling of dot is entirely independent of the handling of  circum-
3993         flex and dollar, the only relationship being  that  they  both  involve         flex  and  dollar,  the  only relationship being that they both involve
3994         newlines. Dot has no special meaning in a character class.         newlines. Dot has no special meaning in a character class.
3995    
3996           The escape sequence \N behaves like  a  dot,  except  that  it  is  not
3997           affected  by  the  PCRE_DOTALL  option.  In other words, it matches any
3998           character except one that signifies the end of a line.
3999    
4000    
4001  MATCHING A SINGLE BYTE  MATCHING A SINGLE BYTE
4002    
4003         Outside a character class, the escape sequence \C matches any one byte,         Outside a character class, the escape sequence \C matches any one byte,
4004         both in and out of UTF-8 mode. Unlike a  dot,  it  always  matches  any         both  in  and  out  of  UTF-8 mode. Unlike a dot, it always matches any
4005         line-ending  characters.  The  feature  is provided in Perl in order to         line-ending characters. The feature is provided in  Perl  in  order  to
4006         match individual bytes in UTF-8 mode. Because it breaks up UTF-8  char-         match  individual bytes in UTF-8 mode. Because it breaks up UTF-8 char-
4007         acters  into individual bytes, what remains in the string may be a mal-         acters into individual bytes, the rest of the string may start  with  a
4008         formed UTF-8 string. For this reason, the \C escape  sequence  is  best         malformed  UTF-8  character. For this reason, the \C escape sequence is
4009         avoided.         best avoided.
4010    
4011         PCRE  does  not  allow \C to appear in lookbehind assertions (described         PCRE does not allow \C to appear in  lookbehind  assertions  (described
4012         below), because in UTF-8 mode this would make it impossible  to  calcu-         below),  because  in UTF-8 mode this would make it impossible to calcu-
4013         late the length of the lookbehind.         late the length of the lookbehind.
4014    
4015    
# Line 3626  SQUARE BRACKETS AND CHARACTER CLASSES Line 4017  SQUARE BRACKETS AND CHARACTER CLASSES
4017    
4018         An opening square bracket introduces a character class, terminated by a         An opening square bracket introduces a character class, terminated by a
4019         closing square bracket. A closing square bracket on its own is not spe-         closing square bracket. A closing square bracket on its own is not spe-
4020         cial. If a closing square bracket is required as a member of the class,         cial by default.  However, if the PCRE_JAVASCRIPT_COMPAT option is set,
4021         it should be the first data character in the class  (after  an  initial         a lone closing square bracket causes a compile-time error. If a closing
4022         circumflex, if present) or escaped with a backslash.         square bracket is required as a member of the class, it should  be  the
4023           first  data  character  in  the  class (after an initial circumflex, if
4024           present) or escaped with a backslash.
4025    
4026         A  character  class matches a single character in the subject. In UTF-8         A character class matches a single character in the subject.  In  UTF-8
4027         mode, the character may occupy more than one byte. A matched  character         mode, the character may be more than one byte long. A matched character
4028         must be in the set of characters defined by the class, unless the first         must be in the set of characters defined by the class, unless the first
4029         character in the class definition is a circumflex, in  which  case  the         character  in  the  class definition is a circumflex, in which case the
4030         subject  character  must  not  be in the set defined by the class. If a         subject character must not be in the set defined by  the  class.  If  a
4031         circumflex is actually required as a member of the class, ensure it  is         circumflex  is actually required as a member of the class, ensure it is
4032         not the first character, or escape it with a backslash.         not the first character, or escape it with a backslash.
4033    
4034         For  example, the character class [aeiou] matches any lower case vowel,         For example, the character class [aeiou] matches any lower case  vowel,
4035         while [^aeiou] matches any character that is not a  lower  case  vowel.         while  [^aeiou]  matches  any character that is not a lower case vowel.
4036         Note that a circumflex is just a convenient notation for specifying the         Note that a circumflex is just a convenient notation for specifying the
4037         characters that are in the class by enumerating those that are  not.  A         characters  that  are in the class by enumerating those that are not. A
4038         class  that starts with a circumflex is not an assertion: it still con-         class that starts with a circumflex is not an assertion; it still  con-
4039         sumes a character from the subject string, and therefore  it  fails  if         sumes  a  character  from the subject string, and therefore it fails if
4040         the current pointer is at the end of the string.         the current pointer is at the end of the string.
4041    
4042         In  UTF-8 mode, characters with values greater than 255 can be included         In UTF-8 mode, characters with values greater than 255 can be  included
4043         in a class as a literal string of bytes, or by using the  \x{  escaping         in  a  class as a literal string of bytes, or by using the \x{ escaping
4044         mechanism.         mechanism.
4045    
4046         When  caseless  matching  is set, any letters in a class represent both         When caseless matching is set, any letters in a  class  represent  both
4047         their upper case and lower case versions, so for  example,  a  caseless         their  upper  case  and lower case versions, so for example, a caseless
4048         [aeiou]  matches  "A"  as well as "a", and a caseless [^aeiou] does not         [aeiou] matches "A" as well as "a", and a