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revision 211 by ph10, Thu Aug 9 09:52:43 2007 UTC revision 654 by ph10, Tue Aug 2 11:00:40 2011 UTC
# Line 2  Line 2 
2  This file contains a concatenation of the PCRE man pages, converted to plain  This file contains a concatenation of the PCRE man pages, converted to plain
3  text format for ease of searching with a text editor, or for use on systems  text format for ease of searching with a text editor, or for use on systems
4  that do not have a man page processor. The small individual files that give  that do not have a man page processor. The small individual files that give
5  synopses of each function in the library have not been included. There are  synopses of each function in the library have not been included. Neither has
6  separate text files for the pcregrep and pcretest commands.  the pcredemo program. There are separate text files for the pcregrep and
7    pcretest commands.
8  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
9    
10    
# Line 18  INTRODUCTION Line 19  INTRODUCTION
19    
20         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
21         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
22         just  a  few differences. (Certain features that appeared in Python and         just  a few differences. Some features that appeared in Python and PCRE
23         PCRE before they appeared in Perl are also available using  the  Python         before they appeared in Perl are also available using the  Python  syn-
24         syntax.)         tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25           items, and there is an option for requesting some  minor  changes  that
26         The  current  implementation of PCRE (release 7.x) corresponds approxi-         give better JavaScript compatibility.
27         mately with Perl 5.10, including support for UTF-8 encoded strings  and  
28         Unicode general category properties. However, UTF-8 and Unicode support         The  current implementation of PCRE corresponds approximately with Perl
29         has to be explicitly enabled; it is not the default. The Unicode tables         5.12, including support for UTF-8 encoded strings and  Unicode  general
30         correspond to Unicode release 5.0.0.         category  properties.  However,  UTF-8  and  Unicode  support has to be
31           explicitly enabled; it is not the default. The  Unicode  tables  corre-
32           spond to Unicode release 6.0.0.
33    
34         In  addition to the Perl-compatible matching function, PCRE contains an         In  addition to the Perl-compatible matching function, PCRE contains an
35         alternative matching function that matches the same  compiled  patterns         alternative function that matches the same compiled patterns in a  dif-
36         in  a different way. In certain circumstances, the alternative function         ferent way. In certain circumstances, the alternative function has some
37         has some advantages. For a discussion of the two  matching  algorithms,         advantages.  For a discussion of the two matching algorithms,  see  the
38         see the pcrematching page.         pcrematching page.
39    
40         PCRE  is  written  in C and released as a C library. A number of people         PCRE  is  written  in C and released as a C library. A number of people
41         have written wrappers and interfaces of various kinds.  In  particular,         have written wrappers and interfaces of various kinds.  In  particular,
# Line 52  INTRODUCTION Line 55  INTRODUCTION
55         library is built. The pcre_config() function makes it  possible  for  a         library is built. The pcre_config() function makes it  possible  for  a
56         client  to  discover  which  features are available. The features them-         client  to  discover  which  features are available. The features them-
57         selves are described in the pcrebuild page. Documentation about  build-         selves are described in the pcrebuild page. Documentation about  build-
58         ing  PCRE for various operating systems can be found in the README file         ing  PCRE  for various operating systems can be found in the README and
59         in the source distribution.         NON-UNIX-USE files in the source distribution.
60    
61         The library contains a number of undocumented  internal  functions  and         The library contains a number of undocumented  internal  functions  and
62         data  tables  that  are  used by more than one of the exported external         data  tables  that  are  used by more than one of the exported external
# Line 69  USER DOCUMENTATION Line 72  USER DOCUMENTATION
72         The user documentation for PCRE comprises a number  of  different  sec-         The user documentation for PCRE comprises a number  of  different  sec-
73         tions.  In the "man" format, each of these is a separate "man page". In         tions.  In the "man" format, each of these is a separate "man page". In
74         the HTML format, each is a separate page, linked from the  index  page.         the HTML format, each is a separate page, linked from the  index  page.
75         In  the  plain text format, all the sections are concatenated, for ease         In  the  plain  text format, all the sections, except the pcredemo sec-
76         of searching. The sections are as follows:         tion, are concatenated, for ease of searching. The sections are as fol-
77           lows:
78    
79           pcre              this document           pcre              this document
80           pcre-config       show PCRE installation configuration information           pcre-config       show PCRE installation configuration information
# Line 79  USER DOCUMENTATION Line 83  USER DOCUMENTATION
83           pcrecallout       details of the callout feature           pcrecallout       details of the callout feature
84           pcrecompat        discussion of Perl compatibility           pcrecompat        discussion of Perl compatibility
85           pcrecpp           details of the C++ wrapper           pcrecpp           details of the C++ wrapper
86             pcredemo          a demonstration C program that uses PCRE
87           pcregrep          description of the pcregrep command           pcregrep          description of the pcregrep command
88           pcrematching      discussion of the two matching algorithms           pcrematching      discussion of the two matching algorithms
89           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
90           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
91                               regular expressions                               regular expressions
          pcresyntax        quick syntax reference  
92           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
93           pcreposix         the POSIX-compatible C API           pcreposix         the POSIX-compatible C API
94           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
95           pcresample        discussion of the sample program           pcresample        discussion of the pcredemo program
96           pcrestack         discussion of stack usage           pcrestack         discussion of stack usage
97             pcresyntax        quick syntax reference
98           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
99    
100         In  addition,  in the "man" and HTML formats, there is a short page for         In  addition,  in the "man" and HTML formats, there is a short page for
# Line 134  UTF-8 AND UNICODE PROPERTY SUPPORT Line 139  UTF-8 AND UNICODE PROPERTY SUPPORT
139    
140         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8
141         support in the code, and, in addition,  you  must  call  pcre_compile()         support in the code, and, in addition,  you  must  call  pcre_compile()
142         with  the PCRE_UTF8 option flag. When you do this, both the pattern and         with  the  PCRE_UTF8  option  flag,  or the pattern must start with the
143         any subject strings that are matched against it are  treated  as  UTF-8         sequence (*UTF8). When either of these is the case,  both  the  pattern
144         strings instead of just strings of bytes.         and  any  subject  strings  that  are matched against it are treated as
145           UTF-8 strings instead of strings of 1-byte characters.
146    
147         If  you compile PCRE with UTF-8 support, but do not use it at run time,         If you compile PCRE with UTF-8 support, but do not use it at run  time,
148         the library will be a bit bigger, but the additional run time  overhead         the  library will be a bit bigger, but the additional run time overhead
149         is limited to testing the PCRE_UTF8 flag occasionally, so should not be         is limited to testing the PCRE_UTF8 flag occasionally, so should not be
150         very big.         very big.
151    
152         If PCRE is built with Unicode character property support (which implies         If PCRE is built with Unicode character property support (which implies
153         UTF-8  support),  the  escape sequences \p{..}, \P{..}, and \X are sup-         UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-
154         ported.  The available properties that can be tested are limited to the         ported.  The available properties that can be tested are limited to the
155         general  category  properties such as Lu for an upper case letter or Nd         general category properties such as Lu for an upper case letter  or  Nd
156         for a decimal number, the Unicode script names such as Arabic  or  Han,         for  a  decimal number, the Unicode script names such as Arabic or Han,
157         and  the  derived  properties  Any  and L&. A full list is given in the         and the derived properties Any and L&. A full  list  is  given  in  the
158         pcrepattern documentation. Only the short names for properties are sup-         pcrepattern documentation. Only the short names for properties are sup-
159         ported.  For example, \p{L} matches a letter. Its Perl synonym, \p{Let-         ported. For example, \p{L} matches a letter. Its Perl synonym,  \p{Let-
160         ter}, is not supported.  Furthermore,  in  Perl,  many  properties  may         ter},  is  not  supported.   Furthermore,  in Perl, many properties may
161         optionally  be  prefixed by "Is", for compatibility with Perl 5.6. PCRE         optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE
162         does not support this.         does not support this.
163    
164     Validity of UTF-8 strings     Validity of UTF-8 strings
165    
166         When you set the PCRE_UTF8 flag, the strings  passed  as  patterns  and         When  you  set  the  PCRE_UTF8 flag, the strings passed as patterns and
167         subjects are (by default) checked for validity on entry to the relevant         subjects are (by default) checked for validity on entry to the relevant
168         functions. From release 7.3 of PCRE, the check is according  the  rules         functions.  From  release 7.3 of PCRE, the check is according the rules
169         of  RFC  3629, which are themselves derived from the Unicode specifica-         of RFC 3629, which are themselves derived from the  Unicode  specifica-
170         tion. Earlier releases of PCRE followed the rules of  RFC  2279,  which         tion.  Earlier  releases  of PCRE followed the rules of RFC 2279, which
171         allows  the  full range of 31-bit values (0 to 0x7FFFFFFF). The current         allows the full range of 31-bit values (0 to 0x7FFFFFFF).  The  current
172         check allows only values in the range U+0 to U+10FFFF, excluding U+D800         check allows only values in the range U+0 to U+10FFFF, excluding U+D800
173         to U+DFFF.         to U+DFFF.
174    
175         The  excluded  code  points are the "Low Surrogate Area" of Unicode, of         The excluded code points are the "Low Surrogate Area"  of  Unicode,  of
176         which the Unicode Standard says this: "The Low Surrogate Area does  not         which  the Unicode Standard says this: "The Low Surrogate Area does not
177         contain  any  character  assignments,  consequently  no  character code         contain any  character  assignments,  consequently  no  character  code
178         charts or namelists are provided for this area. Surrogates are reserved         charts or namelists are provided for this area. Surrogates are reserved
179         for  use  with  UTF-16 and then must be used in pairs." The code points         for use with UTF-16 and then must be used in pairs."  The  code  points
180         that are encoded by UTF-16 pairs  are  available  as  independent  code         that  are  encoded  by  UTF-16  pairs are available as independent code
181         points  in  the  UTF-8  encoding.  (In other words, the whole surrogate         points in the UTF-8 encoding. (In  other  words,  the  whole  surrogate
182         thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)         thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
183    
184         If an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error  return         If an invalid UTF-8 string is passed to PCRE, an error return is given.
185         (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know         At compile time, the only additional information is the offset  to  the
186         that your strings are valid, and therefore want to skip these checks in         first byte of the failing character. The runtime functions (pcre_exec()
187         order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at         and pcre_dfa_exec()), pass back this information  as  well  as  a  more
188         compile time or at run time, PCRE assumes that the pattern  or  subject         detailed  reason  code if the caller has provided memory in which to do
189         it  is  given  (respectively)  contains only valid UTF-8 codes. In this         this.
190         case, it does not diagnose an invalid UTF-8 string.  
191           In some situations, you may already know that your strings  are  valid,
192           and  therefore  want  to  skip these checks in order to improve perfor-
193           mance. If you set the PCRE_NO_UTF8_CHECK flag at compile time or at run
194           time,  PCRE  assumes  that  the pattern or subject it is given (respec-
195           tively) contains only valid UTF-8 codes. In  this  case,  it  does  not
196           diagnose an invalid UTF-8 string.
197    
198         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,
199         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-
200         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
201         string  of  characters  in  the  range 0 to 0x7FFFFFFF. In other words,         string of characters in the range 0  to  0x7FFFFFFF.  In  other  words,
202         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
203         strings  according  to  the more liberal rules of RFC 2279. However, if         strings according to the more liberal rules of RFC  2279.  However,  if
204         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.
205         Your program may crash.         Your program may crash.
206    
207         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
208         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
209         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
210         this situation, you will have to apply your own validity check.         this situation, you will have to apply your own validity check.
211    
212     General comments about UTF-8 mode     General comments about UTF-8 mode
213    
214         1. An unbraced hexadecimal escape sequence (such  as  \xb3)  matches  a         1.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a
215         two-byte UTF-8 character if the value is greater than 127.         two-byte UTF-8 character if the value is greater than 127.
216    
217         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
218         characters for values greater than \177.         characters for values greater than \177.
219    
220         3. Repeat quantifiers apply to complete UTF-8 characters, not to  indi-         3.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-
221         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
222    
223         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-
224         gle byte.         gle byte.
225    
226         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
227         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
228         not available in the alternative matching function, pcre_dfa_exec().         not available in the alternative matching function, pcre_dfa_exec().
229    
230         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
231         test  characters of any code value, but the characters that PCRE recog-         test characters of any code value, but, by default, the characters that
232         nizes as digits, spaces, or word characters  remain  the  same  set  as         PCRE  recognizes  as digits, spaces, or word characters remain the same
233         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
234         includes Unicode property support, because to do otherwise  would  slow         when  PCRE  is built to include Unicode property support, because to do
235         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
236         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
237         \p{Nd}.         and \W. If you really want to test for a wider sense of, say,  "digit",
238           you  can  use  explicit Unicode property tests such as \p{Nd}. Alterna-
239           tively, if you set the PCRE_UCP option,  the  way  that  the  character
240           escapes  work  is changed so that Unicode properties are used to deter-
241           mine which characters match. There are more details in the  section  on
242           generic character types in the pcrepattern documentation.
243    
244         7.  Similarly,  characters that match the POSIX named character classes         7.  Similarly,  characters that match the POSIX named character classes
245         are all low-valued characters.         are all low-valued characters, unless the PCRE_UCP option is set.
246    
247         8. However, the Perl 5.10 horizontal and vertical  whitespace  matching         8. However, the horizontal and  vertical  whitespace  matching  escapes
248         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,
249         acters.         whether or not PCRE_UCP is set.
250    
251         9. Case-insensitive matching applies only to  characters  whose  values         9. Case-insensitive matching applies only to  characters  whose  values
252         are  less than 128, unless PCRE is built with Unicode property support.         are  less than 128, unless PCRE is built with Unicode property support.
253         Even when Unicode property support is available, PCRE  still  uses  its         Even when Unicode property support is available, PCRE  still  uses  its
254         own  character  tables when checking the case of low-valued characters,         own  character  tables when checking the case of low-valued characters,
255         so as not to degrade performance.  The Unicode property information  is         so as not to degrade performance.  The Unicode property information  is
256         used only for characters with higher values. Even when Unicode property         used only for characters with higher values. Furthermore, PCRE supports
257         support is available, PCRE supports case-insensitive matching only when         case-insensitive matching only  when  there  is  a  one-to-one  mapping
258         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-
259         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.  
260    
261    
262  AUTHOR  AUTHOR
# Line 249  AUTHOR Line 265  AUTHOR
265         University Computing Service         University Computing Service
266         Cambridge CB2 3QH, England.         Cambridge CB2 3QH, England.
267    
268         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,
269         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,
270         followed by the two digits 10, at the domain cam.ac.uk.         followed by the two digits 10, at the domain cam.ac.uk.
271    
272    
273  REVISION  REVISION
274    
275         Last updated: 09 August 2007         Last updated: 07 May 2011
276         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
277  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
278    
279    
# Line 271  NAME Line 287  NAME
287  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
288    
289         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
290         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
291         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
292         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
293         includes  the  standard  ones such as the selection of the installation         the  same  options  can be selected in both Unix-like and non-Unix-like
294         directory) can be obtained by running         environments using the GUI facility of cmake-gui if you are using CMake
295           instead of configure to build PCRE.
296    
297           There  is  a  lot more information about building PCRE in non-Unix-like
298           environments in the file called NON_UNIX_USE, which is part of the PCRE
299           distribution.  You  should consult this file as well as the README file
300           if you are building in a non-Unix-like environment.
301    
302           The complete list of options for configure (which includes the standard
303           ones  such  as  the  selection  of  the  installation directory) can be
304           obtained by running
305    
306           ./configure --help           ./configure --help
307    
# Line 287  PCRE BUILD-TIME OPTIONS Line 313  PCRE BUILD-TIME OPTIONS
313         is not described.         is not described.
314    
315    
316    BUILDING SHARED AND STATIC LIBRARIES
317    
318           The  PCRE building process uses libtool to build both shared and static
319           Unix libraries by default. You can suppress one of these by adding  one
320           of
321    
322             --disable-shared
323             --disable-static
324    
325           to the configure command, as required.
326    
327    
328  C++ SUPPORT  C++ SUPPORT
329    
330         By default, the configure script will search for a C++ compiler and C++         By default, the configure script will search for a C++ compiler and C++
# Line 300  C++ SUPPORT Line 338  C++ SUPPORT
338    
339  UTF-8 SUPPORT  UTF-8 SUPPORT
340    
341         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 Unicode character strings, add
342    
343           --enable-utf8           --enable-utf8
344    
345         to  the  configure  command.  Of  itself, this does not make PCRE treat         to  the  configure  command.  Of  itself, this does not make PCRE treat
346         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
347         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()
348         function.         or pcre_compile2() functions.
349    
350           If you set --enable-utf8 when compiling in an EBCDIC environment,  PCRE
351           expects its input to be either ASCII or UTF-8 (depending on the runtime
352           option). It is not possible to support both EBCDIC and UTF-8  codes  in
353           the  same  version  of  the  library.  Consequently,  --enable-utf8 and
354           --enable-ebcdic are mutually exclusive.
355    
356    
357  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
# Line 330  UNICODE CHARACTER PROPERTY SUPPORT Line 374  UNICODE CHARACTER PROPERTY SUPPORT
374    
375  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
376    
377         By  default,  PCRE interprets character 10 (linefeed, LF) as indicating         By  default,  PCRE interprets the linefeed (LF) character as indicating
378         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
379         systems. You can compile PCRE to use character 13 (carriage return, CR)         systems.  You  can compile PCRE to use carriage return (CR) instead, by
380         instead, by adding         adding
381    
382           --enable-newline-is-cr           --enable-newline-is-cr
383    
# Line 356  CODE VALUE OF NEWLINE Line 400  CODE VALUE OF NEWLINE
400    
401         causes PCRE to recognize any Unicode newline sequence.         causes PCRE to recognize any Unicode newline sequence.
402    
403         Whatever line ending convention is selected when PCRE is built  can  be         Whatever  line  ending convention is selected when PCRE is built can be
404         overridden  when  the library functions are called. At build time it is         overridden when the library functions are called. At build time  it  is
405         conventional to use the standard for your operating system.         conventional to use the standard for your operating system.
406    
407    
408  BUILDING SHARED AND STATIC LIBRARIES  WHAT \R MATCHES
409    
410         The PCRE building process uses libtool to build both shared and  static         By  default,  the  sequence \R in a pattern matches any Unicode newline
411         Unix  libraries by default. You can suppress one of these by adding one         sequence, whatever has been selected as the line  ending  sequence.  If
412         of         you specify
413    
414           --disable-shared           --enable-bsr-anycrlf
          --disable-static  
415    
416         to the configure command, as required.         the  default  is changed so that \R matches only CR, LF, or CRLF. What-
417           ever is selected when PCRE is built can be overridden when the  library
418           functions are called.
419    
420    
421  POSIX MALLOC USAGE  POSIX MALLOC USAGE
422    
423         When PCRE is called through the POSIX interface (see the pcreposix doc-         When PCRE is called through the POSIX interface (see the pcreposix doc-
424         umentation),  additional  working  storage  is required for holding the         umentation), additional working storage is  required  for  holding  the
425         pointers to capturing substrings, because PCRE requires three  integers         pointers  to capturing substrings, because PCRE requires three integers
426         per  substring,  whereas  the POSIX interface provides only two. If the         per substring, whereas the POSIX interface provides only  two.  If  the
427         number of expected substrings is small, the wrapper function uses space         number of expected substrings is small, the wrapper function uses space
428         on the stack, because this is faster than using malloc() for each call.         on the stack, because this is faster than using malloc() for each call.
429         The default threshold above which the stack is no longer used is 10; it         The default threshold above which the stack is no longer used is 10; it
# Line 391  POSIX MALLOC USAGE Line 436  POSIX MALLOC USAGE
436    
437  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
438    
439         Within  a  compiled  pattern,  offset values are used to point from one         Within a compiled pattern, offset values are used  to  point  from  one
440         part to another (for example, from an opening parenthesis to an  alter-         part  to another (for example, from an opening parenthesis to an alter-
441         nation  metacharacter).  By default, two-byte values are used for these         nation metacharacter). By default, two-byte values are used  for  these
442         offsets, leading to a maximum size for a  compiled  pattern  of  around         offsets,  leading  to  a  maximum size for a compiled pattern of around
443         64K.  This  is sufficient to handle all but the most gigantic patterns.         64K. This is sufficient to handle all but the most  gigantic  patterns.
444         Nevertheless, some people do want to process enormous patterns,  so  it         Nevertheless,  some  people do want to process truyl enormous patterns,
445         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-
446         adding a setting such as         sets by adding a setting such as
447    
448           --with-link-size=3           --with-link-size=3
449    
450         to the configure command. The value given must be 2,  3,  or  4.  Using         to  the  configure  command.  The value given must be 2, 3, or 4. Using
451         longer  offsets slows down the operation of PCRE because it has to load         longer offsets slows down the operation of PCRE because it has to  load
452         additional bytes when handling them.         additional bytes when handling them.
453    
454    
455  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
456    
457         When matching with the pcre_exec() function, PCRE implements backtrack-         When matching with the pcre_exec() function, PCRE implements backtrack-
458         ing  by  making recursive calls to an internal function called match().         ing by making recursive calls to an internal function  called  match().
459         In environments where the size of the stack is limited,  this  can  se-         In  environments  where  the size of the stack is limited, this can se-
460         verely  limit  PCRE's operation. (The Unix environment does not usually         verely limit PCRE's operation. (The Unix environment does  not  usually
461         suffer from this problem, but it may sometimes be necessary to increase         suffer from this problem, but it may sometimes be necessary to increase
462         the  maximum  stack size.  There is a discussion in the pcrestack docu-         the maximum stack size.  There is a discussion in the  pcrestack  docu-
463         mentation.) An alternative approach to recursion that uses memory  from         mentation.)  An alternative approach to recursion that uses memory from
464         the  heap  to remember data, instead of using recursive function calls,         the heap to remember data, instead of using recursive  function  calls,
465         has been implemented to work round the problem of limited  stack  size.         has  been  implemented to work round the problem of limited stack size.
466         If you want to build a version of PCRE that works this way, add         If you want to build a version of PCRE that works this way, add
467    
468           --disable-stack-for-recursion           --disable-stack-for-recursion
469    
470         to  the  configure  command. With this configuration, PCRE will use the         to the configure command. With this configuration, PCRE  will  use  the
471         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
472         ment  functions. By default these point to malloc() and free(), but you         ment functions. By default these point to malloc() and free(), but  you
473         can replace the pointers so that your own functions are used.         can replace the pointers so that your own functions are used instead.
474    
475         Separate functions are  provided  rather  than  using  pcre_malloc  and         Separate  functions  are  provided  rather  than  using pcre_malloc and
476         pcre_free  because  the  usage  is  very  predictable:  the block sizes         pcre_free because the  usage  is  very  predictable:  the  block  sizes
477         requested are always the same, and  the  blocks  are  always  freed  in         requested  are  always  the  same,  and  the blocks are always freed in
478         reverse  order.  A calling program might be able to implement optimized         reverse order. A calling program might be able to  implement  optimized
479         functions that perform better  than  malloc()  and  free().  PCRE  runs         functions  that  perform  better  than  malloc()  and free(). PCRE runs
480         noticeably more slowly when built in this way. This option affects only         noticeably more slowly when built in this way. This option affects only
481         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.  
482    
483    
484  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
# Line 496  USING EBCDIC CODE Line 540  USING EBCDIC CODE
540    
541         to the configure command. This setting implies --enable-rebuild-charta-         to the configure command. This setting implies --enable-rebuild-charta-
542         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
543         environment (for example, an IBM mainframe operating system).         environment (for example,  an  IBM  mainframe  operating  system).  The
544           --enable-ebcdic option is incompatible with --enable-utf8.
545    
546    
547    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
548    
549           By default, pcregrep reads all files as plain text. You can build it so
550           that it recognizes files whose names end in .gz or .bz2, and reads them
551           with libz or libbz2, respectively, by adding one or both of
552    
553             --enable-pcregrep-libz
554             --enable-pcregrep-libbz2
555    
556           to the configure command. These options naturally require that the rel-
557           evant libraries are installed on your system. Configuration  will  fail
558           if they are not.
559    
560    
561    PCREGREP BUFFER SIZE
562    
563           pcregrep  uses  an internal buffer to hold a "window" on the file it is
564           scanning, in order to be able to output "before" and "after" lines when
565           it  finds  a match. The size of the buffer is controlled by a parameter
566           whose default value is 20K. The buffer itself is three times this size,
567           but because of the way it is used for holding "before" lines, the long-
568           est line that is guaranteed to be processable is  the  parameter  size.
569           You can change the default parameter value by adding, for example,
570    
571             --with-pcregrep-bufsize=50K
572    
573           to the configure command. The caller of pcregrep can, however, override
574           this value by specifying a run-time option.
575    
576    
577    PCRETEST OPTION FOR LIBREADLINE SUPPORT
578    
579           If you add
580    
581             --enable-pcretest-libreadline
582    
583           to the configure command,  pcretest  is  linked  with  the  libreadline
584           library,  and  when its input is from a terminal, it reads it using the
585           readline() function. This provides line-editing and history facilities.
586           Note that libreadline is GPL-licensed, so if you distribute a binary of
587           pcretest linked in this way, there may be licensing issues.
588    
589           Setting this option causes the -lreadline option to  be  added  to  the
590           pcretest  build.  In many operating environments with a sytem-installed
591           libreadline this is sufficient. However, in some environments (e.g.  if
592           an  unmodified  distribution version of readline is in use), some extra
593           configuration may be necessary. The INSTALL file for  libreadline  says
594           this:
595    
596             "Readline uses the termcap functions, but does not link with the
597             termcap or curses library itself, allowing applications which link
598             with readline the to choose an appropriate library."
599    
600           If  your environment has not been set up so that an appropriate library
601           is automatically included, you may need to add something like
602    
603             LIBS="-ncurses"
604    
605           immediately before the configure command.
606    
607    
608  SEE ALSO  SEE ALSO
# Line 513  AUTHOR Line 619  AUTHOR
619    
620  REVISION  REVISION
621    
622         Last updated: 30 July 2007         Last updated: 02 August 2011
623         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
624  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
625    
626    
# Line 601  THE ALTERNATIVE MATCHING ALGORITHM Line 707  THE ALTERNATIVE MATCHING ALGORITHM
707         though  it is not implemented as a traditional finite state machine (it         though  it is not implemented as a traditional finite state machine (it
708         keeps multiple states active simultaneously).         keeps multiple states active simultaneously).
709    
710           Although the general principle of this matching algorithm  is  that  it
711           scans  the subject string only once, without backtracking, there is one
712           exception: when a lookaround assertion is encountered,  the  characters
713           following  or  preceding  the  current  point  have to be independently
714           inspected.
715    
716         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
717         there  are  no more unterminated paths. At this point, terminated paths         there  are  no more unterminated paths. At this point, terminated paths
718         represent the different matching possibilities (if there are none,  the         represent the different matching possibilities (if there are none,  the
719         match  has  failed).   Thus,  if there is more than one possible match,         match  has  failed).   Thus,  if there is more than one possible match,
720         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-
721         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
722         match (which is necessarily the shortest) has been found.         an option to stop the algorithm after the first match (which is  neces-
723           sarily the shortest) is found.
724    
725         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
726         subject. If the pattern         subject. If the pattern
727    
728           cat(er(pillar)?)           cat(er(pillar)?)?
729    
730         is  matched  against the string "the caterpillar catchment", the result         is matched against the string "the caterpillar catchment",  the  result
731         will be the three strings "cat", "cater", and "caterpillar" that  start         will  be the three strings "caterpillar", "cater", and "cat" that start
732         at the fourth character of the subject. The algorithm does not automat-         at the fifth character of the subject. The algorithm does not automati-
733         ically move on to find matches that start at later positions.         cally move on to find matches that start at later positions.
734    
735         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
736         supported by the alternative matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
737    
738         1.  Because  the  algorithm  finds  all possible matches, the greedy or         1. Because the algorithm finds all  possible  matches,  the  greedy  or
739         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
740         ungreedy quantifiers are treated in exactly the same way. However, pos-         ungreedy quantifiers are treated in exactly the same way. However, pos-
741         sessive quantifiers can make a difference when what follows could  also         sessive  quantifiers can make a difference when what follows could also
742         match what is quantified, for example in a pattern like this:         match what is quantified, for example in a pattern like this:
743    
744           ^a++\w!           ^a++\w!
745    
746         This  pattern matches "aaab!" but not "aaa!", which would be matched by         This pattern matches "aaab!" but not "aaa!", which would be matched  by
747         a non-possessive quantifier. Similarly, if an atomic group is  present,         a  non-possessive quantifier. Similarly, if an atomic group is present,
748         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,
749         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
750         pattern.         pattern.
751    
752         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
753         is not straightforward to keep track of  captured  substrings  for  the         is  not  straightforward  to  keep track of captured substrings for the
754         different  matching  possibilities,  and  PCRE's implementation of this         different matching possibilities, and  PCRE's  implementation  of  this
755         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-
756         strings are available.         strings are available.
757    
758         3.  Because no substrings are captured, back references within the pat-         3. Because no substrings are captured, back references within the  pat-
759         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
760    
761         4. For the same reason, conditional expressions that use  a  backrefer-         4.  For  the same reason, conditional expressions that use a backrefer-
762         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
763         supported.         supported.
764    
765         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
766         sequence, which resets the start of the match when encountered (but may         sequence, which resets the start of the match when encountered (but may
767         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
768         error if encountered.         error if encountered.
769    
770         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
771         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.
772    
773         7. The \C escape sequence, which (in the standard algorithm) matches  a         7.  The \C escape sequence, which (in the standard algorithm) matches a
774         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-
775         tive algorithm moves through the subject  string  one  character  at  a         tive  algorithm  moves  through  the  subject string one character at a
776         time, for all active paths through the tree.         time, for all active paths through the tree.
777    
778         8.  None  of  the  backtracking control verbs such as (*PRUNE) are sup-         8. Except for (*FAIL), the backtracking control verbs such as  (*PRUNE)
779         ported.         are  not  supported.  (*FAIL)  is supported, and behaves like a failing
780           negative assertion.
781    
782    
783  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
# Line 676  ADVANTAGES OF THE ALTERNATIVE ALGORITHM Line 790  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
790         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
791         things with callouts.         things with callouts.
792    
793         2. There is much better support for partial matching. The  restrictions         2. Because the alternative algorithm  scans  the  subject  string  just
        on  the content of the pattern that apply when using the standard algo-  
        rithm for partial matching do not apply to the  alternative  algorithm.  
        For  non-anchored patterns, the starting position of a partial match is  
        available.  
   
        3. Because the alternative algorithm  scans  the  subject  string  just  
794         once,  and  never  needs to backtrack, it is possible to pass very long         once,  and  never  needs to backtrack, it is possible to pass very long
795         subject strings to the matching function in  several  pieces,  checking         subject strings to the matching function in  several  pieces,  checking
796         for partial matching each time.         for  partial  matching  each time. Although it is possible to do multi-
797           segment matching using the standard algorithm (pcre_exec()), by retain-
798           ing  partially matched substrings, it is more complicated. The pcrepar-
799           tial documentation gives details  of  partial  matching  and  discusses
800           multi-segment matching.
801    
802    
803  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
# Line 711  AUTHOR Line 823  AUTHOR
823    
824  REVISION  REVISION
825    
826         Last updated: 08 August 2007         Last updated: 17 November 2010
827         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
828  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
829    
830    
# Line 819  PCRE API OVERVIEW Line 931  PCRE API OVERVIEW
931         bers for the library.  Applications can use these  to  include  support         bers for the library.  Applications can use these  to  include  support
932         for different releases of PCRE.         for different releases of PCRE.
933    
934           In a Windows environment, if you want to statically link an application
935           program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC
936           before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-
937           loc()   and   pcre_free()   exported   functions   will   be   declared
938           __declspec(dllimport), with unwanted results.
939    
940         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
941         pcre_exec() are used for compiling and matching regular expressions  in         pcre_exec() are used for compiling and matching regular expressions  in
942         a  Perl-compatible  manner. A sample program that demonstrates the sim-         a  Perl-compatible  manner. A sample program that demonstrates the sim-
943         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
944         the  source distribution. The pcresample documentation describes how to         the PCRE source distribution. A listing of this program is given in the
945         run it.         pcredemo documentation, and the pcresample documentation describes  how
946           to compile and run it.
947    
948         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
949         ble,  is  also provided. This uses a different algorithm for the match-         ble, is also provided. This uses a different algorithm for  the  match-
950         ing. The alternative algorithm finds all possible matches (at  a  given         ing.  The  alternative algorithm finds all possible matches (at a given
951         point  in  the subject), and scans the subject just once. However, this         point in the subject), and scans the subject just  once  (unless  there
952         algorithm does not return captured substrings. A description of the two         are  lookbehind  assertions).  However,  this algorithm does not return
953         matching  algorithms and their advantages and disadvantages is given in         captured substrings. A description of the two matching  algorithms  and
954         the pcrematching documentation.         their  advantages  and disadvantages is given in the pcrematching docu-
955           mentation.
956    
957         In addition to the main compiling and  matching  functions,  there  are         In addition to the main compiling and  matching  functions,  there  are
958         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
# Line 908  NEWLINES Line 1028  NEWLINES
1028         dard. When PCRE is run, the default can be overridden,  either  when  a         dard. When PCRE is run, the default can be overridden,  either  when  a
1029         pattern is compiled, or when it is matched.         pattern is compiled, or when it is matched.
1030    
1031           At compile time, the newline convention can be specified by the options
1032           argument of pcre_compile(), or it can be specified by special  text  at
1033           the start of the pattern itself; this overrides any other settings. See
1034           the pcrepattern page for details of the special character sequences.
1035    
1036         In the PCRE documentation the word "newline" is used to mean "the char-         In the PCRE documentation the word "newline" is used to mean "the char-
1037         acter or pair of characters that indicate a line break". The choice  of         acter  or pair of characters that indicate a line break". The choice of
1038         newline  convention  affects  the  handling of the dot, circumflex, and         newline convention affects the handling of  the  dot,  circumflex,  and
1039         dollar metacharacters, the handling of #-comments in /x mode, and, when         dollar metacharacters, the handling of #-comments in /x mode, and, when
1040         CRLF  is a recognized line ending sequence, the match position advance-         CRLF is a recognized line ending sequence, the match position  advance-
1041         ment for a non-anchored pattern. The choice of newline convention  does         ment for a non-anchored pattern. There is more detail about this in the
1042         not affect the interpretation of the \n or \r escape sequences.         section on pcre_exec() options below.
1043    
1044           The choice of newline convention does not affect the interpretation  of
1045           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
1046           which is controlled in a similar way, but by separate options.
1047    
1048    
1049  MULTITHREADING  MULTITHREADING
1050    
1051         The  PCRE  functions  can be used in multi-threading applications, with         The PCRE functions can be used in  multi-threading  applications,  with
1052         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
1053         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
1054         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
# Line 968  CHECKING BUILD-TIME OPTIONS Line 1097  CHECKING BUILD-TIME OPTIONS
1097         The output is an integer whose value specifies  the  default  character         The output is an integer whose value specifies  the  default  character
1098         sequence  that is recognized as meaning "newline". The four values that         sequence  that is recognized as meaning "newline". The four values that
1099         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,
1100         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
1101         for your operating system.         are returned in EBCDIC environments. The default should normally corre-
1102           spond to the standard sequence for your operating system.
1103    
1104             PCRE_CONFIG_BSR
1105    
1106           The output is an integer whose value indicates what character sequences
1107           the \R escape sequence matches by default. A value of 0 means  that  \R
1108           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1109           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1110           tern is compiled or matched.
1111    
1112           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1113    
1114         The output is an integer that contains the number  of  bytes  used  for         The  output  is  an  integer that contains the number of bytes used for
1115         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
1116         4. Larger values allow larger regular expressions to  be  compiled,  at         4.  Larger  values  allow larger regular expressions to be compiled, at
1117         the  expense  of  slower matching. The default value of 2 is sufficient         the expense of slower matching. The default value of  2  is  sufficient
1118         for all but the most massive patterns, since  it  allows  the  compiled         for  all  but  the  most massive patterns, since it allows the compiled
1119         pattern to be up to 64K in size.         pattern to be up to 64K in size.
1120    
1121           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1122    
1123         The  output  is  an integer that contains the threshold above which the         The output is an integer that contains the threshold  above  which  the
1124         POSIX interface uses malloc() for output vectors. Further  details  are         POSIX  interface  uses malloc() for output vectors. Further details are
1125         given in the pcreposix documentation.         given in the pcreposix documentation.
1126    
1127           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1128    
1129         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-
1130         internal matching function calls in a  pcre_exec()  execution.  Further         ber  of  internal  matching  function calls in a pcre_exec() execution.
1131         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1132    
1133           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1134    
1135         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
1136         recursion when calling the internal matching function in a  pcre_exec()         of   recursion  when  calling  the  internal  matching  function  in  a
1137         execution. Further details are given with pcre_exec() below.         pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1138           below.
1139    
1140           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1141    
# Line 1023  COMPILING A PATTERN Line 1162  COMPILING A PATTERN
1162         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1163         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1164         the  two interfaces is that pcre_compile2() has an additional argument,         the  two interfaces is that pcre_compile2() has an additional argument,
1165         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr, via which a numerical error  code  can  be  returned.  To
1166           avoid  too  much repetition, we refer just to pcre_compile() below, but
1167           the information applies equally to pcre_compile2().
1168    
1169         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
1170         the  pattern  argument.  A  pointer to a single block of memory that is         the  pattern  argument.  A  pointer to a single block of memory that is
# Line 1040  COMPILING A PATTERN Line 1181  COMPILING A PATTERN
1181    
1182         The options argument contains various bit settings that affect the com-         The options argument contains various bit settings that affect the com-
1183         pilation. It should be zero if no options are required.  The  available         pilation. It should be zero if no options are required.  The  available
1184         options  are  described  below. Some of them, in particular, those that         options  are  described  below. Some of them (in particular, those that
1185         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
1186         pattern  (see  the  detailed  description in the pcrepattern documenta-         unset  from  within  the  pattern  (see the detailed description in the
1187         tion). For these options, the contents of the options  argument  speci-         pcrepattern documentation). For those options that can be different  in
1188         fies  their initial settings at the start of compilation and execution.         different  parts  of  the pattern, the contents of the options argument
1189         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
1190         of matching as well as at compile time.         PCRE_ANCHORED,  PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK, and
1191           PCRE_NO_START_OPT options can be set at the time of matching as well as
1192           at compile time.
1193    
1194         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1195         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
1196         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-
1197         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
1198         try to free it. The offset from the start of the pattern to the charac-         try  to  free it. Normally, the offset from the start of the pattern to
1199         ter where the error was discovered is placed in the variable pointed to         the byte that was being processed when  the  error  was  discovered  is
1200         by  erroffset,  which must not be NULL. If it is, an immediate error is         placed  in the variable pointed to by erroffset, which must not be NULL
1201         given.         (if it is, an immediate error is given). However, for an invalid  UTF-8
1202           string,  the offset is that of the first byte of the failing character.
1203         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         Also, some errors are not detected until checks are  carried  out  when
1204         codeptr  argument is not NULL, a non-zero error code number is returned         the  whole  pattern  has been scanned; in these cases the offset passed
1205         via this argument in the event of an error. This is in addition to  the         back is the length of the pattern.
1206    
1207           Note that the offset is in bytes, not characters, even in  UTF-8  mode.
1208           It may sometimes point into the middle of a UTF-8 character.
1209    
1210           If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1211           codeptr argument is not NULL, a non-zero error code number is  returned
1212           via  this argument in the event of an error. This is in addition to the
1213         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1214    
1215         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
1216         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1217         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1218         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
1219         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1220         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
1221         support below.         support below.
1222    
1223         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1224         pile():         pile():
1225    
1226           pcre *re;           pcre *re;
# Line 1083  COMPILING A PATTERN Line 1233  COMPILING A PATTERN
1233             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1234             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1235    
1236         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
1237         file:         file:
1238    
1239           PCRE_ANCHORED           PCRE_ANCHORED
1240    
1241         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
1242         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
1243         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1244         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1245         only way to do it in Perl.         only way to do it in Perl.
1246    
1247           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1248    
1249         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1250         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1251         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1252    
1253             PCRE_BSR_ANYCRLF
1254             PCRE_BSR_UNICODE
1255    
1256           These options (which are mutually exclusive) control what the \R escape
1257           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1258           or to match any Unicode newline sequence. The default is specified when
1259           PCRE is built. It can be overridden from within the pattern, or by set-
1260           ting an option when a compiled pattern is matched.
1261    
1262           PCRE_CASELESS           PCRE_CASELESS
1263    
1264         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
1265         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
1266         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
1267         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1268         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1269         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-
1270         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1271         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1272         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1273         UTF-8 support.         UTF-8 support.
1274    
1275           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1276    
1277         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
1278         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
1279         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
1280         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1281         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
1282         Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1283    
1284           PCRE_DOTALL           PCRE_DOTALL
1285    
1286         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-
1287         acters, including those that indicate newline. Without it, a  dot  does         acter of any value, including one that indicates a newline. However, it
1288         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.
1289         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
1290         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
1291         newline characters, independent of the setting of this option.         be  changed within a pattern by a (?s) option setting. A negative class
1292           such as [^a] always matches newline characters, independent of the set-
1293           ting of this option.
1294    
1295           PCRE_DUPNAMES           PCRE_DUPNAMES
1296    
1297         If this bit is set, names used to identify capturing  subpatterns  need         If  this  bit is set, names used to identify capturing subpatterns need
1298         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
1299         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
1300         matched.  There  are  more details of named subpatterns below; see also         matched. There are more details of named subpatterns  below;  see  also
1301         the pcrepattern documentation.         the pcrepattern documentation.
1302    
1303           PCRE_EXTENDED           PCRE_EXTENDED
1304    
1305         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1306         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1307         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1308         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1309         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1310         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-
1311         ting.         ting.
1312    
1313           Which  characters  are  interpreted  as  newlines  is controlled by the
1314           options passed to pcre_compile() or by a special sequence at the  start
1315           of  the  pattern, as described in the section entitled "Newline conven-
1316           tions" in the pcrepattern documentation. Note that the end of this type
1317           of  comment  is  a  literal  newline  sequence  in  the pattern; escape
1318           sequences that happen to represent a newline do not count.
1319    
1320         This option makes it possible to include  comments  inside  complicated         This option makes it possible to include  comments  inside  complicated
1321         patterns.   Note,  however,  that this applies only to data characters.         patterns.   Note,  however,  that this applies only to data characters.
1322         Whitespace  characters  may  never  appear  within  special   character         Whitespace  characters  may  never  appear  within  special   character
1323         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for example within the sequence (?( that intro-
1324         introduces a conditional subpattern.         duces a conditional subpattern.
1325    
1326           PCRE_EXTRA           PCRE_EXTRA
1327    
# Line 1163  COMPILING A PATTERN Line 1331  COMPILING A PATTERN
1331         letter  that  has  no  special  meaning causes an error, thus reserving         letter  that  has  no  special  meaning causes an error, thus reserving
1332         these combinations for future expansion. By  default,  as  in  Perl,  a         these combinations for future expansion. By  default,  as  in  Perl,  a
1333         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
1334         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
1335         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
1336         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
1337           within a pattern.
1338    
1339           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1340    
1341         If this option is set, an  unanchored  pattern  is  required  to  match         If  this  option  is  set,  an  unanchored pattern is required to match
1342         before  or  at  the  first  newline  in  the subject string, though the         before or at the first  newline  in  the  subject  string,  though  the
1343         matched text may continue over the newline.         matched text may continue over the newline.
1344    
1345             PCRE_JAVASCRIPT_COMPAT
1346    
1347           If this option is set, PCRE's behaviour is changed in some ways so that
1348           it is compatible with JavaScript rather than Perl. The changes  are  as
1349           follows:
1350    
1351           (1)  A  lone  closing square bracket in a pattern causes a compile-time
1352           error, because this is illegal in JavaScript (by default it is  treated
1353           as a data character). Thus, the pattern AB]CD becomes illegal when this
1354           option is set.
1355    
1356           (2) At run time, a back reference to an unset subpattern group  matches
1357           an  empty  string (by default this causes the current matching alterna-
1358           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
1359           set  (assuming  it can find an "a" in the subject), whereas it fails by
1360           default, for Perl compatibility.
1361    
1362           PCRE_MULTILINE           PCRE_MULTILINE
1363    
1364         By default, PCRE treats the subject string as consisting  of  a  single         By default, PCRE treats the subject string as consisting  of  a  single
# Line 1217  COMPILING A PATTERN Line 1403  COMPILING A PATTERN
1403         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1404         cause an error.         cause an error.
1405    
1406         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
1407         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
1408         character class is encountered. This indicates  a  comment  that  lasts         characters, and so are ignored in this mode. Also, an unescaped #  out-
1409         until  after the next line break sequence. In other circumstances, line         side  a  character class indicates a comment that lasts until after the
1410         break  sequences  are  treated  as  literal  data,   except   that   in         next line break sequence. In other circumstances, line break  sequences
1411         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         in patterns are treated as literal data.
        and are therefore ignored.  
1412    
1413         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
1414         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.
1415    
1416           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1417    
# Line 1236  COMPILING A PATTERN Line 1421  COMPILING A PATTERN
1421         be  used  for  capturing  (and  they acquire numbers in the usual way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
1422         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1423    
1424             NO_START_OPTIMIZE
1425    
1426           This is an option that acts at matching time; that is, it is really  an
1427           option  for  pcre_exec()  or  pcre_dfa_exec().  If it is set at compile
1428           time, it is remembered with the compiled pattern and assumed at  match-
1429           ing  time.  For  details  see  the discussion of PCRE_NO_START_OPTIMIZE
1430           below.
1431    
1432             PCRE_UCP
1433    
1434           This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
1435           \w,  and  some  of  the POSIX character classes. By default, only ASCII
1436           characters are recognized, but if PCRE_UCP is set,  Unicode  properties
1437           are  used instead to classify characters. More details are given in the
1438           section on generic character types in the pcrepattern page. If you  set
1439           PCRE_UCP,  matching  one of the items it affects takes much longer. The
1440           option is available only if PCRE has been compiled with  Unicode  prop-
1441           erty support.
1442    
1443           PCRE_UNGREEDY           PCRE_UNGREEDY
1444    
1445         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1446         are  not greedy by default, but become greedy if followed by "?". It is         are not greedy by default, but become greedy if followed by "?". It  is
1447         not compatible with Perl. It can also be set by a (?U)  option  setting         not  compatible  with Perl. It can also be set by a (?U) option setting
1448         within the pattern.         within the pattern.
1449    
1450           PCRE_UTF8           PCRE_UTF8
1451    
1452         This  option  causes PCRE to regard both the pattern and the subject as         This option causes PCRE to regard both the pattern and the  subject  as
1453         strings of UTF-8 characters instead of single-byte  character  strings.         strings  of  UTF-8 characters instead of single-byte character strings.
1454         However,  it is available only when PCRE is built to include UTF-8 sup-         However, it is available only when PCRE is built to include UTF-8  sup-
1455         port. If not, the use of this option provokes an error. Details of  how         port.  If not, the use of this option provokes an error. Details of how
1456         this  option  changes the behaviour of PCRE are given in the section on         this option changes the behaviour of PCRE are given in the  section  on
1457         UTF-8 support in the main pcre page.         UTF-8 support in the main pcre page.
1458    
1459           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1460    
1461         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is         When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is
1462         automatically  checked.  There  is  a  discussion about the validity of         automatically checked. There is a  discussion  about  the  validity  of
1463         UTF-8 strings in the main pcre page. If an invalid  UTF-8  sequence  of         UTF-8  strings  in  the main pcre page. If an invalid UTF-8 sequence of
1464         bytes  is  found,  pcre_compile() returns an error. If you already know         bytes is found, pcre_compile() returns an error. If  you  already  know
1465         that your pattern is valid, and you want to skip this check for perfor-         that your pattern is valid, and you want to skip this check for perfor-
1466         mance  reasons,  you  can set the PCRE_NO_UTF8_CHECK option. When it is         mance reasons, you can set the PCRE_NO_UTF8_CHECK option.  When  it  is
1467         set, the effect of passing an invalid UTF-8  string  as  a  pattern  is         set,  the  effect  of  passing  an invalid UTF-8 string as a pattern is
1468         undefined.  It  may  cause your program to crash. Note that this option         undefined. It may cause your program to crash. Note  that  this  option
1469         can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the         can  also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the
1470         UTF-8 validity checking of subject strings.         UTF-8 validity checking of subject strings.
1471    
1472    
1473  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1474    
1475         The  following  table  lists  the  error  codes than may be returned by         The following table lists the error  codes  than  may  be  returned  by
1476         pcre_compile2(), along with the error messages that may be returned  by         pcre_compile2(),  along with the error messages that may be returned by
1477         both  compiling functions. As PCRE has developed, some error codes have         both compiling functions. As PCRE has developed, some error codes  have
1478         fallen out of use. To avoid confusion, they have not been re-used.         fallen out of use. To avoid confusion, they have not been re-used.
1479    
1480            0  no error            0  no error
# Line 1285  COMPILATION ERROR CODES Line 1489  COMPILATION ERROR CODES
1489            9  nothing to repeat            9  nothing to repeat
1490           10  [this code is not in use]           10  [this code is not in use]
1491           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1492           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1493           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1494           14  missing )           14  missing )
1495           15  reference to non-existent subpattern           15  reference to non-existent subpattern
# Line 1293  COMPILATION ERROR CODES Line 1497  COMPILATION ERROR CODES
1497           17  unknown option bit(s) set           17  unknown option bit(s) set
1498           18  missing ) after comment           18  missing ) after comment
1499           19  [this code is not in use]           19  [this code is not in use]
1500           20  regular expression too large           20  regular expression is too large
1501           21  failed to get memory           21  failed to get memory
1502           22  unmatched parentheses           22  unmatched parentheses
1503           23  internal error: code overflow           23  internal error: code overflow
# Line 1322  COMPILATION ERROR CODES Line 1526  COMPILATION ERROR CODES
1526           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1527           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1528           48  subpattern name is too long (maximum 32 characters)           48  subpattern name is too long (maximum 32 characters)
1529           49  too many named subpatterns (maximum 10,000)           49  too many named subpatterns (maximum 10000)
1530           50  [this code is not in use]           50  [this code is not in use]
1531           51  octal value is greater than \377 (not in UTF-8 mode)           51  octal value is greater than \377 (not in UTF-8 mode)
1532           52  internal error: overran compiling workspace           52  internal error: overran compiling workspace
1533           53  internal  error:  previously-checked  referenced  subpattern  not           53  internal error: previously-checked referenced subpattern
1534         found                 not found
1535           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1536           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1537           56  inconsistent NEWLINE options"           56  inconsistent NEWLINE options
1538           57  \g is not followed by a braced name or an optionally braced           57  \g is not followed by a braced, angle-bracketed, or quoted
1539                 non-zero number                 name/number or by a plain number
1540           58  (?+ or (?- or (?(+ or (?(- must be followed by a non-zero number           58  a numbered reference must not be zero
1541             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1542             60  (*VERB) not recognized
1543             61  number is too big
1544             62  subpattern name expected
1545             63  digit expected after (?+
1546             64  ] is an invalid data character in JavaScript compatibility mode
1547             65  different names for subpatterns of the same number are
1548                   not allowed
1549             66  (*MARK) must have an argument
1550             67  this version of PCRE is not compiled with PCRE_UCP support
1551    
1552           The  numbers  32  and 10000 in errors 48 and 49 are defaults; different
1553           values may be used if the limits were changed when PCRE was built.
1554    
1555    
1556  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1341  STUDYING A PATTERN Line 1558  STUDYING A PATTERN
1558         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1559              const char **errptr);              const char **errptr);
1560    
1561         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
1562         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
1563         matching.  The function pcre_study() takes a pointer to a compiled pat-         matching. The function pcre_study() takes a pointer to a compiled  pat-
1564         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1565         information  that  will  help speed up matching, pcre_study() returns a         information that will help speed up matching,  pcre_study()  returns  a
1566         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
1567         the results of the study.         the results of the study.
1568    
1569         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1570         pcre_exec(). However, a pcre_extra block  also  contains  other  fields         pcre_exec()  or  pcre_dfa_exec(). However, a pcre_extra block also con-
1571         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
1572         described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1573    
1574         If studying the pattern does not  produce  any  additional  information         If  studying  the  pattern  does  not  produce  any useful information,
1575         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1576         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
1577         its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1578    
1579         The  second  argument of pcre_study() contains option bits. At present,         The second argument of pcre_study() contains option bits.  At  present,
1580         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1581    
1582         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.
1583         If  studying  succeeds  (even  if no data is returned), the variable it         If studying succeeds (even if no data is  returned),  the  variable  it
1584         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
1585         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
1586         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
1587         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1588    
1589         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 1377  STUDYING A PATTERN Line 1594  STUDYING A PATTERN
1594             0,              /* no options exist */             0,              /* no options exist */
1595             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1596    
1597         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
1598         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
1599         ble starting bytes is created.         does not mean that there are any strings of that length that match, but
1600           it  does  guarantee that no shorter strings match. The value is used by
1601           pcre_exec() and pcre_dfa_exec() to avoid  wasting  time  by  trying  to
1602           match  strings  that are shorter than the lower bound. You can find out
1603           the value in a calling program via the pcre_fullinfo() function.
1604    
1605           Studying a pattern is also useful for non-anchored patterns that do not
1606           have  a  single fixed starting character. A bitmap of possible starting
1607           bytes is created. This speeds up finding a position in the  subject  at
1608           which to start matching.
1609    
1610           The  two  optimizations  just  described can be disabled by setting the
1611           PCRE_NO_START_OPTIMIZE   option    when    calling    pcre_exec()    or
1612           pcre_dfa_exec().  You  might  want  to do this if your pattern contains
1613           callouts or (*MARK), and you want to make use of  these  facilities  in
1614           cases  where  matching fails. See the discussion of PCRE_NO_START_OPTI-
1615           MIZE below.
1616    
1617    
1618  LOCALE SUPPORT  LOCALE SUPPORT
1619    
1620         PCRE  handles  caseless matching, and determines whether characters are         PCRE handles caseless matching, and determines whether  characters  are
1621         letters, digits, or whatever, by reference to a set of tables,  indexed         letters,  digits, or whatever, by reference to a set of tables, indexed
1622         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
1623         characters with codes less than 128. Higher-valued  codes  never  match         characters  with  codes  less than 128. By default, higher-valued codes
1624         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
1625         with Unicode character property support. The use of locales  with  Uni-         PCRE  is  built with Unicode character property support. Alternatively,
1626         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
1627         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
1628         not try to mix the two.         use of locales with Unicode is discouraged. If you are handling charac-
1629           ters  with codes greater than 128, you should either use UTF-8 and Uni-
1630           code, or use locales, but not try to mix the two.
1631    
1632         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
1633         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many
1634         applications.  Normally, the internal tables recognize only ASCII char-         applications.  Normally, the internal tables recognize only ASCII char-
1635         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-
1636         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,
1637         which may cause them to be different.         which may cause them to be different.
1638    
1639         The internal tables can always be overridden by tables supplied by  the         The  internal tables can always be overridden by tables supplied by the
1640         application that calls PCRE. These may be created in a different locale         application that calls PCRE. These may be created in a different locale
1641         from the default. As more and more applications change  to  using  Uni-         from  the  default.  As more and more applications change to using Uni-
1642         code, the need for this locale support is expected to die away.         code, the need for this locale support is expected to die away.
1643    
1644         External  tables  are  built by calling the pcre_maketables() function,         External tables are built by calling  the  pcre_maketables()  function,
1645         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
1646         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For
1647         example, to build and use tables that are appropriate  for  the  French         example,  to  build  and use tables that are appropriate for the French
1648         locale  (where  accented  characters  with  values greater than 128 are         locale (where accented characters with  values  greater  than  128  are
1649         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1650    
1651           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1652           tables = pcre_maketables();           tables = pcre_maketables();
1653           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1654    
1655         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;
1656         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".
1657    
1658         When  pcre_maketables()  runs,  the  tables are built in memory that is         When pcre_maketables() runs, the tables are built  in  memory  that  is
1659         obtained via pcre_malloc. It is the caller's responsibility  to  ensure         obtained  via  pcre_malloc. It is the caller's responsibility to ensure
1660         that  the memory containing the tables remains available for as long as         that the memory containing the tables remains available for as long  as
1661         it is needed.         it is needed.
1662    
1663         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
1664         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()
1665         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-
1666         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1667         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1668    
1669         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
1670         the  internal  tables)  to  pcre_exec(). Although not intended for this         the internal tables) to pcre_exec(). Although  not  intended  for  this
1671         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
1672         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
1673         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1674    
# Line 1443  INFORMATION ABOUT A PATTERN Line 1678  INFORMATION ABOUT A PATTERN
1678         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1679              int what, void *where);              int what, void *where);
1680    
1681         The pcre_fullinfo() function returns information about a compiled  pat-         The  pcre_fullinfo() function returns information about a compiled pat-
1682         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1683         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1684    
1685         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled
1686         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
1687         the pattern was not studied. The third argument specifies  which  piece         the  pattern  was not studied. The third argument specifies which piece
1688         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
1689         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
1690         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1691    
1692           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1459  INFORMATION ABOUT A PATTERN Line 1694  INFORMATION ABOUT A PATTERN
1694           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1695           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1696    
1697         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
1698         an simple check against passing an arbitrary memory pointer. Here is  a         an  simple check against passing an arbitrary memory pointer. Here is a
1699         typical  call  of pcre_fullinfo(), to obtain the length of the compiled         typical call of pcre_fullinfo(), to obtain the length of  the  compiled
1700         pattern:         pattern:
1701    
1702           int rc;           int rc;
# Line 1472  INFORMATION ABOUT A PATTERN Line 1707  INFORMATION ABOUT A PATTERN
1707             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1708             &length);         /* where to put the data */             &length);         /* where to put the data */
1709    
1710         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
1711         are as follows:         are as follows:
1712    
1713           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1714    
1715         Return  the  number  of  the highest back reference in the pattern. The         Return the number of the highest back reference  in  the  pattern.  The
1716         fourth argument should point to an int variable. Zero  is  returned  if         fourth  argument  should  point to an int variable. Zero is returned if
1717         there are no back references.         there are no back references.
1718    
1719           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1720    
1721         Return  the  number of capturing subpatterns in the pattern. The fourth         Return the number of capturing subpatterns in the pattern.  The  fourth
1722         argument should point to an int variable.         argument should point to an int variable.
1723    
1724           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1725    
1726         Return a pointer to the internal default character tables within  PCRE.         Return  a pointer to the internal default character tables within PCRE.
1727         The  fourth  argument should point to an unsigned char * variable. This         The fourth argument should point to an unsigned char *  variable.  This
1728         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1729         tion.  External  callers  can  cause PCRE to use its internal tables by         tion. External callers can cause PCRE to use  its  internal  tables  by
1730         passing a NULL table pointer.         passing a NULL table pointer.
1731    
1732           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1733    
1734         Return information about the first byte of any matched  string,  for  a         Return  information  about  the first byte of any matched string, for a
1735         non-anchored  pattern. The fourth argument should point to an int vari-         non-anchored pattern. The fourth argument should point to an int  vari-
1736         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
1737         is still recognized for backwards compatibility.)         is still recognized for backwards compatibility.)
1738    
1739         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
1740         (cat|cow|coyote), its value is returned. Otherwise, if either         (cat|cow|coyote), its value is returned. Otherwise, if either
1741    
1742         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every
1743         branch starts with "^", or         branch starts with "^", or
1744    
1745         (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
1746         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1747    
1748         -1 is returned, indicating that the pattern matches only at  the  start         -1  is  returned, indicating that the pattern matches only at the start
1749         of  a  subject string or after any newline within the string. Otherwise         of a subject string or after any newline within the  string.  Otherwise
1750         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1751    
1752           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1753    
1754         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
1755         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
1756         matching string, a pointer to the table is returned. Otherwise NULL  is         matching  string, a pointer to the table is returned. Otherwise NULL is
1757         returned.  The fourth argument should point to an unsigned char * vari-         returned. The fourth argument should point to an unsigned char *  vari-
1758         able.         able.
1759    
1760             PCRE_INFO_HASCRORLF
1761    
1762           Return  1  if  the  pattern  contains any explicit matches for CR or LF
1763           characters, otherwise 0. The fourth argument should  point  to  an  int
1764           variable.  An explicit match is either a literal CR or LF character, or
1765           \r or \n.
1766    
1767           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
1768    
1769         Return 1 if the (?J) option setting is used in the  pattern,  otherwise         Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,
1770         0. The fourth argument should point to an int variable. The (?J) inter-         otherwise  0. The fourth argument should point to an int variable. (?J)
1771         nal option setting changes the local PCRE_DUPNAMES option.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1772    
1773           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1774    
# Line 1538  INFORMATION ABOUT A PATTERN Line 1780  INFORMATION ABOUT A PATTERN
1780         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
1781         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1782    
1783             PCRE_INFO_MINLENGTH
1784    
1785           If the pattern was studied and a minimum length  for  matching  subject
1786           strings  was  computed,  its  value is returned. Otherwise the returned
1787           value is -1. The value is a number of characters, not bytes  (this  may
1788           be  relevant in UTF-8 mode). The fourth argument should point to an int
1789           variable. A non-negative value is a lower bound to the  length  of  any
1790           matching  string.  There  may not be any strings of that length that do
1791           actually match, but every string that does match is at least that long.
1792    
1793           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
1794           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1795           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
# Line 1559  INFORMATION ABOUT A PATTERN Line 1811  INFORMATION ABOUT A PATTERN
1811         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
1812         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-
1813         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-
1814         sponding  name,  zero  terminated. The names are in alphabetical order.         sponding name, zero terminated.
1815         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-  
1816         theses  numbers.  For  example,  consider the following pattern (assume         The  names are in alphabetical order. Duplicate names may appear if (?|
1817         PCRE_EXTENDED is  set,  so  white  space  -  including  newlines  -  is         is used to create multiple groups with the same number, as described in
1818         ignored):         the  section  on  duplicate subpattern numbers in the pcrepattern page.
1819           Duplicate names for subpatterns with different  numbers  are  permitted
1820           only  if  PCRE_DUPNAMES  is  set. In all cases of duplicate names, they
1821           appear in the table in the order in which they were found in  the  pat-
1822           tern.  In  the  absence  of (?| this is the order of increasing number;
1823           when (?| is used this is not necessarily the case because later subpat-
1824           terns may have lower numbers.
1825    
1826           As  a  simple  example of the name/number table, consider the following
1827           pattern (assume PCRE_EXTENDED is set, so white space -  including  new-
1828           lines - is ignored):
1829    
1830           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1831           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
# Line 1584  INFORMATION ABOUT A PATTERN Line 1846  INFORMATION ABOUT A PATTERN
1846    
1847           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
1848    
1849         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
1850         The  fourth  argument  should point to an int variable. The pcrepartial         pcre_exec(),  otherwise  0.  The fourth argument should point to an int
1851         documentation lists the restrictions that apply to patterns  when  par-         variable. From  release  8.00,  this  always  returns  1,  because  the
1852         tial matching is used.         restrictions  that  previously  applied  to  partial matching have been
1853           lifted. The pcrepartial documentation gives details of  partial  match-
1854           ing.
1855    
1856           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1857    
# Line 1624  INFORMATION ABOUT A PATTERN Line 1888  INFORMATION ABOUT A PATTERN
1888         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
1889         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
1890         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
1891         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
1892           data,  zero  is  returned. The fourth argument should point to a size_t
1893         variable.         variable.
1894    
1895    
# Line 1632  OBSOLETE INFO FUNCTION Line 1897  OBSOLETE INFO FUNCTION
1897    
1898         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1899    
1900         The  pcre_info()  function is now obsolete because its interface is too         The pcre_info() function is now obsolete because its interface  is  too
1901         restrictive to return all the available data about a compiled  pattern.         restrictive  to return all the available data about a compiled pattern.
1902         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of
1903         pcre_info() is the number of capturing subpatterns, or one of the  fol-         pcre_info()  is the number of capturing subpatterns, or one of the fol-
1904         lowing negative numbers:         lowing negative numbers:
1905    
1906           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1907           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1908    
1909         If  the  optptr  argument is not NULL, a copy of the options with which         If the optptr argument is not NULL, a copy of the  options  with  which
1910         the pattern was compiled is placed in the integer  it  points  to  (see         the  pattern  was  compiled  is placed in the integer it points to (see
1911         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1912    
1913         If  the  pattern  is  not anchored and the firstcharptr argument is not         If the pattern is not anchored and the  firstcharptr  argument  is  not
1914         NULL, it is used to pass back information about the first character  of         NULL,  it is used to pass back information about the first character of
1915         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1916    
1917    
# Line 1654  REFERENCE COUNTS Line 1919  REFERENCE COUNTS
1919    
1920         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1921    
1922         The  pcre_refcount()  function is used to maintain a reference count in         The pcre_refcount() function is used to maintain a reference  count  in
1923         the data block that contains a compiled pattern. It is provided for the         the data block that contains a compiled pattern. It is provided for the
1924         benefit  of  applications  that  operate  in an object-oriented manner,         benefit of applications that  operate  in  an  object-oriented  manner,
1925         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1926         pattern, but you want to free the block when they are all done.         pattern, but you want to free the block when they are all done.
1927    
1928         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1929         zero.  It is changed only by calling this function, whose action is  to         zero.   It is changed only by calling this function, whose action is to
1930         add  the  adjust  value  (which may be positive or negative) to it. The         add the adjust value (which may be positive or  negative)  to  it.  The
1931         yield of the function is the new value. However, the value of the count         yield of the function is the new value. However, the value of the count
1932         is  constrained to lie between 0 and 65535, inclusive. If the new value         is constrained to lie between 0 and 65535, inclusive. If the new  value
1933         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1934    
1935         Except when it is zero, the reference count is not correctly  preserved         Except  when it is zero, the reference count is not correctly preserved
1936         if  a  pattern  is  compiled on one host and then transferred to a host         if a pattern is compiled on one host and then  transferred  to  a  host
1937         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1938    
1939    
# Line 1680  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1945  MATCHING A PATTERN: THE TRADITIONAL FUNC
1945    
1946         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
1947         compiled pattern, which is passed in the code argument. If the  pattern         compiled pattern, which is passed in the code argument. If the  pattern
1948         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
1949         argument. This function is the main matching facility of  the  library,         argument. This function is the main matching facility of  the  library,
1950         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
1951         an alternative matching function, which is described below in the  sec-         an alternative matching function, which is described below in the  sec-
# Line 1720  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1985  MATCHING A PATTERN: THE TRADITIONAL FUNC
1985           unsigned long int match_limit_recursion;           unsigned long int match_limit_recursion;
1986           void *callout_data;           void *callout_data;
1987           const unsigned char *tables;           const unsigned char *tables;
1988             unsigned char **mark;
1989    
1990         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
1991         are set. The flag bits are:         are set. The flag bits are:
# Line 1729  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1995  MATCHING A PATTERN: THE TRADITIONAL FUNC
1995           PCRE_EXTRA_MATCH_LIMIT_RECURSION           PCRE_EXTRA_MATCH_LIMIT_RECURSION
1996           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1997           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1998             PCRE_EXTRA_MARK
1999    
2000         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
2001         the  pcre_extra  block  that is returned by pcre_study(), together with         the  pcre_extra  block  that is returned by pcre_study(), together with
# Line 1739  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2006  MATCHING A PATTERN: THE TRADITIONAL FUNC
2006         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
2007         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
2008         match, but which have a very large number  of  possibilities  in  their         match, but which have a very large number  of  possibilities  in  their
2009         search  trees.  The  classic  example  is  the  use of nested unlimited         search  trees. The classic example is a pattern that uses nested unlim-
2010         repeats.         ited repeats.
2011    
2012         Internally, PCRE uses a function called match() which it calls  repeat-         Internally, PCRE uses a function called match() which it calls  repeat-
2013         edly  (sometimes  recursively). The limit set by match_limit is imposed         edly  (sometimes  recursively). The limit set by match_limit is imposed
# Line 1762  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2029  MATCHING A PATTERN: THE TRADITIONAL FUNC
2029         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-
2030         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.
2031    
2032         Limiting  the  recursion  depth  limits the amount of stack that can be         Limiting the recursion depth limits the amount of  stack  that  can  be
2033         used, or, when PCRE has been compiled to use memory on the heap instead         used, or, when PCRE has been compiled to use memory on the heap instead
2034         of the stack, the amount of heap memory that can be used.         of the stack, the amount of heap memory that can be used.
2035    
2036         The  default  value  for  match_limit_recursion can be set when PCRE is         The default value for match_limit_recursion can be  set  when  PCRE  is
2037         built; the default default  is  the  same  value  as  the  default  for         built;  the  default  default  is  the  same  value  as the default for
2038         match_limit.  You can override the default by suppling pcre_exec() with         match_limit. You can override the default by suppling pcre_exec()  with
2039         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and         a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
2040         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
2041         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
2042    
2043         The pcre_callout field is used in conjunction with the  "callout"  fea-         The  callout_data  field is used in conjunction with the "callout" fea-
2044         ture, which is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
2045    
2046         The  tables  field  is  used  to  pass  a  character  tables pointer to         The tables field  is  used  to  pass  a  character  tables  pointer  to
2047         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec();  this overrides the value that is stored with the compiled
2048         pattern.  A  non-NULL value is stored with the compiled pattern only if         pattern. A non-NULL value is stored with the compiled pattern  only  if
2049         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
2050         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces         ment.  If NULL is passed to pcre_exec() using this mechanism, it forces
2051         PCRE's internal tables to be used. This facility is  helpful  when  re-         PCRE's  internal  tables  to be used. This facility is helpful when re-
2052         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
2053         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
2054         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
2055         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
2056    
2057           If  PCRE_EXTRA_MARK  is  set in the flags field, the mark field must be
2058           set to point to a char * variable. If the pattern  contains  any  back-
2059           tracking  control verbs such as (*MARK:NAME), and the execution ends up
2060           with a name to pass back, a pointer to the  name  string  (zero  termi-
2061           nated)  is  placed  in  the  variable pointed to by the mark field. The
2062           names are within the compiled pattern; if you wish  to  retain  such  a
2063           name  you must copy it before freeing the memory of a compiled pattern.
2064           If there is no name to pass back, the variable pointed to by  the  mark
2065           field  set  to NULL. For details of the backtracking control verbs, see
2066           the section entitled "Backtracking control" in the pcrepattern documen-
2067           tation.
2068    
2069     Option bits for pcre_exec()     Option bits for pcre_exec()
2070    
2071         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.
2072         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,
2073         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
2074         PCRE_PARTIAL.         PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
2075           PCRE_PARTIAL_HARD.
2076    
2077           PCRE_ANCHORED           PCRE_ANCHORED
2078    
# Line 1801  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2081  MATCHING A PATTERN: THE TRADITIONAL FUNC
2081         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
2082         unachored at matching time.         unachored at matching time.
2083    
2084             PCRE_BSR_ANYCRLF
2085             PCRE_BSR_UNICODE
2086    
2087           These options (which are mutually exclusive) control what the \R escape
2088           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
2089           or to match any Unicode newline sequence. These  options  override  the
2090           choice that was made or defaulted when the pattern was compiled.
2091    
2092           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
2093           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
2094           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
2095           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
2096           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
2097    
2098         These options override  the  newline  definition  that  was  chosen  or         These  options  override  the  newline  definition  that  was chosen or
2099         defaulted  when the pattern was compiled. For details, see the descrip-         defaulted when the pattern was compiled. For details, see the  descrip-
2100         tion of pcre_compile()  above.  During  matching,  the  newline  choice         tion  of  pcre_compile()  above.  During  matching,  the newline choice
2101         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
2102         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
2103         match  failure  for  an  unanchored  pattern.  When  PCRE_NEWLINE_CRLF,         match failure for an unanchored pattern.
2104         PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a  match  attempt  
2105         fails  when the current position is at a CRLF sequence, the match posi-         When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
2106         tion is advanced by two characters instead of one, in other  words,  to         set,  and a match attempt for an unanchored pattern fails when the cur-
2107         after the CRLF.         rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
2108           explicit  matches  for  CR  or  LF  characters,  the  match position is
2109           advanced by two characters instead of one, in other words, to after the
2110           CRLF.
2111    
2112           The above rule is a compromise that makes the most common cases work as
2113           expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
2114           option is not set), it does not match the string "\r\nA" because, after
2115           failing at the start, it skips both the CR and the LF before  retrying.
2116           However,  the  pattern  [\r\n]A does match that string, because it con-
2117           tains an explicit CR or LF reference, and so advances only by one char-
2118           acter after the first failure.
2119    
2120           An explicit match for CR of LF is either a literal appearance of one of
2121           those characters, or one of the \r or  \n  escape  sequences.  Implicit
2122           matches  such  as [^X] do not count, nor does \s (which includes CR and
2123           LF in the characters that it matches).
2124    
2125           Notwithstanding the above, anomalous effects may still occur when  CRLF
2126           is a valid newline sequence and explicit \r or \n escapes appear in the
2127           pattern.
2128    
2129           PCRE_NOTBOL           PCRE_NOTBOL
2130    
2131         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
2132         the beginning of a line, so the  circumflex  metacharacter  should  not         the  beginning  of  a  line, so the circumflex metacharacter should not
2133         match  before it. Setting this without PCRE_MULTILINE (at compile time)         match before it. Setting this without PCRE_MULTILINE (at compile  time)
2134         causes circumflex never to match. This option affects only  the  behav-         causes  circumflex  never to match. This option affects only the behav-
2135         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
2136    
2137           PCRE_NOTEOL           PCRE_NOTEOL
2138    
2139         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
2140         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
2141         in  multiline mode) a newline immediately before it. Setting this with-         in multiline mode) a newline immediately before it. Setting this  with-
2142         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2143         option  affects only the behaviour of the dollar metacharacter. It does         option affects only the behaviour of the dollar metacharacter. It  does
2144         not affect \Z or \z.         not affect \Z or \z.
2145    
2146           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2147    
2148         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
2149         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
2150         the alternatives match the empty string, the entire  match  fails.  For         the  alternatives  match  the empty string, the entire match fails. For
2151         example, if the pattern         example, if the pattern
2152    
2153           a?b?           a?b?
2154    
2155         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
2156         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
2157         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-
2158         rences of "a" or "b".         rences of "a" or "b".
2159    
2160         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2161         cial  case  of  a  pattern match of the empty string within its split()  
2162         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
2163         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
2164         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.
2165         if  that  fails by advancing the starting offset (see below) and trying  
2166         an ordinary match again. There is some code that demonstrates how to do         Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or
2167         this in the pcredemo.c sample program.         PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern
2168           match  of  the empty string within its split() function, and when using
2169           the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after
2170           matching a null string by first trying the match again at the same off-
2171           set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that
2172           fails, by advancing the starting offset (see below) and trying an ordi-
2173           nary match again. There is some code that demonstrates how to  do  this
2174           in  the  pcredemo sample program. In the most general case, you have to
2175           check to see if the newline convention recognizes CRLF  as  a  newline,
2176           and  if so, and the current character is CR followed by LF, advance the
2177           starting offset by two characters instead of one.
2178    
2179             PCRE_NO_START_OPTIMIZE
2180    
2181           There are a number of optimizations that pcre_exec() uses at the  start
2182           of  a  match,  in  order to speed up the process. For example, if it is
2183           known that an unanchored match must start with a specific character, it
2184           searches  the  subject  for that character, and fails immediately if it
2185           cannot find it, without actually running the  main  matching  function.
2186           This means that a special item such as (*COMMIT) at the start of a pat-
2187           tern is not considered until after a suitable starting  point  for  the
2188           match  has been found. When callouts or (*MARK) items are in use, these
2189           "start-up" optimizations can cause them to be skipped if the pattern is
2190           never  actually  used.  The start-up optimizations are in effect a pre-
2191           scan of the subject that takes place before the pattern is run.
2192    
2193           The PCRE_NO_START_OPTIMIZE option disables the start-up  optimizations,
2194           possibly  causing  performance  to  suffer,  but ensuring that in cases
2195           where the result is "no match", the callouts do occur, and  that  items
2196           such as (*COMMIT) and (*MARK) are considered at every possible starting
2197           position in the subject string. If  PCRE_NO_START_OPTIMIZE  is  set  at
2198           compile time, it cannot be unset at matching time.
2199    
2200           Setting  PCRE_NO_START_OPTIMIZE  can  change  the outcome of a matching
2201           operation.  Consider the pattern
2202    
2203             (*COMMIT)ABC
2204    
2205           When this is compiled, PCRE records the fact that a  match  must  start
2206           with  the  character  "A".  Suppose the subject string is "DEFABC". The
2207           start-up optimization scans along the subject, finds "A" and  runs  the
2208           first  match attempt from there. The (*COMMIT) item means that the pat-
2209           tern must match the current starting position, which in this  case,  it
2210           does.  However,  if  the  same match is run with PCRE_NO_START_OPTIMIZE
2211           set, the initial scan along the subject string  does  not  happen.  The
2212           first  match  attempt  is  run  starting  from "D" and when this fails,
2213           (*COMMIT) prevents any further matches  being  tried,  so  the  overall
2214           result  is  "no  match". If the pattern is studied, more start-up opti-
2215           mizations may be used. For example, a minimum length  for  the  subject
2216           may be recorded. Consider the pattern
2217    
2218             (*MARK:A)(X|Y)
2219    
2220           The  minimum  length  for  a  match is one character. If the subject is
2221           "ABC", there will be attempts to  match  "ABC",  "BC",  "C",  and  then
2222           finally  an empty string.  If the pattern is studied, the final attempt
2223           does not take place, because PCRE knows that the subject is too  short,
2224           and  so  the  (*MARK) is never encountered.  In this case, studying the
2225           pattern does not affect the overall match result, which  is  still  "no
2226           match", but it does affect the auxiliary information that is returned.
2227    
2228           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2229    
# Line 1866  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2233  MATCHING A PATTERN: THE TRADITIONAL FUNC
2233         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
2234         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
2235         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,
2236         pcre_exec()  returns  the error PCRE_ERROR_BADUTF8. If startoffset con-         pcre_exec()  returns  the  error  PCRE_ERROR_BADUTF8  or,  if PCRE_PAR-
2237         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
2238           end  of  the  subject, PCRE_ERROR_SHORTUTF8. In both cases, information
2239           about the precise nature of the error may also  be  returned  (see  the
2240           descriptions  of these errors in the section entitled Error return val-
2241           ues from pcre_exec() below).  If startoffset contains a value that does
2242           not  point to the start of a UTF-8 character (or to the end of the sub-
2243           ject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2244    
2245         If you already know that your subject is valid, and you  want  to  skip         If you already know that your subject is valid, and you  want  to  skip
2246         these    checks    for   performance   reasons,   you   can   set   the         these    checks    for   performance   reasons,   you   can   set   the
# Line 1875  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2248  MATCHING A PATTERN: THE TRADITIONAL FUNC
2248         do  this  for the second and subsequent calls to pcre_exec() if you are         do  this  for the second and subsequent calls to pcre_exec() if you are
2249         making repeated calls to find all  the  matches  in  a  single  subject         making repeated calls to find all  the  matches  in  a  single  subject
2250         string.  However,  you  should  be  sure  that the value of startoffset         string.  However,  you  should  be  sure  that the value of startoffset
2251         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is         points to the start of a UTF-8 character (or the end of  the  subject).
2252         set,  the  effect of passing an invalid UTF-8 string as a subject, or a         When  PCRE_NO_UTF8_CHECK is set, the effect of passing an invalid UTF-8
2253         value of startoffset that does not point to the start of a UTF-8  char-         string as a subject or an invalid value of  startoffset  is  undefined.
2254         acter, is undefined. Your program may crash.         Your program may crash.
2255    
2256           PCRE_PARTIAL           PCRE_PARTIAL_HARD
2257             PCRE_PARTIAL_SOFT
2258         This  option  turns  on  the  partial  matching feature. If the subject  
2259         string fails to match the pattern, but at some point during the  match-         These  options turn on the partial matching feature. For backwards com-
2260         ing  process  the  end of the subject was reached (that is, the subject         patibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A  partial
2261         partially matches the pattern and the failure to  match  occurred  only         match  occurs if the end of the subject string is reached successfully,
2262         because  there were not enough subject characters), pcre_exec() returns         but there are not enough subject characters to complete the  match.  If
2263         PCRE_ERROR_PARTIAL instead of PCRE_ERROR_NOMATCH. When PCRE_PARTIAL  is         this happens when PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set,
2264         used,  there  are restrictions on what may appear in the pattern. These         matching continues by testing any remaining alternatives.  Only  if  no
2265         are discussed in the pcrepartial documentation.         complete  match  can be found is PCRE_ERROR_PARTIAL returned instead of
2266           PCRE_ERROR_NOMATCH. In other words,  PCRE_PARTIAL_SOFT  says  that  the
2267           caller  is  prepared to handle a partial match, but only if no complete
2268           match can be found.
2269    
2270           If PCRE_PARTIAL_HARD is set, it overrides  PCRE_PARTIAL_SOFT.  In  this
2271           case,  if  a  partial  match  is found, pcre_exec() immediately returns
2272           PCRE_ERROR_PARTIAL, without  considering  any  other  alternatives.  In
2273           other  words, when PCRE_PARTIAL_HARD is set, a partial match is consid-
2274           ered to be more important that an alternative complete match.
2275    
2276           In both cases, the portion of the string that was  inspected  when  the
2277           partial match was found is set as the first matching string. There is a
2278           more detailed discussion of partial and  multi-segment  matching,  with
2279           examples, in the pcrepartial documentation.
2280    
2281     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2282    
2283         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
2284         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.
2285         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,
2286         Unlike  the  pattern string, the subject may contain binary zero bytes.         pcre_exec() returns PCRE_ERROR_BADOFFSET. When the starting  offset  is
2287         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,
2288         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
2289           must  point  to  the start of a UTF-8 character (or the end of the sub-
2290           ject). Unlike the pattern string, the subject may contain  binary  zero
2291           bytes.
2292    
2293         A  non-zero  starting offset is useful when searching for another match         A  non-zero  starting offset is useful when searching for another match
2294         in the same subject by calling pcre_exec() again after a previous  suc-         in the same subject by calling pcre_exec() again after a previous  suc-
# Line 1919  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2309  MATCHING A PATTERN: THE TRADITIONAL FUNC
2309         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
2310         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2311    
2312         If a non-zero starting offset is passed when the pattern  is  anchored,         Finding all the matches in a subject is tricky  when  the  pattern  can
2313           match an empty string. It is possible to emulate Perl's /g behaviour by
2314           first  trying  the  match  again  at  the   same   offset,   with   the
2315           PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED  options,  and  then  if that
2316           fails, advancing the starting  offset  and  trying  an  ordinary  match
2317           again. There is some code that demonstrates how to do this in the pcre-
2318           demo sample program. In the most general case, you have to check to see
2319           if  the newline convention recognizes CRLF as a newline, and if so, and
2320           the current character is CR followed by LF, advance the starting offset
2321           by two characters instead of one.
2322    
2323           If  a  non-zero starting offset is passed when the pattern is anchored,
2324         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
2325         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
2326         subject.         subject.
2327    
2328     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2329    
2330         In  general, a pattern matches a certain portion of the subject, and in         In general, a pattern matches a certain portion of the subject, and  in
2331         addition, further substrings from the subject  may  be  picked  out  by         addition,  further  substrings  from  the  subject may be picked out by
2332         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2333         this is called "capturing" in what follows, and the  phrase  "capturing         this  is  called "capturing" in what follows, and the phrase "capturing
2334         subpattern"  is  used for a fragment of a pattern that picks out a sub-         subpattern" is used for a fragment of a pattern that picks out  a  sub-
2335         string. PCRE supports several other kinds of  parenthesized  subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2336         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2337    
2338         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2339         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-
2340         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:
2341         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2342    
2343         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-
2344         strings,  each  substring using a pair of integers. The remaining third         strings, each substring using a pair of integers. The  remaining  third
2345         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-
2346         turing  subpatterns, and is not available for passing back information.         turing subpatterns, and is not available for passing back  information.
2347         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
2348         it is not, it is rounded down.         it is not, it is rounded down.
2349    
2350         When  a  match  is successful, information about captured substrings is         When a match is successful, information about  captured  substrings  is
2351         returned in pairs of integers, starting at the  beginning  of  ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2352         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
2353         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
2354         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
2355         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
2356         tor[1],  identify  the  portion  of  the  subject string matched by the         byte offsets, even in UTF-8 mode. They are not character counts.
2357         entire pattern. The next pair is used for the first  capturing  subpat-  
2358         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
2359         highest numbered pair that has been set. For example, if two substrings         portion  of  the subject string matched by the entire pattern. The next
2360         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
2361         subpatterns, the return value from a successful match is 1,  indicating         returned by pcre_exec() is one more than the highest numbered pair that
2362         that just the first pair of offsets has been set.         has been set.  For example, if two substrings have been  captured,  the
2363           returned  value is 3. If there are no capturing subpatterns, the return
2364           value from a successful match is 1, indicating that just the first pair
2365           of offsets has been set.
2366    
2367         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2368         of the string that it matched that is returned.         of the string that it matched that is returned.
2369    
2370         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,
2371         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
2372         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
2373         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
2374         as NULL and ovecsize as zero. However, if  the  pattern  contains  back         ovecsize as zero. However, if the pattern contains back references  and
2375         references  and  the  ovector is not big enough to remember the related         the  ovector is not big enough to remember the related substrings, PCRE
2376         substrings, PCRE has to get additional memory for use during  matching.         has to get additional memory for use during matching. Thus it  is  usu-
2377         Thus it is usually advisable to supply an ovector.         ally advisable to supply an ovector.
2378    
2379         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
2380         subpatterns there are in a compiled  pattern.  The  smallest  size  for         subpatterns there are in a compiled  pattern.  The  smallest  size  for
2381         ovector  that  will allow for n captured substrings, in addition to the         ovector  that  will allow for n captured substrings, in addition to the
2382         offsets of the substring matched by the whole pattern, is (n+1)*3.         offsets of the substring matched by the whole pattern, is (n+1)*3.
# Line 1988  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2392  MATCHING A PATTERN: THE TRADITIONAL FUNC
2392         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
2393         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
2394         matched. The return from the function is 2, because  the  highest  used         matched. The return from the function is 2, because  the  highest  used
2395         capturing subpattern number is 1. However, you can refer to the offsets         capturing  subpattern  number  is 1, and the offsets for for the second
2396         for the second and third capturing subpatterns if  you  wish  (assuming         and third capturing subpatterns (assuming the vector is  large  enough,
2397         the vector is large enough, of course).         of course) are set to -1.
2398    
2399           Note: Elements of ovector that do not correspond to capturing parenthe-
2400           ses in the pattern are never changed. That is, if a pattern contains  n
2401           capturing parentheses, no more than ovector[0] to ovector[2n+1] are set
2402           by pcre_exec(). The other elements retain whatever values  they  previ-
2403           ously had.
2404    
2405         Some  convenience  functions  are  provided for extracting the captured         Some  convenience  functions  are  provided for extracting the captured
2406         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
# Line 2035  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2445  MATCHING A PATTERN: THE TRADITIONAL FUNC
2445         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
2446         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2447    
2448           This error is also given if pcre_stack_malloc() fails  in  pcre_exec().
2449           This  can happen only when PCRE has been compiled with --disable-stack-
2450           for-recursion.
2451    
2452           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2453    
2454         This error is used by the pcre_copy_substring(),  pcre_get_substring(),         This error is used by the pcre_copy_substring(),  pcre_get_substring(),
# Line 2056  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2470  MATCHING A PATTERN: THE TRADITIONAL FUNC
2470           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2471    
2472         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
2473         subject.         subject,  and the PCRE_NO_UTF8_CHECK option was not set. If the size of
2474           the output vector (ovecsize) is at least 2,  the  byte  offset  to  the
2475           start  of  the  the invalid UTF-8 character is placed in the first ele-
2476           ment, and a reason code is placed in the  second  element.  The  reason
2477           codes are listed in the following section.  For backward compatibility,
2478           if PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8  char-
2479           acter   at   the   end   of   the   subject  (reason  codes  1  to  5),
2480           PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2481    
2482           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2483    
2484         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  checked  and
2485           found  to be valid (the PCRE_NO_UTF8_CHECK option was not set), but the
2486         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-
2487         ter.         ter or the end of the subject.
2488    
2489           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2490    
# Line 2071  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2493  MATCHING A PATTERN: THE TRADITIONAL FUNC
2493    
2494           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2495    
2496         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing         This code is no longer in  use.  It  was  formerly  returned  when  the
2497         items  that are not supported for partial matching. See the pcrepartial         PCRE_PARTIAL  option  was used with a compiled pattern containing items
2498         documentation for details of partial matching.         that were  not  supported  for  partial  matching.  From  release  8.00
2499           onwards, there are no restrictions on partial matching.
2500    
2501           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2502    
2503         An unexpected internal error has occurred. This error could  be  caused         An  unexpected  internal error has occurred. This error could be caused
2504         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2505    
2506           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2507    
2508         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.
2509    
2510           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2511    
# Line 2094  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2517  MATCHING A PATTERN: THE TRADITIONAL FUNC
2517    
2518         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2519    
2520             PCRE_ERROR_BADOFFSET      (-24)
2521    
2522           The value of startoffset was negative or greater than the length of the
2523           subject, that is, the value in length.
2524    
2525             PCRE_ERROR_SHORTUTF8      (-25)
2526    
2527           This  error  is returned instead of PCRE_ERROR_BADUTF8 when the subject
2528           string ends with a truncated UTF-8 character and the  PCRE_PARTIAL_HARD
2529           option  is  set.   Information  about  the  failure  is returned as for
2530           PCRE_ERROR_BADUTF8. It is in fact sufficient to detect this  case,  but
2531           this  special error code for PCRE_PARTIAL_HARD precedes the implementa-
2532           tion of returned information; it is retained for backwards  compatibil-
2533           ity.
2534    
2535             PCRE_ERROR_RECURSELOOP    (-26)
2536    
2537           This error is returned when pcre_exec() detects a recursion loop within
2538           the pattern. Specifically, it means that either the whole pattern or  a
2539           subpattern  has been called recursively for the second time at the same
2540           position in the subject string. Some simple patterns that might do this
2541           are  detected  and faulted at compile time, but more complicated cases,
2542           in particular mutual recursions between two different subpatterns, can-
2543           not be detected until run time.
2544    
2545         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().
2546    
2547       Reason codes for invalid UTF-8 strings
2548    
2549           When pcre_exec() returns either PCRE_ERROR_BADUTF8 or PCRE_ERROR_SHORT-
2550           UTF8, and the size of the output vector (ovecsize) is at least  2,  the
2551           offset  of  the  start  of the invalid UTF-8 character is placed in the
2552           first output vector element (ovector[0]) and a reason code is placed in
2553           the  second  element  (ovector[1]). The reason codes are given names in
2554           the pcre.h header file:
2555    
2556             PCRE_UTF8_ERR1
2557             PCRE_UTF8_ERR2
2558             PCRE_UTF8_ERR3
2559             PCRE_UTF8_ERR4
2560             PCRE_UTF8_ERR5
2561    
2562           The string ends with a truncated UTF-8 character;  the  code  specifies
2563           how  many bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8
2564           characters to be no longer than 4 bytes, the  encoding  scheme  (origi-
2565           nally  defined  by  RFC  2279)  allows  for  up to 6 bytes, and this is
2566           checked first; hence the possibility of 4 or 5 missing bytes.
2567    
2568             PCRE_UTF8_ERR6
2569             PCRE_UTF8_ERR7
2570             PCRE_UTF8_ERR8
2571             PCRE_UTF8_ERR9
2572             PCRE_UTF8_ERR10
2573    
2574           The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of
2575           the  character  do  not have the binary value 0b10 (that is, either the
2576           most significant bit is 0, or the next bit is 1).
2577    
2578             PCRE_UTF8_ERR11
2579             PCRE_UTF8_ERR12
2580    
2581           A character that is valid by the RFC 2279 rules is either 5 or 6  bytes
2582           long; these code points are excluded by RFC 3629.
2583    
2584             PCRE_UTF8_ERR13
2585    
2586           A  4-byte character has a value greater than 0x10fff; these code points
2587           are excluded by RFC 3629.
2588    
2589             PCRE_UTF8_ERR14
2590    
2591           A 3-byte character has a value in the  range  0xd800  to  0xdfff;  this
2592           range  of code points are reserved by RFC 3629 for use with UTF-16, and
2593           so are excluded from UTF-8.
2594    
2595             PCRE_UTF8_ERR15
2596             PCRE_UTF8_ERR16
2597             PCRE_UTF8_ERR17
2598             PCRE_UTF8_ERR18
2599             PCRE_UTF8_ERR19
2600    
2601           A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it  codes
2602           for  a  value that can be represented by fewer bytes, which is invalid.
2603           For example, the two bytes 0xc0, 0xae give the value 0x2e,  whose  cor-
2604           rect coding uses just one byte.
2605    
2606             PCRE_UTF8_ERR20
2607    
2608           The two most significant bits of the first byte of a character have the
2609           binary value 0b10 (that is, the most significant bit is 1 and the  sec-
2610           ond  is  0). Such a byte can only validly occur as the second or subse-
2611           quent byte of a multi-byte character.
2612    
2613             PCRE_UTF8_ERR21
2614    
2615           The first byte of a character has the value 0xfe or 0xff. These  values
2616           can never occur in a valid UTF-8 string.
2617    
2618    
2619  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2620    
# Line 2110  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2629  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2629         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2630              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2631    
2632         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
2633         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
2634         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2635         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
2636         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
2637         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
2638         substrings.         substrings.
2639    
2640         A substring that contains a binary zero is correctly extracted and  has         A  substring that contains a binary zero is correctly extracted and has
2641         a  further zero added on the end, but the result is not, of course, a C         a further zero added on the end, but the result is not, of course, a  C
2642         string.  However, you can process such a string  by  referring  to  the         string.   However,  you  can  process such a string by referring to the
2643         length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2644         string().  Unfortunately, the interface to pcre_get_substring_list() is         string().  Unfortunately, the interface to pcre_get_substring_list() is
2645         not  adequate for handling strings containing binary zeros, because the         not adequate for handling strings containing binary zeros, because  the
2646         end of the final string is not independently indicated.         end of the final string is not independently indicated.
2647    
2648         The first three arguments are the same for all  three  of  these  func-         The  first  three  arguments  are the same for all three of these func-
2649         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
2650         matched, ovector is a pointer to the vector of integer offsets that was         matched, ovector is a pointer to the vector of integer offsets that was
2651         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2652         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
2653         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2654         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
2655         it  ran out of space in ovector, the value passed as stringcount should         it ran out of space in ovector, the value passed as stringcount  should
2656         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2657    
2658         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
2659         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
2660         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
2661         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
2662         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
2663         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2664         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2665         The  yield  of  the function is the length of the string, not including         The yield of the function is the length of the  string,  not  including
2666         the terminating zero, or one of these error codes:         the terminating zero, or one of these error codes:
2667    
2668           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2669    
2670         The buffer was too small for pcre_copy_substring(), or the  attempt  to         The  buffer  was too small for pcre_copy_substring(), or the attempt to
2671         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2672    
2673           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2674    
2675         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2676    
2677         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
2678         strings and builds a list of pointers to them. All this is  done  in  a         strings  and  builds  a list of pointers to them. All this is done in a
2679         single block of memory that is obtained via pcre_malloc. The address of         single block of memory that is obtained via pcre_malloc. The address of
2680         the memory block is returned via listptr, which is also  the  start  of         the  memory  block  is returned via listptr, which is also the start of
2681         the  list  of  string pointers. The end of the list is marked by a NULL         the list of string pointers. The end of the list is marked  by  a  NULL
2682         pointer. The yield of the function is zero if all  went  well,  or  the         pointer.  The  yield  of  the function is zero if all went well, or the
2683         error code         error code
2684    
2685           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2686    
2687         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2688    
2689         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
2690         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
2691         the  subject, but subpattern n has not been used at all, they return an         the subject, but subpattern n has not been used at all, they return  an
2692         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2693         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
2694         tive for unset substrings.         tive for unset substrings.
2695    
2696         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2697         string_list()  can  be  used  to free the memory returned by a previous         string_list() can be used to free the memory  returned  by  a  previous
2698         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2699         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
2700         pcre_free, which of course could be called directly from a  C  program.         pcre_free,  which  of course could be called directly from a C program.
2701         However,  PCRE is used in some situations where it is linked via a spe-         However, PCRE is used in some situations where it is linked via a  spe-
2702         cial  interface  to  another  programming  language  that  cannot   use         cial   interface  to  another  programming  language  that  cannot  use
2703         pcre_free  directly;  it is for these cases that the functions are pro-         pcre_free directly; it is for these cases that the functions  are  pro-
2704         vided.         vided.
2705    
2706    
# Line 2200  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2719  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2719              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2720              const char **stringptr);              const char **stringptr);
2721    
2722         To extract a substring by name, you first have to find associated  num-         To  extract a substring by name, you first have to find associated num-
2723         ber.  For example, for this pattern         ber.  For example, for this pattern
2724    
2725           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
# Line 2209  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2728  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2728         be unique (PCRE_DUPNAMES was not set), you can find the number from the         be unique (PCRE_DUPNAMES was not set), you can find the number from the
2729         name by calling pcre_get_stringnumber(). The first argument is the com-         name by calling pcre_get_stringnumber(). The first argument is the com-
2730         piled pattern, and the second is the name. The yield of the function is         piled pattern, and the second is the name. The yield of the function is
2731         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2732         subpattern of that name.         subpattern of that name.
2733    
2734         Given the number, you can extract the substring directly, or use one of         Given the number, you can extract the substring directly, or use one of
2735         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
2736         are also two functions that do the whole job.         are also two functions that do the whole job.
2737    
2738         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
2739         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
2740         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
2741         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
2742         differences:         differences:
2743    
2744         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
2745         ond, there is an extra argument, given at the start, which is a pointer         ond, there is an extra argument, given at the start, which is a pointer
2746         to the compiled pattern. This is needed in order to gain access to  the         to  the compiled pattern. This is needed in order to gain access to the
2747         name-to-number translation table.         name-to-number translation table.
2748    
2749         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2750         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2751         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
2752         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2753    
2754           Warning: If the pattern uses the (?| feature to set up multiple subpat-
2755           terns with the same number, as described in the  section  on  duplicate
2756           subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2757           distinguish the different subpatterns, because names are  not  included
2758           in  the compiled code. The matching process uses only numbers. For this
2759           reason, the use of different names for subpatterns of the  same  number
2760           causes an error at compile time.
2761    
2762    
2763  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
2764    
2765         int pcre_get_stringtable_entries(const pcre *code,         int pcre_get_stringtable_entries(const pcre *code,
2766              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2767    
2768         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2769         subpatterns  are  not  required  to  be unique. Normally, patterns with         subpatterns are not required to be unique. (Duplicate names are  always
2770         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 (?|
2771         subpatterns  participates. An example is shown in the pcrepattern docu-         feature. Indeed, if such subpatterns are named, they  are  required  to
2772         mentation.         use the same names.)
2773    
2774           Normally, patterns with duplicate names are such that in any one match,
2775           only one of the named subpatterns participates. An example is shown  in
2776           the pcrepattern documentation.
2777    
2778         When   duplicates   are   present,   pcre_copy_named_substring()    and         When    duplicates   are   present,   pcre_copy_named_substring()   and
2779         pcre_get_named_substring()  return the first substring corresponding to         pcre_get_named_substring() return the first substring corresponding  to
2780         the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING         the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2781         (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()         (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2782         function returns one of the numbers that are associated with the  name,         function  returns one of the numbers that are associated with the name,
2783         but it is not defined which it is.         but it is not defined which it is.
2784    
2785         If  you want to get full details of all captured substrings for a given         If you want to get full details of all captured substrings for a  given
2786         name, you must use  the  pcre_get_stringtable_entries()  function.  The         name,  you  must  use  the pcre_get_stringtable_entries() function. The
2787         first argument is the compiled pattern, and the second is the name. The         first argument is the compiled pattern, and the second is the name. The
2788         third and fourth are pointers to variables which  are  updated  by  the         third  and  fourth  are  pointers to variables which are updated by the
2789         function. After it has run, they point to the first and last entries in         function. After it has run, they point to the first and last entries in
2790         the name-to-number table  for  the  given  name.  The  function  itself         the  name-to-number  table  for  the  given  name.  The function itself
2791         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2792         there are none. The format of the table is described above in the  sec-         there  are none. The format of the table is described above in the sec-
2793         tion  entitled  Information  about  a  pattern.  Given all the relevant         tion entitled Information about a pattern above.  Given all  the  rele-
2794         entries for the name, you can extract each of their numbers, and  hence         vant  entries  for the name, you can extract each of their numbers, and
2795         the captured data, if any.         hence the captured data, if any.
2796    
2797    
2798  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
2799    
2800         The  traditional  matching  function  uses a similar algorithm to Perl,         The traditional matching function uses a  similar  algorithm  to  Perl,
2801         which stops when it finds the first match, starting at a given point in         which stops when it finds the first match, starting at a given point in
2802         the  subject.  If you want to find all possible matches, or the longest         the subject. If you want to find all possible matches, or  the  longest
2803         possible match, consider using the alternative matching  function  (see         possible  match,  consider using the alternative matching function (see
2804         below)  instead.  If you cannot use the alternative function, but still         below) instead. If you cannot use the alternative function,  but  still
2805         need to find all possible matches, you can kludge it up by  making  use         need  to  find all possible matches, you can kludge it up by making use
2806         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
2807         tation.         tation.
2808    
2809         What you have to do is to insert a callout right at the end of the pat-         What you have to do is to insert a callout right at the end of the pat-
2810         tern.   When your callout function is called, extract and save the cur-         tern.  When your callout function is called, extract and save the  cur-
2811         rent matched substring. Then return  1,  which  forces  pcre_exec()  to         rent  matched  substring.  Then  return  1, which forces pcre_exec() to
2812         backtrack  and  try other alternatives. Ultimately, when it runs out of         backtrack and try other alternatives. Ultimately, when it runs  out  of
2813         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2814    
2815    
# Line 2289  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2820  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2820              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
2821              int *workspace, int wscount);              int *workspace, int wscount);
2822    
2823         The function pcre_dfa_exec()  is  called  to  match  a  subject  string         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2824         against  a  compiled pattern, using a matching algorithm that scans the         against a compiled pattern, using a matching algorithm that  scans  the
2825         subject string just once, and does not backtrack.  This  has  different         subject  string  just  once, and does not backtrack. This has different
2826         characteristics  to  the  normal  algorithm, and is not compatible with         characteristics to the normal algorithm, and  is  not  compatible  with
2827         Perl. Some of the features of PCRE patterns are not  supported.  Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2828         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
2829         a discussion of the two matching algorithms, see the pcrematching docu-         a  discussion  of  the  two matching algorithms, and a list of features
2830         mentation.         that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2831           tion.
2832    
2833         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
2834         pcre_exec(), plus two extras. The ovector argument is used in a differ-         pcre_exec(), plus two extras. The ovector argument is used in a differ-
# Line 2331  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2863  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2863    
2864         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
2865         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-
2866         LINE_xxx,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2867         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last         PCRE_NOTEMPTY_ATSTART,      PCRE_NO_UTF8_CHECK,       PCRE_BSR_ANYCRLF,
2868         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-
2869         not repeated here.         TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.  All but  the  last
2870           four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
2871           PCRE_PARTIAL         description is not repeated here.
2872    
2873         This has the same general effect as it does for  pcre_exec(),  but  the           PCRE_PARTIAL_HARD
2874         details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for           PCRE_PARTIAL_SOFT
2875         pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into  
2876         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
2877         been no complete matches, but there is still at least one matching pos-         details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
2878         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-
2879         set as the first matching string.         ject  is  reached  and there is still at least one matching possibility
2880           that requires additional characters. This happens even if some complete
2881           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2882           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2883           of  the  subject  is  reached, there have been no complete matches, but
2884           there is still at least one matching possibility. The  portion  of  the
2885           string  that  was inspected when the longest partial match was found is
2886           set as the first matching string  in  both  cases.   There  is  a  more
2887           detailed  discussion  of partial and multi-segment matching, with exam-
2888           ples, in the pcrepartial documentation.
2889    
2890           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2891    
# Line 2355  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2896  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2896    
2897           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2898    
2899         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
2900         returns a partial match, it is possible to call it  again,  with  addi-         again, with additional subject characters, and have  it  continue  with
2901         tional  subject  characters,  and have it continue with the same match.         the  same match. The PCRE_DFA_RESTART option requests this action; when
2902         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
2903         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
2904         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
2905         match.  There  is  more  discussion of this facility in the pcrepartial         pcrepartial documentation.
        documentation.  
2906    
2907     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2908    
2909         When pcre_dfa_exec() succeeds, it may have matched more than  one  sub-         When  pcre_dfa_exec()  succeeds, it may have matched more than one sub-
2910         string in the subject. Note, however, that all the matches from one run         string in the subject. Note, however, that all the matches from one run
2911         of the function start at the same point in  the  subject.  The  shorter         of  the  function  start  at the same point in the subject. The shorter
2912         matches  are all initial substrings of the longer matches. For example,         matches are all initial substrings of the longer matches. For  example,
2913         if the pattern         if the pattern
2914    
2915           <.*>           <.*>
# Line 2384  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2924  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2924           <something> <something else>           <something> <something else>
2925           <something> <something else> <something further>           <something> <something else> <something further>
2926    
2927         On success, the yield of the function is a number  greater  than  zero,         On  success,  the  yield of the function is a number greater than zero,
2928         which  is  the  number of matched substrings. The substrings themselves         which is the number of matched substrings.  The  substrings  themselves
2929         are returned in ovector. Each string uses two elements;  the  first  is         are  returned  in  ovector. Each string uses two elements; the first is
2930         the  offset  to  the start, and the second is the offset to the end. In         the offset to the start, and the second is the offset to  the  end.  In
2931         fact, all the strings have the same start  offset.  (Space  could  have         fact,  all  the  strings  have the same start offset. (Space could have
2932         been  saved by giving this only once, but it was decided to retain some         been saved by giving this only once, but it was decided to retain  some
2933         compatibility with the way pcre_exec() returns data,  even  though  the         compatibility  with  the  way pcre_exec() returns data, even though the
2934         meaning of the strings is different.)         meaning of the strings is different.)
2935    
2936         The strings are returned in reverse order of length; that is, the long-         The strings are returned in reverse order of length; that is, the long-
2937         est matching string is given first. If there were too many  matches  to         est  matching  string is given first. If there were too many matches to
2938         fit  into ovector, the yield of the function is zero, and the vector is         fit into ovector, the yield of the function is zero, and the vector  is
2939         filled with the longest matches.         filled with the longest matches.
2940    
2941     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2942    
2943         The pcre_dfa_exec() function returns a negative number when  it  fails.         The  pcre_dfa_exec()  function returns a negative number when it fails.
2944         Many  of  the  errors  are  the  same as for pcre_exec(), and these are         Many of the errors are the same  as  for  pcre_exec(),  and  these  are
2945         described above.  There are in addition the following errors  that  are         described  above.   There are in addition the following errors that are
2946         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2947    
2948           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2949    
2950         This  return is given if pcre_dfa_exec() encounters an item in the pat-         This return is given if pcre_dfa_exec() encounters an item in the  pat-
2951         tern that it does not support, for instance, the use of \C  or  a  back         tern  that  it  does not support, for instance, the use of \C or a back
2952         reference.         reference.
2953    
2954           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2955    
2956         This  return  is  given  if pcre_dfa_exec() encounters a condition item         This return is given if pcre_dfa_exec()  encounters  a  condition  item
2957         that uses a back reference for the condition, or a test  for  recursion         that  uses  a back reference for the condition, or a test for recursion
2958         in a specific group. These are not supported.         in a specific group. These are not supported.
2959    
2960           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2961    
2962         This  return  is given if pcre_dfa_exec() is called with an extra block         This return is given if pcre_dfa_exec() is called with an  extra  block
2963         that contains a setting of the match_limit field. This is not supported         that contains a setting of the match_limit field. This is not supported
2964         (it is meaningless).         (it is meaningless).
2965    
2966           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2967    
2968         This  return  is  given  if  pcre_dfa_exec()  runs  out of space in the         This return is given if  pcre_dfa_exec()  runs  out  of  space  in  the
2969         workspace vector.         workspace vector.
2970    
2971           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2972    
2973         When a recursive subpattern is processed, the matching  function  calls         When  a  recursive subpattern is processed, the matching function calls
2974         itself  recursively,  using  private vectors for ovector and workspace.         itself recursively, using private vectors for  ovector  and  workspace.
2975         This error is given if the output vector  is  not  large  enough.  This         This  error  is  given  if  the output vector is not large enough. This
2976         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2977    
2978    
2979  SEE ALSO  SEE ALSO
2980    
2981         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
2982         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3),  pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2983    
2984    
2985  AUTHOR  AUTHOR
# Line 2451  AUTHOR Line 2991  AUTHOR
2991    
2992  REVISION  REVISION
2993    
2994         Last updated: 09 August 2007         Last updated: 28 July 2011
2995         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
2996  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2997    
2998    
# Line 2481  PCRE CALLOUTS Line 3021  PCRE CALLOUTS
3021    
3022           (?C1)abc(?C2)def           (?C1)abc(?C2)def
3023    
3024         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
3025         called, PCRE automatically  inserts  callouts,  all  with  number  255,         pcre_compile2() is called, PCRE  automatically  inserts  callouts,  all
3026         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
3027         used with the pattern         PCRE_AUTO_CALLOUT is used with the pattern
3028    
3029           A(\d{2}|--)           A(\d{2}|--)
3030    
# Line 2503  PCRE CALLOUTS Line 3043  PCRE CALLOUTS
3043  MISSING CALLOUTS  MISSING CALLOUTS
3044    
3045         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
3046         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
3047         pattern is         example, if the pattern is
3048    
3049           ab(?C4)cd           ab(?C4)cd
3050    
# Line 2513  MISSING CALLOUTS Line 3053  MISSING CALLOUTS
3053         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
3054         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
3055    
3056           If the pattern is studied, PCRE knows the minimum length of a  matching
3057           string,  and will immediately give a "no match" return without actually
3058           running a match if the subject is not long enough, or,  for  unanchored
3059           patterns, if it has been scanned far enough.
3060    
3061           You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
3062           MIZE option to pcre_compile(), pcre_exec(), or pcre_dfa_exec(),  or  by
3063           starting the pattern with (*NO_START_OPT). This slows down the matching
3064           process, but does ensure that callouts such as the  example  above  are
3065           obeyed.
3066    
3067    
3068  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
3069    
3070         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
3071         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
3072         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
3073         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
3074         block. This structure contains the following fields:         block. This structure contains the following fields:
3075    
3076           int          version;           int         version;
3077           int          callout_number;           int         callout_number;
3078           int         *offset_vector;           int        *offset_vector;
3079           const char  *subject;           const char *subject;
3080           int          subject_length;           int         subject_length;
3081           int          start_match;           int         start_match;
3082           int          current_position;           int         current_position;
3083           int          capture_top;           int         capture_top;
3084           int          capture_last;           int         capture_last;
3085           void        *callout_data;           void       *callout_data;
3086           int          pattern_position;           int         pattern_position;
3087           int          next_item_length;           int         next_item_length;
3088             const unsigned char *mark;
3089         The version field is an integer containing the version  number  of  the  
3090         block  format. The initial version was 0; the current version is 1. The         The  version  field  is an integer containing the version number of the
3091         version number will change again in future  if  additional  fields  are         block format. The initial version was 0; the current version is 2.  The
3092           version  number  will  change  again in future if additional fields are
3093         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.
3094    
3095         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 2596  THE CALLOUT INTERFACE Line 3148  THE CALLOUT INTERFACE
3148         in  distinguishing between different automatic callouts, which all have         in  distinguishing between different automatic callouts, which all have
3149         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
3150    
3151           The mark field is present from version 2 of the pcre_callout structure.
3152           In  callouts  from pcre_exec() it contains a pointer to the zero-termi-
3153           nated name of the most recently passed (*MARK) item in  the  match,  or
3154           NULL if there are no (*MARK)s in the current matching path. In callouts
3155           from pcre_dfa_exec() this field always contains NULL.
3156    
3157    
3158  RETURN VALUES  RETURN VALUES
3159    
# Line 2604  RETURN VALUES Line 3162  RETURN VALUES
3162         zero, matching fails at the current point, but  the  testing  of  other         zero, matching fails at the current point, but  the  testing  of  other
3163         matching possibilities goes ahead, just as if a lookahead assertion had         matching possibilities goes ahead, just as if a lookahead assertion had
3164         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
3165         pcre_exec() (or pcre_dfa_exec()) returns the negative value.         pcre_exec() or pcre_dfa_exec() returns the negative value.
3166    
3167         Negative   values   should   normally   be   chosen  from  the  set  of         Negative   values   should   normally   be   chosen  from  the  set  of
3168         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 2622  AUTHOR Line 3180  AUTHOR
3180    
3181  REVISION  REVISION
3182    
3183         Last updated: 29 May 2007         Last updated: 31 July 2011
3184         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3185  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3186    
3187    
# Line 2637  NAME Line 3195  NAME
3195  DIFFERENCES BETWEEN PCRE AND PERL  DIFFERENCES BETWEEN PCRE AND PERL
3196    
3197         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
3198         handle regular expressions. The differences described here  are  mainly         handle regular expressions. The differences  described  here  are  with
3199         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.  
3200    
3201         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
3202         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
3203         main pcre page.         main pcre page.
3204    
3205         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         2. PCRE allows repeat quantifiers only on parenthesized assertions, but
3206         permits  them,  but they do not mean what you might think. For example,         they do not mean what you might think. For example, (?!a){3}  does  not
3207         (?!a){3} does not assert that the next three characters are not "a". It         assert that the next three characters are not "a". It just asserts that
3208         just asserts that the next character is not "a" three times.         the next character is not "a" three times (in principle: PCRE optimizes
3209           this to run the assertion just once). Perl allows repeat quantifiers on
3210         3.  Capturing  subpatterns  that occur inside negative lookahead asser-         other assertions such as \b, but these do not seem to have any use.
3211         tions are counted, but their entries in the offsets  vector  are  never  
3212         set.  Perl sets its numerical variables from any such patterns that are         3. Capturing subpatterns that occur inside  negative  lookahead  asser-
3213           tions  are  counted,  but their entries in the offsets vector are never
3214           set. Perl sets its numerical variables from any such patterns that  are
3215         matched before the assertion fails to match something (thereby succeed-         matched before the assertion fails to match something (thereby succeed-
3216         ing),  but  only  if the negative lookahead assertion contains just one         ing), but only if the negative lookahead assertion  contains  just  one
3217         branch.         branch.
3218    
3219         4. Though binary zero characters are supported in the  subject  string,         4.  Though  binary zero characters are supported in the subject string,
3220         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-
3221         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
3222         the pattern to represent a binary zero.         the pattern to represent a binary zero.
3223    
3224         5.  The  following Perl escape sequences are not supported: \l, \u, \L,         5. The following Perl escape sequences are not supported: \l,  \u,  \L,
3225         \U, and \N. In fact these are implemented by Perl's general string-han-         \U,  and  \N when followed by a character name or Unicode value. (\N on
3226         dling  and are not part of its pattern matching engine. If any of these         its own, matching a non-newline character, is supported.) In fact these
3227         are encountered by PCRE, an error is generated.         are  implemented  by Perl's general string-handling and are not part of
3228           its pattern matching engine. If any of these are encountered  by  PCRE,
3229         6. The Perl escape sequences \p, \P, and \X are supported only if  PCRE         an error is generated.
3230         is  built  with Unicode character property support. The properties that  
3231         can be tested with \p and \P are limited to the general category  prop-         6.  The Perl escape sequences \p, \P, and \X are supported only if PCRE
3232         erties  such  as  Lu and Nd, script names such as Greek or Han, and the         is built with Unicode character property support. The  properties  that
3233         derived properties Any and L&.         can  be tested with \p and \P are limited to the general category prop-
3234           erties such as Lu and Nd, script names such as Greek or  Han,  and  the
3235           derived  properties  Any  and  L&. PCRE does support the Cs (surrogate)
3236           property, which Perl does not; the  Perl  documentation  says  "Because
3237           Perl hides the need for the user to understand the internal representa-
3238           tion of Unicode characters, there is no need to implement the  somewhat
3239           messy concept of surrogates."
3240    
3241           7.  PCRE implements a simpler version of \X than Perl, which changed to
3242           make \X match what Unicode calls an "extended grapheme  cluster".  This
3243           is  more  complicated  than an extended Unicode sequence, which is what
3244           PCRE matches.
3245    
3246         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         8. PCRE does support the \Q...\E escape for quoting substrings. Charac-
3247         ters  in  between  are  treated as literals. This is slightly different         ters  in  between  are  treated as literals. This is slightly different
3248         from Perl in that $ and @ are  also  handled  as  literals  inside  the         from Perl in that $ and @ are  also  handled  as  literals  inside  the
3249         quotes.  In Perl, they cause variable interpolation (but of course PCRE         quotes.  In Perl, they cause variable interpolation (but of course PCRE
# Line 2689  DIFFERENCES BETWEEN PCRE AND PERL Line 3259  DIFFERENCES BETWEEN PCRE AND PERL
3259         The \Q...\E sequence is recognized both inside  and  outside  character         The \Q...\E sequence is recognized both inside  and  outside  character
3260         classes.         classes.
3261    
3262         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})         9. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
3263         constructions. However, there is support for recursive  patterns.  This         constructions. However, there is support for recursive  patterns.  This
3264         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
3265         "callout" feature allows an external function to be called during  pat-         "callout" feature allows an external function to be called during  pat-
3266         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
3267    
3268         9.  Subpatterns  that  are  called  recursively or as "subroutines" are         10.  Subpatterns  that  are  called recursively or as "subroutines" are
3269         always treated as atomic groups in  PCRE.  This  is  like  Python,  but         always treated as atomic groups in  PCRE.  This  is  like  Python,  but
3270         unlike Perl.         unlike  Perl. There is a discussion of an example that explains this in
3271           more detail in the section on recursion differences from  Perl  in  the
3272           pcrepattern page.
3273    
3274         10.  There are some differences that are concerned with the settings of         11.  There are some differences that are concerned with the settings of
3275         captured strings when part of  a  pattern  is  repeated.  For  example,         captured strings when part of  a  pattern  is  repeated.  For  example,
3276         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2
3277         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
3278    
3279         11.  PCRE  does  support  Perl  5.10's  backtracking  verbs  (*ACCEPT),         12. PCRE's handling of duplicate subpattern numbers and duplicate  sub-
3280         (*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
3281         the forms without an  argument.  PCRE  does  not  support  (*MARK).  If         fact the PCRE works internally just with numbers, using an external ta-
3282         (*ACCEPT)  is within capturing parentheses, PCRE does not set that cap-         ble  to  translate  between numbers and names. In particular, a pattern
3283         ture group; this is different to Perl.         such as (?|(?<a>A)|(?<b)B), where the two  capturing  parentheses  have
3284           the  same  number  but different names, is not supported, and causes an
3285         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
3286         ities.   Perl  5.10  will  include new features that are not in earlier         distinguish  which  parentheses matched, because both names map to cap-
3287         versions, some of which (such as named parentheses) have been  in  PCRE         turing subpattern number 1. To avoid this confusing situation, an error
3288         for some time. This list is with respect to Perl 5.10:         is given at compile time.
3289    
3290         (a)  Although  lookbehind  assertions  must match fixed length strings,         13.  Perl  recognizes  comments  in some places that PCRE does not, for
3291         each alternative branch of a lookbehind assertion can match a different         example, between the ( and ? at the start of a subpattern.  If  the  /x
3292         length of string. Perl requires them all to have the same length.         modifier  is set, Perl allows whitespace between ( and ? but PCRE never
3293           does, even if the PCRE_EXTENDED option is set.
3294    
3295           14. PCRE provides some extensions to the Perl regular expression facil-
3296           ities.   Perl  5.10  includes new features that are not in earlier ver-
3297           sions of Perl, some of which (such as named parentheses) have  been  in
3298           PCRE for some time. This list is with respect to Perl 5.10:
3299    
3300           (a)  Although  lookbehind  assertions  in  PCRE must match fixed length
3301           strings, each alternative branch of a lookbehind assertion can match  a
3302           different  length  of  string.  Perl requires them all to have the same
3303           length.
3304    
3305         (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  $
3306         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
3307    
3308         (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe-         (c) If PCRE_EXTRA is set, a backslash followed by a letter with no spe-
3309         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
3310         ignored.  (Perl can be made to issue a warning.)         ignored.  (Perl can be made to issue a warning.)
3311    
3312         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-         (d)  If  PCRE_UNGREEDY is set, the greediness of the repetition quanti-
3313         fiers is inverted, that is, by default they are not greedy, but if fol-         fiers is inverted, that is, by default they are not greedy, but if fol-
3314         lowed by a question mark they are.         lowed by a question mark they are.
3315    
3316         (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
3317         tried only at the first matching position in the subject string.         tried only at the first matching position in the subject string.
3318    
3319         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
3320         TURE options for pcre_exec() have no Perl equivalents.         and  PCRE_NO_AUTO_CAPTURE  options for pcre_exec() have no Perl equiva-
3321           lents.
3322    
3323           (g) The \R escape sequence can be restricted to match only CR,  LF,  or
3324           CRLF by the PCRE_BSR_ANYCRLF option.
3325    
3326         (g) The callout facility is PCRE-specific.         (h) The callout facility is PCRE-specific.
3327    
3328         (h) The partial matching facility is PCRE-specific.         (i) The partial matching facility is PCRE-specific.
3329    
3330         (i) Patterns compiled by PCRE can be saved and re-used at a later time,         (j) Patterns compiled by PCRE can be saved and re-used at a later time,
3331         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
3332    
3333         (j)  The  alternative  matching function (pcre_dfa_exec()) matches in a         (k) The alternative matching function (pcre_dfa_exec())  matches  in  a
3334         different way and is not Perl-compatible.         different way and is not Perl-compatible.
3335    
3336           (l)  PCRE  recognizes some special sequences such as (*CR) at the start
3337           of a pattern that set overall options that cannot be changed within the
3338           pattern.
3339    
3340    
3341  AUTHOR  AUTHOR
3342    
# Line 2756  AUTHOR Line 3347  AUTHOR
3347    
3348  REVISION  REVISION
3349    
3350         Last updated: 08 August 2007         Last updated: 24 July 2011
3351         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3352  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3353    
3354    
# Line 2772  PCRE REGULAR EXPRESSION DETAILS Line 3363  PCRE REGULAR EXPRESSION DETAILS
3363    
3364         The  syntax and semantics of the regular expressions that are supported         The  syntax and semantics of the regular expressions that are supported
3365         by PCRE are described in detail below. There is a quick-reference  syn-         by PCRE are described in detail below. There is a quick-reference  syn-
3366         tax  summary  in  the  pcresyntax  page. Perl's regular expressions are         tax summary in the pcresyntax page. PCRE tries to match Perl syntax and
3367         described in its own documentation, and regular expressions in  general         semantics as closely as it can. PCRE  also  supports  some  alternative
3368         are  covered in a number of books, some of which have copious examples.         regular  expression  syntax (which does not conflict with the Perl syn-
3369         Jeffrey  Friedl's  "Mastering  Regular   Expressions",   published   by         tax) in order to provide some compatibility with regular expressions in
3370         O'Reilly,  covers regular expressions in great detail. This description         Python, .NET, and Oniguruma.
3371         of PCRE's regular expressions is intended as reference material.  
3372           Perl's  regular expressions are described in its own documentation, and
3373           regular expressions in general are covered in a number of  books,  some
3374           of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
3375           Expressions", published by  O'Reilly,  covers  regular  expressions  in
3376           great  detail.  This  description  of  PCRE's  regular  expressions  is
3377           intended as reference material.
3378    
3379         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
3380         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
3381         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
3382         pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern         pcre_compile()  or  pcre_compile2() with the PCRE_UTF8 option. There is
3383         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:
3384         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre  
3385         page.           (*UTF8)
3386    
3387           Starting a pattern with this sequence  is  equivalent  to  setting  the
3388           PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3389           UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3390           below.  There  is  also  a  summary of UTF-8 features in the section on
3391           UTF-8 support in the main pcre page.
3392    
3393         The remainder of this document discusses the  patterns  that  are  sup-         Another special sequence that may appear at the start of a  pattern  or
3394         ported  by  PCRE when its main matching function, pcre_exec(), is used.         in combination with (*UTF8) is:
3395         From  release  6.0,   PCRE   offers   a   second   matching   function,  
3396         pcre_dfa_exec(),  which matches using a different algorithm that is not           (*UCP)
3397    
3398           This  has  the  same  effect  as setting the PCRE_UCP option: it causes
3399           sequences such as \d and \w to  use  Unicode  properties  to  determine
3400           character types, instead of recognizing only characters with codes less
3401           than 128 via a lookup table.
3402    
3403           If a pattern starts with (*NO_START_OPT), it has  the  same  effect  as
3404           setting the PCRE_NO_START_OPTIMIZE option either at compile or matching
3405           time. There are also some more of these special sequences that are con-
3406           cerned with the handling of newlines; they are described below.
3407    
3408           The  remainder  of  this  document discusses the patterns that are sup-
3409           ported by PCRE when its main matching function, pcre_exec(),  is  used.
3410           From   release   6.0,   PCRE   offers   a   second  matching  function,
3411           pcre_dfa_exec(), which matches using a different algorithm that is  not
3412         Perl-compatible. Some of the features discussed below are not available         Perl-compatible. Some of the features discussed below are not available
3413         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the         when pcre_dfa_exec() is used. The advantages and disadvantages  of  the
3414         alternative function, and how it differs from the normal function,  are         alternative  function, and how it differs from the normal function, are
3415         discussed in the pcrematching page.         discussed in the pcrematching page.
3416    
3417    
3418    NEWLINE CONVENTIONS
3419    
3420           PCRE supports five different conventions for indicating line breaks  in
3421           strings:  a  single  CR (carriage return) character, a single LF (line-
3422           feed) character, the two-character sequence CRLF, any of the three pre-
3423           ceding,  or  any Unicode newline sequence. The pcreapi page has further
3424           discussion about newlines, and shows how to set the newline  convention
3425           in the options arguments for the compiling and matching functions.
3426    
3427           It  is also possible to specify a newline convention by starting a pat-
3428           tern string with one of the following five sequences:
3429    
3430             (*CR)        carriage return
3431             (*LF)        linefeed
3432             (*CRLF)      carriage return, followed by linefeed
3433             (*ANYCRLF)   any of the three above
3434             (*ANY)       all Unicode newline sequences
3435    
3436           These override the default and the options given to  pcre_compile()  or
3437           pcre_compile2().  For example, on a Unix system where LF is the default
3438           newline sequence, the pattern
3439    
3440             (*CR)a.b
3441    
3442           changes the convention to CR. That pattern matches "a\nb" because LF is
3443           no  longer  a  newline. Note that these special settings, which are not
3444           Perl-compatible, are recognized only at the very start  of  a  pattern,
3445           and  that  they  must  be  in  upper  case. If more than one of them is
3446           present, the last one is used.
3447    
3448           The newline convention affects the interpretation of the dot  metachar-
3449           acter  when  PCRE_DOTALL is not set, and also the behaviour of \N. How-
3450           ever, it does not affect  what  the  \R  escape  sequence  matches.  By
3451           default,  this is any Unicode newline sequence, for Perl compatibility.
3452           However, this can be changed; see the description of \R in the  section
3453           entitled  "Newline sequences" below. A change of \R setting can be com-
3454           bined with a change of newline convention.
3455    
3456    
3457  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
3458    
3459         A  regular  expression  is  a pattern that is matched against a subject         A regular expression is a pattern that is  matched  against  a  subject
3460         string from left to right. Most characters stand for  themselves  in  a         string  from  left  to right. Most characters stand for themselves in a
3461         pattern,  and  match  the corresponding characters in the subject. As a         pattern, and match the corresponding characters in the  subject.  As  a
3462         trivial example, the pattern         trivial example, the pattern
3463    
3464           The quick brown fox           The quick brown fox
3465    
3466         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
3467         caseless  matching is specified (the PCRE_CASELESS option), letters are         caseless matching is specified (the PCRE_CASELESS option), letters  are
3468         matched independently of case. In UTF-8 mode, PCRE  always  understands         matched  independently  of case. In UTF-8 mode, PCRE always understands
3469         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
3470         caseless matching is always possible. For characters with  higher  val-         caseless  matching  is always possible. For characters with higher val-
3471         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
3472         property support, but not otherwise.   If  you  want  to  use  caseless         property  support,  but  not  otherwise.   If  you want to use caseless
3473         matching  for  characters  128  and above, you must ensure that PCRE is         matching for characters 128 and above, you must  ensure  that  PCRE  is
3474         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
3475    
3476         The power of regular expressions comes  from  the  ability  to  include         The  power  of  regular  expressions  comes from the ability to include
3477         alternatives  and  repetitions in the pattern. These are encoded in the         alternatives and repetitions in the pattern. These are encoded  in  the
3478         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
3479         but instead are interpreted in some special way.         but instead are interpreted in some special way.
3480    
3481         There  are  two different sets of metacharacters: those that are recog-         There are two different sets of metacharacters: those that  are  recog-
3482         nized anywhere in the pattern except within square brackets, and  those         nized  anywhere in the pattern except within square brackets, and those
3483         that  are  recognized  within square brackets. Outside square brackets,         that are recognized within square brackets.  Outside  square  brackets,
3484         the metacharacters are as follows:         the metacharacters are as follows:
3485    
3486           \      general escape character with several uses           \      general escape character with several uses
# Line 2842  CHARACTERS AND METACHARACTERS Line 3499  CHARACTERS AND METACHARACTERS
3499                  also "possessive quantifier"                  also "possessive quantifier"
3500           {      start min/max quantifier           {      start min/max quantifier
3501    
3502         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
3503         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
3504    
3505           \      general escape character           \      general escape character
# Line 2852  CHARACTERS AND METACHARACTERS Line 3509  CHARACTERS AND METACHARACTERS
3509                    syntax)                    syntax)
3510           ]      terminates the character class           ]      terminates the character class
3511    
3512         The  following sections describe the use of each of the metacharacters.         The following sections describe the use of each of the metacharacters.
3513    
3514    
3515  BACKSLASH  BACKSLASH
3516    
3517         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3518         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
3519         character may have. This  use  of  backslash  as  an  escape  character         meaning that character may have. This use of  backslash  as  an  escape
3520         applies both inside and outside character classes.         character applies both inside and outside character classes.
3521    
3522         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
3523         pattern.  This escaping action applies whether  or  not  the  following         pattern.  This escaping action applies whether  or  not  the  following
# Line 2869  BACKSLASH Line 3526  BACKSLASH
3526         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-
3527         slash, you write \\.         slash, you write \\.
3528    
3529           In UTF-8 mode, only ASCII numbers and letters have any special  meaning
3530           after  a  backslash.  All  other characters (in particular, those whose
3531           codepoints are greater than 127) are treated as literals.
3532    
3533         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
3534         the  pattern (other than in a character class) and characters between a         the  pattern (other than in a character class) and characters between a
3535         # 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 2889  BACKSLASH Line 3550  BACKSLASH
3550           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3551    
3552         The \Q...\E sequence is recognized both inside  and  outside  character         The \Q...\E sequence is recognized both inside  and  outside  character
3553         classes.         classes.   An  isolated \E that is not preceded by \Q is ignored. If \Q
3554           is not followed by \E later in the pattern, the literal  interpretation
3555           continues  to  the  end  of  the pattern (that is, \E is assumed at the
3556           end). If the isolated \Q is inside a character class,  this  causes  an
3557           error, because the character class is not terminated.
3558    
3559     Non-printing characters     Non-printing characters
3560    
# Line 2897  BACKSLASH Line 3562  BACKSLASH
3562         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
3563         appearance  of non-printing characters, apart from the binary zero that         appearance  of non-printing characters, apart from the binary zero that
3564         terminates a pattern, but when a pattern  is  being  prepared  by  text         terminates a pattern, but when a pattern  is  being  prepared  by  text
3565         editing,  it  is  usually  easier  to  use  one of the following escape         editing,  it  is  often  easier  to  use  one  of  the following escape
3566         sequences than the binary character it represents:         sequences than the binary character it represents:
3567    
3568           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3569           \cx       "control-x", where x is any character           \cx       "control-x", where x is any ASCII character
3570           \e        escape (hex 1B)           \e        escape (hex 1B)
3571           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3572           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3573           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3574           \t        tab (hex 09)           \t        tab (hex 09)
3575           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or back reference
3576           \xhh      character with hex code hh           \xhh      character with hex code hh
3577           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh..
3578    
3579         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,
3580         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
3581         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 ({
3582         becomes hex 7B.         is  7B),  while  \c; becomes hex 7B (; is 3B). If the byte following \c
3583           has a value greater than 127, a compile-time error occurs.  This  locks
3584           out  non-ASCII  characters in both byte mode and UTF-8 mode. (When PCRE
3585           is compiled in EBCDIC mode, all byte values are  valid.  A  lower  case
3586           letter is converted to upper case, and then the 0xc0 bits are flipped.)
3587    
3588         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
3589         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 2976  BACKSLASH Line 3645  BACKSLASH
3645         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
3646         inside and outside character classes. In addition, inside  a  character         inside and outside character classes. In addition, inside  a  character
3647         class,  the  sequence \b is interpreted as the backspace character (hex         class,  the  sequence \b is interpreted as the backspace character (hex
3648         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-
3649         and  "X", respectively. Outside a character class, these sequences have         ter  class.  Like  any  other  unrecognized  escape sequences, they are
3650         different meanings (see below).         treated as the literal characters "B", "N", "R", and  "X"  by  default,
3651           but cause an error if the PCRE_EXTRA option is set. Outside a character
3652           class, these sequences have different meanings.
3653    
3654     Absolute and relative back references     Absolute and relative back references
3655    
# Line 2987  BACKSLASH Line 3658  BACKSLASH
3658         named back reference can be coded as \g{name}. Back references are dis-         named back reference can be coded as \g{name}. Back references are dis-
3659         cussed later, following the discussion of parenthesized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3660    
3661       Absolute and relative subroutine calls
3662    
3663           For  compatibility with Oniguruma, the non-Perl syntax \g followed by a
3664           name or a number enclosed either in angle brackets or single quotes, is
3665           an  alternative  syntax for referencing a subpattern as a "subroutine".
3666           Details are discussed later.   Note  that  \g{...}  (Perl  syntax)  and
3667           \g<...>  (Oniguruma  syntax)  are  not synonymous. The former is a back
3668           reference; the latter is a subroutine call.
3669    
3670     Generic character types     Generic character types
3671    
3672         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:  
3673    
3674           \d     any decimal digit           \d     any decimal digit
3675           \D     any character that is not a decimal digit           \D     any character that is not a decimal digit
# Line 3003  BACKSLASH Line 3682  BACKSLASH
3682           \w     any "word" character           \w     any "word" character
3683           \W     any "non-word" character           \W     any "non-word" character
3684    
3685         Each pair of escape sequences partitions the complete set of characters         There is also the single sequence \N, which matches a non-newline char-
3686         into  two disjoint sets. Any given character matches one, and only one,         acter.   This  is the same as the "." metacharacter when PCRE_DOTALL is
3687         of each pair.         not set.
3688    
3689         These character type sequences can appear both inside and outside char-         Each pair of lower and upper case escape sequences partitions the  com-
3690         acter  classes.  They each match one character of the appropriate type.         plete  set  of  characters  into two disjoint sets. Any given character
3691         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
3692         of them fail, since there is no character to match.         inside  and outside character classes. They each match one character of
3693           the appropriate type. If the current matching point is at  the  end  of
3694         For  compatibility  with Perl, \s does not match the VT character (code         the  subject string, all of them fail, because there is no character to
3695         11).  This makes it different from the the POSIX "space" class. The  \s         match.
3696         characters  are  HT  (9), LF (10), FF (12), CR (13), and space (32). If  
3697           For compatibility with Perl, \s does not match the VT  character  (code
3698           11).   This makes it different from the the POSIX "space" class. The \s
3699           characters are HT (9), LF (10), FF (12), CR (13), and  space  (32).  If
3700         "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-
3701         ter. In PCRE, it never does.         ter. In PCRE, it never does.
3702    
3703         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
3704         \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-
3705         code  character  property  support is available. These sequences retain         trolled by PCRE's low-valued character tables, and may vary if  locale-
3706         their original meanings from before UTF-8 support was available, mainly         specific  matching is taking place (see "Locale support" in the pcreapi
3707         for efficiency reasons.         page). For example, in a French locale such  as  "fr_FR"  in  Unix-like
3708           systems,  or "french" in Windows, some character codes greater than 128
3709         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
3710         the other sequences, these do match certain high-valued  codepoints  in         use of locales with Unicode is discouraged.
3711         UTF-8 mode.  The horizontal space characters are:  
3712           By  default,  in  UTF-8  mode,  characters with values greater than 128
3713           never match \d, \s, or \w, and always  match  \D,  \S,  and  \W.  These
3714           sequences  retain their original meanings from before UTF-8 support was
3715           available, mainly for efficiency reasons. However, if PCRE is  compiled
3716           with  Unicode property support, and the PCRE_UCP option is set, the be-
3717           haviour is changed so that Unicode properties  are  used  to  determine
3718           character types, as follows:
3719    
3720             \d  any character that \p{Nd} matches (decimal digit)
3721             \s  any character that \p{Z} matches, plus HT, LF, FF, CR
3722             \w  any character that \p{L} or \p{N} matches, plus underscore
3723    
3724           The  upper case escapes match the inverse sets of characters. Note that
3725           \d matches only decimal digits, whereas \w matches any  Unicode  digit,
3726           as  well as any Unicode letter, and underscore. Note also that PCRE_UCP
3727           affects \b, and \B because they are defined in  terms  of  \w  and  \W.
3728           Matching these sequences is noticeably slower when PCRE_UCP is set.
3729    
3730           The  sequences  \h, \H, \v, and \V are features that were added to Perl
3731           at release 5.10. In contrast to the other sequences, which  match  only
3732           ASCII  characters  by  default,  these always match certain high-valued
3733           codepoints in UTF-8 mode, whether or not PCRE_UCP is set. The  horizon-
3734           tal space characters are:
3735    
3736           U+0009     Horizontal tab           U+0009     Horizontal tab
3737           U+0020     Space           U+0020     Space
# Line 3058  BACKSLASH Line 3763  BACKSLASH
3763           U+2028     Line separator           U+2028     Line separator
3764           U+2029     Paragraph separator           U+2029     Paragraph separator
3765    
        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.  
   
3766     Newline sequences     Newline sequences
3767    
3768         Outside a character class, the escape sequence \R matches  any  Unicode         Outside  a  character class, by default, the escape sequence \R matches
3769         newline  sequence. This is a Perl 5.10 feature. In non-UTF-8 mode \R is         any Unicode newline sequence. In non-UTF-8 mode \R is equivalent to the
3770         equivalent to the following:         following:
3771    
3772           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3773    
3774         This is an example of an "atomic group", details  of  which  are  given         This  is  an  example  of an "atomic group", details of which are given
3775         below.  This particular group matches either the two-character sequence         below.  This particular group matches either the two-character sequence
3776         CR followed by LF, or  one  of  the  single  characters  LF  (linefeed,         CR  followed  by  LF,  or  one  of  the single characters LF (linefeed,
3777         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage
3778         return, U+000D), or NEL (next line, U+0085). The two-character sequence         return, U+000D), or NEL (next line, U+0085). The two-character sequence
3779         is treated as a single unit that cannot be split.         is treated as a single unit that cannot be split.
3780    
3781         In  UTF-8  mode, two additional characters whose codepoints are greater         In UTF-8 mode, two additional characters whose codepoints  are  greater
3782         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
3783         rator,  U+2029).   Unicode character property support is not needed for         rator, U+2029).  Unicode character property support is not  needed  for
3784         these characters to be recognized.         these characters to be recognized.
3785    
3786         Inside a character class, \R matches the letter "R".         It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3787           the complete set  of  Unicode  line  endings)  by  setting  the  option
3788           PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3789           (BSR is an abbrevation for "backslash R".) This can be made the default
3790           when  PCRE  is  built;  if this is the case, the other behaviour can be
3791           requested via the PCRE_BSR_UNICODE option.   It  is  also  possible  to
3792           specify  these  settings  by  starting a pattern string with one of the
3793           following sequences:
3794    
3795             (*BSR_ANYCRLF)   CR, LF, or CRLF only
3796             (*BSR_UNICODE)   any Unicode newline sequence
3797    
3798           These override the default and the options given to  pcre_compile()  or
3799           pcre_compile2(),  but  they  can  be  overridden  by  options  given to
3800           pcre_exec() or pcre_dfa_exec(). Note that these special settings, which
3801           are  not  Perl-compatible,  are  recognized only at the very start of a
3802           pattern, and that they must be in upper case. If more than one of  them
3803           is present, the last one is used. They can be combined with a change of
3804           newline convention; for example, a pattern can start with:
3805    
3806             (*ANY)(*BSR_ANYCRLF)
3807    
3808           They can also be combined with the (*UTF8) or (*UCP) special sequences.
3809           Inside  a  character  class,  \R  is  treated as an unrecognized escape
3810           sequence, and so matches the letter "R" by default, but causes an error
3811           if PCRE_EXTRA is set.
3812    
3813     Unicode character properties     Unicode character properties
3814    
3815         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
3816         tional  escape sequences that match characters with specific properties         tional escape sequences that match characters with specific  properties
3817         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
3818         limited  to  testing characters whose codepoints are less than 256, but         limited to testing characters whose codepoints are less than  256,  but
3819         they do work in this mode.  The extra escape sequences are:         they do work in this mode.  The extra escape sequences are:
3820    
3821           \p{xx}   a character with the xx property           \p{xx}   a character with the xx property
3822           \P{xx}   a character without the xx property           \P{xx}   a character without the xx property
3823           \X       an extended Unicode sequence           \X       an extended Unicode sequence
3824    
3825         The property names represented by xx above are limited to  the  Unicode         The  property  names represented by xx above are limited to the Unicode
3826         script names, the general category properties, and "Any", which matches         script names, the general category properties, "Any", which matches any
3827         any character (including newline). Other properties such as "InMusical-         character   (including  newline),  and  some  special  PCRE  properties
3828         Symbols"  are  not  currently supported by PCRE. Note that \P{Any} does         (described in the next section).  Other Perl properties such as  "InMu-
3829         not match any characters, so always causes a match failure.         sicalSymbols"  are  not  currently supported by PCRE. Note that \P{Any}
3830           does not match any characters, so always causes a match failure.
3831    
3832         Sets of Unicode characters are defined as belonging to certain scripts.         Sets of Unicode characters are defined as belonging to certain scripts.
3833         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 3117  BACKSLASH Line 3839  BACKSLASH
3839         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
3840         "Common". The current list of scripts is:         "Common". The current list of scripts is:
3841    
3842         Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,         Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille,
3843         Buhid,  Canadian_Aboriginal,  Cherokee,  Common,   Coptic,   Cuneiform,         Buginese, Buhid, Canadian_Aboriginal, Carian, Cham,  Cherokee,  Common,
3844         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,         Coptic,   Cuneiform,  Cypriot,  Cyrillic,  Deseret,  Devanagari,  Egyp-
3845         Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew,  Hira-         tian_Hieroglyphs,  Ethiopic,  Georgian,  Glagolitic,   Gothic,   Greek,
3846         gana,  Inherited,  Kannada,  Katakana,  Kharoshthi,  Khmer, Lao, Latin,         Gujarati,  Gurmukhi,  Han,  Hangul,  Hanunoo,  Hebrew,  Hiragana, Impe-
3847         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,         rial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian,
3848         Ogham,  Old_Italic,  Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician,         Javanese,  Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Lao,
3849         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,         Latin,  Lepcha,  Limbu,  Linear_B,  Lisu,  Lycian,  Lydian,  Malayalam,
3850         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.         Meetei_Mayek,  Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham, Old_Italic,
3851           Old_Persian, Old_South_Arabian, Old_Turkic, Ol_Chiki,  Oriya,  Osmanya,
3852         Each  character has exactly one general category property, specified by         Phags_Pa,  Phoenician,  Rejang,  Runic, Samaritan, Saurashtra, Shavian,
3853         a two-letter abbreviation. For compatibility with Perl, negation can be         Sinhala, Sundanese, Syloti_Nagri, Syriac,  Tagalog,  Tagbanwa,  Tai_Le,
3854         specified  by  including a circumflex between the opening brace and the         Tai_Tham,  Tai_Viet,  Tamil,  Telugu,  Thaana, Thai, Tibetan, Tifinagh,
3855         property name. For example, \p{^Lu} is the same as \P{Lu}.         Ugaritic, Vai, Yi.
3856    
3857           Each character has exactly one Unicode general category property, spec-
3858           ified  by a two-letter abbreviation. For compatibility with Perl, nega-
3859           tion can be specified by including a  circumflex  between  the  opening
3860           brace  and  the  property  name.  For  example,  \p{^Lu} is the same as
3861           \P{Lu}.
3862    
3863         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-
3864         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 3194  BACKSLASH Line 3922  BACKSLASH
3922         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
3923         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-
3924         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
3925         the pcreapi page).         the pcreapi page). Perl does not support the Cs property.
3926    
3927         The  long  synonyms  for  these  properties that Perl supports (such as         The  long  synonyms  for  property  names  that  Perl supports (such as
3928         \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
3929         any of these properties with "Is".         any of these properties with "Is".
3930    
# Line 3219  BACKSLASH Line 3947  BACKSLASH
3947         None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X         None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X
3948         matches any one character.         matches any one character.
3949    
3950           Note that recent versions of Perl have changed \X to match what Unicode
3951           calls an "extended grapheme cluster", which has a more complicated def-
3952           inition.