/[pcre]/code/trunk/doc/pcre.txt
ViewVC logotype

Diff of /code/trunk/doc/pcre.txt

Parent Directory Parent Directory | Revision Log Revision Log | View Patch Patch

revision 123 by ph10, Mon Mar 12 15:19:06 2007 UTC revision 678 by ph10, Sun Aug 28 15:23:03 2011 UTC
# Line 2  Line 2 
2  This file contains a concatenation of the PCRE man pages, converted to plain  This file contains a concatenation of the PCRE man pages, converted to plain
3  text format for ease of searching with a text editor, or for use on systems  text format for ease of searching with a text editor, or for use on systems
4  that do not have a man page processor. The small individual files that give  that do not have a man page processor. The small individual files that give
5  synopses of each function in the library have not been included. There are  synopses of each function in the library have not been included. Neither has
6  separate text files for the pcregrep and pcretest commands.  the pcredemo program. There are separate text files for the pcregrep and
7    pcretest commands.
8  -----------------------------------------------------------------------------  -----------------------------------------------------------------------------
9    
10    
# Line 18  INTRODUCTION Line 19  INTRODUCTION
19    
20         The  PCRE  library is a set of functions that implement regular expres-         The  PCRE  library is a set of functions that implement regular expres-
21         sion pattern matching using the same syntax and semantics as Perl, with         sion pattern matching using the same syntax and semantics as Perl, with
22         just  a  few differences. (Certain features that appeared in Python and         just  a few differences. Some features that appeared in Python and PCRE
23         PCRE before they appeared in Perl are also available using  the  Python         before they appeared in Perl are also available using the  Python  syn-
24         syntax.)         tax,  there  is  some  support for one or two .NET and Oniguruma syntax
25           items, and there is an option for requesting some  minor  changes  that
26         The  current  implementation of PCRE (release 7.x) corresponds approxi-         give better JavaScript compatibility.
27         mately with Perl 5.10, including support for UTF-8 encoded strings  and  
28         Unicode general category properties. However, UTF-8 and Unicode support         The  current implementation of PCRE corresponds approximately with Perl
29         has to be explicitly enabled; it is not the default. The Unicode tables         5.12, including support for UTF-8 encoded strings and  Unicode  general
30         correspond to Unicode release 5.0.0.         category  properties.  However,  UTF-8  and  Unicode  support has to be
31           explicitly enabled; it is not the default. The  Unicode  tables  corre-
32           spond to Unicode release 6.0.0.
33    
34         In  addition to the Perl-compatible matching function, PCRE contains an         In  addition to the Perl-compatible matching function, PCRE contains an
35         alternative matching function that matches the same  compiled  patterns         alternative function that matches the same compiled patterns in a  dif-
36         in  a different way. In certain circumstances, the alternative function         ferent way. In certain circumstances, the alternative function has some
37         has some advantages. For a discussion of the two  matching  algorithms,         advantages.  For a discussion of the two matching algorithms,  see  the
38         see the pcrematching page.         pcrematching page.
39    
40         PCRE  is  written  in C and released as a C library. A number of people         PCRE  is  written  in C and released as a C library. A number of people
41         have written wrappers and interfaces of various kinds.  In  particular,         have written wrappers and interfaces of various kinds.  In  particular,
# Line 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
81           pcreapi           details of PCRE's native C API           pcreapi           details of PCRE's native C API
82           pcrebuild         options for building PCRE           pcrebuild         options for building PCRE
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             pcrejit           discussion of the just-in-time optimization support
89             pcrelimits        details of size and other limits
90           pcrematching      discussion of the two matching algorithms           pcrematching      discussion of the two matching algorithms
91           pcrepartial       details of the partial matching facility           pcrepartial       details of the partial matching facility
92           pcrepattern       syntax and semantics of supported           pcrepattern       syntax and semantics of supported
# Line 85  USER DOCUMENTATION Line 94  USER DOCUMENTATION
94           pcreperform       discussion of performance issues           pcreperform       discussion of performance issues
95           pcreposix         the POSIX-compatible C API           pcreposix         the POSIX-compatible C API
96           pcreprecompile    details of saving and re-using precompiled patterns           pcreprecompile    details of saving and re-using precompiled patterns
97           pcresample        discussion of the sample program           pcresample        discussion of the pcredemo program
98           pcrestack         discussion of stack usage           pcrestack         discussion of stack usage
99             pcresyntax        quick syntax reference
100           pcretest          description of the pcretest testing command           pcretest          description of the pcretest testing command
101             pcreunicode       discussion of Unicode and UTF-8 support
102    
103         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
104         each C library function, listing its arguments and results.         each C library function, listing its arguments and results.
105    
106    
 LIMITATIONS  
   
        There  are some size limitations in PCRE but it is hoped that they will  
        never in practice be relevant.  
   
        The maximum length of a compiled pattern is 65539 (sic) bytes  if  PCRE  
        is compiled with the default internal linkage size of 2. If you want to  
        process regular expressions that are truly enormous,  you  can  compile  
        PCRE  with  an  internal linkage size of 3 or 4 (see the README file in  
        the source distribution and the pcrebuild documentation  for  details).  
        In  these  cases the limit is substantially larger.  However, the speed  
        of execution is slower.  
   
        All values in repeating quantifiers must be less than 65536. The  maxi-  
        mum  compiled  length  of  subpattern  with an explicit repeat count is  
        30000 bytes. The maximum number of capturing subpatterns is 65535.  
   
        There is no limit to the number of parenthesized subpatterns, but there  
        can be no more than 65535 capturing subpatterns.  
   
        The maximum length of name for a named subpattern is 32 characters, and  
        the maximum number of named subpatterns is 10000.  
   
        The maximum length of a subject string is the largest  positive  number  
        that  an integer variable can hold. However, when using the traditional  
        matching function, PCRE uses recursion to handle subpatterns and indef-  
        inite  repetition.  This means that the available stack space may limit  
        the size of a subject string that can be processed by certain patterns.  
        For a discussion of stack issues, see the pcrestack documentation.  
   
   
 UTF-8 AND UNICODE PROPERTY SUPPORT  
   
        From  release  3.3,  PCRE  has  had  some support for character strings  
        encoded in the UTF-8 format. For release 4.0 this was greatly  extended  
        to  cover  most common requirements, and in release 5.0 additional sup-  
        port for Unicode general category properties was added.  
   
        In order process UTF-8 strings, you must build PCRE  to  include  UTF-8  
        support  in  the  code,  and, in addition, you must call pcre_compile()  
        with the PCRE_UTF8 option flag. When you do this, both the pattern  and  
        any  subject  strings  that are matched against it are treated as UTF-8  
        strings instead of just strings of bytes.  
   
        If you compile PCRE with UTF-8 support, but do not use it at run  time,  
        the  library will be a bit bigger, but the additional run time overhead  
        is limited to testing the PCRE_UTF8 flag occasionally, so should not be  
        very big.  
   
        If PCRE is built with Unicode character property support (which implies  
        UTF-8 support), the escape sequences \p{..}, \P{..}, and  \X  are  sup-  
        ported.  The available properties that can be tested are limited to the  
        general category properties such as Lu for an upper case letter  or  Nd  
        for  a  decimal number, the Unicode script names such as Arabic or Han,  
        and the derived properties Any and L&. A full  list  is  given  in  the  
        pcrepattern documentation. Only the short names for properties are sup-  
        ported. For example, \p{L} matches a letter. Its Perl synonym,  \p{Let-  
        ter},  is  not  supported.   Furthermore,  in Perl, many properties may  
        optionally be prefixed by "Is", for compatibility with Perl  5.6.  PCRE  
        does not support this.  
   
        The following comments apply when PCRE is running in UTF-8 mode:  
   
        1.  When you set the PCRE_UTF8 flag, the strings passed as patterns and  
        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.  
   
        2.  An  unbraced  hexadecimal  escape sequence (such as \xb3) matches a  
        two-byte UTF-8 character if the value is greater than 127.  
   
        3. Octal numbers up to \777 are recognized, and  match  two-byte  UTF-8  
        characters for values greater than \177.  
   
        4.  Repeat quantifiers apply to complete UTF-8 characters, not to indi-  
        vidual bytes, for example: \x{100}{3}.  
   
        5. The dot metacharacter matches one UTF-8 character instead of a  sin-  
        gle byte.  
   
        6.  The  escape sequence \C can be used to match a single byte in UTF-8  
        mode, but its use can lead to some strange effects.  This  facility  is  
        not available in the alternative matching function, pcre_dfa_exec().  
   
        7.  The  character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly  
        test characters of any code value, but the characters that PCRE  recog-  
        nizes  as  digits,  spaces,  or  word characters remain the same set as  
        before, all with values less than 256. This remains true even when PCRE  
        includes  Unicode  property support, because to do otherwise would slow  
        down PCRE in many common cases. If you really want to test for a  wider  
        sense  of,  say,  "digit",  you must use Unicode property tests such as  
        \p{Nd}.  
   
        8. Similarly, characters that match the POSIX named  character  classes  
        are all low-valued characters.  
   
        9.  Case-insensitive  matching  applies only to characters whose values  
        are less than 128, unless PCRE is built with Unicode property  support.  
        Even  when  Unicode  property support is available, PCRE still uses its  
        own character tables when checking the case of  low-valued  characters,  
        so  as not to degrade performance.  The Unicode property information is  
        used only for characters with higher values. Even when Unicode property  
        support is available, PCRE supports case-insensitive matching only when  
        there is a one-to-one mapping between a letter's  cases.  There  are  a  
        small  number  of  many-to-one  mappings in Unicode; these are not sup-  
        ported by PCRE.  
   
   
107  AUTHOR  AUTHOR
108    
109         Philip Hazel         Philip Hazel
# Line 215  AUTHOR Line 111  AUTHOR
111         Cambridge CB2 3QH, England.         Cambridge CB2 3QH, England.
112    
113         Putting an actual email address here seems to have been a spam  magnet,         Putting an actual email address here seems to have been a spam  magnet,
114         so I've taken it away. If you want to email me, use my initial and sur-         so  I've  taken  it away. If you want to email me, use my two initials,
115         name, separated by a dot, at the domain ucs.cam.ac.uk.         followed by the two digits 10, at the domain cam.ac.uk.
116    
117    
118  REVISION  REVISION
119    
120         Last updated: 06 March 2007         Last updated: 24 August 2011
121         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
122  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
123    
124    
125  PCREBUILD(3)                                                      PCREBUILD(3)  PCREBUILD(3)                                                      PCREBUILD(3)
126    
127    
# Line 236  NAME Line 132  NAME
132  PCRE BUILD-TIME OPTIONS  PCRE BUILD-TIME OPTIONS
133    
134         This  document  describes  the  optional  features  of PCRE that can be         This  document  describes  the  optional  features  of PCRE that can be
135         selected when the library is compiled. They are all selected, or  dese-         selected when the library is compiled. It assumes use of the  configure
136         lected, by providing options to the configure script that is run before         script,  where the optional features are selected or deselected by pro-
137         the make command. The complete list of  options  for  configure  (which         viding options to configure before running the make  command.  However,
138         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
139         directory) can be obtained by running         environments using the GUI facility of cmake-gui if you are using CMake
140           instead of configure to build PCRE.
141    
142           There  is  a  lot more information about building PCRE in non-Unix-like
143           environments in the file called NON_UNIX_USE, which is part of the PCRE
144           distribution.  You  should consult this file as well as the README file
145           if you are building in a non-Unix-like environment.
146    
147           The complete list of options for configure (which includes the standard
148           ones  such  as  the  selection  of  the  installation directory) can be
149           obtained by running
150    
151           ./configure --help           ./configure --help
152    
153         The following sections describe certain options whose names begin  with         The following sections include  descriptions  of  options  whose  names
154         --enable  or  --disable. These settings specify changes to the defaults         begin with --enable or --disable. These settings specify changes to the
155         for the configure command. Because of the  way  that  configure  works,         defaults for the configure command. Because of the way  that  configure
156         --enable  and  --disable  always  come  in  pairs, so the complementary         works,  --enable  and --disable always come in pairs, so the complemen-
157         option always exists as well, but as it specifies the  default,  it  is         tary option always exists as well, but as it specifies the default,  it
158         not described.         is not described.
159    
160    
161    BUILDING SHARED AND STATIC LIBRARIES
162    
163           The  PCRE building process uses libtool to build both shared and static
164           Unix libraries by default. You can suppress one of these by adding  one
165           of
166    
167             --disable-shared
168             --disable-static
169    
170           to the configure command, as required.
171    
172    
173  C++ SUPPORT  C++ SUPPORT
# Line 265  C++ SUPPORT Line 183  C++ SUPPORT
183    
184  UTF-8 SUPPORT  UTF-8 SUPPORT
185    
186         To build PCRE with support for UTF-8 character strings, add         To build PCRE with support for UTF-8 Unicode character strings, add
187    
188           --enable-utf8           --enable-utf8
189    
190         to  the  configure  command.  Of  itself, this does not make PCRE treat         to  the  configure  command.  Of  itself, this does not make PCRE treat
191         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
192         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()
193         function.         or pcre_compile2() functions.
194    
195           If you set --enable-utf8 when compiling in an EBCDIC environment,  PCRE
196           expects its input to be either ASCII or UTF-8 (depending on the runtime
197           option). It is not possible to support both EBCDIC and UTF-8  codes  in
198           the  same  version  of  the  library.  Consequently,  --enable-utf8 and
199           --enable-ebcdic are mutually exclusive.
200    
201    
202  UNICODE CHARACTER PROPERTY SUPPORT  UNICODE CHARACTER PROPERTY SUPPORT
# Line 288  UNICODE CHARACTER PROPERTY SUPPORT Line 212  UNICODE CHARACTER PROPERTY SUPPORT
212         to the configure command. This implies UTF-8 support, even if you  have         to the configure command. This implies UTF-8 support, even if you  have
213         not explicitly requested it.         not explicitly requested it.
214    
215         Including  Unicode  property  support  adds around 90K of tables to the         Including  Unicode  property  support  adds around 30K of tables to the
216         PCRE library, approximately doubling its size. Only the  general  cate-         PCRE library. Only the general category properties such as  Lu  and  Nd
217         gory  properties  such as Lu and Nd are supported. Details are given in         are supported. Details are given in the pcrepattern documentation.
        the pcrepattern documentation.  
218    
219    
220  CODE VALUE OF NEWLINE  CODE VALUE OF NEWLINE
221    
222         By default, PCRE interprets character 10 (linefeed, LF)  as  indicating         By  default,  PCRE interprets the linefeed (LF) character as indicating
223         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
224         systems. You can compile PCRE to use character 13 (carriage return, CR)         systems.  You  can compile PCRE to use carriage return (CR) instead, by
225         instead, by adding         adding
226    
227           --enable-newline-is-cr           --enable-newline-is-cr
228    
229         to  the  configure  command.  There  is  also  a --enable-newline-is-lf         to the  configure  command.  There  is  also  a  --enable-newline-is-lf
230         option, which explicitly specifies linefeed as the newline character.         option, which explicitly specifies linefeed as the newline character.
231    
232         Alternatively, you can specify that line endings are to be indicated by         Alternatively, you can specify that line endings are to be indicated by
# Line 313  CODE VALUE OF NEWLINE Line 236  CODE VALUE OF NEWLINE
236    
237         to the configure command. There is a fourth option, specified by         to the configure command. There is a fourth option, specified by
238    
239             --enable-newline-is-anycrlf
240    
241           which causes PCRE to recognize any of the three sequences  CR,  LF,  or
242           CRLF as indicating a line ending. Finally, a fifth option, specified by
243    
244           --enable-newline-is-any           --enable-newline-is-any
245    
246         which causes PCRE to recognize any Unicode newline sequence.         causes PCRE to recognize any Unicode newline sequence.
247    
248         Whatever  line  ending convention is selected when PCRE is built can be         Whatever  line  ending convention is selected when PCRE is built can be
249         overridden when the library functions are called. At build time  it  is         overridden when the library functions are called. At build time  it  is
250         conventional to use the standard for your operating system.         conventional to use the standard for your operating system.
251    
252    
253  BUILDING SHARED AND STATIC LIBRARIES  WHAT \R MATCHES
254    
255         The  PCRE building process uses libtool to build both shared and static         By  default,  the  sequence \R in a pattern matches any Unicode newline
256         Unix libraries by default. You can suppress one of these by adding  one         sequence, whatever has been selected as the line  ending  sequence.  If
257         of         you specify
258    
259           --disable-shared           --enable-bsr-anycrlf
          --disable-static  
260    
261         to the configure command, as required.         the  default  is changed so that \R matches only CR, LF, or CRLF. What-
262           ever is selected when PCRE is built can be overridden when the  library
263           functions are called.
264    
265    
266  POSIX MALLOC USAGE  POSIX MALLOC USAGE
# Line 357  HANDLING VERY LARGE PATTERNS Line 286  HANDLING VERY LARGE PATTERNS
286         nation metacharacter). By default, two-byte values are used  for  these         nation metacharacter). By default, two-byte values are used  for  these
287         offsets,  leading  to  a  maximum size for a compiled pattern of around         offsets,  leading  to  a  maximum size for a compiled pattern of around
288         64K. This is sufficient to handle all but the most  gigantic  patterns.         64K. This is sufficient to handle all but the most  gigantic  patterns.
289         Nevertheless,  some  people do want to process enormous patterns, so it         Nevertheless,  some  people do want to process truyl enormous patterns,
290         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-
291         adding a setting such as         sets by adding a setting such as
292    
293           --with-link-size=3           --with-link-size=3
294    
# Line 367  HANDLING VERY LARGE PATTERNS Line 296  HANDLING VERY LARGE PATTERNS
296         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
297         additional bytes when handling them.         additional bytes when handling them.
298    
        If  you  build  PCRE with an increased link size, test 2 (and test 5 if  
        you are using UTF-8) will fail. Part of the output of these tests is  a  
        representation  of the compiled pattern, and this changes with the link  
        size.  
   
299    
300  AVOIDING EXCESSIVE STACK USAGE  AVOIDING EXCESSIVE STACK USAGE
301    
302         When matching with the pcre_exec() function, PCRE implements backtrack-         When matching with the pcre_exec() function, PCRE implements backtrack-
303         ing  by  making recursive calls to an internal function called match().         ing by making recursive calls to an internal function  called  match().
304         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-
305         verely  limit  PCRE's operation. (The Unix environment does not usually         verely limit PCRE's operation. (The Unix environment does  not  usually
306         suffer from this problem, but it may sometimes be necessary to increase         suffer from this problem, but it may sometimes be necessary to increase
307         the  maximum  stack size.  There is a discussion in the pcrestack docu-         the maximum stack size.  There is a discussion in the  pcrestack  docu-
308         mentation.) An alternative approach to recursion that uses memory  from         mentation.)  An alternative approach to recursion that uses memory from
309         the  heap  to remember data, instead of using recursive function calls,         the heap to remember data, instead of using recursive  function  calls,
310         has been implemented to work round the problem of limited  stack  size.         has  been  implemented to work round the problem of limited stack size.
311         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
312    
313           --disable-stack-for-recursion           --disable-stack-for-recursion
314    
315         to  the  configure  command. With this configuration, PCRE will use the         to the configure command. With this configuration, PCRE  will  use  the
316         pcre_stack_malloc and pcre_stack_free variables to call memory  manage-         pcre_stack_malloc  and pcre_stack_free variables to call memory manage-
317         ment  functions.  Separate  functions are provided because the usage is         ment functions. By default these point to malloc() and free(), but  you
318         very predictable: the block sizes requested are always  the  same,  and         can replace the pointers so that your own functions are used instead.
319         the  blocks  are always freed in reverse order. A calling program might  
320         be able to implement optimized functions that perform better  than  the         Separate  functions  are  provided  rather  than  using pcre_malloc and
321         standard  malloc()  and  free()  functions.  PCRE  runs noticeably more         pcre_free because the  usage  is  very  predictable:  the  block  sizes
322         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
323         function; it is not relevant for the the pcre_dfa_exec() function.         reverse order. A calling program might be able to  implement  optimized
324           functions  that  perform  better  than  malloc()  and free(). PCRE runs
325           noticeably more slowly when built in this way. This option affects only
326           the pcre_exec() function; it is not relevant for pcre_dfa_exec().
327    
328    
329  LIMITING PCRE RESOURCE USAGE  LIMITING PCRE RESOURCE USAGE
# Line 429  LIMITING PCRE RESOURCE USAGE Line 356  LIMITING PCRE RESOURCE USAGE
356         time.         time.
357    
358    
359    CREATING CHARACTER TABLES AT BUILD TIME
360    
361           PCRE uses fixed tables for processing characters whose code values  are
362           less  than 256. By default, PCRE is built with a set of tables that are
363           distributed in the file pcre_chartables.c.dist. These  tables  are  for
364           ASCII codes only. If you add
365    
366             --enable-rebuild-chartables
367    
368           to  the  configure  command, the distributed tables are no longer used.
369           Instead, a program called dftables is compiled and  run.  This  outputs
370           the source for new set of tables, created in the default locale of your
371           C runtime system. (This method of replacing the tables does not work if
372           you  are cross compiling, because dftables is run on the local host. If
373           you need to create alternative tables when cross  compiling,  you  will
374           have to do so "by hand".)
375    
376    
377  USING EBCDIC CODE  USING EBCDIC CODE
378    
379         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
380         character  code  is  ASCII  (or Unicode, which is a superset of ASCII).         character code is ASCII (or Unicode, which is  a  superset  of  ASCII).
381         PCRE can, however, be compiled to  run  in  an  EBCDIC  environment  by         This  is  the  case for most computer operating systems. PCRE can, how-
382         adding         ever, be compiled to run in an EBCDIC environment by adding
383    
384           --enable-ebcdic           --enable-ebcdic
385    
386         to the configure command.         to the configure command. This setting implies --enable-rebuild-charta-
387           bles.  You  should  only  use  it if you know that you are in an EBCDIC
388           environment (for example,  an  IBM  mainframe  operating  system).  The
389           --enable-ebcdic option is incompatible with --enable-utf8.
390    
391    
392    PCREGREP OPTIONS FOR COMPRESSED FILE SUPPORT
393    
394           By default, pcregrep reads all files as plain text. You can build it so
395           that it recognizes files whose names end in .gz or .bz2, and reads them
396           with libz or libbz2, respectively, by adding one or both of
397    
398             --enable-pcregrep-libz
399             --enable-pcregrep-libbz2
400    
401           to the configure command. These options naturally require that the rel-
402           evant libraries are installed on your system. Configuration  will  fail
403           if they are not.
404    
405    
406    PCREGREP BUFFER SIZE
407    
408           pcregrep  uses  an internal buffer to hold a "window" on the file it is
409           scanning, in order to be able to output "before" and "after" lines when
410           it  finds  a match. The size of the buffer is controlled by a parameter
411           whose default value is 20K. The buffer itself is three times this size,
412           but because of the way it is used for holding "before" lines, the long-
413           est line that is guaranteed to be processable is  the  parameter  size.
414           You can change the default parameter value by adding, for example,
415    
416             --with-pcregrep-bufsize=50K
417    
418           to the configure command. The caller of pcregrep can, however, override
419           this value by specifying a run-time option.
420    
421    
422    PCRETEST OPTION FOR LIBREADLINE SUPPORT
423    
424           If you add
425    
426             --enable-pcretest-libreadline
427    
428           to the configure command,  pcretest  is  linked  with  the  libreadline
429           library,  and  when its input is from a terminal, it reads it using the
430           readline() function. This provides line-editing and history facilities.
431           Note that libreadline is GPL-licensed, so if you distribute a binary of
432           pcretest linked in this way, there may be licensing issues.
433    
434           Setting this option causes the -lreadline option to  be  added  to  the
435           pcretest  build.  In many operating environments with a sytem-installed
436           libreadline this is sufficient. However, in some environments (e.g.  if
437           an  unmodified  distribution version of readline is in use), some extra
438           configuration may be necessary. The INSTALL file for  libreadline  says
439           this:
440    
441             "Readline uses the termcap functions, but does not link with the
442             termcap or curses library itself, allowing applications which link
443             with readline the to choose an appropriate library."
444    
445           If  your environment has not been set up so that an appropriate library
446           is automatically included, you may need to add something like
447    
448             LIBS="-ncurses"
449    
450           immediately before the configure command.
451    
452    
453  SEE ALSO  SEE ALSO
# Line 455  AUTHOR Line 464  AUTHOR
464    
465  REVISION  REVISION
466    
467         Last updated: 06 March 2007         Last updated: 02 August 2011
468         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
469  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
470    
471    
472  PCREMATCHING(3)                                                PCREMATCHING(3)  PCREMATCHING(3)                                                PCREMATCHING(3)
473    
474    
# Line 508  REGULAR EXPRESSIONS AS TREES Line 517  REGULAR EXPRESSIONS AS TREES
517    
518  THE STANDARD MATCHING ALGORITHM  THE STANDARD MATCHING ALGORITHM
519    
520         In the terminology of Jeffrey Friedl's book Mastering  Regular  Expres-         In the terminology of Jeffrey Friedl's book "Mastering Regular  Expres-
521         sions,  the  standard  algorithm  is  an "NFA algorithm". It conducts a         sions",  the  standard  algorithm  is an "NFA algorithm". It conducts a
522         depth-first search of the pattern tree. That is, it  proceeds  along  a         depth-first search of the pattern tree. That is, it  proceeds  along  a
523         single path through the tree, checking that the subject matches what is         single path through the tree, checking that the subject matches what is
524         required. When there is a mismatch, the algorithm  tries  any  alterna-         required. When there is a mismatch, the algorithm  tries  any  alterna-
# Line 543  THE ALTERNATIVE MATCHING ALGORITHM Line 552  THE ALTERNATIVE MATCHING ALGORITHM
552         though  it is not implemented as a traditional finite state machine (it         though  it is not implemented as a traditional finite state machine (it
553         keeps multiple states active simultaneously).         keeps multiple states active simultaneously).
554    
555           Although the general principle of this matching algorithm  is  that  it
556           scans  the subject string only once, without backtracking, there is one
557           exception: when a lookaround assertion is encountered,  the  characters
558           following  or  preceding  the  current  point  have to be independently
559           inspected.
560    
561         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
562         there  are  no more unterminated paths. At this point, terminated paths         there  are  no more unterminated paths. At this point, terminated paths
563         represent the different matching possibilities (if there are none,  the         represent the different matching possibilities (if there are none,  the
564         match  has  failed).   Thus,  if there is more than one possible match,         match  has  failed).   Thus,  if there is more than one possible match,
565         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-
566         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
567         match (which is necessarily the shortest) has been found.         an option to stop the algorithm after the first match (which is  neces-
568           sarily the shortest) is found.
569    
570         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
571         subject. If the pattern         subject. If the pattern
572    
573           cat(er(pillar)?)           cat(er(pillar)?)?
574    
575         is  matched  against the string "the caterpillar catchment", the result         is matched against the string "the caterpillar catchment",  the  result
576         will be the three strings "cat", "cater", and "caterpillar" that  start         will  be the three strings "caterpillar", "cater", and "cat" that start
577         at the fourth character of the subject. The algorithm does not automat-         at the fifth character of the subject. The algorithm does not automati-
578         ically move on to find matches that start at later positions.         cally move on to find matches that start at later positions.
579    
580         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
581         supported by the alternative matching algorithm. They are as follows:         supported by the alternative matching algorithm. They are as follows:
582    
583         1.  Because  the  algorithm  finds  all possible matches, the greedy or         1. Because the algorithm finds all  possible  matches,  the  greedy  or
584         ungreedy nature of repetition quantifiers is not relevant.  Greedy  and         ungreedy  nature  of repetition quantifiers is not relevant. Greedy and
585         ungreedy quantifiers are treated in exactly the same way. However, pos-         ungreedy quantifiers are treated in exactly the same way. However, pos-
586         sessive quantifiers can make a difference when what follows could  also         sessive  quantifiers can make a difference when what follows could also
587         match what is quantified, for example in a pattern like this:         match what is quantified, for example in a pattern like this:
588    
589           ^a++\w!           ^a++\w!
590    
591         This  pattern matches "aaab!" but not "aaa!", which would be matched by         This pattern matches "aaab!" but not "aaa!", which would be matched  by
592         a non-possessive quantifier. Similarly, if an atomic group is  present,         a  non-possessive quantifier. Similarly, if an atomic group is present,
593         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,
594         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
595         pattern.         pattern.
596    
597         2. When dealing with multiple paths through the tree simultaneously, it         2. When dealing with multiple paths through the tree simultaneously, it
598         is not straightforward to keep track of  captured  substrings  for  the         is  not  straightforward  to  keep track of captured substrings for the
599         different  matching  possibilities,  and  PCRE's implementation of this         different matching possibilities, and  PCRE's  implementation  of  this
600         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-
601         strings are available.         strings are available.
602    
603         3.  Because no substrings are captured, back references within the pat-         3. Because no substrings are captured, back references within the  pat-
604         tern are not supported, and cause errors if encountered.         tern are not supported, and cause errors if encountered.
605    
606         4. For the same reason, conditional expressions that use  a  backrefer-         4.  For  the same reason, conditional expressions that use a backrefer-
607         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
608         supported.         supported.
609    
610         5. Callouts are supported, but the value of the  capture_top  field  is         5.  Because  many  paths  through the tree may be active, the \K escape
611           sequence, which resets the start of the match when encountered (but may
612           be  on  some  paths  and not on others), is not supported. It causes an
613           error if encountered.
614    
615           6. Callouts are supported, but the value of the  capture_top  field  is
616         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.
617    
618         6.  The \C escape sequence, which (in the standard algorithm) matches a         7.  The \C escape sequence, which (in the standard algorithm) matches a
619         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-
620         tive  algorithm  moves  through  the  subject string one character at a         tive  algorithm  moves  through  the  subject string one character at a
621         time, for all active paths through the tree.         time, for all active paths through the tree.
622    
623           8. Except for (*FAIL), the backtracking control verbs such as  (*PRUNE)
624           are  not  supported.  (*FAIL)  is supported, and behaves like a failing
625           negative assertion.
626    
627    
628  ADVANTAGES OF THE ALTERNATIVE ALGORITHM  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
629    
# Line 610  ADVANTAGES OF THE ALTERNATIVE ALGORITHM Line 635  ADVANTAGES OF THE ALTERNATIVE ALGORITHM
635         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
636         things with callouts.         things with callouts.
637    
638         2. There is much better support for partial matching. The  restrictions         2. Because the alternative algorithm  scans  the  subject  string  just
        on  the content of the pattern that apply when using the standard algo-  
        rithm for partial matching do not apply to the  alternative  algorithm.  
        For  non-anchored patterns, the starting position of a partial match is  
        available.  
   
        3. Because the alternative algorithm  scans  the  subject  string  just  
639         once,  and  never  needs to backtrack, it is possible to pass very long         once,  and  never  needs to backtrack, it is possible to pass very long
640         subject strings to the matching function in  several  pieces,  checking         subject strings to the matching function in  several  pieces,  checking
641         for partial matching each time.         for  partial  matching  each time. Although it is possible to do multi-
642           segment matching using the standard algorithm (pcre_exec()), by retain-
643           ing  partially matched substrings, it is more complicated. The pcrepar-
644           tial documentation gives details  of  partial  matching  and  discusses
645           multi-segment matching.
646    
647    
648  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM  DISADVANTAGES OF THE ALTERNATIVE ALGORITHM
# Line 645  AUTHOR Line 668  AUTHOR
668    
669  REVISION  REVISION
670    
671         Last updated: 06 March 2007         Last updated: 17 November 2010
672         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
673  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
674    
675    
676  PCREAPI(3)                                                          PCREAPI(3)  PCREAPI(3)                                                          PCREAPI(3)
677    
678    
# Line 753  PCRE API OVERVIEW Line 776  PCRE API OVERVIEW
776         bers for the library.  Applications can use these  to  include  support         bers for the library.  Applications can use these  to  include  support
777         for different releases of PCRE.         for different releases of PCRE.
778    
779           In a Windows environment, if you want to statically link an application
780           program against a non-dll pcre.a  file,  you  must  define  PCRE_STATIC
781           before  including  pcre.h or pcrecpp.h, because otherwise the pcre_mal-
782           loc()   and   pcre_free()   exported   functions   will   be   declared
783           __declspec(dllimport), with unwanted results.
784    
785         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and         The   functions   pcre_compile(),  pcre_compile2(),  pcre_study(),  and
786         pcre_exec() are used for compiling and matching regular expressions  in         pcre_exec() are used for compiling and matching regular expressions  in
787         a  Perl-compatible  manner. A sample program that demonstrates the sim-         a  Perl-compatible  manner. A sample program that demonstrates the sim-
788         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
789         the  source distribution. The pcresample documentation describes how to         the PCRE source distribution. A listing of this program is given in the
790         run it.         pcredemo documentation, and the pcresample documentation describes  how
791           to compile and run it.
792    
793         A second matching function, pcre_dfa_exec(), which is not Perl-compati-         A second matching function, pcre_dfa_exec(), which is not Perl-compati-
794         ble,  is  also provided. This uses a different algorithm for the match-         ble, is also provided. This uses a different algorithm for  the  match-
795         ing. The alternative algorithm finds all possible matches (at  a  given         ing.  The  alternative algorithm finds all possible matches (at a given
796         point  in  the subject), and scans the subject just once. However, this         point in the subject), and scans the subject just  once  (unless  there
797         algorithm does not return captured substrings. A description of the two         are  lookbehind  assertions).  However,  this algorithm does not return
798         matching  algorithms and their advantages and disadvantages is given in         captured substrings. A description of the two matching  algorithms  and
799         the pcrematching documentation.         their  advantages  and disadvantages is given in the pcrematching docu-
800           mentation.
801    
802         In addition to the main compiling and  matching  functions,  there  are         In addition to the main compiling and  matching  functions,  there  are
803         convenience functions for extracting captured substrings from a subject         convenience functions for extracting captured substrings from a subject
# Line 828  PCRE API OVERVIEW Line 859  PCRE API OVERVIEW
859    
860  NEWLINES  NEWLINES
861    
862         PCRE  supports four different conventions for indicating line breaks in         PCRE  supports five different conventions for indicating line breaks in
863         strings: a single CR (carriage return) character, a  single  LF  (line-         strings: a single CR (carriage return) character, a  single  LF  (line-
864         feed)  character,  the two-character sequence CRLF, or any Unicode new-         feed) character, the two-character sequence CRLF, any of the three pre-
865         line sequence.  The Unicode newline sequences are the three  just  men-         ceding, or any Unicode newline sequence. The Unicode newline  sequences
866         tioned, plus the single characters VT (vertical tab, U+000B), FF (form-         are  the  three just mentioned, plus the single characters VT (vertical
867         feed, U+000C), NEL (next line, U+0085), LS  (line  separator,  U+2028),         tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS  (line
868         and PS (paragraph separator, U+2029).         separator, U+2028), and PS (paragraph separator, U+2029).
869    
870         Each  of  the first three conventions is used by at least one operating         Each  of  the first three conventions is used by at least one operating
871         system as its standard newline sequence. When PCRE is built, a  default         system as its standard newline sequence. When PCRE is built, a  default
# Line 842  NEWLINES Line 873  NEWLINES
873         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
874         pattern is compiled, or when it is matched.         pattern is compiled, or when it is matched.
875    
876           At compile time, the newline convention can be specified by the options
877           argument of pcre_compile(), or it can be specified by special  text  at
878           the start of the pattern itself; this overrides any other settings. See
879           the pcrepattern page for details of the special character sequences.
880    
881         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-
882         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
883         newline  convention  affects  the  handling of the dot, circumflex, and         newline convention affects the handling of  the  dot,  circumflex,  and
884         dollar metacharacters, the handling of #-comments in /x mode, and, when         dollar metacharacters, the handling of #-comments in /x mode, and, when
885         CRLF  is a recognized line ending sequence, the match position advance-         CRLF is a recognized line ending sequence, the match position  advance-
886         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
887         not affect the interpretation of the \n or \r escape sequences.         section on pcre_exec() options below.
888    
889           The choice of newline convention does not affect the interpretation  of
890           the  \n  or  \r  escape  sequences, nor does it affect what \R matches,
891           which is controlled in a similar way, but by separate options.
892    
893    
894  MULTITHREADING  MULTITHREADING
895    
896         The  PCRE  functions  can be used in multi-threading applications, with         The PCRE functions can be used in  multi-threading  applications,  with
897         the  proviso  that  the  memory  management  functions  pointed  to  by         the  proviso  that  the  memory  management  functions  pointed  to  by
898         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
899         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 868  SAVING PRECOMPILED PATTERNS FOR LATER US Line 908  SAVING PRECOMPILED PATTERNS FOR LATER US
908         The compiled form of a regular expression can be saved and re-used at a         The compiled form of a regular expression can be saved and re-used at a
909         later time, possibly by a different program, and even on a  host  other         later time, possibly by a different program, and even on a  host  other
910         than  the  one  on  which  it  was  compiled.  Details are given in the         than  the  one  on  which  it  was  compiled.  Details are given in the
911         pcreprecompile documentation.         pcreprecompile documentation. However, compiling a  regular  expression
912           with  one version of PCRE for use with a different version is not guar-
913           anteed to work and may cause crashes.
914    
915    
916  CHECKING BUILD-TIME OPTIONS  CHECKING BUILD-TIME OPTIONS
# Line 899  CHECKING BUILD-TIME OPTIONS Line 941  CHECKING BUILD-TIME OPTIONS
941    
942         The output is an integer whose value specifies  the  default  character         The output is an integer whose value specifies  the  default  character
943         sequence  that is recognized as meaning "newline". The four values that         sequence  that is recognized as meaning "newline". The four values that
944         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, and -1 for ANY.         are supported are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for ANYCRLF,
945         The default should normally be the standard sequence for your operating         and  -1  for  ANY.  Though they are derived from ASCII, the same values
946         system.         are returned in EBCDIC environments. The default should normally corre-
947           spond to the standard sequence for your operating system.
948    
949             PCRE_CONFIG_BSR
950    
951           The output is an integer whose value indicates what character sequences
952           the \R escape sequence matches by default. A value of 0 means  that  \R
953           matches  any  Unicode  line ending sequence; a value of 1 means that \R
954           matches only CR, LF, or CRLF. The default can be overridden when a pat-
955           tern is compiled or matched.
956    
957           PCRE_CONFIG_LINK_SIZE           PCRE_CONFIG_LINK_SIZE
958    
959         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
960         internal linkage in compiled regular expressions. The value is 2, 3, or         internal linkage in compiled regular expressions. The value is 2, 3, or
961         4. Larger values allow larger regular expressions to  be  compiled,  at         4.  Larger  values  allow larger regular expressions to be compiled, at
962         the  expense  of  slower matching. The default value of 2 is sufficient         the expense of slower matching. The default value of  2  is  sufficient
963         for all but the most massive patterns, since  it  allows  the  compiled         for  all  but  the  most massive patterns, since it allows the compiled
964         pattern to be up to 64K in size.         pattern to be up to 64K in size.
965    
966           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD           PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
967    
968         The  output  is  an integer that contains the threshold above which the         The output is an integer that contains the threshold  above  which  the
969         POSIX interface uses malloc() for output vectors. Further  details  are         POSIX  interface  uses malloc() for output vectors. Further details are
970         given in the pcreposix documentation.         given in the pcreposix documentation.
971    
972           PCRE_CONFIG_MATCH_LIMIT           PCRE_CONFIG_MATCH_LIMIT
973    
974         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-
975         internal matching function calls in a  pcre_exec()  execution.  Further         ber  of  internal  matching  function calls in a pcre_exec() execution.
976         details are given with pcre_exec() below.         Further details are given with pcre_exec() below.
977    
978           PCRE_CONFIG_MATCH_LIMIT_RECURSION           PCRE_CONFIG_MATCH_LIMIT_RECURSION
979    
980         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
981         recursion when calling the internal matching function in a  pcre_exec()         of   recursion  when  calling  the  internal  matching  function  in  a
982         execution. Further details are given with pcre_exec() below.         pcre_exec() execution.  Further  details  are  given  with  pcre_exec()
983           below.
984    
985           PCRE_CONFIG_STACKRECURSE           PCRE_CONFIG_STACKRECURSE
986    
# Line 955  COMPILING A PATTERN Line 1007  COMPILING A PATTERN
1007         Either of the functions pcre_compile() or pcre_compile2() can be called         Either of the functions pcre_compile() or pcre_compile2() can be called
1008         to compile a pattern into an internal form. The only difference between         to compile a pattern into an internal form. The only difference between
1009         the  two interfaces is that pcre_compile2() has an additional argument,         the  two interfaces is that pcre_compile2() has an additional argument,
1010         errorcodeptr, via which a numerical error code can be returned.         errorcodeptr, via which a numerical error  code  can  be  returned.  To
1011           avoid  too  much repetition, we refer just to pcre_compile() below, but
1012           the information applies equally to pcre_compile2().
1013    
1014         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
1015         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 972  COMPILING A PATTERN Line 1026  COMPILING A PATTERN
1026    
1027         The options argument contains various bit settings that affect the com-         The options argument contains various bit settings that affect the com-
1028         pilation. It should be zero if no options are required.  The  available         pilation. It should be zero if no options are required.  The  available
1029         options  are  described  below. Some of them, in particular, those that         options  are  described  below. Some of them (in particular, those that
1030         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
1031         pattern  (see  the  detailed  description in the pcrepattern documenta-         unset  from  within  the  pattern  (see the detailed description in the
1032         tion). For these options, the contents of the options  argument  speci-         pcrepattern documentation). For those options that can be different  in
1033         fies  their initial settings at the start of compilation and execution.         different  parts  of  the pattern, the contents of the options argument
1034         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
1035         of matching as well as at compile time.         PCRE_ANCHORED,  PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK, and
1036           PCRE_NO_START_OPT options can be set at the time of matching as well as
1037           at compile time.
1038    
1039         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,         If errptr is NULL, pcre_compile() returns NULL immediately.  Otherwise,
1040         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and         if compilation of a pattern fails,  pcre_compile()  returns  NULL,  and
1041         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-
1042         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
1043         try to free it. The offset from the start of the pattern to the charac-         try  to  free it. Normally, the offset from the start of the pattern to
1044         ter where the error was discovered is placed in the variable pointed to         the byte that was being processed when  the  error  was  discovered  is
1045         by  erroffset,  which must not be NULL. If it is, an immediate error is         placed  in the variable pointed to by erroffset, which must not be NULL
1046         given.         (if it is, an immediate error is given). However, for an invalid  UTF-8
1047           string,  the offset is that of the first byte of the failing character.
1048         If pcre_compile2() is used instead of pcre_compile(),  and  the  error-         Also, some errors are not detected until checks are  carried  out  when
1049         codeptr  argument is not NULL, a non-zero error code number is returned         the  whole  pattern  has been scanned; in these cases the offset passed
1050         via this argument in the event of an error. This is in addition to  the         back is the length of the pattern.
1051    
1052           Note that the offset is in bytes, not characters, even in  UTF-8  mode.
1053           It may sometimes point into the middle of a UTF-8 character.
1054    
1055           If  pcre_compile2()  is  used instead of pcre_compile(), and the error-
1056           codeptr argument is not NULL, a non-zero error code number is  returned
1057           via  this argument in the event of an error. This is in addition to the
1058         textual error message. Error codes and messages are listed below.         textual error message. Error codes and messages are listed below.
1059    
1060         If  the  final  argument, tableptr, is NULL, PCRE uses a default set of         If the final argument, tableptr, is NULL, PCRE uses a  default  set  of
1061         character tables that are  built  when  PCRE  is  compiled,  using  the         character  tables  that  are  built  when  PCRE  is compiled, using the
1062         default  C  locale.  Otherwise, tableptr must be an address that is the         default C locale. Otherwise, tableptr must be an address  that  is  the
1063         result of a call to pcre_maketables(). This value is  stored  with  the         result  of  a  call to pcre_maketables(). This value is stored with the
1064         compiled  pattern,  and used again by pcre_exec(), unless another table         compiled pattern, and used again by pcre_exec(), unless  another  table
1065         pointer is passed to it. For more discussion, see the section on locale         pointer is passed to it. For more discussion, see the section on locale
1066         support below.         support below.
1067    
1068         This  code  fragment  shows a typical straightforward call to pcre_com-         This code fragment shows a typical straightforward  call  to  pcre_com-
1069         pile():         pile():
1070    
1071           pcre *re;           pcre *re;
# Line 1015  COMPILING A PATTERN Line 1078  COMPILING A PATTERN
1078             &erroffset,       /* for error offset */             &erroffset,       /* for error offset */
1079             NULL);            /* use default character tables */             NULL);            /* use default character tables */
1080    
1081         The following names for option bits are defined in  the  pcre.h  header         The  following  names  for option bits are defined in the pcre.h header
1082         file:         file:
1083    
1084           PCRE_ANCHORED           PCRE_ANCHORED
1085    
1086         If this bit is set, the pattern is forced to be "anchored", that is, it         If this bit is set, the pattern is forced to be "anchored", that is, it
1087         is constrained to match only at the first matching point in the  string         is  constrained to match only at the first matching point in the string
1088         that  is being searched (the "subject string"). This effect can also be         that is being searched (the "subject string"). This effect can also  be
1089         achieved by appropriate constructs in the pattern itself, which is  the         achieved  by appropriate constructs in the pattern itself, which is the
1090         only way to do it in Perl.         only way to do it in Perl.
1091    
1092           PCRE_AUTO_CALLOUT           PCRE_AUTO_CALLOUT
1093    
1094         If this bit is set, pcre_compile() automatically inserts callout items,         If this bit is set, pcre_compile() automatically inserts callout items,
1095         all with number 255, before each pattern item. For  discussion  of  the         all  with  number  255, before each pattern item. For discussion of the
1096         callout facility, see the pcrecallout documentation.         callout facility, see the pcrecallout documentation.
1097    
1098             PCRE_BSR_ANYCRLF
1099             PCRE_BSR_UNICODE
1100    
1101           These options (which are mutually exclusive) control what the \R escape
1102           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1103           or to match any Unicode newline sequence. The default is specified when
1104           PCRE is built. It can be overridden from within the pattern, or by set-
1105           ting an option when a compiled pattern is matched.
1106    
1107           PCRE_CASELESS           PCRE_CASELESS
1108    
1109         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
1110         case letters. It is equivalent to Perl's  /i  option,  and  it  can  be         case  letters.  It  is  equivalent  to  Perl's /i option, and it can be
1111         changed  within a pattern by a (?i) option setting. In UTF-8 mode, PCRE         changed within a pattern by a (?i) option setting. In UTF-8 mode,  PCRE
1112         always understands the concept of case for characters whose values  are         always  understands the concept of case for characters whose values are
1113         less  than 128, so caseless matching is always possible. For characters         less than 128, so caseless matching is always possible. For  characters
1114         with higher values, the concept of case is supported if  PCRE  is  com-         with  higher  values,  the concept of case is supported if PCRE is com-
1115         piled  with Unicode property support, but not otherwise. If you want to         piled with Unicode property support, but not otherwise. If you want  to
1116         use caseless matching for characters 128 and  above,  you  must  ensure         use  caseless  matching  for  characters 128 and above, you must ensure
1117         that  PCRE  is  compiled  with Unicode property support as well as with         that PCRE is compiled with Unicode property support  as  well  as  with
1118         UTF-8 support.         UTF-8 support.
1119    
1120           PCRE_DOLLAR_ENDONLY           PCRE_DOLLAR_ENDONLY
1121    
1122         If this bit is set, a dollar metacharacter in the pattern matches  only         If  this bit is set, a dollar metacharacter in the pattern matches only
1123         at  the  end  of the subject string. Without this option, a dollar also         at the end of the subject string. Without this option,  a  dollar  also
1124         matches immediately before a newline at the end of the string (but  not         matches  immediately before a newline at the end of the string (but not
1125         before  any  other newlines). The PCRE_DOLLAR_ENDONLY option is ignored         before any other newlines). The PCRE_DOLLAR_ENDONLY option  is  ignored
1126         if PCRE_MULTILINE is set.  There is no equivalent  to  this  option  in         if  PCRE_MULTILINE  is  set.   There is no equivalent to this option in
1127         Perl, and no way to set it within a pattern.         Perl, and no way to set it within a pattern.
1128    
1129           PCRE_DOTALL           PCRE_DOTALL
1130    
1131         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-
1132         acters, including those that indicate newline. Without it, a  dot  does         acter of any value, including one that indicates a newline. However, it
1133         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.
1134         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
1135         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
1136         newline characters, independent of the setting of this option.         be  changed within a pattern by a (?s) option setting. A negative class
1137           such as [^a] always matches newline characters, independent of the set-
1138           ting of this option.
1139    
1140           PCRE_DUPNAMES           PCRE_DUPNAMES
1141    
1142         If this bit is set, names used to identify capturing  subpatterns  need         If  this  bit is set, names used to identify capturing subpatterns need
1143         not be unique. This can be helpful for certain types of pattern when it         not be unique. This can be helpful for certain types of pattern when it
1144         is known that only one instance of the named  subpattern  can  ever  be         is  known  that  only  one instance of the named subpattern can ever be
1145         matched.  There  are  more details of named subpatterns below; see also         matched. There are more details of named subpatterns  below;  see  also
1146         the pcrepattern documentation.         the pcrepattern documentation.
1147    
1148           PCRE_EXTENDED           PCRE_EXTENDED
1149    
1150         If this bit is set, whitespace  data  characters  in  the  pattern  are         If  this  bit  is  set,  whitespace  data characters in the pattern are
1151         totally ignored except when escaped or inside a character class. White-         totally ignored except when escaped or inside a character class. White-
1152         space does not include the VT character (code 11). In addition, charac-         space does not include the VT character (code 11). In addition, charac-
1153         ters between an unescaped # outside a character class and the next new-         ters between an unescaped # outside a character class and the next new-
1154         line, inclusive, are also ignored. This  is  equivalent  to  Perl's  /x         line,  inclusive,  are  also  ignored.  This is equivalent to Perl's /x
1155         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-
1156         ting.         ting.
1157    
1158           Which  characters  are  interpreted  as  newlines  is controlled by the
1159           options passed to pcre_compile() or by a special sequence at the  start
1160           of  the  pattern, as described in the section entitled "Newline conven-
1161           tions" in the pcrepattern documentation. Note that the end of this type
1162           of  comment  is  a  literal  newline  sequence  in  the pattern; escape
1163           sequences that happen to represent a newline do not count.
1164    
1165         This option makes it possible to include  comments  inside  complicated         This option makes it possible to include  comments  inside  complicated
1166         patterns.   Note,  however,  that this applies only to data characters.         patterns.   Note,  however,  that this applies only to data characters.
1167         Whitespace  characters  may  never  appear  within  special   character         Whitespace  characters  may  never  appear  within  special   character
1168         sequences  in  a  pattern,  for  example  within the sequence (?( which         sequences in a pattern, for example within the sequence (?( that intro-
1169         introduces a conditional subpattern.         duces a conditional subpattern.
1170    
1171           PCRE_EXTRA           PCRE_EXTRA
1172    
# Line 1095  COMPILING A PATTERN Line 1176  COMPILING A PATTERN
1176         letter  that  has  no  special  meaning causes an error, thus reserving         letter  that  has  no  special  meaning causes an error, thus reserving
1177         these combinations for future expansion. By  default,  as  in  Perl,  a         these combinations for future expansion. By  default,  as  in  Perl,  a
1178         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
1179         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
1180         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
1181         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
1182           within a pattern.
1183    
1184           PCRE_FIRSTLINE           PCRE_FIRSTLINE
1185    
1186         If this option is set, an  unanchored  pattern  is  required  to  match         If  this  option  is  set,  an  unanchored pattern is required to match
1187         before  or  at  the  first  newline  in  the subject string, though the         before or at the first  newline  in  the  subject  string,  though  the
1188         matched text may continue over the newline.         matched text may continue over the newline.
1189    
1190             PCRE_JAVASCRIPT_COMPAT
1191    
1192           If this option is set, PCRE's behaviour is changed in some ways so that
1193           it is compatible with JavaScript rather than Perl. The changes  are  as
1194           follows:
1195    
1196           (1)  A  lone  closing square bracket in a pattern causes a compile-time
1197           error, because this is illegal in JavaScript (by default it is  treated
1198           as a data character). Thus, the pattern AB]CD becomes illegal when this
1199           option is set.
1200    
1201           (2) At run time, a back reference to an unset subpattern group  matches
1202           an  empty  string (by default this causes the current matching alterna-
1203           tive to fail). A pattern such as (\1)(a) succeeds when this  option  is
1204           set  (assuming  it can find an "a" in the subject), whereas it fails by
1205           default, for Perl compatibility.
1206    
1207           PCRE_MULTILINE           PCRE_MULTILINE
1208    
1209         By default, PCRE treats the subject string as consisting  of  a  single         By default, PCRE treats the subject string as consisting  of  a  single
# Line 1125  COMPILING A PATTERN Line 1224  COMPILING A PATTERN
1224           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
1225           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
1226           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
1227             PCRE_NEWLINE_ANYCRLF
1228           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1229    
1230         These  options  override the default newline definition that was chosen         These  options  override the default newline definition that was chosen
1231         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
1232         newline  is  indicated  by a single character (CR or LF, respectively).         newline  is  indicated  by a single character (CR or LF, respectively).
1233         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the         Setting PCRE_NEWLINE_CRLF specifies that a newline is indicated by  the
1234         two-character  CRLF  sequence.  Setting PCRE_NEWLINE_ANY specifies that         two-character  CRLF  sequence.  Setting  PCRE_NEWLINE_ANYCRLF specifies
1235         any Unicode newline sequence should be recognized. The Unicode  newline         that any of the three preceding sequences should be recognized. Setting
1236         sequences  are  the three just mentioned, plus the single characters VT         PCRE_NEWLINE_ANY  specifies that any Unicode newline sequence should be
1237         (vertical tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085),         recognized. The Unicode newline sequences are the three just mentioned,
1238         LS  (line separator, U+2028), and PS (paragraph separator, U+2029). The         plus  the  single  characters  VT (vertical tab, U+000B), FF (formfeed,
1239         last two are recognized only in UTF-8 mode.         U+000C), NEL (next line, U+0085), LS (line separator, U+2028),  and  PS
1240           (paragraph  separator,  U+2029).  The  last  two are recognized only in
1241           UTF-8 mode.
1242    
1243         The newline setting in the  options  word  uses  three  bits  that  are         The newline setting in the  options  word  uses  three  bits  that  are
1244         treated  as  a  number, giving eight possibilities. Currently only five         treated as a number, giving eight possibilities. Currently only six are
1245         are used (default plus the four values above). This means that  if  you         used (default plus the five values above). This means that if  you  set
1246         set  more  than  one  newline option, the combination may or may not be         more  than one newline option, the combination may or may not be sensi-
1247         sensible. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is  equiva-         ble. For example, PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to
1248         lent  to PCRE_NEWLINE_CRLF, but other combinations yield unused numbers         PCRE_NEWLINE_CRLF,  but other combinations may yield unused numbers and
1249         and cause an error.         cause an error.
1250    
1251         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
1252         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
1253         character class is encountered. This indicates  a  comment  that  lasts         characters, and so are ignored in this mode. Also, an unescaped #  out-
1254         until  after the next line break sequence. In other circumstances, line         side  a  character class indicates a comment that lasts until after the
1255         break  sequences  are  treated  as  literal  data,   except   that   in         next line break sequence. In other circumstances, line break  sequences
1256         PCRE_EXTENDED mode, both CR and LF are treated as whitespace characters         in patterns are treated as literal data.
        and are therefore ignored.  
1257    
1258         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
1259         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.
1260    
1261           PCRE_NO_AUTO_CAPTURE           PCRE_NO_AUTO_CAPTURE
1262    
# Line 1165  COMPILING A PATTERN Line 1266  COMPILING A PATTERN
1266         be  used  for  capturing  (and  they acquire numbers in the usual way).         be  used  for  capturing  (and  they acquire numbers in the usual way).
1267         There is no equivalent of this option in Perl.         There is no equivalent of this option in Perl.
1268    
1269             NO_START_OPTIMIZE
1270    
1271           This is an option that acts at matching time; that is, it is really  an
1272           option  for  pcre_exec()  or  pcre_dfa_exec().  If it is set at compile
1273           time, it is remembered with the compiled pattern and assumed at  match-
1274           ing  time.  For  details  see  the discussion of PCRE_NO_START_OPTIMIZE
1275           below.
1276    
1277             PCRE_UCP
1278    
1279           This option changes the way PCRE processes \B, \b, \D, \d, \S, \s,  \W,
1280           \w,  and  some  of  the POSIX character classes. By default, only ASCII
1281           characters are recognized, but if PCRE_UCP is set,  Unicode  properties
1282           are  used instead to classify characters. More details are given in the
1283           section on generic character types in the pcrepattern page. If you  set
1284           PCRE_UCP,  matching  one of the items it affects takes much longer. The
1285           option is available only if PCRE has been compiled with  Unicode  prop-
1286           erty support.
1287    
1288           PCRE_UNGREEDY           PCRE_UNGREEDY
1289    
1290         This option inverts the "greediness" of the quantifiers  so  that  they         This  option  inverts  the "greediness" of the quantifiers so that they
1291         are  not greedy by default, but become greedy if followed by "?". It is         are not greedy by default, but become greedy if followed by "?". It  is
1292         not compatible with Perl. It can also be set by a (?U)  option  setting         not  compatible  with Perl. It can also be set by a (?U) option setting
1293         within the pattern.         within the pattern.
1294    
1295           PCRE_UTF8           PCRE_UTF8
1296    
1297         This  option  causes PCRE to regard both the pattern and the subject as         This option causes PCRE to regard both the pattern and the  subject  as
1298         strings of UTF-8 characters instead of single-byte  character  strings.         strings  of  UTF-8 characters instead of single-byte character strings.
1299         However,  it is available only when PCRE is built to include UTF-8 sup-         However, it is available only when PCRE is built to include UTF-8  sup-
1300         port. If not, the use of this option provokes an error. Details of  how         port.  If not, the use of this option provokes an error. Details of how
1301         this  option  changes the behaviour of PCRE are given in the section on         this option changes the behaviour of PCRE are given in the  pcreunicode
1302         UTF-8 support in the main pcre page.         page.
1303    
1304           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
1305    
1306         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
1307         automatically  checked. If an invalid UTF-8 sequence of bytes is found,         automatically checked. There is a  discussion  about  the  validity  of
1308         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
1309         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
1310         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-
1311         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
1312         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
1313         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
1314         ing of subject strings.         can  also be passed to pcre_exec() and pcre_dfa_exec(), to suppress the
1315           UTF-8 validity checking of subject strings.
1316    
1317    
1318  COMPILATION ERROR CODES  COMPILATION ERROR CODES
# Line 1213  COMPILATION ERROR CODES Line 1334  COMPILATION ERROR CODES
1334            9  nothing to repeat            9  nothing to repeat
1335           10  [this code is not in use]           10  [this code is not in use]
1336           11  internal error: unexpected repeat           11  internal error: unexpected repeat
1337           12  unrecognized character after (?           12  unrecognized character after (? or (?-
1338           13  POSIX named classes are supported only within a class           13  POSIX named classes are supported only within a class
1339           14  missing )           14  missing )
1340           15  reference to non-existent subpattern           15  reference to non-existent subpattern
# Line 1221  COMPILATION ERROR CODES Line 1342  COMPILATION ERROR CODES
1342           17  unknown option bit(s) set           17  unknown option bit(s) set
1343           18  missing ) after comment           18  missing ) after comment
1344           19  [this code is not in use]           19  [this code is not in use]
1345           20  regular expression too large           20  regular expression is too large
1346           21  failed to get memory           21  failed to get memory
1347           22  unmatched parentheses           22  unmatched parentheses
1348           23  internal error: code overflow           23  internal error: code overflow
# Line 1230  COMPILATION ERROR CODES Line 1351  COMPILATION ERROR CODES
1351           26  malformed number or name after (?(           26  malformed number or name after (?(
1352           27  conditional group contains more than two branches           27  conditional group contains more than two branches
1353           28  assertion expected after (?(           28  assertion expected after (?(
1354           29  (?R or (?digits must be followed by )           29  (?R or (?[+-]digits must be followed by )
1355           30  unknown POSIX class name           30  unknown POSIX class name
1356           31  POSIX collating elements are not supported           31  POSIX collating elements are not supported
1357           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 1238  COMPILATION ERROR CODES Line 1359  COMPILATION ERROR CODES
1359           34  character value in \x{...} sequence is too large           34  character value in \x{...} sequence is too large
1360           35  invalid condition (?(0)           35  invalid condition (?(0)
1361           36  \C not allowed in lookbehind assertion           36  \C not allowed in lookbehind assertion
1362           37  PCRE does not support \L, \l, \N, \U, or \u           37  PCRE does not support \L, \l, \N{name}, \U, or \u
1363           38  number after (?C is > 255           38  number after (?C is > 255
1364           39  closing ) for (?C expected           39  closing ) for (?C expected
1365           40  recursive call could loop indefinitely           40  recursive call could loop indefinitely
# Line 1250  COMPILATION ERROR CODES Line 1371  COMPILATION ERROR CODES
1371           46  malformed \P or \p sequence           46  malformed \P or \p sequence
1372           47  unknown property name after \P or \p           47  unknown property name after \P or \p
1373           48  subpattern name is too long (maximum 32 characters)           48  subpattern name is too long (maximum 32 characters)
1374           49  too many named subpatterns (maximum 10,000)           49  too many named subpatterns (maximum 10000)
1375           50  repeated subpattern is too long           50  [this code is not in use]
1376           51  octal value is greater than \377 (not in UTF-8 mode)           51  octal value is greater than \377 (not in UTF-8 mode)
1377           52  internal error: overran compiling workspace           52  internal error: overran compiling workspace
1378           53   internal  error:  previously-checked  referenced  subpattern not           53  internal error: previously-checked referenced subpattern
1379         found                 not found
1380           54  DEFINE group contains more than one branch           54  DEFINE group contains more than one branch
1381           55  repeating a DEFINE group is not allowed           55  repeating a DEFINE group is not allowed
1382           56  inconsistent NEWLINE options"           56  inconsistent NEWLINE options
1383             57  \g is not followed by a braced, angle-bracketed, or quoted
1384                   name/number or by a plain number
1385             58  a numbered reference must not be zero
1386             59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
1387             60  (*VERB) not recognized
1388             61  number is too big
1389             62  subpattern name expected
1390             63  digit expected after (?+
1391             64  ] is an invalid data character in JavaScript compatibility mode
1392             65  different names for subpatterns of the same number are
1393                   not allowed
1394             66  (*MARK) must have an argument
1395             67  this version of PCRE is not compiled with PCRE_UCP support
1396             68  \c must be followed by an ASCII character
1397             69  \k is not followed by a braced, angle-bracketed, or quoted name
1398    
1399           The  numbers  32  and 10000 in errors 48 and 49 are defaults; different
1400           values may be used if the limits were changed when PCRE was built.
1401    
1402    
1403  STUDYING A PATTERN  STUDYING A PATTERN
# Line 1275  STUDYING A PATTERN Line 1414  STUDYING A PATTERN
1414         the results of the study.         the results of the study.
1415    
1416         The  returned  value  from  pcre_study()  can  be  passed  directly  to         The  returned  value  from  pcre_study()  can  be  passed  directly  to
1417         pcre_exec().  However,  a  pcre_extra  block also contains other fields         pcre_exec()  or  pcre_dfa_exec(). However, a pcre_extra block also con-
1418         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
1419         described below in the section on matching a pattern.         passed; these are described below in the section on matching a pattern.
1420    
1421         If  studying  the  pattern  does not produce any additional information         If  studying  the  pattern  does  not  produce  any useful information,
1422         pcre_study() returns NULL. In that circumstance, if the calling program         pcre_study() returns NULL. In that circumstance, if the calling program
1423         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
1424         its own pcre_extra block.         pcre_dfa_exec(), it must set up its own pcre_extra block.
1425    
1426         The second argument of pcre_study() contains option bits.  At  present,         The second argument of pcre_study() contains option bits.  At  present,
1427         no options are defined, and this argument should always be zero.         no options are defined, and this argument should always be zero.
# Line 1302  STUDYING A PATTERN Line 1441  STUDYING A PATTERN
1441             0,              /* no options exist */             0,              /* no options exist */
1442             &error);        /* set to NULL or points to a message */             &error);        /* set to NULL or points to a message */
1443    
1444         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
1445         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
1446         ble starting bytes is created.         does not mean that there are any strings of that length that match, but
1447           it  does  guarantee that no shorter strings match. The value is used by
1448           pcre_exec() and pcre_dfa_exec() to avoid  wasting  time  by  trying  to
1449           match  strings  that are shorter than the lower bound. You can find out
1450           the value in a calling program via the pcre_fullinfo() function.
1451    
1452           Studying a pattern is also useful for non-anchored patterns that do not
1453           have  a  single fixed starting character. A bitmap of possible starting
1454           bytes is created. This speeds up finding a position in the  subject  at
1455           which to start matching.
1456    
1457           The  two  optimizations  just  described can be disabled by setting the
1458           PCRE_NO_START_OPTIMIZE   option    when    calling    pcre_exec()    or
1459           pcre_dfa_exec().  You  might  want  to do this if your pattern contains
1460           callouts or (*MARK), and you want to make use of  these  facilities  in
1461           cases  where  matching fails. See the discussion of PCRE_NO_START_OPTI-
1462           MIZE below.
1463    
1464    
1465  LOCALE SUPPORT  LOCALE SUPPORT
1466    
1467         PCRE handles caseless matching, and determines whether  characters  are         PCRE handles caseless matching, and determines whether  characters  are
1468         letters  digits,  or whatever, by reference to a set of tables, indexed         letters,  digits, or whatever, by reference to a set of tables, indexed
1469         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
1470         characters  with  codes  less than 128. Higher-valued codes never match         characters  with  codes  less than 128. By default, higher-valued codes
1471         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
1472         with  Unicode  character property support. The use of locales with Uni-         PCRE  is  built with Unicode character property support. Alternatively,
1473         code is discouraged.         the PCRE_UCP option can be set at compile  time;  this  causes  \w  and
1474           friends to use Unicode property support instead of built-in tables. The
1475         An internal set of tables is created in the default C locale when  PCRE         use of locales with Unicode is discouraged. If you are handling charac-
1476         is  built.  This  is  used when the final argument of pcre_compile() is         ters  with codes greater than 128, you should either use UTF-8 and Uni-
1477         NULL, and is sufficient for many applications. An  alternative  set  of         code, or use locales, but not try to mix the two.
1478         tables  can,  however, be supplied. These may be created in a different  
1479         locale from the default. As more and more applications change to  using         PCRE contains an internal set of tables that are used  when  the  final
1480         Unicode, the need for this locale support is expected to die away.         argument  of  pcre_compile()  is  NULL.  These  are sufficient for many
1481           applications.  Normally, the internal tables recognize only ASCII char-
1482         External  tables  are  built by calling the pcre_maketables() function,         acters. However, when PCRE is built, it is possible to cause the inter-
1483         which has no arguments, in the relevant locale. The result can then  be         nal tables to be rebuilt in the default "C" locale of the local system,
1484         passed  to  pcre_compile()  or  pcre_exec()  as often as necessary. For         which may cause them to be different.
1485         example, to build and use tables that are appropriate  for  the  French  
1486         locale  (where  accented  characters  with  values greater than 128 are         The  internal tables can always be overridden by tables supplied by the
1487           application that calls PCRE. These may be created in a different locale
1488           from  the  default.  As more and more applications change to using Uni-
1489           code, the need for this locale support is expected to die away.
1490    
1491           External tables are built by calling  the  pcre_maketables()  function,
1492           which  has no arguments, in the relevant locale. The result can then be
1493           passed to pcre_compile() or pcre_exec()  as  often  as  necessary.  For
1494           example,  to  build  and use tables that are appropriate for the French
1495           locale (where accented characters with  values  greater  than  128  are
1496         treated as letters), the following code could be used:         treated as letters), the following code could be used:
1497    
1498           setlocale(LC_CTYPE, "fr_FR");           setlocale(LC_CTYPE, "fr_FR");
1499           tables = pcre_maketables();           tables = pcre_maketables();
1500           re = pcre_compile(..., tables);           re = pcre_compile(..., tables);
1501    
1502           The  locale  name "fr_FR" is used on Linux and other Unix-like systems;
1503           if you are using Windows, the name for the French locale is "french".
1504    
1505         When pcre_maketables() runs, the tables are built  in  memory  that  is         When pcre_maketables() runs, the tables are built  in  memory  that  is
1506         obtained  via  pcre_malloc. It is the caller's responsibility to ensure         obtained  via  pcre_malloc. It is the caller's responsibility to ensure
1507         that the memory containing the tables remains available for as long  as         that the memory containing the tables remains available for as long  as
# Line 1437  INFORMATION ABOUT A PATTERN Line 1604  INFORMATION ABOUT A PATTERN
1604         returned. The fourth argument should point to an unsigned char *  vari-         returned. The fourth argument should point to an unsigned char *  vari-
1605         able.         able.
1606    
1607             PCRE_INFO_HASCRORLF
1608    
1609           Return  1  if  the  pattern  contains any explicit matches for CR or LF
1610           characters, otherwise 0. The fourth argument should  point  to  an  int
1611           variable.  An explicit match is either a literal CR or LF character, or
1612           \r or \n.
1613    
1614             PCRE_INFO_JCHANGED
1615    
1616           Return 1 if the (?J) or (?-J) option setting is used  in  the  pattern,
1617           otherwise  0. The fourth argument should point to an int variable. (?J)
1618           and (?-J) set and unset the local PCRE_DUPNAMES option, respectively.
1619    
1620           PCRE_INFO_LASTLITERAL           PCRE_INFO_LASTLITERAL
1621    
1622         Return  the  value of the rightmost literal byte that must exist in any         Return the value of the rightmost literal byte that must exist  in  any
1623         matched string, other than at its  start,  if  such  a  byte  has  been         matched  string,  other  than  at  its  start,  if such a byte has been
1624         recorded. The fourth argument should point to an int variable. If there         recorded. The fourth argument should point to an int variable. If there
1625         is no such byte, -1 is returned. For anchored patterns, a last  literal         is  no such byte, -1 is returned. For anchored patterns, a last literal
1626         byte  is  recorded only if it follows something of variable length. For         byte is recorded only if it follows something of variable  length.  For
1627         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
1628         /^a\dz\d/ the returned value is -1.         /^a\dz\d/ the returned value is -1.
1629    
1630             PCRE_INFO_MINLENGTH
1631    
1632           If the pattern was studied and a minimum length  for  matching  subject
1633           strings  was  computed,  its  value is returned. Otherwise the returned
1634           value is -1. The value is a number of characters, not bytes  (this  may
1635           be  relevant in UTF-8 mode). The fourth argument should point to an int
1636           variable. A non-negative value is a lower bound to the  length  of  any
1637           matching  string.  There  may not be any strings of that length that do
1638           actually match, but every string that does match is at least that long.
1639    
1640           PCRE_INFO_NAMECOUNT           PCRE_INFO_NAMECOUNT
1641           PCRE_INFO_NAMEENTRYSIZE           PCRE_INFO_NAMEENTRYSIZE
1642           PCRE_INFO_NAMETABLE           PCRE_INFO_NAMETABLE
1643    
1644         PCRE  supports the use of named as well as numbered capturing parenthe-         PCRE supports the use of named as well as numbered capturing  parenthe-
1645         ses. The names are just an additional way of identifying the  parenthe-         ses.  The names are just an additional way of identifying the parenthe-
1646         ses, which still acquire numbers. Several convenience functions such as         ses, which still acquire numbers. Several convenience functions such as
1647         pcre_get_named_substring() are provided for  extracting  captured  sub-         pcre_get_named_substring()  are  provided  for extracting captured sub-
1648         strings  by  name. It is also possible to extract the data directly, by         strings by name. It is also possible to extract the data  directly,  by
1649         first converting the name to a number in order to  access  the  correct         first  converting  the  name to a number in order to access the correct
1650         pointers in the output vector (described with pcre_exec() below). To do         pointers in the output vector (described with pcre_exec() below). To do
1651         the conversion, you need  to  use  the  name-to-number  map,  which  is         the  conversion,  you  need  to  use  the  name-to-number map, which is
1652         described by these three values.         described by these three values.
1653    
1654         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT         The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT
1655         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size         gives the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size
1656         of  each  entry;  both  of  these  return  an int value. The entry size         of each entry; both of these  return  an  int  value.  The  entry  size
1657         depends on the length of the longest name. PCRE_INFO_NAMETABLE  returns         depends  on the length of the longest name. PCRE_INFO_NAMETABLE returns
1658         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
1659         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-
1660         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-
1661         sponding name, zero terminated. The names are  in  alphabetical  order.         sponding name, zero terminated.
1662         When PCRE_DUPNAMES is set, duplicate names are in order of their paren-  
1663         theses numbers. For example, consider  the  following  pattern  (assume         The  names are in alphabetical order. Duplicate names may appear if (?|
1664         PCRE_EXTENDED  is  set,  so  white  space  -  including  newlines  - is         is used to create multiple groups with the same number, as described in
1665         ignored):         the  section  on  duplicate subpattern numbers in the pcrepattern page.
1666           Duplicate names for subpatterns with different  numbers  are  permitted
1667           only  if  PCRE_DUPNAMES  is  set. In all cases of duplicate names, they
1668           appear in the table in the order in which they were found in  the  pat-
1669           tern.  In  the  absence  of (?| this is the order of increasing number;
1670           when (?| is used this is not necessarily the case because later subpat-
1671           terns may have lower numbers.
1672    
1673           As  a  simple  example of the name/number table, consider the following
1674           pattern (assume PCRE_EXTENDED is set, so white space -  including  new-
1675           lines - is ignored):
1676    
1677           (?<date> (?<year>(\d\d)?\d\d) -           (?<date> (?<year>(\d\d)?\d\d) -
1678           (?<month>\d\d) - (?<day>\d\d) )           (?<month>\d\d) - (?<day>\d\d) )
1679    
1680         There are four named subpatterns, so the table has  four  entries,  and         There  are  four  named subpatterns, so the table has four entries, and
1681         each  entry  in the table is eight bytes long. The table is as follows,         each entry in the table is eight bytes long. The table is  as  follows,
1682         with non-printing bytes shows in hexadecimal, and undefined bytes shown         with non-printing bytes shows in hexadecimal, and undefined bytes shown
1683         as ??:         as ??:
1684    
# Line 1487  INFORMATION ABOUT A PATTERN Line 1687  INFORMATION ABOUT A PATTERN
1687           00 04 m  o  n  t  h  00           00 04 m  o  n  t  h  00
1688           00 02 y  e  a  r  00 ??           00 02 y  e  a  r  00 ??
1689    
1690         When  writing  code  to  extract  data from named subpatterns using the         When writing code to extract data  from  named  subpatterns  using  the
1691         name-to-number map, remember that the length of the entries  is  likely         name-to-number  map,  remember that the length of the entries is likely
1692         to be different for each compiled pattern.         to be different for each compiled pattern.
1693    
1694             PCRE_INFO_OKPARTIAL
1695    
1696           Return 1  if  the  pattern  can  be  used  for  partial  matching  with
1697           pcre_exec(),  otherwise  0.  The fourth argument should point to an int
1698           variable. From  release  8.00,  this  always  returns  1,  because  the
1699           restrictions  that  previously  applied  to  partial matching have been
1700           lifted. The pcrepartial documentation gives details of  partial  match-
1701           ing.
1702    
1703           PCRE_INFO_OPTIONS           PCRE_INFO_OPTIONS
1704    
1705         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
1706         fourth argument should point to an unsigned long  int  variable.  These         fourth argument should point to an unsigned long  int  variable.  These
1707         option bits are those specified in the call to pcre_compile(), modified         option bits are those specified in the call to pcre_compile(), modified
1708         by any top-level option settings within the pattern itself.         by any top-level option settings at the start of the pattern itself. In
1709           other  words,  they are the options that will be in force when matching
1710           starts. For example, if the pattern /(?im)abc(?-i)d/ is  compiled  with
1711           the  PCRE_EXTENDED option, the result is PCRE_CASELESS, PCRE_MULTILINE,
1712           and PCRE_EXTENDED.
1713    
1714         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
1715         alternatives begin with one of the following:         alternatives begin with one of the following:
# Line 1520  INFORMATION ABOUT A PATTERN Line 1733  INFORMATION ABOUT A PATTERN
1733           PCRE_INFO_STUDYSIZE           PCRE_INFO_STUDYSIZE
1734    
1735         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
1736         a pcre_extra block. That is,  it  is  the  value  that  was  passed  to         a pcre_extra block. If pcre_extra is NULL, or there is no  study  data,
1737         pcre_malloc() when PCRE was getting memory into which to place the data         zero  is  returned.  The fourth argument should point to a size_t vari-
1738         created by pcre_study(). The fourth argument should point to  a  size_t         able.  The study_data field is set by pcre_study() to  record  informa-
1739         variable.         tion  that will speed up matching (see the section entitled "Studying a
1740           pattern" above). The format of the study_data block is private, but its
1741           length  is  made  available via this option so that it can be saved and
1742           restored (see the pcreprecompile documentation for details).
1743    
1744    
1745  OBSOLETE INFO FUNCTION  OBSOLETE INFO FUNCTION
1746    
1747         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);         int pcre_info(const pcre *code, int *optptr, int *firstcharptr);
1748    
1749         The  pcre_info()  function is now obsolete because its interface is too         The pcre_info() function is now obsolete because its interface  is  too
1750         restrictive to return all the available data about a compiled  pattern.         restrictive  to return all the available data about a compiled pattern.
1751         New   programs   should  use  pcre_fullinfo()  instead.  The  yield  of         New  programs  should  use  pcre_fullinfo()  instead.  The   yield   of
1752         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-
1753         lowing negative numbers:         lowing negative numbers:
1754    
1755           PCRE_ERROR_NULL       the argument code was NULL           PCRE_ERROR_NULL       the argument code was NULL
1756           PCRE_ERROR_BADMAGIC   the "magic number" was not found           PCRE_ERROR_BADMAGIC   the "magic number" was not found
1757    
1758         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
1759         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
1760         PCRE_INFO_OPTIONS above).         PCRE_INFO_OPTIONS above).
1761    
1762         If  the  pattern  is  not anchored and the firstcharptr argument is not         If the pattern is not anchored and the  firstcharptr  argument  is  not
1763         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
1764         any matched string (see PCRE_INFO_FIRSTBYTE above).         any matched string (see PCRE_INFO_FIRSTBYTE above).
1765    
1766    
# Line 1552  REFERENCE COUNTS Line 1768  REFERENCE COUNTS
1768    
1769         int pcre_refcount(pcre *code, int adjust);         int pcre_refcount(pcre *code, int adjust);
1770    
1771         The  pcre_refcount()  function is used to maintain a reference count in         The pcre_refcount() function is used to maintain a reference  count  in
1772         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
1773         benefit  of  applications  that  operate  in an object-oriented manner,         benefit of applications that  operate  in  an  object-oriented  manner,
1774         where different parts of the application may be using the same compiled         where different parts of the application may be using the same compiled
1775         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.
1776    
1777         When a pattern is compiled, the reference count field is initialized to         When a pattern is compiled, the reference count field is initialized to
1778         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
1779         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
1780         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
1781         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
1782         is outside these limits, it is forced to the appropriate limit value.         is outside these limits, it is forced to the appropriate limit value.
1783    
1784         Except when it is zero, the reference count is not correctly  preserved         Except  when it is zero, the reference count is not correctly preserved
1785         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
1786         whose byte-order is different. (This seems a highly unlikely scenario.)         whose byte-order is different. (This seems a highly unlikely scenario.)
1787    
1788    
# Line 1578  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1794  MATCHING A PATTERN: THE TRADITIONAL FUNC
1794    
1795         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
1796         compiled pattern, which is passed in the code argument. If the  pattern         compiled pattern, which is passed in the code argument. If the  pattern
1797         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
1798         argument. This function is the main matching facility of  the  library,         argument. This function is the main matching facility of  the  library,
1799         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
1800         an alternative matching function, which is described below in the  sec-         an alternative matching function, which is described below in the  sec-
# Line 1618  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1834  MATCHING A PATTERN: THE TRADITIONAL FUNC
1834           unsigned long int match_limit_recursion;           unsigned long int match_limit_recursion;
1835           void *callout_data;           void *callout_data;
1836           const unsigned char *tables;           const unsigned char *tables;
1837             unsigned char **mark;
1838    
1839         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
1840         are set. The flag bits are:         are set. The flag bits are:
# Line 1627  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1844  MATCHING A PATTERN: THE TRADITIONAL FUNC
1844           PCRE_EXTRA_MATCH_LIMIT_RECURSION           PCRE_EXTRA_MATCH_LIMIT_RECURSION
1845           PCRE_EXTRA_CALLOUT_DATA           PCRE_EXTRA_CALLOUT_DATA
1846           PCRE_EXTRA_TABLES           PCRE_EXTRA_TABLES
1847             PCRE_EXTRA_MARK
1848    
1849         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
1850         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 1637  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1855  MATCHING A PATTERN: THE TRADITIONAL FUNC
1855         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
1856         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
1857         match, but which have a very large number  of  possibilities  in  their         match, but which have a very large number  of  possibilities  in  their
1858         search  trees.  The  classic  example  is  the  use of nested unlimited         search  trees. The classic example is a pattern that uses nested unlim-
1859         repeats.         ited repeats.
1860    
1861         Internally, PCRE uses a function called match() which it calls  repeat-         Internally, PCRE uses a function called match() which it calls  repeat-
1862         edly  (sometimes  recursively). The limit set by match_limit is imposed         edly  (sometimes  recursively). The limit set by match_limit is imposed
# Line 1660  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1878  MATCHING A PATTERN: THE TRADITIONAL FUNC
1878         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-
1879         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.
1880    
1881         Limiting  the  recursion  depth  limits the amount of stack that can be         Limiting the recursion depth limits the amount of  stack  that  can  be
1882         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
1883         of the stack, the amount of heap memory that can be used.         of the stack, the amount of heap memory that can be used.
1884    
1885         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
1886         built; the default default  is  the  same  value  as  the  default  for         built;  the  default  default  is  the  same  value  as the default for
1887         match_limit.  You can override the default by suppling pcre_exec() with         match_limit. You can override the default by suppling pcre_exec()  with
1888         a  pcre_extra  block  in  which  match_limit_recursion  is   set,   and         a   pcre_extra   block  in  which  match_limit_recursion  is  set,  and
1889         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
1890         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.         limit is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT.
1891    
1892         The pcre_callout field is used in conjunction with the  "callout"  fea-         The  callout_data  field is used in conjunction with the "callout" fea-
1893         ture, which is described in the pcrecallout documentation.         ture, and is described in the pcrecallout documentation.
1894    
1895         The  tables  field  is  used  to  pass  a  character  tables pointer to         The tables field  is  used  to  pass  a  character  tables  pointer  to
1896         pcre_exec(); this overrides the value that is stored with the  compiled         pcre_exec();  this overrides the value that is stored with the compiled
1897         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
1898         custom tables were supplied to pcre_compile() via  its  tableptr  argu-         custom  tables  were  supplied to pcre_compile() via its tableptr argu-
1899         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
1900         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-
1901         using  patterns  that  have been saved after compiling with an external         using patterns that have been saved after compiling  with  an  external
1902         set of tables, because the external tables  might  be  at  a  different         set  of  tables,  because  the  external tables might be at a different
1903         address  when  pcre_exec() is called. See the pcreprecompile documenta-         address when pcre_exec() is called. See the  pcreprecompile  documenta-
1904         tion for a discussion of saving compiled patterns for later use.         tion for a discussion of saving compiled patterns for later use.
1905    
1906           If  PCRE_EXTRA_MARK  is  set in the flags field, the mark field must be
1907           set to point to a char * variable. If the pattern  contains  any  back-
1908           tracking  control verbs such as (*MARK:NAME), and the execution ends up
1909           with a name to pass back, a pointer to the  name  string  (zero  termi-
1910           nated)  is  placed  in  the  variable pointed to by the mark field. The
1911           names are within the compiled pattern; if you wish  to  retain  such  a
1912           name  you must copy it before freeing the memory of a compiled pattern.
1913           If there is no name to pass back, the variable pointed to by  the  mark
1914           field  set  to NULL. For details of the backtracking control verbs, see
1915           the section entitled "Backtracking control" in the pcrepattern documen-
1916           tation.
1917    
1918     Option bits for pcre_exec()     Option bits for pcre_exec()
1919    
1920         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.
1921         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,
1922         PCRE_NOTBOL,   PCRE_NOTEOL,   PCRE_NOTEMPTY,   PCRE_NO_UTF8_CHECK   and         PCRE_NOTBOL,    PCRE_NOTEOL,    PCRE_NOTEMPTY,   PCRE_NOTEMPTY_ATSTART,
1923         PCRE_PARTIAL.         PCRE_NO_START_OPTIMIZE,  PCRE_NO_UTF8_CHECK,   PCRE_PARTIAL_SOFT,   and
1924           PCRE_PARTIAL_HARD.
1925    
1926           PCRE_ANCHORED           PCRE_ANCHORED
1927    
# Line 1699  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 1930  MATCHING A PATTERN: THE TRADITIONAL FUNC
1930         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
1931         unachored at matching time.         unachored at matching time.
1932    
1933             PCRE_BSR_ANYCRLF
1934             PCRE_BSR_UNICODE
1935    
1936           These options (which are mutually exclusive) control what the \R escape
1937           sequence  matches.  The choice is either to match only CR, LF, or CRLF,
1938           or to match any Unicode newline sequence. These  options  override  the
1939           choice that was made or defaulted when the pattern was compiled.
1940    
1941           PCRE_NEWLINE_CR           PCRE_NEWLINE_CR
1942           PCRE_NEWLINE_LF           PCRE_NEWLINE_LF
1943           PCRE_NEWLINE_CRLF           PCRE_NEWLINE_CRLF
1944             PCRE_NEWLINE_ANYCRLF
1945           PCRE_NEWLINE_ANY           PCRE_NEWLINE_ANY
1946    
1947         These options override  the  newline  definition  that  was  chosen  or         These  options  override  the  newline  definition  that  was chosen or
1948         defaulted  when the pattern was compiled. For details, see the descrip-         defaulted when the pattern was compiled. For details, see the  descrip-
1949         tion of pcre_compile()  above.  During  matching,  the  newline  choice         tion  of  pcre_compile()  above.  During  matching,  the newline choice
1950         affects  the  behaviour  of the dot, circumflex, and dollar metacharac-         affects the behaviour of the dot, circumflex,  and  dollar  metacharac-
1951         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
1952         match  failure  for  an  unanchored  pattern. When PCRE_NEWLINE_CRLF or         match failure for an unanchored pattern.
1953         PCRE_NEWLINE_ANY is set, and a match attempt  fails  when  the  current  
1954         position  is  at a CRLF sequence, the match position is advanced by two         When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF,  or  PCRE_NEWLINE_ANY  is
1955         characters instead of one, in other words, to after the CRLF.         set,  and a match attempt for an unanchored pattern fails when the cur-
1956           rent position is at a  CRLF  sequence,  and  the  pattern  contains  no
1957           explicit  matches  for  CR  or  LF  characters,  the  match position is
1958           advanced by two characters instead of one, in other words, to after the
1959           CRLF.
1960    
1961           The above rule is a compromise that makes the most common cases work as
1962           expected. For example, if the  pattern  is  .+A  (and  the  PCRE_DOTALL
1963           option is not set), it does not match the string "\r\nA" because, after
1964           failing at the start, it skips both the CR and the LF before  retrying.
1965           However,  the  pattern  [\r\n]A does match that string, because it con-
1966           tains an explicit CR or LF reference, and so advances only by one char-
1967           acter after the first failure.
1968    
1969           An explicit match for CR of LF is either a literal appearance of one of
1970           those characters, or one of the \r or  \n  escape  sequences.  Implicit
1971           matches  such  as [^X] do not count, nor does \s (which includes CR and
1972           LF in the characters that it matches).
1973    
1974           Notwithstanding the above, anomalous effects may still occur when  CRLF
1975           is a valid newline sequence and explicit \r or \n escapes appear in the
1976           pattern.
1977    
1978           PCRE_NOTBOL           PCRE_NOTBOL
1979    
# Line 1740  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2001  MATCHING A PATTERN: THE TRADITIONAL FUNC
2001    
2002           a?b?           a?b?
2003    
2004         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
2005         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
2006         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-
2007         rences of "a" or "b".         rences of "a" or "b".
2008    
2009         Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a spe-           PCRE_NOTEMPTY_ATSTART
2010         cial case of a pattern match of the empty  string  within  its  split()  
2011         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
2012         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
2013         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.
2014         if that fails by advancing the starting offset (see below)  and  trying  
2015         an ordinary match again. There is some code that demonstrates how to do         Perl     has    no    direct    equivalent    of    PCRE_NOTEMPTY    or
2016         this in the pcredemo.c sample program.         PCRE_NOTEMPTY_ATSTART, but it does make a special  case  of  a  pattern
2017           match  of  the empty string within its split() function, and when using
2018           the /g modifier. It is  possible  to  emulate  Perl's  behaviour  after
2019           matching a null string by first trying the match again at the same off-
2020           set with PCRE_NOTEMPTY_ATSTART and  PCRE_ANCHORED,  and  then  if  that
2021           fails, by advancing the starting offset (see below) and trying an ordi-
2022           nary match again. There is some code that demonstrates how to  do  this
2023           in  the  pcredemo sample program. In the most general case, you have to
2024           check to see if the newline convention recognizes CRLF  as  a  newline,
2025           and  if so, and the current character is CR followed by LF, advance the
2026           starting offset by two characters instead of one.
2027    
2028             PCRE_NO_START_OPTIMIZE
2029    
2030           There are a number of optimizations that pcre_exec() uses at the  start
2031           of  a  match,  in  order to speed up the process. For example, if it is
2032           known that an unanchored match must start with a specific character, it
2033           searches  the  subject  for that character, and fails immediately if it
2034           cannot find it, without actually running the  main  matching  function.
2035           This means that a special item such as (*COMMIT) at the start of a pat-
2036           tern is not considered until after a suitable starting  point  for  the
2037           match  has been found. When callouts or (*MARK) items are in use, these
2038           "start-up" optimizations can cause them to be skipped if the pattern is
2039           never  actually  used.  The start-up optimizations are in effect a pre-
2040           scan of the subject that takes place before the pattern is run.
2041    
2042           The PCRE_NO_START_OPTIMIZE option disables the start-up  optimizations,
2043           possibly  causing  performance  to  suffer,  but ensuring that in cases
2044           where the result is "no match", the callouts do occur, and  that  items
2045           such as (*COMMIT) and (*MARK) are considered at every possible starting
2046           position in the subject string. If  PCRE_NO_START_OPTIMIZE  is  set  at
2047           compile time, it cannot be unset at matching time.
2048    
2049           Setting  PCRE_NO_START_OPTIMIZE  can  change  the outcome of a matching
2050           operation.  Consider the pattern
2051    
2052             (*COMMIT)ABC
2053    
2054           When this is compiled, PCRE records the fact that a  match  must  start
2055           with  the  character  "A".  Suppose the subject string is "DEFABC". The
2056           start-up optimization scans along the subject, finds "A" and  runs  the
2057           first  match attempt from there. The (*COMMIT) item means that the pat-
2058           tern must match the current starting position, which in this  case,  it
2059           does.  However,  if  the  same match is run with PCRE_NO_START_OPTIMIZE
2060           set, the initial scan along the subject string  does  not  happen.  The
2061           first  match  attempt  is  run  starting  from "D" and when this fails,
2062           (*COMMIT) prevents any further matches  being  tried,  so  the  overall
2063           result  is  "no  match". If the pattern is studied, more start-up opti-
2064           mizations may be used. For example, a minimum length  for  the  subject
2065           may be recorded. Consider the pattern
2066    
2067             (*MARK:A)(X|Y)
2068    
2069           The  minimum  length  for  a  match is one character. If the subject is
2070           "ABC", there will be attempts to  match  "ABC",  "BC",  "C",  and  then
2071           finally  an empty string.  If the pattern is studied, the final attempt
2072           does not take place, because PCRE knows that the subject is too  short,
2073           and  so  the  (*MARK) is never encountered.  In this case, studying the
2074           pattern does not affect the overall match result, which  is  still  "no
2075           match", but it does affect the auxiliary information that is returned.
2076    
2077           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2078    
2079         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
2080         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8 string is automatically checked when pcre_exec() is  subsequently
2081         called.  The value of startoffset is also checked  to  ensure  that  it         called.   The  value  of  startoffset is also checked to ensure that it
2082         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
2083         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
2084         startoffset  contains  an  invalid  value, PCRE_ERROR_BADUTF8_OFFSET is         main pcre page. If  an  invalid  UTF-8  sequence  of  bytes  is  found,
2085         returned.         pcre_exec()  returns  the  error  PCRE_ERROR_BADUTF8  or,  if PCRE_PAR-
2086           TIAL_HARD is set and the problem is a truncated UTF-8 character at  the
2087           end  of  the  subject, PCRE_ERROR_SHORTUTF8. In both cases, information
2088           about the precise nature of the error may also  be  returned  (see  the
2089           descriptions  of these errors in the section entitled Error return val-
2090           ues from pcre_exec() below).  If startoffset contains a value that does
2091           not  point to the start of a UTF-8 character (or to the end of the sub-
2092           ject), PCRE_ERROR_BADUTF8_OFFSET is returned.
2093    
2094         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
2095         these    checks    for   performance   reasons,   you   can   set   the         these    checks    for   performance   reasons,   you   can   set   the
# Line 1770  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2097  MATCHING A PATTERN: THE TRADITIONAL FUNC
2097         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
2098         making repeated calls to find all  the  matches  in  a  single  subject         making repeated calls to find all  the  matches  in  a  single  subject
2099         string.  However,  you  should  be  sure  that the value of startoffset         string.  However,  you  should  be  sure  that the value of startoffset
2100         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).
2101         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
2102         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.
2103         acter, is undefined. Your program may crash.         Your program may crash.
2104    
2105           PCRE_PARTIAL           PCRE_PARTIAL_HARD
2106             PCRE_PARTIAL_SOFT
2107         This  option  turns  on  the  partial  matching feature. If the subject  
2108         string fails to match the pattern, but at some point during the  match-         These  options turn on the partial matching feature. For backwards com-
2109         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
2110         partially matches the pattern and the failure to  match  occurred  only         match  occurs if the end of the subject string is reached successfully,
2111         because  there were not enough subject characters), pcre_exec() returns         but there are not enough subject characters to complete the  match.  If
2112         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,
2113         used,  there  are restrictions on what may appear in the pattern. These         matching continues by testing any remaining alternatives.  Only  if  no
2114         are discussed in the pcrepartial documentation.         complete  match  can be found is PCRE_ERROR_PARTIAL returned instead of
2115           PCRE_ERROR_NOMATCH. In other words,  PCRE_PARTIAL_SOFT  says  that  the
2116           caller  is  prepared to handle a partial match, but only if no complete
2117           match can be found.
2118    
2119           If PCRE_PARTIAL_HARD is set, it overrides  PCRE_PARTIAL_SOFT.  In  this
2120           case,  if  a  partial  match  is found, pcre_exec() immediately returns
2121           PCRE_ERROR_PARTIAL, without  considering  any  other  alternatives.  In
2122           other  words, when PCRE_PARTIAL_HARD is set, a partial match is consid-
2123           ered to be more important that an alternative complete match.
2124    
2125           In both cases, the portion of the string that was  inspected  when  the
2126           partial match was found is set as the first matching string. There is a
2127           more detailed discussion of partial and  multi-segment  matching,  with
2128           examples, in the pcrepartial documentation.
2129    
2130     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2131    
2132         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
2133         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.
2134         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,
2135         Unlike  the  pattern string, the subject may contain binary zero bytes.         pcre_exec() returns PCRE_ERROR_BADOFFSET. When the starting  offset  is
2136         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,
2137         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
2138           must  point  to  the start of a UTF-8 character (or the end of the sub-
2139           ject). Unlike the pattern string, the subject may contain  binary  zero
2140           bytes.
2141    
2142         A  non-zero  starting offset is useful when searching for another match         A  non-zero  starting offset is useful when searching for another match
2143         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 1814  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2158  MATCHING A PATTERN: THE TRADITIONAL FUNC
2158         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
2159         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2160    
2161         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
2162           match an empty string. It is possible to emulate Perl's /g behaviour by
2163           first  trying  the  match  again  at  the   same   offset,   with   the
2164           PCRE_NOTEMPTY_ATSTART  and  PCRE_ANCHORED  options,  and  then  if that
2165           fails, advancing the starting  offset  and  trying  an  ordinary  match
2166           again. There is some code that demonstrates how to do this in the pcre-
2167           demo sample program. In the most general case, you have to check to see
2168           if  the newline convention recognizes CRLF as a newline, and if so, and
2169           the current character is CR followed by LF, advance the starting offset
2170           by two characters instead of one.
2171    
2172           If  a  non-zero starting offset is passed when the pattern is anchored,
2173         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
2174         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
2175         subject.         subject.
2176    
2177     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2178    
2179         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
2180         addition, further substrings from the subject  may  be  picked  out  by         addition,  further  substrings  from  the  subject may be picked out by
2181         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,
2182         this is called "capturing" in what follows, and the  phrase  "capturing         this  is  called "capturing" in what follows, and the phrase "capturing
2183         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-
2184         string. PCRE supports several other kinds of  parenthesized  subpattern         string.  PCRE  supports several other kinds of parenthesized subpattern
2185         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2186    
2187         Captured  substrings are returned to the caller via a vector of integer         Captured substrings are returned to the caller via a vector of integers
2188         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-
2189         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:
2190         Note: this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2191    
2192         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-
2193         strings,  each  substring using a pair of integers. The remaining third         strings, each substring using a pair of integers. The  remaining  third
2194         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-
2195         turing  subpatterns, and is not available for passing back information.         turing subpatterns, and is not available for passing back  information.
2196         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
2197         it is not, it is rounded down.         it is not, it is rounded down.
2198    
2199         When  a  match  is successful, information about captured substrings is         When a match is successful, information about  captured  substrings  is
2200         returned in pairs of integers, starting at the  beginning  of  ovector,         returned  in  pairs  of integers, starting at the beginning of ovector,
2201         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
2202         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
2203         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
2204         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
2205         tor[1],  identify  the  portion  of  the  subject string matched by the         byte offsets, even in UTF-8 mode. They are not character counts.
2206         entire pattern. The next pair is used for the first  capturing  subpat-  
2207         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
2208         highest numbered pair that has been set. For example, if two substrings         portion  of  the subject string matched by the entire pattern. The next
2209         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
2210         subpatterns, the return value from a successful match is 1,  indicating         returned by pcre_exec() is one more than the highest numbered pair that
2211         that just the first pair of offsets has been set.         has been set.  For example, if two substrings have been  captured,  the
2212           returned  value is 3. If there are no capturing subpatterns, the return
2213           value from a successful match is 1, indicating that just the first pair
2214           of offsets has been set.
2215    
2216         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2217         of the string that it matched that is returned.         of the string that it matched that is returned.
2218    
2219         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,
2220         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
2221         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
2222         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
2223         as NULL and ovecsize as zero. However, if  the  pattern  contains  back         ovecsize as zero. However, if the pattern contains back references  and
2224         references  and  the  ovector is not big enough to remember the related         the  ovector is not big enough to remember the related substrings, PCRE
2225         substrings, PCRE has to get additional memory for use during  matching.         has to get additional memory for use during matching. Thus it  is  usu-
2226         Thus it is usually advisable to supply an ovector.         ally advisable to supply an ovector.
2227    
2228         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
2229         subpatterns there are in a compiled  pattern.  The  smallest  size  for         subpatterns there are in a compiled  pattern.  The  smallest  size  for
2230         ovector  that  will allow for n captured substrings, in addition to the         ovector  that  will allow for n captured substrings, in addition to the
2231         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 1883  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2241  MATCHING A PATTERN: THE TRADITIONAL FUNC
2241         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
2242         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
2243         matched. The return from the function is 2, because  the  highest  used         matched. The return from the function is 2, because  the  highest  used
2244         capturing subpattern number is 1. However, you can refer to the offsets         capturing  subpattern  number  is 1, and the offsets for for the second
2245         for the second and third capturing subpatterns if  you  wish  (assuming         and third capturing subpatterns (assuming the vector is  large  enough,
2246         the vector is large enough, of course).         of course) are set to -1.
2247    
2248           Note: Elements of ovector that do not correspond to capturing parenthe-
2249           ses in the pattern are never changed. That is, if a pattern contains  n
2250           capturing parentheses, no more than ovector[0] to ovector[2n+1] are set
2251           by pcre_exec(). The other elements retain whatever values  they  previ-
2252           ously had.
2253    
2254         Some  convenience  functions  are  provided for extracting the captured         Some  convenience  functions  are  provided for extracting the captured
2255         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
# Line 1930  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2294  MATCHING A PATTERN: THE TRADITIONAL FUNC
2294         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
2295         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2296    
2297           This error is also given if pcre_stack_malloc() fails  in  pcre_exec().
2298           This  can happen only when PCRE has been compiled with --disable-stack-
2299           for-recursion.
2300    
2301           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2302    
2303         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 1951  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2319  MATCHING A PATTERN: THE TRADITIONAL FUNC
2319           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2320    
2321         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
2322         subject.         subject,  and the PCRE_NO_UTF8_CHECK option was not set. If the size of
2323           the output vector (ovecsize) is at least 2,  the  byte  offset  to  the
2324           start  of  the  the invalid UTF-8 character is placed in the first ele-
2325           ment, and a reason code is placed in the  second  element.  The  reason
2326           codes are listed in the following section.  For backward compatibility,
2327           if PCRE_PARTIAL_HARD is set and the problem is a truncated UTF-8  char-
2328           acter   at   the   end   of   the   subject  (reason  codes  1  to  5),
2329           PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8.
2330    
2331           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2332    
2333         The UTF-8 byte sequence that was passed as a subject was valid, but the         The UTF-8 byte sequence that was passed as a subject  was  checked  and
2334           found  to be valid (the PCRE_NO_UTF8_CHECK option was not set), but the
2335         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-
2336         ter.         ter or the end of the subject.
2337    
2338           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2339    
# Line 1966  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2342  MATCHING A PATTERN: THE TRADITIONAL FUNC
2342    
2343           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2344    
2345         The PCRE_PARTIAL option was used with  a  compiled  pattern  containing         This code is no longer in  use.  It  was  formerly  returned  when  the
2346         items  that are not supported for partial matching. See the pcrepartial         PCRE_PARTIAL  option  was used with a compiled pattern containing items
2347         documentation for details of partial matching.         that were  not  supported  for  partial  matching.  From  release  8.00
2348           onwards, there are no restrictions on partial matching.
2349    
2350           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2351    
2352         An unexpected internal error has occurred. This error could  be  caused         An  unexpected  internal error has occurred. This error could be caused
2353         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2354    
2355           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
2356    
2357         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.
2358    
2359           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2360    
# Line 1985  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2362  MATCHING A PATTERN: THE TRADITIONAL FUNC
2362         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field  in  a  pcre_extra  structure (or defaulted) was reached. See the
2363         description above.         description above.
2364    
          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.  
   
2365           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
2366    
2367         An invalid combination of PCRE_NEWLINE_xxx options was given.         An invalid combination of PCRE_NEWLINE_xxx options was given.
2368    
2369         Error numbers -16 to -20 are not used by pcre_exec().           PCRE_ERROR_BADOFFSET      (-24)
2370    
2371           The value of startoffset was negative or greater than the length of the
2372           subject, that is, the value in length.
2373    
2374             PCRE_ERROR_SHORTUTF8      (-25)
2375    
2376           This  error  is returned instead of PCRE_ERROR_BADUTF8 when the subject
2377           string ends with a truncated UTF-8 character and the  PCRE_PARTIAL_HARD
2378           option  is  set.   Information  about  the  failure  is returned as for
2379           PCRE_ERROR_BADUTF8. It is in fact sufficient to detect this  case,  but
2380           this  special error code for PCRE_PARTIAL_HARD precedes the implementa-
2381           tion of returned information; it is retained for backwards  compatibil-
2382           ity.
2383    
2384             PCRE_ERROR_RECURSELOOP    (-26)
2385    
2386           This error is returned when pcre_exec() detects a recursion loop within
2387           the pattern. Specifically, it means that either the whole pattern or  a
2388           subpattern  has been called recursively for the second time at the same
2389           position in the subject string. Some simple patterns that might do this
2390           are  detected  and faulted at compile time, but more complicated cases,
2391           in particular mutual recursions between two different subpatterns, can-
2392           not be detected until run time.
2393    
2394           Error numbers -16 to -20 and -22 are not used by pcre_exec().
2395    
2396       Reason codes for invalid UTF-8 strings
2397    
2398           When pcre_exec() returns either PCRE_ERROR_BADUTF8 or PCRE_ERROR_SHORT-
2399           UTF8, and the size of the output vector (ovecsize) is at least  2,  the
2400           offset  of  the  start  of the invalid UTF-8 character is placed in the
2401           first output vector element (ovector[0]) and a reason code is placed in
2402           the  second  element  (ovector[1]). The reason codes are given names in
2403           the pcre.h header file:
2404    
2405             PCRE_UTF8_ERR1
2406             PCRE_UTF8_ERR2
2407             PCRE_UTF8_ERR3
2408             PCRE_UTF8_ERR4
2409             PCRE_UTF8_ERR5
2410    
2411           The string ends with a truncated UTF-8 character;  the  code  specifies
2412           how  many bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8
2413           characters to be no longer than 4 bytes, the  encoding  scheme  (origi-
2414           nally  defined  by  RFC  2279)  allows  for  up to 6 bytes, and this is
2415           checked first; hence the possibility of 4 or 5 missing bytes.
2416    
2417             PCRE_UTF8_ERR6
2418             PCRE_UTF8_ERR7
2419             PCRE_UTF8_ERR8
2420             PCRE_UTF8_ERR9
2421             PCRE_UTF8_ERR10
2422    
2423           The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of
2424           the  character  do  not have the binary value 0b10 (that is, either the
2425           most significant bit is 0, or the next bit is 1).
2426    
2427             PCRE_UTF8_ERR11
2428             PCRE_UTF8_ERR12
2429    
2430           A character that is valid by the RFC 2279 rules is either 5 or 6  bytes
2431           long; these code points are excluded by RFC 3629.
2432    
2433             PCRE_UTF8_ERR13
2434    
2435           A  4-byte character has a value greater than 0x10fff; these code points
2436           are excluded by RFC 3629.
2437    
2438             PCRE_UTF8_ERR14
2439    
2440           A 3-byte character has a value in the  range  0xd800  to  0xdfff;  this
2441           range  of code points are reserved by RFC 3629 for use with UTF-16, and
2442           so are excluded from UTF-8.
2443    
2444             PCRE_UTF8_ERR15
2445             PCRE_UTF8_ERR16
2446             PCRE_UTF8_ERR17
2447             PCRE_UTF8_ERR18
2448             PCRE_UTF8_ERR19
2449    
2450           A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it  codes
2451           for  a  value that can be represented by fewer bytes, which is invalid.
2452           For example, the two bytes 0xc0, 0xae give the value 0x2e,  whose  cor-
2453           rect coding uses just one byte.
2454    
2455             PCRE_UTF8_ERR20
2456    
2457           The two most significant bits of the first byte of a character have the
2458           binary value 0b10 (that is, the most significant bit is 1 and the  sec-
2459           ond  is  0). Such a byte can only validly occur as the second or subse-
2460           quent byte of a multi-byte character.
2461    
2462             PCRE_UTF8_ERR21
2463    
2464           The first byte of a character has the value 0xfe or 0xff. These  values
2465           can never occur in a valid UTF-8 string.
2466    
2467    
2468  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
# Line 2013  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2478  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2478         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2479              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2480    
2481         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
2482         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
2483         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2484         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
2485         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
2486         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
2487         substrings.         substrings.
2488    
2489         A substring that contains a binary zero is correctly extracted and  has         A  substring that contains a binary zero is correctly extracted and has
2490         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
2491         string.  However, you can process such a string  by  referring  to  the         string.   However,  you  can  process such a string by referring to the
2492         length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2493         string().  Unfortunately, the interface to pcre_get_substring_list() is         string().  Unfortunately, the interface to pcre_get_substring_list() is
2494         not  adequate for handling strings containing binary zeros, because the         not adequate for handling strings containing binary zeros, because  the
2495         end of the final string is not independently indicated.         end of the final string is not independently indicated.
2496    
2497         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-
2498         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
2499         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
2500         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2501         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
2502         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2503         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
2504         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
2505         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2506    
2507         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
2508         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
2509         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
2510         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
2511         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
2512         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2513         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2514         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
2515         the terminating zero, or one of these error codes:         the terminating zero, or one of these error codes:
2516    
2517           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2518    
2519         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
2520         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2521    
2522           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2523    
2524         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2525    
2526         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
2527         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
2528         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
2529         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
2530         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
2531         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
2532         error code         error code
2533    
2534           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2535    
2536         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2537    
2538         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
2539         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
2540         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
2541         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2542         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
2543         tive for unset substrings.         tive for unset substrings.
2544    
2545         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2546         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
2547         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2548         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
2549         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.
2550         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-
2551         cial  interface  to  another  programming  language  that  cannot   use         cial   interface  to  another  programming  language  that  cannot  use
2552         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-
2553         vided.         vided.
2554    
2555    
# Line 2103  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2568  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2568              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2569              const char **stringptr);              const char **stringptr);
2570    
2571         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-
2572         ber.  For example, for this pattern         ber.  For example, for this pattern
2573    
2574           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
# Line 2112  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2577  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2577         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
2578         name by calling pcre_get_stringnumber(). The first argument is the com-         name by calling pcre_get_stringnumber(). The first argument is the com-
2579         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
2580         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2581         subpattern of that name.         subpattern of that name.
2582    
2583         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
2584         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
2585         are also two functions that do the whole job.         are also two functions that do the whole job.
2586    
2587         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
2588         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
2589         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
2590         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
2591         differences:         differences:
2592    
2593         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
2594         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
2595         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
2596         name-to-number translation table.         name-to-number translation table.
2597    
2598         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2599         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2600         ate.         ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
2601           behaviour may not be what you want (see the next section).
2602    
2603           Warning: If the pattern uses the (?| feature to set up multiple subpat-
2604           terns with the same number, as described in the  section  on  duplicate
2605           subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2606           distinguish the different subpatterns, because names are  not  included
2607           in  the compiled code. The matching process uses only numbers. For this
2608           reason, the use of different names for subpatterns of the  same  number
2609           causes an error at compile time.
2610    
2611    
2612  DUPLICATE SUBPATTERN NAMES  DUPLICATE SUBPATTERN NAMES
# Line 2141  DUPLICATE SUBPATTERN NAMES Line 2615  DUPLICATE SUBPATTERN NAMES
2615              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2616    
2617         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2618         subpatterns are not required to  be  unique.  Normally,  patterns  with         subpatterns are not required to be unique. (Duplicate names are  always
2619         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 (?|
2620         subpatterns participates. An example is shown in the pcrepattern  docu-         feature. Indeed, if such subpatterns are named, they  are  required  to
2621         mentation. When duplicates are present, pcre_copy_named_substring() and         use the same names.)
2622    
2623           Normally, patterns with duplicate names are such that in any one match,
2624           only one of the named subpatterns participates. An example is shown  in
2625           the pcrepattern documentation.
2626    
2627           When    duplicates   are   present,   pcre_copy_named_substring()   and
2628         pcre_get_named_substring() return the first substring corresponding  to         pcre_get_named_substring() return the first substring corresponding  to
2629         the  given  name  that  is  set.  If  none  are set, an empty string is         the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2630         returned.  The pcre_get_stringnumber() function returns one of the num-         (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2631         bers  that are associated with the name, but it is not defined which it         function  returns one of the numbers that are associated with the name,
2632         is.         but it is not defined which it is.
2633    
2634         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
2635         name,  you  must  use  the pcre_get_stringtable_entries() function. The         name,  you  must  use  the pcre_get_stringtable_entries() function. The
# Line 2159  DUPLICATE SUBPATTERN NAMES Line 2639  DUPLICATE SUBPATTERN NAMES
2639         the  name-to-number  table  for  the  given  name.  The function itself         the  name-to-number  table  for  the  given  name.  The function itself
2640         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2641         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-
2642         tion entitled Information about a  pattern.   Given  all  the  relevant         tion entitled Information about a pattern above.  Given all  the  rele-
2643         entries  for the name, you can extract each of their numbers, and hence         vant  entries  for the name, you can extract each of their numbers, and
2644         the captured data, if any.         hence the captured data, if any.
2645    
2646    
2647  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
# Line 2195  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2675  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2675         characteristics to the normal algorithm, and  is  not  compatible  with         characteristics to the normal algorithm, and  is  not  compatible  with
2676         Perl.  Some  of the features of PCRE patterns are not supported. Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2677         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
2678         a discussion of the two matching algorithms, see the pcrematching docu-         a  discussion  of  the  two matching algorithms, and a list of features
2679         mentation.         that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2680           tion.
2681    
2682         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
2683         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-
2684         ent way, and this is described below. The other  common  arguments  are         ent  way,  and  this is described below. The other common arguments are
2685         used  in  the  same way as for pcre_exec(), so their description is not         used in the same way as for pcre_exec(), so their  description  is  not
2686         repeated here.         repeated here.
2687    
2688         The two additional arguments provide workspace for  the  function.  The         The  two  additional  arguments provide workspace for the function. The
2689         workspace  vector  should  contain at least 20 elements. It is used for         workspace vector should contain at least 20 elements. It  is  used  for
2690         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2691         workspace  will  be  needed for patterns and subjects where there are a         workspace will be needed for patterns and subjects where  there  are  a
2692         lot of potential matches.         lot of potential matches.
2693    
2694         Here is an example of a simple call to pcre_dfa_exec():         Here is an example of a simple call to pcre_dfa_exec():
# Line 2229  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2710  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2710    
2711     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2712    
2713         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
2714         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-
2715         LINE_xxx, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY,  PCRE_NO_UTF8_CHECK,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2716         PCRE_PARTIAL, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All but the last         PCRE_NOTEMPTY_ATSTART,      PCRE_NO_UTF8_CHECK,       PCRE_BSR_ANYCRLF,
2717         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-
2718         not repeated here.         TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.  All but  the  last
2719           four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
2720           PCRE_PARTIAL         description is not repeated here.
2721    
2722         This  has  the  same general effect as it does for pcre_exec(), but the           PCRE_PARTIAL_HARD
2723         details  are  slightly  different.  When  PCRE_PARTIAL   is   set   for           PCRE_PARTIAL_SOFT
2724         pcre_dfa_exec(),  the  return code PCRE_ERROR_NOMATCH is converted into  
2725         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
2726         been no complete matches, but there is still at least one matching pos-         details  are  slightly  different.  When  PCRE_PARTIAL_HARD  is set for
2727         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-
2728         set as the first matching string.         ject  is  reached  and there is still at least one matching possibility
2729           that requires additional characters. This happens even if some complete
2730           matches have also been found. When PCRE_PARTIAL_SOFT is set, the return
2731           code PCRE_ERROR_NOMATCH is converted into PCRE_ERROR_PARTIAL if the end
2732           of  the  subject  is  reached, there have been no complete matches, but
2733           there is still at least one matching possibility. The  portion  of  the
2734           string  that  was inspected when the longest partial match was found is
2735           set as the first matching string  in  both  cases.   There  is  a  more
2736           detailed  discussion  of partial and multi-segment matching, with exam-
2737           ples, in the pcrepartial documentation.
2738    
2739           PCRE_DFA_SHORTEST           PCRE_DFA_SHORTEST
2740    
2741         Setting  the  PCRE_DFA_SHORTEST option causes the matching algorithm to         Setting the PCRE_DFA_SHORTEST option causes the matching  algorithm  to
2742         stop as soon as it has found one match. Because of the way the alterna-         stop as soon as it has found one match. Because of the way the alterna-
2743         tive  algorithm  works, this is necessarily the shortest possible match         tive algorithm works, this is necessarily the shortest  possible  match
2744         at the first possible matching point in the subject string.         at the first possible matching point in the subject string.
2745    
2746           PCRE_DFA_RESTART           PCRE_DFA_RESTART
2747    
2748         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
2749         returns  a  partial  match, it is possible to call it again, with addi-         again, with additional subject characters, and have  it  continue  with
2750         tional subject characters, and have it continue with  the  same  match.         the  same match. The PCRE_DFA_RESTART option requests this action; when
2751         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
2752         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
2753         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
2754         match. There is more discussion of this  facility  in  the  pcrepartial         pcrepartial documentation.
        documentation.  
2755    
2756     Successful returns from pcre_dfa_exec()     Successful returns from pcre_dfa_exec()
2757    
# Line 2339  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2828  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2828  SEE ALSO  SEE ALSO
2829    
2830         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-         pcrebuild(3), pcrecallout(3), pcrecpp(3)(3), pcrematching(3),  pcrepar-
2831         tial(3),  pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).         tial(3), pcreposix(3), pcreprecompile(3), pcresample(3), pcrestack(3).
2832    
2833    
2834  AUTHOR  AUTHOR
# Line 2351  AUTHOR Line 2840  AUTHOR
2840    
2841  REVISION  REVISION
2842    
2843         Last updated: 06 March 2007         Last updated: 13 August 2011
2844         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
2845  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2846    
2847    
2848  PCRECALLOUT(3)                                                  PCRECALLOUT(3)  PCRECALLOUT(3)                                                  PCRECALLOUT(3)
2849    
2850    
# Line 2379  PCRE CALLOUTS Line 2868  PCRE CALLOUTS
2868         default value is zero.  For  example,  this  pattern  has  two  callout         default value is zero.  For  example,  this  pattern  has  two  callout
2869         points:         points:
2870    
2871           (?C1)eabc(?C2)def           (?C1)abc(?C2)def
2872    
2873         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
2874         called, PCRE automatically  inserts  callouts,  all  with  number  255,         pcre_compile2() is called, PCRE  automatically  inserts  callouts,  all
2875         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
2876         used with the pattern         PCRE_AUTO_CALLOUT is used with the pattern
2877    
2878           A(\d{2}|--)           A(\d{2}|--)
2879    
# Line 2403  PCRE CALLOUTS Line 2892  PCRE CALLOUTS
2892  MISSING CALLOUTS  MISSING CALLOUTS
2893    
2894         You  should  be  aware  that,  because of optimizations in the way PCRE         You  should  be  aware  that,  because of optimizations in the way PCRE
2895         matches patterns, callouts sometimes do not happen. For example, if the         matches patterns by default, callouts  sometimes  do  not  happen.  For
2896         pattern is         example, if the pattern is
2897    
2898           ab(?C4)cd           ab(?C4)cd
2899    
# Line 2413  MISSING CALLOUTS Line 2902  MISSING CALLOUTS
2902         ever  start,  and  the  callout is never reached. However, with "abyd",         ever  start,  and  the  callout is never reached. However, with "abyd",
2903         though the result is still no match, the callout is obeyed.         though the result is still no match, the callout is obeyed.
2904    
2905           If the pattern is studied, PCRE knows the minimum length of a  matching
2906           string,  and will immediately give a "no match" return without actually
2907           running a match if the subject is not long enough, or,  for  unanchored
2908           patterns, if it has been scanned far enough.
2909    
2910           You  can disable these optimizations by passing the PCRE_NO_START_OPTI-
2911           MIZE option to pcre_compile(), pcre_exec(), or pcre_dfa_exec(),  or  by
2912           starting the pattern with (*NO_START_OPT). This slows down the matching
2913           process, but does ensure that callouts such as the  example  above  are
2914           obeyed.
2915    
2916    
2917  THE CALLOUT INTERFACE  THE CALLOUT INTERFACE
2918    
2919         During matching, when PCRE reaches a callout point, the external  func-         During  matching, when PCRE reaches a callout point, the external func-
2920         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
2921         both the pcre_exec() and the pcre_dfa_exec()  matching  functions.  The         both  the  pcre_exec()  and the pcre_dfa_exec() matching functions. The
2922         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
2923         block. This structure contains the following fields:         block. This structure contains the following fields:
2924    
2925           int          version;           int         version;
2926           int          callout_number;           int         callout_number;
2927           int         *offset_vector;           int        *offset_vector;
2928           const char  *subject;           const char *subject;
2929           int          subject_length;           int         subject_length;
2930           int          start_match;           int         start_match;
2931           int          current_position;           int         current_position;
2932           int          capture_top;           int         capture_top;
2933           int          capture_last;           int         capture_last;
2934           void        *callout_data;           void       *callout_data;
2935           int          pattern_position;           int         pattern_position;
2936           int          next_item_length;           int         next_item_length;
2937             const unsigned char *mark;
2938         The version field is an integer containing the version  number  of  the  
2939         block  format. The initial version was 0; the current version is 1. The         The  version  field  is an integer containing the version number of the
2940         version number will change again in future  if  additional  fields  are         block format. The initial version was 0; the current version is 2.  The
2941           version  number  will  change  again in future if additional fields are
2942         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.
2943    
2944         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 2454  THE CALLOUT INTERFACE Line 2955  THE CALLOUT INTERFACE
2955         The subject and subject_length fields contain copies of the values that         The subject and subject_length fields contain copies of the values that
2956         were passed to pcre_exec().         were passed to pcre_exec().
2957    
2958         The start_match field contains the offset within the subject  at  which         The start_match field normally contains the offset within  the  subject
2959         the  current match attempt started. If the pattern is not anchored, the         at  which  the  current  match  attempt started. However, if the escape
2960         callout function may be called several times from the same point in the         sequence \K has been encountered, this value is changed to reflect  the
2961         pattern for different starting points in the subject.         modified  starting  point.  If the pattern is not anchored, the callout
2962           function may be called several times from the same point in the pattern
2963           for different starting points in the subject.
2964    
2965         The  current_position  field  contains the offset within the subject of         The  current_position  field  contains the offset within the subject of
2966         the current match pointer.         the current match pointer.
# Line 2494  THE CALLOUT INTERFACE Line 2997  THE CALLOUT INTERFACE
2997         in  distinguishing between different automatic callouts, which all have         in  distinguishing between different automatic callouts, which all have
2998         the same callout number. However, they are set for all callouts.         the same callout number. However, they are set for all callouts.
2999    
3000           The mark field is present from version 2 of the pcre_callout structure.
3001           In  callouts  from pcre_exec() it contains a pointer to the zero-termi-
3002           nated name of the most recently passed (*MARK) item in  the  match,  or
3003           NULL if there are no (*MARK)s in the current matching path. In callouts
3004           from pcre_dfa_exec() this field always contains NULL.
3005    
3006    
3007  RETURN VALUES  RETURN VALUES
3008    
# Line 2502  RETURN VALUES Line 3011  RETURN VALUES
3011         zero, matching fails at the current point, but  the  testing  of  other         zero, matching fails at the current point, but  the  testing  of  other
3012         matching possibilities goes ahead, just as if a lookahead assertion had         matching possibilities goes ahead, just as if a lookahead assertion had
3013         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
3014         pcre_exec() (or pcre_dfa_exec()) returns the negative value.         pcre_exec() or pcre_dfa_exec() returns the negative value.
3015    
3016         Negative   values   should   normally   be   chosen  from  the  set  of         Negative   values   should   normally   be   chosen  from  the  set  of
3017         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 2520  AUTHOR Line 3029  AUTHOR
3029    
3030  REVISION  REVISION
3031    
3032         Last updated: 06 March 2007         Last updated: 31 July 2011
3033         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3034  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3035    
3036    
3037  PCRECOMPAT(3)                                                    PCRECOMPAT(3)  PCRECOMPAT(3)                                                    PCRECOMPAT(3)
3038    
3039    
# Line 2535  NAME Line 3044  NAME
3044  DIFFERENCES BETWEEN PCRE AND PERL  DIFFERENCES BETWEEN PCRE AND PERL
3045    
3046         This  document describes the differences in the ways that PCRE and Perl         This  document describes the differences in the ways that PCRE and Perl
3047         handle regular expressions. The differences described here  are  mainly         handle regular expressions. The differences  described  here  are  with
3048         with  respect  to  Perl 5.8, though PCRE version 7.0 contains some fea-         respect to Perl versions 5.10 and above.
3049         tures that are expected to be in the forthcoming Perl 5.10.  
3050           1.  PCRE has only a subset of Perl's UTF-8 and Unicode support. Details
3051         1. PCRE has only a subset of Perl's UTF-8 and Unicode support.  Details         of what it does have are given in the pcreunicode page.
3052         of  what  it does have are given in the section on UTF-8 support in the  
3053         main pcre page.         2. PCRE allows repeat quantifiers only on parenthesized assertions, but
3054           they  do  not mean what you might think. For example, (?!a){3} does not
3055         2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl         assert that the next three characters are not "a". It just asserts that
3056         permits  them,  but they do not mean what you might think. For example,         the next character is not "a" three times (in principle: PCRE optimizes
3057         (?!a){3} does not assert that the next three characters are not "a". It         this to run the assertion just once). Perl allows repeat quantifiers on
3058         just asserts that the next character is not "a" three times.         other assertions such as \b, but these do not seem to have any use.
3059    
3060         3.  Capturing  subpatterns  that occur inside negative lookahead asser-         3.  Capturing  subpatterns  that occur inside negative lookahead asser-
3061         tions are counted, but their entries in the offsets  vector  are  never         tions are counted, but their entries in the offsets  vector  are  never
# Line 2561  DIFFERENCES BETWEEN PCRE AND PERL Line 3070  DIFFERENCES BETWEEN PCRE AND PERL
3070         the pattern to represent a binary zero.         the pattern to represent a binary zero.
3071    
3072         5.  The  following Perl escape sequences are not supported: \l, \u, \L,         5.  The  following Perl escape sequences are not supported: \l, \u, \L,
3073         \U, and \N. In fact these are implemented by Perl's general string-han-         \U, and \N when followed by a character name or Unicode value.  (\N  on
3074         dling  and are not part of its pattern matching engine. If any of these         its own, matching a non-newline character, is supported.) In fact these
3075         are encountered by PCRE, an error is generated.         are implemented by Perl's general string-handling and are not  part  of
3076           its  pattern  matching engine. If any of these are encountered by PCRE,
3077           an error is generated.
3078    
3079         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
3080         is  built  with Unicode character property support. The properties that         is  built  with Unicode character property support. The properties that
3081         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-
3082         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
3083         derived properties Any and L&.         derived properties Any and L&. PCRE does  support  the  Cs  (surrogate)
3084           property,  which  Perl  does  not; the Perl documentation says "Because
3085         7. PCRE does support the \Q...\E escape for quoting substrings. Charac-         Perl hides the need for the user to understand the internal representa-
3086         ters  in  between  are  treated as literals. This is slightly different         tion  of Unicode characters, there is no need to implement the somewhat
3087         from Perl in that $ and @ are  also  handled  as  literals  inside  the         messy concept of surrogates."
3088         quotes.  In Perl, they cause variable interpolation (but of course PCRE  
3089           7. PCRE implements a simpler version of \X than Perl, which changed  to
3090           make  \X  match what Unicode calls an "extended grapheme cluster". This
3091           is more complicated than an extended Unicode sequence,  which  is  what
3092           PCRE matches.
3093    
3094           8. PCRE does support the \Q...\E escape for quoting substrings. Charac-
3095           ters in between are treated as literals.  This  is  slightly  different
3096           from  Perl  in  that  $  and  @ are also handled as literals inside the
3097           quotes. In Perl, they cause variable interpolation (but of course  PCRE
3098         does not have variables). Note the following examples:         does not have variables). Note the following examples:
3099    
3100             Pattern            PCRE matches      Perl matches             Pattern            PCRE matches      Perl matches
# Line 2584  DIFFERENCES BETWEEN PCRE AND PERL Line 3104  DIFFERENCES BETWEEN PCRE AND PERL
3104             \Qabc\$xyz\E       abc\$xyz          abc\$xyz             \Qabc\$xyz\E       abc\$xyz          abc\$xyz
3105             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz             \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
3106    
3107         The \Q...\E sequence is recognized both inside  and  outside  character         The  \Q...\E  sequence  is recognized both inside and outside character
3108         classes.         classes.
3109    
3110         8. Fairly obviously, PCRE does not support the (?{code}) and (??{code})         9. Fairly obviously, PCRE does not support the (?{code}) and (??{code})
3111         constructions. However, there is support for recursive  patterns.  This         constructions.  However,  there is support for recursive patterns. This
3112         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
3113         "callout" feature allows an external function to be called during  pat-         "callout"  feature allows an external function to be called during pat-
3114         tern matching. See the pcrecallout documentation for details.         tern matching. See the pcrecallout documentation for details.
3115    
3116         9.  Subpatterns  that  are  called  recursively or as "subroutines" are         10. Subpatterns that are called recursively  or  as  "subroutines"  are
3117         always treated as atomic groups in  PCRE.  This  is  like  Python,  but         always  treated  as  atomic  groups  in  PCRE. This is like Python, but
3118         unlike Perl.         unlike Perl. There is a discussion of an example that explains this  in
3119           more  detail  in  the section on recursion differences from Perl in the
3120         10.  There are some differences that are concerned with the settings of         pcrepattern page.
3121         captured strings when part of  a  pattern  is  repeated.  For  example,  
3122         matching  "aba"  against  the  pattern  /^(a(b)?)+$/  in Perl leaves $2         11. There are some differences that are concerned with the settings  of
3123           captured  strings  when  part  of  a  pattern is repeated. For example,
3124           matching "aba" against the  pattern  /^(a(b)?)+$/  in  Perl  leaves  $2
3125         unset, but in PCRE it is set to "b".         unset, but in PCRE it is set to "b".
3126    
3127         11. PCRE provides some extensions to the Perl regular expression facil-         12.  PCRE's handling of duplicate subpattern numbers and duplicate sub-
3128         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
3129         versions, some of which (such as named parentheses) have been  in  PCRE         fact the PCRE works internally just with numbers, using an external ta-
3130         for some time. This list is with respect to Perl 5.10:         ble to translate between numbers and names. In  particular,  a  pattern
3131           such  as  (?|(?<a>A)|(?<b)B),  where the two capturing parentheses have
3132         (a)  Although  lookbehind  assertions  must match fixed length strings,         the same number but different names, is not supported,  and  causes  an
3133         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
3134         length of string. Perl requires them all to have the same length.         distinguish which parentheses matched, because both names map  to  cap-
3135           turing subpattern number 1. To avoid this confusing situation, an error
3136           is given at compile time.
3137    
3138           13. Perl recognizes comments in some places that  PCRE  does  not,  for
3139           example,  between  the  ( and ? at the start of a subpattern. If the /x
3140           modifier is set, Perl allows whitespace between ( and ? but PCRE  never
3141           does, even if the PCRE_EXTENDED option is set.
3142    
3143           14. PCRE provides some extensions to the Perl regular expression facil-
3144           ities.  Perl 5.10 includes new features that are not  in  earlier  ver-
3145           sions  of  Perl, some of which (such as named parentheses) have been in
3146           PCRE for some time. This list is with respect to Perl 5.10:
3147    
3148           (a) Although lookbehind assertions in  PCRE  must  match  fixed  length
3149           strings,  each alternative branch of a lookbehind assertion can match a
3150           different length of string. Perl requires them all  to  have  the  same
3151           length.
3152    
3153         (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 $
3154         meta-character matches only at the very end of the string.         meta-character matches only at the very end of the string.
3155    
3156         (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-
3157         cial  meaning  is  faulted.  Otherwise,  like  Perl,  the  backslash is         cial meaning is faulted. Otherwise, like Perl, the backslash is quietly
3158         ignored. (Perl can be made to issue a warning.)         ignored.  (Perl can be made to issue a warning.)
3159    
3160         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-         (d) If PCRE_UNGREEDY is set, the greediness of the  repetition  quanti-
3161         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 2625  DIFFERENCES BETWEEN PCRE AND PERL Line 3164  DIFFERENCES BETWEEN PCRE AND PERL
3164         (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
3165         tried only at the first matching position in the subject string.         tried only at the first matching position in the subject string.
3166    
3167         (f)  The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, and PCRE_NO_AUTO_CAP-         (f) The PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART,
3168         TURE options for pcre_exec() have no Perl equivalents.         and PCRE_NO_AUTO_CAPTURE options for pcre_exec() have no  Perl  equiva-
3169           lents.
3170    
3171         (g) The callout facility is PCRE-specific.         (g)  The  \R escape sequence can be restricted to match only CR, LF, or
3172           CRLF by the PCRE_BSR_ANYCRLF option.
3173    
3174         (h) The partial matching facility is PCRE-specific.         (h) The callout facility is PCRE-specific.
3175    
3176         (i) Patterns compiled by PCRE can be saved and re-used at a later time,         (i) The partial matching facility is PCRE-specific.
3177    
3178           (j) Patterns compiled by PCRE can be saved and re-used at a later time,
3179         even on different hosts that have the other endianness.         even on different hosts that have the other endianness.
3180    
3181         (j)  The  alternative  matching function (pcre_dfa_exec()) matches in a         (k)  The  alternative  matching function (pcre_dfa_exec()) matches in a
3182         different way and is not Perl-compatible.         different way and is not Perl-compatible.
3183    
3184           (l) PCRE recognizes some special sequences such as (*CR) at  the  start
3185           of a pattern that set overall options that cannot be changed within the
3186           pattern.
3187    
3188    
3189  AUTHOR  AUTHOR
3190    
# Line 2648  AUTHOR Line 3195  AUTHOR
3195    
3196  REVISION  REVISION
3197    
3198         Last updated: 06 March 2007         Last updated: 24 August 2011
3199         Copyright (c) 1997-2007 University of Cambridge.         Copyright (c) 1997-2011 University of Cambridge.
3200  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
3201    
3202    
3203  PCREPATTERN(3)                                                  PCREPATTERN(3)  PCREPATTERN(3)                                                  PCREPATTERN(3)
3204    
3205    
# Line 2662  NAME Line 3209  NAME
3209    
3210  PCRE REGULAR EXPRESSION DETAILS  PCRE REGULAR EXPRESSION DETAILS
3211    
3212         The  syntax  and semantics of the regular expressions supported by PCRE         The  syntax and semantics of the regular expressions that are supported
3213         are described below. Regular expressions are also described in the Perl         by PCRE are described in detail below. There is a quick-reference  syn-
3214         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
3215         examples.  Jeffrey Friedl's "Mastering Regular Expressions",  published         semantics as closely as it can. PCRE  also  supports  some  alternative
3216         by  O'Reilly, covers regular expressions in great detail. This descrip-         regular  expression  syntax (which does not conflict with the Perl syn-
3217         tion of PCRE's regular expressions is intended as reference material.         tax) in order to provide some compatibility with regular expressions in
3218           Python, .NET, and Oniguruma.
3219    
3220           Perl's  regular expressions are described in its own documentation, and
3221           regular expressions in general are covered in a number of  books,  some
3222           of  which  have  copious  examples. Jeffrey Friedl's "Mastering Regular
3223           Expressions", published by  O'Reilly,  covers  regular  expressions  in
3224           great  detail.  This  description  of  PCRE's  regular  expressions  is
3225           intended as reference material.
3226    
3227         The original operation of PCRE was on strings of  one-byte  characters.         The original operation of PCRE was on strings of  one-byte  characters.
3228         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
3229         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
3230         pcre_compile()  with  the  PCRE_UTF8  option.  How this affects pattern         pcre_compile()  or  pcre_compile2() with the PCRE_UTF8 option. There is
3231         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:
3232         of  UTF-8  features  in  the  section on UTF-8 support in the main pcre  
3233             (*UTF8)
3234    
3235           Starting a pattern with this sequence  is  equivalent  to  setting  the
3236           PCRE_UTF8  option.  This  feature  is  not Perl-compatible. How setting
3237           UTF-8 mode affects pattern matching  is  mentioned  in  several  places
3238           below.  There  is  also  a summary of UTF-8 features in the pcreunicode
3239         page.         page.
3240    
3241         The remainder of this document discusses the  patterns  that  are  sup-         Another special sequence that may appear at the start of a  pattern  or
3242         ported  by  PCRE when its main matching function, pcre_exec(), is used.         in combination with (*UTF8) is:
3243         From  release  6.0,   PCRE   offers   a   second   matching   function,  
3244         pcre_dfa_exec(),  which matches using a different algorithm that is not           (*UCP)
3245         Perl-compatible. The advantages and disadvantages  of  the  alternative  
3246         function, and how it differs from the normal function, are discussed in         This  has  the  same  effect  as setting the PCRE_UCP option: it causes
3247         the pcrematching page.         sequences such as \d and \w to  use  Unicode  properties  to  determine
3248           character types, instead of recognizing only characters with codes less
3249           than 128 via a lookup table.
3250    
3251           If a pattern starts with (*NO_START_OPT), it has  the  same  effect  as
3252           setting the PCRE_NO_START_OPTIMIZE option either at compile or matching
3253           time. There are also some more of these special sequences that are con-
3254           cerned with the handling of newlines; they are described below.
3255    
3256           The  remainder  of  this  document discusses the patterns that are sup-
3257           ported by PCRE when its main matching function, pcre_exec(),  is  used.
3258           From   release   6.0,   PCRE   offers   a   second  matching  function,
3259           pcre_dfa_exec(), which matches using a different algorithm that is  not
3260           Perl-compatible. Some of the features discussed below are not available
3261           when pcre_dfa_exec() is used. The advantages and disadvantages  of  the
3262           alternative  function, and how it differs from the normal function, are
3263           discussed in the pcrematching page.
3264    
3265    
3266    NEWLINE CONVENTIONS
3267    
3268           PCRE supports five different conventions for indicating line breaks  in
3269           strings:  a  single  CR (carriage return) character, a single LF (line-
3270           feed) character, the two-character sequence CRLF, any of the three pre-
3271           ceding,  or  any Unicode newline sequence. The pcreapi page has further
3272           discussion about newlines, and shows how to set the newline  convention
3273           in the options arguments for the compiling and matching functions.
3274    
3275           It  is also possible to specify a newline convention by starting a pat-
3276           tern string with one of the following five sequences:
3277    
3278             (*CR)        carriage return
3279             (*LF)        linefeed
3280             (*CRLF)      carriage return, followed by linefeed
3281             (*ANYCRLF)   any of the three above
3282             (*ANY)       all Unicode newline sequences
3283    
3284           These override the default and the options given to  pcre_compile()  or
3285           pcre_compile2().  For example, on a Unix system where LF is the default
3286           newline sequence, the pattern
3287    
3288             (*CR)a.b
3289    
3290           changes the convention to CR. That pattern matches "a\nb" because LF is
3291           no  longer  a  newline. Note that these special settings, which are not
3292           Perl-compatible, are recognized only at the very start  of  a  pattern,
3293           and  that  they  must  be  in  upper  case. If more than one of them is
3294           present, the last one is used.
3295    
3296           The newline convention affects the interpretation of the dot  metachar-
3297           acter  when  PCRE_DOTALL is not set, and also the behaviour of \N. How-
3298           ever, it does not affect  what  the  \R  escape  sequence  matches.  By
3299           default,  this is any Unicode newline sequence, for Perl compatibility.
3300           However, this can be changed; see the description of \R in the  section
3301           entitled  "Newline sequences" below. A change of \R setting can be com-
3302           bined with a change of newline convention.
3303    
3304    
3305  CHARACTERS AND METACHARACTERS  CHARACTERS AND METACHARACTERS
# Line 2741  CHARACTERS AND METACHARACTERS Line 3357  CHARACTERS AND METACHARACTERS
3357                    syntax)                    syntax)
3358           ]      terminates the character class           ]      terminates the character class
3359    
3360         The following sections describe the use of each of the  metacharacters.         The following sections describe the use of each of the metacharacters.
3361    
3362    
3363  BACKSLASH  BACKSLASH
3364    
3365         The backslash character has several uses. Firstly, if it is followed by         The backslash character has several uses. Firstly, if it is followed by
3366         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
3367         character  may  have.  This  use  of  backslash  as an escape character         meaning that character may have. This use of  backslash  as  an  escape
3368         applies both inside and outside character classes.         character applies both inside and outside character classes.
3369    
3370         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
3371         pattern.   This  escaping  action  applies whether or not the following         pattern.  This escaping action applies whether  or  not  the  following
3372         character would otherwise be interpreted as a metacharacter, so  it  is         character  would  otherwise be interpreted as a metacharacter, so it is
3373         always  safe  to  precede  a non-alphanumeric with backslash to specify         always safe to precede a non-alphanumeric  with  backslash  to  specify
3374         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-
3375         slash, you write \\.         slash, you write \\.
3376    
3377         If  a  pattern is compiled with the PCRE_EXTENDED option, whitespace in         In UTF-8 mode, only ASCII numbers and letters have any special  meaning
3378         the pattern (other than in a character class) and characters between  a         after  a  backslash.  All  other characters (in particular, those whose
3379           codepoints are greater than 127) are treated as literals.
3380    
3381           If a pattern is compiled with the PCRE_EXTENDED option,  whitespace  in
3382           the  pattern (other than in a character class) and characters between a
3383         # outside a character class and the next newline are ignored. An escap-         # outside a character class and the next newline are ignored. An escap-
3384         ing backslash can be used to include a whitespace  or  #  character  as         ing  backslash  can  be  used to include a whitespace or # character as
3385         part of the pattern.         part of the pattern.
3386    
3387         If  you  want  to remove the special meaning from a sequence of charac-         If you want to remove the special meaning from a  sequence  of  charac-
3388         ters, you can do so by putting them between \Q and \E. This is  differ-         ters,  you can do so by putting them between \Q and \E. This is differ-
3389         ent  from  Perl  in  that  $  and  @ are handled as literals in \Q...\E         ent from Perl in that $ and  @  are  handled  as  literals  in  \Q...\E
3390         sequences in PCRE, whereas in Perl, $ and @ cause  variable  interpola-         sequences  in  PCRE, whereas in Perl, $ and @ cause variable interpola-
3391         tion. Note the following examples:         tion. Note the following examples:
3392    
3393           Pattern            PCRE matches   Perl matches           Pattern            PCRE matches   Perl matches
# Line 2777  BACKSLASH Line 3397  BACKSLASH
3397           \Qabc\$xyz\E       abc\$xyz       abc\$xyz           \Qabc\$xyz\E       abc\$xyz       abc\$xyz
3398           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz           \Qabc\E\$\Qxyz\E   abc$xyz        abc$xyz
3399    
3400         The  \Q...\E  sequence  is recognized both inside and outside character         The \Q...\E sequence is recognized both inside  and  outside  character
3401         classes.         classes.   An  isolated \E that is not preceded by \Q is ignored. If \Q
3402           is not followed by \E later in the pattern, the literal  interpretation
3403           continues  to  the  end  of  the pattern (that is, \E is assumed at the
3404           end). If the isolated \Q is inside a character class,  this  causes  an
3405           error, because the character class is not terminated.
3406    
3407     Non-printing characters     Non-printing characters
3408    
3409         A second use of backslash provides a way of encoding non-printing char-         A second use of backslash provides a way of encoding non-printing char-
3410         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
3411         appearance of non-printing characters, apart from the binary zero  that         appearance  of non-printing characters, apart from the binary zero that
3412         terminates  a  pattern,  but  when  a pattern is being prepared by text         terminates a pattern, but when a pattern  is  being  prepared  by  text
3413         editing, it is usually easier  to  use  one  of  the  following  escape         editing,  it  is  often  easier  to  use  one  of  the following escape
3414         sequences than the binary character it represents:         sequences than the binary character it represents:
3415    
3416           \a        alarm, that is, the BEL character (hex 07)           \a        alarm, that is, the BEL character (hex 07)
3417           \cx       "control-x", where x is any character           \cx       "control-x", where x is any ASCII character
3418           \e        escape (hex 1B)           \e        escape (hex 1B)
3419           \f        formfeed (hex 0C)           \f        formfeed (hex 0C)
3420           \n        newline (hex 0A)           \n        linefeed (hex 0A)
3421           \r        carriage return (hex 0D)           \r        carriage return (hex 0D)
3422           \t        tab (hex 09)           \t        tab (hex 09)
3423           \ddd      character with octal code ddd, or backreference           \ddd      character with octal code ddd, or back reference
3424           \xhh      character with hex code hh           \xhh      character with hex code hh
3425           \x{hhh..} character with hex code hhh..           \x{hhh..} character with hex code hhh..
3426    
3427         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,
3428         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
3429         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 ({
3430         becomes hex 7B.         is  7B),  while  \c; becomes hex 7B (; is 3B). If the byte following \c
3431           has a value greater than 127, a compile-time error occurs.  This  locks
3432         After \x, from zero to two hexadecimal digits are read (letters can  be         out  non-ASCII  characters in both byte mode and UTF-8 mode. (When PCRE
3433         in  upper  or  lower case). Any number of hexadecimal digits may appear         is compiled in EBCDIC mode, all byte values are  valid.  A  lower  case
3434         between \x{ and }, but the value of the character  code  must  be  less         letter is converted to upper case, and then the 0xc0 bits are flipped.)
3435         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode (that is,  
3436         the maximum hexadecimal value is 7FFFFFFF). If  characters  other  than         After  \x, from zero to two hexadecimal digits are read (letters can be
3437         hexadecimal  digits  appear between \x{ and }, or if there is no termi-         in upper or lower case). Any number of hexadecimal  digits  may  appear
3438         nating }, this form of escape is not recognized.  Instead, the  initial         between  \x{  and  },  but the value of the character code must be less
3439         \x will be interpreted as a basic hexadecimal escape, with no following         than 256 in non-UTF-8 mode, and less than 2**31 in UTF-8 mode. That is,
3440         digits, giving a character whose value is zero.         the  maximum value in hexadecimal is 7FFFFFFF. Note that this is bigger
3441           than the largest Unicode code point, which is 10FFFF.
3442    
3443           If characters other than hexadecimal digits appear between \x{  and  },
3444           or if there is no terminating }, this form of escape is not recognized.
3445           Instead, the initial \x will be  interpreted  as  a  basic  hexadecimal
3446           escape,  with  no  following  digits, giving a character whose value is
3447           zero.
3448    
3449         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
3450         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-
# Line 2862  BACKSLASH Line 3493  BACKSLASH
3493         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
3494         inside and outside character classes. In addition, inside  a  character         inside and outside character classes. In addition, inside  a  character
3495         class,  the  sequence \b is interpreted as the backspace character (hex         class,  the  sequence \b is interpreted as the backspace character (hex
3496         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-
3497         and  "X", respectively. Outside a character class, these sequences have         ter  class.  Like  any  other  unrecognized  escape sequences, they are
3498         different meanings (see below).         treated as the literal characters "B", "N", "R", and  "X"  by  default,
3499           but cause an error if the PCRE_EXTRA option is set. Outside a character
3500           class, these sequences have different meanings.
3501    
3502     Absolute and relative back references     Absolute and relative back references
3503    
3504         The sequence \g followed by a positive or negative  number,  optionally         The sequence \g followed by an unsigned or a negative  number,  option-
3505         enclosed  in  braces,  is  an absolute or relative back reference. Back         ally  enclosed  in braces, is an absolute or relative back reference. A
3506         references are discussed later, following the discussion  of  parenthe-         named back reference can be coded as \g{name}. Back references are dis-
3507         sized subpatterns.         cussed later, following the discussion of parenthesized subpatterns.
3508    
3509       Absolute and relative subroutine calls
3510    
3511           For  compatibility with Oniguruma, the non-Perl syntax \g followed by a
3512           name or a number enclosed either in angle brackets or single quotes, is
3513           an  alternative  syntax for referencing a subpattern as a "subroutine".
3514           Details are discussed later.   Note  that  \g{...}  (Perl  syntax)  and
3515           \g<...>  (Oniguruma  syntax)  are  not synonymous. The former is a back
3516           reference; the latter is a subroutine call.
3517    
3518     Generic character types     Generic character types
3519    
3520         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:  
3521    
3522           \d     any decimal digit           \d     any decimal digit
3523           \D     any character that is not a decimal digit           \D     any character that is not a decimal digit
3524             \h     any horizontal whitespace character
3525             \H     any character that is not a horizontal whitespace character
3526           \s     any whitespace character           \s     any whitespace character
3527           \S     any character that is not a whitespace character           \S     any character that is not a whitespace character
3528             \v     any vertical whitespace character
3529             \V     any character that is not a vertical whitespace character
3530           \w     any "word" character           \w     any "word" character
3531           \W     any "non-word" character           \W     any "non-word" character
3532    
3533         Each pair of escape sequences partitions the complete set of characters         There is also the single sequence \N, which matches a non-newline char-
3534         into  two disjoint sets. Any given character matches one, and only one,         acter.   This  is the same as the "." metacharacter when PCRE_DOTALL is
3535         of each pair.         not set.
3536    
3537         These character type sequences can appear both inside and outside char-         Each pair of lower and upper case escape sequences partitions the  com-
3538         acter  classes.  They each match one character of the appropriate type.         plete  set  of  characters  into two disjoint sets. Any given character
3539         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
3540         of them fail, since there is no character to match.         inside  and outside character classes. They each match one character of
3541           the appropriate type. If the current matching point is at  the  end  of
3542         For  compatibility  with Perl, \s does not match the VT character (code         the  subject string, all of them fail, because there is no character to
3543         11).  This makes it different from the the POSIX "space" class. The  \s         match.
3544         characters  are  HT (9), LF (10), FF (12), CR (13), and space (32). (If  
3545           For compatibility with Perl, \s does not match the VT  character  (code
3546           11).   This makes it different from the the POSIX "space" class. The \s
3547           characters are HT (9), LF (10), FF (12), CR (13), and  space  (32).  If
3548         "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-
3549         ter. In PCRE, it never does.)         ter. In PCRE, it never does.
3550    
3551         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
3552         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-
3553         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-
3554         specific matching is taking place (see "Locale support" in the  pcreapi         specific  matching is taking place (see "Locale support" in the pcreapi
3555         page).  For  example,  in  the  "fr_FR" (French) locale, some character         page). For example, in a French locale such  as  "fr_FR"  in  Unix-like
3556         codes greater than 128 are used for accented  letters,  and  these  are         systems,  or "french" in Windows, some character codes greater than 128
3557         matched by \w.         are used for accented letters, and these are then matched  by  \w.  The
3558           use of locales with Unicode is discouraged.
3559         In  UTF-8 mode, characters with values greater than 128 never match \d,  
3560         \s, or \w, and always match \D, \S, and \W. This is true even when Uni-         By  default,  in  UTF-8  mode,  characters with values greater than 128
3561         code  character  property support is available. The use of locales with         never match \d, \s, or \w, and always  match  \D,  \S,  and  \W.  These
3562         Unicode is discouraged.         sequences  retain their original meanings from before UTF-8 support was
3563           available, mainly for efficiency reasons. However, if PCRE is  compiled
3564           with  Unicode property support, and the PCRE_UCP option is set, the be-
3565           haviour is changed so that Unicode properties  are  used  to  determine
3566           character types, as follows:
3567    
3568             \d  any character that \p{Nd} matches (decimal digit)
3569             \s  any character that \p{Z} matches, plus HT, LF, FF, CR
3570             \w  any character that \p{L} or \p{N} matches, plus underscore
3571    
3572           The  upper case escapes match the inverse sets of characters. Note that
3573           \d matches only decimal digits, whereas \w matches any  Unicode  digit,
3574           as  well as any Unicode letter, and underscore. Note also that PCRE_UCP
3575           affects \b, and \B because they are defined in  terms  of  \w  and  \W.
3576           Matching these sequences is noticeably slower when PCRE_UCP is set.
3577    
3578           The  sequences  \h, \H, \v, and \V are features that were added to Perl
3579           at release 5.10. In contrast to the other sequences, which  match  only
3580           ASCII  characters  by  default,  these always match certain high-valued
3581           codepoints in UTF-8 mode, whether or not PCRE_UCP is set. The  horizon-
3582           tal space characters are:
3583    
3584             U+0009     Horizontal tab
3585             U+0020     Space
3586             U+00A0     Non-break space
3587             U+1680     Ogham space mark
3588             U+180E     Mongolian vowel separator
3589             U+2000     En quad
3590             U+2001     Em quad
3591             U+2002     En space
3592             U+2003     Em space
3593             U+2004     Three-per-em space
3594             U+2005     Four-per-em space
3595             U+2006     Six-per-em space
3596             U+2007     Figure space
3597             U+2008     Punctuation space
3598             U+2009     Thin space
3599             U+200A     Hair space
3600             U+202F     Narrow no-break space
3601             U+205F     Medium mathematical space
3602             U+3000     Ideographic space
3603    
3604           The vertical space characters are:
3605    
3606             U+000A     Linefeed
3607             U+000B     Vertical tab
3608             U+000C     Formfeed
3609             U+000D     Carriage return
3610             U+0085     Next line
3611             U+2028     Line separator
3612             U+2029     Paragraph separator
3613    
3614     Newline sequences     Newline sequences
3615    
3616         Outside a character class, the escape sequence \R matches  any  Unicode         Outside  a  character class, by default, the escape sequence \R matches
3617         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
3618         equivalent to the following:         following:
3619    
3620           (?>\r\n|\n|\x0b|\f|\r|\x85)           (?>\r\n|\n|\x0b|\f|\r|\x85)
3621    
3622         This is an example of an "atomic group", details  of  which  are  given         This  is  an  example  of an "atomic group", details of which are given
3623         below.  This particular group matches either the two-character sequence         below.  This particular group matches either the two-character sequence
3624         CR followed by LF, or  one  of  the  single  characters  LF  (linefeed,         CR  followed  by  LF,  or  one  of  the single characters LF (linefeed,
3625         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage         U+000A), VT (vertical tab, U+000B), FF (formfeed, U+000C), CR (carriage
3626         return, U+000D), or NEL (next line, U+0085). The two-character sequence         return, U+000D), or NEL (next line, U+0085). The two-character sequence
3627         is treated as a single unit that cannot be split.         is treated as a single unit that cannot be split.
3628    
3629         In  UTF-8  mode, two additional characters whose codepoints are greater         In UTF-8 mode, two additional characters whose codepoints  are  greater
3630         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-         than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa-
3631         rator,  U+2029).   Unicode character property support is not needed for         rator, U+2029).  Unicode character property support is not  needed  for
3632         these characters to be recognized.         these characters to be recognized.
3633    
3634         Inside a character class, \R matches the letter "R".         It is possible to restrict \R to match only CR, LF, or CRLF (instead of
3635           the complete set  of  Unicode  line  endings)  by  setting  the  option
3636           PCRE_BSR_ANYCRLF either at compile time or when the pattern is matched.
3637           (BSR is an abbrevation for "backslash R".) This can be made the default
3638           when  PCRE  is  built;  if this is the case, the other behaviour can be
3639           requested via the PCRE_BSR_UNICODE option.   It  is  also  possible  to
3640           specify  these  settings  by  starting a pattern string with one of the
3641           following sequences:
3642    
3643             (*BSR_ANYCRLF)   CR, LF, or CRLF only
3644             (*BSR_UNICODE)   any Unicode newline sequence
3645    
3646           These override the default and the options given to  pcre_compile()  or
3647           pcre_compile2(),  but  they  can  be  overridden  by  options  given to
3648           pcre_exec() or pcre_dfa_exec(). Note that these special settings, which
3649           are  not  Perl-compatible,  are  recognized only at the very start of a
3650           pattern, and that they must be in upper case. If more than one of  them
3651           is present, the last one is used. They can be combined with a change of
3652           newline convention; for example, a pattern can start with:
3653    
3654             (*ANY)(*BSR_ANYCRLF)
3655    
3656           They can also be combined with the (*UTF8) or (*UCP) special sequences.
3657           Inside  a  character  class,  \R  is  treated as an unrecognized escape
3658           sequence, and so matches the letter "R" by default, but causes an error
3659           if PCRE_EXTRA is set.
3660    
3661     Unicode character properties     Unicode character properties
3662    
3663         When PCRE is built with Unicode character property support, three addi-         When PCRE is built with Unicode character property support, three addi-
3664         tional  escape  sequences  to  match character properties are available         tional escape sequences that match characters with specific  properties
3665         when UTF-8 mode is selected. They are:         are  available.   When not in UTF-8 mode, these sequences are of course
3666           limited to testing characters whose codepoints are less than  256,  but
3667           they do work in this mode.  The extra escape sequences are:
3668    
3669           \p{xx}   a character with the xx property           \p{xx}   a character with the xx property
3670           \P{xx}   a character without the xx property           \P{xx}   a character without the xx property
3671           \X       an extended Unicode sequence           \X       an extended Unicode sequence
3672    
3673         The property names represented by xx above are limited to  the  Unicode         The  property  names represented by xx above are limited to the Unicode
3674         script names, the general category properties, and "Any", which matches         script names, the general category properties, "Any", which matches any
3675         any character (including newline). Other properties such as "InMusical-         character   (including  newline),  and  some  special  PCRE  properties
3676         Symbols"  are  not  currently supported by PCRE. Note that \P{Any} does         (described in the next section).  Other Perl properties such as  "InMu-
3677         not match any characters, so always causes a match failure.         sicalSymbols"  are  not  currently supported by PCRE. Note that \P{Any}
3678           does not match any characters, so always causes a match failure.
3679    
3680         Sets of Unicode characters are defined as belonging to certain scripts.         Sets of Unicode characters are defined as belonging to certain scripts.
3681         A  character from one of these sets can be matched using a script name.         A  character from one of these sets can be matched using a script name.
# Line 2961  BACKSLASH Line 3687  BACKSLASH
3687         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
3688         "Common". The current list of scripts is:         "Common". The current list of scripts is:
3689    
3690         Arabic,  Armenian,  Balinese,  Bengali,  Bopomofo,  Braille,  Buginese,         Arabic, Armenian, Avestan, Balinese, Bamum, Bengali, Bopomofo, Braille,
3691         Buhid,  Canadian_Aboriginal,  Cherokee,  Common,   Coptic,   Cuneiform,         Buginese, Buhid, Canadian_Aboriginal, Carian, Cham,  Cherokee,  Common,
3692         Cypriot, Cyrillic, Deseret, Devanagari, Ethiopic, Georgian, Glagolitic,         Coptic,   Cuneiform,  Cypriot,  Cyrillic,  Deseret,  Devanagari,  Egyp-
3693         Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew,  Hira-         tian_Hieroglyphs,  Ethiopic,  Georgian,  Glagolitic,   Gothic,   Greek,
3694         gana,  Inherited,  Kannada,  Katakana,  Kharoshthi,  Khmer, Lao, Latin,         Gujarati,  Gurmukhi,  Han,  Hangul,  Hanunoo,  Hebrew,  Hiragana, Impe-
3695         Limbu,  Linear_B,  Malayalam,  Mongolian,  Myanmar,  New_Tai_Lue,  Nko,         rial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian,
3696         Ogham,  Old_Italic,  Old_Persian, Oriya, Osmanya, Phags_Pa, Phoenician,         Javanese,  Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Lao,
3697         Runic,  Shavian,  Sinhala,  Syloti_Nagri,  Syriac,  Tagalog,  Tagbanwa,         Latin,  Lepcha,  Limbu,  Linear_B,  Lisu,  Lycian,  Lydian,  Malayalam,
3698         Tai_Le, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Yi.         Meetei_Mayek,  Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham, Old_Italic,
3699           Old_Persian, Old_South_Arabian, Old_Turkic, Ol_Chiki,  Oriya,  Osmanya,
3700         Each  character has exactly one general category property, specified by         Phags_Pa,  Phoenician,  Rejang,  Runic, Samaritan, Saurashtra, Shavian,
3701         a two-letter abbreviation. For compatibility with Perl, negation can be         Sinhala, Sundanese, Syloti_Nagri, Syriac,  Tagalog,  Tagbanwa,  Tai_Le,
3702         specified  by  including a circumflex between the opening brace and the         Tai_Tham,  Tai_Viet,  Tamil,  Telugu,  Thaana, Thai, Tibetan, Tifinagh,
3703         property name. For example, \p{^Lu} is the same as \P{Lu}.         Ugaritic, Vai, Yi.
3704    
3705           Each character has exactly one Unicode general category property, spec-
3706           ified  by a two-letter abbreviation. For compatibility with Perl, nega-
3707           tion can be specified by including a  circumflex  between  the  opening
3708           brace  and  the  property  name.  For  example,  \p{^Lu} is the same as
3709           \P{Lu}.
3710    
3711         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-
3712         eral  category properties that start with that letter. In this case, in         eral  category properties that start with that letter. In this case, in
# Line 3034  BACKSLASH Line 3766  BACKSLASH
3766         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
3767         classified as a modifier or "other".         classified as a modifier or "other".
3768    
3769         The  long  synonyms  for  these  properties that Perl supports (such as         The  Cs  (Surrogate)  property  applies only to characters in the range
3770           U+D800 to U+DFFF. Such characters are not valid in UTF-8  strings  (see
3771           RFC 3629) and so cannot be tested by PCRE, unless UTF-8 validity check-
3772           ing has been turned off (see the discussion  of  PCRE_NO_UTF8_CHECK  in
3773           the pcreapi page). Perl does not support the Cs property.
3774    
3775           The  long  synonyms  for  property  names  that  Perl supports (such as
3776         \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix         \p{Letter}) are not supported by PCRE, nor is it  permitted  to  prefix
3777         any of these properties with "Is".         any of these properties with "Is".
3778    
# Line 3053  BACKSLASH Line 3791  BACKSLASH
3791         That  is,  it matches a character without the "mark" property, followed         That  is,  it matches a character without the "mark" property, followed
3792         by zero or more characters with the "mark"  property,  and  treats  the         by zero or more characters with the "mark"  property,  and  treats  the
3793         sequence  as  an  atomic group (see below).  Characters with the "mark"         sequence  as  an  atomic group (see below).  Characters with the "mark"
3794         property are typically accents that affect the preceding character.         property are typically accents that  affect  the  preceding  character.
3795           None  of  them  have  codepoints less than 256, so in non-UTF-8 mode \X
3796           matches any one character.
3797    
3798           Note that recent versions of Perl have changed \X to match what Unicode
3799           calls an "extended grapheme cluster", which has a more complicated def-
3800           inition.
3801    
3802         Matching characters by Unicode property is not fast, because  PCRE  has         Matching characters by Unicode property is not fast, because  PCRE  has
3803         to  search  a  structure  that  contains data for over fifteen thousand         to  search  a  structure  that  contains data for over fifteen thousand
3804         characters. That is why the traditional escape sequences such as \d and         characters. That is why the traditional escape sequences such as \d and
3805         \w do not use Unicode properties in PCRE.         \w  do  not  use  Unicode properties in PCRE by default, though you can
3806           make them do so by setting the PCRE_UCP option for pcre_compile() or by
3807           starting the pattern with (*UCP).
3808    
3809       PCRE's additional properties
3810    
3811           As  well  as  the standard Unicode properties described in the previous
3812           section, PCRE supports four more that make it possible to convert  tra-
3813           ditional escape sequences such as \w and \s and POSIX character classes
3814           to use Unicode properties. PCRE uses these non-standard, non-Perl prop-
3815           erties internally when PCRE_UCP is set. They are:
3816    
3817             Xan   Any alphanumeric character
3818             Xps   Any POSIX space character
3819             Xsp   Any Perl space character
3820             Xwd   Any Perl "word" character
3821    
3822           Xan  matches  characters that have either the L (letter) or the N (num-
3823           ber) property. Xps matches the characters tab, linefeed, vertical  tab,
3824           formfeed,  or  carriage  return, and any other character that has the Z
3825           (separator) property.  Xsp is the same as Xps, except that vertical tab
3826           is excluded. Xwd matches the same characters as Xan, plus underscore.
3827    
3828       Resetting the match start
3829    
3830           The  escape sequence \K causes any previously matched characters not to
3831           be included in the final matched sequence. For example, the pattern:
3832    
3833             foo\Kbar
3834    
3835           matches "foobar", but reports that it has matched "bar".  This  feature
3836           is  similar  to  a lookbehind assertion (described below).  However, in
3837           this case, the part of the subject before the real match does not  have
3838           to  be of fixed length, as lookbehind assertions do. The use of \K does
3839           not interfere with the setting of captured  substrings.   For  example,
3840           when the pattern
3841    
3842             (foo)\Kbar
3843    
3844           matches "foobar", the first substring is still set to "foo".
3845    
3846           Perl  documents  that  the  use  of  \K  within assertions is "not well
3847           defined". In PCRE, \K is acted upon  when  it  occurs  inside  positive
3848           assertions, but is ignored in negative assertions.
3849    
3850     Simple assertions     Simple assertions
3851    
# Line 3076  BACKSLASH Line 3863  BACKSLASH
3863           \z     matches only at the end of the subject           \z     matches only at the end of the subject
3864           \G     matches at the first matching position in the subject           \G     matches at the first matching position in the subject
3865    
3866         These  assertions may not appear in character classes (but note that \b         Inside  a  character  class, \b has a different meaning; it matches the
3867         has a different meaning, namely the backspace character, inside a char-         backspace character. If any other of  these  assertions  appears  in  a
3868         acter class).         character  class, by default it matches the corresponding literal char-
3869           acter  (for  example,  \B  matches  the  letter  B).  However,  if  the
3870         A  word  boundary is a position in the subject string where the current         PCRE_EXTRA  option is set, an "invalid escape sequence" error is gener-
3871         character and the previous character do not both match \w or  \W  (i.e.         ated instead.
3872         one  matches  \w  and the other matches \W), or the start or end of the  
3873         string if the first or last character matches \w, respectively.         A word boundary is a position in the subject string where  the  current
3874           character  and  the previous character do not both match \w or \W (i.e.
3875           one matches \w and the other matches \W), or the start or  end  of  the
3876   &nbs