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2  This file contains a concatenation of the PCRE man pages, converted to plain  This file contains a concatenation of the PCRE man pages, converted to plain
3  text format for ease of searching with a text editor, or for use on systems  text format for ease of searching with a text editor, or for use on systems
4  that do not have a man page processor. The small individual files that give  that do not have a man page processor. The small individual files that give
5  synopses of each function in the library have not been included. There are  synopses of each function in the library have not been included. Neither has
6  separate text files for the pcregrep and pcretest commands.  the pcredemo program. There are separate text files for the pcregrep and
7    pcretest commands.
8  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
9    
10    
# Line 18  INTRODUCTION Line 19  INTRODUCTION
19    
20         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
21         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
22         just  a  few differences. (Certain features that appeared in Python and         just  a few differences. Some features that appeared in Python and PCRE
23         PCRE before they appeared in Perl are also available using  the  Python         before they appeared in Perl are also available using the  Python  syn-
24         syntax.)         tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25           items, and there is an option for requesting some  minor  changes  that
26         The  current  implementation of PCRE (release 7.x) corresponds approxi-         give better JavaScript compatibility.
27         mately with Perl 5.10, including support for UTF-8 encoded strings  and  
28         Unicode general category properties. However, UTF-8 and Unicode support         The  current implementation of PCRE corresponds approximately with Perl
29         has to be explicitly enabled; it is not the default. The Unicode tables         5.12, including support for UTF-8 encoded strings and  Unicode  general
30         correspond to Unicode release 5.0.0.         category  properties.  However,  UTF-8  and  Unicode  support has to be
31           explicitly enabled; it is not the default. The  Unicode  tables  corre-
32           spond to Unicode release 5.2.0.
33    
34         In  addition to the Perl-compatible matching function, PCRE contains an         In  addition to the Perl-compatible matching function, PCRE contains an
35         alternative matching function that matches the same  compiled  patterns         alternative function that matches the same compiled patterns in a  dif-
36         in  a different way. In certain circumstances, the alternative function         ferent way. In certain circumstances, the alternative function has some
37         has some advantages. For a discussion of the two  matching  algorithms,         advantages.  For a discussion of the two matching algorithms,  see  the
38         see the pcrematching page.         pcrematching page.
39    
40         PCRE  is  written  in C and released as a C library. A number of people         PCRE  is  written  in C and released as a C library. A number of people
41         have written wrappers and interfaces of various kinds.  In  particular,         have written wrappers and interfaces of various kinds.  In  particular,
# Line 45  INTRODUCTION Line 48  INTRODUCTION
48    
49         Details of exactly which Perl regular expression features are  and  are         Details of exactly which Perl regular expression features are  and  are
50         not supported by PCRE are given in separate documents. See the pcrepat-         not supported by PCRE are given in separate documents. See the pcrepat-
51         tern and pcrecompat pages.         tern and pcrecompat pages. There is a syntax summary in the  pcresyntax
52           page.
53    
54         Some features of PCRE can be included, excluded, or  changed  when  the         Some  features  of  PCRE can be included, excluded, or changed when the
55         library  is  built.  The pcre_config() function makes it possible for a         library is built. The pcre_config() function makes it  possible  for  a
56         client to discover which features are  available.  The  features  them-         client  to  discover  which  features are available. The features them-
57         selves  are described in the pcrebuild page. Documentation about build-         selves are described in the pcrebuild page. Documentation about  build-
58         ing PCRE for various operating systems can be found in the README  file         ing  PCRE  for various operating systems can be found in the README 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
63         functions,  but  which  are  not  intended for use by external callers.         functions, but which are not intended  for  use  by  external  callers.
64         Their names all begin with "_pcre_", which hopefully will  not  provoke         Their  names  all begin with "_pcre_", which hopefully will not provoke
65         any name clashes. In some environments, it is possible to control which         any name clashes. In some environments, it is possible to control which
66         external symbols are exported when a shared library is  built,  and  in         external  symbols  are  exported when a shared library is built, and in
67         these cases the undocumented symbols are not exported.         these cases the undocumented symbols are not exported.
68    
69    
70  USER DOCUMENTATION  USER DOCUMENTATION
71    
72         The  user  documentation  for PCRE comprises a number of different sec-         The user documentation for PCRE comprises a number  of  different  sec-
73         tions. In the "man" format, each of these is a separate "man page".  In         tions.  In the "man" format, each of these is a separate "man page". In
74         the  HTML  format, each is a separate page, linked from the index page.         the HTML format, each is a separate page, linked from the  index  page.
75         In the plain text format, all the sections are concatenated,  for  ease         In  the  plain  text format, all the sections, except the pcredemo sec-
76         of searching. The sections are as follows:         tion, are concatenated, for ease of searching. The sections are as fol-
77           lows:
78    
79           pcre              this document           pcre              this document
80           pcre-config       show PCRE installation configuration information           pcre-config       show PCRE installation configuration information
# Line 78  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
# Line 86  USER DOCUMENTATION Line 92  USER DOCUMENTATION
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
101         each C library function, listing its arguments and results.         each C library function, listing its arguments and results.
102    
103    
104  LIMITATIONS  LIMITATIONS
105    
106         There  are some size limitations in PCRE but it is hoped that they will         There are some size limitations in PCRE but it is hoped that they  will
107         never in practice be relevant.         never in practice be relevant.
108    
109         The maximum length of a compiled pattern is 65539 (sic) bytes  if  PCRE         The  maximum  length of a compiled pattern is 65539 (sic) bytes if PCRE
110         is compiled with the default internal linkage size of 2. If you want to         is compiled with the default internal linkage size of 2. If you want to
111         process regular expressions that are truly enormous,  you  can  compile         process  regular  expressions  that are truly enormous, you can compile
112         PCRE  with  an  internal linkage size of 3 or 4 (see the README file in         PCRE with an internal linkage size of 3 or 4 (see the  README  file  in
113         the source distribution and the pcrebuild documentation  for  details).         the  source  distribution and the pcrebuild documentation for details).
114         In  these  cases the limit is substantially larger.  However, the speed         In these cases the limit is substantially larger.  However,  the  speed
115         of execution is slower.         of execution is slower.
116    
117         All values in repeating quantifiers must be less than 65536. The  maxi-         All values in repeating quantifiers must be less than 65536.
        mum  compiled  length  of  subpattern  with an explicit repeat count is  
        30000 bytes. The maximum number of capturing subpatterns is 65535.  
118    
119         There is no limit to the number of parenthesized subpatterns, but there         There is no limit to the number of parenthesized subpatterns, but there
120         can be no more than 65535 capturing subpatterns.         can be no more than 65535 capturing subpatterns.
# Line 117  LIMITATIONS Line 122  LIMITATIONS
122         The maximum length of name for a named subpattern is 32 characters, and         The maximum length of name for a named subpattern is 32 characters, and
123         the maximum number of named subpatterns is 10000.         the maximum number of named subpatterns is 10000.
124    
125         The maximum length of a subject string is the largest  positive  number         The  maximum  length of a subject string is the largest positive number
126         that  an integer variable can hold. However, when using the traditional         that an integer variable can hold. However, when using the  traditional
127         matching function, PCRE uses recursion to handle subpatterns and indef-         matching function, PCRE uses recursion to handle subpatterns and indef-
128         inite  repetition.  This means that the available stack space may limit         inite repetition.  This means that the available stack space may  limit
129         the size of a subject string that can be processed by certain patterns.         the size of a subject string that can be processed by certain patterns.
130         For a discussion of stack issues, see the pcrestack documentation.         For a discussion of stack issues, see the pcrestack documentation.
131    
132    
133  UTF-8 AND UNICODE PROPERTY SUPPORT  UTF-8 AND UNICODE PROPERTY SUPPORT
134    
135         From  release  3.3,  PCRE  has  had  some support for character strings         From release 3.3, PCRE has  had  some  support  for  character  strings
136         encoded in the UTF-8 format. For release 4.0 this was greatly  extended         encoded  in the UTF-8 format. For release 4.0 this was greatly extended
137         to  cover  most common requirements, and in release 5.0 additional sup-         to cover most common requirements, and in release 5.0  additional  sup-
138         port for Unicode general category properties was added.         port for Unicode general category properties was added.
139    
140         In order process UTF-8 strings, you must build PCRE  to  include  UTF-8         In  order  process  UTF-8 strings, you must build PCRE to include UTF-8
141         support  in  the  code,  and, in addition, you must call pcre_compile()         support in the code, and, in addition,  you  must  call  pcre_compile()
142         with the PCRE_UTF8 option flag. When you do this, both the pattern  and         with  the  PCRE_UTF8  option  flag,  or the pattern must start with the
143         any  subject  strings  that are matched against it are treated as UTF-8         sequence (*UTF8). When either of these is the case,  both  the  pattern
144         strings instead of just strings of bytes.         and  any  subject  strings  that  are matched against it are treated as
145           UTF-8 strings instead of 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
# Line 155  UTF-8 AND UNICODE PROPERTY SUPPORT Line 161  UTF-8 AND UNICODE PROPERTY SUPPORT
161         optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE         optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE
162         does not support this.         does not support this.
163    
164         The following comments apply when PCRE is running in UTF-8 mode:     Validity of UTF-8 strings
165    
166           When  you  set  the  PCRE_UTF8 flag, the strings passed as patterns and
167           subjects are (by default) checked for validity on entry to the relevant
168           functions.  From  release 7.3 of PCRE, the check is according the rules
169           of RFC 3629, which are themselves derived from the  Unicode  specifica-
170           tion.  Earlier  releases  of PCRE followed the rules of RFC 2279, which
171           allows the full range of 31-bit values (0 to 0x7FFFFFFF).  The  current
172           check allows only values in the range U+0 to U+10FFFF, excluding U+D800
173           to U+DFFF.
174    
175           The excluded code points are the "Low Surrogate Area"  of  Unicode,  of
176           which  the Unicode Standard says this: "The Low Surrogate Area does not
177           contain any  character  assignments,  consequently  no  character  code
178           charts or namelists are provided for this area. Surrogates are reserved
179           for use with UTF-16 and then must be used in pairs."  The  code  points
180           that  are  encoded  by  UTF-16  pairs are available as independent code
181           points in the UTF-8 encoding. (In  other  words,  the  whole  surrogate
182           thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
183    
184           If  an  invalid  UTF-8  string  is  passed  to  PCRE,  an  error return
185           (PCRE_ERROR_BADUTF8) is given. In some situations, you may already know
186           that your strings are valid, and therefore want to skip these checks in
187           order to improve performance. If you set the PCRE_NO_UTF8_CHECK flag at
188           compile  time  or at run time, PCRE assumes that the pattern or subject
189           it is given (respectively) contains only valid  UTF-8  codes.  In  this
190           case, it does not diagnose an invalid UTF-8 string.
191    
192           If  you  pass  an  invalid UTF-8 string when PCRE_NO_UTF8_CHECK is set,
193           what happens depends on why the string is invalid. If the  string  con-
194           forms to the "old" definition of UTF-8 (RFC 2279), it is processed as a
195           string of characters in the range 0  to  0x7FFFFFFF.  In  other  words,
196           apart from the initial validity test, PCRE (when in UTF-8 mode) handles
197           strings according to the more liberal rules of RFC  2279.  However,  if
198           the  string does not even conform to RFC 2279, the result is undefined.
199           Your program may crash.
200    
201           If you want to process strings  of  values  in  the  full  range  0  to
202           0x7FFFFFFF,  encoded in a UTF-8-like manner as per the old RFC, you can
203           set PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in
204           this situation, you will have to apply your own validity check.
205    
206         1.  When you set the PCRE_UTF8 flag, the strings passed as patterns and     General comments about UTF-8 mode
        subjects are checked for validity on entry to the  relevant  functions.  
        If an invalid UTF-8 string is passed, an error return is given. In some  
        situations, you may already know  that  your  strings  are  valid,  and  
        therefore want to skip these checks in order to improve performance. If  
        you set the PCRE_NO_UTF8_CHECK flag at compile time  or  at  run  time,  
        PCRE  assumes  that  the  pattern or subject it is given (respectively)  
        contains only valid UTF-8 codes. In this case, it does not diagnose  an  
        invalid  UTF-8 string. If you pass an invalid UTF-8 string to PCRE when  
        PCRE_NO_UTF8_CHECK is set, the results are undefined. Your program  may  
        crash.  
207    
208         2.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a         1.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a
209         two-byte UTF-8 character if the value is greater than 127.         two-byte UTF-8 character if the value is greater than 127.
210    
211         3. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8         2. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8
212         characters for values greater than \177.         characters for values greater than \177.
213    
214         4.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-         3.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-
215         vidual bytes, for example: \x{100}{3}.         vidual bytes, for example: \x{100}{3}.
216    
217         5. The dot metacharacter matches one UTF-8 character instead of a  sin-         4. The dot metacharacter matches one UTF-8 character instead of a  sin-
218         gle byte.         gle byte.
219    
220         6.  The  escape sequence \C can be used to match a single byte in UTF-8         5.  The  escape sequence \C can be used to match a single byte in UTF-8
221         mode, but its use can lead to some strange effects.  This  facility  is         mode, but its use can lead to some strange effects.  This  facility  is
222         not available in the alternative matching function, pcre_dfa_exec().         not available in the alternative matching function, pcre_dfa_exec().
223    
224         7.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly         6.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly
225         test characters of any code value, but the characters that PCRE  recog-         test characters of any code value, but, by default, the characters that
226         nizes  as  digits,  spaces,  or  word characters remain the same set as         PCRE  recognizes  as digits, spaces, or word characters remain the same
227         before, all with values less than 256. This remains true even when PCRE         set as before, all with values less than 256. This  remains  true  even
228         includes  Unicode  property support, because to do otherwise would slow         when  PCRE  is built to include Unicode property support, because to do
229         down PCRE in many common cases. If you really want to test for a  wider         otherwise would slow down PCRE in many common cases. Note in particular
230         sense  of,  say,  "digit",  you must use Unicode property tests such as         that this applies to \b and \B, because they are defined in terms of \w
231         \p{Nd}.         and \W. If you really want to test for a wider sense of, say,  "digit",
232           you  can  use  explicit Unicode property tests such as \p{Nd}. Alterna-
233         8. Similarly, characters that match the POSIX named  character  classes         tively, if you set the PCRE_UCP option,  the  way  that  the  character
234         are all low-valued characters.         escapes  work  is changed so that Unicode properties are used to deter-
235           mine which characters match. There are more details in the  section  on
236         9.  Case-insensitive  matching  applies only to characters whose values         generic character types in the pcrepattern documentation.
237         are less than 128, unless PCRE is built with Unicode property  support.  
238         Even  when  Unicode  property support is available, PCRE still uses its         7.  Similarly,  characters that match the POSIX named character classes
239         own character tables when checking the case of  low-valued  characters,         are all low-valued characters, unless the PCRE_UCP option is set.
240         so  as not to degrade performance.  The Unicode property information is  
241         used only for characters with higher values. Even when Unicode property         8. However, the horizontal and  vertical  whitespace  matching  escapes
242         support is available, PCRE supports case-insensitive matching only when         (\h,  \H,  \v, and \V) do match all the appropriate Unicode characters,
243         there is a one-to-one mapping between a letter's  cases.  There  are  a         whether or not PCRE_UCP is set.
244         small  number  of  many-to-one  mappings in Unicode; these are not sup-  
245         ported by PCRE.         9. Case-insensitive matching applies only to  characters  whose  values
246           are  less than 128, unless PCRE is built with Unicode property support.
247           Even when Unicode property support is available, PCRE  still  uses  its
248           own  character  tables when checking the case of low-valued characters,
249           so as not to degrade performance.  The Unicode property information  is
250           used only for characters with higher values. Furthermore, PCRE supports
251           case-insensitive matching only  when  there  is  a  one-to-one  mapping
252           between  a letter's cases. There are a small number of many-to-one map-
253           pings in Unicode; these are not supported by PCRE.
254    
255    
256  AUTHOR  AUTHOR
# Line 222  AUTHOR Line 266  AUTHOR
266    
267  REVISION  REVISION
268    
269         Last updated: 18 April 2007         Last updated: 13 November 2010
270         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
271  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
272    
273    
# Line 237  NAME Line 281  NAME
281  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
282    
283         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
284         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
285         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
286         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
287         includes  the  standard  ones such as the selection of the installation         the  same  options  can be selected in both Unix-like and non-Unix-like
288         directory) can be obtained by running         environments using the GUI facility of cmake-gui if you are using CMake
289           instead of configure to build PCRE.
290    
291           There  is  a  lot more information about building PCRE in non-Unix-like
292           environments in the file called NON_UNIX_USE, which is part of the PCRE
293           distribution.  You  should consult this file as well as the README file
294           if you are building in a non-Unix-like environment.
295    
296           The complete list of options for configure (which includes the standard
297           ones  such  as  the  selection  of  the  installation directory) can be
298           obtained by running
299    
300           ./configure --help           ./configure --help
301    
# Line 266  C++ SUPPORT Line 320  C++ SUPPORT
320    
321  UTF-8 SUPPORT  UTF-8 SUPPORT
322    
323         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 Unicode character strings, add
324    
325           --enable-utf8           --enable-utf8
326    
327         to  the  configure  command.  Of  itself, this does not make PCRE treat         to  the  configure  command.  Of  itself, this does not make PCRE treat
328         strings as UTF-8. As well as compiling PCRE with this option, you  also         strings as UTF-8. As well as compiling PCRE with this option, you  also
329         have  have to set the PCRE_UTF8 option when you call the pcre_compile()         have  have to set the PCRE_UTF8 option when you call the pcre_compile()
330         function.         or pcre_compile2() functions.
331    
332           If you set --enable-utf8 when compiling in an EBCDIC environment,  PCRE
333           expects its input to be either ASCII or UTF-8 (depending on the runtime
334           option). It is not possible to support both EBCDIC and UTF-8  codes  in
335           the  same  version  of  the  library.  Consequently,  --enable-utf8 and
336           --enable-ebcdic are mutually exclusive.
337    
338    
339  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
# Line 296  UNICODE CHARACTER PROPERTY SUPPORT Line 356  UNICODE CHARACTER PROPERTY SUPPORT
356    
357  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
358    
359         By  default,  PCRE interprets character 10 (linefeed, LF) as indicating         By  default,  PCRE interprets the linefeed (LF) character as indicating
360         the end of a line. This is the normal newline  character  on  Unix-like         the end of a line. This is the normal newline  character  on  Unix-like
361         systems. You can compile PCRE to use character 13 (carriage return, CR)         systems.  You  can compile PCRE to use carriage return (CR) instead, by
362         instead, by adding         adding
363    
364           --enable-newline-is-cr           --enable-newline-is-cr
365    
# Line 322  CODE VALUE OF NEWLINE Line 382  CODE VALUE OF NEWLINE
382    
383         causes PCRE to recognize any Unicode newline sequence.         causes PCRE to recognize any Unicode newline sequence.
384    
385         Whatever line ending convention is selected when PCRE is built  can  be         Whatever  line  ending convention is selected when PCRE is built can be
386         overridden  when  the library functions are called. At build time it is         overridden when the library functions are called. At build time  it  is
387         conventional to use the standard for your operating system.         conventional to use the standard for your operating system.
388    
389    
390    WHAT \R MATCHES
391    
392           By  default,  the  sequence \R in a pattern matches any Unicode newline
393           sequence, whatever has been selected as the line  ending  sequence.  If
394           you specify
395    
396             --enable-bsr-anycrlf
397    
398           the  default  is changed so that \R matches only CR, LF, or CRLF. What-
399           ever is selected when PCRE is built can be overridden when the  library
400           functions are called.
401    
402    
403  BUILDING SHARED AND STATIC LIBRARIES  BUILDING SHARED AND STATIC LIBRARIES
404    
405         The PCRE building process uses libtool to build both shared and  static         The  PCRE building process uses libtool to build both shared and static
406         Unix  libraries by default. You can suppress one of these by adding one         Unix libraries by default. You can suppress one of these by adding  one
407         of         of
408    
409           --disable-shared           --disable-shared
# Line 342  BUILDING SHARED AND STATIC LIBRARIES Line 415  BUILDING SHARED AND STATIC LIBRARIES
415  POSIX MALLOC USAGE  POSIX MALLOC USAGE
416    
417         When PCRE is called through the POSIX interface (see the pcreposix doc-         When PCRE is called through the POSIX interface (see the pcreposix doc-
418         umentation),  additional  working  storage  is required for holding the         umentation), additional working storage is  required  for  holding  the
419         pointers to capturing substrings, because PCRE requires three  integers         pointers  to capturing substrings, because PCRE requires three integers
420         per  substring,  whereas  the POSIX interface provides only two. If the         per substring, whereas the POSIX interface provides only  two.  If  the
421         number of expected substrings is small, the wrapper function uses space         number of expected substrings is small, the wrapper function uses space
422         on the stack, because this is faster than using malloc() for each call.         on the stack, because this is faster than using malloc() for each call.
423         The default threshold above which the stack is no longer used is 10; it         The default threshold above which the stack is no longer used is 10; it
# Line 357  POSIX MALLOC USAGE Line 430  POSIX MALLOC USAGE
430    
431  HANDLING VERY LARGE PATTERNS  HANDLING VERY LARGE PATTERNS
432    
433         Within  a  compiled  pattern,  offset values are used to point from one         Within a compiled pattern, offset values are used  to  point  from  one
434         part to another (for example, from an opening parenthesis to an  alter-         part  to another (for example, from an opening parenthesis to an alter-
435         nation  metacharacter).  By default, two-byte values are used for these         nation metacharacter). By default, two-byte values are used  for  these
436         offsets, leading to a maximum size for a  compiled  pattern  of  around         offsets,  leading  to  a  maximum size for a compiled pattern of around
437         64K.  This  is sufficient to handle all but the most gigantic patterns.         64K. This is sufficient to handle all but the most  gigantic  patterns.
438         Nevertheless, some people do want to process enormous patterns,  so  it         Nevertheless,  some  people do want to process truyl enormous patterns,
439         is  possible  to compile PCRE to use three-byte or four-byte offsets by         so it is possible to compile PCRE to use three-byte or  four-byte  off-
440         adding a setting such as         sets by adding a setting such as
441    
442           --with-link-size=3           --with-link-size=3
443    
444         to the configure command. The value given must be 2,  3,  or  4.  Using         to  the  configure  command.  The value given must be 2, 3, or 4. Using
445         longer  offsets slows down the operation of PCRE because it has to load         longer offsets slows down the operation of PCRE because it has to  load
446         additional bytes when handling them.         additional bytes when handling them.
447    
448    
449  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
450    
451         When matching with the pcre_exec() function, PCRE implements backtrack-         When matching with the pcre_exec() function, PCRE implements backtrack-
452         ing  by  making recursive calls to an internal function called match().         ing by making recursive calls to an internal function  called  match().
453         In environments where the size of the stack is limited,  this  can  se-         In  environments  where  the size of the stack is limited, this can se-
454         verely  limit  PCRE's operation. (The Unix environment does not usually         verely limit PCRE's operation. (The Unix environment does  not  usually
455         suffer from this problem, but it may sometimes be necessary to increase         suffer from this problem, but it may sometimes be necessary to increase
456         the  maximum  stack size.  There is a discussion in the pcrestack docu-         the maximum stack size.  There is a discussion in the  pcrestack  docu-
457         mentation.) An alternative approach to recursion that uses memory  from         mentation.)  An alternative approach to recursion that uses memory from
458         the  heap  to remember data, instead of using recursive function calls,         the heap to remember data, instead of using recursive  function  calls,
459         has been implemented to work round the problem of limited  stack  size.         has  been  implemented to work round the problem of limited stack size.
460         If you want to build a version of PCRE that works this way, add         If you want to build a version of PCRE that works this way, add
461    
462           --disable-stack-for-recursion           --disable-stack-for-recursion
463    
464         to  the  configure  command. With this configuration, PCRE will use the         to the configure command. With this configuration, PCRE  will  use  the
465         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
466         ment  functions.  Separate  functions are provided because the usage is         ment functions. By default these point to malloc() and free(), but  you
467         very predictable: the block sizes requested are always  the  same,  and         can replace the pointers so that your own functions are used instead.
468         the  blocks  are always freed in reverse order. A calling program might  
469         be able to implement optimized functions that perform better  than  the         Separate  functions  are  provided  rather  than  using pcre_malloc and
470         standard  malloc()  and  free()  functions.  PCRE  runs noticeably more         pcre_free because the  usage  is  very  predictable:  the  block  sizes
471         slowly when built in this way. This option affects only the pcre_exec()         requested  are  always  the  same,  and  the blocks are always freed in
472         function; it is not relevant for the the pcre_dfa_exec() function.         reverse order. A calling program might be able to  implement  optimized
473           functions  that  perform  better  than  malloc()  and free(). PCRE runs
474           noticeably more slowly when built in this way. This option affects only
475           the pcre_exec() function; it is not relevant for pcre_dfa_exec().
476    
477    
478  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
# Line 451  USING EBCDIC CODE Line 527  USING EBCDIC CODE
527    
528         PCRE  assumes  by  default that it will run in an environment where the         PCRE  assumes  by  default that it will run in an environment where the
529         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
530         PCRE  can,  however,  be  compiled  to  run in an EBCDIC environment by         This  is  the  case for most computer operating systems. PCRE can, how-
531         adding         ever, be compiled to run in an EBCDIC environment by adding
532    
533           --enable-ebcdic           --enable-ebcdic
534    
535         to the configure command. This setting implies --enable-rebuild-charta-         to the configure command. This setting implies --enable-rebuild-charta-
536         bles.         bles.  You  should  only  use  it if you know that you are in an EBCDIC
537           environment (for example,  an  IBM  mainframe  operating  system).  The
538           --enable-ebcdic option is incompatible with --enable-utf8.
539    
540    
541    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
542    
543           By default, pcregrep reads all files as plain text. You can build it so
544           that it recognizes files whose names end in .gz or .bz2, and reads them
545           with libz or libbz2, respectively, by adding one or both of
546    
547             --enable-pcregrep-libz
548             --enable-pcregrep-libbz2
549    
550           to the configure command. These options naturally require that the rel-
551           evant libraries are installed on your system. Configuration  will  fail
552           if they are not.
553    
554    
555    PCRETEST OPTION FOR LIBREADLINE SUPPORT
556    
557           If you add
558    
559             --enable-pcretest-libreadline
560    
561           to  the  configure  command,  pcretest  is  linked with the libreadline
562           library, and when its input is from a terminal, it reads it  using  the
563           readline() function. This provides line-editing and history facilities.
564           Note that libreadline is GPL-licensed, so if you distribute a binary of
565           pcretest linked in this way, there may be licensing issues.
566    
567           Setting  this  option  causes  the -lreadline option to be added to the
568           pcretest build. In many operating environments with  a  sytem-installed
569           libreadline this is sufficient. However, in some environments (e.g.  if
570           an unmodified distribution version of readline is in use),  some  extra
571           configuration  may  be necessary. The INSTALL file for libreadline says
572           this:
573    
574             "Readline uses the termcap functions, but does not link with the
575             termcap or curses library itself, allowing applications which link
576             with readline the to choose an appropriate library."
577    
578           If your environment has not been set up so that an appropriate  library
579           is automatically included, you may need to add something like
580    
581             LIBS="-ncurses"
582    
583           immediately before the configure command.
584    
585    
586  SEE ALSO  SEE ALSO
# Line 474  AUTHOR Line 597  AUTHOR
597    
598  REVISION  REVISION
599    
600         Last updated: 16 April 2007         Last updated: 29 September 2009
601         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2009 University of Cambridge.
602  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
603    
604    
# Line 562  THE ALTERNATIVE MATCHING ALGORITHM Line 685  THE ALTERNATIVE MATCHING ALGORITHM
685         though  it is not implemented as a traditional finite state machine (it         though  it is not implemented as a traditional finite state machine (it
686         keeps multiple states active simultaneously).         keeps multiple states active simultaneously).
687    
688           Although the general principle of this matching algorithm  is  that  it
689           scans  the subject string only once, without backtracking, there is one
690           exception: when a lookaround assertion is encountered,  the  characters
691           following  or  preceding  the  current  point  have to be independently
692           inspected.
693    
694         The scan continues until either the end of the subject is  reached,  or         The scan continues until either the end of the subject is  reached,  or
695         there  are  no more unterminated paths. At this point, terminated paths         there  are  no more unterminated paths. At this point, terminated paths
696         represent the different matching possibilities (if there are none,  the         represent the different matching possibilities (if there are none,  the
697         match  has  failed).   Thus,  if there is more than one possible match,         match  has  failed).   Thus,  if there is more than one possible match,
698         this algorithm finds all of them, and in particular, it finds the long-         this algorithm finds all of them, and in particular, it finds the long-
699         est.  In PCRE, there is an option to stop the algorithm after the first         est.  The  matches are returned in decreasing order of length. There is
700         match (which is necessarily the shortest) has been found.         an option to stop the algorithm after the first match (which is  neces-
701           sarily the shortest) is found.
702    
703         Note that all the matches that are found start at the same point in the         Note that all the matches that are found start at the same point in the
704         subject. If the pattern         subject. If the pattern
705    
706           cat(er(pillar)?)           cat(er(pillar)?)?
707    
708         is  matched  against the string "the caterpillar catchment", the result         is matched against the string "the caterpillar catchment",  the  result
709         will be the three strings "cat", "cater", and "caterpillar" that  start         will  be the three strings "caterpillar", "cater", and "cat" that start
710         at the fourth character of the subject. The algorithm does not automat-         at the fifth character of the subject. The algorithm does not automati-
711         ically move on to find matches that start at later positions.         cally move on to find matches that start at later positions.
712    
713         There are a number of features of PCRE regular expressions that are not         There are a number of features of PCRE regular expressions that are not
714         supported by the alternative matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
715    
716         1.  Because  the  algorithm  finds  all possible matches, the greedy or         1. Because the algorithm finds all  possible  matches,  the  greedy  or
717         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
718         ungreedy quantifiers are treated in exactly the same way. However, pos-         ungreedy quantifiers are treated in exactly the same way. However, pos-
719         sessive quantifiers can make a difference when what follows could  also         sessive  quantifiers can make a difference when what follows could also
720         match what is quantified, for example in a pattern like this:         match what is quantified, for example in a pattern like this:
721    
722           ^a++\w!           ^a++\w!
723    
724         This  pattern matches "aaab!" but not "aaa!", which would be matched by         This pattern matches "aaab!" but not "aaa!", which would be matched  by
725         a non-possessive quantifier. Similarly, if an atomic group is  present,         a  non-possessive quantifier. Similarly, if an atomic group is present,
726         it  is matched as if it were a standalone pattern at the current point,         it is matched as if it were a standalone pattern at the current  point,
727         and the longest match is then "locked in" for the rest of  the  overall         and  the  longest match is then "locked in" for the rest of the overall
728         pattern.         pattern.
729    
730         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
731         is not straightforward to keep track of  captured  substrings  for  the         is  not  straightforward  to  keep track of captured substrings for the
732         different  matching  possibilities,  and  PCRE's implementation of this         different matching possibilities, and  PCRE's  implementation  of  this
733         algorithm does not attempt to do this. This means that no captured sub-         algorithm does not attempt to do this. This means that no captured sub-
734         strings are available.         strings are available.
735    
736         3.  Because no substrings are captured, back references within the pat-         3. Because no substrings are captured, back references within the  pat-
737         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
738    
739         4. For the same reason, conditional expressions that use  a  backrefer-         4.  For  the same reason, conditional expressions that use a backrefer-
740         ence  as  the  condition or test for a specific group recursion are not         ence as the condition or test for a specific group  recursion  are  not
741         supported.         supported.
742    
743         5. Because many paths through the tree may be  active,  the  \K  escape         5.  Because  many  paths  through the tree may be active, the \K escape
744         sequence, which resets the start of the match when encountered (but may         sequence, which resets the start of the match when encountered (but may
745         be on some paths and not on others), is not  supported.  It  causes  an         be  on  some  paths  and not on others), is not supported. It causes an
746         error if encountered.         error if encountered.
747    
748         6.  Callouts  are  supported, but the value of the capture_top field is         6. Callouts are supported, but the value of the  capture_top  field  is
749         always 1, and the value of the capture_last field is always -1.         always 1, and the value of the capture_last field is always -1.
750    
751         7.  The \C escape sequence, which (in the standard algorithm) matches a         7.  The \C escape sequence, which (in the standard algorithm) matches a
752         single  byte, even in UTF-8 mode, is not supported because the alterna-         single byte, even in UTF-8 mode, is not supported because the  alterna-
753         tive algorithm moves through the subject  string  one  character  at  a         tive  algorithm  moves  through  the  subject string one character at a
754         time, for all active paths through the tree.         time, for all active paths through the tree.
755    
756           8. Except for (*FAIL), the backtracking control verbs such as  (*PRUNE)
757           are  not  supported.  (*FAIL)  is supported, and behaves like a failing
758           negative assertion.
759    
760    
761  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
762    
763         Using  the alternative matching algorithm provides the following advan-         Using the alternative matching algorithm provides the following  advan-
764         tages:         tages:
765    
766         1. All possible matches (at a single point in the subject) are automat-         1. All possible matches (at a single point in the subject) are automat-
767         ically  found,  and  in particular, the longest match is found. To find         ically found, and in particular, the longest match is  found.  To  find
768         more than one match using the standard algorithm, you have to do kludgy         more than one match using the standard algorithm, you have to do kludgy
769         things with callouts.         things with callouts.
770    
771         2.  There is much better support for partial matching. The restrictions         2. Because the alternative algorithm  scans  the  subject  string  just
772         on the content of the pattern that apply when using the standard  algo-         once,  and  never  needs to backtrack, it is possible to pass very long
773         rithm  for  partial matching do not apply to the alternative algorithm.         subject strings to the matching function in  several  pieces,  checking
774         For non-anchored patterns, the starting position of a partial match  is         for  partial  matching  each time. Although it is possible to do multi-
775         available.         segment matching using the standard algorithm (pcre_exec()), by retain-
776           ing  partially matched substrings, it is more complicated. The pcrepar-
777         3.  Because  the  alternative  algorithm  scans the subject string just         tial documentation gives details  of  partial  matching  and  discusses
778         once, and never needs to backtrack, it is possible to  pass  very  long         multi-segment matching.
        subject  strings  to  the matching function in several pieces, checking  
        for partial matching each time.  
779    
780    
781  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
782    
783         The alternative algorithm suffers from a number of disadvantages:         The alternative algorithm suffers from a number of disadvantages:
784    
785         1. It is substantially slower than  the  standard  algorithm.  This  is         1.  It  is  substantially  slower  than the standard algorithm. This is
786         partly  because  it has to search for all possible matches, but is also         partly because it has to search for all possible matches, but  is  also
787         because it is less susceptible to optimization.         because it is less susceptible to optimization.
788    
789         2. Capturing parentheses and back references are not supported.         2. Capturing parentheses and back references are not supported.
# Line 669  AUTHOR Line 801  AUTHOR
801    
802  REVISION  REVISION
803    
804         Last updated: 29 May 2007         Last updated: 17 November 2010
805         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
806  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
807    
808    
# Line 777  PCRE API OVERVIEW Line 909  PCRE API OVERVIEW
909         bers for the library.  Applications can use these  to  include  support         bers for the library.  Applications can use these  to  include  support
910         for different releases of PCRE.         for different releases of PCRE.
911    
912           In a Windows environment, if you want to statically link an application
913           program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC
914           before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-
915           loc()   and   pcre_free()   exported   functions   will   be   declared
916           __declspec(dllimport), with unwanted results.
917    
918         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
919         pcre_exec() are used for compiling and matching regular expressions  in         pcre_exec() are used for compiling and matching regular expressions  in
920         a  Perl-compatible  manner. A sample program that demonstrates the sim-         a  Perl-compatible  manner. A sample program that demonstrates the sim-
921         plest way of using them is provided in the file  called  pcredemo.c  in         plest way of using them is provided in the file  called  pcredemo.c  in
922         the  source distribution. The pcresample documentation describes how to         the PCRE source distribution. A listing of this program is given in the
923         run it.         pcredemo documentation, and the pcresample documentation describes  how
924           to compile and run it.
925    
926         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
927         ble,  is  also provided. This uses a different algorithm for the match-         ble, is also provided. This uses a different algorithm for  the  match-
928         ing. The alternative algorithm finds all possible matches (at  a  given         ing.  The  alternative algorithm finds all possible matches (at a given
929         point  in  the subject), and scans the subject just once. However, this         point in the subject), and scans the subject just  once  (unless  there
930         algorithm does not return captured substrings. A description of the two         are  lookbehind  assertions).  However,  this algorithm does not return
931         matching  algorithms and their advantages and disadvantages is given in         captured substrings. A description of the two matching  algorithms  and
932         the pcrematching documentation.         their  advantages  and disadvantages is given in the pcrematching docu-
933           mentation.
934    
935         In addition to the main compiling and  matching  functions,  there  are         In addition to the main compiling and  matching  functions,  there  are
936         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
# Line 866  NEWLINES Line 1006  NEWLINES
1006         dard. When PCRE is run, the default can be overridden,  either  when  a         dard. When PCRE is run, the default can be overridden,  either  when  a
1007         pattern is compiled, or when it is matched.         pattern is compiled, or when it is matched.
1008    
1009           At compile time, the newline convention can be specified by the options
1010           argument of pcre_compile(), or it can be specified by special  text  at
1011           the start of the pattern itself; this overrides any other settings. See
1012           the pcrepattern page for details of the special character sequences.
1013    
1014         In the PCRE documentation the word "newline" is used to mean "the char-         In the PCRE documentation the word "newline" is used to mean "the char-
1015         acter or pair of characters that indicate a line break". The choice  of         acter  or pair of characters that indicate a line break". The choice of
1016         newline  convention  affects  the  handling of the dot, circumflex, and         newline convention affects the handling of  the  dot,  circumflex,  and
1017         dollar metacharacters, the handling of #-comments in /x mode, and, when         dollar metacharacters, the handling of #-comments in /x mode, and, when
1018         CRLF  is a recognized line ending sequence, the match position advance-         CRLF is a recognized line ending sequence, the match position  advance-
1019         ment for a non-anchored pattern. The choice of newline convention  does         ment for a non-anchored pattern. There is more detail about this in the
1020         not affect the interpretation of the \n or \r escape sequences.         section on pcre_exec() options below.
1021    
1022           The choice of newline convention does not affect the interpretation  of
1023           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
1024           which is controlled in a similar way, but by separate options.
1025    
1026    
1027  MULTITHREADING  MULTITHREADING
1028    
1029         The  PCRE  functions  can be used in multi-threading applications, with         The PCRE functions can be used in  multi-threading  applications,  with
1030         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
1031         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the         pcre_malloc, pcre_free, pcre_stack_malloc, and pcre_stack_free, and the
1032         callout function pointed to by pcre_callout, are shared by all threads.         callout function pointed to by pcre_callout, are shared by all threads.
# Line 926  CHECKING BUILD-TIME OPTIONS Line 1075  CHECKING BUILD-TIME OPTIONS
1075         The output is an integer whose value specifies  the  default  character         The output is an integer whose value specifies  the  default  character
1076         sequence  that is recognized as meaning "newline". The four values that         sequence  that is recognized as meaning "newline". The four values that
1077         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
1078         and  -1  for  ANY. The default should normally be the standard sequence         and  -1  for  ANY.  Though they are derived from ASCII, the same values
1079         for your operating system.         are returned in EBCDIC environments. The default should normally corre-
1080           spond to the standard sequence for your operating system.
1081    
1082             PCRE_CONFIG_BSR
1083    
1084           The output is an integer whose value indicates what character sequences
1085           the \R escape sequence matches by default. A value of 0 means  that  \R
1086           matches  any  Unicode  line ending sequence; a value of 1 means that \R
1087           matches only CR, LF, or CRLF. The default can be overridden when a pat-
1088           tern is compiled or matched.
1089    
1090           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
1091    
1092         The output is an integer that contains the number  of  bytes  used  for         The  output  is  an  integer that contains the number of bytes used for
1093         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
1094         4. Larger values allow larger regular expressions to  be  compiled,  at         4.  Larger  values  allow larger regular expressions to be compiled, at
1095         the  expense  of  slower matching. The default value of 2 is sufficient         the expense of slower matching. The default value of  2  is  sufficient
1096         for all but the most massive patterns, since  it  allows  the  compiled         for  all  but  the  most massive patterns, since it allows the compiled
1097         pattern to be up to 64K in size.         pattern to be up to 64K in size.
1098    
1099           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
1100    
1101         The  output  is  an integer that contains the threshold above which the         The output is an integer that contains the threshold  above  which  the
1102         POSIX interface uses malloc() for output vectors. Further  details  are         POSIX  interface  uses malloc() for output vectors. Further details are
1103         given in the pcreposix documentation.         given in the pcreposix documentation.
1104    
1105           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
1106    
1107         The output is an integer that gives the default limit for the number of         The output is a long integer that gives the default limit for the  num-
1108         internal matching function calls in a  pcre_exec()  execution.  Further         ber  of  internal  matching  function calls in a pcre_exec() execution.
1109         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
1110    
1111           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
1112    
1113         The  output is an integer that gives the default limit for the depth of         The output is a long integer that gives the default limit for the depth
1114         recursion when calling the internal matching function in a  pcre_exec()         of   recursion  when  calling  the  internal  matching  function  in  a
1115         execution. Further details are given with pcre_exec() below.         pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
1116           below.
1117    
1118           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
1119    
# Line 981  COMPILING A PATTERN Line 1140  COMPILING A PATTERN
1140         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1141         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1142         the  two interfaces is that pcre_compile2() has an additional argument,         the  two interfaces is that pcre_compile2() has an additional argument,
1143         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr, via which a numerical error  code  can  be  returned.  To
1144           avoid  too  much repetition, we refer just to pcre_compile() below, but
1145           the information applies equally to pcre_compile2().
1146    
1147         The pattern is a C string terminated by a binary zero, and is passed in         The pattern is a C string terminated by a binary zero, and is passed in
1148         the  pattern  argument.  A  pointer to a single block of memory that is         the  pattern  argument.  A  pointer to a single block of memory that is
# Line 998  COMPILING A PATTERN Line 1159  COMPILING A PATTERN
1159    
1160         The options argument contains various bit settings that affect the com-         The options argument contains various bit settings that affect the com-
1161         pilation. It should be zero if no options are required.  The  available         pilation. It should be zero if no options are required.  The  available
1162         options  are  described  below. Some of them, in particular, those that         options  are  described  below. Some of them (in particular, those that
1163         are compatible with Perl, can also be set and  unset  from  within  the         are compatible with Perl, but some others as well) can also be set  and
1164         pattern  (see  the  detailed  description in the pcrepattern documenta-         unset  from  within  the  pattern  (see the detailed description in the
1165         tion). For these options, the contents of the options  argument  speci-         pcrepattern documentation). For those options that can be different  in
1166         fies  their initial settings at the start of compilation and execution.         different  parts  of  the pattern, the contents of the options argument
1167         The PCRE_ANCHORED and PCRE_NEWLINE_xxx options can be set at  the  time         specifies their settings at the start of compilation and execution. The
1168         of matching as well as at compile time.         PCRE_ANCHORED,  PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK, and
1169           PCRE_NO_START_OPT options can be set at the time of matching as well as
1170           at compile time.
1171    
1172         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1173         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
1174         sets the variable pointed to by errptr to point to a textual error mes-         sets the variable pointed to by errptr to point to a textual error mes-
1175         sage. This is a static string that is part of the library. You must not         sage. This is a static string that is part of the library. You must not
1176         try to free it. The offset from the start of the pattern to the charac-         try  to  free  it. The offset from the start of the pattern to the byte
1177         ter where the error was discovered is placed in the variable pointed to         that was being processed when the error was discovered is placed in the
1178         by  erroffset,  which must not be NULL. If it is, an immediate error is         variable  pointed to by erroffset, which must not be NULL. If it is, an
1179         given.         immediate error is given. Some errors are not detected until checks are
1180           carried  out  when the whole pattern has been scanned; in this case the
1181           offset is set to the end of the pattern.
1182    
1183           Note that the offset is in bytes, not characters, even in  UTF-8  mode.
1184           It  may  point  into the middle of a UTF-8 character (for example, when
1185           PCRE_ERROR_BADUTF8 is returned for an invalid UTF-8 string).
1186    
1187         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-
1188         codeptr  argument is not NULL, a non-zero error code number is returned         codeptr  argument is not NULL, a non-zero error code number is returned
# Line 1058  COMPILING A PATTERN Line 1227  COMPILING A PATTERN
1227         all with number 255, before each pattern item. For  discussion  of  the         all with number 255, before each pattern item. For  discussion  of  the
1228         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1229    
1230             PCRE_BSR_ANYCRLF
1231             PCRE_BSR_UNICODE
1232    
1233           These options (which are mutually exclusive) control what the \R escape
1234           sequence matches. The choice is either to match only CR, LF,  or  CRLF,
1235           or to match any Unicode newline sequence. The default is specified when
1236           PCRE is built. It can be overridden from within the pattern, or by set-
1237           ting an option when a compiled pattern is matched.
1238    
1239           PCRE_CASELESS           PCRE_CASELESS
1240    
1241         If  this  bit is set, letters in the pattern match both upper and lower         If  this  bit is set, letters in the pattern match both upper and lower
# Line 1082  COMPILING A PATTERN Line 1260  COMPILING A PATTERN
1260    
1261           PCRE_DOTALL           PCRE_DOTALL
1262    
1263         If this bit is set, a dot metacharater in the pattern matches all char-         If  this bit is set, a dot metacharacter in the pattern matches a char-
1264         acters, including those that indicate newline. Without it, a  dot  does         acter of any value, including one that indicates a newline. However, it
1265         not  match  when  the  current position is at a newline. This option is         only  ever  matches  one character, even if newlines are coded as CRLF.
1266         equivalent to Perl's /s option, and it can be changed within a  pattern         Without this option, a dot does not match when the current position  is
1267         by  a (?s) option setting. A negative class such as [^a] always matches         at a newline. This option is equivalent to Perl's /s option, and it can
1268         newline characters, independent of the setting of this option.         be changed within a pattern by a (?s) option setting. A negative  class
1269           such as [^a] always matches newline characters, independent of the set-
1270           ting of this option.
1271    
1272           PCRE_DUPNAMES           PCRE_DUPNAMES
1273    
# Line 1107  COMPILING A PATTERN Line 1287  COMPILING A PATTERN
1287         option,  and  it  can be changed within a pattern by a (?x) option set-         option,  and  it  can be changed within a pattern by a (?x) option set-
1288         ting.         ting.
1289    
1290         This option makes it possible to include  comments  inside  complicated         Which characters are interpreted  as  newlines  is  controlled  by  the
1291         patterns.   Note,  however,  that this applies only to data characters.         options  passed to pcre_compile() or by a special sequence at the start
1292         Whitespace  characters  may  never  appear  within  special   character         of the pattern, as described in the section entitled  "Newline  conven-
1293         sequences  in  a  pattern,  for  example  within the sequence (?( which         tions" in the pcrepattern documentation. Note that the end of this type
1294         introduces a conditional subpattern.         of comment is  a  literal  newline  sequence  in  the  pattern;  escape
1295           sequences that happen to represent a newline do not count.
1296    
1297           This  option  makes  it possible to include comments inside complicated
1298           patterns.  Note, however, that this applies only  to  data  characters.
1299           Whitespace   characters  may  never  appear  within  special  character
1300           sequences in a pattern, for example within the sequence (?( that intro-
1301           duces a conditional subpattern.
1302    
1303           PCRE_EXTRA           PCRE_EXTRA
1304    
1305         This option was invented in order to turn on  additional  functionality         This  option  was invented in order to turn on additional functionality
1306         of  PCRE  that  is  incompatible with Perl, but it is currently of very         of PCRE that is incompatible with Perl, but it  is  currently  of  very
1307         little use. When set, any backslash in a pattern that is followed by  a         little  use. When set, any backslash in a pattern that is followed by a
1308         letter  that  has  no  special  meaning causes an error, thus reserving         letter that has no special meaning  causes  an  error,  thus  reserving
1309         these combinations for future expansion. By  default,  as  in  Perl,  a         these  combinations  for  future  expansion.  By default, as in Perl, a
1310         backslash  followed by a letter with no special meaning is treated as a         backslash followed by a letter with no special meaning is treated as  a
1311         literal. (Perl can, however, be persuaded to give a warning for  this.)         literal. (Perl can, however, be persuaded to give an error for this, by
1312         There  are  at  present no other features controlled by this option. It         running it with the -w option.) There are at present no other  features
1313         can also be set by a (?X) option setting within a pattern.         controlled  by this option. It can also be set by a (?X) option setting
1314           within a pattern.
1315    
1316           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1317    
# Line 1131  COMPILING A PATTERN Line 1319  COMPILING A PATTERN
1319         before  or  at  the  first  newline  in  the subject string, though the         before  or  at  the  first  newline  in  the subject string, though the
1320         matched text may continue over the newline.         matched text may continue over the newline.
1321    
1322             PCRE_JAVASCRIPT_COMPAT
1323    
1324           If this option is set, PCRE's behaviour is changed in some ways so that
1325           it  is  compatible with JavaScript rather than Perl. The changes are as
1326           follows:
1327    
1328           (1) A lone closing square bracket in a pattern  causes  a  compile-time
1329           error,  because this is illegal in JavaScript (by default it is treated
1330           as a data character). Thus, the pattern AB]CD becomes illegal when this
1331           option is set.
1332    
1333           (2)  At run time, a back reference to an unset subpattern group matches
1334           an empty string (by default this causes the current  matching  alterna-
1335           tive  to  fail). A pattern such as (\1)(a) succeeds when this option is
1336           set (assuming it can find an "a" in the subject), whereas it  fails  by
1337           default, for Perl compatibility.
1338    
1339           PCRE_MULTILINE           PCRE_MULTILINE
1340    
1341         By default, PCRE treats the subject string as consisting  of  a  single         By  default,  PCRE  treats the subject string as consisting of a single
1342         line  of characters (even if it actually contains newlines). The "start         line of characters (even if it actually contains newlines). The  "start
1343         of line" metacharacter (^) matches only at the  start  of  the  string,         of  line"  metacharacter  (^)  matches only at the start of the string,
1344         while  the  "end  of line" metacharacter ($) matches only at the end of         while the "end of line" metacharacter ($) matches only at  the  end  of
1345         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY         the string, or before a terminating newline (unless PCRE_DOLLAR_ENDONLY
1346         is set). This is the same as Perl.         is set). This is the same as Perl.
1347    
1348         When  PCRE_MULTILINE  it  is set, the "start of line" and "end of line"         When PCRE_MULTILINE it is set, the "start of line" and  "end  of  line"
1349         constructs match immediately following or immediately  before  internal         constructs  match  immediately following or immediately before internal
1350         newlines  in  the  subject string, respectively, as well as at the very         newlines in the subject string, respectively, as well as  at  the  very
1351         start and end. This is equivalent to Perl's /m option, and  it  can  be         start  and  end.  This is equivalent to Perl's /m option, and it can be
1352         changed within a pattern by a (?m) option setting. If there are no new-         changed within a pattern by a (?m) option setting. If there are no new-
1353         lines in a subject string, or no occurrences of ^ or $  in  a  pattern,         lines  in  a  subject string, or no occurrences of ^ or $ in a pattern,
1354         setting PCRE_MULTILINE has no effect.         setting PCRE_MULTILINE has no effect.
1355    
1356           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
# Line 1154  COMPILING A PATTERN Line 1359  COMPILING A PATTERN
1359           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
1360           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1361    
1362         These  options  override the default newline definition that was chosen         These options override the default newline definition that  was  chosen
1363         when PCRE was built. Setting the first or the second specifies  that  a         when  PCRE  was built. Setting the first or the second specifies that a
1364         newline  is  indicated  by a single character (CR or LF, respectively).         newline is indicated by a single character (CR  or  LF,  respectively).
1365         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the         Setting  PCRE_NEWLINE_CRLF specifies that a newline is indicated by the
1366         two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies         two-character CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF  specifies
1367         that any of the three preceding sequences should be recognized. Setting         that any of the three preceding sequences should be recognized. Setting
1368         PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be         PCRE_NEWLINE_ANY specifies that any Unicode newline sequence should  be
1369         recognized. The Unicode newline sequences are the three just mentioned,         recognized. The Unicode newline sequences are the three just mentioned,
1370         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,         plus the single characters VT (vertical  tab,  U+000B),  FF  (formfeed,
1371         U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS         U+000C),  NEL  (next line, U+0085), LS (line separator, U+2028), and PS
1372         (paragraph  separator,  U+2029).  The  last  two are recognized only in         (paragraph separator, U+2029). The last  two  are  recognized  only  in
1373         UTF-8 mode.         UTF-8 mode.
1374    
1375         The newline setting in the  options  word  uses  three  bits  that  are         The  newline  setting  in  the  options  word  uses three bits that are
1376         treated as a number, giving eight possibilities. Currently only six are         treated as a number, giving eight possibilities. Currently only six are
1377         used (default plus the five values above). This means that if  you  set         used  (default  plus the five values above). This means that if you set
1378         more  than one newline option, the combination may or may not be sensi-         more than one newline option, the combination may or may not be  sensi-
1379         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1380         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and         PCRE_NEWLINE_CRLF, but other combinations may yield unused numbers  and
1381         cause an error.         cause an error.
1382    
1383         The only time that a line break is specially recognized when  compiling         The  only  time  that a line break in a pattern is specially recognized
1384         a  pattern  is  if  PCRE_EXTENDED  is set, and an unescaped # outside a         when compiling is when PCRE_EXTENDED is set. CR and LF  are  whitespace
1385         character class is encountered. This indicates  a  comment  that  lasts         characters,  and so are ignored in this mode. Also, an unescaped # out-
1386         until  after the next line break sequence. In other circumstances, line         side a character class indicates a comment that lasts until  after  the
1387         break  sequences  are  treated  as  literal  data,   except   that   in         next  line break sequence. In other circumstances, line break sequences
1388         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         in patterns are treated as literal data.
        and are therefore ignored.  
1389    
1390         The newline option that is set at compile time becomes the default that         The newline option that is set at compile time becomes the default that
1391         is  used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.         is used for pcre_exec() and pcre_dfa_exec(), but it can be overridden.
1392    
1393           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1394    
1395         If this option is set, it disables the use of numbered capturing paren-         If this option is set, it disables the use of numbered capturing paren-
1396         theses  in the pattern. Any opening parenthesis that is not followed by         theses in the pattern. Any opening parenthesis that is not followed  by
1397         ? behaves as if it were followed by ?: but named parentheses can  still         ?  behaves as if it were followed by ?: but named parentheses can still
1398         be  used  for  capturing  (and  they acquire numbers in the usual way).         be used for capturing (and they acquire  numbers  in  the  usual  way).
1399         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1400    
1401             NO_START_OPTIMIZE
1402    
1403           This  is an option that acts at matching time; that is, it is really an
1404           option for pcre_exec() or pcre_dfa_exec(). If  it  is  set  at  compile
1405           time,  it is remembered with the compiled pattern and assumed at match-
1406           ing time. For details  see  the  discussion  of  PCRE_NO_START_OPTIMIZE
1407           below.
1408    
1409             PCRE_UCP
1410    
1411           This  option changes the way PCRE processes \B, \b, \D, \d, \S, \s, \W,
1412           \w, and some of the POSIX character classes.  By  default,  only  ASCII
1413           characters  are  recognized, but if PCRE_UCP is set, Unicode properties
1414           are used instead to classify characters. More details are given in  the
1415           section  on generic character types in the pcrepattern page. If you set
1416           PCRE_UCP, matching one of the items it affects takes much  longer.  The
1417           option  is  available only if PCRE has been compiled with Unicode prop-
1418           erty support.
1419    
1420           PCRE_UNGREEDY           PCRE_UNGREEDY
1421    
1422         This option inverts the "greediness" of the quantifiers  so  that  they         This option inverts the "greediness" of the quantifiers  so  that  they
# Line 1213  COMPILING A PATTERN Line 1436  COMPILING A PATTERN
1436           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1437    
1438         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
1439         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically  checked.  There  is  a  discussion about the validity of
1440         pcre_compile() returns an error. If you already know that your  pattern         UTF-8 strings in the main pcre page. If an invalid  UTF-8  sequence  of
1441         is  valid, and you want to skip this check for performance reasons, you         bytes  is  found,  pcre_compile() returns an error. If you already know
1442         can set the PCRE_NO_UTF8_CHECK option. When it is set,  the  effect  of         that your pattern is valid, and you want to skip this check for perfor-
1443         passing an invalid UTF-8 string as a pattern is undefined. It may cause         mance  reasons,  you  can set the PCRE_NO_UTF8_CHECK option. When it is
1444         your program to crash.  Note that this option can  also  be  passed  to         set, the effect of passing an invalid UTF-8  string  as  a  pattern  is
1445         pcre_exec()  and pcre_dfa_exec(), to suppress the UTF-8 validity check-         undefined.  It  may  cause your program to crash. Note that this option
1446         ing of subject strings.         can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress  the
1447           UTF-8 validity checking of subject strings.
1448    
1449    
1450  COMPILATION ERROR CODES  COMPILATION ERROR CODES
1451    
1452         The following table lists the error  codes  than  may  be  returned  by         The  following  table  lists  the  error  codes than may be returned by
1453         pcre_compile2(),  along with the error messages that may be returned by         pcre_compile2(), along with the error messages that may be returned  by
1454         both compiling functions. As PCRE has developed, some error codes  have         both  compiling functions. As PCRE has developed, some error codes have
1455         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.
1456    
1457            0  no error            0  no error
# Line 1242  COMPILATION ERROR CODES Line 1466  COMPILATION ERROR CODES
1466            9  nothing to repeat            9  nothing to repeat
1467           10  [this code is not in use]           10  [this code is not in use]
1468           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1469           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1470           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1471           14  missing )           14  missing )
1472           15  reference to non-existent subpattern           15  reference to non-existent subpattern
# Line 1250  COMPILATION ERROR CODES Line 1474  COMPILATION ERROR CODES
1474           17  unknown option bit(s) set           17  unknown option bit(s) set
1475           18  missing ) after comment           18  missing ) after comment
1476           19  [this code is not in use]           19  [this code is not in use]
1477           20  regular expression too large           20  regular expression is too large
1478           21  failed to get memory           21  failed to get memory
1479           22  unmatched parentheses           22  unmatched parentheses
1480           23  internal error: code overflow           23  internal error: code overflow
# Line 1259  COMPILATION ERROR CODES Line 1483  COMPILATION ERROR CODES
1483           26  malformed number or name after (?(           26  malformed number or name after (?(
1484           27  conditional group contains more than two branches           27  conditional group contains more than two branches
1485           28  assertion expected after (?(           28  assertion expected after (?(
1486           29  (?R or (?digits must be followed by )           29  (?R or (?[+-]digits must be followed by )
1487           30  unknown POSIX class name           30  unknown POSIX class name
1488           31  POSIX collating elements are not supported           31  POSIX collating elements are not supported
1489           32  this version of PCRE is not compiled with PCRE_UTF8 support           32  this version of PCRE is not compiled with PCRE_UTF8 support
# Line 1279  COMPILATION ERROR CODES Line 1503  COMPILATION ERROR CODES
1503           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1504           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1505           48  subpattern name is too long (maximum 32 characters)           48  subpattern name is too long (maximum 32 characters)
1506           49  too many named subpatterns (maximum 10,000)           49  too many named subpatterns (maximum 10000)
1507           50  repeated subpattern is too long           50  [this code is not in use]
1508           51  octal value is greater than \377 (not in UTF-8 mode)           51  octal value is greater than \377 (not in UTF-8 mode)
1509           52  internal error: overran compiling workspace           52  internal error: overran compiling workspace
1510           53   internal  error:  previously-checked  referenced  subpattern not           53  internal error: previously-checked referenced subpattern
1511         found                 not found
1512           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1513           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1514           56  inconsistent NEWLINE options"           56  inconsistent NEWLINE options
1515             57  \g is not followed by a braced, angle-bracketed, or quoted
1516                   name/number or by a plain number
1517             58  a numbered reference must not be zero
1518             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1519             60  (*VERB) not recognized
1520             61  number is too big
1521             62  subpattern name expected
1522             63  digit expected after (?+
1523             64  ] is an invalid data character in JavaScript compatibility mode
1524             65  different names for subpatterns of the same number are
1525                   not allowed
1526             66  (*MARK) must have an argument
1527             67  this version of PCRE is not compiled with PCRE_UCP support
1528    
1529           The numbers 32 and 10000 in errors 48 and 49  are  defaults;  different
1530           values may be used if the limits were changed when PCRE was built.
1531    
1532    
1533  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1295  STUDYING A PATTERN Line 1535  STUDYING A PATTERN
1535         pcre_extra *pcre_study(const pcre *code, int options         pcre_extra *pcre_study(const pcre *code, int options
1536              const char **errptr);              const char **errptr);
1537    
1538         If a compiled pattern is going to be used several times,  it  is  worth         If  a  compiled  pattern is going to be used several times, it is worth
1539         spending more time analyzing it in order to speed up the time taken for         spending more time analyzing it in order to speed up the time taken for
1540         matching. The function pcre_study() takes a pointer to a compiled  pat-         matching.  The function pcre_study() takes a pointer to a compiled pat-
1541         tern as its first argument. If studying the pattern produces additional         tern as its first argument. If studying the pattern produces additional
1542         information that will help speed up matching,  pcre_study()  returns  a         information  that  will  help speed up matching, pcre_study() returns a
1543         pointer  to a pcre_extra block, in which the study_data field points to         pointer to a pcre_extra block, in which the study_data field points  to
1544         the results of the study.         the results of the study.
1545    
1546         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1547         pcre_exec().  However,  a  pcre_extra  block also contains other fields         pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block  also  con-
1548         that can be set by the caller before the block  is  passed;  these  are         tains  other  fields  that can be set by the caller before the block is
1549         described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1550    
1551         If  studying  the  pattern  does not produce any additional information         If studying the  pattern  does  not  produce  any  useful  information,
1552         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1553         wants  to  pass  any of the other fields to pcre_exec(), it must set up         wants  to  pass  any  of   the   other   fields   to   pcre_exec()   or
1554         its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1555    
1556         The second argument of pcre_study() contains option bits.  At  present,         The  second  argument of pcre_study() contains option bits. At present,
1557         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
1558    
1559         The  third argument for pcre_study() is a pointer for an error message.         The third argument for pcre_study() is a pointer for an error  message.
1560         If studying succeeds (even if no data is  returned),  the  variable  it         If  studying  succeeds  (even  if no data is returned), the variable it
1561         points  to  is  set  to NULL. Otherwise it is set to point to a textual         points to is set to NULL. Otherwise it is set to  point  to  a  textual
1562         error message. This is a static string that is part of the library. You         error message. This is a static string that is part of the library. You
1563         must  not  try  to  free it. You should test the error pointer for NULL         must not try to free it. You should test the  error  pointer  for  NULL
1564         after calling pcre_study(), to be sure that it has run successfully.         after calling pcre_study(), to be sure that it has run successfully.
1565    
1566         This is a typical call to pcre_study():         This is a typical call to pcre_study():
# Line 1331  STUDYING A PATTERN Line 1571  STUDYING A PATTERN
1571             0,              /* no options exist */             0,              /* no options exist */
1572             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1573    
1574         At present, studying a pattern is useful only for non-anchored patterns         Studying a pattern does two things: first, a lower bound for the length
1575         that  do not have a single fixed starting character. A bitmap of possi-         of subject string that is needed to match the pattern is computed. This
1576         ble starting bytes is created.         does not mean that there are any strings of that length that match, but
1577           it does guarantee that no shorter strings match. The value is  used  by
1578           pcre_exec()  and  pcre_dfa_exec()  to  avoid  wasting time by trying to
1579           match strings that are shorter than the lower bound. You can  find  out
1580           the value in a calling program via the pcre_fullinfo() function.
1581    
1582           Studying a pattern is also useful for non-anchored patterns that do not
1583           have a single fixed starting character. A bitmap of  possible  starting
1584           bytes  is  created. This speeds up finding a position in the subject at
1585           which to start matching.
1586    
1587           The two optimizations just described can be  disabled  by  setting  the
1588           PCRE_NO_START_OPTIMIZE    option    when    calling    pcre_exec()   or
1589           pcre_dfa_exec(). You might want to do this  if  your  pattern  contains
1590           callouts  or  (*MARK),  and you want to make use of these facilities in
1591           cases where matching fails. See the discussion  of  PCRE_NO_START_OPTI-
1592           MIZE below.
1593    
1594    
1595  LOCALE SUPPORT  LOCALE SUPPORT
1596    
1597         PCRE handles caseless matching, and determines whether  characters  are         PCRE  handles  caseless matching, and determines whether characters are
1598         letters,  digits, or whatever, by reference to a set of tables, indexed         letters, digits, or whatever, by reference to a set of tables,  indexed
1599         by character value. When running in UTF-8 mode, this  applies  only  to         by  character  value.  When running in UTF-8 mode, this applies only to
1600         characters  with  codes  less than 128. Higher-valued codes never match         characters with codes less than 128. By  default,  higher-valued  codes
1601         escapes such as \w or \d, but can be tested with \p if  PCRE  is  built         never match escapes such as \w or \d, but they can be tested with \p if
1602         with  Unicode  character property support. The use of locales with Uni-         PCRE is built with Unicode character property  support.  Alternatively,
1603         code is discouraged. If you are handling characters with codes  greater         the  PCRE_UCP  option  can  be  set at compile time; this causes \w and
1604         than  128, you should either use UTF-8 and Unicode, or use locales, but         friends to use Unicode property support instead of built-in tables. The
1605         not try to mix the two.         use of locales with Unicode is discouraged. If you are handling charac-
1606           ters with codes greater than 128, you should either use UTF-8 and  Uni-
1607           code, or use locales, but not try to mix the two.
1608    
1609         PCRE contains an internal set of tables that are used  when  the  final         PCRE  contains  an  internal set of tables that are used when the final
1610         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many         argument of pcre_compile() is  NULL.  These  are  sufficient  for  many
1611         applications.  Normally, the internal tables recognize only ASCII char-         applications.  Normally, the internal tables recognize only ASCII char-
1612         acters. However, when PCRE is built, it is possible to cause the inter-         acters. However, when PCRE is built, it is possible to cause the inter-
1613         nal tables to be rebuilt in the default "C" locale of the local system,         nal tables to be rebuilt in the default "C" locale of the local system,
1614         which may cause them to be different.         which may cause them to be different.
1615    
1616         The  internal tables can always be overridden by tables supplied by the         The internal tables can always be overridden by tables supplied by  the
1617         application that calls PCRE. These may be created in a different locale         application that calls PCRE. These may be created in a different locale
1618         from  the  default.  As more and more applications change to using Uni-         from the default. As more and more applications change  to  using  Uni-
1619         code, the need for this locale support is expected to die away.         code, the need for this locale support is expected to die away.
1620    
1621         External tables are built by calling  the  pcre_maketables()  function,         External  tables  are  built by calling the pcre_maketables() function,
1622         which  has no arguments, in the relevant locale. The result can then be         which has no arguments, in the relevant locale. The result can then  be
1623         passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For
1624         example,  to  build  and use tables that are appropriate for the French         example, to build and use tables that are appropriate  for  the  French
1625         locale (where accented characters with  values  greater  than  128  are         locale  (where  accented  characters  with  values greater than 128 are
1626         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1627    
1628           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1629           tables = pcre_maketables();           tables = pcre_maketables();
1630           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1631    
1632         The  locale  name "fr_FR" is used on Linux and other Unix-like systems;         The locale name "fr_FR" is used on Linux and other  Unix-like  systems;
1633         if you are using Windows, the name for the French locale is "french".         if you are using Windows, the name for the French locale is "french".
1634    
1635         When pcre_maketables() runs, the tables are built  in  memory  that  is         When  pcre_maketables()  runs,  the  tables are built in memory that is
1636         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         obtained via pcre_malloc. It is the caller's responsibility  to  ensure
1637         that the memory containing the tables remains available for as long  as         that  the memory containing the tables remains available for as long as
1638         it is needed.         it is needed.
1639    
1640         The pointer that is passed to pcre_compile() is saved with the compiled         The pointer that is passed to pcre_compile() is saved with the compiled
1641         pattern, and the same tables are used via this pointer by  pcre_study()         pattern,  and the same tables are used via this pointer by pcre_study()
1642         and normally also by pcre_exec(). Thus, by default, for any single pat-         and normally also by pcre_exec(). Thus, by default, for any single pat-
1643         tern, compilation, studying and matching all happen in the same locale,         tern, compilation, studying and matching all happen in the same locale,
1644         but different patterns can be compiled in different locales.         but different patterns can be compiled in different locales.
1645    
1646         It  is  possible to pass a table pointer or NULL (indicating the use of         It is possible to pass a table pointer or NULL (indicating the  use  of
1647         the internal tables) to pcre_exec(). Although  not  intended  for  this         the  internal  tables)  to  pcre_exec(). Although not intended for this
1648         purpose,  this facility could be used to match a pattern in a different         purpose, this facility could be used to match a pattern in a  different
1649         locale from the one in which it was compiled. Passing table pointers at         locale from the one in which it was compiled. Passing table pointers at
1650         run time is discussed below in the section on matching a pattern.         run time is discussed below in the section on matching a pattern.
1651    
# Line 1397  INFORMATION ABOUT A PATTERN Line 1655  INFORMATION ABOUT A PATTERN
1655         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,         int pcre_fullinfo(const pcre *code, const pcre_extra *extra,
1656              int what, void *where);              int what, void *where);
1657    
1658         The  pcre_fullinfo() function returns information about a compiled pat-         The pcre_fullinfo() function returns information about a compiled  pat-
1659         tern. It replaces the obsolete pcre_info() function, which is neverthe-         tern. It replaces the obsolete pcre_info() function, which is neverthe-
1660         less retained for backwards compability (and is documented below).         less retained for backwards compability (and is documented below).
1661    
1662         The  first  argument  for  pcre_fullinfo() is a pointer to the compiled         The first argument for pcre_fullinfo() is a  pointer  to  the  compiled
1663         pattern. The second argument is the result of pcre_study(), or NULL  if         pattern.  The second argument is the result of pcre_study(), or NULL if
1664         the  pattern  was not studied. The third argument specifies which piece         the pattern was not studied. The third argument specifies  which  piece
1665         of information is required, and the fourth argument is a pointer  to  a         of  information  is required, and the fourth argument is a pointer to a
1666         variable  to  receive  the  data. The yield of the function is zero for         variable to receive the data. The yield of the  function  is  zero  for
1667         success, or one of the following negative numbers:         success, or one of the following negative numbers:
1668    
1669           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
# Line 1413  INFORMATION ABOUT A PATTERN Line 1671  INFORMATION ABOUT A PATTERN
1671           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1672           PCRE_ERROR_BADOPTION  the value of what was invalid           PCRE_ERROR_BADOPTION  the value of what was invalid
1673    
1674         The "magic number" is placed at the start of each compiled  pattern  as         The  "magic  number" is placed at the start of each compiled pattern as
1675         an  simple check against passing an arbitrary memory pointer. Here is a         an simple check against passing an arbitrary memory pointer. Here is  a
1676         typical call of pcre_fullinfo(), to obtain the length of  the  compiled         typical  call  of pcre_fullinfo(), to obtain the length of the compiled
1677         pattern:         pattern:
1678    
1679           int rc;           int rc;
# Line 1426  INFORMATION ABOUT A PATTERN Line 1684  INFORMATION ABOUT A PATTERN
1684             PCRE_INFO_SIZE,   /* what is required */             PCRE_INFO_SIZE,   /* what is required */
1685             &length);         /* where to put the data */             &length);         /* where to put the data */
1686    
1687         The  possible  values for the third argument are defined in pcre.h, and         The possible values for the third argument are defined in  pcre.h,  and
1688         are as follows:         are as follows:
1689    
1690           PCRE_INFO_BACKREFMAX           PCRE_INFO_BACKREFMAX
1691    
1692         Return the number of the highest back reference  in  the  pattern.  The         Return  the  number  of  the highest back reference in the pattern. The
1693         fourth  argument  should  point to an int variable. Zero is returned if         fourth argument should point to an int variable. Zero  is  returned  if
1694         there are no back references.         there are no back references.
1695    
1696           PCRE_INFO_CAPTURECOUNT           PCRE_INFO_CAPTURECOUNT
1697    
1698         Return the number of capturing subpatterns in the pattern.  The  fourth         Return  the  number of capturing subpatterns in the pattern. The fourth
1699         argument should point to an int variable.         argument should point to an int variable.
1700    
1701           PCRE_INFO_DEFAULT_TABLES           PCRE_INFO_DEFAULT_TABLES
1702    
1703         Return  a pointer to the internal default character tables within PCRE.         Return a pointer to the internal default character tables within  PCRE.
1704         The fourth argument should point to an unsigned char *  variable.  This         The  fourth  argument should point to an unsigned char * variable. This
1705         information call is provided for internal use by the pcre_study() func-         information call is provided for internal use by the pcre_study() func-
1706         tion. External callers can cause PCRE to use  its  internal  tables  by         tion.  External  callers  can  cause PCRE to use its internal tables by
1707         passing a NULL table pointer.         passing a NULL table pointer.
1708    
1709           PCRE_INFO_FIRSTBYTE           PCRE_INFO_FIRSTBYTE
1710    
1711         Return  information  about  the first byte of any matched string, for a         Return information about the first byte of any matched  string,  for  a
1712         non-anchored pattern. The fourth argument should point to an int  vari-         non-anchored  pattern. The fourth argument should point to an int vari-
1713         able.  (This option used to be called PCRE_INFO_FIRSTCHAR; the old name         able. (This option used to be called PCRE_INFO_FIRSTCHAR; the old  name
1714         is still recognized for backwards compatibility.)         is still recognized for backwards compatibility.)
1715    
1716         If there is a fixed first byte, for example, from  a  pattern  such  as         If  there  is  a  fixed first byte, for example, from a pattern such as
1717         (cat|cow|coyote), its value is returned. Otherwise, if either         (cat|cow|coyote), its value is returned. Otherwise, if either
1718    
1719         (a)  the pattern was compiled with the PCRE_MULTILINE option, and every         (a) the pattern was compiled with the PCRE_MULTILINE option, and  every
1720         branch starts with "^", or         branch starts with "^", or
1721    
1722         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not         (b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not
1723         set (if it were set, the pattern would be anchored),         set (if it were set, the pattern would be anchored),
1724    
1725         -1  is  returned, indicating that the pattern matches only at the start         -1 is returned, indicating that the pattern matches only at  the  start
1726         of a subject string or after any newline within the  string.  Otherwise         of  a  subject string or after any newline within the string. Otherwise
1727         -2 is returned. For anchored patterns, -2 is returned.         -2 is returned. For anchored patterns, -2 is returned.
1728    
1729           PCRE_INFO_FIRSTTABLE           PCRE_INFO_FIRSTTABLE
1730    
1731         If  the pattern was studied, and this resulted in the construction of a         If the pattern was studied, and this resulted in the construction of  a
1732         256-bit table indicating a fixed set of bytes for the first byte in any         256-bit table indicating a fixed set of bytes for the first byte in any
1733         matching  string, a pointer to the table is returned. Otherwise NULL is         matching string, a pointer to the table is returned. Otherwise NULL  is
1734         returned. The fourth argument should point to an unsigned char *  vari-         returned.  The fourth argument should point to an unsigned char * vari-
1735         able.         able.
1736    
1737             PCRE_INFO_HASCRORLF
1738    
1739           Return 1 if the pattern contains any explicit  matches  for  CR  or  LF
1740           characters,  otherwise  0.  The  fourth argument should point to an int
1741           variable. An explicit match is either a literal CR or LF character,  or
1742           \r or \n.
1743    
1744           PCRE_INFO_JCHANGED           PCRE_INFO_JCHANGED
1745    
1746         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,
1747         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)
1748         nal option setting changes the local PCRE_DUPNAMES value.         and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1749    
1750           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1751    
# Line 1492  INFORMATION ABOUT A PATTERN Line 1757  INFORMATION ABOUT A PATTERN
1757         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for         example, for the pattern /^a\d+z\d+/ the returned value is "z", but for
1758         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1759    
1760             PCRE_INFO_MINLENGTH
1761    
1762           If  the  pattern  was studied and a minimum length for matching subject
1763           strings was computed, its value is  returned.  Otherwise  the  returned
1764           value  is  -1. The value is a number of characters, not bytes (this may
1765           be relevant in UTF-8 mode). The fourth argument should point to an  int
1766           variable.  A  non-negative  value is a lower bound to the length of any
1767           matching string. There may not be any strings of that  length  that  do
1768           actually match, but every string that does match is at least that long.
1769    
1770           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
1771           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1772           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
# Line 1513  INFORMATION ABOUT A PATTERN Line 1788  INFORMATION ABOUT A PATTERN
1788         a  pointer  to  the  first  entry of the table (a pointer to char). The         a  pointer  to  the  first  entry of the table (a pointer to char). The
1789         first two bytes of each entry are the number of the capturing parenthe-         first two bytes of each entry are the number of the capturing parenthe-
1790         sis,  most  significant byte first. The rest of the entry is the corre-         sis,  most  significant byte first. The rest of the entry is the corre-
1791         sponding name, zero terminated. The names are  in  alphabetical  order.         sponding name, zero terminated.
1792         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-  
1793         theses numbers. For example, consider  the  following  pattern  (assume         The names are in alphabetical order. Duplicate names may appear if  (?|
1794         PCRE_EXTENDED  is  set,  so  white  space  -  including  newlines  - is         is used to create multiple groups with the same number, as described in
1795         ignored):         the section on duplicate subpattern numbers in  the  pcrepattern  page.
1796           Duplicate  names  for  subpatterns with different numbers are permitted
1797           only if PCRE_DUPNAMES is set. In all cases  of  duplicate  names,  they
1798           appear  in  the table in the order in which they were found in the pat-
1799           tern. In the absence of (?| this is the  order  of  increasing  number;
1800           when (?| is used this is not necessarily the case because later subpat-
1801           terns may have lower numbers.
1802    
1803           As a simple example of the name/number table,  consider  the  following
1804           pattern  (assume  PCRE_EXTENDED is set, so white space - including new-
1805           lines - is ignored):
1806    
1807           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1808           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
# Line 1538  INFORMATION ABOUT A PATTERN Line 1823  INFORMATION ABOUT A PATTERN
1823    
1824           PCRE_INFO_OKPARTIAL           PCRE_INFO_OKPARTIAL
1825    
1826         Return  1 if the pattern can be used for partial matching, otherwise 0.         Return  1  if  the  pattern  can  be  used  for  partial  matching with
1827         The fourth argument should point to an int  variable.  The  pcrepartial         pcre_exec(), otherwise 0. The fourth argument should point  to  an  int
1828         documentation  lists  the restrictions that apply to patterns when par-         variable.  From  release  8.00,  this  always  returns  1,  because the
1829         tial matching is used.         restrictions that previously applied  to  partial  matching  have  been
1830           lifted.  The  pcrepartial documentation gives details of partial match-
1831           ing.
1832    
1833           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1834    
1835         Return a copy of the options with which the pattern was  compiled.  The         Return a copy of the options with which the pattern was  compiled.  The
1836         fourth  argument  should  point to an unsigned long int variable. These         fourth  argument  should  point to an unsigned long int variable. These
1837         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1838         by any top-level option settings within the pattern itself.         by any top-level option settings at the start of the pattern itself. In
1839           other words, they are the options that will be in force  when  matching
1840           starts.  For  example, if the pattern /(?im)abc(?-i)d/ is compiled with
1841           the PCRE_EXTENDED option, the result is PCRE_CASELESS,  PCRE_MULTILINE,
1842           and PCRE_EXTENDED.
1843    
1844         A  pattern  is  automatically  anchored by PCRE if all of its top-level         A  pattern  is  automatically  anchored by PCRE if all of its top-level
1845         alternatives begin with one of the following:         alternatives begin with one of the following:
# Line 1574  INFORMATION ABOUT A PATTERN Line 1865  INFORMATION ABOUT A PATTERN
1865         Return the size of the data block pointed to by the study_data field in         Return the size of the data block pointed to by the study_data field in
1866         a  pcre_extra  block.  That  is,  it  is  the  value that was passed to         a  pcre_extra  block.  That  is,  it  is  the  value that was passed to
1867         pcre_malloc() when PCRE was getting memory into which to place the data         pcre_malloc() when PCRE was getting memory into which to place the data
1868         created  by  pcre_study(). The fourth argument should point to a size_t         created  by  pcre_study().  If pcre_extra is NULL, or there is no study
1869           data, zero is returned. The fourth argument should point  to  a  size_t
1870         variable.         variable.
1871    
1872    
# Line 1582  OBSOLETE INFO FUNCTION Line 1874  OBSOLETE INFO FUNCTION
1874    
1875         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1876    
1877         The pcre_info() function is now obsolete because its interface  is  too         The  pcre_info()  function is now obsolete because its interface is too
1878         restrictive  to return all the available data about a compiled pattern.         restrictive to return all the available data about a compiled  pattern.
1879         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of
1880         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-
1881         lowing negative numbers:         lowing negative numbers:
1882    
1883           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1884           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1885    
1886         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
1887         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
1888         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1889    
1890         If the pattern is not anchored and the  firstcharptr  argument  is  not         If  the  pattern  is  not anchored and the firstcharptr argument is not
1891         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
1892         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1893    
1894    
# Line 1604  REFERENCE COUNTS Line 1896  REFERENCE COUNTS
1896    
1897         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1898    
1899         The pcre_refcount() function is used to maintain a reference  count  in         The  pcre_refcount()  function is used to maintain a reference count in
1900         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
1901         benefit of applications that  operate  in  an  object-oriented  manner,         benefit  of  applications  that  operate  in an object-oriented manner,
1902         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1903         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.
1904    
1905         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1906         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
1907         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
1908         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
1909         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
1910         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1911    
1912         Except  when it is zero, the reference count is not correctly preserved         Except when it is zero, the reference count is not correctly  preserved
1913         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
1914         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1915    
1916    
# Line 1630  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1922  MATCHING A PATTERN: THE TRADITIONAL FUNC
1922    
1923         The function pcre_exec() is called to match a subject string against  a         The function pcre_exec() is called to match a subject string against  a
1924         compiled  pattern, which is passed in the code argument. If the pattern         compiled  pattern, which is passed in the code argument. If the pattern
1925         has been studied, the result of the study should be passed in the extra         was studied, the result of the study should  be  passed  in  the  extra
1926         argument.  This  function is the main matching facility of the library,         argument.  This  function is the main matching facility of the library,
1927         and it operates in a Perl-like manner. For specialist use there is also         and it operates in a Perl-like manner. For specialist use there is also
1928         an  alternative matching function, which is described below in the sec-         an  alternative matching function, which is described below in the sec-
# Line 1670  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1962  MATCHING A PATTERN: THE TRADITIONAL FUNC
1962           unsigned long int match_limit_recursion;           unsigned long int match_limit_recursion;
1963           void *callout_data;           void *callout_data;
1964           const unsigned char *tables;           const unsigned char *tables;
1965             unsigned char **mark;
1966    
1967         The flags field is a bitmap that specifies which of  the  other  fields         The flags field is a bitmap that specifies which of  the  other  fields
1968         are set. The flag bits are:         are set. The flag bits are:
# Line 1679  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1972  MATCHING A PATTERN: THE TRADITIONAL FUNC
1972           PCRE_EXTRA_MATCH_LIMIT_RECURSION           PCRE_EXTRA_MATCH_LIMIT_RECURSION
1973           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1974           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1975             PCRE_EXTRA_MARK
1976    
1977         Other  flag  bits should be set to zero. The study_data field is set in         Other  flag  bits should be set to zero. The study_data field is set in
1978         the pcre_extra block that is returned by  pcre_study(),  together  with         the pcre_extra block that is returned by  pcre_study(),  together  with
# Line 1689  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1983  MATCHING A PATTERN: THE TRADITIONAL FUNC
1983         The match_limit field provides a means of preventing PCRE from using up         The match_limit field provides a means of preventing PCRE from using up
1984         a vast amount of resources when running patterns that are not going  to         a vast amount of resources when running patterns that are not going  to
1985         match,  but  which  have  a very large number of possibilities in their         match,  but  which  have  a very large number of possibilities in their
1986         search trees. The classic  example  is  the  use  of  nested  unlimited         search trees. The classic example is a pattern that uses nested  unlim-
1987         repeats.         ited repeats.
1988    
1989         Internally,  PCRE uses a function called match() which it calls repeat-         Internally,  PCRE uses a function called match() which it calls repeat-
1990         edly (sometimes recursively). The limit set by match_limit  is  imposed         edly (sometimes recursively). The limit set by match_limit  is  imposed
# Line 1712  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2006  MATCHING A PATTERN: THE TRADITIONAL FUNC
2006         the total number of calls, because not all calls to match() are  recur-         the total number of calls, because not all calls to match() are  recur-
2007         sive.  This limit is of use only if it is set smaller than match_limit.         sive.  This limit is of use only if it is set smaller than match_limit.
2008    
2009         Limiting the recursion depth limits the amount of  stack  that  can  be         Limiting  the  recursion  depth  limits the amount of stack that can be
2010         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
2011         of the stack, the amount of heap memory that can be used.         of the stack, the amount of heap memory that can be used.
2012    
2013         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
2014         built;  the  default  default  is  the  same  value  as the default for         built; the default default  is  the  same  value  as  the  default  for
2015         match_limit. You can override the default by suppling pcre_exec()  with         match_limit.  You can override the default by suppling pcre_exec() with
2016         a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and
2017         PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in  the  flags  field.  If  the         PCRE_EXTRA_MATCH_LIMIT_RECURSION  is  set  in  the  flags field. If the
2018         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
2019    
2020         The  pcre_callout  field is used in conjunction with the "callout" fea-         The callout_data field is used in conjunction with the  "callout"  fea-
2021         ture, which is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
2022    
2023         The tables field  is  used  to  pass  a  character  tables  pointer  to         The  tables  field  is  used  to  pass  a  character  tables pointer to
2024         pcre_exec();  this overrides the value that is stored with the compiled         pcre_exec(); this overrides the value that is stored with the  compiled
2025         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
2026         custom  tables  were  supplied to pcre_compile() via its tableptr argu-         custom tables were supplied to pcre_compile() via  its  tableptr  argu-
2027         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
2028         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-
2029         using patterns that have been saved after compiling  with  an  external         using  patterns  that  have been saved after compiling with an external
2030         set  of  tables,  because  the  external tables might be at a different         set of tables, because the external tables  might  be  at  a  different
2031         address when pcre_exec() is called. See the  pcreprecompile  documenta-         address  when  pcre_exec() is called. See the pcreprecompile documenta-
2032         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
2033    
2034           If PCRE_EXTRA_MARK is set in the flags field, the mark  field  must  be
2035           set  to  point  to a char * variable. If the pattern contains any back-
2036           tracking control verbs such as (*MARK:NAME), and the execution ends  up
2037           with  a  name  to  pass back, a pointer to the name string (zero termi-
2038           nated) is placed in the variable pointed to  by  the  mark  field.  The
2039           names  are  within  the  compiled pattern; if you wish to retain such a
2040           name you must copy it before freeing the memory of a compiled  pattern.
2041           If  there  is no name to pass back, the variable pointed to by the mark
2042           field set to NULL. For details of the backtracking control  verbs,  see
2043           the section entitled "Backtracking control" in the pcrepattern documen-
2044           tation.
2045    
2046     Option bits for pcre_exec()     Option bits for pcre_exec()
2047    
2048         The  unused  bits of the options argument for pcre_exec() must be zero.         The unused bits of the options argument for pcre_exec() must  be  zero.
2049         The only bits that may  be  set  are  PCRE_ANCHORED,  PCRE_NEWLINE_xxx,         The  only  bits  that  may  be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx,
2050         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,   PCRE_NOTEOL,    PCRE_NOTEMPTY,    PCRE_NOTEMPTY_ATSTART,
2051         PCRE_PARTIAL.         PCRE_NO_START_OPTIMIZE,   PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,  and
2052           PCRE_PARTIAL_HARD.
2053    
2054           PCRE_ANCHORED           PCRE_ANCHORED
2055    
# Line 1751  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2058  MATCHING A PATTERN: THE TRADITIONAL FUNC
2058         turned out to be anchored by virtue of its contents, it cannot be  made         turned out to be anchored by virtue of its contents, it cannot be  made
2059         unachored at matching time.         unachored at matching time.
2060    
2061             PCRE_BSR_ANYCRLF
2062             PCRE_BSR_UNICODE
2063    
2064           These options (which are mutually exclusive) control what the \R escape
2065           sequence matches. The choice is either to match only CR, LF,  or  CRLF,
2066           or  to  match  any Unicode newline sequence. These options override the
2067           choice that was made or defaulted when the pattern was compiled.
2068    
2069           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
2070           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
2071           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
2072           PCRE_NEWLINE_ANYCRLF           PCRE_NEWLINE_ANYCRLF
2073           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
2074    
2075         These  options  override  the  newline  definition  that  was chosen or         These options override  the  newline  definition  that  was  chosen  or
2076         defaulted when the pattern was compiled. For details, see the  descrip-         defaulted  when the pattern was compiled. For details, see the descrip-
2077         tion  of  pcre_compile()  above.  During  matching,  the newline choice         tion of pcre_compile()  above.  During  matching,  the  newline  choice
2078         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-
2079         ters.  It may also alter the way the match position is advanced after a         ters. It may also alter the way the match position is advanced after  a
2080         match  failure  for  an  unanchored  pattern.  When  PCRE_NEWLINE_CRLF,         match failure for an unanchored pattern.
2081         PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY is set, and a match attempt  
2082         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
2083         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-
2084         after the CRLF.         rent  position  is  at  a  CRLF  sequence,  and the pattern contains no
2085           explicit matches for  CR  or  LF  characters,  the  match  position  is
2086           advanced by two characters instead of one, in other words, to after the
2087           CRLF.
2088    
2089           The above rule is a compromise that makes the most common cases work as
2090           expected.  For  example,  if  the  pattern  is .+A (and the PCRE_DOTALL
2091           option is not set), it does not match the string "\r\nA" because, after
2092           failing  at the start, it skips both the CR and the LF before retrying.
2093           However, the pattern [\r\n]A does match that string,  because  it  con-
2094           tains an explicit CR or LF reference, and so advances only by one char-
2095           acter after the first failure.
2096    
2097           An explicit match for CR of LF is either a literal appearance of one of
2098           those  characters,  or  one  of the \r or \n escape sequences. Implicit
2099           matches such as [^X] do not count, nor does \s (which includes  CR  and
2100           LF in the characters that it matches).
2101    
2102           Notwithstanding  the above, anomalous effects may still occur when CRLF
2103           is a valid newline sequence and explicit \r or \n escapes appear in the
2104           pattern.
2105    
2106           PCRE_NOTBOL           PCRE_NOTBOL
2107    
2108         This option specifies that first character of the subject string is not         This option specifies that first character of the subject string is not
2109         the  beginning  of  a  line, so the circumflex metacharacter should not         the beginning of a line, so the  circumflex  metacharacter  should  not
2110         match before it. Setting this without PCRE_MULTILINE (at compile  time)         match  before it. Setting this without PCRE_MULTILINE (at compile time)
2111         causes  circumflex  never to match. This option affects only the behav-         causes circumflex never to match. This option affects only  the  behav-
2112         iour of the circumflex metacharacter. It does not affect \A.         iour of the circumflex metacharacter. It does not affect \A.
2113    
2114           PCRE_NOTEOL           PCRE_NOTEOL
2115    
2116         This option specifies that the end of the subject string is not the end         This option specifies that the end of the subject string is not the end
2117         of  a line, so the dollar metacharacter should not match it nor (except         of a line, so the dollar metacharacter should not match it nor  (except
2118         in multiline mode) a newline immediately before it. Setting this  with-         in  multiline mode) a newline immediately before it. Setting this with-
2119         out PCRE_MULTILINE (at compile time) causes dollar never to match. This         out PCRE_MULTILINE (at compile time) causes dollar never to match. This
2120         option affects only the behaviour of the dollar metacharacter. It  does         option  affects only the behaviour of the dollar metacharacter. It does
2121         not affect \Z or \z.         not affect \Z or \z.
2122    
2123           PCRE_NOTEMPTY           PCRE_NOTEMPTY
2124    
2125         An empty string is not considered to be a valid match if this option is         An empty string is not considered to be a valid match if this option is
2126         set. If there are alternatives in the pattern, they are tried.  If  all         set.  If  there are alternatives in the pattern, they are tried. If all
2127         the  alternatives  match  the empty string, the entire match fails. For         the alternatives match the empty string, the entire  match  fails.  For
2128         example, if the pattern         example, if the pattern
2129    
2130           a?b?           a?b?
2131    
2132         is applied to a string not beginning with "a" or "b",  it  matches  the         is  applied  to  a  string not beginning with "a" or "b", it matches an
2133         empty  string at the start of the subject. With PCRE_NOTEMPTY set, this         empty string at the start of the subject. With PCRE_NOTEMPTY set,  this
2134         match is not valid, so PCRE searches further into the string for occur-         match is not valid, so PCRE searches further into the string for occur-
2135         rences of "a" or "b".         rences of "a" or "b".
2136    
2137         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2138         cial case of a pattern match of the empty  string  within  its  split()  
2139         function,  and  when  using  the /g modifier. It is possible to emulate         This is like PCRE_NOTEMPTY, except that an empty string match  that  is
2140         Perl's behaviour after matching a null string by first trying the match         not  at  the  start  of  the  subject  is  permitted. If the pattern is
2141         again at the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and then         anchored, such a match can occur only if the pattern contains \K.
2142         if that fails by advancing the starting offset (see below)  and  trying  
2143         an ordinary match again. There is some code that demonstrates how to do         Perl    has    no    direct    equivalent    of    PCRE_NOTEMPTY     or
2144         this in the pcredemo.c sample program.         PCRE_NOTEMPTY_ATSTART,  but  it  does  make a special case of a pattern
2145           match of the empty string within its split() function, and  when  using
2146           the  /g  modifier.  It  is  possible  to emulate Perl's behaviour after
2147           matching a null string by first trying the match again at the same off-
2148           set  with  PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED,  and then if that
2149           fails, by advancing the starting offset (see below) and trying an ordi-
2150           nary  match  again. There is some code that demonstrates how to do this
2151           in the pcredemo sample program. In the most general case, you  have  to
2152           check  to  see  if the newline convention recognizes CRLF as a newline,
2153           and if so, and the current character is CR followed by LF, advance  the
2154           starting offset by two characters instead of one.
2155    
2156             PCRE_NO_START_OPTIMIZE
2157    
2158           There  are a number of optimizations that pcre_exec() uses at the start
2159           of a match, in order to speed up the process. For  example,  if  it  is
2160           known that an unanchored match must start with a specific character, it
2161           searches the subject for that character, and fails  immediately  if  it
2162           cannot  find  it,  without actually running the main matching function.
2163           This means that a special item such as (*COMMIT) at the start of a pat-
2164           tern  is  not  considered until after a suitable starting point for the
2165           match has been found. When callouts or (*MARK) items are in use,  these
2166           "start-up" optimizations can cause them to be skipped if the pattern is
2167           never actually used. The start-up optimizations are in  effect  a  pre-
2168           scan of the subject that takes place before the pattern is run.
2169    
2170           The  PCRE_NO_START_OPTIMIZE option disables the start-up optimizations,
2171           possibly causing performance to suffer,  but  ensuring  that  in  cases
2172           where  the  result is "no match", the callouts do occur, and that items
2173           such as (*COMMIT) and (*MARK) are considered at every possible starting
2174           position  in  the  subject  string. If PCRE_NO_START_OPTIMIZE is set at
2175           compile time, it cannot be unset at matching time.
2176    
2177           Setting PCRE_NO_START_OPTIMIZE can change the  outcome  of  a  matching
2178           operation.  Consider the pattern
2179    
2180             (*COMMIT)ABC
2181    
2182           When  this  is  compiled, PCRE records the fact that a match must start
2183           with the character "A". Suppose the subject  string  is  "DEFABC".  The
2184           start-up  optimization  scans along the subject, finds "A" and runs the
2185           first match attempt from there. The (*COMMIT) item means that the  pat-
2186           tern  must  match the current starting position, which in this case, it
2187           does. However, if the same match  is  run  with  PCRE_NO_START_OPTIMIZE
2188           set,  the  initial  scan  along the subject string does not happen. The
2189           first match attempt is run starting  from  "D"  and  when  this  fails,
2190           (*COMMIT)  prevents  any  further  matches  being tried, so the overall
2191           result is "no match". If the pattern is studied,  more  start-up  opti-
2192           mizations  may  be  used. For example, a minimum length for the subject
2193           may be recorded. Consider the pattern
2194    
2195             (*MARK:A)(X|Y)
2196    
2197           The minimum length for a match is one  character.  If  the  subject  is
2198           "ABC",  there  will  be  attempts  to  match "ABC", "BC", "C", and then
2199           finally an empty string.  If the pattern is studied, the final  attempt
2200           does  not take place, because PCRE knows that the subject is too short,
2201           and so the (*MARK) is never encountered.  In this  case,  studying  the
2202           pattern  does  not  affect the overall match result, which is still "no
2203           match", but it does affect the auxiliary information that is returned.
2204    
2205           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2206    
2207         When PCRE_UTF8 is set at compile time, the validity of the subject as a         When PCRE_UTF8 is set at compile time, the validity of the subject as a
2208         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8  string is automatically checked when pcre_exec() is subsequently
2209         called.  The value of startoffset is also checked  to  ensure  that  it         called.  The value of startoffset is also checked  to  ensure  that  it
2210         points  to the start of a UTF-8 character. If an invalid UTF-8 sequence         points  to  the start of a UTF-8 character. There is a discussion about
2211         of bytes is found, pcre_exec() returns the error PCRE_ERROR_BADUTF8. If         the validity of UTF-8 strings in the section on UTF-8  support  in  the
2212         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,
2213         returned.         pcre_exec() returns  the  error  PCRE_ERROR_BADUTF8  or,  if  PCRE_PAR-
2214           TIAL_HARD  is set and the problem is a truncated UTF-8 character at the
2215           end of the subject, PCRE_ERROR_SHORTUTF8.  If  startoffset  contains  a
2216           value  that does not point to the start of a UTF-8 character (or to the
2217           end of the subject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2218    
2219         If you already know that your subject is valid, and you  want  to  skip         If you already know that your subject is valid, and you  want  to  skip
2220         these    checks    for   performance   reasons,   you   can   set   the         these    checks    for   performance   reasons,   you   can   set   the
# Line 1824  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2222  MATCHING A PATTERN: THE TRADITIONAL FUNC
2222         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
2223         making repeated calls to find all  the  matches  in  a  single  subject         making repeated calls to find all  the  matches  in  a  single  subject
2224         string.  However,  you  should  be  sure  that the value of startoffset         string.  However,  you  should  be  sure  that the value of startoffset
2225         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).
2226         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
2227         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.
2228         acter, is undefined. Your program may crash.         Your program may crash.
2229    
2230           PCRE_PARTIAL           PCRE_PARTIAL_HARD
2231             PCRE_PARTIAL_SOFT
2232         This  option  turns  on  the  partial  matching feature. If the subject  
2233         string fails to match the pattern, but at some point during the  match-         These  options turn on the partial matching feature. For backwards com-
2234         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
2235         partially matches the pattern and the failure to  match  occurred  only         match  occurs if the end of the subject string is reached successfully,
2236         because  there were not enough subject characters), pcre_exec() returns         but there are not enough subject characters to complete the  match.  If
2237         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,
2238         used,  there  are restrictions on what may appear in the pattern. These         matching continues by testing any remaining alternatives.  Only  if  no
2239         are discussed in the pcrepartial documentation.         complete  match  can be found is PCRE_ERROR_PARTIAL returned instead of
2240           PCRE_ERROR_NOMATCH. In other words,  PCRE_PARTIAL_SOFT  says  that  the
2241           caller  is  prepared to handle a partial match, but only if no complete
2242           match can be found.
2243    
2244           If PCRE_PARTIAL_HARD is set, it overrides  PCRE_PARTIAL_SOFT.  In  this
2245           case,  if  a  partial  match  is found, pcre_exec() immediately returns
2246           PCRE_ERROR_PARTIAL, without  considering  any  other  alternatives.  In
2247           other  words, when PCRE_PARTIAL_HARD is set, a partial match is consid-
2248           ered to be more important that an alternative complete match.
2249    
2250           In both cases, the portion of the string that was  inspected  when  the
2251           partial match was found is set as the first matching string. There is a
2252           more detailed discussion of partial and  multi-segment  matching,  with
2253           examples, in the pcrepartial documentation.
2254    
2255     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2256    
2257         The subject string is passed to pcre_exec() as a pointer in subject,  a         The  subject string is passed to pcre_exec() as a pointer in subject, a
2258         length  in  length, and a starting byte offset in startoffset. In UTF-8         length (in bytes) in length, and a starting byte offset in startoffset.
2259         mode, the byte offset must point to the start  of  a  UTF-8  character.         If  this  is  negative  or  greater  than  the  length  of the subject,
2260         Unlike  the  pattern string, the subject may contain binary zero bytes.         pcre_exec() returns PCRE_ERROR_BADOFFSET. When the starting  offset  is
2261         When the starting offset is zero, the search for a match starts at  the         zero,  the  search  for a match starts at the beginning of the subject,
2262         beginning of the subject, and this is by far the most common case.         and this is by far the most common case. In UTF-8 mode, the byte offset
2263           must  point  to  the start of a UTF-8 character (or the end of the sub-
2264           ject). Unlike the pattern string, the subject may contain  binary  zero
2265           bytes.
2266    
2267         A  non-zero  starting offset is useful when searching for another match         A  non-zero  starting offset is useful when searching for another match
2268         in the same subject by calling pcre_exec() again after a previous  suc-         in the same subject by calling pcre_exec() again after a previous  suc-
# Line 1868  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2283  MATCHING A PATTERN: THE TRADITIONAL FUNC
2283         rence  of "iss" because it is able to look behind the starting point to         rence  of "iss" because it is able to look behind the starting point to
2284         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2285    
2286         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
2287           match an empty string. It is possible to emulate Perl's /g behaviour by
2288           first  trying  the  match  again  at  the   same   offset,   with   the
2289           PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED  options,  and  then  if that
2290           fails, advancing the starting  offset  and  trying  an  ordinary  match
2291           again. There is some code that demonstrates how to do this in the pcre-
2292           demo sample program. In the most general case, you have to check to see
2293           if  the newline convention recognizes CRLF as a newline, and if so, and
2294           the current character is CR followed by LF, advance the starting offset
2295           by two characters instead of one.
2296    
2297           If  a  non-zero starting offset is passed when the pattern is anchored,
2298         one attempt to match at the given offset is made. This can only succeed         one attempt to match at the given offset is made. This can only succeed
2299         if the pattern does not require the match to be at  the  start  of  the         if  the  pattern  does  not require the match to be at the start of the
2300         subject.         subject.
2301    
2302     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2303    
2304         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
2305         addition, further substrings from the subject  may  be  picked  out  by         addition,  further  substrings  from  the  subject may be picked out by
2306         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2307         this is called "capturing" in what follows, and the  phrase  "capturing         this  is  called "capturing" in what follows, and the phrase "capturing
2308         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-
2309         string. PCRE supports several other kinds of  parenthesized  subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2310         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2311    
2312         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2313         offsets whose address is passed in ovector. The number of  elements  in         whose  address is passed in ovector. The number of elements in the vec-
2314         the  vector is passed in ovecsize, which must be a non-negative number.         tor is passed in ovecsize, which must be a non-negative  number.  Note:
2315         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2316    
2317         The first two-thirds of the vector is used to pass back  captured  sub-         The  first  two-thirds of the vector is used to pass back captured sub-
2318         strings,  each  substring using a pair of integers. The remaining third         strings, each substring using a pair of integers. The  remaining  third
2319         of the vector is used as workspace by pcre_exec() while  matching  cap-         of  the  vector is used as workspace by pcre_exec() while matching cap-
2320         turing  subpatterns, and is not available for passing back information.         turing subpatterns, and is not available for passing back  information.
2321         The length passed in ovecsize should always be a multiple of three.  If         The  number passed in ovecsize should always be a multiple of three. If
2322         it is not, it is rounded down.         it is not, it is rounded down.
2323    
2324         When  a  match  is successful, information about captured substrings is         When a match is successful, information about  captured  substrings  is
2325         returned in pairs of integers, starting at the  beginning  of  ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2326         and  continuing  up  to two-thirds of its length at the most. The first         and continuing up to two-thirds of its length at the  most.  The  first
2327         element of a pair is set to the offset of the first character in a sub-         element  of  each pair is set to the byte offset of the first character
2328         string,  and  the  second  is  set to the offset of the first character         in a substring, and the second is set to the byte offset of  the  first
2329         after the end of a substring. The  first  pair,  ovector[0]  and  ovec-         character  after  the end of a substring. Note: these values are always
2330         tor[1],  identify  the  portion  of  the  subject string matched by the         byte offsets, even in UTF-8 mode. They are not character counts.
2331         entire pattern. The next pair is used for the first  capturing  subpat-  
2332         tern, and so on. The value returned by pcre_exec() is one more than the         The first pair of integers, ovector[0]  and  ovector[1],  identify  the
2333         highest numbered pair that has been set. For example, if two substrings         portion  of  the subject string matched by the entire pattern. The next
2334         have  been captured, the returned value is 3. If there are no capturing         pair is used for the first capturing subpattern, and so on.  The  value
2335         subpatterns, the return value from a successful match is 1,  indicating         returned by pcre_exec() is one more than the highest numbered pair that
2336         that just the first pair of offsets has been set.         has been set.  For example, if two substrings have been  captured,  the
2337           returned  value is 3. If there are no capturing subpatterns, the return
2338           value from a successful match is 1, indicating that just the first pair
2339           of offsets has been set.
2340    
2341         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2342         of the string that it matched that is returned.         of the string that it matched that is returned.
2343    
2344         If the vector is too small to hold all the captured substring  offsets,         If the vector is too small to hold all the captured substring  offsets,
2345         it is used as far as possible (up to two-thirds of its length), and the         it is used as far as possible (up to two-thirds of its length), and the
2346         function returns a value of zero. In particular, if the substring  off-         function returns a value of zero. If the substring offsets are  not  of
2347         sets are not of interest, pcre_exec() may be called with ovector passed         interest,  pcre_exec()  may  be  called with ovector passed as NULL and
2348         as NULL and ovecsize as zero. However, if  the  pattern  contains  back         ovecsize as zero. However, if the pattern contains back references  and
2349         references  and  the  ovector is not big enough to remember the related         the  ovector is not big enough to remember the related substrings, PCRE
2350         substrings, PCRE has to get additional memory for use during  matching.         has to get additional memory for use during matching. Thus it  is  usu-
2351         Thus it is usually advisable to supply an ovector.         ally advisable to supply an ovector.
2352    
2353         The  pcre_info()  function  can  be used to find out how many capturing         The pcre_fullinfo() function can be used to find out how many capturing
2354         subpatterns there are in a compiled  pattern.  The  smallest  size  for         subpatterns there are in a compiled  pattern.  The  smallest  size  for
2355         ovector  that  will allow for n captured substrings, in addition to the         ovector  that  will allow for n captured substrings, in addition to the
2356         offsets of the substring matched by the whole pattern, is (n+1)*3.         offsets of the substring matched by the whole pattern, is (n+1)*3.
# Line 1937  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2366  MATCHING A PATTERN: THE TRADITIONAL FUNC
2366         expression are also set to -1. For example,  if  the  string  "abc"  is         expression are also set to -1. For example,  if  the  string  "abc"  is
2367         matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not         matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not
2368         matched. The return from the function is 2, because  the  highest  used         matched. The return from the function is 2, because  the  highest  used
2369         capturing subpattern number is 1. However, you can refer to the offsets         capturing  subpattern  number  is 1, and the offsets for for the second
2370         for the second and third capturing subpatterns if  you  wish  (assuming         and third capturing subpatterns (assuming the vector is  large  enough,
2371         the vector is large enough, of course).         of course) are set to -1.
2372    
2373           Note: Elements of ovector that do not correspond to capturing parenthe-
2374           ses in the pattern are never changed. That is, if a pattern contains  n
2375           capturing parentheses, no more than ovector[0] to ovector[2n+1] are set
2376           by pcre_exec(). The other elements retain whatever values  they  previ-
2377           ously had.
2378    
2379         Some  convenience  functions  are  provided for extracting the captured         Some  convenience  functions  are  provided for extracting the captured
2380         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
# Line 1984  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2419  MATCHING A PATTERN: THE TRADITIONAL FUNC
2419         purpose.  If the call via pcre_malloc() fails, this error is given. The         purpose.  If the call via pcre_malloc() fails, this error is given. The
2420         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2421    
2422           This error is also given if pcre_stack_malloc() fails  in  pcre_exec().
2423           This  can happen only when PCRE has been compiled with --disable-stack-
2424           for-recursion.
2425    
2426           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2427    
2428         This error is used by the pcre_copy_substring(),  pcre_get_substring(),         This error is used by the pcre_copy_substring(),  pcre_get_substring(),
# Line 2005  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2444  MATCHING A PATTERN: THE TRADITIONAL FUNC
2444           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2445    
2446         A string that contains an invalid UTF-8 byte sequence was passed  as  a         A string that contains an invalid UTF-8 byte sequence was passed  as  a
2447         subject.         subject.   However,  if  PCRE_PARTIAL_HARD  is set and the problem is a
2448           truncated UTF-8 character at the end of the subject,  PCRE_ERROR_SHORT-
2449           UTF8 is used instead.
2450    
2451           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2452    
2453         The UTF-8 byte sequence that was passed as a subject was valid, but the         The UTF-8 byte sequence that was passed as a subject was valid, but the
2454         value of startoffset did not point to the beginning of a UTF-8  charac-         value of startoffset did not point to the beginning of a UTF-8  charac-
2455         ter.         ter or the end of the subject.
2456    
2457           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2458    
# Line 2020  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2461  MATCHING A PATTERN: THE TRADITIONAL FUNC
2461    
2462           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2463    
2464         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing         This code is no longer in  use.  It  was  formerly  returned  when  the
2465         items  that are not supported for partial matching. See the pcrepartial         PCRE_PARTIAL  option  was used with a compiled pattern containing items
2466         documentation for details of partial matching.         that were  not  supported  for  partial  matching.  From  release  8.00
2467           onwards, there are no restrictions on partial matching.
2468    
2469           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2470    
2471         An unexpected internal error has occurred. This error could  be  caused         An  unexpected  internal error has occurred. This error could be caused
2472         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2473    
2474           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2475    
2476         This  error is given if the value of the ovecsize argument is negative.         This error is given if the value of the ovecsize argument is negative.
2477    
2478           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2479    
# Line 2039  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2481  MATCHING A PATTERN: THE TRADITIONAL FUNC
2481         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2482         description above.         description above.
2483    
          PCRE_ERROR_NULLWSLIMIT    (-22)  
   
        When a group that can match an empty  substring  is  repeated  with  an  
        unbounded  upper  limit, the subject position at the start of the group  
        must be remembered, so that a test for an empty string can be made when  
        the  end  of the group is reached. Some workspace is required for this;  
        if it runs out, this error is given.  
   
2484           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
2485    
2486         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2487    
2488         Error numbers -16 to -20 are not used by pcre_exec().           PCRE_ERROR_BADOFFSET      (-24)
2489    
2490           The value of startoffset was negative or greater than the length of the
2491           subject, that is, the value in length.
2492    
2493             PCRE_ERROR_SHORTUTF8      (-25)
2494    
2495           The  subject  string ended with an incomplete (truncated) UTF-8 charac-
2496           ter, and the PCRE_PARTIAL_HARD option was  set.  Without  this  option,
2497           PCRE_ERROR_BADUTF8 is returned in this situation.
2498    
2499           Error numbers -16 to -20 and -22 are not used by pcre_exec().
2500    
2501    
2502  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
# Line 2067  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2512  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2512         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2513              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2514    
2515         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
2516         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
2517         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2518         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
2519         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
2520         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
2521         substrings.         substrings.
2522    
2523         A substring that contains a binary zero is correctly extracted and  has         A  substring that contains a binary zero is correctly extracted and has
2524         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
2525         string.  However, you can process such a string  by  referring  to  the         string.   However,  you  can  process such a string by referring to the
2526         length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2527         string().  Unfortunately, the interface to pcre_get_substring_list() is         string().  Unfortunately, the interface to pcre_get_substring_list() is
2528         not  adequate for handling strings containing binary zeros, because the         not adequate for handling strings containing binary zeros, because  the
2529         end of the final string is not independently indicated.         end of the final string is not independently indicated.
2530    
2531         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-
2532         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
2533         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
2534         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2535         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
2536         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2537         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
2538         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
2539         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2540    
2541         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
2542         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
2543         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
2544         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
2545         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
2546         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2547         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2548         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
2549         the terminating zero, or one of these error codes:         the terminating zero, or one of these error codes:
2550    
2551           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2552    
2553         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
2554         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2555    
2556           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2557    
2558         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2559    
2560         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
2561         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
2562         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
2563         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
2564         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
2565         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
2566         error code         error code
2567    
2568           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2569    
2570         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2571    
2572         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
2573         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
2574         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
2575         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2576         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
2577         tive for unset substrings.         tive for unset substrings.
2578    
2579         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2580         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
2581         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2582         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
2583         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.
2584         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-
2585         cial  interface  to  another  programming  language  that  cannot   use         cial   interface  to  another  programming  language  that  cannot  use
2586         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-
2587         vided.         vided.
2588    
2589    
# Line 2157  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2602  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2602              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2603              const char **stringptr);              const char **stringptr);
2604    
2605         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-
2606         ber.  For example, for this pattern         ber.  For example, for this pattern
2607    
2608           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
# Line 2166  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2611  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2611         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
2612         name by calling pcre_get_stringnumber(). The first argument is the com-         name by calling pcre_get_stringnumber(). The first argument is the com-
2613         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
2614         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2615         subpattern of that name.         subpattern of that name.
2616    
2617         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
2618         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
2619         are also two functions that do the whole job.         are also two functions that do the whole job.
2620    
2621         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
2622         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
2623         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
2624         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
2625         differences:         differences:
2626    
2627         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
2628         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
2629         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
2630         name-to-number translation table.         name-to-number translation table.
2631    
2632         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2633         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2634         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the         ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
2635         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2636    
2637           Warning: If the pattern uses the (?| feature to set up multiple subpat-
2638           terns with the same number, as described in the  section  on  duplicate
2639           subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2640           distinguish the different subpatterns, because names are  not  included
2641           in  the compiled code. The matching process uses only numbers. For this
2642           reason, the use of different names for subpatterns of the  same  number
2643           causes an error at compile time.
2644    
2645    
2646  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
2647    
2648         int pcre_get_stringtable_entries(const pcre *code,         int pcre_get_stringtable_entries(const pcre *code,
2649              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2650    
2651         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2652         subpatterns  are  not  required  to  be unique. Normally, patterns with         subpatterns are not required to be unique. (Duplicate names are  always
2653         duplicate names are such that in any one match, only one of  the  named         allowed  for subpatterns with the same number, created by using the (?|
2654         subpatterns  participates. An example is shown in the pcrepattern docu-         feature. Indeed, if such subpatterns are named, they  are  required  to
2655         mentation. When duplicates are present, pcre_copy_named_substring() and         use the same names.)
2656         pcre_get_named_substring()  return the first substring corresponding to  
2657         the given name that is set.  If  none  are  set,  an  empty  string  is         Normally, patterns with duplicate names are such that in any one match,
2658         returned.  The pcre_get_stringnumber() function returns one of the num-         only one of the named subpatterns participates. An example is shown  in
2659         bers that are associated with the name, but it is not defined which  it         the pcrepattern documentation.
2660         is.  
2661           When    duplicates   are   present,   pcre_copy_named_substring()   and
2662           pcre_get_named_substring() return the first substring corresponding  to
2663           the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2664           (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2665           function  returns one of the numbers that are associated with the name,
2666           but it is not defined which it is.
2667    
2668         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
2669         name, you must use  the  pcre_get_stringtable_entries()  function.  The         name,  you  must  use  the pcre_get_stringtable_entries() function. The
2670         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
2671         third and fourth are pointers to variables which  are  updated  by  the         third  and  fourth  are  pointers to variables which are updated by the
2672         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
2673         the name-to-number table  for  the  given  name.  The  function  itself         the  name-to-number  table  for  the  given  name.  The function itself
2674         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2675         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-
2676         tion  entitled  Information  about  a  pattern.  Given all the relevant         tion entitled Information about a  pattern.   Given  all  the  relevant
2677         entries for the name, you can extract each of their numbers, and  hence         entries  for the name, you can extract each of their numbers, and hence
2678         the captured data, if any.         the captured data, if any.
2679    
2680    
2681  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
2682    
2683         The  traditional  matching  function  uses a similar algorithm to Perl,         The traditional matching function uses a  similar  algorithm  to  Perl,
2684         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
2685         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
2686         possible match, consider using the alternative matching  function  (see         possible  match,  consider using the alternative matching function (see
2687         below)  instead.  If you cannot use the alternative function, but still         below) instead. If you cannot use the alternative function,  but  still
2688         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
2689         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
2690         tation.         tation.
2691    
2692         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-
2693         tern.   When your callout function is called, extract and save the cur-         tern.  When your callout function is called, extract and save the  cur-
2694         rent matched substring. Then return  1,  which  forces  pcre_exec()  to         rent  matched  substring.  Then  return  1, which forces pcre_exec() to
2695         backtrack  and  try other alternatives. Ultimately, when it runs out of         backtrack and try other alternatives. Ultimately, when it runs  out  of
2696         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2697    
2698    
# Line 2244  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2703  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2703              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
2704              int *workspace, int wscount);              int *workspace, int wscount);
2705    
2706         The function pcre_dfa_exec()  is  called  to  match  a  subject  string         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2707         against  a  compiled pattern, using a matching algorithm that scans the         against a compiled pattern, using a matching algorithm that  scans  the
2708         subject string just once, and does not backtrack.  This  has  different         subject  string  just  once, and does not backtrack. This has different
2709         characteristics  to  the  normal  algorithm, and is not compatible with         characteristics to the normal algorithm, and  is  not  compatible  with
2710         Perl. Some of the features of PCRE patterns are not  supported.  Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2711         theless,  there are times when this kind of matching can be useful. For         theless, there are times when this kind of matching can be useful.  For
2712         a discussion of the two matching algorithms, see the pcrematching docu-         a  discussion  of  the  two matching algorithms, and a list of features
2713         mentation.         that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2714           tion.
2715    
2716         The  arguments  for  the  pcre_dfa_exec()  function are the same as for         The  arguments  for  the  pcre_dfa_exec()  function are the same as for
2717         pcre_exec(), plus two extras. The ovector argument is used in a differ-         pcre_exec(), plus two extras. The ovector argument is used in a differ-
# Line 2286  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2746  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2746    
2747         The  unused  bits  of  the options argument for pcre_dfa_exec() must be         The  unused  bits  of  the options argument for pcre_dfa_exec() must be
2748         zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-         zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-
2749         LINE_xxx,  PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NO_UTF8_CHECK,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2750         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last         PCRE_NOTEMPTY_ATSTART,      PCRE_NO_UTF8_CHECK,       PCRE_BSR_ANYCRLF,
2751         three of these are the same as for pcre_exec(), so their description is         PCRE_BSR_UNICODE,  PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD, PCRE_PAR-
2752         not repeated here.         TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.  All but  the  last
2753           four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
2754           PCRE_PARTIAL         description is not repeated here.
2755    
2756         This has the same general effect as it does for  pcre_exec(),  but  the           PCRE_PARTIAL_HARD
2757         details   are   slightly   different.  When  PCRE_PARTIAL  is  set  for           PCRE_PARTIAL_SOFT
2758         pcre_dfa_exec(), the return code PCRE_ERROR_NOMATCH is  converted  into  
2759         PCRE_ERROR_PARTIAL  if  the  end  of the subject is reached, there have         These have the same general effect as they do for pcre_exec(), but  the
2760         been no complete matches, but there is still at least one matching pos-         details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
2761         sibility.  The portion of the string that provided the partial match is         pcre_dfa_exec(), it returns PCRE_ERROR_PARTIAL if the end of  the  sub-
2762         set as the first matching string.         ject  is  reached  and there is still at least one matching possibility
2763           that requires additional characters. This happens even if some complete
2764           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2765           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2766           of  the  subject  is  reached, there have been no complete matches, but
2767           there is still at least one matching possibility. The  portion  of  the
2768           string  that  was inspected when the longest partial match was found is
2769           set as the first matching string  in  both  cases.   There  is  a  more
2770           detailed  discussion  of partial and multi-segment matching, with exam-
2771           ples, in the pcrepartial documentation.
2772    
2773           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2774    
# Line 2310  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2779  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2779    
2780           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2781    
2782         When  pcre_dfa_exec()  is  called  with  the  PCRE_PARTIAL  option, and         When pcre_dfa_exec() returns a partial match, it is possible to call it
2783         returns a partial match, it is possible to call it  again,  with  addi-         again, with additional subject characters, and have  it  continue  with
2784         tional  subject  characters,  and have it continue with the same match.         the  same match. The PCRE_DFA_RESTART option requests this action; when
2785         The PCRE_DFA_RESTART option requests this action; when it is  set,  the         it is set, the workspace and wscount options must  reference  the  same
2786         workspace  and wscount options must reference the same vector as before         vector  as  before  because data about the match so far is left in them
2787         because data about the match so far is left in  them  after  a  partial         after a partial match. There is more discussion of this facility in the
2788         match.  There  is  more  discussion of this facility in the pcrepartial         pcrepartial documentation.
        documentation.  
2789    
2790     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2791    
2792         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-
2793         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
2794         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
2795         matches  are all initial substrings of the longer matches. For example,         matches are all initial substrings of the longer matches. For  example,
2796         if the pattern         if the pattern
2797    
2798           <.*>           <.*>
# Line 2339  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2807  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2807           <something> <something else>           <something> <something else>
2808           <something> <something else> <something further>           <something> <something else> <something further>
2809    
2810         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,
2811         which  is  the  number of matched substrings. The substrings themselves         which is the number of matched substrings.  The  substrings  themselves
2812         are returned in ovector. Each string uses two elements;  the  first  is         are  returned  in  ovector. Each string uses two elements; the first is
2813         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
2814         fact, all the strings have the same start  offset.  (Space  could  have         fact,  all  the  strings  have the same start offset. (Space could have
2815         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
2816         compatibility with the way pcre_exec() returns data,  even  though  the         compatibility  with  the  way pcre_exec() returns data, even though the
2817         meaning of the strings is different.)         meaning of the strings is different.)
2818    
2819         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-
2820         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
2821         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
2822         filled with the longest matches.         filled with the longest matches.
2823    
2824     Error returns from pcre_dfa_exec()     Error returns from pcre_dfa_exec()
2825    
2826         The pcre_dfa_exec() function returns a negative number when  it  fails.         The  pcre_dfa_exec()  function returns a negative number when it fails.
2827         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
2828         described above.  There are in addition the following errors  that  are         described  above.   There are in addition the following errors that are
2829         specific to pcre_dfa_exec():         specific to pcre_dfa_exec():
2830    
2831           PCRE_ERROR_DFA_UITEM      (-16)           PCRE_ERROR_DFA_UITEM      (-16)
2832    
2833         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-
2834         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
2835         reference.         reference.
2836    
2837           PCRE_ERROR_DFA_UCOND      (-17)           PCRE_ERROR_DFA_UCOND      (-17)
2838    
2839         This  return  is  given  if pcre_dfa_exec() encounters a condition item         This return is given if pcre_dfa_exec()  encounters  a  condition  item
2840         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
2841         in a specific group. These are not supported.         in a specific group. These are not supported.
2842    
2843           PCRE_ERROR_DFA_UMLIMIT    (-18)           PCRE_ERROR_DFA_UMLIMIT    (-18)
2844    
2845         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
2846         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
2847         (it is meaningless).         (it is meaningless).
2848    
2849           PCRE_ERROR_DFA_WSSIZE     (-19)           PCRE_ERROR_DFA_WSSIZE     (-19)
2850    
2851         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
2852         workspace vector.         workspace vector.
2853    
2854           PCRE_ERROR_DFA_RECURSE    (-20)           PCRE_ERROR_DFA_RECURSE    (-20)
2855    
2856         When a recursive subpattern is processed, the matching  function  calls         When  a  recursive subpattern is processed, the matching function calls
2857         itself  recursively,  using  private vectors for ovector and workspace.         itself recursively, using private vectors for  ovector  and  workspace.
2858         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
2859         should be extremely rare, as a vector of size 1000 is used.         should be extremely rare, as a vector of size 1000 is used.
2860    
2861    
2862  SEE ALSO  SEE ALSO
2863    
2864         pcrebuild(3),  pcrecallout(3), pcrecpp(3)(3), pcrematching(3), pcrepar-         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
2865         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3),  pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2866    
2867    
2868  AUTHOR  AUTHOR
# Line 2406  AUTHOR Line 2874  AUTHOR
2874    
2875  REVISION  REVISION
2876    
2877         Last updated: 04 June 2007         Last updated: 21 November 2010
2878         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
2879  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2880    
2881    
# Line 2436  PCRE CALLOUTS Line 2904  PCRE CALLOUTS
2904    
2905           (?C1)abc(?C2)def           (?C1)abc(?C2)def
2906    
2907         If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() is         If  the  PCRE_AUTO_CALLOUT  option  bit  is  set when pcre_compile() or
2908         called, PCRE automatically  inserts  callouts,  all  with  number  255,         pcre_compile2() is called, PCRE  automatically  inserts  callouts,  all
2909         before  each  item in the pattern. For example, if PCRE_AUTO_CALLOUT is         with  number  255,  before  each  item  in the pattern. For example, if
2910         used with the pattern         PCRE_AUTO_CALLOUT is used with the pattern
2911    
2912           A(\d{2}|--)           A(\d{2}|--)
2913    
# Line 2458  PCRE CALLOUTS Line 2926  PCRE CALLOUTS
2926  MISSING CALLOUTS  MISSING CALLOUTS
2927    
2928         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
2929         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
2930         pattern is         example, if the pattern is
2931    
2932           ab(?C4)cd           ab(?C4)cd
2933    
# Line 2468  MISSING CALLOUTS Line 2936  MISSING CALLOUTS
2936         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
2937         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
2938    
2939           If the pattern is studied, PCRE knows the minimum length of a  matching
2940           string,  and will immediately give a "no match" return without actually
2941           running a match if the subject is not long enough, or,  for  unanchored
2942           patterns, if it has been scanned far enough.
2943    
2944           You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
2945           MIZE option to pcre_compile(), pcre_exec(), or pcre_dfa_exec(),  or  by
2946           starting the pattern with (*NO_START_OPT). This slows down the matching
2947           process, but does ensure that callouts such as the  example  above  are
2948           obeyed.
2949    
2950    
2951  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2952    
2953         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
2954         tion  defined by pcre_callout is called (if it is set). This applies to         tion defined by pcre_callout is called (if it is set). This applies  to
2955         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
2956         only  argument  to  the callout function is a pointer to a pcre_callout         only argument to the callout function is a pointer  to  a  pcre_callout
2957         block. This structure contains the following fields:         block. This structure contains the following fields:
2958    
2959           int          version;           int          version;
# Line 2490  THE CALLOUT INTERFACE Line 2969  THE CALLOUT INTERFACE
2969           int          pattern_position;           int          pattern_position;
2970           int          next_item_length;           int          next_item_length;
2971    
2972         The version field is an integer containing the version  number  of  the         The  version  field  is an integer containing the version number of the
2973         block  format. The initial version was 0; the current version is 1. The         block format. The initial version was 0; the current version is 1.  The
2974         version number will change again in future  if  additional  fields  are         version  number  will  change  again in future if additional fields are
2975         added, but the intention is never to remove any of the existing fields.         added, but the intention is never to remove any of the existing fields.
2976    
2977         The callout_number field contains the number of the  callout,  as  com-         The callout_number field contains the number of the  callout,  as  com-
# Line 2559  RETURN VALUES Line 3038  RETURN VALUES
3038         zero, matching fails at the current point, but  the  testing  of  other         zero, matching fails at the current point, but  the  testing  of  other
3039         matching possibilities goes ahead, just as if a lookahead assertion had         matching possibilities goes ahead, just as if a lookahead assertion had
3040         failed. If the value is less than zero, the  match  is  abandoned,  and         failed. If the value is less than zero, the  match  is  abandoned,  and
3041         pcre_exec() (or pcre_dfa_exec()) returns the negative value.         pcre_exec() or pcre_dfa_exec() returns the negative value.
3042    
3043         Negative   values   should   normally   be   chosen  from  the  set  of         Negative   values   should   normally   be   chosen  from  the  set  of
3044         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-         PCRE_ERROR_xxx values. In particular, PCRE_ERROR_NOMATCH forces a stan-
# Line 2577  AUTHOR Line 3056  AUTHOR
3056    
3057  REVISION  REVISION
3058    
3059         Last updated: 29 May 2007         Last updated: 21 November 2010
3060         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
3061  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3062    
3063    
# Line 2592  NAME Line 3071  NAME
3071  DIFFERENCES BETWEEN PCRE AND PERL  DIFFERENCES BETWEEN PCRE AND PERL
3072    
3073         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
3074         handle regular expressions. The differences described here  are  mainly         handle regular expressions. The differences  described  here  are  with
3075         with  respect  to  Perl 5.8, though PCRE version 7.0 contains some fea-         respect to Perl versions 5.10 and above.
        tures that are expected to be in the forthcoming Perl 5.10.  
3076    
3077         1. PCRE has only a subset of Perl's UTF-8 and Unicode support.  Details         1.  PCRE has only a subset of Perl's UTF-8 and Unicode support. Details
3078         of  what  it does have are given in the section on UTF-8 support in the         of what it does have are given in the section on UTF-8 support  in  the
3079         main pcre page.         main pcre page.
3080    
3081         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl
3082         permits  them,  but they do not mean what you might think. For example,         permits them, but they do not mean what you might think.  For  example,
3083         (?!a){3} does not assert that the next three characters are not "a". It         (?!a){3} does not assert that the next three characters are not "a". It
3084         just asserts that the next character is not "a" three times.         just asserts that the next character is not "a" three times.
3085    
3086         3.  Capturing  subpatterns  that occur inside negative lookahead asser-         3. Capturing subpatterns that occur inside  negative  lookahead  asser-
3087         tions are counted, but their entries in the offsets  vector  are  never         tions  are  counted,  but their entries in the offsets vector are never
3088         set.  Perl sets its numerical variables from any such patterns that are         set. Perl sets its numerical variables from any such patterns that  are
3089         matched before the assertion fails to match something (thereby succeed-         matched before the assertion fails to match something (thereby succeed-
3090         ing),  but  only  if the negative lookahead assertion contains just one         ing), but only if the negative lookahead assertion  contains  just  one
3091         branch.         branch.
3092    
3093         4. Though binary zero characters are supported in the  subject  string,         4.  Though  binary zero characters are supported in the subject string,
3094         they are not allowed in a pattern string because it is passed as a nor-         they are not allowed in a pattern string because it is passed as a nor-
3095         mal C string, terminated by zero. The escape sequence \0 can be used in         mal C string, terminated by zero. The escape sequence \0 can be used in
3096         the pattern to represent a binary zero.         the pattern to represent a binary zero.
3097    
3098         5.  The  following Perl escape sequences are not supported: \l, \u, \L,         5. The following Perl escape sequences are not supported: \l,  \u,  \L,
3099         \U, and \N. In fact these are implemented by Perl's general string-han-         \U, and \N. In fact these are implemented by Perl's general string-han-
3100         dling  and are not part of its pattern matching engine. If any of these         dling and are not part of its pattern matching engine. If any of  these
3101         are encountered by PCRE, an error is generated.         are encountered by PCRE, an error is generated.
3102    
3103         6. The Perl escape sequences \p, \P, and \X are supported only if  PCRE         6.  The Perl escape sequences \p, \P, and \X are supported only if PCRE
3104         is  built  with Unicode character property support. The properties that         is built with Unicode character property support. The  properties  that
3105         can be tested with \p and \P are limited to the general category  prop-         can  be tested with \p and \P are limited to the general category prop-
3106         erties  such  as  Lu and Nd, script names such as Greek or Han, and the         erties such as Lu and Nd, script names such as Greek or  Han,  and  the
3107         derived properties Any and L&.         derived  properties  Any  and  L&. PCRE does support the Cs (surrogate)
3108           property, which Perl does not; the  Perl  documentation  says  "Because
3109           Perl hides the need for the user to understand the internal representa-
3110           tion of Unicode characters, there is no need to implement the  somewhat
3111           messy concept of surrogates."
3112    
3113         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-
3114         ters  in  between  are  treated as literals. This is slightly different         ters in between are treated as literals.  This  is  slightly  different
3115         from Perl in that $ and @ are  also  handled  as  literals  inside  the         from  Perl  in  that  $  and  @ are also handled as literals inside the
3116         quotes.  In Perl, they cause variable interpolation (but of course PCRE         quotes. In Perl, they cause variable interpolation (but of course  PCRE
3117         does not have variables). Note the following examples:         does not have variables). Note the following examples:
3118    
3119             Pattern            PCRE matches      Perl matches             Pattern            PCRE matches      Perl matches
# Line 2641  DIFFERENCES BETWEEN PCRE AND PERL Line 3123  DIFFERENCES BETWEEN PCRE AND PERL
3123             \Qabc\$xyz\E       abc\$xyz          abc\$xyz             \Qabc\$xyz\E       abc\$xyz          abc\$xyz
3124             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
3125    
3126         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
3127         classes.         classes.
3128    
3129         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
3130         constructions. However, there is support for recursive  patterns.  This         constructions.  However,  there is support for recursive patterns. This
3131         is  not available in Perl 5.8, but will be in Perl 5.10. Also, the PCRE         is not available in Perl 5.8, but it is in Perl 5.10.  Also,  the  PCRE
3132         "callout" feature allows an external function to be called during  pat-         "callout"  feature allows an external function to be called during pat-
3133         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
3134    
3135         9.  Subpatterns  that  are  called  recursively or as "subroutines" are         9. Subpatterns that are called  recursively  or  as  "subroutines"  are
3136         always treated as atomic groups in  PCRE.  This  is  like  Python,  but         always  treated  as  atomic  groups  in  PCRE. This is like Python, but
3137         unlike Perl.         unlike Perl. There is a discussion of an example that explains this  in
3138           more  detail  in  the section on recursion differences from Perl in the
3139         10.  There are some differences that are concerned with the settings of         pcrepattern page.
3140         captured strings when part of  a  pattern  is  repeated.  For  example,  
3141         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2         10. There are some differences that are concerned with the settings  of
3142           captured  strings  when  part  of  a  pattern is repeated. For example,
3143           matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2
3144         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
3145    
3146         11. PCRE provides some extensions to the Perl regular expression facil-         11.  PCRE's handling of duplicate subpattern numbers and duplicate sub-
3147         ities.   Perl  5.10  will  include new features that are not in earlier         pattern names is not as general as Perl's. This is a consequence of the
3148         versions, some of which (such as named parentheses) have been  in  PCRE         fact the PCRE works internally just with numbers, using an external ta-
3149         for some time. This list is with respect to Perl 5.10:         ble to translate between numbers and names. In  particular,  a  pattern
3150           such  as  (?|(?<a>A)|(?<b)B),  where the two capturing parentheses have
3151         (a)  Although  lookbehind  assertions  must match fixed length strings,         the same number but different names, is not supported,  and  causes  an
3152         each alternative branch of a lookbehind assertion can match a different         error  at compile time. If it were allowed, it would not be possible to
3153         length of string. Perl requires them all to have the same length.         distinguish which parentheses matched, because both names map  to  cap-
3154           turing subpattern number 1. To avoid this confusing situation, an error
3155           is given at compile time.
3156    
3157           12. Perl recognizes comments in some  places  that  PCRE  doesn't,  for
3158           example, between the ( and ? at the start of a subpattern.
3159    
3160           13. PCRE provides some extensions to the Perl regular expression facil-
3161           ities.  Perl 5.10 includes new features that are not  in  earlier  ver-
3162           sions  of  Perl, some of which (such as named parentheses) have been in
3163           PCRE for some time. This list is with respect to Perl 5.10:
3164    
3165           (a) Although lookbehind assertions in  PCRE  must  match  fixed  length
3166           strings,  each alternative branch of a lookbehind assertion can match a
3167           different length of string. Perl requires them all  to  have  the  same
3168           length.
3169    
3170         (b)  If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $         (b)  If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $
3171         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
3172    
3173         (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-
3174         cial  meaning  is  faulted.  Otherwise,  like  Perl,  the  backslash is         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
3175         ignored. (Perl can be made to issue a warning.)         ignored.  (Perl can be made to issue a warning.)
3176    
3177         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-
3178         fiers is inverted, that is, by default they are not greedy, but if fol-         fiers is inverted, that is, by default they are not greedy, but if fol-
# Line 2682  DIFFERENCES BETWEEN PCRE AND PERL Line 3181  DIFFERENCES BETWEEN PCRE AND PERL
3181         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be         (e) PCRE_ANCHORED can be used at matching time to force a pattern to be
3182         tried only at the first matching position in the subject string.         tried only at the first matching position in the subject string.
3183    
3184         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
3185         TURE options for pcre_exec() have no Perl equivalents.         and PCRE_NO_AUTO_CAPTURE options for pcre_exec() have no  Perl  equiva-
3186           lents.
3187    
3188           (g)  The  \R escape sequence can be restricted to match only CR, LF, or
3189           CRLF by the PCRE_BSR_ANYCRLF option.
3190    
3191         (g) The callout facility is PCRE-specific.         (h) The callout facility is PCRE-specific.
3192    
3193         (h) The partial matching facility is PCRE-specific.         (i) The partial matching facility is PCRE-specific.
3194    
3195         (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,
3196         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
3197    
3198         (j)  The  alternative  matching function (pcre_dfa_exec()) matches in a         (k)  The  alternative  matching function (pcre_dfa_exec()) matches in a
3199         different way and is not Perl-compatible.         different way and is not Perl-compatible.
3200    
3201           (l) PCRE recognizes some special sequences such as (*CR) at  the  start
3202           of a pattern that set overall options that cannot be changed within the
3203           pattern.
3204    
3205    
3206  AUTHOR  AUTHOR
3207    
# Line 2705  AUTHOR Line 3212  AUTHOR
3212    
3213  REVISION  REVISION
3214    
3215         Last updated: 06 March 2007         Last updated: 31 October 2010
3216         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
3217  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3218    
3219    
# Line 2719  NAME Line 3226  NAME
3226    
3227  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
3228    
3229         The  syntax  and semantics of the regular expressions supported by PCRE         The  syntax and semantics of the regular expressions that are supported
3230         are described below. Regular expressions are also described in the Perl         by PCRE are described in detail below. There is a quick-reference  syn-
3231         documentation  and  in  a  number  of books, some of which have copious         tax summary in the pcresyntax page. PCRE tries to match Perl syntax and
3232         examples.  Jeffrey Friedl's "Mastering Regular Expressions",  published         semantics as closely as it can. PCRE  also  supports  some  alternative
3233         by  O'Reilly, covers regular expressions in great detail. This descrip-         regular  expression  syntax (which does not conflict with the Perl syn-
3234         tion of PCRE's regular expressions is intended as reference material.         tax) in order to provide some compatibility with regular expressions in
3235           Python, .NET, and Oniguruma.
3236    
3237           Perl's  regular expressions are described in its own documentation, and
3238           regular expressions in general are covered in a number of  books,  some
3239           of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
3240           Expressions", published by  O'Reilly,  covers  regular  expressions  in
3241           great  detail.  This  description  of  PCRE's  regular  expressions  is
3242           intended as reference material.
3243    
3244         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
3245         However,  there is now also support for UTF-8 character strings. To use         However,  there is now also support for UTF-8 character strings. To use
3246         this, you must build PCRE to  include  UTF-8  support,  and  then  call         this, PCRE must be built to include UTF-8 support, and  you  must  call
3247         pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern         pcre_compile()  or  pcre_compile2() with the PCRE_UTF8 option. There is
3248         matching is mentioned in several places below. There is also a  summary         also a special sequence that can be given at the start of a pattern:
3249         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre  
3250         page.           (*UTF8)
3251    
3252           Starting a pattern with this sequence  is  equivalent  to  setting  the
3253           PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3254           UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3255           below.  There  is  also  a  summary of UTF-8 features in the section on
3256           UTF-8 support in the main pcre page.
3257    
3258           Another special sequence that may appear at the start of a  pattern  or
3259           in combination with (*UTF8) is:
3260    
3261         The remainder of this document discusses the  patterns  that  are  sup-           (*UCP)
3262         ported  by  PCRE when its main matching function, pcre_exec(), is used.  
3263         From  release  6.0,   PCRE   offers   a   second   matching   function,         This  has  the  same  effect  as setting the PCRE_UCP option: it causes
3264         pcre_dfa_exec(),  which matches using a different algorithm that is not         sequences such as \d and \w to  use  Unicode  properties  to  determine
3265           character types, instead of recognizing only characters with codes less
3266           than 128 via a lookup table.
3267    
3268           If a pattern starts with (*NO_START_OPT), it has  the  same  effect  as
3269           setting the PCRE_NO_START_OPTIMIZE option either at compile or matching
3270           time. There are also some more of these special sequences that are con-
3271           cerned with the handling of newlines; they are described below.
3272    
3273           The  remainder  of  this  document discusses the patterns that are sup-
3274           ported by PCRE when its main matching function, pcre_exec(),  is  used.
3275           From   release   6.0,   PCRE   offers   a   second  matching  function,
3276           pcre_dfa_exec(), which matches using a different algorithm that is  not
3277         Perl-compatible. Some of the features discussed below are not available         Perl-compatible. Some of the features discussed below are not available
3278         when  pcre_dfa_exec()  is used. The advantages and disadvantages of the         when pcre_dfa_exec() is used. The advantages and disadvantages  of  the
3279         alternative function, and how it differs from the normal function,  are         alternative  function, and how it differs from the normal function, are
3280         discussed in the pcrematching page.         discussed in the pcrematching page.
3281    
3282    
3283    NEWLINE CONVENTIONS
3284    
3285           PCRE supports five different conventions for indicating line breaks  in
3286           strings:  a  single  CR (carriage return) character, a single LF (line-
3287           feed) character, the two-character sequence CRLF, any of the three pre-
3288           ceding,  or  any Unicode newline sequence. The pcreapi page has further
3289           discussion about newlines, and shows how to set the newline  convention
3290           in the options arguments for the compiling and matching functions.
3291    
3292           It  is also possible to specify a newline convention by starting a pat-
3293           tern string with one of the following five sequences:
3294    
3295             (*CR)        carriage return
3296             (*LF)        linefeed
3297             (*CRLF)      carriage return, followed by linefeed
3298             (*ANYCRLF)   any of the three above
3299             (*ANY)       all Unicode newline sequences
3300    
3301           These override the default and the options given to  pcre_compile()  or
3302           pcre_compile2().  For example, on a Unix system where LF is the default
3303           newline sequence, the pattern
3304    
3305             (*CR)a.b
3306    
3307           changes the convention to CR. That pattern matches "a\nb" because LF is
3308           no  longer  a  newline. Note that these special settings, which are not
3309           Perl-compatible, are recognized only at the very start  of  a  pattern,
3310           and  that  they  must  be  in  upper  case. If more than one of them is
3311           present, the last one is used.
3312    
3313           The newline convention affects the interpretation of the dot  metachar-
3314           acter  when  PCRE_DOTALL is not set, and also the behaviour of \N. How-
3315           ever, it does not affect  what  the  \R  escape  sequence  matches.  By
3316           default,  this is any Unicode newline sequence, for Perl compatibility.
3317           However, this can be changed; see the description of \R in the  section
3318           entitled  "Newline sequences" below. A change of \R setting can be com-
3319           bined with a change of newline convention.
3320    
3321    
3322  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
3323    
3324         A  regular  expression  is  a pattern that is matched against a subject         A regular expression is a pattern that is  matched  against  a  subject
3325         string from left to right. Most characters stand for  themselves  in  a         string  from  left  to right. Most characters stand for themselves in a
3326         pattern,  and  match  the corresponding characters in the subject. As a         pattern, and match the corresponding characters in the  subject.  As  a
3327         trivial example, the pattern         trivial example, the pattern
3328    
3329           The quick brown fox           The quick brown fox
3330    
3331         matches a portion of a subject string that is identical to itself. When         matches a portion of a subject string that is identical to itself. When
3332         caseless  matching is specified (the PCRE_CASELESS option), letters are         caseless matching is specified (the PCRE_CASELESS option), letters  are
3333         matched independently of case. In UTF-8 mode, PCRE  always  understands         matched  independently  of case. In UTF-8 mode, PCRE always understands
3334         the  concept  of case for characters whose values are less than 128, so         the concept of case for characters whose values are less than  128,  so
3335         caseless matching is always possible. For characters with  higher  val-         caseless  matching  is always possible. For characters with higher val-
3336         ues,  the concept of case is supported if PCRE is compiled with Unicode         ues, the concept of case is supported if PCRE is compiled with  Unicode
3337         property support, but not otherwise.   If  you  want  to  use  caseless         property  support,  but  not  otherwise.   If  you want to use caseless
3338         matching  for  characters  128  and above, you must ensure that PCRE is         matching for characters 128 and above, you must  ensure  that  PCRE  is
3339         compiled with Unicode property support as well as with UTF-8 support.         compiled with Unicode property support as well as with UTF-8 support.
3340    
3341         The power of regular expressions comes  from  the  ability  to  include         The  power  of  regular  expressions  comes from the ability to include
3342         alternatives  and  repetitions in the pattern. These are encoded in the         alternatives and repetitions in the pattern. These are encoded  in  the
3343         pattern by the use of metacharacters, which do not stand for themselves         pattern by the use of metacharacters, which do not stand for themselves
3344         but instead are interpreted in some special way.         but instead are interpreted in some special way.
3345    
3346         There  are  two different sets of metacharacters: those that are recog-         There are two different sets of metacharacters: those that  are  recog-
3347         nized anywhere in the pattern except within square brackets, and  those         nized  anywhere in the pattern except within square brackets, and those
3348         that  are  recognized  within square brackets. Outside square brackets,         that are recognized within square brackets.  Outside  square  brackets,
3349         the metacharacters are as follows:         the metacharacters are as follows:
3350    
3351           \      general escape character with several uses           \      general escape character with several uses
# Line 2789  CHARACTERS AND METACHARACTERS Line 3364  CHARACTERS AND METACHARACTERS
3364                  also "possessive quantifier"                  also "possessive quantifier"
3365           {      start min/max quantifier           {      start min/max quantifier
3366    
3367         Part of a pattern that is in square brackets  is  called  a  "character         Part  of  a  pattern  that is in square brackets is called a "character
3368         class". In a character class the only metacharacters are:         class". In a character class the only metacharacters are:
3369    
3370           \      general escape character           \      general escape character
# Line 2799  CHARACTERS AND METACHARACTERS Line 3374  CHARACTERS AND METACHARACTERS
3374                    syntax)                    syntax)
3375           ]      terminates the character class           ]      terminates the character class
3376    
3377         The  following sections describe the use of each of the metacharacters.         The following sections describe the use of each of the metacharacters.
3378    
3379    
3380  BACKSLASH  BACKSLASH
3381    
3382         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3383         a  non-alphanumeric  character,  it takes away any special meaning that         a character that is not a number or a letter, it takes away any special
3384         character may have. This  use  of  backslash  as  an  escape  character         meaning that character may have. This use of  backslash  as  an  escape
3385         applies both inside and outside character classes.         character applies both inside and outside character classes.
3386    
3387         For  example,  if  you want to match a * character, you write \* in the         For  example,  if  you want to match a * character, you write \* in the
3388         pattern.  This escaping action applies whether  or  not  the  following         pattern.  This escaping action applies whether  or  not  the  following
# Line 2816  BACKSLASH Line 3391  BACKSLASH
3391         that  it stands for itself. In particular, if you want to match a back-         that  it stands for itself. In particular, if you want to match a back-
3392         slash, you write \\.         slash, you write \\.
3393    
3394           In UTF-8 mode, only ASCII numbers and letters have any special  meaning
3395           after  a  backslash.  All  other characters (in particular, those whose
3396           codepoints are greater than 127) are treated as literals.
3397    
3398         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in         If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
3399         the  pattern (other than in a character class) and characters between a         the  pattern (other than in a character class) and characters between a
3400         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
# Line 2836  BACKSLASH Line 3415  BACKSLASH
3415           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3416    
3417         The \Q...\E sequence is recognized both inside  and  outside  character         The \Q...\E sequence is recognized both inside  and  outside  character
3418         classes.         classes.  An isolated \E that is not preceded by \Q is ignored.
3419    
3420     Non-printing characters     Non-printing characters
3421    
# Line 2844  BACKSLASH Line 3423  BACKSLASH
3423         acters in patterns in a visible manner. There is no restriction on  the         acters in patterns in a visible manner. There is no restriction on  the
3424         appearance  of non-printing characters, apart from the binary zero that         appearance  of non-printing characters, apart from the binary zero that
3425         terminates a pattern, but when a pattern  is  being  prepared  by  text         terminates a pattern, but when a pattern  is  being  prepared  by  text
3426         editing,  it  is  usually  easier  to  use  one of the following escape         editing,  it  is  often  easier  to  use  one  of  the following escape
3427         sequences than the binary character it represents:         sequences than the binary character it represents:
3428    
3429           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3430           \cx       "control-x", where x is any character           \cx       "control-x", where x is any ASCII character
3431           \e        escape (hex 1B)           \e        escape (hex 1B)
3432           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3433           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3434           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3435           \t        tab (hex 09)           \t        tab (hex 09)
3436           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or back reference
3437           \xhh      character with hex code hh           \xhh      character with hex code hh
3438           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh..
3439    
3440         The precise effect of \cx is as follows: if x is a lower  case  letter,         The precise effect of \cx is as follows: if x is a lower  case  letter,
3441         it  is converted to upper case. Then bit 6 of the character (hex 40) is         it  is converted to upper case. Then bit 6 of the character (hex 40) is
3442         inverted.  Thus \cz becomes hex 1A, but \c{ becomes hex 3B,  while  \c;         inverted.  Thus \cz becomes hex 1A (z is 7A), but \c{ becomes hex 3B ({
3443         becomes hex 7B.         is  7B),  while  \c; becomes hex 7B (; is 3B). If the byte following \c
3444           has a value greater than 127, a compile-time error occurs.  This  locks
3445           out  non-ASCII  characters in both byte mode and UTF-8 mode. (When PCRE
3446           is compiled in EBCDIC mode, all byte values are  valid.  A  lower  case
3447           letter is converted to upper case, and then the 0xc0 bits are flipped.)
3448    
3449         After  \x, from zero to two hexadecimal digits are read (letters can be         After  \x, from zero to two hexadecimal digits are read (letters can be
3450         in upper or lower case). Any number of hexadecimal  digits  may  appear         in upper or lower case). Any number of hexadecimal  digits  may  appear
3451         between  \x{  and  },  but the value of the character code must be less         between  \x{  and  },  but the value of the character code must be less
3452         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode (that is,         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,
3453         the  maximum  hexadecimal  value is 7FFFFFFF). If characters other than         the  maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger
3454         hexadecimal digits appear between \x{ and }, or if there is  no  termi-         than the largest Unicode code point, which is 10FFFF.
3455         nating  }, this form of escape is not recognized.  Instead, the initial  
3456         \x will be interpreted as a basic hexadecimal escape, with no following         If characters other than hexadecimal digits appear between \x{  and  },
3457         digits, giving a character whose value is zero.         or if there is no terminating }, this form of escape is not recognized.
3458           Instead, the initial \x will be  interpreted  as  a  basic  hexadecimal
3459           escape,  with  no  following  digits, giving a character whose value is
3460           zero.
3461    
3462         Characters whose value is less than 256 can be defined by either of the         Characters whose value is less than 256 can be defined by either of the
3463         two syntaxes for \x. There is no difference in the way  they  are  han-         two  syntaxes  for  \x. There is no difference in the way they are han-
3464         dled. For example, \xdc is exactly the same as \x{dc}.         dled. For example, \xdc is exactly the same as \x{dc}.
3465    
3466         After  \0  up  to two further octal digits are read. If there are fewer         After \0 up to two further octal digits are read. If  there  are  fewer
3467         than two digits, just  those  that  are  present  are  used.  Thus  the         than  two  digits,  just  those  that  are  present  are used. Thus the
3468         sequence \0\x\07 specifies two binary zeros followed by a BEL character         sequence \0\x\07 specifies two binary zeros followed by a BEL character
3469         (code value 7). Make sure you supply two digits after the initial  zero         (code  value 7). Make sure you supply two digits after the initial zero
3470         if the pattern character that follows is itself an octal digit.         if the pattern character that follows is itself an octal digit.
3471    
3472         The handling of a backslash followed by a digit other than 0 is compli-         The handling of a backslash followed by a digit other than 0 is compli-
3473         cated.  Outside a character class, PCRE reads it and any following dig-         cated.  Outside a character class, PCRE reads it and any following dig-
3474         its  as  a  decimal  number. If the number is less than 10, or if there         its as a decimal number. If the number is less than  10,  or  if  there
3475         have been at least that many previous capturing left parentheses in the         have been at least that many previous capturing left parentheses in the
3476         expression,  the  entire  sequence  is  taken  as  a  back reference. A         expression, the entire  sequence  is  taken  as  a  back  reference.  A
3477         description of how this works is given later, following the  discussion         description  of how this works is given later, following the discussion
3478         of parenthesized subpatterns.         of parenthesized subpatterns.
3479    
3480         Inside  a  character  class, or if the decimal number is greater than 9         Inside a character class, or if the decimal number is  greater  than  9
3481         and there have not been that many capturing subpatterns, PCRE  re-reads         and  there have not been that many capturing subpatterns, PCRE re-reads
3482         up to three octal digits following the backslash, and uses them to gen-         up to three octal digits following the backslash, and uses them to gen-
3483         erate a data character. Any subsequent digits stand for themselves.  In         erate  a data character. Any subsequent digits stand for themselves. In
3484         non-UTF-8  mode,  the  value  of a character specified in octal must be         non-UTF-8 mode, the value of a character specified  in  octal  must  be
3485         less than \400. In UTF-8 mode, values up to  \777  are  permitted.  For         less  than  \400.  In  UTF-8 mode, values up to \777 are permitted. For
3486         example:         example:
3487    
3488           \040   is another way of writing a space           \040   is another way of writing a space
# Line 2914  BACKSLASH Line 3500  BACKSLASH
3500           \81    is either a back reference, or a binary zero           \81    is either a back reference, or a binary zero
3501                     followed by the two characters "8" and "1"                     followed by the two characters "8" and "1"
3502    
3503         Note  that  octal  values of 100 or greater must not be introduced by a         Note that octal values of 100 or greater must not be  introduced  by  a
3504         leading zero, because no more than three octal digits are ever read.         leading zero, because no more than three octal digits are ever read.
3505    
3506         All the sequences that define a single character value can be used both         All the sequences that define a single character value can be used both
3507         inside  and  outside character classes. In addition, inside a character         inside and outside character classes. In addition, inside  a  character
3508         class, the sequence \b is interpreted as the backspace  character  (hex         class,  the  sequence \b is interpreted as the backspace character (hex
3509         08),  and the sequences \R and \X are interpreted as the characters "R"         08). The sequences \B, \N, \R, and \X are not special inside a  charac-
3510         and "X", respectively. Outside a character class, these sequences  have         ter  class.  Like  any  other  unrecognized  escape sequences, they are
3511         different meanings (see below).         treated as the literal characters "B", "N", "R", and  "X"  by  default,
3512           but cause an error if the PCRE_EXTRA option is set. Outside a character
3513           class, these sequences have different meanings.
3514    
3515     Absolute and relative back references     Absolute and relative back references
3516    
3517         The  sequence  \g followed by a positive or negative number, optionally         The sequence \g followed by an unsigned or a negative  number,  option-
3518         enclosed in braces, is an absolute or relative back reference. A  named         ally  enclosed  in braces, is an absolute or relative back reference. A
3519         back  reference can be coded as \g{name}. Back references are discussed         named back reference can be coded as \g{name}. Back references are dis-
3520         later, following the discussion of parenthesized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3521    
3522       Absolute and relative subroutine calls
3523    
3524           For  compatibility with Oniguruma, the non-Perl syntax \g followed by a
3525           name or a number enclosed either in angle brackets or single quotes, is
3526           an  alternative  syntax for referencing a subpattern as a "subroutine".
3527           Details are discussed later.   Note  that  \g{...}  (Perl  syntax)  and
3528           \g<...>  (Oniguruma  syntax)  are  not synonymous. The former is a back
3529           reference; the latter is a subroutine call.
3530    
3531     Generic character types     Generic character types
3532    
3533         Another use of backslash is for specifying generic character types. The         Another use of backslash is for specifying generic character types:
        following are always recognized:  
3534    
3535           \d     any decimal digit           \d     any decimal digit
3536           \D     any character that is not a decimal digit           \D     any character that is not a decimal digit
3537             \h     any horizontal whitespace character
3538             \H     any character that is not a horizontal whitespace character
3539           \s     any whitespace character           \s     any whitespace character
3540           \S     any character that is not a whitespace character           \S     any character that is not a whitespace character
3541             \v     any vertical whitespace character
3542             \V     any character that is not a vertical whitespace character
3543           \w     any "word" character           \w     any "word" character
3544           \W     any "non-word" character           \W     any "non-word" character
3545    
3546         Each pair of escape sequences partitions the complete set of characters         There is also the single sequence \N, which matches a non-newline char-
3547         into two disjoint sets. Any given character matches one, and only  one,         acter.   This  is the same as the "." metacharacter when PCRE_DOTALL is
3548         of each pair.         not set.
3549    
3550         These character type sequences can appear both inside and outside char-         Each pair of lower and upper case escape sequences partitions the  com-
3551         acter classes. They each match one character of the  appropriate  type.         plete  set  of  characters  into two disjoint sets. Any given character
3552         If  the current matching point is at the end of the subject string, all         matches one, and only one, of each pair. The sequences can appear  both
3553         of them fail, since there is no character to match.         inside  and outside character classes. They each match one character of
3554           the appropriate type. If the current matching point is at  the  end  of
3555           the  subject string, all of them fail, because there is no character to
3556           match.
3557    
3558         For compatibility with Perl, \s does not match the VT  character  (code         For compatibility with Perl, \s does not match the VT  character  (code
3559         11).   This makes it different from the the POSIX "space" class. The \s         11).   This makes it different from the the POSIX "space" class. The \s
3560         characters are HT (9), LF (10), FF (12), CR (13), and space  (32).  (If         characters are HT (9), LF (10), FF (12), CR (13), and  space  (32).  If
3561         "use locale;" is included in a Perl script, \s may match the VT charac-         "use locale;" is included in a Perl script, \s may match the VT charac-
3562         ter. In PCRE, it never does.)         ter. In PCRE, it never does.
3563    
3564         A "word" character is an underscore or any character less than 256 that         A "word" character is an underscore or any character that is  a  letter
3565         is  a  letter  or  digit.  The definition of letters and digits is con-         or  digit.   By  default,  the definition of letters and digits is con-
3566         trolled by PCRE's low-valued character tables, and may vary if  locale-         trolled by PCRE's low-valued character tables, and may vary if  locale-
3567         specific  matching is taking place (see "Locale support" in the pcreapi         specific  matching is taking place (see "Locale support" in the pcreapi
3568         page). For example, in a French locale such  as  "fr_FR"  in  Unix-like         page). For example, in a French locale such  as  "fr_FR"  in  Unix-like
3569         systems,  or "french" in Windows, some character codes greater than 128         systems,  or "french" in Windows, some character codes greater than 128
3570         are used for accented letters, and these are matched by \w.         are used for accented letters, and these are then matched  by  \w.  The
3571           use of locales with Unicode is discouraged.
3572    
3573         In UTF-8 mode, characters with values greater than 128 never match  \d,         By  default,  in  UTF-8  mode,  characters with values greater than 128
3574         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-         never match \d, \s, or \w, and always  match  \D,  \S,  and  \W.  These
3575         code character property support is available. The use of  locales  with         sequences  retain their original meanings from before UTF-8 support was
3576         Unicode is discouraged.         available, mainly for efficiency reasons. However, if PCRE is  compiled
3577           with  Unicode property support, and the PCRE_UCP option is set, the be-
3578           haviour is changed so that Unicode properties  are  used  to  determine
3579           character types, as follows:
3580    
3581             \d  any character that \p{Nd} matches (decimal digit)
3582             \s  any character that \p{Z} matches, plus HT, LF, FF, CR
3583             \w  any character that \p{L} or \p{N} matches, plus underscore
3584    
3585           The  upper case escapes match the inverse sets of characters. Note that
3586           \d matches only decimal digits, whereas \w matches any  Unicode  digit,
3587           as  well as any Unicode letter, and underscore. Note also that PCRE_UCP
3588           affects \b, and \B because they are defined in  terms  of  \w  and  \W.
3589           Matching these sequences is noticeably slower when PCRE_UCP is set.
3590    
3591           The  sequences  \h, \H, \v, and \V are features that were added to Perl
3592           at release 5.10. In contrast to the other sequences, which  match  only
3593           ASCII  characters  by  default,  these always match certain high-valued
3594           codepoints in UTF-8 mode, whether or not PCRE_UCP is set. The  horizon-
3595           tal space characters are:
3596    
3597             U+0009     Horizontal tab
3598             U+0020     Space
3599             U+00A0     Non-break space
3600             U+1680     Ogham space mark
3601             U+180E     Mongolian vowel separator
3602             U+2000     En quad
3603             U+2001     Em quad
3604             U+2002     En space
3605             U+2003     Em space
3606             U+2004     Three-per-em space
3607             U+2005     Four-per-em space
3608             U+2006     Six-per-em space
3609             U+2007     Figure space
3610             U+2008     Punctuation space
3611             U+2009     Thin space
3612             U+200A     Hair space
3613             U+202F     Narrow no-break space
3614             U+205F     Medium mathematical space
3615             U+3000     Ideographic space
3616    
3617           The vertical space characters are:
3618    
3619             U+000A     Linefeed
3620             U+000B     Vertical tab
3621             U+000C     Formfeed
3622             U+000D     Carriage return
3623             U+0085     Next line
3624             U+2028     Line separator
3625             U+2029     Paragraph separator
3626    
3627     Newline sequences     Newline sequences
3628    
3629         Outside  a  character class, the escape sequence \R matches any Unicode         Outside  a  character class, by default, the escape sequence \R matches
3630         newline sequence. This is an extension to Perl. In non-UTF-8 mode \R is         any Unicode newline sequence. In non-UTF-8 mode \R is equivalent to the
3631         equivalent to the following:         following:
3632    
3633           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3634    
# Line 2991  BACKSLASH Line 3644  BACKSLASH
3644         rator, U+2029).  Unicode character property support is not  needed  for         rator, U+2029).  Unicode character property support is not  needed  for
3645         these characters to be recognized.         these characters to be recognized.
3646    
3647         Inside a character class, \R matches the letter "R".         It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3648           the complete set  of  Unicode  line  endings)  by  setting  the  option
3649           PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3650           (BSR is an abbrevation for "backslash R".) This can be made the default
3651           when  PCRE  is  built;  if this is the case, the other behaviour can be
3652           requested via the PCRE_BSR_UNICODE option.   It  is  also  possible  to
3653           specify  these  settings  by  starting a pattern string with one of the
3654           following sequences:
3655    
3656             (*BSR_ANYCRLF)   CR, LF, or CRLF only
3657             (*BSR_UNICODE)   any Unicode newline sequence
3658    
3659           These override the default and the options given to  pcre_compile()  or
3660           pcre_compile2(),  but  they  can  be  overridden  by  options  given to
3661           pcre_exec() or pcre_dfa_exec(). Note that these special settings, which
3662           are  not  Perl-compatible,  are  recognized only at the very start of a
3663           pattern, and that they must be in upper case. If more than one of  them
3664           is present, the last one is used. They can be combined with a change of
3665           newline convention; for example, a pattern can start with:
3666    
3667             (*ANY)(*BSR_ANYCRLF)
3668    
3669           They can also be combined with the (*UTF8) or (*UCP) special sequences.
3670           Inside  a  character  class,  \R  is  treated as an unrecognized escape
3671           sequence, and so matches the letter "R" by default, but causes an error
3672           if PCRE_EXTRA is set.
3673    
3674     Unicode character properties     Unicode character properties
3675    
3676         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
3677         tional escape sequences to match  character  properties  are  available         tional escape sequences that match characters with specific  properties
3678         when UTF-8 mode is selected. They are:         are  available.   When not in UTF-8 mode, these sequences are of course
3679           limited to testing characters whose codepoints are less than  256,  but
3680           they do work in this mode.  The extra escape sequences are:
3681    
3682           \p{xx}   a character with the xx property           \p{xx}   a character with the xx property
3683           \P{xx}   a character without the xx property           \P{xx}   a character without the xx property
3684           \X       an extended Unicode sequence           \X       an extended Unicode sequence
3685    
3686         The  property  names represented by xx above are limited to the Unicode         The  property  names represented by xx above are limited to the Unicode
3687         script names, the general category properties, and "Any", which matches         script names, the general category properties, "Any", which matches any
3688         any character (including newline). Other properties such as "InMusical-         character   (including  newline),  and  some  special  PCRE  properties
3689         Symbols" are not currently supported by PCRE. Note  that  \P{Any}  does         (described in the next section).  Other Perl properties such as  "InMu-
3690         not match any characters, so always causes a match failure.         sicalSymbols"  are  not  currently supported by PCRE. Note that \P{Any}
3691           does not match any characters, so always causes a match failure.
3692    
3693         Sets of Unicode characters are defined as belonging to certain scripts.         Sets of Unicode characters are defined as belonging to certain scripts.
3694         A character from one of these sets can be matched using a script  name.         A  character from one of these sets can be matched using a script name.
3695         For example:         For example:
3696    
3697           \p{Greek}           \p{Greek}
3698           \P{Han}           \P{Han}
3699    
3700         Those  that are not part of an identified script are lumped together as         Those that are not part of an identified script are lumped together  as
3701         "Common". The current list of scripts is:         "Common". The current list of scripts is:
3702    
3703         Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,         Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille,
3704         Buhid,   Canadian_Aboriginal,   Cherokee,  Common,  Coptic,  Cuneiform,         Buginese, Buhid, Canadian_Aboriginal, Carian, Cham,  Cherokee,  Common,
3705         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,         Coptic,   Cuneiform,  Cypriot,  Cyrillic,  Deseret,  Devanagari,  Egyp-
3706         Gothic,  Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hira-         tian_Hieroglyphs,  Ethiopic,  Georgian,  Glagolitic,   Gothic,   Greek,
3707         gana, Inherited, Kannada,  Katakana,  Kharoshthi,  Khmer,  Lao,  Latin,         Gujarati,  Gurmukhi,  Han,  Hangul,  Hanunoo,  Hebrew,  Hiragana, Impe-
3708         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,         rial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian,
3709         Ogham, Old_Italic, Old_Persian, Oriya, Osmanya,  Phags_Pa,  Phoenician,         Javanese,  Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Lao,
3710         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,         Latin,  Lepcha,  Limbu,  Linear_B,  Lisu,  Lycian,  Lydian,  Malayalam,
3711         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.         Meetei_Mayek,  Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham, Old_Italic,
3712           Old_Persian, Old_South_Arabian, Old_Turkic, Ol_Chiki,  Oriya,  Osmanya,
3713         Each character has exactly one general category property, specified  by         Phags_Pa,  Phoenician,  Rejang,  Runic, Samaritan, Saurashtra, Shavian,
3714         a two-letter abbreviation. For compatibility with Perl, negation can be         Sinhala, Sundanese, Syloti_Nagri, Syriac,  Tagalog,  Tagbanwa,  Tai_Le,
3715         specified by including a circumflex between the opening brace  and  the         Tai_Tham,  Tai_Viet,  Tamil,  Telugu,  Thaana, Thai, Tibetan, Tifinagh,
3716         property name. For example, \p{^Lu} is the same as \P{Lu}.         Ugaritic, Vai, Yi.
3717    
3718           Each character has exactly one Unicode general category property, spec-
3719           ified  by a two-letter abbreviation. For compatibility with Perl, nega-
3720           tion can be specified by including a  circumflex  between  the  opening
3721           brace  and  the  property  name.  For  example,  \p{^Lu} is the same as
3722           \P{Lu}.
3723    
3724         If only one letter is specified with \p or \P, it includes all the gen-         If only one letter is specified with \p or \P, it includes all the gen-
3725         eral category properties that start with that letter. In this case,  in         eral  category properties that start with that letter. In this case, in
3726         the  absence of negation, the curly brackets in the escape sequence are         the absence of negation, the curly brackets in the escape sequence  are
3727         optional; these two examples have the same effect:         optional; these two examples have the same effect:
3728    
3729           \p{L}           \p{L}
# Line 3088  BACKSLASH Line 3775  BACKSLASH
3775           Zp    Paragraph separator           Zp    Paragraph separator
3776           Zs    Space separator           Zs    Space separator
3777    
3778         The special property L& is also supported: it matches a character  that         The  special property L& is also supported: it matches a character that
3779         has  the  Lu,  Ll, or Lt property, in other words, a letter that is not         has the Lu, Ll, or Lt property, in other words, a letter  that  is  not
3780         classified as a modifier or "other".         classified as a modifier or "other".
3781    
3782         The long synonyms for these properties  that  Perl  supports  (such  as         The  Cs  (Surrogate)  property  applies only to characters in the range
3783         \p{Letter})  are  not  supported by PCRE, nor is it permitted to prefix         U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see
3784           RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
3785           ing has been turned off (see the discussion  of  PCRE_NO_UTF8_CHECK  in
3786           the pcreapi page). Perl does not support the Cs property.
3787    
3788           The  long  synonyms  for  property  names  that  Perl supports (such as
3789           \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix
3790         any of these properties with "Is".         any of these properties with "Is".
3791    
3792         No character that is in the Unicode table has the Cn (unassigned) prop-         No character that is in the Unicode table has the Cn (unassigned) prop-
3793         erty.  Instead, this property is assumed for any code point that is not         erty.  Instead, this property is assumed for any code point that is not
3794         in the Unicode table.         in the Unicode table.
3795    
3796         Specifying caseless matching does not affect  these  escape  sequences.         Specifying  caseless  matching  does not affect these escape sequences.
3797         For example, \p{Lu} always matches only upper case letters.         For example, \p{Lu} always matches only upper case letters.
3798    
3799         The  \X  escape  matches  any number of Unicode characters that form an         The \X escape matches any number of Unicode  characters  that  form  an
3800         extended Unicode sequence. \X is equivalent to         extended Unicode sequence. \X is equivalent to
3801    
3802           (?>\PM\pM*)           (?>\PM\pM*)
3803    
3804         That is, it matches a character without the "mark"  property,  followed         That  is,  it matches a character without the "mark" property, followed
3805         by  zero  or  more  characters with the "mark" property, and treats the         by zero or more characters with the "mark"  property,  and  treats  the
3806         sequence as an atomic group (see below).  Characters  with  the  "mark"         sequence  as  an  atomic group (see below).  Characters with the "mark"
3807         property are typically accents that affect the preceding character.         property are typically accents that  affect  the  preceding  character.
3808           None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X
3809           matches any one character.
3810    
3811         Matching  characters  by Unicode property is not fast, because PCRE has         Matching characters by Unicode property is not fast, because  PCRE  has
3812         to search a structure that contains  data  for  over  fifteen  thousand         to  search  a  structure  that  contains data for over fifteen thousand
3813         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
3814         \w do not use Unicode properties in PCRE.         \w  do  not  use  Unicode properties in PCRE by default, though you can
3815           make them do so by setting the PCRE_UCP option for pcre_compile() or by
3816